Objective This paper aims to explore the patterns of soil erodibility variation under the influence of preferential flow in the gully system of Jinsha River Dry Hot Valley, and in doing so, revealing the interaction mechanism between soil and water in the gully development area, so as to provide a theoretical basis for soil and water loss control and ecological restoration in dry hot valleys.
Method A complete gully in a typical gully development area of the dry hot valley was selected as the research object. Based on dye tracing, soil erosion resistance and soil physicochemical experiments, statistical analysis methods such as principal component analysis (PCA) were used to obtain the soil preferential flow, soil erodibility indicators and their correlations, clarify the soil preferential flow characteristics of the complete gully system at the catchment area, gully wall, gully bed and gully bottom, as well as explore the correlation between preferential flow and soil erodibility.
Result The findings showed that the preferential flow in the gully of the dry hot valley was mainly “macropore flow”, accompanied by “finger flow” and “funnel flow”. Preferential flow percentages in catchment > gully wall > gully bed > gully bottom. This indicated that the development degree of preferential flow in the upstream of the gully was higher than that in the downstream. Moreover, the gully’s preferential flow area also featured higher organic matter and soil moisture contents, better mechanical composition (clay, silt and sand), and lower soil bulk density relative to those in the matrix flow area. Also to take note is that the soil anti-scour coefficient in the gully’s preferential flow area was smaller compared with that in the matrix flow area, suggesting that the preferential flow can reduce soil stability. Furthermore, the erosion resistance index of each gully section in the preferential flow area was higher than that in the matrix flow area, indicating that soil water and solute transport can improve local soil erosion resistance. The soil erodibility factor (K) of the gully system was positively correlated with the percentage of preferential pathway, the dry coverage of preferential pathway and the maximum dyed depth. Additionally, PCA showed that the above three factors were all the main factors affecting soil erodibility.
Conclusion In soil layers with high preferential flow development, the K in the preferential flow area is always higher than that in the matrix flow area, which is contrary to the soil layer with insufficient preferential flow development. This implies that the development of preferential flow improves soil erodibility to some extent.
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