Plant Species Composition Of Main Green Space And Their Relationship With Artificial Environment In The Built-up Area Of Chongqing Main Area

With the rapid urbanization in China in recent years,the pattern of land using in the rapidly expanding urban areas has changed drastically,resulting in great changes in the urban ecological environment.A large number of studies at home and abroad show that urbanization is an important cause of extinction of native species,invasion of alien species,and homogenization of plants,which leads to urban biodiversity face many severe challenges.Urban plants are the key elements of the urban environment and have important social and ecological service functions for humans and wildlife in cities.However,urban plant communities are complex social-environmental systems whose species composition,diversity,and influencing factors is affected by social factors and environmental factors have a common influence on time and space,which means that the urban environment has strong environmental filtering effect on urban plant communities.Therefore,studying the composition and distribution of urban plant species is of great significance in exploring changes of flora under the influence of human activities and the protection for urban plant diversity,which can improve urban sustainability and protect wildlife for urban managers.The study provides a scientific basis to promote the construction of eco-livable cities and achieve the sustainable development goal of harmonious coexistence between man and nature.This paper based on Stratified Random Survey investigating the four main types of green space in roads,parks,residential areas,and units in the main urban built-up area of Chongqing main area in order to analysis plant species composition and their relationship with the artificial environment,and provide scientific and reliable data references to urban green spaces construction and management optimization and urban biodiversity protection.The main conclusions reached are as follows:(1)Green space plant species compositionA total of 550 plant species including varieties belonging to 376 genera and 135 families were concerned.In family and genus composition,there are 123 species of trees belonging to 85 genera and 50 families,110 species of shrubs belonging to 77 genera and 42 families,298 species of herbs belonging to 213 genera and 74 families,and 19 species of vines belonging to 16 genera and 11 families.The five families with the most plant species are Compositae,Gramineae,Rosaceae,Leguminosae,and Cyperaceae,and the three genera with the most plant species are Ficus,Ligustrum,and Pilea.There are 49 families and 266 genera in a single species.The most abundant families and genera were recorded in park green spaces and residential green spaces,while relatively fewer inroad green spaces.In plant sources composition,native plants and alien plants accounted for 58% and 42% of the total plant species,the proportion of alien plants is large and 81% of the alien plants were introduced ornamental plant which means that the proportion of alien plants is closely related to their ornamental value;domestic alien plants accounted for 49% of total alien plants,mainly from East China Coastal and South China;foreign alien plants of account for 51% of total alien plants,mainly from Asia and the Americas.The four types of green space are mainly dominated by native plants.Except for the relatively small number of native plants in road green space,the distribution of plants from various sources is not much different.In life form composition,the plant life form is divided into evergreen trees,deciduous trees,evergreen shrubs,deciduous shrubs,perennial herbs,annual herbs,grassy vines,and woody vines,and the ratio is about 11: 7: 13: 2: 23 : 21: 2: 1.The life forms are mainly herbaceous plants,with a total of 298 species,accounting for 55.1% of the total number of plants;in trees and shrubs,the evergreen plants are dominating plants,with a total of 166 species,accounting for 71.6% of the total number of trees and shrubs.Among the plant life forms of different sources,the native plant life forms are dominated by perennial herbs and annual herbs,accounting for 33.8% and 27.7% of the total number of native plants.The domestic alien plant life forms are dominated by evergreen trees and perennial herbs account for 23.6% of the total number of domestic alien plants;the life forms of foreign plants are mainly evergreen shrubs and annual herbs,which account for 23.5% and 29.4% of the total number of foreign alien plants.The plant life forms of four types of green space are mainly herbaceous plants,and the herbaceous plants are dominated by perennial herbs.The plant life forms of the four types of green space are relatively evenly distributed except for the evergreen trees in the road green space.In flora,the flora involves 14 geographic area types and 13 geographic area variants.Native plants are mainly composed of Pantropic and North Temperate;domestic alien plants are mainly composed of Pantropic and Trop.Asia(Indo-Malesia);the foreign alien plants are mainly composed of Trop.Asia and Trop.Amer.disjuncted.In general,flora components are predominantly Pantropic.In dominant species,the top three importance value of trees is Ficus microcarpa,Ficus virens,Cinnamomum camphora;the top three importance values of shrubs are Loropetalum chinense var.rubrum,Ligustrum × vicaryi,Ligustrum sinense;the top three importance value of herbs is Zoysia pacifica,Ophiopogon japonicus,Digitaria sanguinalis.The dominant species of trees and shrubs are artificially cultivated plants,while the dominant species of herbaceous plants are mostly spontaneous plants.The top ten importance value of trees,shrubs,and herbs in the four types of green spaces are highly similar.Herbs have the absolute advantage of Zoysia pacifica and Ophiopogon japonicus.In addition,the vast majority of other plants are spontaneous plants.In species diversity index,the Simpson index,Shannon-Wiener index,Pilou evenness index,and Patrick's index of the four types of green space as follow,the green space in the residential area is 0.92,3.49,0.59,355,the green space in the park is 0.56,1.92,0.33,358,the road green space is 0.71,2.39,0.43,270,and the unit green space is 0.70,2.41,0.41,346.In general,the species diversity index has the highest green space in the residential area and the lowest green space in the park.The road green space and the unit green space are in the middle and there is not much difference between the two.In the composition of invasive species,there are 26 invasive plants in the four main green spaces,and the life form is mainly herbaceous plants,accounting for 58% of the total number of invasive plant species.Among the herbaceous plants,annual herbs are the main species,accounting for 80% of the invasive herbaceous plants.Therefore,the control of invasive species should focus on herbaceous plants.(2)Association classification and its characteristicsAccording to the characteristics of the species composition of urban plants,divided into herbs,and trees and shrubs for TWINSPAN classification separately.The classification results divided the 393 trees and shrubs plot into 47 groups,13 groups were more than 2% of total plots,which have 249 plots,accounting for 63.4% of the total plots;1181 herb plots were divided into 60 groups,14 groups were larger than 2% of the total plots,with a total of 781 plots,accounting for the total plot 66.1% of the amount.The classification results are analyzed from four aspects including sample plot(square)quantity,indicator species,distribution in various types of green space,and species diversity index,which can provide references for urban green space plant selection and management and maintenance optimization.(3)Relationship between plant species composition of green space and artificial environmentThe species structure of green space plants is mainly influenced by the artificial environment conditions created through four types of pathways: green plants design,management,human interference,and lighting conditions.For the design of green space plants,on the one hand,selectively retains and transforms natural green space during urban construction,on the other hand,artificial green space selects and configures plant species during design and construction,thereby determining the initial composition of urban green space plants.For management,that is,artificially shaping,pruning,weeding,pest control,plant replacement,etc.of plants in the built green space,mainly affects the growth of plant species to affect the composition of plant species.For human interference mainly refers to the interference that occurs when people use the green space in their daily life,such as trampling,soil consolidation,and garbage dumping.On the one hand,through human activities,consciously or unconsciously helped the spread of certain plants in green spaces.For lighting conditions,on the one hand,the introduction to tropical plants that like light and heat change the proportion of foreign plants,on the other hand,the trees used for shading to make the trees densely opaque,making it difficult for shrubs and herbs to grow.