, Volume 13, Issue 6, pp 917-931

First online:

Future Spruce Budworm Outbreak May Create a Carbon Source in Eastern Canadian Forests

  • Caren C. DymondAffiliated withNatural Resources Canada, Canadian Forest ServiceMinistry of Forests and Range, Government of British Columbia Email author 
  • , Eric T. NeilsonAffiliated withNatural Resources Canada, Canadian Forest Service
  • , Graham StinsonAffiliated withNatural Resources Canada, Canadian Forest Service
  • , Kevin PorterAffiliated withNatural Resources Canada, Canadian Forest Service
  • , David A. MacLeanAffiliated withFaculty of Forestry and Environmental Management, University of New Brunswick
  • , David R. GrayAffiliated withNatural Resources Canada, Canadian Forest Service
  • , Michel CampagnaAffiliated withRessources Naturelles et faune Québec
  • , Werner A. KurzAffiliated withNatural Resources Canada, Canadian Forest Service

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Spruce budworm (Choristoneura fumiferana Clem.) is an important and recurrent disturbance throughout spruce (Picea sp.) and balsam fir (Abies balsamea L.) dominated forests of North America. Forest carbon (C) dynamics in these ecosystems are affected during insect outbreaks because millions of square kilometers of forest suffer growth loss and mortality. We tested the hypothesis that a spruce budworm outbreak similar to those in the past could switch a forest from a C sink to a source in the near future. We used a model of ecosystem C to integrate past spruce budworm impact sequences with current forest management data on 106,000 km2 of forest in eastern Québec. Spruce budworm-caused mortality decreased stand-level merchantable C stocks by 11–90% and decreased ecosystem C stocks by 2–10% by the end of the simulation. For the first 13 years (2011–2024), adding spruce budworm significantly reduced ecosystem C stock change for the landscape from a sink (4.6 ± 2.7 g C m−2 y−1 in 2018) to a source (−16.8 ± 3.0 g C m−2 y−1 in 2018). This result was mostly due to reduced net primary production. The ecosystem stock change was reduced on average by 2 Tg C y−1 for the entire simulated area. This study provides the first estimate that spruce budworm can significantly affect the C sink or source status of a large landscape. These results indicate that reducing spruce budworm impacts on timber may also provide an opportunity to mitigate a C source.


carbon cycle net primary production net biome production boreal forest defoliation ecosystem carbon CBM-CFS3 ecosystem stock change