Coupling
effects of
topography
and
the
spatial distribution of cypress on
surface
runoff
coefficient
on a steep forested slope in southwest China
Bingchen
Wu1, Shi Qi11Corresponding author: Shi Qiqishi@bjfu.edu.cn; +86
13522046290
35 Tsinghua East Road, Beijing, 100083, P.R.China*
1 Beijing Forestry University, Beijing, 100083, PR 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.
Key
words: Spatial
distribution of cypress; topography; surface runoff coefficient; SEM
(Structural equation modeling);
coupling
effects