Interspecific Association among Understory Species of the Low-efficiency Plantation in the Jiufeng National Forest Park

Interspecific relationship can reflect the structure and function of plant community,the type and stage of succession and the degree of community stability. It is of great significance for biodiversity conservation and vegetation restoration. In order to clarify the interspecific relationship of understory species in Jiufeng National Forest Park during restoration period,the experiment was conducted based on the 2 × 2 table to analyze the interspecific associations among the main species with high frequency by χ2-test,association coefficient( AC)and Spearman's rank correlation coefficient test. In shrub layer,11 species pairs showed significant( P 0. 05)or highly significant( P 0. 01) association in χ2-test,while 23 species pairs in Spearman's rank correlation coefficient test. In herb layer,15 species pairs showed significant( P 0. 05) or highly significant( P 0. 01)association in χ2-test,while 27 species pairs in Spearman's rank correlation coefficient test. For majority of the species pairs in two layers,their interspecific association did not reach significant level. In shrub layer,there was roughly an equal amount of the species pairs with positive association and those with negative association. In herb layer, the ratio of species pairs having positive association to those having negative association approximately was 1 ∶ 2. The species compositions of the two layers were fluctuating. The understory species interactions resulted from many factors including the effects of upper tree,the community succession process,species ecological characteristics and environmental conditions. By principal components analysis,the main species in herb layer and shrub layer were divided into four ecological species groups separately.