Investigation Of Tree Species And Community Structure In Xi'an City Parks

In order to have a more thorough and comprehensive understanding of the current situation of tree resources and obtain comprehensive information of tree species resources in Xi'an city parks,this study made a comparative analysis of the species composition of arbor and shrub resources,the source of life forms,tree species composition and the difference of vegetation species among parks.On this basis,the vegetation community structure under the gray space,green space and blue space was studied by mapping the structure of vegetation,and the biodiversity index of each type of ecological unit was calculated.The community structure of different ecological units was analyzed synthetically through the combination of atlas and data.The main findings are as follows:(1)Xi 'an city park tree resourcesThe survey involved 14 typical urban parks in six districts of xi 'an,A total of 164 species of trees and shrubs from 51 families,99 genera were investigated.Among them,the families with more species include Rosaceae,Oleaceae,Leguminosae sp,Aceraceae,Caprifoliaceae,Cupressaceae,Ulmaceae mirb,and the genera with more species include Acer Linn.,Prunus L.,Ligustrum Linn.,Euonymus L.,Magnolia L..The number of species in a single family,genus and species is the largest,such as Ginkgoaceae,Platanaceae T.Lestib.,Punicaceae,Calycanthaecae,Taxaceae.There were 25 species in total,And it accounted for 49.02% of the total species.In terms of species resource composition of trees and shrubs in xi 'an city park,the number of species of trees is slightly higher than that of shrubs.The proportion of native tree species was slightly lower than that of exotic tree species and most native tree species are less frequently used in urban parks.However,a few species are used frequently,such as:Sabina chinensis,Cercis chinensis,Ligustrum lucidum,Photinia serrulata,Pinus bungeana,Nandina domestica,which makes the use of native tree species in urban parks tend to be simplified.The variety is not rich,the quantity is small,and the configuration is not innovative.17 species of conifers were surveyed,and the number of species was significantly lower than that of broad-leaved species.Evergreen 49 species,also significantly lower than deciduous species.Through the comparative analysis of tree and shrub resources among parks,it is found that the species compositions of trees were significantly different among xi 'an city parks,and the species configuration among each city park was greatly different.This shows that the total number of species is not high and the species composition lacks rationality in Xi'an city parks.Meanwhile,the use frequency of native tree species is low with fewer species.Many native tree species with high ornamental value,strong adaptability and good application prospects were not used in the greening construction of xi'an parks.The proportion of coniferous and deciduous species was significantly lower,which reduces the ornamental effect of vegetation landscape in urban parks.The frequent use of a few species in urban parks increases the uniformity of vegetation configuration,at the same time,due to the low frequency of use of a large number of species with only once or twice appearances in the greening of the park.Therefore,the application of tree species resources in Xi 'an city parks is obviously similar,but the species difference between parks is also large.(2)Analysis on the configuration structure of trees and shrubs in xi 'an city parksIn xi 'an city park,different spatial types of trees and shrubs had different configuration structures:In the gray space,with the increase of hard cover area,the biodiversity of the three types of ecological units gradually decreases.The vertical structure is mainly composed of double-layer or multi-layer trees and shrubs,and forming the community structure was arbor-shrub-grass.The configuration is mainly of shrub-grass or lawn in the gray space with a large area.Meanwhile,The horizontal distribution of vegetation in gray space is not uniform because of the large area of hard separation.In the green space,The biodiversity of open spaces,semi-open spaces and semi-closed spaces was higher,and was lower in the closed spaces.In the vertical structure of the green space,the community configuration structure of mixed planting of double or multi-layer arbor-shrub-grass.And both coniferous and hardwood species are available.It makes the vegetation community structure more obvious and the biodiversity more abundant by combining the configuration of colored leaf species and evergreen species.At the same time,part of the open space was planted with shurb-grass or lawn.Sometimes small trees are planted in combination to ensure the openness of the space.It can be concluded that in the gray space and green space of xi 'an city park,the community configuration is mainly composed of multiple layers of shrub grass,and the vegetation configuration of shrub grass or lawn often appears in some hard covered areas or green open Spaces.The horizontal distribution of vegetation in green space is relatively uniform,while in gray space,plants are often distributed according to the actual situationof space design,and the horizontal distribution uniformity was relatively low.Based on the above conclusions,a series of optimization strategies were proposed to improve the application of vegetation in urban parks in xi 'an:(1)Increase the proportion of native tree species and control the application of exotic species.Improve the diversity of plant configuration,enrich the vegetation structure layer,and increase the application of color leaf species.(2)Supplement and improve the background information of ecological unit mapping in Shaanxi and perfect an ecological green system in cities to build intelligent development garden.