Abstract Check dams are used for soil and water conservation worldwide, especially on the Chinese Loess Plateau, which has suffered from severe soil and water loss. To promote ecological conservation and high‐quality development in the Yellow River basin, considerable effort should be devoted to building check dams in the small watersheds where the conditions permit on the Loess Plateau. Therefore, suitable small watersheds must be identified for constructing new check dams. In this study, the weighted overlay method (WOM) of the multi‐criteria decision‐making analysis method, the random forest (RF), and the support vector machine (SVM) of machine learning methods were first applied to simulate the suitability of small watersheds for check dam construction in the Ganguyi upstream area of the Yanhe River basin on the Loess Plateau. Accuracy assessment showed that the accuracy of the three models was almost perfect and RF had the highest accuracy of 0.95, followed by SVM (0.87), and WOM (0.83). Meanwhile, the impacts of topographic factors and soil erodibility were found to be generally higher than those of the other factors, and 56% of small watersheds had high and very high suitability for check dam construction, 67% of these small watersheds have already been built as check dams. Finally, a total of 108 small watersheds were found to be suitable in the study area when considering their environmental characteristics. The methodology developed in the study can be used as a preliminary planning step for check dam construction and as a foundation for detailed field investigations in the future, which help to realize the sustainable use of soil and water resources.
Abstract Widespread shallow landslides typically result in the loss of productive soils and grasslands. Deposits of landslide tails have received much attention, while the severity of rill erosion on the landslide scar is generally neglected or underestimated. Thirty‐five rainfall‐induced shallow landslides were selected on Lishi (finer texture) and Malan loess (coarser texture) on the hilly and gully Loess Plateau, China. The rill erosion intensity and rill morphological parameters of these landslide scars were measured by on‐site investigation 3 years after the landslides. Landslide characteristics were investigated by unmanned aerial vehicle photogrammetry, and soil properties were also evaluated. We found that landslide scars suffered rill erosion for more than 8 years after landslides. Rill erosion intensities of the Lishi (22.91 × 10 3 t km −2 ) and Malan landslides (16.90 × 10 3 t km −2 ) in 3 years occupied 11.43% of the landslide deposit amounts. The structural equation model demonstrated that catchment area, soil bulk density, soil organic matter, water stable aggregate content (WSA), and sand content explained 87% of the variance in rill intensity through paths of rill depth, width, and distribution. Additionally, the negative effect of rill distribution on rill depth led to the unusual result that coarse soils with low WSA had low rill erosion intensities. In summary, the rill erosion of shallow landslide scars reached a non‐negligible value. The effect of initial rill distribution masked the effect of soil properties on rill intensity. Therefore, this study casts fresh insight into the sediment source of landslides, increasing theoretical support for landslide control strategies.
Soil erosion is a severe environmental problem on the Loess Plateau, China. Vegetation restoration is the most efficient method to control soil erosion and introducing late-successional plant species may accelerate natural succession. However, the progress is affected by soil conditions and the appropriate thresholds of soil condition for seed addition are needed. Our objectives were to identify the vegetation types, examine the key soil factors affecting the vegetation variation, and determine the thresholds of the soil factors for each vegetation type. Five vegetation types in secondary succession were identified: association (assoc.) Artemisia scoparia assoc. Bothriochloa ischaemum assoc. Artemisia gmelinii Artemisia giraldii assoc. Ostryopsis davidiana Rubus parvifolius L., Syringa oblate and assoc. Sophora viciifolia Years since abandonment (YEAR), alkali-hydrolysable nitrogen (AHN), soil water content (SW), and total phosphorus (TP) were the key factors used to discriminate among vegetation types. Assoc. A. scoparia developed in croplands that had been abandoned for less than 11 years. Assoc. B. ischaemum developed in croplands abandoned for more than 11 years with lower soil nutrient levels (0.30 ≤ TP ≤ 0.646 g kg−1 and 16.72 ≤ AHN ≤ 32.62 mg kg−1). Assoc. A. gmelinii + A. giraldii always required greater TP (0.646 ≤ TP ≤ 0.79 g kg−1) to develop. When soil water content was lower (6.6 ≤ SW ≤ 8.4%), the assoc. S. viciifolia developed; otherwise, other associations, such as assoc. O. davidiana, developed. These soil thresholds can be used as references for guiding restoration, such as specifying proper soil conditions for seed sowing.
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