Interspecific Relationships among the Herbage Species of Abandoned Farmlands alongside Jinshui River in the Qinling Mountains

Based on the field data collected from 51 plots on abandoned farmlands alongside Jinshui River in the Qinling Mountains,the interspecific relationships among the 40 main herbage species were studied using Fisher's exact test for 2×2 contingency tables,Pearson's correlation coefficient and Spearman's rank correlation coefficient test,coupled with DCA ordination.According to Spearman's rank correlation coefficient,90 species-pairs had significant(p0.05 or p0.01) correlation,including 9 negative correlation species-pairs and 81 positive correlation species-pairs,accounting for 1.15%,10.38% in the total 780 species-pairs,respectively.In the Pearson's correlation coefficient test,the number of species-pairs being significantly positive was 55 while the negative was 2.In addition,positive association coefficients of 28 species-pairs and negative association coefficients of 5 species-pairs for the Fisher's exact test were significant.Forty species were classified into three ecological species groups in the ordination space representing different succession stages,and the variation in species along the first DCA axis represented the species turnover along the succession and environment gradient.The species-pairs with the similar environment and resources requirement tended to display positive correlation,while the negative correlation species-pairs always occurred in different succession stages.