MultiForDiv: a trait-based, multi-taxon analysis of forest understory biodiversity

Forest ecosystems provide essential ecosystem services but face increasing threats from global changes. Although conservation of forest biodiversity is prioritized in international and national policies, many components, especially those in the understory (vascular plants, fungi, lichens) remain overlooked. These organisms are crucial for forest functioning and sensitive to environmental change. The MultiForDiv project investigates spatio-temporal patterns and drivers of forest understory biodiversity using a multi-taxon, trait-based approach. This research integrates long-term data collected in the Italian permanent plots of the ICP Forests LII network distributed across all the national territory. Analyses on the vascular plants reveals significant species richness declines over the last 25 years. Using linear mixed models, forest structural variables, soil pH, and climate features are identified as key drivers of diversity, with biome-specific responses. Preliminary results on epiphytic lichens suggest temporal stability in species richness. Functional traits of epiphytic non-vascular communities - including lichens and bryophytes - are explored. The relationships among air, bark and cryptogams thermal and hydric regimes under different environmental conditions are disentangled based on IR and NIR spectrum signatures and measured photosynthetic parameters. This allows to better understand their energy balance and their contribution to forest microclimate regulation and ecosystem functioning. Soil microfungal diversity is investigated through functional traits (including xerotolerance, thermotolerance, and solubilization of phosphates) to explore their responses to environmental variables. This trait-based, multi-taxon approach reveals group-specific responses to environmental conditions, highlighting the need to integrate diverse biological components for a better understanding of forest biodiversity dynamics and effective forests management.