Study On The Spatial Variation Characteristics Of Urban Plants Along 'City-suburban' Gradient In Yangzhou

With the development of urbanization,the complete urban ecological environment has gradually been being damaged.The urban plant,as an important part of urban environment,is facing many problems such as microbial reduction,plant species change and plant diversity decrease.The environment of human being living is under threat.Therefore,it is vital to protect the urban ecological environment.This paper researches 4 types of green space on the continuous gradient zones of Yangzhou from the center(Wenchang Pavilion)to the suburbs(Yangzi Village Convenience Service Center).According to their species composition,life form,geographical area and changes in plant diversity,this paper reveals the effects of urbanization on distribution of urban plants,and provides a reference on urban plant landscape construction and plant diversity conservation in Yangzhou.The main results are as follows:(1)In the research areas,there are 251 species and 193 genera belonging to 86 families,66 species and 53 genera belonging to 30 families of arbor,67 species and 55 genera belonging to 35 families of bush(woody vines included),115 species and 94 genera belonging to 39 families of herb,3 species and 2 genera belonging to 1 families of bamboo.The most common families are Theaceae,Chenopodiaceae,Caprifoliaceae and Moraceae.The most common genera are Ligustrum,Polygonum,Acer and Sabina.The main types of distribution of plant genera are north temperate and pan-tropical,and there is a certain transition between the two types.This is consistent with Yangzhou's transition area where climate is transiting from subtropical humid monsoon climate to temperate monsoon climate.(2)Plant species in different types of city green space(from largest to smallesr)is park green space(174 species and 141 genera belonging to 68 families),residential green space(166 species and 142 genera belonging to 73 families),unit green space(107 species and 95 genera belonging to 55 families)and street green space(100 species and 88 genera belonging to 50 families).The number of plant species is declining from city center to suburbs.To life form,the ratio of evergreen trees to deciduous trees is 0.5,and ratios of park green space,unit green space,street green space,and residential green space respectively were:0.75,0.69,0.6,0.4;The ratio of evergreen shrub to deciduous shrub is 2,ratios of unit green space,street green space,park green space,and residential green space respectively were:8.5,3,2.27,2.07;The ratio of annual herb to perennial herb is 0.95,and ratios of unit green space,park green space,residential green space,and street green space respectively were:0.94,0.79,0.69,0.66.(3)From the city to the suburbs,The average of Margalef index,Shannon-Wiener index,Simpson index and Pielou index are declining both in arbor and shrub.The average of Margalef index on herbis is rising from the city to the suburbs.The average of Shannon-Wiener index,Simpson index and Pielou index on herb rise after declining.Biological diversity in different types of green space presents different changed trends from the city to the suburbs,and the park green space shows the greatest influence to urbanization.