Competition and synergistic mechanisms of species in association based on niche theory.

We examined the niche characteristics and interspecific covariant relationship of main species in association in Chishui National Nature Reserve under disturbance condition, and analyzed the mechanism of competition and coexistence across different species. The results showed that there were 67 species from 53 genera and 40 families in the association. The importance values, Shannon niche breadth index (), and Levins niche breadth index () of were the largest, indicating its absolute dominant status in association. The importance value and of . ranked the second, while was the third. There were 190 pairs of 20 main species. The niche overlap between and was the largest, with niche overlap value of 0.64. 71.6% of species pairs had niche overlap of less than 0.2, indicating low niche overlap and high degree of niche differentiation among species. The overall association of main species in association was significantly positive, and the community was relatively stable. The correlation among the main species was not significant, the linkage was not strong, and the species were independent from each other. showed significant positive correlation with . , , , and , while showed significant negative correlation with , , and . Niche difference and fitness between and natives affected the coexistence and competition among species. Controlling the expansion of and limiting the size of species with negative correlation with . could create a favorable living environment for . .