| Plant species diversity and spatial distribution have always been the focus of scientific researchers.Especially in areas with rapid urbanization,human disturbance is strong,and plant species diversity in the region will be greatly affected.Seed plants in the ecological "green-core" area of Changzhutan urban cluster were selected as the research object to study their species composition and distribution,and to analyze the influence of human disturbance on their composition and distribution.According to the habitat and land use types,the succession status of arbores in the top community of subtropical evergreen broad-leaved forest in the sample square was scored from the perspective of forest origin and succession.A mathematical model was constructed.With the help of ArcGIS 10.2 software,kilometer grid method,color classification method,symbol classification method and natural discontinuous point classification method were used to quantify fine forest vegetation and human disturbance,and statistical analysis and results were presented.The main results obtained were as follows:(1)Wild seed plant resources are abundant.There are 154 families,559 genera and 936 species of seed plants in Changzhutan Lvxin area.Except exotic and cultivated species,there are 132 families,416 genera and 678 species of indigenous plants in Changzhutan Lvxin area,accounting for 38.37%,13.07%and 2.36%of the families,genera and species of seed plants in China,and 62.56%,28.75%and 13.75%of the families,genera and species of seed plants in Hunan province,respectively.Among them,there are 2 species of wild gymnosperms belonging to 2 genera and 2 families,and 676 species of wild angiosperms belonging to 414 genera and 130 families.(2)Abundant wild plants under state key protection.It's known that there are 10 species of national key protected wild plants,including the national first-grade protected wild plants,Ranalisma rostrata,and other 9 species of the national second-grade protected wild plants,Cibotium barometz,Cinnamomum camphora,Trapa incisa,Myriophyllum ussuriense,Ormosia henryi,Glycine soja,Camptotheca acuminata,Fagopyrum dibotrys,Zoysia sinica(not including Nelumbo nucifera)in the ecological "green-core" area of Changzhutan urban cluster.(3)There is a great variety of exotic plants in the field.Sixty-one species,49 genera and 25 families of exotic-plants were counted,which accounted for 16.23%,8.94%and 6.62%of the total families,genera and species of seed plants in the ecological "green-core" area of Changzhutan urban cluster,respectively.(4)Significant discoveries have been made in the area under investigation.In the course of this investigation and research,the discovery of a species of the national first-grade protected wild plants,Ranalisma rostrata,in the ecological "green-core"area of Changzhutan urban cluster,is an important discovery.This species is extremely rare.(5)The flora composition is complex.There are 14 of the 15 geographical distribution types of seed plants in China(except for the Central Asian distribution)in the ecological "green-core" area of Changzhutan urban cluster,which fully demonstrates the complexity of the floristic composition in this area.Among the distribution types,the Pantropical,North Temperate and East Asian distribution types are the most abundant,with 93 genera,66 genera and 47 genera,respectively.(6)There are many tropical components and rich temperate components.The distribution of wild seed plants in the ecological "green-core" area of Changzhutan urban cluster area is mainly tropical,and the distribution of Pantropical is the absolute dominance.There are 56 tropical families in total,accounting for 42.42%of the total families.There are 24 families of temperate elements,accounting for 18.18%of the total number of families.According to the analysis of geographical components,the tropical floristic composition of wild seed plants in the ecological "green-core" area of Changzhutan urban cluster is similar to that of the temperate floristic composition,and the distribution of wild seed plants in the ecological "green-core" area of Changzhutan urban cluster is mainly Pantropical,North Temperate and East Asian.There were 179 genera of all tropical constituents and 180 genera of all temperate constituents,accounting for 49.18%and 49.45%of the total genera,respectively.(7)Using Arcgis 10.2 software,the use of km grid method,the natural discontinuities classification method,the species richness of data and vector data overlay km grid,using color classification method for intuitive map rendering,found that the distribution of species richness is uneven distribution of overall,present gathered in a small scale distribution,city at the junction between higher species richness.And it was divided into 8 hot spots of wild seed plants.(8)The author innovatively graded the succession status of tree species in the top community of the zonal vegetation,subtropical evergreen broad-leaved forest,constructed a mathematical model,and used the ArcGIS 10.2 software to draw the distribution map of human disturbance level by using the symbol classification method and the natural break point classification method.According to the origin and succession of forest,the degree of human disturbance was statistically analyzed,and the areas of severe human disturbance,moderate human disturbance and mild human disturbance were delimit based on habitat type and land use type in the ecological"green-core" area of Changzhutan urban cluster.The results showed that "severe disturbance" was mainly in urban construction land,basic farmland,general farmland,nursery land,river system,etc."Moderate disturbance" was found in 8 distribution sites such as Pingtang area."Mild disturbance" areas include Shiyan Lake Forest Park in Vaulting Horse Area,Gaoyun Country Park between Tongsheng Area and Vaulting Horse Area,and Zhaoshan Area.At the same time,the differences of species composition and distribution of seed plants under the three human disturbance modes were analyzed.(9)Human disturbance has seriously affected the composition and distribution of wild seed plants in the ecological "green-core" area of Changzhutan urban cluster.Human disturbance is common in the Changsha-Zhuzhou-Xiangtan ecological green center area,with various disturbance types and different disturbance intensities,resulting in uneven composition and distribution of seed plants in the area. |
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