Regulation Effects Of Close-to-natural And Traditional Community Parks On Temperature And Humidity And Airborne Particles In Central Beijing

With the improvement of the whole society’s ecological awareness and the challenges facing to the quality of living environment,the construction of close-to-natural green space is in the ascendant in our country,but whether its sustainability can meet the dual-driven needs of rapid urbanization and urban ecological construction,there is still a lack of systematic and deepening research.This study takes 6representative community parks（including three close-to-natural community parks（referred to as close-to-natural green spaces）built in central Beijing since 2017,and three traditional community parks of similar size in central Beijing（referred to as traditional green spaces））as the research objects.Through the field measurement of air temperature,humidity and airborne particles concentration indicators,regulation effects of different green spaces on temperature,humidity and airborne particles are compared,and the key landscape characteristics that affect regulation effects on temperature and humidity and airborne particles are analyzed and discussed.This research can provide basic data and optimization guidance for the study of the ecological benefits of close-to-natural green spaces in Beijing’s high-density urban area and the construction of close-to-natural green spaces.The main conclusions of the research are as follows:1.Regulation effects and influencing factors of plant communities in the close-to-natural green space and traditional green space on temperature and humidityIn terms of cooling effect,among the three types of communities tested in the close-to-natural green space and traditional green space,including the coniferous-broad-leaved arbor-shrub-grass community,the broad-leaved arbor-shrub-grass community and the coniferous-broad-leaved arbor-grass community,the coniferous-broad-leaved arbor-grass community in the close-to-natural green space had the weakest cooling effects,whose cooling intensity was nearly 1.50℃,lower than that of the coniferous-broad-leaved arbor-shrub-grass community in the close-to-natural green space,and nearly 1.00℃lower than that of the coniferous-broad-leaved arbor-grass community in the traditional green space.As to humidification effect,the humidification effect of communities tested in the close-to-natural green space and traditional green space was basically the same.The average shrub height,average shrub crown width,average height of tree branches and canopy closure have significant effects on the cooling and humidification effects of plant communities tested in the close-to-natural green space.Among them,the cooling and humidification effects of plant communities are positively correlated with the average shrub crown width and canopy closure,but negatively correlated with the average shrub height and average height of tree branches.Cluster trees with low branches and low shrubs with large size can increase the"green quantity"in a limited space,and they can play an important role in upgrading cooling and humidification effects in the initial stage of the close-to-natural green space.2.Regulation effects and influencing factors of plant communities in the close-to-natural green space and traditional green space on airborne particles（1）In terms of PM₁₀ reduction effect,among the three types of communities tested in the close-to-natural green space and traditional green space,the PM₁₀ reduction effect of the coniferous-broad-leaved arbor-grass community and the coniferous-broad-leaved arbor-shrub-grass community in the close-to-natural green space were weaker,while the PM₁₀ reduction effect of the coniferous-broad-leaved arbor-grass community in the traditional green space was stronger,and the PM₁₀ reduction amount of the former is only about 50%of the latter.The proportion of evergreen trees,average tree height and average tree diameter at breast height have significant effects on the PM₁₀ concentration in plant communities tested in the close-to-natural green space.Among them,the PM₁₀ concentration in plant communities in the close-to-natural green space is positively correlated with the proportion of evergreen trees and average tree height,but negatively correlated with the average tree diameter at breast height.In the later management and maintenance of the close-to-natural green space,the growth and development of broad-leaved trees should be paid more attention,and its main role in the regulation of PM₁₀ should be given full play to exert.（2）In terms of PM_2.5reduction effect,plant communities in the close-to-natural and traditional green space was basically the same.The preliminary study in this paper found that the average shrub height,average shrub crown width and canopy closure have a significant impact on the PM_2.5concentration in plant communities in the close-to-natural green space,among which the PM_2.5concentration of plant communities is negatively correlated with the average shrub height,but positively correlated with the average shrub height and canopy closure.It can be conducive to enhancing the regulation effect of communities on PM_2.5by improving the canopy structure of the arbor layer and appropriately removing the denser shrubs of communities in the close-to-natural green space.3.Regulation effects of close-to-natural and traditional green spaces on temperature and humidity and airborne particlesIn terms of multi-season comprehensive regulation effects on temperature and humidity and airborne particles,the close-to-natural green space Changlefang urban forest and Xinzhongjie urban forest are more prominent.While in terms of regulation effects on temperature and humidity,the traditional green space Xuanwu park performed more prominently throughout the year.As to the regulation effect on airborne particles,the traditional green space Guangning Park had significant advantages in autumn and winter.A small area of close-to-natural green space with reasonable layout and large forest coverage can exert strong regulation effects on temperature and humidity and airborne particles in high-density urban areas.In high-density urban areas with limited land use,making full use of the shade and isolation of dust sources of tall buildings,and making rational use of urban street valley building close-to-natural green spaces can effectively improve regulation effects of urban green spaces on temperature and humidity and airborne particles.