Tree drought–mortality risk depends more on intrinsic species resistance than on stand species diversity

Tree drought–mortality risk depends more on intrinsic species resistance than on stand species diversity

Increasing tree diversity is considered a key management option to adapt forests to climate change. However, the effect of species diversity on a forest's ability to cope with extreme drought remains elusive. In this study, we assessed drought tolerance (xylem vulnerability to cavitation) and w...

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Published in:Global change biology Vol. 30; no. 9; pp. e17503 - n/a
Main Authors: Decarsin, Renaud, Guillemot, Joannès, Maire, Guerric, Blondeel, Haben, Meredieu, Céline, Achard, Emma, Bonal, Damien, Cochard, Hervé, Corso, Déborah, Delzon, Sylvain, Doucet, Zoé, Druel, Arsène, Grossiord, Charlotte, Torres‐Ruiz, José Manuel, Bauhus, Jürgen, Godbold, Douglas L., Hajek, Peter, Jactel, Hervé, Jensen, Joel, Mereu, Simone, Ponette, Quentin, Rewald, Boris, Ruffault, Julien, Sandén, Hans, Scherer‐Lorenzen, Michael, Serrano‐León, Hernán, Simioni, Guillaume, Verheyen, Kris, Werner, Ramona, Martin‐StPaul, Nicolas
Format: Journal Article
Language:English
Published: England Blackwell Publishing Ltd 01-09-2024
Wiley
Subjects:
Biodiversity
Cavitation
Climate Change
Drought
Drought resistance
Droughts
Environmental Sciences
Europe
Extreme drought
forest adaptation
Forest management
Forest Science
Forests
Health risks
hydraulic traits
Mixtures
Mortality
Mortality risk
Plant diversity
Risk
Safety margins
Skogsvetenskap
Species diversity
species interactions
Species richness
tree diversity
Trees
Trees - physiology
Variability
Water potential
Water stress
Xylem
Xylem - physiology
xylem embolism
Europe
species richness
xylem embolism
tree diversity
hydraulic traits
species interactions
water stress
forest adaptation
forest management
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Summary:Increasing tree diversity is considered a key management option to adapt forests to climate change. However, the effect of species diversity on a forest's ability to cope with extreme drought remains elusive. In this study, we assessed drought tolerance (xylem vulnerability to cavitation) and water stress (water potential), and combined them into a metric of drought–mortality risk (hydraulic safety margin) during extreme 2021 or 2022 summer droughts in five European tree diversity experiments encompassing different biomes. Overall, we found that drought–mortality risk was primarily driven by species identity (56.7% of the total variability), while tree diversity had a much lower effect (8% of the total variability). This result remained valid at the local scale (i.e within experiment) and across the studied European biomes. Tree diversity effect on drought–mortality risk was mediated by changes in water stress intensity, not by changes in xylem vulnerability to cavitation. Significant diversity effects were observed in all experiments, but those effects often varied from positive to negative across mixtures for a given species. Indeed, we found that the composition of the mixtures (i.e., the identities of the species mixed), but not the species richness of the mixture per se, is a driver of tree drought–mortality risk. This calls for a better understanding of the underlying mechanisms before tree diversity can be considered an operational adaption tool to extreme drought. Forest diversification should be considered jointly with management strategies focussed on favouring drought‐tolerant species. Written Summary: Working with more than 20 species and 5 experimental forests in different European biomes, we show that the risk of a tree dying under extreme drought is mainly determined by its species identity, rather than whether it grows in a monoculture or a mixture. However, even if the effects of species richness are weak on average, certain species mixtures can drastically limit the risk of tree mortality under drought in certain species combinations. Understanding these mechanisms is essential for developing predictive and operational tools for management strategies to adapt forests to extreme drought.
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ISSN:1354-1013
1365-2486
1365-2486
DOI:10.1111/gcb.17503