Interspecific Associations of Dominant Tree Species at Different Structural Levels and Community Stability in the Habitat of Endangered Plant <i>Hopea hainanensis</i> Merr. & Chun

The endangered plant <i>Hopea hainanensis</i> serves as both an indicator and keystone species in tropical rainforests, and its survival status is influenced by the interspecific relationships among coexisting tree species within the community. To explore these relationships, species resource utilization patterns, and community succession dynamics within the endangered plant community, this study utilized survey data from the <i>Hopea hainanensis</i> community in the Bawangling and Jianfengling branches of the National Park of Hainan Tropical Rainforest. Various analytical methods were employed, including the Variance Ratio (<i>VR</i>) method, test statistic (<i>W</i>), <i>χ</i>² test, Spearman’s rank correlation, and M. Godron’s stability analysis, to examine the interspecific associations among dominant tree species at different structural levels in the two regions and their effects on community stability. The results indicate that: (1) <i>Hopea hainanensis</i> is the dominant species in the medium tree layer in both study areas, while it functions as an associated species in other structural layers. (2) In communities where <i>Hopea hainanensis</i> is present in both Bawangling and Jianfengling, the dominant tree species across various structural layers generally show a non-significant positive association. (3) The results of the <i>χ</i>² test and Spearman’s rank correlation test reveal that the interspecific associations across different structural layers of the <i>Hopea hainanensis</i> communities in both regions are predominantly non-significant. This suggests weak interspecific relationships and a high degree of species independence. The communities at different structural levels in both Bawangling and Jianfengling are in an unstable state, with ongoing dynamic adjustments to their internal tree species composition and structure. In terms of stability, the community stability across structural levels in these two regions follows the order: middle shrub layer > middle arbor layer > small arbor layer > large shrub layer. This study reveals the interspecific relationships, community succession status, and stability of dominant tree species at different structural levels in slope barrier communities across regions. These findings provide a theoretical basis for developing scientifically sound and reasonable protection strategies for slope barrier populations, as well as for the restoration and sustainable development of tropical rainforest vegetation.