Studies On Ecological Effect And Selection Of Roof Greening Plants In Chengdu City

Developing and utilizing large urban roof greening space benefits for expanding urban greening area, increasing greening capacity , meditating the effect of urban heat island and drought island and decreasing usage of energy by buildings, which becomes important works on urban greenin. Present research on urban roof greening concentrates on heat-proof property, technological standard, water-proof treatment, plants usage and planting base, etc. In addition, more reserch on urban greening land focuses on ecological effects of lowering temperature, increasing humidity . However , research on plants selection and its ecological effect on roof greening in different climate zone is less, which doesn't benefit for urban development . It limits greening policy of government Investigation on existing roof greening plants in Chengdu city was conducted in order to guide right selection of roof greening plants. Comparative investigation on temperature and humidity was done in three landscaping roofs including lawn , non-landscaped land and green space with combination of arbors, shrubs and grass. Meanwhile, photosynthesis and transpiration of 25 roof greening plants are tested. The effect of killing bacteria of 9 kinds of arbor was measured by natural sediment method. To promote development of urban roof greening and improve urban ecological environment, reseach conclusion provides basic supports.The investigation results revealed that 170 species of 122 genuses, 71 families have been used in roof gardens of Chengdu. The Arbors took 21.8%, the bushes took 34.6%, the bamboo took 3.5%, the lianas took 9.3% and the herbs took 28.8%. The plants environmental adaptabilities and growth potential were appraisedwith 5-point appraisal system. Accordingly, 89 species were screened out by their good performances on the basis of existing roof garden.The results showed that changing of temperature per day in roof greening in comparison greening land and non-greening land takes on single peak distribution. Minimum temperature is at 8 o'clock in the morning .Maximum temperature is at half past three in the afternoon. Changing of humidity per day in roof greening to greening land and non-landscaped land takes on U-shaped distribution. Maximum humidity is at 8 o'clock in the morning. Minimum humidity is half past four in the afternoon . In the measuring of temperature and humidity in non-greening land, the lawn and the combination pattern of arbor , shurbs and grass , greening land has the effect of lowering temperture and increasing humidity . The effect of lowering temperture and increasing humidity on the combination pattern of arbor , shurbs and grass is the best Reserch on adjusting CO₂ concentration of 25 roof greening plants shows that the optimal effect of CO₂ concentration is Erythrina corallodendron,Hibiscus mutabiliS and Sophora japonica, var. pendula in ardor, Cassia corymbosa and Chaenomeles lagenaria in shurb. CO₂ concentration per leaf area per year surpasses 3000g ,oxygen disperses above 2000g. In the transpiration test ,the biggest evaporation is Erythrina corallodendron and Hibiscus mutabilis in arbor, Chaenomeles lagenaria in shrub, Evaporation per leaf area per year is beyond 1000kg. Study on bactericidal of 9 arbors on roof greening shows that the optimal bactericidal is Ervthrina corallodendron,Hibiscus mutabilis,Cinnamomum japonicum,Elaeocarpus sylvestris, beyond 40%.The conclusion are as followings . Suitable roof palnts used for Chengdu roof greening is suggesteed to select Erythrina corallodendron,Hibiscus mutabilis and Sophora japonica, var. pendula in arbor , Prunus cerasifera cv. atropurpurea, Cassia corymbosa and Chaenomeles lagenaria in shurb.