PARENT SESSION
Monday, August 7, 8:00-11:30 am
OOS 2 - Alteration of North American forest communities by invasive invertebrates
Ballroom D, Ballroom Level, Cook Convention Center
Organized by: LE Frelich (freli001@umn.edu) and D Foster

This session will provide a survey of invasive insects, earthworms, and slugs that threaten to remove tree species from forests of North America, change community composition by selective herbivory, and re-engineer ecosystems by changing nutrient cycles and seedbed properties, as well as potential policy and management responses.

Effects of gypsy moth outbreaks on plant community dynamics.

Muzika, Rose-Marie^*,1, ¹ University of Missouri, Columbia, MO

ABSTRACT- For over a century, gypsy moth (Lymantria dispar) has influenced forests of eastern North America, affording a significant opportunity to evaluate long term effects of this non-native pest. Gypsy moth larvae are early season polyphagous defoliators that can feed on numerous host species but oak species rank among the most preferred. Since oaks are a dominant species in the eastern deciduous forest, the long term consequences of gypsy moth outbreaks may be substantial. Dendrochronological studies reveal predictable losses in growth of preferred species, e.g. oaks. The growth losses have resulted in changing competitive relationships among overstory species as evident by concomitant growth increases in non-host tree species. Studies examining long term species composition changes suggest that host tree species could be substantially reduced at the stand level, but such loss is not evident at the landscape level. Alpha diversity decreased in overstory species, but beta (landscape) diversity increased or remained unchanged following moderate to severe gypsy moth defoliation. Ground flora species, however, increased at the local level in response to changing canopy dynamics. While gypsy moth defoliation and subsequent mortality may accelerate succession in some parts of the eastern deciduous forests, there is concern that oak regeneration is inadequate to replace the overstory, and that gypsy moth defoliation exacerbates that concern. Overall, successional patterns and species compositional shifts are strongly influenced by severity of defoliation, site characteristics, current species composition and disturbance history.

Key words: disturbance, deciduous forest, Lymantria dispar