Response Of Microclimate To Plant Configuration In Parks Along The Yellow River In Ningxia

Urban park green space is an important component of slowing down the urban heat island effect and improving the urban thermal environment.Reasonable park plant configuration can improve the park microclimate and make urban residents have good thermal comfort.In this study,urban parks(Forest Park,Zhongshan Park,Diannonghe Park,Pearl Park,Yellow River Wetland Park and Xiangshan Park)in Yinchuan,Wuzhong and Zhongwei cities along the Yellow River in Ningxia were selected.Different plant configuration modes(non-shading hard pavement and meteorological stations as control)were selected.Microclimate indexes(air temperature,relative humidity and heat index)were synchronously measured during sunny and cloudy days in summer and winter,respectively.The effects of different plant configuration modes on different microclimate indexes in cold and arid regions were revealed.The mean values of temperature and relative humidity in each measurement period of each selected plant configuration were compared with the mean values of temperature and relative humidity in the same period provided by Ningxia Meteorological Bureau,which were the differences of temperature and relative humidity.The configuration was classified according to tree species and underlying surface.The temperature difference of each plant configuration was analyzed by descriptive statistics,correlation analysis,variance analysis and paired sample T test.The results show that:(1)In summer,almost all the plant configuration types in the park along the Yellow River in Ningxia had a significant cooling effect compared with the hard pavement(P<0.05).The main influencing factor was canopy density,and the greater the canopy density,the more significant the cooling effect.The plant configuration types with canopy density≥40%had a cooling effect throughout the day.(2)Winter canopy density had no effect on the temperature of coniferous tree plots and deciduous broad-leaved tree plots.Compared with meteorological stations,coniferous trees had significant heat preservation effect,and it was slightly stronger than that of broad-leaved tree species.Although deciduous broad-leaved tree plots had heat preservation effect on the whole,some configurations also showed cooling effect under specific weather.(3)In summer,the park green space in Ningxia along the Yellow River has a significant humidification effect compared with the hard pavement,and the overall relative humidity in the park is higher than that outside.No matter the canopy density or the underlying surface type,the humidifying effect of broadleaf species is stronger than that of coniferous species,and the humidifying effect is more obvious in the morning and noon.(4)The heat index in summer is mainly affected by canopy density.The difference between the heat index in sunny days and the temperature is negative all day,indicating that the heat felt by human body under all plant configuration types in sunny days is lower than the measured temperature.On the premise of high temperature,the greater the humidity,the higher the heat index,the worse the comfort of people.The green space with plant configuration,especially the sample plot with higher canopy density,the temperature is relatively low,the humidity increases,and the heat index does not increase significantly,so the human comfort is better.In order to improve the microclimate of the park,hard paving+broadleaf trees,grassland+coniferous trees,ground cover+broadleaf trees and hard paving+vines(corridors)are preferred in the plant configuration mode of greening.The selection of tree species in each plant configuration mode is not limited,but the local canopy density must reach more than 40%,and the effect of canopy density more than 60% is better.