Modeling Northern Peatland Decomposition and Peat Accumulation |
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Authors: | Steve Frolking Nigel T Roulet Tim R Moore Pierre J H Richard Martin Lavoie Serge D Muller |
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Institution: | (1) Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824, USA, US;(2) Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, H3A 2K6, Canada, CA;(3) Centre for Climate and Global Change Research, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, H3A 2K6, Canada, CA;(4) Départment de Géographie, Université de Montréal, C.P. 6128, Montréal, Quebec, H3C 3J7, Canada, CA |
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Abstract: | To test the hypothesis that long-term peat accumulation is related to contemporary carbon flux dynamics, we present the Peat
Decomposition Model (PDM), a new model of long-term peat accumulation. Decomposition rates of the deeper peat are directly
related to observable decomposition rates of fresh vegetation litter. Plant root effects (subsurface oxygenation and fresh
litter inputs) are included. PDM considers two vegetation types, vascular and nonvascular, with different decomposition rates
and aboveground and belowground litter input rates. We used PDM to investigate the sensitivities of peat accumulation in bogs
and fens to productivity, root:shoot ratio, tissue decomposability, root and water table depths, and climate. Warmer and wetter
conditions are more conducive to peat accumulation. Bogs are more sensitive than fens to climate conditions. Cooler and drier
conditions lead to the lowest peat accumulation when productivity is more temperature sensitive than decomposition rates.
We also compare peat age–depth profiles to field data. With a very general parameterization, PDM fen and bog age–depth profiles
were similar to data from the the most recent 5000 years at three bog cores and a fen core in eastern Canada, but they overestimated
accumulation at three other bog cores in that region. The model cannot reliably predict the amount of fen peat remaining from
the first few millennia of a peatland's development. This discrepancy may relate to nonanalogue, early postglacial climatic
and nutrient conditions for rich-fen peat accumulation and to the fate of this fen peat material, which is overlain by a bog
as the peatland evolves, a common hydroseral succession in northern peatlands. Because PDM sensitivity tests point to these
possible factors, we conclude that the static model represents a framework that shows a consistent relationship between contemporary
productivity and fresh-tissue decomposition rates and observed long-term peat accumulation.
Received 19 June 2000; accepted 24 January 2001. |
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Keywords: | : peatland decomposition carbon accumulation model peat |
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