Neighbourhood diversity increases tree growth in experimental forests more in wetter climates but not in wetter years.

Tree diversity often increases stand-level growth, but whether neighbourhood diversity effects on individual tree growth change with climatic conditions remains unclear. Here, using 852,170 records of 113,701 individuals from 129 species in 15 tree diversity experiments across four biomes, we address this knowledge gap with a synthesis of tree growth data spanning a broad climate gradient. We examine how neighbourhood-scale (defined as a focal tree and the adjacent trees) taxonomic and functional diversity effects on tree growth vary with climate, both spatially (across sites) and temporally (within sites).

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 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.

Intra-specific leaf trait variability of F. sylvatica, Q. petraea and P. abies in response to inter-specific competition and implications for forest functioning.

Variability in functional traits (FT) is increasingly used to understand the mechanisms behind tree species interactions and ecosystem functioning. In order to explore how FT differ due to interactions between tree species and its influence on stand productivity and other ecological processes, we examined the effects of tree species composition on the intra-specific variability of four widely measured FT: specific leaf area, leaf nitrogen content, leaf angle and stomatal conductance response to vapor pressure deficit. This study focused on three major central European tree species: European beech (Fagus sylvatica L.