Water balance, nutrient and carbon export from a heath forest catchment in central Amazonia, Brazil

Carbon storage values in the Amazon basin have been studied through different approaches in the last decades in order to clarify whether the rainforest ecosystem is likely to act as a sink or source for carbon in the near future. This water balance, dissolved organic carbon (DOC) and nutrient export study were carried out in a micro-scale heath forest (Campina) catchment in central Amazonia, Brazil. For a 1-year study period (18 March 2007 until 19 March 2008), rainfall amounted to 3054mm; of which, 1532mm was evaporated by the forest (4.1mmday-1). Rainfall interception loss amounted to 15.6% of gross rainfall. Surface runoff amounted to 485mm, whereas another 1071mm was discharged as regional groundwater outflow. Accumulated DOC exports in surface runoff amounted to 15.3gm-2year-1, whereas the total carbon exported was 55.9gm-2. This is much higher than that observed for a nearby tall rainforest catchment in central Amazonia (DOC export<20gm-2). As Campina heath forest areas cover a significant proportion of the Amazon Basin, these differences in ecosystem hydrological carbon exports should be taken into account in future studies assessing the carbon budget for the Amazon Basin. Macro-nutrient exports were low, but those of calcium and potassium were higher than those observed for tall rainforest in the Amazon, which may be caused by a lower retention capacity of the heath forest ecosystem.