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Seasonal variations in soil salinity were recorded under the canopy of two halophyte shrubs typical of the hot, dry Negev desert, Zygophyllum dumosum and Reaumuria negevensis. The effects of the fluctuating soil salinity levels on total soluble N and on microbial biomass N and P were also monitored. The microhabitat of the shrubs showed differences in trend and magnitude of soil mineral N, the NO3-:NH4+ ratio, and microbial N and P. The trends were assumed to be governed by the various mechanisms operating in the shrubs in order to survive salty environments. Data from the current study are discussed in terms of the assumption that the halophyte has developed ecophysiological strategies that force microbial communities coexisting in its microhabitat towards adaptation aimed at withstanding a fluctuating environment, and hence towards a beneficial plant-microorganism relationship.