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Microclimate moderates plant responses to macroclimate warming
ISSN
0027-8424
Date Issued
2013
Author(s)
De Frenne, Pieter
Rodriguez-Sanchez, Francisco
Coomes, David Anthony
Baeten, Lander
Verstraeten, Gorik
Vellend, Mark
Bernhardt-Roemermann, Markus
Brown, Carissa D.
Brunet, Joerg
Cornelis, Johnny
Decocq, Guillaume M.
Eriksson, Ove
Gilliam, Frank S.
Hedl, Radim
Heinken, Thilo
Hermy, Martin
Hommel, Patrick
Jenkins, Michael A.
Kelly, Daniel L.
Kirby, Keith J.
Mitchell, Fraser J. G.
Naaf, Tobias
Newman, Miles
Peterken, George
Petrik, Petr
Schultz, Jan
Sonnier, Gregory
van Calster, Hans
Waller, Donald M.
Walther, Gian-Reto
White, Peter S.
Woods, Kerry D.
Wulf, Monika
Graae, Bente Jessen
Verheyen, Kris
DOI
10.1073/pnas.1311190110
Abstract
Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., "thermophilization" of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that "climatic lags" may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12-67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass-e.g., for bioenergy-may open forest canopies and accelerate thermophilization of temperate forest biodiversity.