Use of biochemical indices in the mediterranean environment: comparison among soils under different forest vegetation.

In the present study, soil biomass activity, organic carbon storage, and turnover times were compared in adjacent mediterranean biotopes with different forest vegetation, to analyze the effects of litter diversity and soil management protocols on microbial decomposition rates. Samples of forest soil from four vegetation types were collected at depths of 0-20 and 20-40 cm in the 'Tenuta Presidenziale di Castelporziano' Reserve on the Tyrrhenian coast, near Rome (Italy). The samples were incubated under standard laboratory conditions (-33 kPa water tension, and 30 degrees C), in order to compare the microbial activity independently of temperature and humidity. The CO2-C accumulation curves over a 28-d incubation period showed substantially different kinetics between the samples; in particular, soils with above-ground diversity were characterised by high mineralization activity when compared with those sampled under monospecific vegetation. For all the sites, statistically significant linear correlation was observed between nitrogen concentration and potentially mineralizable carbon (r = 0.97), and microbial biomass carbon (Cmic) to total organic carbon (Corg) ratio and the microbial metabolic quotient q(CO2) (r = -0.96). The q(CO2), indicator of the stability of ecosystems, was enhanced by plant diversity, while the Cmic:Corg ratio was reduced.