reached an advanced shrub stage with densities as high as 990 stems per 

 0.004 ha by the 13th year. Thickets averaged 2 to 3 m in height. During site 

 inspection these thickets most likely were equally as dense and practically 

 as tall. 



At most above mentioned sites, following rapid invasion and development 

 of pioneer communities (both by seed and adventitious stems), early shrub 

 communities usual ly were wel I estabi ished in 3 to 5 years. The majority of 

 these areas were small (0.5 to 2 ha) and were usually scattered throughout 

 the scraped sites or surrounding the flooded sites. Usually only one to 

 three isolated patches of early shrub communities occurred in the scraped 

 sites. Those sites that were of sufficient age (including Penny River, 

 Oregon Creek, Washington Creek, Sinuk River, McManus Creek, and Tanana 

 Ri ver-Upstream) began to provide sufficient cover for nesting and feeding 

 passerines and summer and winter cover for sma I I mammals about 10 years 

 after initial disturbance. 



Thus, at sites that provide areas (of various sizes) for revegetative 

 growth without severe stresses from flooding or aufeis scour, habitats that 

 provided food and cover for passerines and sma I I mammals (primary shrub 

 thicket occupants) were naturally replaced about 10 years after completion 

 of gravel removal activities. 



No Significant Change in Vegetative Habitats 



Contrasted to long-term loss of habitat and short-term alteration of 

 habitat structure are gravel removal operations that resulted in no measur- 

 able change in the vegetative structure of the study areas. 



Gravel mining did not affect vegetation at 5 of the 25 study sites, 

 either because of the disturbance location, or the floodplain character- 

 istics, or both (Table 28). At two additional sites, the Nome River and 

 Kavik River, only slight reductions in vegetative cover were observed. 



Three of the five sites with no vegetative disturbance were large flood- 

 plains with large- and medium-width channels flowing in braided patterns. At 



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