Abstract: Bark is composed of all tissues outside vascular cambium, the functional characteristics of which reflect important ecological adaptation strategies of plants. To reveal the differences in bark thickness of common tree species in the karst seasonal rainforest among different taxonomic groups and functional groups, as well as the impacts of biological and environmental factors, 128 common tree species with an abundance greater than 20 in a 15 hm² permanent monitoring plot of Nonggang were analyzed. The differences in bark thickness between different taxa and functional groups, as well as the impacts of biological and environmental factors on bark thickness were quantified. The results showed that the average total bark thickness, outer bark thickness, and inner bark thickness of the 128 tree species were 2.95, 0.70, and 2.26 mm, respectively. The bark of trees from Linaceae, Bignoniaceae, and Icacinaceae families was relatively thicker. The thickness of bark showed significant differences among different taxa and functional groups, with inner bark thickness > outer bark thickness. Among different functional groups, bark thickness was in order of: deciduous species > evergreen species (excluding outer bark thickness), and tree species > small tree species > shrub species. The phylogenetic signal for bark thickness was relatively weak, so bark thickness was primarily influenced by habitat factors. Among various biological factors affecting bark thickness, species identity had the highest explanatory power. Additionally, bark thickness variation was driven by topographical and soil factors, with similar patterns across different locations. Total bark thickness correlated with stand factors and environmental factors. In summary, bark thickness of tree species in the karst seasonal rainforest community in Nonggang is relatively thin, with significant variation among different tree species and functional groups. This indicates the adaptability of these tree species to the local humid climate. The explanation of bark thickness by environmental factors reveals the strategies employed by tree species to adapt to different environmental conditions and ecological niches by adjusting their bark thickness.

Key words: total thickness of bark, inner bark thickness, outer bark thickness, seasonal rainforest, niche differentiation, environmental factor