1.Forestry College of Guangxi University;2.Agricultural College of Guangxi University
Supported by the Guangxi Natural Science Foundation Project (No. 2021GXNSFBA075017) and the National Natural Science Foundation of China (Nos. 42007055,41630858)
【Objective】Collapsing gully is an erosion phenomenon of hillside soil under the effect of gravity damage collapse and hydraulic scouring. It is also the most serious and harmful typical soil erosion mode in the granite red soil area in South China. Collapsing gully is mainly distributed in granite hilly areas in seven provinces of Guangdong, Jiangxi, Guangxi, Fujian, Hunan, Hubei and Anhui, and their erosion modulus is large and widely distributed. This causes serious concerns for the local ecological environment and economic development. Limiting water content is an important parameter of soil hydraulic properties, which can characterize the ability of the soil state to change with a change in water content. Given that this is closely related to the stability of collapsing gullies soil, it is of great significance to predict the relationship between rainfall and collapsing gullies erosion.【Method】We selected three types of granite collapsing gullies in southeastern Guangxi, active, semi-stable and stable, as the object of study to analyze the spatial variation of soil limiting water content in each collapsing gullies and to reveal the influencing factors by using the method of path analysis.【Result】The main results were as follows: (1) Soil limiting water content of each part of collapsing gully varies spatially, the liquid plastic limit of active and semi-stable collapsing gullies soils had maximum value at top of collapsing wall (the liquid limit was 54.45% and 57.08%, the plastic limit was 32.84% and 34.04%, respectively ) and minimum value at the top of the pluvial cone (the liquid limit was 35.39% and 30.72%, the plastic limit was 21.92% and 20.23% respectively ). Also, the liquid plastic limit of stable collapsing gully had the lowest value at the bottom of the colluvial deposit (the liquid limit was 33.78% and the plastic limit was 22.47%). After gradually stabilizing the development of collapsing gullies, the limiting water content of the soil in each part showed an overall increasing trend. (2) Correlation analysis showed that clay content, organic matter, total porosity and capillary porosity were positively correlated with soil liquid plastic limit and plasticity index, with total porosity having the most significant effect on soil liquid plastic limit. Nevertheless, soil bulk, gravel content and sand content were negatively correlated with soil liquid plastic limit and plasticity index. (3) Path analysis showed that total porosity, clay content, organic matter and capillary porosity played a dominant role in the variation of the limiting water content. Furthermore, total porosity, clay content and capillary porosity were the main factors influencing the liquid plastic limit, plasticity index and liquidity index of soil, respectively. The higher the clay content, total porosity and organic matter, the higher the liquid plastic limit and plasticity index of soil. Also, the stronger the cohesion of the soil, the better the water retention performance of the soil, and the more difficult it is for the soil to crumble and be lost. Capillary porosity negatively affects the liquidity index, that is, the larger the capillary porosity, the lower the liquidity index and the more stable the soil is.【Conclusion】The limiting water content is closely related to the start-up and stability of collapsing gullies. When the limiting water content is low and is washed by rain, the soil state is easy to change, and surface runoff is produced, which causes soil collapse and fertility loss. Therefore, the results of this study can help to clarify the soil erosion process, further clarify the erosion hazards of collapsing gullies and identify high erosion risk areas. It can also provide theoretical support for the prevention and management of collapsing gullies hazard and have important significance for the prediction of regional soil and water conservation.
WEI Jiangxing, DENG Yusong, LIAO Dalan, HUANG Wanxia, HUANG Juan, JIANG Daihua. Spatial Variation and Influencing Factors of Soil Limiting Water Content of Granite Collapsing Gullies in Southeast Guangxi[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202107120359,[In Press]