03509nas a2200313 4500008004100000245008500041210006900126300001600195490000800211520253200219653000902751653001902760653003002779653001202809653002502821653002802846100003002874700002102904700002402925700002402949700002102973700002302994700002403017700001603041700002503057700002003082700001703102856007603119 2019 eng d00aShifts in plant functional composition following long-term drought in grasslands0 aShifts in plant functional composition following longterm drough a2133 - 21480 v1073 a

 1. Plant traits can provide unique insights into plant performance at the community scale. Functional composition, defined by both functional diversity and community-weighted trait means (CWMs), can affect the stability of above‐ground net primary production (ANPP) in response to climate extremes. Further complexity arises, however, when functional composition itself responds to environmental change. The duration of climate extremes, such as drought, is expected to increase with rising global temperatures; thus, understanding the impacts of long-term drought on functional composition and the corresponding effect that has on ecosystem function could improve predictions of ecosystem sensitivity to climate change.
 2. We experimentally reduced growing season precipitation by 66% across six temperate grasslands for 4 years and measured changes in three indices of functional diversity (functional dispersion, richness and evenness), community-weighted trait means and phylogenetic diversity (PD). Specific leaf area (SLA), leaf nitrogen content (LNC) and (at most sites) leaf turgor loss point (πTLP) were measured for species cumulatively representing ~90% plant cover at each site.
 3. Long-term drought led to increased community functional dispersion in three sites, with negligible effects on the remaining sites. Species re-ordering following the mortality/senescence of dominant species was the main driver of increased functional dispersion. The response of functional diversity was not consistently matched by changes in phylogenetic diversity. Community-level drought strategies (assessed as CWMs) largely shifted from drought tolerance to drought avoidance and/or escape strategies, as evidenced by higher community-weighted πTLP, SLA and LNC. Lastly, ecosystem drought sensitivity (i.e. relative reduction in ANPP in drought plots) was positively correlated with community-weighted SLA and negatively correlated with functional diversity.
 4. Synthesis. Increased functional diversity following long-term drought may stabilize ecosystem functioning in response to future drought. However, shifts in community-scale drought strategies may increase ecosystem drought sensitivity, depending on the nature and timing of drought. Thus, our results highlight the importance of considering both functional diversity and abundance‐weighted traits means of plant communities as their collective effect may either stabilize or enhance ecosystem sensitivity to drought.

10aANPP10aClimate change10acommunity weighted traits10aDrought10aFunctional diversity10aplant functional traits1 aGriffin-Nolan, Robert, J.1 aBlumenthal, D.M.1 aCollins, Scott., L.1 aFarkas, Timothy, E.1 aHoffman, Ava, M.1 aMueller, Kevin, E.1 aOcheltree, Troy, W.1 aSmith, M.D.1 aWhitney, Kenneth, D.1 aKnapp, Alan, K.1 aJones, Holly uhttps://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.1325202693nas a2200265 4500008004100000245008500041210006900126300001500195490000800210520191600218653000902134653002002143653001902163653000802182653002002190653001502210100002302225700002002248700001702268700001702285700001402302700002802316700001702344856006602361 2011 eng d00aLinking plant growth responses across topographic gradients in tallgrass prairie0 aLinking plant growth responses across topographic gradients in t a1131 -11420 v1663 a

Aboveground biomass in grasslands varies according to landscape gradients in resource availability and seasonal patterns of growth. Using a transect spanning a topographic gradient in annually burned ungrazed tallgrass prairie, we measured changes in the height of four abundant C4 grass species, LAI, biomass, and cumulative carbon flux using two closely located eddy flux towers. We hypothesized that seasonal patterns of plant growth would be similar across the gradient, but the magnitude of growth and biomass accumulation would vary by topographic position, reflecting spatial differences in microclimate, slope, elevation, and soil depth. Thus, identifying and measuring local growth responses according to topographic variability should significantly improve landscape predictions of aboveground biomass. For most of the growth variables measured, classifying topography into four positions best captured the inherent spatial variability. Biomass produced, seasonal LAI and species height increased from the upland and break positions to the slope and lowland. Similarly, cumulative carbon flux in 2008 was greater in lowland versus upland tower locations (difference of 64 g m−2 by DOY 272). Differences in growth by topographic position reflected increased production of flowering culms by Andropogon gerardii and Sorghastrum nutans in lowland. Varying growth responses by these species may be a significant driver of biomass and carbon flux differences by topographic position, at least for wet years. Using a digital elevation model to classify the watershed into topographic positions, we performed a geographically weighted regression to predict landscape biomass. The minimum and maximum predictions of aboveground biomass for this watershed had a large range (86–393 t per 40.4 ha), illustrating the drastic spatial variability in growth within this annually-burned grassland.

10aANPP10aEddy covariance10aFlux footprint10aLAI10aMesic grassland10atopography1 aNippert, Jesse, B.1 aOcheltree, T.W.1 aSkibbe, A.M.1 aKangas, L.C.1 aHam, J.M.1 aShonkwiler-Arnold, K.B.1 aBrunsell, N. uhttps://link.springer.com/article/10.1007%2Fs00442-011-1948-602607nas 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%2Fs10021-009-9273-102389nas a2200205 4500008004100000245011200041210006900153260004800222300001000270490001400280520168300294653000901977653000901986653001501995653001202010653001302022653001302035100001302048856012202061 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  aFort Collins, CObColorado State University a1 -500 vMS Thesis3 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. uhttp://knz.lternet.edu/content/controls-aboveground-net-primary-production-mesic-savanna-grasslands-inter-hemispheric02991nas a2200217 4500008004100000245009600041210006900137300001100206490000800217520225200225653000902477653001902486653001402505653003002519653001802549653002202567100002302589700002002612700001902632856012202651 2006 eng d00aIntra-annual rainfallvariability and grassland productivity: can the past predictthe future0 aIntraannual rainfallvariability and grassland productivity can t a65 -740 v1843 aPrecipitation quantity has been shown to influence grassland aboveground net primary productivity (ANPP) positively whereas experimental increases in of temporal variability in water availability commonly exhibit a negative relationship with ANPP. We evaluated long term ANPP datasets from the Konza Prairie Long Term Ecological Research (LTER) program (1984–1999) to determine if similar relationships could be identified based on patterns of natural variability (magnitude and timing) in precipitation. ANPP data were analyzed from annually burned sites in native mesic grassland and productivity was partitioned into graminoid (principally C4 grasses) and forb (C3 herbaceous) components. Although growing season precipitation amount was the best single predictor of total and grass ANPP (r 2=0.62), several measures of precipitation variability were also significantly and positively correlated with productivity, independent of precipitation amount. These included soil moisture variability, expressed as CV, for June (r 2=0.45) and the mean change in soil moisture between weekly sampling periods in June and August (%wv) (r 2=0.27 and 0.32). In contrast, no significant relationships were found between forb productivity and any of the precipitation variables (p>0.05). A multiple regression model combining precipitation amount and both measures of soil moisture variability substantially increased the fit with productivity (r 2=0.82). These results were not entirely consistent with those of short-term manipulative experiments in the same grassland, however, because soil moisture variability was often positively, not negatively related to ANPP. Differences in results between long and short term experiments may be due to low variability in the historic precipitation record compared to that imposed experimentally as experimental levels of variability exceeded the natural variability of this dataset by a factor of two. Thus, forecasts of ecosystem responses to climate change (i.e. increased climatic variability), based on data constrained by natural and recent historical rainfall patterns may be inadequate for assessing climate change scenarios if precipitation variability in the future is expected to exceed current levels.10aANPP10aClimate change10agrassland10aPrecipitation variability10asoil moisture10atallgrass prairie1 aNippert, Jesse, B.1 aKnapp, Alan, K.1 aBriggs, J., M. uhttp://knz.lternet.edu/content/intra-annual-rainfallvariability-and-grassland-productivity-can-past-predictthe-future02161nas a2200217 4500008004100000245006400041210006400105300001100169490000700180520151900187653000901706653002201715653001801737653001101755653002201766100001501788700001801803700001801821700001801839856008601857 2004 eng d00aInfluence of prey abundance on raptors in tallgrass prairie0 aInfluence of prey abundance on raptors in tallgrass prairie a23 -320 v363 a

We examined relationships between winter abundance of diurnal raptors (red-tailed hawk, Buteo jamaicensis; rough-legged hawk, B. lagopus; ferruginous hawk, B. regalis; and northern harrier, Circus cyaneus) and both the abundance of microtine rodents (prairie vole, Microtus ochrogaster; and southern bog lemming, Synaptomys cooperi) and aboveground net primary productivity (ANPP) in tallgrass prairie. We used Christmas Bird Count data for each year during 1975 through 1999 from Manhattan, Kansas to index winter raptor abundance (number of hawks per party hour). Microtine rodent abundance (average number of microtine rodents per trapline in burned and unburned prairie) was estimated by using long-term data gathered from autumn and spring surveys along 14 permanent traplines from autumn 1981 to spring 2000 in tallgrass prairie on the Konza Prairie Biological Station. An estimate of ANPP for each year during 1975 through 1999 was provided by the Konza Prairie Long-Term Ecological Research Program. Winter raptor abundance was related positively to ANPP during the preceding growing season (P = 0.01) and to microtine abundance in the previous spring (P = 0.03). Based on a stepwise regression, 39% of the annual variation in winter raptor counts was explained by ANPP and the log of spring microtine abundance. Overall, our analyses suggested that winter raptor abundance was higher in years with higher than lower prey availability, but that other factors also influenced winter raptor abundance.

10aANPP10amicrotine rodents10apredator-prey10araptor10atallgrass prairie1 aReed, A.W.1 aKaufman, G.A.1 aRintoul, D.A.1 aKaufman, D.W. uhttp://knz.lternet.edu/content/influence-prey-abundance-raptors-tallgrass-prairie02373nas a2200265 4500008004100000245010300041210006900144300001300213490000700226520149600233653002101729653000901750653003001759653002701789653001801816653001901834653001801853653002301871100001801894700001901912700001501931700001601946700002001962856012501982 2002 eng d00aInfluence of climate variability on plant production and N-mineralization in Central US grasslands0 aInfluence of climate variability on plant production and Nminera a383 -3940 v133 aWe assessed the influence of annual and seasonal climate variability over soil organic matter (SOM), above-ground net primary production (ANPP) and in situ net nitrogen (N) mineralization in a regional field study across the International Geosphere Biosphere Programme (IGBP) North American mid-latitude transect (Koch et al. 1995). We hypothesized that while trends in SOM are strongly correlated with mean climatic parameters, ANPP and net N-mineralization are more strongly influenced by annual and seasonal climate because they are dynamic processes sensitive to short-term variation in temperature and water availability. Seasonal and monthly deviations from long-term climatic means, particularly precipitation, were greatest at the semi-arid end of the transect. ANPP is sensitive to this climatic variability, but is also strongly correlated with mean annual climate parameters. In situ net N-mineralization and nitrification were weakly influenced by soil water content and temperature during the incubation and were less sensitive to seasonal climatic variables than ANPP, probably because microbial transformations of N in the soil are mediated over even finer temporal scales. We found no relationship between ANPP and in situ net N-mineralization. These results suggests that methods used to estimate in situ net N-mineralization are inadequate to represent N-availability across gradients where microbial biomass, N-immobilization or competition among plants and microbes vary.10aAnnual variation10aANPP10aCentral Grasslands region10aEnvironmental gradient10aIGBP Transect10aMineralization10aNitrogen flux10aSeasonal variation1 aBarrett, J.E.1 aMcCulley, R.L.1 aLane, D.R.1 aBurke, I.C.1 aLauenroth, W.K. uhttp://knz.lternet.edu/content/influence-climate-variability-plant-production-and-n-mineralization-central-us-grasslands