Abstract: [Objective]By clarification of compositional and structural traits of 3 forest types in Liangshui National Nature Reserve, this paper was aimed to provide suggestions for the scientific management and forest conservation for whole Xiaoxing'anling Mountains.[Method]Three typical forest types (conifer, broadleaf and conifer-broadleaf forests) distributed inLiangshui National Nature Reserve (the core region in Xiaoxing'anling Mt.) were surveyed in 80 plots (30 m×30 m for arbor layer), 160 plots of 5 m×5 m for shrub layer, and 160 plots of 1 m×1 m for herb layer; Plant sizes and community traits(height of tree, shrub and herb, diameter at breast height for trees, shrub diameter, under branch height of tree, crown breadth, tree canopy density and shrub coverage, herb species abundance, and density of tree, shrub and herbs), and compositional traits(species name, genus and family) were recorded in details and diversity indices (Shannon-Wiener and Simpson index),evenness indices (Alatalo and Pielou index), richness index (R) were calculated thereafter. Analysis of variance and redundancy analysis (RDA) were used to explore the differences and coupling relationships in different forest types.[Result]1) Totally, 28-30 tree species, 22-25 shrub speciesand 78-90 herb species were observed in 3 different forest types; The most abundant broadleaf species was Betula platyphylla, while the conifer was Larix gmelinii; The most frequent shrub species was Corylus mandshurica and the most-observed herbs were Aegopodium alpestre and Filipendula palmate. 2) In the 3 forest types, the highest species evenness was in the broadleaf forest, and the highest richness index and diversity index were respectively observed in the conifer forest and the conifer-broadleaf mixed forest. The diversity and richness indices in the same forest showed that the herb layer > tree layer > shrub layer, and 3 forest types showed the similar pattern. The evenness of shrub layer was higher than that in other layers in general. 3) Tree height andunderbranch height ofthe coniferforest was higher than those of the conifer-broadleafmixed forest, and followed by the broadleaf forest. Tree height and DBH (diameter at breast height) in this region averaged at about 14 and 18 cm, respectively. Shrub crown of the conifer-broadleaf mixed forests was larger than the broad-leaved forest, and the lowest was in the conifer forest. Species abundance and coverage of the herb layer of the conifer forest was significantly higher than that of conifer-broad leaf mixed forest. 4) RDA ordination of the broadleaf forest and conifer forest showed that herb layer could explain much more diversity's variation than did in arbor and shrub layers, while the conifer-broadleaf mixed forest's diversity variation was mainly explained by arbor and shrub layers (rather than herb layer). Of them, herb's abundance, density and height could explain 48.4%-62.1% of the diversity variation in the broadleaf forest, and the conifer forest's explaining percentage was 30.5%-44.3%. In the conifer-broadleaf forest, the variation explained by different forest types from high to low was shrub diameter, tree under-branch height, herb height and DBH, and pooled data showed that arbor and shrub layer structural traits could explain 38.8%-4.1% and 27.4%-50.7% of the total variation.[Conclusion]Our results indicate that Liangshui National Nature Reserve had rather abundant plant resources, and dominant arbor species were pioneer species of birch and larch (afforested species), and they are still rather young and long-term protection are needed to ensure development of high-quality forest resources. Herb layer had much higher plant diversity than those from arbor and shrub layers, and more attention should be paid to herb species conservation in the biodiversity protection practices. Plant species conservation and timber resource rehabilitation could be co-improved, while different forests should take different measures; For example, conifer-broadleaf mixed forest should prefer to manage tree under branch height and shrub density, while broad forest and conifer forest should change herb density etc. or other measures to improve herb's growth environment. Our findings provide the basic data support for the Natural Forest Protection Program and administration of National Nature Reserve in NE China.

Key words: arbor-shrub-herb layer, species diversity, evenness, richness, stand structure difference, coupling relationship, redundancy analysis (RDA), Xiaoxing' anling Mts