Snapshot of Carbon Distribution and Degradation in Arctic Valleys

justine.ramage [ at ]


Thermo-erosional valleys (TEVs) and gullies are important but poorly studied components of the western Canadian and American Arctic. Through combined mechanical and thermal processes, TEVs incise the landscapes and modify the carbon stocks through their impact on soils, deeper permafrost layers, and water drainage. To better understand the impact of TEVs on the biogeochemical cycling of lowland permafrost terrains, we investigated the distribution of soil organic carbon (SOC) and total nitrogen (TN) in three TEVs located on Herschel Island, Yukon Territory (Canada). The objective of this study is to describe the state of carbon stocks in the active layer and permafrost along toposequences of the TEVs. We 1) describe the geomorphology of the three TEVs and 2) assess the distribution and spatial variability of SOC and TN in the TEVs. The estimated SOC and TN stock in the upper meter of soils of 43 pits located along and across the 3 TEVs was 26.3 ± 8.8 kg/m3 and 2.1± 0.6 kg/m3 per site, respectively. There was a large variability among sites, SOC stocks varied between 9.9 and 46.7 kg/m3 and TN stocks between 0.9 and 3.7 kg/m3. Along the TEVs, SOC and TN stocks were higher in sites located upstream of the TEVs compared to downstream sites. Across the TEVs, stocks of SOC and TN were highest at the sites located at the bottom of the TEVs and lowest on the convex portion of their slopes. The C/N and δ13C mean values showed significantly less degraded organic-matter at less disturbed sites in the upper level of the TEVs. This study highlights the importance of thermo-erosional valleys on SOC stocks in Arctic landscapes.

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Arctic Change, 11 Dec 2017 - 15 Dec 2017, Quebec City, Canada.
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Ramage, J. , Fortier, D. , Hugelius, G. , Lantuit, H. and Morgenstern, A. (2017): Snapshot of Carbon Distribution and Degradation in Arctic Valleys , Arctic Change, Quebec City, Canada, 11 December 2017 - 15 December 2017 .

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