01111nas a2200373 4500008004100000022001400041245012600055210007100181300001600252490000700268100001700275700001700292700001700309700002200326700001700348700001800365700001900383700002100402700002000423700001800443700001900461700001900480700001700499700001800516700001400534700001700548700001700565700002300582700001800605700002000623700001800643700001800661856005800679 2023 eng d a1354-101300aAccounting for herbaceous communities in process‐based models will advance our understanding of “grassy” ecosystems0 aAccounting for herbaceous communities in process‐based models wi a6453 - 64770 v291 aWilcox, K.R.1 aChen, Anping1 aAvolio, M.L.1 aButler, Ethan, E.1 aCollins, S.L1 aFisher, Rosie1 aKeenan, Trevor1 aKiang, Nancy, Y.1 aKnapp, Alan, K.1 aKoerner, S.E.1 aKueppers, Lara1 aLiang, Guopeng1 aLieungh, Eva1 aLoik, Michael1 aLuo, Yiqi1 aPoulter, Ben1 aReich, Peter1 aRenwick, Katherine1 aSmith, M., D.1 aWalker, Anthony1 aWeng, Ensheng1 aKomatsu, K.J. uhttps://onlinelibrary.wiley.com/doi/10.1111/gcb.1695000607nas a2200181 4500008004100000245011700041210006900158300001600227490000700243100001700250700001700267700002000284700002100304700001500325700001800340700001400358856005300372 2023 eng d00aAssessing carbon storage capacity and saturation across six central US grasslands using data–model integration0 aAssessing carbon storage capacity and saturation across six cent a2707 - 27250 v201 aWilcox, K.R.1 aCollins, S.L1 aKnapp, Alan, K.1 aPockman, William1 aShi, Zheng1 aSmith, M., D.1 aLuo, Yiqi uhttps://bg.copernicus.org/articles/20/2707/2023/01036nas a2200337 4500008004100000022001400041245009300055210007100148300001000219490000800229100001800237700001700255700001700272700001700289700002600306700002300332700001800355700001800373700002400391700002000415700002100435700001900456700001900475700001900494700002000513700002600533700002900559700002400588700001700612856006900629 2022 eng d a0012-965800aDo trade‐offs govern plant species’ responses to different global change treatments?0 aDo trade‐offs govern plant species responses to different global ae36260 v1031 aLangley, Adam1 aGrman, Emily1 aWilcox, K.R.1 aAvolio, M.L.1 aKomatsu, Kimberly, J.1 aCollins, Scott, L.1 aKoerner, S.E.1 aSmith, M., D.1 aBaldwin, Andrew, H.1 aBowman, William1 aChiariello, Nona1 aEskelinen, Anu1 aHarmens, Harry1 aHovenden, Mark1 aKlanderud, Kari1 aMcCulley, Rebecca, L.1 aOnipchenko, Vladimir, G.1 aRobinson, Clare, H.1 aSuding, K.N. uhttps://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.362601017nas a2200337 4500008004100000245008200041210006900123300001000192490000700202100001700209700002600226700001800252700001700270700001900287700002300306700001700329700002200346700002400368700002400392700002400416700002200440700001900462700002300481700001200504700002400516700002100540700001600561700001400577700001800591856007000609 2022 eng d00aMaking sense of multivariate community responses in global change experiments0 aMaking sense of multivariate community responses in global chang ae42490 v131 aAvolio, M.L.1 aKomatsu, Kimberly, J.1 aKoerner, S.E.1 aGrman, Emily1 aIsbell, Forest1 aJohnson, David, S.1 aWilcox, K.R.1 aAlatalo, Juha, M.1 aBaldwin, Andrew, H.1 aBeierkuhnlein, Carl1 aBritton, Andrea, J.1 aFoster, Bryan, L.1 aHarmens, Harry1 aKern, Christel, C.1 aLi, Wei1 aMcLaren, Jennie, R.1 aReich, Peter, B.1 aSouza, Lara1 aYu, Qiang1 aZhang, Yunhai uhttps://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.424900874nas a2200277 4500008004100000245012500041210006900166300001000235490000700245100002000252700002100272700002200293700002000315700001400335700002300349700001600372700001800388700001500406700001600421700001600437700001900453700001700472700001700489700001600506856007400522 2022 eng d00aN and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry0 aN and P constrain C in ecosystems under climate change role of n ae26840 v321 aRastetter, E.B.1 aKwiakowski, B.L.1 aKicklighter, D.W.1 aPlotkin, Barker1 aGenet, H.1 aNippert, Jesse, B.1 aO'Keefe, K.1 aPerakis, S.R.1 aPorder, S.1 aRoley, S.S.1 aReuss, R.W.1 aThompson, J.R.1 aWieder, W.R.1 aWilcox, K.R.1 aYanai, R.D. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/eap.268402163nas 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.
Univariate and multivariate methods are commonly used to explore the spatial and temporaldynamics of ecological communities, but each has limitations, including oversimplification or abstractionof communities. Rank abundance curves (RACs) potentially integrate these existing methodologies bydetailing species-level community changes. Here, we had three goals:first, to simplify analysis of commu-nity dynamics by developing a coordinated set of R functions, and second, to demystify the relationshipsamong univariate, multivariate, and RACs measures, and examine how each is influenced by the commu-nity parameters as well as data collection methods. We developed new functions for studying temporalchanges and spatial differences in RACs in an update to the R package library(“codyn”), alongside othernew functions to calculate univariate and multivariate measures of community dynamics. We also devel-oped a new approach to studying changes in the shape of RAC curves. The R package update presentedhere increases the accessibility of univariate and multivariate measures of community change over timeand difference over space. Next, we use simulated and real data to assess the RAC and multivariate mea-sures that are output from our new functions, studying (1) if they are influenced by species richness andevenness, temporal turnover, and spatial variability and (2) how the measures are related to each other.Lastly, we explore the use of the measures with an example from a long-term nutrient addition experiment.Wefind that the RAC and multivariate measures are not sensitive to species richness and evenness andthat all the measures detail unique aspects of temporal change or spatial differences. We alsofind that spe-cies reordering is the strongest correlate of a multivariate measure of compositional change and explainsmost community change observed in long-term nutrient addition experiment. Overall, we show that spe-cies reordering is potentially an understudied determinant of community changes over time or differencesbetween treatments. The functions developed here should enhance the use of RACs to further explore thedynamics of ecological communities.
1 aAvolio, M.L.1 aCarroll, I.1 aCollins, Scott., L.1 aHouseman, Gregory, R.1 aHallett, L.M.1 aIsbell, F.L.1 aKoerner, S.E.1 aKomatsu, Kimberly, J.1 aSmith, M.D.1 aWilcox, K.R. uhttps://esajournals.onlinelibrary.wiley.com/doi/epdf/10.1002/ecs2.288104634nas 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 aGlobal 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/2019/08/14/181902711602830nas a2200409 4500008004100000245011100041210006900152300001600221490000700237520170300244653001701947653001301964653001501977653002001992653001202012653001002024100001602034700001802050700002802068700001702096700001702113700001602130700001502146700001702161700001502178700001702193700002002210700001802230700001502248700001802263700001502281700001402296700001602310700001702326700001502343856006202358 2018 eng d00aAmbient changes exceed treatment effects on plant species abundance in long-term global change experiments0 aAmbient changes exceed treatment effects on plant species abunda a5668 - 56790 v243 aThe responses of species to environmental changes will determine future community composition and ecosystem function. Many syntheses of global change experiments examine the magnitude of treatment effect sizes, but we lack an understanding of how plant responses to treatments compare to ongoing changes in the unmanipulated (ambient or background) system. We used a database of long-term global change studies manipulating CO2 , nutrients, water, and temperature to answer three questions: (a) How do changes in plant species abundance in ambient plots relate to those in treated plots? (b) How does the magnitude of ambient change in species-level abundance over time relate to responsiveness to global change treatments? (c) Does the direction of species-level responses to global change treatments differ from the direction of ambient change? We estimated temporal trends in plant abundance for 791 plant species in ambient and treated plots across 16 long-term global change experiments yielding 2,116 experiment-species-treatment combinations. Surprisingly, for most species (57%) the magnitude of ambient change was greater than the magnitude of treatment effects. However, the direction of ambient change, whether a species was increasing or decreasing in abundance under ambient conditions, had no bearing on the direction of treatment effects. Although ambient communities are inherently dynamic, there is now widespread evidence that anthropogenic drivers are directionally altering plant communities in many ecosystems. Thus, global change treatment effects must be interpreted in the context of plant species trajectories that are likely driven by ongoing environmental changes.
10aelevated CO210anitrogen10aPhosphorus10aplant community10aWarming10awater1 aLangley, A.1 aChapman, S.K.1 aLa Pierre, Kimberly, J.1 aAvolio, M.L.1 aBowman, W.D.1 aJohnson, D.1 aIsbell, F.1 aWilcox, K.R.1 aFoster, B.1 aHovenden, M.1 aKnapp, Alan, K.1 aKoerner, S.E.1 aLortie, C.1 aMegonigal, J.1 aNewton, P.1 aReich, B.1 aSmith, M.D.1 aSuttle, B.K.1 aTilman, D. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1444204101nas a2200613 4500008004100000245014300041210006900184300001600253490000700269520236400276100001602640700002002656700001902676700002002695700001702715700001802732700001602750700001602766700002002782700002402802700001202826700001602838700001702854700001802871700001702889700001702906700002602923700002202949700001902971700002102990700002203011700002103033700001703054700001903071700001503090700002303105700002703128700002003155700002103175700001803196700002103214700001803235700001503253700001803268700002203286700002503308700001903333700001803352700001903370700001403389700001703403700001803420856004903438 2018 eng d00aAsymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites0 aAsymmetric responses of primary productivity to altered precipit a3421 - 34370 v153 aField measurements of aboveground net primary productivity (ANPP) in temperate grasslands suggest that both positive and negative asymmetric responses to changes in precipitation (P) may occur. Under normal range of precipitation variability, wet years typically result in ANPP gains being larger than ANPP declines in dry years (positive asymmetry), whereas increases in ANPP are lower in magnitude in extreme wet years compared to reductions during extreme drought (negative asymmetry). Whether the current generation of ecosystem models with a coupled carbon–water system in grasslands are capable of simulating these asymmetric ANPP responses is an unresolved question. In this study, we evaluated the simulated responses of temperate grassland primary productivity to scenarios of altered precipitation with 14 ecosystem models at three sites: Shortgrass steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a rainfall gradient from dry to moist. We found that (1) the spatial slopes derived from modeled primary productivity and precipitation across sites were steeper than the temporal slopes obtained from inter-annual variations, which was consistent with empirical data; (2) the asymmetry of the responses of modeled primary productivity under normal inter-annual precipitation variability differed among models, and the mean of the model ensemble suggested a negative asymmetry across the three sites, which was contrary to empirical evidence based on filed observations; (3) the mean sensitivity of modeled productivity to rainfall suggested greater negative response with reduced precipitation than positive response to an increased precipitation under extreme conditions at the three sites; and (4) gross primary productivity (GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground NPP (BNPP) all showed concave-down nonlinear responses to altered precipitation in all the models, but with different curvatures and mean values. Our results indicated that most models overestimate the negative drought effects and/or underestimate the positive effects of increased precipitation on primary productivity under normal climate conditions, highlighting the need for improving eco-hydrological processes in those models in the future.
1 aWu, Donghai1 aCiais, Philippe1 aViovy, Nicolas1 aKnapp, Alan, K.1 aWilcox, K.R.1 aBahn, Michael1 aSmith, M.D.1 aVicca, Sara1 aFatichi, Simone1 aZscheischler, Jakob1 aHe, Yue1 aLi, Xiangyi1 aIto, Akihiko1 aArneth, Almut1 aHarper, Anna1 aUkkola, Anna1 aPaschalis, Athanasios1 aPoulter, Benjamin1 aPeng, Changhui1 aRicciuto, Daniel1 aReinthaler, David1 aChen, Guangsheng1 aTian, Hanqin1 aGenet, élène1 aMao, Jiafu1 aIngrisch, Johannes1 aNabel, Julia, E. S. M.1 aPongratz, Julia1 aBoysen, Lena, R.1 aKautz, Markus1 aSchmitt, Michael1 aMeir, Patrick1 aZhu, Qiuan1 aHasibeder, R.1 aSippel, Sebastian1 aDangal, Shree, R. S.1 aSitch, Stephen1 aShi, Xiaoying1 aWang, Yingping1 aLuo, Yiqi1 aLiu, Yongwen1 aPiao, Shilong uhttps://www.biogeosciences.net/15/3421/2018/00968nas a2200169 4500008004100000245010500041210006900146300001400215490000700229520040300236100001600639700001700655700002100672700002200693700002000715856006300735 2017 eng d00aAssessing community and ecosystem sensitivity to climate change - toward a more comparative approach0 aAssessing community and ecosystem sensitivity to climate change a235 - 2370 v283 aPlant communities can vary widely in their sensitivity to changing precipitation regimes, as reported by Byrne et al., Mulhouse et al. and Sternberg et al. in this issue of Journal of Vegetation Science. But to understand why communities differ in their sensitivity, we argue that clearly defined metrics of sensitivity and coordinated research approaches are needed to elucidate mechanisms.
1 aSmith, M.D.1 aWilcox, K.R.1 aPower, Sally, A.1 aTissue, David, T.1 aKnapp, Alan, K. uhttps://onlinelibrary.wiley.com/doi/full/10.1111/jvs.1252403566nas a2200421 4500008004100000245014000041210006900181260001400250490000700264520229900271100001702570700001502587700002702602700002402629700002302653700002202676700001702698700002102715700001802736700002402754700001702778700002102795700001602816700001702832700002002849700001902869700001702888700002702905700002102932700002502953700001602978700001802994700002303012700002003035700001303055700001403068856006203082 2017 eng d00aAsymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments0 aAsymmetric responses of primary productivity to precipitation ex c4376-43850 v233 aClimatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.
1 aWilcox, K.R.1 aShi, Zheng1 aGherardi, Laureano, A.1 aLemoine, Nathan, P.1 aKoerner, Sally, E.1 aHoover, David, L.1 aBork, Edward1 aByrne, Kerry, M.1 aCahill, James1 aCollins, Scott., L.1 aEvans, Sarah1 aGilgen, Anna, K.1 aHolub, Petr1 aJiang, Lifen1 aKnapp, Alan, K.1 aLeCain, Daniel1 aLiang, Junyi1 aGarcia-Palacios, Pablo1 aPeñuelas, Josep1 aPockman, William, T.1 aSmith, M.D.1 aSun, Shanghua1 aWhite, Shannon, R.1 aYahdjian, Laura1 aZhu, Kai1 aLuo, Yiqi uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1370603310nas a2200733 4500008004100000245008800041210006900129520119600198653002001394653002201414653001901436653001701455653002001472653001501492653002201507653002501529653002201554100001701576700002701593700002301620700001701643700002401660700001701684700002801701700002601729700001901755700002701774700002201801700002401823700002101847700002801868700001701896700002401913700002201937700002401959700001101983700001901994700001702013700001802030700001902048700002002067700002002087700002202107700001402129700002402143700002302167700002502190700001902215700002002234700002402254700002202278700001602300700003202316700001602348700001802364700002302382700001502405700002002420700001402440700001902454700001802473700002302491856006202514 2017 eng d00aAsynchrony among local communities stabilises ecosystem function of metacommunities0 aAsynchrony among local communities stabilises ecosystem function3 aTemporal stability of ecosystem functioning increases the predictability and reliability of ecosystem services, and understanding the drivers of stability across spatial scales is important for land management and policy decisions. We used species-level abundance data from 62 plant communities across five continents to assess mechanisms of temporal stability across spatial scales. We assessed how asynchrony (i.e. different units responding dissimilarly through time) of species and local communities stabilised metacommunity ecosystem function. Asynchrony of species increased stability of local communities, and asynchrony among local communities enhanced metacommunity stability by a wide range of magnitudes (1–315%); this range was positively correlated with the size of the metacommunity. Additionally, asynchronous responses among local communities were linked with species’ populations fluctuating asynchronously across space, perhaps stemming from physical and/or competitive differences among local communities. Accordingly, we suggest spatial heterogeneity should be a major focus for maintaining the stability of ecosystem services at larger spatial scales.
10aAlpha diversity10aalpha variability10abeta diversity10aBiodiversity10aCoRRE data base10apatchiness10aPlant communities10aPrimary productivity10aspecies synchrony1 aWilcox, K.R.1 aTredennick, Andrew, T.1 aKoerner, Sally, E.1 aGrman, Emily1 aHallett, Lauren, M.1 aAvolio, M.L.1 aLa Pierre, Kimberly, J.1 aHouseman, Gregory, R.1 aIsbell, Forest1 aJohnson, David, Samuel1 aAlatalo, Juha, M.1 aBaldwin, Andrew, H.1 aBork, Edward, W.1 aBoughton, Elizabeth, H.1 aBowman, W.D.1 aBritton, Andrea, J.1 aCahill, James, F.1 aCollins, Scott., L.1 aDu, G.1 aEskelinen, Anu1 aGough, Laura1 aJentsch, Anke1 aKern, Christel1 aKlanderud, Kari1 aKnapp, Alan, K.1 aKreyling, Juergen1 aLuo, Yiqi1 aMcLaren, Jennie, R.1 aMegonigal, Patrick1 aOnipchenko, Vladimir1 aPrevéy, Janet1 aPrice, Jodi, N.1 aRobinson, Clare, H.1 aSala, Osvaldo, E.1 aSmith, M.D.1 aSoudzilovskaia, Nadejda, A.1 aSouza, Lara1 aTilman, David1 aWhite, Shannon, R.1 aXu, Zhuwen1 aYahdjian, Laura1 aYu, Qiang1 aZhang, Pengfei1 aZhang, Yunhai1 aGurevitch, Jessica uhttp://onlinelibrary.wiley.com/doi/10.1111/ele.12861/epdf02040nas 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 aCentral 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/10.1890/15-1437.103182nas a2200181 4500008004100000245012000041210006900161300001400230490000800244520254700252100001802799700001702817700002802834700001702862700001602879700002402895856008102919 2016 eng d00aNutrient additions cause divergence of tallgrass prairie plant communities resulting in loss of ecosystem stability0 aNutrient additions cause divergence of tallgrass prairie plant c a1478-14870 v1043 a1.Nitrogen (N) and phosphorus (P) deposition due to pollution and land-use change are dramatically altering biogeochemical cycles. These altered nutrient inputs affect plant communities by generally increasing dominance and reducing diversity, as well as altering community variability (heterogeneity). Less well studied are effects of changes in community variability on ecosystem functions, such as productivity, or the stability of those functions. 2.Here we use a twelve-year nutrient addition experiment in tallgrass prairie to determine variability in community responses to N and P additions and link these responses to ecosystem productivity and stability. We added two levels of N and four levels of P in a fully factorial design to 25-m2 plots in native tallgrass prairie in northeastern Kansas, USA. Each year percent cover of each species was measured in June and August in a 1-m2 subplot of each plot, and annual net primary productivity was measured in two 0.1-m2 subplots in each plot at the end of each growing season. 3.The addition of N and P together increased plant community variability across space (i.e., the replicates were significantly more different from each other in the N + P treatments than they were in the control treatment). We also found that variability of the plant community within a single plot through time increased with the addition of N alone and N and P together. The highest level of both spatial and temporal variability occurred in plots with the highest level of nutrient addition (10 g m−2 of both N and P). 4.While we found no linkage between spatial variability of community composition and the spatial stability of productivity, the temporal stability of productivity decreased with increasing temporal plant community variability. Additionally, the ability to predict the productivity response to growing season precipitation, a key environmental variable, also decreased under higher temporal community variability. 5.Synthesis. Using a 12-yr nutrient addition experiment, we found that nutrient addition leads to both spatial and temporal community variability in mesic tallgrass prairie. The changes in community variability through time were directly related to ecosystem stability. While overall shifts in community structure in response to nutrient additions are important, the change in variability of local communities has significant implications for our ability to predict how patterns of biodiversity and ecosystem function will respond to a rapidly changing world.
1 aKoerner, S.E.1 aAvolio, M.L.1 aLa Pierre, Kimberly, J.1 aWilcox, K.R.1 aSmith, M.D.1 aCollins, Scott., L. uhttps://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.1261002102nas 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 aFire 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 aGlobal 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/10.1002/2016JG00337000428nas a2200121 4500008004100000245005300041210005300094260004800147490002200195100001700217700002000234856005200254 2015 eng d00aAssessing grassland sensitivity to global change0 aAssessing grassland sensitivity to global change aFort Collins, CObColorado State University0 vPhD. Dissertation1 aWilcox, K.R.1 aKnapp, Alan, K. uhttps://mountainscholar.org/handle/10217/16714702723nas a2200241 4500008004100000245013000041210006900171300001500240490000700255520196000262653002202222100002002244700001702264700001702281700001702298700001802315700002802333700001502361700001202376700001502388700001602403856006202419 2015 eng d00aCharacterizing differences in precipitation regimes of extreme wet and dry years: Implications for climate change experiments0 aCharacterizing differences in precipitation regimes of extreme w a2624 -26330 v213 aClimate change is intensifying the hydrologic cycle and is expected to increase the frequency of extreme wet and dry years. Beyond precipitation amount, extreme wet and dry years may differ in other ways, such as the number of precipitation events, event size, and the time between events. We assessed 1614 long-term (100 year) precipitation records from around the world to identify key attributes of precipitation regimes, besides amount, that distinguish statistically extreme wet from extreme dry years. In general, in regions where mean annual precipitation (MAP) exceeded 1000 mm, precipitation amounts in extreme wet and dry years differed from average years by ~40% and 30%, respectively. The magnitude of these deviations increased to >60% for dry years and to >150% for wet years in arid regions (MAP<500 mm). Extreme wet years were primarily distinguished from average and extreme dry years by the presence of multiple extreme (large) daily precipitation events (events >99th percentile of all events); these occurred twice as often in extreme wet years compared to average years. In contrast, these large precipitation events were rare in extreme dry years. Less important for distinguishing extreme wet from dry years were mean event size and frequency, or the number of dry days between events. However, extreme dry years were distinguished from average years by an increase in the number of dry days between events. These precipitation regime attributes consistently differed between extreme wet and dry years across 12 major terrestrial ecoregions from around the world, from deserts to the tropics. Thus, we recommend that climate change experiments and model simulations incorporate these differences in key precipitation regime attributes, as well as amount into treatments. This will allow experiments to more realistically simulate extreme precipitation years and more accurately assess the ecological consequences.
10arainfall patterns1 aKnapp, Alan, K.1 aHoover, D.L.1 aWilcox, K.R.1 aAvolio, M.L.1 aKoerner, S.E.1 aLa Pierre, Kimberly, J.1 aLoik, M.E.1 aLuo, Y.1 aSala, O.E.1 aSmith, M.D. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1288802659nas a2200169 4500008004100000245011200041210006900153300001300222490000700235520209000242100001702332700002202349700001702371700001902388700002002407856006202427 2015 eng d00aContrasting above- and belowground sensitivity of three Great Plains grasslands to altered rainfall regimes0 aContrasting above and belowground sensitivity of three Great Pla a335 -3440 v213 aIntensification of the global hydrological cycle with atmospheric warming is expected to increase interannual variation in precipitation amount and the frequency of extreme precipitation events. Although studies in grasslands have shown sensitivity of aboveground net primary productivity (ANPP) to both precipitation amount and event size, we lack equivalent knowledge for responses of belowground net primary productivity (BNPP) and NPP. We conducted a 2-year experiment in three US Great Plains grasslands – the C4-dominated shortgrass prairie (SGP; low ANPP) and tallgrass prairie (TGP; high ANPP), and the C3-dominated northern mixed grass prairie (NMP; intermediate ANPP) – to test three predictions: (i) both ANPP and BNPP responses to increased precipitation amount would vary inversely with mean annual precipitation (MAP) and site productivity; (ii) increased numbers of extreme rainfall events during high-rainfall years would affect high and low MAP sites differently; and (iii) responses belowground would mirror those aboveground. We increased growing season precipitation by as much as 50% by augmenting natural rainfall via (i) many (11–13) small or (ii) fewer (3–5) large watering events, with the latter coinciding with naturally occurring large storms. Both ANPP and BNPP increased with water addition in the two C4 grasslands, with greater ANPP sensitivity in TGP, but greater BNPP and NPP sensitivity in SGP. ANPP and BNPP did not respond to any rainfall manipulations in the C3-dominated NMP. Consistent with previous studies, fewer larger (extreme) rainfall events increased ANPP relative to many small events in SGP, but event size had no effect in TGP. Neither system responded consistently above- and belowground to event size; consequently, total NPP was insensitive to event size. The diversity of responses observed in these three grassland types underscores the challenge of predicting responses relevant to C cycling to forecast changes in precipitation regimes even within relatively homogeneous biomes such as grasslands.
1 aWilcox, K.R.1 aVon Fischer, J.C.1 aMuscha, J.M.1 aPetersen, M.K.1 aKnapp, Alan, K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1267301709nas a2200193 4500008004100000245011500041210006900156260001200225300000900237490000700246520108400253100001101337700001701348700002801365700002001393700001201413700001601425856007401441 2015 eng d00aStoichiometric homeostasis predicts plant species dominance, temporal stability and responses to global change0 aStoichiometric homeostasis predicts plant species dominance temp c09/2015 a23350 v963 aWhy some species are consistently more abundant than others, and predicting how species will respond to global change, are fundamental questions in ecology. Long-term observations indicate that plant species with high stoichiometric homeostasis for nitrogen (HN), i.e., the ability to decouple foliar N levels from variation in soil N availability, were more common and stable through time than low HN species in a central US grassland. However, with 9-yrs of nitrogen addition, species with high HN decreased in abundance, while those with low HN increased in abundance. In contrast, in climate change experiments simulating a range of forecast hydrologic changes - extreme drought (2-yrs), increased rainfall variability (14-yrs), and chronic increases in rainfall (21-yrs) - plant species with the highest HN were least responsive to changes in soil water availability. These results suggest that HN may be predictive of plant species success and stability, and how plant species and ecosystems will respond to global-change driven alterations in resource availability.
1 aYu, Q.1 aWilcox, K.R.1 aLa Pierre, Kimberly, J.1 aKnapp, Alan, K.1 aHan, X.1 aSmith, M.D. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/14-1897.102883nas a2200193 4500008004100000245016700041210006900208300001500277490000800292520217100300100001702471700001802488700002802506700001702534700001702551700001602568700002402584856008102608 2014 eng d00aChanges in plant community composition, not diversity, during a decade of nitrogen and phosphorus additions drive above-ground productivity in a tallgrass prairie0 aChanges in plant community composition not diversity during a de a1649 -16600 v1023 aNutrient additions typically increase terrestrial ecosystem productivity, reduce plant diversity and alter plant community composition; however, the effects of P additions and interactions between N and P are understudied. We added both N (10 g m−2) and three levels of P (2.5, 5 and 10 g m−2) to a native, ungrazed tallgrass prairie burned biennially in northeastern Kansas, USA, to determine the independent and interactive effects of N and P on plant community composition and above-ground net primary productivity (ANPP). After a decade of nutrient additions, we found few effects of P alone on plant community composition, N alone had stronger effects, and N and P additions combined resulted in much larger effects than either alone. The changes in the plant community were driven by decreased abundance of C4 grasses, perhaps in response to altered interactions with mycorrhizal fungi, concurrent with increased abundance of non-N-fixing perennial and annual forbs. Surprisingly, this large shift in plant community composition had little effect on plant community richness, evenness and diversity. The shift in plant composition with N and P combined had large but variable effects on ANPP over time. Initially, N and N and P combined increased above-ground productivity of C4 grasses, but after 4 years, productivity returned to ambient levels as grasses declined in abundance and the community shifted to dominance by non-N-fixing and annual forbs. Once these forbs increased in abundance and became dominant, ANPP was more variable, with pulses in forb production only in years when the site was burned. Synthesis. We found that a decade of N and P additions interacted to drive changes in plant community composition, which had large effects on ecosystem productivity but minimal effects on plant community diversity. The large shift in species composition increased variability in ANPP over time as a consequence of the effects of burning. Thus, increased inputs of N and P to terrestrial ecosystems have the potential to alter stability of ecosystem function over time, particularly within the context of natural disturbance regimes.
1 aAvolio, M.L.1 aKoerner, S.E.1 aLa Pierre, Kimberly, J.1 aWilcox, K.R.1 aWilson, G.T.1 aSmith, M.D.1 aCollins, Scott., L. uhttps://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.1231202488nas a2200337 4500008004100000245011500041210006900156300001300225490000800238520150100246653001601747653000901763653001201772653002901784653002201813100001201835700002001847700001701867700001601884700001701900700001601917700001801933700001901951700001901970700001701989700002402006700001802030700002002048700001602068856006602084 2014 eng d00aLoss of a large grazer impacts savanna grassland plant communities similarly in North America and South Africa0 aLoss of a large grazer impacts savanna grassland plant communiti a293 -3030 v1753 aLarge herbivore grazing is a widespread disturbance in mesic savanna grasslands which increases herbaceous plant community richness and diversity. However, humans are modifying the impacts of grazing on these ecosystems by removing grazers. A more general understanding of how grazer loss will impact these ecosystems is hampered by differences in the diversity of large herbivore assemblages among savanna grasslands, which can affect the way that grazing influences plant communities. To avoid this we used two unique enclosures each containing a single, functionally similar large herbivore species. Specifically, we studied a bison (Bos bison) enclosure at Konza Prairie Biological Station, USA and an African buffalo (Syncerus caffer) enclosure in Kruger National Park, South Africa. Within these enclosures we erected exclosures in annually burned and unburned sites to determine how grazer loss would impact herbaceous plant communities, while controlling for potential fire-grazing interactions. At both sites, removal of the only grazer decreased grass and forb richness, evenness and diversity, over time. However, in Kruger these changes only occurred with burning. At both sites, changes in plant communities were driven by increased dominance with herbivore exclusion. At Konza, this was caused by increased abundance of one grass species, Andropogon gerardii, while at Kruger, three grasses, Themeda triandra, Panicum coloratum, and Digitaria eriantha increased in abundance.
10adisturbance10afire10aGrazing10aPlant community richness10aSpecies diversity1 aEby, S.1 aBurkepile, D.E.1 aFynn, R.W.S.1 aBurns, C.E.1 aGovender, N.1 aHagenah, N.1 aKoerner, S.E.1 aMatchett, K.J.1 aThompson, D.I.1 aWilcox, K.R.1 aCollins, Scott., L.1 aKirkman, K.P.1 aKnapp, Alan, K.1 aSmith, M.D. uhttps://link.springer.com/article/10.1007%2Fs00442-014-2895-902306nas a2200277 4500008004100000245012500041210006900166300001300235490000700248520144900255100001801704700002001722700001701742700001601759700001201775700001701787700001601804700001901820700001901839700001701858700002401875700001801899700002001917700001601937856007501953 2014 eng d00aPlant community response to loss of large herbivores differs between North American and South African savanna grasslands0 aPlant community response to loss of large herbivores differs bet a808 -8160 v953 aHerbivory and fire shape plant community structure in grass-dominated ecosystems, but these disturbance regimes are being altered around the world. To assess the consequences of such alterations, we excluded large herbivores for seven years from mesic savanna grasslands sites burned at different frequencies in North America (Konza Prairie Biological Station, Kansas, USA) and South Africa (Kruger National Park). We hypothesized that the removal of a single grass-feeding herbivore from Konza would decrease plant community richness and shift community composition due to increased dominance by grasses. Similarly, we expected grass dominance to increase at Kruger when removing large herbivores, but because large herbivores are more diverse, targeting both grasses and forbs, at this study site, the changes due to herbivore removal would be muted. After seven years of large-herbivore exclusion, richness strongly decreased and community composition changed at Konza, whereas little change was evident at Kruger. We found that this divergence in response was largely due to differences in the traits and numbers of dominant grasses between the study sites rather than the predicted differences in herbivore assemblages. Thus, the diversity of large herbivores lost may be less important in determining plant community dynamics than the functional traits of the grasses that dominate mesic, disturbance-maintained savanna grasslands.
1 aKoerner, S.E.1 aBurkepile, D.E.1 aFynn, R.W.S.1 aBurns, C.E.1 aEby, S.1 aGovender, N.1 aHagenah, N.1 aMatchett, K.J.1 aThompson, D.I.1 aWilcox, K.R.1 aCollins, Scott., L.1 aKirkman, K.P.1 aKnapp, Alan, K.1 aSmith, M.D. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/13-1828.103618nas a2200385 4500008004100000245009200041210006900133300001300202490000700215520250400222653002202726653001502748653001902763653003702782653002002819653001302839653002202852653001302874653002202887653002702909100001602936700002402952700001602976700002002992700002003012700001603032700001703048700001603065700001803081700001903099700001903118700001703137700001603154856006203170 2014 eng d00aResponses to fire differ between South African and North American grassland communities0 aResponses to fire differ between South African and North America a793 -8040 v253 aQuestion Does fire frequency affect mesic grassland plant community structure and composition similarly in North America and South Africa? Location Konza Prairie Biological Station (KNZ), Kansas, USA, and Ukulinga Research Farm (URF), KwaZulu-Natal, South Africa. Methods Plant community structure and composition were compared among annually burned, unburned and intermediate treatments within two long-term fire frequency manipulation experiments in native grasslands in North America and South Africa using comparable methodology over a 5-yr period. Because fire may reduce soil nitrogen (N) availability and thus affect plant community structure, N additions were superimposed on the fire treatments as a means of assessing direct vs indirect mechanisms driving responses to fire. Results The total number of species was higher at URF (183) than at KNZ (57). Overall divergence in plant community response to fire frequency occurred despite similar responses to nutrient additions. At KNZ, more frequent fire resulted in dominance by a few, tall, deep-rooted rhizomatous grasses (e.g. Andropogon gerardii). On unburned sites, shorter, more shade-tolerant species such as Poa pratensis increased in abundance, although A. gerardii remained dominant. Species richness increased with decreasing fire frequency at KNZ. At URF, frequent fire resulted in short, diverse grassland weakly dominated by a range of grass species, including Themeda triandra, Tristachya leucothrix and Hyparrhenia hirta. Decreasing fire frequency reduced species richness and resulted in dominance by a few, relatively tall caespitose grasses such as Aristida junciformis. There was a complete turnover of dominant species between annually burned and unburned treatments at URF, while at KNZ A. gerardii and Sorghastrum nutans occurred across the range of treatments. N addition reduced species richness in both sites. Conclusions Different responses to fire frequency between KNZ and URF are likely linked to the dominant species and their characteristic traits, including height and method of clonal reproduction, with the rhizomatous growth form of A. gerardii dominating the North American grassland. South Africa does not have an equivalent grass species; instead, a range of tufted, non-rhizomatous species dominate across the fire frequency treatments at URF. Reductions in soil N due to frequent fire did not appear to be a common mechanism driving responses in community composition in these two grasslands.
10aCommunity ecology10aDivergence10aFire frequency10aKonza Prairie Biological Station10aMesic grassland10anitrogen10aNutrient addition10aRichness10atallgrass prairie10aUkulinga Research Farm1 aKirkman, K.1 aCollins, Scott., L.1 aSmith, M.D.1 aKnapp, Alan, K.1 aBurkepile, D.E.1 aBurns, C.E.1 aFynn, R.W.S.1 aHagenah, N.1 aKoerner, S.E.1 aMatchett, K.J.1 aThompson, D.I.1 aWilcox, K.R.1 aWragg, P.D. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/jvs.12130