Composition Characteristics of Alsophila spinulosa Community and Vertical Change on Species Diversity in Danxia Landform

In order to study the species diversity of A.spinulosa community in Danxia Landform,an investigation of A.spinulosa community was conducted in Chang-Qian-Gou scenic spot of Xishui,Guizhou Province.Species richness index,Shannon-wiener index,Simpson index and Pielou's evenness index were used in this investigation and analysis.The results showed that the sample plot was a association of subtropical evergreen broadleaf mixed forest: Ass.Alsophila spinulosa+Beilschmiedia intermedia-Mallotus philippinensis-Rhynchotechum obovatum.The results indicated that the sample plot was made of 82 plant species,including 31 species in tree layer,31 species in shrub layer,17 species in herb layer,and 3 woody climbers,belonging to 56 genera and 39 families.There were 317 trees in this sample plot,including 153 A.spinulosa that important value was 0.5313.A.spinulosa was the dominant species in tree layer,and constructive species in whole plots.The numbers of plants in shrub layer and seedling layer were very little.The height of 90% of plants was at a concentration of 0 ~ 9 m,and the most plants were in the height of 3 ~ 6 m.The numbers of plants decreased as height classes raised;the number of plants decreased as diameter classes raised in a general tendency.The species richness index and Shannon-wiener index of tree layer was significantly greater than shrub layer's or seedling layer's.The tendency of Simpson index and Pielou's evenness index are as follows: tree layershrub layerseedling layer,but no significant differences compared with each other.The Species richness index of tree layer was always greater than shrub layer's or seedling layer's with the increase of altitude.The general change of these diversity indices of shrub layer with the increase of altitude tends to be uniform,show that: decreasing→increasing→decreasing→increasing.The Shannon-wiener index and Pielou's evenness index of tree layer at 620m was less than shrub layer's.The Species richness index,Shannon-wiener index,Simpson index and Pielou's evenness index of shrub layer at 770m was the least,,SW shrub=0,SN shrub=0,PW shrub=0,R shrub=0.5,and the tendency was reversedbetween Shannon-wiener indexand Species richness index of shrub layer at 670m and 770m.The Jaccard coefficient was the largest between 670m and 770m,CJ=0.394 7,and the least was between 620m and 770m,CJ=0.1833.