LAUSR

In order to achieve of the spatial association and optimum collocation, a 1-ha natural spruce-fir mixed forest plot which was established on Changbai Mountains, PR China. Diameter at breast height, height, and the crown width of the standing free trees with >1 cm DBH trees were measured, and species were identified. O-ring statistics and the nearest neighbor analysis were applied to test the spatial correlations and distribution of number of dominant species at different vertical layers. We found that: (1) according to the importance values, the top four species were Abies nephrolepis (Trautv.) Maxim., Picea koraiensis Nakai, Pinus. koraiensis Sieb. et Zucc. and Tilia. amurensis Rupr.; (2) most of species pairs have positive associations at small scales, while few are no relevance or have negative associations; (3) the number of juveniles and lower layer trees showed positive skewness under the upper layer trees and the maximum number for coniferous species was at a distance 4.5-6.5 m, while it was 6.5-8.5 m for broadleaved species. Our results provide a new insight into the development of reforestation technique in spruce-fir forests in the Changbai Mountains.