Mitigation of the Stages of Arid Soil Degradation Under the Influence of Tree Plantations

In natural biological systems, living organisms function as a system responsible for soil, botanical, climatic, and hydrological changes, as well as for the conditions created by the organisms themselves. Today, when the climate is changing and human activity is intensified, while biological resources are severely depleted, arid ecosystems are unable to regulate the contradictions in the relationships between natural and anthropogenic factors using their own resources. The dynamic escalation of these emerging contradictions results in increasing deviations from the background level with a significantly expanding range of these changes. According to our evaluation, the common system of soil cover indicators for the tree plantations of the Botanical Garden of Dagestan State University is represented by two zones: (1) the zone of a suppressed state with the beginning of a mitigated aridization process and (2) the zone of the destabilization of drought-resistant tree species, such as the English oak and tillet. The start of the negative influence of aridization stages is mainly associated with a deficiency of moisture and nutrients. One can state that the beginning of the desertification process represents mitigated desiccation of the soil profile, when the moisture content in the root-inhabited layer has decreased to 18–20% and the content of hydrolysable nitrogen is 25–30 mg/100 g of soil. Due to changes in the existing tree cultivation technology, mineral fertilizers are applied in insufficient volumes and with a lack of periodic irrigation.