Abstract: Aims The rough bark provides essential physical support for vascular epiphytic plants while also creating diverse microhabitats that enhance species diversity. Methods Vascular epiphyte diversity and spore colonization were studied in 21 20m×20m plots in the Bawangling area of Hainan Tropical Rainforest National Park, examining the effects of host tree bark roughness and diameter at breast height，the effects of bark roughness of host tree on the diversity and spore colonization of epiphytic vascular plants were studied. Important findings From sampling to adult trees, bark roughness of host trees significantly increased at different growth stages. Bark roughness significantly influenced the richness and abundance of vascular epiphytes, explaining 79.4% and 81.9% of the variance, respectively. The host tree growth stage had minimal effect on vascular epiphyte diversity, with a near-zero explained variance. However, the interaction between bark roughness and host tree growth stage explained 4% and 5.6% of the variance in epiphyte richness and abundance, respectively, suggesting that the host tree growth stage affects epiphytic plant diversity via bark roughness. Host bark roughness also significantly impacts the colonization of vascular epiphytic spores; greater roughness provides a more suitable microenvironment, significantly increasing spore attachment. In summary, rough bark provides physical support and diverse microhabitats, enhancing species diversity.

Key words: Roughness, Vascular epiphyte, Host tree, Growth stage, Diversity, Colonization