Do stem functional traits determine the phenology of tree species in semiarid highland forest, Brazil?

Abstract

The phenology of tree species in tropical forests is better understood when both environmental factors and functional traits of plants are analyzed. However, the relation between phenology and functional traits is still poorly explored, especially in forest ecosystems. This study analyzed the relation between phenology, wood density (WD) and wood water storage capacity (Qwsat) of 21 tree species from highland forest, montane wetland in the semiarid region of Brazil, as well as their relation with environmental factors. Most species are semideciduous (43 %) or evergreen (43 %), while only three (14 %) are deciduous. Many species (86 %) have shown WD between 0.52 and 0.62 g/cm³, with low Qwsat, while only three species (14 %) have presented lower wood density (0.38–0.48 g/cm³), with higher Qwsat in their stems (105–157 % of dry mass). Leaf budding was positively influenced by rainfall. Leaf fall was the phenophase affected by the greatest number of variables, showing negative relationships with both humidity and wood density. Additionally, evergreen species exhibited a 22.4 % lower leaf fall rate compared to the other groups. These results indicate that stem functional traits were not relevant to explain the phenology of plant species in this environment, but that budding and leaf fall have a great contribution to understanding the functioning and distribution of functional groups in an upland forests. These results reveal that, unlike the surrounding Caatinga vegetation, in the highland forest the stem functional traits were not good indicators of plant functioning, but leaf traits are of great relevance.