MICROBIAL BIOMASS RESPONSE TO SEASONAL FLUCTUATION IN SOIL-SALINITY UNDER THE CANOPY OF DESERT HALOPHYTES

The relationships between seasonal changes in soil salinity and the mi crobial biomass and activity (represented by the quotient For basal re spiration-qCO(2)) were monitored year-round under the canopy of two ha lophytes; Zygophyllum dumosum and Reaumuria negevensis, typical of the hot, dry Negev Desert. Fluctuations in soil salinity were assumed to be the result of different ecophysiological strategics employed by the halophytes in order to survive in saline environments. The amount of the microbial biomass was not directly affected by the degree of soil salinity, especially in the R. negevensis microhabitat where the highe st biomass (245 mu g g(-1)) was observed in high salty soil (12.8 dS m (-1)) during the summer. A negative relationship was found between the microbial biomass and qCO(2) values, indicating the possibility of ch anneling organic substrates to metabolic activity aimed at overcoming conditions of temporary stress.