Contributors: School of Geography Leeds; University of Leeds; Computational & Applied Vegetation Ecology (CAVElab); Universiteit Gent = Ghent University = Université de Gand (UGENT); Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS); Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE); Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS); Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE); Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA); Potsdam Institute for Climate Impact Research (PIK); Technische Universität Munchen - Technical University Munich - Université Technique de Munich (TUM); Instituto Nacional de Pesquisas Espaciais (INPE); Ministério da Ciência, Tecnologia e Inovação; Missouri Botanical Garden; Geography, College of Life and Environmental Sciences; University of Exeter; Instituto Nacional de Pesquisas da Amazônia = National Institute of Amazonian Research (INPA); School of Geosciences Edinburgh; University of Edinburgh (Edin.); Earth and Environmental Sciences Division Los Alamos (EES); Los Alamos National Laboratory (LANL); ICOS-ATC (ICOS-ATC); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)); Alterra Wageningen (ESS-CC); Centre for Water and Climate Wageningen; Research School of Biology; Australian National University (ANU); Department of Organismic and Evolutionary Biology Cambridge (OEB); Harvard University; Cooperative Institute for Mesoscale Meteorological Studies (CIMMS); Fundación Con-Vida; Museo de Historia Natural Noel Kempff Mercado; Universidad Autonoma Gabriel René Moreno; Programa Cienclas Agro & Mar, UNELLEZ Guanare; Herbario Universitario PORT; Department of Biological Sciences Miami; Florida International University Miami (FIU); Universidade Federal do Acre (UFAC); Ecologie et Ecophysiologie Forestières devient SILVA en 2018 (EEF); Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL); Tropenbos International (TBI); Evolution et Diversité Biologique (EDB); Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3); Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS); Jardín Botánico de Medellín; Andes to Amazon Biodiversity Program Madre de Dios; Centro de Geociencias; Federal University of Para - Universidade Federal do Pará - UFPA Belém, Brazil (UFPA); Dpt of Anthropology Austin; University of Texas at Austin Austin; Museu Paraense Emílio Goeldi Belém, Brésil (MPEG); Instituto de Investigaciones de la Amazonía Peruana (IIAP); World Wide Fund (WWF); Centre for Tropical Environmental and Sustainability Science (TESS); James Cook University (JCU); Instituto Boliviano de Investigacion Forestal (IBIF); Environmental Science and Policy Department and the Department of Public and International Affairs; George Mason University Fairfax; Environmental Change Institute; University of Oxford; Universidade do Estado de Mato Grosso (UNEMAT); Escuela de Ciencias Forestales (ESFOR); Facultad de Ingeniería y Ciencias Ambientales; Universidad Nacional Intercultural de la Amazonía; Universidad Autonoma del Beni; Forest Ecology and Forest Management Group; Wageningen University and Research Wageningen (WUR); Center for Tropical Conservation; Duke University Durham; Doctorado Instituto de Ciencias Naturales; Universidad Nacional de Colombia Bogotà (UNAL); Instituto de Investigaciones para el Desarrollo Forestal; Universidad de los Andes Bogota (UNIANDES); Iwokrama International Centre for Rainforest Conservation and Development; Museu Universitário; Institute of Biological Sciences, Medical and Health; Universidade Paranaense (UNIPAR); Naturalis Biodiversity Center Leiden; School of Geography Nottingham; University of Nottingham, UK (UON); Centro de Investigación y Promoción del Campesinado; regional Norte Amazónico; 282664, AMAZALERT Raising the alert about critical feedbacks between climate and long-term land use change in the Amazon; Gordon and Betty Moore Foundation; ERC; Natural Environment Research Council (NERC) Urgency; Consortium and Standard Grant 'AMAZONICA' NE/F005806/1; Consortium and Standard Grant 'TROBIT' NE/D005590/1; Consortium and Standard Grant 'Niche Evolution of South American Trees' NE/I028122/1; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico of Brazil (CNPq); project Programa de Pesquisas Ecologicas de Longa Duracao PELD-403725/2012-7; Helmholtz Alliance 'Remote Sensing and Earth System Dynamics'; EU FP7 project 'ROBIN' 283093; Dutch Ministry of Economic Affairs KB-14-003-030; US DOE (BER) NGEE-Tropics project; ERC Advanced Grant
نبذة مختصرة : International audience ; Understanding the processes that determine above-ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. The relationship between stem mortality rates and AGB varies among different regions of Amazonia, indicating that variation in wood density and height/diameter relationships also influences AGB. In contrast to previous findings, we find that woody NPP is not correlated with stem mortality rates and is weakly positively correlated with AGB. Across the four models, basin-wide average AGB is similar to the mean of the observations. However, the models consistently overestimate woody NPP and poorly represent the spatial patterns of both AGB and woody NPP estimated using plot data. In marked contrast to the observations, DGVMs typically show strong positive relationships between woody NPP and AGB. Resolving these differences will require incorporating forest size structure, mechanistic models of stem mortality and variation in functional composition in DGVMs.
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