2.2 Removal of consumer groups habitat within the roadway 



2.3 Loss of soil structure within the road easement due to con- 

 struction machinery activities 



2.4 Alteration of surface water drainages 



2.5 Displacement of sensitive wildlife species from adjacent areas 

 Attribute alterations 



Road construction removes all plant and animal populations within 

 the road base alignment through cutting and clearing, grading, and 

 filling and compaction. The effects are similar for all community 

 types. Biotic components not in the alignment proper, but within 

 the easement, are subjected to various levels of disturbance during 

 construction processes. Large, well-maintained, and frequently- 

 traveled primary roads produce the most extensive changes. Narrow, 

 one-lane tracks, frequently unused, and secondary roads cause fewer 

 alterations. In any event the original biotic communities within 

 the easement are either completely removed or reduced in complexity. 



Vegetation removal results in direct losses of food and cover 

 resources for dependent consumers. Secondary consumers are affected 

 indirectly because of removal or reduction of herbivorous prey 

 organisms as well as loss of cover. Nesting, foraging, escape, and 

 resting areas are altered or destroyed. Avian and mammalian species 

 vary widely in their tolerance to habitat disturbance. Some species 

 tolerate little alteration, while others prefer severely disturbed 

 situations. In each case, species response is a function of time 

 elapsed and the creation or destruction of the required niche. 

 Impact magnitude is a function of a species' resource base (home 

 range size) and the indispensabi lity of the vegetation. Mobile, 

 wide-ranging herbivores (white-tailed deer, javelina) or predators 

 (coyote, red-tailed hawk) are not influenced as severely by such 

 localized habitat alterations as are the less mobile smaller mammals 

 (hispid cotton rat), breeding or strongly territorial songbirds, and 

 reptiles which are restricted to limited areas. Less mobile species 

 experience alteration of a larger proportion of their available 

 habitat; thus, local populations may be severely depressed. The 

 mean width of a typical access road is 6 to 7 m (20 ft) which 

 results in a direct habitat loss of 0.6 ha per km (2.4 acres per mi) 

 of road. 



Detrital and nutrient cycle aspects of the vegetation are not 

 treated further since those alterations with biotic consequences are 

 not pertinent, as roadway activity precludes plant reestablishment. 



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