| Vegetation restoration is one of the effective means to control soil erosion and an essential method of eco-environmental restoration in fragile karst rocky desertification areas.The shallow karst fissure（SKF）filled with soil has become one of the most important root habitats and ecological functions in this area.It is essential to system reveals the main ecological function of SKF and the soil.We explore and gain insight into the characteristics of the SKF soil quality,the characteristics of the response of SKF soil moisture to rainfall,importance of SKF soil water to plants and conservation of“fissure-soil-plant”based on system-divided the vertical section of SKFs.The result of this study can supply some reference for future studies of karst rocky desertification control and vegetation restoration in the karst area.The main results are as follows:（1）High heterogeneity of morphological characteristics exists for shallow karst fissures.According to the different characteristics of the vertical section,the SKFs can be divided into 5 types.These types are Rectangle-type,Pyramid-type,Funnel-type,Net-type and Diamond-type,The proportion of Funnel-type is the largest.In addition,the SKF dip angles were mainly between 60°and 90°,the width of the top aperture was mainly between 20 and 40 cm,and the trace lengths were mainly between 80 and160 cm（76.39%）.（2）In the vertical space of the surface-SKF,soil presents a distribution characteristic of“upper pine lower tight”.The structure,nutrient and microbial structural characteristics of surface soils are stronger than that of SKF soils.While SKF soils have better water properties.The soil properties inside the SKF deteriorated with the depth of the soil layer,but the difference was not significant.Moreover,the difference in soil properties between the surface and the SKF was mainly reflected in the U1 layer in the transition zone between the surface and the SKF soil.Vegetation succession has significant improvements in surface and fissure soil quality.The positive succession of vegetation significantly reduced the difference in soil quality between the surface and the SKF,thus,for the vegetation growth,it is feasible to use the SKF soil to carry out vegetation restoration in rocky desertification areas.（3）In the vertical space of the surface-SKF,the soil water content generally increased with the depth of soil layer.The soil water content of surface was significantly（p<0.05）lower than that of SKF soil.In addition,the response characteristics of surface and SKF soil moisture were obviously different under different rainfall conditions.During rainfall process,the response rate of surface soil moisture to rainfall was the faster than SKF soil.Soil in U2 layer play a buffering effect in vertical movement of soil water.Moreover,U3 layer in SKF was the main aquifer in karst slope.（4）SKF soil was the main groundwater storage space of karst groundwater system,and which also the main water sources for vegetation.During the rainy season,the main water sources of plants were SKF soil water and surface soil water.The contribution rate of SKF soil water were 35.0%67.3%,and surface soil water were 20.4%49.8%.During the dry season,the main sources of plant water were shallow karst fissure soil water and deep fissure water.Soil water and deep fissure water.The contribution rate of SKF soil water were 44.2%49.5%,and deep fissure water were 18.9%33.7%.（5）"Fissure-soil-plant"system have significant effects on soil physical and chemical properties and enhance the soil ant-erodibility.Soil corrosion resistance in SKF soil with vegetation was significantly improved.Furthermore,the improvement effect was increases with vegetation succession.The result indicated that"Fissure-soil-plant"system has a positive effect on soil conservation.In combination with the status of vegetation restoration in rocky desertification areas,deep-rooted shrubs could be selected as the main afforestation vegetation in the early stage of rocky desertification control.Which may have better soil and water conservation and vegetation restoration benefits.（6）Shallow karst fissures serve as a“container”for soil."Fissure-soil"system has become one of major repository of moisture and plant water supply source in the fragile karst area.The system has a significantly effect on improve SKF soil properties and play an important role in prevent underground leakage.Furthermore,acidic substances secreted by plants and organic acids in soils can accelerate the weathering of rock inside cracks.Which greatly promotes the formation and development of fissures.Therefore,the ecological function of the fissure-soil is in a benign process. |
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