Study On Spatial Distribution Pattern Of Vascular Plants And Wild Ornamental Plant Resources In Danjiangkou City

Danjiangkou City,located in the east of Shiyan City,Hubei Province,is an important part of the ecological function area of Qinling-Dabashan Mountain,and also a strategic resource bearing place for building a national ecological security barrier.Previously,the investigation of plant resources in Danjiangkou City was mostly concentrated in important mountains and local areas around the reservoir area,but the overall situation of plant resources in Danjiangkou City was still unclear.In this study,Danjiangkou City was divided into 36 grids of 10 km×10 km,and a total of 77 survey sample lines of not less than 3 km were laid,and the plant resources in Danjiangkou City were investigated in spring and autumn.Based on the field investigation data and literature,the vascular plant data set of Danjiangkou City,the regional control data set and the wild ornamental plant data set of Danjiangkou City were assembled.Based on the data set of vascular plants,the species composition characteristics,spatial distribution pattern,distribution and floristic characteristics of rare and endangered protected plants in Danjiangkou City were analyzed.Based on the regional control data set,the flora similarity between Danjiangkou City and its surrounding seven regions was compared,and the origin and biogeographic function of Danjiangkou City flora were explored.Based on the data set of wild ornamental plants,we provide a new view on the development and utilization of native plants in Danjiangkou City.The main results are as follows:(1)There are 1434 species and subspecies of vascular plants belonging to 629 genera and 156 families in Danjiangkou City.Among them,there are 18 families,38 genera and 79species and sub-species units of Lycopodium,3 families,10 genera and 18 species and sub-species units of gymnosperms,and 1337 species and sub-species units of angiosperms in 135 families and 581 genera.The order of magnitude analysis of vascular plants shows that monotypic families,oligodendrofamilies and various families are the main components of the family level.The order of magnitude analysis of genera shows that few species and single species constitute the main components of genus level.(2)In the horizontal dimension,the richness of vascular plants and phylogenetic diversity(PD)of in Danjiangkou City showed a distribution pattern that the main mountain areas in the Southwest were high and the reservoir areas in the middle were low.The species richness(SR)and PD value of Wudang Mountain and Wuduofeng area in southern Danjiangkou City are the highest.In the vertical dimension,with the elevation increasing,the families,genera and species of vascular plants gradually decrease,and the number of each group is the largest in the altitude range of 0～300 m.There are 24 families,29 genera and 31 species of rare and endangered plants in Danjiangkou City,with the most concentrated grid distribution of C1,C5,C17,C23,C24,C25,C26,C27 and C31.In addition,there are 13 species of national key protected plants belonging to 8 families,11genera in Danjiangkou city,among which C24,C23,C31 and C5 have the most species.At vertical altitude,the species of rare and endangered plants and national key protected plants reached the maximum at 900～1200 m.(3)The results of family-level distribution types of vascular plants show that 156families in this area can be divided into 12 distribution types,of which tropical distribution types are the most(67 families).The results of genus-level distribution types show that 629genera can be divided into 14 distribution types,of which temperate distribution genera are the most(327 genera).(4)The flora similarity comparison and seed plant similarity cluster analysis between Danjiangkou City and seven surrounding areas by using S_Ccoefficient show that the flora of vascular plants is closer to that of Jianghan Plain in East China.In contrast,it is far from Daba Mountain and Shennongjia forestry district,which belong to Central China.The conclusion of similarity analysis by using S_Ccoefficient is inconsistent with Wu Zhengyi’s theory of plant division.It is speculated that the reason may be that S_Ccoefficient is not suitable for two(or more)flora with large difference in species data.The calculation with S_Scoefficient is effective,and the result is consistent with the classical theory of flora division.The results of floristic similarity analysis based on S_Scoefficient show that Danjiangkou City is closely related to the flora of Central China and East China,and has a certain distance from Xi’an City in North China.(5)In this study,363 species of wild ornamental plant resources with high ornamental value and certain application prospects were screened out,including flowering plants,foliage plants,fruit plants,stem plants,posture plants and aromatic plants according to their ornamental characteristics.According to garden purposes,it includes ornamental trees,garden greening plants,street trees,hedgerows,flowers and trees,ground cover plants,vertical greening plants,flower beds,landscape plants,wet plants and rock plants.The results show that Danjiangkou City is rich in wild vascular plant resources,with complex flora elements,where tropical and temperate elements meet,and the flora transition is prominent.Wudang Mountain and Wuduofeng area in the south of Danjiangkou City are the distribution centers of ancient components and species diversity.In addition,the wild ornamental plant resources in Danjiangkou City have outstanding characteristics,a wide variety,a wide range of garden uses,and a broad prospect of utilization.