Study of the structure and composition of microbial communities formed during the process of forest overgrowth of former arable soils in the Republic of Tatarstan

This study presents a detailed analysis of the soil microbial community in the Republic of Tatarstan, which has developed under the influence of different types of vegetation—mixed and pure pine communities—on former arable lands. Soil samples were collected from both the upper horizon and the previously cultivated layer, allowing for an assessment of changes in microbial structure depending on land use history. The research aims to identify relationships between various groups of microorganisms involved in the nitrogen cycle and organic matter decomposition, as well as their roles in soil fertility recovery processes. Correlation analysis using Pearson’s and Spearman’s coefficients revealed moderate to strong positive relationships among microorganisms. These connections indicate similar environmental conditions and participation in a common trophic chain. As a result of the study, several groups of samples were distinguished based on differing populations of nitrogen-fixing bacteria and actinomycetes, reflecting the dynamics of humus formation and changes in soil fertility levels. The work emphasizes the importance of microbial communities in soil selfremediation after cessation of agricultural use. The established relationships between microorganisms and their roles in ecosystem restoration open new avenues for further research, including studies on forest structure and agrochemical soil indicators. The obtained data will be utilized in future publications to deepen understanding of complex changes occurring in abandoned agricultural lands.

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