Table 2. Features of typical old-growth forest types. (A) Generic features for moist and dry forest types; (B) features found in specific geographic regions reported in the section on case studies.
A. Generic descriptions
|Forest type||Intervals (yrs.)||Severity||Typical|
|Mixed conifer, moist||35–75+||mixed||1s–100s||Douglas-fir,|
|Mixed conifer, dry||10–35||mixed||0.08–2||Douglas-fir,|
|150–300+||moderate to extensive|
|100–300+||low to high
|Ponderosa pine, moist||15–50+||mixed||0.08–12||ponderosa pine,|
|Ponderosa pine, dry||2–15||low||0.04–0.08||ponderosa pine||200–400+||low extent,|
B. Geographic specific descriptions
|Forest type||Intervals (yrs)||Severity||Typical patch (ha)||Ages||Min. sizes5||Woody debris accumulation||Canopy variability6|
|2–35||low/mixed||0.04–2||500–3000+||180+ cm||moderate, scattered||high|
|2–15||low||0.04–0.8||200–300+||50+ cm||low, scattered||moderate|
|25–40||low/mixed||1s–100s||200–500+||40+ cm||moderate, scattered||high|
|3–25||low||0.004–1.2||200–400+||40+ cm||low, scattered||moderate|
1 Fire regime characteristics are generalized
to typical ranges of intervals between widespread fire events at the stand level
(i.e., 4.0–40 ha) and fire severity on a qualitative scale of low, mixed,
and high. Mixed severity refers to a combination of fire severities, including
some high-severity burn areas within a matrix of low- and moderate-severity burn
2 Typical patch (or stand) sizes refer to the area
occupied by even-aged or relatively even-aged groups of trees. These may be
cohorts that established within a period of time following a disturbance, such as
fire or insect outbreak.
3 Ages of trees include minimum ages of oldest trees in the patch or stand identified as old growth.
4Wood debris accumulation refers to snags, logs, and branch material in the patch or stand.
5 Minimum sizes are diameters at breast height of the largest trees in the patch or stand identified as old growth.
6 Canopy variability refers to heterogeneity of the canopy structure on a qualitative scale (high, moderate, low), with high variability indicating multiple canopy layers across most of the patch or stands, moderate indicating multiple canopy layers in part of the patch (but less than half), and low indicating typically a single canopy layer throughout a patch or stand.