Saproxylic beetles in three relict beech forests of central Italy: Analysis of environmental parameters and implications for forest management

Abstract

Three relict beech forest of central Italy were surveyed by different trap types: pitfall traps, and three different types of windows flight traps. Species richness and similarity of saproxylic beetles among the study areas were compared using Chao’s indexes. Species composition and abundance were compared in order to test the influence of two trap factors on the catches of saproxylic beetles: the height effect and the colour effect (transparent or black panels). Redundancy Analysis was used to describe the factors affecting abundance and the occurrence of saproxylic beetles through some selected environmental variables at tree scale (tree diameter, canopy closure, tree cavity) and at plot scale (dead wood typology and decay class). The species richness and composition do not vary among the studied areas. The comparison among traps type showed changes in saproxylic beetle assemblages from the ground level to the canopy closure. On the contrary, trap colour did not influence the species composition. A combination of standardized and replicable pitfall and windows traps is suitable to compare the saproxylic fauna. The analysis performed at tree scale, revealed a different correlation between tree-dependent variables and saproxylic beetle richness and abundance for each trap type. Three dead wood variables at plot scale (the amount of standing dead trees, stumps and large branches on the ground) appeared to be good predictors of saproxylic beetle richness.