The area burned, total biomass above and below-ground, charcoal formation, burning efficiency and the carbon concentration were estimated for the different natural landscapes and agricultural systems that were exposed to fire during the “El Niño” of 1997-98 in the state of Roraima, in the northernmost part of Brazilian Amazonia. The objective was to calculate the gross emissions of greenhouse gases released by combustion from the various biomass classes comprising each landscape type. The total area burned was 38,14440,678 km2, of which 11,394-13,928 km2 was intact primary forest, 22,583 km2 was savanna, 1,388 km2 was white sand scrub formations, and 2,780 km2 was pastures, secondary forest and agricultural plots. Total carbon affected by the fire was 42.58 x 106 tons (t), with 19.73 x 106 t being released from combustion, 22.33 x 106 t from decomposition, and 0.552 x 106 t converted to charcoal (long-term carbon storage) formed during the bums. Gross emissions of greenhouse gases emitted by combustion were 17.3 x 106 t CO2, 0.21-0.35 x 106 t CH4, 1.99-3.68 x 106 t CO, 0.001-0.003 x 106 t N2O, 0.06-0.09 x 106 t NOx and 0.25 x 106 t NMHC (non-methane hydrocarbons). The total emission in carbon equivalent to CO2 emitted by combustion, based on the global warming potentials for each gas over the 100-yr horizon used by the IPCC, was 6.1-7.0 x 106 t C.
forest fires; carbon; Amazônia; Roraima; greenhouse effect; El Niño; global warming