Ecological Benefit Analysis And Corresponding Countermeasures Of Urban Residential Green Space

Intensified urban population density,promoted urban expansion,caused by the process of quasi-modernization,resulting in the boundless expansion of building area and excessively building plot ratio,consequently reduce the urban residential green area and deteriorate the residential ecological environment.Based on the current situation of urban residential environment,this paper proposes the concept of ecological environment benefit（EEB）of urban residential green space.Through the investigation and experimental sampling on the main effecting factors(CO₂,PM_2.5,PM₁₀,negative oxygen ions,surface runoff,temperature and humidity,etc.)of the residential green space ecosystem in four typical southern cities,the relationship between EEB and mentioned influencing factors was established,and then the EEB based sustainable development threshold of green space system among urban residential regions was proposed.The main works are present as follow:（1）The concept of ecological environment benefit（EEB）of urban residential green space was put forward.The main influencing factors of EEB over urban residential green space were expounded,on this basis,both the analysis and evaluation model of EEB and calculation method of each influencing factor for urban green space were established.Afterwards,the evaluation threshold of each influencing factor was obtained.（2）Through the one-year experiment and sampling of 4 typical urban residential areas in Changsha,the regulation effect of green space samples distributed in each residential area and three typical plant types on CO₂at the residential environment was tested and analyzed,and the corresponding carbon sequestration effect was quantitatively evaluated as well.The results showed that the arbor-shrub-grass type of green space exhibited noticeable stronger ability in environmental carbon balance improvement of residential area than that shrub-grass and lawn ones.Moreover,the patch area of green space and total green amount were also found great importance for the carbon sequestration to atmosphere.Based on the experimental study,the index threshold of CO₂concentration capacity of green space in each typical urban residential area and the corresponding requirements and thresholds of green space configuration in urban residential area were analyzed and calculated.（3）The regulation effect on the concentration of PM_2.5and PM₁₀in 4different typical urban residential areas was studied.The regulation ability of plant in growing season was significantly greater than that in non-growing season.The dust removal effect of tree-shrub-grass type was the most significant,followed by shrub-grass type,and the lawn was relatively weak.The larger the patch area and total green amount of green space are,the more obvious the reduction of PM_2.5and PM₁₀concentration will be.Through the experimental results,the EEB index of PM_2.5and PM₁₀concentration threshold and its corresponding requirement and threshold value for urban residential greening configuration was calculated for each typical residential green space.The calculation results indicated that the daily average EEB index of PM_2.5concentration in three residential community green space was level one as a whole,Ginkgo community was level two and the overall daily average EEB index of PM₁₀concentration was all in level one.（4）The regulation effect of different community types on the concentration of negative oxygen ions in green space of four typical urban residential areas was studied.The regulation ability of plant in growing season was found much greater than that in non-growing season.The order of impact extent on negative oxygen ions of plant community structure is shrub and grass type.More patch area and total green amount of green space leading higher concentration of negative oxygen ion.The negative oxygen ion concentration of the EEB index and its corresponding requirement for urban residential greening configuration and threshold were analyzed and calculated on the basis of former sampling results.The calculation results showed that the EEB index of Xiangjiang-1 and New-Wastin-Bund was level one,both Tingtai and Ginkgo estates were level two.（5）The relationship between the underlying surface of urban residential area and human comfort was investigated through four typical urban residential green space tests.Determination of soil moisture content of underlying surface:arbor>shrub>grass>bare soil>permeable brick flooring>Stone floor.Among the samples,the soil moisture content of arbor was about 4.1 times that of bare soil,indicating that the green space and its plant community type can adjust the temperature and humidity evidently.Lager patch area and total green amount of green space brought higher comfort level of human body.The comfortable annual ecological benefit index of Ginkgo home was level four,while the other three communities were level two.The results showed that the urban residential green space system cooling and humidifying the circumstances to a large extent,the urban residential area temperature was effectively reduced as the increase of green space quantity.Besides,the microcirculation and heat island effect were simultaneously adjusted and alleviated.77 figures,77tables and 126 references were contained in this paper.