Impacts of landscape factors on gully retreat and its morphological characteristics in hilly areas of Northeast China

The black soil region in Northeast China is an important commodity grain base. In recent years, with the intensification of agricultural activities, the formation and development of gullies on sloping farmland have accelerated, severely affecting food and ecological security. In order to effectively control regional soil erosion, this study comprehensively utilized historical databases of gullies, remote sensing images, field surveys, spatial analysis, and multivariate statistical techniques to reveal the morphological characteristics, development rates, and main driving factors of 116 gullies in typical agricultural watersheds in the low hills of Northeast China. The results showed that linear gully retreat rate in the study area ranged from 4.3 to 8.4 m y−1, with an average of approximately 6.34 m y−1, between 2011 and 2021. The areal gully retreat rate ranged from 90.7 to 1224.4 m2 y−1, with an average growth rate of approximately 339.17 m2 y−1. Compared with other regions in the world, the development rate of gullies in black soil region of Northeast China is relatively fast, especially in terms of lateral expansion, which is about 7 times greater than longitudinal extension. Gully side-wall retreat (approximately 56.8 m2 y−1) was found to be the dominant factor influencing the change in gully area. Environmental variables explained 60.2 % of the variation in gully morphological characteristics, with natural factors having a greater impact on the linear development of gullies than human factors. However, human factors were closely related to lateral expansion. Due to the large proportion of agricultural landscapes and high spatial homogeneity in the study area, micro-topographic features (such as catchment area and elevation) and the spatial configuration of agricultural landscape patches (patch density and edge density) were identified as the main influencing factors of gully erosion development in study area. Therefore, targeted measures and control strategies should be designed based on a comprehensive assessment of terrain factors and landscape pattern indicators to mitigate gully erosion risks. In the future, based on obtaining more three-dimensional data of gullies, empirical coefficient equations should be constructed using gully area and length as independent variables to predict gully volume. This will help identify the main factors influencing sediment and organic matter loss caused by gully erosion in black soil region, and provide technical support for improving the predictive capabilities of gully erosion risks and developing more rational prevention and control strategies.