Understory herb-layer dynamics and conservation strategies in the Casentinesi Forests National Park, Central Italy

This thesis aims to enhance the conservation of forest biodiversity by exploring the dynamics of understory herb-layer vascular plants in the National Park "Foreste Casentinesi, Monte Falterona and Campigna." The investigation focuses on i) the influence of elevation on inter- and intraspecific trait variation; ii) the temporal changes in taxonomic and functional diversity in relation to forest management practices; and iii) the role of dark diversity in understanding alien plant species and invasion risks. In Chapter I, I examined how elevation affects intraspecific trait variation and temporal turnover in understory herb-layer vascular plants, revealing insights into trait convergence and habitat filtering. Chapter II focused on the changes in taxonomic and functional diversity in an undisturbed forest over a decade, highlighting shifts in species composition and functional traits. Chapter III explored dark diversity and community completeness, assessing how unobserved species influence invasion risks posed by alien species. Our findings indicate that elevation significantly influences intraspecific trait variability, with higher elevations exhibiting greater trait convergence and distinct community compositions. The analysis of taxonomic and functional diversity over time demonstrated substantial changes, reflecting altered habitat quality and ecosystem stability following a strict protection regime, which has allowed natural processes to remain undisturbed. Dark diversity provided insights into potential community gaps and how unobserved species may influence invasion risk and habitat integrity. This research underscores the importance of incorporating intraspecific trait variation, functional diversity metrics, and dark diversity into conservation frameworks for forest understory vascular plants. By providing a more comprehensive understanding of community dynamics, functional traits complement existing biodiversity assessments and support the development of effective conservation strategies, ultimately enhancing forest biodiversity resilience in the face of ongoing environmental changes.