Abstract: The Yinshan Mountains delineate the northwestern boundary of natural Platycladus orientalis (L.) Franco forest distribution in China, characterized by harsh site conditions and low ecological stability. This study investigated 22 dominant species within these forest communities using a comprehensive suite of analytical methods, including Levins’ niche breadth index, Pianka’s niche overlap index, variance ratio, χ² test, Pearson correlation analysis, Spearman rank correlation analysis, M. Gordon’s stability assessment, and redundancy analysis (RDA), to quantify niche characteristics, interspecific associations, and environmental determinants of community structure. Based on floristic clustering and environmental correlations, dominant species were grouped into ecologically meaningful assemblages. A total of 105 species (including infraspecific taxa) belonging to 70 genera and 32 families were recorded under the APG Ⅳ classification. Among these, P. orientalis, Aster altaicus Willd., and Setaria viridis (L.) P. Beauv. exhibited relatively high niche breadth. Dominant species showed low niche overlap, indicating spatial segregation and weak co-occurrence. Interspecific relationships within the natural P. orientalis community were predominantly negative, indicating limited ecological integration among co-occurring species. Results from χ², Pearson, and Spearman correlation analyses consistently demonstrated that negative associations outnumbered positive ones, with the majority of species pairs showing no statistically significant relationship. Stability analysis further confirmed an ecologically unstable community state. These findings underscore the fragility of natural P. orientalis forests in the Yinshan Mountains and provide a theoretical basis for selecting appropriate species in future restoration efforts.