Detection of deforestation and land conversion and estimation of atmosperic emissions and elemental pool losses from biomass burning in Rondônia, Brazil

Abstract

Biomass burning associated with deforestation and land use in the Amazon, greatly contributes to emissions as well as depletion of elemental pools. We identified deforestation and pasture formation and quantified resultant burning emissions and terrestrial aboveground elemental pool losses during a period of early colonization in the vicinity of Jamari, Rondonia. Using the Tasseled Cap transformation on multi-date Landsat Thematic Mapper (TM) data (1984-1992), we developed a land cover and change map for a 94,372-ha study area. Between 1984 and 1992, 8,250 ha of primary and 828 ha of regenerating forest were cleared (18% and 1% of the study area, respectively). Cleared land increased from 1,231 ha to 2,692 ha (1% to 3% of the study area) by 1986 and this area was in a cleared state in 1992. We developed equations using realistic pasture management burn scenarios to model cumulative area of pasture burned (19,008 ha). We computed emissions using a model that scaled up ground-based data (biomass, combustion factors, and flaming and smoldering combustion emission factors) by land cover type (primary forest, regenerating forest, and pasture). Over the extent of the entire study area, an average of 138,920, and 16 kg C ha-¹ y-¹ in CO, CO₂, and CH₄, respectively, were generated from primary forest slash burns. Regenerating forest slash fires contributed 4, 31, and <1 kg C ha-¹ y-¹ in CO, CO₂, and CH₄, respectively. The cumulative area of pasture burned produced 46, 316, and 4 kg C ha-¹ y-¹ in CO, CO₂, and CH₄, respectively. Site estimates of C, N, and Spools and losses were applied to the land cover change map to estimate elemental pool losses from slash and pasture fires during the study period. In 1984, study area elemental pools were 163,297 kg C ha-¹, 1,971 kg N ha-¹ and 199 kg S ha-¹. Between 1984 and 1992, 5%, 7%, and 5% of the terrestrial aboveground C, N, and S pools, respectively, were lost from primary forest slash fires. Also, cumulative pasture burning contributed to losses of 1%, 2%, and 1% of the C, N, and Spools, respectively