Date of Award

2-2009

Degree Type

Thesis

Degree Name

Master of Science (MSc)

Department

Geography

Supervisor

James M. Waddington

Language

English

Abstract

Pristine peatlands store approximately one-third of the world's soil carbon through the long-term accumulation of carbon as peat (Gorham, 1991). In Canada and Europe, peatlands are exploited for peat fuel and horticultural peat, which has an impact on the hydrological conditions and carbon balance of these ecosystems. Recent advances in peatland restoration techniques (e.g., Rochefort, 2000) have succeeded in the revegetation of Sphagnum moss on previously cutover surfaces. However, a peatland can only be considered functionally 'restored' after the newly formed moss layer has achieved a thickness such that the water table position in a drought year does not extend into the underlying formerly cutover peat surface (i.e. an acrotelm is developed). This study determines ecohydrological and hydrophysical properties of a newly formed peat layer, compares them to those of a nearby natural site and a naturally revegetated site and examines the spatio-temporal development of a new peat layer at a restored peatland, and from this, estimates of when the newly developing moss layer in a restored peatland will become a functional acrotelm are made.

The properties of the new peat layer differed significantly between the sites, especially for the lower (8-12 cm) layer. Lower samples for the natural and naturally revegetated sites had a bulk density of 43 ± 5 kg m-3 and 41 ± 11 kg m-3 respectively, almost twice as high as the value for lower samples from the restored site (24 ± 4 kg m-3 ). Sphagnum rubellum capitula density (ρc) was significantly higher (p < 0.05) for the restored peatland (28726 # m-2 ) compared to the natural site (26050 # m-2 ). Residual moisture content at 200 mb (- 200 cm in soil tension) (θr ) was significantly lower (p < 0.05) for the restored site in comparison to the natural and naturally revegetated sites for the lower samples (8-12 cm). This suggests that Sphagnum rubellum in a natural peatland is able to hold onto more moisture under increasing soil-tension than the same species growing in a restored site likely due to its higher bulk density and relatively more decomposed state.

The new moss layer thickness increased from 2.3 ± 1.7 cm in 2003 to 13.6 ± 6.5 cm in 2007 at the restored site. For the cutover (unrestored) portion of the peatland, the mean thickness values were significantly lower than the mean values for the restored portion of the site for each year (p < 0.001 for all years). Accumulated new peat layer biomass at the restored site increased over the six years post-restoration, ranging from 47 ± 43 g m-2 in 2000 to 1692 ± 932 g m-2 in 2005. The cutover (unrestored) portion of the site showed higher biomass accumulation for ericaceous vegetation, but lower Sphagnum, other mosses and other vascular biomass accumulation. A simple hydrological model was developed and determined that for the Bois-des-Bel peatland, given the mean summer water deficit at the site (-64 mm) and the storativity properties of the new moss layer (Sy = 0.34), a 19 cm thick moss layer would be required to offset summer deficit induced water table drop. elymo's (1984) model for acrotelm growth was parameterized to estimate how long it would take to develop a 19 cm moss layer at the restored site. Model results coupled to a GIS database for the site suggest that within 17 years post-restoration, more than 50% of the site would be above the 19 cm thickness threshold, an indication that peatland ecosystem restoration from a carbon accumulation and hydrologic perspective may be achieved in the medium-term. This ecohydrological approach will aid in designing a sampling strategy that can be useful in assessing the long-term impact of restoration on peatland ecohydrology and modelling carbon sequestration.

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