Towards an integrated checklist and forest affinity assessment of the Italian woodland flora

In the framework of research projects on forest biodiversity, it recently came out the need for a reasoned checklist of the vascular plant species that are constituent to, or associated with, the Italian woodlands. A nomenclaturally updated floristic compilation was therefore initiated by integrating relevant lists and datasets in the literature, on-line repositories and personal unpublished data collected across Italian woodlands during the last 30 years. The question of “what is a forest” was central to this work. Two slightly different forest definitions were considered, that in the National Forest Inventory (1) and that in (2), which largely follows those adopted in the central European countries. However, defining the limits of the “forest” habitat in the contrasting biogeographical contexts of the Italian territory remained sometimes doubtful and required subjective decisions, ultimately influencing the number of species included the checklist. In this context, a preliminary evaluation of the degree of affinity of species for forest habitats was carried out using the system recently proposed the central and northern European flora (2). This information is of primary relevance when evaluating forests in terms of biodiversity, naturalness, dynamic stage and impact of disturbances. The system distinguishes two main groups, forest specialists (group 1) and generalists (group 2). The former includes species of forest interiors (1.1) and species of forest edges and forest openings (1.2); the second includes species that can be found in forest as well as open vegetation (2.1) and species that can be found partly in forest, but mainly in open vegetation (2.2). An additional “O” category is distinguished, covering species typical for non-forest vegetation. Since the category of a species may shift among the different biogeographic contexts of Italy, the evaluation will be implemented separately for the northern, central-southern and insular regions, also involving expert botanists from these areas. Other species-level information will be integrated in the checklist, such as, life-form, main morpho-functional group, Ellenberg indicator values, and other. The preliminary checklist includes around 1400 species (native and naturalized alien) in the four main forest affinity categories depicted above. Adding those in the “O” category considerable increases the checklist, as many habitats technically representing “forests” are rich in species of primarily open-habitat, due to anthropic disturbances and low levels of naturalness. The list will be continuously integrated with data from the understory diversity monitoring implemented in the National Forest Inventory 2025 (3). Overall, this work will contribute to expand the European forest species list to the Mediterranean region and support the evaluation of the Italian woodland plant diversity for management and conservation purposes.