02136nas a2200169 4500008004100000245012200041210006900163300001400232490000800246520156400254100001801818700001701836700001801853700002001871700001801891856005701909 2023 eng d00aMultiple global change drivers show independent, not interactive effects: a long-term case study in tallgrass prairie0 aMultiple global change drivers show independent not interactive  a143–1540 v2013 a

Ecosystems are faced with an onslaught of co-occurring global change drivers. While frequently studied independently, the effects of multiple global change drivers have the potential to be additive, antagonistic, or synergistic. Global warming, for example, may intensify the effects of more variable precipitation regimes with warmer temperatures increasing evapotranspiration and thereby amplifying the effect of already dry soils. Here, we present the long-term effects (11 years) of altered precipitation patterns (increased intra-annual variability in the growing season) and warming (1 °C year-round) on plant community composition and aboveground net primary productivity (ANPP), a key measure of ecosystem functioning in mesic tallgrass prairie. Based on past results, we expected that increased precipitation variability and warming would have additive effects on both community composition and ANPP. Increased precipitation variability altered plant community composition and increased richness, with no effect on ANPP. In contrast, warming decreased ANPP via reduction in grass stems and biomass but had no effect on the plant community. Contrary to expectations, across all measured variables, precipitation and warming treatments had no interactive effects. While treatment interactions did not occur, each treatment did individually impact a different component of the ecosystem (i.e., community vs. function). Thus, different aspects of the ecosystem may be sensitive to different global change drivers in mesic grassland ecosystems.

1 aKoerner, S.E.1 aAvolio, M.L.1 aBlair, J., M.1 aKnapp, Alan, K.1 aSmith, M., D. uhttps://link.springer.com/10.1007/s00442-022-05295-500633nas a2200169 4500008004100000245014200041210006900183300001100252490000800263100002500271700001800296700001800314700002000332700001600352700002300368856007200391 2023 eng d00aThirty years of increased precipitation modifies soil organic matter fractions but not bulk soil carbon and nitrogen in a mesic grassland0 aThirty years of increased precipitation modifies soil organic ma a1091450 v1851 aRocci, Katherine, S.1 aBird, Michael1 aBlair, J., M.1 aKnapp, Alan, K.1 aLiang, Chao1 aCotrufo, Francesca uhttps://www.sciencedirect.com/science/article/pii/S003807172300207900591nas a2200157 4500008004100000245014300041210006900184300001400253490000700267100001800274700002200292700002300314700002400337700001800361856005400379 2022 eng d00aAssessing transport and retention of nitrate and other materials through the riparian zone and stream channel with simulated precipitation0 aAssessing transport and retention of nitrate and other materials a757 - 7660 v131 aDodds, W., K.1 aWichman, Gretchen1 aGuinnip, James, P.1 aCorman, Jessica, R.1 aBlair, J., M. uhttps://onlinelibrary.wiley.com/toc/2041210x/13/300652nas a2200181 4500008004100000245010500041210006900146260004300215490002100258653001900279653002100298653002100319653001600340653002200356100002000378700001800398856005400416 2022 eng d00aClimate legacies and restoration history as drivers of tallgrass prairie carbon and nitrogen cycling0 aClimate legacies and restoration history as drivers of tallgrass aManhattan, KSbKansas State University0 vPhD Dissertation10acarbon cycling10aClimate legacies10aNitrogen cycling10arestoration10atallgrass prairie1 aBroderick, C.M.1 aBlair, J., M. uhttps://krex.k-state.edu/dspace/handle/2097/4210100485nas a2200145 4500008004100000245007800041210006900119300001400188490000700202100002000209700001600229700001800245700001800263856005800281 2022 eng d00aClimate legacies determine grassland responses to future rainfall regimes0 aClimate legacies determine grassland responses to future rainfal a2639-26560 v281 aBroderick, C.M.1 aWilkins, K.1 aSmith, M., D.1 aBlair, J., M. uhttps://onlinelibrary.wiley.com/doi/10.1111/gcb.1608400527nas a2200157 4500008004100000022001400041245006800055210006800123300001800191490000800209100002000217700002300237700001700260700001800277856007400295 2022 eng d a2169-895300aClimate legacy effects shape tallgrass prairie nitrogen cycling0 aClimate legacy effects shape tallgrass prairie nitrogen cycling ae2022JG0069720 v1271 aBroderick, C.M.1 aFreeman, Kiona, M.1 aZeglin, L.H.1 aBlair, J., M. uhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JG006972?af=R00857nas a2200265 4500008004100000245010600041210006900147300001400216490000700230100001900237700001900256700001800275700002400293700002000317700001700337700002100354700002400375700002000399700002400419700002500443700001800468700002200486700001800508856006500526 2022 eng d00a Cross-site comparisons of climate change on drylands in the US Long-term Ecological Research network0 aCrosssite comparisons of climate change on drylands in the US Lo a889 - 9070 v721 aHudson, Amy, R1 aPeters, D.P.C.1 aBlair, J., M.1 aChilders, Daniel, L1 aDoran, Peter, T1 aGeil, Kerrie1 aGooseff, Michael1 aGross, Katherine, L1 aHaddad, Nick, M1 aPastore, Melissa, A1 aRudgers, Jennifer, A1 aSala, Osvaldo1 aSeabloom, Eric, W1 aShaver, Gaius uhttps://academic.oup.com/bioscience/article/72/9/889/665484001990nas a2200205 4500008004100000245009500041210006900136300001600205490000800221520135500229100001801584700001701602700001801619700001801637700001801655700001801673700001701691700002301708856005301731 2022 eng d00aReintroducing bison results in long-running and resilient increases in grassland diversity0 aReintroducing bison results in longrunning and resilient increas ae22104331190 v1193 a

The widespread extirpation of megafauna may have destabilized ecosystems and altered biodiversity globally. Most megafauna extinctions occurred before the modern record, leaving it unclear how their loss impacts current biodiversity. We report the long-term effects of reintroducing plains bison (Bison bison) in a tallgrass prairie versus two land uses that commonly occur in many North American grasslands: 1) no grazing and 2) intensive growing-season grazing by domesticated cattle (Bos taurus). Compared to ungrazed areas, reintroducing bison increased native plant species richness by 103% at local scales (10 m2) and 86% at the catchment scale. Gains in richness continued for 29 y and were resilient to the most extreme drought in four decades. These gains are now among the largest recorded increases in species richness due to grazing in grasslands globally. Grazing by domestic cattle also increased native plant species richness, but by less than half as much as bison. This study indicates that some ecosystems maintain a latent potential for increased native plant species richness following the reintroduction of native herbivores, which was unmatched by domesticated grazers. Native-grazer gains in richness were resilient to an extreme drought, a pressure likely to become more common under future global environmental change.

1 aRatajczak, Z.1 aCollins, S.L1 aBlair, J., M.1 aKoerner, S.E.1 aLouthan, A.M.1 aSmith, M., D.1 aTaylor, J.H.1 aNippert, Jesse, B. uhttps://www.pnas.org/doi/10.1073/pnas.221043311902268nas a2200145 4500008004100000245011500041210006900156520176300225100001701988700001802005700001402023700001802037700002002055856004702075 2021 eng d00aEffects of compounded precipitation pattern intensification and drought occur belowground in a mesic grassland0 aEffects of compounded precipitation pattern intensification and 3 a

Climate change is altering precipitation regimes globally, with expectations of intensified precipitation patterns (for example, larger but fewer rainfall events) and more frequent and extreme drought. Both aspects of precipitation change can impact ecosystem function individually, but it is more likely that they will occur in combination. In a central US mesic grassland, we imposed an extreme 2-year drought (growing season precipitation reduced by 66%) on plots with a long-term (16-year) history of exposure to either ambient or intensified precipitation patterns (average threefold increase in event size and threefold decrease in event number during the growing season). While this intensified pattern did not alter total precipitation amount, it generally led to ecosystem responses consistent with a drier environment (for example, reduced soil moisture, aboveground net primary production (ANPP), and soil CO2 flux, but little evidence for altered root biomass). Surprisingly, this history of intensified precipitation patterns did not affect the response of ANPP to the subsequent extreme drought. In contrast, previous exposure to intensified precipitation patterns reduced root production and muted soil CO2 flux responses to rainfall events during drought. Reduced root production in plots experiencing compounded precipitation extremes was driven not by the dominant C4 grass species, Andropogon gerardii, but collectively by the subdominant species in the plant community. Overall, our results reveal that compound changes in precipitation patterns and amount affected this grassland in ways that were less apparent (that is, belowground) than responses to either change individually and significantly reduced ecosystem carbon uptake.

1 aSlette, I.J.1 aBlair, J., M.1 aFay, P.A.1 aSmith, M., D.1 aKnapp, Alan, K. uhttps://doi.org/10.1007/s10021-021-00714-900814nas a2200241 4500008004100000245012700041210006900168300001100237490000600248100002200254700002400276700002200300700001700322700002300339700002200362700001500384700001800399700001700417700002700434700002600461700001800487856006700505 2021 eng d00aPatterns and trends of organic matter processing and transport: Insights from the US Long-Term Ecological Research network0 aPatterns and trends of organic matter processing and transport I a1000250 v21 aHarms, Tamara, K.1 aGroffman, Peter, M.1 aAluwihare, Lihini1 aCraft, Chris1 aWieder, William, R1 aHobbie, Sarah, E.1 aBaer, S.G.1 aBlair, J., M.1 aFrey, Serita1 aRemucal, Christina, K.1 aRudgers, Jennifer, A.1 aCollins, S, L uhttps://linkinghub.elsevier.com/retrieve/pii/S266690052100025300465nas a2200133 4500008004100000245008200041210006900123300001100192490000800203100001800211700001700229700001800246856006700264 2021 eng d00aPlant legacies and soil microbial community dynamics control soil respiration0 aPlant legacies and soil microbial community dynamics control soi a1083500 v1601 aConnell, Kent1 aZeglin, L.H.1 aBlair, J., M. uhttps://linkinghub.elsevier.com/retrieve/pii/S003807172100223601110nas a2200373 4500008004100000245008000041210006900121260001100190490000700201100002300208700001800231700002600249700002500275700002400300700001800324700001500342700001800357700001700375700001800392700002300410700002200433700002200455700002400477700001900501700002200520700001200542700002200554700001800576700002200594700002500616700001900641700002200660856005400682 2021 eng d00aState changes: insights from the U.S. Long Term Ecological Research Network0 aState changes insights from the US Long Term Ecological Research ce034330 v121 aZinnert, Julie, C.1 aNippert, J.B.1 aRudgers, Jennifer, A.1 aPennings, Steven, C.1 aGonzález, Grizelle1 aAlber, Merryl1 aBaer, S.G.1 aBlair, J., M.1 aBurd, Adrian1 aCollins, S, L1 aCraft, Christopher1 aDi Iorio, Daniela1 aDodds, Walter, K.1 aGroffman, Peter, M.1 aHerbert, Ellen1 aHladik, Christine1 aLi, Fan1 aLitvak, Marcy, E.1 aNewsome, Seth1 aO’Donnell, John1 aPockman, William, T.1 aSchalles, John1 aYoung, Donald, R. uhttps://onlinelibrary.wiley.com/toc/21508925/12/500493nas a2200121 4500008004100000245008800041210006900129260004400198490002100242100002000263700001800283856007000301 2020 eng d00aEffects of plant-soil interactions on grassland carbon dynamics in a changing world0 aEffects of plantsoil interactions on grassland carbon dynamics i aManhattan, KS.bKansas State University0 vPhD Dissertation1 aConnell, R., K.1 aBlair, J., M. uhttps://search.proquest.com/docview/2427237261?pq-origsite=summon03603nas a2200517 4500008004100000245014500041210006900186490000700255520197200262100002102234700002302255700001902278700002002297700002002317700001902337700002002356700002102376700002402397700001802421700002502439700002902464700002302493700002202516700002402538700002202562700002402584700002102608700001902629700002702648700002702675700002602702700002502728700002202753700002102775700002402796700002302820700001902843700002402862700002502886700002302911700002402934700002002958700002002978700002402998856006303022 2020 eng d00aGlobal impacts of fertilization and herbivore removal on soil net nitrogen mineralization are modulated by local climate and soil properties0 aGlobal impacts of fertilization and herbivore removal on soil ne0 v263 a

Soil nitrogen (N) availability is critical for grassland functioning. However, human activities have increased the supply of biologically limiting nutrients, and changed the density and identity of mammalian herbivores. These anthropogenic changes may alter net soil N mineralization (soil net Nmin), that is, the net balance between N mineralization and immobilization, which could severely impact grassland structure and functioning. Yet, to date, little is known about how fertilization and herbivore removal individually, or jointly, affect soil net Nmin across a wide range of grasslands that vary in soil and climatic properties. Here we collected data from 22 grasslands on five continents, all part of a globally replicated experiment, to assess how fertilization and herbivore removal affected potential (laboratory‐based) and realized (field‐based) soil net Nmin. Herbivore removal in the absence of fertilization did not alter potential and realized soil net Nmin. However, fertilization alone and in combination with herbivore removal consistently increased potential soil net Nmin. Realized soil net Nmin, in contrast, significantly decreased in fertilized plots where herbivores were removed. Treatment effects on potential and realized soil net Nmin were contingent on site‐specific soil and climatic properties. Fertilization effects on potential soil net Nmin were larger at sites with higher mean annual precipitation (MAP) and temperature of the wettest quarter (T.q.wet). Reciprocally, realized soil net Nmin declined most strongly with fertilization and herbivore removal at sites with lower MAP and higher T.q.wet. In summary, our findings show that anthropogenic nutrient enrichment, herbivore exclusion and alterations in future climatic conditions can negatively impact soil net Nmin across global grasslands under realistic field conditions. This is an important context‐dependent knowledge for grassland management worldwide.

1 aRisch, Anita, C.1 aZimmermann, Stefan1 aMoser, Barbara1 aSchütz, Martin1 aHagedorn, Frank1 aFirn, Jennifer1 aFay, Philip, A.1 aAdler, Peter, B.1 aBiederman, Lori, A.1 aBlair, J., M.1 aBorer, Elizabeth, T.1 aBroadbent, Arthur, A. D.1 aBrown, Cynthia, S.1 aCadotte, Marc, W.1 aCaldeira, Maria, C.1 aDavies, Kendi, F.1 aVirgilio, Augustina1 aEisenhauer, Nico1 aEskelinen, Anu1 aKnops, Johannes, M. H.1 aMacDougall, Andrew, S.1 aMcCulley, Rebecca, L.1 aMelbourne, Brett, A.1 aMoore, Joslin, L.1 aPower, Sally, A.1 aProber, Suzanne, M.1 aSeabloom, Eric, W.1 aSiebert, Julia1 aSilveira, Maria, L.1 aSpeziale, Karina, L.1 aStevens, Carly, J.1 aTognetti, Pedro, M.1 aVirtanen, Risto1 aYahdjian, Laura1 aOchoa‐Hueso, Raul uhttps://onlinelibrary.wiley.com/doi/full/10.1111/gcb.1530802163nas a2200301 4500008004100000245007600041210006900117300001200186490000800198520129700206100001601503700001801519700002001537700001701557700001701574700001701591700001701608700001701625700001301642700001801655700001701673700002601690700001701716700001701733700001101750700002001761856008001781 2020 eng d00aMass ratio effects underlie ecosystem responses to environmental change0 aMass ratio effects underlie ecosystem responses to environmental a855-8640 v1083 a

1. Random species loss has been shown experimentally to reduce ecosystem function, sometimes more than other anthropogenic environmental changes. Yet, controversy surrounds the importance of this finding for natural systems where species loss is non‐random.
2. We compiled data from 16 multi‐year experiments located at a single native tallgrass prairie site. These experiments included responses to 11 anthropogenic environmental changes, as well as non‐random biodiversity loss either the removal of uncommon/rare plant species or the most common (dominant) species.
3. As predicted by the mass ratio hypothesis, loss of a dominant species had large impacts on productivity that were comparable to other anthropogenic drivers. In contrast, the loss of uncommon/rare species had small effects on productivity despite having the largest effects on species richness.
4. The anthropogenic drivers that had the largest effects on productivity nitrogen, irrigation, and fire experienced not only loss of species but also significant changes in the abundance and identity of dominant species.
5. Synthesis. These results suggest that mass ratio effects, rather than species loss per se, are an important determinant of ecosystem function with environmental change.

1 aSmith, M.D.1 aKoerner, S.E.1 aKnapp, Alan, K.1 aAvolio, M.L.1 aChaves, F.A.1 aDenton, E.M.1 aDietrich, J.1 aGibson, D.J.1 aGray, J.1 aHoffman, A.M.1 aHoover, D.L.1 aKomatsu, Kimberly, J.1 aSilletti, A.1 aWilcox, K.R.1 aYu, Q.1 aBlair, John, M. uhttps://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.1333003157nas a2200169 4500008004100000245011300041210006900154300001100223490000700234520253800241100001502779700001402794700001602808700002002824700002402844856011902868 2020 eng d00aSoil heterogeneity increases plant diversity after twenty years of manipulation during grassland restoration0 aSoil heterogeneity increases plant diversity after twenty years  ae020140 v303 a

The “environmental heterogeneity hypothesis” predicts that variability in resources promotes species coexistence, but few experiments support this hypothesis in plant communities. A previous 15‐yr test of this hypothesis in a prairie restoration experiment demonstrated a weak effect of manipulated soil resource heterogeneity on plant diversity. This response was attributed to a transient increase in richness following a post‐restoration supplemental propagule addition, occasionally higher diversity under nutrient enrichment, and reduced cover of a dominant species in a subset of soil treatments. Here, we report community dynamics under continuous propagule addition in the same experiment, corresponding to 16–20 yr of restoration, in response to altered availability and heterogeneity of soil resources. We also quantified traits of newly added species to determine if heterogeneity increases the amount and variety of niches available for new species to exploit. The heterogeneous treatment contained a factorial combination of altered nutrient availability and soil depth; control plots had no manipulations. Total diversity and richness were higher in the heterogeneous treatment during this 5‐yr study due to higher cover, diversity, and richness of previously established forbs, particularly in the N‐enriched subplots. All new species added to the experiment exhibited unique trait spaces, but there was no evidence that heterogeneous plots contained a greater variety of new species representing a wider range of trait spaces relative to the control treatment. The richness and cover of new species was higher in N‐enriched soil, but the magnitude of this response was small. Communities assembling under long‐term N addition were dominated by different species among subplots receiving added N, leading to greater dispersion of communities among the heterogeneous relative to control plots. Contrary to the deterministic mechanism by which heterogeneity was expected to increase diversity (greater variability in resources for new species to exploit), higher diversity in the heterogeneous plots resulted from destabilization of formerly grass‐dominated communities in N‐enriched subplots. While we do not advocate increasing available soil N at large scales, we conclude that the positive effect of environmental heterogeneity on diversity can take decades to materialize and depend on development of stochastic processes in communities with strong establishment limitation.

1 aBaer, S.G.1 aAdams, T.1 aScott, D.A.1 aBlair, John, M.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/soil-heterogeneity-increases-plant-diversity-after-twenty-years-manipulation-during02267nas a2200145 4500008004100000245011600041210006900157300001800226490000800244520175300252100001802005700001502023700001802038856006502056 2020 eng d00aThree decades of divergent land use and plant community change alters soil C and N content in tallgrass prairie0 aThree decades of divergent land use and plant community change a ae2020JG0057230 v1253 a

Frequent fire and grazing by megafauna are important determinants of tallgrass prairie plant community structure. However, fire suppression and removal of native grazers have altered these natural disturbance regimes and changed grassland plant communities with potential long‐term consequences for soil carbon (C) and nitrogen (N) storage. We investigated multi‐decade changes in soil C and N pools in response to contrasting long‐term burning and grazing treatments. Fire suppression with or without grazers, and exclusion of grazers in annually‐burned prairie increased soil C content and shifted the δ13C signature of soil C over time, concomitant with changes in plant community composition. Soil δ13C values indicated that increased soil C content was associated with an increased contribution from plants using a C3 photosynthetic pathway (i.e., woody shrubs) under fire suppression. Soil N content also increased when fire was suppressed, relative to frequently burned grassland, but the rate of increase was slower when grazers were present. Additionally, changes in δ15N values suggested that grazing increased the openness of the N cycle, presumably due to greater N losses. By coupling long‐term fire and grazing treatments with plant community data and soil samples archived over three decades, we demonstrate that human‐caused changes to natural disturbance regimes in a tallgrass prairie significantly alters soil C and N cycles through belowground changes associated with shifts in the plant community. Since natural disturbance regimes have been altered in grasslands across the world, our results are relevant for understanding the long‐term biogeochemical consequences of these ongoing land‐use changes.

1 aConnell, K.R.1 aNippert, J1 aBlair, J., M. uhttps://onlinelibrary.wiley.com/doi/abs/10.1029/2020JG00572301634nas a2200157 4500008004100000245007500041210006900116300001400185490000700199520109500206100001601301700002101317700001501338700002001353856010301373 2019 eng d00aChanges in potential nitrous oxide efflux during grassland restoration0 aChanges in potential nitrous oxide efflux during grassland resto a1913-19170 v483 a

14 Nitrous oxide efflux from soil is an important ecological process in terms of global climate 15 impacts, stratospheric chemistry, and soil fertility. The effects of grassland restoration on nitrous 16 oxide (N 2 O) efflux in formerly cultivated agricultural soils are not well known. Restoration 17 changes the storage and availability of soil C and N, with potential consequences for N 2 O efflux. 18 We examined changes in potential N 2 O efflux across a 35-year chronosequence of grassland 19 restorations, using lab incubations at moisture levels that maximized N 2 O emissions, to quantify 20 the relationship between N 2 O efflux and soil properties known to change predictably during 21 grassland restoration. We found that restoring cultivated agricultural land to grassland rapidly 22 decreased N 2 O efflux from soils, though native prairie had a potential N 2 O efflux higher than the 23 agricultural land. The oldest restoration had N 2 O efflux 50 times lower than native prairie. 24 Changes in N 2 O efflux were more strongly correlated with N mineralization than C.

1 aScott, D.A.1 aRosenzweig, S.T.1 aBaer, S.G.1 aBlair, John, M. uhttp://knz.lternet.edu/content/changes-potential-nitrous-oxide-efflux-during-grassland-restoration01464nas a2200181 4500008004100000245008700041210006900128300001300197490000600210520090200216100001701118700001601135700001701151700001701168700002001185700002001205856005701225 2019 eng d00aDecadal-scale shifts in soil hydraulic properties induced by altered precipitation0 aDecadalscale shifts in soil hydraulic properties induced by alte aeaau66350 v53 a

Soil hydraulic properties influence the partitioning of rainfall into infiltration versus runoff, determine plant-available water, and constrain evapotranspiration. Although rapid changes in soil hydraulic properties from direct human disturbance are well documented, climate change may also induce such shifts on decadal time scales. Using soils from a 25-year precipitation manipulation experiment, we found that a 35% increase in water inputs substantially reduced infiltration rates and modestly increased water retention. We posit that these shifts were catalyzed by greater pore blockage by plant roots and reduced shrink-swell cycles. Given that precipitation regimes are expected to change at accelerating rates globally, shifts in soil structure could occur over broad regions more rapidly than expected and thus alter water storage and movement in numerous terrestrial ecosystems.

1 aCaplan, J.S.1 aGimenez, D.1 aHirmas, D.R.1 aBrunsell, N.1 aBlair, John, M.1 aKnapp, Alan, K. uhttps://advances.sciencemag.org/content/5/9/eaau663502170nas a2200181 4500008004100000245009200041210007100133300001400204490000700218520157000225100002401795700001201819700002001831700001801851700002001869700001901889856008001908 2019 eng d00aFire, grazing and climate shape plant–grasshopper interactions in a tallgrass prairie0 aFire grazing and climate shape plant–grasshopper interactions in a735 - 7450 v333 a

1. Species interactions are integral to ecological community function, and the      structure of species interactions has repercussions for the consequences of species extinctions. Few studies  have examined the role of environmental factors in controlling species interaction networks across time.
2. We examined variation in plant–grasshopper network structural properties in response to three major grassland drivers: periodic fire, ungulate grazing and climate.
3. We sequenced a plant barcoding gene from extracted grasshopper gut contents to characterize diets of 26 grasshopper species. Resulting grasshopper species’ diets were combined with long‐term plant and grasshopper surveys to assemble plant–grasshopper networks across 13–19 years for six watersheds subjected to varying fire and grazing treatments.
4. Network modularity, generality and predicted grasshopper community robustness to plant species loss all increased in grazed watersheds. Temperature decreased predicted grasshopper community robustness to plant species loss.
5. Grasshopper communities were found to be vulnerable to climatic warming due to host plant loss. However, intermediate disturbance from ungulate grazers may maintain grasshopper diversity and buffer community robustness to species loss. Our results suggest that climate and disturbance shape the structure of ecological interaction networks and thus have many indirect effects on species persistence though direct effects on interaction partners.

1 aWelti, Ellen, A. R.1 aFan, Q.1 aTetreault, H.M.1 aUngerer, M.C.1 aBlair, John, M.1 aJoern, Anthony uhttps://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.1327204634nas a2201021 4500008004100000245011700041210006900158300001600227490000800243520186900251100002602120700001702146700002402163700001902187700001702206700002602223700002302249700001802272700001702290700002202307700001902329700001402348700001502362700002402377700001402401700002202415700001702437700002002454700001802474700001702492700002102509700002802530700001702558700002402575700002202599700002602621700002102647700001802668700002402686700002402710700001102734700001902745700001902764700001502783700001402798700001402812700001802826700001202844700001602856700001902872700001902891700001602910700001902926700002002945700002002965700002202985700001103007700001403018700001903032700002403051700002303075700001703098700002503115700001903140700001803159700002003177700001603197700002403213700001803237700001503255700001903270700001603289700003203305700001603337700001703353700001703370700001603387700001803403700001703421700001903438700001403457700001503471700001703486700001103503700001903514700001803533856006103551 2019 eng d00aGlobal change effects on plant communities are magnified by time and the number of global change factors imposed0 aGlobal change effects on plant communities are magnified by time a17867-178730 v1163 a

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.

1 aKomatsu, Kimberly, J.1 aAvolio, M.L.1 aLemoine, Nathan, P.1 aIsbell, Forest1 aGrman, Emily1 aHouseman, Gregory, R.1 aKoerner, Sally, E.1 aJohnson, D.S.1 aWilcox, K.R.1 aAlatalo, Juha, M.1 aAnderson, J.P.1 aAerts, R.1 aBaer, S.G.1 aBaldwin, Andrew, H.1 aBates, J.1 aBeierkuhnlein, C.1 aBelote, R.T.1 aBlair, John, M.1 aBloor, J.M.G.1 aBohlen, P.J.1 aBork, Edward, W.1 aBoughton, Elizabeth, H.1 aBowman, W.D.1 aBritton, Andrea, J.1 aCahill, James, F.1 aChaneton, Enrique, J.1 aChiariello, N.R.1 aCheng, Jimin.1 aCollins, Scott., L.1 aCornelissen, J.H.C.1 aDu, G.1 aEskelinen, Anu1 aFirn, Jennifer1 aFoster, B.1 aGough, L.1 aGross, K.1 aHallett, L.M.1 aHan, X.1 aHarmens, H.1 aHovenden, M.J.1 aJagerbrand, A.1 aJentsch, A.1 aKern, Christel1 aKlanderud, Kari1 aKnapp, Alan, K.1 aKreyling, Juergen1 aLi, W.1 aLuo, Yiqi1 aMcCulley, R.L.1 aMcLaren, Jennie, R.1 aMegonigal, Patrick1 aMorgan, J.W.1 aOnipchenko, Vladimir1 aPennings, S.C.1 aPrevéy, J.S.1 aPrice, Jodi, N.1 aReich, P.B.1 aRobinson, Clare, H.1 aRussell, L.F.1 aSala, O.E.1 aSeabloom, E.W.1 aSmith, M.D.1 aSoudzilovskaia, Nadejda, A.1 aSouza, Lara1 aSuding, K.N.1 aSuttle, B.K.1 aSvejcar, T.1 aTilman, David1 aTognetti, P.1 aTurkington, R.1 aWhite, S.1 aXu, Zhuwen1 aYahdjian, L.1 aYu, Q.1 aZhang, Pengfei1 aZhang, Yunhai uhttps://www.pnas.org/content/early/2019/08/14/181902711601712nas a2200157 4500008004100000245011500041210006900156300001200225490000700237520114100244100002601385700001801411700002001429700002201449856008301471 2019 eng d00aSoil fungal community changes in response to long-term fire cessation and N fertilization in tallgrass prairie0 aSoil fungal community changes in response to longterm fire cessa a45 - 550 v413 a

In grasslands, fire management and fertilization are established drivers of plant community change, but associated soil fungal responses are less well defined. We predicted that soil fungal communities would change seasonally, that decades of fire cessation and nitrogen (N) fertilization would alter fungal distributions, and that plant and fungal community change would be correlated. Surface soils were sampled monthly for 1 y from a 30-y fire by fertilization experiment to evaluate fungal community dynamics and assess correlation with plant community heterogeneity. ITS gene community composition was seasonally stable, excepting increased arbuscular mycorrhizal fungal summer abundance in the burned, fertilized treatment. Long-term treatments affected soil fungal and plant communities, with correlated heterogeneity patterns. Despite woody encroachment in the fire cessation treatment, soil fungal communities did not resemble those of forests. This study provides evidence supporting the strength of feedbacks between fungal and plant community change in response to long-term grassland fire and N management changes.

1 aCarson, Christine, M.1 aJumpponen, A.1 aBlair, John, M.1 aZeglin, Lydia, H. uhttps://www.sciencedirect.com/science/article/pii/S1754504818302538?via%3Dihub02714nas a2200625 4500008004100000245006200041210006200103490000700165520105900172100001601231700001901247700002001266700001601286700001301302700001701315700001601332700001701348700001601365700002101381700002001402700002101422700002101443700002501464700002001489700002101509700001401530700001401544700002001558700002001578700001801598700002101616700002401637700001401661700002001675700001601695700001901711700001301730700001801743700001601761700001601777700002001793700002301813700002201836700001801858700001901876700001601895700001701911700001601928700002101944700002101965700001701986700001702003700001402020856005402034 2019 eng d00aSoil net nitrogen mineralisation across global grasslands0 aSoil net nitrogen mineralisation across global grasslands0 v103 a

Soil nitrogen mineralisation (Nmin), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net Nmin) varies with soil properties and climate. However, because most global-scale assessments of net Nmin are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net Nmin across 30 grasslands worldwide. We find that realised Nmin is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential Nmin only weakly correlates with realised Nmin, but contributes to explain realised net Nmin when combined with soil and climatic variables. We provide novel insights of global realised soil net Nmin and show that potential soil net Nmin data available in the literature could be parameterised with soil and climate data to better predict realised Nmin.

1 aRisch, A.C.1 aZimmermann, S.1 aOchoa-Hueso, R.1 aschütz, M.1 aFrey, B.1 aFirn, J., L.1 aFay, P., A.1 aHagedorn, F.1 aBorer, E.T.1 aSeabloom, E., W.1 aHarpole, W., S.1 aKnops, J., M. H.1 aMcCulley, R., L.1 aBroadbent, A., A. D.1 aStevens, C., J.1 aSilveira, M., L.1 aAdler, P.1 aBáez, S.1 aBiederman, L.A.1 aBlair, John, M.1 aBrown, C., S.1 aCaldeira, M., C.1 aCollins, Scott., L.1 aDaleo, P.1 adi Virgilio, A.1 aEbeling, A.1 aEisenhauer, N.1 aEsch, E.1 aEskelinen, A.1 aHagenah, N.1 aHautier, Y.1 aKirkman, K., P.1 aMacDougall, A., S.1 aMoore, Joslin, L.1 aPower, S., A.1 aProber, S., M.1 aRoscher, C.1 aSankaran, M.1 aSiebert, J.1 aSpeziale, K., L.1 aTognetti, P., M.1 aVirtanen, R.1 aYahdjian, L.1 aMoser, B. uhttp://www.nature.com/articles/s41467-019-12948-202777nas a2200253 4500008004100000245012200041210006900163300001600232490000700248520194500255100002402200700002502224700001302249700002002262700002402282700002402306700002302330700002702353700002602380700002202406700002402428700002202452856004902474 2018 eng d00aRegional grassland productivity responses to precipitation during multiyear above- and below-average rainfall periods0 aRegional grassland productivity responses to precipitation durin a1935 - 19510 v243 a

There is considerable uncertainty in the magnitude and direction of changes in precipitation associated with climate change, and ecosystem responses are also uncertain. Multiyear periods of above- and below-average rainfall may foretell consequences of changes in rainfall regime. We compiled long-term aboveground net primary productivity (ANPP) and precipitation (PPT) data for eight North American grasslands, and quantified relationships between ANPP and PPT at each site, and in 1-3 year periods of above- and below-average rainfall for mesic, semiarid cool, and semiarid warm grassland types. Our objective was to improve understanding of ANPP dynamics associated with changing climatic conditions by contrasting PPT-ANPP relationships in above- and below-average PPT years to those that occurred during sequences of multiple above- and below-average years. We found differences in PPT-ANPP relationships in above- and below-average years compared to long-term site averages, and variation in ANPP not explained by PPT totals that likely are attributed to legacy effects. The correlation between ANPP and current- and prior-year conditions changed from year to year throughout multiyear periods, with some legacy effects declining, and new responses emerging. Thus, ANPP in a given year was influenced by sequences of conditions that varied across grassland types and climates. Most importantly, the influence of prior-year ANPP often increased with the length of multiyear periods, whereas the influence of the amount of current-year PPT declined. Although the mechanisms by which a directional change in the frequency of above- and below-average years imposes a persistent change in grassland ANPP require further investigation, our results emphasize the importance of legacy effects on productivity for sequences of above- vs. below-average years, and illustrate the utility of long-term data to examine these patterns.

1 aPetrie, Matthew, D.1 aPeters, Debra, P. C.1 aYao, Jin1 aBlair, John, M.1 aBurruss, Nathan, D.1 aCollins, Scott., L.1 aDerner, Justin, D.1 aGherardi, Laureano, A.1 aHendrickson, John, R.1 aSala, Osvaldo, E.1 aStarks, Patrick, J.1 aSteiner, Jean, L. uhttps://www.ncbi.nlm.nih.gov/pubmed/2926556802567nas a2200217 4500008004100000245005900041210005900100260004300159490002100202520191100223653002302134653001202157653001302169653001402182653001502196653002202211100002402233700001902257700002002276856005302296 2017 eng d00aEcological networks of grassland plants and arthropods0 aEcological networks of grassland plants and arthropods aManhattan, KSbKansas State University0 vPhD Dissertation3 a

Ecological communities are comprised both of species and their interactions. The importance of species interactions is embraced by ecological network analysis, a framework used to identify non-random patterns in species interactions, and the consequences of these patterns for maintaining species diversity. Here, I investigated environmental drivers of the structure of plant-pollinator and plant-herbivore networks. Specifically, I asked: (1) Do global-scale climate gradients shape mutualistic and antagonistic networks? (2) At a landscape scale (within a 3,487 ha research site), how do contrasting regimes of major grassland disturbances - fire frequency and grazing by bison (Bison bison) - shape plant-pollinator network structure? (3) How do fire and grazing affect plant-grasshopper network structure? And, (4) What is the role of plant species diversity in determining plant-herbivore network structure? At the global scale, variability in temperature was the key climatic factor regulating both antagonistic and mutualistic network structural properties. At the landscape scale, fire and grazing had major consequences for plant-pollinator and plant-herbivore communities. In particular, bison grazing increased network complexity and resistance to species loss for both plant-pollinator and plant-herbivore systems. Results from an experimental grassland restoration that manipulated plant diversity suggest that plant diversity directly affects plant-herbivore structure and increases network stability. Collectively, these results suggest that environmental gradients and plant species diversity regulate the network structure of ecological communities. Determining how the structure of ecological interactions change with environmental conditions and species diversity improves our ability to identify vulnerable communities, and to predict responses of biodiversity to global change.

10aEcological network10aecology10aFood web10aHerbivore10aPollinator10atallgrass prairie1 aWelti, Ellen, A. R.1 aJoern, Anthony1 aBlair, John, M. uhttp://krex.k-state.edu/dspace/handle/2097/3528403493nas a2200217 4500008004100000245013500041210006900176300000900245490000700254520282100261653001003082653001403092653002203106653001303128653001603141653001603157100001803173700001503191700002003206856004903226 2017 eng d00aEffects of grazing and fire frequency on floristic quality and its relationship to indicators of soil quality in tallgrass prairie0 aEffects of grazing and fire frequency on floristic quality and i a10750 v603 a

Fire and grazing are widely used to manage grasslands for conservation purposes, but few studies have evaluated the effects of these drivers on the conservation value of plant communities measured by the floristic quality index (FQI). Further, the influence of fire and grazing on soil properties and functions are difficult for land managers and restoration practitioners to assess. The objectives of this study were to: (1) quantify the independent and interactive effects of grazing and fire frequency on floristic quality in native tallgrass prairie to provide potential benchmarks for community assessment, and (2) to explore whether floristic quality can serve as an indicator of soil structure and function for more holistic ecosystem assessments. A factorial combination of fire frequencies (1–2, 4, and 20 years return intervals) and grazing (by bison or ungrazed) treatments were sampled for plant species composition, and for several indicators of soil quality in lowland tallgrass prairie. Floristic quality, diversity, and richness were higher in grazed than ungrazed prairie over all fire frequencies (P < 0.05). Available inorganic N, microbial biomass N, total N, and soil bulk density were also higher in grazed prairie soil over all fire frequencies (P < 0.05). Microbial biomass C, total organic C, and total soil N were positively correlated with FQI (P < 0.05). This study shows that floristic quality and soil N pools are more strongly influenced by grazing than fire and that floristic quality can be an indicator of total soil C and N stocks in never cultivated lowland prairie.

10abison10agrassland10aMicrobial biomass10anitrogen10arestoration10aSoil carbon1 aManning, G.C.1 aBaer, S.G.1 aBlair, John, M. uhttps://www.ncbi.nlm.nih.gov/pubmed/2896357202504nas a2200145 4500008004100000245015200041210006900193300001000262490000700272520195500279100001602234700001502250700002002265856007302285 2017 eng d00aRecovery and relative influence of root, microbial, and structural properties of soil on physically sequestered carbon stocks in restored grassland0 aRecovery and relative influence of root microbial and structural a50-600 v813 a

Managing soil to sequester C can help mitigate increasing CO2 in the atmosphere. To maximize this ecosystem service, more knowledge of factors influencing C sequestration is needed. The objectives of this study were to (i) quantify recovery of the roots, microbial biomass and composition, and soil structure across a chronosequence of grassland restorations and (ii) use a structural equation model to develop a data-based hypothesis on the relative influence of physical and biological soil properties on the soil C aggregate fraction diagnostic of sequestered C. Belowground plant biomass and tissue quality (C/N ratio), soil microbial biomass C, phospholipid fatty acid (PLFA) concentrations, soil structure, and soil C stocks in the bulk soil and each aggregate fraction were quantified from a cultivated field, prairies restored for 1 to 35-yr (n = 6), and a never-cultivated (native) prairie. Root biomass, microbial biomass C, arbuscular mycorrhizal fungi (AMF) PLFA biomass across the chronosequence increase to resemble native prairie following 35 yr of restoration. Many aspects of soil structure (i.e., bulk density, proportional mass of aggregate fractions, and aggregate mean weighted diameter) and the distribution C among soil fractions, including C in the micro-within-macro aggregate fraction (sequestered C), also became representative of native prairie within 35 yr of restoration. Total soil C stock and physically protected C increased at a similar rate (23 and 27 g C m-2 yr-1) respectively, across the chronosequence. After 35 yr of restoration, 50% of the total C pool was physically protected. The structural equation modeling developed by these data hypothesizes that microbial biomass C and AMF biomass (microbial composition) have the strongest causal influence on physically protected C. This model needs to be tested using independent sites to achieve greater inference.

1 aScott, D.A.1 aBaer, S.G.1 aBlair, John, M. uhttps://dl.sciencesocieties.org/publications/sssaj/abstracts/81/1/5001743nas a2200145 4500008004100000245009500041210006900136520124400205100002201449700002401471700002001495700001601515700002001531856004601551 2016 eng d00aAltered rainfall patterns increase forb abundance and richness in native tallgrass prairie0 aAltered rainfall patterns increase forb abundance and richness i3 a

Models predict that precipitation variability will increase with climate change. We used a 15-year precipitation manipulation experiment to determine if altering the timing and amount of growing season rainfall will impact plant community structure in annually burned, native tallgrass prairie. The altered precipitation treatment maintained the same total growing season precipitation as the ambient precipitation treatment, but received a rainfall regime of fewer, larger rain events, and longer intervals between events each growing season. Although this change in precipitation regime significantly lowered mean soil water content, overall this plant community was remarkably resistant to altered precipitation with species composition relatively stable over time. However, we found significantly higher forb cover and richness and slightly lower grass cover on average with altered precipitation, but the forb responses were manifest only after a ten-year lag period. Thus, although community structure in this grassland is relatively resistant to this type of altered precipitation regime, forb abundance in native tallgrass prairie may increase in a future characterized by increased growing season precipitation variability.

1 aJones, Sydney, K.1 aCollins, Scott., L.1 aBlair, John, M.1 aSmith, M.D.1 aKnapp, Alan, K. uhttps://www.nature.com/articles/srep2012003012nas a2200229 4500008004100000022001300041245013100054210006900185300001400254490000800268520225400276653001702530653001902547653002102566653001702587653002202604100002102626700001702647700001502664700002002679856008302699 2016 eng d a0929139300aChanges in soil properties, microbial biomass, and fluxes of C and N in soil following post-agricultural grassland restoration0 aChanges in soil properties microbial biomass and fluxes of C and a186 - 1940 v1003 a

Understanding the dynamics of soil C and N pools and fluxes following grassland restoration in formerly cultivated soils is needed to assess the capacity of this land-use change to return soil properties and function to pre-disturbance conditions. We examined changes in physical (bulk density) and chemical (pH, available P and N, and total stocks of C and N) properties, microbial biomass C and N, and transformation rates of C and N in soil (0–10 cm depth) across a 35-year chronosequence of prairie restorations and never-cultivated (native) prairie to evaluate the rate and extent to which sowing native perennial plants into formerly cultivated soils returns soil to steady state conditions. Bulk density, available P, and extractable inorganic N decreased exponentially across the chronosequence. Soil pH increased linearly across the chronosequence to exceed that in native prairie soil. Total C and N stocks in cultivated soil were <50% that of native prairie, and increased at rates of 26.2 g C m−2 year−1 and 1.68 g N m−2 year−1 across the chronosequence. In the oldest restoration, total C and N stocks were 55% and 41% higher than the cultivated soil, respectively. Recovery of C and N stocks to levels comparable to native prairie soil was estimated to take 350 years. Microbial biomass C and N increased 5-fold. Potential C mineralization rate was comparable to native prairie soil following two decades of restoration, and exceeded native prairie in the 35-years restoration. In situ soil CO2 efflux reached equilibrium in <30 years. Potential net N mineralization rate, however, did not exhibit a directional change across the restoration chronosequence, but was lowest in the oldest restored grasslands. Thus, cessation of tillage and sowing native vegetation leads to rapid decreases in available N and P, and promotes rapid (decadal scale) recovery of labile soil organic matter pools, but recovery of total C and N pools requires several centuries. This study suggests that soil properties related to nutrient retention and regulation of nutrient availability can be reestablished within the first few decades of restoration, while C sequestration will continue on a longer time scale.

10aBulk density10achronosequence10asoil respiration10aSOM recovery10atallgrass prairie1 aRosenzweig, S.T.1 aCarson, M.A.1 aBaer, S.G.1 aBlair, John, M. uhttps://www.sciencedirect.com/science/article/pii/S0929139316300014?via%3Dihub02040nas a2200157 4500008004100000245010500041210006900146300001200215490000700227520150000234100001701734700002001751700001601771700002001787856007501807 2016 eng d00aDoes ecosystem sensitivity to precipitation at the site-level conform to regional-scale predictions?0 aDoes ecosystem sensitivity to precipitation at the sitelevel con a561-5680 v973 a

Central to understanding global C cycle dynamics is the functional relationship between precipitation and net primary production (NPP). At large spatial (regional) scales, the responsiveness of aboveground NPP (ANPP) to inter-annual variation in annual precipitation (AP; ANPPsensitivity) is inversely related to site-level ANPP, coinciding with turnover of plant communities along precipitation gradients. Within ecosystems experiencing chronic alterations in water availability, plant community change will also occur with unknown consequences for ANPPsensitivity. To examine the role plant community shifts may play in determining alterations in site-level ANPPsensitivity, we experimentally increased precipitation by ~35% for two decades in a native Central US grassland. Consistent with regional models, ANPPsensitivity decreased initially as water availability and ANPP increased. However, ANPPsensitivity shifted back to ambient levels when mesic species increased in abundance in the plant community. Similarly, in grassland sites with distinct mesic and xeric plant communities and corresponding 50% differences in ANPP, ANPPsensitivity did not differ over almost three decades. We conclude that responses in ANPPsensitivity to chronic alterations in water availability within an ecosystem may not conform to regional AP-ANPP patterns, despite expected changes in ANPP and plant communities. The result is unanticipated functional resistance to climate change at the site scale.

1 aWilcox, K.R.1 aBlair, John, M.1 aSmith, M.D.1 aKnapp, Alan, K. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/15-1437.100472nas a2200145 4500008004100000022001400041245008700055210006900142300001100211490000800222100001900230700002000249700001600269856004100285 2016 eng d a0022-844300aEcohydrological and climate change studies at the Konza Prairie Biological Station0 aEcohydrological and climate change studies at the Konza Prairie  a5 - 110 v1191 aBriggs, J., M.1 aBlair, John, M.1 aHorne, E.A. uhttps://doi.org/10.1660/062.119.010303068nas a2200145 4500008004100000245011000041210006900151300001300220490000700233520254900240100001502789700002002804700002402824856007402848 2016 eng d00aEnvironmental heterogeneity has a weak effect on diversity during community assembly in tallgrass prairie0 aEnvironmental heterogeneity has a weak effect on diversity durin a94 - 1060 v863 a

Understanding what constrains the persistence of species in communities is at the heart of community assembly theory and its application to conserving and enhancing biodiversity. The “environmental heterogeneity hypothesis” predicts greater species coexistence in habitats with greater resource variability. In the context of community assembly, environmental heterogeneity may influence the variety and strength of abiotic conditions and competitive interactions (environmental filters) to affect the relative abundance of species and biodiversity. We manipulated key resources that influence plant diversity in tallgrass prairie (i.e., soil depth and nitrogen availability) to increase environmental heterogeneity prior to sowing native prairie species into a former agricultural field. We compared variability in nutrient availability, aboveground annual net primary productivity (ANPP), and the composition of species between replicate plots containing soil heterogeneity manipulations and plots with no resource manipulations (n = 4 per treatment) during the first 15 yr of community assembly as a test of the “environmental heterogeneity hypothesis.” The manipulations increased environmental heterogeneity, measured as the coefficient of variation in NO3-N availability and ANPP. Plant diversity, however, was similar and decayed exponentially and indiscriminately over time between the heterogeneity treatments. Species richness declined linearly over time in both heterogeneity treatments, but richness was higher in the more heterogeneous soil 2 yr following a second propagule addition 8 yr after the initial sowing. As a result, there was a lower rate of species loss over time in the more heterogeneous soil (0.60 species yr−1) relative to the control soil (0.96 species yr−1). Communities in each treatment exhibited strong convergence over time resulting from a shift in dominant species across all treatments and a gradual increase in the clonal C4 grass, Andropogon gerardii. We attribute the weak effect of heterogeneity on diversity to increasing dominance of a clonal species, which decreased the scale of soil treatments relative to plant size, dispersal limitation, and absence of a key driver (grazing) known to increase plant diversity under a frequent fire regime. Thus, steering community assembly to attain high biodiversity may depend more on manipulating processes that reduce dominance and facilitate the arrival of new species than promoting environmental heterogeneity.

1 aBaer, S.G.1 aBlair, John, M.1 aCollins, Scott., L. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/15-0888.103800nas a2200733 4500008004100000245006500041210006500106300001400171490000800185520189700193653002002090653001702110100002102127700002602148700001702174700001902191700001802210700002302228700001802251700001302269700001302282700002002295700002002315700002102335700001902356700001702375700001802392700001802410700002002428700002102448700001802469700001902487700001702506700001702523700001202540700001402552700001402566700002002580700002102600700001902621700001502640700002102655700001202676700001602688700001502704700001502719700001802734700001402752700001202766700001602778700001602794700002402810700001302834700001602847700002102863700002002884700001502904700001802919700002002937700002102957700001902978700002102997856004803018 2016 eng d00aQuantifying global soil carbon losses in response to warming0 aQuantifying global soil carbon losses in response to warming a104 - 1080 v5403 a

The majority of the Earth’s terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming, Despite evidence that warming enhances carbon fluxes to and from the soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30 ± 30 petagrams of carbon to 203 ± 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12–17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon–climate feedback that could accelerate climate change.

10aBiogeochemistry10acarbon cycle1 aCrowther, T., W.1 aTodd-Brown, K., E. O.1 aRowe, C., W.1 aWieder, W., R.1 aCarey, J., C.1 aMachmuller, M., B.1 aSnoek, B., L.1 aFang, S.1 aZhou, G.1 aAllison, S., D.1 aBlair, John, M.1 aBridgham, S., D.1 aBurton, A., J.1 aCarrillo, Y.1 aReich, P., B.1 aClark, J., S.1 aClassen, A., T.1 aDijkstra, F., A.1 aElberling, B.1 aEmmett, B., A.1 aEstiarte, M.1 aFrey, S., D.1 aGuo, J.1 aHarte, J.1 aJiang, L.1 aJohnson, B., R.1 aKröel-Dulay, G.1 aLarsen, K., S.1 aLaudon, H.1 aLavallee, J., M.1 aLuo, Y.1 aLupascu, M.1 aMa, L., N.1 aMarhan, S.1 aMichelsen, A.1 aMohan, J.1 aNiu, S.1 aPendall, E.1 añuelas, J.1 aPfeifer-Meister, L.1 aPoll, C.1 aReinsch, S.1 aReynolds, L., L.1 aSchmidt, I., K.1 aSistla, S.1 aSokol, N., W.1 aTempler, P., H.1 aTreseder, K., K.1 aWelker, J., M.1 aBradford, M., A. uhttps://www.nature.com/articles/nature2015002102nas a2200361 4500008004100000245011900041210006900160300001400229490000700243520104200250653004101292653000901333653001401342653001201356653002001368100001601388700002001404700002401424700002001448700001801468700001801486700001901504700002001523700001601543700001201559700002001571700001701591700001701608700001601625700001701641700001701658856006501675 2016 eng d00aShared drivers but divergent ecological responses: Insights from long-term experiments in mesic savanna grasslands0 aShared drivers but divergent ecological responses Insights from  a666 - 6820 v663 a

Fire and grazing, key determinants of structure and function of savanna grasslands worldwide, have been extensively altered by humans. We used existing long-term manipulations of fire and grazing in North American and South African mesic savanna grasslands, as well as new experiments, to determine whether the impacts of fire and grazing by large herbivores differed between these systems. We found that despite a body of literature suggesting that these savanna grasslands respond uniquely to fire and grazing, their ecosystem responses (aboveground productivity) were generally similar. In contrast, plant-community responses to fire and herbivores diverged strongly between systems. The differences in plant-community responses, as well as convergence in ecosystem function, were underpinned by a common mechanism: the response of grass dominance to changing fire and grazing regimes. As a result, divergent responses of plant communities to altered fire and grazing regimes did not preclude convergence in ecosystem function.

10aAboveground net primary productivity10afire10agrassland10aGrazing10aplant community1 aSmith, M.D.1 aKnapp, Alan, K.1 aCollins, Scott., L.1 aBurkepile, D.E.1 aKirkman, K.P.1 aKoerner, S.E.1 aThompson, D.I.1 aBlair, John, M.1 aBurns, C.E.1 aEby, S.1 aForrestel, E.J.1 aFynn, R.W.S.1 aGovender, N.1 aHagenah, N.1 aHoover, D.L.1 aWilcox, K.R. uhttps://academic.oup.com/bioscience/article/66/8/666/246414102124nas a2200145 4500008004100000245011100041210006900152300001600221490000800237520160200245100001701847700002001864700002001884856007401904 2016 eng d00aStability of grassland soil C and N pools despite 25 years of an extreme climatic and disturbance regime0 aStability of grassland soil C and N pools despite 25 years of an a1934 - 19450 v1213 a

Global changes are altering many important drivers of ecosystem functioning, with precipitation amount and disturbance frequency being especially important. Carbon (C) and nitrogen (N) pools are key contemporary attributes of ecosystems that can also influence future C uptake via plant growth. Thus, understanding the impacts of altered precipitation amounts (through controls of primary production inputs) and disturbance regimes (through losses of C and N in biomass) is important to project how ecosystem services will respond to future global changes. A major difficulty inherent within this task is that drivers of ecosystem function and processes often interact, resulting in novel ecosystem responses. To examine how changes in precipitation affect grassland ecosystem responses under a frequent disturbance regime (annual fire), we assessed the biogeochemical and ecological consequences of more than two decades of irrigation in an annually burned mesic grassland in the central United States. In this experiment, precipitation amount was increased by 31% relative to ambient and 1 in 3 years were statistically extreme relative to the long-term historical record. Despite evidence that irrigation decreased root:shoot ratios and increased rates of N cycling—each expected to reduce soil C and N with annual burning—we detected no changes in these biogeochemical pools. This surprising biogeochemical resistance highlights the need to explore additional mechanisms within long-term experiments concerning the consequences of global change impacts on ecosystems.

1 aWilcox, K.R.1 aBlair, John, M.1 aKnapp, Alan, K. uhttps://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JG00337002633nas a2200253 4500008004100000245013900041210006900180300001500249490000800264520182600272653001002098653001502108653001202123653001502135653001202150653003102162653001002193653001502203100001802218700002302236700001902259700002002278856008102298 2014 eng d00aFire dynamics distinguish grasslands, shrublands, and woodlands as alternative attractors in the Central Great Plains of North America0 aFire dynamics distinguish grasslands shrublands and woodlands as a1374 -13850 v1023 a

Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1–2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1–2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency.

10abison10aEcosystems10aForests10aGrasslands10aGrazing10aLinear regression analysis10aTrees10aWatersheds1 aRatajczak, Z.1 aNippert, Jesse, B.1 aBriggs, J., M.1 aBlair, John, M. uhttps://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.1231100428nas a2200157 4500008004100000245002200041210002200063260003800085300001200123490000600135100002000141700002300161700001900184700001400203856005300217 2014 eng d00aGrassland Ecology0 aGrassland Ecology bSpringer-Verlag Berlin Heidelberg a389-4230 v81 aBlair, John, M.1 aNippert, Jesse, B.1 aBriggs, J., M.1 aMonson, R uhttp://knz.lternet.edu/content/grassland-ecology03975nas a2200145 4500008004100000245018800041210006900229260004300298490001400341520328000355653011903635100001803754700002003772856003703792 2014 eng d00aHow does your prairie (re)grow?: Interactions of seed additions with resource availability, heterogeneity, and disturbance on recruitment and diversity in a restored tallgrass prairie0 aHow does your prairie regrow Interactions of seed additions with aManhattan, KSbKansas State University0 vMS Thesis3 a

Temperate grasslands are among the most threatened biomes in the world, with the largest historical losses due to conversion to agricultural land. While much of this biome has already been converted, there is concern the last remaining remnants in North America will be converted in response to increasing demand for crops used for ethanol production. Thus, restoring grasslands post-anthropogenic disturbance is increasingly important for conserving grassland biodiversity. Two major challenges for prairie restorations are establishing the many subdominant and rarer species found in native prairie, and offsetting the typical decline in richness and diversity over time as restorations age. Repeated seed addition of targeted species is commonly used to override low and declining plant richness and diversity. While this is generally effective early in restoration (i.e., as communities are establishing), its effectiveness in later stages (i.e., when established communities are often losing diversity) remains unknown. I investigated plant community responses to combinations of resource manipulations and disturbances coupled with a seed addition in a 15-yr old restored grassland to test the hypothesis that spatial resource heterogeneity increases the rate of colonization into established prairie restoration communities. Seeds were added to a long-term restoration experiment involving soil depth manipulations (deep, shallow) crossed with nutrient manipulations (reduced N, ambient N, enriched N). Seedling emergence was generally low and only 8 of the 14 forb species added were detected in the first growing season. I found no effect of increased resource heterogeneity on the abundance or richness of seedlings. There was a significant nutrient effect (p<0.1, α=0.1) on seedling abundance, with higher emergence in the enriched N than the ambient N treatment. I also found unexpected nutrient effects on richness, diversity and Mean C (Mean C = Σ CoCi*Ai, where CoC=Coefficient of Conservatism and A=relative abundance of the ith species). All values, except Mean C, were higher in the enriched N treatment than in either the reduced or ambient N treatments. Mean C was lowest in the enriched N treatment, and highest in the whole-plot control, suggesting that the majority of species contributing to higher richness and diversity in the enriched N treatment were “weedier” species. In a separate experiment, I found no effect of small-scale disturbances (aboveground biomass removal or soil disturbance) on seedling abundance or seedling richness. I did find a marginal effect of disturbance type on seedling richness (p=0.11, α=0.1), with higher seedling richness in the soil disturbance than the aboveground biomass removal treatment. I did not find any disturbance effects on community response variables. These results indicate that recruitment from seed additions into well-established restored communities is relatively low in the first year following a seed addition, regardless of resource availability and heterogeneity. Follow-up studies to determine recruitment rates in subsequent years are needed to elucidate whether recruitment responses are driven more by individual species differences or by environmental mechanisms.

10aTallgrass prairie; Ecological restoration; Resource availability and heterogeneity; Long-term; Propagule; Seedling1 aStanton, N.L.1 aBlair, John, M. uhttp://hdl.handle.net/2097/1820502943nas a2200277 4500008004100000245008900041210006900130300001100199490000700210520211800217653003402335653001902369653001302388653001602401653001402417653002902431653001002460653001802470653001702488100001802505700002402523700002002547700002002567700001602587856006202603 2014 eng d00aRainfall variability has minimal effects on grassland recovery from repeated grazing0 aRainfall variability has minimal effects on grassland recovery f a36 -440 v253 a

Question Mesic grasslands experience a complex disturbance regime including frequent fire, grazing by large ungulates and strong inter-annual climate variability. As a result of climate change, growing season precipitation regimes are predicted to become more variable, with larger event sizes and longer dry periods resulting in more temporally dynamic soil moisture regimes. Increased climate variability is likely to interact with other disturbances, such as grazing, in grassland ecosystems. We investigated the individual and combined effects of increased rainfall variability and grazing on plant community composition, structure and function in an annually burned, native tallgrass prairie. Our overarching question was: are grazing impacts modified under a more variable precipitation regime? Location Konza Prairie, Kansas, USA. Methods Plots were established within a long-term rainfall manipulation experiment in which larger, but less frequent, rain events were imposed during the growing season without altering the total rain amount. We then simulated intense grazing pressure during one growing season by repeatedly clipping all graminoids to 5 cm and monitored recovery over 3 yr. Results Neither grazing nor rainfall treatments affected species richness; however, grazing decreased total and grass above-ground net primary production (ANPP) and increased forb ANPP relative to ungrazed plots. Grass stem density recovered from intense grazing under ambient rainfall but did not fully recover, even after 2 yr in the altered rainfall treatment. Conclusions We found that increased rainfall variability had little effect on tallgrass prairie structure and function, while grazing had large effects. Grazing and increased rainfall variability interacted to suppress grass stem density and delayed recovery relative to controls. Although stem density was reduced, individual stem size increased, resulting in no net change in ANPP. This suggests that ANPP in grazed and ungrazed North American tallgrass prairie may be relatively resilient under more temporally variable precipitation regimes.

10aAnnual net primary production10aClimate change10aClipping10adisturbance10adiversity10aGrass–forb interaction10aKonza10aPrecipitation10aStem density1 aKoerner, S.E.1 aCollins, Scott., L.1 aBlair, John, M.1 aKnapp, Alan, K.1 aSmith, M.D. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.1206503098nas a2200145 4500008004100000245013200041210006900173300001500242490000700257520259200264100001102856700001602867700002002883856004902903 2013 eng d00aEstimating aboveground net primary productivity of the tallgrass prairie ecosystem of the Central Great Plains using AVHRR NDVI0 aEstimating aboveground net primary productivity of the tallgrass a3717 -37350 v343 a

Above-ground net primary productivity (ANPP) is indicative of an ecosystem's ability to capture solar energy and convert it to organic carbon (or biomass), which may be used by consumers or decomposers, or stored in the form of living and nonliving organic matter. Annual and interannual variation in ANPP is often linked to climate dynamics and anthropogenic influences, such as fertilization, irrigation, above-ground biomass harvest, and so on. The Central Great Plains grasslands occupy over 1.5 million km2 and are a primary resource for livestock production in North America. The tallgrass prairies are the most productive grasslands in this region, and the Flint Hills of North America represent the largest contiguous area of unploughed tallgrass prairie (1.6 million ha). Measurements of ANPP are of critical importance to the proper management and understanding of climatic and anthropogenic influences on tallgrass prairie. Yet, accurate, detailed, and systematic measurements of ANPP over large geographic regions do not exist for this ecosystem. For these reasons, this study was conducted to investigate the use of the normalized difference vegetation index (NDVI) to model ANPP of the tallgrass prairie. Many studies have established a positive relationship between the NDVI and ANPP, but the strength of this relationship is influenced by vegetation types and can vary significantly from year to year depending on land use and climatic conditions. The goal of this study was to develop a robust model using the Advanced Very High Resolution Radiometer (AVHRR) biweekly NDVI values to predict tallgrass ANPP. This study was conducted using ANPP measurements from a watershed within the Konza Prairie Biological Station (KPBS) as the primary study area, with additional measurements from the Rannells Flint Hills Prairie Preserve (RFHPP) and biennial ANPP measurements by Kansas State University (KSU) students from tallgrass areas near Manhattan, Kansas. Data from the primary study site covered the period of 1989–2005. The optimal period for estimating ANPP using AVHRR NDVI composite data sets was found to be late July. The Tallgrass ANPP Model (TAM) explained 54% (coefficient of determination, R 2 = 0.54, p < 0.001) of the year-to-year variation in ANPP. The creation of 1.0 km × 1.0 km resolution ANPP maps for a four-county (∼7000 ha) area for years 1989–2007 showed considerable variation in annual and interannual ANPP spatial patterns, suggesting complex interactions among factors influencing ANPP spatially and temporally.

1 aAn, N.1 aPrice, K.P.1 aBlair, John, M. uhttps://doi.org/10.1080/01431161.2012.75737603310nas a2200193 4500008004100000245009900041210006900140260004300209490002200252520267700274653001902951653001902970653001802989653002103007653001403028100001703042700002003059856003703079 2013 eng d00aGrassland restoration in a changing world: consequences of practices and variable environments0 aGrassland restoration in a changing world consequences of practi aManhattan, KSbKansas State University0 vPhD. Dissertation3 a

The feasibility of restoration, which traditionally targets historical conditions, is questionable in the context of global change. To address this, my dissertation investigated (Chapter 2) the patterns of restoration establishment along a chronosequence of restored prairies with respect to nearby remnant prairies, (Chapters 3-4) responses of plant communities in restorations initiated using different methods (levels of species richness and sowing density) to drought, which is projected to increase in frequency, and (Chapters 5-6) the effects of propagule source and variation (mixing among sources) on restoration establishment and the generality of restoration outcomes across variable environments using reciprocal common gardens of multi-species restoration seedings. Chapter 2, published in Restoration Ecology, showed that restoration led to the recovery of desirable characteristics within several years, but restorations utilizing primarily fall-collected seeds likely diminished the representation of early phenology species, so biodiversity may be further enhanced by including early phenology species in seeding mixes. Chapters 3 and 4, published respectively in Ecological Applications and Applied Vegetation Science, examined the establishment of native plant communities after seeding and their responses to experimentally imposed drought. Both high seed mixture richness and high density seeding resulted in greater establishment of native, seeded species compared to low richness and low density treatments, and exotic species were less prevalent in high richness and high density treatments. However, we found little evidence of differential drought resistance, recovery, and resilience among treatments. This result coupled with increases in exotic species following drought suggest that other forms of active management may be needed to produce restored plant communities that are robust to climate change. Chapter 5 (published in Ecosphere) and Chapter 6 found that seed source affects individual species establishment, community structure, and productivity. However, there was no consistent advantage for any source, including local sources, across sites or species. This suggests that source effects on single species or effects observed at single locations should not be broadly generalized. Together, this dissertation shows that restoration can recover many characteristics of native prairies and that manipulation of seeding practices (seed mixture richness, seeding density, seed source) influence grassland establishment in terms of productivity, community structure, invasion, and the abundance and survival of individual species.

10achronosequence10aClimate change10acommon garden10alocal adaptation10atallgrass1 aCarter, D.L.1 aBlair, John, M. uhttp://hdl.handle.net/2097/1535702899nas a2200265 4500008004100000245012000041210006900161300001200230490000600242520206400248653001302312653001702325653002602342653001502368653002502383653002202408653001802430653002202448100001702470700001602487700001502503700002002518700001702538856007802555 2013 eng d00aLong-term nitrogen amendment alters the diversity and assemblage of soil bacterial communities in tallgrass prairie0 aLongterm nitrogen amendment alters the diversity and assemblage  a67884 -0 v83 a

Anthropogenic changes are altering the environmental conditions and the biota of ecosystems worldwide. In many temperate grasslands, such as North American tallgrass prairie, these changes include alteration in historically important disturbance regimes (e.g., frequency of fires) and enhanced availability of potentially limiting nutrients, particularly nitrogen. Such anthropogenically-driven changes in the environment are known to elicit substantial changes in plant and consumer communities aboveground, but much less is known about their effects on soil microbial communities. Due to the high diversity of soil microbes and methodological challenges associated with assessing microbial community composition, relatively few studies have addressed specific taxonomic changes underlying microbial community-level responses to different fire regimes or nutrient amendments in tallgrass prairie. We used deep sequencing of the V3 region of the 16S rRNA gene to explore the effects of contrasting fire regimes and nutrient enrichment on soil bacterial communities in a long-term (20 yrs) experiment in native tallgrass prairie in the eastern Central Plains. We focused on responses to nutrient amendments coupled with two extreme fire regimes (annual prescribed spring burning and complete fire exclusion). The dominant bacterial phyla identified were Proteobacteria, Verrucomicrobia, Bacteriodetes, Acidobacteria, Firmicutes, and Actinobacteria and made up 80% of all taxa quantified. Chronic nitrogen enrichment significantly impacted bacterial community diversity and community structure varied according to nitrogen treatment, but not phosphorus enrichment or fire regime. We also found significant responses of individual bacterial groups including Nitrospira and Gammaproteobacteria to long-term nitrogen enrichment. Our results show that soil nitrogen enrichment can significantly alter bacterial community diversity, structure, and individual taxa abundance, which have important implications for both managed and natural grassland ecosystems.

10aBacteria10aBiodiversity10aEcosystem functioning10aGrasslands10aMicrobial ecosystems10aPlant communities10aRibosomal RNA10aSequence analysis1 aCoolon, J.D.1 aJones, K.L.1 aTodd, T.C.1 aBlair, John, M.1 aHerman, M.A. uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.006788403088nas a2200181 4500008004100000245013200041210006900173260004300242490001400285520245500299653002002754653002102774653001702795653002202812100001502834700002002849856003702869 2013 eng d00aResponses to long-term fertilization and burning: impacts on nutrient dynamics and microbial composition in a tallgrass prairie0 aResponses to longterm fertilization and burning impacts on nutri aManhattan, KSbKansas State University0 vMS Thesis3 a

Anthropogenic activities impact ecosystems in numerous direct and indirect ways, affecting the cycling of carbon (C) and nitrogen (N) on local, regional and global scales. North America tallgrass prairie is an ecosystem profoundly altered by anthropogenic activities, with most native prairie converted to alternate land uses or heavily impacted by other environmental changes. While aboveground responses to anthropogenic drivers have received much attention, the responses of belowground biota, ecological processes, and nutrient allocation to land management and environmental change are poorly documented, especially over long timeframes. This research builds upon a long-term experiment (the Belowground Plot Experiment) initiated in 1986 at Konza Prairie Biological Station (Manhattan, KS). I utilized a subset of treatments to address the effects of annual burning vs. fire suppression and/or chronic N additions on soil C and N dynamics and microbial communities in tallgrass prairie. I measured a suite of soil variables related to C and N cycling during the 2012 growing season, including total soil C and N, microbial biomass C and N, in situ net N mineralization, potential N mineralization, in situ CO2 efflux, and potentially mineralizable soil C. I also assessed changes in microbial community composition using microbial phospholipid fatty acids (PLFA) profiles. Annual burning significantly (p≤0.05) increased the soil C:N ratio and in situ CO2 efflux, while decreasing potential ammonification and nitrification rates. Annual burning also increased total PLFA mass and relative abundance of fungi. Chronic N addition (100 kg N ha-1 year-1) significantly reduced the soil C:N ratio, while increasing total soil N and potential nitrification and ammonification rates. Chronic N addition reduced potential C mineralization, microbial biomass C and N, and altered microbial community composition by increasing abundance of bacterial PLFAs and reducing fungal PLFAs. Sampling date also significantly affected many variables. These results indicate that different fire regimes and chronic N enrichment over decades affects soil C and N pools and transformations, as well as microbial biomass and composition. In total, this study highlights the importance of long-term ecological research and identifies likely changes in tallgrass prairie nutrient dynamics and soil microbial communities under increased N and frequent burning.

10aBiogeochemistry10aCarbon; Nitrogen10aSoil ecology10atallgrass prairie1 aCarson, M.1 aBlair, John, M. uhttp://hdl.handle.net/2097/1602903012nas a2200265 4500008004100000245011300041210006900154300000900223490000600232520219900238653001802437653002402455653001402479653002202493653002102515653002802536653001702564653001502581653001602596653002302612653001402635100001702649700002002666856006002686 2013 eng d00aSeed source has variable effects on species, communities, and ecosystem properties in grassland restorations0 aSeed source has variable effects on species communities and ecos a93 -0 v43 aResearch to date regarding the relative advantages of local versus non-local sources of plantmaterial for restoration has produced equivocal results. This research has typically focused on theperformance of individual species at individual locations and without addressing higher order communityand ecosystem properties. We investigated the effects of seed source (local, non-local, and mixed-sourcetreatments) on species, community, and ecosystem properties under a range of environmental conditionsusing reciprocal common gardens at locations in three states (Nebraska, Kansas, and Oklahoma). In orderto mimic the restoration of grassland vegetation under realistic conditions where multiple species interactwith one another during establishment, we seeded twelve species together between December, 2009 andJanuary, 2010, and assessed responses in 2010, 2011, and 2012. Both common garden location and seedsource affected the establishment of individual species (measured as species-specific biomass), butresponses were not consistent among species. No seed source had a consistent advantage across all sites oracross all species. In a few cases, the local source was most productive for a particular species at onelocation, but no species showed a consistent local advantage across locations or years. Rather, in two out ofthree species that exhibited a local advantage at one location, the same source was also the most productiveat a non-local site. Community structure and species richness differed among locations in all years, butsource did not significantly affect seeded species richness, and source only affected community structure in2011. Despite source effects on individual species and community structure, seed source had no significanteffects on the combined productivity of seeded species. These results do not support the targeted use oflocal sources when the establishment of sown species and primary productivity are restoration objectives.Using mixed-source species mixtures may increase chances of restoration success, given the idiosyncrasy ofindividual species’ responses among locations and potential site-specific environmental changes likely tooccur in the future.10acommon garden10acommunity structure10adispersal10agenetic diversity10alocal adaptation10amanaged relocationplant10aproductivity10aprovenance10arestoration10aseed transfer zone10atallgrass1 aCarter, D.L.1 aBlair, John, M. uhttp://www.esajournals.org/doi/pdf/10.1890/ES13-00090.102680nas a2200229 4500008004100000245009800041210006900139300001300208490000700221520195100228653002002179653002102199653002002220653002402240653002202264653002302286100002002309700002002329700001702349700001802366856006602384 2013 eng d00aWoody vegetation removal stimulates riparian and benthic denitrification in tallgrass prairie0 aWoody vegetation removal stimulates riparian and benthic denitri a547 -5600 v163 a

Expansion of woody vegetation into areas that were historically grass-dominated is a significant contemporary threat to grasslands, including native tallgrass prairie ecosystems of the Midwestern United States. In tallgrass prairie, much of this woody expansion is concentrated in riparian zones with potential impacts on biogeochemical processes there. Although the effects of woody riparian vegetation on denitrification in both riparian soils and streams have been well studied in naturally wooded ecosystems, less is known about the impacts of woody vegetation encroachment in ecosystems that were historically dominated by herbaceous vegetation. Here, we analyze the effect of afforestation and subsequent woody plant removal on riparian and benthic denitrification. Denitrification rates in riparian soil and selected benthic compartments were measured seasonally in naturally grass-dominated riparian zones, woody encroached riparian zones, and riparian zones with woody vegetation removed in two separate watersheds. Riparian soil denitrification was highly seasonal, with the greatest rates in early spring. Benthic denitrification also exhibited high temporal variability, but no seasonality. Soil denitrification rates were greatest in riparian zones where woody vegetation was removed. Additionally, concentrations of nitrate, carbon, and soil moisture (indicative of potential anoxia) were greatest in wood removal soils. Differences in the presence and abundance of benthic compartments reflected riparian vegetation, and may have indirectly affected denitrification in streams. Riparian soil denitrification increased with soil water content and NO3 −. Management of tallgrass prairies that includes removal of woody vegetation encroaching on riparian areas may alter biogeochemical cycling by increasing nitrogen removed via denitrification while the restored riparian zones return to a natural grass-dominated state.

10adenitrification10anitrogen removal10aprairie streams10ariparian vegetation10atallgrass prairie10awoody encroachment1 aReisinger, A.J.1 aBlair, John, M.1 aRice, C., W.1 aDodds, W., K. uhttps://link.springer.com/article/10.1007%2Fs10021-012-9630-302048nas a2200265 4500008004100000245007800041210006900119300001300188490000700201520130200208653001701510653001901527653001401546653000901560653001001569653000801579653001301587653001001600653001201610653002601622100001701648700002001665700002001685856007701705 2012 eng d00aDrought-mediated stem and belowground bud dynamics in restored grasslands0 aDroughtmediated stem and belowground bud dynamics in restored gr a470 -4780 v153 a

Question Does the below-ground bud bank mediate response to drought in restored grasslands? Location Platte River Valley region of south-central Nebraska, USA. Methods We imposed severe drought for one growing season using rainfall manipulation structures and measured the response of above- and below-ground plant communities (ramet and below-ground bud densities) with respect to non-drought controls during the drought year and a recovery year. Results Drought reduced below-ground bud bank density and above-ground stem density. However, bud bank density recovered, and bud production was higher on previously droughted subplots relative to controls in the year following drought. The response of below-ground bud and above-ground stem density to drought differed according to functional identity (C3 grass, C4 grass, and forb), with forbs least resistant to, but having the greatest recovery from, drought. Conclusions While overall density in restored grasslands was resilient, drought effects on below-ground bud banks may have longer-term impacts on plant community structure. Reduced density above- or below-ground during the growing season following drought may allow for the persistence of species relatively more reliant on recruitment from seed banks in favourable micro-sites.

10aBelow-ground10aClimate change10aCommunity10aforb10agrass10aLag10aMeristem10aplant10aprairie10aRainfall manipulation1 aCarter, D.L.1 aVanderweide, B.1 aBlair, John, M. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1654-109X.2012.01200.x01977nas a2200265 4500008004100000245015800041210006900199300001500268490000700283520111400290100002001404700002001424700001601444700001501460700001701475700001801492700001901510700001801529700001601547700001701563700001901580700001901599700001601618856007701634 2012 eng d00aThe effect of experimental warming and precipitation change on proteolytic enzyme activity: positive feedbacks to nitrogen availability are not universal0 aeffect of experimental warming and precipitation change on prote a2617 -26250 v183 a

Nitrogen regulates the Earth's climate system by constraining the terrestrial sink for atmospheric CO2. Proteolytic enzymes are a principal driver of the within-system cycle of soil nitrogen, yet there is little to no understanding of their response to climate change. Here, we use a single methodology to investigate potential proteolytic enzyme activity in soils from 16 global change experiments. We show that regardless of geographical location or experimental manipulation (i.e., temperature, precipitation, or both), all sites plotted along a single line relating the response ratio of potential proteolytic activity to soil moisture deficit, the difference between precipitation and evapotranspiration. In particular, warming and reductions in precipitation stimulated potential proteolytic activity in mesic sites – temperate and boreal forests, arctic tundra – whereas these manipulations suppressed potential activity in dry grasslands. This study provides a foundation for a simple representation of the impacts of climate change on a central component of the nitrogen cycle.

1 aBrozostek, E.R.1 aBlair, John, M.1 aDukes, J.S.1 aFrey, S.D.1 aHobbie, S.E.1 aMelillo, J.M.1 aMitchell, R.J.1 aPendall, E.S.1 aReich, P.B.1 aShaver, G.R.1 aStefanskii, A.1 aTjoelker, M.G.1 aFinzi, A.C. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2012.02685.x02622nas a2200133 4500008004100000245012400041210006900165300001500234490000700249520212100256100001702377700002002394856007402414 2012 eng d00aHigh richness and dense seeding enhance grassland restoration establishment, but have little effect on drought response0 aHigh richness and dense seeding enhance grassland restoration es a1308 -13190 v223 a

Restorations commonly utilize seed addition to formerly arable lands where the development of native plant communities is severely dispersal limited. However, variation in seed addition practices may profoundly affect restoration outcomes. Theory and observations predict that species-rich seed mixtures and seeding at high densities should enhance native plant community establishment, minimize exotic species cover, and may promote resistance and resilience to, and recovery from, environmental perturbations. We studied the post-seeding establishment of native plant communities in large grassland restoration plots, which were sown at two densities crossed with two levels of species richness on formerly arable land in Nebraska, USA, and their responses to drought. To evaluate drought resistance, recovery, and resilience of restored plant communities, we erected rainfall manipulation structures and tracked the response of seeded species cover and total plant biomass during experimental drought relative to controls and in the post-drought growing season. High seed richness and high-density seeding treatments resulted in greater richness and cover of native, seeded species per 0.5 m2 compared to low-richness and low-density treatments. Cover differences in response to seed mixture richness were driven by native forbs. Richness and cover of exotic species were lowest in high-richness and high-density treatments. We found little evidence of differential drought resistance, recovery, and resilience among seeding treatments. Increases in exotic species across years were restricted to drought subplots, and were not affected by seeding treatments. Grassland restoration was generally enhanced and exotic cover reduced both by the use of high-richness seed mixtures and high-density seeding. Given the lack of restoration treatment effects on the resistance, recovery, or resilience of seeded species exposed to drought, and the increases in exotic species following drought, other forms of active management may be needed to produce restored plant communities that are robust to climate change.

1 aCarter, D.L.1 aBlair, John, M. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/11-1970.102396nas a2200205 4500008004100000245013800041210006900179300001300248490000700261520172700268653001401995653001302009653001102022653001402033653001502047653001402062100001702076700002002093856007702113 2012 eng d00aRecovery of native plant community characteristics on a chronosequence of restored prairies seeded into pastures in West-Central Iowa0 aRecovery of native plant community characteristics on a chronose a170 -1790 v203 a

Restored grasslands comprise an ever-increasing proportion of grasslands in North America and elsewhere. However, floristic studies of restored grasslands indicate that our ability to restore plant communities is limited. Our goal was to assess the effectiveness of restoration seeding for recovery of key plant community components on former exotic, cool-season pastures using a chronosequence of six restoration sites and three nearby remnant tallgrass prairie sites in West-Central Iowa. We assessed trends in Simpson's diversity and evenness, richness and abundance of selected native and exotic plant guilds, and mean coefficient of conservatism (mean C). Simpson's diversity and evenness and perennial invasive species abundance all declined with restoration site age. As a group, restoration sites had greater richness of native C3 species with late phenology, but lower richness and abundance of species with early phenology relative to remnant sites. Total native richness, total native abundance (cover), mean C, and abundance of late phenology C3 plants were similar between restoration and remnant sites. Observed declines in diversity and evenness with restoration age reflect increases in C4 grass abundance rather than absolute decreases in the abundance of perennial C3 species. In contrast to other studies, restoration seeding appears to have led to successful establishment of tallgrass prairie species that were likely to be included in seeding mixtures. While several floristic measures indicate convergence of restoration and remnant sites, biodiversity may be further enhanced by including early phenology species in seeding mixes in proportion to their abundance on remnant prairies.

10agrassland10aInvasive10amean C10aphenology10asuccession10atallgrass1 aCarter, D.L.1 aBlair, John, M. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1526-100X.2010.00760.x02195nas a2200133 4500008004100000245011500041210006900156300001000225490000600235520170500241100001701946700002001963856007801983 2012 eng d00aSeed source affects establishment and survival for three grassland species sown into reciprocal common gardens0 aSeed source affects establishment and survival for three grassla a102 -0 v33 a

The source of plant material can affect the successful establishment and subsequent survival of plant species in restoration. Sometimes a local advantage is assumed or advocated, but research to date is equivocal on the relative success of local versus non-local plant sources in restoration. Global change, which is altering environmental conditions broadly and within local sites, raises additional questions regarding whether local sources will consistently perform best in the future. We investigated the effects of seed source (local vs. non-local) on the performance of three grassland species across variable environments using reciprocal common gardens in three states (Nebraska, Kansas, and Oklahoma). In order to mimic the restoration of grassland vegetation from seed under realistic conditions where species interact with one-another during establishment, we focused on three species (Elymus canadensis, Oligoneuron rigidum, and Sorghastrum nutans) that were seeded together into communities with nine additional grassland species, simultaneously and identically manipulating source for all species. Both common garden site and seed source affected initial (first year) establishment in terms of density and survival, but responses differed among seed sources and were not consistent among species. No seed source, including local, had a consistent advantage. Effects of seed source on initial density, in addition to survival, suggest that experiments utilizing transplants might miss important effects of seed source on establishment and that the relative performance of different sources within a single site or that of any one species across sites cannot be easily generalized.

1 aCarter, D.L.1 aBlair, John, M. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES12-00223.103337nas a2200349 4500008004100000245011600041210006900157300001300226490000600239520233700245653003902582653000902621653001002630653001502640653001202655100002002667700001702687700002002704700001302724700002002737700002202757700002402779700001702803700001802820700001602838700001402854700001702868700001702885700001602902700001302918856005602931 2012 eng d00aA test of two mechanisms proposed to optimize grassland aboveground primary productivity in response to grazing0 atest of two mechanisms proposed to optimize grassland abovegroun a357 -3650 v53 a

Aims Mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence, grassland species have numerous adaptations allowing them to respond favourably to grazing. Although empirical evidence has been equivocal, theory predicts that such adaptations combined with alterations in resources can lead to grazing-induced overcompensation in aboveground net primary production (ANPP; grazed ANPP > ungrazed ANPP) under certain conditions. We tested two specific predictions from theory. First, overcompensation is more likely to occur in annually burned grasslands because limiting nutrients that would be lost with frequent fires are recycled through grazers and stimulate ANPP. Second, overcompensation of biomass lost to grazers is more likely to occur in unburned sites where grazing has the greatest effect on increasing light availability through alterations in canopy structure. Methods We tested these nutrient versus light-based predictions in grazed grasslands that had been annually burned or protected from fire for >20 years. We assessed responses in ANPP to grazing by large ungulates using both permanent and moveable grazing exclosures (252 exclosures from which biomass was harvested from 3192 quadrats) in a 2-year study. Study sites were located at the Konza Prairie Biological Station (KPBS) in North America and at Kruger National Park (KNP) in South Africa. At KPBS, sites were grazed by North American bison whereas in KNP sites were grazed either by a diverse suite of herbivores (e.g. blue wildebeest, Burchell’s zebra, African buffalo) or by a single large ungulate (African buffalo). Important Findings We found no evidence for overcompensation in either burned or unburned sites, regardless of grazer type. Thus, there was no support for either mechanism leading to overcompensation. Instead, complete compensation of total biomass lost to grazers was the most common response characterizing grazing–ANPP relationships with, in some cases, undercompensation of grass ANPP being offset by increased ANPP of forbs likely due to competitive release. The capability of these very different grass-dominated systems to maintain ANPP while being grazed has important implications for energy flow, ecosystem function and the trophic dynamics of grasslands.

10aaboveground net primary production10afire10aforbs10aherbivores10asavanna1 aKnapp, Alan, K.1 aHoover, D.L.1 aBlair, John, M.1 aBuis, G.1 aBurkepile, D.E.1 aChamberlain, A.J.1 aCollins, Scott., L.1 aFynn, R.W.S.1 aKirkman, K.P.1 aSmith, M.D.1 aBlake, D.1 aGovender, N.1 aO’Neal, P.1 aSchreck, T.1 aZinn, A. uhttps://academic.oup.com/jpe/article/5/4/357/90869502710nas a2200205 4500008004100000245010000041210006900141260005000210490001400260520205900274653001902333653001502352653002002367653001402387653001002401653001602411100002102427700002002448856003602468 2011 eng d00aLong-term effects of climate change on grassland soil systems: A reciprocal transplant approach0 aLongterm effects of climate change on grassland soil systems A r aManhattan, KS. 80 ppbKansas State University0 vMS Thesis3 a

Climate change predictions for the Great Plains region of North America include increased temperatures, changes to annual precipitation, and reduced growing season precipitation, which will likely alter grassland soil systems. To date, few studies have examined belowground community responses to predicted climate change scenarios, with fewer assessing long-term changes. My research focused on the impacts of long-term changes in precipitation and associated soil water content on belowground grassland systems (belowground plant biomass, soil carbon (C) and nitrogen (N) pools, microbial biomass C and N, and invertebrate communities) using recently collected samples from a long-term (16-yr) reciprocal core transplant between Konza Prairie Biological Station (MAP = 850 mm) and Kansas State Agricultural Research Center at Hays (MAP = 580 mm), with the Hays site having a long-term average annual precipitation amount that is ~30% less than the Konza site. Results from the experiment indicate that either increases or decreases in annual precipitation can have profound effects on belowground grassland systems. Belowground plant biomass, microbial biomass, and potential C mineralization rates were greater at the wetter Konza site regardless of soil origin. Total C stored in soils incubated at Konza was significantly greater as well, likely due to greater root inputs. The effects of precipitation were most apparent in the surface soil layers (0-20 cm), while soil origin impacted soil properties to a greater extent with increasing depth. This contrasted with results for the soil mesofauna, where total microarthropods responded negatively and nematodes responded positively to increased annual precipitation. Results of this study indicate important changes in soil C and N pools, belowground plant biomass, and soil mesofauna within grassland systems subject to changing precipitation regimes, and suggest more mesic prairie systems are more sensitive to changes in soil water availability than those in more arid grassland systems.

10aClimate change10aGrasslands10aMicroarthropods10aNematodes10aRoots10aSoil carbon1 aRostkowski, S.C.1 aBlair, John, M. uhttp://hdl.handle.net/2097/706802610nas a2200205 4500008004100000245011800041210006900159300001500228490000800243520192600251653003302177653001002210653001402220653002602234653002202260100001902282700001702301700002002318856006602338 2011 eng d00aMycorrhizal suppression alters plant productivity and forb establishment in a grass-dominated prairie restoration0 aMycorrhizal suppression alters plant productivity and forb estab a1675 -16850 v2123 a

A fundamental goal of restoration is the re-establishment of plant diversity representative of native vegetation. However, many prairie restorations or Conservation Reserve Program sites have been seeded with warm-season grasses, leading to grass-dominated, low-diversity restorations not representative of native grasslands. These dominant grasses are strongly mycotrophic, while many subordinate forb species appear to be less dependent on mycorrhizal symbiosis. Therefore, manipulating arbuscular mycorrhizal fungi (AMF) may be useful in promoting establishment and growth of forb species in grass-dominated prairie restorations. To assess the potential role of mycorrhizae in affecting the productivity and community composition of restored tallgrass prairie, we conducted a 4-year field experiment on an 8-year-old grassland restoration at the Konza Prairie in northeastern Kansas, USA. At the initiation of our study, seeds of 12 forb species varying in degree of mycorrhizal dependence were added to established grass-dominated plots. Replicate plots were treated bi-weekly with a soil drench of fungicide (Topsin-M®) over four growing seasons and compared to non-treated control plots to assess the role of AMF in affecting plant species composition, productivity, leaf tissue quality, and diversity in restored tallgrass prairie. Topsin applications successfully reduced mycorrhizal colonization of grass roots to approximately 60–80% relative to roots in control plots. Four years of mycorrhizal suppression reduced productivity of the dominant grasses and increased plant species richness and diversity. These results highlight the importance of mycorrhizae as mediators of plant productivity and community dynamics in restored tallgrass prairie and indicate that temporarily suppressing AMF decreases productivity of the dominant C4 grasses and allows for establishment of seeded forb species

10aArbuscular mycorrhizal fungi10aforbs10aFungicide10aGrassland restoration10aWarm-season grass1 aMcCain, K.N.S.1 aWilson, G.T.1 aBlair, John, M. uhttps://link.springer.com/article/10.1007%2Fs11258-011-9940-002899nas a2200181 4500008004100000245010200041210006900143300001500212490000600227520232400233100001402557700002002571700001602591700002302607700001902630700002002649856004802669 2011 eng d00aRelative effects of precipitation variability and warming on tallgrass prairie ecosystem function0 aRelative effects of precipitation variability and warming on tal a3053 -30680 v83 a

Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenarios predict increasing precipitation variability and temperature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual) rainfall variability, and warming. We present results from an experiment applying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ~50–200% interannual variability in plant growth and aboveground net primary productivity (ANPP), leaf carbon assimilation (ACO2), and soil CO2 efflux (JCO2) despite only ~40% variation in mean volumetric soil water content (0–15 cm, Θ15). Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Differences between years in Θ15 explained the greatest portion (14–52%) of the variation in these processes. Experimentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture variation and reduced Θ15 by 15%, causing most ecosystem processes to decrease 8–40% in some or all years with increased rainfall variability compared to ambient rainfall timing, suggesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, particularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter JCO2, and reduced summer JCO2 and forb ANPP, suggesting that the effects of warming differed in cooler versus warmer parts of the year. We conclude that (1) major ecosystem processes in this grassland may be substantially altered by predicted changes in interannual climate variability, intra-annual rainfall variability, and temperature, (2) interannual climate variation was a larger source of variation in ecosystem function than intra-annual rainfall variability and warming, and (3) effects of increased growing season rainfall variability and warming were small, but ecologically important. The relative effects of these climate drivers are likely to vary for different ecosystem processes and in wetter or drier ecosystems.

1 aFay, P.A.1 aBlair, John, M.1 aSmith, M.D.1 aNippert, Jesse, B.1 aCarlisle, J.D.1 aKnapp, Alan, K. uhttps://www.biogeosciences.net/8/3053/2011/02758nas a2200253 4500008004100000245008300041210006900124300001300193490000700206520200300213653001302216653002402229653001302253653000902266653001202275653001602287100001502303700001902318700002402337700002002361700001802381700001802399856008702417 2010 eng d00aDevelopment of soil microbial communities during tallgrass prairie restoration0 aDevelopment of soil microbial communities during tallgrass prair a302 -3120 v423 a

Soil microbial communities were examined in a chronosequence of four different land-use treatments at the Konza Prairie Biological Station, Kansas. The time series comprised a conventionally tilled cropland (CTC) developed on former prairie soils, two restored grasslands that were initiated on former agricultural soils in 1998 (RG98) and 1978 (RG78), and an annually burned native tallgrass prairie (BNP), all on similar soil types. In addition, an unburned native tallgrass prairie (UNP) and another grassland restored in 2000 (RG00) on a different soil type were studied to examine the effect of long-term fire exclusion vs. annual burning in native prairie and the influence of soil type on soil microbial communities in restored grasslands. Both 16S rRNA gene clone libraries and phospholipid fatty acid analyses indicated that the structure and composition of bacterial communities in the CTC soil were significantly different from those in prairie soils. Within the time series, soil physicochemical characteristics changed monotonically. However, changes in the microbial communities were not monotonic, and a transitional bacterial community formed during restoration that differed from communities in either the highly disturbed cropland or the undisturbed original prairie. The microbial communities of RG98 and RG00 grasslands were also significantly different even though they were restored at approximately the same time and were managed similarly; a result attributable to the differences in soil type and associated soil chemistry such as pH and Ca. Burning and seasonal effects on soil microbial communities were small. Similarly, changing plot size from 300 m2 to 150 m2 in area caused small differences in the estimates of microbial community structure. In conclusion, microbial community structure and biochemical properties of soil from the tallgrass prairie were strongly impacted by cultivation, and the microbial community was not fully restored even after 30 years.

10a16S rRNA10aBacterial community10aCropland10aPLFA10aprairie10arestoration1 aJangid, K.1 aWilliams, M.A.1 aFranzluebbers, A.J.1 aBlair, John, M.1 aColeman, D.C.1 aWhitman, W.B. uhttps://www.sciencedirect.com/science/article/abs/pii/S0038071709004222?via%3Dihub02329nas a2200229 4500008004100000245007600041210006900117300001100186490000700197520162000204653002401824653001601848653001401864653003201878653002101910653002001931100001901951700001501970700002001985700001702005856007702022 2010 eng d00aDominant grasses suppress local diversity in restored tallgrass prairie0 aDominant grasses suppress local diversity in restored tallgrass  a40 -490 v183 a

Warm-season (C4) grasses commonly dominate tallgrass prairie restorations, often at the expense of subordinate grasses and forbs that contribute most to diversity in this ecosystem. To assess whether the cover and abundance of dominant grass species constrain plant diversity, we removed 0, 50, or 100% of tillers of two dominant species (Andropogon gerardii or Panicum virgatum) in a 7-year-old prairie restoration. Removing 100% of the most abundant species, A. gerardii, significantly increased light availability, forb productivity, forb cover, species richness, species evenness, and species diversity. Removal of a less abundant but very common species, P. virgatum, did not significantly affect resource availability or the local plant community. We observed no effect of removal treatments on critical belowground resources, including inorganic soil N or soil moisture. Species richness was inversely correlated with total grass productivity and percent grass cover and positively correlated with light availability at the soil surface. These relationships suggest that differential species richness among removal treatments resulted from treatment induced differences in aboveground resources rather than the belowground resources. Selective removal of the dominant species A. gerardii provided an opportunity for seeded forb species to become established leading to an increase in species richness and diversity. Therefore, management practices that target reductions in cover or biomass of the dominant species may enhance diversity in established and grass-dominated mesic grassland restorations.

10aAndropogon gerardii10aCompetition10adiversity10amesic grassland restoration10aPanicum virgatum10aspecies removal1 aMcCain, K.N.S.1 aBaer, S.G.1 aBlair, John, M.1 aWilson, G.T. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1526-100X.2010.00669.x02698nas a2200241 4500008004100000245009200041210006900133300001300202490000700215520193900222653002002161653003002181653003202211653002302243100001702266700002002283700001702303700001802320700001602338700002002354700001602374856006602390 2010 eng d00aFire and grazing impacts on silica production and storage in grass dominated ecosystems0 aFire and grazing impacts on silica production and storage in gra a263 -2780 v973 a

Grassland ecosystems are an important terrestrial component of the global biogeochemical silicon cycle. Although the structure and ecological functioning of grasslands are strongly influenced by fire and grazing, the role of these key ecological drivers in the production and storage of silicon represents a significant knowledge gap, particularly since they are being altered worldwide by human activities. We evaluated the effects of fire and grazing on the range and variability of plant derived biogenic silica stored in plant biomass and soils by sampling plants and soils from long-term experimental plots with known fire and grazing histories. Overall, plants and soils from grazed sites in the South African ecosystems had up to 76 and 54% greater biogenic silica totals (kg ha−1), respectively, than grazed North American sites. In North American soils, the combination of grazing and annual fire resulted in the greatest abundance of biogenic silica, whereas South African soils had the highest biogenic silica content where grazed regardless of burn frequency. These results as well as those that show greater Si concentrations in grazed South African plants indicate that South African plants and soils responded somewhat differently to fire and grazing with respect to silicon cycling, which may be linked to differences in the evolutionary history and in the grazer diversity and grazing intensity of these ecosystems. We conclude that although fire and grazing (as interactive and/or independent factors) do not affect the concentration of Si taken up by plants, they do promote increased silicon storage in aboveground biomass and soil as a result of directly affecting other site factors such as aboveground net primary productivity. Therefore, as management practices, fire and grazing have important implications for assessing global change impacts on the terrestrial biogeochemical cycling of silicon.

10aBiogenic silica10aNorth American grasslands10aSoil South African savannas10aTerrestrial plants1 aMelzer, S.E.1 aKnapp, Alan, K.1 aFynn, R.W.S.1 aKirkman, K.P.1 aSmith, M.D.1 aBlair, John, M.1 aKelly, E.F. uhttps://link.springer.com/article/10.1007%2Fs10533-009-9371-302174nas a2200229 4500008004100000245010200041210006900143300001300212490000700225520140200232653002501634653003101659653003701690653002001727100001901747700001801766700001801784700001901802700002001821700001601841856008701857 2010 eng d00aPhosphorus biogeochemistry across a precipitation gradient in grasslands of central North America0 aPhosphorus biogeochemistry across a precipitation gradient in gr a954 -9610 v743 a

Soil P transformations and distribution studies under water limited conditions that characterize many grasslands may provide further insight into the importance of abiotic and biotic P controls within grass-dominated ecosystems. We assessed transformations between P pools across four sites spanning the shortgrass steppe, mixed grass prairie, and tallgrass prairie along a 400-mm precipitation gradient across the central Great Plains. Pedon total elemental and constituent mass balance analyses reflected a pattern of increased chemical weathering from the more arid shortgrass steppe to the more mesic tallgrass prairie. Soil surface A horizon P accumulation was likely related to increased biocycling and biological mining. Soluble P, a small fraction of total P in surface A horizons, was greatest at the mixed grass sites. The distribution of secondary soil P fractions across the gradient suggested decreasing Ca-bound P and increasing amounts of occluded P with increasing precipitation. Surface A horizons contained evidence of Ca-bound P in the absence of CaCO3, while in subsurface horizons the Ca-bound P was associated with increasing CaCO3 content. Calcium-bound P, which dominates in water-limited systems, forms under different sets of soil chemical conditions in different climatic regimes, demonstrating the importance of carbonate regulation of P in semi-arid ecosystems.

10aGrassland ecosystems10aPhosphorus biogeochemistry10aSequential phosphorus extraction10aSoil weathering1 aIppolito, J.A.1 aBlecker, S.W.1 aFreeman, C.L.1 aMcCulley, R.L.1 aBlair, John, M.1 aKelly, E.F. uhttps://www.sciencedirect.com/science/article/abs/pii/S014019631000011X?via%3Dihub02495nas a2200205 4500008004100000245007400041210006900115300001500184490000800199520186400207653001902071653001902090653001502109653001502124653002202139100001802161700001602179700002002195856007402215 2010 eng d00aVertical distribution of fungal communities in tallgrass prairie soil0 aVertical distribution of fungal communities in tallgrass prairie a1027 -10410 v1023 a

We used 454 sequencing of the internal transcribed spacer region to characterize fungal communities in tallgrass prairie soils subdivided into strata 0–10, 10–20, 30–40 and 50–60 cm deep. The dataset included more than 14 000 fungal sequences distributed across Basidiomycota, Ascomycota, basal fungal lineages and Glomeromycota in order of decreasing frequency. As expected the community richness and diversity estimators tended to decrease with increasing depth. Although species richness was significantly reduced for samples from the deeper profiles, even the deepest stratum sampled contained richness of more than a third of that in the topmost stratum. More importantly, nonparametric multidimensional scaling (NMS) ordination analyses indicated that the fungal communities differed across vertical profiles, although only the topmost and deepest strata were significantly different when the NMS axis scores were compared by ANOVA. These results emphasize the importance of considering the fungal communities across the vertical strata because the deeper soil horizons might maintain a distinct community composition and thus contribute greatly to overall richness. The majority of operational taxonomic units (OTUs) declined in frequency with increasing depth, although a linear regression analysis indicated that some increased with increasing depth. The OTUs and BLAST-assigned taxa that showed increasing frequencies were mainly unculturable fungi, but some showed likely affinities to families Nectriaceae and Venturiaceae or to genus Pachnocybe. Although the ecological roles of the fungi in the deeper strata remain uncertain, we hypothesize that the fungi with preferences for deeper soil have adequate access to substrates and possess environmental tolerances that enable their persistence in those environments.

10a454 sequencing10apyrosequencing10asoil depth10aSoil fungi10atallgrass prairie1 aJumpponen, A.1 aJones, K.L.1 aBlair, John, M. uhttps://www.tandfonline.com/doi/abs/10.3852/09-316?journalCode=umyc2002499nas a2200217 4500008004100000245012100041210006900162300001300231490000800244520179700252653000902049653001402058653001102072653003602083653001702119653002202136100001802158700002002176700001902196856006602215 2009 eng d00aAnnual fire and mowing alter biomass, depth distribution, and C and N content of roots and soil in tallgrass prairie0 aAnnual fire and mowing alter biomass depth distribution and C an a235 -2470 v3233 a

Management practices, such as fire and mowing, can affect the distribution and quality of roots and soil C and N in grasslands. We examined long-term (13 years) effects of annual fire and mowing on fine (<2 mm) roots and soil C and N content in a native tallgrass prairie at Konza Prairie Biological Station in northeastern Kansas, USA. Using 90 cm deep soil cores, we determined that fire and mowing independently and interactively influenced the quantity and depth distribution of fine root biomass, root C and N concentration, and soil C and N content. Annual burning increased total fine root biomass by 48% and total C storage in roots by 47% compared to unburned unmowed plots, and resulted in a deeper distribution of roots. There was a significant interaction of fire and mowing, whereby mowing reduced root biomass and root C storage by ~30% in annually burned plots, but did not affect total root biomass in unburned plots. Mowing also resulted in shallower distribution of roots regardless of fire treatment. Root N concentration was reduced by 15–25% in plots that were burned, mowed, or both. Mowing effects on soil C and N were restricted to surface soils (0–10 cm), where mowing reduced soil C concentrations by ~20% and N concentrations by 17% regardless of burning treatment. In contrast, burning alone did not significantly influence soil C and N concentrations. In general, root biomass, root C and N mass, and soil C and N concentrations declined with depth, and most responses to burning and mowing exhibited significant interactions with depth. Different long-term fire and mowing regimes can significantly alter belowground root biomass and C and N dynamics in grasslands, and in particular at depths in the profile that are not typically sampled.

10afire10agrassland10aMowing10aRoot biomass depth distribution10aSoil C and N10atallgrass prairie1 aKitchen, D.J.1 aBlair, John, M.1 aCallaham, M.A. uhttps://link.springer.com/article/10.1007%2Fs11104-009-9931-202509nas a2200169 4500008004100000245009600041210006900137300001500206490000700221520193700228100002402165700002002189700001602209700001702225700002002242856007702262 2009 eng d00aContingent productivity responses to more extreme rainfall regimes across a grassland biome0 aContingent productivity responses to more extreme rainfall regim a2894 -29040 v153 a

Climate models predict, and empirical evidence confirms, that more extreme precipitation regimes are occurring in tandem with warmer atmospheric temperatures. These more extreme rainfall patterns are characterized by increased event size separated by longer within season drought periods and represent novel climatic conditions whose consequences for different ecosystem types are largely unknown. Here, we present results from an experiment in which more extreme rainfall patterns were imposed in three native grassland sites in the Central Plains Region of North America, USA. Along this 600 km precipitation–productivity gradient, there was strong sensitivity of temperate grasslands to more extreme growing season rainfall regimes, with responses of aboveground net primary productivity (ANPP) contingent on mean soil water levels for different grassland types. At the mesic end of the gradient (tallgrass prairie), longer dry intervals between events led to extended periods of below-average soil water content, increased plant water stress and reduced ANPP by 18%. The opposite response occurred at the dry end (semiarid steppe), where a shift to fewer, but larger, events increased periods of above-average soil water content, reduced seasonal plant water stress and resulted in a 30% increase in ANPP. At an intermediate mixed grass prairie site with high plant species richness, ANPP was most sensitive to more extreme rainfall regimes (70% increase). These results highlight the inherent complexity in predicting how terrestrial ecosystems will respond to forecast novel climate conditions as well as the difficulties in extending inferences from single site experiments across biomes. Even with no change in annual precipitation amount, ANPP responses in a relatively uniform physiographic region differed in both magnitude and direction in response to within season changes in rainfall event size/frequency.

1 aHeisler-White, J.L.1 aBlair, John, M.1 aKelly, E.F.1 aHarmoney, K.1 aKnapp, Alan, K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2009.01961.x02607nas a2200325 4500008004100000245011200041210006900153300001300222490000700235520168300242653000901925653000901934653001501943653001201958653001301970653001301983100001501996700002002011700002002031700001602051700002202067700001602089700002402105700001702129700001702146700001602163700001602179700002002195856006602215 2009 eng d00aControls of aboveground net primary production in mesic savanna grasslands: An inter-hemispheric comparison0 aControls of aboveground net primary production in mesic savanna  a982 -9950 v123 a

Patterns and controls of annual aboveground net primary productivity (ANPP) are fundamental metrics of ecosystem functioning. It is generally assumed, but rarely tested, that determinants of ANPP in one region within a biome will operate similarly throughout that biome, as long as physiognomy and climate are broadly consistent. We tested this assumption by quantifying ANPP responses to fire, grazing history, and nitrogen (N) addition in North American (NA) and South African (SA) savanna grasslands. We found that total ANPP responded in generally consistent ways to fire, grazing history, and N addition on both continents. Annual fire in both NA and SA consistently stimulated total ANPP (28–100%) relative to unburned treatments at sites with deep soils, and had no effect on ANPP in sites with shallow soils. Fire did not affect total ANPP in sites with a recent history of grazing, regardless of whether a single or a diverse suite of large herbivores was present. N addition interacted strongly and consistently with fire regime in both NA and SA. In annually burned sites that were not grazed, total ANPP was stimulated by N addition (29–39%), but there was no effect of N fertilization in the absence of fire. In contrast, responses in forb ANPP to fire and grazing were somewhat divergent across this biome. Annual fire in NA reduced forb ANPP, whereas grazing increased forb ANPP, but neither response was evident in SA. Thus, despite a consistent response in total ANPP, divergent responses in forb ANPP suggest that other aspects of community structure and ecosystem functioning differ in important ways between these mesic savanna grasslands.

10aANPP10afire10aGrasslands10aGrazing10anitrogen10aSavannas1 aBuis, G.M.1 aBlair, John, M.1 aBurkepile, D.E.1 aBurns, C.E.1 aChamberlain, A.J.1 aChapman, P.1 aCollins, Scott., L.1 aFynn, R.W.S.1 aGovender, N.1 aKirkman, K.1 aSmith, M.D.1 aKnapp, Alan, K. uhttps://link.springer.com/article/10.1007%2Fs10021-009-9273-102276nas a2200229 4500008004100000245011900041210006900160300001100229490000700240520154400247653001201791653001801803653001201821653001901833653002201852653002201874100001501896700002001911700001301931700001901944856008301963 2009 eng d00aImpacts of management legacies on litter decomposition in response to reduced precipitation in a tallgrass prairie0 aImpacts of management legacies on litter decomposition in respon a79 -850 v423 a

The response of ecosystem processes to current and future climatic events may be affected by historical disturbance regimes. Here, we address the interaction between reduced precipitation and the legacy effects of two contrasting long-term burn regimes in a tallgrass prairie (20 years of annual burning versus fire suppression). We examined rates of decomposition and the response of decomposition to reduced precipitation under rainout shelters in these two prairie types to assess potential interactions between legacy effects and reduced precipitation. To test the legacy effects of the different burn regimes, we placed experimental plots in each prairie type under a standardized management regime. In each plot, we ceased burning, mowed to maintain a standard canopy height, and maintained standard surface litter accumulation. We measured decay rates for surface litter, buried roots, and buried wooden dowels. While decomposition rates of substrates were reduced an average of approximately 29% under reduced precipitation, we found no significant main effects of burn history on decomposition on any of the substrates. However, in the recovery period following 2 years of an experimentally imposed drought, we did find an effect of burn history on decomposition and this effect varied for different substrates. Historical effects of management or natural disturbances on ecosystem processes may often be subtle or negated by compensatory responses, and in this study few legacy effects on decomposition rate were detected.

10aburning10adecomposition10aDrought10aLegacy effects10aManagement regime10atallgrass prairie1 aReed, H.E.1 aBlair, John, M.1 aWall, D.1 aSeastedt, T.R. uhttps://www.sciencedirect.com/science/article/pii/S0929139309000274?via%3Dihub00602nas a2200157 4500008004100000245009100041210006900132260002400201300001300225100001900238700001700257700001800274700002000292700002000312856011200332 2008 eng d00aBiogeochemical changes associated with Juniperus virginia encroachment into grasslands0 aBiogeochemical changes associated with Juniperus virginia encroa bSpringer-Verlag, NY a170 -1871 aMcKinley, D.C.1 aNorris, M.D.1 aJohnson, L.C.1 aBlair, John, M.1 aVan Auken, O.W. uhttp://knz.lternet.edu/content/biogeochemical-changes-associated-juniperus-virginia-encroachment-grasslands02839nas a2200265 4500008004100000245010400041210006900145300001500214490000700229520201100236653001802247653002402265653001402289653002102303653001402324653002202338653001902360653001802379653002102397653001202418100001902430700001702449700002002466856008702486 2008 eng d00aConversion of grassland to coniferous woodland has limited effects on soil nitrogen cycle processes0 aConversion of grassland to coniferous woodland has limited effec a2627 -26330 v403 a

In the last century, conversion of native North American grasslands to Juniperus virginiana forests or woodlands has dramatically altered ecosystem structure and significantly increased ecosystem carbon (C) stocks. We compared soils under recently established J. virginiana forests and adjacent native C4-dominated grassland to assess changes in potential soil nitrogen (N) transformations and plant available N. Over a 2-year period, concentrations of extractable inorganic N were measured in soils from forest and grassland sites. Potential gross N ammonification, nitrification, and consumption rates were determined using 15N isotope-dilution under laboratory conditions, controlling for soil temperature and moisture content. Potential nitrification rates (Vmax) and microbial biomass, as well as soil physical and chemical properties were also assessed. Extractable NH4+ concentrations were significantly greater in grassland soils across the study period (P ≤ 0.01), but analysis by date indicated that differences in extractable inorganic N occurred more frequently in fall and winter, when grasses were senescent but J. virginiana was still active. Laboratory-based rates of gross N mineralization (ammonification) and nitrification were greater in grassland soils (P ≤ 0.05), but only on one of four dates. Potential nitrification rates (Vmax) were an order of magnitude greater than gross nitrification rates in both ecosystems, suggesting that nitrification is highly constrained by NH4+ availability. Differences in plant uptake of N, C inputs, and soil microclimate as forests replace grasslands may influence plant available N in the field, as evidenced by seasonal differences in soil extractable NH4+, and total soil C and N accumulation. However, we found few differences in potential soil N transformations under laboratory conditions, suggesting that this grassland-to-forest conversion caused little change in mineralizable organic N pools or potential microbial activity.

10aExtractable N10aForest encroachment10agrassland10aIsotope dilution10aJuniperus10aMicrobial biomass10aMineralization10anitrification10aNitrogen cycling10aprairie1 aMcKinley, D.C.1 aRice, C., W.1 aBlair, John, M. uhttps://www.sciencedirect.com/science/article/abs/pii/S0038071708002320?via%3Dihub02031nas a2200229 4500008004100000245011400041210006900155260002400224300001300248520129100261100002001552700001901572700001901591700001501610700001801625700001501643700002001658700001901678700001601697700002001713856006801733 2008 eng d00aEcological consequences of the replacement of native grassland by Juniperus virginiana and other woody plants0 aEcological consequences of the replacement of native grassland b bSpringer-Verlag, NY a156 -1693 a

Although grasslands have been altered by humans for thousands of years (Wedel 1961; Bond et al. 2003), the loss of grassland as a result of anthropogenic activities has increased dramatically over the past 150 years. When Europeans first settled the Midwest and Great Plains, the greatest threat to native grasslands was the conversion of the most highly productive of these ecosystems to row-crop agriculture (Samson and Knopf 1994). Later, with improvements in soil moisture management and irrigation technology, even low-productivity grasslands were plowed. Today, those remnants of the most productive grasslands that escaped the plow are threatened, as are most of Earth’s ecosystems, by a variety of global change phenomena (Vitousek et al. 1997), with the invasion and expansion of woody species into grasslands one of the greatest of these threats. The replacement of grasslands by shrubland, woodland, and forest is a concern not only in the United States but worldwide (Archer et al. 1988; Van Auken 2000; Roques et al. 2001; Silva et al. 2001). Species of woody plants that invade grasslands may include both native plants which previously existed as more minor components of the ecosystem as well as alien species (Bragg and Hulbert 1976; Harcombe et al. 1993).

1 aKnapp, Alan, K.1 aMcCarron, J.K.1 aSilletti, A.M.1 aHoch, G.A.1 aHeisler, J.L.1 aLett, M.S.1 aBlair, John, M.1 aBriggs, J., M.1 aSmith, M.D.1 aVan Auken, O.W. uhttps://link.springer.com/chapter/10.1007%2F978-0-387-34003-6_802838nas a2200133 4500008004100000245010600041210006900147300001500216490000700231520235700238100001502595700002002610856007402630 2008 eng d00aGrassland establishment under varying resource availability: A test of positive and negative feedback0 aGrassland establishment under varying resource availability A te a1859 -18710 v893 a

The traditional logic of carbon (C) and nitrogen (N) interactions in ecosystems predicts further increases or decreases in productivity (positive feedback) in response to high and low fertility in the soil, respectively; but the potential for development of feedback in ecosystems recovering from disturbance is less well understood. Furthermore, this logic has been challenged in grassland ecosystems where frequent fires or grazing may reduce the contribution of aboveground litter inputs to soil organic matter pools and nutrient supply for plant growth, relative to forest ecosystems. Further, if increases in plant productivity increase soil C content more than soil N content, negative feedback may result from increased microbial demand for N making less available for plant growth. We used a field experiment to test for feedback in an establishing grassland by comparing aboveground net primary productivity (ANPP) and belowground pools and fluxes of C and N in soil with enriched, ambient, and reduced N availability. For eight years annual N enrichment increased ANPP, root N, and root tissue quality, but root C:N ratios remained well above the threshold for net mineralization of N. There was no evidence that N enrichment increased root biomass, soil C or N accrual rates, or storage of C in total, microbial, or mineralizable pools within this time frame. However, the net nitrogen mineralization potential (NMP) rate was greater following eight years of N enrichment, and we attributed this to N saturation of the microbial biomass. Grassland developing under experimentally imposed N limitation through C addition to the soil exhibited ANPP, root biomass and quality, and net NMP rate similar to the ambient soil. Similarity in productivity and roots in the reduced and ambient N treatments was attributed to the potentially high nitrogen-use efficiency (NUE) of the dominant C4 grasses, and increasing cover of legumes over time in the C-amended soil. Thus, in a developing ecosystem, positive feedback between soil N supply and plant productivity may promote enhanced long-term N availability and override progressive N limitation as C accrues in plant and soil pools. However, experimentally imposed reduction in N availability did not feed back to reduce ANPP, possibly due to shifts in NUE and functional group composition.

1 aBaer, S.G.1 aBlair, John, M. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/07-0417.101800nas a2200181 4500008004100000245008400041210006900125300001500194490000700209520120500216100002301421700001801444700002001462700001901482700001601501700001801517856008301535 2008 eng d00aIncreasing shallow groundwater CO2 and limestone weathering, Konza Prairie, USA0 aIncreasing shallow groundwater CO2 and limestone weathering Konz a5581 -55990 v723 a

In a mid-continental North American grassland, solute concentrations in shallow, limestone-hosted groundwater and adjacent surface water cycle annually and have increased steadily over the 15-year study period, 1991–2005, inclusive. Modeled groundwater CO2, verified by measurements of recent samples, increased from 10−2.05 atm to 10−1.94 atm, about a 20% increase, from 1991 to 2005. The measured groundwater alkalinity and alkaline-earth element concentrations also increased over that time period. We propose that carbonate minerals dissolve in response to lowered pH that occurs during an annual carbonate-mineral saturation cycle. The cycle starts with low saturation during late summer and autumn when dissolved CO2 is high. As dissolved CO2 decreases in the spring and early summer, carbonates become oversaturated, but oversaturation does not exceed the threshold for precipitation. We propose that groundwater is a CO2 sink through weathering of limestone: soil-generated CO2 is transformed to alkalinity through dissolution of calcite or dolomite. The annual cycle and long-term increase in shallow groundwater CO2 is similar to, but greater than, atmospheric CO2.

1 aMacpherson, G., L.1 aRoberts, J.A.1 aBlair, John, M.1 aTownsend, M.A.1 aFowle, D.A.1 aBeisner, K.R. uhttps://www.sciencedirect.com/science/article/pii/S001670370800536X?via%3Dihub02483nas a2200157 4500008004100000245014000041210006900181300001300250490000800263520190200271100001502173700002002188700001602208700002402224856007702248 2008 eng d00aInfluence of grazing and fire frequency on small-scale plant community structure and resource variability in native tallgrass prairie0 aInfluence of grazing and fire frequency on smallscale plant comm a859 -8660 v1173 a

In grasslands worldwide, grazing by ungulates and periodic fires are important forces affecting resource availability and plant community structure. It is not clear, however, whether changes in community structure are the direct effects of the disturbance (i.e. fire and grazing) or are mediated indirectly through changes in resource abundance and availability. In North American tallgrass prairies, fire and grazing often have disparate effects on plant resources and plant diversity, yet, little is known about the individual and interactive effects of fire and grazing on resource variability and how that variability relates to heterogeneity in plant community structure, particularly at small scales. We conducted a field study to determine the interactive effects of different long-term fire regimes (annual vs four-year fire frequency) and grazing by native ungulates (Bos bison) on small-scale plant community structure and resource variability (N and light) in native tallgrass prairie. Grazing enhanced light and nitrogen availability, but did not affect small-scale resource variability. In addition, grazing reduced the dominance of C4 grasses which enhanced species richness, diversity and community heterogeneity. In contrast, annual fire increased community dominance and reduced species richness and diversity, particularly in the absence of grazing, but had no effect on community heterogeneity, resource availability and resource variability. Variability in the abundance of resources showed no relationship with community heterogeneity at the scale measured in this study, however we found a relationship between community dominance and heterogeneity. Therefore, we conclude that grazing generated small-scale community heterogeneity in this mesic grassland by directly affecting plant community dominance, rather than indirectly through changes in resource variability.

1 aVeen, G.F.1 aBlair, John, M.1 aSmith, M.D.1 aCollins, Scott., L. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.0030-1299.2008.16515.x01819nas a2200181 4500008004100000245009300041210006900134300001300203490000600216520124100222100001901463700002001482700001901502700001301521700001401534700001701548856007201565 2008 eng d00aPredicting and understanding ecosystem responses to climate change at continental scales0 aPredicting and understanding ecosystem responses to climate chan a273 -2800 v63 a

Climate is changing across a range of scales, from local to global, but ecological consequences remain difficult to understand and predict. Such projections are complicated by change in the connectivity of resources, particularly water, nutrients, and propagules, that influences the way ecological responses scale from local to regional and from regional to continental. This paper describes ecological responses to expected changes in four key meso-scale drivers that influence the ecosystems of the North American continental interior: drought, warming, snowpack disappearance, and altered fire regimes. Changes in these drivers will affect, for example, atmospheric smoke, dust, and reactive nitrogen concentrations; stream discharge; nitrate concentrations; sediment loads; and the vector-borne spread of invasive species and infectious diseases. A continental network of sensors and simulation models is required to detect changes in the transport vectors – atmospheric, hydrologic, and mechanized –that connect spatial scales. Knowledge of these downwind, downstream, and down-corridor effects will be critical if we are to understand and forecast responses to climate change at regional to continental scales.

1 aMarshall, J.D.1 aBlair, John, M.1 aPeters, D.P.C.1 aOkin, G.1 aRango, A.1 aWilliams, M. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/07016502695nas a2200241 4500008004100000245012400041210006900165300001300234490000700247520189300254653001902147653002502166653001302191653002502204653002202229653001902251653002102270653002802291653002902319100001902348700002002367856006602387 2008 eng d00aWoody plant encroachment by Juniperus virginiana in a mesic native grassland promotes rapid carbon and nitrogen accrual0 aWoody plant encroachment by Juniperus virginiana in a mesic nati a454 -4680 v113 a

The cover and abundance of Juniperus virginiana L. in the U.S. Central Plains are rapidly increasing, largely as a result of changing land-use practices that alter fire regimes in native grassland communities. Little is known about how conversion of native grasslands to Juniperus-dominated forests alters soil nutrient availability and ecosystem storage of carbon (C) and nitrogen (N), although such land-cover changes have important implications for local ecosystem dynamics, as well as regional C and N budgets. Four replicate native grasslands and adjacent areas of recent J. virginiana encroachment were selected to assess potential changes in soil N availability, leaf-level photosynthesis, and major ecosystem C and N pools. Net N mineralization rates were assessed in situ over two years, and changes in labile soil organic pools (potential C and N mineralization rates and microbial biomass C and N) were determined. Photosynthetic nitrogen use efficiencies (PNUE) were used to examine differences in instantaneous leaf-level N use in C uptake. Comparisons of ecosystem C and N stocks revealed significant C and N accrual in both plant biomass and soils in these newly established forests, without changes in labile soil N pools. There were few differences in monthly in situ net N mineralization rates, although cumulative annual net N mineralization was greater in forest soils compared to grasslands. Conversely, potential C mineralization was significantly reduced in forest soils. Encroachment by J. virginiana into grasslands results in rapid accretion of ecosystem C and N in plant and soil pools with little apparent change in N availability. Widespread increases in the cover of woody plants, like J. virginiana, in areas formerly dominated by graminoid species suggest an increasing role of expanding woodlands and forests as regional C sinks in the central U.S.

10acarbon storage10agrassland conversion10ainvasion10aJuniperus virginiana10aland cover change10aMineralization10aNitrogen cycling10aNitrogen use efficiency10awoody plant encroachment1 aMcKinley, D.C.1 aBlair, John, M. uhttps://link.springer.com/article/10.1007%2Fs10021-008-9133-403122nas a2200145 4500008004100000245009900041210006900140300001300209490000800222520257200230100001702802700002002819700001802839856011902857 2007 eng d00aAltered ecosystem nitrogen dynamics as a consequence of land cover change in tallgrass prairie0 aAltered ecosystem nitrogen dynamics as a consequence of land cov a432 -4450 v1583 aIn recent decades, substantial areas of North American tallgrass prairie have been lost to the establishment and expansion of woodlands and forests, including those dominated by eastern redcedar (Juniperus virginiana). This shift in dominant plant life form, from C4 grasses to coniferous trees, may be accompanied by changes in productivity, standing stocks of biomass and nutrients and biogeochemical cycles. The goal of this study was to quantify and compare major pools and fluxes of nitrogen in recently established (≤ 80 y) redcedar forests and adjacent native grasslands. Three former grassland sites in the Flint Hills region of Kansas that developed closed-canopy redcedar forests in the recent past were paired with adjacent grassland sites on similar soil type and topographic position (n  =  3 sites/land cover type), and selected soil and plant nitrogen pools and fluxes were measured in replicate plots (n  =  6/site) along transects in each forest or grassland site over a 20-mo period. We found few significant differences in median soil inorganic N pools or net N mineralization rates between the forest and grassland sites, though there was a trend for greater concentrations of inorganic N in grassland sites on most sample dates, and cumulative growing season net N mineralization averaged 15% less in forest sites (14.3 kg N·ha−1·yr−1) than in grassland sites (16.9 kg N·ha−1·yr−1). Mean aboveground plant productivity of forest sites (9162 kg ha−1 yr−1) was about 2.5× greater than that of comparable grasslands (similar soils and topographic position), in spite of similar levels of soil N availability. This resulted in an ecosystem-level nitrogen use efficiency (ANPP∶litterfall N) in forests that was more than double that of the grasslands they replaced. Additional changes in N cycling associated with redcedar forest development included large accumulations of N in aboveground biomass and transfer to the forest floor via litterfall; redcedar aboveground biomass contained 617 kg N/ha, forest floor litter N was 253 kg N/ha, and litterfall N flux was 41 kg ha−1·yr−1. These are substantial increases in aboveground biomass N accumulation, surface litter N inputs, and surface litter N accumulation compared to the native grasslands characteristic of this region. These fundamental shifts in ecosystem patterns and processes have the potential to alter regional biogeochemistry and both nitrogen and carbon storage throughout areas of the eastern Central Plains where coverage of redcedars is increasing.1 aNorris, M.D.1 aBlair, John, M.1 aJohnson, L.C. uhttp://knz.lternet.edu/content/altered-ecosystem-nitrogen-dynamics-consequence-land-cover-change-tallgrass-prairie02631nas a2200181 4500008004100000245014300041210006900184300001500253490000700268520194700275100001602222700001502238700002002253700001702273700002002290700001702310856012202327 2006 eng d00aMolecular approach for assessing responses of microbial-feeding nematodes to burning and chronic nitrogen enrichment in a native grassland0 aMolecular approach for assessing responses of microbialfeeding n a2601 -26090 v153 aA substantial proportion of the primary productivity in grassland ecosystems is allocated belowground, sustaining an abundant and diverse community of microbes and soil invertebrates. These belowground communities drive many important ecosystem functions and are responsive to a variety of environmental changes. Nematodes, an abundant and diverse component of grassland soil communities, are particularly responsive to altered environmental conditions, such as those associated with reduced fire frequency and nitrogen enrichment, with the most consistent responses displayed by microbial-feeding nematodes. However, much of the available research characterizing nematode responses to environmental change has been carried out at the taxonomic level of family or by broad trophic categories (e.g. fungivores, bacterivores). The extent to which differential responses to environmental change occurs at the genus level or below is unclear. Therefore, the objective of this study was to use molecular methods to quantify the response of microbial-feeding nematodes, at the lowest levels of taxonomic resolution, to nitrogen enrichment and changes in fire frequency. Using sequencing and quantitative polymerase chain reaction (PCR) probes for the 18S ribosomal RNA gene and the ITS1 region, we identified 19 microbial-feeding nematode taxa across four families. When nematodes were sampled across treatments, we found that some nematode taxa within a family responded similarly to nitrogen and burning treatments, while other taxa within the same family respond quite differently. Additionally, although nematodes from different families on average responded differently to nitrogen enrichment and burning, similar responses were seen in nematode taxa that span three taxonomic families. Thus, if nematodes are to be used as indicators of environmental change, care should be taken to assess the response at the lowest taxonomic level possible.1 aJones, K.L.1 aTodd, T.C.1 aWall-Beam, J.L.1 aCoolon, J.D.1 aBlair, John, M.1 aHerman, M.A. uhttp://knz.lternet.edu/content/molecular-approach-assessing-responses-microbial-feeding-nematodes-burning-and-chronic00453nas a2200109 4500008004100000245011400041210006900155490000600224100002300230700002000253856007000273 2005 eng d00aComparing the influence of precipitation, fire, and topography on plant productivity in the tallgrass prairie0 aComparing the influence of precipitation fire and topography on 0 v31 aNippert, Jesse, B.1 aBlair, John, M. uhttp://tiee.ecoed.net/vol/v3/issues/data_sets/konza/abstract.html02766nas a2200145 4500008004100000245009300041210006900134300001500203490000700218520223400225100001302459700001902472700002002491856010902511 2005 eng d00aEcological consequences of C4 grass invasion of a C4 grassland: A dilemma for management0 aEcological consequences of C4 grass invasion of a C4 grassland A a1560 -15690 v153 aMany successful exotic invasive species are functionally distinct from the dominant native species they displace. Occasionally invasion occurs where the exotic species possesses functional traits relatively similar to those of the dominant native. We examined the ecological consequences of such an invasion within a mesic, temperate grassland at the Konza Prairie Long-Term Ecological Research site. We assessed potential changes in carbon (C) and nitrogen (N) cycling and plant diversity following the invasion of a C4 bunch grass species, Andropogon bladhii, into a tallgrass prairie dominated by the native C4 grass species, A. gerardii. In these prairies burning is an important management tool used to maintain native-species dominance. We determined how frequent spring fires affected the impacts of A. bladhii in this system. Over a two-year study our results show that burning regulated the effects that the invasive species has on the native prairie. Compared to the native species, A. bladhii exhibited significantly greater plant biomass, significantly lower pools of soil N, significantly lower rates of decay and C cycling, and higher foliar and root tissue C:N ratio in response to burning. Notable spatial heterogeneity in C and N cycling was evident in areas dominated by the invasive bunch grass. In addition to altered ecosystem processes, areas dominated by the invasive, A. bladhii, had significantly lower plant species diversity. In a grassland ecosystem where burning is an important management tool for controlling exotic-species establishment, maintaining native-species dominance, and increasing productivity, A. bladhii may be able to successfully out-compete the native C4 grass species by using traits typically used to explain the dominance of the native species. With frequent fire, the invasive species has the potential to decrease long-term fertility by lowering N inputs in litter and increasing erosion in non-vegetated soil between bunches, while also having a negative effect on plant diversity. By using fire to promote native C4 grasses and maintain these tallgrass prairies, the threat of invasion by nonnative C4 species may raise a dilemma for future management of these C4 grasslands.1 aReed, H.1 aSeastedt, T.R.1 aBlair, John, M. uhttp://knz.lternet.edu/content/ecological-consequences-c4-grass-invasion-c4-grassland-dilemma-management01955nas a2200253 4500008004100000245010600041210006900147300001300216490000700229520114300236653000901379653001501388653001201403653002201415653002101437100001901458700002001477700002001497700001801517700001501535700001501550700001901565856011701584 2005 eng d00aAn ecosystem in transition: causes and consequences of the conversion of mesic grassland to shrubland0 aecosystem in transition causes and consequences of the conversio a243 -2540 v553 aWoody plant expansion is one of the greatest contemporary threats to mesic grasslands of the central United States. In this article, we synthesize more than 20 years of research to elucidate the causes and consequences of the ongoing transition of C4-dominated grasslands to savanna-like ecosystems codominated by grasses and woody plants. This transition is contingent on fire-free intervals, which provide the opportunity for recruitment both of new individuals and of additional shrub and tree species into this grassland. Once shrubs establish, their cover increases regardless of fire frequency, and infrequent fires accelerate the spread of some shrub species. This process has resulted in a new dynamic state of shrub–grass coexistence in the mesic grasslands of North America. Important consequences of this shift in plant life-form abundance include alterations in plant productivity, species diversity, and carbon storage. Without drastic measures such as mechanical removal of shrubs, it is unlikely that management of fire and grazing regimes alone will be sufficient to restore historic grass dominance in these ecosystems.10afire10aGrasslands10aGrazing10atallgrass prairie10awoody vegetation1 aBriggs, J., M.1 aKnapp, Alan, K.1 aBlair, John, M.1 aHeisler, J.L.1 aHoch, G.A.1 aLett, M.S.1 aMcCarron, J.K. uhttp://knz.lternet.edu/content/ecosystem-transition-causes-and-consequences-conversion-mesic-grassland-shrubland03504nas a2200169 4500008004100000245011200041210006900153300001300222490000700235520287400242100001703116700002003133700001403153700002003167700001903187856012803206 2005 eng d00aIncreased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystem0 aIncreased rainfall variability and reduced rainfall amount decre a322 -3440 v113 aPredicted climate changes in the US Central Plains include altered precipitation regimes with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control C cycling and storage. Soil carbon dioxide (CO2) flux is an important component of C cycling in terrestrial ecosystems, and is strongly influenced by climate. While many studies have assessed the influence of soil water content on soil CO2 flux, few have included experimental manipulation of rainfall amounts in intact ecosystems, and we know of no studies that have explicitly addressed the influence of the timing of rainfall events. In order to determine the responses of soil CO2 flux to altered rainfall timing and amounts, we manipulated rainfall inputs to plots of native tallgrass prairie (Konza Prairie, Kansas, USA) over four growing seasons (1998–2001). Specifically, we altered the amounts and/or timing of growing season rainfall in a factorial combination that included two levels of rainfall amount (100% or 70% of naturally occurring rainfall quantity) and two temporal patterns of rain events (ambient timing or a 50% increase in length of dry intervals between events). The size of individual rain events in the altered timing treatment was adjusted so that the quantity of total growing season rainfall in the ambient and altered timing treatments was the same (i.e. fewer, but larger rainfall events characterized the altered timing treatment). Seasonal mean soil CO2 flux decreased by 8% under reduced rainfall amounts, by 13% under altered rainfall timing, and by 20% when both were combined (P<0.01). These changes in soil CO2 flux were consistent with observed changes in plant productivity, which was also reduced by both reduced rainfall quantity and altered rainfall timing. Soil CO2 flux was related to both soil temperature and soil water content in regression analyses; together they explained as much as 64% of the variability in CO2 flux across dates under ambient rainfall timing, but only 38–48% of the variability under altered rainfall timing, suggesting that other factors (e.g. substrate availability, plant or microbial stress) may limit CO2 flux under a climate regime that includes fewer, larger rainfall events. An analysis of the temperature sensitivity of soil CO2 flux indicated that temperature had a reduced effect (lower correlation and lower Q10 values) under the reduced quantity and altered timing treatments. Recognition that changes in the timing of rainfall events may be as, or more, important than changes in rainfall amount in affecting soil CO2 flux and other components of the carbon cycle highlights the complex nature of ecosystem responses to climate change in North American grasslands.1 aHarper, C.W.1 aBlair, John, M.1 aFay, P.A.1 aKnapp, Alan, K.1 aCarlisle, J.D. uhttp://knz.lternet.edu/content/increased-rainfall-variability-and-reduced-rainfall-amount-decreases-soil-co2-flux-grassland02664nas a2200241 4500008004100000245013500041210006900176300001300245490000700258520183200265653001402097653002102111653001602132653002302148653001602171653002202187100001502209700002402224700002002248700001602268700002002284856011802304 2005 eng d00aSoil heterogeneity effects on tallgrass prairie community heterogeneity: anapplication of ecological theory to restoration ecology0 aSoil heterogeneity effects on tallgrass prairie community hetero a413 -4240 v133 aSpatial heterogeneity of resources can influence plant community composition and diversity in natural communities. We manipulated soil depth (two levels) and nutrient availability (three levels) to create four heterogeneity treatments (no heterogeneity, depth heterogeneity, nutrient heterogeneity, and depth + nutrient heterogeneity) replicated in an agricultural field seeded to native prairie species. Our objective was to determine whether resource heterogeneity influences species diversity and the trajectory of community development during grassland restoration. The treatments significantly increased heterogeneity of available inorganic nitrogen (N), soil water content, and light penetration. Plant diversity was indirectly related to resource heterogeneity through positive relationships with variability in productivity and cover established by the belowground manipulations. Diversity was inversely correlated with the average cover of the dominant grass, Switchgrass (Panicum virgatum), which increased over time in all heterogeneity treatments and resulted in community convergence among the heterogeneity treatments over time. The success of this cultivar across the wide range of resource availability was attributed to net photosynthesis rates equivalent to or higher than those of the native prairie plants in the presence of lower foliar N content. Our results suggest that resource heterogeneity alone may not increase diversity in restorations where a dominant species can successfully establish across the range of resource availability. This is consistent with theory regarding the role of ecological filters on community assembly in that the establishment of one species best adapted for the physical and biological conditions can play an inordinately important role in determining community structure.10agrassland10aPanicum virgatum10arestoration10asoil heterogeneity10aswitchgrass10atallgrass prairie1 aBaer, S.G.1 aCollins, Scott., L.1 aBlair, John, M.1 aFiedler, A.1 aKnapp, Alan, K. uhttp://knz.lternet.edu/content/soil-heterogeneity-effects-tallgrass-prairie-community-heterogeneity-anapplication02291nas a2200145 4500008004100000245011500041210006900156300001300225490000700238520171500245100001901960700002001979700002001999856012602019 2004 eng d00aCompetition and coexistence in grassland co-dominants: responses to neighbor removal and resource availability0 aCompetition and coexistence in grassland codominants responses t a450 -4600 v823 aWe examined the role of interspecific competition in the regulation of abundance and coexistence of the dominant grasses in tallgrass prairie using a removal experiment with Andropogon gerardii Vitman and Sorghastrum nutans L. Nash, two of the most abundant grasses in tallgrass prairie. Plant removal treatments (using foliar herbicide), applied to 0.3-m2 plots at the Konza Prairie Biological Station (northeast Kansas, USA), included removal of all A. gerardii, removal of all S. nutans, and no removal. To determine whether soil fertility altered the outcome, we included a fertilizer addition treatment (10 g N·m–2) fully crossed with the removal treatments. Andropogon gerardii removal resulted in significantly increased net photosynthesis, stomatal conductance, and tiller mass in S. nutans. Sorghastrum nutans removal had little effect on A. gerardii, suggesting asymmetric competition. Fertilizer significantly increased tiller mass and flowering stalk production in S. nutans, but had little effect on A. gerardii. The ability of A. gerardii to suppress the performance of S. nutans is consistent with the greater abundance of A. gerardii over much of the tallgrass prairie, while the ability of S. nutans to take advantage of increased resources may be one mechanism by which it avoids competitive exclusion. Because of the greater variability in the performance of S. nutans than in that of A. gerardii, any natural or anthropogenic alterations to this grassland that lead to shifts in dominance between these species may affect ecosystem productivity and stability.Key words: Andropogon gerardii, competition, grassland, neighbour removal, photosynthesis, Sorghastrum nutans, tallgrass prairie.1 aSilletti, A.M.1 aKnapp, Alan, K.1 aBlair, John, M. uhttp://knz.lternet.edu/content/competition-and-coexistence-grassland-co-dominants-responses-neighbor-removal-and-resource02939nas a2200169 4500008004100000245010700041210006900148300001500217490000700232520231200239100001802551700001902569700002002588700002002608700001402628856012702642 2004 eng d00aDirect and indirect effects of fire on shrub density and aboveground productivity in a mesic grassland0 aDirect and indirect effects of fire on shrub density and abovegr a2245 -22570 v853 aDeterminants of the balance between grass and woody vegetation in grasslands and savannas have received considerable attention because of the potential for dramatic shifts in ecosystem structure and function as one growth form replaces the other. We studied a mesic grassland where recently established “shrub islands” are increasing in abundance due to fire suppression. Our objective was to assess the role of the direct effects of fire vs. indirect alterations in resource availability (N and light), as mechanisms that may constrain/facilitate shrub (Cornus drummondii) encroachment. The direct effects of fire in 2001 and 2002 were 100% aboveground mortality of C. drummondii shoots and removal of the detrital layer. Post-fire resprouting resulted in ∼600% increase in stem density compared to a 200% increase in shrub islands protected from fire. In burned shrub islands with an added detrital layer, temperature and light penetration to the soil surface were reduced (by 6.5°C and to <3% of full sunlight), but stem density still increased by ∼400%. Thus, both the direct effects of fire and the indirect effect on the energy environment increased C. drummondii stem densities. In contrast, N additions did not influence new stem production or aboveground net primary productivity (ANPP; grams per square meter per year), suggesting that N availability did not constrain shrub growth during this study. While fire did not impact total ANPP, it did shift the relative abundance of growth forms. Grass productivity (360.7 ± 20.1 g/m2 [mean ± 1 se]) was stimulated (an increase of ∼30%) by the high light conditions of the post-fire environment, while C. drummondii ANPP (34.2 ± 2.4 g/m2) was reduced by ∼30%. In shrub islands protected from fire, C. drummondii ANPP was greatest (50.4 ± 2.2 g/m2), whereas lower graminoid ANPP (282.5 ± 19.9 g/m2) was observed. The persistence of woody vegetation, despite two successive fires, along with a significant reduction in grass ANPP (∼30%) suggests that once established, C. drummondii can persist and exclude C4 grasses. Thus, restoring fire to mesic grasslands may prevent further conversion to shrub/woodland, but the abundance of shrubs is likely to remain unchanged with community structure co-dominated by multiple growth forms.1 aHeisler, J.L.1 aBriggs, J., M.1 aKnapp, Alan, K.1 aBlair, John, M.1 aSeery, A. uhttp://knz.lternet.edu/content/direct-and-indirect-effects-fire-shrub-density-and-aboveground-productivity-mesic-grassland02236nas a2200157 4500008004100000245012800041210006900169300001500238490000700253520161900260100001501879700002001894700001901914700002001933856012501953 2004 eng d00aInfluence of shrub encroachment on aboveground net primary productivity and carbon and nitrogen pools in a mesic grassland0 aInfluence of shrub encroachment on aboveground net primary produ a1363 -13700 v823 aThe clonal shrub Cornus drummondii C.A. Mey. is rapidly increasing in cover and displacing mesic grassland species in the central USA as a consequence of fire suppression. We assessed the impact of C. drummondii on carbon (C) and nitrogen (N) pools and C fluxes in a tallgrass prairie in eastern Kansas, USA, through a comparison of both burned and unburned C. drummondii islands with open grassland areas. Allometric equations relating C. drum mondii foliage and wood biomass to basal stem diameter were developed to estimate aboveground biomass and net primary productivity (ANPP) of C. drummondii. Within C. drummondii islands, ANPP was 496 ± 45 g C·m–2·year–1, nearly three times that within open grassland (167 ± 13 g C·m–2·year–1). As a result of greater aboveground biomass, aboveground C and N storage within shrub islands (3270 ± 466 g C·m–2, 37.9 ± 5.3 g N·m–2) was substantially greater than that within open grassland (241 ± 33 g C·m–2, 6.1 ± 0.8 g N·m–2). No change in soil organic C or total N to 10-cm depth was evident; however, soil CO2 flux was significantly reduced in C. drummondii islands relative to the open grassland. The storage of C in aboveground biomass of C. drummondii represents a significant short-term increase in C storage relative to open grassland. However, potential alterations in belowground processes must be quantified before the long-term net effect of shrub encroachment on C and N pools within this mesic grassland can be determined.Key words: aboveground biomass, Cornus drummondii, net primary productivity, shrub encroachment, tallgrass prairie.1 aLett, M.S.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aBlair, John, M. uhttp://knz.lternet.edu/content/influence-shrub-encroachment-aboveground-net-primary-productivity-and-carbon-and-nitrogen03493nas a2200205 4500008004100000245009200041210006900133300001300202490000800215520280200223653001403025653001403039653001303053653002203066100001503088700002003103700002403123700002003147856012003167 2004 eng d00aPlant community responses to resource availability and heterogeneity during restoration0 aPlant community responses to resource availability and heterogen a617 -6290 v1393 aAvailability and heterogeneity of resources have a strong influence on plant community structure in undisturbed systems, as well as those recovering from disturbance. Less is known about the role of resource availability and heterogeneity in restored communities, although restoration provides a valuable opportunity to test our understanding of factors that influence plant community assembly. We altered soil nitrogen (N) availability and soil depth during a prairie restoration to determine if the availability and/or heterogeneity of soil resources influenced plant community composition in restored grassland communities. Plant community responses to three levels of N availability (ambient, enriched by fertilization, and reduced by carbon amendment) and two levels of soil depth (deep and shallow) were evaluated. In addition, we evaluated plant community responses to four whole plot heterogeneity treatments created from the six possible combinations of soil N availability and soil depth. The soil depth treatment had little influence on community structure during the first 3 years of restoration. Total diversity and richness declined over time under annual N enrichment, whereas diversity was maintained and richness increased over time in soil with reduced N availability. Non-native species establishment was lowest in reduced-N soil in the initial year, but their presence was negligible in all of the soil N treatments by the second year of restoration. Panicum virgatum, a native perennial C4 grass, was the dominant species in all soil N treatments by year three, but the magnitude of its dominance was lowest in the reduced-N soil and highest in enriched-N soil. Consequently, the relative cover of P. virgatum was strongly correlated with community dominance and inversely related to diversity. The differential growth response of P. virgatum to soil N availability led to a higher degree of community similarity to native prairie in the reduced-N treatment than in the enriched-N treatment. There were no differences in plant community structure among the four whole plot-level heterogeneity treatments, which all exhibited the same degree of similarity to native prairie. Diversity and community heterogeneity in the whole-plot treatments appeared to be regulated by the dominant species’ effect on light availability, rather than soil N heterogeneity per se. Our results indicate that a strong differential response of a dominant species to resource availability in a restored community can regulate community structure, diversity, and similarity to the native (or target) community, but the importance of resource heterogeneity in restoring diversity may be dampened in systems where a dominant species can successfully establish across a range of resource availability.10adiversity10agrassland10anitrogen10atallgrass prairie1 aBaer, S.G.1 aBlair, John, M.1 aCollins, Scott., L.1 aKnapp, Alan, K. uhttp://knz.lternet.edu/content/plant-community-responses-resource-availability-and-heterogeneity-during-restoration02570nas a2200205 4500008004100000245010900041210006900150300001300219490000800232520185800240653001702098653001202115653001802127653002102145653002202166100001502188700002002203700002002223856012102243 2003 eng d00aA comparative assessment of potential mechanisms influencing plant species richness in grazed grasslands0 acomparative assessment of potential mechanisms influencing plant a385 -3910 v1373 aGrazing by large ungulates often increases plant species richness in grasslands of moderate to high productivity. In a mesic North American grassland with and without the presence of bison (Bos bison), a native ungulate grazer, three non-exclusive hypotheses for increased plant species richness in grazed grasslands were evaluated: (1) bison grazing enhances levels of resource (light and N) availability, enabling species that depend on higher resource availability to co-occur; (2) spatial heterogeneity in resource availability is enhanced by bison, enabling coexistence of a greater number of plant species; (3) increased species turnover (i.e. increased species colonization and establishment) in grazed grassland is associated with enhanced plant species richness. We measured availability and spatial heterogeneity in light, water and N, and calculated species turnover from long-term data in grazed and ungrazed sites in a North American tallgrass prairie. Both regression and path analyses were performed to evaluate the potential of the three hypothesized mechanisms to explain observed patterns of plant species richness under field conditions. Experimental grazing by bison increased plant species richness by 25% over an 8-year period. Neither heterogeneity nor absolute levels of soil water or available N were related to patterns of species richness in grazed and ungrazed sites. However, high spatial heterogeneity in light and higher rates of species turnover were both strongly related to increases in plant species richness in grazed areas. This suggests that creation of a mosaic of patches with high and low biomass (the primary determinant of light availability in mesic grasslands) and promotion of a dynamic species pool are the most important mechanisms by which grazers affect species richness in high productivity grasslands.10acolonization10aGrazing10aheterogeneity10aSpecies richness10atallgrass prairie1 aBakker, C.1 aBlair, John, M.1 aKnapp, Alan, K. uhttp://knz.lternet.edu/content/comparative-assessment-potential-mechanisms-influencing-plant-species-richness-grazed02814nas a2200337 4500008004100000245014100041210006900182300001500251490000700266520177500273653001202048653001402060653001802074653001602092653001502108653001502123653001802138653001502156653000902171653001402180653002202194653001302216653001502229653001702244100001902261700002002280700001502300700001802315700001702333856012602350 2003 eng d00aEffects of fire, mowing and fertilization effects on density and biomass of macroinvertebrates in North American tallgrass prairie soils0 aEffects of fire mowing and fertilization effects on density and  a1079 -10930 v353 aThe responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.10abiomass10aCicadidae10aCurculionidae10adisturbance10aearthworms10aElateridae10aFertilization10aFertilizer10afire10agrassland10ainsect herbivores10anitrogen10aPhosphorus10aScarabaeidae1 aCallaham, M.A.1 aBlair, John, M.1 aTodd, T.C.1 aKitchen, D.J.1 aWhiles, M.R. uhttp://knz.lternet.edu/content/effects-fire-mowing-and-fertilization-effects-density-and-biomass-macroinvertebrates-north02608nas a2200229 4500008004100000245008400041210006900125300001300194490000800207520185900215653001902074653001802093653002902111653001802140653001802158100001202176700001902188700002002207700002002227700002402247856010702271 2003 eng d00aProductivity responses to altered rainfall patterns in a C4-dominated grassland0 aProductivity responses to altered rainfall patterns in a C4domin a245 -2510 v1373 aRainfall variability is a key driver of ecosystem structure and function in grasslands worldwide. Changes in rainfall patterns predicted by global climate models for the central United States are expected to cause lower and increasingly variable soil water availability, which may impact net primary production and plant species composition in native Great Plains grasslands. We experimentally altered the timing and quantity of growing season rainfall inputs by lengthening inter-rainfall dry intervals by 50%, reducing rainfall quantities by 30%, or both, compared to the ambient rainfall regime in a native tallgrass prairie ecosystem in northeastern Kansas. Over three growing seasons, increased rainfall variability caused by altered rainfall timing with no change in total rainfall quantity led to lower and more variable soil water content (0–30 cm depth), a ~10% reduction in aboveground net primary productivity (ANPP), increased root to shoot ratios, and greater canopy photon flux density at 30 cm above the soil surface. Lower total ANPP primarily resulted from reduced growth, biomass and flowering of subdominant warm-season C4 grasses while productivity of the dominant C4 grass Andropogon gerardii was relatively unresponsive. In general, vegetation responses to increased soil water content variability were at least equal to those caused by imposing a 30% reduction in rainfall quantity without altering the timing of rainfall inputs. Reduced ANPP most likely resulted from direct effects of soil moisture deficits on root activity, plant water status, and photosynthesis. Altered rainfall regimes are likely to be an important element of climate change scenarios in this grassland, and the nature of interactions with other climate change elements remains a significant challenge for predicting ecosystem responses to climate change.10aClimate change10aKonza Prairie10aNet primary productivity10aPrecipitation10asoil moisture1 aFay, P.1 aCarlisle, J.D.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/productivity-responses-altered-rainfall-patterns-c4-dominated-grassland00772nas a2200205 4500008004100000245010400041210006900145260004400214300001300258653002200271100001200293700002000305700002000325700001900345700001700364700001900381700001800400700002000418856012800438 2003 eng d00aRainfall timing, soil moisture dynamics, and plant responses in a mesic tallgrass prairie ecosystem0 aRainfall timing soil moisture dynamics and plant responses in a  aTucson, AZbUniversity of Arizona Press a147 -16310atallgrass prairie1 aFay, P.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCarlisle, J.D.1 aDanner, B.T.1 aMcCarron, J.K.1 aWeltzin, J.F.1 aMcPherson, G.R. uhttp://knz.lternet.edu/content/rainfall-timing-soil-moisture-dynamics-and-plant-responses-mesic-tallgrass-prairie-ecosystem02062nas a2200205 4500008004100000245007300041210006900114300001300183490000800196520140000204653001901604653002101623653001901644653001801663653002001681100001901701700002001720700002001740856009601760 2003 eng d00aSoil C and N responses to woody plant expansion in a mesic grassland0 aSoil C and N responses to woody plant expansion in a mesic grass a183 -1920 v2573 aChanges in land management and reductions in fire frequency have contributed to increased cover of woody species in grasslands worldwide. These shifts in plant community composition have the potential to alter ecosystem function, particularly through changes in soil processes and properties. In semi-arid grasslands, the invasion of shrubs and trees is often accompanied by increases in soil resources and more rapid N and C cycling. We assessed the effects of shrub encroachment in a mesic grassland in Kansas (USA) on soil CO2 flux, extractable inorganic N, and N mineralization beneath shrub communities (Cornus drummondii) and surrounding undisturbed grassland sites. In this study, a shift in plant community composition from grassland to shrubland resulted in a 16% decrease in annual soil CO2 flux(4.78 kg CO2 m−2 year−1 for shrub dominated sites versus 5.84 kg CO2 m−2 year−1 for grassland sites) with no differences in total soil C or N or inorganic N. There was considerable variability in N mineralization rates within sites, which resulted in no overall difference in cumulative N mineralized during this study (4.09 g N m−2 for grassland sites and 3.03 g N m−2 for shrub islands). These results indicate that shrub encroachment into mesic grasslands does not significantly alter N availability (at least initially), but does alter C cycling by decreasing soil CO2 flux.10aN availability10aN mineralization10ashrub invasion10asoil CO2 flux10asoil properties1 aMcCarron, J.K.1 aKnapp, Alan, K.1 aBlair, John, M. uhttp://knz.lternet.edu/content/soil-c-and-n-responses-woody-plant-expansion-mesic-grassland03030nas a2200169 4500008004100000245009400041210006900135300001300204490000700217520241300224653002202637100001502659700002002674700002002694700002402714856012202738 2003 eng d00aSoil resources regulate productivity and diversity in newly established tallgrass prairie0 aSoil resources regulate productivity and diversity in newly esta a724 -7350 v843 aIn native tallgrass prairie, soil depth and nitrogen (N) availability strongly influence aboveground net primary productivity (ANPP) and plant species composition. We manipulated these factors in a newly restored grassland to determine if these resources similarly constrain productivity and diversity during the initial three years of grassland establishment. Four types of experimental plots with six treatment combinations of deep and shallow soil at reduced-, ambient-, and enriched-N availability formed the basis of this study. The soil responses to the experimental treatments were examined over three years, and patterns in diversity and productivity were examined in year 3. The soil depth treatment did not significantly affect soil carbon (C) and N pools or ANPP and diversity. A pulse amendment of C added to the soil prior to planting increased soil microbial biomass and decreased potential net N mineralization rates to effectively reduce N availability throughout the study. Nitrogen availability declined over time in nonamended soils as a result of plant establishment, but adding fertilizer N alleviated the increasing immobilization potential of the soil. The level of ANPP was lowest and diversity highest in the reduced-N treatment, whereas the enriched-N treatment resulted in high productivity, but low diversity. As a result, diversity was inversely correlated with productivity in these newly established communities. The same mechanism invoked to explain decreased diversity under nutrient enrichment in old-field ecosystems and native grasslands (e.g., reduced light availability with increased production) was supported in the restored prairie by the positive relationship between ANPP and intercepted light, and a strong correlation between light availability and diversity. The effects of nutrient availability on plant community composition (diversity and richness) were due primarily to the responses of prairie species, as the productivity of early successional, nonprairie species was less than 1% of total ANPP after three years of establishment. These results show that the effects of resource availability on productivity and diversity are similar in young and mature grasslands, and that manipulation of a limiting nutrient during grassland establishment can influence floristic composition, with consequences for long-term patterns of diversity in restored ecosystems.10atallgrass prairie1 aBaer, S.G.1 aBlair, John, M.1 aKnapp, Alan, K.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/soil-resources-regulate-productivity-and-diversity-newly-established-tallgrass-prairie00700nas a2200205 4500008004100000245008600041210006900127300001300196490000800209100001400217700001900231700001700250700001500267700001900282700001600301700002000317700002000337700002400357856011300381 2002 eng d00aAltered rainfall patterns, gas exchange and growth in C3 and C4 grassland species0 aAltered rainfall patterns gas exchange and growth in C3 and C4 g a549 -5570 v1631 aFay, P.A.1 aCarlisle, J.D.1 aDanner, B.T.1 aLett, M.S.1 aMcCarron, J.K.1 aStewart, C.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/altered-rainfall-patterns-gas-exchange-and-growth-c3-and-c4-grassland-species02242nas a2200157 4500008004100000245010800041210006900149300001200218490000800230520164700238653002201885100001901907700001701926700002001943856012101963 2002 eng d00aAnnual fire, mowing and fertilization effects on two cicadas (Homoptera:Cicadidae) in tallgrass prairie0 aAnnual fire mowing and fertilization effects on two cicadas Homo a90 -1010 v1483 aIn tallgrass prairie, cicadas emerge annually, are abundant and their emergence can be an important flux of energy and nutrients. However, factors influencing the distribution and abundance of these cicadas are virtually unknown. We examined cicada emergence in plots from a long-term (13 y) experimental manipulation involving common tallgrass prairie management practices. The plots were arranged in a factorial experimental design, incorporating annual burning, mowing and fertilization (10 g N m−2 and 1 g P m−2). One cicada species, Cicadetta calliope, responded positively to fire, but negatively to mowing, and was most abundant in plots that were burned, unmowed and fertilized. Increased density of C. calliope in this treatment combination is related, in part, to increased availability of oviposition sites aboveground. Furthermore, C. calliope females from fertilized plots were significantly larger in body size relative to females from unfertilized prairie. Another cicada species, Tibicen aurifera, emerged only from unburned plots. The mechanism underlying this negative response to fire is unclear, but may be related to the presence of standing dead vegetation or improved quality (i.e., N content) of belowground plant tissue in unburned plots. In contrast to C. calliope, the density of T. aurifera was not affected by mowing or fertilization. However, like C. calliope, the body size of T. aurifera females was significantly greater in fertilized plots. Cicada emergence resulted in N flux ranging from 0.05–0.16 g N m−2 in unburned plots, but N flux (as cicada biomass) from annually burned plots was negligible.10atallgrass prairie1 aCallaham, M.A.1 aWhiles, M.R.1 aBlair, John, M. uhttp://knz.lternet.edu/content/annual-fire-mowing-and-fertilization-effects-two-cicadas-homopteracicadidae-tallgrass02696nas a2200205 4500008004100000245009500041210006900136300001500205490000700220520202100227653001402248653001302262653001402275653001402289100001502303700001802318700002002336700001702356856011702373 2002 eng d00aChanges in ecosystem structure and function along a chronosequence of restored grasslands0 aChanges in ecosystem structure and function along a chronosequen a1688 -17010 v123 aChanges in aboveground vegetation, roots, and soil characteristics were examined from a 12-yr chronosequence of formerly cultivated fields restored to native C4 grasses through the Conservation Reserve Program (CRP). Following 6–8 yr in the CRP, the native grasses dominated vegetation composition, and the presence of forbs was negligible. Productivity of the restored grasslands did not exhibit any directional changes with the number of years in the CRP, and productivity was generally higher than native prairie in this region. Over time, the restored grasslands accumulated root biomass of decreasing quality as indicated by increasing root biomass and C:N ratio of roots along the 12-yr chronosequence. Root biomass, root C:N ratio, C storage in roots, and N storage in roots of restored grasslands approached that of native tallgrass prairie within the 12 yr of restoration. Establishment of the perennial vegetation also affected soil physical, chemical, and biological characteristics. Soil bulk density in the surface 10 cm decreased with time since restoration. Total C, microbial biomass C, and C mineralization rates increased as a function of time since restoration. The greatest change in total C occurred in the surface 5 cm, where total C was 26% greater in 12- vs. 2-yr restored grasslands. Extractable soil nitrate and soil N transformations (i.e., net N mineralization rates and net nitrification rates) declined over the restoration chronosequence, but these values were not representative of steady-state conditions due to the high variability in these measures among the native prairies. Although complete restoration of ecosystem structure and function was not the primary intention of the CRP, this study demonstrates that establishment of the matrix vegetation (i.e., native C4 grasses) drives ecosystem processes in the trajectory of the original system. Moreover, restoration may hasten the recovery of soil C pools relative to formerly cultivated systems undergoing natural succession.10aecosystem10afunction10agrassland10astructure1 aBaer, S.G.1 aKitchen, D.J.1 aBlair, John, M.1 aRice, C., W. uhttp://knz.lternet.edu/content/changes-ecosystem-structure-and-function-along-chronosequence-restored-grasslands01540nas a2200229 4500008004100000245009000041210006900131300001500200490000800215520084900223100002001072700001401092700002001106700002401126700001601150700001901166700001701185700001701202700001501219700001901234856005701253 2002 eng d00aRainfall variability, carbon cycling and plant species diversity in a mesic grassland0 aRainfall variability carbon cycling and plant species diversity  a2202 -22050 v2983 a

Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.

1 aKnapp, Alan, K.1 aFay, P.A.1 aBlair, John, M.1 aCollins, Scott., L.1 aSmith, M.D.1 aCarlisle, J.D.1 aHarper, C.W.1 aDanner, B.T.1 aLett, M.S.1 aMcCarron, J.K. uhttps://science.sciencemag.org/content/298/5601/220202091nas a2200169 4500008004100000245013900041210006900180300001500249490000700264520143200271653002201703100001701725700002001742700001801762700001701780856012401797 2001 eng d00aAssessing changes in biomass, productivity, and C and N stores following Juniperus virginiana forest expansion into tallgrass prairie0 aAssessing changes in biomass productivity and C and N stores fol a1940 -19460 v313 aAn increase in woody plant abundance in regions historically dominated by grasses is a recent land cover change in grasslands worldwide. In tallgrass prairies of North America, this increase in woody plant cover includes the development of dense stands of eastern redcedar (Juniperus virginiana L.). To evaluate the consequences of this ongoing land cover change for ecosystem functioning, we developed allometric equations, using data from Kansas and Oklahoma, to estimate aboveground biomass and productivity in closed-canopy redcedar stands. We then applied these equations to three closed-canopy redcedar stands, 35–80 years old, which developed on sites formerly dominated by tallgrass prairie in eastern Kansas. Aboveground plant biomass for these redcedar-dominated sites ranged from 114 100 kg/ha for the youngest stand to 210 700 kg/ha for the oldest. Annual aboveground net primary productivity (ANPP) ranged from 7250 to 10 440 kg·ha–1·year–1 for the oldest and younger redcedar stands, respectively. Estimates of ANPP in comparable tallgrass prairie sites in this region average 3690 kg·ha–1·year–1 indicating a large increase in C uptake and aboveground storage as a result of the change from prairie to redcedar forests. Therefore, the widespread occurrence of redcedars across the woodland–prairie ecotone suggests that this land-cover change may have important consequences for regional net C storage.10atallgrass prairie1 aNorris, M.D.1 aBlair, John, M.1 aJohnson, L.C.1 aMcKane, R.B. uhttp://knz.lternet.edu/content/assessing-changes-biomass-productivity-and-c-and-n-stores-following-juniperus-virginiana02614nas a2200277 4500008004100000245008000041210006900121300001300190490000700203520177300210653001201983653001701995653002102012653001202033653002202045100001402067700001902081700001702100700001502117700001902132700001602151700002002167700002002187700002402207856010502231 2001 eng d00aCarbon and water relations of juvenile Quercus species in tallgrass prairie0 aCarbon and water relations of juvenile Quercus species in tallgr a807 -8160 v123 aIn ecosystems where environments are extreme, such as deserts, adult plant species may facilitate the establishment and growth of seedlings and juveniles. Because high temperatures and evaporative demand characterize tall-grass prairies of the central United States (relative to forests), we predicted that the grassland-forest ecotone, by minimizing temperature extremes and moderating water stress, may function to facilitate the expansion of Quercus species into undisturbed tall-grass prairie. We assessed the carbon and water relations of juvenile Quercus macrocarpa and Q. muhlenbergii, the dominant tree species in gallery forests of northeast Kansas, in ecotone and prairie sites. To evaluate the potentially competitive effects of neighboring herbaceous biomass on these oaks, juveniles (< 0.5 m tall) of both species also were subjected to either: (1) removal of surrounding above-ground herbaceous biomass, or (2) control (prairie community intact) treatments. Herbaceous biomass removal had no significant effect on gas exchange or water relations in these oak species in either the prairie or the ecotone environment. Although the ecotone did alleviate some environmental extremes, photosynthetic rates and stomatal conductance were ca. 20 % higher (p < 0.05) in both oaks in prairie sites vs. the ecotone. Moreover, although leaf temperatures on average were higher in oaks in the prairie, high leaf temperatures in the ecotone had a greater negative effect on photosynthesis. These data suggest that the grassland-forest ecotone did not facilitate the growth of Quercus juveniles expanding into this grassland. Moreover, the carbon and water relations of juvenile oaks in the prairie appeared to be unaffected by the presence of the dominant C4 grasses.10aEcotone10aFacilitation10aforest expansion10aQuercus10atallgrass prairie1 aFay, P.A.1 aCarlisle, J.D.1 aDanner, B.T.1 aLett, M.S.1 aMcCarron, J.K.1 aStewart, C.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/carbon-and-water-relations-juvenile-quercus-species-tallgrass-prairie02462nas a2200205 4500008004100000245015900041210006900200300001100269490000700280520169400287653001401981653002201995653001302017653002302030653002002053100001902073700002002092700001802112856012602130 2001 eng d00aDifferent behavioral patterns of the earthworms Octolasion tyrtaeum and Diplocardia spp . in tallgrass prairie soils: potential influences on plant growth0 aDifferent behavioral patterns of the earthworms Octolasion tyrta a49 -560 v343 aThis study addressed differences between Diplocardia spp. (a native North American earthworm) and Octolasion tyrtaeum (an introduced European species), with respect to behavior, influence on soil microbial biomass, and plant uptake of N in tallgrass prairie soils. We manipulated earthworms in PVC-encased soil cores (20 cm diameter) over a 45-day period under field conditions. Treatments included: (1) control with no earthworms, (2) Diplocardia spp. only, and (3) O. tyrtaeum only. Prior to addition of earthworms, seedlings of Andropogon gerardii (a dominant tallgrass) were established in each core, and a dilute solution of 13C-labeled glucose and 15N-labeled (NH4)2SO4 was added to the soil to facilitate examination of earthworm/microbe/plant interactions. We found that Diplocardia spp. were significantly more active than O. tyrtaeum, and quickly assimilated 13C and 15N from the tracer. Individuals of Diplocardia spp. were present at shallower soil depths than O. tyrtaeum throughout the study. Contrary to expectation, this greater activity of Diplocardia spp. did not result in increased plant productivity. Rather, the activity of Diplocardia spp. was associated with less plant growth and smaller amounts of N acquired by A. gerardii seedlings compared to controls or O. tyrtaeum treatments. We observed few significant influences of earthworm treatments on microbial biomass C or N pool sizes, but the microbial C/N ratio was consistently greater in the presence of Diplocardia spp. relative to O. tyrtaeum. Results of this study indicate that activity of earthworms may enhance competition for N between microbes and plants during the growing season in tallgrass prairie.10agrassland10aMicrobial biomass10anitrogen10aSoil invertebrates10aStable isotopes1 aCallaham, M.A.1 aBlair, John, M.1 aHendrix, P.F. uhttp://knz.lternet.edu/content/different-behavioral-patterns-earthworms-octolasion-tyrtaeum-and-diplocardia-spp-tallgrass02202nas a2200157 4500008004100000245012000041210006900161300001300230490000700243520159400250653002201844100001701866700002001883700001801903856012301921 2001 eng d00aLand cover change in eastern Kansas: litter dynamics of closed-canopy eastern redcedar forests in tallgrass prairie0 aLand cover change in eastern Kansas litter dynamics of closedcan a214 -2220 v793 aIn the Great Plains region, eastern redcedar (Juniperus virginiana L.) abundance has increased dramatically in areas historically occupied by tallgrass prairie. This shift in dominant vegetation is likely to be accompanied by changes in ecosystem structure and function, including quantity, quality, and location (above- vs. below-ground) of litter inputs and subsequent effects on decomposition dynamics. The purpose of this study was to quantify and compare patterns of litterfall and decomposition in mature redcedar forests and adjacent prairie. Annual redcedar litterfall was 500 g·m-2·year-1, a large increase in foliar litter inputs compared with annually burned grassland (52 g·m-2·year-1). Using a reciprocal transplant decomposition study with four substrates, redcedar leaves and roots, and big bluestem (Andropogon gerardii Vitman) foliage and roots, we found marginal habitat effects, but greater differences between species, presumably owing to litter quality (including both C:N and lignin content). Decay rates were significantly higher in the prairie relative to the forest for each substrate. Additionally, within any particular habitat, grass litter had significantly faster decay rates than forest litter. These results suggest a shift in patterns of litter input and decomposition processes with afforestation of tallgrass prairie, which may result in long-term changes in C sequestration and storage.Key words: litter dynamics, eastern redcedar (Juniperus virginiana), big bluestem (Andropogon gerardii), decomposition, tallgrass prairie, nitrogen immobilization.10atallgrass prairie1 aNorris, M.D.1 aBlair, John, M.1 aJohnson, L.C. uhttp://knz.lternet.edu/content/land-cover-change-eastern-kansas-litter-dynamics-closed-canopy-eastern-redcedar-forests02886nas a2200289 4500008004100000245013100041210006900172300001300241490000600254520190600260653001902166653002402185653001502209653001802224653001902242653002302261653002702284653002702311653002102338653001802359100001402377700001902391700002002410700002002430700002402450856012202474 2000 eng d00aAltering rainfall timing and quantity in a mesic grassland ecosystem: Design and performance of rainfall manipulation shelters0 aAltering rainfall timing and quantity in a mesic grassland ecosy a308 -3190 v33 aGlobal climate change is predicted to alter growing season rainfall patterns, potentially reducing total amounts of growing season precipitation and redistributing rainfall into fewer but larger individual events. Such changes may affect numerous soil, plant, and ecosystem properties in grasslands and ultimately impact their productivity and biological diversity. Rainout shelters are useful tools for experimental manipulations of rainfall patterns, and permanent fixed-location shelters were established in 1997 to conduct the Rainfall Manipulation Plot study in a mesic tallgrass prairie ecosystem in northeastern Kansas. Twelve 9 x 14–m fixed-location rainfall manipulation shelters were constructed to impose factorial combinations of 30% reduced rainfall quantity and 50% greater interrainfall dry periods on 6 x 6–m plots, to examine how altered rainfall regimes may affect plant species composition, nutrient cycling, and above- and belowground plant growth dynamics. The shelters provided complete control of growing season rainfall patterns, whereas effects on photosynthetic photon flux density, nighttime net radiation, and soil temperature generally were comparable to other similar shelter designs. Soil and plant responses to the first growing season of rainfall manipulations (1998) suggested that the interval between rainfall events may be a primary driver in grassland ecosystem responses to altered rainfall patterns. Aboveground net primary productivity, soil CO2 flux, and flowering duration were reduced by the increased interrainfall intervals and were mostly unaffected by reduced rainfall quantity. The timing of rainfall events and resulting temporal patterns of soil moisture relative to critical times for microbial activity, biomass accumulation, plant life histories, and other ecological properties may regulate longer-term responses to altered rainfall patterns.10aClimate change10afloristic diversity10aGrasslands10aKonza Prairie10alife histories10along-term research10aNet primary production10aprecipitation patterns10arainout shelters10asoil moisture1 aFay, P.A.1 aCarlisle, J.D.1 aKnapp, Alan, K.1 aBlair, John, M.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/altering-rainfall-timing-and-quantity-mesic-grassland-ecosystem-design-and-performance01409nas a2200145 4500008004100000245008900041210006900130300001300199490000700212520093600219100001501155700001701170700002001187856005601207 2000 eng d00aAssessment of soil quality in fields with short- and long-term enrollment in the CRP0 aAssessment of soil quality in fields with short and longterm enr a142 -1460 v553 aSurface [5 to10 cm, (2 to 4 in) depth] soil quality was examined from fields representing short and long term enrollment in the Conservation Reserve Program (CRP). Total carbon (C) and nitrogen (N) amounts were similar in soil with recent and long term enrollment in the CRP and were lower than a native prairie field. Active pools of C and N, however, did increase through the CRP. Soil with long term establishment of native grasses in the CRP exhibited 141% and 33% greater microbial biomass C and N, respectively, than soil recently enrolled in the CRP. Total inorganic N was significantly lower in CRP soil with ten versus no growing seasons and was more representative of levels in a native prairie due to reductions in nitrate availability. Our study indicates that CRP promotes soil restoration; however, ten growing seasons are not adequate for recovery of total soil C and N pools at this depth to pre-cultivation levels.1 aBaer, S.G.1 aRice, C., W.1 aBlair, John, M. uhttp://www.jswconline.org/content/55/2/142.abstract00419nas a2200133 4500008004100000245004500041210004500086300001300131490000700144100002000151700002400171700002000195856007000215 2000 eng d00aEcosystems as functional units in nature0 aEcosystems as functional units in nature a150 -1550 v141 aBlair, John, M.1 aCollins, Scott., L.1 aKnapp, Alan, K. uhttp://knz.lternet.edu/content/ecosystems-functional-units-nature01410nas a2200169 4500008004100000245008800041210006900129260004200198300001100240520078600251100002001037700001501057700001901072700001801091700001801109856011301127 2000 eng d00aResponses of grassland soil invertebrates to natural and anthropogenic disturbances0 aResponses of grassland soil invertebrates to natural and anthrop aNew York, NYbCAB International Press a43 -713 ahis chapter aims to (1) summarize the major factors influencing invertebrate abundance and distribution in tallgrass prairie soils, focusing on the responses of selected soil invertebrate groups to natural disturbances (such as fire, grazing and drought); (2) identify potential linkages between changes in soil communities and the effects of disturbances on key plant and soil characteristics or processes; and (3) to discuss potential effects of novel anthropogenic perturbations (altered amounts of precipitation, elevated CO2 and increased N inputs) on soil communities and processes. It focuses on North American tallgrass prairies and draws upon studies undertaken at the Konza Prairie Long-Term Ecological Research site, with results from other grasslands where appropriate.1 aBlair, John, M.1 aTodd, T.C.1 aCallaham, M.A.1 aColeman, D.C.1 aHendrix, P.F. uhttp://knz.lternet.edu/content/responses-grassland-soil-invertebrates-natural-and-anthropogenic-disturbances02307nas a2200205 4500008004100000245008900041210006900130300001100199490000700210520162200217653001901839653002401858653001301882653001801895653002201913100001501935700002001950700001901970856011201989 1999 eng d00aEffects of altered soil water availability on a tallgrass prairie nematode community0 aEffects of altered soil water availability on a tallgrass prairi a45 -550 v133 aClimate change predictions for the Great Plains region of North America include reduced growing season precipitation. The consequence of this prediction for soil fauna and belowground processes was investigated at two spatial scales by integrating experimental manipulation of soil moisture levels with natural variation in soil-water availability. Experiments consisted of (1) reciprocal core transplants across a regional precipitation gradient and (2) supplemental irrigation applied across a local topographic gradient. This report examines functional-level responses by the tallgrass prairie nematode community to differences in soil moisture levels over a four-year period. Effects on nematode community structure were complex and dependent upon nematode trophic habit and depth in the soil profile. The strongest and most consistent responses to changes in soil-water availability were displayed by herbivorous taxa, with 71% higher densities observed under wetter soil conditions across experiments and years. Responses of microbial-feeding nematodes were more variable, with lower densities observed, in some cases, in the presence of experimentally-increased soil moisture levels. Effects of regional differences in soil-water availability on the nematode community were uniformly restricted to depths >20 cm. Community responses to short-term changes in soil moisture were not consistent with patterns in community structure developed under different natural moisture regimes, suggesting divergent short-term and long-term responses of belowground biota and processes to changes in soil-water availability.10aClimate change10acommunity structure10aNematode10asoil moisture10atallgrass prairie1 aTodd, T.C.1 aBlair, John, M.1 aMilliken, G.A. uhttp://knz.lternet.edu/content/effects-altered-soil-water-availability-tallgrass-prairie-nematode-community00577nas a2200133 4500008004100000245012400041210006900165300001300234490000700247653002200254100001900276700002000295856012800315 1999 eng d00aInfluence of differing land management on the invasion of North American tallgrass prairie soils by European earthworms0 aInfluence of differing land management on the invasion of North  a507 -5120 v4310atallgrass prairie1 aCallaham, M.A.1 aBlair, John, M. uhttp://knz.lternet.edu/content/influence-differing-land-management-invasion-north-american-tallgrass-prairie-soils-european00565nas a2200181 4500008004100000245006700041210006300108300001100171490000700182100002000189700002000209700001900229700002400248700001900272700001800291700001600309856005800325 1999 eng d00aThe keystone role of bison in North American tallgrass prairie0 akeystone role of bison in North American tallgrass prairie a39 -500 v491 aKnapp, Alan, K.1 aBlair, John, M.1 aBriggs, J., M.1 aCollins, Scott., L.1 aHartnett, D.C.1 aJohnson, L.C.1 aTowne, E.G. uhttp://www.jstor.org/stable/10.1525/bisi.1999.49.1.3902807nas a2200241 4500008004100000245008300041210006900124260005100193300001100244520196600255653003202221653003902253653001702292653002302309653001902332653001802351653002202369100001502391700002002406700002002426700001902446856010002465 1999 eng d00aManipulation of soil resource heterogeneity in a tallgrass prairie restoration0 aManipulation of soil resource heterogeneity in a tallgrass prair aKearney, NEbUniversity of Nebraska at Kearney a78 -873 aPlant species diversity in native prairie ecosystems is influenced by heterogeneity of soil resources, which results from interactions among plant communities, soil properties, topography, and disturbance. Key factors which promote plant diversity in native prairie include soil moisture, rooting depth, and nutrient availability. Most prairie restorations in the Great Plains occur on former agricultural land and the soil template for these restorations has been physically homogenized through tillage practices. The reduction in soil resource heterogeneity in restored prairies may be causally related to low plant species diversity commonly encountered in these sites. To examine the role of soil heterogeneity in restoring prairie ecosystems, replicated blocks (n=4) of 4 plots consisting of different levels of soil heterogeneity were established in an agricultural field. The 4 plot types included: control (least heterogeneous with respect to soil resources), altered plant rooting depth, altered nutrient availability, and combined variation in plant rooting depth and nutrient availability (maximum heterogeneity). Plant rooting depth was varied by burying limestone barriers at 25 cm to create alternating strips of deep and shallow soil. Variation in soil nutrient (inorganic N) availability was established via increased N (+fertilizer), decreased N (+ recalcitrant C), and no change in N. All plots were seeded with the dominant native grasses and >30 forb species. Incorporation of recalcitrant C reduced total inorganic N availability 90% as a result of 98% reduction in available nitrate. Plots containing strips of low N availability exhibited significantly (p < 0.05) greater spatial variability than plots without this manipulation. Thus, the experimental design and methods implemented have increased heterogeneity of soil nutrients, and this will enable us to address the role of variation in soil resources on restoring tallgrass prairie.10aaltered plant rooting depth10aaltered soil nutrient availability10aGreat Plains10alimestone barriers10arecalcitrant C10asoil template10aSpecies diversity1 aBaer, S.G.1 aBlair, John, M.1 aKnapp, Alan, K.1 aSpringer, J.T. uhttp://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC16/reference/econatres.napc16.sbaer.pdf00652nas a2200181 4500008004100000245007400041210006900115260003800184300001300222100001700235700002300252700002000275700002000295700001800315700001800333700001800351856010100369 1999 eng d00aMeasuring decomposition, nutrient turnover and stores in plant litter0 aMeasuring decomposition nutrient turnover and stores in plant li aNew YorkbOxford University Press a202 -2401 aHarmon, M.E.1 aNaddlehoffer, K.J.1 aBlair, John, M.1 aRobertson, G.P.1 aBledsoe, C.S.1 aColeman, D.C.1 aSollins, P.S. uhttp://knz.lternet.edu/content/measuring-decomposition-nutrient-turnover-and-stores-plant-litter02604nas a2200193 4500008004100000245009700041210006900138300001300207490000700220520193300227653001002160653001902170653002002189653002502209653002302234100001702257700002002274856011602294 1999 eng d00aResponses of soil microarthropods to changes in soil water availability in tallgrass prairie0 aResponses of soil microarthropods to changes in soil water avail a207 -2170 v293 aChanges in precipitation and soil water availability predicted to accompany global climate change would impact grasslands, where many ecosystem processes are influenced by water availability. Soil biota, including microarthropods, also are affected by soil water content, although little is known about how climate change might affect their abundance and distribution. The goal of this study was to examine soil microarthropod responses to altered soil water availability in tallgrass prairie ecosystems. Two separate experiments were done. The first utilized control and irrigated plots along a topographic gradient to examine the effects of soil water content on microarthropod densities. Microarthropods, mainly Acari, were significantly less abundant in irrigated plots and were generally less abundant at the wetter lowland sites. The second study utilized reciprocal core transplants across an east-west regional precipitation gradient. Large, intact cores were transplanted between a more mesic tallgrass site (Konza Prairie) and a more arid mixed-grass site (Hays) to determine the effects of different soil water regimes on microarthropod abundance and vertical distribution. Data from non-transplanted cores indicated greater total microarthropod densities at the drier Hays site, relative to the wetter Konza Prairie site. Data from the transplanted cores indicated significant effects of location on Acari densities in cores originating from Hays, with higher densities in cores remaining at Hays, relative to those transplanted to Konza. Acari densities in cores originating from Konza were not affected by location; however, oribatid mite densities generally were greater in cores remaining at Konza Prairie. These results confirm the importance of soil water content in affecting microarthropod densities and distributions in grasslands, and suggest complex, non-linear responses to changes in water availability.10aAcari10aClimate change10aGrassland soils10aSoil microarthropods10aSoil water content1 aO'Lear, H.E.1 aBlair, John, M. uhttp://knz.lternet.edu/content/responses-soil-microarthropods-changes-soil-water-availability-tallgrass-prairie00830nas a2200229 4500008004100000245011100041210006900152260003800221300001300259100002000272700001400292700001900306700002000325700001600345700002200361700001500383700002000398700001800418700001800436700001800454856012800472 1999 eng d00aSoil Carbon and nitrogen availability: Nitrogen mineralization, nitrification, soil respiration potentials0 aSoil Carbon and nitrogen availability Nitrogen mineralization ni aNew YorkbOxford University Press a258 -2711 aRobertson, G.P.1 aWedin, D.1 aGroffman, P.M.1 aBlair, John, M.1 aHolland, E.1 aNadelhoffer, K.J.1 aHarris, D.1 aRobertson, G.P.1 aBledsoe, C.S.1 aColeman, D.C.1 aSollins, P.S. uhttp://knz.lternet.edu/content/soil-carbon-and-nitrogen-availability-nitrogen-mineralization-nitrification-soil-respiration00531nas a2200193 4500008004100000245002300041210002300064260003800087300001300125100001800138700002000156700001800176700001500194700002000209700001800229700001800247700001800265856005400283 1999 eng d00aSoil invertebrates0 aSoil invertebrates aNew YorkbOxford University Press a349 -3771 aColeman, D.C.1 aBlair, John, M.1 aElliott, E.T.1 aWall, D.H.1 aRobertson, G.P.1 aBledsoe, C.S.1 aColeman, D.C.1 aSollins, P.S. uhttp://knz.lternet.edu/content/soil-invertebrates00677nas a2200229 4500008004100000245003800041210003800079260003800117300001300155653002200168100001700190700001500207700002000222700001900242700001800261700001700279700002000296700001900316700001900335700002400354856006900378 1998 eng d00aBelowground biology and processes0 aBelowground biology and processes aNew YorkbOxford University Press a244 -26410atallgrass prairie1 aRice, C., W.1 aTodd, T.C.1 aBlair, John, M.1 aSeastedt, T.R.1 aRamundo, R.A.1 aWilson, G.T.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aHartnett, D.C.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/belowground-biology-and-processes03993nas a2200157 4500008004100000245009400041210006900135300001300204490000600217520343500223653000903658100002003667700001703687700002003704856011103724 1998 eng d00aDeterminants of soil CO2 flux from a sub-humid grassland: Effect of fire and fire history0 aDeterminants of soil CO2 flux from a subhumid grassland Effect o a760 -7700 v83 aSoil CO2 flux (JCO2) was measured at midday over a 2-yr period in undisturbed tallgrass prairie (Konza Prairie, Kansas, USA) to quantify seasonal and annual budgets, to evaluate temperature and moisture as determinants of soil CO2 flux, and to assess the effect of a common land management tool, spring fire, and fire history on soil respiration. We hypothesized that: (1) maximum rates and annual estimates of soil JCO2 would be greater in more productive burned sites than in unburned sites, (2) soil JCO2 would be greater in newly burned sites with a history of fire exclusion than in annually burned sites (consistent with differences in aboveground production), and (3) soil temperature and water availability would be primary abiotic determinants of soil JCO2 in tallgrass prairie. A preliminary assessment of the effects of large herbivores on soil JCO2 was included to evaluate the hypothesis that removal of aboveground biomass would reduce soil JCO2. Results indicated that spring fire increased maximum monthly soil JCO2 by 20–55% relative to unburned tallgrass prairie, with greatest monthly differences measured in April (fourfold higher in burned sites). In burned sites that differed in fire history, maximum monthly JCO2 in annually burned prairie was 33% greater than in burned sites with a history of fire exclusion. Soil JCO2 in these latter sites was still significantly higher than in unburned sites. Soil JCO2 in sites grazed by bison was reduced by as much as 30% relative to adjacent ungrazed areas. Reduced root biomass and activity in grazed areas, unburned sites, and sites with a history of fire exclusion suggest that plants play a major role in determining soil JCO2 in this grassland. Soil temperature at 5 cm was related strongly to midday JCO2 in both annually burned sites (r2 = 0.58) and unburned sites (r2 = 0.71). In contrast, differences in soil moisture among sites, enhanced by comparing irrigated grassland to control areas, increased maximum monthly JCO2 by only 8%. Thus, soil temperature was the primary abiotic determinant of soil JCO2 during this study. Maximum monthly estimates of soil JCO2 in tallgrass prairie ranged from 10.3 μmol CO2·m−2·s−1 in unburned sites to 15.1 μmol·m−2·s−1 in annually burned irrigated sites, whereas annual estimates varied from 4.7 to 7.8 kg CO2/m2. Over the 2-yr period, spring fire increased estimated annual soil JCO2 by 38–51% relative to unburned sites, while irrigation increased annual soil JCO2 by 13%. These estimates for tallgrass prairie are much higher than those reported for most temperate ecosystems but are similar to estimates for tropical forests. Characteristics of undisturbed tallgrass prairie that may lead to high levels of soil JCO2 include: high above- and belowground productivity; a relatively high proportion of C stored belowground; levels of soil microbial biomass and activity that are among the highest in native ecosystems in the United States; and the lack of a single dominant factor such as temperature, moisture, or nutrient availability, that consistently limits biotic processes during the growing season. The sensitivity of soil JCO2 in tallgrass prairie to different land use practices (fire and grazing) suggests that it is critical to include these factors in the development of grassland C budgets, as well as in regional models that estimate biogeochemical responses to land use change.10afire1 aKnapp, Alan, K.1 aConard, S.L.1 aBlair, John, M. uhttp://knz.lternet.edu/content/determinants-soil-co2-flux-sub-humid-grassland-effect-fire-and-fire-history00640nas a2200169 4500008004100000245008500041210006900126260005100195300001300246653000900259100002000268700002000288700001900308700001700327700001800344856010800362 1998 eng d00aLong-term ecological consequences of varying fire frequency in a humid grassland0 aLongterm ecological consequences of varying fire frequency in a  aTallahassee, FLbTall Timbers Research Station a173 -17810afire1 aKnapp, Alan, K.1 aBlair, John, M.1 aBriggs, J., M.1 aPruden, T.L.1 aBrennan, L.A. uhttp://knz.lternet.edu/content/long-term-ecological-consequences-varying-fire-frequency-humid-grassland01416nas a2200181 4500008004100000245007800041210006900119300001300188490000800201520080000209653002201009100002401031700002001055700001901075700002001094700002001114856010001134 1998 eng d00aModulation of diversity by grazing and mowing in native tallgrass prairie0 aModulation of diversity by grazing and mowing in native tallgras a745 -7470 v2803 aSpecies diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically stressed grasslands enhanced biodiversity.10atallgrass prairie1 aCollins, Scott., L.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aBlair, John, M.1 aSteinauer, E.M. uhttp://knz.lternet.edu/content/modulation-diversity-grazing-and-mowing-native-tallgrass-prairie00742nas a2200205 4500008004100000245008500041210006900126260003800195300001300233653002200246100002000268700001900288700002000307700001700327700002000344700001900364700001900383700002400402856011000426 1998 eng d00aPatterns and controls of aboveground net primary production in tallgrass prairie0 aPatterns and controls of aboveground net primary production in t aNew YorkbOxford University Press a193 -22110atallgrass prairie1 aKnapp, Alan, K.1 aBriggs, J., M.1 aBlair, John, M.1 aTurner, C.L.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aHartnett, D.C.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/patterns-and-controls-aboveground-net-primary-production-tallgrass-prairie00666nas a2200205 4500008004100000245005400041210005400095260003800149300001300187653002200200100002000222700001900242700001700261700001800278700002000296700001900316700001900335700002400354856008200378 1998 eng d00aTerrestrial nutrient cycling in tallgrass prairie0 aTerrestrial nutrient cycling in tallgrass prairie aNew YorkbOxford University Press a222 -24310atallgrass prairie1 aBlair, John, M.1 aSeastedt, T.R.1 aRice, C., W.1 aRamundo, R.A.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aHartnett, D.C.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/terrestrial-nutrient-cycling-tallgrass-prairie02612nas a2200133 4500008004100000245010100041210006900142300001600211490000700227520209700234653000902331100002002340856011802360 1997 eng d00aFire, N availability and plant response in grasslands: A test of the transient maxima hypothesis0 aFire N availability and plant response in grasslands A test of t a2559 - 23680 v783 a

In tallgrass prairie, periodic spring fires often result in enhanced aboveground net primary productivity (ANPP) that exceeds the productivity of either annually burned or unburned sites. This study evaluated two alternate hypotheses for the “pulse” in productivity following an infrequent fire: (1) enhanced ANPP results from increased net N mineralization rates due to the removal of surface litter and elevated soil temperatures following fire (the enhanced mineralization hypothesis) or (2) enhanced ANPP results from a transient release from both light and N limitation during a nonequilibrium period as a switch from energy to N limitation occurs (the transient maxima hypothesis). The former hypothesis predicts greater N availability following an infrequent fire, relative to either annually burned or unburned prairie. The latter predicts that N availability following an infrequent fire will decline to intermediate levels, relative to unburned and annually burned prairie, and continue to decline with successive annual fires. To test these hypotheses, I measured inorganic soil N, net N mineralization rates, and plant productivity and N content at Konza Prairie in sites with several different burn histories (unburned, annually burned, infrequently burned). Inorganic soil N and cumulative net N mineralization rates were greatest on the unburned sites, lowest in annually burned sites, and intermediate in infrequently burned sites. Net N mineralization rates and plant tissue N content both declined with successive spring burning. These results did not support the enhanced mineralization hypothesis but indicated that enhanced ANPP following an infrequent fire resulted from an accumulation of inorganic and mineralizable N in the absence of fire which, under conditions of adequate light availability, was utilized following a spring fire. This is consistent with the transient maxima hypothesis and suggests that nonequilibrium responses to multiple, variable resources (light, energy, N) are an important aspect of tallgrass prairie ecosystem dynamics.

10afire1 aBlair, John, M. uhttp://knz.lternet.edu/content/fire-n-availability-and-plant-response-grasslands-test-transient-maxima-hypothesis02955nas a2200169 4500008004100000245009100041210006900132300001500201490000700216520235500223653002202578100001702600700002002617700001802637700001502655856011502670 1997 eng d00aSoil N and plant responses to fire, topography and supplemental N in tallgrass prairie0 aSoil N and plant responses to fire topography and supplemental N a1832 -18430 v783 aTallgrass prairie in the Flint Hills region of Kansas is characterized by considerable topographic relief coupled with variation in soil properties. These topoedaphic gradients, together with variation in fire regimes, result in temporal and landscape-level variability in soil resource availability and plant responses. Nitrogen usually is considered to be the nutrient most limiting to primary productivity in tallgrass prairie, but few studies have addressed how N availability varies seasonally, or across the landscape and with fire frequency. We measured soil inorganic N, in situ net N mineralization, aboveground net primary productivity (ANPP), and N mass on plots either fertilized with N in 1993 or in 1994, or unfertilized, in uplands and lowlands of two annually burned and two long-term unburned sites during the 1994 growing season. In addition, our study was conducted in the year following record rainfall, allowing us to assess the potential for high precipitation amounts to affect subsequent N cycling and plant production. Both fire treatment and topography affected soil N availability. In general, N mineralization was greater on unburned than on burned sites and was up to five times greater on uplands than lowlands. Total extractable soil N was highest early in the season and least at midseason, and it also tended to be higher in unburned sites than burned sites on unfertilized plots. Added N increased ANPP, but there were no differences between plots fertilized in 1994 and those fertilized in 1993. In general, patterns of ANPP on control plots were consistent with known production responses to topography and burning (higher in annually burned sites and in lowland sites) but were inversely related or unrelated to patterns of N availability (higher in unburned sites and at upland topographic positions). Potential loss of N by volatilization during spring burning was greater than in years with normal rainfall amounts and represented a significant portion of aboveground plant N mass. Potential N losses did not appear to limit ANPP or N availability in the current growing season. Our results suggest that different factors control soil N mineralization and plant productivity, which explains, in part, why patterns of ANPP are not well correlated with patterns of N availability in tallgrass prairie ecosystems.10atallgrass prairie1 aTurner, C.L.1 aBlair, John, M.1 aSchartz, R.J.1 aNeel, J.C. uhttp://knz.lternet.edu/content/soil-n-and-plant-responses-fire-topography-and-supplemental-n-tallgrass-prairie01455nas a2200169 4500008004100000245012000041210006900161300001500230520080800245653002201053100001101075700001901086700002001105700002001125700001801145856012201163 1996 eng d00aDetecting spatial and temporal patterns of aboveground production in a tallgrass prairie using remotely-sensed data0 aDetecting spatial and temporal patterns of aboveground productio a2361 -23653 aSpatial and temporal patterns of aboveground production in a tallgrass prairie ecosystem constitute one of the important spatial components associated with ecological processes and biophysical resources (e.g., water and nutrients). This study addresses the effects of disturbance, topography, and climate on the spatial and temporal patterns of North American tallgrass prairie at a landscape level by using high resolution satellite data. Spatial heterogeneity (SH) derived from the satellite data was related to the impacts of the disturbance of fire and grazing, topographical gradient, and amount of precipitation during the growing season. The result suggests that ecological processes and biophysical resources can be quantified with high resolution satellite data for tallgrass prairie management10atallgrass prairie1 aSu, H.1 aBriggs, J., M.1 aKnapp, Alan, K.1 aBlair, John, M.1 aKrummel, J.R. uhttp://knz.lternet.edu/content/detecting-spatial-and-temporal-patterns-aboveground-production-tallgrass-prairie-using02948nas a2200181 4500008004100000245011400041210006900155300001300224490000700237520227900244653002202523100001702545700001902562700001902581700002002600700001802620856012802638 1996 eng d00aFire and topographic effects on decomposition rates and nitrogen dynamics of buried wood in tallgrass prairie0 aFire and topographic effects on decomposition rates and nitrogen a323 -3290 v283 aDecay rates and N dynamics of wood in soils of annually burned and unburned tallgrass prairie were measured over a 3-y period. Wooden dowels were placed at upland, mid-slope and lowland sites in two annually burned and two unburned watersheds. After 3 y, an average of only 15% of initial wood mass remained in burned watersheds, while 34% remained in unburned watersheds. Topographic position also significantly affected decay rates, with dowels decaying faster in the shallow-soil, upland sites and slope sites than in the deep-soil, lowland sites. This pattern is opposite of that generally observed for plant productivity (i.e. greater at lowland sites compared to uplands), and suggests that the controls of belowground decomposition and plant productivity are dissimilar. Dowels in both burned and unburned watersheds showed significant increases in N concentration over 3 y. Topographic position did not affect N concentration in the residual dowel material. Burn treatment, however, did affect N concentration, with dowels decomposing in burned watersheds having a higher average N concentration (0.5% after 3 y exposure) than dowels in unburned watersheds (0.43%). Relatively rapid decay rates resulted in net release of N, despite increased N concentration in the residual material. Faster net N release on the annually burned watershed was due to faster mass loss, since there were no differences in the rate of increase in N concentration per unit mass lost. Surface soil temperatures on burned prairie following spring fire usually exceed those on unburned prairie. However, average monthly summer soil temperatures (May–August) at a 10 cm depth in burned and unburned plots during the study were not statistically different and could not explain decay rate differences. Additionally, one of our unburned watersheds was accidentally burned during the first year of the study. Surprisingly, there were no significant differences in rates of wood decay between that watershed and the other unburned watershed. This suggests that indirect effects of annual fire (i.e. changes in the composition of soil flora and fauna) may override the short-term effects of fire (i.e. changes in soil temperature and moisture) on belowground decomposition in tallgrass prairie.10atallgrass prairie1 aO'Lear, H.A.1 aSeastedt, T.R.1 aBriggs, J., M.1 aBlair, John, M.1 aRamundo, R.A. uhttp://knz.lternet.edu/content/fire-and-topographic-effects-decomposition-rates-and-nitrogen-dynamics-buried-wood-tallgrass02129nas a2200193 4500008004100000245005700041210005700098300001300155490000700168520154600175653002201721100001801743700002001761700001801781700002001799700001801819700001501837856008301852 1996 eng d00aNitrogen transport from tallgrass prairie watersheds0 aNitrogen transport from tallgrass prairie watersheds a973 -9810 v253 aDischarge and N content of surface water flowing from four Karst watersheds on Konza Prairie Research Natural Area, Kansas, managed with different burn frequencies, were monitored from 1986 to 1992. The goal was to establish the influence of natural processes (climate, fire, and bison grazing) on N transport and concentration in streams. Streams were characterized by variable flow, under conditions that included an extreme flood and a drought during which all channels were dry for over a year. The estimated groundwater/stream water discharge ratio varied between 0.15 to 6.41. Annual N transport by streams, averaged across all watersheds and years, was 0.16 kg N ha−1 yr−1. Annual N transport per unit area also increased as the watershed area increased and as precipitation increased. Total annual transport of N from the prairie via streams ranged from 0.01 to 6.0% of the N input from precipitation. Nitrate and total N concentrations in surface water decreased (P < 0.001, r values ranged from 0.14–0.26) as length of time since last fire increased. Increased watershed area was correlated negatively (P < 0.0001) to stream water concentrations of NO−3N and total N (r values = −0.43 and −0.20, respectively). Low N concentration is typical of these streams, with NH+4-N concentrations below 1.0 µg L−1, NO−3-N ranging from below 1.4 to 392 µg L−1, and total N from 3.0 to 714 µg L−1. These data provide an important baseline for evaluating N transport and stream water quality from unfertilized grasslands.10atallgrass prairie1 aDodds, W., K.1 aBlair, John, M.1 aHenebry, G.M.1 aKoelliker, J.K.1 aRamundo, R.A.1 aTate, C.M. uhttp://knz.lternet.edu/content/nitrogen-transport-tallgrass-prairie-watersheds00537nas a2200157 4500008004100000245005300041210005300094260005300147300001300200100002000213700001700233700001900250700001600269700001600285856007800301 1996 eng d00aSoil invertebrates as indicators of soil quality0 aSoil invertebrates as indicators of soil quality aMadison, WIbSoil Science Society of America Inc a283 -3011 aBlair, John, M.1 aBohlen, P.J.1 aFreckman, D.W.1 aDoran, J.W.1 aJones, A.J. uhttp://knz.lternet.edu/content/soil-invertebrates-indicators-soil-quality00478nas a2200145 4500008004100000245004800041210004800089260003600137300001300173100002000186700001900206700001600225700001800241856007300259 1995 eng d00aInfluences of earthworms on biogeochemistry0 aInfluences of earthworms on biogeochemistry bCRC Press Inc. Lewis Publishers a125 -1561 aBlair, John, M.1 aParmelee, R.W.1 aLavelle, P.1 aHendrix, P.F. uhttp://knz.lternet.edu/content/influences-earthworms-biogeochemistry02714nas a2200145 4500008004100000245009400041210006900135300001300204490000700217520216900224100001502393700002002408700001802428856012202446 1995 eng d00aUsing anion exchange membranes to measure soil nitrate availability and net nitrification0 aUsing anion exchange membranes to measure soil nitrate availabil a911 -9170 v273 aThere are few methods that provide adequate integrative measures of soil N availability to plants. We evaluated a new ion-exchange membrane (IEM) technique for measuring soil NO3 availability and nitrification by burying commercially-available anion-exchange membranes (IEMs) in a silt-loam Luvisol (fine, mixed, mesic Typic Fragiudalf) and in the same soil amended with either wheat straw, legume leaves or both materials. Soil was incubated in the laboratory for periods ranging from 1 to 27 days before removing the IEMs and determining membrane-bound NO3 and soil inorganic N concentrations. The soil amendments led to large differences in soil N dynamics and rates of net N mineralization and nitrification among treatments. In all soil treatments, rates of NO3N uptake by IEMs were rapid initially, but slowed after 7 days. On all dates, significantly less NO3N was recovered from IEMs in the amended soils than from those in the control soil, probably because of greater microbial immobilization of NO3 due to the added organic substrates. The IEMs did not act as infinite sinks for NO3, since under strongly N-immobilizing conditions in the wheat straw-amended soil membrane-bound NO3N declined between 3–14 days. Across all soil treatments and sampling dates, membrane-bound NO3N was significantly correlated with soil NO3N concentrations and net soil nitrification (r2 = 0.53 and 0.86, respectively), even when net nitrification was negative. Correlations improved when data from the initial membrane equilibration period (days 1 and 3) were excluded (r2 = 0.85 and 0.96, respectively). The presence of IEMs significantly reduced soil NO3N concentrations in 3 of the 4 soil treatments, and in all of the soil treatments, net soil nitrification and N mineralization were significantly greater in the presence of the IEMs. Results from our correlative study suggest that the IEM technique can be a useful tool for assessing soil nutrient availability and mineralization processes. However, more work is needed to develop this technique before reliable interpretations can be made under a wide variety of field and laboratory conditions.1 aSubler, S.1 aBlair, John, M.1 aEdwards, C.A. uhttp://knz.lternet.edu/content/using-anion-exchange-membranes-measure-soil-nitrate-availability-and-net-nitrification