PARENT SESSION
Oral Session #78: Insect Population and Community Ecology. Presiding: R. Denno.
Friday, August 10, 2001. 8:00 AM to 11:45 AM. Hall of Ideas I.
Go towards the light: butterfly species richness increases following ponderosa pine restoration.
Waltz, Amy1, Covington, W. Wallace1, 1
ABSTRACT- Ecosystem restoration projects often overlook invertebrate populations as critical components of ecosystem structure and function. Butterflies contribute significantly to ecosystem energy transfer and pollination processes and may indicate returning ecosystem interconnections. We test the hypothesis that ponderosa pine restoration increases adult butterfly abundance and richness and examine potential mechanisms of butterfly distribution. Ponderosa pine restoration treatments reduce tree density and restore fire resulting in higher understory plant species richness and abundance. Butterfly assemblages were sampled in a randomized block design of four blocks, each consisting of a paired restoration treatment and control. In addition, in each block we quantified nectar resources (flowering plants) and sampled temperature, relative humidity and light intensity. Two years each of pre-treatment and post-treatment data showed a 100% increase in adult butterfly species richness and a 400% increase in butterfly abundance in treated forests. We found no differences in ambient temperature or relative humidity between treated and control forests, but light intensity was significantly higher in restoration treatment units. Nectar resource availability did not differ between treated and control forests one year following treatment, but was significantly greater in treated forests 2 years following treatment. These results suggest that thinned and burned ponderosa pine forests increase adult butterfly abundance due to increased light intensity and nectar resources. Increased butterfly abundances may indicate changes in understory plant diversity, and reflect increases in other arthropod groups (i.e. pollinators) in restored forests.
KEY WORDS: butterfly, restoration, ponderosa pine, community structure