The positive compound leaf-drought association is shrub-specific in Chinese forests

The classic hypothesis that compound leaves are associated with drought has largely treated all woody plants as a single functional group, overlooking potential ecological divergence among shrubs, trees, and lianas.

Using 2,727 species across 63 forest plots in China, we quantified compound-leaf proportion within shrubs, trees, and lianas, respectively, and assessed their climatic associations, and employed PLS-SEM to disentangle direct and indirect pathways of drought influence.

Compound-leaf distribution differed markedly among life forms. The shrub compound-leaf proportion showed strong positive correlations with drought index and negative correlations with mean annual precipitation (MAP) and temperature (MAT). Trees exhibited a weak negative correlation with MAP and no significant relationship with MAT or drought index. while lianas displayed no climatic relationships-their proportion instead varying geographically. Structural equation modeling revealed that drought is associated with woody compound-leaf proportion primarily through indirect pathways: increasing shrub proportion (which carries high compound-leaf proportion) while reducing tree proportion, together with direct positive effects on compound-leaf proportion within shrubs and trees.

Our findings demonstrate that compound leaf-drought relationships are life-form-specific, challenging the view of compound leaves as a universal drought-associated trait. Integrating life-form information into ecological models is essential for accurately predicting vegetation responses to climate change.