Study On The Ecology Of Endangering Plant Taxus Chinensis Var. Mairei

Taxus chinensis var. mairei, being one of the state-protected one-grade rare and endangered plants, is one of the tertiary relic species and endemic to China. It is mainly distributed alongside Yangzi River Watershed, in Nanling Mountains and some mountains in Guangdong, Guangxi, Jiangxi, Henan, Shaanxi, Gansu, Taiwan and Shanxi etc. Shanxi is the boundary of its distribution. Areas where T. chinensis var. mairei is distributed in Shanxi are between 110o31'-112°31' E, 35°12' -36°12' N, including Qingshui, Yangcheng, Lingchuan, Huguan counties, among which T.chinensis var. mairei population is mainly distributed in Huguan and Lingchuan counties.The study stands in the field were located in Lingchuan, Yangcheng and Huguan. Based on the field investigation, T. chinensis var. mairei population and community characteristics were studied systematically and comprehensively by using quantitative ecology methods, including community structure and composition, classification and ordination, species diversity, age structure, spatial distribution pattern, interspecific relationship and niche breadth and niche overlapping of dominant population etc. The aims of this study were to reveal its endangered condition and endangered reasons, promote some theory proof so as to protect the endangered species from damage, product plantation and utilize sustainable the resource.There were 128 species of seed plants, belonging to 108 genera, 55 families, among which pteridophyte had 4 families, 5 genera and 5 species, gymnosperm had 3 families, 3 genera and 3 species, dicotyledon had 42 families, 87 genera and 108 species, and monocotyledon had 6 families, 13 genera and 15 species in T. chinensis var. mairei communities. The flora of carpophyte genera in T. chinensis var. mairei communities was complicated. Among them, temperate distribution elements, having 66 genera and accounting for 70.21% in total genera (excluding cosmopolitan), made significant dominant and had important function in flora composition. Moreover, among the floristic elements of species, endemic species to China had 42 species, accounting for 34.43% in total species, and made evidently dominant. The vertical structure of T.chinensis var. mairei communities consisted of arborous layer, shrub layer, herb layer, and interlamellar plants. The sequence of the life forms composition in T.chinensis var. maireicommunities is phanerophyte (62 species, 48.44%) > geophytes (45 species, 35.16%) > hemicryptophyte > therophyte > chamaephyte (5 species, 3.91%). The physiognomy of T.chinensis var. mairei communities was influenced by phanerophyte with chartaceous, monophyllous, microphylline, deciduous and broad leaf. It is consistent with that in warm-temperature zone, showing the vertical zonal spectra characteristics in warm-temperature montane.The ecological relationship between T.chinensis var. mairei communities and environment was analyzed by using TWINSPAN, DCA, CCA and DCCA. The results were as following: T.chinensis var. mairei communities was classified into 12 types by TWINSPAN, and the main factors that restricted community distribution were soil humidity and altitude gradient. The results of DCA ordination indicated that the main factors that restricted community distribution were soil thickness, soil humidity, and aspect. The ordination of species and quadrats showed that the ordination of the dominant species in the communities was similar to that of the community types, and to some extent, the distribution pattern of the dominant species determined that of the community type. By using DCCA, the species-environment correlation increase considerably, and it was in favor of interpreting the ecological meaning of the ordination axes. Compared with DCA, two-dimension ordinations by DCCA makes quadrats with similar composition and environments and species with similar habitat more concentrated on the center of the ordination figure. Therefore the results of DCA were better than that of DCCA and CCA.The relationships between species diversity and community types, environmental variables, community structure were studied by using the richness indices, diversity indices and evenness indices. The results showed that: Firstly, the order of evenness indices was as follows: Ass. X > Ass. XII > Ass. VII > Ass. DC > Ass. VI > Ass. V > Ass. IV > Ass. XI > Ass. I > Ass. III> Ass. II > Ass. VIII. Secondly, the main factors influencing species distribution pattern are induration, slope direction, slope, soil thickness and organic content which are negative correlation. Thirdly, the sequence of diversity sensitivity to environment was the arborous layer > the shrub layer > the herb layer, among which the richness indices and the diversity indices of arborous layer had high significant positive correlation (p<0.01) with environment, the diversity indices of shrub layer had high significant negative correlation (p<0.01) with environment, while thediversity of herb layer had no significant correlation with environment. Fourthly, the Simpson indices, Shannon-Wiener indices, Mcintosh indices and Brillouin indices were all influenced by S (the total species in a plot) . hi all communities, the richness indices, Simpson indices, Shannon-Wiener indices, Mcintosh indices and Brillouin indices of herb layer were all digger than that of arborous layer.The overall association and interspecific correlation of dominant populations in the communities were studied by using ^-test for 2x2 contingency table, variance test, Pearson's correlation coefficient test and Spearman's rank correlation coefficient test. The results indicated that the overall association of the community was significant (p>0.05). The species-pairs having similar adaptive to environment were significant positive correlation. Although the results by X2-test, Pearson's correlation coefficient test and Spearman's rank correlation coefficient test were some dissimilar, the overall results were consistent with that of variance ratio test, that was, the species-pairs between dominant populations had some association, showing that the communities were relatively stable stage.The niche breadth and niche overlapping of dominant populations of T. chinensis var. maireii communities were studied by using Shannon-Weaver index and Portraits's methods. The results were that: The niche breadth of T.chinensis var. mairei was biggest in all populations, and had wider niche overlapping with the other populations which had also wider niche, and made up mixed forest with those populations such as Carpinus turczaninowii, Dioapyros lotus, Pteroceltis tatarinowii et. ah These results can be used as theory to guide afforesting T.chinensis var. mairei mixed forest so as to constitute effect ecological system. The more the niche breadth of populations were, the wider the adaptive range of species to ecological factors, the more extensive the distribution range of species. The more the niche overlapping of populations were, the more the ecological similarities between populations. This was because that the populations with wider breadth niche might have higher niche overlapping, and the populations with narrower breadth niche might have smaller niche overlapping. The number of species-pairs with general niche overlapping was 88.12%, showing that there were the complicated relationship between populations and there were some common adaptive to environment resource.The pattern of T chinensis var. mairei in different plots, different development stageand different sampling scale was measured by using 5 typical aggregation indices and Poisson distribution, goodness-of-fit testO^-test) for negative binomial distribution, the results showed that the pattern of T. chinensis var. mairei was aggregation, and the each aggregation index indicated same tendency. However, in different plots, the pattern was not consistent with each other because of the habitat condition difference and the population structure difference between plots. The patterns in different development stages changed from aggregation to random, that was, the aggregation degree were smaller and smaller from seedling to mature plant. The seedling pattern was aggregation and the mature plant was random because of the difference of habitat condition besides dispersing characteristics of the seeds. Although the patterns of T.chinensis var. mairei were all aggregation, the aggregation degree was different. The aggregation degree of Taxus mairei var. mairei were bigger in 1 Ox 10m2 sampling scale than in the plots on other scales.The structure characteristics of T. chinensis var. mairei population were analyzed by using the method "spatial sequence replacement temporal sequence", and "diameter structure replacement age structure", moreover, the life table was got, survival curves was drawn. The results indicated that the age structure of the population were made up of increase type, stable type and declined type in different plots, showing that the population structure change were influenced by habitat conditions so as to form different development types. Moreover, in the process from seedling to juvenile stage, there was a stronger environmental sieve which restricted individual growth and development so as to cause most of individual death. The environmental sieve consisted of intraspecific competition, interspecific competition, the change of microclimatology and soil. Analysis to life table of the population showed that the high peak of death rate of the population appeared in II stadium, IV stadium and VI stadium. This may be because of the bio-ecological characteristics of the population and environmental factors. According to the statistics test, the life curve of the population trended to Deevey-II type. The results of spectra analysis revealed that the population existed periodism, which was in concert with the periodism of the population in natural regeneration process, showing that the characteristics of the population was periodism fluctuation.The endangered causes of T.chinensis var. mairei were analyzed, the results showed that there were some reasons which threatened this species, such as the less seeds, thelower sprouting rate and viability rate, the higher death rate, the weaker competition, the narrower distribution range and the special adaptive to environment. In addition, the human disturbance was one of the important factors, which threatened this species. Finally, some suggestions and strategies were discussed for protecting the rare species from human disturbance based on the situation of T. chinensis var. mairei in the field.