Carbon-isotope ratios and carbon, nitrogen and sulfur abundances in flora and soil organic matter from a temperate-zone bog and marsh

Stable carbon-isotope ratios (C-13/C-12) and the abundance of carbon, nitrogen and sulfur were measured in flora and soil organic matter from the Sifton Bog and Point Pelee Marsh, which are located in the temperate climatic zone of southwestern, Ontario, Canada. Characteristic bog vegetation contains less N and S than marsh flora; however, invasive species (e.g., Typha) at the Sifton Bog have N and S contents that are similar to vegetation from the Point Pelee Marsh. Flora from both wetlands have delta(13)C values that are similar and characteristic of vegetation possessing the C-3 photosynthetic pathway. The only exception is Utricularia vulgaris L. at the Point Pelee Marsh, which is C-13-enriched (average delta(13)C = -18.4 parts per thousand; range -18.8 to -17.6 parts per thousand) probably because of CO2 limitation during growth. Organic matter from peat soils at each wetland exhibits a similar depth distribution of C:N ratios and delta(13)C values. The C:N ratio of soil organic matter decreases with depth, consistent with consumption of labile carbohydrates and fixation of nitrogen by soil microorganisms. Both C:N ratios and delta(13)C values stabilize at a shallow depth in soils at the Point Pelee Marsh, consistent with greater decay efficiency and less recalcitrant vegetation in marsh than in bog environments. Paleovegetational changes associated with a fen to bog succession also may have contributed to the more gradual and larger change in delta(13)C values and C:N ratios observed for soil organic matter at the Sifton Bog.