Objective To study the variations of age structure and spatial distribution pattern of Pinus yunnanensis forest as well as the spatial distribution pattern and spatial association of individuals in different growth stages, so as to further understand the intrinsic mechanism of the P. yunnanensis population structure and distribution pattern and its formation from the view point of spatial pattern.

Method This study is based on data from sampling plots of P. yunnanensis natural population in Tianchi Nature Reserve of Yunlong County, Yunnan Province. The method of substituting space for time and Ripley's L function (based on the derivatives of Ripley's K function) was used to analyze the structure, spatial distribution patterns and spatial association at different growth stages under different scales of a P. yunnanensis natural forest population.

Result The results showed that the DBH class and height class structure of P. yunnanensis natural population were complete, presented an invert J shape. With the scale increased, the distribution of P. yunnanensis natural population presented an "aggregate-random" type. At juvenile and small tree stages, the spatial distribution pattern presented an aggregate distribution at large scales, transformed into a random distribution with the scale increased. At medium tree stage, the spatial distribution pattern presented an aggregate distribution. To the stage of large tree, the spatial distribution pattern presented a random distribution. The different growth stages of P. yunnanensis natural population was significantly positively correlated at all scales.

Conclusion The structure of P. yunnanensis natural population belonged to a increasing type. P. yunnanensis natural population at different growth stages presents different distribution pattern, indicating a strong spatial dynamic characteristic. The positive relationship between the growth stages of P. yunnanensis natural population has the advantage for population maintenance.