Modern Sphagnumδ13C signatures follow a surface moisture gradient in two boreal peat bogs,James Bay lowlands,Québec |
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Authors: | Julie Loisel Michelle Garneau Jean‐François Hélie |
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Institution: | 1. GEOTOP‐UQAM‐McGill and Département de Géographie, Université du Québec à Montréal, Montreal, Quebec, Canada;2. GEOTOP‐UQAM‐McGill and Département des Sciences de la Terre, Université du Québec à Montréal, Montreal, Quebec, Canada |
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Abstract: | Carbon isotopic composition of Sphagnum macrofossils can potentially be used as a palaeohydrological tool for peat‐based climatic studies since a relationship between Sphagnum δ13C values and peatland surface moisture has been presented in previous studies. In order to verify this hypothesis, modern Sphagnum δ13C values were measured along a moisture (microtopographic) gradient in two boreal peat bogs. Isotopic measurements were performed on bulk material of S. fuscum, S. magellanicum, S. capillifolium and S. pulchrum. Isotopic variations found within and between Sphagnum species along the microtopographic gradient were compared using analysis of variance. A significant positive correlation (P < 0.0001) was found between Sphagnum δ13C values and their position along the surface moisture gradient. Results show that 13C‐depleted values are related to low water table depths (WTD), while 13C‐enriched values correspond to a water table that is close to the peat surface. Although the mechanisms underlying carbon fractionation processes in mosses are not well understood, we demonstrate that water resistance to CO2 diffusion is an important fractionation process that is observed in bulk Sphagnum δ13C measurements, since drier and wetter samples exhibit consistent and very different isotopic signatures. Copyright © 2008 John Wiley & Sons, Ltd. |
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Keywords: | stable carbon isotopes ombrotrophic peatland Sphagnum microtopographic gradient boreal Quebec |
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