Structure and floristic diversity in permanent monitoring plots in forest ecosystems of Tuscany

The sampling method is described which is used for the sampling of plant species richness and cover in a monitoring project on forest ecosystems in Tuscany (named MONITO). Species richness is sampled through a nested plot design, with plot size ranging from 1 to 2500 m(2), whereas species abundance is estimated in 100 m(2) plots. This sampling design is simple to install and to manage through time. Species diversity can be monitored not just at one single spatial scale but at many scales, and species-area relations can also be calculated. The analyses of the data that were collected produced the first available data on species richness in relation to plot size for Tuscan forest ecosystems, indeed for any Italian forests. The Arrhenius Power function and the General Root models showed the best fit. Turkey oak (Quercus cerris) woods located on slightly acidic soil were found to be the forest ecosystems with the highest species richness, confirming and quantifying well-established floristic-phytosociological knowledge. Habitat heterogeneity, measured by plot floristic resemblance, showed how the Turkey oak woods were the most heterogeneous at the smaller spatial scales, but not at larger ones. (C) 2001 Elsevier Science B.V. All rights reserved.