Microclimatic Gradient as a Source of Variations in Cultivable soil Microfungal Communities at the Negev Desert, Israel

Abstract

We studied the effect of microclimatic gradient on the spatial (8 habitats) and seasonal (autumn, winter, and summer) variations of culturable soil microfungal communities at the north-facing slope (NFS) and the south-facing slope (SFS) of Nahal Boker, the Central Negev Desert, Israel. Using the soil dilution plate method, a total of 122 species from 56 genera was isolated. The communities' composition was subjected to pronounced interslope variations in each season. While xerotolerant melanin-containing species (mainly with the protective multicellular spore morphology) predominated in the soil of NFS, peaking up in the summer, thermotolerant and thermophilic Aspergillus spp. were especially abundant at the SFS. Aspergilli also dominated the thermotolerant communities isolated at 37 °C from both slopes. The more severe microclimatic regime at the SFS resulted in the least pronounced spatial and seasonal intraslope variability of the community composition as compared to the more benign and heterogeneous NFS. The quantitative parameter—the density of microfungal isolates, exhibited significant and positive relationship with organic matter and moisture content. In seasonal dynamics, the severe summer conditions significantly reduced the differences in isolate density at the NFS, which were markedly expressed in the autumn and winter between habitats receiving additional water by runoff and the adjacent habitats that did not benefit from runoff water.