Study On The Law Of Stony Desertification In Xichuan County Based On DEM Spatial Distribution

Xichuan County is the canal head of the Central Line Project of South-to-North Water Diversion and the core source area of Danjiangkou Reservoir in Henan Province.The rocky desertification in Xichuan County occupies a wide area and has a rapid development tendency,which has caused serious peril to the local ecological environment.The study on the rocky desertification based on Spatial distribution of DEM has important engineering theoretical and practical significance for precise control of rocky desertification,control of soil erosion,restoration of vegetation,improvement of ecological environment,protection of natural resources and guarantee the safety of the water diversion.In this study,the author was using the theories of geography,geomorphology,soil and water conservation,statistics,system analysis and other disciplines,using 3S technology combined with field investigation and verification,based on 1:50,000 DEM and 1:10,000 topographic maps,the lithology,elevation,gradient,slope direction,spatial distribution area of rocky desertification land in Xichuan County(interpretation of geographic distribution of porphyry centroid coordinates)were obtained,and used mathematical statistics and systems to analyze the spatial distribution characteristics of rocky desertification and the spatial distribution regularity.The main conclusions are as follows:(1)The area of rocky desertification in Xichuan County is 745.5393 km~2,accounting for26.44%of the total land area of Xichuan County;the severe area is 54.7506 km~2,accounting for 1.94%;the moderate area is 80.5671 km~2,accounting for 2.86%,the mild area is 228.2166km~2,accounting for 8.09%,the potential area is 382.005 km~2,accounting for 13.55%.(2)Re lithology,the spatial distribution characteristics and regularities of lithologic rocky are as follows:the area belonging to the intrusive rock group,metamorphic rock group,carbonate rock group,clastic rock group,and multi-layered soil body lithology is 40.637 km~2,66.8634 km~2,461.5819 km~2,164.5348 km~2 and 11.91 km~2 respectively.The average occurrence rates of lithologic rocky desertification are 24.99%,30.74%,58.26%,23.55%,and1.96%respectively.The distribution shows that the area of rocky desertification is closely related to the lithology of the land.The area of rocky desertification in carbonate rock group is the largest and the highest incidence is 71.03%.The proportion of the area of rocky desertification in different lithology is highly consistent.The proportion of carbonate rock group is much higher than that in other lithologies.(3)Re elevation:the spatial distribution characteristics and regularities are as follows:it mainly distributes in the 200-450m elevation zone with an area of 490.4419 km~2 and accounts for 65.78%of the total area,of which 36.8766 km~2,57.50 km~2,164.11 km~2 and 231.50 km~2are severe,moderate,mild and potential areas,respectively;and the regularity shows with the elevation rising,The area of rocky desertification increased,reaching a peak of 113.7339 km~2at 200-250 m elevation,accounting for 15.26%of the total area.The area decreased slightly with elevation rising between 250-300m,increased slightly with elevation rising between300-350 m,decreased with elevation rising between 350-800 m and increased slightly when elevation exceeded 800m.(4)Re slope:the spatial distribution characteristics and regularities are as follows:the slope mainly concentrates in the range of 9 to 18 degrees,with an area of 382.599 km~2 and accounting for 51.32%of the total area,with the severe,moderate,mild and potential areas of19.9251 km~2,36.63 km~2,115.55 km~2 and 210.4785 km~2 respectively;and the regularity is when the slope is less than 12 degrees,the area increases with the increase of the slope,decreases slightly with the increase of the slope between 12 degrees and 15 degrees,increases rapidly after the slope exceeds 15 degrees,and reaches the maximum between 15 degrees and18 degrees.After the slope exceeds 18 degrees,the area decreases with the increase of the slope and tends to zero after the slope exceeds 36 degrees.(5)Re slope direction:the spatial distribution characteristics and regularities are as follows:it mainly distributes on the South(S)slope,with an area of 229.3893 km~2,accounting 30.77%of the total area.The severe,moderate,mild and potential areas are10.818 km~2,15.6348 km~2,65.7556 km~2,and 137.1609 km~2,respectively.The distribution pattern shows that it distributes from the north(N)turns clockwise and increases,reaching its maximum in the South(S)direction and decreases clockwise along the slope direction;the area of rocky desertification turns clockwise along the North(from large to small)in the order of potential,mild,moderate and severe rocky desertification.(6)Geographically,the spatial distribution characteristics and rocky desertification are as follows:in the geodetic coordinate system with the centroid of Xichuan County as the coordinate origin,rocky desertification has a larger distribution area in the X-axis(-20~10)of coordinate plane,the largest distribution area in the X-axis(-10~0)is 163.7163 km~2,larger in the Y-axis(-20~30),and the largest area in the Y-axis(-20~30)is 182.0052 km~2;The distribution law appears as the farther the distribution area of the rocky desertified land in the coordinate plane from the coordinate center,the area reaches the peak after the X-axis range reaches(-10~0),and then the area begins to decrease;the coordinate plane Y-axis coordinate range The area(20~30)reached the maximum,and then the area change trend began to decline.In summary,the spatial distribution and area of rocky desertification in Xichuan County show obvious regularity in lithology,elevation,slope,slope direction,and geographical distribution.The research results can provide technical support for the precise implementation of rocky desertification control.