Interspecific Relationships and Community Stability in the Evergreen and Semi-Deciduous Forests of Nui Cau–Dau Tieng, Southern Vietnam

Interspecific relationships among plants represent fundamental structural and quantitative attributes that critically influence the formation, organization, and evolutionary dynamics of plant communities. The analysis of these relationships provides essential theoretical foundations and methodological tools for deciphering the mechanisms of community stability and succession, as well as for informing ecological restoration and reconstruction practices. However, the specific mechanisms through which community stability emerges in tropical forest ecosystems remain inadequately elucidated. This study investigated patterns of interspecific association and correlation, as well as community stability, in evergreen and semi-deciduous forests within the Nui Cau-Dau Tieng Protection Forest in southern Vietnam. Using data from 27 systematically surveyed sample plots, each covering 0.1 ha and containing a total of 2475 individual trees, an integrated analytical approach was applied. This approach incorporated the variance ratio method, chi-square tests, Pearson and Spearman correlation analyses, and Godron’s method. The findings revealed a significantly higher proportion of positive interspecific associations in the evergreen forest (68.33% of species pairs) compared to the semi-deciduous forest (46.43%), suggesting that the climax community achieves greater stability through facilitative interactions and niche differentiation. Methodologically, the Spearman correlation detected 55% more significant positive associations than the Pearson correlation, highlighting the prevalence of monotonic non-linear relationships within these forest types. Stability analysis confirmed that both forest types are stable, with the evergreen community demonstrating superior resilience, a trait attributed to its higher species diversity and more complexly interwoven network structure. Together, the consistent evidence derived from interspecific connectivity metrics and the community stability index provides a complementary framework for assessing forest structure. This study provides critical insights into the successional dynamics of tropical forests. Besides, it establishes a robust theoretical foundation for designing effective conservation strategies, sustainable management protocols, and restoration initiatives that enhance biodiversity and the multifunctionality of tropical forests.