Contrasting microclimates among hedgerows and woodlands across temperate Europe

Thomas Vanneste (1) , Sanne Govaert , Fabien Spicher (2) , Jörg Brunet (3) , Sara A.O. Cousins , Guillaume Decocq (2) , Martin Diekmann (4) , Bente J. Graae , Per-Ola Hedwall , Rozália E. Kapás , Jonathan Roger Michel Henri Lenoir (2) , Jaan Liira (5) , Sigrid Lindmo , Kathrin Litza , Tobias Naaf (6) , Anna Orczewska , Jan Plue (7) , Monika Wulf (8) , Kris Verheyen (9) , Pieter de Frenne (10)

1 UGENT - Universiteit Gent = Ghent University
2 EDYSAN - Ecologie et Dynamique des Systèmes Anthropisés - UMR CNRS 7058
3 Southern Swedish Forest Research Centre
4 Institute of Ecology [University of Bremen]
5 Inst Ecol & Earth Sci
6 Institute of Land Use Systems
7 UCL - Université Catholique de Louvain = Catholic University of Louvain
8 ZALF - Leibniz Centre for Agricultural Landscape Research
9 Forest & Nature Laboratory, Department of Forest and Water Management
10 Forest & Nature Lab - Department of Plant Production

Hedgerows have the potential to facilitate the persistence and migration of species across landscapes, mostly due to benign microclimatic conditions. This thermal buffering function may become even more important in the future for species migration under climate change. Unfortunately, there is a lack of empirical studies quantifying the microclimate of hedgerows, particularly at broad geographical scales. Here we monitored sub-canopy temperatures using 168 miniature temperature sensors distributed along woodland-hedgerow transects, and spanning a 1600-km macroclimatic gradient across Europe. First, we assessed the variation in the temperature offset (that is, the difference between sub-canopy and corresponding macroclimate temperatures) for minimum, mean and maximum temperatures along the woodland-hedgerow transects. Next, we linked the observed patterns to macroclimate temperatures as well as canopy structure, overstorey composition and hedgerow characteristics. The sub-canopy versus macroclimate temperature offset was on average 0.10 °C lower in hedgerows than in woodlands. Minimum winter temperatures were consistently lower by 0.10 °C in hedgerows than in woodlands, while maximum summer temperatures were 0.80 °C higher, albeit mainly around the woodland-hedgerow ecotone. The temperature offset was often negatively correlated with macroclimate temperatures. The slope of this relationship was lower for maximum temperatures in hedgerows than in woodlands. During summer, canopy cover, tree height and hedgerow width had strong cooling effects on maximum mid-day temperatures in hedgerows. The effects of shrub height, shrub cover and shade-casting ability, however, were not significant. To our knowledge, this is the first study to quantify hedgerow microclimates along a continental-scale environmental gradient. We show that hedgerows are less efficient thermal insulators than woodlands, especially at high ambient temperatures (e.g. on warm summer days). This knowledge will not only result in better predictions of species distribution across fragmented landscapes, but will also help to elaborate efficient strategies for biodiversity conservation and landscape planning.

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

Thomas Vanneste, Sanne Govaert, Fabien Spicher, Jörg Brunet, Sara A.O. Cousins, et al.. Contrasting microclimates among hedgerows and woodlands across temperate Europe. Agricultural and Forest Meteorology, 2020, 281, pp.107818. ⟨10.1016/j.agrformet.2019.107818⟩. ⟨hal-02357017⟩