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
Fire regime1 Old-growth Characteristics
Forest typeIntervals (yrs.)SeverityTypical
patch
(ha)2
Tree SpeciesAges3Woody debris4
Coastal, moist200–300+high100s–1000sDouglas-fir,
hemlock,
red cedar
200–300+very extensive
Mixed conifer, moist35–75+mixed1s–100sDouglas-fir,
white fir,
pines
150–300+extensive
Mixed conifer, dry10–35mixed0.08–2Douglas-fir,
white fir,
pines
150–300+moderate to extensive
Semi-arid/arid
woodlands,
warm
10–100shigh10s–1000spinyon pine,
juniper
100–300+low to high productivity
Semi-arid/arid
woodlands
cold
500+mixedsingle treebristlecone pine,
whitebark,
foxtail
300–1000+low extent,
scattered
Ponderosa pine, moist15–50+mixed0.08–12ponderosa pine,
Douglas-fir
200–400+low extent,
very scattered
Ponderosa pine, dry2–15low0.04–0.08ponderosa pine200–400+low extent,
very scattered

B. Geographic specific descriptions
Fire regimeOld-growth Characteristics
Forest typeIntervals (yrs)SeverityTypical patch (ha)AgesMin. sizes5Woody debris accumulationCanopy variability6
Giant sequoia/
mixed conifer
2–35low/mixed0.04–2500–3000+180+ cmmoderate, scatteredhigh
Southwest
ponderosa pine
2–15low0.04–0.8200–300+50+ cmlow, scatteredmoderate
Front Range
ponderosa pine
30–70mixed0.8–12200–500+30+ cmmoderate, scatteredhigh
Northern Rockies
mixed conifer
25–40low/mixed1s–100s200–500+40+ cmmoderate, scatteredhigh
East-side
ponderosa/Jeffrey pine
3–25low0.004–1.2200–400+40+ cmlow, scatteredmoderate

Footnotes:
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 areas.
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.