Abstract
The southernmost European beech forests are located in the upper forest vegetation belt on Mount Etna volcano. Their stand-structural patterns were analysed to assess the effects of the site-ecological factors and previous management practices on the forest structure. Five main structural-silvicultural types were identified among the main beech forest types: coppice, high-mountain coppice (HMCo), high forest, coppice in conversion to high-forest and non-formal stand. A detailed stand-structural analysis was carried out through measured dendrometric parameters and derived structural characters linked to both the horizontal and the vertical profiles. Plant regeneration processes were also assessed, and several biodiversity indicators were calculated. The collected data indicate a high variability of beech stand structures in relation to the heterogeneity of the site-ecological characteristics as well as to the effects of both natural and anthropic disturbance factors. The occurrence of particular stand structures along the altitude gradient on Mount Etna is evident. It is especially visible in the multi-stemmed HMCos in relation to the changing, and increasingly limiting, ecological factors, although at higher altitudes historical anthropic actions (felling) also have had an influence. Inside the Mediterranean area, these stands highlight their ecological marginality, in terms of both latitude and altitude, especially regarding current climate change processes.
Acknowledgements
The authors wish to thank Prof. A. Motisi for the practical indications on the statistical analysis. We are grateful to Prof. F. G. Maetzke for useful comments on an earlier version of the manuscript. We also thank the anonymous reviewers for their valuable indications.