The diversity of Italian forests: a interactive product of biogeography and ecology.

Background: Italian forests contains a high total diversity of plants species and this is likely due to the huge biogeographical gradients covered by the country (from the Alps to the Mediterranean) as well as to the long lasting human exploitation and management practices. This study aims to investigate the interactive effects of ecology and biogeography in determining the total plant diversity of Italian forests using a spatially representative sample of forests made of 201 plots sampled all over the country (CONECOFOR LI network). The general hypothesis to be tested is that the effects of present day ecological factors are less important than biogeographical factors in determining the total diversity of forested areas. The plant diversity of the sampled forest plan communities was divided into different spatial components, in particular: plot, site, forest type (used as a proxy for present day ecological conditions) and biogeographical region. Species presence\ absence was only used. The three following hypotheses have then been tested: Hypothesis 1: The diversity component accounted by the biogeographical region is higher that the diversity accounted by the lower scale components (plot, site, forest type). Hypothesis 2: Distance decay rate across biogeographical regions is higher than distance decay rate within biogeographical regions (after correction for extent). Hypothesis 3: Beta nestedness is higher within than across biogeographical regions (after correction for extent); on the other hand Beta complementarity is lower within than across biogeographical regions (after correction for extent). Results encouraged to enlarge the study in order to consider a wider range of forest types and bigeographical features in determining the forest plant diversity patterns.