Interspecific correlations among dominant populations of ligneous species in Mianshan Mountain of Shanxi

The study on the interspecific correlations among 210 species-pairs of 21 dominant populations of ligneous species showed that 109,87 and 99 species-pairs were positively correlated,while 101,122 and 111 species-pairs had negative correlations,and the ratios of positive and negative correlations were 1.08,0.71 and 0.89,based on χ~2-test for 2×2 contingency table,Pearson correlation coefficient test,and Spearman rank correlation coefficient test,respectively.According to the adaptability to the environment and the relationships between plants and environment,21 species were divided into two ecological species groups,i.e.,light-favoring and shade-tolerant plants.Compared with Pearson correlation coefficient test,Spearman rank correlation coefficient test was more sensitive.A positive association and correlation occurred between the species having similar biological traits,e.g.,the ecological adaptability to similar habitats and the overlapping niches in some degree,while the negative association and correlation occurred between the species having different biological features,e.g.,different adaptability to habits or segregated niches in some degree.