Canadian Forest Service Publications

Effect of drainage and wildfire on peat hydrophysical properties. 2013. Sherwood, J.H.; Kettridge, N.; Thompson, D.K.; Morris, P.J.; Silins, U.; Waddington, J.M. Hydrological Processes 27(13):1866-1874.

Year: 2013

Issued by: Northern Forestry Centre

Catalog ID: 35505

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1002/hyp.9820

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Consecutive multiple disturbances to northern peatlands can dramatically impact peat hydrophysical properties. We examine the impact of a double disturbance (drainage and wildfire) on the hydrophysical and moisture retention properties of peat, a key regulator of peatland ecohydrological resilience, and compare this with the impact to each individual disturbance (drainage and wildfire). The compound effect of drainage and wildfire resulted in a shift of the surface datum down the peat profile, revealing denser peat. Less-dense near-surface peats that regulate water-table position and near-surface moisture content, both favourable to Sphagnum recolonization, were lost. At a drained peatland that was then subject to wildfire, peat bulk density increased by 14.1%, von Post humification class increased by two categories and water retention increased by 15.6%, compared with an adjacent burned but undrained (single disturbance) portion of the fen. We discuss the key hydrophysical metrics of peatland vulnerability and outline how they are affected by the isolated impacts of drainage and wildfire, as well as their combined effects.We demonstrate that multiple peatland disturbances have likely led to an increase in hydrological limitations to Sphagnum recovery, which may impact peatland ecohydrological resilience.

Plain Language Summary

We examined the effects of a double disturbance (drainage followed by fire) on the peat properties of a peatland near Slave Lake, Alberta. We had data about the study area both before and after the disturbances occurred. Drainage, which took place in 1987, increased near-surface peat density and caused a substantial decline in the water table. The subsequent fire, which occurred in 2001, exposed the high density peat at the surface, leading to a risk of even further declines in the water table. This dramatic change in peat properties and the subsequent decline in the water table could have contributed to the lack of recolonization of sphagnum mosses in the peatland after the fire. As a result, the ecosystem may have become less able to store carbon over the long term.