Assessment Of The Structure And Functions For Urban Green Space Plant Diversity In Beijing Urban Built Area

Cities, as the centers of gathering and housing for human beings, provide the crucial material base for the sustainable and stable development of the industry and agriculture and the main support for the physical life as well as the most important environmental value, such as modulating regional climate, lowing noise, degradation pollutants, beautifying environment etc., depending on its biodiversity. At the same time, they play an important role in recreation, aesthetics, social culture, science and education, spirit and history. Urban plant biodiversity forms basis units of urban green space service, and provides the foundation of urban landscape diversity. It also symbolizes the level of urban greening, and which has turned to effect the city's sustainable development and ecological city construction. In this paper urban green space plant diversity was investigated based on floristic composition and ecological structure, and a comprehensive assessment was got by applying analytic herarchy process, expect to show its actuality and characteristics, and make some reasonal suggestions to urban plant diversity conservation and gardens construction in Beijing.Total 694 samples were selected to investigate the plants of different communities, basis of differdnt types of green space in Beijing urban built area (within the fifth ring zone). The composition and origination of plant species and exotic species condition was analyzed in detailed. The species diversity of different structure communities was compared, and an evaluating system for biodversity of urban built area was established by selecting some suitable indexes through comparison. The results showed that:(1) There were 632 plants species, based of the sample investigation in Beijing built area green space, which belonged to 365 genera and 111 families in green space of Beijing built area, was accounted for 27.93% of total vascular plants in Beijing area. There were 133 arbor species, 103 shrub species, 375 herbage species, 11 herbaceous-liana species and 10 ligneous-liana species according to various life types.(2) The richness of Beijing native plants in urban built area is very high ensued from the field survey, sum to 451 species were accounted for 71.4% of total. Compared to various types of green space, the large-scale parks has the most plants species, the following was affiliated green space, while road greenbelts and isolating green space had the lowest plants species. All types of green space had a quite high proportion of native species in Beijing urban built area. But just 138 native species accounted for 44.37% of cultivated species, 12.11% of the wild species were applied broad in urban green space gardening in Beijing.There were 178 exotic species, which belonged to 58 families and 128 genera. There were 20 invasive species, some diffused or trend to spread exotic weeds had the most threaten to urban green space, in which 8 species was origin of America flora.(3) The mostly type of the plant community of green space was the mulriple type combined of arbor, shrub and herb, the mulriple type combined of arbor and herb was following, and the single types composed of arbor, shrub and herb were least in Beijing urban built area. Compared to biodiversity indexes of various community types of green space and the result show that: Species abundance of mulriple type of green space were richer than singularities, and the sequence as follow: arbor-shrub-herb community > arbor-herb community > shrub-herb community > arbor-shrub community > tree > shrub > lawn; Species diversity had a positive correlation to the complexity of the community.The richness of shrub species was higher than arbor species richness, the ratio of hardwood and conifer was between 5 and 10. Both of dominant arbors and underwood shrubs and herbs were abundant, but most of which did not applied frequently in urban green space.(4) An index system for the biodiversity of urban green space was established, and got the assignment of weight of every part by applying analytic herarchy process. By combining AHP with fuzzy assessment method, an application of such method in Beijing city and the result was shown "better".