Linking individual- and species-level leaf traits with ontogenetic size to explain tree performance within competitive and environmental contexts

Establishing the relationship between functional traits and tree performance is critical to understanding forest ecosystem dynamics. However, how individual and species traits work together to influence tree growth and survival under complex environmental conditions remains a topic of debate. To clarify this issue, we analyzed leaf traits from 1320 individual trees of 17 species within a stem-mapped temperate natural forest to develop growth and survival models at both individual and species levels from 2010 to 2020. These traits were linked to ontogenetic size, competition, topography and soil properties to elucidate the drivers of tree performance. Our results showed that species-level traits moderated the influence of size and environment factors on growth., while individual-level traits mediated the effects of size, competition, and environmental conditions on tree performance. Providing new insights for trait-based studies in temperate forest ecosystems, this study uses mature natural forests to identify mechanisms by which species and individual traits interact with ontogenetic size, competition and environmental variables to explain tree performance. • Individual traits directly explain tree growth and survival. • Ontogenetic size indirectly affects tree growth and survival via traits. • Species traits moderate the relationship between ontogenetic size and growth. • Size and traits jointly explain competition and environment effects on performance.