Insect herbivory alters impact of atmospheric change on northern temperate forests

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Stimulation of forest productivity by elevated concentrations of CO2 is expected to partially offset continued increases in anthropogenic CO2 emissions. However, multiple factors can impair the capacity of forests to act as carbon sinks; prominent among these are tropospheric O3 and nutrient limitations1,2. Herbivorous insects also influence carbon and nutrient dynamics in forest ecosystems, yet are often ignored in ecosystem models of forest productivity. Here we assess the effects of elevated levels of CO2 and O3 on insect-mediated canopy damage and organic matter deposition in aspen and birch stands at the Aspen FACE facility in northern Wisconsin, United States. Canopy damage was markedly higher in the elevated CO2 stands, as was the deposition of organic substrates and nitrogen. The opposite trends were apparent in the elevated O3 stands. Using a light-use efficiency model, we show that the negative impacts of herbivorous insects on net primary production more than doubled under elevated concentrations of CO2, but decreased under elevated concentrations of O3. We conclude that herbivorous insects may limit the capacity of forests to function as sinks for anthropogenic carbon emissions in a high CO2 world.

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Author notes

    • J. J. Couture

    Present address: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.


  1. Department of Entomology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

    • J. J. Couture
    • , T. D. Meehan
    •  & R. L. Lindroth
  2. Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

    • E. L. Kruger


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R.L.L. designed the experiment and secured funding for the project; J.J.C. and T.D.M. collected field and laboratory data; J.J.C. and E.L.K. designed and performed the modelling exercise relating canopy damage to forest productivity; J.J.C. analysed the data and wrote the manuscript with the participation of R.L.L., T.D.M. and E.L.K.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to J. J. Couture.

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