Abstract: Understanding niche characteristics and interspecific relationships of dominant populations in the shrub layer of forest communities can provide scientific basis for the conservation and management of forest resource. In this study, we characterized the niche of the dominant species of shrub layer in typical forest communities in the western part of the Qinling Mountains by Levins niche breadth, Shannon niche breadth and Levins niche overlap indices. The interspecific relationships were analyzed by using the variance ratio method, χ² test, association coefficient (AC), and Pearson correlation test. The results showed that among 190 species pairs formed by the 20 dominant species in the shrub layer, Lonicera fragrantissima had the largest niche breadth and Corylus heterophylla was the smallest. The mean value of niche overlap was 0.32. Species pairs with small niche overlap were predominated, indicating a high degree of differentiation among the dominant species in the shrub layer, which was conducive to the formation of species diversity. The dominant populations in the shrub layer showed significant positive associations, indicating that forest communities were in a relatively stable stage of late succession. The results of both χ² test and Pearson correlation test showed that the positive and negative association ratios were greater than 1, and the majority of species pairs were non-significant associations, indicating an independent distribution pattern among species. The niche overlap index was positively correlated with the association coefficient (AC) and Pearson correlation coefficient.

Key words: species pair, interspecific relationship, shrub layer, natural forest, western part of the Qinling Mountains