Role of humo-enzyme complexes in restoring of soil ecosystems

Conventional chemical (total organic carbon, total nitrogen, C/N ratio), biochemical (total and extracellular b-glucosidase, ATP, dehydrogenase) and unconventional IEF parameters (active humic carbon, humic-bound b-glucosidase activity), were used in the monitoring of the changes in biochemical properties caused by organic amendment practices. Two soil ecosystems characterized by a gradient of different grass covers, i.e. (1) a natural Catena (control) and (2) a managed Catena altered by amending practices were selected in a semi arid zone of the Mediterranean (Murcia region, Spain). Both natural and managed Catenas showed activation of carbon cycle which gradually shifted vegetal carbon toward the humic substance formation and accumulation of active humic-b-glucosidase complexes. The model of study and the correlation among the selected parameters, has permitted to discriminate even little differences in soil biochemical properties and, on the basis of these properties, to rank the soil ecosystems in a decreasing order of quality: forest[shrub[bare. There was a narrow correlation between amount of humic carbon forms and humic-associated enzyme-activity, demonstrating that a sort of humification in situ was steadily taking place even after years and likely sustained by plant root exudates. The combination of UF and IEF resulted very efficient in the characterization of humic-enzyme complexes and biochemical processes which drive the humic substances formation, storage and activity in soils.