certainly altered at the specific activity site, but are of little 

 consequence when compared to other contributing ecosystem sources. 

 Therefore, further consideration of these aspects is not warranted. 



Alterations associated with buried utility and flowlines are usually 

 too small and localized to cause changes in surface water hydrology 

 of the ecosystem. 



Nearby flora are usually allowed to reclaim the disturbed sites. 

 However, overhead electrical line easements are periodically main- 

 tained with herbicide applications or by mowing to suppress recovery 

 of woody growth. 



Placement of jas and oil transport pipelines involve the same basic 

 installation procedures and create the same ecological alterations 

 as placement of buried utility and flowlines. The operational scale 

 in all respects, however, is much larger, and as a result, several 

 formerly unimportant alterations subsequently require renewed con- 

 sideration. A typical pipeline easement may be approximately 45 m 

 (150 ft) wide, which results in direct habitat alterations of 4.5 ha 

 per km (18.2 acres per mi) of easement. Large-scale plant removal 

 means long-term changes in vegetation structure and composition. 

 Food and cover for consumer groups are removed directly with loss of 

 food-bearing and cover-producing plants, or indirectly by removal of 

 prey organisms. Habitat losses are more significant due to the 

 larger area affected. 



Plant recovery following completion of activities creates long cor- 

 ridors of diversified, rapidly changing flora (Cody, 1975), which 

 initiates utilization by early successional consumer groups such as 

 small mammals, granivorous songbirds and gamebirds, and inverte- 

 brates. Further plant development encourages more characteristic 

 ecotonal species to make use of pipeline corridors. Whether long- 

 term compensatory changes result for particular consumer components 

 is a function of the species' specific habitat requirements, the 

 original cover type replaced, and the maintenance regime employed in 

 the right-of-way. Secondary consumers find such heterogeneous sites 

 productive feeding locations and readjust their movement patterns to 

 visit such areas. Plant removal and soil alterations interrupt 

 nutrient and detrital cycles within the corridor, which may contrib- 

 ute to site impoverishment if leaching and surface runoff are exten- 

 sive. Recovery by more complex plant assemblages is prevented until 

 suitable site microenvironmental conditions (soil moisture, soil 

 heat, soil air, and nutrients) are restablished. 



Large areas of vegetation removal, decreased soil structure (from 

 soil compaction), short-term increased slope (from stockpiled earth 

 along the trench), and temporarily increased surface water (from 

 pumping seepage and rainwater from trench) increase surface-water 



163 



