Fruit Characteristics And Seedling Adaptation Of Endangered Species Abies Chensiensis

The Dissertation focuses on characteristics of seeds and seedlings of an endangered species, Abies chensiensis(Qinling fir). A. chensiensis, an evergreen arbor endemic to China, is an endangered plant distributed mainly in Qinling Mountain, China. We examined four aspects of Qinling fir in both core and border distribution in China: fruiting characteristics, morphological variation of cone and seed, germination character of seed and seedling adaptation in field, and also in combination with some comparisons to A. fargesii. The purpose of our study is to reveal some reproductive characteristics of Qinling fir, and to discuss the endangerment mechanism based on our results.Results of fruiting characteristics suggested low quality of Qinling fir seed and very high abortion. For this species, the cone and seed, and the number of seeds per cone were greater than that of most other firs of Abies, but fewer seeds were fully developed per cone due to so many empty, rigid or worm-damaged seeds. With the increase of elevation, the ratio of fruited tree to adult trees, and the number of cones per tree reduced, which indicated better reproduction for A. chensiensis in low elevation.Statistical differences of cone and seed traits were significant between regions with the same elevation and among trees within regions, as well as between natural and managed forests. The variance component analysis indicated that about 85 percent of the variation attributed to differences between individual trees and within trees, providing strong evidence of substantial genetic control over cone and seed traits. The mean values of traits of cone and seed from the core region were higher than that of in the border area, which also indicated that A. chensensis reproduced better in the core region.The germination research is mainly about the dormancy mechanism and some breaking approaches. It is light dormancy for A. chensiensis. Some physical and chemical methods are helpful to break dormancy of Qinling fir except for cold stratification. Compared to the latter, the formers did take short time to promote germination. No significant differences were found among different treatments. There were higher germination percentage and quickly germination speed in core region than that of in border region, mainly due to better quality of seed in core region. For the same reason, germination percentage of A. fargesii was also higher than A. chensiensis.Seedling adaptation was revealed by field experiments under different conditions.Values such as seedling emergence, seedling survival over a 1-year period, seedling growth per month were measured under different conditions. It was found that the mean seedling emergence was only 16.9 percent, and mean seedling mortality was 57.6 percent after one year. The highest seedling emergence was found in forest gap in combination with mineral soil and 2~3cm soil cover, which indicated little contribution of soil seedbank to regeneration. Seedling emergence was higher for seed suffering from cold stratification of 30 days than the control group, but no significant effect on seedling growth. Higher speed of seedling growth out of forest than that of under forest and forest gap indicated that seedlings prefer light in initial growth stage. Seedling growth in mineral soil was quicker than in forest floor.