*4.3. Challenges and Perspectives*

The RUSLE model, based on the elements of topography, soil, and vegetation, can simulate regional soil erosion effectively. However, the model should be modified according to the actual environment. Considering the unique rocky desertification phenomenon in the karst area, the RUSLE model with the introduction of rocky desertification factors was chosen for an attempt. However, there are still shortcomings and further research needs to be strengthened. Factors such as data accuracy, the algorithm of each factor within the model, and the karst environment all add to the uncertainty of the model simulation and subsequent analysis. In this paper, the results of RUSLE calculations for the rocky desertification factors introduced due to data limitations could not be compared with the results of field surveys. To reduce the uncertainty of RUSLE models in karst areas, the following aspects should receive attention in future studies. Firstly, the study of soil erosion should be analyzed dynamically with local economies, national strategies [60], and climate change [61]. Secondly, there are biases in the results of each factor of the RUSLE model due to different algorithms, and different sets of equations have been developed by scholars in different regions [62]. Analysis of equation factor algorithms should be strengthened in future research to select the most appropriate algorithm for the study area. Finally, there are both surface loss and subsurface leakage in karst areas, and future research could focus on subsurface leakage.

#### **5. Conclusions**

This paper used a modified RUSLE model to estimate soil erosion in the karst plateaugorge area over the past 20 years. The spatial and temporal evolution of soil erosion was quantified on the basis of slope units, and the influence of single and interactive factors on soil erosion was investigated using the geographical detector.

Soil erosion determined on the basis of slope units can more accurately reflect soil erosion in the actual environment and provide better decision support for regional erosion control and management. In 2000–2020, regional soil erosion showed an increasing trend. The results of this study further confirm the significant effect of the regional perennial rocky desertification control project. Soil erosion is serious in the high slope–low elevation and high slope–high elevation units, and relevant authorities should pay more attention to these areas to improve soil erosion control.

The contribution of the six factors to soil erosion fluctuates, but in the last 20 years, the pattern was slope > LUCC > KRD > FVC > rainfall > elevation. Slope played a dominant role in soil erosion differentiation on the karst plateau, while rock desertification and land use, which are closely related to human activities, also had a stronger influence on soil erosion. The influence of multiple factors on soil erosion is significantly stronger than that of single factors, and the dominant interaction factor varies with changes in rock desertification and land use. The dominant combination of soil erosion changed from KRD-slope (2000,2005) to LUCC-slope (2010) and finally to elevation-slope (2015, 2020). On the basis of this study, we recommend adjusting unreasonable human activities, insisting on natural restoration measures such as returning farmland to forest, and at the same time establishing soil consolidation projects for areas where the soil is gradually recovering.

**Author Contributions:** Conceptualization, C.S. and K.X.; methodology, T.S.; software, C.S.; formal analysis, C.S.; resources, T.S.; data curation, C.S. and T.S.; writing—original draft preparation, C.S.; writing—review and editing, C.S., K.X., and T.S.; visualization, C.S.; supervision, K.X.; project administration, K.X.; funding acquisition, K.X. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Key Science and Technology Program of Guizhou Provence: Poverty Alleviation Model and Technology demonstration for Ecoindustries Derivated from the karst desertification control (no. 5411 2017 QianKehe Pingtai Rencai), the World Top Discipline Program of Guizhou Provence: "Karst Eco-environment Science (no. 125 2019 Qianjiao Keyan Fa), and the China Overseas Expertise Introduction Program for Discipline Innovation: Overseas Expertise Introduction Center for South China Karst Eco-environment Discipline Innovation (D17016).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
