WATEM/SEDEM verification by soil truncation method (Moscow region, Russia)

<p>The popularity of soil erosion modeling is growing rapidly. However, less attention is given to the erosion model verification, which is mainly based on sediment yield estimates. Spatial model verifications are very few.</p><p>In this study soil losses over the 250 years (calculated by WATEM/SEDEM) have been verified by the soil truncation method on the site in the Moscow region, Russia. Just over 1,500 soil sampling points were analyzed on the area 100 km<sup>2</sup>.</p><p>Methods for spatiotemporal reconstruction of input parameters and calculations of soil erosion losses are presented in [1]. The degree of soil erosion, assessed at the sampling points, was compared with the soil losses calculated by the model. A clear tendency was revealed in the change in the proportion of non-eroded soils with an increase in the volume of modeled erosion losses: with losses <50 mm non-eroded soils was 87%; 50-100 mm 86%; 100-150 mm 81%; 150-200 mm 78%; 200-250 mm 70%;  250-300 mm 63%. 13% of points with losses <50 mm were diagnosed as weakly and moderately eroded soils. All such points are located nearby the multi-temporal borders of the arable land. This discrepancy is probably related to the inaccurate calculation of erosion due to the inaccuracy of restoring the cropland boundaries.</p><p>It is important to note that the relief and significant changes in the configuration of the cropland led to significant redeposition of sediments and the formation of a large area of warp and washed-warp soils.</p><p>It remains unclear why non-eroded soils predominate even in areas with erosion losses >250 mm calculated by the model. There are two possible explanations: i) model calculations are universally overestimated; ii) plowing changed the soil-forming process and contributed to a change in the depth of the subsurface horizons of Umbric Albeluvisols. Overestimation of erosion losses is unlikely since soil erosion rates have been verified on several slopes by independent magnetic tracer method [1]. The role of the soil-forming process needs further research.</p><p>In general, the spatial verification of the WATEM/SEDEM can be considered successful given the complexity of the historical reconstruction of input parameters over the past 250 years.</p><p><em>This work was supported by the Russian Science Foundation No. 22-27-00170 and state research program No. 0439-2022-0015.</em></p><p> </p><p>[1] Zhidkin A., Fomicheva D., Ivanova N., Dostál T., Yurova A., Komissarov M., Krása J., 2022. A detailed reconstruction of changes in the factors and parameters of soil erosion over the past 250 years in the forest zone of European Russia (Moscow region). <em>International Soil and Water Conservation Research</em>, 10 (1), 149-160, https://doi.org/10.1016/j.iswcr.2021.06.003</p>