Tree diversity does not always improve resistance of forest ecosystems to drought

Charlotte Grossiord (1) , André Granier (1) , Sophia Ratcliffe (2) , Olivier Bouriaud (3) , Helge Bruelheide (4, 5) , Ewa Chećko (6) , David Ian Forrester (7) , Seid Muhie Dawud (8) , Leena Finér (9) , Martina Pollastrini (10) , Michael Scherer-Lorenzen (11) , Fernando Valladares (12) , Damien Bonal (1) , Arthur Gessler (13)

1 EEF - Ecologie et Ecophysiologie Forestières [devient SILVA en 2018]
2 Institut für Spezielle Botanik und Funktionelle Biodiversität
3 Forestry Faculty
4 Institute of Biology/Geobotany and Botanical Garden
5 DFG - Deutsche Forschungsgemeinschaft - German Research Foundation
6 Faculty of Biology, Bialowieza Geobotanical Station
7 Faculty of Environment and Natural Resources
8 IGN - Department of Geosciences and Natural Resource Management [Copenhagen]
9 Finnish Forest Research Institute
10 Department of Agri-Food and Environmental Sciences, Section of Soil and Plant Science
11 Faculty of Biology/Geobotany
12 MNCN - Museo Nacional de Ciencias Naturales [Madrid]
13 Long-Term Forest Ecosystem Research

Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year (Δδ(13)CS). Δδ(13)CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the drought exposure of the ecosystem. However, the other three forest types were unaffected by tree species diversity. We conclude that higher diversity enhances resistance to drought events only in drought-prone environments. Managing forest ecosystems for high tree species diversity does not necessarily assure improved adaptability to the more severe and frequent drought events predicted for the future.

Mots clés: FundivEUROPE; carbon isotope composition; climate change; ecology; species interaction

Domaines: Milieux et Changements globaux; Biodiversité et Ecologie

Charlotte Grossiord, André Granier, Sophia Ratcliffe, Olivier Bouriaud, Helge Bruelheide, et al.. Tree diversity does not always improve resistance of forest ecosystems to drought. Proceedings of the National Academy of Sciences of the United States of America, 2014, 111 (41), pp.14812-14815. ⟨10.1073/pnas.1411970111⟩. ⟨hal-01190150⟩