| With the acceleration of urbanization,the ecological environment problems are becoming increasingly prominent,such as urban heat island,haze,noise pollution,etc.As an important part of urban open space,urban green space is the only element with ecological function in the city.Compared with other elements in the city,urban green space plays a significant role in purifying air,blocking noise,cooling and humidifying,beautifying the environment and so on.Plant community is one of the basic units of urban green space,and it is also the basic unit to bring the ecological benefits of urban green space into play.The plants within the plant community play an important role in relieving urban heat island effect,improving air quality,cooling and humidifying through their own photosynthesis and transpiration.Green volume is an important index reflecting and measuring the quantity and quality of urban green environment,which can reflect the city's green level and ecological benefits more accurately.Therefore,based on the plant community in the urban green space and taking the four types of plant community as the research object,the thesis analyzed the correlation between green volume and plant community characteristic values through field investigation and measurement,in order to find out the factors of influencing plant community characteristic values and effects of different plant communities on micro climate.Finally,based on the analysis results,the plant community configuration of urban green space was optimized.The results were as follows.(1)In the survey,the green volume of 36 plant communities ranged from 10m~3 to 2701.04m~3,and the green volume order of four plant community types was as follows:arbor-bush-grass>arbor-grass>bush-grass>grassland.Among eight plant community characteristics,there was an extremely prominent negative correlation between sky view factor(Sky View Factor,SVF)and green volume(P<0.01),and there was a prominent negative correlation between arbor-bush density and green volume(P<0.05),and there was a prominent positive correlation between mean arbor height,mean arbor DBH,arbor crown area and green volume(P<0.01).Nevertheless,there was no prominent correlation between arbor-bush Shannon-Wiener index,arbor-bush Pielou evenness index and green volume.As for the fitting results between green volume and plant community characteristics,it could be seen that green volume was getting lower with the increasing of SVF,when the SVF of plant community was between 0 and 0.8,green volume was getting higher as mean arbor height increased from 3m to 11m.Also,green volume was getting higher with the increasing of mean arbor DBH and crown area,when mean arbor DBH was between 0.09m and 0.21m and crown area was between 200m~2 and 700m~2,respectively.(2)The changes of temperature and solar radiation at different plant communities and their corresponding control points increased firstly and then decreased,while the changes of humidity at different plant communities and their corresponding control points decreased firstly and then increased.The maximum temperature of the plant community appeared during14:00-15:00,the minimum temperature appeared at 9:00,the maximum humidity appeared at 9:00,the minimum humidity appeared during14:00-15:00,the maximum solar radiation value appeared at 12:00 and the minimum solar radiation value appeared at 16:00.(3)The order of mean temperature variation of different plant community types was:Grassland>bush-grass>arbor-grass>arbor-bush-grass.The order of average humidity variation of different plant community types was:Grassland>bush-grass>arbor-grass>arbor-bush-grass.The order of mean solar radiation variation of different plant community types was:Grassland>bush-grass>arbor-bush-grass>arbor-grass.The order of mean wind speed variation of different plant community types was:Grassland>bush-grass>arbor-grass>arbor-bush-grass.By analyzing the microclimate effects of different plant communities relative to their control quadrats,it could be seen that the arbor-bush-grass community type performed best in cooling,humidifying and wind blocking,and the arbor-grass community type performed best in weakening solar radiation.(4)There was an extremely prominent correlation between mean cooling rate,mean humidification rate,mean solar weakening rate and green volume(P<0.01),and there was no correlation between mean wind blocking and green volume.It could be seen that mean cooling rate,mean humidification rate and mean solar radiation weakening rate were increasing with the increase of green volume when green volume was between 0 to 3000m~2,however,the increase rate was getting slower. |
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