| In this paper,the Landsat satellite image is used to extract wetlands information of the Everest Nature Reserve by object-oriented classification method,and the wetland dynamics and its response to regional climate change in the reserve from 1975 to 2015 are analyzed.The results show:(1)Nearly 40 years,Everest Nature Reserve Wetland is mainly distributed in the Pumqu Basin and between 4000-6000 m asl,there are a small amount of river wetlandand lake wetland above 6000 m above sea level.At 4000-5000 masl,the proportion of various types of wetlands is more than 80%,the proportion also showed a decreasing trend.In the range of 5000-6000 m altitude,the proportion of river wetland and lake wetland increased gradually in 40 years,and the proportion of marsh wetland decreased.(2)During1975-2015,the wetlandand marsh wetland area showed a decreasing trend,with an annual decrease rate of-0.82km2/a and-0.34km2/a,respectively.The total area of lake wetland in the reserve increased by 0.21km2.From 1975 to 2000,the wetlands and the wetlands of the lakes in reserve continued to grow.The two types of wetlands reached the peak in 2000,which were 963.95km2 and 533.41km2 respectively.During the period from 2000-2005,the wetland area was significantly reduced,among which the reduction of lake wetland was the most prominent,with an average annual decrease of 9.36km2.From 2005-2015,the wetland area of rivers and lakes increased to a certain extent,while the area of marsh wetlands continued to decrease.(3)Due to the trend of warm and drying of the reserve,lake evapotranspiration was greater than the supply of precipitation,melting of glacier permafrost,inland lakes gradually shrinking,the number and the area of glacier lakes in the southernregion of reserve is continuously increasing,The area of marsh area in the water supply area of the snow melt increased,and the area of the wetland of the high altitude river decreased,and the patch density and fragmentation index of the protected area showed an increasing trend.The degree of fragmentation was becoming more and more serious.Resulting inthe geocentric of lacustrinewetland move southwest by 6.27 km,marsh wet geocentric eastward migration,river wetland centroid is gradually eastward.Wetland landscape diversity as a whole showed an increasing trend,all kinds of wetland plaque distribution gradually balanced.The degree of landscape aggregation is decreasing,and the connectivity between wetland patches is reduced.(4)Throughout the year,the annual correlation between the lake wetland and the extra-maximum air temperatureof northearn slope was the highest,and the extreme temperature had the most significant effect on the change of river and marsh wetland area.In 4300-4400 masl,cooling-humidifyingeffects is more significant in the area with more wetlandstyles.At 4400-4500 masl,the wetland of Everest Nature Reserve is dominated by river wetland,and the area of wetland in Nyalam is relatively larger,the cooling-humidifying effects is the most significant,the effects of Lake Peiku wetland is stronger than the wetland areas of Gyirong wetlands between 4500-4600 m,.(5)The NDVI values of all kinds of wetland vegetation were significantly different throughout the year,and the NDVI maximum appeared in August.With the change of climate,the NDVI values of Kobresia humilis and Carex decreased,and the value of shrubs increased gradually.The changes of wetland weeds and aquatic plants were relatively more stable,and showed a weak growth.The average annual NDVI values were from large to small: Kobresia humilis and Carex,shrubs,weeds,aquatic plants.The optimum growth temperature of marsh wetland vegetation is 6-7?.The change rate of glacier lake is faster in the south slope than the north,The change of the glacier lakearea is the most obvious between 4700-5500 m in the south slope,and the placethat glacier lake area change most obvious in the north slope occur at 5000-6000 masl. |
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