PARENT SESSION
Poster Session #55: Plant-Animal Interactions II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Changes in insect herbivore communities along an ozone and nitrogen deposition gradient in the San Bernardino Mountains.

Eatough Jones, Michele^*,1, Paine, Timothy¹, ¹ University of California, Riverside., Riverside, CA

ABSTRACT- The mixed conifer forest of the San Bernardino Mountains has been impacted by air pollution arising from the Los Angeles basin. Ozone has decreased in recent years, but nitrogen deposition in the forests of Southern California is expected to increase as urban centers continue to grow. Both these pollutants alter patterns of plant growth and allocation, and affect nutritional quality of foliage for insects which may subsequently affect the diversity and abundance of insect herbivore communities on plants in areas impacted by LA air pollution. The impact of LA Basin emissions on surrounding forest ecosystems may therefore be optimally examined by assessing the herbivore populations of affected plant species. If atmospheric inputs of ozone and nitrogen deposition lead to ecologically significant changes plant growth and chemistry, then the composition of the herbivore insect community of those plants will also be altered. The goal of this research was to examine the impact of ozone and nitrogen deposition on three prominent plant species (ponderosa pine, California black oak and bracken fern) in the San Bernardino National Forest and the impact on the associated arthropod herbivore communities of these plants. We sampled insect communities at six sites along the naturally occurring air pollution gradient. Three western sites were associated with high ozone and nitrogen input, while three eastern sites were expected to have lower atmospheric input. Insects were extracted from foliage samples collected in spring, as plant tissue reached full expansion. Communities were evaluated using discriminant function analysis. Herbivore groups on all three plant species show patterns of change that followed the air pollution gradient. For bracken fern and oak, chewing insects were more abundant at high pollution sites. On pine, some groups of sucking insects had increased abundance on high pollution sites, while chewing insects were more abundant on low pollution sites.

KEY WORDS: nitrogen deposition, ozone, insect herbivore community, mixed conifer forest