Management of Biological Invasions (2012) Volume 3, Issue 2: 89–96 doi: http://dx.doi.org/10.3391/mbi.2012.3.2.03 Open Access © 2012 The Author(s). Journal compilation © 2012 REABIC Research Article Crested wheatgrass (Agropyron cristatum) seedings in Western Colorado: What can we learn? M. Nikki Grant-Hoffman*, Amanda Clements, Anna Lincoln and James Dollerschell Colorado National Landscape Conservation System, Bureau of Land Management, Grand Junction Field Office, USA E-mail: [email protected] (MNGH), [email protected] (AC), [email protected] (AL), [email protected] (JD) *Corresponding author Received: 17 September 2012 / Accepted: 10 October 2012 / Published online: 15 December 2012 Handling editor: Elias Dana, University of Almeria, Spain Abstract Non-native species have been widely transported, becoming components of ecosystems worldwide. In some cases this can change the structure and function of an ecosystem. Crested wheatgrass (Agropyron cristatum, Agropyron spp.) was introduced into the Western U.S. in the late 18th and early 19th centuries. Since introduction, it has been planted in western rangelands currently occupying millions of acres. Crested wheatgrass causes significant changes in areas where it dominates the vegetation, and restoring rangelands planted with crested wheatgrass to higher plant diversity and ecosystem function has been met with limited success. Here we revisit historical frequency monitoring data collected in western Colorado on public lands that were planted with crested wheatgrass between 1940 and 1980. We also monitored vegetation before and after mechanical treatment (removal of vegetation with the use of a dixie harrow pulled behind a tractor) and re-seeding of desirable species in three areas dominated by crested wheatgrass. We looked for increasing or decreasing trends in plant species, and for plant species that persist with crested wheatgrass. We found that crested wheatgrass increased significantly (p=0.09) over time, we also found five species of grasses, two shrub species, and one forb species that were persistent in areas planted with crested wheatgrass. We found that in mechanically treated areas, the only significant trend was a reduction of native grasses (p<0.05). Our findings suggest that in areas planted with crested wheatgrass, frequency of crested wheatgrass can increase over time. Further, mechanical treatments coupled with seeding were not effective at reducing crested wheatgrass cover, or at increasing native and desirable species. These sites may have experienced a shift to a stable state. Key words: rangeland; vegetative diversity; native species; mechanical treatment; management Introduction 19th century, and since its introduction has been widely planted in western rangelands currently Restoration of semi-arid and arid western lands occupying an estimated 5 million acres of can be difficult at best and the use of native rangeland (Lesica and DeLuca 1996; Pellant and seeds, while desirable, can be problematic Lynse 2005). (Banerjee et al. 2006). Native seeds may be Despite evidence against the use of crested difficult to germinate, expensive, and unable to wheatgrass, it is often used in seed mixes. compete with non-native and invasive seeds Crested wheatgrass is competitive with native which are often present in the seed bank and can plants (Bakker and Wilson 2004; Gunnell et al. establish before natives (Banerjee et al. 2006). 2010), partially through prolific seed production Historically, non-native plants have been used in (Hedinga and Wilson 2002). Crested wheatgrass re-seeding projects on public lands for reasons often excludes native plants, thereby reducing such as increasing forage production, erosion species richness of an area and producing almost control, and reduced cover of less-desirable monotypic stands (e.g. Fansler and Mangold invasive plant species (Pellant and Lynse 2005). 2010; Henderson and Naeth 2005; Hedinga and Crested wheatgrass (Agropyron cristatum and Wilson 2002; Christian and Wilson 1999; Lesica other Agropyron species) was introduced into the and Deluca 1996; Reynolds and Trost 1980; Hull Western U.S. beginning in the late 18th and early and Klomp 1966). In addition, in areas planted 89 M.N. Grant-Hoffman et al. with crested wheatgrass there is increased bare http://www.wrcc.dri.edu/summary/mtj.co.html, ground (Sutter and Brigham 1998), decreased downloaded August 2012). Precipitation can be available soil nitrogen and carbon (Christian and quite variable in this area, both temporally and Wilson 1999), and decreased soil organic matter spatially. and phosphorus (Dormaar et al. 1995) compared Mechanically treated areas sampled were to areas not planted with crested wheatgrass and within the McInnis Canyons National with more intact native communities. Areas Conservation Area within the Grand Junction planted with crested wheatgrass can be less Field Office (specific locations are available favorable for not only native plants, but also upon request). Over the sample period for the birds and wildlife (Reynolds and Trost 1980). treated areas, precipitation was 30.9cm in 2010 While crested wheatgrass does not spread as and 30.6cm in 2011. However, during the spring readily as some other invasive species, it may growing season (from April until July when data invade in areas where it has not been planted was collected) precipitation was approximately (Hedinga and Wilson 2002). 7.1cm in 2010 and 14.9cm in 2011 (data from One reason for the continued use of crested Western Regional climate Center, Colorado wheatgrass in the western U.S. is the ability of National Monument weather station used; crested wheatgrass to compete with other more http://www.wrcc.dri.edu/summary/Climsmco.html). detrimental invasive plants, most notably Bromus tectorum (Francis and Pyke 1996). In GJFO and UFO – Review of rangeland addition, there have been reports of early success frequency monitoring with planting native species into areas with crested wheatgrass present, a process known as We reviewed data from rangeland monitoring ‘assisted succession’ (Cox and Anderson 2004). points from the Grand Junction Field office While Cox and Anderson (2004) showed good (GJFO) and Uncompahgre Field Office (UFO). emergence, longer term establishment and Historical crested wheatgrass plantings were persistence of native species in an area planted identified by reviewing range improvement with crested wheatgrass is unknown (Cox and projects listed in the Rangeland Improvement Anderson 2004) and may be unlikely (Fansler Project System (RIPS) and through conver- and Mangold 2010). sations with rangeland management specialists There has been research on the establishment and other BLM staff. In order to be included in of native species in the presence of crested this study as crested wheatgrass plantings, wheatgrass (e.g. Wilson and Partel 2003; projects needed to be seeded with a seed mix Gunnell et al. 2010) and after removal of crested including crested wheatgrass between 1940 and wheatgrass (e.g. Hulet et al. 2010), but the long 1980. Once identified, historical wheatgrass term persistence of native species in the presence planting GIS layers were reviewed to see where of crested wheatgrass is less certain. Here we projects intersected vegetation frequency explore historical data, to look for longer term monitoring, and how often monitoring was vegetation trends in areas planted with crested performed. We included sites that had at least wheatgrass, and current data, to look for initial two samplings since planting crested wheatgrass, changes in vegetation after mechanical treatment and had no further treatments since the original of historic crested wheatgrass plantings. treatment/planting. This yielded five sites within the GJFO and six sites within the UFO that were analyzed. These sites have all been grazed by Methods cattle in winter or early spring. Frequency monitoring of rangelands in these Site description field offices consists of sampling one hundred The sampling area included lands in western 0.36m2 (2ft2) nested frequency plots approxima- Colorado, within the boundaries of the Bureau of tely every 1.2 meters (4 feet) along ten transects. Land Management’s Grand Junction Field Office Transects are approximately 12.2 meters (40 (GJFO) and Uncompahgre Field Office (UFO) feet) in length and placed on alternating sides of (http://www.blm.gov/co/st/en.html). Elevation of a fixed 50 meter transect. This method is used sampling points ranged from 1813 meters (5950 because it is relatively quick and results are feet) to 1838 meters (6030 feet), with an average repeatable between different observers (Elzinga yearly precipitation of 17-28 cm (7-11 inches) et al. 1998). In addition, results are more robust (http://www.wrcc.dri.edu/summary/gjt.co.html, to short term climate variation and levels of 90 Crested wheatgrass seedings in Western Colorado Figure 1. Photo of a dixie harrow. Toothed metal pipes are drug behind a tractor. This can remove some of the shrubby overstory and thin out understory plants (grasses and forbs). Desirable seeds are spread in front of the tractor so that they are incorporated into the soil as the harrow passes over them (Photograph by J. Dollerschell). herbivory than other common ways of measuring Table 1. Seed mix used for seeding efforts in treatment areas. vegetation such as density, cover, or biomass (West 1985). Sites were sampled between May Common Name Scientific name and August from 1984 to 2008. common yarrow Achilea millefolium