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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 11 | Copyright
Biogeosciences, 15, 3421-3437, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Jun 2018

Research article | 11 Jun 2018

Asymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites

Donghai Wu1, Philippe Ciais2, Nicolas Viovy2, Alan K. Knapp3, Kevin Wilcox4, Michael Bahn5, Melinda D. Smith3, Sara Vicca6, Simone Fatichi7, Jakob Zscheischler8, Yue He1, Xiangyi Li1, Akihiko Ito9, Almut Arneth10, Anna Harper11, Anna Ukkola12, Athanasios Paschalis13, Benjamin Poulter14, Changhui Peng15,16, Daniel Ricciuto17, David Reinthaler5, Guangsheng Chen18, Hanqin Tian18, Hélène Genet19, Jiafu Mao17, Johannes Ingrisch5, Julia E. S. M. Nabel20, Julia Pongratz20, Lena R. Boysen20, Markus Kautz10, Michael Schmitt5, Patrick Meir21,22, Qiuan Zhu16, Roland Hasibeder5, Sebastian Sippel23, Shree R. S. Dangal18,24, Stephen Sitch25, Xiaoying Shi17, Yingping Wang26, Yiqi Luo4,27, Yongwen Liu1, and Shilong Piao1 Donghai Wu et al.
  • 1Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
  • 2Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-Sur-Yvette 91191, France
  • 3Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
  • 4Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019, USA
  • 5Institute of Ecology, University of Innsbruck, 6020 Innsbruck, Austria
  • 6Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
  • 7Institute of Environmental Engineering, ETH Zurich, 8093 Zurich, Switzerland
  • 8Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
  • 9National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
  • 10Karlsruhe Institute of Technology, 82467 Garmisch-Partenkirchen, Germany
  • 11College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK
  • 12ARC Centre of Excellence for Climate System Science, University of New South Wales, Kensington, NSW 2052, Australia
  • 13Department of Civil and Environmental Engineering, Imperial College London, London, SW7 2AZ, UK
  • 14NASA Goddard Space Flight Center, Biospheric Sciences Laboratory, Greenbelt, MD 20771, USA
  • 15Institute of Environment Sciences, Biology Science Department, University of Quebec at Montreal, Montréal H3C 3P8, Québec, Canada
  • 16State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Forestry, Northwest A&F University, Yangling 712100, China
  • 17Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6301, USA
  • 18International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA
  • 19Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA
  • 20Max Planck Institute for Meteorology, 20146 Hamburg, Germany
  • 21School of Geosciences, University of Edinburgh, Edinburgh EH9 3FF, UK
  • 22Research School of Biology, Australian National University, Canberra, ACT 2601, Australia
  • 23Norwegian Institute of Bioeconomy Research, 1431 Ås, Norway
  • 24Woods Hole Research Center, Falmouth, Massachusetts 02540-1644, USA
  • 25College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK
  • 26CSIRO Oceans and Atmosphere, PMB #1, Aspendale, Victoria 3195, Australia
  • 27Center for Ecosystem Sciences and Society, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA

Abstract. 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.

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Our results indicate that most ecosystem models do not capture the observed asymmetric responses under normal precipitation conditions, suggesting an overestimate of the drought effects and/or underestimate of the watering impacts on primary productivity, which may be the result of inadequate representation of key eco-hydrological processes. Collaboration between modelers and site investigators needs to be strengthened to improve the specific processes in ecosystem models in following studies.
Our results indicate that most ecosystem models do not capture the observed asymmetric responses...