Comparative study on the community characteristics and population dynamics of Bruguiera sexangula (Lour.) Poiret at different intertidal elevations in Dongzhaigang National Nature Reserve

Understanding how intertidal elevation influences the community characteristics and population dynamics of Bruguiera sexangula (Lour.) Poiret is essential for the effective conservation and sustainable management of mangrove ecosystems. This study investigated variations in community characteristics, age structure, spatial distribution pattern, static life-table parameters, and survival functions of B. sexangula along an intertidal gradient in the Hainan Dongzhaigang National Nature Reserve. Results showed the following key findings: (1) B. sexangula was the dominant species in the community. Species diversity, Pielou index, and stand density increased with increasing intertidal elevation, while the importance value, diameter at breast height, tree height, and crown width of B. sexangula decreased. (2) The spatial distribution pattern of B. sexangula exhibited significant clumping. The diameter distribution exhibited a convex-shaped pattern at low intertidal elevations and an inverted J-shaped pattern at both mid and high intertidal elevations. (3) Survival curves varied with intertidal elevation. Low intertidal zones exhibited a Deevey Type Ⅱ curve, while mid and high intertidal elevations showed Deevey Type Ⅲ curves. (4) The equilibrium points of survival and cumulative mortality functions occurred during the seedling stage across all intertidal elevations, and the magnitude of changes in the survival function curves at each intertidal elevation decreased after age Ⅴ. These findings demonstrate that intertidal elevation strongly affects the community characteristics and population dynamics of B. sexangula. This study provides critical baseline data for the protection and optimized management of mangrove ecosystems, particularly in regions experiencing dynamic intertidal changes.