Aboveground peat and carbon accumulation potentials along a bog-fen-marsh wetland gradient in southern boreal Alberta, Canada

Abstract

Production-to-decomposition quotients and asymptotic limits of peat accumulation were determined to estimate peat and carbon accumulation potentials along a bog-fen-marsh wetland gradient in southern boreal Alberta. The wetlands were a bog, a poor fen (PF), a wooded moderate-rich fen (WRF), a lacustrine sedge fen (LSF), a riverine sedge fen (RSF), a riverine marsh (RM), and a lacustrine marsh (LM). First year mass losses increased along this gradient (bog 14%, fens 25–61%, marshes 57–62%), with second year total mass losses increasing from 18 to 38% from the bog to the moderate-rich fens. Ratios of aboveground net primary production to decomposition and asymptotic limits of peat accumulation showed decreasing trends from the bog to the fens to the marshes as decay rates increased along the same gradient. TheSphagnum-dominated sites (bog, PF) showed greater peat accumulation potentials than the brown moss-dominated sites (WRF, LSF) and those sites with an insignificant-to-no moss stratum (RSF, RM, LM), which is paralleled by their decreasing peat thicknesses. Rates of litter accumulation in the first year averaged 170 g m−2 yr−1 inSphagnum-dominated sites, 130 g m−2 yr−1 in brown moss-dominated sites, and 103 g m−2 yr−1 in sites with an insignificant-to-no moss stratum. All three wetland types showed similar carbon accumulation potentials (83, 67, and 50 g m−2 yr−1, respectively) after the first year of decomposition. Peat depth, asymptotic limits of peat accumulation, and production-to-decomposition ratios correlated negatively with water levels, pH, and Ca2+, and they correlated positively with moss and woody plant production (shrubs, trees). Peatlands with strong moss and shrub/tree strata (bog, PF, WRF) accumulate more peat than those wetlands dominated by graminoids (LSF, RSF, RM, LM). In the bog, high peat accumulation potentials may be related to low rates of decomposition. The peat accumulation potentials of some fens (PF, WRF) are similar to the bog and may be maintained by higher decomposition rates, which are offset by higher litter inputs. In the graminoid-dominated fens and marshes, peat accumulation potentials are lowest and may be related to higher litter quality, resulting in higher decomposition rates.