Abstract: The niche characteristics and interspecific associations are of great significance for understanding the structure and classification of plant communities, as well as judging community stability and development trends. The Levins (B_L) and Shannon (B_S) niche breadth indices and Pianka’s niche overlap index (O_ik) were estimated for 22 dominant wild herbaceous medicinal plant species in Huguan County, Changzhi City, Shanxi Province. Those indices were used to analyze their niche characteristics. Based on a 2×2 contingency table, methods such as interspecific association coefficient (AC), Jaccard index (JD), Ochiai index (OI), χ² test, Pearson correlation coefficient test were used to analyze the interspecific association of those species. The results showed that: (1) Among the 22 species, Sanguisorba officinalis had highest B_L index at 63.369, followed by Artemisia stechmanniana at 58.276, with Astragalus membranaceus having lowest B_L at 2.489. Sanguisorba officinalis also had highest B_S at 4.290, followed by Adenophora stricta at 4.247, with Astragalus membranaceus having lowest B_S at 1.097. Maximum O_ik was shared between Cirsium arvense var. integrifolium and Chrysanthemum lavandulifolium (0.562), followed by Artemisia stechmanniana and Siphonostegia chinensis (0.534). Minimum overlap was zero, which occurred in 112 species pairs, indicating low overall degree of niche overlap among herbaceous medicinal plant species, less intense interspecies competition, and highly dispersed distributions of herbal medicinal plant species. (2) For AC values, 77 out of the 231 species pairs were positive association pairs, with 11 pairs being strongly positively associated. There were 154 negative association pairs, with 116 of them being strongly negatively associated. The χ² test showed that there were 77 positively associated species pairs, of which 24 were very significantly positively associated; and 154 negatively associated species pairs, of which 7 were very significantly negatively associated. In terms of Pearson correlation coefficients, there were 56 positively associated species pairs, of which 17 were extremely significantly positively associated, and 175 negatively associated species pairs, of which 8 were extremely significantly negatively associated. (3) By considering AC coefficient, JD index, OI index, χ² test and Pearson correlation coefficient, there were more negatively associated species pairs than positively associated species pairs for the 22 medicinal plant species in Huguan County. The number of species pairs with no significant association was more than the number of species pairs with significant association, which indicates low similarity among species pairs of herb medicinal plants thus revealing independent distribution characteristics making them susceptible external disturbances. Overall, Huguan County is rich in wild herbal medicinal plant resources. The species distributed rather randomly, with weak interspecific competition and strong species independence. The community structure can be unstable due to external disturbances. Our results will provide an important basis for understanding the distribution patterns of local medicinal plants, as well as for sustainable use and development.

Key words: medicinal plant, importance value, niche breadth, niche overlap, interspecific association