PASTURE BURNING IN AMAZONIA: DYNAMICS OF RESIDUAL BIOMASS AND THE STORAGE AND RELEASE OF ABOVEGROUND CARBON

Aboveground biomass in cattle pasture converted from tropical dense forest was studied both before and after reburning in Brazilian Amazonia. In a seven-year-old pasture studied in Apiaú, Roraima, the aboveground dry-weight of biomass (live + dead) exposed to burning consisted of 96.3 t ha-1 of original forest remains, 6.2 t ha-1 of secondary successional vegetation (woody invaders in the pasture), and 8.0 t ha-1 of pasture grass (carbon contents 48.2%, 45.4 % and 42.2%, respectively). In terms of carbon, burning efficiencies for these three categories were 13.2%, 66.7 % and 94.6%, respectively. Net charcoal formation was 0.35 t C ha-1, or 0.63 % of the carbon exposed to the reburn, while the total accumulated since conversion (including the initial burn) is estimated at 2.3 t ha-1 (1.82 % of the pre-deforestation aboveground biomass carbon stock)