Woody species diversity as predictor of vascular plant species diversity in forest ecosystems

Despite a considerable effort of scientific community and a huge amount of literature, the capacity to assess and monitor biodiversity at coarser spatial scales in short time periods is still limited. Thus assessing indicator or surrogate information from existing data sets, such as forest inventories, is a challenge for biodiversity management and monitoring. We used two forest data sets (woody plants and all vascular plants) to test whether the diversity of woody plant species can be used as predictor of the diversity of all vascular plant species. Our study was performed in the forests of Liguria, Italy. In order to take into account several levels of community organisation, we calculated different measures of species diversity at different levels of sampling hierarchy for both data sets (alpha, beta and gamma diversity). We used ordinary linear regression to test the predictive power of the diversity measures obtained by the occurrences of woody plant species with respect to those obtained by all vascular plant species. Our results suggest that beta diversity and gamma diversity of woody species can be used to predict the beta diversity and the gamma diversity of all vascular plant species, at different levels of sampling hierarchy, while the alpha diversity of woody species cannot be used to predict the alpha diversity of all vascular plant species. These results point out the importance to consider measures based non only on species richness and to interpret the relation between species richness of woody plants and species richness of all vascular plants taking into account the scale dependence of this relations. Thus, our work demonstrates the feasibility of using data on woody plant species as recorded by forest inventories to predict the diversity patterns of all plant species in forest ecosystems.