Peat chemistry of a continental mire complex in western Canada

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Abstract
A continental peatland complex in western Canada containing varied vegetational landforms was studied to relate surface physiognomy to peatland development. Peat chemistry was used to determine the influence of water chemistry on landform formation and to assess the development of ombrotrophy on forested Sphagnum islands. Surface water chemistry at the site showed the following: pH 3.7–6.3; calcium content 0.9–15.6 mg/L; magnesium content 0.5–2.8 mg/L; and reduced conductivity 0–232 μS/cm. Peat cores were subdivided into two peat types, fen and forested Sphagnum islands. Spearman rank correlations and the Mann–Whitney U-test were used to determine significant differences in ash, bulk density, calcium, and magnesium. Elemental contents of surface peats are directly related to landform features. Elemental peat profiles exhibit three accumulation trends: stable, increasing, and declining. Fen peats have profiles that are stable or increase towards the peat surface, whereas forested Sphagnum island peats have profiles that decline toward the peat surface. During the development of the mire, fen peats receiving mineral-enriched waters have accumulated higher amounts of mineral ions. Forested Sphagnum islands have developed in hydrologically sheltered areas, resulting in the formation of mineral-poor peat. Surface water, vegetation, and peat stratigraphy suggest that the forested Sphagnum islands have become ombrotrophic, forming local recharge zones with a gradual transition from a mineral-poor environment to ombrotrophy.