NCEAS Working Group "Why Don't We Understand Old-growth Forests (and Other Slow Systems) Very Well?" documented significant thermophilization of understory vegetation using a database of more than 1,400 vegetation plots which had been resurveyed repeatedly in forests across Europe and North America. What the project team also found was a reduction in the response to macroclimate warming in forests whose canopies have become denser. The increased shading of the denser overstory keeps forest-floor temperatures cooler during the growing season, creating a microclimate buffer to the warming climate. With the increase of trees in many temperate forests in recent decades, the microclimate buffering of understory plants has delayed responses to macroclimate warming, thus explaining the apparent climate lag of thermophilization.
Microclimate moderates plant responses to macroclimate warming
Pieter De Frenne, Francisco Rodríguez-Sánchez, David Anthony Coomes, Lander Baeten, Gorik Verstraeten, Mark Vellend, Markus Bernhardt-Römermann, Carissa D. Brown, Jörg Brunet, Johnny Cornelis, Guillaume M. Decocq, Hartmut Dierschke, Ove Eriksson, Frank S. Gilliam, Radim Hédl, Thilo Heinken, Martin Hermy, Patrick Hommel, Michael A. Jenkins, Daniel L. Kelly, Keith J. Kirby, Fraser J. G. Mitchell, Tobias Naaf, Miles Newman, George Peterken, Petr Petrík, Jan Schultz, Grégory Sonnier, Hans Van Calster, Donald M. Waller, Gian-Reto Walther, Peter S. White, Kerry D. Woods, Monika Wulf, Bente Jessen Graae, and Kris Verheyen
Proceedings of the National Academy of Sciences, October 2013: 1311190110v1-201311190.
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