CO sub(2)-normalized emission ratios (Delta X/ Delta CO sub(2); V/V; where Delta X and Delta CO sub(2) identical with the enhancement of trace gas and CO sub(2), respectively, above background levels) for carbon monoxide (CO), hydrogen (H sub(2)), methane (CH sub(4)), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N sub(2)O) were determined from smoke samples collected during low-altitude helicopter flights over two prescribed fires in northern Ontario, Canada. The emission ratios determined from these prescribed boreal forest fires are compared to emission ratios determined over two graminoid (grass) wetlands fires in central Florida and are found to be substantially higher (elevated levels of reduced gas production relative to CO sub(2)) during all stages of combustion. These results argue strongly for the need to characterize biomass burning emissions from the major global vegetation/ecosystems in order to couple combustion emissions to their vegetation/ecosystem type. Such a process should improve the quality of any assessments of biomass burning impacts on atmospheric chemistry and climate.