Seasonal Changes Of Harbin Urban Forest Landscape On A Quantitative Study On The Influence Of Surface Temperature

With the rapid high-density development of cities,the urban sub-surface landscape has undergone drastic changes and the urban forest landscape space has been shrinking,leading to an imbalance in the radiant energy of the city and a significant increase in surface temperature in urban areas,which has brought serious harm to the social economy,ecological environment and the health of urban residents.The urban heat island effect is becoming increasingly serious and is a major issue for urban development in China in the 21 st century,and urban forest landscapes are pivotal in regulating environmental surface temperatures.This study takes Harbin,a typical cold city in China,as the research object,and uses Landsat 8 OLI/TIRS as the main remote sensing data source to extract the spatial distribution of urban forest landscape in the study area during the spring,summer and autumn seasons by using the "object-oriented" human-computer interaction interpretation method;Using Landsat 8 TIRS as the main thermal infrared remote sensing data source,a single-window algorithm was used to invert the surface temperature to characterize the spatial distribution pattern of the surface thermal environment in the study area during the three seasonal periods,and the accuracy of the inversion results was verified by combining with MODIS surface temperature data;the spatial analysis,landscape pattern analysis and classical statistical analysis functions of the GIS platform were used to explore the spatial distribution of the urban forest landscape on the urban thermal environment during each seasonal period.The influence and contribution of the urban forest landscape to the heterogeneity of the spatial distribution of the urban thermal environment in each seasonal period is explored by using the functions of spatial analysis,landscape pattern analysis and classical statistical analysis;two types of indices,landscape composition and landscape configuration,are selected to characterize the key elements of the urban forest landscape according to the research needs,and the best composite explanation model is established by correlation analysis and multiple regression analysis.The relationship between urban forest landscape and urban surface temperature is systematically analysed from the perspective of spatial configuration synergy,and suggestions are made for optimising the urban forest landscape based on the mitigation of urban heat load,so as to better utilise the ecological benefits of urban forest landscape and achieve the goal of green,healthy and sustainable urban development.The main research findings are as follows:(1)The overall coverage of urban forest landscape in Harbin in the study area is good,but the landscape distribution within each administrative district is uneven,showing a scattered fragmented distribution of "central dotted-peripheral concentrated",and the urban forest landscape is mainly concentrated in the Songbei,Daoli and Dawai districts along the river.The urban forest landscape in the central part of the city is less covered.The urban forest landscape in the study area is dominated by grassland and broad-leaved forest,which together form the matrix of the urban forest landscape in Harbin in this year.The area and landscape richness of the urban forest landscape is high during the summer period,but the urban forest landscape is dominated by small patches and there is a lack of connectivity between landscapes.In the spring and autumn periods,although the extent of urban forest landscape coverage decreased,the connectivity between landscape patches increased significantly compared to the summer period.(2)The urban forest landscape exhibits a warming effect during the cold season,with areas of high vegetation cover such as urban forest landscapes and croplands showing higher surface temperatures compared to built-up areas during this period,resulting in an urban ’cold island’ phenomenon.During the summer months,when temperatures are higher in the study area,the ’cold island’ phenomenon decreases and the urban heat island effect increases.At the same time,it was found that the four types of urban forest landscapes had similar trends in their contribution to the thermal environment during different seasonal periods.Among them,the contribution of grassland and broad-leaved forest landscapes is more obvious in the three seasonal periods,while the contribution of coniferous forests is weaker.(3)The correlation between the urban forest landscape composition index and surface temperature was most significant in different seasonal periods,but there were differences in the correlation between different types of woodland landscapes and surface temperature.During relatively warm seasonal periods,the shape,connectivity or diversity of the urban forest landscape had a more pronounced effect on surface temperature.When temperatures decreased,the effect of urban forest landscape configuration and diversity on surface temperature was suppressed by other factors,with the area of the urban forest landscape becoming the main explanatory factor.In addition,it was found that the number of explanatory variables included in the best composite explanatory model decreased as the surface temperature increased,suggesting that as the temperature in the study area gradually decreased,the mechanisms determining surface temperature changes became more complex and more factors were needed to explain the changes in surface temperature.The shape,connectivity and diversity indices of the urban forest landscape all entered the best composite explanatory model for each seasonal period,and these three indices explained surface temperature changes to a more stable degree,while they were also the most significantly correlated with surface temperature.(4)In view of the uneven distribution of urban forest landscapes in Harbin,micro urban forest landscapes should be added to the central urban areas where the coverage of urban forest landscapes is low,and the coverage and area of urban forest landscapes in weak areas should be increased.Moreover,the fragmented urban forest landscape patches should be trimmed to increase the complexity of their shapes,and to promote the gathering of fragmented urban forest landscape patches to form a good linkage.At the same time,in the process of building the urban forest landscape,attention should be paid to enriching the allocation of broad-leaved forest species in the urban forest to improve the surface temperature regulation of the urban forest landscape.