Abstract: The niche theory is widely used to explain the interspecific coexistence andcompetition mechanisms in the communities, which is of significance for understanding the coupling between plant community assembly and environmental factors. By investigating the herbaceous communities in the understory of mature Chinese fir plantation (Cunninghamia lanceolata), Shannon, Levins niche width indexes, Levins niche overlapping indexes and ecological responding were used to analyze the niche characteristics of the herbaceous plants. The results showed that the niche width of the herbaceous plants in the mature Chinese fir plantation was not high. The niche width index ofB_(SW) (3.6254) and B_(L) (0.7069) were the largest for Woodwardia japonicadue to its wide distribution and strong adaptation to environment. W. japonica and Mussaenda pubescens with large niche width had higher niche overlapping with other dominant species. In general, relatively lower niche overlapping among species were apparent in the herb layer in the understory of Chinese fir plantation, indicating that the ability of species for sharing resources was weak. Our study suggested that most of the dominant species of herbaceous plants were in developing stage due to low niche overlapping, and that Chinese fir plantation community tended to be relatively stable.

Key words: rhizosphere soil, archaeal community, high-throughput sequencing, fine root growth, poplar plantation