Effects of Anthropogenic Disturbance on the Structure, Competition, and Succession of Abies ziyuanensis Communities

Attention to habitat dynamics in subtropical mid-mountain forest plant communities containing endangered vegetation is critical for understanding the responses of ecosystems to global climate change and for their effective conservation. This study examines the species composition, structure, and interspecies competition within endemic and endangered Abies ziyuanensis (Abies ziyuanensis L.K.Fu and S.L.Mo) communities in China, comparing undisturbed and anthropogenically disturbed conditions. The survey recorded a total of 71 plant species across 39 families and 60 genera. PERMANOVA analysis highlighted significant disparities in species composition between the two forest community conditions. Communities impacted by anthropogenic disturbances showed a higher diversity of shrub and herbaceous species compared to those that were undisturbed, coupled with a significant increase in the number of Abies ziyuanensis seedlings, suggesting a greater potential for self-renewal. Nonetheless, the distribution of diameter class structures in these two community conditions indicates a declining trend in population numbers. In undisturbed Abies ziyuanensis communities, the Weighted Hegyi Competition Index (WCI) for Abies ziyuanensis was 6.04, below the average WCI of 12.24 for all trees within these communities. In contrast, within communities affected by anthropogenic disturbances, the WCI for Abies ziyuanensis reached 7.76, higher than the average WCI of 7.43 for all trees, indicating that Abies ziyuanensis in disturbed communities face heightened competitive pressure compared to undisturbed settings. These findings underscore that previous anthropogenic disturbances have altered the community composition, competition dynamics, growth environment, and succession trends of Abies ziyuanensis communities. While these disturbances promote the regeneration of Abies ziyuanensis, they also reduce its current dominance as a target species.