Microbiological Analysis of the Soil Cover of the Kamennaya Steppe Agroforestry Landscapes

Abstract

The microbial biomass content is the most informative indicator for early detection of soil condition. Soil microorganisms support the homeostasis of forest ecosystems due to the unique ability of rapid adaptation to changing environmental conditions. The article presents the results of soil microbiological assessment carried out within the framework of comprehensive monitoring studies of the forest ecosystems of the Kamennaya Steppe. The following objects of the agroforestry permanent study area served as options: a mowing fallow of 1882; forest belt no. 40 of 1903 laying out, located on the watershed area; forest belt no. 133 of 1950 planting; and forest belt no. 131 of 1959 planting. Additionally, arable lands adjacent to forest belts no. 40 and 133 (watershed, slope) were included in the research scheme. The research purpose was to determine the biological activity of soils of the Kamennaya Steppe, as well as the direction and intensity of soil and biological processes in agroforestry arrangement of the territory. The total number and structure of ecological and trophic groups of the microbial community were determined by the method of E.Z. Tepper by seeding on solid nutrient media. It is shown that the soil cover under the tree plantation is defined by a higher content of ammonifiers and actinomycetes. Intensive agricultural land use significantly reduces the intensity of microbiological processes. The undertaken studies allow stating that the optimum conditions for the development of micromycetes are formed in soils under woody and native steppe vegetation. The involvement of chernozems in active agricultural production leads to a decrease in the number of fungal flora. A high concentration of nitrifiers was revealed in arable lands. The lands with woody vegetation and steppe cenoses had lower indices and were somewhat inferior to agrogenic soils. Annual soil cultivation is crucial and drives up the activity of bacterial colonies (genus Azotobacter) on arable lands. The activity is much lower under the tree crops and steppe vegetation in most cases. Mineralization coefficients are calculated for the studied soils. Due to the fact that these coefficients in all the studied objects are above one (except the field under winter wheat and bordering the forest belt no. 133), it follows that the mineralization processes of soil organic matter prevail over the decomposition of organic residues.