METHANE PRODUCTION IN CONTRASTING WETLAND SITES - RESPONSE TO ORGANIC-CHEMICAL COMPONENTS OF PEAT AND TO SULFATE REDUCTION

We used methane-production measurements of slurried peat to study controls of methane production in six contrasting Appalachian wetland sites. The sites differed widely in plant-community composition and in rates of methane production, which varied from 3-mu-mol/L/day in slurried-peat samples from a shrub-dominated bog to 216-mu-mol/L/day in peat from a spruce-forested wetland. Three controlling factors of methane production were examined: organic-chemical components of the peat (e.g., hot-water soluble, sulfuric acid soluble, sulfuric acid insoluble), concentrations of dissolved organic carbon, and rates of sulfate reduction. Peats from shrub-dominated sites contained mostly acid-insoluble organic matter, which was presumably recalcitrant to microbial decomposition. In contrast, peats from moss-and sedge-dominated sites contained mostly acid-soluble organic matter, which was presumably labile. Differences of organic-chemical components of the peat could explain about 50% of the variation in rates of methane production among samples from the sites. Rates of sulfate reduction in peat samples were relatively high (5-397-mu-mol/L/day), despite low in situ concentrations of dissolved sulfate (< 250-mu-mol/L), but sulfate reduction was not well correlated with rates of methane production, nor were concentrations of dissolved organic carbon. Amendments of methanol and trimethylamine to peat samples from any individual site did not stimulate rates of methane production. In general but not always, glucose, hydrogen, and acetate amendments stimulated rates of methane production. Sulfate amendments that stimulated sulfate reduction also inhibited methane production by 90%; however, reversal of the inhibition was achieved by acetate and hydrogen amendments. Control of methane production in these organic-rich wetlands is related more to organic-chemical components of the peat than to the activity of coincident sulfate-reducing bacteria.