Interspecific association of the main tree populations of the Quercus acutissima community in the Qiaoshan forest area

Through adaptation of the variance ratio (VR) method and the χ~2 test,the association coefficient (AC), percentage co-occurrence coefficient (PC) and point correlation coefficients (Ф), which are all based on 2×2 contingency tables, were analyzed for the 17 most important tree populations of the Quercus acutissima community in the Qiaoshan forest area. The results showed no significant negative correlations among these 17 tree populations, as the species tended to be distributed independently and the community was unstable. The χ~2 test results showed that among the 136 species pairs of the 17 dominant populations, 44.85% had a positive association and 55.15% had a negative one,and the vast majority of these associations was not significant. This indicated that the association among the tree populations was weak, and the community was in an unstable succession stage. Analysis of the AC and PC results revealed that the 17 main populations had different habitat demands, and the probability of simultaneous emergence of each species pair was small. The Ф measurement results showed that 62 (45.59%) species pairs had a positive association and 74 (54.41%) species pairs had a negative association. Based on the cluster analysis and interspecific association results, the habitats of the 17 main populations were divided into three ecological groups.