Dissolved Organic Carbon Concentration Affected by Warming and Water Table Lowering in a Boreal Continental Bog

English Abstract:

Mid-latitude peatlands have accumulated significant carbon (C) stocks as a result of their persistent C sink function. The large C stocks are predicted to respond to global climate changes with increased C losses from these ecosystems. An increase in air and soil temperature and subsequent lowering of water level in bogs may elevate dissolved organic carbon (DOC) concentration in the pore water and can add to the ecosystem C losses in the forms of peat respiration and hydrologic export. During the growing seasons (May to October) of 2012 and 2013, we compared pore water DOC concentration across hummock-hollow microtopography among three sites situated in a continental boreal treed bog located near the town of Wandering River, Alberta. The three sites were; control, recent (2-3 years; experimental) and older drained (12-13 years; drained) with water levels on average at 38, 74 and 120 cm below peat surface, respectively. Pore water DOC concentration was significantly different among the sites with the highest at the drained site (111 mg l^-1) followed by 95 mg l^-1 at the experimental and the lowest at the control site (81 mg l^-1). A peat surface warming of ~ 1℃ significantly increased DOC concentration and interacted with microform to result in highest concentration at the drained warmed hummocks. Therefore, we conclude that warming and water table lowering may influence the concentration and chemistry of pore water DOC and feedback to carbon biogeochemical cycling both within the peatland and downstream ecosystems.