Jonathan E. Nichols, Dorothy M. Peteet, Peter D. Isles, Yongsong Huang
Proceedings of the 14th International Peat Congress
carbon-isotopes, evaporation, hydrogen-isotopes, methane, organic-geochemistry
Theme I. Inventory, stratigraphy and conservation of mires and peatlands
We have developed several new approaches to quantitatively assess past changes in precipitation δD, evaporation, and methane release based on compound-specific hydrogen and carbon isotope ratios of biomarkers in ombrotrophic peatland sediments. Vascular plant leaf waxes record the δD of acrotelm water, which is little affected by evaporation, whereas Sphagnum leaf waxes record the δD of surface water, strongly affected by evaporation. The contrast in δD of water available to living Sphagnum and in the rooting zone of vascular plants can be used to estimate “ƒ”—the fraction of water remaining after evaporation. The influence of peatlands on the concentrations of atmospheric methane is poorly understood. To constrain the relationships among methane release, vegetation type, and climate, we compare the δ13C of biomarkers in several microhabitats in ombrotrophic peatlands. We use these compound-specific carbon isotope measurements to understand changes in the amount of methane-derived CO2 incorporated by Sphagnum from symbiosis with methanotrophic bacteria.