Abstract: Based on survey data of a 0.32 hm² plot in Beijing Jiulong Mountain, the spatial structure diversity of a Platycladus orientalis plantation was analyzed using traditional approaches and a bivariate distribution of three structural parameters, i.e., uniform angle index (W), dominance (U) and mingling (M). The community structure was relatively simple. The P. orientalis population was in an obviously dominant position, and in a state of low mingling, insignificant size differentiation and uniform distribution, while other accompanying species were in a state of high mingling and relative disadvantage. The diameter and height distribution of the stand presented as unimodal. 59% of individual trees in the P. orientalis forest were surrounded by the same species, and 22% were surrounded by only one other species among their nearest four neighbors, i.e., the forest was in a state of low mingling. More than half (52%) of the trees in the plot were in a random pattern, in which most trees (57%) were surrounded by the same species, while 50% of the trees in high mixture (mingling=0.75, 1.00) were randomly distributed. The trees of different extents of dominance had a similar frequency, but the number of dominant trees was slightly more than that of nondominants, and most of the dominant trees were in a state of low mingling and random pattern. The spatial diversity in the P. orientalis plantation resulted from mingling and diameter differentiation. Such a result was not only closely related to the development stage of community but also connected to its origin, anthropogenic disturbance and species composition.

Key words: deltamethrin, tissue damage, DNA damage, Pagrosomus major, comet assay