West Mojave Plan FEIR/S - Desert Managers Group

OHV Impacts to Soils: OHV use has resulted in the following impacts to soils (see alsoNational Ecology Research Center 1990): damage or destruction of soil crusts (24), soil erosion(Trombulak and Frissell 2000, USFWS 1994b), and interrupted run-off patterns (Trombulak andFrissell 2000). Vollmer et al. (1976) found that OHV use changed soil compaction andpermeability, and that disruption of soils may not be fully expressed until years after the originalimpact. Berry (1996) found alterations to and erosion (wind, water) of soil and soil crusts, andadverse effects to soil porosity, chemistry, moisture, and temperature. Lovich and Bainbridge(1999) observed that areas they considered least susceptible to water and wind erosion, followingOHV use, were dunes, playas, and areas with abundant coarse surface material.3.3.2.6.4 Indirect Impacts of OHVs on Desert Tortoises and HabitatHuman Access: Berry (1996) indicated that human access results in increased damage toplants, animals, and soils. This access results in exploitation, removal, unintentional orintentional disturbance, and harassment of wildlife. She also reported adverse effects on othervisitors and increased deposition of garbage and refuse. Fire regimes are altered as a result ofhuman-induced fires and the proliferation of alien or non-indigenous plants.USFWS (1994b) indicated that the presence of routes facilitates the removal of deserttortoises (predation for food, collecting for pets, and commercial trade), vandalism, and releaseof captive desert tortoises. Dumping, numbers and locations of wild fires, harvest and vandalismof vegetation, and predation by dogs and ravens may increase proportionate to available access.Routes have been implicated in the proliferation of weeds, resulting in more wildfire (USFWS2002, USFWS 1994b). Berry (1996) found that tortoise populations decreased with increasingpercentages of introduced annual plants.Spread of Weeds: Lovich (1992) concluded that, among other things, tortoise habitatshave been negatively affected by construction of roads and utility corridors. Brooks (1998) andFrenkel (1970) concluded that dominance of alien annual plants is the highest where roaddensities are high, and that minimizing the number of paved and dirt roads and maintaining nonroadedwilderness areas may reduce the dominance of aliens.Trombulak and Frissell (2000) listed seven general effects of roads, including spread ofexotic species, and indicated that roads are commonly identified as important correlates orindicators of loss of ecological health. They reported that roads provide dispersal of exoticspecies via three mechanisms: providing habitat by altering conditions, making invasion morelikely by stressing or removing native species, and allowing easier movement by wild or humanvectors. Hourdequin (2000) found that, whereas roads negatively affect some species, others maybenefit; that many exotic plant species thrive along roadsides; that roads can act as corridors forthe dispersal of plant seeds; and that roads may also provide habitat and movement corridors foropportunistic species such as weeds. Tracy (1995) showed that fires are mainly started alongroads, and that a majority of those are along paved roads.Route Proliferation: USFWS (1994b) identified route proliferation as a threat. LaRue(1997) reported that there had been a 27% increase in detectable routes between 1978 and 1989in the Ord Mountain area. Much of it resulted from motorcycle use in the southern parts of theChapter 3 3-127