Effetti dell'abbandono della gestione forestale sull'avifauna nelle abetine miste: un caso di studio nelle Alpi Orientali

Currently, relatively large parts of Alpine forests, where management has ceased for some time, show old-growth characteristics. To explore the effects of forest abandonment, we compared species richness and composition of birds between two forested watersheds of equal size (1,040 ha): Val Tovanella, where forest management ceased around 50 years ago, and Cajada, where forests are still managed. Both watersheds are located in the Dolomites of Zoldo and are found between 500 and 2,400 m a.s.l. During the breeding season in two subsequent years (2010-2011), 10 sampling plots were used to survey bird presence. In both watersheds, listening points were located within mature r forests. The abandoned forest had higher values for several structural variables: soil nitrogen, beech proportion, tree species richness and quantity of deadwood. Furthermore, composition of the tree and ground layers differed signicantly. To test differences in bird species richness we used linear mixed models by applying the REML method. The differences in composition were computed through the application of PERMANOVA and PERMDISP. Bird species richness was higher in the managed forest (REML, P=0.013, F=7.691). Overall, the composition was signicantly different (PERMANOVA, R2=0.198, P<0.001) even with similar community dispersion (i.e., variability) among treatments (PERMDISP, P=0.153, F=2.224). Some species showed signicantly higher frequencies in the managed forest: Cuculus canorus, Dendrocopos major, and Turdus viscivorus; whereas Poecile palustris was the only species with higher frequency in the abandoned forest. Fifty years of management abandonment has led to a reduction in bird species richness and a different community composition. Nevertheless, it is likely that such a short period without management did not allow the establishment of forest structures suitable to support richer and diverse bird communities, also due to a rather abundant beech proportion in the Val Tovanella forest.