1 Forest, Nature and Biomass, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet2 Institut National de la Recherche Agronomique3 University of Leipzig4 University of Suceava5 German Centre for Integrative Biodiversity Research6 University of Warsaw7 University of Freiburg8 Applied ecology, Forest & Landscape Denmark, Faculty of Life Sciences, Københavns Universitet9 Finnish Forest Research Institute10 University of Firenze11 Museo Nacional de Ciencias Naturales12 Swiss Federal Institute for Forest, Snow and Landscape Research13 University of Leipzig14 University of Warsaw15 University of Freiburg16 Applied ecology, Forest & Landscape Denmark, Faculty of Life Sciences, Københavns Universitet
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 (Δδ13CS). Δδ13CS 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.
National Academy of Sciences. Proceedings, 2014, Vol 111, Issue 41, p. 14812-14815