A Study On The Species Variety Of Plant Community And The Physiological Adaptability Of Typical Plants In The Road Green Belts Of Chengdu City

This paper takes the typical roads of Chengdu city as the location,the widespread roadside greenbelts,avenue greenbelts,car greenbelts are chosen as the research object,the192 community quadrats in a total of 48 sample areas in 30 road sections,Chengdu city are investigated,the community plant composition,community structure,species diversity and so on in the sample areas are analyzed and compared.At the same time,the four tree species with the highest frequency of application are selected as the research objects after the statistics,in order to study whether their physiological indexes are affected by the road pollution in the different road habitats.On this basis,the studies on the plant communities in the existing road greenbelts in Chengdu city are supplemented,and the optimization schemes are further proposed.The research results are as follows:1.A survey of road greenbelt plants in Chengdu city(1)In the surveyed 48 sample areas,30 rode sections,Chengdu city,according to an incomplete statistics,there are the 95 species of plant resources in the road green belts of Chengdu city,there are the species distribution in all the trees,shrubs and herb layers.The total 33 species of trees,respectively belonging to the 24 families and 31 genera,account for the 33.33% of the total number of species;there were the total 25 families and34 genera with the 37 species of shrubs in total,accounting for the 37.37% of the total species;there are the total 16 families and 27 genera with the 29 species of herbaceous plants in total,(the herbaceous survey is dominated by the artificially planted species),which are mainly concentrated in the leguminous family,rosaceae family,lauraceae family,mulberry family and other world large families.(2)The 13 evergreen tree species and 20 deciduous tree species are applied in the investigated tree layers,most of the roads are configured in the collocation form of evergreen tree species and deciduous tree species;from the shrub layer,the evergreen shrub species are the 23 species,the deciduous shrub species are the 14 species,the evergreen plants account for the 51.43% of the total numbers(the wild herbaceous ground cover plants are not considered for the time being),the deciduous plants account for the 48.57% of the total numbers.The application ratio of the evergreen plants to deciduous plants is 11:8,and the application between the evergreen plants and deciduous plants is close to the same.(3)In this survey,the ginkgo in the road green areas,Chengdu city has the highest frequency of occurrence,the frequency is up to the 42.71%,the frequency of camphor tree species is 23.44%,the goldenrain tree,Cinnamomum pedunculatum and privet are the 17.19%,16.67% and 14.58% respectively,followed by ficus lacor,erythrina variegate,ficus microcarpa,biaceae,poplar,French phoenix tree,cedar,purple-leaf plum,in which,the cinnamomum pedunculatum and ficus microcarpa,purple-leaf plum are the alien species which have become the urban roads of Chengdu city;In the shrub layer,the highest frequency of occurrence is the lobular privet,pittosporum tobira,safflower loropetalum chinense,fatsia,heather,the application of the road green belt shrubs in Chengdu city has strong integrity,but the application situations in the most of sections are relatively single.There are the 33 kinds of flowering plants with the flower observation effect in this investigation of typical road green belts in Chengdu city,the foliage plant,fruit plant and so on are counted up at the same time.2.Plant community diversity in the road green belt in Chengdu cityFrom the perspective of community ecology,a comprehensive analysis of the diversity indexes for the 48 road green belts,including the richness,diversity,evenness and community similarity and so on has been carried out,the diversity differences among the trees,shrub layers and communities in the different sample areas have been clarified.The results are as follows:(1)In the different types of road sample belts,there are the high abundant plant species in the roadside green space in the tree layer.The number of species in the other two green belts ranges from 1 to 6,the plant species are single,and have the obvious differences.The Simpson diversity index,the average value of the roadside green belt is about 0.8,both the avenue greenbelt and car green belt are lower than the roadside green belt,and the floating range is large.The trend of Shannon-Wiener diversity index is similar to that of the Simpson diversity index,but the amplitude of variation is larger.All the Jsw evenness index and Jsi evenness index in the various sample areas have shown a good consistency.In all types of road sample areas,the richness of roadside greenbelt shrub layer is the highest,with an average value of 6.The average value of the Simpson diversity index ranges from 0.09 to 0.77 with a very large difference,the Shrub species are rare in the avenue greenbelt.The average values of Shannon-Wiener diversity index are1.72,0.64 and 0.18 respectively,the trend is consistent with the Simpson diversity index.(3)The mean values of the community richness indexes in the avenue greenbelt and car green belt are similar,0.42 and 0.49,respectively,the mean values of Shannon-wiener diversity index is 0.58 and 0.71 respectively.The community richness index of roadside green belt,Simpson diversity index and Shannon-Wiener diversity index are 13.72,0.77 and 1.71 respectively,and the richness and evenness in the species are high.(4)The similarity between the communities is low,which is basically in the range of the moderately dissimilarity and extremely dissimilarity.(5)The comprehensive indexes of plant diversity have been ranked for the three sample transects,a basis is provided for the selection of configuration mode in the greening plants on road.3.Physiological adaptability of typical plantsUnder the different road pollution habitats and different scale environments,with the aggravation of tail gas pollution caused by the road traffic flow,the relative water content of leaves,cytoplasmic membrane permeability,MDA content,SOD enzyme activity,POD enzyme activity,soluble protein content and other resistant physiological indexes in the four typical species have been all increased in different degrees.It shows that although all the four plants can grow normally in the road sections polluted by the traffic fumes,they are all adapted to the polluted environment by adjusting their own physiological indexes.The comprehensive evaluation results of resistance were as follows: Camphor tree>goldenrain tree> gingko> Cinnamomum pedunculatum.