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<br />. <br /> <br />. <br /> <br />Area Manager <br />DRAFT <br /> <br />30 <br /> <br />and limit water loss through evapotranspiration (Horton and Campbell 1974). Methods <br />include rnowing, cutting, root plowing, and application of herbicides. The results are that <br />riparian habitat is diulinaieu VI fnalntaliied at V'-'lj carly successiancl ~t~ges net suitable <br />as breeding habitat for willow flycatchers (Taylor and Littlefield 1986). Clearing or <br />mowing habitat can also result in establishment of exotic plants species, which can <br />further reduce suitability. <br /> <br />. Livestock Grazing. Overgrazing by domestic livestock has been a significant factor in <br />the modification and loss of riparian habitats in the arid Western United States (USDA <br />Forest Service 1979, Rickard and Cushing 1982, Cannon and Knopf 1984, Klebenow <br />and Oakleaf 1984, Clary and Webster 1989, Schultz and Leininger 1990, Belsky et al. <br />1999). If not properly managed, livestock grazing can significantly alter plant <br />community structure, species composition, relative abundance of species, and stream <br />channel morphology. The primary mechanism of effect is by livestock feeding in and on <br />riparian habitats. Overutilization of riparian vegetation by livestock can also reduce the <br />overall density of vegetation, which is a primary attribute of flycatcher breeding habitat. <br />Palatable broadleafplants like willows and cottonwood saplings may also be preferred by <br />livestock, as are grasses and forbs comprising the understory, depending on season and <br />the availability of upland forage. Livestock may also physically contact and destroy <br />nests, especially in low-stature habitats (Valentine et al. 1988). Livestock also physically <br />degrade nesting habitat by trampling and seeking shade and creating trails that nest <br />predators and people can use. Furthermore, improper livestock grazing in watershed <br />uplands above riparian systems can cause bank destabilization, increased runoff, <br />increased sedimentation, increased erosion, and reduced capacity of soils to hold water. <br /> <br />. Recreation. In the warm, arid Southwest, recreation is often concentrated in riparian <br />areas because of the shade, water, aesthetic values, and opportunities for fishing, boating, <br />swimming, and other activities. As regional human populations grow, the magnitude and <br />cumulative effects of these activities can be considerable. Effects may include reduction <br />in vegetation through trampling, clearing, woodcutting and prevention of seedling <br />germination due to soil compaction; bank erosion; increased incidence of fire; promoting <br />invasion by exotic plant species; promoting increases in predators and scavengers due to <br />food scraps and garbage; promoting increases in parasitic cowbirds; and noise <br />disturbance. Recreational development can also lead to increased need for foot and <br />vehicle access, roads, pavement, trails, boating, and structures that fragment habitat. <br /> <br />. Fire. Fire is an imminent threat in many locations of occupied and potential flycatcher <br />breeding habitat. Although fires occurred to some extent in some of these habitats <br />historically, many native riparian plants are neither fire-adapted nor fire-regenerated. <br />Thus, fires in riparian habitats are typically catastrophic, causing drastic changes in <br />riparian plant density and species composition. Busch (1995) documented that the <br />current frequency and size of fires in riparian habitats on two regulated rivers (Colorado <br />and Bill Williams) is greater than historical levels because reduced floods have allowed <br />buildup of fuels, and because of the expansion and dominance of the highly-flanunable <br /> <br />OIl 1 1.'.'7 <br />.."J, <br />