Articles

The aim of the work was to evaluate the effect of shallow–water flows on the morphometric characteristics of aggre- gates of typical Сhernozems of varying degrees of erosion. A number of model erosion experiments were carried out with capillary–moistened bulk samples of the upper 10–centimeter layer of the humus horizon of typical plowed Сhernozems of the Kursk region. The control variant is a comparable sample of chernozem from a typical site of the virgin steppe Chernozem in the Central Black Earth State Natural Biosphere Reserve named after Professor
V.V. Alekhin. Morphometric parameters of soil aggregates transported by model flows with minimum, average and maximum velocity (0,3, 0,41–0,45 and 0,54–0,58 m∙s–1, respectively) were determined. It was shown that smaller aggregates have higher form factor, roundness, and a lower edge unevenness. Larger aggregates, on the contrary, are less rounded and isometric and have higher unevenness. In erosion experiments with shallow–water flows, roundness and unevenness of the aggregate surface change inversely to each other. The change in form factor and unevenness is influenced by both the degree of soil erosion and the flow rate, and these factors mutually enhance the influence of each other. Aggregate roundness is mainly influenced by the degree of soil erosion, but its effect is enhanced by the addition of a flow rate factor. Depending on the flow rate, its effect on the morphometric parameters of aggregates varies: in the area of low speeds, a rolling effect occurs, in the area of high speeds, a destructive one. The continuation and expansion of such studies will expand the understanding of the mechanisms and patterns of formation of washed soils.

Kuznetsov’s formula relates the parameters of erosion resistance and soil water stability. However, the mechanism of occurrence of these properties is different: water stability is explained by the action of intra–aggregate hydrophobic bonds in organomineral soil gels, and erosion resistance is explained by water stable aggregates and their adhesion to each other. At the same time, the nature of the interaggregate bonds that ensure erosion resistance remains unclear. The purpose of the work was to clarify the mechanism of erosion resistance of soils and compare it with the mecha- nism of formation of water stability. The work used samples of humus-accumulative soil horizons: sod-podzolic and leached chernozem. To obtain samples with the same aggregate composition, but differing in erosion resistance, it is proposed to use soil polymer ameliorants (SPM). The erosion resistance of soils was determined on a hydrolotter and the critical rate of flushing was calculated. The water stability of the soils was assessed by the blade method. The particle size in the solutions was estimated by laser diffractometry. It was found that on soils treated with SPM, the results of the tray and blade methods correlate by 99%. The high correlation suggests a common nature of intra- and interaggregate bonds. To test the role of hydrophobic interactions in the formation of aggregates resistant to water, polymers of varying degrees of hydrophobicity were added to aqueous humate solutions in a model experiment: polyethylene glycol (PEG), polyacrylamide (PAA) and polyvinyl alcohol (PVA). In parallel, the water stability of soils treated with PEG, PAA and PVA was evaluated. The analysis of the results showed that the greatest water stability of the aggregates was noted when the most hydrophobic polymer, polyvinyl alcohol, was added to the soil, which formed the largest particles when interacting with humate in the model experiment. These results confirm the role of hydrophobic interactions in the formation of aggregates and indicate that when selecting polymer structures, their interaction should be taken into account not with clay minerals, but with soil gels, which include clay minerals and humic substances.

The dynamics of sedimentation in the bottoms of small catchments in the forest–steppe zone of the Central Russian Upland was assessed using the soil–morphological, radiocesium and magnetic tracer methods, which made it possible to calculate the rate of soil loss 1) since 1986, 2) since 1954, 3) since the launch and active operation of the railway, 4) since the mass plowing the entire catchment area. Two groups of small dry valleys have been identified: the catchment area of the first group includes tributaries of larger dry valleys, where the average rate of loss during the agricultural period is 2,1–2,4 t∙ha-1 per year and exceeds modern ones (since 1986) by 0,6–0,7 t∙ha-1 per year. The catchments of the second group include the sources of larger valleys, where the average rate of loss during the agri- cultural period is 0,6–0,9 t∙ha-1 per year and less than modern ones (since 1986) by 0.3–0.8 t∙ha-1 per year. The max- imum rates within all catchments were observed in the period 1954–1986, which is associated with soil compaction by heavy agricultural machinery, as well as the contribution of snowmelt runoff, which was regular for this period.

The article presents an analysis of the thickness of humus horizons of chernozems and gray forest soils, measured at more than a thousand survey points in three areas with an area of about 10 thousand hectares each in the northern (Oryol region), central (Kursk region) and southern (Belgorod region) forest-steppe on the Central Russian Upland. Th e measured thicknesses of the humus horizons was compared with the modeled thicknesses. Modeling of the thickness of humus horizons was carried out based soil erosion modelling and taking into account soils development. An assessment of soil erosion rates was carried out by WaTEM/SEDEM (rainfall erosion) and State Hydrological Institute in the Larionov modifi cation (snowmelt erosion), previously verifi ed on small catchments within or in close proximity to the study sites. Land use history was reconstructed using historical maps. Th e approach made it possible to model with suffi cient accuracy the average erosion losses of soils and calculate the average current thickness of the humus horizon. The obtained results of comparisons of measured and modeled thicknesses of the humus horizon clearly indicate the signifi cant role of soil development in the formation of erosion-accumulative structures of the soil cover. Insuffi cient consideration of soil development leads to a signifi cant underestimation of the calculated thickness of the humus horizon and, as a consequence, to an overestimation of the degree of soil degradation. The rate of development of chernozems and dark gray forest soils is about 0.4 mm∙year–1, which is consistent with literature data from case studies. An increase in diff erences between the modeled and measured thicknesses of the humus layer was noted in the series: chernozem - dark gray forest soil - gray forest soil - light gray forest soil. Perhaps the plowing of gray forest soils contributes to an increase in the fl ow of dissolved humus, as well as pedoturbations, which could potentially contribute to a measurement distortion of the thickness of the humus horizon and an underestimation of the degree of degradation of the soil cover in the northern forest-steppe.

Despite the large number of diff erent anti-erosion practices used in the country, the dynamics of the areas of eroded
lands remains multidirectional and unstable. Th e goal of the work was to propose a methodological approach for semantic modeling of sustainable land management with a focus on anti-erosion measures, the methods for such modeling and land management in the areas prone to soil erosion in order to maintain and restore degraded lands. A variety of erosion control techniques, methods, approaches, technologies and activities described in diff erent sources, including databases on best practices, educational and scientifi c literature serves as objects of the study. Th e study was based on the integration of several working hypotheses and approaches proposed by the authors in earlier publications. Th e methodological basis of these approaches is the concept of land degradation neutrality (LDN) and the principles for assessing the «sustainability» of environmental management based on it. Using the example of several sites, methods for semantic modeling of the sustainability of anti-erosion land management are considered. These methods are based on assessing the achievement of LDN using the so-called «good» practices. For the assessment, the following parameters of the model were applied: «natural potential» (refl ecting resource potential, adaptive potential and the ability to self-recovery of land), «expanded potential» (refl ecting human improvements in natural potential and the suffi ciency of socio-economic conditions); «actual adverse impacts», including natural processes and phenomena and those caused by human impact; «potential adverse impacts», including natural and anthropogenic risks. Model parameters can be combined in the required combination and refl ect diff erent modeling tasks in order to determine the adequacy of erosion control practices, including general approaches and techniques for regional models, methods and technologies for sub-regional and local ones, specifi c activities and measures for
local models implemented for individual land plots and farms. Th e proposed method for visualizing models, based on the construction of radar diagrams, is a fl exible solution that provides opportunity to consider the suffi ciency of practices, combine them into groups, and also generalize sustainability parameters depending on the goals of modeling.

The paper presents the results of assessing the eff ect of the degree of soil erodibility on the abundance and diversity of cultivated fungi and actinomycetes in diff erent seasons of the annual cycle. The objects of the study are sod—podzolic soils (Umbric Retisols (Abruptic)) of diff erent degrees of washout, located on the slope of the southeastern exposure (Moscow region, Solnechnogorsk district), used for a long time for the cultivation of agricultural crops. The indicators of microbial abundance were determined by the cup method, identifi cation was carried out on the basis of phenotypic characters. It is shown that the decline in physical and agrochemical parameters of the soil, which is a result of erosion processes, leads to a change in microbiological parameters. A decrease in the abundance and species diversity of fungi and actinomycetes was found with an increase in the degree of soil erosion. Significant diff erences were found in the taxonomic composition of microbial communities of non-eroded and washed away soils (the Sorensen species similarity coeffi cient does not exceed 0.42 for fungi and 0.30 for actinomycetes). Taxonomic units of mycelial microorganisms have been identifi ed. Among the fungi are representatives of the species Aspergillus, Cladosporium and Scopulariopsis, among the actinomycetes are Streptomyces malachitospinus, S. candidus and Micromonospora aurantiaca.

The humus state of gray forest soil formed on loess-like loams on the slopes of the northern and southern exposures at slopes of 1, 3, 5° was studied. Soil samples were taken in sections laid in the middle part of the horizon (Apax, A1, A1A2, B), in three-fold repetition. The determination of organic carbon and the fractional group composition of humus was carried out according to the scheme of I.V. Tyurin, modified by V.V. Ponomareva and T.A. Plotnikova. The content of mobile humic substances was studied in 0,1n NaOH extraction from soil without decalcification in the modification of the V.V. Dokuchaev Soil Institute with preliminary composting.
Gross nitrogen was determined by the Ginzburg wet salting method with ammonia distillation according to Kjeldahl. It was found that the content of organic carbon in gray forest soil was higher on the northern slope than on the south- ern one. At the same time, the process of mineralization of organic matter occurs faster in the soil of the southern slope, which is due to a narrower ratio of C:N compared to the soil of the northern slope. It was revealed that for gray forest soil, the degree of mobility of humic substances depends more on the exposure of the slope than on its steepness. At the same time, the ratio of organic matter components in the studied soils is determined by agroeco- logical conditions, therefore, the regulation of the qualitative and quantitative composition of organic matter must be carried out taking them into account.

Summary Soil erosion as one of the types of land degradation aff ects various economic interests of people. It is shown that the most promising areas of erosion studies, where economic methods can be applied, are — assessment of actual damage fr om soil erosion, determination of the magnitude of probable damage from the occurrence of erosion
processes in soils, economic analysis in the development of sustainable land use systems for territories whose soils are subject to erosion. Th e group of methods for determining economic damage is characterized by the greatest development, including taking into account ecosystem services that soils «lose» as a result of erosion processes. Methods for assessing the risk of soil erosion have signifi cant development potential, since by now a powerful database of predictive models and equations (USLE, RUSLE, RUSLE2, WEPP, EUROSE, CREAMS, EPIC, VNIIZiZPE, etc.) has been created, allowing to assess indicators of soil erosion in the future. Th e neoclassical theory of capital is used in the development of sustainable land use systems, which requires that the fertility of the soil and the net social benefits from non-market goods and services from agricultural land should be maintained over time. Th us, it is possible to
create compensatory taxation mechanisms for territories wh ere soil erosion processes occur.