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Research article - Peer-reviewed, 2021

ForestTemp - Sub-canopy microclimate temperatures of European forests

Haesen, Stef; Lembrechts, Jonas J.; De Frenne, Pieter; Lenoir, Jonathan; Aalto, Juha; Ashcroft, Michael B.; Kopecky, Martin; Luoto, Miska; Maclean, Ilya; Nijs, Ivan; Niittynen, Pekka; van den Hoogen, Johan; Arriga, Nicola; Bruna, Josef; Buchmann, Nina; Ciliak, Marek; Collalti, Alessio; De Lombaerde, Emiel; Descombes, Patrice; Gharun, Mana;
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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.


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

Published in

Global Change Biology
2021, volume: 27, number: 23, pages: 6307-6319
Publisher: WILEY

Authors' information

Haesen, Stef
KU Leuven
Lembrechts, Jonas J.
University of Antwerp
De Frenne, Pieter
Ghent University
Lenoir, Jonathan
Universite de Picardie Jules Verne (UPJV)
Aalto, Juha
Finnish Meteorological Institute
Ashcroft, Michael B.
University of Wollongong
Kopecky, Martin
Czech University of Life Sciences Prague
Luoto, Miska
University of Helsinki
Maclean, Ilya
University of Exeter
Nijs, Ivan
University of Antwerp
Niittynen, Pekka
Univ Helsinki
van den Hoogen, Johan
ETH Zurich
Arriga, Nicola
European Commission Joint Research Centre
Bruna, Josef
Institute of Botany of the Czech Academy of Sciences
Buchmann, Nina
ETH Zurich
Ciliak, Marek
Technical University Zvolen
Collalti, Alessio
Istituto per i Sistemi Agricoli e Forestali del Mediterraneo (ISAFoM-CNR)
De Lombaerde, Emiel
Ghent University
Descombes, Patrice
University of Lausanne
Gharun, Mana
ETH Zurich
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Sustainable Development Goals

SDG13 Climate action

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