The Research Of The Plant Community In Dong'an Shunhuang Mountain National Nature Reserve Of Hunan

Vegetation is the core of the structure and function of terrestrial ecosystems.It could provide a series of valuable ecosystem services for human beings.Understanding the characteristics of vegetation and their relationship with the environment is of great significance for ecosystem restoration and management.In this study,the species composition and vegetation types of the plant community in Dong'an Shunhuang Mountain National Nature Reserve of Hunan were recorded and described.The species flora characteristics and main vegetation type characteristics of the plant community were analyzed.Using the stratified random canonical sampling method,39 typical plant communities were selected in different areas and different habitats of the reserve.Used R software to perform flexible cluster,DCA ordination,and CCA ordination to study the relationship between the plant community distribution pattern and the four environmental factors of elevation,slope position,slope,and aspect.Patrick richness index,Shannon-Wiener diversity index,Simpson diversity index and Pielou evenness index were used to analyze the vertical distribution pattern of plant community species diversity.The main results obtained were as follows:1.The species composition of the plant community was rich,and the flora was diverse and complex.A total of 347 species of vascular plants,belonged to 221 genera and 92 families.Among them,there were 25 species in 14 families and 21 genera of ferns;gymnosperms in 3 families and 3 genera and 3 species;and angiosperms in 75 families and 197 genera of 319 species,occupied an absolute advantage.The dominant families of the community were obvious,mainly Lauraceae,Fagaceae,Rosaceae,Gramineae,Ericaceae,Theaceae.And there were more single species.Seed plants were divided into 10 distribution types at the family level,of which tropical distribution components(34 families)were more than temperate distribution components(22 families).At genus level was divided into 14 distribution types,with temperate distribution components(96 genera)slightly more than tropical distribution components(85 genera).The flora within the community had tropical affinities and was associated with neighboring flora.It was greatly affected by temperate plant and had the general characteristics of flora in the central and subtropical regions of China.2.The vegetation types were abundant and the secondary vegetation types were diverse,which could be divided into 2 vegetation groups,7 vegetation types and 46 alliance.It has typical Nanling forest vegetation types,such as Castanopsis fabri forest,Pinus kwangtungensis forest,Lithocarpus cleistocarpus&Fagus lucida forest.Evergreen broadleaf forest account for 1/4 of the total types of vegetation.There were many types of deciduous broadleaf forest and shrubland.Phyllostachys edulis forest had a large distribution area in the middle and low elevation areas of the reserve.The dominant vegetation types in the subtropical region with stable community structure were mostly distributed in high elevation areas or hillsides and ridges with poor site conditions at low and medium elevations.Broadleaf forest communities were mostly patchy.3.The flexible cluster divided the 39 sample plots in the reserve into 6 plant community types according to the species composition and structural characteristics of the dominant layer of the plant community,and named them according to the characteristics of the habitat.High-elevation hillside shrubland and elfin forest was distributed on uphill positions,ridges,and mountain tops above 1500 m elevation,the indicator species included Symplocos paniculata,etc.;middle-elevation valley broadleaf forest was distributed in the valley about 1000 m elevation,the indicator species included Melliodendron xylocarpum;middle-elevation hillside shrubland and elfin forest was distributed on hillsides with large slopes and poor soil about 1000 m elevation.the indicator species included Camellia pitardii,etc.;high-elevation hillside broadleaf forest was distributed on uphill positions above 1500 m elevation,the indicator species included Cyclobalanopsis multinervis,etc.;low-elevation valley broadleaf forest was distributed in the valley about 600 m elevation,the indicator species included Acer fabri,etc.;low-elevation hillside broadleaf forest was distributed on the hillside about 600 m elevation,the indicator species included Castanopsis eyrei,etc..4.The eigenvalues of the two axes before DCA ordination were 0.9221 and 0.8525,respectively.The distribution range and boundary of six plant community types in DCA ordination were basically consistent with the results of flexible cluster.The relationship between different community types was as follows:high-elevation hillside shrubland and elfin forest was closely related to high-elevation hillside broadleaf forest,low-elevation valley broadleaf forest was closely related to low-elevation hillside broadleaf forest,and habitat characteristics were similar.The middle-elevation hillside shrubland and elfin forest was separated from other community types by long distances,was not closely related,and had strong habitat specificity.The middle-elevation valley broadleaf forest was not concentrated in the ordinal map,the community type was not typical,and it was greatly affected by other environmental factors besides elevation and slope position.5.The cumulative interpretation of the first three ordination axes of CCA ordination was 84.37%,and slope position,aspect,slope,and elevation all had significant effects on plant community distribution(P<0.05).Among the ordination results of Axis 1 and Axis 2,the slope position had the greatest influence on the community distribution(R2=0.7443),and the ordination results of Axis 1 and Axis 3,the elevation had the greatest influence on the community distribution(R2=0.7331).The slope position and elevation were the most important environmental factors affecting plant community distribution.The interpretation rate of the four environmental factors to the plant community distribution was only 12.37%,and the unexplained part was far more than 50%.There may be other environmental factors that had a significant impact on the plant community distribution.6.The relationship between the four species diversity indices and the elevation gradient was inconsistent.Patrick richness index and Pielou evenness index gradually decreased with increasing elevation.Patrick richness index was extremely significantly negatively correlated with elevation(P<0.001),and Pielou evenness index was significantly negatively correlated with elevation(P<0.05).The changes in Shannon-Wiener diversity index and Simpson diversity index on the elevation gradient were similar to the Patrick richness index,shown a downward trend,but there was no significant relationship with the elevation(P>0.05),and there was no significant change along the elevation gradient.