Cellulases are enzymatic proteins which hydrolyze cellulose polymers to smaller oligosaccharides, cellobiose and glucose. The aim in this study was mainly to determine the parameters which affect cellulase activity in semiarid calcareous soils of Hamadan, northwestern Iran. The lands have been utilized as pastures; have been under deciduous and coniferous forests, and as well have been used as dry and irrigated farms for many decades. Some farmlands have been irrigated with river water whereas some with untreated municipal wastewater. Sampling was carried out at a depth of 0-30 cm in a completely randomized design with an unequal number of repetitions. Some physical, chemical and biological soil properties were assessed employing standard methods. The results revealed that cellulase activity in the differently utilized and managed soils was significantly different. It ranged from 0.170 ?g glucose released, g-1 soil min-1, in dry farmlands to 0.384 ?g released, g-1 soil min-1, in deciduous forests. Cellulase activity exhibited a significant and positive correlation with soil OC, TN, C/N ratio, substrate induced respiration, basal respiration, acid and alkaline phosphatases, but a significant and negative correlation with soil pH. Among soil microbial populations analyzed, cellulase activity exhibited a very significant correlation (p<0.001) with soil fungal population. It may be concluded that cellulase activity in calcareous soils is mainly correlated with those soil factors that affect microbial activity.
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