| Guizhou Chishui Alsophila spinulata National Nature Reserve is a nature reserve with A.spinulosa and its habitats as the main targets of protection.It has one of the world’s largest number and widest area of A.spinulosa.The ancient relict plants A.spinulosa in the reserve,the diversity of wild animals and plants,the typical vegetation of evergreen broad-leaved forests in the mid-subtropical area,and the unique Danxia geological landscape have extremely high protection value and important scientific value.In this study,Chishui A.spinulata National Nature Reserve was used as the research area.According to the vegetation type,50 fixed plots,15 random plots and 8 typical plots representing different vegetation types were set in the reserve.Based on field surveys conducted in the reserve,the community characteristics were analyzed from the aspects of species composition,floristic characteristics,plant diversity,and community structure,using methods such as floristics and quantitative ecology.The R software was used to perform cluster analysis and CCA sorting analysis.To provide scientific basis for the effective protection of rare and endangered plants and forest ecosystems of typical mid-subtropical evergreen broad-leaved forests,At the same time,it provides the basic data for the protection and management of plant diversity in the area,and lays a foundation for the dynamic monitoring of plant communities.The results of the study are as follows:(1)In this study,a total of 251 species of vascular plants belonging to 91 families and 180 genera in Chishui A.spinulosa Nature Reserve were obtained.Among them,25 species of 21 species and 21 genera of 16 families of ferns,accounting for 9.96% of the total species,and 226 species of 159 genera of 75 families of seed plants.There are 2 kinds of gymnosperms.There are 65 families,139 genera and 201 species of dicotyledonous plants in the angiosperm,and 8 families,18 genera and 21 species of monocotyledons.The species with the largest community importance value was Musa,followed by Phyllostachys pubescens,and Phyllostachys edulis ranked the third;Fauna analysis found that the families of community seed plants were divided into 10 distribution types and 4 variants,and the world distribution was 9 families.Tropical distribution 44 families,21 families in temperate zones,1 family in China;14 genera and 11 species,including 9 genera in the world,91 genera in the tropics,56 genera in the temperate zone,and 3 in China.The genus and community are dominated by the tropics and contain a certain proportion of temperate components.In the tropics,the pantropical areas are the most,and the temperate areas are the north temperate areas.This is in line with the geographical characteristics of the subtropical zone.(2)The analysis of plant diversity found that the plant diversity in Chishui A.spinulosa Nature Reserve is high,the communities types are diverse.and species richness in each layer of the community varies greatly,Species richness,diversity index and the evenness indices were expressed as: herb layer> shrub layer> tree layer;The average number of species in each quadrats was 16.79,the average number of plants was 92.26,and the average richness was 20.24%;The calculations found that the Simpson index ranged from 0.15 to 0.94 with an average of 0.78;the Shannon-Weiner index ranged from 0.36 to 4.48 with an average of 2.97;and the Pielou index ranged from 0.33 to 1.38 with an average of 1.07.Significant differences in the diversity of plant species in different survey areas.(3)Analyze the life styles of the 251 plants investigated.The results showed that the highest number of phanerophytes was 64.94%.The therothyes were the least,accounting for only 3.59%.The phanerophytes are dominated by microphanerophytes,which account for 22.33% of the phanerophytes,and the life style spectrum of the reserve has obvious characteristics,which represent the plant life style characteristics of the forest communities in this climate zone.The vertical structure analysis of the community showed that the height of the tree layer was 3~6m,and the dominant species were Musa basjoo and Phyllostachys pubescens.The shrub layer was the most with height greater than 2m,the dominant position was A.spinulosa,and there were more herbaceous layer ferns without obvious dominant species.The maximum plant height is less than 0.4m,and the vertical structure of the community is divided into four levels: tree layer(>6m),sub-tree layer(3-6m),shrub layer(1-3m)and herb layer(<1m);It was shown that the arbor layer was dominated by small trees,and the DBH was mostly 2-6cm.The shrub layer had the largest number of plants with breast diameter less than 2cm,and the number of plants decreased linearly with increasing DBH.(4)Community CCA analysis found that slope,rock bareness,and herb cover were negatively correlated with soil thickness and canopy density in the environmental factors,Altitude was the dominant factor affecting the community distribution,and slopes gradually decreased with elevation.The species composition of the quadrats is interrupted by multiple environmental factors,resulting in a number of clusters adapted to their habitats.With the increasing of altitude,the main species composition from Musa basjoo,Phyllostachys pubescens,A.spinulosa,Mallotus philippensis,Lasianthus chinensis,Brassaiopsis glomerulata,a gradual transition to Casearia balansae,Symplocos sumuntia,Aidia cochinchinensis,Vernicia fordii,Mallotus barbatus,Choerospondias axillaris var.pubinervis etc,eventually becoming Cunninghamia lanceolate,Phoebe zhennan,Bothrocaryum controversum,Betula luminifera,Quercus fabri,Gordonia acuminate etc.It is consistent with the deep terrain features of the study area and the subtropical monsoon climate,in which the A.spinulosa is located on the negative half of the first ordinal axis,with elevation and soil inclusion.There was a significant negative correlation between alfalfa and altitude and soil water content,and a positive correlation with soil thickness.(5)Cluster analysis was conducted on 73 survey quadrats.It was found that using Ward’s minimum variance to cluster into 14 categories was the most reasonable,The communities of 14 clusters belonged to 10 formation,which were Form.P.pubescens,Form.M.basjoo,Form.A.spinulosa-M.basjoo-B.glomerulata,Form.Pinus massoniana,Form.P.zhennan,Form.C.lanceolata,Form.B.luminifera,Form.Liquidambar formosana-Gordonia acuminata,Form.P.zhennan-B.controversum-C.axillaris var.pubinervis,and Form.B.controversum,Among them,the group belonging to the subtropical evergreen broad-leaved shrub-grass group is the largest.Form.P.pubescens,Form.M.basjoo,Form.A.spinulosa-M.basjoo-B.glomerulata and Form.Pinus massoniana in lower elevation areas.Form.C.lanceolata,and Form.B.luminifera,Form.Liquidambar formosana-Gordonia acuminata,Form.P.zhennan-B.controversum-C.axillaris var.pubinervis,and Form.B.controversum are in higher elevation areas.(6)A comparison of the communities revealed that the diversity of species richness in 14 communities was small,and the diversity and evenness of plants increased with increasing elevation.Among them,the diversity and evenness of the Form.P.pubescens,Form.M.basjoo,Form.A.spinulosa-M.basjoo-B.glomerulata are relatively small.Form.L.formosana-G.acuminata,Form.P.zhennan-B.controversum-C.axillaris var.pubinervis,and Form.B.controversum were more diverse and evenly distributed.The comparison of vertical structures revealed that the height distribution of Form.P.pubescens is even and the height is more than 8m.The height of the M.basjoo community is mostly about 6m.The Form.Pinus massoniana and the Form.C.lanceolata are dominated by plants whose height is greater than 6m.The distribution of the heights of the Form.L.formosana-G.acuminata and the Form.B.controversum is the most reasonable;the plant height of the Form.B.luminifera is concentrated at 5-7m,and the vertical height of the community is low.Comparing the DBH structure,it is found that the DBH structure of the community is related to its height structure,and species composition plays a decisive role in the DBH structure of the community.The DBH structure of the Form.Pinus massoniana and Form.C.lanceolata is similar in all communities.The ratio of DBH distribution is the most uneven in the Form.A.spinulosa-M.basjoo-B.glomerulata.The percentage of plants with large DBH in the Form.B.luminifera is extremely low,and the proportion of plants with a DBH above 9 cm is only 11.24%,The Form.P.zhennan-B.controversum-C.axillaris var.pubinervis DBH distribution is the most reasonable.The species in Chishuiyu A.spinulata Nature Reserve is rich in species diversity and high in plant diversity.It is affected by geographical and environmental factors and forms a variety of community types.There are significant differences in plant diversity and structural characteristics among communities,and elevation is the main factor affecting community distribution.The Musa basjoo and P.pubescens communities are located on both sides of the valley,the climate is warm and humid,and the southern subtropical evergreen broad-leaved shrubs are formed.The dominant species are prominent,the species composition and community structure are single,and the community stability is low.It is the main growth environment of the A.spinulata population;The higher elevations of the hillside are dominated by evergreen and deciduous broad-leaved mixed forests and typical broad-leaved forests,with rich species composition,high plant diversity,diverse community structure,and high community stability.The A.spinulata population is distributed in the valley area,the habitat range is relatively narrow,the breeding process has a relatively high requirement for the environment,and is affected by human activities and P.pubescens invasion.The special protection and strict management of the communities where the A.spinulata are located should be carried out to protect the forest area biodiversity and at the same time promote the steady growth of the A.spinulata population. |
