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 tu rnover times were compared in adjacent mediterranean biotopes with differen t forest vegetation, to analyze the effects of litter diversity and soil ma nagement protocols on microbial decomposition rates. Samples of forest soil from four vegetation types were collected at depths of 0-20 and 20-40 cm i n the 'Tenuta Presidenziale di Castelporziano' Reserve on the Tyrrhenian co ast, near Rome (Italy). The samples were incubated under standard laborator y 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 di fferent kinetics between the samples; in particular, soils with above-groun d diversity were characterised by high mineralization activity when compare d with those sampled under monospecific vegetation. For all the sites, stat istically significant linear correlation was observed between nitrogen conc entration and potentially mineralizable carbon (r = 0.97), and microbial bi omass carbon (C-mic) to total organic carbon (C-org) ratio and the microbia l metabolic quotient q(CO2) (r = -0.96). The q(CO2), indicator of the stabi lity of ecosystems, was enhanced by plant diversity, while the C-mic:C-org ratio was reduced. (C) 1999 Elsevier Science B.V. All rights reserved.