Canadian Forest Service Publications
Moderate drop in water table increases peatland vulnerability to post-fire regime shift. 2015. Kettridge, N.; Turetsky, M.R.; Sherwood, J.H.; Thompson, D.K.; Miller, C.A.; Benscoter, B.W.; Flannigan, M.D.; Wotton, B.M.; Waddington, J.M. Scientific Reports 5(8063):1-4.
Issued by: Northern Forestry Centre
Catalog ID: 35909
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Northern and tropical peatlands represent a globally significant carbon reserve accumulated over thousands of years of waterlogged conditions. It is unclear whether moderate drying predicted for northern peatlands will stimulate burning and carbon losses as has occurred in their smaller tropical counterparts where the carbon legacy has been destabilized due to severe drainage and deep peat fires. Capitalizing on a unique long-term experiment, we quantify the post-wildfire recovery of a northern peatland subjected to decadal drainage. We show that the moderate drop in water table position predicted for most northern regions triggers a shift in vegetation composition previously observed within only severely disturbed tropical peatlands. The combined impact of moderate drainage followed by wildfire converted the low productivity, moss-dominated peatland to a non-carbon accumulating shrub-grass ecosystem. This new ecosystem is likely to experience a low intensity, high frequency wildfire regime, which will further deplete the legacy of stored peat carbon.
Plain Language Summary
This paper is a case study of a peatland located 35 km southeast of Slave Lake, Alberta, that was drained experimentally in the early 1980s to study the impact of peatland drainage on tree growth. After being drained for nearly 20 years, the 2001 Chisholm wildfire burned over the entire drained peatland area. We visited the site and examined the vegetation and peat soil structure in 2008. We found that none of the peat-forming mosses grew back in the drained area of the peatland after the fire, while the un-drained areas of the peatland recovered their peat-forming mosses in abundance. In place of the peat-forming mosses, shrubs and grass dominated the drained area. By examining both the sunlight levels at the ground surface and the drained peat’s physical properties, we conclude that both of those factors are likely responsible for making the drained and burned portion of the peatland inhospitable to the growth of the peat-forming mosses that were responsible for the formation of the peatland in the first place. This shift towards a non-peat forming grass-shrub ecosystem is likely irreversible without direct human intervention such as blocking the drainage ditches. This site may serve as a model for future climate change where increasing temperatures may affect peatlands similar to the drainage impact observed here, resulting in an increased frequency of this post-fire vegetation shift.