Using leaf phenology patterns to investigate net ecosystem exchange controls in tropical vegetations

Abstract

Fluxes of carbon, water, and energy are among the most important components of the biogeochemical cycling between biosphere and atmosphere. Tropical forests play an important role in the global carbon budget, however further studies are needed to better understand some uncertainties about temporal patterns of the carbon exchange and its main controls. The vegetation phenology can have an important role describing the seasonality and inter-annual variability of carbon exchange. Temporal changes in the vegetation may drive carbon exchange processes via influencing the photosynthesis process, respiration, and litter production. Digital repeat photography is able to track leafing throughout the color changes of the vegetation at a daily temporal scale, which can be associated with eddy covariance measurements to investigate ecosystem-scale energy flux. Our main goal during the BEPE is to address the third question of the PhD theses: Which are the relationships between the temporal patterns of leaf phenology and the ecosystem carbon fluxes? We have been monitoring the phenology and the flux of energy exchange in three sites, which are: a tropical dry forest, which belongs to the biome of Caatinga; a savanna woodland, called cerrado sensu stricto; and an Atlantic rainforest. The objectives are: (i) to describe the trends and to determine the main climatic controls triggering leaf flushing and senescence for each one of the different tropical vegetation sites, (ii) to investigate the relationship between the vegetative phenological patterns and the ecosystem metabolism components, (iii) and to investigate whether different seasonality conditions may influence vegetation phenology and its ecosystem-scale energy fluxes controls. (AU)