Above-ground biomass and the fate of carbon after burning in the savannas of Roraima, Brazilian Amazonia

Above-ground biomass (live + dead), was estimated pre- and post-burn in eight types of savanna ecosystem in Roraima, in the extreme northern part of the Brazilian Amazon. The objective was to investigate the stock of pre-burn above-ground carbon and its fate after experimental fires that were set during the dry season (December-March). The total biomass in each ecosystem was divided into two groups (“fine-fuels” and “trees and shrubs”), and the combustion factor and the concentration of carbon were determined for of each of the biomass components within these groups. The ecosystems with the lowest biomasses were the grasslands (1627-4045 kg ha−1), followed by parkland (6127-8038 kg ha−1) and open woodland savanna (10,246-11,731 kg ha−1). The percentage of “live biomass” was higher in the open woodland vegetation types (77.1-85.6%), and lower in the grassland and parkland types (11.4-51.4%). The total emitted carbon (“presumed release”) in each ecosystem varied from 551 to 1474 kg C ha−1. These results differ from those observed in the savannas of central Brazil (2909 kg C ha−1 emitted), which were used as the standard in the Brazilian national inventory of greenhouse-gas emissions for the burning of non-anthropic savannas. This suggests that the calculations of Brazilian emissions for savannas should be disaggregated by region instead of using standard national values. Savanna ecosystems in Amazonia, although defined phytoecologically in the same way as those of central Brazil (despite being separated by great geographical distances), possess fire dynamics of their own, implying differences in the emissions of greenhouse gases.