Relação entre deciduidade e concentrações foliares de nutrientes em espécies lenhosas do cerrado

Abstract

The main objective of the present study was to compare the variations in leaf nutrient concentrations among 15 woody species of a cerrado sensu stricto belonging to different phenological groups to determine the influence of deciduousness on mineral nutrition. The main hypothesis was that evergreen species would present lower foliar concentrations, less specific leaf area, and smaller seasonal variations than deciduous species, because their leaves would persist beyond one annual cycle of dry and wet season. The study was conducted in a cerrado sensu stricto at the Reserva Ecologica do IBGE in the Federal District of Brazil. Fully expanded leaves collected from three individuals of each species at two-month intervals for a year were analyzed. Specific leaf area was also determined. The concentrations of N, P, K, Ca and Mg and seasonal variation were lower in the evergreen species than in the deciduous species. Deciduous species showed higher concentrations of N, P and K at the beginning of the rainy season when leaves were recently formed and their concentrations decreased toward the beginning of the next dry season. Concentrations of Ca increased toward the end of the rainy season. Brevideciduous species had lower concentrations of N and P than deciduous species and higher concentrations of N, P and Ca than evergreens. Mean specific leaf area of evergreen species (54.0 cm2 g-1) was smaller than that of deciduous (67.0 cm2 g-1) and brevideciduous species (83.5 cm2 g-1). Specific leaf area was correlated with N and P. Thus there were significant differences not only between evergreen and deciduous species but also between deciduous and brevideciduous species.