MOLECULAR CHARACTERIZATION OF DISSOLVED ORGANIC MATTER (DOM) IN NORTHERN PEATLANDS: IDENTIFYING THE CHEMICAL SIGNATURES OF CLIMATE CHANGE

Northern peatlands are the most effective terrestrial ecosystems for storing carbon. While covering only 3% (>350 million ha) of the Earth’s surface, they account for about 1/3 of the carbon stored in global soils. Although the formation of this large carbon sink would tend to damp climatic warming, peatlands are an important source for the greenhouse gases CO₂ and CH₄. The chemical and biochemical processes that link solid phase peat and dissolved organic matter (DOM) within peatlands porewaters are not well understood, and thus the response of these large carbon reservoirs to climate change remains uncertain. In this presentation we will describe the results of experiments designed to identify the differences in the reactive and refractory DOM pools from two distinctly different peatland formations within the Glacial Lake Agassiz Peatlands (GLAP) of northern Minnesota: bogs and fens. UV-Vis absorption spectroscopy, Excitation/Emission Matrix (EEM) fluorescence spectroscopy and ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) were used for DOM characterization. The optical spectroscopy data confirm qualitative and quantitative differences in porewater DOM. These data are supported by molecular level analyses of DOM from FT-ICR-MS, and were consistent with the hypothesis that DOM in Sphagnum-dominated peatlands is much less reactive than sedge-dominated fen DOM.