Population Characteristics Of Taxus Chinensis Var.mairei Of Taibaishan In Qinling Mountains And Its Relationship With Environmental Factors

To study the population of Taxus chinensis var.mairei, field investigation was conducted in Taibaishan National Nature Reserve in Qinling Mountains. The structure and spatial distribution pattern of population, species compositionand biodiversity of community and their relationships with environmental factors were studied by using methods of quantitative ecology. And this study might be contribute to the protection and sustainable development of T.chinensis var mairei population.The age structure of T.chinensis var mairei population was analyzed. A time specific life table was constructed, then the survivorship method were subsequently conducted, which was based on the data from field experiment and was carried out by means of space-for time substitution. The results showed that the age structure of T.chinensis var mairei population in Taibaishan were stable. There was a strong environmental sieve which restricted individual growth and development so as to cause most of individual death from seedling to juvenile stage. The results of life table showed that the peak of death rate of the population appeared inⅡstage and Ⅵstage,which might be caused by the co-effect of both bio-ecological characteristics of the population and environmental factors. According to the statistics test, the life curve of the population is Deevey-Ⅱ type.The spatial pattern of T.chinensis var mairei in different age class and different sampling scale was measured by 7 indicators, the results showed that the distribution of T.chinensis var maireiwas aggregation in different sampling scale, and the aggregation degree were decreased with the increase of sampling scale. The aggregation degree of T.chinensis var mairei were more intense in 25m2 sampling scale than other scales. The distribution pattern in different age class changed from aggregation to random. The seedling pattern was aggregation and the aggregation degree was most intense, because of the dispersing characteristics of seeds.Richness index, evenness index and diversity index were used to study the species diversities of T.chinensis var.mairei community.The results showed that there are 85 species in T.chinensis var.maireimixed forest and they belong to 33 families and 59 genus. In general, the species composition of T.chinensis var.maireimixed forest was abundant and there are great differences among the number of individual for different species.The importance value of tree species and elevation, slope gradient, aspect, slope position and canopy density were measured. CAA was used to analyze the relationship between the distribution of tree species and the environmental factors. The results of importance value indicated that T.chinensis var.mairei was dominant tree species in the community. The results of CAA showed that 5 explanatory variablesexplained 83.94% of the variation of tree species data. There was a positive correlation between elevation and the distribution of T.chinensis var.mairei, while the correlation between canopy density and T.chinensis var.mairei distribution was negative.The study of relationship between T.chinensis var.mairei distribution and environmental factors showed that the number of individual and seedling were significantly higher in the plot that located in north downhill at an altitude below 1990 m, which would be the appropriate environmental condition for the protection and development of T.chinensis var.mairei population.