• Heller, R.C.
  Remote sensing project, pacific southwest, forest and range experiment station, forest service, USDA, Berkeley, CA.
  
• Aldrich, R.C.
  Remote sensing project, pacific southwest, forest and range experiment station, forest service, USDA, Berkeley, CA.
  

When spruce budworm (Choristoneaura fumiferrana Clem) attacks a spruce-fir forest and populations rise to epidemic levels, the forest community may undergo changes. The best evidence of this change is the increasing number of dead and dying balsam fir (Abies balsamea [L] Mill), favorite host of the budworm. As the stands gradually decline and growing space increases, there may be greater competition for newly available air space.