Investigation of Habitats and Causes of Population Decline of Euonymus sanguineus in Tibet

Tibet is one of the core distribution areas of the Chinese endemic plant Euonymus sanguineus, but the population decline is obvious. In order to protect and develop the plant resources in Tibet rationally, the ecological environment and growth conditions in Milin County, Nyingchi City, Tibet were investigated by means of sampling method in order to provide the theoretical basis for the protection, introduction, breeding and cultivation of Euonymus sanguineus. The results were as follows: (i) The population quantity of Euonymus sanguineus was too small and the survival area was too small, which seriously affected the interspecific mating, seed development and regeneration, and greatly reduced the genetic diversity within the population; (ii) The dry and hot river valley climate and human and animal activities inhibited the seed germination and seedling growth of Euonymus sanguineus, resulting in very low survival rate of seedlings, and hindering the population expansion of Euonymus sanguineus; (iii) The distribution area is located in the Yarlung Tsangpo river valley, and the natural habitat fragmentation has affected the interspecific gene exchange, resulting in the low seed bearing capacity and germination rate of Euonymus sanguineus, which is the direct cause of the population decline of Euonymus sanguineus; (iv) The litterfall of Euonymus sanguineus had autotoxicity, which inhibited the growth of seedlings under the forest, caused slow natural regeneration of the population, and then caused the population of Euonymus sanguineus to be unable to spread and develop.