Biological activity of anthropogenic mountain soils of medieval agricultural terraces of mountainous Dagestan

Resumo

The study of agricultural terraces in mountainous Dagestan that date to the Middle Ages revealed the polygenetic character of anthropogenic soils, which reflects the main stages of their evolution. In light of their long-term burial, the soil layers of the preanthropogenic stage of evolution were characterized by fairly high values of biological activity, with the exception of the biomass of fungal mycelium, a small amount of which remained. At the early agrogenic stage, soil plowing without irrigation did not significantly change their microbiological properties; however, the increase in urease activity in some studied profiles may indicate that cattle fertilizers were applied in some areas of the terraces. During the Little Ice Age (the 16–18th centuries A.D.) the terraces were abandoned, which led to the accumulation of organic carbon in the soils as a result of the fallow process, as well as an increase in their enzymatic activity. The second agrogenic stage with irrigation was characterized by a noticeable growth in the active microbial biomass, the soil phosphatase activity, and, in particular, the urease activity, which may indicate that farming was intensive and organic fertilizers were applied. In the last 20 years, the development of terraces under natural conditions led to a noticeable growth in the biological activity of upper fallow horizons. However, the urease activity significantly decreased in nonirrigated areas, whereas the indicators of microbial biomass remained at the same level.