Analysis On The Relationship Between The Urban Forest Spatial Patterns And Heat Island Effect In Wuhan

With the rapid development of industrialization and the acceleration of urbanization, the urban heat island effect become more and more outstanding. As an important part of the urban ecological system,urban forests play a positive role in the heat island effect and urban forest construction. The research of the relationships between the urban forest spatial location and heat island effect has an important significance on relieving the heat island effect.Based on urban LST inversion and the classify of land use type in April 2007 and using remote sensing and gis technology,this study represents the urban forest space distribution on three aspects of vegetation coverage,patch characteristics,three aspects of urban forest spatial pattern to explorate the relationships between the urban forest spatial location and heat island effect. The main research results are as follows:1. The patch density,average patch area,maximum patches index,average patch fractal dimension,patch cohesion index of urban forest under the main urban are less than suburbs,and the landscape division index is more than suburbs.In addition,the patch density,average patch area and the maximum patches index of forest under the main urban and suburbs vary considerably.2. The high temperature areas under the main urban in Wuhan are mainly in high-tech development zone,Tijiao industrial zone,Yijiadun industrial zone,Wugang industrial zone and other industrial zones. Moreover,the high temperature area in the southwestern and northwest suburbs is the town area in Hannan zone and Caidian zone. By contrast,the low temperature areas under the main urban are mainly the water and urban forest.As the report shows,the water mainly include Yangtze river, Hanjiang river, east lake nanhu lake and the other lakes and the urban forests consist of Jiangtan park, the east lake park land,Jiefang park and some other large parks.Moreover,the low temperature areas under suburbs distribute in the water and large landslides, such as Liangzi lake, WuHu and Mulan mountain in Huangpi zone.3. The spatial distribution of MSAVI and LST are opposite.MSAVI under suburbs is obviously higer than the main urban and LST is opposite. Where the rich vegetation is located, where they are both strongly contrasted. This section is for the main urban.The vegetation cooling effect under the main urban has an efficient regime.When MSAVI is less than 0.2 or more than 0.5,the local cooling effect will be better as the Vegetation coverage increase.And when MSAVI is more than 0.2 and less than 0.5,increasing the Vegetation coverage will not effect the local cooling effect.There is another pattern about the local LST.Fristly,when the local LST is more than 27℃and less than 37℃,MSAVI less than 0.2 can have an remarkable local cooling effect.Secondly, when the local LST is more than 25℃and less than 27℃,MSAVI which is more than 0.2 and less than 0.5 has a Little impact on local temperature. Thirdly, when the local LST is less than 25℃,the increased MSAVI has a little effect.This section is for suburbs. When MSAVI is less than 0.2, Local cooling effect is not obvious.When MSAVI is more than 0.2, the increased MSAVI will have a better effect on local LST. When MSAVI is less than 0.8, the increased MSAVI will not have an obvious effect on local LST. There is also another pattern about the local LST.Fristly, when the local LST is more than 27℃and less than 28℃, MS AVI less than 0.2 have not an effect on local LST.Secondly, when the local LST is more than 22℃and less than 26℃,MSAVI which is more than 0.2 has a Little impact on local temperature. Thirdly, when the local LST is less than 22℃, the increased MSAVI will not an obvious effect on local LST.4. Under the main urban and suburbs,urban forest area does not have an influence on Internal cooling. Otherwise forest shape and internal average MSAVI would effect the inter LST.At the same time, internal average MSAVI has a larger effect than forest shape. This paper proves that the more the forest shape index is,the greater the cooling effect is. In other words,the closer to circle the forest is,the better the internal cooling effect is.Also,under the main urban the more the MSAVI in internal forest patches is, the better effect of relieving heat island effect is.5. The cooling rate in the construction land around the forest have some significant correlation with the distance to the forest,the distance to the nearest water and the area of construction land,and have no correlation with the forest area and the nearest water. Results show that the cooling rate in the construction land will be better when there are the smaller area of construction land,the larger area of the forest area and the nearest water or the nearer distance to the forest and water. On the construction land of the main urban, when the total area of forest is less than 20000m2,the cooling effect will be better as the total area increase, but when the total area of forest is more than 20000m2 and less than 50000 m2,the increasing area will not effect the cooling rate.Then when the the total area of forest increase to 50000 m2,the cooling rate will rise with the area become more and more. On the construction land of suburbs, generally speaking,as the total area of forest increase,the cooling rate will rise.If the total area of forest is less than 50000m2,the cooling rate will increase obviously with the rising total area of forest.And if the total area of forest is more than 50000 m2,Cooling rate curves will rise slowly when the area grows.6. The average LST have a negative relationship with the percentage of landscape (PLAND),average patch area (AREA-MN),patch cohesion index (COHESION) and area-weigthe Shape index (FRAC-AM),and have a positive relationship with the landscape division index (DIVISION).The absolute value of absolute values show that under the main urban,patch area>landscape division index> percentage of landscape> patch cohesion index>area-weigthe Shape index and under suburbs, percentage of landscape> landscape division index>patch cohesion index>average patch area> area-weigthe shape index.This study can provide certain theoretical basis and practical guide for landscape layout optimization and construction of urban forest.Moreover,it has important meaning to sustainable development of residential environment.