Geometry Morphology and Distribution Characteristics of Permanent Gullies in the Greater and Lesser Khingan Mountains Forest Region of China

The Greater and Lesser Khingan Mountains (GKM and LKM), together form one of the main resources of the terrestrial natural ecosystem in northeast Asia and play a crucial role in climate regulation and soil and water conservation due to their distinctive geographical features and abundant vegetation cover. Nonetheless, the morphology and distribution of gullies in the two study areas remain unclear. This study focused on an investigation area of approximately 100 km(2) within the forest areas of the GKM and LKM, where field measurements were conducted to record and analyze the morphological characteristics of the gullies. The study also explored the impact of slope and the aspects of gully development and established a gully volume estimation model in the study area. The findings indicate the following. Firstly, that the proportions of gullies with a length of 200-1000 m, a width of 2-6 m and a depth of 1-2 is 59.4%, 51.3% and 45.9%, respectively in the GKM, and 42.5%, 75.7% and 56%, respectively in the LKM. The measured gully density in the GKM was 0.3 gullies per km(2), with an average length, width, and depth of 524.4 m, 2.4 m, and 1.0 m, respectively. In contrast, the measured gully density in the LKM was 0.45 gullies per km(2), with an average length, width, and depth of 560.1 m, 3.9 m, and 1.8 m, respectively. Secondly, as the slope increased, the density of gullies and the degree of surface fragmentation gradually decreased. In the measured area of the GKM, gullies developed faster on the semi-sunny slope. However, in the measured area of the LKM, gullies were more evenly distributed across different slopes. A significant power function relationship between the volume and area (V-A) of gullies in the measured areas of the GKM (V = 0.37 A(1.11), R-2 = 0.94) and LKM (V = 0.32 A(1.17), R-2 = 0.94) was observed. These findings have important implications for soil conversation in forested areas of the black soil region in Northeast China.