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~ Plant Competition. Total coverage of competing species ranged from 6.8 to 22.9% (Table A-3). <br />Total competing coverage consists of both grass and forb species, the forbs being predominantly <br />' annual and perennial weeds, In general, cover was minimal on all sites and plant competition <br />does not appear to be a major factor in limiting shrub establishment. Dominant forbs are Canada <br />thistle (Cirsium arvense), Bull thistle (Cirsium vulgare), yellow sweetclover (Melilotus alba), <br />' houndstongue (Cynoglossum oj~cinale), lambsquarters (Chenopodium sp. ), and mullein <br />(Verbascum thapsus). Dominant grasses aze orchazdgrass (Dactylis glomerata), smooth <br />brome(Bromus inermis), and cheatgrass (Bromus tectorum). <br />I Canada thistle is the weed species of greatest concern on shrub planting units and was the <br />' dominant species on 10 of 11 planting units. Canada thistle is a native of southeastern Eurasia <br />and is acolony-forming perennial from deep and extensive horizontal roots. As such, it <br />represents the greatest potential competition fot moisture with shrubs. Although this plant was <br />' present on all plots, in instances where it was observed in direct competition with shrubs, it <br />appeazed to provide a protective affect from browsers. Shrubs should be able to overtop this <br />plant and out compete it for light resources, however. The competitive nature of this species may <br />' be overstated unless it exudes allelopathic chemicals. <br />Cheatgrass is another species of concern on planting units. Cheatgrass is an aggressive annual <br />' grass that grows in eazly spring competing with more desirable grasses and shrubs for moisture. <br />As well, dense stands become a fire hazard. This species is not broadly established on the site <br />and given the tall nature of the perennial grasses and their ability to form dense stands, this <br />' species will likely be a minor problem once the grass canopy closes. In shrub planting units <br />where ground cover is generally open, this species does present a potential threat. Planting of <br />non-aggressive grass species which provide ground cover but compete poorly with planted <br />shrubs may prevent the spread of this species. <br />Crested wheatgrass is an introduced grass commonly planted for range purposes. Although this <br />' species occurred in only one plot, it does represent a potential threat to shrub plantings as an <br />aggressive rhizomatous grass species. This species is drought resistant and forms a dense sod in <br />azeas where planted. This species will compete directly with shrubs for moisture and slow <br />growth dramatically. Crested wheatgrass should not be introduced onto or adjacent to sites <br />intended for woody plant re-introduction. <br />Other species aze not of major concern due to their ]ow frequency even three yeazs after planting. <br />Of greater concern may be the lack of coverage on sites. Erosion from shrub planting units is a <br />visible problem on certain sites. In addition, lack of cover promotes growth of weedy species <br />and may exacerbate browse damage. <br />