title: Microclimate moderates plant responses to macroclimate warming.
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.
authors.affiliation: Forest and Nature Lab, Ghent University, BE-9090 Gontrode-Melle, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: De Frenne
authors.forename: Francisco
authors.initials: F
authors.lastname: Rodríguez-Sánchez
authors.forename: David Anthony
authors.initials: DA
authors.lastname: Coomes
authors.forename: Lander
authors.initials: L
authors.lastname: Baeten
authors.forename: Gorik
authors.initials: G
authors.lastname: Verstraeten
authors.forename: Mark
authors.initials: M
authors.lastname: Vellend
authors.forename: Markus
authors.initials: M
authors.lastname: Bernhardt-Römermann
authors.forename: Carissa D
authors.initials: CD
authors.lastname: Brown
authors.forename: Jörg
authors.initials: J
authors.lastname: Brunet
authors.forename: Johnny
authors.initials: J
authors.lastname: Cornelis
authors.forename: Guillaume M
authors.initials: GM
authors.lastname: Decocq
authors.forename: Hartmut
authors.initials: H
authors.lastname: Dierschke
authors.forename: Ove
authors.initials: O
authors.lastname: Eriksson
authors.forename: Frank S
authors.initials: FS
authors.lastname: Gilliam
authors.forename: Radim
authors.initials: R
authors.lastname: Hédl
authors.forename: Thilo
authors.initials: T
authors.lastname: Heinken
authors.forename: Martin
authors.initials: M
authors.lastname: Hermy
authors.forename: Patrick
authors.initials: P
authors.lastname: Hommel
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jenkins
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Kelly
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Kirby
authors.forename: Fraser J G
authors.initials: FJ
authors.lastname: Mitchell
authors.forename: Tobias
authors.initials: T
authors.lastname: Naaf
authors.forename: Miles
authors.initials: M
authors.lastname: Newman
authors.forename: George
authors.initials: G
authors.lastname: Peterken
authors.forename: Petr
authors.initials: P
authors.lastname: Petrík
authors.forename: Jan
authors.initials: J
authors.lastname: Schultz
authors.forename: Grégory
authors.initials: G
authors.lastname: Sonnier
authors.forename: Hans
authors.initials: H
authors.lastname: Van Calster
authors.forename: Donald M
authors.initials: DM
authors.lastname: Waller
authors.forename: Gian-Reto
authors.initials: GR
authors.lastname: Walther
authors.forename: Peter S
authors.initials: PS
authors.lastname: White
authors.forename: Kerry D
authors.initials: KD
authors.lastname: Woods
authors.forename: Monika
authors.initials: M
authors.lastname: Wulf
authors.forename: Bente Jessen
authors.initials: BJ
authors.lastname: Graae
authors.forename: Kris
authors.initials: K
authors.lastname: Verheyen
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D058448:Biota / Q000502:physiology*; D005060:Europe; D057232:Global Warming; D008834:Microclimate; D009656:North America; D011157:Population Dynamics; D012621:Seasons; D013045:Species Specificity; D013696:Temperature; D014197:Trees / Q000502:physiology*
keywords: climate change; climatic debt; forest management; range shifts; understory