Numerical analysis on interspecific relationships in Davidia involucrata community in Sanjiang Wolong Nature Reserve

Employing Fisher's precise test for 2×2 contingency table,Pearson's correlation coefficient and Spearman's rank correlation coefficient,this paper studied the 3 403 species-pairs' interspecific relationships of 83 species in D.involucrata community in Sanjiang Wolong Nature Reserve.The results showed that through Fisher's precise test for 2×2 contingency table,the positive association coefficients of 186 species-pairs were either significant(P0.05) or highly significant(P0.01),and the negative association coefficients of other 100 species-pairs were significant or highly significant.The positive correlation coefficients of 295 and 448 species-pairs were significant or highly significant by using Pearson's correlation coefficient and Spearman's rank correlation coefficient,respectively,while 129 and 244 species-pairs had significant or highly significant negative correlation coefficients by using the same tests.Because Fisher's precise test for 2×2 contingency table could not numerically reflect the contrasting correlation between species,Pearson's correlation coefficient and Spearman's rank correlation coefficient were applied to test the interspecific relationships.Compared with Pearson's correlation coefficient,Spearman's rank correlation coefficient test was more sensitive.Positive association and correlation between species occurred where the members of species-pairs had similar biological characteristics or traits,which made them ecologically adaptive for similar habitats but with segregated niches,while negative association and correlation between species occurred where species had different biological features,which made them differently adaptive for habitats or with overlapping niches.