Soil pore network response to freeze-thaw cycles in permafrost aggregates
Climate change in Arctic landscapes may increase freeze-thaw frequency within the active layer as well as newly thawed permafrost. A highly disruptive process, freeze-thaw can deform soil pores and alter the architecture of the soil pore network with varied impacts to water transport and retention,...
| Published in: | Geoderma |
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| Main Authors: | , , , , , , , , , , , , , |
| Language: | unknown |
| Published: |
2023
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| Subjects: | |
| Online Access: | http://www.osti.gov/servlets/purl/1845008 https://www.osti.gov/biblio/1845008 https://doi.org/10.1016/j.geoderma.2021.115674 |
| Summary: | Climate change in Arctic landscapes may increase freeze-thaw frequency within the active layer as well as newly thawed permafrost. A highly disruptive process, freeze-thaw can deform soil pores and alter the architecture of the soil pore network with varied impacts to water transport and retention, redox conditions, and microbial activity. Our objective was to investigate how freeze-thaw cycles impacted the pore network of newly thawed permafrost aggregates to improve understanding of what type of transformations can be expected from warming Arctic landscapes. We measured the impact of freeze-thaw on pore morphology, pore throat size distribution, and pore connectivity with X-ray computed tomography (XCT) using six permafrost aggregates with sizes of 2.5 cm 3 from mineral soil (28-50 cm depths) in Toolik, Alaska. Freeze-thaw cycles were performed using a laboratory incubation consisting of five freeze-thaw cycles (-10°C to 20°C) over five weeks. Our findings indicated decreasing connectedness of individual pores across all aggregates with higher frequencies of singly connected pores following freeze-thaw. Water-filled pores that were connected to the larger pore network decreased in volume while the overall connected pore volume was not affected. Shifts in the pore throat size distribution were mostly observed in pore throats ranges of 100 microns or less with no corresponding changes to the pore shape factor of pore throats. Responses of the pore network to freeze-thaw varied with aggregate, suggesting that initial pore morphology may determine freeze-thaw response. Our research suggests that freeze-thaw alters the microenvironment of permafrost aggregates during the incipient stage of deformation following permafrost thaw, impacting soil properties and function in Arctic landscapes undergoing transition. |
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