Soil fungal communities as bioindicators of ancient human impacts in medieval settlements in different geographic regions of Russia and southwestern Kazakhstan

The aim of our study was to examine the ability of soil fungal communities to serve as indicators of human impact in anthropogenically transformed soils of medieval settlements. The investigations were carried out as long-term studies (from 1999 through 2013) of fungal communities in habitation deposits of medieval settlements (7th–11th centuries AD) in the European part of Russia (Komi Republic, Smolensk Region, Samara Region, Stavropol Region), Tuva Republic and South-Western Kazakhstan. Total fungal biomass and biomass structure in soils were evaluated by using luminescent microscopy with Calcofluor white. Isolation of fungal trophic groups was performed on different solid media by means of the soil dilution plate method and by the bite technique. For the description of microfungal communities, use was made of such indexes as spore/mycelium ratio in fungal biomass, species diversity and species composition. The examined habitation deposits of ancient settlements differed from the horizons of the surrounding natural soils because of a larger share of fungal spores in fungal biomass, more mosaic distribution of microfungal communities, as well as differences in species composition and in dominant microfungal species. For reconstructions of certain types of human activities, use can be made of phytopathogenic, keratinophilic, and coprophylous fungi serving as bioindicators. The increase of phytopathogenic fungi (namely Fusarium species) in the cultural layer presumably marked grain pit locations. Accumulation of keratinophilic fungi could be observed in domestic animal shelters, as well as in household pits, and storage sites of wool, skins, and feathers. Increased abundance of keratinophilic fungi was most obvious in the sites of ancient streets and dwelling floors. The increased content of coprophylous fungi was indicative of accumulation of dung on certain plots. There was a distinct correlation between presence of both these fungal groups and the assumption that the sites in question were occupied by herbivores in the past. The mycological properties of soil offer information about ancient human–landscape interaction and can be used in paleo-environmental reconstructions of medieval settlements.