Pattern Of Spontaneous Plants Diversity And Its Factors In 9 Cities Of Yunnan Province,China

Yunnan province is considered as the hotspot for plant biodiversity in China.The urbanization process has significantly affected its biodiversity in recent years.However,there still lacks a multi-scale,multi-dimensional,and dynamic perspective in the urban ecology study to reveal the mechanism behind the pattern of spontaneous plants in urban area.In this study,we selected 9 cities(Zhaotong,Lijiang,Baoshan,Chuxiong,Kunming,Qujing,Mengzi,Wenshan and Jinghong)distributing in various climatic and floristic zones in Yunnan province.In total of 82 sites with a radius of 500 m were set up in the built-up area,and 709 patches were selected for spontaneous plants richness survey in the study sites.On this basis,used natural environmental factors and urbanization characteristics,factors of the diversity of spontaneous plants are revealed at the three scales of city-site-patch,to provide a scientific basis for the conservation and management of urban greening and planning in Yunnan province.The main research results of this thesis are as follows:1)Species composition and characteristics of ecological species groupsA total of 1,047 spontaneous plant species from 657 genera of 158 families were recorded during the survey,of which 73.4%are native species.At the family level,the species composition was mainly the families contain species more than 5.The dominant species were single-genera species(species=1),accounting for over 51.8%.The proportion of herbaceous plants was 63.9%,which was mainly autogenous dispersal and wind dispersal species.Trees and shrubs(29.6%)were mainly dispersed through animals,and liana(6.5%)was mainly dispersed through the wind.Furthermore,according to the occurrence frequency of species on urbanization intensity divided spontaneous plants into four ecological species groups,i.e.,urban extremely widespread species(UEW),urban widespread species(UW),urban moderately distributed species(UM),and urban rare species(UR).The life form of all ecological groups is mainly dominated by herbaceous plants(>76.9%).The dispersal type of UEW,UW and UM are mainly through wind dispersal(>42.1%,respectively),while autologous dispersal is the main dispersal type of UR.In addition,invasive plants were the main nonnative plants(77.8%)in UEW and UW.Therefore,the risk of invasive plants should be fully assessed when introducing alien plants.2)Regional difference of spontaneous plantsThe results of the linear regression at city scale showed that cities with frequent disturbances(e.g.faster urbanization rate),relatively warm(higher mean annual temperature,lower altitude)and humid conditions(higher mean annual precipitation),and abundant sunlight were more conducive to the colonization of species with strong dispersal ability(such as,multi-family,medium-family,invasive species,autogenous dispersal etc.),In addition,the proportion of spontaneous woody plants in cities with longer sunshine duration was lower and the pedigree structure was more concentrated(dominated by single-genera species),while the cities with more precipitation may be unfavorable to the colonization of spontaneous plants of animal dispersal.3)Factors shaping spontaneous plant richnessThe richness of spontaneous plants is driven by natural environmental factors and urbanization characteristic factors.At the city scale,the total species richness is significantly positively correlated with MAP,regional seed bank size(PSR),and ULER._city.The richness of native species is significantly positively correlated with the MSD,while the richness of non-native species is significantly negatively correlated with Altitude,and significantly positively correlated with the coldest monthly mean temperature and maximum monthly precipitation.At the site scale,the spontaneous plants richness of each group was negatively correlated with the distance from patch to city boundary.In addition,at the site scale,there was a significant negative correlation between the richness of total spontaneous plants and the proportion of impervious of the site and urbanization rate,a significant negative correlation between native plant richness and PSR,and a significant positive correlation between non-native plant richness and MAT(mean annual temperature).At the patch scale,species richness of each group is significantly positively correlated with the patch area,patch landscape shape index,and significantly negatively correlated with perimeter-area ratio and urbanization rate.In addition,the proportion of impervious of the surface around patch is significantly negatively correlated with the total species and native species richness.While PSR and MAP significantly positively correlated with the richness of native and non-native species,respectively.The results of various scales indicated that,native plants were more affected by regional species pool,and the effects of PSR showed scale-dependent.However,non-native plants were more affected by climate factors.4)Factors shaping?-diversity in spontaneous plantsThe results show that the?-diversity of native plants is higher than those of non-native plants at both city and site levels,indicating that the species composition of native plants is more heterogeneous.At the city scale,the patch size coefficient of variance(PSV)is significantly negatively correlated with?-diversity of all species groups.Furthermore,?-diversity of total species was negatively correlated with MSD.At the site scale,the?-diversity of all species groups decreased significantly with the increase of?-diversity,and?-diversity is the most important explanatory factor explaining the?-diversity variation.The higher the impermeability of the site is,the higher the?-diversity of each species group is.The higher the urbanization rate is,the higher the?-diversity of total species and non-native species are.There are significant positive and negative correlations between the?-diversity of non-native species and the patches'Shannon diversity index and Altitude.