| Eurycorymbus cavaleriei is a national class II key protected wild plant unique to China,the distribution range of natural population is small and the quantity is small.A small survival community of E.cavaleriei is naturally preserved in Sanming City,Fujian Province.The population is less disturbed.Although the number is small,the tree is tall and grows well.On investigation of the community,the community structure,species diversity,dominant population ecological niche,interspecies relationship characteristics,population structure and dynamic characteristics,etc.,to master the distribution of the plant community,the competitive relationship between the layers of dominant population,E.cavaleriei in the future development trend.And,the relationship between the population and the environment and the dominant population was revealed,which provided the basis for the protection and management of the population.The main conclusions are as follows:(1)There are 204 species of vascular plants belonging to 167 genera and 84 families in the habitat community of E.cavaleriei.The dominant families are Fabaceae,Asteraceae,Labiatae,Rubiaceae,Moraceae,etc.They are the main components of the community.Single family and single species(41.67%)and single genus and single species(86.23%)account for a large proportion.(2)At the family and genus levels,the ratio of tropical distribution to temperate distribution is 2.85:1 and 1.64:1 respectively.The community is mainly distributed in the tropics,followed by the temperate zone,with a strong subtropical distribution characteristics and a certain temperate nature.(3)The community is divided into tree layer,shrub layer and herb layer.Osmanthus fragrans and Quercus glauca are the constructive species in the tree layer,the important values are 22.59 and 20.04respectively.The important value of E.cavaleriei is 5.58,which is an associated species of the community.The shrub layer is rich in species and has no obvious dominant species.Small diameter trees(DBH≤10 cm)account for 47.74%of all trees,shrubs and grasses in the community.The diameter step structure of the community as a whole shows an inverted"J"shape,which belongs to a developmental community,and its regeneration is in good condition.(4)Margalef index(DM)of species richness in E.cavaleriei habitat community:shrub layer>herb layer>tree layer.Shannon Wiener index of species diversity(H):shrub layer>herb layer>tree layer.Species dominance Simpson index(D):shrub layer>herb layer>tree layer.Pielou index of species evenness(E):herb layer>shrub layer>tree layer.(5)The R~2values obtained from the simulation curves of three layer of tree,shrub and grass are greater than 0.9.The fitting curve and linear equation points obtained are close to the European distance(tree layer17.8474,shrub layer 8.1019,herb layer 18.2151)of the stable point(20,80).The whole community is in a stable state.(6)The niche overlap and niche similarity between herb layer and tree layer are not different,and the shrub layer is relatively small.The niche breadth of Osmanthus fragrans was the first in both tree layer and shrub layer,then its niche overlap and niche similarity with other dominant populations are above the average level of this layer.(7)The niche width of E.cavaleriei is relatively high in tree layer and shrub layer,which are 1.5085 and 1.2395 respectively,it has certain competitiveness in the community.E.cavaleriei has high niche overlap and niche similarity with Swida wilsoniana,Quercus glauca,Sinoadina racemosa and other dominant populations.(8)In terms of overall connectivity,the variance ratio VR of each layer of the community is greater than 1,which is a positive correlation.Shrub layer and herb layer showed significant positive connection,It has formed a stable interspecific collocation relationship.The habitat community of E.cavaleriei is relatively stable and overall succession to the top as a whole.(9)From the perspective of interspecific connectivity,the number of negative association groups among dominant populations in tree layer and shrub layer is greater than that of positive association groups.The stability of the community is weak.E.cavaleriei was significantly associated with the dominant populations in the tree layer and shrub layer and produce interspecific competition,especially Osmanthus fragrans and Quercus glauca.(10)The population of E.cavaleriei in this sample plot is small,with only 38 trees.The number of age class I is large and is in the young forest stage.The population of E.cavaleriei showed a fluctuating state in the whole age class structure.Considering the disturbance,the dynamic index is 0.103,so it is a stable population at present.(11)There are many trees in the young stage(age class I)of E.cavaleriei population.However,in the process of age class I to age class II,the number decreases sharply,and there are few trees in middle and old age.The community as a whole is of"L"type and belongs to a developing community,but the development speed is slow.(12)The survival curve of E.cavaleriei flower and tree population was tested and the fitting curve was obtained,then the R(0.3261)value of the power function is greater than the R(0.1812)value of the exponential function.The survival curve of the population tends to Deevey-Ⅲtype.The performance of the results is predicted by the one-time moving average method.E.cavaleriei population number in the next 2,4 and 6years,the results showed that the middle-aged individuals were rich and showed an overall growth trend. |
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