Masters Theses

Date of Award

8-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Jerome F. Grant

Committee Members

Paris L. Lambdin, M. L. Pan

Abstract

A total of 12,028 specimens was collected in the grassland barrens at Arnold Air Force Base, Tullahoma, TN, in 1997 and 1998. From these specimens, 709 arthropod species, representing 21 orders and 165 families, were identified. Two sites in 1997, burned and non-burned, and three sites in 1998, initial burned, recent burned, and non-bumed, were evaluated. Abundance, seasonality, and species composition of insects associated with the barrens, along with the effectiveness of various sampling methods in assessing insect communities, were included in the study. The impact of burning on arthropod communities and incidence of selected arthropods occurring on Eggert's sunflower, Helianthus eggertii Small, also were examined.

In regard to arthropods associated with the grassland barrens in middle Tennessee, Coleoptera was the most species-rich order, with 208 species representing 30 families. Diptera (127 species in 33 families) and Hymenoptera (94 species in 27 families) also were well represented. However, the Collembola (31 species in 8 families) contained the most number of individuals collected.

Species richness in the burned sites was slightly higher than in the non-burned sites in both 1997 and 1998. For instance, 185 species were collected in the burned site in 1997 compared to 135 species in the non-burned site. In 1998, 328, 327, and 318 species were collected in the recent burned, initial burned, and non-burned sites, respectively. The variation in species numbers in the burned and non-burned sites may be a result of plant species succession and the influx of many insect species into the burned sites after burning.

During August and September 1998, 67 insect species were collected from Eggert's sunflower. Peduncle collapse, a condition caused by clipped stems, was commonly observed on Eggert's sunflower throughout this study. The incidence of clipped stems was greater in the burned sites than the non-burned site. Spittlebug masses also were encountered throughout the monitoring of Eggert's sunflower. Infestation levels were highest in the burned sites and lowest in the non-burned site. Of all groups collected from Eggert's sunflower in 1998, perhaps no insects affected the plant as much as the beetles. Even though leaf-feeding beetles were found on Eggert's sunflower, the weevils seemed to have the most impact on the plant. Larvae of Odontocorynus spp. were found inside the stem of plants, and it is plausible that adult weevils were responsible for the clipped stems often observed on H. eggertii in the barrens.

The results of this study provide evidence that burning has a major influence on the presence and persistence of arthropod species in grassland ecosystems. The variation in the bum tolerance of species and the changes in the physical environment, i.e., succession of plant communities, following burning may result in different arthropod communities in frequently burned sites compared to non-bumed sites. However, the effects of burning on some plants, such as Eggert's sunflower, presents a paradox. That is, even though burning perpetuates and maintains populations of this plant, it also causes a higher incidence of damage by insects in burned areas. In general, an area (region or landscape) containing sites at different successional stages, and sites varying in the frequency of burning, may support more species than a site protected from burning (non-bumed).

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