Seasonal changes in photosynthetic nitrogen of tree species differing in leaf phenology in a south-eastern brazilian savanna

Abstract

Dominant tree species from a south-eastern Brazilian savanna showing different leaf phenologies (evergreen, semi-deciduous and deciduous) were characterized regarding photosynthetic potential (A), leaf nitrogen content (% N), specific leaf area (SLA), photosynthetic nitrogen (PN) and photosynthetic nitrogen use efficiency (PNUE). The ecophysiological traits evaluated seasonally (dry and wet season) characterized a gradient of strategies among three species: the evergreen species that dominates lower strata, showed low % N, SLA, Amax and Amass and high PNUE the semi-deciduous species that dominates intermediate strata, showed medium leaf nitrogen and SLA and high Amax, Amass and PNUE the deciduous species that dominates the canopy, showed high leaf N, SLA, Amax and Amass and low PNUE. Non deciduous species invested relatively more nitrogen in photosynthesis during the wet season, while the deciduous species maintained higher PN in the dry season. Photosynthetic N and PNUE appear to be the key to a better understanding of the relations among leaf traits, N content and photosynthetic potential in species with different leaf phenologies and subjected to climatic seasonality.