Coupling effects of topography and the spatial distribution of cypress on surface runoff coefficient on a steep forested slope in southwest China

Abstract

Interactions between topography and the spatial distribution of cypress give rise to the spatial heterogeneity of surface runoff on steep forested slopes in southwest China. To reduce surface runoff and improve the water conservation capacity of cypress forests, the coupling effects of topography and the spatial distribution of cypress on surface runoff coefficient were studied through the Structural Equation Modeling (SEM) and the Response Surface Method (RSM) based on twelve natural runoff plots. Results showed that the surface runoff coefficient increased monotonically with the increase of the composite index of topography (topographic relief× runoff path density/ surface roughness), and increased first and decreased later with the increase of the composite index of the spatial distribution of cypress (stand density of cypress× contagion index of cypress).To reduce surface runoff coefficient from a larger value (>0.5) to less than 0.3, two strategies of stand structure adjustment could be adopted, including only increasing the stand density of cypress or increasing both the stand density and the contagion index of cypress, and which strategy should be adopted depended on the initial stand density of cypress. When the initial stand density of cypress was relatively low (<20 ind/100m2), the first step was to increase the stand density of cypress, and until the stand density of cypress reached to a moderate level (20-50 ind/100m2), adjusting the spatial structure of cypress from relatively regular to relatively clumped could reduce surface runoff coefficient to a greater extent.

Acquisition of Spatial and Temporal Characteristics of Shallow Groundwater Movement Based on Long-Term Temperature Time Series in the Kangding Area, Eastern Tibetan Plateau

“…Some tests have shown that groundwater infiltration decreases as the slope increases [41][42][43][44][45][46][47]. Zhu et al showed that each effect factor on the seepage field plays the strongest role on the slope toe, a weaker role on the middle part of the slope, and the weakest role on the top slope [48].…”