B025-04
Assessing the decomposition potential of peat from the tropics to the Arctic

Tuesday, 8 December 2020: 10:39
Virtual
Katy J. Sparrow, Florida State University, Department of Earth, Ocean, & Atmospheric Science, Tallahassee, FL, United States, Jeff Chanton, Florida State University, Department of Earth, Ocean & Atmospheric Science, Tallahassee, United States, Ulrich M Hanke, Woods Hole Oceanographic Institution, Woods Hole, MA, United States, Ann P McNichol, Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA, United States, Mark D Kurz, WHOI, Woods Hole, MA, United States and Alison Hoyt, Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, Cambridge, CA, United States
Abstract:
We present the use of two compelling, complementary methods of characterizing organic matter (OM) to examine the decomposition potential of peat across a wide range of latitudes. Depth profiles of peatlands from four climates (Tropical, Subtropical, Boreal, and Polar) were investigated with a combination of (a) ramped oxidation paired with 14C and δ13C analyses and (b) Fourier transform infrared spectroscopy (FTIR). Our goals are to better understand the factors that govern OM storage globally and evaluate the effect of warming on contemporary peatland reservoirs, which reside in a variety of climates. The data produced from the ramped oxidation procedure, in which peat is combusted at progressively higher temperatures and the resulting CO2 is collected in low, medium, and high temperature aliquots (for 14C dating), has been translated into activation energy models and used to interpret the biological lability and reactivity of the peat OM. We use FTIR analyses to quantify the relative abundances of carbohydrate, aliphatic, and aromatic functional groups. The ramped oxidation results show that the subsurface Boreal and Polar peats, which are 1000s of years old below ~30 cm depth, contain substantial labile carbon components, greater than or comparable to the surface peat at those sites, as well as varying degrees of more recalcitrant OM. The thermally separated fractions of each sample were found to share the same 14C signature, equivalent to the bulk peat 14C signature, suggesting a high degree of interchange occurring in the OM pool at each horizon. The FTIR analyses complement the ramped oxidation data and suggest that the Tropical and Subtropical peats contain the bulk of its labile, carbohydrate-rich material in the surface and that it largely does not persist to deeper horizons, while the higher latitudes have comparably greater carbohydrate content than the lower latitude peats, at all depths. These results offer a fresh analytical perspective on global peatlands and the fate of the carbon stored within them.
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