Soil heating to distinguish the contribution of abiotic and extracellular activities to the overall enzyme activity in soil

This work attempts to distinguish the contributions of abiotic from extrace llular activities to the soil overall enzyme activity by using heating. Soi ls from three surface horizons, differing in physical and chemical properti es, were used. Fresh or air-dried and long stored samples were exposed to i ncreasing temperature values up to 200 degrees C during a period of 34 days . Microbial biomass as number of culturable colonies, ATP content and dehydro genase, urease, beta-glucosidase and casein-hydrolysing activities were mor e resistant to high temperature in air-dried and long stored than in fresh soils. Significant correlations were observed between all parameters, excep t for the ATP content of the air-dried poor organic soil and for the dehydr ogenase activities of both fresh and air dried organic soil. At zero ATP, t he intercepts of enzyme activities on the ordinate were close to zero in ai r-dried soils while positive intercepts were found in fresh soils. The corr elations between enzyme activity and ATP values were not always significant . Abiotic activities seems less important in air dried and long stored than fresh soils.