Abstract: Exploring the relationships of niche characteristics and species diversity of shrub layer with the spatial distribution pattern of the stands is important for better understanding understory community structure and quantitative distribution of Quercus wutaishanica secondary forests. In this study, we used the investigation data of shrub communities collected from 110 quadrats in 22 plots of Quercus wutaishanica secondary forest in Qiaoshan forest area. The variance ratio test (VR), χ² test, association coefficient (AC) and Spearman’s rank correlation coefficient test were used for analyzing the association and correlation of 28 main species. One-way analysis of variance was used to reveal the difference of niche and diversity characteristics in shrub layer community under different spatial distribution patterns. Our results showed that the niche overlap of main species in shrub layer was generally low, and that the interspecific competition was not strong. The species with larger importance values and niche breadth were Celastrus orbiculatus, Lespedeza chinensis, and Viburnum schensianum. The main species in the shrub layer showed a significant positive association (P<0.05), the positive/negative association ratios of the χ² test, AC, and the Spearman’s rank correlation coefficient test were 1.12, 1.17, and 1.37, respectively. Community structure tended to be stable. The significance rates of positive and negative associations by χ² test were 5.8% and 0.6%, respectively, while the significance rates of positive and negative associations by Spearman’s rank correlation test were 28.0% and 6.3%, respectively. The degree of association between species pairs was small, and tended to be distributed independently. The niche breadth of the shrub layer was not significantly affected by the spatial distribution pattern, while the niche overlap showed significant differences among different spatial distribution patterns. Margalef richness index, Shannon index and Pielou evenness index of the randomly distributed stands were significantly different from those of the stands with uniform and aggregated distribution (P<0.05). The niche characteristics and species diversity level of shrub community were the best for the randomly distributed stands. In forest management, it is necessary to adjust the shrub species configuration while taking into account the spatial distribution pattern of stands, which would facilitate random distribution and improve the stability of forest ecosystems.

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