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Soil organic carbon storage, distribution and characteristics in two contrasting permafrostaffected environments: Evaluating the role of alpine and lowland tundra areas in the permafrost carbon feedback
Stockholm University, Faculty of Science, Department of Physical Geography.
2018 (English)Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
Abstract [en]

An important portion of the large northern permafrost soil organic carbon (SOC) pool might be released into the atmosphere as greenhouse gases following permafrost thawing and subsequent SOC decomposition under future warming conditions, resulting in a warming amplification known as the permafrost carbon feedback. Improved knowledge about the amount, composition and distribution of the permafrost SOC pool is essential when assessing the potential magnitude and timing of the permafrost carbon feedback. This study investigates and compares the SOC storage, composition and distribution in two contrasting permafrost environments: a lowland tundra area in NE Siberia (Tiksi study site), and an alpine area in the Russian Altai Mountains (Aktru Valley study site). Soil pedons were sampled down to 1 m depth and analyzed for key soil properties, i.e., DBD, water content, coarse fraction content, %OC, %IC, C/N ratios and δ¹⁵N values. These soil properties are upscaled by vertical subdivisions based on land cover classes. The role of geomorphology in the accumulation and distribution of SOC in the alpine study site is tested by using a landform and a combined land cover-land form upscaling approach. The estimated mean SOC storage in the upper meter of soils in the alpine site is 3.5 ± 0.8 kg C m¯² compared to 21.4 ± 3.2 kg C m¯² in the lowland tundra site (95% confidence intervals). The inclusion of geomorphology in the upscaling in some cases allows identification of SOC hotspots and areas with very low SOC storage within former land cover classes, therefore improving the landscape SOC storage distribution in the area. The much lower SOC stocks in the alpine site of Aktru Valley can be largely explained by the presence of extensive unvegetated areas in high altitudes (60%), the occurrence active layers deeper than the active soil formation, the enhanced SOM decomposition due to coarse grained, well-drained non-frozen soils, and the negligible occurrence of peatlands and buried organics. Instead, the lowland tundra site in NE Siberia presents important amounts of relatively undecomposed SOM in the permafrost layer. Thus, under future climate warming, alpine permafrost environments such as Aktru Valley may become a net C sink due to an upward shift of vegetation zones and an increase in plant productivity and soil development. Contrarily, lowland tundra areas such as Tiksi may become important C sources since the small increase in C uptake by photosynthetic plants will be outweighed by the thawing and subsequent decomposition of the much larger permafrost SOC pool.

Place, publisher, year, edition, pages
2018. , p. 85
Keywords [en]
soil organic carbon, permafrost, tundra, alpine, climate change, feedback, mapping, landcover, landform
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-159797OAI: oai:DiVA.org:su-159797DiVA, id: diva2:1246657
Presentation
2018-06-07, 15:00 (English)
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Examiners
Available from: 2018-09-10 Created: 2018-09-09 Last updated: 2018-09-10Bibliographically approved

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CiteExportLink to record
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