How effective are different protection strategies in promoting the plant diversity of temperate forests in national parks?

Protected areas are supposed to mitigate the loss of diversity caused by human activities in forests. However, different management strategies applied across protected areas affect diversity in various ways. This study compares the taxonomic, functional, and phylogenetic diversity, and the species composition of understory plants, between sustainably managed forests and strictly protected forests. From temperate beech (Fagus sylvatica L.) forests within the Foreste Casentinesi National Park (Northern Apennine, Italy), we selected 28 quadrats in strictly protected and managed zones. In each quadrat, we recorded the cover abundance of vascular plant species and measured two functional traits (specific leaf area and clonal lateral spread) on the most abundant understory species. We used generalized linear models to test for differences in taxonomic (species richness and the percentage of forest specialist species), functional (functional richness for single and multiple traits), and phylogenetic diversity (mean pairwise distance) between protection zones. Lastly, we evaluated differences in species composition between protection zones using non-metric multidimensional scaling, supported by PERMANOVA and indicator species analyses. Species richness and phylogenetic diversity did not differ between strictly protected and managed zones. Strictly protected forests had a significantly higher percentage of forest specialist species and functional richness of clonal lateral spread than forests allowing sustainable logging. Species composition was significantly different between strictly protected and managed forests; the most important indicator species detected within managed zones were Sanicula europaea and Aremonia agrimonoides, while Veronica montana, Oxalis acetosella, and Salvia glutinosa were indicator species within strictly protected forests. The difference between strictly protected forests and forests managed with sustainable logging is reflected in the proportion of forest specialist species and the diversity of belowground space occupation and resource acquisition strategies. Instead, species richness and phylogenetic diversity do not discriminate between the two protection zones. We suggest incorporating specialist species, functional and compositional diversity metrics into the evaluation framework to guide future conservation and management practices.