iDiv Annual Conference 2025

Traits in the light of diversity: Exploring intra-individual leaf trait responses to local light availability and biodiversity in a subtropical forest experiment

1 Oct 2025, 14:30

15m

Lecture Hall XXIII (Audimax)

Talk Biodiversity and the functioning of Ecosystems Biodiversity and the functioning of Ecosystems

Speaker

Tobias Proß (Martin Luther University Halle-Wittenberg)

Description

Leaf traits are key indicators of ecosystem functioning and vary not only between species but also within species and within individuals. However, within-individual variation is often neglected due to measurement limitations. Light availability, influenced by surrounding vegetation, is a major driver of leaf trait variability, especially across the strong vertical light gradients found in forest canopies.
In the BEF-China subtropical forest experiment, we investigated how within-individual leaf traits respond to local light availability and tree species richness. We sampled leaves across vertical light gradients in monocultures and mixtures of up to 24 species. Light availability was measured with sensors placed adjacent to each sampled leaf. Using visible and near-infrared spectroscopy, we predicted 14 leaf traits from 4,981 leaves across 15 native tree species. We assessed whether neighboring species identity or overall species richness had a stronger influence on the leaf trait–light relationship.
Most trait values responded to light availability, though this response differed between deciduous and evergreen species. We found that tree species richness and a tree’s direct neighbour could modify the light–trait relationship at the individual level. In some instances, a focal tree’s direct neighbour influenced its leaf trait values more than the tree species richness in its local neighbourhood. Specifically, in conspecific tree pairs of evergreens, specific leaf area and leaf nitrogen displayed a stronger response to changing light conditions.
This response to light availability suggests a mechanism for avoiding within-species competition that is observable at the within-individual level. Our results show that biodiversity influences ecosystem functions through its effects on within-individual leaf trait variation. The fact that the interplay between light availability, biodiversity and leaf traits can be observed within individual trees highlights the importance of within-individual leaf trait variation in biodiversity research.