Features of Soil Bacterial Communities of Varying Degree of Salinity on the Example of the Shaulder Irrigation Massif of the Turkestan Region of the Republic of Kazakhstan

A comparative assessment of bacterial communities of meadow-serozem soils of different degrees of salinity was carried out. Significant differences in the structure of microbiomes of arable horizons of weakly saline and highly saline meadow-serozem soil were revealed. A significant reduction in the diversity of the microbiome at the phylum level with an increase in the level of soil salinity was established (on the example of meadow-serozem soils of the Shaulder irrigation massif). The structure of bacterial communities of the meadow-serozem highly saline soil is represented by four bacterial phyla: (Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria), while 13 bacterial phyla were identified in weakly salinized soil (Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Acidobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, Planctomycetes, Saccharibacteria, Cyanobacteria, Chlorobi, Nitrospirae). According to the Shannon index, the species diversity of the microbiome of the meadow-serozem soils of the Shaulder irrigation massif is about 20% higher on weakly saline soils compared to highly saline ones. The Chao1 index and the number of taxonomic units (OTUs) also indicate a roughly halving of alpha diversity in the highly saline soil microbiome. The ecological significance of the problem of secondary soil salinization was confirmed. With an increase of salt content in soils, the species diversity of the bacterial community decreases, which can be considered as one of the indicators of soil degradation.