Weak effect of plant canopy but strong impact of depth on variation of cultivable microfungal communities through soil profiles in semiarid Spain

We studied the effect of plant canopy on the distribution of microfungi through 0−30-cm soil profiles under canopies of three plant species and in their adjacent interspace at sun-exposed plain and north-facing slope in the Tabernas Desert, Spain. Using the soil dilution plate method, 142 species from 68 genera were isolated. Melanin-containing fungi dominated in the topsoil layers because of high temperatures and dryness. By contrast, light-colored fungi generating a high amount of small thin-walled conidia substantially increased their abundance in the deeper soil layers – thermotolerant Aspergillus spp. in the 1−5-cm layers and mesophilic Penicillium spp. in the 10−20-cm layers. The significant increase in density of microfungal isolates at 1−10 cm-depth could be associated with the deposition of conidia of aspergilli and penicillii caused by shallow water infiltration in the fine-grained soil and their survival at these depths due to more appropriate edaphic conditions (mainly higher water availability and root concentration). Generally, the effect of plant canopy on microfungal communities was only weakly expressed in higher variations of isolate densities and species richness through the profiles, and in reduced abundance of melanized species with protective multicellular spore morphology in the topsoil layers; at the same time, soil depth strongly influenced all community characteristics. The study highlights the remarkable role of edaphic factors (temperature, water regime, and soil texture) in the distribution of microfungi through soil depth in semi-arid areas.