Rate of permafrost thaw and associated plant community dynamics in peatlands of northwestern Canada

• Published in: Journal of Ecology
• Main Authors: Errington, Ruth C., Macdonald, S. Ellen, Bhatti, Jagtar S.
• Other Authors: University of Alberta, Canadian Forest Service
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: Ice; Northwest Territories; Peat; Peat plateau; permafrost; Subarctic
• Online Access: http://dx.doi.org/10.1111/1365-2745.14339; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2745.14339

Abstract The most rapid climate warming is occurring in northern, permafrost environments. Peatlands of these regions are particularly sensitive to climate warming, with the high ground ice content of peat plateaux resulting in the formation of collapse scars as ground temperatures warm. To quantify the rates of permafrost thaw and associated vegetation changes, we sampled the plant and lichen communities in transects spanning actively thawing collapse scar margins at sites from mid‐Boreal to Low Subarctic conditions, within Canada's Northwest Territories. Seventeen transects were sampled in 2007/08 and 14 of these were resampled 10 years later. The rate of lateral permafrost thaw of collapse scar margins ranged from −6 to 63 cm year −1 (mean: 22.0 cm ± 4.7 cm year −1 (SE)); variability was high and no trends with respect to latitude or temperature gradients were detected. Plant communities displayed a clear gradient from lichen‐ and ericaceous shrub‐dominated peat plateaux, to collapse scars primarily characterized by Sphagnum mosses and graminoids. Both space‐for‐time (distance from collapsing margin) and direct measurement of 10‐year changes showed a successional sequence following permafrost thaw; floating mat communities characterized by Sphagnum riparium or S. balticum proceeded to lawn communities of S. angustifolium and, finally, to hummock communities with Mylia anomala or S. fuscum . This successional sequence was associated with increased water table depth and lower soil water content in plant communities farther from the actively collapsing front, illustrating that peat growth above the water table was driving plant community successional changes. The most rapid plant community succession occurred in recently thawed environments as peat growth propelled the ground surface above the water table while the slowest succession occurred in the collapse scar hummock communities located farthest from the actively collapsing peat plateau margin. Synthesis . In just 10 years, significant vegetation change was ...