Canadian Forest Service Publications

Seasonal variation in albedo and radiation exchange between a burned and unburned forested peatland: implications for peatland evaporation. 2015. Thompson, D.K.; Baisley, A.S.; Waddington, J.M. Hydrological Processes 29(14):3227-3235.

Year: 2015

Issued by: Northern Forestry Centre

Catalog ID: 35971

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1002/hyp.10436

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Forested boreal peatlands represent a precipitation-dependent ecosystem that is prone to wildfire disturbance. Solar radiation exchange in forested peatlands is modified by the growth of a heterogeneous, open-crown tree canopy, as well as by likely disturbance from wildfire. Radiation exchange at the peat surface is important in peatlands, as evaporation from the peat surface is the dominant pathway of water loss in peatlands of continental western North America. We examined shortwave and longwave radiation exchange in two forested ombrotrophic peatlands of central Alberta, Canada: one with (>75 years since wildfire; unburned) and another without a living spruce canopy (1–4 years since wildfire; burned) between the autumn of 2007 and 2010. Above-canopy winter albedo was nearly two times greater in the recently burned peatland than the unburned peatland. Incoming shortwave radiation at the peat surface was much higher at the burned peatland, which increases the amount of energy available for evaporation. This is especially true for hollow microforms that are generally shaded by the tree canopy in unburned peatlands. Snow-free albedo was similar between peatlands, although an increase in longwave losses at the burned site resulted in slightly greater net radiation at the unburned site.

Plain Language Summary

In this paper, we examine the transfer of solar radiation through the forest canopy to two forested peatlands in Alberta: one 75 years since the last fire, and the other three years since fire. In the site more recently burned, the black spruce tree cover was completely burned away; this layer formerly intercepted 20–40% of the solar radiation. In addition to the trees, the shrub canopy, which in an unburned stand intercepts an additional 40–50% of solar radiation, grew in quickly within three years of the fire. This relatively quick-growing shrub layer was able to intercept 20–40% of the solar radiation within three years of the fire, which provided shade cover to the peat surface and minimized evaporation. This finding is important in the post-wildfire ecological succession in forested peatlands because the shrub layer has been found to provide interim shading to the peat surface until a substantial tree cover can regrow, which can take upwards of 50 years after fire in this ecosystem.