The Community Structure And Genetic Diversity Of Abies Chensiensis

This paper studied the community structure of Abies chensiensis, reveals the community appearance, community vertical structure, species composition and population characteristics of A. chensiensis, provided the ecological evidence for the further study of the community structure of A. chensiensis. At the same time, using microsatellite (SSR) molecular markers, the paper marked 120 individuals of A. chensiensis in 6 natural populations, through the data analysis, detected the genetic diversity of A. chensiensis, clarified genetic structure and variation of A. chensiensis in natural populations. By this study on community structure and genetic diversity of A. chensiensis, we analyzed possible reasons leading to its endangered, proposed a viable protection strategy, provided useful suggestions for further study on genetic diversity and the protection measures of A. chensiensis.The study on the community structure of A. chensiensis showed that:(1) In the total of 15 investigative plots, there were 94 kinds of vascular plants, belonging to 46 families,79 generas, including fern of 1 family,1 genus and 1 species. The composition of plant families and genera are more dispersed, vertical structure of community stratification is obvious, divided into tree layer, shrub layer and herb layer, dominant species of understory herbaceous layer was not obvious. Community life-form spectrum shown in the tree layer, shrub layer and herb layer, including a dominant high shoots of plants, accounting for 61.6%. (2) Through the analysis of the importance values of species in the plots, the A. chensiensis community in five distribution points is divided into four groups. (3) Population characteristics of the A. chensiensis analysis shows that, A. chensiensis seedlings are scarce majority of adult plant, the entire population was declining type.In this paper, the genetic structure and genetic diversity of 6 natural populations of A. chensiensis, were studied based on microsatellite markers. The results showed that:(1)The natural populations of A. chensiensis has low levels of genetic diversity,149 alleles were detected in 10 microsatellite loci, the average number of alleles per locus A is 14.9, the average effective number of alleles per locus Ne is 7.7, the expected heterozygosity He and observed heterozygosity Ho of Per locus were 0.841 and 0.243; Shannon diversity index I is 2.13, the rate of heterozygous gene diversity of natural populations(FST) is 6.7%, these show that the genetic differentiation of natural populations of A. chensiensis mainly exist within the populations. (2) The gene flow among 6 natural populations of A. chensiensis is high (Nm= 3.455), enough to resist the role of genetic drift, to maintain the similarity between populations. (3) The correlation analysis in genetic distance and geographical distance of various populations showed that Populations genetic distance and geographical distance was no significant correlation (r=0.4906, p> 0.05).Through this research, the endangered causes of A. chensiensis may be due to the following points:(1) Affected by the climate of Quaternary Ice Age, stocks of A. chensiensis in low altitudes was becoming extinct, existing stocks all retreated to high altitudes. So, the distribution area of A. chensiensis was decreasing. (2) Because of the poor natural regeneration, low seed set and the phenomenon of fruiting in following year, great canopy density of communities and weak light intensity, the young plant of A. chensiensis can not grow normally, the conditions seedlings into saplings were limited. (3) The destruction of human led to the forest area of A. chensiensis decrease, exacerbated its islands distribution. (4) The genetic differentiation of A, chensiensis mainly concentrated within populations, gene flow was Large, thereby maintaining the similarity between populations, which made the genetic diversity of A. chensiensis was low.According to the results of this study, the protection of A. chensiensis can be proposed from the following aspects:(1)Strengthen the situ conservation of existing forest of A. chensiensis. In the slope zone, we should protect forest gap, while create a canopy environment in sunny areas to promote the natural regeneration; (2) Protect the adult plants, take full advantage of adult plants seed in good condition of A. chensiensis, while harvesting, establish nursery and expanse the artificial populations timely and properly; (3) Strengthen the management of natural forests of A. chensiensis, reduce the habitat destruction of human activities.