Light-demanding tree species are more susceptible to lianas than shade-tolerant tree species in a subtropical secondary

1. Tree-tree competition has been widely studied as a mechanism responsible for maintaining forest plant species diversity. Other common plant types, such as lianas, may influence tree species competition. Previous studies reported the negative effects of lianas on trees; however, variation in susceptibility to lianas among tree species and the species-specificity of liana species for tree hosts remain unclear. If lianas have species-specific interactions with trees, based either on tree or liana species identity, then lianas may influence tree-tree interactions by altering tree species-specific competitiveness. 2. We surveyed 5676 lianas (DBH >= 0.5 cm) and 61,538 trees (DBH >= 1 cm) in a 12-ha subtropical secondary forest plot to assess liana-tree interactions. We tested variation among the 20 most common tree species in their susceptibility to lianas, including whether light-demanding and shade-tolerant tree species differed. We quantified liana-tree network structure and evaluated the specificity between the 20 most common tree species and the 15 most common liana species. We expected that: (1) tree species would vary in their susceptibility to lianas, and the extent of this variation would be predicted by tree shade-tolerance; and (2) liana species would have distinct species-specific interactions with host trees. 3. Tree species differed greatly in their susceptibility to lianas, with some tree species accumulating many more lianas than others. Light-demanding tree species particularly had greater susceptibility to lianas than shade-tolerant tree species. Both the liana-tree network structure and the interaction intensity between the 15 liana species and 20 tree species showed distinct specialization of liana-tree interactions. 4. Synthesis. Variation in trees species' susceptibility to lianas implies that lianas may alter tree species-specific competitive abilities by disproportionately affecting some tree species more than others. In contrast to studies in neotropical forests, light-demanding tree species were more susceptible to lianas than shade-tolerant tree species, suggesting that lianas could reduce light-demanding tree performance in this forest. The distinct species specialization between liana and tree species suggests that increases in the relative abundance of liana species, which is occurring in many forests, may alter the tree community composition by reducing the relative abundance of preferred host tree species.