lieved to have significantly affected their population levels. However, at 

 sites where large areas of vegetation were removed (including Dietrich 

 R i ver-Upstream, Sinuk River, Sagavan i rk tok River, Penny River, and Jim 

 River) the loss of habitat may influence the winter distribution and move- 

 ment patterns of these animals. 



No Apparent Response 



Mammals that have large home ranges (including bears, caribou, wolves, 

 and foxes) generally displayed no apparent attraction to or avoidance of the 

 disturbed f I oodp I a i n areas. Hence, the only apparent effects of gravel 

 removal on these animals would be those associated with reducing their cover 

 and food supplies (vegetation, small mammals, passerines, and fish) or 

 increasing their cover and food supplies (water birds, ground squirrels, and 

 f ish) . 



An exception to this pattern was recorded at a few of the sites located 

 along the Trans-Alaska Pipeline corridor. At these sites (Jim River, 

 Dietrich Ri ver-Upstream, West Fork Tolovana River, and Middle Fork Koyukuk 

 River-Downstream) individual bears and wolves have become attracted to these 

 areas by associating them with discarded food and garbage. 



FACTORS AFFECTING RECOVERY RATE OF FAUNAL COMMUNITIES 



For species whose populations were reduced as a result of gravel min- 

 ing, specifically passerines and small mammals, the rate at which they began 

 to recolonize disturbed areas was directly related to redevelopment of vege- 

 tative habitats. Vegetative recovery was most directly influenced by hydrau- 

 lic parameters as discussed in previous sections. 



At sites that were of sufficient age and contained sufficient vegeta- 

 tive recovery, passerines did not begin to again use the disturbed areas as 

 nesting and feeding habitat until shrub thickets of an intermediate stage 

 with densities approaching 200 to 500 stems per 0.004 ha and 1.0 to 1.5 m in 

 height were present. In addition, small mammals did not begin to use vege- 

 tated areas as primary habitats until the ground cover developed to a multi- 

 layered cover with densities of at least 60 to 70 percent surface coverage. 



255 



