Summer 2005 Russian Olive Report
Introduction
The Animas River is the largest river in southwestern Colorado. It is a major tributary to the San Juan River, which it joins in the city of Farmington, New Mexico, roughly 25 miles south of the Colorado, New Mexico State Line. Like most rivers in the continental United States, the Animas River has seen dramatic changes, the majority of which have occurred under the influence of European settlers and the generations that followed their arrival. Water development, trapping, agriculture, grazing, mining, timber harvesting, and urbanization and suburban sprawl have impacted river systems. The most profound impacts have occurred during the last half century. One recently recognized threat to river ecosystems are invasions of non-native trees and shrubs. While saltcedar (Tamarix spp.) has, to date, been discussed to the greatest extent, the influence of Russian olive (Elaeagnus angustifolia L.) on river ecosystems is becoming more prevalent. In Colorado, there is still an opportunity to suppress the invasion of Russian olive along the Animas River. The portion of the Animas River that flows through New Mexico has been heavily infested with both Russian olive and saltcedar. Friends of the Animas River (FOAR) has received grant money for the past three years and has been working to keep the Colorado stretches of the river clear of invasive species, with specific attention to Russian olive.
Russian Olive has been classified as a noxious weed by the Colorado Weed Management Association. Noxious weeds are characterized by reproducing rapidly in disturbed soils with the ability to out compete native species. Russian olive was originally introduced to the United States in the early 1900’s from the temperate regions of Asia. It became a popular choice for use as ornamentals and wind breaks because of its attractive, hardy nature and its capability for easy to initiate, rapid growth. As recently as the early 1990’s state and federal agencies were subsidizing the distribution of Russian olive. The seed dispersal mechanism of Russian olive has allowed it to escape cultivation, and it has become problematic in seasonally wet riparian habitats, meadows, and ponds and ditches in Southwestern and the inter-mountain western United States.
In 2002, FOAR and Rhea Environmental began a counter attack on the initial infestation of Russian olive that was observed along the Animas River. Grant money from the Colorado Division of Wildlife’s wetland program and time donated by dedicated by volunteers have helped to prevent an outbreak. In 2005, funds from the Southwest Wetlands Conservation Group allowed FOAR to contract the Southwest Conservation Corps to conduct extensive removal project. In addition, the Four Corners RiparianRestoration Project donated 10 trees in memory of writer Ellen Meloy. The trees were planted on the property located behind the Durango Mall to help reestablish native plant populations.Treatment and Control Methods
In the fall of 2005, removal efforts were concentrated along the bike path that extends transects the City of Durango. Trees located on the banks of the river along the bike path, and on small islands within the river, were treated using established protocols, between 32nd Street and the “High Bridge” just above the Walmart River Access in Durango. Efforts were restricted to city property. Trees located within private property were not treated unless approval was granted by the landowner.
Treatment of Russian olive was conducted according to the current established protocols. Large trees (greater than inches in diameter) required that holes be drilled into the trunk at an approximately 30 to 45 degree angle and approximately 3 inches apart, girdling the tree in an effort to disrupt nutrient flow to the tree. Rodeo is poured into the holes. It is thought that, in relation to the seasonal (fall) aspect of the treatment, the Rodeo is drawn to the root system with the goal of preventing the root system from supporting new growth in the years following treatment. Trees smaller than 3 inches in diameter were cut completely, leaving an exposed stump. The stump was painted with Rodeo to prevent any new growth from the remaining tissue. When possible (i.e. in moist soils), saplings were pulled from the ground, with effort made to ensure that the entire root system was extracted. The larger trees that were not cut down were left to maintain soils and serve as habitat for wildlife until native species had an opportunity to get established.
Why our method?
Removal of larger trees is not recommended because the resulting soil disturbance could promote the germination of Russian olive seeds. Cutting without Rodeo treatment can result in the generation of dense stands because of sprouting from main trunk and root systems. Burning has similar results. The application of herbicides to foliage has proven to be effective but the application can be indiscriminate and the impacts can be extend to other vegetation.
Results
During the fall of 2005 approximately 6.1 miles of river bank and 2 small islands, 0.65 and 1.1 acres, were treated. A total of 25 large trees required boring treatments. Eight (8) liters of Rodeo was applied to trees during treatment. In addition 10 cottonwood trees, donated by the Four Corners Riparian Restoration Project in memory of writer Ellen Meloy, were planted on the Carleeno Property, located behind the Durango Mall.Conclusions
Though the 2005 efforts were a success, they were restricted to property owned by the City of Durango. Russian olive has the potential to establish itself at very rapid rates. Trees left on private property have the ability to spread to the river corridor and maintain the threat of infestation of the Animas River Corridor in Colorado. Russian olive infestation is a community level problem that crosses property, county, and state lines. Participation by all landowners is required to stem the progression of infestation. FOAR was able to provide 10 cottonwoods, donated to the project by Four Corners Riparian Restoration, as an incentive for 1 private landowner to remove Russian olive. The expansion of this incentive and the cooperation of governments to encourage Russian olive removal will be required to ensure the future health of the Animas River Ecosystem.