• Seymour, Robert S.
  

Red Spruce and Balsam Fir differ in important ways that influence silvicultural treatments. These species differ in important ways that influence silvicultural treatment. Fir produces abundant seeds, but is so susceptible to various heart-rot fungi that its potential life span is limited by the high risk of wind breakage or uprooting. Balsam fir is often cited as the classic example of a species ruled by a pathological rotation, effectively limited to ages 40-70, depending on site quality. It is also the preferred host and suffers extensive mortality from defoliation by the sprucebudworm.  In contrast, red spruce produces seeds infrequently, but is quite resistant to decay and tends to survive budworm defoliation. As a result, red spruce is inherently long-lived, and 300+ year-old trees were not uncommon in virgin forests. Perhaps its most important silvical properties are the abilities to persist as advance regeneration and to respond well to release after many decades of suppression in very low-light conditions in the understory.