Study On The Relationship Between Species Diversity And Functional Diversity Of Davidia Involucrate Community In Sichuan

Species diversity(SD)and Functional diversity(FD)are important components of biodiversity.Plant community species diversity reflects the stability and complexity of the ecosystem structure and plays a very important role in maintaining the health and stability of the ecosystem.Plant community functional diversity is mainly through the complementary use of growth resources,so that species and ecosystem functions have a close relationship,play a very good interpretation to the community aggregation process and the degree of disturbance,play an irreplaceable role in the function of the ecosystem.It is of great significance to study the internal relationship between plant community species diversity and functional diversity in order to reveal the mechanism of ecosystem functional maintenance.Davidia involucrata belongs to the genus Davidia Baill in the Nyssaceae family.Its unique taxonomic status determines its irreplaceable role in global biodiversity conservation.This study was conducted to assess the relationship between species diversity and functional diversity of the Davidia involucrata community in Sichuan.Four species diversity indices(Species richness,Simpson dominance index,Shannon Wiener diversity index and Pielou evenness index)and five functional diversity indices(Functional richness,Function evenness,Functional divergence,Rao’s quadratic entropy and Functional dispersion)were selected to analyze.The following four relationships were analyzed and discussed by principal component analysis,Pearson correlation analysis and linear regression analysis: 1)relationship between species diversity index and functional diversity index;2)relationship between principal component and functional diversity index of species diversity index;3)relationship between principal component and species diversity index of functional diversity index;4)species diversity index The relationship between the main component of the set main component and the functional diversity index set.The main results are as follows:(1)In the tree layer,the average values of species richness(R),shannn-wiener index(H),Simpson dominance index(D)and Pielou evenness index(J)were 3.91±5.13,0.66±0.13,1.36±0.46,and 2.75±2.35,respectively.The level of tree layer was significantly higher than that of herb layer and shrub layer(p <0.05).The D and J indexes in the herb layer were significantly higher than those in the shrub layer,while there was no significant difference between the H and D indexes and those in the shrub layer.(2)The functional richness(FRic),functional uniformity(FEve),functional divergence(FDis)and Rao’s secondary entropy index(Rao Q)at the level of tree layer were3.91±5.13,0.66±0.13,1.36±0.46 and 2.75±2.35,respectively,which were significantly higher than those of shrub layer and herb layer.The average value of functional dispersion(FDiv)of tree layer was 0.76±0.13,significantly higher than that of shrub layer(0.68±0.19),and no significant difference was found between tree layer and herb layer(0.71±0.11).(3)There was a significant positive or negative correlation between functional diversity index and species diversity index at different levels of Davidia involucrata community,and there was a general correlation between individual indices.There was a significant positive correlation between FDis,Rao Q and species diversity index at different community levels(p <0.05).R-FRic showed a significant positive correlation at different community levels(tree,shrub,and herb).The coefficients are 0.48,0.71 and 0.73,respectively.(4)In the concentration of functional diversity index,the first principal component(FD＿1,FD＿3,FD＿5)and the species diversity index had extremely significant positive correlation at different community levels(p < 0.01),in which the correlation coefficient between FD＿5 and H index was the strongest on the herb layer,and the correlation coefficient was 0.72.The second principal component ha d significant or extremely significant negative correlation with H,D and J indexes at the level of tree layer and shrub layer,and only had significant positive correlation with R at the herb layer(0.28).(5)In the concentration of functional diversity index,the first principal component(FD＿1,FD＿3,FD＿5)and the species diversity index had extremely significant positive correlation at different community levels(p < 0.01),in which the correlation coefficient between FD＿5 and H index was the strongest on the herb layer,and the correlation coefficient was 0.72.The second principal component had significant or extremely significant negative correlation with H,D and J indexes at the level of tree layer and shrub layer,and only had significant positive correlation with R at the herb layer(0.28).(6)The first principal component of the functional diversity index of the Davidia involucrata community and the first principal component(SD)of the species diversity index were significantly positively correlated at different community levels(p<0.01).The fitting curve of the second principal component(FD＿2,FD＿4)on the tree layer and shrub layer of the functional diversity index showed a trend of "U"-type change after increasing first and then increasing,and there was no significant change trend in the herb layer..It is indicated that in the Davidia involucrata community,the first principal component of functional diversity is mainly affected by the interspecific competition in the community,and the second principal component is affected by the combination of "trait divergence"and "trait convergence".