The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
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Acknowledgements This paper is an outcome of the sTundra working group supported by sDiv, the Synthesis Centre of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (DFG FZT 118). A.D.B. was supported by an iDiv postdoctoral fellowship and The Danish Council for Independent Research - Natural Sciences (DFF 4181-00565 to S.N.). A.D.B., I.H.M.-S., H.J.D.T. and S.A.-B. were funded by the UK Natural Environment Research Council (ShrubTundra Project NE/M016323/1 to I.H.M.-S.). S.N., A.B.O., S.S.N. and U.A.T. were supported by the Villum Foundation’s Young Investigator Programme (VKR023456 to S.N.) and the Carlsberg Foundation (2013-01-0825). N.R. was supported by the DFG-Forschungszentrum ‘German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig’ and Deutsche Forschungsgemeinschaft DFG (RU 1536/3-1). A.Buc. was supported by EU-F7P INTERACT (262693) and MOBILITY PLUS (1072/MOB/2013/0). A.B.O. was additionally supported by the Danish Council for Independent Research - Natural Sciences (DFF 4181-00565 to S.N.). J.M.A. was supported by the Carl Tryggers stiftelse för vetenskaplig forskning, A.H. by the Research Council of Norway (244557/E50), B.E. and A.Mic. by the Danish National Research Foundation (CENPERM DNRF100), B.M. by the Soil Conservation Service of Iceland and E.R.F. by the Swiss National Science Foundation
(155554). B.C.F. was supported by the Academy of Finland (256991) and JPI Climate (291581). B.J.E. was supported by an NSF ATB, CAREER and Macrosystems award. C.M.I. was supported by the Office of Biological and Environmental Research in the US Department of Energy’s Office of Science as part of the Next-Generation Ecosystem Experiments in the Arctic (NGEE Arctic) project. D.B. was supported by The Swedish Research Council (2015-00465) and Marie Skłodowska Curie Actions co-funding (INCA 600398). E.W. was supported by the National Science Foundation (DEB-0415383), UWEC–ORSP and UWEC–BCDT. G.S.-S. and M.I.-G. were supported by the University of Zurich Research Priority Program on Global Change and Biodiversity. H.D.A. was supported by NSF PLR (1623764, 1304040). I.S.J. was supported by the Icelandic Research Fund (70255021) and the University of Iceland Research Fund. J.D.M.S. was supported by the Research Council of Norway (262064). J.S.P. was supported by the US Fish and Wildlife Service. J.C.O. was supported by Klimaat voor ruimte, Dutch national research program Climate Change and Spatial Planning. J.F.J., P.G., G.H.R.H., E.L., N.B.-L., K.A.H., L.S.C. and T.Z. were supported by the Natural Sciences and Engineering Research Council of Canada (NSERC). G.H.R.H., N.B.-L., E.L., L.S.C. and L.H. were supported by ArcticNet. G.H.R.H., N.B.-L., M.Tr. and L.S.C. were supported by the Northern Scientific Training Program. G.H.R.H., E.L. and N.B.-L. were additionally supported by the Polar Continental Shelf Program. N.B.-L. was additionally supported by the Fonds de recherche du Quebec: Nature et Technologies and the Centre d’études Nordiques. J.P. was supported by the European Research Council Synergy grant SyG-2013-610028 IMBALANCE-P. A.A.-R., O.G. and J.M.N. were supported by the Spanish OAPN (project 534S/2012) and European INTERACT project (262693 Transnational Access). K.D.T. was supported by NSF ANS-1418123. L.E.S. and P.A.W. were supported by the UK Natural Environment Research Council Arctic Terrestrial Ecology Special Topic Programme and Arctic Programme (NE/K000284/1 to P.A.W.). P.A.W. was additionally supported by the European Union Fourth Environment and Climate Framework Programme (Project Number ENV4-CT970586). M.W. was supported by DFG RTG 2010. R.D.H. was supported by the US National Science Foundation. M.J.S. and K.N.S. were supported by the Niwot Ridge LTER (NSF DEB-1637686). H.J.D.T. was funded by a NERC doctoral training partnership grant (NE/L002558/1). V.G.O. was supported by the Russian Science Foundation (14-50-00029). L.B. was supported by NSF ANS (1661723) and S.J.G. by NASA ABoVE (NNX15AU03A/NNX17AE44G). B.B.-L. was supported as part of the Energy Exascale Earth System Model (E3SM) project, funded by the US Department of Energy, Office of Science, Office of Biological and Environmental Research. A.E. was supported by the Academy of Finland (projects 253385 and 297191). E.K. was supported by Swedish Research Council (2015-00498), and S.Dí. was supported by CONICET, FONCyT and SECyT-UNC, Argentina. The study has been supported by the TRY initiative on plant traits (http://www.try-db.org), which is hosted at the Max Planck Institute for Biogeochemistry, Jena, Germany and is currently supported by DIVERSITAS/Future Earth and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. A.D.B. and S.C.E. thank the US National Science Foundation for support to receive training in Bayesian methods (grant 1145200 to N. Thompson Hobbs). We thank H. Bruelheide and J. Ramirez-Villegas for helpful input at earlier stages of this project. We acknowledge the contributions of S. Mamet, M. Jean, K. Allen, N. Young, J. Lowe, O. Eriksson and many others to trait and community composition data collection, and thank the governments, parks, field stations and local and indigenous people for the opportunity to conduct research on their land.