Litter as a regulator of N and C dynamics in macrophytic patches in Negev desert soils

Abstract

In desert ecosystems, nutrient cycling activity is concentrated in brief periods of intense biological activity following wetting events. Release and uptake of N from litter and microbial biomass may be important regulators of N availability to plants and N loss to denitrification and NH 3 volatilization. Litter and microbial biomass dynamics may also be important to the maintenance of shrub-dominated patches of high fertility in desert ecosystems. We have measured soil C and N cycling processes (respiration, NH 4 + and NO 3 − dynamics, denitrification and microbial biomass C and N dynamics) in rewetted Negev desert soil treated with different size classes of desert plant litter in 30-day laboratory incubations. The results suggest that litter plays a strong role in conserving N following wetting events in Negev soils. Amounts of soil NH 4 + and NO 3 − and microbial biomass N were reduced in litter-amended treatments, suggesting that significant quantities of N were sequestered in litter, especially the largest size classes of litter. Denitrification was a significant sink for N, and was stimulated by the presence of litter, but was less important than immobilization of N in litter. Immobilization and release of N by litter may be especially important in the N cycle in desert ecosystems, moderating seasonal patterns of N availability and regulating patch interactions that facilitate the development of “islands of fertility” in these ecosystems.