PREDICTING METHANE EMISSION FROM BRYOPHYTE DISTRIBUTION IN NORTHERN CANADIAN PEATLANDS

A predictive model for bryophyte distribution, water table position, and seasonal mean methane (CH4) emission was developed for two areas of northern peatland: the Clay Belt of Ontario and the Labrador Trough of Quebec. Water table position and CH4 flux were the most important environmental variables in canonical correspondence analyses (CCA) of bryophyte data. Water chemistry constituted a second environmental gradient, independent of hydrology and CH4 flux. Weighted averaging regression and calibration were used to develop a model for predicting log CH4 flux from bryophyte distribution. The model showed an increase in log CH4 flux from hummock to carpet and pool species, corresponding with a decrease in height above the mean water table position. The exceptions were rich-fen pool species, which had low CH4 flux optima in spite of their moisture status. Tolerances were greatest for mid-hummock species and least for carpet and pool species. No overlap in tolerances occurred between hummock and pool species, suggesting that species at either end of the height gradient are the best predictors of CH4 flux. Error analyses showed that bryophytes are equally as effective as water table position for predicting mean CH4 flux even though bryophytes are only surrogates for the degree of anaerobism/aerobism in the peat profile. Bryophytes are distributed in well-defined zones along microtopographic gradients; they integrate long-term changes in the water table, which fluctuates on a daily and seasonal basis along with CH4 flux, and may be more easily mapped with remote-sensing techniques. Bryophytes, however, are only useful for predicting CH4 flux within a region; similar species values cannot be extrapolated to other northern peatlands where different climatic and biogeochemical factors may result in different ranges of CH4 emission. The model may be used in paleoreconstructions of methane emission and for biological monitoring of climate change.