Studies On The Population Structure And Endangered Factors Of Heptacodium Miconioides

Heptacodium miconioides Rehd(Caprifoliaceae), seven-son-flower, is an endangered species endemic to China. It is valuable for science research in phylogeny, systematic classification, species evolution of Caprifoliaceae and a excellent ornamental treespecies. In this paper, we investigated the distribution of H. miconioides in Zhejiang and Anhui province, totally 9 sites, including Dapan Mountain, Tiantai Mountain, Bei Mountain, Qingliang Mountain, Siming Mountain, Dongbai Mountain, Kuocang Mountain, Tangyuan Mountain and Ningguo in Anhui province. The population structure of H. miconioides was analyzed at genet and ramet levels, respectively. Population Viability Analysis was made on H. miconioides by the model of Time Series. We analyzed the endangered situation of H. miconioides, and put forward protecting strategy in order to provide some suggestions on protection of it. 1. The population structure of H.miconioides at genet and ramet levels(1) H. miconioides mainly occurs in valley and shady slops, where the habitat conditions is bad, with high rate of rock outcrop, thin soil, low vegetation coverage, high light transparence of community and scarce accompanying plant species. However, there are some differentiations among each sites.(2) The number of H. miconioides is larger in Zhejiang province. The largest size of population among 9 sites is in Dapan Mountain, the second is in Tiantai Mountain, the third is in Kuocang and Tangyuan Mountain, the smallest size is in Qingliang and Dongbai Mountain. There are few individuals found in Ningguo, more less than in Zhejiang province.(3) The population structure of H. miconioides at genet level indicates that they are declining, and differentiated on age-class structure among each sites. Due to the high ability of asexual propagation, the number of individual at each age-class increases. The population structure of H, miconioides at ramet level indicated a relatively stable situation.(4) The asexual propagation of H. miconioides is ubiquitous, but the ability of asexual propagation is discriminate among the site. The proportion of ramet number to genet number is higher than 5.00 in Dongbai Mountain, Bei Mountain and Kuocang Mountain. The proportion is lower in Dapan Mountain, Qingliang Mountain, Ningguo and Tangyuan Mountain. Among 9 sites, the proportion in Tiantai Mountain is the lowest, only 2.54.2.The Population Viability Analysis on H. miconioides by the model of Time Series(1) At genet level, the number of low age-class will be decreased in 10 years. In 15 years, low age-class will gradually develop to middle age-class. After 15 years to 20 years, middle age-class will develop to high age-class, which will keep the trend of increasing. Generally, the population structure of H. miconioides is obviously declining and lends to be extinct in future.(2) At ramet level, due to the high ability of asexual propagation, the number of individual at each age-class is increase to the extent in Dapan Mountain, Tiantai Mountain and Tangyuan Mountain, which is complementary to the weak regeneration ability of H. miconioides at genet level. Due to the complementary of asexual ramet, the change of individual number at each age-class indicates a relatively stable situation. The extinct possibility of population at ramet level will be lower than at genet level.