Temporal And Spatial Analysis Of Ruoergai Wetland Reserve Based On RS

Ruoergai Wetland National Nature Reserve, China’s first large plateau wetlands, is not only the world’s largest and best-preserved highland peat swamps, but also a typical representative of the Tibetan Plateau alpine wetland ecosystems. The area is extremely rich in biodiversity, the main breeding ground for many rare wild animals, is one of the upper reaches of the Yellow River Water Conservation land. At present, Ruoergai wetland is facing overgrazing, livestock increasingly acute contradictions, grassland degradation and other issues, serious damage to the local grassland ecosystem.Accurately grasp the characteristics of temporal and spatial variation of grassland desertification, grassland desertification prevention and planning for the development of science and rational plan, effective protection of wetland resources has important practical significance.But research on the protected area of degraded grassland desertification monitoring and temporal variation of grassland has not been reported.The remote sensing imagines in 1990,2000 and 2013 were used as information source in this paper. Based on the ERDAS IMAGINE9.2、ARCGIS9.3 software, the human-computer interaction interpretation had been worked on the imagines of three periods. At last, the change of desertified grassland in the study area in 24 years had been analyzed in this paper. The results indicated as follows:(1) non-desertification grassland concentrated in the northwest, southeast, and on both sides of the Heihe River Basin study area,middle-desertification grassland and serious-desertification grassland scattered in the east and southwest of the study area,Slight-desertification grassland overall present a sheet and zonal distribution. In the three period of the study area desertification grassland area accounts for the total area of the study area ratio between 23%～25%, Among them, the largest area is slight-desertification grassland, which accounted for more than 18% of the total area of the three periods;the proportion of middle-desertification grassland area in between 2.5%～3.5%, The minimum area ratio is serious-desertification grassland,the proportion of area less than 0.5%.(2) The study area from 1990 to 2013 in grassland degradation trend upward, which increased 3162.81 hm2 in 23 years,average annual increase 137.51 hm2. Among them, the slight-desertification grassland area area is the fastest growing, with an average annual increase of 106.32 hm2, the rate of increase is7.8%;The second is middle-desertification grassland, with an average annual increase of 25.88 hm, serious-desertification grassland increased 122.38 hm2.(3) Non-desertification grassland turn out more than transferred in the study area from 1990 to 2000,showed a decreasing trend,its whereabouts are mainly into slight-desertification grassland and middle-desertification grassland; slight-desertification grassland,middle-desertification grassland and serious-desertification grassland turn more than turn out, which was totally increased. From 2000 to 2013 in the study area Non-desertification grassland into more than turn out, showed a increasing trend, and transferred to the main source of slight-desertification grassland; slight-desertification grassland showed a trend of decrease, Mainly converted to non-desertification grassland and middle-desertification grassland. middle-desertification grassland and serious-desertification grassland show the same variation of slight-desertification grassland.(4) Slight-desertification grassland,middle-desertification grassland and serious-desertification grassland area in different altitude are increased during the period of 23 years, slight-desertification grassland area at an altitude of 3450-3480m is the largest increase,the increase range is 55%,middle-desertification grassland and serious-desertification grassland area increased mainly in the altitude of <3450m. In each slope,slight-desertification grassland and middle-desertification grassland area in each slope increased,which increased significantly is in 0～5°, serious-desertification grassland area in 0～10° slope increased, decreased in slope>10°. In each aspect, slight-desertification grassland increased in the sunny slope, half -sunny slope, half-shady slope and shady slope, the rate of increase were 5.4%,9.4%,7.7% and 8.4%; middle-desertification grassland and serious-desertification grassland did not change significantly.(5) The analysis results show that buffer has obvious influence on the distribution and variation characteristics of grassland desertification in the lakes and rivers. In lakes buffer analysis, slight-desertification grassland,middle-desertification grassland and serious-desertification grassland area reduced in the buffer of 0-500m, while increased in the area of 500-1000m and 1000-1500m buffer. In the river buffer analysis, with more and more distant from the river, slight-desertification grassland,middle-desertification grassland and serious-desertification grassland area proportion is more and more large,however, non-desertification grassland meet opposite regular.(6) Lead to increased desertification of grassland area is mainly caused by the natural and human factors.Natural factors include climate change,precipitation and soil parent material androdent and pest,human factors including overgrazing,open ditch drainage,peat and Chinese herbal medicine mining. Between 1990 and 2013, Ruoergai Wetland Nature Reserve showing an overall degradation of grasslands because of a common factor in the long-term effects of these two results.