About erosion activity by dells (on example of Transbaikalia)

In Transbaikalia, a number of natural factors favour development of water and wind erosion. The article presents quantitative indicators of soil loss as a result of the permanent erosion in dells – linear grooves. A dell lifetime is more than one year. They are formed by slope waters, which carry out temporary runoff and transport of soil material. According to observations, the dells have a triangular or trapezoidideal shape in a cross section, and in the longitudinal direction a profile of the slope is copied. Detailed morphometric measurements of the model slope were carried out, which allowed increasing reliability of the research results. The difference in the shape of constructed empirical polygons of distribution of volume of dells objectively indicates a different intensity of erosion activity in different parts of the model slope. This is also evidenced by the differentiation of different parts of the slope by the conditional work on the transport of soil material under erosion by dells. For calculations, the model of Wishmeyer and Smith, given in the metric system, is implemented. Thus, for the first time in the region such important characteristics as EPR-erosion potential of relief, EPP – erosion potential of precipitation are determined. In accordance with a concept of allowable losses, which was developed for the first time in the United States in the 30-ies of XX century, the calculation of the value of MAEL – maximum allowable erosion losses of soils is conducted. The humus state of chestnut soils in the 50s of the XX century (0-moment), i.e. before the beginning of the virgin soil epic, was used as the initial indicators for the calculation of MAEL. These data were previously used to calculate the kinetics of humus content for the XX century. The actual humus status is assumed to be equal to the moderately eroded soils. At the same time, we believe that exactly this category of land is still able to meet the needs of plants. The calculations show that in the dry steppe landscapes of Transbaikalia the losses in compensated soil formation are approximately 2 t/ha/a. Soil degradation is exacerbated by desertification and aridization. Spatial differentiation of the model slope according to the form of the cross section of the dells and a diagnosing role of the empirical polygons of statistical distribution are shown. The soil erosion losses are estimated energetically. The indicators of the maximum permissible losses during the erosion, corresponding to the rate of the soil formation, as well as the temporal parameters of the service (durability) of soils, were obtained.

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