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Carbon dioxide fluxes in a northern fen during a hot, dry summer
Author(s) -
Schreader Cheryl P.,
Rouse Wayne R.,
Griffis Timothy J.,
Boudreau L. Dale,
Blanken P. D.
Publication year - 1998
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/98gb02738
Subject(s) - carbon dioxide , environmental science , ecosystem respiration , photosynthesis , atmospheric sciences , respiration , subarctic climate , water table , hydrology (agriculture) , ecosystem , zoology , oceanography , chemistry , ecology , primary production , geology , botany , biology , biochemistry , geotechnical engineering , groundwater
Atmospheric gradient techniques were used to measure the net ecosystem exchange of CO 2 for a subarctic sedge fen near Churchill, Manitoba, during the summer of 1994. This was the second driest and wannest summer since 1943. The mean daily temperature was 2°C above average, and the rainfall was 55% below normal. More than half of the rain fell after the main growth period. The fen landscape comprises hummocks and hollows. Equilibrium retention storage occurs at an average standing water depth of 80 mm above the hollow bottoms (water table reference is O). During the summer of 1994 the average water table position at −117 mm resided well below the zero equilibrium retention depth. Periodically this decreased to −265 mm, well below a 30‐year average depth of −70 mm. During the full summer period, measurements indicate that the fen was a source of CO 2 . Only during a relatively short period of most active photosynthesis in midseason was there a small net CO 2 uptake. A deep and warm soil aerobic layer promoted a large respiration flux, and this exceeded the photosynthetic CO 2 uptake of the stressed sedge community. Diurnally, changes in surface temperature and incident solar radiation can explain most of the changes in the net CO 2 exchange. It is hypothesized that in 1994 photosynthesis was significantly decreased and the respiration loss enhanced by the hot, dry conditions. If this hypothesis is correct, by analogy, climate warming would need to be accompanied by a substantial rainfall increase to maintain a condition of net CO 2 gain to this peatland.