Partnerships Provide Solutions to Invasive Plant Management

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Located on the southeast flank of the Uinta Mountains, Dinosaur National Monument encompasses over 210,000 acres on the Colorado and Utah border. The original 80-acre monument was dedicated in 1915 and included a quarry rich in dinosaur fossils.

However, by 1938 the boundaries were expanded to take in the spectacular canyons of the Green and Yampa Rivers. The canyons and diverse landscape are home to many native plants and animals including the previously endangered peregrine falcon (Falco peregrines) and bald eagle (Haliaeetus leucocephalus), and endangered Colorado pikeminnow (Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus). In addition to these endangered species and the dinosaur fossils, the National Park Service manages and protects a variety of natural and cultural resources [Box 1].

Tamara Naumann, ecologist and vegetation management specialist at Dinosaur National Monument is responsible for coordinating the invasive plant management effort. “Our program is built upon strong partnerships we formed with volunteers and Utah State University Weed Science Program,” explains Naumann.

Naumann credits the volunteer Weed Warrior Program she started in 1997 as largely responsible for the success of her well-planned invasive plant management program. More than 6000 volunteers have contributed 27,000 hours since 1997 toward manual removal of non-native plants in the Monument. Volunteers not only controlled weeds but also brought attention to the invasive species issue and the need for additional funding within the Monument. “Our budget increased from $500 a year in 1997 to an annual base budget of about $100,000 today,” says Naumann. “The additional funding would never have happened without the volunteers increasing awareness of the issue, identifying needs, and supporting our invasive plant program.” The larger budget allowed Naumann to expand the program to include weed inventories and support cooperative weed research projects with Utah State University.

The monument recognized that the key to developing a viable invasive plant management strategy was to have accurate information on the species, location and extent of invasive plant populations. Dr. Steve Dewey, Weed Scientist (retired) at Utah State University and his mapping crew were hired in 2002 to inventory invasive plants within the Monument. From 2002 through 2005, the crew mapped more than 46,000 acres or about 22 percent of the monument. The five most abundant species recorded during the inventory include saltcedar (Tamarix spp.), perennial pepperweed (Lepidium latifolium), yellow sweetclover (Melilotus officinalis), Russian knapweed (Acroptilon repens), and Canada thistle (Cirsium arvense). Less abundant species, such as Russian olive (Elaeagnus angustifolia), were targeted for eradication.

Weed inventory data were used as a basis for developing the Dinosaur National Monument Invasive Plant Management Plan and Environmental Assessment, which was completed in 2005 and approved in 2006. The plan (available at describes a process for making weed management decisions based on a combination of ecological impacts attributed to specific weed species, wildlife habitat and recreational values associated with particular areas, and feasibility of management. The Cub Creek watershed located near the west end of the monument was identified as a high priority management area because it contained high value habitat and recreational resources and the largest Russian knapweed infestation in the park.

Box 2. Russian Knapweed Response to Grazing and Milestone® Applications (

Weed management activities began in the Cub Creek watershed in 2006 and were concentrated on containing and reducing infested areas. Saltcedar and Russian olive trees were cut and a 25% volume/volume solution of Garlon® 4 Ultra in basal oil (1 qt herbicide in 3 qts oil) was applied as a cut-stump treatment. Russian knapweed and Canada thistle were treated with Milestone® at 6 fluid ounces per acre (fl oz/A). “The first time we applied Milestone on Russian knapweed we made the mistake of treating in June, which was too early to get good control of the weed,” explained Naumann. “Since we started applying in October the control has been excellent and we can focus our energy and resources where we can make a difference.” Goat grazing alone and in combination with Milestone was also included in the integrated control program on Russian knapweed [Box 2].

In 2010, Naumann wanted to evaluate the effectiveness of their weed management effort. She contacted Dr. Corey Ransom and Kimberly Edvarchuk with Utah State University to re-inventory key areas within the Monument. The inventory included approximately 1,600 acres in the Cub Creek watershed where invasive plants had been controlled, and a similar number of acres in the Island Park area where no control work had been implemented. The objectives of the project were to utilize time-repeated weed inventories to evaluate the effects of applied management on the distribution and abundance of targeted weed species. The second objective was to compare changes in weed populations between treated and non-treated areas.

Similar inventory methods were used in both 2002 and 2010 to record and characterize invasive plant populations. Trimble XM Global Position System (GPS) units were used in the initial survey and Juniper Systems Archer units were used for the re-inventory in 2010. Species location, area infested and relative canopy cover were recorded for 25 invasive plant species. Infestations were mapped as buffered points, polygons, and line features with plants less than 150 feet apart considered a single infestation. Canopy cover of invasive plants within an infestation (polygon) was classified into five categories based on visual observations. The canopy cover categories included: Majority (51-100% cover), High (26-50% cover), Moderate (6-25% cover), Low (1-5% cover) and Trace (less than 1% cover).

Results of the 2010 inventory in the Cub Creek watershed showed that the six-year control program greatly reduced acreage infested by invasive plant populations. The size of infestations was reduced 79, 74, 89, and 55 percent respectively for Russian knapweed, saltcedar, Russian olive and Canada thistle (Figure 1). There was a significant reduction in Russian knapweed along roads, trails, and parking lots (high traffic areas), which will help to prevent the spread along these corridors. “Our target is 95 percent reduction for priority weeds so we are getting close to our goal in some areas,” Naumann explained. (Photo)

Infestation of Russian knapweed before (left) and after (right) treatment with Milestone in the Cub Creek watershed.

In comparison, weed infestations in the non-treated Island Park area increased significantly during the same period (Figure 1). In 2010, the area infested by Russian knapweed increased 14 percent and there were 13 new infestations that were not detected in 2002. Saltcedar and Russian olive increased in abundance whereas populations of Canada thistle and perennial pepperweed decreased in acreage. Water levels were high during the 2010 inventory and some plants may not have been detected during the inventory. This may account for the decline in Canada thistle and perennial pepperweed observed in the river corridor. Perennial pepperweed may also be declining as a result of a fungus that appears to adversely affect health and vigor of individual plants and may reduce seed set.

Conducting pre- and post-treatment inventories allowed Naumann to measure progress of the invasive plant management program. Results showed that control techniques effectively reduced abundance, cover, and distribution of invasive plants on the landscape. Areas where weed populations were not treated showed a range of response with some species increasing and others declining. “Managing invasive plants in national parks and monuments is not just about killing weeds, but about building partnerships, constituencies, and community involvement,” says Naumann. “In Dinosaur National Monument we hope to continue a sustainable program of on-ground control, public education and outreach, monitoring, and research to effectively manage invasive plants. The goal in the Cub Creek watershed is to continue control efforts on Russian knapweed and other priority invasive plants and foster research to identify the best way to achieve our long-term vegetation management goals.”

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Published 2011; reviewed and trademark updated June 2019.