Soil organic matter is an index of soil quality and health. Intensive cultivation without crop rotation, deforestation, residue burning and land use change have resulted in decreasing the soil C storage and hence, on some soil biological properties. The objectives of this study were to investigate i) the effects of soil organic C management history on the sensitivity of different pools of Beta-glucosidase to heavy metals; ii) kinetic behavior of the enzyme as affected by Pb contamination. The soil samples were collected from 0-15 cm depth of two regions: 1) An oak forest with its cultivated counterpart in Lordegan region; and 2) a soil under two long-term cultivation of alfalfa and festuca in Fozveh region. Net N mineralization, L-arginine ammonification, microbial biomass C, metabolic quotient, microbial quotient, Beta-glucosidase activity and the enzyme activity to OC ratio were determined. Results indicated that in the Lordegan region, most of the biological properties decreased, significantly. In the Fozveh region the biological properties were often higher in the soil under alfalfa cultivation. Similarly, potentially mineralizable C were also greater in forested versus cultivated and alfalfa versus festuca in the Lordegan and Fozveh regions, respectively. It was also observed that, the sensitivity of the stabilized pools of the enzyme were less sensitive to the heavy metals, except for Pb. The kinetic parameters of Beta-glucosidase (V max and K m ) were both decreased when the soils were contaminated with Pb and therefore, a non-competitive inhibition has happened by Pb to the enzyme. Overall, we can clearly conclude that management practices may influence the sensitivity of Beta-glucosidase to heavy metals through changing the quantity and quality of the soil C storage. Moreover, the degrees of enzyme inhibition among different fractions of the soil enzyme pool were not identical. It was also concluded that Pb has a non-competitive inhibition mechanism on soil Beta-glucosidase.
