, Volume 13, Issue 6, pp 917-931
Date: 23 Jul 2010

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

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Abstract

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.

Author Contributions

CD led writing of the article and performed research. EN performed research and contributed to the article. GS performed research, contributed to the study design study, and contributed to the article. KP, DM, and DG contributed to the study design, models, and contributed to the article. MC analyzed data, and WK conceived of the study and contributed to the article.