Variation in CO2 exchange over three summers at microform scale in a boreal bog, Eastmain region, Québec, Canada

Abstract

We examine variability in carbon dioxide (CO2) exchange as a function of meteorological conditions using static chambers across a peatland microtopographic gradient (high hummock, low hummock, lawn and hollow microforms) between June and August 2006, 2007, and 2008. Total June to August precipitation increased during the study period with 285 mm in 2006, 320 mm in 2007, and 369 mm in 2008, whereas monthly average temperature was similar among years, with the exception of August 2008, which was 2.4C warmer than previous years. Significantly different relationships between photosynthetic photon flux density and net ecosystem exchange (NEE) were observed in 2008 on three of the four microforms corresponding with the different meteorological conditions. The controls on CO2 exchange varied among microforms: a water table closer to the peat surface increased NEE on the high and low hummocks by increasing maximum rates of photosynthesis (PSNmax) but reduced NEE on the hollow microform by flooding the surface vegetation and reducing PSN max. Water table position was a significant control on ecosystem respiration (ER) only on the lawn microform. We examine relationships between water table position and PSNmax and ER, and propose a theoretical relationship, which supports results from other studies examining water table position and peat accumulation. Copyright © 2011 by the American Geophysical Union.