Abstract: The height niche of trees reflects the complementarity of resource utilization of different tree species in varied height grade in the forest ecosystem, and is also one of the main characteristics of forest succession and cycle. The height niche overlaps are greater between those species that have similar biological and ecological characteristics, and vice versa. In gaps, the height niche overlaps between Acer mono and A.triflorum are the biggest, and comparatively small between A. tegmentosum and Carpinus cordata, A.ukurunduense and Fraxinus mandshurica, and A.tegmentosum and Ulmus laciniata. While in non gaps, the height niche overlaps between A. tegmentosum and A.mandshurica are the biggest, and comparatively small between A.tegmentosum and U.laciniata, A.tegmentosum and C.cordata, and A. ukurunduense and F.mandshurica . The height niche overlaps between Korean pine and most broad leaved trees are comparatively small, which means that, to some extent, Korean pine and most broad leaved trees are compensatory in their utilization of space and ecological resources, which may be one of the mechanisms by which they could coexist persistently. The height niche overlaps between Korean pine and most broad leaved trees in gaps are bigger than in non gaps, showing an evident that the species competition between Korean pine and most broad leave trees are increased by gaps, and that the compensating ability of resources between them are reduced by gaps. Species competition due to the large height niche overlaps is reduced by gaps, while that due to the small height niche overlaps is increased by them.

Key words: Height niche, Gap, Korean pine broad leaved forest, Changbai Mountain, paper bag, grape berries, volatile constituent