Wildfire combustion and carbon stocks in the southern Canadian boreal forest: Implications for a warming world. (12th June 2020)

• Record Type: Journal Article
• Authors: Dieleman, Catherine M.; Rogers, Brendan M.; Potter, Stefano; Veraverbeke, Sander; Johnstone, Jill F.; Laflamme, Jocelyne; Solvik, Kylen; Walker, Xanthe J.; Mack, Michelle C.; Turetsky, Merritt R.
• Is Part Of: Global change biology. Volume 26:Number 11(2020)
• Page Start: 6062
• Page End: 6079
• Publication Date: 2020-06-12
• Subjects: climate change -- ecozone -- harvesting -- land use -- latitudinal gradient -- soil moisture -- stand age; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15158
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Boreal wildfires are increasing in intensity, extent, and frequency, potentially intensifying carbon emissions and transitioning the region from a globally significant carbon sink to a source. The productive southern boreal forests of central Canada already experience relatively high frequencies of fire, and as such may serve as an analog of future carbon dynamics for more northern forests. Fire–carbon dynamics in southern boreal systems are relatively understudied, with limited investigation into the drivers of pre‐fire carbon stocks or subsequent combustion. As part of NASA's Arctic‐Boreal Vulnerability Experiment, we sampled 79 stands (47 burned, 32 unburned) throughout central Saskatchewan to characterize above‐ and belowground carbon stocks and combustion rates in relation to historical land use, vegetation characteristics, and geophysical attributes. We found southern boreal forests emitted an average of 3.3 ± 1.1 kg C/m 2 from field sites. The emissions from southern boreal stands varied as a function of stand age, fire weather conditions, ecozone, and soil moisture class. Sites affected by historical timber harvesting had greater combustion rates due to faster carbon stock recovery rates than sites recovering from wildfire events, indicating that different boreal forest land use practices can generate divergent carbon legacy effects. We estimate the 2015 fire season in Saskatchewan emitted a total of 36.3 ± 15.0 Tg C, emphasizing the importance of southern boreal fires for regional carbon budgets. Using the southern boreal as an analog, the northern boreal may undergo fundamental shifts in forest structure and carbon dynamics, becoming dominated by stands <70 years old that hold 2–7 kg C/m 2 less than current mature northern boreal stands. Our latitudinal approach reinforces previous studies showing that northern boreal stands are at a high risk of holding less carbon under changing disturbance conditions. Abstract : Boreal wildfires are increasing in frequency, potentially transitioning the biome from a significant carbon sink to a source. The southern boreal forests experience relatively high frequencies of fire and may serve as an analogue of future carbon dynamics for northern forests. Using field sampling and spatial upscaling techniques we demonstrate the northern boreal may undergo shifts in forest structure and carbon dynamics, becoming dominated by stands <70 years that hold 2–7 kg C/m 2 less. Our latitudinal approach reinforces previous studies showing that northern boreal stands are at a high risk of holding less carbon under changing disturbance conditions. See also the Commentary: https://onlinelibrary.wiley.com/doi/10.1111/gcb.15214