Research On Landscape Pattern And Dynamic Of Xiannangou Watershed

Based on investigation and geographical information technology, the landscape pattern and dynamic change of Xiannangou watershed, which is located in loess hilly-gully region, were researched. After drawing the landscape patch types maps in field and digitizing it indoor, the landscape classification system and patch types database of Xiannangou watershed were established. Then the correlative landscape indices were calculated in order to analyse the landscape character of this watershed. By overlay the landscape types maps and digtal elevation model, the distribution of landscape types in different elevation,slope and aspect grades can be obtained.Then by summering the composition data of landscape types in 2004,the landscape pattern dynamic of Xiannangou watershed for 5 years was researched, which would provide evidence for optimizing landscape pattern and evaluating the watershed management effection .The result showed:(1) The landscape composition is relatively good and the area ratio of three landscape function types was almost proper. In these Landscape types,Robinia pseudoacacia(both mature and young) was the largest area-part of Xiannangou watershed,and followed by Bothriochloa ischaemun -Artemisia giraldii +Artemisia sacrorum association, farmland, Sophora viciifolia and Artemisia sacrorum + Artemisia giraldii association. The 6 kinds of landscape types mentioned above occupied 82.26% of landscape area and 60.23% of landscape patches, so they constituted the main part of Xiannangou watershed. 2)The eco-protection type occupied more than 3/4 of total patch number and area in Xiannangou watershed. The area ratio of three landscape function types which were eco-protection type, pro-economics type and living-service type was around 3.63:1:0.08. The area ratio of human directed landscape and natural landscape was almost 2:1 and the area of eco-protection type occupied about 2/3 of human directed landscape of this area. Human had great influence on landscape composition in this watershed.(2) Terrain was the main reason for the spatial Topographic variation of landscape types in Xiannangou watershed: The policy of Conversion of Cropland to Forest(Grass) was the fundamental cause for the change of local landscape types in different grades of elevation,slope aspect and aspect in Xiannangou watershed,meanwhile natural recovery had an active role on the change of landscape pattern .Elevation from 1165 to 1265m,slope from 15°to 35°and the semi-shady is the important recovery regions of vegetation, where natual recovey and artificial management measures and should be adopted to improve biodiversity and water conservation.(3) Xiannangou watershed was characterized by diverse landscape types, abundant patches, large difference in types area, tiny landscape granularity, landscape fragmentation, complex shape and high connectivity(4) The landscape pattern of Xiannangou watershed is optimizing continuously by comprehensive treatment. Landscape diversity and Patch Richness density is improving.The area of eco-protection type is improving and ecological security was enhanced. pro-economics type has reduced and living-service type changed little. The policy of Conversion of Cropland to Forest and comprehensive treatment is main reason of landscape change.(5) The landscape pattern should be optimized in the future:, the vegetation quality and ecological function of eco-protection type should be improved completely and prevented from pollution caused by pro-economics type, furturemore Pro-economics type should be stabilized and the improvement of the yield is important,meanwhile the living-service type should be planned reasonably, Then policy of Conversion of Cropland to Forest should be made further improvement and the achievement should be consolidated ,and all of these measures can be in favor of establishing the small watershed model which is healthy in ecology and sustainable development in economy. The composition of landscape function types of Xiannangou watershed would supply reference for management of the small watershed which is similar with Xiannangou watershed in geography and land features.