Date of Award:

5-2013

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Corey V. Ransom

Committee

Corey V. Ransom

Committee

Christopher A. Call

Committee

Thomas A. Monaco

Committee

Ralph E. Whitesides

Abstract

Invasion of natural communities by introduced plants is considered one of the biggest threats to biodiversity. Weeds in rangelands cause an estimated loss of $2 billion per year in the United States. These costs include losses in forage quality and yield, grazing interference, animal poisoning, lowering land values, depleting soil water and resources available to native plants, increasing costs of managing livestock, and impacts on wildlife habitat and forage. Integrated weed management (IWM) is a way for land managers such as farmers, ranchers, and government agencies to control invasive weeds. IWM uses several different control methods working in conjunction to produce the most effective results in ways that are both economical and, in many cases, better for the environment than a single method alone. Because of the immense impacts invasive weeds have on wildlife habitat and the overall health of the infested land, Dinosaur National Monument (DNM) is especially interested in IWM for invasive species. Land managers at DNM and other national parks have been targeting invasive species for several years with a combination of management techniques including, but not limited to, chemical applications, targeted grazing, and mechanical removal of selected species with much success.

Russian knapweed (Acroptilon repens) is an invasive perennial forb found throughout DNM. This species typically invades recently disturbed sites, abandoned pastures, and otherwise low-quality landscapes and like many invasive perennial weeds, causes problems by quickly displacing native vegetation important to the survival of wildlife and the overall quality of the landscape. Control of Russian knapweed is important to maintain plant and animal species diversity in these invaded areas and throughout the DNM.

In 2009, approximately $50,000 was allocated to Utah State University for a twoyear study researching IWM methods for control of Russian knapweed in DNM. These methods included targeted grazing of an area infested with Russian knapweed and a lateseason application of the herbicide aminopyralid (Milestone®). Part of the resources were used for greenhouse and field trials evaluating the relative tolerance of perennial grass species to growth regulator-type herbicides commonly used to control broadleaf species like Russian knapweed. All of the grass species studied are native to the Western United States and are often present in areas where Russian knapweed has invaded or are used in revegetation efforts in areas recently treated for invasive perennial weeds like Russian knapweed.

The effects of these herbicides on non-target species such as perennial grasses are important to quantify and while these effects are only a part of what needs to be considered when creating an integrated management plan, the data will be used to assess the economics and safety of the herbicides to non-target plants in the areas they are to be applied. Land managers will have better information from which to make informed decisions when forming land management plans for different areas like those at DNM.

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