Soil pore network response to freeze-thaw cycles in permafrost aggregates
Erin C. Rooney,
Vanessa L. Bailey,
Kaizad F. Patel,
Maria Dragila,
Anil K. Battu,
Alexander C. Buchko,
Adrian C. Gallo,
Jeffery Hatten,
Angela R. Possinger,
Odeta Qafoku,
Loren.R. Reno,
Michael SanClements,
Tamas Varga,
Rebecca A. Lybrand
Affiliations
Erin C. Rooney
Dept. of Crop and Soil Science, Oregon State University, Corvallis, OR, USA; Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA; Corresponding authors at: Oregon State University, Dept. of Crop and Soil Science, USA (E.C. Rooney). Dept of Land, Air, and Water Resources, University of California-Davis, Davis, CA USA (R.A. Lybrand).
Vanessa L. Bailey
Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
Kaizad F. Patel
Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
Maria Dragila
Dept. of Crop and Soil Science, Oregon State University, Corvallis, OR, USA
Anil K. Battu
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
Alexander C. Buchko
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
Adrian C. Gallo
Dept. of Crop and Soil Science, Oregon State University, Corvallis, OR, USA
Jeffery Hatten
Dept. of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, OR, USA
Angela R. Possinger
Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA, USA
Odeta Qafoku
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
Loren.R. Reno
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
Michael SanClements
National Ecological Observatory Network, Boulder, CO, USA
Tamas Varga
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA
Rebecca A. Lybrand
Dept. of Crop and Soil Science, Oregon State University, Corvallis, OR, USA; Corresponding authors at: Oregon State University, Dept. of Crop and Soil Science, USA (E.C. Rooney). Dept of Land, Air, and Water Resources, University of California-Davis, Davis, CA USA (R.A. Lybrand).
Climate change in Arctic landscapes may increase freeze–thaw frequency within the active layer as well as newly thawed permafrost. Freeze-thaw is a highly disruptive process that 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 diameter distribution, and pore connectivity with X-ray computed tomography (XCT) using six permafrost aggregates with sizes of 2.5 cm3 from a mineral soil horizon (Bw; 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 spatial connectivity of the pore network across all aggregates with higher frequencies of singly connected pores following freeze–thaw. Water-filled pores that were connected to the pore network decreased in volume while the overall connected pore volumetric fraction was not affected. Shifts in the pore throat diameter distribution were mostly observed in pore throats ranges of 100 µm or less with no corresponding changes to the pore shape factor of pore throats. Responses of the pore network to freeze–thaw varied by aggregate, suggesting that initial pore morphology may play a role in driving 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.
