The influence of species interactions on the response of Abies alba‘s water-use efficiency to extreme drought events
(Mixed stand effect on Abies alba functioning in drought conditions)

PI : Damien Bonal (UMR 1137 Ecologie et Ecophysiologie Forestières – EEF)

Co-applicants :  LERFOB

Collaboration : Nicolas ANGELI, Paulina PINTO & Stéphane PONTON (UMR EEF), Jean-Claude GEGOUT, Ignacio BARBEITO, Francois LEBOURGEOIS & Cyrille RATHGEBER (UMR Lerfob)

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Context — In mixed forest ecosystems, interactions among tree species influence ecosystem productivity and functioning, but environmental conditions also play an important role in shaping relationships between species diversity and ecosystem functioning. In the context of environmental changes, the carbon and water balance in pure vs. mixed forest stands may thus be differentially influenced by changing soil water availability.

Objectives — In this study, we intend to analyze the growth and functional response of Abies alba trees growing in the Vosges region to species competition for water and nutrient resources during extreme drought events.

Approach —  We will analyze the response of radial growth, carbon isotope composition (d¹³C, ‰), and oxygen isotope composition (d¹⁸C, ‰) in tree rings of Abies alba during two drought events (the severe drought of 1976 and the less intense but long-lasting drought episode of 1989-1991). We will use wood cores previously collected in the framework of a previous study from 86 stands regularly distributed in the Vosges mountains over three altitude ranges (from 330 to 1100 m), three humus forms (moder to mull), and three species mixture types (pure stands of A. alba (Aa), mixed stands of A. alba with Fagus sylvatica (Aa-Fs), mixed stands of A. alba with Picea abies (Aa-Pa)).

Expected results and impacts — Expected results of this project will improve our understanding of the influence of species mixtures on the adaptation and/or resilience of trees to climate changes. This is of great importance, particularly because the outcomes from such research will find direct applications for forest management practices to be conducted in the near future.