The community type regulates the clearing methods utilized to pre- 

 pare a location for seismic testing. Where the vegetation type 

 consists of low or medium grasses, small spot-clearing (widths up to 

 4 m, or 13 ft) may be sufficient; where dense brush or woodlands 

 dominate, a dozer or clearing crew may be required for lane clear- 

 ance. Thus, the net biological effects within a seismic lane can 

 vary widely between community types. 



Where the terrain is open and mobility is unrestricted, lightweight 

 seismic vehicles move about the test area, temporarily crushing 

 vegetation. Rapid regrowth occurs due to the survival of the root 

 system and most of the aerial stems. 



Where dozers are required to clear shot lanes, vegetation removal is 

 complete. An immediate loss of wildlife food and cover resources 

 results. Food and cover losses, however, are relatively minor for 

 most mammalian and avian species due to the restricted areal extent 

 of the line as compared to adjacent undistrubed areas. Quantitative 

 assessment of the direct effects may be made by calculation of the 

 area directly affected. Partial compensation is provided by pioneer- 

 ing herbaceous annuals and perennials and shrubs that invade and 

 temporarily dominate newly exposed soils following removal of commu- 

 nity dominants and later abandonment of the site. Long narrow 

 corridors of more diversified flora are created, increasing local 

 habitat diversity and "edge effect." Subsequent effects on local 

 consumer populations are probably not noticeable, even though such 

 ecotonal species as the cottontail, white-tailed deer, bobwhite, and 

 numerous granivorous songbirds find such heterogeneous sites attrac- 

 tive feeding locations and may readjust their movement patterns to 

 visit these areas. Therefore, energy links to the various consumer 

 levels are not followed any further. Plant removal temporarily 

 interrupts nutrient and detrital cycles on the specific site but is 

 considered to be of minor ecosystem consequence because of the 

 limited areal extent. 



Indirect effects of corridor clearing are more difficult to assess. 

 They are largely dependent upon intensity of seismic operations and 

 the density of shotline placement. The greater the segmentation of 

 the area by corridor clearing and seismic operations, the greater 

 may be the indirect effects upon such aspects as nesting and repro- 

 ductive behavior, territoriality, and habitat selection. Segmentation 

 rarely results in isolation of areas as small as one km^. However, 

 shot corridors this dense could affect such species as javelina with 

 a home range of 125 to 222 ha, or 313 to 555 acres (Ellisor and 

 Harwell, 1969). Minimum habitat requirements of sensitive species 

 should be considered in planning shot corridor layout. 



Within the dozed shot lane, changes in soil structure occur as 

 vehicular activity compacts the soil. Water infiltration rates are 



150 



