| As an integral part of the city ecosystem, urban green space plays an important role in relieving the pressure of urban ecosystem and improving the environment of urban human settlements. With the development of the urbanization process and increasing urban population, contradictions and conflicts between human and the environment are growing. Human activities mainly have an impact on the urban environment in the city, resulting in declining urban plant diversity and ecological function. Researching on plant diversity of urban greenbelt, the number of plant species, important value, life forms, richness index, diversity index, evenness index and other indicators were considered. 150 selected representative samples were conducted in parks, institutions, residential areas, squares, streets within the third ring road of Xi’an City, Shaanxi province, north of China.This research which divided into different types of urban greenbelt was focused on discussing the plant species, plant community diversity and distribution of life forms. Besides, different types of green vegetation were also compared. The results of the study were as follows:(1) Within the scope of the investigation, there were 176 species of trees in total and one of the largest families was Rosaceae with up to 30 species. The dominant species in the arbor layer were Ligustrum lucidum, Ginkgo biloba, Sophora japonica, Cedrus deodara, Pinus tabuliformis, Cerasus serrulata, etc.In shrub layer, there were Ligustrum lucidum, Ligustrum sinense, Photinia serrulata, Pittosporum tobira, Punica granatum, etc.(2) Plant species distribution, richness, diversity and evenness varyed with different types of green space. Mainly because of the composition of plant communities were changing adaptively depending on the different functions and properties of green space.(3) The Simpson index, Shannon-Weinner index and evenness index of arbor layer were 0.648, 0.980 and 0.893, respectively. In contrast, the index of shrub layer were 0.456, 0.891, 0.512. About plant diversity: The Margalef index, Simpson index, Shannon-Weinner index and evenness index of arbor layer is larger than shrub.(4) The distribution of species richness in Xi’an parkland was substantially uniform and reasonable, with Margalef index ranged from 1-1.5. The trend of Simpson index and Shannon-wiener index was similar. Comparing the parkland diversity index in this survey, the area of park had an impact on plant diversity, and it was inversely proportional to the plant diversity index.(5) In Xi’an greenbelt, the ratio of the species of trees to shrubs was 0.56, and evergreen to deciduous was 0.65. Popular application in road green space is shrubs, especially evergreen shrubs(46.67%). The highest ratio of tree species was used in park green space, with evergreen trees and deciduous trees reached 9.76% and 32.93%. For the five types of greenbelt, ratio of evergreen to deciduous plants in road green space was 1.3, while the ratio of parkland was lowest(0.49).(6) Native trees accounted for 55.5% of the greening trees in Xi’an, during which square green space was the highest(61.5%), and road green space was the lowest(50%). In Xi’an, the application of native trees was insufficient, so it should be strengthened in the future.This study which divided by different types of artificial plant communities in greenbelt focused on the composition of plant species, plant diversity and application of native trees. The research can provide a reference basis for the construction of Xi’an city and may also play an important role in improving the urban plant diversity, landscape heterogeneity and urban ecological environment. |
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