02341nas a2200109 4500008004100000245010400041210006900145520190700214100002302121700002202144856006502166 2019 eng d00aHistorical drought affects microbial population dynamics and activity during soil drying and re-wet0 aHistorical drought affects microbial population dynamics and act3 a

A history of drought exposure promoted by variable precipitation regimes can select for drought-tolerant soil microbial taxa, but the mechanisms of survival and death of microbial populations through the selective stresses of soil drying and re-wet are not well understood. We subjected soils collected from a 15-year field drought experiment (“Altered” precipitation history with extended dry periods, versus the “Ambient” field control) to a laboratory drying/re-wetting experiment, to learn whether selective population survival, death, or maintenance of protein synthesis potential and microbial respiration through variable soil water conditions was affected by field drought legacy. Microbial community composition, as measured by Illumina MiSeq sequencing of the 16S rRNA and 16S rRNA gene, shifted with laboratory drying/re-wet and field drought treatments. In Ambient soils, there was a higher proportion of reduced OTU abundance (indicative of mortality) during re-wet, whereas Altered soils had a greater proportion of stable OTU populations that did not change in abundance (indicative of survival) through drying/re-wet. Altered soils also had a lower proportion of rRNA:rRNA genes (lower protein synthesis potential) during dry-down, a greater weighted mean rRNA operon number (potential growth rate and r-selection) which was associated with higher abundance of Firmicutes (order Bacillales), and lower average microbial respiration rates. These data demonstrate that soils with a weaker historical drought legacy exhibit a higher prevalence of microbial water-stress mortality and differential survival and death at OTU levels following short-term dryingand re-wetting, concurrent with higher carbon loss potential. This work provides novel insight into the mechanisms and consequences of soil microbial changes resulting from extended drought conditions.

1 aVeach, Allison, M.1 aZeglin, Lydia, H. uhttps://link.springer.com/article/10.1007/s00248-019-01432-501712nas 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%3Dihub03243nas a2200145 4500008004100000022001300041245013600054210006900190300001400259490000800273520268500281100002602966700002202992856008303014 2018 eng d a0038071700aLong-term fire management history affects N-fertilization sensitivity, but not seasonality, of grassland soil microbial communities0 aLongterm fire management history affects Nfertilization sensitiv a231 - 2390 v1213 a

Nitrogen (N) availability is a driver of soil microbial diversity and function, and is affected by prescribed burning (N removal through volatilization) and fertilization (N addition). Because soil microbes control critical feedbacks to ecosystem function, it is important to understand the dynamics and responses of microbial populations under conditions of contrasting N availability. This study took place at a long-term field manipulation in which native tallgrass prairie was annually burned or not burned, and annually fertilized or not fertilized, in a factorial design, since 1986. Composite surface soil samples (0–15 cm) were collected monthly between November 2014 and December 2015 from replicate plots to evaluate event-based (post-fire, post-fertilization), seasonal, and long-term responses of soil microbial communities to management and environmental changes. Bacterial 16S rRNA gene and fungal ITS population sizes were estimated using qPCR, and bacterial community composition (BCC) was measured using Illumina MiSeq sequencing of 16S rRNA genes. We expected seasonal and event-based change in all parameters, and that total microbial population sizes and diversity would be lower in soils with higher N availability, due to greater competitive dominance of nitrophilic or copiotrophic taxa. Bacterial and fungal population sizes varied significantly by sampling month, in that bacterial populations were approximately 10× greater in summer (June–August), but did not change in response to management events or long-term treatments. In contrast, very few individual taxonomic groups displayed seasonal or event-based responses, and there was no significant whole-community turnover on weekly or monthly time-scales; instead, BCC was strongly impacted by both the long-term fire and fertilization treatments. Specifically, there were increases and decreases in putatively "copiotrophic" and "oligotrophic" prokaryotic Phyla in response to long-term N fertilization, which were significantly stronger and more predictable in soils following long-term fire suppression. These results reveal that while long-term grassland management changes BCC beyond the detected range of seasonal variability, total bacterial populations change coherently month-to-month, potentially due to significant plant inputs of labile carbon during the growing season. Furthermore, because prescribed burning reduces soil N availability, the interactive responses to fire suppression plus fertilization suggest that higher background levels of soil N availability may increase the magnitude of soil microbial sensitivity to N fertilization.

1 aCarson, Christine, M.1 aZeglin, Lydia, H. uhttps://www.sciencedirect.com/science/article/pii/S0038071718301068?via%3Dihub00680nam a2200193 4500008004100000245009500041210006900136260001300205300001400218100002200232700001800254700002200272700002500294700002000319700001900339700002000358700002200378856008600400 2017 eng d00aThe biota of intermittent rivers and ephemeral streams: prokaryotes, fungi, and protozoans0 abiota of intermittent rivers and ephemeral streams prokaryotes f bElsevier a161 - 1881 aRomaní, Anna, M.1 aChauvet, Eric1 aFebria, Catherine1 aMora-Gómez, Juanita1 aRisse-Buhl, Ute1 aTimoner, Xisca1 aWeitere, Markus1 aZeglin, Lydia, H. uhttps://www.sciencedirect.com/science/article/pii/B9780128038352000097?via%3Dihub03014nas a2200301 4500008004100000245009900041210006900140300001400209490000700223520204700230100002402277700002402301700002002325700001802345700002202363700002702385700002502412700002402437700002002461700002102481700002602502700002202528700002702550700002602577700002502603700002202628856006202650 2017 eng d00aGlobal synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers0 aGlobal synthesis of the temperature sensitivity of leaf litter b a3064-30750 v233 a

Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (Ea, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which Ea could be calculated. Higher values of Ea were correlated with lower-quality litter, but these correlations were influenced by a single, N-fixing genus (Alnus). Ea values converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the Ea was 0.34 ± 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5–21% with a 1–4 °C rise in water temperature, rather than a 10–45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in Ea values for these regions (0.75 ± 0.13 eV and 0.27 ± 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that Ea values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.

1 aFollstad-Shah, J.J.1 aKominoski, John, S.1 aArdón, Marcelo1 aDodds, W., K.1 aGessner, Mark, O.1 aGriffiths, Natalie, A.1 aHawkins, Charles, P.1 aJohnson, Sherri, L.1 aLecerf, Antoine1 aLeRoy, Carri, J.1 aManning, David, W. P.1 aRosemond, Amy, D.1 aSinsabaugh, Robert, L.1 aSwan, Christopher, M.1 aWebster, Jackson, R.1 aZeglin, Lydia, H. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1360904404nas a2200193 4500008004100000245008100041210006900122260004300191490001400234520378900248653001604037653001404053653001504067653001304082653001804095100002204113700002204135856005304157 2017 eng d00aGrassland soil microbial responses to long-term management of N availability0 aGrassland soil microbial responses to longterm management of N a aManhattan, KSbKansas State University0 vMS Thesis3 a

Anthropogenic actions have significantly increased biological nitrogen (N) availability on a global scale. In tallgrass prairies, this phenomenon is exacerbated by land management changes, such as fire suppression. Historically, tallgrass prairie fire removed N through volatilization, but fire suppression has contributed to increased soil N availability as well as woody encroachment. Because soil microbes respond to N availability and plant growth, these changes may alter microbial composition and important microbially-mediated functions. Grassland management affects the soil environment on multiple time scales including short (fertilization or fire event), seasonal (growing vs. non-growing season), and long-term (decadal plant turnover and nutrient accumulation), therefore my goal was to understand community variability at different time scales affecting the population and community dynamics of soil microbes. I predicted soil microbes would be sensitive to environmental changes at all time scales, seasonal variation would reflect increased plant rhizodeposit-supported populations during summer and decomposers during winter, and long-term fire suppression and chronic fertilization would drive soil microbial community turnover associated with accumulation of plant litter and N.

To address these predictions, soils were collected from the Belowground Plot Experiment (BGPE) at Konza Prairie Biological Station: a 30-y factorial field manipulation of N fertilization and burning. Surface soils (0-15 cm) were sampled monthly between Nov 2014 – Dec 2015, including one week post-fire (April) and post-fertilization (June). Genomic DNA was extracted from each sample for qPCR and PCR for Illumina MiSeq library sequencing of the prokaryotic 16S rRNA gene and fungal ITS, to estimate population and community dynamics of soil microbes. Soil environmental characteristics and plant communities were measured in July 2015 to evaluate correlations between plant and microbial communities, and environmental variability.

Soil microbial responses to short-term fire/fertilization events were minimal, while microbial population sizes fluctuate seasonally and synchronously, and microbial community composition varied more with management history than at shorter time scales. Bacterial populations increased 10x during growing-season plant rhizodeposition, while fungal populations were less dynamic, but decreased in fall, possibly reflecting a shift to subsistence on soil organic matter. In contrast, microbial community composition was seasonally stable, but distinct between long-term management treatments, which may indicate accumulation of niche-defining plant or soil properties over decades. Prokaryotic communities responded to altered N availability via both fertilization and loss due to fire, with the highest abundance of "copiotrophic" (r-selected) taxa in unburned, fertilized soils. Fungal communities responded to N fertilization with higher abundance of arbuscular mycorrhizal fungi, pathogens, and saprotrophs, possibly due to changes in nutrient stoichiometry and litter availability in fertilized plots. However, fungal response to fire was largely independent of N availability, and plant community differences were correlated with fungal, but not bacterial, community composition, highlighting the likely nutritional codependence of fungi and plants, and fungal competitive advantages for plant litter substrates. The timing of changes in soil microbial communities is critical for plant nutrition and nutrient cycling in prairies, and this novel dataset on the temporal resolution of microbial responses to environmental variability contributes to the broader understanding of ecosystem responses to global change.

10aCommunities10agrassland10amanagement10anitrogen10aSoil microbes1 aCarson, Christine1 aZeglin, Lydia, H. uhttp://krex.k-state.edu/dspace/handle/2097/3622802618nas a2200181 4500008004100000245011100041210006900152260001600221490000600237520198000243653003702223653002102260653002402281653001102305653001202316100002202328856008602350 2015 eng d00aStream microbial diversity in response to environmental changes: review and synthesis of existing research0 aStream microbial diversity in response to environmental changes  cJun-05-20150 v63 aThe importance of microbial activity to ecosystem function in aquatic ecosystems is well established, but microbial diversity has been less frequently addressed. This review and synthesis of 100s of published studies on stream microbial diversity shows that factors known to drive ecosystem processes, such as nutrient availability, hydrology, metal contamination, contrasting land-use and temperature, also cause heterogeneity in bacterial diversity. Temporal heterogeneity in stream bacterial diversity was frequently observed, reflecting the dynamic nature of both stream ecosystems and microbial community composition. However, within-stream spatial differences in stream bacterial diversity were more commonly observed, driven specifically by different organic matter (OM) compartments. Bacterial phyla showed similar patterns in relative abundance with regard to compartment type across different streams. For example, surface water contained the highest relative abundance of Actinobacteria, while epilithon contained the highest relative abundance of Cyanobacteria and Bacteroidetes. This suggests that contrasting physical and/or nutritional habitats characterized by different stream OM compartment types may select for certain bacterial lineages. When comparing the prevalence of physicochemical effects on stream bacterial diversity, effects of changing metal concentrations were most, while effects of differences in nutrient concentrations were least frequently observed. This may indicate that although changing nutrient concentrations do tend to affect microbial diversity, other environmental factors are more likely to alter stream microbial diversity and function. The common observation of connections between ecosystem process drivers and microbial diversity suggests that microbial taxonomic turnover could mediate ecosystem-scale responses to changing environmental conditions, including both microbial habitat distribution and physicochemical factors.10aecosystem structure and function10alotic ecosystems10amicrobial diversity10arivers10astreams1 aZeglin, Lydia, H. uhttp://www.frontiersin.org/Aquatic_Microbiology/10.3389/fmicb.2015.00454/abstract03323nas a2200217 4500008004100000245012400041210006900165300001500234490000700249520261700256100002202873700002002895700001802915700001702933700001502950700001702965700001602982700001602998700001703014856007403031 2013 eng d00aAltered precipitation regime affects the function and composition of soil microbial communities on multiple time scales0 aAltered precipitation regime affects the function and compositio a2334 -23450 v943 a

Climate change models predict that future precipitation patterns will entail lower-frequency but larger rainfall events, increasing the duration of dry soil conditions. Resulting shifts in microbial C cycling activity could affect soil C storage. Further, microbial response to rainfall events may be constrained by the physiological or nutrient limitation stress of extended drought periods; thus seasonal or multiannual precipitation regimes may influence microbial activity following soil wet-up. We quantified rainfall-driven dynamics of microbial processes that affect soil C loss and retention, and microbial community composition, in soils from a long-term (14-year) field experiment contrasting “Ambient” and “Altered” (extended intervals between rainfalls) precipitation regimes. We collected soil before, the day following, and five days following 2.5-cm rainfall events during both moist and dry periods (June and September 2011; soil water potential = −0.01 and −0.83 MPa, respectively), and measured microbial respiration, microbial biomass, organic matter decomposition potential (extracellular enzyme activities), and microbial community composition (phospholipid fatty acids). The equivalent rainfall events caused equivalent microbial respiration responses in both treatments. In contrast, microbial biomass was higher and increased after rainfall in the Altered treatment soils only, thus microbial C use efficiency (CUE) was higher in Altered than Ambient treatments (0.70 ± 0.03 > 0.46 ± 0.10). CUE was also higher in dry (September) soils. C-acquiring enzyme activities (β-glucosidase, cellobiohydrolase, and phenol oxidase) increased after rainfall in moist (June), but not dry (September) soils. Both microbial biomass C:N ratios and fungal : bacterial ratios were higher at lower soil water contents, suggesting a functional and/or population-level shift in the microbiota at low soil water contents, and microbial community composition also differed following wet-up and between seasons and treatments. Overall, microbial activity may directly (C respiration) and indirectly (enzyme potential) reduce soil organic matter pools less in drier soils, and soil C sequestration potential (CUE) may be higher in soils with a history of extended dry periods between rainfall events. The implications include that soil C loss may be reduced or compensated for via different mechanisms at varying time scales, and that microbial taxa with better stress tolerance or growth efficiency may be associated with these functional shifts.

1 aZeglin, Lydia, H.1 aBottomley, P.J.1 aJumpponen, A.1 aRice, C., W.1 aArango, M.1 aLindsley, A.1 aMcGowan, A.1 aMfombep, P.1 aMyrold, D.D. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/12-2018.100790nas a2200241 4500008004100000245009700041210006900138300001000207490000800217100001800225700002200243700001400265700001600279700001400295700001600309700001700325700001600342700001600358700001700374700001500391700001700406856012500423 2013 eng d00aFungal community responses to discrete precipitation pulses under altered rainfall intervals0 aFungal community responses to discrete precipitation pulses unde a182 -0 v1031 aJumpponen, A.1 aZeglin, Lydia, H.1 aDavid, M.1 aPrestat, E.1 aBrown, S.1 aDvornik, J.1 aLothamer, K.1 aHettich, R.1 aJansson, J.1 aRice, C., W.1 aTringe, S.1 aMyrold, D.D. uhttp://knz.lternet.edu/content/fungal-community-responses-discrete-precipitation-pulses-under-altered-rainfall-intervals02203nas a2200385 4500008004100000245009000041210006900131300001300200490000600213520111200219100001701331700001601348700001601364700001901380700001901399700002101418700002001439700001901459700001701478700001901495700001701514700001801531700001801549700001701567700001901584700001801603700001901621700001701640700001501657700001701672700001701689700001801706700002201724856007101746 2011 eng d00aThinking outside the channel: modeling nitrogen cycling in networked river ecosystems0 aThinking outside the channel modeling nitrogen cycling in networ a229 -2380 v93 a

Agricultural and urban development alters nitrogen and other biogeochemical cycles in rivers worldwide. Because such biogeochemical processes cannot be measured empirically across whole river networks, simulation models are critical tools for understanding river-network biogeochemistry. However, limitations inherent in current models restrict our ability to simulate biogeochemical dynamics among diverse river networks. We illustrate these limitations using a river-network model to scale up in situ measures of nitrogen cycling in eight catchments spanning various geophysical and land-use conditions. Our model results provide evidence that catchment characteristics typically excluded from models may control river-network biogeochemistry. Based on our findings, we identify important components of a revised strategy for simulating biogeochemical dynamics in river networks, including approaches to modeling terrestrial–aquatic linkages, hydrologic exchanges between the channel, floodplain/riparian complex, and subsurface waters, and interactions between coupled biogeochemical cycles.

1 aHelton, A.M.1 aPoole, G.C.1 aMeyer, J.L.1 aWollheim, W.M.1 aPeterson, B.J.1 aMulholland, P.J.1 aBernhardt, E.S.1 aStanford, J.A.1 aArango, C.P.1 aAshkenas, L.R.1 aCooper, L.W.1 aDodds, W., K.1 aGregory, S.V.1 aO’Hall, R.1 aHamilton, S.K.1 aJohnson, S.L.1 aMcDowell, W.H.1 aPotter, J.D.1 aTank, J.L.1 aThomas, S.M.1 aValett, H.M.1 aWebster, J.R.1 aZeglin, Lydia, H. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/08021102677nas a2200181 4500008004100000245008700041210006900128300001300197490000800210520203100218653003402249653001602283100002202299700001702321700002102338700002402359856011202383 2007 eng d00aMicrobial responses to nitrogen addition in three contrasting grassland ecosystems0 aMicrobial responses to nitrogen addition in three contrasting gr a349 -3590 v1543 a

The effects of global N enrichment on soil processes in grassland ecosystems have received relatively little study. We assessed microbial community response to experimental increases in N availability by measuring extracellular enzyme activity (EEA) in soils from three grasslands with contrasting edaphic and climatic characteristics: a semiarid grassland at the Sevilleta National Wildlife Refuge, New Mexico, USA (SEV), and mesic grasslands at Konza Prairie, Kansas, USA (KNZ) and Ukulinga Research Farm, KwaZulu-Natal, South Africa (SAF). We hypothesized that, with N enrichment, soil microbial communities would increase C and P acquisition activity, decrease N acquisition activity, and reduce oxidative enzyme production (leading to recalcitrant soil organic matter [SOM] accumulation), and that the magnitude of response would decrease with soil age (due to higher stabilization of enzyme pools and P limitation of response). Cellulolytic activities followed the pattern predicted, increasing 35–52% in the youngest soil (SEV), 10–14% in the intermediate soil (KNZ) and remaining constant in the oldest soil (SAF). The magnitude of phosphatase response did not vary among sites. N acquisition activity response was driven by the enzyme closest to its pH optimum in each soil: i.e., leucine aminopeptidase in alkaline soil, β-N-acetylglucosaminidase in acidic soil. Oxidative enzyme activity varied widely across ecosystems, but did not decrease with N amendment at any site. Likewise, SOM and %C pools did not respond to N enrichment. Between-site variation in both soil properties and EEA exceeded any treatment response, and a large portion of EEA variability (leucine aminopeptidase and oxidative enzymes), 68% as shown by principal components analysis, was strongly related to soil pH (r = 0.91, P < 0.001). In these grassland ecosystems, soil microbial responses appear constrained by a molecular-scale (pH) edaphic factor, making potential breakdown rates of SOM resistant to N enrichment.

10aExtracellular enzyme activity10aSoil carbon1 aZeglin, Lydia, H.1 aStursova, M.1 aSinsabaugh, R.L.1 aCollins, Scott., L. uhttp://knz.lternet.edu/content/microbial-responses-nitrogen-addition-three-contrasting-grassland-ecosystems