Patch Dynamic Characteristics Based On The Expand Of Zhangye Oasis

This thesis builded land use and cover types database for Zhangye oasis in Gansu Province based on the 3S technology through the interpretation and integration of multi-source data, regarding two vector data of the 1985 and 1995 and Landsat TM images in 2009 as the information source. First, the thesis analysed landscape static features of the Zhangye oasis in patch, type and landscape three-levels, in order to illustrate the impact of different analysis scales for the same study area. Second, based on the previous patch dynamic classification, the thesis classified patch dynamic types of different landscape in different periods into the unchanged patches,newly generated patches,expanded patches,shrunk patches and dissolved patches by the inheritance, so that analyzed the spatial pattern of the different landscape types in the oasis process from the perspective of patch dynamics. Finally, the paper analyzed the area transfer traits of different patch types and the main driving factors of influencing landscape change of the study area. The results as followed:1. the analysis of the landscape static characteristics(1) Index analysis based on the patch scale showed that the small patch calss had highest fragmentation degree in landscape, followed by the medium patch class, the larger patch class and huge patch class had higer concentrative degree. In terms of the different landcape types, the small and medium patch classes took the greatest proportion in cropland; the medium patch class was the dominant patch type in woodland and grassland, while the patch numbers in grassland was more than those in woodland, and there was no huge patches in woodland; patch numbers of the small,medium,huge patches were almost the same in water body, and all of them were less than 100, while patch numbers of the huge patches were the least; In the terms of patch area, the huge patches had the absolute advantage in the landscape types which were mentioned in the above; patch numbes and patch area of the small patches were much more than the other classes in the construction land, taking the dominant position; while the medium and larger patches took the greatest proportion in the number, the huge and larger patches were the dominant patch types in the area in the unused land.In terms of mean fractal dimension of the different patch classes, huge patches were the largest, so the shapes was most complex, and its borders were more sensitive for the infullences of human activities and natural factors fluctuation. The correlation analysis of fractal dimension and patch size of the different landscape types showed that there was a quadratic equation relationship.(2) Index analysis based on the type scale showed: the cropland trended towards concentrative distribution in the landscape; grassland was fragment in the landscape because of the over-grazing;water bodies affected by human activities, which owned the highest fractal dimension, and shape were the most complex;construction land trended towards fragmentation, showing scattered distribution in the oasis; forest accounted the smallest proportion in the landscape and fractal dimension was relatively higher, indicating that the type was stable, and would not lead to larger fluctuations in the short period of time.(3)Index analysis based on the landscape scale showed: there were richer landscape types and higer diversity in Zhangye oasis in 2009, having fragment distribition in landscape scale; the shape was relatively simple beacause of the higher interferences from human activities. Among them, there were quite different landscape features in different oasis (based on the county border). The patch shape were relatively simpler in Gaotai oasis, and there was a certain advantage types, while landscape type were relatively abundant. Patch shape were more complex in Ganzhou oasis, landscape heterogeneity was the highest. Linze Oasis mainly distributed in low hills residual hill areas of the north, the patch shape were more complex, and there was the clear advantage type in the landscape.2,Spatial pattern of landscape patches in different periodsIn terms of the distribution pattern, In 1995-1985 to 1995-2009, the unchanged, shrunk and newly generated patches trended towards the fragmentation, the expanded and dissolved patches trended towards the concentrative distribution in the cropland landscape. The unchanged,newly generated and expanded patches had the fragmentary trend in woodland landscape, while the shrunk and dissolved patches trended towards concentrative distribution in landscape scale. Dissolved patches had concentrative distribution,other four categories had the fragmentary trend in grassland landscape. Five changed patterns had the fragmentary trends in water body. Dissolved patches tended to concentrative distribution in construction land, while other types tended to fragment.3,Patches dynamic transformation of the different landscape typesThe analysis of origins and traces of patches showed that the most obvious of the patches dynamic transformation were between cropland and grassland, cropland and unused land, cropland and construction land in different landscape types.In the two different periods, grassland and unused land were the main source of cropland expansion, and mostly extended to the periphery in the form of small patches; at the same time, accompanied by the larger numbers of the shrunk and dissolved patches in cropland, in which shrunk patches accounted the larger proportion, which the expansion of construction land were the main trace of the shrunk patches in the cropland. In the oasis process, the construction land and cropland had always been a pair of conflicting factors. The expansion of construction land occupied much cropland during the two period, mainly appeared in the form of the small patches in the surrounding of construction land, and builded a number of construction land which were concentrative distribution in the suitable cropland.4,The analysis of driving forces indicated that,with the increasing of the amount of ground-water exploitation, the promotion of water-saving irrigation technologies, the increase of the annual average temperature year by year, the decrease of the annual sunshine hours and the evaporation etc. climatic factors, which has greatly improved water use utility, all these were the the most important factores in the oasis process of Zhangye Oasis; the increased intensity of human activities caused degradation of the oasis landscape to a certain extent, and its main formes were the degradation of the grassland,shrinking of water body and the expansion of unused land (desert) .