Effects of Tree Species Biodiversity on Soil C and N Pools: A regional Case Study in Northern Italy

Site conditions are known to affect local resource availability, therefore being an important driver of plant species diversity. In this context, soil fertility is thought to influence the relationship between plant species diversity and climate in forests ecosystems. The data collected with the Regional Forest Carbon Inventory of the Trento Province (InFoCarb), on 150 plots of 600 m2 size, were used to investigate possible impacts of tree biodiversity on local soil conditions. Biodiversity was quantified both as Species Richness and with Biodiversity Indexes (Simpson's Index and Shannon-Wiener index) moreover, canopy species evenness was expressed by the Simpson's dominance index by using the proportions of basal area for each constituent species. Forest floor and mineral soil were collected on three mini-pits inside each sampling plot. Relationships between the soil C and N pools and tree biodiversity were investigated with linear regressions whereas Boosted Regression Trees models were used to highlight the main determinants of canopy species diversity.