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The use of terrestrial photogrammetry to estimate soil motion rates in non-sorted circles
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Soil motion induced by cryogenic processes is known for creating soil surface structures (patterned ground) and redistributing carbon within Arctic soils. Lateral and vertical soil motion created by cryogenic processes proceeds over annual to millennial time-scales and is difficult to quantify without adopting disruptive soil sampling techniques. In this study, we evaluate the use of terrestrial close range photogrammetry to calculate soil motion rates within a patterned ground system (non-sorted circles). The measured rates of lateral and vertical motion were estimated and used to infer the importance of physical soil transport for the formation of non-sorted circles as well as the trajectories of soil carbon. Soil experiencing significant vertical displacement between years covered approximately 65% of the non-sorted circles and had surface levels fluctuating between 4 and -2.1 cm. Systematic lateral motion of surface stones allowed detection of lateral motion working outwards from the centre towards the sides, at rates ranging between 0.1 and 6.3 cm yr-1. We conclude that terrestrial close range photogrammetry can be used to identify the main soil movements within non-sorted circles and that this transport is an important factor controlling the trajectories of soil carbon over centennial to millennial timescales. 

Keyword [en]
Soil motion, Terrestrial photogrammetry, Carbon storage, Non-sorted circles
National Category
Geology
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:umu:diva-112508OAI: oai:DiVA.org:umu-112508DiVA: diva2:882507
Available from: 2015-12-15 Created: 2015-12-09 Last updated: 2015-12-17Bibliographically approved
In thesis
1. Cryogenic soil processes in a changing climate
Open this publication in new window or tab >>Cryogenic soil processes in a changing climate
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Kryogena mark processer i ett föränderligt klimat
Abstract [en]

A considerable part of the global pool of terrestrial carbon is stored in high latitude soils. In these soils, repeated cycles of freezing and thawing creates soil motion (cryoturbation) that in combination with other cryogenic disturbance processes may play a profound role in controlling the carbon balance of the arctic soil. Conditions for cryogenic soil processes are predicted to dramatically change in response to the ongoing climate warming, but little is known how these changes may affect the ability of arctic soils to accumulate carbon. In this thesis, I utilize a patterned ground system, referred to as non-sorted circles, as experimental units and quantify how cryogenic soil processes affect plant communities and carbon fluxes in arctic soils. I show that the cryoturbation has been an important mechanism for transporting carbon downwards in the studied soil over the last millennia. Interestingly, burial of organic material by cryoturbation appears to have mainly occurred during bioclimatic events occurring around A.D. 900-1250 and A.D. 1650-1950 as indicated by inferred 14C ages. Using a novel photogrammetric approach, I estimate that about 0.2-0.8 % of the carbon pool is annually subjected to a net downward transport induced by the physical motion of soil. Even though this flux seems small, it suggests that cryoturbation is an important transporter of carbon over centennial and millennial timescales and contributes to translocate organic matter to deeper soil layers where respiration proceeds at slow rates. Cryogenic processes not only affect the trajectories of the soil carbon, but also generate plant community changes in both species composition and abundance, as indicated by a conducted plant survey on non-sorted circles subjected to variable differential frost heave during the winter. Here, disturbance-tolerant plant species, such as Carex capillaris and Tofieldia pusilla, seem to be favoured by disturbance generated by the differential heave. Comparison with findings from a previous plant survey on the site conducted in the 1980s suggest that the warmer temperatures during the last decades have resulted in decreased differential heave in the studied non-sorted circles. I argue that this change in cryogenic activity has increased abundance of plants present in the 1980s. The fact that the activity and function of the non-sorted circles in Abisko are undergoing changes is further supported by their contemporary carbon dioxide (CO2) fluxes. Here, my measurements of CO2 fluxes suggest that all studied non-sorted circles act as net CO2 sources and thus that the carbon balance of the soils are in a transition state. My results highlight the complex but important relationship between cryogenic soil processes and the carbon balance of arctic soils.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2016. 18 p.
Keyword
Non-sorted circle, Carbon storage, Soil motion, Terrestrial photogrammetry, Cryoturbation, Carbon fluxes
National Category
Other Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:umu:diva-112509 (URN)978-91-7601-361-8 (ISBN)
Public defence
2016-01-22, Stora Hörsalen, KBC-huset, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2015-12-18 Created: 2015-12-09 Last updated: 2015-12-17Bibliographically approved

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Becher, MarinaBörlin, NiclasKlaminder, Johan
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Department of Ecology and Environmental SciencesDepartment of Computing Science
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