ABSTRACT: Hydrology of an old abandoned block-cut peat bog, Cacouna, Québec.

CGRG Bibliography of Canadian Geomorphology
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Abstract

A manually block-cut peatland near Rivière-du-Loup, Québec abandoned in 1975 has experienced slow and incomplete natural revegetation. Understanding the changes over itsdevelopment, degradation and incomplete restoration provides lessons for managing the restoration of old and newly abandoned peatland systems. The Cacouna bog developedapproximately 5 m of peat over 8730±90 years. Following drainage in 1942, the peat surface subsided an average of 0.56±.15 m as a consequence of overburden pressure no longer providing buoyancy to the peat, and from oxidation. Peat cutting removed an additional 0.93±.37 m of peat, in a sequence of basins typically 180 m long, 12 m wide, and separated by 4 to 6 m baulks. Subsidence and oxidation, combined with surface cutting, has reduced the specific yield from 0.5 to about 0.05, and the hydraulic conductivity from 4 x 10 -5 to 1.2 x 10 -5 cm s -1 . Consequently water table rises are rapid, and drainage is primarily by surface flow through the partly collapsed ditch network. Runoff ratios outside the snowmelt period range from 0.16 to 0.35, but during this period evaporation exceeds precipitation, and is 5 to 10 times greater than runoff. However, the accumulation of a litter, primarily of ericaceae leaves, notably reduced evaporation losses from bare peat surfaces. Water collects preferentially in the basins,notably along the lateral ditches. While many bog plants have returned, 83% of Sphagnum revegetation is restricted to these wetter sites, which themselves have a Sphagnum cover up to25%. In total, only 16% of the bog had a Sphagnum cover. Sites recolonized by Sphagnum generally maintained soil moisture above 50%, and water tension above –100 mb throughoutthe season, whereas sites without Sphagnum cover did not.

Bibliography of Canadian Geomorphology