04101nas 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 a
Field 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/