Response Of Spatial Distribution Characteristics Of Gully To Topographic Factors In Yuanmou Dry-hot Valley

Soil erosion is one of the most important environmental problems in the world.Gully erosion is the main type of soil erosion,which causes to soil displacement,deposition and degradation,farmland erosion and damage to the integrity of the land.The Yuanmou Dry-Hot Valley is located in the Jinsha River Basin,where gully erosion is very active.Gully erosion is the most prominent eco-environmental problem in this area.Due to t he combined effects of topography,climate,hydrology,soil and human factors,the formation and evolution mechanism of erosion gully in in Yuanmou Dry-hot valley is different from other areas.Therefore,in order to study the spatial concentration and di stribution of erosion gullies in Yuanmou Dry-hot valley and the impact of terrain on gully,this paper is based on kernel density estimation,spatial autocorrelation analysis,the Geographic Detector,geographically weighted regression and factor analy sis.Evaluate the spatial accumulation degree of erosion gull y,analyze the topographic differentiation law of gully accumulation,and clarify the influence of single topographic factor and multi topographic factor coupling on the accumulation and distribution of gully.The main contents and conclusi ons are as follows:(1)The distribution pattern of gully in the dry-hot valley of Yuanmou is obviously uneven and concentrated.Remote sensing images were used to interpret and extract 51227 gullies.The total length of gullies is 14835.28 km,the average gully density is 1.28 km/km~2,and the length of gullies ranges from0.1 km to 5.9 km.The Moran’s I value of gully kernel density is 0.89(p<0.01).The analysis of hot spots shows that there are obvious hot spots and cold spots in the spatial distribution of gully.(2)The spatial concentration degree of gully has certain rules on different topographic gradients.Evaluate the differentiation characteristics of gully based on topographic factors,and study the distribution of gully under different topographic conditions.The high-value areas of slope,Ra,Si and TRI are mainly distributed in Dongshan Mountain and around mountain valley in the middle and south of the study area.The low value areas are mainly located in Yuanmou basin,Mumao Basin and other basins.The study found that the average and maximum kernel density of gully in the dry-hot valley of Yuanmou increased with the increase of slope,Ra,Si and TRI.It first increased and then decreased.There was little change in the density of gully on each slope,but the average density of gully on the northeast slope was the highest,and the maximum kernel density of the gully on the northeast and south slopes was the largest;the average density of the gully on the west slope was the smallest.The maximum kernel density of the erosion gully upwards from the southwest slope is the smallest.The average kernel density of concave slope and convex slope is higher than that of flat slope,indicating that concave slope and convex slope are more favorable to the development of gully.However,the maximum and standard deviation of the kernel density on the flat slope are larger,and the change of the kernel density on the flat slope is larger.(3)The influence of single topographic factor and coupling of multiple topographic factors on the distribution of gully is explored.The results show that:(1)The correlation between a single topographic factor and the kernel density of gully is the first,followed by the Si,and the TPI factor ranks last.The profile curvature and plane curvature did not pass the two tailed test(P<0.01),and there was no significant correlation.Therefore,the topographic relief and fragmentation are the most basic and primary factors in the development of gully.(2)The average explanatory power(Q value)of the main factors that affect the spatial differentiation of the gully is significantly higher than that of other topographic factors.The ecological detection shows th at the factors representing the degree of topographic relief and other factors have a greater impact on the spatial distribution of gully,while the factors with similar functions and attributes have a weak difference on the spatial distribution.The interaction detector shows that the interaction between multiple factors is not a simple superposition,but a result of mutual enhancement or nonlinear enhancement.(3)There is obvious spatial heterogeneity in the goodness of fit of topographic factors to gully kernel density.Local R~2 is larger in the east and west of the study area,and smaller in the central basin.The geographically weighted regression model has different explanatory abilities in different areas of the study area.The mean correlation degree between kernel density and topographic factors from large to small is slope,Ra,TPI,elevation,TWI,which is negatively correlated with kernel density.(4)The greater the terrain comprehensive factor,the greater the probability of producing gully.The spatial pattern of terrain comprehensive factors is similar to the spatial pattern of the distribution of elevation,slope,Ra,Si,and TRI,which indicates that the development risk of erosion gully is higher in the region with higher elevation,greater slope and more broken topographic relief than in other regions.