CHARACTERISTICS OF OLD-GROWTH 
DOUGLAS-FIRS


Old-growth Douglas-fir (Pseudotsuga menziesii) trees are a significant though minor component of most old-growth redwood (Sequoia sempervirens) forests in the Santa Cruz Mountains, sharing the canopy with redwoods.   Unlike redwood, they succumb readily to such tree-damaging agents as disease, insects, windfall, and wildfire.   In the Santa Cruz Mountains they are very susceptible to a heart rot fungus not found further north and thus seldom live more than 350 years.  Consequently Douglas-firs are the major source of recruitment for large snags and large down logs in redwood-Douglas-fir stands.   They also assume old-growth characteristics at a much earlier age than redwood, at about 175 years.

The softer heartwood of old-growth Douglas-fir is the primary resource used by our three species of cavity-excavating woodpeckers and it typically provides the majority of tree cavities in younger old-growth stands.  These cavities are used by small mammals for denning, bats for roosting, and are required for nesting by 12 species of forest birds.  Thus old-growth Douglas-firs are critically important in sustaining wildlife habitat in our redwood – Douglas-fir forests.

Identifying Characteristics of Old-growth Douglas fir Trees in the Santa Cruz Mountains 
not all need be present

  • Outline of the live crown is irregular
  • Tree top is dead, damaged, or broken
  • Epicormic branching* or reiterations** are present
  • Large horizontal branches (>8") are present in the upper half of the tree
  • Cavities, hollows, broken limbs or other "defect" is present
  • Burn scars are present on the trunk
  • Bark is thick, loose, and "punky" to the touch


- prepared by S. Singer, forest biologist, October 2009 

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*  Multiple very small branches arising from the same point on the trunk.
** A tree-like branch growing from a dormant bud in the trunk or in a large limb.