| Being a common human treasure, the wetland plays an important role in adjusting global climate, keeping regional ecological balance and providing habitat for wild plants and animals, thus the study on wetland has become one of the hottest global research topics. As a natural resource with quick dynamic changes, dynamic monitoring on wetland resources is very significant. At present, one of the study area is to analyze and obtain wetland information with fast and quantitative methods, such as GIS, GPS and RS (3S) techniques.The techniques of remote sensing provide real-time information which is multi-platform, multi-spectrum, multi-temporal and large-range for dynamic changes of the earth's surface. The advantages of applying remote sensing techniques for studying wetlands mainly include quick information update, wide range, flexibility, real-time dynamics, easy comparison, good for medium & long term study and human and material resource saving. Based on related research information and achievements collected and summarized at home or abroad, we took the Xixi wetland in Hangzhou as an example, made supervised classification of TM image (1991,1999 and 2004) with 3S techniques and divided the Xixi wetland into five landscape types, and conducted spatial pattern analysis following the theory and methods of landscape ecology. Meanwhile, we contrasted precision between TM image and merged image(SPOT and TM) and finally explored the technique of virtual reality in the study of dynamic changes of wetland. Main results and conclusions are shown as follows:(1) A series pre-treatments of TM images, such as radiation correction, geometrical correction and image subset, and so on. Indexes for optimum combinations of bands were compared after it was found that 3,4,5 band combination was the optimum. The result of supervised classification accuracy assessment showed that the Kappa indexes of the three studied years were similar, not notable, being 0.8678 (the maximum) and 0.8543 (the minimum);the Kappa index of the merged image (TM and SPOT) was 0.8868, being higher than those of TM image, but notsignificant. The minor differences between the merged Kappa index and the common ones might be attributable to small field check area and the high scale of topographic maps.(2) The result of analysis on dynamic changes of landscape pattern showed that, from 1991 to 2004, the areas of ponds, river and idle land all decreased, particularly for the river area that reduced about 50%;whereas the areas of farmland and construction land increased drastically, which caused a notable change of landscape pattern of the Xixi wetland in Hangzhou. Diversity index decreased from 1.5683 in 1991 to 1.2681 in 2004, which reflected that the differences of the ratios of various landscape patterns increased. Along with the constructed land expanding gradually, its largest patch area exerted more impact on the total area;farmland showed similar changes. Artificial landscape has been replacing the original landscape and changing ecological functions of the wetland.(3)In last 15 years, the constructed land and farmland played more and more controlling roles on the Xixi wetland, which caused the space of wetland decreased day by day, particularly for the ponds around the farmland and beside the roads, which received the largest impact from human activities and faced to disappear. The decrease of areas of ponds, river and the simplification of landscape patches will ultimately decrease the flow of material and energy, reduce biodiversity, and aggravated environmental pollution.(4)The virtual reality technique was applied in the study of dynamic changes of the wetland landscape, which vividly showed the dynamic changes of the Xixi wetland in last 15 years. The future Xixi wetland park with different development plans can also be shown with the VR technique and released to the web, which can make the management and plan of the wetland park more scientifically and systematically, and enhanced the utilization ratio of wetland resources.
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