La biodiversità dei boschi siciliani. Parte I: l’avifauna

We collected data on bird diversity in the main Sicilian forest types and related them to silvicultural management and a number of abiotic and biotic factors. The results show that bird species richness is influencedby bioclimate, maximum tree diameter, nutritive value of all vegetation layers. Forests in meso-/supramediterranean bioclimate are richer in species than forests in thermo-/mesomediterranean bioclimate. The importance of maximum tree diameter, which indirectly reflects alsothe silvicultural management of a forest, is due to the dependency of some corticicolous species on large trees, and of some other bird species on crowns of high trees which have usually large diameters. The nutritive value of a forest was quantified by data sampling: for the herbaceous,shrub and tree layers we recorded all species with nutritive value. The absence of plant species with nutritive value strongly reduces the number of bird species present in a forest; it is, however, noteworthy that an abundance of plant species with nutritive value does not automatically lead to abundant bird species. In addition, it has to be underlinedthat neither species richness nor Shannon’s diversity indexare influenced by the diameter of standing dead wood or by the volume of fallen dead wood. The guidelines whichresult from our analysis for the silvicultural management of Sicilian forests are: 1) in order to increase bird diversity do not cut large adult trees, also in coppices; 2) leave plantswith high nutritive value in coppices; 3) in reforestations do not cut the underbrush and do not prune the lowerbranches of trees, these actions have to be taken only in the forest edge for wildfire prevention.