Abstract: By using TWINSPAN, the 23 sampling plots of spruce-fir forests in Changbai Mountains were divided into eight community types, and, taking this division as one-dimensional resource state, the niche characteristics of 12 main trees, 13 main shrubs, and 18 main herbs in the spruce-fir forest communities were analyzed by using Levins and Hurlbert formulae of niche breadth and Pianka formula of niche overlap. In tree layer, Abies nephrolepis and Picea jezoensis had the biggest niche breadth, and were the main constructive species of the forest communities in this region. In shrub layer, Euonymus pauciflorus and Acer ssp. had larger niche breadth than other species. In herb layer, Dryopteris crassirhizoma, Oxalis acetosella,and Maianthemum bifolium had higher niche breadth, showing that these species widely distributed under the dense canopy of the forests, and had strong capability to adapt to the environment. The populations with larger niche breadth could produce smaller niche overlap, while those with smaller niche breadth would have larger niche overlap, mainly depending on the biological characteristics of plant species and their demands for environmental resources. From the viewpoint of the distribution pattern of niche overlap, there generally existed niche overlaps among main populations, but the niche overlaps were mostly at low level, indicating that the interspecific competition generated by utilizing same resources or occupying specific resources was not intense, and the environmental resources could be sufficiently shared by different populations. The spruce-fir forest communities in Changbai Mountains were at relatively stable stage.

Key words: Yangtze estuary, Suspended silt, Brachionus plicatilis