Nitrogen and sulfur input and accumulation in continental ombrotrophic peatland ecosystems in Alberta, Canada

Abstract

Models predict increases in N and S deposition in the Athabasca Oil Sands Region of Alberta that often exceed critical load values for sensitive ecosystems. I used 10 bog sites within a modeled deposition gradient to assess current SO₄^2-, NO₃^-, and NH ₄⁺ deposition rates compared to historical N and S accumulations. There were no spatial patterns in NO₃^-, NH ₄⁺, total inorganic N, and SO₄^2- deposition rates, and deposition from all sites were low and not above predicted background levels. There were also no spatial patterns in C, N, and S accumulation data. An interesting pattern persisted across all sites: data showed substantially more peat N accumulation than can be accounted for through atmospheric deposition alone. I examined whether biological N2 fixation could be an additional source and found evidence of nitrogenase activity in all bryophyte communities sampled. This phenomenon may represent a previously underestimated source of N to boreal bogs.