Spatial distribution characteristics of discontinuous hillslope gullies on the Loess Plateau of China: A special focus on spoon gullies

Gullies characterized by frequent material exchanges and dramatic morphological changes sculpt fragmented surface landscapes and generate severe soil erosion, yet research on discontinuous gullies is currently lacking on the Loess Plateau of China. A special kind of discontinuous gully isolated on a hillslope, termed a spoon gully, was observed during a field investigation on the Loess Plateau. Spoon gullies are permanent gullies that are basically spoon-shaped with fat heads and thin tails. The confluences between spoon gullies and other gullies mainly occur in the subsurface. According to image interpretations and field verifications, 4077 spoon gullies were recognized on the Loess Plateau. These gullies were mainly distributed in the western part and northern fringes of the Loess Plateau with an obvious spatial clustering tendency, forming four concentrated areas with high gully densities. The topography distinctly affects the spatial distribution of spoon gullies. A total of 81.92% of the spoon gullies were located on slopes of 10–30°, and 73.29% of these gullies were located on semi-sunny or semi-shady slopes. Furthermore, the spatial distribution of spoon gullies was associated with loess landforms and soil erosion intensities. A total of 66.37% of the spoon gullies occurred in loess ridge, loess tableland, or loess hill regions, and more than 50% of them arose in areas of strong or moderate water erosion. Overall, spoon gullies were mainly distributed in areas where continuous gullies developed insufficiently, and this finding can be regarded as the integrated result of precipitation, loess thickness and texture, vegetation coverage, and agricultural activities, suggesting that spoon gullies may represent an early stage in the development of continuous loess gully systems. These results not only provide new insights for understanding the formation and evolution of gully landforms but also have significant implications for soil erosion management on the Loess Plateau.