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Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soils
Stockholm University, Faculty of Science, Department of Physical Geography.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This meta-analysis aims to describe the relationship between grain size distributions and soil organic carbon (SOC) storage in mineral subsoil and carbon (C)-enriched cryoturbated pockets in five areas of continuous permafrost that differ in glaciation history and soil parent materials. Our results show a positive relationship between fine-grained (colloid to medium silt) fractions and SOC storage. Finer textured soils had a significantly higher SOC storage in mineral subsoil samples (not C-enriched through cryoturbation) than coarser textured soils. However, the process of C-enrichment through cryoturbation was most pronounced in soils with coarser grain sizes in the range of coarse silt and very fine sand. Even though fine-grained textures provide a better physical and biochemical protection for soil organic matter, their strong cohesion reduces the mixing of soil horizons and the effectiveness of cryoturbation. A higher % coarse silt to % clay ratio in samples was a good predictor of C-enrichment through cryoturbation across soil samples, soil profiles and study areas.

Keyword [en]
permafrost soils, SOC storage, cryoturbation, soil parent materials, soil texture, grain size distributions
National Category
Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-137284OAI: oai:DiVA.org:su-137284DiVA: diva2:1061499
Available from: 2017-01-02 Created: 2017-01-02 Last updated: 2017-01-05Bibliographically 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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