Slope Aspect Differentiation of Pisha Sandstone Slide Erosion and Its Response to Meteorological Factors

[Objective] As a typical mode of gravity erosion in the Pisha sandstone area, debris sliding has become a significant source of coarse sand material within gullies, seriously threatening the ecological security of the basin. Clarifying the erosion mechanisms in this region is of great importance for the ecological protection and high-quality development strategy of the Yellow River Basin. [Methods] Using the gully slope system in Inner Mongolia as the study area, field monitoring and three-dimensional laser scanning technology were employed to analyze the spatial and temporal changes in micro-topography and erosion characteristics of the erosion interface under different slope aspects. Additionally, the relationships between these changes and meteorological factors were investigated. [Results] (1) The Pisha sandstone gully slopes exhibited significant debris sliding erosion, with distinct slope aspect differentiation. The average erosion areas of the shady slope and the sunny slope accounted for 43.11% and 45.48% of the total study area, respectively. The erosion intensity on the sunny slope was greater than that on the shady slope, with the variation in surface roughness being more pronounced on the sunny slope. However, the variations in surface relief, surface dissection and elevation variation coefficient were more significant on the shady slope. Slope aspect was a critical topographic factor influencing gravity erosion on gully slopes. (2) There was a highly significant positive correlation (p<0.01) between the retreat rate of gully slopes and surface relief and surface dissection. The correlation between the retreat rate of gully slopes and micro-topographic factors was better for shady slopes (R2=0.721) compared to sunny slopes (R2=0.631). The fitting effect of micro-topographic factors with gully slope retreat rate was superior to that with erosion area and erosion volume. (3) During the period from July to August in the Pisha sandstone area, the importance of meteorological factors affecting the erosion of the shaded slope was temperature>rainfall>solar radiation>relative humidity>wind speed. For the sunny slope, the order was temperature>relative humidity>wind speed>rainfall>solar radiation. The GAM model demonstrated a good explanatory ability for the slope aspect variation in erosion characteristics. [Conclusion] The results of this study provide a theoretical reference for the study of gravity erosion mechanisms and ecological construction in the Pisha Sandstone area.