• Newton, Michael
  College of Forestry, Oregon State University
  
• Cole, Elizabeth C.
  College of Forestry, Oregon State University
  
• McCormack, Maxwell L. Jr.
  College of Forest Resources, University of Maine
  
• White, Diane E.
  USDA Forest Service, Umpqua National Forest
  

Responses of conifers and other vegetation to 9 aerial herbicide treatments were evaluated in a replicated conifer-release experiment in a 7-year-old spruce-fir clearcut in central Maine. Development of the naturally regenerated conifers was inversely related to residual hardwood cover and conifer stocking during the 9 years after treatment. All herbicides and rates of application initially reduced hardwood cover by 50% or more. Cover more than 1.5 m tall was nearly eliminated by several treatments, and release from overtopping provided long-term increase in conifer growth. Untreated hardwoods severely reduced dominance and stocking of conifers by age 16. Spruce heights and diameters were less affected by hardwood competition than were those of fir; current growth in released fir was greater than that in released spruce; but unreleased spruce, where present, grew faster than unreleased fir. Conifir growth was affected both by residual hardwood overtopping and by number of conifers within 0.91 m.