Effects of Btk management of spruce budworm on soil carbon sequestration

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Spruce budworm is the most damaging forest pest in eastern North America, and is currently un-dergoing an**outbreak, with severe defoliation in Quebec spreading into New Brunswick. Current efforts to control spruce**budworm involve spraying with novel biological insecticides, with two primary goals: protecting tree foliage so**forests continue to grow for harvest, and arresting or limiting geographic spread of the budworm outbreak.**However, there may be a third benefit to budworm spray programs: maintenance of soil carbon storage in forest**soils. Soils accumulate and release carbon from organic matter such as leaf or needle litter, and in doing so are**linked to the atmospheric carbon dioxide pool that is driving global climate change. Defoliation of fir and**spruce trees under budworm attack might add organic matter to soils in the short term, enhancing carbon**storage. In the longer term, reduced tree growth and survival might reduce organic matter accumulation in**soils, and loss of shading from tree canopies may warm soils and thus increase their rate of carbon release.**Understanding the short- and longer-term effects of budworm control on soil carbon storage will be important**for cost-benefit assessment of spray programs.