Davrinche, A. | bioRxiv Science

bioRxiv2023

Improving forest ecosystem functions by optimizing tree species spatial arrangement

Reforestation and afforestation programs are promoted as strategies to mitigate rising atmospheric CO2 concentrations and enhance ecosystem services. Planting diverse forests is supposed to foster such benefits, but optimal tree planting techniques, especially regarding species spatial arrangement, are underexplored. Here, using field measurements from the subtropical BEF-China experiment, we simulated leaf litterfall and decomposition, as a function of various spatial arrangements of tree species, from clusters of species to random distributions. We show that increasing tree species spatial heterogeneity in forests composed of nine tree species led to more evenly distributed litterfall, increased litter decomposition and associated nitrogen cycling by 45%. These effects were amplified with increasing plot species richness, while species functional trait identity and diversity modulated these relationships. The spatial arrangement of tree species is a critical component determining biodiversity-ecosystem functioning relationships, and considering such spatial aspects is crucial for operationalizing biodiversity-ecosystem functioning theory in realistic re-/afforestation projects.

ecology↗

bioRxiv2023

High within-tree leaf trait variation and its response to species diversity and soil nutrients

O_LILeaf functional traits provide important insights into plants responses to different environments. Leaf traits have been increasingly studied within-species in the last decade, following the growing realisation that neglecting the intra-specific scale can result in misreading plants response to environmental change. However, while likely to lead to similar pitfalls, within-individual leaf traits are under-researched despite being the scale at which elementary interactions shape ecosystem processes. C_LIO_LITo address this critical lack of understanding at the local scale, we assessed leaf trait variation in a large biodiversity-ecosystem functioning experiment in subtropical China. We used optical spectroscopy to determine nine morphological and biochemical traits of >5800 leaves from 414 trees representing 14 species. We evaluated the relative importance of the intra-individual level for total leaf trait variation, and the interacting effect of two trait variations drivers, soil nutrient availability, and a local species richness gradient. C_LIO_LIComparing the amount of trait variation at the between-species, between-individuals and intra-individual levels, we found that intra-individual variation accounted on average for >25% of total trait variation. Additionally, intra-individual variation was the most prominent component of intra-specific variation. We found partial support for positive effects of soil nutrient availability and species diversity on intra-individual trait variation, and a strong interdependence of both effects. Contrary to the amplifying effects we expected, trait variation increased with soil nutrient availability at intermediate diversity, but decreased at low and high diversity. C_LIO_LIOur findings quantify the relevance of intra-individual level for leaf trait variation, and expose a complex interaction between its drivers. In particular, interactive effects of soil nutrient availability and local species diversity on trait variation suggest responses ranging from alleviating competition to enhancing complementarity. Taken together, our work highlights the importance of integrating an intra-individual perspective to understand trait-based mechanisms in biodiversity-ecosystem functioning relationships. C_LI

ecology↗