Research On Temperature Regulation Function Of Ecosystem In Beijing-Tianjin-Hebei Urban Agglomeration

With the continuous progress of urbanization,the urban underlying surface was constantly replaced by impervious surfaces areas,and the urban thermal environment problem is becoming more and more serious.The urban expansion of large and medium-sized urban agglomerations is more rapid especially.The blue-green spaces of urban agglomeration ecosystem can provide temperature regulation function and reduce the urban heat island effect.Taking the Beijing-Tianjin-Hebei urban agglomeration as the research object,this paper used Land Surface Temperature(LST)to represent the characteristics of urban thermal environment.Based on MODIS product data,Landsat remote sensing data and Land use data,the urban thermal environment at different urban scales and the cooling benefit of ecological patches was studied,and the temperature regulation function of urban ecosystem was simulated.The main conclusions are as follows:(1)The thermal environment of the Beijing-Tianjin-Hebei urban agglomeration is becoming increasingly serious.The high temperature areas are mainly distributed in the city center of Shijiazhuang,Cangzhou,Beijing,Tianjin,Baoding and Zhangjiakou,while the low temperature areas are mainly located in the southwest of Chengde,Zhangjiakou and the northwest of Beijing.During 2010-2020,the high temperature area showed an increasing trend,and the average LST of the district and county units had a strong negative correlation with NDVI.For every 0.1 increase in NDVI,the temperature of the district decreased by about 2-3?.(2)The temperature zoning in Beijing urban area and Xiongan New Area overlaps with the urban underlying surface.The farmland was dominated by the middle temperature zone,the forest land was dominated by the low temperature zone,and the water body was dominated by the low temperature zone,which plays the main role of cooling.The building land was mainly composed of the high temperature zone,which was the main source of heat island effect.In Beijing urban area,the cooling distance of lake is the largest,which is 500 m,and the cooling range is 4.57?.In the green land,the cooling distance of forest is the largest,which is 300 meters,and the cooling range is 3.5?.In Xiongan New Area,the cooling distance of lakes is the largest,which is350 m,and the cooling range is 1.29?.In the green land the cooling distance of woodlands and gardens is the largest,which is 300 meters,and the cooling range is0.79? and 0.62?.There was a certain correlation between different ecological patch temperatures and landscape pattern indexes,among which area(AERA),perimeter(Perim),perimeter area ratio(PARA)and proximity(CONTAG)index were strongly correlated.According to the fitting equation,the overall relationship was as follows:The larger the area,the longer the perimeter,the higher the proximity and the closer the distance of the patch,the lower the internal temperature of the patch.Different patch types have different thresholds,which the temperature tends to be flat after the threshold.In the process of urban blue-green space planning,the cooling threshold of each ecological patch can be referred to for construction.(3)The urban ecosystem in Beijing urban area and Xiongan New Area plays an important role in alleviating the urban thermal environment.The temperature regulation quantity of Beijing urban area is between 1.6?and 1.21?.The areas with outstanding temperature regulation ability are mainly distributed in urban parks,among them water bodies play the biggest role.The second is the woodland and grassland distributed between the north fourth ring road and the north fifth Ring road.The temperature regulation ability of river channels is medium,while the greenland and grassland near road facilities are the weakest.The temperature regulation quantity of Xiongan New Area is between 0.4? and 5.62?.Providing maximum temperature regulation function areas mainly distributed in the Baiyang Lake,which the lakes paly the most important role and the second is the part of woodland and grassland in urban areas.The temperature regulation ability of the river channels is relatively low,and the weakest is a few grasslands and woodlands distributed in the northern urban area of Xiongan New Area.