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
* 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.