Vertical distribution and activity of soil microbial population in a sandy desert ecosystem.

The vertical distribution of a microbial community on a temporal and spatial (vertical) scale under the Tamarix aphylla salt-resistant plant was studied. The uniqueness of this plant is in the creation of "islands of salinity" beneath the plant, due to salt excretion and leaf shedding at the plant base. Our working hypothesis was that the activity and biomass of the soil microbial population and the ratio between bacterial biomass and fungal biomass will decrease toward the driest season. Soil samples were collected beneath and between plants under the T. aphylla canopy down to the 0- to 50-cm depth at 10-cm intervals. The substrate-induced respiration method was used to estimate the total soil microbial biomass (MB), CO2 evolution, metabolic quotient (qCO2) index, and MB of both the fungal and bacterial communities. A significant difference was observed (p < 0.05) in MB and qCO2 index between the different soil layers in the control samples, whereas there was no significant difference in the soil samples in the vicinity of the plant (p > 0.05) between the depths, due to the plant rhizosphere effect.