Search

The abandonment of silvicultural activities can lead to changes in species richness and composition of biological communities, when compared to those found in managed forests. The aim of this study was to compare the multi-taxonomical diversity of two mature silver fir-beech-spruce forests in the southern Dolomites (Italy), corresponding to the European Union habitat type 9130. The two sites share similar ecological and structural characteristics, but differ in their recent management histories. In the last 50 years, one site underwent non-intensive management, while the other was left unmanaged and was included in a forest reserve. The species richness and composition of eight taxa were surveyed in the two sites between 2009 and 2011. The difference in mean species richness between the two forest management types was tested through permutation tests, while differences in species composition were tested by principal coordinates analysis and the permutational multivariate analysis of variance. Mean species richness of soil macrofungi, deadwood lichens, bark beetles, and longhorn beetles were significantly higher in the abandoned than in the non-intensively managed forests. Deadwood fungi and epiphytic lichens did not differ in mean species richness between the two study sites, while mean species richness of ground beetles and birds were higher in the non-intensively managed than in the abandoned forest. Significant differences in species composition between the two sites were found for all the taxa, except for longhorn beetles. These results indicate that improving forest landscape heterogeneity through the creation of a mosaic of abandoned and extensively managed forests should better fulfill the requirements of ecologically different taxa.

Invasive alien tree species can strongly impact biodiversity and future projections predict their spread over natural, semi-natural and human habitats. However, little is known about plant communities that form during the first stages of invasion. We investigated the composition of plant communities in alien Robinia pseudoacacia L. secondary forests growing on grasslands and cultivated areas abandoned during the last 35-40 years in north-eastern Italy to understand whether these formations could cause floristic homogenization of plant communities composition. On the basis of a cluster analysis, plant communities were assigned to seven syntaxonomic categories and split into four groups characterized by the occurrence of 20 species indicative of (a) nitrogen-rich, (b) true forest and (c) open habitat conditions. RDA analysis enabled main stand and environmental variables filtering these communities to be identified and β-diversity components were partitioned through the SDR (Similarity - richness Difference - species Replacement) simplex approach. Plant composition patterns were significantly associated to variability in elevation, stand vertical structure, shrub cover, mean tree diameter and height, and basal area. Shrub cover discriminates between plant communities associated with open or shaded conditions. The partition of β-diversity components revealed that replacement is the prominent process structuring plant communities in these secondary forests. Our study showed that secondary Robinia forests growing on abandoned lands may host compositionally heterogeneous plant communities, thus contributing to regional biodiversity.