Peatlands are an important component of the global carbon cycle, storing 23 g C m-2 yr-1 to comprise a global carbon pool of approximately 455 Pg. Peat drainage and harvesting results in removal of surface vegetation, thereby reducing gross photosynthesis to zero. Moreover, lowering the water table increases carbon oxidation. Consequently, peatland drainage and mining can reduce or eliminate the carbon sink function of the peatland. In the first part of this study, net ecosystem CO2 exchange was studied in a natural (NATURAL), two-year (YOUNG) and seven-year (OLD) post cutover peatland near Ste. Marguerite Marie, Quebec during the summer of 1998. Although the NATURAL site was a source of CO2 during the study season, CO2 emissions were 270 to 300% higher in the cutover sites (138, 363, and 399 g CO2-C m-2; NATURAL, YOUNG and OLD, respectively). Active restoration practices and natural re-vegetation of peatlands have the potential to return these ecosystems to net carbon sinks by increasing net ecosystem production (NEP) and therefore decreasing CO2 emissions to the atmosphere. Net ecosystem CO2 exchange in a natural (NATURAL) peatland and a partly restored peatland (REST) near Ste. Marguerite Marie, Quebec, was compared with a naturally re-vegetated peatland (RVEG) near Riviere-du-Loup, Quebec. Ecophysiological parameters indicate that the REST site was more than twice as productive as the natural LAWNS and three times as the RVEG site (GPmax=18.0, 8.3, and 6.5 g CO2 m-2 d-1, respectively). These results indicate that active restoration improves carbon sequestration over natural re-vegetation but that the net carbon sink function at both sites has not been restored. The presence of Sphagnum cover at the RVEG site resulted in a significant decrease in net ecosystem respiration (NER), indicating the potential for decreasing soil respiration at restored cutover sites through increasing the volumetric soil moisture content.

Master of Science (MSc)

Thesis