Micromorphological and microbiological diagnostics of initial pedogenesis on the bottom of an artificial mesodepression in the northern caspian semidesert

The results of micromorphological and microbiological studies of the initial pedogenesis on the gypsum-bearing calcareous heavy loams exposed within an artificially created mesodepression in the northern Caspian semidesert are discussed. Under conditions of an increased moistening and dense cover of trees and shrubs, the initial soil profile developed in 30 years has specific microfeatures related to the high activity of macro-, meso-, and microbiota. Micromorphological studies of large (5.5 × 8 cm) thin sections allowed us to trace the direction of humification processes, the degree of the biological decomposition of plant residues, and the character of structural changes under the impact of seasonal soil freezing against the background of the layered character of parent materials. Microbiological investigations demonstrated certain changes in the distribution patterns of different ecotrophic groups of soil microorganisms related to the input of fresh leave litter onto the soil surface and the decay of the roots of arboreal and herbaceous plants in the mineral soil profile. The layered distribution of plant residues in the soil profile predetermined specific functioning patterns of these groups.