PARENT SESSION
Oral Session # 41: Herbivory III: Forests and Soils.
Presiding: R Jones
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.

Insect herbivory in a forest community exposed to free-air CO₂ enrichment.

Knepp, Rachel^*,1, Hamilton, Jason², DeLucia, Evan ¹, ¹ University of Illinois, Urbana, Il, 61801² Ithaca College, Ithaca, NY, 14850

ABSTRACT- Increased atmospheric CO₂ concentration alters leaf structure and chemistry, but how these changes affect leaf herbivory in a complex multi-species forest community is largely unknown. Leaf damage was quantified on hardwood seedlings planted in the understory of a loblolly pine plantation in North Carolina. Seedlings were exposed to ambient (370 ppm) or elevated (570 ppm) [CO₂] with free-air CO₂ enrichment (FACE). In 2001, insect herbivores removed 51% less leaf area from seedlings growing under elevated compared to ambient [CO₂] (f = 9.33, P = 0.0926). In 2002, a drought year, there was consistently lower herbivory than in 2001, and there was no significant effect of the treatment on the amount of tissue removed. However, the number of leaves experiencing insect herbivory decreased under elevated [CO₂] (f = 3.75, P = 0.0245). The consistent reduction of insect herbivory, at least in a wet year, suggests that elevated [CO₂] may change the population dynamics of affected insect species and their interactions with other plants and animals.

Key words: Seedling, Understory, Hardwood, Drought