Leaf phenology and functional traits interplay along an aridity gradient in tropical dry forests

In Caatinga, a Brazilian tropical dry forest and woodland (STDFW), deciduous and evergreen species display complementary phenological strategies for carbon and water acquisition. These differences shape the functional composition of plant communities across dry forest types and environmental gradients remain poorly understood. We assess how the functional composition and redundancy varies depending on the crystalline and sedimentary substrates along an aridity gradient and examine the relationship between leaf phenology and functional traits. To test this relationship, we measured leaf, wood, and dispersal traits across species from crystalline and sedimentary substrates along an aridity gradient, applying multivariate and community-weighted analyses to link functional composition with phenological strategies. Crystalline caatinga favored a drought prevention strategy compared to the sedimentary caatinga community, which employs a drought tolerance strategy. The aridity index, which ranged from 0.33 to 0.55, was a significant factor selecting for most traits, although not all, suggesting the involvement of other environmental variables. The high functional redundancy observed in both caatinga types suggests some degree of niche filtering. We observed a significant relation between leaf phenology and almost all functional traits. Deciduous species tended to present more conservative traits compared to evergreen species. Our findings reveal that the interplay between leaf phenology and functional traits governs species’ adaptive responses to seasonal water limitation, highlighting how these trait phenology linkages contribute to the functional resilience and ecological stability of the Caatinga.