Phenological seasonality and contribution of inter- and intraspecific variation to relationships with morpho-biochemical traits in seasonal Atlantic forests

Seasonality and trait variability influence leaf phenology's duration, intensity, onset, and end. Focusing on species instead of intraspecific variability may oversimplify forest dynamics and limit predictions of morphological-biochemical trait associations. Over two years, leaf flush, fall, and seven morpho-biochemical traits were quantified to explore functional traits related to leaf phenology and the contribution of inter- and intraspecific variability. The study involved 423 individuals of ten deciduous and 21 evergreen species in a seasonal evergreen and a semideciduous forest in the Atlantic Forest, Brazil. In the seasonal semideciduous forest, deciduous species showed a seasonality of 0.74–1.02 in leaf flush and fall, compared to evergreens (0.23–0.66). Seasonality in leaf flush and fall was correlated in this forest, regardless of inter- and intraspecific variability. In contrast, leaf flush and fall did not differ between leaf habits in the seasonal evergreen forest. They were not correlated, which may indicate that drought resistance is a prevalent mechanism in this forest, resulting in longer leaf longevity and more continuous phenological patterns. Thickness, specific leaf area, and the carbon/nitrogen ratio were associated with leaf phenology and varied between forests and interspecific and intraspecific variations. Intraspecific variability contributed more to trait variance in the semideciduous forest, while interspecific variability and leaf habit were more influential in the seasonal evergreen forest. Our study highlights the importance of quantifying seasonality in leaf phenology for individuals, not only for species, for enhanced understanding of forest dynamics, particularly where seasonal abiotic factors impact community assembly.