SPATIAL DISTRIBUTION PATTERN OF PINUS TABULAEFORMIS CARR. POPULATION ON THE LOESS PLEATEAU, CHINA

Spatial pattern analysis is an important method to research population biological characteristics, interactions among populations and relationships between population and environment. In this study, two 1-hectare permanent sample plots were established within a natural, secondary P. tabulaeformis forest in the Huanglong Mountain region to investigate the spatial distribution patterns of individuals at different growth stages, and the spatial relationships among individuals. Results showed that (1) the diameter structure of P. tabulaeformis was complete and the plants were distributed each diameter class in the two plots, individuals in Plot I were mainly concentrated at saplings and small trees, fewer number of middle and large trees, belonging to growing population; the individuals in Plot II were mainly concentrated at small and middle trees, fewer number of saplings and large trees, the stable population. (2) The distribution pattern of each growth stage and the spatial scale were closely related, saplings and small trees express as aggregated distribution at small scales, and the aggregated intensity is higher in plot I, with the scales increased, individuals tend to be randomly distributed, middle and large trees show random distribution. (3) In terms of the correlation between individuals at different growth stages, there is a significantly positive correlation between saplings and small trees, and saplings and middle trees at small and medium scales, and no significant correlation at large scales; the saplings and large trees are negatively correlated at some scales; there is no significant correlation between small trees and large trees, and between middle trees and large trees.