Document: THE-3-66-22

The effects of elevated CO₂ on insects at the Nevada Desert FACE Facility.

CHARLET, T.N.* ¹, S.F.ZITZER ², W.E.SMITH ¹ and S.D.SMITH ¹

University of Nevada Las Vegas, Las Vegas, NV 89154 ¹
University of Nevada Reno, Reno, NV 89517 ²

Abstract:
While some research has examined the effects of elevated CO₂ on insects, most has focused on agriculturally important species and has been conducted in glasshouses. In this study we present data on insects collected at the Nevada Desert FACE Facility (NDFF) during the growing season of 1998, a wet year with above average primary production. FACE (Free-Air-CO₂-Enrichment) technology allows a unique opportunity to study the effects of elevated CO₂ on a natural ecosystem without barriers to insect movement and without providing an artificially warm or humid environment. Bimonthly, sticky-traps were placed for a period of one week in the upper canopy of 5 species of Mojave Desert plants including an evergreen shrub (Larrea tridentata), two deciduous shrubs (Lycium pallidum and Ambrosia dumosa), and two grasses (Pleuraphis rigida and Achnatherum hymenoides). Of 13 insect orders identified, 5 orders made up 95% of all the insects collected . These five (Collembola, Diptera, Homoptera, Hymenoptera, Thysanoptera) were included in further analyses. We did not observe a significant difference in the number of insects in the elevated CO₂ rings versus ambient rings, nor between the blowing and non-blowing ambient rings. Significant effects were observed in the collection date for all orders of insects, most dramatic was the sudden increase of Collembola (7000%) and the sudden decrease of Thysanoptera (6500%) June 15-21. Significant effects were also observed in host plant use by different insect orders. Thysanoptera (thrips) were highest on shrub species while Collembola (springtails) were most abundant on grass species. Homoptera (leaf-hoppers) were common on all host species except Larrea while Diptera (flys) were most abundant on Lycium. The absence of CO₂ treatment effect on the number of insects suggests that we may not see any differential effects on pollination, foliar damage or predation in this ecosystem, but it also could be due to the fact that this ecosystem had experienced only one year of elevated CO₂ treatment at the time of the study.

Keywords: insects, FACE, elevated CO₂, Mojave Desert

This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.