Dynamics and Biogeochemistry of River Corridors and Wetlands (Proceedings of symposium S4 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 294, 2005, 130-138

Abstract Over the last 200 years land-use change in southern Ontario, Canada, has reduced wetland area and altered peatland vegetation. More recent threats to wetlands include enhanced nutrient loading from agricultural areas, which may have a profound impact on bog vegetation and carbon dynamics—potentially leading to peat degradation. We examined vegetation pattern change (1964–1999) and contemporary carbon dioxide exchange in a kettle-hole bog in an agricultural landscape undergoing a shift to crops with nonpoint source nutrient loading. Many of the zones of bog vegetation change (loss in Sphagnum sp. and Chamaedaphne calyculata and increase in Carex spp. and Thelypteris palustris) occurred near the lagg in zones that also had high NO₃^- concentrations (10–20 mg l^-1). The loss of typical bog species along the margin of the peatland (adjacent to the lagg) was accompanied by an expansion of the lagg from 11 to 17% of the overall peatland area. Carbon dioxide exchange results suggest that some sections of the bog are degrading (large loss of CO₂ to the atmosphere). Although it has been suggested that watershed deforestation by European settlement led to the expansion of southern Ontario kettle-hole bogs, the patterns of vegetation change in this study suggest that this bog is reverting to a poor fen.

Key words agriculture; carbon dioxide exchange; GIS; hydrology; nitrate; vegetation; wetland