| T. ciliata var. pubescens, a national secondary endangered species, is now facing serious resource destruction, and the situation of being endangered is getting worse even if being located in natural protection reserves. In order to explore endangered processes and mechanisms of natural population, and to seek the key factors to its population multiply and regeneration in this paper, materials as natural dominant community and its plantation of T. ciliata var. pubescens in Jiulianshan National Reserve in Jiangxi Province, the population dynamics characteristics being studied, including sexual and clone breeding traits, seed rain, soil seed bank and forest gaps for the effects on natural regeneration at population level. The main results show that:(1) The observation data from T. ciliata ver pubescens natural communities in between in Xiagongtang and in Daqiutian station, and the comparison with the composition, structure and diversity were analyzed in Jiulianshan nature reserve. The results indicated that T. ciliata var pubescens occupied an advantage position on different communities, and plant species belonged to63families,95genera,138species and62families,94genera,128species, respectively. Their species diversity indices ware both in order layer of shrub, herb and arboraceous layer. The community composition was more plant species, complex structure, more dispersed of the family and genus composed.(2) The reference to T. ciliata var pubescens plantation in Xiagongtang observatory, flowering of the standard seed setting trees were observed and analyzed by comparison with them. The results indicated flowering of T. ciliata var pubescens begins at end of May to early July.. Flowers per flowering branch were normally above200flowers in2010. However the flower dropping rate is above70percent in natural forest, which indicated that the seed setting rate was much low. The flowering position is the main spatial pattern of seed setting in different population, so fruiting branches were often concentrated in the middle and upper positions of main floral axis. The seed setting was mainly concentrated on vertical distribution of middle, upper canopy, and of east, south for horizontal distribution. Seed tree, seed yield and forest conditions were large difference between in different populations. The analysis of mainly factors indicated that the seed yield per seed tree mainly depended on the basis of predicted indexes such.as the number of seed trees, percent of seed trees, tree density on canopy layer, stem diameter of seed tree. The number of cones per branch and of seeds per cone, setting rate, percentage of full-developed seeds in difference forests were12～ 44,23～ 43,7.99%～ 13.19%,2.9%～ 40.4%, respectively. Their genetic variation coefficients were within2%～ 37%, of which, genetic variation in the number of cones per branch is the largest.(3) The dynamics of seed rain and seed bank, seed germination and seedling status in T. ciliata var. pubescens natural populations were investigated and evaluated. Results showed the seed rain of T. ciliata var. pubescens was dispersed from late September to the end of November. Seed densities of different natural populations in2010decreased in order of:Xiagongtang protection station (284.7±24.2) seeds-m"2and Daqiutian protection station (251.6±24.7) seeds·m-2, and supplied intact seeds of34.3seeds·m-2, and22.6seeds·m-2into soil for seed germination update, respectively. The spatial differences of seed rain in natural populations were little significant, but a certain differences within time. The seed density of seed bank occupied largest over litter layer under3～6m canopy, the rotting rate and number of seeds rotted showed significantly difference in different populations, for north was the most. Seed bank reserves were affected by such factors as strong volume, bird feeding, seed viability, etc. of which birds feeding was the prime factor for a substantial drop of seed bank. A large number of seeds rotted with seed intolerance so that seeds could hardly be effectively stored beyond the length of one month. Soil seed reserves in December were8.8～15.7seeds m-2in natural populations, and its germination seedlings were less than2stands·m-2, the following year being the minimum of soil seed reserves (6.7～11.8seeds m-2) in January, and seedling of0.4～ 0.6stands·m-2, which was consistent with rare distribution of natural seedlings of T. ciliata var. pubescens, natural populations.(4) Results from forest gaps for T. ciliata var pubescens regeneration in the natural community showed that its everage germination rate in forest gaps was extremely low to5.98%. High soil moisture is an important factor to low seed germination. Light is a main impact factor for seed germination, but was positively related uncentainly. Seedling dynamics passed the first time of high mortality rate within May-Jun., then the second of a low high mortality rate of within Jul.-Aug., and the same of the third for during winter, other times tended a stable change. On December there total lived38stands, survival rate of only2.89%.(5) The analysis from the population dynamics and life process of T. ciliata var pubescens in Jiulianshan nature reserve showed a higher level of mortality rate and fatality rate at the I age class, they tended to level off totally entering and after the II age class, but a slight increase at ⅩⅡ, Ⅷ age class. Their population structures existed in a large fluctuation, of which, short of young seedlings, and the proportion of elderly individuals increasing, indicated that population of the species inclined to the type of decline. The breeding system of natural population in Xiagongtang is mainly sexual reproduction, but whose sexual reproduction was weak. Its survival curve of the natural population appeared to be a type of Deevey-Ⅰ. While clonal reproduction for population in Daqiutian, it showed a certain renewal ability to clone reproduction. And the survival curve of natural population appeared to be a type of Deevey-Ⅲ. |
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