UNCERTAINTY IN PREDICTING THE EFFECT OF CLIMATIC-CHANGE ON THE CARBONCYCLING OF CANADIAN PEATLANDS

Northern peatlands play an important role globally in the cycling of C , through the exchange of CO2 with the atmosphere, the emission of CH4 , the production and export of dissolved organic carbon (DOC) and the storage of C. Under 2 x CO2 GCM scenarios, most Canadian peatlands wil l be exposed to increases in mean annual temperature ranging between 2 and 6 degrees C and increases in mean annual precipitation of 0 to 15 %, with the most pronounced changes occurring during the winter. The increase in CO2 uptake by plants, through warmer temperatures and elev ated atmospheric CO2, is likely to be offset by increased soil respira tion rates in response to warmer soils and lowered water tables. CH4 e missions are likely to decrease in most peatlands because of lowered w ater tables, except where the peat surface adjusts to fluctuating wate r tables, and in permafrost, where the collapse of dry plateau and pal sa will lead to increased CH4 emission. There likely will be little ch ange in DOC production, but DOC export to water bodies will decrease a s runoff decreases. The storage of C in peatlands is sensitive to all C cycle components and is difficult to predict. The challenge is to de velop quantitative models capable of making these predictions for diff erent peatlands. We present some qualitative responses, with levels of uncertainty. There will be, however, as much variation in response to climatic change within a peatland as there will be among peatland reg ions.