Features of Manifestation and Modeling of Soil Erosion in the Eastern Part of the Bugulma–Belebey Upland

Abstract— The Bugulma–Belebey Upland (BBU) is considered a zone of active soil erosion in the European part of Russia. According to various estimates, the duration of widespread agricultural land use in the BBU is about 85–140 years, which is several times shorter than the average for the European part of Russia. The duration of agricultural land use has determined the characteristics of natural and anthropogenic soil erosion and the degree of soil loss. The study’ aim was to investigate soil properties, spatial structure and extend of soil degradation from erosion; to evaluate its factors; and to consider specific features of erosion modeling in the eastern part of the BBU. Research was conducted on arable land of two sites of 22 000–28 000 ha in area, located under different physiographic conditions in the Chishminsky and Ufimsky districts of the Republic of Bashkortostan. The morphological properties, organic matter content, and particle-size distribution of soils were studied, and soil erodibility values (K-factor) were calculated. These soil properties were found to be largely similar, despite differences in the parent rocks and relief morphology. A relationship was found between the K-factor values and the soil types. The average calculated soil erosion rates at the sites were 2.1–2.5 t/(ha yr). The share of moderately eroded soils was 20–25% of the survey points, while that of severely eroded soils was 4–5%. Soil erosion rate estimates obtained based on erosion modeling (by WaTEM/SEDEM) were 2–5 times lower than those obtained using the soil profile truncation method at survey points with moderately and severely eroded soils. The differences observed are likely due to the assumption of the soil profile truncation method regarding the relative homogeneity of the thickness of humus–accumulative soil layer in the pre-agricultural period, which may not be entirely accurate in the context of a complicated topography with hollows and karst sinkholes. The calculated soil erosion rates may also be underestimated due to the insufficient spatial resolution (30 m) of the digital elevation model used for this terrain. Further refinement of scientific and methodological approaches to soil erosion assessments under conditions of hollow topography, including that in the eastern part of the BBU, is necessary, taking into account the identified characteristics.