Abstract: By using static life table, fecundity schedule, and Leslie matrix model, this paper studied the numeric dynamics of ex-situ population of endangered orchid Dendrobium fimbriatum in Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, and assessed the ex-situ conservation effect of the species. The age pyramid of the population was kettle-shaped, and the net reproduction rate (R₀), intrinsic increase rate (r_m), and finite increase rate (λ) were lower, being 0.569, -0.089, and 0.915, respectively, indicating that the ex-situ population was in a decreasing trend. The analysis of Leslie matrix model showed that in the next 50 years, the individual number and the total number of the ex-situ population would have a continuous decrease. Based on this analysis, it was suggested that 1) increase the lithophytic habitat in ex-situ conservation to make the asexual reproduction buds grow better after leaving maternal, and 2) enhance the mature individuals’ reproductive capability by assisted management and carry out further study to realize the seed symbiotic germination.

Key words: the Yellow River irrigation area of Ningxia, swine manure, winter wheat field, nitrate N, leaching.