Abstract: This paper studied the quantitative characteristics of main tree species along a forest gap gradient (gap center-near gap center-gap border) of mixed broadleaved Korean pine forest in Xiaoxing’an Mountains, as well as the effects of forest gap size on the regeneration of the tree species. In forest gap, the density of shrub species was obviously larger than that in non-gap, and the density ratio of the same shrub species in forest gap to in non-gap ranged from 1.08 to 18.15. With the increase of gap size, the regeneration density of tree seedlings increased, and that of saplingⅠ(H≥1 m, DBH≤2 cm) and saplingⅡ(H≥1 m, 2 cm＜DBH≤5 cm) exhibited multiple peak curve. The overall regeneration density of shrubs in forest gaps varied mainly with the amounts of tree seedlings and saplingⅠ. The mean height, mean basal diameter, species density, and individual density of trees in different locations of forest gaps were all different. From gap center to non-gap, the importance value of tree species seedlings in regeneration layer was ranked in gap center > near gap center > gap border > non-gap, the tree species evenness presented a variation of high-low-high, and the species diversity decreased in the order of early phase gap > mid phase gap > late phase gap.

Key words: Xiaoxing’an Mountains, mixed broadleaved Korean pine forest, forest gap, regeneration, gap gradient