Abstract: We explored the effects of disturbance densities on the spatial pattern and the association of tree species in the coniferous broadleaved mixed forest in Pangquangou Nature Reserve of Guandi Mountain. Using three factors including canopy density, stand density and number of stumps, we classified the disturbance intensities of different forest stands into three levels, non-disturbance, moderate disturbance, and severe disturbance. The spatial distribution pattern and the association of different tree species were analyzed by spatial point pattern K2 function. The results showed that the diameter distribution of trees in undisturbed plots was inverted ‘J' type, while that of moderate disturbance and serious disturbance plots was under bimodal curve distribution. The stand distribution pattern showed a small-scale aggregated distribution under undisturbed and moderately distur-bance, and a random distribution under heavy disturbance. At the small scale, the coniferous and broadleaved species showed no correlation in undisturbed stands, were positively correlated in moderately disturbed stands, and negatively correlated in seriously disturbed stands. At large scale, they were no correlated in both moderately and seriously disturbed stands. The results suggested that abundance of trees with small diameter in the forests was negatively with disturbance intensity, which led to the lower degree of intraspecific aggregation at small scale. Meanwhile, appropriate levels of disturbance would benefit the collaborative use of environmental resources for trees. Our results revealed the impacts of disturbance density on forest community structure and could provide theoretical basis for forest management.

Key words: disturbance, spatial pattern, interspecific association, diameter structure, K2 function