Moscow University Soil Studies Bulletin. 2020. 3.

The features of the dynamics of the morphology and chemical properties of forest litter during post-agrogenic reforestation of arable land in the southern taiga subzone are studied. The relationship between the dynamics of the structure of litter with the floristic composition and the ecological-coenotic structure of the soil cover is shown. The increase in stocks, as well as the diversity of the structure and the degree of spatial variation of the main morphological indicators of litter as the regeneration of the stand has been established. Acidification and a decrease in the ash content of litter, as well as a decrease in the fraction of easily decomposed fractions, are adequately reflected in the composition of the soil cover, in which the role of species adapted for increased acidity and low content of nutrients in the substrate increases. After spruce enters the first tier, the spatial distribution of the structure, reserves, power, and fractional composition of litter is determined by the position in the tesser. In general, the course of succession, as well as the dynamics of the morphology and chemical properties of litter, indicates a decrease in the rate of circulation in biogeocenosis. The ecological scales of Ellenberg, Landolt, Tsyganov and Ramensky as applied to ground cover can serve as an important tool in analyzing the dynamics of forest litter in forest ecosystems.

The current study presented a genesis characterisation of iron-illuvial podzols formed on esker mainly coarse-grained deposits consisting of coarse and moderately coarse-grained sands including the gravel-pebble fractions with rubblestones. Under similar bio-climatic conditions, the iron-illuvial podzols on esker showed quantitative differences in composition and their properties from the iron-illuvial podzols formed on sandy moraines. The source of these differences were the relief and lithology of deposit genesis of uncommon structure of esker. The still commonly used description of fluvioglacial deposits, without their differentiation in esker as an inner-glacial deposit and periglacial deposits formed out of glacier range were insufficient in terms of a pedogenesis with special features in relief and sediments.

Sewage sludge introduced 28 years ago in sod-podzolic sandy loam soils determines the increased content and mobility of Zn, Cd, Cu, and Ni compounds, and it is the most characteristic for Cd and Zn. The most polluted are the arable horizons of soils. The contaminated layer is within the arable horizon, which indicates on the low rate of heavy metals (HM) migration, which were introduced into the studied soils as part of SS. Heavy metals are washed out of soils with intrasoil runoff insignificantly. This is determined by their chemical properties: low solubility of their compounds, adsorption by mineral and organic components of soils, as well as neutral pH values of the soils themselves. Plants grown on contaminated soils are characterized by an increased content of HM, which varies in 5-7 times depending on the type of plants and their ability to accumulate HM.

The process of natural remediation of oil-polluted and salt-polluted raised bogs of KhMAO - Yugra reclaimed 14-16 years ago is analyzed. In general, the revegetation is proceeding successfully, although mesophytic grasses sown during reclamation have almost completely fallen out of the grass stand. In salt-contaminated areas, there is a gradual desalination of peat soil, accompanied by a succession of halophytic (hemigalophytic) plant communities dominated by Calamagrostis epigeios, Eriophorum angustifolium and Phragmites australis with the participation of sphagnum and brown mosses, as well as liverworts. A characteristic feature of these habitats is the settlement of a number of rare protected species ( Heterogemma laxa, Thelypteris palustris, Triglochin maritimum ). In oil-polluted bogs, during the re-vegetation, hydrocarbons often flow from the underlying peat soil horizons to form the surface crust. At the same time, grass stands from Eriophorum angustifolium and some other species with powerful root systems are replacing grass-sedge-cotton grass communities. Sphagnum riparium and Warnstorfia fluitans play also a certain role in the overgrowth of crusted surfaces. Unsuccessful recovery is typical for hollows with difficult runoff in the case of salt-contaminated bogs and the most dry locations in the case of oil - contaminated ones.

The laboratory study of the solid phase of salted peat by X-ray fluorescence analysis revealed the presence of some halogen-organic compounds. Cl-organic compounds were formed in one third of peat samples, while their share is small: 14-15% of the total Cl. On the contrary, Br-organic compounds are formed more often and Br_org proportion is higher: from 12 to 23% of total Br. Relatively weak development of halogenisation of the organic matter in salted peat bog is explained by the recovery conditions that prevent the synthesis of halogen-organic compounds. In X-ray diffraction analysis of peat ash, errors are possible, both due to the growth of minerals, and due to incomplete identification of the number of phases in high-ash peat samples. The second type of error can be corrected using data on the content of chlorine in peat by X-ray fluorescence analysis. In the characteristic of peat bog contamination, in addition to salt profiles in the solution, it is necessary to determine the number and composition of halogen-organic compounds, some of which have herbicide properties.

In laboratory conditions, the decomposition of glyphosate with the formation of aminomethylphosphonic acid (AMPA) and its effect on the total abundance of bacteria and fungi, as well as the number of copies of genes encoding the enzymes C-P lyase of a-proteobacteria ( phnJ ), acid and alkaline phosphatase ( phoC and phoD ) and Fe-protein nitrogenase ( nifH ). It is shown that when applying glyphosate in recommended doses (5-10 mg/kg) 5-7% of the introduced herbicide is detected after 14 days, but when the dose is increased to 100 mg/kg, this value increases to 23%. Slowing down the rate of degradation of the herbicide appears only in the first week of incubation and is accompanied by a decrease in the number of copies of the phoC, phoD, nifH genes and an increase in the abundance of fungi. The obtained results indicate a predominant degradation of glyphosate with the C-P bond breaking and the formation of phosphates, as well as a possible inhibition of the nitrogen fixation process. It is shown that at an application dose of glyphosate 100 mg/kg, the accumulation of the first metabolite AMPA can occur during the degradation of the herbicide with a break in the C—N bond. Bioassay using wheat showed that when applying glyphosate at a dose of 100 mg/kg, there is an inhibition of plant development: the length of the roots and the biomass of the shoots reduced by 60 and 20% compared to the control, respectively. Based on the obtained data, it is proposed to use the reduction in the content of copies of the phoC gene and the growth of copies of ITS rRNA as indicators of the predominant decomposition of glyphosate through the sarcosin pathway. A reduction of copies of ITS rRNA gene by 40% or more can be used as an indicator of the possibility of AMPA accumulation during glyphosate degradation.