Shifts in tree functional composition amplify the response of forest biomass to climate

Forests have a key role in global ecosystems, hosting much of the world’s terrestrial biodiversity and acting as a net sink for atmospheric carbon. These and other ecosystem services that are provided by forests may be sensitive to climate change as well as climate variability on shorter time scales (for example, annual to decadal). Previous studies have documented responses of forest ecosystems to climate change and climate variability, including drought-induced increases in tree mortality rates. However, relationships between forest biomass, tree species composition and climate variability have not been quantified across a large region using systematically sampled data. Here we use systematic forest inventories from the 1980s and 2000s across the eastern USA to show that forest biomass responds to decadal-scale changes in water deficit, and that this biomass response is amplified by concurrent changes in community-mean drought tolerance, a functionally important aspect of tree species composition. The amplification of the direct effects of water stress on biomass occurs because water stress tends to induce a shift in tree species composition towards species that are more tolerant to drought but are slower growing. These results demonstrate concurrent changes in forest species composition and biomass carbon storage across a large, systematically sampled region, and highlight the potential for climate-induced changes in forest ecosystems across the world, resulting from both direct effects of climate on forest biomass and indirect effects mediated by shifts in species composition.

[1]  T. Simons,et al.  Spatial autocorrelation and autoregressive models in ecology , 2002 .

[2]  L. Anderegg,et al.  Consequences of widespread tree mortality triggered by drought and temperature stress , 2013 .

[3]  W. Cornwell,et al.  Regional and local patterns in plant species richness with respect to resource availability , 2003 .

[4]  J. Terborgh,et al.  Drought Sensitivity of the Amazon Rainforest , 2009, Science.

[5]  Daniel M. Kashian,et al.  Effects of biotic disturbances on forest carbon cycling in the United States and Canada , 2012 .

[6]  C. Dussault,et al.  Ecological Impacts of Deer Overabundance , 2004 .

[7]  C. Peng,et al.  A drought-induced pervasive increase in tree mortality across Canada's boreal forests , 2011 .

[8]  G. Bonan.  Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests , 2008, Science.

[9]  T. M. Bezemer,et al.  Biodiversity increases the resistance of ecosystem productivity to climate extremes , 2015, Nature.

[10]  Markus Reichstein,et al.  Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts , 2015, Global change biology.

[11]  R. Birdsey,et al.  National-Scale Biomass Estimators for United States Tree Species , 2003, Forest Science.

[12]  E. Davidson,et al.  Climate change impacts of US reactive nitrogen , 2012, Proceedings of the National Academy of Sciences.

[13]  G. Yohe,et al.  A globally coherent fingerprint of climate change impacts across natural systems , 2003, Nature.

[14]  S. Levin,et al.  Competition for Water and Light in Closed-Canopy Forests: A Tractable Model of Carbon Allocation with Implications for Carbon Sinks , 2013, The American Naturalist.

[15]  Yves Rosseel,et al.  lavaan: An R Package for Structural Equation Modeling , 2012 .

[16]  Jonathan D. G. Jones,et al.  Assemblage Time Series Reveal Biodiversity Change but Not Systematic Loss , 2018 .

[17]  E. Wood,et al.  Development of a 50-Year High-Resolution Global Dataset of Meteorological Forcings for Land Surface Modeling , 2006 .

[18]  Alice Boit,et al.  Resilience of Amazon forests emerges from plant trait diversity , 2016 .

[19]  Niklaus E. Zimmermann,et al.  Climate change may cause severe loss in the economic value of European forest land , 2013 .

[20]  A. Lehtonen,et al.  Climate‐ and successional‐related changes in functional composition of European forests are strongly driven by tree mortality , 2017, Global change biology.

[21]  James S. Clark,et al.  The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States , 2016, Global change biology.

[22]  Ü. Niinemets,et al.  Tolerance to shade, drought, and waterlogging of temperate northern hemisphere trees and shrubs , 2006 .

[23]  Roger Bivand,et al.  Computing the Jacobian in Gaussian Spatial Autoregressive Models: An Illustrated Comparison of Available Methods , 2013 .

[24]  Houghton,et al.  The U.S. Carbon budget: contributions from land-Use change , 1999, Science.

[25]  E. Wood,et al.  Little change in global drought over the past 60 years , 2012, Nature.

[26]  R. B. Jackson,et al.  A Large and Persistent Carbon Sink in the World’s Forests , 2011, Science.

[27]  Erich Barke,et al.  Hierarchical partitioning , 1996, Proceedings of International Conference on Computer Aided Design.

[28]  G. Nowacki,et al.  Is climate an important driver of post‐European vegetation change in the Eastern United States? , 2015, Global change biology.

[29]  S. Fei,et al.  Divergence of species responses to climate change , 2017, Science Advances.

[30]  R. Shaw,et al.  Range shifts and adaptive responses to Quaternary climate change. , 2001, Science.

[31]  L. Iverson,et al.  Long-term droughtiness and drought tolerance of eastern US forests over five decades , 2015 .

[32]  Mark C. Vanderwel,et al.  Quantifying variation in forest disturbance, and its effects on aboveground biomass dynamics, across the eastern United States , 2013, Global change biology.

[33]  N. McDowell,et al.  A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests , 2010 .

[34]  F. Chapin,et al.  EFFECTS OF BIODIVERSITY ON ECOSYSTEM FUNCTIONING: A CONSENSUS OF CURRENT KNOWLEDGE , 2005 .

[35]  T. Stocker,et al.  Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of IPCC Intergovernmental Panel on Climate Change , 2012 .