Multiyear Drought Strengthens Positive and Negative Functional Diversity Effects on Tree Growth Response

Mixed-species forests are proposed to enhance tree resistance and resilience to drought. However, growing evidence shows that tree species richness does not consistently improve tree growth responses to drought. The underlying mechanisms remain uncertain, especially under unprecedented multiyear droughts. We used a network of planted tree diversity experiments to investigate how neighborhood tree diversity and species' functional traits influence individual tree responses to drought. We analyzed tree cores (948 trees across 16 species) from nine young experiments across Europe featuring tree species richness gradients (1-6 species), which experienced recent severe droughts. Radial growth response to drought was quantified as tree-ring biomass increment using X-ray computed tomography. We applied hydraulic trait-based growth models to analyze single-year drought responses across all sites and site-specific responses during consecutive drought years. Growth responses to a single-year drought were partially explained by the focal species' hydraulic safety margin (representing species' drought tolerance) and drought intensity, but were independent of neighborhood species richness. The effects of neighborhood functional diversity on growth responses shifted from positive to negative with increasing drought duration during a single growing season. Tree diversity effects on growth responses strengthened during consecutive drought years and were site-specific with contrasting directions (both positive and negative). This indicates opposing diversity effects pathways under consecutive drought events, possibly resulting from competitive release or greater water consumption in diverse mixtures. We conclude that tree diversity effects on growth under single-year droughts may differ considerably from responses to consecutive drought years. Our study highlights the need to consider trait-based approaches (specifically, hydraulic traits) and neighborhood scale processes to understand the multifaceted responses of tree mixtures under prolonged drought stress. This experimental approach provides a robust framework to test biodiversity-ecosystem functioning (BEF) relationships relevant for young, planted forests under increased drought stress.

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Publication Details

Journal
Global Change Biology
Published
2025-09-01
DOI
https://doi.org/10.1111/gcb.70394
Citations
9
Primary Topic
Plant Water Relations and Carbon Dynamics
Type
article
Field-Weighted Citation Impact
9.95

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article

Multiyear Drought Strengthens Positive and Negative Functional Diversity Effects on Tree Growth Response

Matthieu Boone, Douglas L. Godbold, Quentin Ponette, Nicolas Martin‐StPaul et al.
9 citations
Global Change Biology
Plant Water Relations and Carbon Dynamics
9.95
article

Multiyear Drought Strengthens Positive and Negative Functional Diversity Effects on Tree Growth Response

Matthieu Boone, Douglas L. Godbold, Quentin Ponette, Nicolas Martin‐StPaul, Arsène Druel, Hervé Jactel, Jürgen Bauhus, Peter Hajek, Kris Verheyen, Ramona Werner, Georgios Skiadaresis, Haben Blondeel, Boris Rewald, Julia Koricheva, Simone Mereu, Joannès Guillemot, Jan Van den Bulcke, Michael Scherer‐Lorenzen, Hans Sandén, Lander Baeten, Florian Schnabel, Damien Bonal, Hernán Serrano‐León, Renaud Decarsin, Jialiang Gong, Paula Glenz, Johannes Steurer
article en
9 citations

Abstract

Mixed-species forests are proposed to enhance tree resistance and resilience to drought. However, growing evidence shows that tree species richness does not consistently improve tree growth responses to drought. The underlying mechanisms remain uncertain, especially under unprecedented multiyear droughts. We used a network of planted tree diversity experiments to investigate how neighborhood tree diversity and species' functional traits influence individual tree responses to drought. We analyzed tree cores (948 trees across 16 species) from nine young experiments across Europe featuring tree species richness gradients (1-6 species), which experienced recent severe droughts. Radial growth response to drought was quantified as tree-ring biomass increment using X-ray computed tomography. We applied hydraulic trait-based growth models to analyze single-year drought responses across all sites and site-specific responses during consecutive drought years. Growth responses to a single-year drought were partially explained by the focal species' hydraulic safety margin (representing species' drought tolerance) and drought intensity, but were independent of neighborhood species richness. The effects of neighborhood functional diversity on growth responses shifted from positive to negative with increasing drought duration during a single growing season. Tree diversity effects on growth responses strengthened during consecutive drought years and were site-specific with contrasting directions (both positive and negative). This indicates opposing diversity effects pathways under consecutive drought events, possibly resulting from competitive release or greater water consumption in diverse mixtures. We conclude that tree diversity effects on growth under single-year droughts may differ considerably from responses to consecutive drought years. Our study highlights the need to consider trait-based approaches (specifically, hydraulic traits) and neighborhood scale processes to understand the multifaceted responses of tree mixtures under prolonged drought stress. This experimental approach provides a robust framework to test biodiversity-ecosystem functioning (BEF) relationships relevant for young, planted forests under increased drought stress.

Global Change BiologyVol. 31(9)
CEA CESTA (FR), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (FR), Université de Bordeaux (FR), University of Freiburg (DE), Universidade de São Paulo (BR), Royal Holloway University of London (GB), Chinese Academy of Sciences (CN), Université de Montpellier (FR), Research Institute for Nature and Forest (BE), Cornell University (US), AgroParisTech (FR), Ghent University Hospital (BE), Ghent University (BE), Institute of Forest Ecology of the Slovak Academy of Sciences (SK), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (FR), Ecologie fonctionnelle & biogéochimie des sols & des agro-systèmes (FR), Silva (FR), Institute of Subtropical Agriculture (CN), Institute of Molecular Biology and Pathology (IT), CMCC Foundation - Euro-Mediterranean Center on Climate Change (IT), Écologie des Forêts Méditerranéennes (FR), Forest Research Institute (BG), Institut Agro Montpelier (FR), UMR BIOdiversity, GEnes & Communities (FR), VIB-UGent Center for Medical Biotechnology (BE), Zhanjiang Experimental Station (CN), GFZ Helmholtz Centre for Geosciences (DE), Agence de la transition écologique (FR), Institut de Recherche pour le Développement (FR), Mendel University in Brno (CZ), Université de Lorraine (FR), BOKU University (AT), UCLouvain (BE)
Biodiversa+, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Fundação de Amparo à Pesquisa do Estado de São Paulo, Svenska Forskningsrådet Formas, Austrian Science Fund, Albert-Ludwigs-Universität Freiburg, Belgian Federal Science Policy Office, BNP Paribas Cardif, Fonds Wetenschappelijk Onderzoek, Mendelova Univerzita v Brně, Vlaamse regering, U.S. Forest Service, Bijzonder Onderzoeksfonds UGent, Fondation BNP Paribas
Openalex Percentile: Top 2%
Plant Water Relations and Carbon Dynamics
9.95
DOIOpen Access PDFOpenAlex
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