The Relationship Between Wetland Evolution And Spatial Pattern Of Land Surface Temperature In Dongting Lake Area

As the second largest fresh lake in China, Dongting lake plays a significant role in regulating regional climate and stabilizing environment. However, due to global warming and other factors, wetland area is dramatically decreased, wetland function is seriously degenerated, and eco-system is severely affected.For a better understanding of the spatial-temporal variation characteristics of wetland and land surface temperature (LST) change, investigating the responses to global warming of LST, and also for a better exploring the influence of wetland change in LST. The wetland and LST information were retrieved and analyzed using wintertime TM/ETM+ images in 1995,2001,2004 and 2013 by remote sensing (RS) and geographical information system (GIS) technology.The result shows that:(1) The landscape of Dongting lake area mainly consists of Paddy field, dry land, forest land and water body. From 1995 to 2013, the wetland area was declining, especially water body, from 2670.59 km2 to 2078.12 km2. The conversion relationship was complex in different land types, mainly indicated in paddy field into construction land and dry land, dry land into forest, water body into grass beach, reed beach and mudflat.(2) The landscape fragmentation and landscape shaper index were continuously rising. The more obvious change of landscapes structure were observed in water body, construction land, paddy field and dry land, and the stable in reed beach, grass beach.(3) The area of each LST grade in Dongting lake was of the normal distribution, and it mainly consist of middle temperature area, higher temperature area and lower temperature. In terms of spatial distribution, the lower temperature area was mainly in water body, and there was no distinct distribution characteristic in higher temperature area. From 1995 to 2013, the average LST increases about 3.5℃ in winter, and its spatial diverse decreases. The proportion change of each LST grade suggests that the LST of East Dongting Lake was greatly affected by global warming, while the West’s was minimal.(4) The average LST of wetland landscapes was smaller than others, and water can reduce the surrounding LST, and its influence distance was about 300 m when the water area is bigger than 1 km2.(5) In winter, water vapor was the most important influence factor to LST. The correlation between NDVI and LST was non-significant, while the NDMI was in significant negative correlation with LST, especially when its value was between 0.2 and 0.5. DEM was in positive correlation with LST when its value was smaller than 65m, and the correlation was non-significant when the value was between 65 m and 365m, when the value was bigger than 365m, the correlation was negative, but not obviously.