Seasonal drivers of understorey temperature buffering in temperate deciduous forests across Europe

Florian Zellweger (1) , David Coomes (2) , Jonathan Roger Michel Henri Lenoir (3) , Leen Depauw , Sybryn Maes , Monika Wulf (4) , Keith Kirby (5) , Jörg Brunet (6) , Martin Kopecký , František Máliš , Wolfgang Schmidt , Steffi Heinrichs , Jan den Ouden (7) , Bogdan Jaroszewicz (8) , Gauthier Buyse , Fabien Spicher (3) , Kris Verheyen (9) , Pieter de Frenne (10)

1 Unibas - Université de Bâle = University of Basel = Basel Universität
2 CAM - University of Cambridge [UK]
3 EDYSAN - Ecologie et Dynamique des Systèmes Anthropisés - UMR CNRS 7058
4 ZALF - Leibniz Centre for Agricultural Landscape Research
5 University of Oxford
6 Southern Swedish Forest Research Centre
7 Forest Ecol & Forest Management,
8 UW - University of Warsaw
9 Forest & Nature Laboratory, Department of Forest and Water Management
10 Forest & Nature Lab - Department of Plant Production

Aim. Forest understorey microclimates are often buffered against extreme heat or cold, with important implications for the organisms living in these environments. We quantified seasonal effects of understorey microclimate predictors describing canopy structure, canopy composition and topography (i.e., local factors) and the forest patch size and distance to the coast (i.e., landscape factors). Location. Temperate forests in Europe. Time period. 2017–2018. Major taxa studied. Woody plants. Methods. We combined data from a microclimate sensor network with weather‐station records to calculate the difference, or offset, between temperatures measured inside and outside forests. We used regression analysis to study the effects of local and landscape factors on the seasonal offset of minimum, mean and maximum temperatures. Results. The maximum temperature during the summer was on average cooler by 2.1 °C inside than outside forests, and the minimum temperatures during the winter and spring were 0.4 and 0.9 °C warmer. The local canopy cover was a strong nonlinear driver of the maximum temperature offset during summer, and we found increased cooling beneath tree species that cast the deepest shade. Seasonal offsets of minimum temperature were mainly regulated by landscape and topographic features, such as the distance to the coast and topographic position. Main conclusions. Forest organisms experience less severe temperature extremes than suggested by currently available macroclimate data; therefore, climate–species relationships and the responses of species to anthropogenic global warming cannot be modelled accurately in forests using macroclimate data alone. Changes in canopy cover and composition will strongly modulate the warming of maximum temperatures in forest understories, with important implications for understanding the responses of forest biodiversity and functioning to the combined threats of land‐use change and climate change. Our predictive models are generally applicable across lowland temperate deciduous forests, providing ecologically important microclimate data for forest understories.

Mots clés: Canopy density; Climate change; Forest composition; Forest structure; Global warming; Macroclimate; Microclimate; Temperature buffering; Understorey

Domaines: Biodiversité; Ecologie, Environnement; Milieux et Changements globaux; Biodiversité et Ecologie

Florian Zellweger, David Coomes, Jonathan Roger Michel Henri Lenoir, Leen Depauw, Sybryn Maes, et al.. Seasonal drivers of understorey temperature buffering in temperate deciduous forests across Europe. Global Ecology and Biogeography, 2019, 28 (12), pp.1774-1786. ⟨10.1111/geb.12991⟩. ⟨hal-02357312⟩