Multitrophic Effects of Elevated Atmospheric CO2 on Understory Plant and Arthropod Communities

Rising levels of atmospheric [CO2] will directly affect the responses and community composition of plants. However, few studies have examined how these changes to plant communities will alter insect communities that rely on them. Here, we report on a study that examined the community-level responses of plants, herbivores, detritivores, predators, parasitoids, and omnivores to increased [CO2] at a Free Air Carbon Enrichment (FACE) facility at Oak Ridge National Laboratory. We found that aboveground net primary productivity for the five dominant plant species in the understory community, C:N ratios of leaf tissue for four of the five dominant understory taxa, amounts of herbivory, and arthropod abundance and richness across all trophic groups did not differ between ambient and elevated CO2 plots. Abundance and richness of particular trophic groups were higher in ambient than in elevated CO2 plots. There were also strong temporal effects on community composition, but no distinct treatment effects. These results, although preliminary, suggest that community-level responses to future atmospheric [CO2] are likely to be species- and trophic-group specific.