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Mass transformations were estimated in burns in the clearings of three colonist lots near Altamira, Pará, Brazil. In each lot, two groupings of six 60-m² plots were established in sites where the forest had been recently felled; plots were arranged as rays in a star-shaped pattern, with pre- and post-burn measurements made in alternate rays. Pre- and post-burn above-ground biomass was estimated by cutting and weighing the felled vegetation in 15 pre-burn and 18 post-burn plots (three pre-burn plots could not be weighed before one of the colonists burned the clearing) and by line intersect sampling (LIS) done along the axis of each of the 36 plots. Because of the high variability of the initial biomass present in the plots, volume data from LIS were more reliable for assessing change in the biomass of material over 10cm in diameter (because this technique permits measuring the same trees before, and after, burning …