DENITRIFICATION - ENZYME CONTENT AND ACTIVITY IN DESERT SOILS

The content of denitrifying enzymes in upland desert soil was strongly associated with indices of N and C availability. Combinations of several predictors could explain 71% of the variance in enzyme content in Chihuahuan desert soils and 87% of the variance in soils from various deserts in the southwestern U.S.A. A significant fraction of the enzyme content in wet desert soil is derived from a persistent pool of enzymes capable of tolerating extended periods of desiccation. The synthesis of new denitrifying enzymes appears to involve a complex interaction between available C, N, and soil moisture. The activity of denitrifying enzymes in desert soil was optimal at a pH 7.0 and a temperature of 40-degrees-C. The Q10 for denitrification was 1.74, and the activation energy was about 41 kJ mol-1. In addition, enzyme activity in freshly wet soil was not limited by NO3- availability, and only slightly limited by the availability of C. Thus, wet desert soil appears to provide optimal conditions for several variables that can influence denitrification.