Old Growth Forests - Definitions - Other Definitions

Other Definitions

A 2001 scientific symposium in Canada found that defining old growth in a scientifically meaningful, yet policy-relevant, manner presents some basic difficulties, especially if a simple, unambiguous, and rigorous scientific definition is sought. Symposium participants identified some attributes of late-successional, temperate-zone, old-growth forest types that could be considered in developing an index of "old-growthness" and for defining old-growth forests:

Structural features:

• Uneven or multi-aged stand structure, or several identifiable age cohorts
• Average age of dominant species approaching half the maximum longevity for species (approximately 150+ years for most shade-tolerant trees)
• Some old trees at close to their maximum longevity (ages of 300+ years)
• Presence of standing dead and dying trees in various stages of decay
• Fallen, coarse woody debris
• Natural regeneration of dominant tree species within canopy gaps or on decaying logs

Compositional features:

• Long-lived, shade-tolerant tree species associations (e.g., sugar maple, American beech, yellow birch, red spruce, eastern hemlock, white pine)

Process features:

• Characterized by small-scale disturbances creating gaps in forest canopy
• A long natural rotation for catastrophic or stand-replacing disturbance (e.g., a period greater than the maximum longevity of the dominant tree species)
• Minimal evidence of human disturbance
• Final stages of stand development before a relatively steady state is reached