Research On Influence Of Spatial Characteristics Of Plant Communities On Microclimate

As an important component of urban green space,plant community has a critical influence on the formation of microclimate environment.Researching the regulating effect of the spatial characteristics of plant communities on microclimate plays an important role in improving the city microclimate and human comfort in the outdoor environment.The paper starts from field monitoring to quantitatively analyze the effect of plant communities with different spatial characteristics on microclimate and human comfort in the autumn urban green space in Beijing.Then it simulates the autumn microclimate of the measured plant community through ENVI-met software to analysis the practicality and accuracy of ENVI-met in researching the microclimate effect of plant community.The paper thereafter uses ENVI-met to change and simulate the spatial characteristics of plant communities to further explore the impact of canopy morphological characteristics and spatial layout characteristics on the microclimate effect.Based on the entire research,suggestions on the microclimate adaptation design of plant communities in Beijing are put forward.The main conclusions of this paper are as follow:(1)The plant community can significantly reduce the air temperature,increase the relative humidity and improve human comfort in autumn.During the daytime,the average cooling intensity ranges from 0.95 to 2.84 ?,the average humidifying intensity ranges from 4.52 to 8.85%,and the average comfort improvement intensity ranges from 0.32 to 1.55.The cooling and humidifying intensity and human comfort improvement intensity of different plant communities are different.These three aspects increase with the growth of LAI and three-dimensional green density.(2)ENVI-met numerical simulation method is effective and reliable in researching microclimate of small-scale plant communities.(3)The microclimate effects of plant communities vary with canopy morphology and spatial distribution.For the canopy morphological characteristics of the plant community,the influence of tree height and crown width is relatively significant,while the influence of under crown height and crown shape is weak.The community with trees that have higher height and larger crown makes a better effect on cooling and humidifying,and also the improvement intensity of human comfort.The higher the under crown height,the smaller the improvement intensity of plant community cooling and human comfort.The humidifying intensity has increased before reach the peak when the under crown height equal to two meters,then decreased at the end.For the crown shape,the cylinder shape works relatively good for microclimate regulation and the inverted cone shape,on the contract,is relatively poor.From the perspective of spatial distribution characteristics of plant communities,the higher the planting density and the richer the vertical hierarchical structure leads to the greater the intensity of community cooling and humidification and the improvement of human comfort.The horizontal layout has little effect on the microclimate of the community.Relatively speaking,natural cluster works better on lowering air temperature and random scatter works better on increasing relative humidity.According to the research results,suggestions for the microclimate adaptation plant design are proposed:(1)increasing the green quantity in the plant community properly;(2)constructing a complex plant community with high species diversity and multi-layer;(3)choosing trees with higher height,lower under crown height,larger canopy width,and fuller shape canopy.