Humus e vegetazione come indicatori della qualità dell’ecosistema suburbano nella Tenuta di Castelporziano. Ricerche sulla complessità di un ecosistema forestale costiero mediterraneo.

Humus and vegetation as indicators of the Habitat quality in the Castel- porziano Reserve. In this study an innovative integrated approach based on soil/humus and vegetation was used in order to detect the habitats quality and to test the relationship between vegetation and humus forms. This type of relationship, in fact, has never been investigated in the mediterranean region of Italy. 65 phytosociological relevés and humus profiles were carried out in the same sampling sites. Ellenberg’s indicator values were used to test the relationships between vegetation and humus; in particular, the product R*N, corresponding to the aggregation of the two indica- tors R-pH and N-nutrients; this index, is considered linked to humus quality and function- ality, was applied for the first time to a mediterranean data set. A matrix of 178 plant species x 65 relevés was subjected to statistical multivariate treat- ment by the procedure of Cluster Analysis; the Spearman’s rank correlation test was used to verify the correlations between indicators and measured humus/soil parameters (i.e. pH, content of carbon). The humus forms are related with the index of humus quality R*N and were classified into three main categories: mull with elevated functionality, exclusive of the most meso- hygrophilous woodlands, moder with intermediate functionality, mainly present in the decid- uous oak woodlands, amphi with low functionality in the evergreen sclerophyllous wood- lands. In the more disturbed habitats the humus forms show a mosaic pattern, in corre- spondence with a very low diversity of the understorey flora.horizons. Furthemore it reveals how the humus forms data, at the level of diagnostic horizons, are related to vegetation and soil types.