The Floristic Geography Of Seed Plant In Xingshan County

Xingshan County is located in the western of Hubei Province,being adjacent to the Yangtse Gorges and Shennongjia.This county is rich in seed plant species with complex floristic characteristics.In this study,we divide the county into 28 working grids(10km×10km).And we investigated the seed plant species in the whole Xingshan County on the base of grid-based method;moreover,through combining the 3450 specimens collected from the field with the 17035 specimens obtained from some herbarium,we analyzed the species composition,floristic characteristics,vertical distribution pattern of the seed plants in Xingshan county and its relationship with the floristic characteristics in surrounding mountains,meanwhile,the distribution and protection of its rare and endangered plants were also studied.This work provides both important basic scientific data for the study and protection of plant diversity in Xingshan County,and a demonstration for the following county-based biodiversity survey in China.The main results are:(1)There were 1883 species of seed plants in Xingshan County,belonging to 145 families and 705 genera,which accounts for 33.33% of the total species of seed plants in Hubei Province.Among which,the gymnosperms had 16 species,belonging to 6 families and 12 genus;the angiosperms had 1867 species,belonging to 139 families and 693 genus.The seed plants in Xingshan County had 12 types of distribution patterns at the family level and 15 types at the genus level,with 21 types of variants included.The geographical components were mutual penetrative in this area,and the flora was characterized with complexity and diversity.(2)On the horizontal scale,the geographical distribution of seed plants in Xingshan County was concentrated in the western and southern regions,with the highest species grew in the grid that located near the Wanchao Mountain and Longmen River.On the vertical elevation gradient,with the increase of altitude,the number of seed plants species in this county showed an obvious unimodal pattern with an increase at first and a decrease subsequently.The seed plants were most abundant in the middle elevation area ranged from 700 m to 1300 m both on the terms of families,genus and species.Among all the families of the seed plants in Xingshan County,there were only 5 families that have species more than 50,and only 7 genera that have species more than 20,accounting for 3.45% of the total number of families and 0.99% of the total genera,respectively.The number of families that have species less than 10 accounted for 63.45% of the total families,and the number of genera that have species less than 5 accounted for 90.21% of the total genera in the county.The seed plants in Xingshan County were characterized by both the diversity and the vulnerability.(3)There were 63 families of tropical elements,and 40 familiesof temperate elements,accounting for 43.45% and 27.59% of the total number of families in the Xingshan County,respectively;which suggested the tropical elements are dominant at the families level.There were 242 genus and 379 genus of tropical elements,accounting for 34.33% and 53.76% of the total number of genus,respectively.Moreover,the genera proportion of temperate elements in each elevation range was always higher than that of tropical elements,and the genera proportion difference between them increased with the increasing elevation.Therefore,the floristic characteristics of seed plants in Xingshan County were dominated by temperate element at the genus level,but show a district transitional nature.The moisture and heat were the main limiting factors affecting the vertical distribution of geographical components of seed plants in Xingshan County.Being compared to the flora of seed plants in the surrounding mountains,the flora of seed plants in Xingshan County is similar to that of Wuduofeng,Zhangheyuan and Qizimei Mountains.All of them belonged to the floristic region of central China.(4)There were 32 species of rare and endangered plants in Xingshan County,which are distributed dispersedly in 26 grids of the whole county.Specifically,the rare and endangered species were most abundant in the grid of W15 and W16,which were located near the Wanchao Mountain and Longmen River.The rare and endangered plants in Xingshan County were highly threatened withthe outstanding problems included the lack of effective protection,the destruction from resource development activities,the uncontrolled collection and utilization of rare and endangered plants and the irrational land use.