| Summary: | Development of the oil sands has led to increasing atmospheric N deposition, with values as high as 17 kg N ha -1 yr -1 ; regional background levels <2 kg N ha -1 yr -1 . Bogs, being ombrotrophic, may be especially susceptible to increasing N deposition. To examine responses to N deposition, over five years, we experimentally applied N (as NH 4 NO 3 ) to a bog near Mariana Lakes, Alberta, at rates of 0, 5, 10, 15, 20, and 25 kg N ha -1 yr -1 , plus controls (no water or N addition). We collected surface pore water from all plots several times a year throughout the 5 year experiment. Porewater NH 4 + -N, NO 3 - -N, and DON concentrations were unaffected by N input in any of the five years (rmANOVA; p = 0.44, 0.37, and 0.82, respectively). We hypothesized that as N deposition increases to a level that exceeds the capacity of the bog vegetation to take up N, net N mineralization in surface peat would be inhibited by higher NH 4 + -N availability, net nitrification would be stimulated by higher NH 4 + -N availability, and concentrations of DIN in porewater at the top of the water table would increase, as DIN bypasses interception by the ground layer vegetation. None of these hypotheses was supported with nitrogen being immediately taken up by vegetation. It is unclear if longer term study would reveal similar responses.
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