Abstract: An investigation was conducted on the population structure and dynamics of Pinus armandii in Caohai National Nature Reserve with the typical plot survey method. Diameter class was adopted to represent age class, the static life table and survival curves were compiled to analyze its current population structure and the survival analysis and time sequence analysis were used to predict its future quantitative dynamics. These can provide a scientific basis for the protection, resource management and restoration of karst forest ecosystems. The results show that: (1) The P. armandii population showed a spindle-shaped age structure, the survival curve tended to be Deevey-II type. The quantitative dynamic index (V_n) fluctuated greatly with the increase of age, the quantitative dynamic index neglecting (V_pi) and considering outside interference (V_pi')were both greater than 0, which showed that the P. armandii population belonged to the growing type. (2) Survival analysis show that the survival rate gradually decreased and the cumulative mortality gradually increased. The curve of death density decreased smoothly and that of risk rate increased gradually, which meant that the population of P. armandii was stable in the early stage, increased in the middle stage, and declined in the later stage. (3) The forecasting model of time sequence analysis indicated that after 2, 4, 6 and 8 age classes in the future, there will be a gradually decreasing trend from Ⅰ to Ⅲ age class, and a gradually increasing trend from Ⅴ to Ⅸ age class. Consequently,the regeneration of P. armandii population is mainly restricted by the built-up mechanism. It is suggested to strengthen tending, management and maintenance measures for seedlings and young trees.

Key words: Pinus armandii, karst region, population structure, population quantitative dynamics