| Urban heat islands have brought a lot of adverse effects, it had becomed the constraint of people's life quality further enhancement and city further development. Urban wetlands were important part of urban ecosystems and it exerted urban heat island mitigation, water conservation, flood regulation and storage and other ecosystem services. Depth study of the detemperature effect of lake wetlands had a greatly significant improvement of the urban environment and people's life quality. In this paper, based on the urban heat island distribution and the land use types surrounding lake wetlands in Wuhan on April,2007, the thermal field distribution of Wuhan and the relationship between land types surrounding lake wetlands and urban heat island had been reseached, and explored level of lake wetland functional connectivity and the decreasing heat island effect.The main results as follows:1. Urban Heat Island of Wuhan gradually spreaded from the main city to the suburbs with the increase of urbanization process and the artificial heat source, Huangpi District, East and west Lake District, Caidian District, Hannan District were new center of heat island and the strength was no less than the main city. Heat island of the main city of Wuhan had same distribution as the construction distribution, industrial areas in Dijiao industrial area, Yijiadun industrial area and Wuhan Iron and Steel Industrial Park, and several other old industrial areas were all the strongest heat island. Small and middle scale lakes were surrounded by high temperatures, the city's water patches becamed isolated "cold island", it had a strong contrast of high temperature surrounding and its center of low temperature. Because of the development of urban construction in recent years led to a sharp reduction of the natural land surface and the areas of wetlands and vegetation decreased quickly, East and west Lake District, Caidian District, Hannan District, Huangpi District resulted in a bare ground becaused of the exploitation of mine, these districts appeared intense heat island, Jiangxia and Xinzhou District which containded plenty of wetland and vegetation area only had middle and low temperature distribution. Yangtze River had the minimum water temperature, Han River and large lakes in the outskirts were not very different, the lakes of main city had higher temperature, and Hankou District had higher temperature than Wuchang District because of the water areas smaller, but, all of the temperature of inside water pathes lower than the edge of pathes.2. Among all the land types of Wuhan City, wetlands, forest, shrub and grassland, farmland land, construction land and bare land, construction land and bare ground accounted most of the highest temperature distribution, while wetlands and forest accounted most all the lowest temperature distribution. Lake wetlands accountted for the ratio of city areas were the same as ratio of accountted for the city low temperature, the number of small lake wetland patches and forest patches were very large but only among the city area of 28.77%, the number of large patches were twice of middle lake wetland patches, and covered half of low temperature region, and there were no heat island distrubution in all the wetlands. There were mainly high density construction land in the main city, a lot of small wetlands patches and forest areas showed a high degree of fragmentation, East Lake was the only large patch, so the main city was still the main heat island distribution of Wuhan. In the environment of suburban, wetlands, farm land, and forest had a better situation of other land types, especially lake wetland areas which were larger than 1 km2 was 8 times of the main city, the wetland areas which were larger than 10km2 increased more than 17 to the main city, super large (larger than 20km2) of an increase of 7, therefore, the temperature of suburban was lower than the main urban areas.3. The results of the regression analysis of distances or the lake areas and dereasing temperature rate of lake wetland surrounding of Wuhan reached high significance. The relationship of dereasing temperature rate of lake wetland surrounding and distance of dereasing temperature showed that, a buffer from the main city was 500m, suburbs was 1000m. The relationship of dereasing temperature rate of lake wetland surrounding and areas of lake patches indicated that, the lake wetlands of dereasing heat island area with the critical value was1km2. The correlation analysis of various land types of lake wetland surrounding and dereasing temperature rate of lake wetland surrounding as follows:agricultural land was no significant correlation, woodland, shrub and grassland were the very significant negative correlation, construction land and bare land were the very significant positive correlation. The contribution of all the land types of dereasing heat island were as follows:forest>shrub and grassland>farmland land>construction land>bare land.4. The functional connectivity of 75 lake wetlands decreased heat island of Wuhan city were divided into four grade distribution as follows:high connectivity area, less high connectivity area, low connectivity area and no connectivity area. Each grade distribution covered the low temperature areas were 88.3%,7.5%,4.2% and 0%, and covered the high temperature areas were 15.8%,23.4%,50.6% and 10.2%. The functional connectivity of 75 lake wetlands presented a island model, the high functional connectivity composed by lake wetlands of high area proportion and vegetation distributed relatively concentrated, but these areas were divided by high temperature areas or the terrain factors. No functional connectivity area which lake wetland decreasing heat island distributed in the chain of Dabie mountain and little lake wetlands and vegetation of Huangpi District and Xinzhou District.5. The higher landscape functional connectivity of decreasing heat island, the smaller area of heat island. Protecting these lake wetlands could keep the function of lake decreasing heat island. The net structure of large lake wetlands and vegetation distributed relatively concentrated were almostly covered all the heat island areas of the whole city, and achieved the need of functional connectivity, but needed to take some measures such as roof greening and plumb greening of construction areas, and streets greening, current wetlands protection to enhance the greening rate and furtherly decreasing heat island. Low connectivity area and no connectivity area almostly did not cover the heat island areas.
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