The role of regional and local scale predictors for plant species richness in Mediterranean forests

Abstract

Both local and regional predictors play a role in determining plant community structure and composition. Climate, soil features as well as different local history and management affect forest understorey and tree species composition, but to date their specific role is relatively unknown. Few studies have addressed the importance of these predictors, especially in the Mediterranean area, where environmental conditions and human impacts have generated heterogeneous forest communities. In this study, the relationships between environmental variables and species richness of different groups of vascular plants (vascular species, woody species and open habitat species) and bryophytes were investigated in Tuscan forests. A total of 37 environmental variables were used by generalised linear model fitting in order to find parsimonious sub-sets of environmental factors (predictors) that are able to explain species diversity patterns at the local scale. Moreover, the role of regional and local variable groups on species richness of the considered plant groups was estimated by using the variance partitioning approach. We found that local variables, such as forest management and structure, explained more variance than regional variables for total species richness, open habitat species richness and bryophyte species richness. On the other hand, regional variables (such as elevation) played a central role for woody species richness.

Keywords:

• Biodiversity
• bryophytes
• plant communities
• species diversity
• vegetation
• woody species

Acknowledgements

This work is part of the research project MONITO, funded by the Regional Administration of Tuscany and the European Community under the Regulations EEC 2157/92 and 3528/86. Many people contributed to this work and we wish to express our gratitude to all of them: A. Gabellini, F. Casini, A. Riva. L. Frati, M. Cetoloni, F. Ghini, D. Viciani, M. Boddi and G. Nicoletti who participated in the field sampling. Special thanks are due to Ramona Magno who allowed us to analyse the climatic data-set of the project “DESERNET” INTERREG IIIB – MEDOCC – Regione Toscana – IBIMET – CNR. Comments by M. Diekmann and an anonymous referee on previous drafts of this paper are greatly appreciated.