Soil phosphorus availability drives decade-scale stability across life stages in a subtropical forest

The potential of tree diversity to stabilize community productivity is well established. However, how different forms of soil nutrients regulate tree diversity and stability across life stages remains unclear. Using high-resolution soil nutrient mapping and inventory data from a subtropical forest in southern China, we examined how different forms of soil nitrogen (N) and phosphorus (P) regulate tree diversity and stability across seedling and adult stages. Tree diversity was consistently associated with greater stability, with both seedling richness and adult evenness driving stability, respectively. Inorganic P alleviated interspecific competition, and enhanced seedling richness and stability, but suppressed adult asynchrony and stability. Conversely, organic P was consistently associated with reduced diversity and stability across both stages, coupled with strengthened interspecific competition. Inorganic and organic N exhibited comparatively weaker influences on diversity and stability. These findings highlight the importance of considering tree life stage and soil P form in managing and conserving forest ecosystems.