Studies On Ecological Structure Of Plant Communities In Nanjing Urban Road Greenbelt And Optimize On Landscape

With the development of our society and economic, urban road greenbelt need to be satisfied with aesthetic landscape, and we also need to have satisfactory ecological benefit from the plant communities. This paper takes the plant communities on urban road greenbelt of Nanjing for study. The research include the greenbelt of road traffic system, the greenbelt of Linear Park along the truck and greenbelt beside streets, whose width of Green band are more than 5 meter wide and Green rate of road are more than 40 percent in Nanjing city. The investigation contains seven main city zone of Nanjing, 23 urban trunk roads, and 45 samples of typical plant communities.Based on the thorough investigation and analysis, 15 typical plant communities were appraisaled on vision and ecological benefit. Secondly, 10 typical plant communities were analyzed and the ichnography of plant communities'disposal was made. In the end, based on the investigation and the result of comprehensive appraisals system, some advices were put forward to plant communities, and the ways were further discussed to build plant communities with high ecological effect. The main results are as follows:(1)In the 45 sample of plant communities of the research, there are 133 spices belonging to 96 genera in 59 families, which occupy 15.7 percent in spices, 27.7 percent in genera, 54.1 percent of families, existing city ornamental garden plants in Jiangsu. There are 69 spices, 45genera, 26 families in arbor, 34 spices, 26 genera, 19 families in shrub, 21 spices, 19 genera, 13 families in grass plant, 9 spices, 6 genera, 5 families in liane. There are 46 zone indigenous plants belonging to Jiangsu, which is about 34.6 percent in all species of investigative range. That is not enough to express the species richness and indigenous characters in Nanjing.(2)The type of plant communities is various in urban road greenbelt of Nanjing. There are 5 community types in sample communities of Nanjing's road greenbelt: mixed stand of conifer and broad-leaved trees which appears regularly in all sample takes 53.3 percent in all types. And next is mixed stand of evergreen–defoliation broadleaf forest (26.7%), and defoliation-broadleaf forest (13.3%), evergreen broad-leaved forest (4.5%), deciduous conifer forest (2.2%). The types of plant communities are richness, and the type of mixed stand of plant communities is distinct.(3)In the urban road greenbelt of Nanjing, the structure of plant communities is multiple structures combined with arbor, bush and grass on the whole. And the ratio of spices of arbor to shrub is 2:1, the ratio of their number is 1:3.8.And in arbor trees, the ratio of spices of evergreen to defoliation is 1:1.3. The ratio of number of evergreen to defoliation is 1:0.65. The structure of plant communities on urban road greenbelt are richness.(4)From the ornamental plant survey, the plants which are domestic of shape and flower take obvious advantage to as much as 71.9 percent, colorful-leavf plants in all sample takes 17.7 percent. The plants which are viewed as fruits take 10.4 percent. Application of the plants that has ornamental flowers has more abundant than the colorful-leavf plants, so the Colorful plant species can be suitably increased the types and quantities in order to meet the urban road greenbelt to be more colorful, and receive the better effect of landscape.(5)In the invitation inquisitional sample, The highest frequency of emergence is 42 percent that belongs to Platatnus orientalis and Cinnamomum camphora in arbor. In shrub, the application of several species is used frequently, such as Pittosporum tobira(64%), Loropetalum chinense var. rubrum (58%), Ligustrum quihoui(49%), that had a negative impact for the creation of city road and landscape features of plant diversity.(6)The average of species abundance degree in sample communities is 4.800, the average of Margalef index is 0.997, the average of Simpson index is 0.712,the average of Shannon-Wienner index is 1.348, and the average of Berger-Parker index which reflect ecological predominance degree of preponderant species is 0.356. The diversity of diversity index is notable in sample communities for the difference of area, function and the construction time in urban road greenbelt's plant communities. But the plant communities in the sample which were built before 1990s and after1990s have no obvious difference in diversity index.(7)The result of the 15 comprehensive appraisals of the plant communities on Nanjing's road greenbelt showed the GradeⅠtakes 33 percent, GradeⅡtakes 47 percent GradeⅢtakes 20 percent. It also showed that there is much need to be improved. From the analysis of comprehensive appraisals GradeⅠof the plant communities on Nanjing's road greenbelt, in arbor trees, the ratio of spices of evergreen to defoliation is 1:1-1:2, the ratio of their number is 1:2-1:2.5. Further more, the arbor and shrubs of species abundance degree in sample communities is 7.000 and 6.400, the average of Gleason index is 1.268 and 0.968, the average of Margalef index is 1.668 and 0.720, est.(8)The ways of optimizing the plant community structure of urban road greenbelts: to increase the present plant spices, to strengthen the application of zone indigenous plants, to step up diversity of ornamental plants; to consult the plant communities'structure which is GradeⅠof comprehensive appraisals on Nanjing urban road greenbelt, we can adjust the ratio of evergreen to defoliation, arbor to shrub; to emphasize biodiversity conservation of urban road greenbelts; to design the plant communities in light of the local conditions.