PARENT SESSION
Oral Session #49: Restoration Ecology. Presiding: J. Callaway.
Wednesday, August 8, 2001. 1:00 PM to 4:30 PM. Madison Ballroom D.
Response of a butterfly community to habitat structure along a continuum of degraded savanna sites.
Grundel, Ralph1, Dulin, Gary1, Pavlovic, Noel1, 1
ABSTRACT- Oak savanna was a dominant terrestrial ecosystem in the Midwest United States two centuries ago but is now greatly diminished in extent. Today, fundamental questions exist concerning the nature of savannas and the attainment of restoration goals. Do these savanna ecosystems host a biota uniquely different from surrounding grasslands and forests? How might restoration, and prescribed burning, change the composition of animal and plant communities currently residing in degraded savanna remnants? We consider these questions by asking how butterfly communities vary along a current habitat gradient resulting from a variety of past management practices applied to savannas. This gradient ranges from open grasslands to savannas to oak sprout dominated habitats to fire-suppressed forests. This gradient has arisen on historic savanna sites due to past land practices including sandmining, frequent burning, and long-term fire suppression. Based on an indicator species analysis, we found butterfly species that were obligated to open conditions but not to savanna conditions along this gradient. Canopy cover and flowering plant density most strongly structured the butterfly community along this gradient with butterfly richness declining after woody vegetation (> 10 cm dbh) reached a density > 200 stems/ ha. Flowering plant richness increased linearly with fire frequency but butterfly richness did not, perhaps because very frequent fires can diminish the viability of butterfly populations.
KEY WORDS: oak savanna, butterfly community, fire frequency, indicator species