- 32 - 

 Foggin and Forcier (26) noted that while clearcut basins near Missoula 

 have larger discharges than matched forested areas, cation concentrations 

 and specific conductances of streams in clearcut basins are not signifi- 

 cantly reduced. Dissolved nutrient loads from clearcuts are generally 

 higher than loads in forested counterparts. 



G. Biological Changes 



The dissolved oxygen content of stream water is a primary determinant 

 of aquatic life composition. This factor can be influenced by several 

 silvicultural activities including: use of pesticides, harvest methods, 

 and burning. 



Research shows that logging debris left in streams can have a high enough 

 biological oxygen demand (B.O.D.) to reduce the stream's dissolved oxygen 

 content below the minimum required for fish development (newly hatched 

 fry or developing embryos) (6). Another study found dissolved oxygen 

 levels below that needed to sustain fish life in a watershed that was 

 clearcut and burned (41). 



There are no studies which directly address the biological impacts of 

 silvicultural activities in Montana. 



