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, nitro gen and sulfur were measured in flora and soil organic matter from the Sift on Bog and Point Pelee Marsh, which are located in the temperate climatic z one of southwestern, Ontario, Canada. Characteristic bog vegetation contain s 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 t he Point Pelee Marsh. Flora from both wetlands have delta(13)C values that are similar and characteristic of vegetation possessing the C-3 photosynthe tic pathway. The only exception is Utricularia vulgaris L. at the Point Pel ee Marsh, which is C-13-enriched (average delta(13)C = -18.4 parts per thou sand; range -18.8 to -17.6 parts per thousand) probably because of CO2 limi tation during growth. Organic matter from peat soils at each wetland exhibi ts 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 consum ption of labile carbohydrates and fixation of nitrogen by soil microorganis ms. Both C:N ratios and delta(13)C values stabilize at a shallow depth in s oils at the Point Pelee Marsh, consistent with greater decay efficiency and less recalcitrant vegetation in marsh than in bog environments. Paleoveget ational changes associated with a fen to bog succession also may have contr ibuted to the more gradual and larger change in delta(13)C values and C:N r atios observed for soil organic matter at the Sifton Bog.