Niche, Interspecific Association and Stability of Fagus hayatae Community in Wangcang County, Sichuan Province

Community structure and interspecific relationships are important indicators for evaluating the stability and resource utilization status of plant communities. Fagus hayatae is a rare and endangered tree species in China and a national second-class key protected plant. Its community structure and interspecific relationships are of great significance to the stability of regional forest ecosystems. To reveal the interspecific relationships and community stability of Fagus hayatae communities, 21 sample plots were established in Wangcang County, Guangyuan City, Sichuan Province. Woody plants within the communities were investigated, and the importance values of major species were calculated. The niche breadth and niche overlap of dominant species were analyzed. Meanwhile, interspecific associations were examined using χ² test, association coefficient (AC), Dice index (DI), and Ochiai index (OI), and community stability was evaluated using the M. Godron method. The results showed that Fagus hayatae had the highest importance value (19.61%) and relatively wide niche breadth (B_L=9.67, B_S=2.52), serving as the constructive species of the community. Species pairs with niche overlap index less than 0.5 accounted for 70.48%, indicating obvious resource utilization differentiation among species. Interspecific association analysis showed that significantly associated species pairs accounted for 11.43%, with most species pairs exhibiting non-significant associations and relatively loose interspecific relationships. The overall community association was significantly positive (VR=1.74, W=36.45), and the distance between the intersection point of the M. Godron stability curve and the theoretical stable point was 2.53, indicating that the community was in a stable state. It is recommended to reduce human disturbance on the community and focus on the protection of constructive species such as Fagus hayatae, Fagus engleriana, and Quercus serrata to maintain the stability of community structure.