Soil Biota in the Arava Valley of Negev Desert, Israel

Soil microorganism biomass and respiration and the soil nematode community were observed in the hypersaline desert valley that is found between the Dead Sea and the Red Sea. The lowest point of the valley is approximately 400 m below sea level, and is the lowest point on earth. Soil samples （n -- 72） were collected from the 0-10 and 10-20 cm soil layers at different altitudes （from -400 to ＋100 m） in the open spaces between plants during one of the most extreme xeric periods. Both soil microbial respiration and microbial biomass were found to be negatively dependent on soil moisture （SM） and organic matter （OM）, and positively dependent on pH values. The physical-chemical characteristics of this hypersaline area were extremely unfavorable for the soil nematode communities, and the nematodes were entirely absent in the open area below sea level. The bacterivores were found to be the most resistant nematodes in this hyperarid region, with the Wilsonema being the most widespread genus. We suggest that nitrogen availability may play a crucial role in the below-ground soil interaction in this region, with bacterivore nematodes as indicators of nitrogen availability.