Ecosystem‐Scale Methane Emissions From Peatlands of the Hudson Bay Lowlands

Abstract Northern peatlands are important sources of methane (CH 4 ) in the atmosphere. However, the magnitude of CH 4 emissions and their response to environmental factors are poorly constrained within the Hudson Bay Lowlands (HBL), the largest contiguous peatland complex in North America. This study investigated seasonal (April–November) eddy covariance‐derived ecosystem scale CH 4 emissions and their predictors from 16 site‐years over four different HBL peatlands. Average seasonal emissions were greatest at a permafrost‐free treed fen over 7 years (6.0 g CH 4 m −2 ; wettest and warmest peatland) and about 40% lower at a co‐located bog over 6 years (3.8 g CH 4 m −2 ). Emissions were least at a permafrost peat plateau 250 km to the north near the Hudson Bay coast over 1 year (2.6 g CH 4 m −2 ; driest and coolest peatland) and about 60% higher at a co‐located thawed peatland over 2 years (4.1 g CH 4 m −2 ). The combined temporal and spatial variability was not well explained by average air temperature or water table depth but instead was related to measures of soil temperature, soil moisture, and gross primary productivity, which were also significantly and positively correlated. At the daily scale, hysteresis was observed in the exponential CH 4 flux–soil temperature relationship. Water table depth was an important predictor of day‐to‐day variations in CH 4 flux. Results from these paired peatlands suggest that warming will generally increase CH 4 emissions in the HBL, which may be moderated by peat drying or exacerbated by peat plateau collapse and wetting in permafrost‐affected peatlands.