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Improved landscape partitioning and estimates of deep storage of soil organic carbon in the Zackenberg area (NE Greenland) using geomorphological landforms
Stockholm University, Faculty of Science, Department of Physical Geography.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This study aims to improve the previous soil organic carbon (SOC) storage estimates for the Zackenberg area (NE Greenland) that were based on a land cover classification (LCC) approach, by using geomorphological upscaling. In addition, novel SOC estimates for deeper deposits (to 300 cm depth) are presented. We hypothesize that landforms will better represent the long-term slope and depositional processes that result in deep SOC burial in this type of mountain permafrost environments. The updated mean SOC storage for the 0–100 cm soil depth is 4.8 kg C m−2, which is 42% lower than the previous estimate of 8.3 kg C m−2 based on land cover upscaling. We ascribe the difference to a previous areal overestimate of SOC-rich vegetated land cover classes. The landform-based approach more correctly constrains the depositional areas in alluvial fans and deltas with high SOC storage. These are also areas of deep carbon storage with an additional 2.4 kg C m−2 in the 100–300 cm depth interval. This research emphasizes the need to consider geomorphology when assessing SOC pools in mountain permafrost landscapes.

National Category
Climate Research
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-137312OAI: oai:DiVA.org:su-137312DiVA: diva2:1061762
Available from: 2017-01-03 Created: 2017-01-03 Last updated: 2017-01-09Bibliographically approved
In thesis
1. Landscape partitioning and burial processes of soil organic carbon in contrasting areas of continuous permafrost
Open this publication in new window or tab >>Landscape partitioning and burial processes of soil organic carbon in contrasting areas of continuous permafrost
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recent studies have shown that permafrost soils in the northern circumpolar region store almost twice as much carbon as the atmosphere. Since soil organic carbon (SOC) pools have large regional and landscape-level variability, detailed SOC inventories from across the northern permafrost region are needed to assess potential remobilization of SOC with permafrost degradation and to quantify the permafrost carbon-climate feedback on global warming.

This thesis provides high-resolution data on SOC storage in five study areas located in undersampled regions of the continuous permafrost zone (Zackenberg in NE Greenland; Shalaurovo and Cherskiy in NE Siberia; Ary-Mas and Logata in Taymyr Peninsula). The emphasis throughout the five different study areas is put on SOC partitioning within the landscape and soil horizon levels as well as on soil forming processes under periglacial conditions. Our results indicate large differences in mean SOC 0–100 cm storage among study areas, ranging from 4.8 to 30.0 kg C m-2, highlighting the need to consider numerous factors as topography, geomorphology, land cover, soil texture, soil moisture, etc. in the assessment of landscape-level and regional SOC stock estimates.

In the high arctic mountainous area of Zackenberg, the mean SOC storage is low due to the high proportion of bare grounds. The geomorphology based upscaling resulted in a c. 40% lower estimate compared to a land cover based upscaling (4.8 vs 8.3 kg C m-2, respectively). A landform approach provides a better tool for identifying hotspots of SOC burial in the landscape, which in this area corresponds to alluvial fan deposits in the foothills of the mountains. SOC burial by cryoturbation was much more limited and largely restricted to soils in the lower central valley. In the lowland permafrost study areas of Russia the mean SOC 0–100 cm storage ranged from 14.8 to 30.0 kg C m-2. Cryoturbation is the main burial process of SOC, storing on average c. 30% of the total landscape SOC 0–100 cm in deeper C-enriched pockets in all study areas. In Taymyr Peninsula, the mean SOC storage between the Ary-Mas and Logata study areas differed by c. 40% (14.8 vs 20.8 kg C m-2, respectively). We ascribe this mainly to the finer soil texture in the latter study area. Grain size analyses show that cryoturbation is most prominent in silt loam soils with high coarse silt to very fine sand fractions. However, in profiles and samples not affected by C-enrichment, C concentrations and densities were higher in silt loam soils with higher clay to medium silt fractions.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholm University, 2017
Series
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 61
Keyword
soil organic carbon, total nitrogen, permafrost, cryoturbation, geomorphology, land cover classification, slope processes, texture, upscaling, carbon/nitrogen ratio
National Category
Physical Geography Climate Research
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-136383 (URN)978-91-7649-610-7 (ISBN)978-91-7649-611-4 (ISBN)
Public defence
2017-02-10, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
European Science Foundation (ESF), 282700EU, FP7, Seventh Framework Programme, 282700Nordic Council of Ministers, 23001
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2017-01-18 Created: 2016-12-05 Last updated: 2017-01-17Bibliographically approved

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