Experimental production and analysis of microscopic charcoal from wood, leaves and grasses

Study of microscopic charcoal from lake sediments has led to a greater understanding of past veg etation, climate and fire ecology. We investigated the potential of charcoal morphology as an indicator of vegetation type. Grasses, leaves and wood were burned under controlled conditions in the laboratory, and we used a dissecting scope, video camera, and image-capture software to image-sieved (125-μm screen) micro-scopic charcoal. Charcoal from grasses was significantly longer (562 μm) and had a greater length:width ratio (3.62) than charcoal derived from leaves (380 μm; 1.91) or wood (348 μm; 2.13). Length:width ratios of mixtures of grass and leaf charcoal were intermediate (50:50 mixture; 2.36) between ratios for grass or leaf charcoal alone, and charcoal yield (on a weight basis) declined as a function of combustion temperature. While a number of issues may complicate the application of these results to the field, the results do suggest that length:width ratios can be used as an indicator of vegetation type.