Contribution analysis on spatial tradeoff/synergy of Karst soil conservation and water retention for various geomorphological types: Geographical detector application

Rocky desertification is the most typical ecological and environmental problem in Karst mountainous areas, which hinders sustainable development. Clarifying spatial relationship of ecosystem services including soil conservation and water retention and their dominant factors can provide scientific basis for containment of rocky desertification. The spatialization and quantification of dominant, interaction and sensitive factors affecting synergistic relationships between sediment yield and surface/slope runoff, water yield and slope runoff would be achieved in diverse geomorphological types. Geographically Weighted Regression (GWR) was used to quantitatively analyze spatial relationships between ecosystem services and variables using Soil and Water Assessment Tool (SWAT). Dominant, interaction and sensitive factors were quantitative identification based on Geographical Detector which can accurately reveal the driving factors and their explanatory power through stratification heterogeneity. Precipitation was dominant factor of synergistic relationship between sediment yield and surface/slope runoff, water yield and slope runoff, especially its explanatory power up to 55% in middle elevation plain, middle elevation hill, small relief mountain, and middle relief mountain. Precipitation is the driving force for the runoff and sediment yield occurrence, which was the important factor affecting the ecosystem service synergetic relationship variables. In middle elevation terrace, elevation dominated synergistic relationship between sediment yield and surface/slope runoff. Land use had different explanatory powers to the synergetic relationships of ecosystem service variables, due to diverse land coverages and impervious areas. As for synergistic relationship between sediment yield and slope runoff, the explanatory power of land use types declined with increase in relief degree of landform in mountainous areas. However, it was not related to relief degree of landform between sediment yield and surface runoff, water yield and slope runoff. Land use types, which are mostly determined by human activities, affect the soil erosion and water cycling processes. Besides, lithology types proved to be the sensitive factor because geological conditions are the background of soil erosion and also the important factor affecting runoff. Furthermore, multi-factor interaction significantly increased explanatory power of synergistic relationship. Moreover, their dominating power varied significantly with relief degree of landform, and these findings should be essential for rocky desertification containment.