Masters Theses

Date of Award

12-1998

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Paris L. Lambdin

Committee Members

Jerome Grant, Roberto Pereira

Abstract

The southern Appalachian mountains of eastern Tennessee support a diverse array of flora and fauna, many of which are unique to specific forest ecosystems in this region. These organisms help sustain the proper functioning of these habitats, but the presence of exotic forest pests may threaten our native forests. The gypsy moth, Lymantria dispar L., is one such pest that can cause mass defoliation of hardwood forests. The southern limit of this pest's range is currently located near Roanoke, VA, but is expected to enter the forests of eastern Tennessee within the next decade. Some isolated infestations have been reported in the Great Smoky Mountains National Park, as well as 23 counties in Tennessee.

Currently, no studies have been performed in the southeastern United States to determine the potential impact of this pest on mixed hardwood forests. Therefore, a study was initiated in 1997 in The University of Tennessee Forestry Experiment Station and Arboretum located in Oak Ridge, TN. The objectives of this study were to; 1) assess the overall diversity of ground-dwelling insects, 2) determine the possible influence of habitat on insects collected using pitfall traps placed under three different tree species in four different collection plots, and 3) assess the species composition, seasonality, and abundance of selected insects collected.

Collections from pitfall traps yielded 20,906 insects identified with 187 species in 87 families representing 18 insect orders. The four most abundant orders collected included the Collembola (49%), Hymenoptera (20%), Diptera (15%), and Coleoptera m (9%). Ants (Formicidae) composed approximately 88% of the Hymenopterans collected with 24 species identified. Many of the beetles collected may be potential beneficial predators against exotic pests, such as the gypsy moth. Twenty one families of beetles were collected with 79% represented by four families; Staphylinidae (41%), Scarabaeidae (13%), Nitidulidae (13%), and Carabidae (12%). Of the carabid beetles, 21 species were Identified.

Species diversity and evenness were significantly higher in the cove plot (P<0.05), most likely due to the isolated location of the plot and the increased moisture levels retained after heavy rains. Ant species diversity was highest in the cove and slope plots and lowest in the tornado plot. Natural disturbances disrupt ant activity and downed trees may deter ground-dwelling ant populations from inhabiting these areas. The slope plot had the highest ant species evenness, suggesting a more even distribution of ants in this community. Many of the ants inhabiting the slope plot may build their nests in leaf litter and debris, both of which have been accumulated and deposited in this plot due to heavy rain water runoff. Beetle species diversity and richness did not differ among the four plots, although species evenness was significantly (P<0.05) higher in the natural plot and lower in the tornado plot when compared among the four plots.

Significantly (P<0.05) more insects were collected in the cove plot and significantly fewer were collected in the slope plot. Similarly, significantly more ants and beetles were collected in the cove plot than the other three plots. Also, more ants and beetles were collected in the traps placed under sugar maple, Acer saccharum Marsh, and significantly fewer were collected in the traps placed under tulip poplar, Liriodendron iv tulipifera L. The traps under white oak, Quercus alba L., did not yield significantly different numbers of ants and beetles in comparison to the other two tree species. Significant differences may have been found if all samples collected throughout this study had been sorted and used in the analyses.

Overall seasonality trends were similar for most of the insects collected with highest population numbers in the summer months. Collections made in these forest habitats reveal a stable community with many different guilds represented. When comparing the four collection plots, a more diverse group of organisms was represented in the cove plot. The differences found in these plots are representative of the types of disturbance found in mixed hardwood ecosystems. Similar analyses performed on data collected after the gypsy moth is established in eastern Tennessee may help determine the impact of this pest on native southern Appalachian forests.

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