Study On The Coupling Relationship Between Urban Green Space Landscape Pattern Evolution And Heat Island Effect In Fuzhou

The surge of urbanization has driven the continued development of the economy,however,it also brings a series of ecological environment problems,among which the urban heat island effect is the most prominent one.As an organic part of the urban ecosystem,urban green space plays an important role in the methods and measures to alleviate the heat island effect.This study takes Fuzhou Central City as the research object,using Landsat TM/OLI＿TIRS images for three periods as data source,using RS and GIS technology to analyze the evolution of urban green space landscape pattern on the patch type scale and landscape scale in the central urban area.The single-window algorithm is used to invert the LST and to divide the heat island intensity,so as to analyze the urban heat island effect of Fuzhou Central City,and the coupling relationship between the urban green space landscape pattern and the heat island effect in Fuzhou was studied on the above basis.The major research results are as follows:1.The landscape type of Fuzhou Central City has undergone tremendous changes in the past 20 years.One of those is that the two types of landscapes with the largest degree of net increase and decrease are construction land and urban green space,which indicates that the urbanization process in Fuzhou continues to accelerate,leading to the expansion of construction land area and encroachment on other types of landscape land,and agricultural land is also forced to transfer to the periphery of the city to encroach on the urban green area of the mountain forest type.Combining with the changes of various landscape indices,it shows that the degree of human disturbance caused by urban green space is gradually increasing,and the trend of landscape fragmentation increased first and then decreased,but the overall trend shows an increasing trend;the whole shape of urban green space begins to become complex,and the degree of dominance is becoming more and more obvious.2.The urban heat island proportion coefficient in Fuzhou Central City has gradually increased,and the heat island effect has become more and more serious in the past 20 years.The distribution of the main heat island effect areas above the heat islands in each year is roughly the same as that of the urbanization expansion,and the difference between the heat island intensity and the urban-rural gradient is particularly significant.The heat island intensity is radiated from the downtown area where the building density and population density are large.The greening area to the outer mountain is showing a decreasing trend.Among them,the area of the heat island,the strong heat island and the extremely strong heat island increased year by year with multi-point developing and multi-center distribution pattern of the heat island;while the weak heat island area was basically distributed on the edge of each heat island gathering area,with a large degree of reduction and more shifting to a higher level of heat island intensity;the area of green island first decreased and then increased,but the range of increase and decrease was not large,showing a stable trend.Judging from the change of heat island intensity in different stages,Fuzhou Central City is basically warming up with the increase of the heat island effect,but its heat island effect growth rate is gradually decreasing.3.There is a significant negative correlation between vegetation coverage and LST in the study area.For every 10%increase in vegetation coverage,the LST can be reduced by about 0.86 to 1.59℃.By calculating the correlation between the landscape index of different landscape types and the heat island effect,it can be seen that the CA,the LPI of urban green space and the heat island intensity are significantly negatively correlated.Through establishing a temperature buffer to analyze the cooling effect of 12 urban green spaces,it can be seen that the urban green space forms a relatively cold island area within the urban heat island,and the internal cooling effect is very significant;the urban green space area has a significant negative correlation with the internal average temperature,with every 10hm~2increases in urban green space,the internal average temperature being reduced by about 0.198℃;urban green space has obvious cooling effect on the surrounding environment,but the farther the cooling distance is,the smaller the average cooling effect is;within the range of 60m from the boundary of urban green space,the cooling effect is the largest,which has nothing to do with the urban green space;while within the range of 120m,the cooling effect of the urban green space on the surrounding environment is related to the size of the area;when exceeding the range of 120m,there is no significant difference in the cooling effect of urban green space with different area.4.Finally,three suggestions for future urban green space planning in the central urban area of Fuzhou based on the mitigation of heat island effect are proposed:(1)Improve the green coverage rate around the constructed land and save the“heat island”through“cold island”.(2)Strengthen the centralized contiguous urban green space and improve the layout of urban green space.(3)Create a complex urban green space with high ecological benefits and high quality.