Nitrogen dynamics in floating and non-floating peatlands in the Western Boreal Plain

The overall objective of this study was to measure the major nitrogen pools and fluxes in nutrient- and peat-rich, vegetated marshes and fens surrounding shallow ponds in the Western Boreal Plain (WBP) of Canada. Within the same peatland-pond complex, marshes and fens did not differ from each other in major N fluxes and pool sizes; however, significant differences in N dynamics were measured between different peatland-ponds. Specifically, N cycling rates (gross and net mineralization) were much greater in a floating peatland than in a non-floating peatland. Gross N mineralization rates were 59 and 453 mg N m-2 d-1 in the non-floating and floating peatlands, respectively. Gross ammonification rates were approximately 4–10 times net rates while gross nitrification rates were 500–800 times net rates, indicating rapid turnover of extractable inorganic N pools. Increased moisture and carbon in the floating peat supported higher microbial biomass and activity, however net primary production values were lower, presumably due to competition by microbes for available inorganic N. Monthly measurements of N fluxes were combined to provide an estimate of annual internal N cycling within marshes and fens surrounding shallow ponds in the WBP. Key words: Gross mineralization, microbial biomass, nitrogen, peatland