摘要：Coniferous and broad-leaf mixed forest is an important vegetation formation and has a large distribution area in Huanglong Mountain Nature Reserve, Shaanxi Province, China. The spatial patterns of dominant woody species give important clues about the underlying processes driving regeneration and succession of the forest. In this paper, the trees of a forest were mapped, characterized and the spatial distribution patterns and spatial associations of dominant woody species (Pinus tabulaeformis Carr., Quercus wutaishanica Mayr., Acer ginnala Maxim. and Populus davidiana Dode) were analyzed using O-ring univariate O(r) and bivariate O_(12)(r) statistics. We found that: (1) there are 28 species of trees which DBH is greater than 1 cm, the species are rich and the density of trees is larger. The stand diameter distribution appears an inverted "J" curve and the tree height distribution is similar to normal distribution. (2) P. tabulaeformis, A. ginnala and P. davidiana population show aggregative distribution on a small scale of 0-5m, and the aggregation intensity decreased with scale increase, and behaves randomly at other scales. The spatial patterns of Q. wutaishanica population are aggregative distribution from 0 to 44 m. Meanwhile the distribution patterns get more and more aggregative as its density increased, and the degree of aggregation decreases with the increasing of scales. (3) P. tabulaeformis and Q. wutaishanica, P.tabulaeformis and P. davidiana, Q. wutaishanica and P. davidiana show positive correlation at medium and small scales, while A. ginnala shows negative correlation with other species at some scales.
