Masters Theses

Date of Award

5-1995

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

David A. Buehler, J. Mark Fly

Committee Members

Ralph W. Dimmick, Kenneth R. Newton

Abstract

I measured woody and herbaceous vegetation in fall before (1992) and for 2 years after (1993-1994) tebuthiuron treatment (6.8 kg active ingredient/ha) on 2 electric transmission-line rights-of-way (ROWs) on the University of Tennessee Oak Ridge Forest. I used vegetation measures to evaluate tebuthiuron-induced habitat changes for several wildlife species. I also held focus groups on ROW management with eastern Tennessee residents. I interviewed participants about their perceptions of different vegetative cover types on ROWs, chemical and mechanical treatment types, and wildlife habitat.

Vegetation changes were similar across ROWs following tebuthiuron treatment. Tree density decreased (P ≤ 0.001) 84-95% 2 years following treatment. Shrub density decreased (P ≤ 0.05) 55-59% 2 years following treatment. Vine density increased 17-36% 2 years post-treatment (P ≤ 0.05). Grass and sedge density increased 477-790% from 1992 to 1994 (P < 0.001). Forb density increased 115-167% during the study (P < 0.004); fern density increased 475% on 1 ROW 1992-1994 (P = 0.022).

Eight of the 10 most dominant tree and shrub species decreased in frequency of occurrence across plots after treatment (P < 0.001). Frequency of occurrence across plots for the 8 most dominant herbaceous plant and vine species did not differ 2 years after treatment (P < 0.001). Species richness of trees and shrubs decreased (P < 0.001) from 5-6 species/plot, on average, in 1992 to 1-2 species/plot, on average, in 1994. Species richness of grasses, sedges, forbs, ferns, and vines increased (P < 0.001) across plots from 5-6 species/plot in 1992 to 8-11 species/plot in 1994.

Maximum tree and shrub height on plots decreased (P < 0.001) from 2-5 m pretreatment to 1-2 m 2-years post-treatment. Estimated heights for many of the most dominant tree and shrub species decreased (P < 0.001) following tebuthiuron treatment. Vertical cover decreased (P < 0.001) 55-75% 1 year following treatment, but only differed (25% decrease) on 1 ROW after 2 years (P = 0.006).

Total ground cover by low-growing plants increased from 63-72% before treatment to 120-130% 2 years after treatment (P < 0.001). Coverage by grasses and sedges, and forbs increased (P < 0.001) from 286-470% and 239-340%, respectively. Coverage by ferns and vines varied by ROW.

Total plant biomass declined after tebuthiuron treatment. Dry weight of trees decreased 97-99% 2 years after tebuthiuron treatment (P < 0.001). Shrub dry weights increased slightly on one ROW after treatment (P < 0.003). Vine dry weights decreased 74-86% (P < 0.001). Grass and sedge dry weights increased 558- 624% (P < 0.001). Forb and fern dry weights decreased 29% on one ROW after treatment (P = 0.023).

Wildlife habitat improved for species that use openings for food or cover such as white-tailed deer (Odocoileus virginianus), wild turkey (Meleagris gallopavo), grasshopper sparrow (Ammodramus savannarum), and northern bobwhite (Colinus virginianus). Increased herbaceous plant density, ground cover, and grass biomass probably increased forage abundance and availability for eastern cottontails (Sylvilagus floridanus), meadow vole (Microtus pennsylvanicus), white-footed mouse (Peromyscus leucopus), gray fox (Urocyon cinereoargenteus), and red-tailed hawk (Buteo jamaicensis). Reduction of trees and shrubs probably decreased the ROWs food and cover value to prairie warbler (Dendroica discolor), wood thrush (Hylocichla mustelina), ruffed grouse (Bonasa umbellus), and other species that require woody stems for food or cover. Vegetation changes on ROWs following tebuthiuron treatment diversified the Oak Ridge Forest and provided herbaceous cover largely unavailable on the Forest before treatment.

A majority of focus group participants preferred mechanical cutting over herbicide use for ROW management, though several expressed approval of herbicides if chemicals used were proven safe and effective. Participants wanted detailed information about any herbicide being considered for use on large areas like ROWs. Tebuthiuron was unfamiliar to most respondents; a description of the chemical was received by many with the same skepticism about safety, effectiveness, and cost shown toward other pesticides. Landowners identified contact by the utility prior to ROW treatment as the most important ROW management consideration.

Most participants were skeptical of federal pesticide regulation, and they trusted few sources of information on herbicides. Data from popular media, chemical companies, and government agencies were believed to be biased because of financial or other motivations. Participants placed more trust in university and independent research data.

Most focus group participants preferred grass or shrub cover to tall brush cover on ROWs for aesthetic, safety, or utilitarian reasons. ROWs were perceived as wildlife habitat by very few. Most participants thought of habitat as "parks," "forests" and "natural areas""areas without human intervention or management.

Results indicated that ROWs can be managed to benefit people and wildlife. Managers should: (1) solicit input from landowners and other groups to improve public relations and understand public perceptions; (2) provide detailed information about ROW treatments and the importance of wildlife management on private lands; and (3) promote grass or shrub cover to maximize ROW benefits.

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