Combustion completeness in a rainforest clearing experiment in Manaus, Brazil

Abstract

Results are described for a forest clearing experiment conducted in the forest reserve of the Tropical Silviculture Experimental Station of the National Institute for Resarch in the Amazon (INPA), located 60 km from Manaus, the capital of the Brazilian state of Amazonas. An area of 1 ha of virgin forest was cut in July 1995 and left to dry until October of the same year. It was burnt using a procedure similar to that followed by native people in the region to prepare the land for cultivation. The fresh biomass content in the test location, 684.8 t ha-1, was determined using a formula with parameters from forest inventory. The dry biomass content was 401.5 t ha-1. Combustion completeness, 20.5%, was estimated by selecting ten 2x2 m2 subareas, 20 trunks with diameter at breast height (DBH) between 10 and 30 cm, and 71 trunks with DBH higher than 30 cm. Their consumption rates by fire were measured. The 2x2 m2 areas were used to determine the combusion completeness of smaller plant components (characteristic diameters lower than 10 cm) and the trunks to determine the efficiency of the medium and large components (characteristic diameters between 10 and 30 cm, and larger than 30 cm, respectively). Combustion completeness for small, medium and large components were 88.2%, 4.39% and 0.43%, respectively. On the basis of the biomass content (684.4 t ha-1), the average biomass moisture and carbon contents (41.6% and 47.8%, respectively, the latter on dry basis), and the obtained combustion completeness (20.5%), the average carbon, CO2 and CO mass rates released to the atmosphere were estimated to be 37.7, 121 and 8.6 t ha-1, respectively.