Paper No. 3
Presentation Time: 8:40 AM
INTERANNUAL VARIABILITY IN THE CARBON BUDGET OF A TEMPERATE PEATLAND
OLSON, Donna1, GRIFFIS, Tim
2, KOLKA, Randy
1 and NOORMETS, Asko
3, (1)USDA Forest Service - Northern Research Station, Center for Research on Ecosystem Change, 1831 Hwy. 169 E, Grand Rapids, MN 55744, (2)Dept. Soil, Water, & Climate, University of Minnesota - Twin Cities, Land & Atmospheric Science, 1991 Upper Buford Circle, Soil Science Room 331, St. Paul, MN 55108, (3)North Carolina State University & Eastern Forest Environmental Threat Assessment Center, USDA FS, Department of Forestry and Environmental Resources, Venture Center II, Suite 300, Campus Box 7260, 920 Main Campus Drive, Raleigh, NC 27695, dmolson@fs.fed.us
Peatlands store significant amounts of carbon and may influence atmospheric radiative forcing through carbon dioxide (CO
2) and methane (CH
4) exchange with the atmosphere. While long-term records of net ecosystem CO
2 exchange (NEE) have been established, CH
4 flux measurements remain relatively rare and their influence on the annual carbon budget is not well known. Here, we report on a two-year (2009-2010) study of near-continuous CO
2 and CH
4 eddy flux measurements at a temperate peatland (Bog Lake Fen), Minnesota, USA. The objectives were to: 1) determine the annual carbon budget and contributions associated with CO
2 and CH
4 exchange; 2) examine interannual variability and sensitivity of the carbon budget to hydroclimatological conditions; and 3) quantify the relative importance of CH
4 fluxes on the carbon budget and examine its global warming potential (GWP) relative to the CO
2 budget.
Climate variations include antecedent moisture conditions, precipitation, and water table position. In 2009, snow cover remained about one full month later than 2010. Spring 2009 experienced a prolonged elevated water table position (75 days), while spring 2010 did not (10 days). Precipitation received in 2009 was approximately half (362.2 mm) that was received in 2010 (656.3 mm).
NEE in 2009 indicated greater carbon uptake than 2010. Spring and summer 2009 showed significantly greater carbon gains when compared to 2010. Carbon sequestration peaked in July 2009 when water table was subdued and soil temperatures were high (15°C). Warm fall temperatures and relatively low water table in 2009 resulted in significant carbon losses, while carbon sequestration continued in fall 2010.
CH4 fluxes increased from spring into summer and then decreased from late summer into fall. A more rapid increase in CH4 efflux was observed in 2009 versus 2010, coinciding with an elevated water table position and increase in soil temperature during early spring. A similar pattern was observed in fall 2010. While NEE was greater (more sequestration) during 2009, CH4 effluxes were greater in 2010.
The total carbon budget at Bog Lake Fen indicates that changes in key parameters influence CO2 and CH4 differently and that CH4 emissions nearly canceled the CO2 gained when considering the GWP of each greenhouse gas.
