The Effect of Restoration on CO2 Exchange in a Cutover Peatland

Abstract

<p>Natural peatlands are important components in the global carbon cycle as they represent a net long-term sink of atmospheric carbon dioxide (C02), however, peatland extraction converts these ecosystems to persistent sources of atmospheric C02 following abandonment. Peatland restoration techniques have been developed with the aim to restore cutover peatlands to carbon-accumulating ecosystem. This is accomplished by raising the water table and reintroducing Sphagnum peat-forming species. The goal of this thesis was to examine effect of restoration on peatland-atmosphere C02 exchange at a cutover peatland.</p> <p>Peat respiration decreased in the restored site post-restoration, which was partially due to the rewetting. However, the seasonal average peat respiration from both the restored and cutover sites were not significantly different from each other. Subsequently, rates of gross ecosystem production have increased over the same period due to the emerging vegetative cover, with seasonal mean net ecosystem exchange fluxes for both herbaceous and moss vegetation displaying significant improved net C02 fixation with time post restoration. Light response curves showing the relationship between gross ecosystem production of C02 (GEP) and photosynthetically active radiation (PAR) indicate that both the apparent quantum efficiency and the maximum GEP (Amax) increased with time post-restoration.</p> <p>Chamber flux measurements upscaled to the ecosystem level based on the percent cover of each plant species, indicate that the restored site, both one and two years postrestoration (2000, 2001) was a net sink of C02 over the study season (May-October), storing~ 13.5 and 20.2 g C m^-2 respectively. Over the same study seasons, the cutover site remained a large source of C02, releasing ~ 136.8 and 83.0 g C m^-2 in 2000 and 2001 respectively.</p> <p>Biomass measurements suggest that the restored site is storing substantial amounts of carbon in above and belowground biomass five years post-restoration. Total biomass estimates at the restored site ranged from 2227.23 g m^-2 for Carex canescense to 489.32 g m^-2 for Polytrichum strictum, corresponding to a mean annual NPP of 222.72 g C m^-2 and 48.99 g C m^-2 respectively.</p> <p>Results of this thesis suggest that active ecosystem scale restoration techniques have the potential to return cutover peatlands to a net sink of atmospheric C02 within three to five years. The resultant increased storage of C02 post-restoration can be attributed in part by a reduction in peat respiration via active rewetting, in addition to the significant increase in ecosystem productivity from an evolving vegetative cover.</p>