Distribution Pattern And Influencing Factors Of Seed Plant Diversity In Hunan

Clarifying the distribution pattern of plant diversity and its influencing factors is the basis for effectively protecting the level of plant diversity and how to balance the stability of the ecosystem.It is also an important basis for formulating plant diversity protection countermeasures.Historically,China’s subtropical forest communities,after frequent human activities,most of the original vegetation in the lower elevation areas have disappeared,and most of the preserved original forests have been destroyed,so the restoration work is imminent.Therefore,this study takes 14 national nature reserves in Hunan Province as the research area,based on the collected seed plant species data,statistical analysis of plant species composition,floristic geographical composition and calculation of different dimensions of angiosperm diversity index.The Shannon-Wiener index,PD(Phylogenetic diversity)index,Jaccard dissimilarity coefficient,Bray-Curtis dissimilarity coefficient,βMNTD and PryloSor index were used to characterize the species diversity and phylogenetic diversity of plant communities in 14 protected areas of Hunan.Through the analysis of hierarchical variance separation model,the main environmental factors affecting the distribution pattern of β diversity of plant communities in this area were determined,and the general linear model was used to analyze the elevation pattern and environmental gradient pattern of species diversity and phylogenetic diversity.The main results are as follows:(1)Based on 14 nature reserves in Hunan Province,a total of 5198 species of seed plants belonging to 1322 genera and 208 families were collected,including 5122 species of angiosperm belonging to 1282 genera and 200 families,and 76 species of gymnosperm belonging to 40 genera and 8 families.The species richness and diversity of Hupingshan Nature Reserve were the highest,and the species richness and diversity of Dupangling Nature Reserve were the lowest.Large families and medium genera are dominant in the study area.According to statistics,there are 18 species of critically endangered(CR)plants,56 species of endangered(EN)plants and 118 species of vulnerable(VU)plants in 14 nature reserves in Hunan Province,a total of 192 species and 69 families.There are 7 species of gymnosperms under national first-class protection and 9 species under national second-class protection.In addition,there are 115 endemic seed plants,belonging to 73 genera and 42 families.It accounts for about 2.25%of the total seed plant species in the study area.The distribution types of internal medicine and genera in 14 nature reserves in Hunan are mainly ’pan-tropical distribution’,which is particularly prominent at the community scale.The phytogeographical elements of 14 nature reserves have significant subtropical properties.(2)The species richness and diversity of plant communities in 14 nature reserves in Hunan were high.In this study,the Shannon-Wiener index showed angiosperms>herbs>woody plants.On the altitudinal gradient,the Shannon-Wiener index showed an insignificant upward trend with the increase of altitude,and the vertical pattern was not significant,but it was obviously affected by the area factor:the larger the core area,the higher the species richness.The species β diversity in 14 protected areas in Hunan showed an upward trend with the increase of altitude difference and geographical distance,that is,in the vertical direction and horizontal direction,the species β diversity between protected areas was increasing,and the species β diversity showed obvious distance attenuation effect.In terms of spatial distance,the horizontal direction has a more significant effect on the species β diversity of plant communities than the vertical direction,and the performance of species β diversity of woody plants is more significant than that of angiosperms and herbs.(3)The phylogenetic alpha diversity index of 14 protected areas in Hunan showed a significant upward trend with the increase of species alpha diversity(Shannon-Wiener index),that is,the higher the species richness,the higher the phylogenetic diversity;along the altitudinal gradient,the vertical pattern of lineage αdiversity was not significant,and the vertical pattern of lineage β diversity was also not significant,but in the horizontal direction,lineage β diversity showed a significant distance attenuation effect.The environmental differences(temperature difference and precipitation difference)in the study area had a more obvious effect on the phylogenetic β diversity than altitude difference and geographical distance,and the phylogenetic β diversity of woody plants was more significantly affected by the environment than that of herbaceous plants.Climate difference(precipitation difference and temperature difference)and geographical distance were the main environmental factors affecting the distribution pattern of β diversity of plant communities in this area.This paper describes the composition and characteristics of plant community diversity in 14 protected areas in Hunan,and analyzes the relationship between different plant community diversity distribution patterns and environmental factors,so as to provide theoretical basis for plant diversity protection in Hunan.