ForestTemp - Sub-canopy microclimate temperatures of European forests

Stef Haesen (1) , Jonas J. Lembrechts , Pieter de Frenne (2) , Jonathan Roger Michel Henri Lenoir (3) , Juha Aalto (4) , Michael B. Ashcroft (5) , Martin Kopecký (6, 7) , Miska Luoto (4) , Ilya Maclean (8) , Ivan Nijs (9) , Pekka Niittynen (4) , Johan van Den Hoogen , Nicola Arriga (10) , Josef Bruna , Nina Buchmann (11) , Marek Ciliak , Alessio Collalti (12) , Emiel de Lombaerde , Patrice Descombes (13, 11) , Mana Gharun (14) , Ignacio Goded (15) , Sanne Govaert (2) , Caroline Greiser (16) , Achim Grelle (17) , Carsten Gruening (15) , Lucia Hederová (6) , Kristoffer Hylander (16) , Jürgen Kreyling (18) , Bart Kruijt (19) , Martin Macek , Frantisek Malis , Matej Man , Giovanni Manca , Radim Matula (20) , Camille Meeussen (2) , Sonia Merinero (21) , Stefano Minerbi (22) , Leonardo Montagnani (23) , Lena Muffler (18, 24) , Romá Ogaya (25) , Josep Peñuelas (25) , Roman Plichta (26) , Miguel Portillo-Estrada (9) , Jonas Schmeddes (18) , Ankit Shekhar , Fabien Spicher (3) , Mariana Ujházyová (27) , Pieter Vangansbeke (2) , Robert Weigel (24) , Jan Wild (6) , Florian Zellweger (13) , Koenraad van Meerbeek (28)

1 KU Leuven - Catholic University of Leuven = Katholieke Universiteit Leuven
2 UGENT - Universiteit Gent = Ghent University
3 EDYSAN - Ecologie et Dynamique des Systèmes Anthropisés - UMR CNRS 7058
4 Helsingin yliopisto = Helsingfors universitet = University of Helsinki
5 Australian Museum [Sydney]
6 IB / CAS - Institute of Botany of the Czech Academy of Sciences
7 CZU - Czech University of Life Sciences Prague
8 University of Exeter
9 UA - University of Antwerp
10 Department of Biology
11 D-USYS - Department of Environmental Systems Science [ETH Zürich]
12 Università degli studi della Tuscia [Viterbo]
13 Swiss Federal Institute for Forest, Snow and Landscape Research WSL
14 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]
15 JRC - European Commission - Joint Research Centre [Ispra]
16 Department of Ecology, Environment and Plant Sciences [Stockholm]
17 Department of Ecology
18 Universität Greifswald - University of Greifswald
19 WUR - Wageningen University and Research [Wageningen]
20 Faculty of Forestry and Wood Sciences
21 Stockholm University
22 Provincia Autonoma di Bolzano Servizi Forestali
23 Free University of Bozen-Bolzano
24 Georg-August-University = Georg-August-Universität Göttingen
25 CREAF - Centre for Ecological Research and Applied Forestries
26 MENDELU - Mendel University in Brno
27 TUZVO - Technical University in Zvolen
28 Department of Earth and Environmental Sciences [Leuven-Heverlee]

Ecological research heavily relies on coarse-gridded climate data based on standardized temperature measurements recorded at 2 m height in open landscapes. However, many organisms experience environmental conditions that differ substantially from those captured by these macroclimatic (i.e. free air) temperature grids. In forests, the tree canopy functions as a thermal insulator and buffers sub-canopy microclimatic conditions, thereby affecting biological and ecological processes. To improve the assessment of climatic conditions and climate-change-related impacts on forest-floor biodiversity and functioning, high-resolution temperature grids reflecting forest microclimates are thus urgently needed. Combining more than 1200 time series of in situ near-surface forest temperature with topographical, biological and macroclimatic variables in a machine learning model, we predicted the mean monthly offset between sub-canopy temperature at 15 cm above the surface and free-air temperature over the period 2000-2020 at a spatial resolution of 25 m across Europe. This offset was used to evaluate the difference between microclimate and macroclimate across space and seasons and finally enabled us to calculate mean annual and monthly temperatures for European forest understories. We found that sub-canopy air temperatures differ substantially from free-air temperatures, being on average 2.1 degrees C (standard deviation +/- 1.6 degrees C) lower in summer and 2.0 degrees C higher (+/- 0.7 degrees C) in winter across Europe. Additionally, our high-resolution maps expose considerable microclimatic variation within landscapes, not captured by the gridded macroclimatic products. The provided forest sub-canopy temperature maps will enable future research to model below-canopy biological processes and patterns, as well as species distributions more accurately.

Mots clés: biodiversity; boosted regression trees; climate change; ecosystem processes; forest microclimate; SoilTemp; species distributions; thermal buffering

Domaines: Biodiversité et Ecologie; Sylviculture, foresterie; Bioclimatologie

Stef Haesen, Jonas J. Lembrechts, Pieter de Frenne, Jonathan Roger Michel Henri Lenoir, Juha Aalto, et al.. ForestTemp - Sub-canopy microclimate temperatures of European forests. Global Change Biology, 2021, 27 (23), pp.6307-6319. ⟨10.1111/gcb.15892⟩. ⟨hal-03614155⟩