EFFECT OF DIFFERENT LAND USE ON SOIL ORGANIC MATTER IN BROWN SOILS OF THE EMILIAN APPENNINE.

In the present study, the organic carbon storage, the organic matter turnover times and the microbial activity in the epipedon (A1 and A2) of soil profiles, formed and evolved over a same parent substrate of sandstones and conglomerate in land stations characterized by different and alternative used of the soil, such as mixed deciduous forest, reforesting area with pinewoods (Pseudotsuga menziesii Franco) and cropping area, were compared. Samples of these last two areas, were collected at depths of 0-5 cm and 5-15 cm. All the soils, have a pH-range between neutral and alkaline. The Monte delle Formiche profile (THAPTOEUTRI HAPLIC CAMBISOLS hypereutric; WRB, 2006) under mixed deciduous forest was compared with an adjacent alfalfa (Medicago sativa L.) cultivated soil. The soil profile of Monte Zena (HAPLIC CAMBISOLS calcaric hypereutric; WRB, 2006) under mixed deciduous forest was compared with an adjacent alfalfa cultivated soil and with a nearly profile under a reforestation area, with a predominance of Douglasia threes. The contents of Total Organic Carbon (TOC), Total Exctractable Carbon (TEC), of Humic and Fulvic Acids decrease with increasing of the depth of the profile, as common in the brown italian soils. The value of such parameters, is greater in the soils placed under mixed deciduous cover, regarding those placed under coniferous; the lowest equipments are found in the cropping area. The humification index of forest soil showed a lower degree of humification of the organic matter in the A2 horizons of the epipedon, regarding the A1. The values of the humification index in the samples under conifer and cropped, are approached those typical finds in agricultural soil with monocultivation management. The Microbial Indices, as Microbial Quotient (microbial-C/total-C) and Respiratoty Quotient (qCO2) shown a different situation between the two sites. Forest soil of Monte delle Formiche were caracterised by an high mineralization activity when compared with those sampled under cropping; therefore there is a high fraction of Not-microbial Carbon in the Total Organic Carbon of this soil, respect to alfalfa crop soil. The potentially mineralizable C (Co) of the epipedon under natural mixed forest, is much advanced compared to that one of the cropped. The low Microbial Quotient and the elevated value of the qCO2 indicate that the organo-mineral horizons of the soil under mixed forest still find in a development phase. All the organic and biological parameters of carbon of the soils of the station Monte Zena are low; that can indicate an impoverishment situation of the system, especially in the more disturbed situations as the reforestation and the cultivated soil . In particular, the reforestation site, show in the superficial sample a low values of microbial-C (Cmic), a low Microbial Quotient and an elevating qCO2. The qCO2 increment can be interpreted like an answer of the microbial biomass to the change of the quality of the organic carbon of the residual vegetables.