Unraveling radial growth patterns in tropical karst forests: A seasonal perspective

Radial growth, a key indicator of forest carbon sequestration, exhibits strong seasonal dynamics. However, tropical karst forests remain poorly understood, largely due to their complex topography, shallow soils, and high diversity. This study investigated seasonal radial growth patterns in a northern tropical karst seasonal rainforest in southern China by monitoring 348 trees (30 species) over five years. We analyzed correlations between annual and seasonal growth, compared wet- and dry-season growth, and examined interspecific differences. Environmental drivers (climate, topography, soil, and community factors) were assessed through multivariate analyses and mixed-effects modeling. We found that annual growth significantly correlated with both wet- and dry-season growth ( p < 0.001), with wet-season growth significantly higher ( p < 0.001). However, some trees exhibited enhanced dry-season growth, exceeding 36 % across all habitats and 47 % in depressions, highlighting dual-season importance and high carbon sink potential. Despite high species richness, few significant interspecific differences emerged within seasons. This suggests that carbon sequestration relative variation can be reliably assessed with minimal species sampling, providing a critical insight for managing species-rich forests. Climate variables (temperature, precipitation) were key predictors across seasons, with lagged effects from prior conditions. Notably, community factors (gap area, vertical structure diversity) dominated in the dry season, surpassing climatic influences and buffering environmental fluctuations. These findings highlight the importance of integrating seasonal dynamics, climatic legacies, and community processes into forest management. Such integration can improve carbon sequestration assessments in tropical karst regions under environmental change. • Both wet and dry seasons drive radial growth, with wet season dominance. • Wet season growth exceeds dry season, yet some trees surge in dry season. • Minimal species sampling suffices for carbon sequestration relative variation assessment in species-rich forests. • Community factors rival climate on growth in wet season, dominate in dry season. • Community structure can buffer climate impacts on forests.