Postfire carbon balance in boreal bogs of Alberta, Canada

• Published in: Global Change Biology
• Main Authors: WIEDER, R. KELMAN, SCOTT, KIMBERLI D., KAMMINGA, KATHERINE, VILE, MELANIE A., VITT, DALE H., BONE, TIFFANY, XU, BIN, BENSCOTER, BRIAN W., BHATTI, JAGTAR S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Canada; Wabasca
• Online Access: http://dx.doi.org/10.1111/j.1365-2486.2008.01756.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2486.2008.01756.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2486.2008.01756.x

Abstract Boreal peatland ecosystems occupy about 3.5 million km 2 of the earth's land surface and store between 250 and 455 Pg of carbon (C) as peat. While northern hemisphere boreal peatlands have functioned as net sinks for atmospheric C since the most recent deglaciation, natural and anthropogenic disturbances, and most importantly wildfire, may compromise peatland C sinks. To examine the effects of fire on local and regional C sink strength, we focused on a 12 000 km 2 region near Wabasca, AB, Canada, where ombrotrophic Sphagnum ‐dominated bogs cover 2280 km 2 that burn with a fire return interval of 123±26 years. We characterized annual C accumulation along a chronosequence of 10 bog sites, spanning 1–102 years‐since‐fire (in 2002). Immediately after fire, bogs represent a net C source of 8.9±8.4 mol m −2 yr −1 . At about 13 years after fire, bogs switch from net C sources to net C sinks, mainly because of recovery of the moss and shrub layers. Subsequently, black spruce biomass accumulation contributes to the net C sink, with fine root biomass accumulation peaking at 34 years after fire and aboveground biomass and coarse root accumulation peaking at 74 years after fire. The overall C sink strength peaks at 18.4 mol C m −2 yr −1 at 75 years after fire. As the tree biomass accumulation rate declines, the net C sink decreases to about 10 mol C m −2 yr −1 at 100 years‐since‐fire. We estimate that across the Wabasca study region, bogs currently represent a C sink of 14.7±5.1 Gmol yr −1 . A decrease in the fire return interval to 61 years with no change in air temperature would convert the region's bogs to a net C source. An increase in nonwinter air temperature of 2 °C would decrease the regional C sink to 6.8±2.3 Gmol yr −1 . Under scenarios of predicted climate change, the current C sink status of Alberta bogs is likely to diminish to the point where these peatlands become net sources of atmospheric CO 2 ‐C.