Microbiota's response to natural-anthropogenic changes in moisture in a trans-zonal aspect: A case study for the south part of East European Plain

In semi-arid areas, irrigation changes not only the chemically and physical properties of soil, but also the activity of microbiota. We undertook a study of algal flora and enzyme in the trans-zonal range: from the forest-steppe to the dry-steppe, which is lacking precipitation and where surface irrigation is widely used. The aims of the study were to reveal the activity of five soil enzymes and abundance of algae under the influence of irrigation on the south of the East European Plain (Ukraine, Moldova) and to determine the contribution of the biological factor to the increase of wind and water erosion resistance of irrigated soils. The activity of algae during irrigation had the most favourable conditions in the fall (3-42 thousand / g of soil), which was facilitated by optimal soil moisture (21-24%). Soils in irrigated conditions in spring and summer featured a higher content of dehydrogenase (on 41%) and polyphenol oxidase (on 34%) compared to non-irrigated soils. Irrigated soils also differed by higher urease content (on 17%) than on non-irrigated soils and in spring these differences were up to 50%. The explanation for this phenomenon is associated with the action of irrigation in respect of increasing the role of humus coagulation of elementary soil particles, the increase in the proportion of particles <0.001 mm as products of weathering and the increase of bacterial origin cement.