Soil microbial metabolic profiles in two geomorphological units in a semistable sand-dune ecosystem

The playas and microbiotic crust-covered interdunes are two geomorphological units in the Hallamish sand-dune field, Israel. As a depositional unit, a lack of vegetation and microbiotic crusts, as well as high contents of fine particles and salinity, may lead to low microbial activity and functional diversity at the playa. The present study was initiated in order to illuminate the spatiotemporal changes in the activity, biomass and metabolic profiles of soil microbial communities at the two habitats. Soil samples were collected from the 0–50-cm depth at the playa and interdune during the wet and dry seasons of 2010. Soil moisture and organic-carbon contents recorded at the playa were 2- to above 10-fold higher than at the crust-covered interdune throughout the study period. Nevertheless, opposite trends were recorded for fungal and bacterial CFUs, as well as microbial basal respiration and biomass, in most soil depths at the playa compared to the crust-covered interdune. The total substrate utilization rates of soil microbial communities fluctuated between 4.9 and 6.4 and between 3.9 and 14.9 μg CO2–C g−1 dry soil h−1 at the playa and interdune during the wet season, while 3-fold higher values were recorded at the two habitats during the dry season. The total substrate utilization rates, carbohydrates and carboxylic-acid utilization rates, and functional diversity of soil microbial communities at the playa, were lower than at the crust-covered interdune at most soil depths, while higher utilization rates of aromatic acid were recorded in at least three soil layers at the playa.