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.

摘要

我们研究了小气候梯度对 Nahal 北坡 (NFS) 和南坡 (SFS) 可培养土壤微真菌群落空间（8 个栖息地）和季节（秋季、冬季和夏季）变化的影响博克，内盖夫中部沙漠，以色列。使用土壤稀释平板法，共分离出 56 属 122 种。社区的组成在每个季节都受到明显的坡间变化。虽然耐旱的含黑色素物种（主要具有保护性的多细胞孢子形态）在 NFS 的土壤中占主导地位，并在夏季达到顶峰，但耐热和嗜热曲霉属 在 SFS 中尤其丰富。曲霉也主导了在 37 °C 下从两个斜坡分离的耐热群落。与更良性和异质性的 NFS 相比，SFS 更严重的小气候状况导致群落组成的空间和季节性坡内变化最不明显。定量参数——微真菌分离株的密度，与有机质和水分含量呈显着正相关。在季节性动态中，严酷的夏季条件显着降低了 NFS 分离株密度的差异，这种差异在秋季和冬季通过径流获得额外水分的栖息地和没有受益于径流水的相邻栖息地之间表现得尤为明显。