Shallow karst fissures are the main hydrological paths, underground loss channels, and one of the most critical root habitats in fragile karst rocky desertification areas. Revegetation may alter the type of vegetation cover in fissures, resulting in changes to soil properties and erosion reduction. In this study, we evaluate the influence of revegetation on the soil erosion reduction of fissure‐soil–plant systems (FSPS) for three vegetation types (herbs, shrubs, and trees) in FSPS and use bare FSPS without vegetation as a control in a karst rocky desertification area. The results show that the soil physicochemical properties of FSFS degraded first and then improved after abandonment, resulting in the order of soil erosion reduction of FSPS with vegetation succession being: shrub < herb < bare < tree. Vegetation restoration can significantly improve the soil erosion resistance of the 10–20 cm soil layer in the fissure zone, making it stronger than that in the non‐fissure zone, thus reducing the risk of underground leakage on the slope. The results obtained in this study deepen our knowledge of the impact of vegetation restoration type on soil erosion reduction and has significant implications for guiding vegetation restoration and preventing underground leakage in karst areas.

Surface soil water shortages are among the primary factors limiting revegetation in most degraded regions with shallow soil, especially in karst areas. Finding water sources for plants is an urgent task to ensure maximum vegetation restoration in these areas. We combined soil water content monitoring and isotope tracing to reveal the principal water source supply systems for plants in karst areas. The results showed that the content and storage of water in the shallow fissure soil system (SFSS) of the epikarst zone were consistently higher and more temporally stable than that of the surface soil. Thus, epikarsts with dissolution voids and fissures are important, stable aquifers that provide water to plants. Moreover, the IsoSource results showed that the SFSS was the primary water source for three monitored tree species (Cupressus torulosa D. Don, Pyracantha fortuneana [Maxim.] Li and Rosa cymosa Tratt.), especially C. torulosa and P. fortuneana. The water-uptake patterns of C. torulosa and P. fortuneana changed from dominant SFSS and surface soil water sources during the rainy period to the dominant SFSS and transfer zone (TZ) of vadose zone water sources during the dry period. In contrast, Rhynchospora cymosa uses water from SFSS and TZ water sources only during drought. These results suggest that the SFSS is key to eliminating vegetation restoration limitations due to surface drought in karst areas. It is proposed that deeply rooted plants with dimorphic root systems are optimal for sustainable vegetation restoration in karst areas.

In response to the global food shortage, a large amount of abandoned land in karst areas has been reclaimed as cultivated land, causing severe nonpoint source pollution. Preferential flow-driven soil nutrient transport on karst slopes remains poorly studied, though it is a major factor in nonpoint source pollution, as it responds to changes caused by reclamation. We explored the characteristics of soil preferential flow differences in recultivated land, grassland, and shrubland from returning farmland by dye tracer experiments and quantitatively examined the effect of preferential flow on nutrient transport. Under the condition of 40 mm precipitation, the preferential flow paths (PFP) of the three types of plots were mainly distributed from 0– 40 cm. The total porosity in the 20–40 cm soil layer was significantly reduced by reclamation, and the number of preferred flow paths in the 20–40 cm soil layer was significantly reduced from 60 to less than 10, which was significantly less than that in grassland and shrubland. But, reclamation results in the transport of more soil nutrients by preferential flow. The contribution rate of preferential flow to other nutrient indexes in the reclaimed land, in contrast to grassland and shrubland, was lower than zero, except for OM and TK. Moreover, when the PFP was connected to the rock-soil interface, the soil water can leak underground through the rock-soil interface quickly. Therefore, our findings indicated that reclamation reduces the distribution depth of the PFP. Still, the connection of soil preferential flow to the rock-soil interface increases the transport of soil nutrients to deep fissures and even underground rivers, thereby causing recultivated land to become one of the main sources of groundwater pollution in karst areas.