Compositional and ecological diversity of Cansiglio forest (Friuli Venezia Giulia, Italy)

Aim: The aim of this study is to describe the compositional and ecological diversity of the Natura 2000 Site ‘Cansiglio Forest’ (IT3310006). Study area: The study area is located in the South-Eastern Prealps between the Venetian-Friulian plain and the Cansiglio plateau, a typical karstic system. Methods: A total of 25 vegetation relevés, each of 250 m2, were sampled in the LIFE SPAN (LIFE19 NAT/IT/000104) project plots and were subjected to cluster analysis (Bray-Curtis, Ward) and NMDS ordination. Variables such as Ellenberg Indicator Values, environmental parameters, life forms, chorotypes, and phytosociological units were tested using ANOVA and the Kruskal-Wallis test to assess significant differences between clusters. The indicspecies package was applied to study the association between species patterns and combinations of clusters. Results: We distinguished three clusters. Cluster A, characterized by several species, including Chaerophyllum hirsutum and Phegopteris connectilis, shows higher EIVs for moisture, acidic soil reaction and lower temperature, a more open canopy and mainly Circumboreal and Euro Asian species of Vaccinio-Piceetea. Cluster B1, a mixed forest of Fagus sylvatica and Abies alba with Circaea alpina, has intermediate EIVs, a closed canopy, low herbaceous layer cover, and higher cover of SE-European species. Cluster B2, a pure Fagus sylvatica forest with Lathyrus venetus, has lower EIVs for humidity and higher for temperature, and mainly Central European species of Carpino-Fagetea. Conclusion: The anthropogenic spruce forest is developing in the Cansiglio plateau and is favored by thermal inversion. It could be identified with Senecioni cacaliaster-Piceetum, but further study is needed to confirm. The mixed forest of Fagus sylvatica and Abies alba and the pure beech forest represent two facies of the Cardamino pentaphylli-Fagetum fagetosum, with the first one dominating on the coldest slopes and the second one on the highest and warmer belt. This community can be included in the Aremonio-Fagion alliance. Taxonomic reference: Euro+Med PlantBase (2023). Syntaxonomic references: Mucina et al. (2016) for classes, orders and alliances; Willner et al. (2017) for suballiances. Abbreviations: ANOVA = analysis of variance; EIV = Ellenberg indicator value; FVG = Autonomous Region of Friuli Venezia-Giulia; HSD = honestly significant difference; NMDS = non-metric multidimensional scaling.