Abstract
Spatial distribution patterns of trees are important keys to understanding forest structure and for proposing forest management solutions. Management of rainforests in Vietnam is constrained by a shortage of spatial forest data. Therefore, research was conducted in an upland secondary forest in Tuyen Quang, Vietnam to assess spatial distributions of species and quality levels, and associations between them. Tree diameter, height, coordinates and quality (good, medium and bad) were recorded in three one-hectare plots. Tree density ranged from 920–1050 trees ha-1, and there were 61–69 species ha-1. The highest percentages of good and bad trees were 25.1 and 42.9%, respectively. The habitat was determined as heterogeneous to homogeneous. The spatial distribution of all species and ecological important species was mostly random and clustered. Associations among ecological important species was mainly independent. Tree qualities were randomly distributed, but bad trees were more abundant in the understorey. Associations between tree qualities were mostly independent. The results on spatial distribution patterns and associations between species and qualities will be useful in helping to eliminate competition of trees in clusters, assist regeneration in gaps and determine options for reducing the frequency of bad trees in the future.
