Studies On Population Distribution, Community Features And External Morphological As Well As Anatomical Differentiations Of Wild Cymbidium Goeringii In Chongqing

In order to make clear the present survival situation, to explore the adapting mechanism and to discusses the protection strategy and sustainable usage of Cymbidium goeringii, we studied the population distribution, community features, external morphological as well as anatomical differentiations of wild C. goeringii in Chongqing.Wild populations of C. goeringii in Daba Mountain and Wuling Mountain and their surrounding areas are studied. Sampling locations include Chengkou county (Houping, Lantian, Dong'an), Wuxi County (Long'an,Liping,Qingzhuan,Baiguo,Linkouzi,Shengli and Fenghuang), Fengjie County (Xinglong, Difeng),Wulong County (Zhongxin Temple),and Qianjiang county (Zhengyang).The study includes following aspects of the wild C. goeringii in Chongqing : 1) population size and spatial distribution pattern; 2) external morphological differentiation at the population level and the individual level , 3) the species composition and quantitative classification of the communities where this species populated ; 4) the anatomical structure differentiation between populations.The following conclusions were drawn:1)Population distribution: C. goeringii can be distributed in natural forests as well as in artificial forests . Nine of 14 populations (64.3%) were found in artificial forests. Five Populations with the highest population densities are all found in the artificial communities. This may due to sampling error, as one plot which is convenient and easy to investigate is generally the artificial community. If one plot has medium artificial interference, its shrub and herb layers are certainly much easier to be harvested by farmers, which will also indirectly enhance competitiveness of C. goeringii in the communities and the species will be more easily to get advantageous position in competition in the artificial communities than in the natural ones. Population densities of C. goeringii were correlated with both Fagaceae tree densities and coverage of the shrub and herb layer of communities . Fagaceae tree densities were positively correlated, while the shrub and herb layer coverage were negatively correlated with population densities of C. goeringii. As to the spatial distribution patter of wild populations of C. goeringii, it was clumped distribution in plots 2 X 2 as well as in plots 100×100, while randomly distributed in the 10×10 plots.2) Community features: There are found with 123 species of 105 genera in 64 families of vascular plants in the studied communities where C. goeringii populated. From analysis of species diversity of the communities, 5 in 14 communities belong to the natural communities with tree species diversity at a relatively higher levels. Species diversity of studied communities was not associated with the altitude gradients.The results produced by TWINSPAN indicated that the studied communities where C. goeringii sampled can be divided as seven associations. The results produced by DCA indicated that DCA axis I represents wet condition, DCA axis II represents the soil acidity. The results reflect the relationship between the communities and the environment. Soil pH and wet conditions are main factors associated with vegetation types.In the spatial structure of 14 communities where C. goeringii sampled the tree layers can mostly be divided into three sub-layers.The results produced by Euclidean distance cluster analysis of communities basically indicated the geographic relationship of these communities and could reflect similarity of them at a certain extent.3) External morphological differentiation: 8 vegetative characters and 25 reproductive characters of 20 individuals for each population were measured. One-way analysis of SPSS was used to detect variance indicators. Hierarchical cluster procedures SPSS software was applied for individual cluster and population cluster. By comparing results calculated separately from vegetative characters and reproductive characters, and through comparing phenotypic variation at the populations level and the individual level, we studied the external morphological differentiation and inferred the genetic variation within and among populations of C. goeringii in Chongqing. There is significant variance both within populations and among populations. For vegetative characters, C. goeringii populations that lies north of the Yangtze River manifested significant variation to those populations which lies south of the Yangtze River, moreover variance among populations was stronger than that within population. For reproductive characters , there is significant variation in the individual level but no significant variation at the population level, and variance within population was higher than that among populations. Because vegetative organs have larger phenotypic plasticity and reproductive organs are more conservative morphologically. Conclusions from reproductive characters are more credible. Though there are significant morphological variances both at the individuals levels and at the population levels, most of the genetic variations are within population. Therefore, it can be inferred that the main reason why C. goeringii is going to be endangered is not the lose of genetic diversity.4) Anatomical structure differentiation: Three pieces of roots of each individual for 5 individuals of each population were collected to make permanent root slices by the traditional method of slices of paraffin wax. With Motic microscopy system, pictures of cells and structures were taken, size of several kinds of cell and kinds of structures were measured . These data was used in the course of variance analysis. The result produced by variance analysis revealed that 6 of 12 structure characters indicate notable differentiation among individuals.