Spatiotemporal changes in abiotic properties, microbial CO ₂ evolution, and biomass in playa and crust-covered interdune soils in a sand-dune desert ecosystem

The playas are common geomorphological units in the western Negev Desert, Israel. Playa soils greatly differ from the interdune soils in their structural and physicochemical properties due to their depositional origin. The present study was initiated at the Nizzana sand-dune field in order to determine the effects of physical and chemical properties of the playa soils on the dynamics of activity and biomass of soil microflora in space and time. Soil samples were collected from the 0-50 cm depth (at 10 cm intervals) at the playa and interdune during the wet and dry seasons of 2010. Soil moisture, organic carbon, electrical conductivity, and sodium- and calcium-cation concentration were two to forty times higher at the playa than at the interdune, respectively. Nevertheless, the values of microbial CO ₂ evolution and biomass were approximately two-fold higher at the interdune. The two biotic variables exhibited significant negative correlation with sodium- and calcium-cation contents regardless of sampling locality. In comparison with the wet season pronounced decreases in microbial CO ₂ evolution and biomass were observed at both habitats during the dry season. Although the two biotic variables exhibited significantly negative correlation with soil depth at the interdune, no identical trends were observed at the playa.