O-18 COMPOSITION OF SPHAGNUM, AND MICROENVIRONMENTAL WATER RELATIONS

The O-18 isotope content of five species of Sphagnum from three peatlands in Ontario was analyzed. Sphagnum fuscum and S. capillifolium had significantly more enriched deltaO-18 values than S. fallax, S. magellanicum, and S. papillosum. The enriched values in the former species indicate that water involved in photosynthesis in hummock species is much more affected by evapotranspiration than in adjacent species situated in depressions. These data suggest that microenvironmental water relations regulate evapotranspiration in Sphagnum species. Environmental isotope analysis (O-18, H-2) is another technique that may shed light on understanding Sphagnum ecophysiology and water relations along microenvironmental gradients in northern peatlands.