Author(s): LIANE S GUILD, J BOONE KAUFFMA, WARREN B COHEN, CHRISTINE A HLAVK, DAROLD E WARD
As a source of atmospheric carbon, biomass burning emissions associated with deforestation in the Amazon are globally significant. Once deforested, these lands continue to be sources of substantial burning emissions for many years due to frequent pasture burning. The objective of this research was to quantify biomass-burning emissions at a local scale. We estimated carbon emissions from three sources: fires associated with primary forest slash, regenerating forest slash, and pastures. The study was conducted on a 94370-ha section of land surrounding Jamari, RondGnia, Brazil. In the emissions computation, we integrated site-specific, ground-based data (biomass, emission factors for flaming and smoldering combustion, and combustion factors for land-cover types) with a Landsat TM land cover change map of the study area for 1984-1992. This map was used to ascertain changes in land cover based on TM image dates during a period of early colonization and rapid deforestation in Rond8nia. Emissions of CO, CO,, CH,, and other hydrocarbon trace gases were calculated. Between 1984 and 1992, we found CO, emissions generated by primary forest slash burning were 694 379 Mg C (920 kg C-ha-I-yr-I) and regenerating forest slash burning contributed 23 436 Mg C (31 kg C.ha-'.yr-l), whereas cumulative pasture burning produced 238 180 Mg C (316 kg C.ha-l.yr-l). CO and CH, folIowed the same trends by land cover type. Primary forest slash burns contributed 73% of the total C emissions whereas burning regenerating forest slash and pasture produced 2% and 2596, respectively. The major finding of this work is the identification of pasture burning as a potentially important source of pyrogenic emissions, but better data on biomass and combustion efficiency could confirm this finding. Further we demonstrated a novel method for estimating area burned that links land cover type and change to burn frequency.