Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands

Abstract

Ecosystem-scale methane (CH₄) flux (<i>F</i>_CH₄) over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. <i>F</i>_CH₄ was measured using eddy covariance with a closed-path analyzer in four years (2008–2011). Cumulative measured annual <i>F</i>_CH₄ (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH₄ m⁻² yr⁻¹ among the four study years, with a mean of 6.5 to 7.1 g CH₄ m⁻² yr⁻¹ depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with <i>F</i>_CH₄, with near surface soil temperature at 5 cm most correlated across spring, fall, and the whole season. The response of <i>F</i>_CH₄ to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but water table also exerted influence with <i>F</i>_CH₄ highest when water was 2–13 cm below and least when it was at or above the mean peat surface

Net ecosystem methane and carbon dioxide exchanges in a Lake Erie coastal marsh and a nearby cropland

“…Soil temperature, highly associated with methanogenesis activity and the production of CH 4 [ Le Mer and Roger , ], was the major controlling factor of the daily‐to‐yearly F CH4 . The regulation of seasonal F CH4 by soil temperature was also reported in the previous studies [ Hanis et al , ; Herbst et al , ; Tagesson et al , ]. The high R 2 and similar temperature sensitivity between 2011 and 2012 suggested a relatively stable seasonal temperature dependency at the marsh.…”

Evidence for a nonmonotonic relationship between ecosystem‐scale peatland methane emissions and water table depth

“…Like us, Hanis et al . [] found both soil temperature (60 cm) and air temperature produced the best model, although in this case as a linear response. Daily air temperature peaks earlier and demonstrates both greater seasonal and day‐to‐day variability (see supporting information).…”

“…Total summer (mid‐May to end of September) CH 4 emissions reported here using eddy covariance methods are similar to the growing season totals for a number of sites including a western Canadian boreal treed fen (2.4 g C m −2 ) [ Long et al ., ], a high Arctic fen in Greenland (2.8 g C m −2 ) [ Friborg et al ., ], and Siberian tundra with a short Arctic growing season (1.9 g C m −2 ) [ Parmentier et al ., ]. Summer methane emissions at Mer Bleue are less than emissions from a subarctic fen in Canada (4 year average of 5.3 g C m −2 ) through the growing season and shoulder seasons [ Hanis et al ., ], a Finnish fen (11.4 g C m −2 ) during the snow‐free period [ Rinne et al ., ], and a boreal fen in Saskatchewan, Canada (16.3 g C m −2 ) from mid‐May to early October [ Suyker et al ., ]. However, unlike a number of the ecosystem‐scale studies of F CH4 listed above [ Suyker et al ., ; Friborg et al ., ; Parmentier et al ., ], the relationship between F CH4 and WT at Mer Bleue displayed considerable hysteresis and appeared to be nonmonotonic.…”

“…Overall, our model for daily F CH4 was not as successful as other studies where as much as 65% [ Suyker et al ., ], 74% [ Wille et al ., ; Hanis et al ., ], 82% [ Friborg et al ., ], and 87% [ Parmentier et al ., ] of the variation in F CH4 could be explained by environmental/climate variables. These were typically wetter sites that did not experience extended dry periods with very deep WT.…”

Mechanistic modeling of microbial interactions at pore to profile scale resolve methane emission dynamics from permafrost soil

“…It well established that soil methane emissions are strongly influenced by the seasonal dynamics of air temperature, active layer thickness, and water table position. Yet little is known regarding the production, oxidation, and storage mechanisms that directly shape methane fluxes during the spring melt and fall freezeup [ Hargreaves et al , ; Mastepanov et al , ; Hanis et al , ] .…”