[Interspecific association and functional group classification of the dominant populations in shrub layer in secondary forest of Pinus tabuliformis in Qinling Mountain, China.].

We analyzed the interspecific association among 20 dominant populations in shrub layer in secondary natural forest of Pinus tabuliformis in Qinling Mountain, China, with X-test, the association coefficients and the percentage of common occurrence. The results showed that the species pairs with significant positive associations accounted for only 7.4% of the total 190 species pairs. The species pairs such as Lespedeza bicolor and Elaeagnus pungens, Toxicodendron vernicifluum and Pinus tabuliformis, Euonymus alatus and Cerasus tomentosa had extremely significant positive correlations, whereas most of the species pairs showed weak interspecific association. The ratio of positive and negative correlations was less than 1. The results suggested that the interspecific association was relatively weak. Species were with certain independence among dominant populations. Community structure was at an unstable mid-stage with dynamic succession. According to the interspecific association and cluster analysis, combined with biological and ecological characters, the 20 dominant populations in shrub layer were classified into four functional groups. The ecological requirement and resource use pattern of species within the same functional groups were similar, exhibiting a close connection between the shrub species. The connection between different functional groups was relatively loose.