AbstractThe Taibai larch, Larix potaninii var. chinensis, is an endangered plant only found in the Qinling Mountains in China. It is densely distributed on Mount Taibai and plays an important role in environmental protection in the high altitude zone. In order to characterize the age structure and dynamics of the L. potaninii var. chinensis population so as to better conserve its resources, 29 plots (10 m ×10 m) were investigated on Mount Taibai. The analysis of the age structure of five populations of L. potaninii var.chinensis showed that most individuals (68.6%) were concentrated in the 60-140 year age classes. Younger and older individuals were dramatically few. Because of different environmental conditions, different populations developed their own characteristic age structure. The population in L. potaninii var. chinensis-Abies fargesii-Lonicera hylocomium-moss association showed a stable development tendency. However, another four populations in L. potaninii var. chinensis-A. fargesii-Betula utilis var. sinensis-Rhododendron clementinae association, L. potaninii var. chinensis-Rhododendron clementinae-Lonicera hylocomium-moss association, L. potaninii var. chinensis-Rhododendron capitatum-Juniperus pingii var. wilsonii-Carex sp. association and L. potaninii var. chinensis-Rhododendron purdomii-R. capitatum association all showed obvious declining tendencies. The analysis of life tables and survival curves showed that even under different environmental conditions, survival curves of L. potaninii var. chinensis populations belonged to Deevey type III, and death peaks of different populations were the in period of 100-180 years old. Time sequence prediction models for different populations after 20, 60, 100, 200 years indicated that the numbers of old individuals would increase in the beginning and finally decrease, giving rise to difficulties for maintenance of these populations. The age structure and dynamic trends of L. potaninii var. chinensis populations were similar to those of other endangered species in China, such as Cathaya argyrophylla. The key cause for population decline was that shade in the forest obstructed germination and seedling growth. In situ conservation should be strengthened in future, especially for middle and old individuals with reproductive ability. The heliophytic and xerophytic characteristics of L. potaninii var. chinensis should be considered and special countermeasures for fostering the species should be made according to these biological characteristics and habitats. In the lower altitudes, nontarget species in the tree layer and some shrub species should be thinned. In higher altitude areas, actions for fostering forest, such as cutting shrubs, clearing herbs, etc. should be taken, so as to create the environmental condition for development of young seedlings of L． potaninii var. chinensis.