The influence of flint stones on a soil microbial community in the northern Negev Desert

In the Negev Desert ecosystems, flint-stone cover on slopes acts as a barrier against water flow. As a result, soil moisture increases and organic matter accumulates under the stone and in the immediate surroundings, both affecting the duration of soil microbial activity. On the other hand, during the dry season (characterized by approximately 210 dew nights), flint-stone cover plays an important role in the formation of dew, which eventually trickles down beneath the stone, correspondingly enhancing biological activity. The present study examined the possible role of flint stones as hotspots for soil microbial-community activity and diversity. The results were compared with those obtained from the adjacent stone-free soils in the open spaces (OS), which served as controls. Microbial activity (respiration and biomass) and functional diversity were determined by the MicroResp™ method. In addition, estimates of genetic diversity and viable counts of bacteria and fungi [colony-forming units (CFUs)] were obtained. The soil was significantly wetter and contained more organic matter beneath the flint stones (BFS). As hypothesized, biological activity was enhanced under the stones, as described by CO(2) evolution, microbial-community biomass functional diversity, and fungal phylogenetic diversity. BFS environments favored a greater range of catabolic functions. Taxa generally known for their stress resilience were found in the OS habitats. The results of this study elucidate the importance of flint-stone cover to soil microbial biomass, community activity, and functional diversity in the northern Negev Desert.