Elevated concentrations of atmospheric CO₂ and ozone (O₃) can alter plant quality sufficiently to influence insect herbivory. Although phytophagous insects are the major consumers in temperate forests, little research has investigated how these gases will impact rates of herbivory at the community level. To address this need, we analyzed community-level canopy herbivory for several forest species (trembling aspen and paper birch) that represent a dominant carbon pool in the Great Lakes region. To determine if elevated CO₂ and/or elevated O₃ influence foliar quality in a manner consistent with rates of herbivory, we also analyzed the chemical quality of foliar samples collected to determine herbivory rates. 

Results/Conclusions

Here we present data from the first year of a three-year study investigating the impacts of elevated CO₂ and O₃ on community herbivory in a maturing northern temperate forest at the Aspen-FACE site in Rhinelander, WI, U.S.A. Elevated CO₂ acted in a species-specific manner, increasing cumulative levels of herbivory in aspen by 17% but not affecting herbivory in birch. Enriched CO₂ did not, however, shift the distribution of damage across the season.  Elevated O₃ did not affect herbivory levels in either aspen or birch. Analysis of foliar quality revealed that changes in atmospheric composition altered foliar quality in ways consistent with the patterns of herbivory.