United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

May 2011

Forest Resources of the 

Clearwater National Forest

Ryan P. Hughes
About the author __________________________

Ryan P. Hughes is a Forester with the Interior West Forest Inventory and 

Analysis Program, Rocky Mountain Research Station in Grangeville, Idaho. 

He has also worked for the Bitterroot and Lolo National Forests.

Contents___________________________________

Page

Description of the Clearwater National Forest .................................................1

Forest land highlights of the Clearwater National Forest................................2

Nonreserved timberland highlights of the Clearwater National Forest ......9

Inventory methods................................................................................................11

Documentation......................................................................................................13

For further information........................................................................................13

Rocky Mountain Research Station

240 West Prospect Road 

Fort Collins, CO 80526-2098
1

Forest Resources of the Clearwater National Forest

Ryan P. Hughes

The Interior West Forest Inventory and Analysis 

(IWFIA) Program of the USDA Forest Service, Rocky 

Mountain Research Station, as part of our National Forest System cooperative inventories, conducted a forest 

resource inventory on the Clearwater National Forest 

using a nationally standardized mapped-plot design (for 

more details see section “Inventory methods”). This 

report presents the highlights of this 1999 inventory 

using commonly requested variables and summaries. 

The data could be summarized in other ways for different purposes (see “For further information” on the 

inside back cover). The information presented in this 

report is based solely on the IWFIA inventory sample 

(USDA 1999). Supplementary documentation and inventory terminology can be located in USDA 2002. Additional data collected by the Clearwater National Forest 

and used separately or in combination with IWFIA data 

may produce varying results. Changes since the inventory, such as the impact of recent disturbances on the forest, have not been incorporated into this report. Annual 

inventories will soon replace periodic inventories to help 

monitor these changes at shorter intervals. 

13% 

82% 

5% 

Nonreserved forest land 

Reserved forest land 

Nonforest and water 

Figure 1—Percent area by land class and reserved status, 

Clearwater National Forest, 1999.

Description of the Clearwater 

National Forest

The Clearwater National Forest administers 1,825,422 

acres (USDA 1999) of which 95 percent is forest land, 

and 5 percent is nonforest or water (fig. 1). This report 

describes the characteristics of the forest land sampled 

on the Clearwater. Forest land is land that is at least 

10 percent stocked (or formerly stocked) with live tally 

tree species and is greater than 1 acre in size and 120 feet 

wide. Based on tree species present, forest land is subdivided into timberland, where most trees are timber 

species commonly used for wood products (such as 

Douglas-fir and lodgepole pine), and woodland, where 

most trees often have a multi-stem growth form and are 

not typically used for industrial wood products (such 

as Rocky Mountain Maple). Thirteen percent of the 

total area on the Clearwater National Forest is reserved 

designation in the Selway-Bitterroot Wilderness area. 

This report focuses on forest resources of all the forest 

land administered by the Clearwater National Forest. A 

subsequent section will address nonreserved timberland. 
2

Forest land highlights of the 

Clearwater National Forest

Forest type—Forest resources are often described 

using a forest type classification. Forest type refers to the 

predominant tree species in a stand, based on plurality 

of tree stocking. Stocking is an expression of the extent 

to which growing space is effectively utilized by live 

trees. 

Forest types are dynamic and can change slowly 

through forest succession, or rapidly due to disturbances 

such as logging, fire, or insect and disease epidemics. 

Figure 2 presents the distribution of forest land area 

on the Clearwater National Forest by forest type. The 

spruce-fir forest type is the most common at 26 percent, 

followed in abundance by Douglas-fir at 21 percent. The 

grand fir forest type comprises 19 percent of the forest 

land area; lodgepole pine, 13 percent; western redcedar, 

8 percent; Engelmann spruce, 4 percent; mountain hemlock and maple woodland 3 percent; and paper birch, 

western larch and ponderosa pine, 1 percent.

Tree and stand size—The size distribution of trees is an 

indicator of structural diversity. Figure 3 displays the distribution of the 730 million live trees, 1 inch diameter at 

breast height or greater, on the Clearwater National Forest by diameter class. Overall, this shows a typical diameter distribution with a higher number of small trees than 

large trees. Trees often reproduce prolifically, but thin 

out naturally over time due to competition for resources.

0% 5% 

10% 15% 20% 25% 30% 

Spruce-fir 

Douglas-fir 

Grand fir 

Lodgepole pine 

Western redcedar 

Engelmann spruce 

Mountain hemlock 

Maple woodland 

Paper birch 

Western larch 

Ponderosa pine 

Percentage forest area 

Forest type 

0 

50 

100 

150 

200 

250 

300 

350 

400 

1.0-2.9 3.0-4.9 5.0-6.9 7.0-8.9 

9.0-10.9 

11.0-12.9 

13.0-14.9 15.0-16.9 17.0-18.9 19.0-20.9 

21.0-22.9 

23+ 

Million trees 

Diameter class 

Figure 2—Percent of total forest land area by forest type, Clearwater National Forest, 1999.

Figure 3—Number of live trees on forest land by 2-inch diameter class, Clearwater 

National Forest, 1999.
3

Stand-size class is a classification of forest land based 

on the dominant diameter-size of live trees that contribute 

to stand stocking. Large trees are timber-type softwoods 

and all woodland tree species 9.0 inches diameter and 

greater, and timber-type hardwoods 11.0 inches diameter 

and greater; medium trees include timber-type softwoods 

and all woodland tree species 5.0 to 8.9 inches diameter, 

and timber-type hardwoods 5.0 to 10.9 inches diameter; 

and saplings/seedlings comprise all trees under 5.0 inches 

diameter. Nonstocked stands are typically those that 

have been recently disturbed by tree cutting, forest fire, 

or other large-scale change. For tree stocking, fewer 

large-diameter trees compared to small-diameter trees 

are required to fully stock a site. Figure 4 shows a breakdown of forest land on the Clearwater National Forest 

by area and stand-size class. Seventy-one percent of the 

stands have a majority of stocking from large trees, while 

4 percent are nonstocked. 

Figure 5 shows the area of forest land by forest type 

and stand-size class on the Clearwater National Forest. 

The two most common forest types in the large (9 inches 

or greater) tree class are the spruce-fir and Douglas-fir 

forest types, which together make up 46 percent of the 

large tree stands. Forty-two percent of the stands in the 

medium (5-8.9 inches) tree class are the lodgepole pine 

forest type.

Number of live trees—Another way to assess forest 

diversity is by examining the composition of forest land 

by tree diameter and species. Figure 6 shows the 730 million live trees by species in three diameter-size classes. 

Sixty-five percent of all live trees on the Clearwater National Forest are from 1.0 to 4.9 inches diameter, 17 percent are from 5.0 to 8.9 inches diameter, and 18 percent 

are 9.0 inches diameter and greater. Grand fir makes up 

22 percent of the total number of trees; subalpine fir, 

19 percent; western redcedar, 14 percent; Douglas-fir, 

Nonstocked

0 200 400 600 800 1000 1200 1400

Medium diameter

Saplings/seedlings

Large diameter

Thousand acres 

Stand-size class 

0

50

100

150

200

250

300

350

Spruce-fir 

Douglas-fir 

Grand fir 

Western redcedar 

Lodgepole pine 

Engelmann spruce 

Mountain hemlock 

Paper birch 

Ponderosa pine 

Western larch 

Maple woodland 

Thousand acres 

Forest type 

 Large diameter 

Medium diameter 

Saplings/seedlings 

Nonstocked 

Figure 5—Area of forest land by forest type and stand-size class, Clearwater National 

Forest, 1999.

Figure 4—Area of forest land by stand-size class, Clearwater National Forest, 1999.
4

11 percent; lodgepole pine, 10 percent; Rocky Mountain 

maple, 9 percent; Engelmann spruce, 8 percent; mountain hemlock, 4 percent; paper birch, 1 percent; and the 

remaining species in figure 6 comprise the final 1 percent. 

Species that are scarce may not be encountered with the 

extensive sampling strategy used for this inventory.

Figure 7 shows the number of live trees by species and 

elevation class. Elevation is closely correlated with variations in local climate. Precipitation generally increases 

with rising elevation, while temperature decreases. 

Aspect complicates this general rule; allowing relatively warmer- and drier-site species to grow at higher elevations on south- and west-facing slopes. These factors 

have a profound effect on competition between tree 

species. The Clearwater National Forest displays some 

distinct elevation patterns in tree distribution: whitebark pine and subalpine fir do well at higher elevations 

(above 6,000 feet), while grand fir is a dominant species 

at both lower (below 4,000 feet) and mid elevations 

(4,000-6000 feet). Lodgepole pine is most common at 

the middle elevations. 

Number and weight of dead trees—Standing and down 

dead trees are important for wildlife and in fire ecology, 

as well as acting as nutrient sinks and erosion controls. 

Approximately 44 million standing dead trees (snags) 

and 40 million down dead trees 5.0 inches diameter and 

greater are on forest land on the Clearwater National 

Forest. If trees 1.0 inch diameter and greater are included 

there are 115 million standing dead trees and 100 million 

down dead trees. 

0 

20 

40 

60 

80 

100 

120 

Grand fir 

Subalpine fir 

Western redcedar 

Rocky Mountain maple 

Douglas-fir 

Engelmann spruce 

Lodgepole pine 

Mountain hemlock 

Paper birch 

Western white pine 

Whitebark pine 

Pacific yew 

Western larch 

Western hemlock 

Black cottonwood 

Ponderosa pine 

Million trees 

Species 

1"-4.9" 

5.0"-8.9" 

9.0" and greater 

Figure 6—Number of live trees 1.0 inch diameter and greater on forest land by 

species and diameter class, Clearwater National Forest, 1999.

0 10 20 30 40 50 60 70 80 90 

Million Trees 

Grand fir 

Lodgepole pine 

Douglas-fir 

Subalpine fir 

Engelmann spruce 

Western redcedar 

Mountain hemlock 

Western larch 

Rocky Mountain maple 

Western white pine 

Ponderosa pine 

Whitebark pine 

1,000-1,999

Elevation Class (feet)2,000-2,999

3,000-3,999

5,000-5,999

6,000-6,999

7,000-7,999

4,000-4,999

Figure 7—Number of live trees 5.0 inches diameter and greater on forest land by species and 

elevation class, Clearwater National Forest, 1999.
5

 Many animals are dependent upon standing dead trees, 

but the species, size, and density of these trees required 

for quality habitat vary depending on wildlife species. 

Large diameter (11 inches or greater) dead trees are generally infrequent relative to smaller trees. Figure 8 shows 

the number of snags by forest type for three diameter 

classes. Of the total number of snags, 61 percent are between 1 inch and 4.9 inches diameter, with 40.5 snags per 

acre in this diameter range; and 26 percent are between 

5 and 10.9 inches diameter, with 16.9 snags per acre. Snags 

11 inches diameter and larger make up 13 percent of the 

total, with 8.5 snags per acre. Most of these large snags 

are found on spruce-fir (32 percent; 2.7 snags per acre), 

grand fir (22 percent; 1.9 snags per acre), and Douglas-fir 

(17 percent; 1.4 snags per acre) forest types.

The amount of dead material is a component of forest 

fuel loads. On the Clearwater, about 16.3 million tons 

of standing dead trees and 11.8 million tons of down 

dead trees are on forest land. This estimate includes the 

merchantable bole and bark of trees 5.0 inches diameter and greater. Figure 9 shows the weight per acre of 

down dead trees by stand-size class for each of the forest 

types and all forest types combined. For all forest types 

combined, the large tree stand-size class has the highest 

weight at 8.3 tons per acre, followed by the medium class 

at 4.2 tons per acre. For all stand-size classes combined, 

the mountain hemlock has the highest weight at 11.7 tons 

per acre, followed by western redcedar, and spruce-fir at 

11.4 and 7.7 tons per acre, respectively. Some class breakdowns such as the western larch nonstocked class may 

not be representative due to small sample size.

Stand age—Stand age for this report is estimated from 

core samples of live trees. The estimate is limited to trees 

with diameters that fall in a stand’s designated stand-size 

class. Many other factors affect the number of sample 

trees available for determining stand age. In general, stand 

age for dense stands that contain more core sample trees 

is more representative than stand age for sparse stands 

that contain less. 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

Million snags 

1.0"-4.9" 

5.0"-10.9" 

11.0" and greater 

Grand fir

Douglas-fir

Spruce-fir

Lodgepole pine

Western redcedar

Maple woodland

Engelmann spruce

Mountain hemlock

Western larch

Paper birch

Ponderosa pine

Forest type

Figure 8—Number of standing dead trees 1.0 inch diameter and greater on forest land by 

forest type and diameter-size class, Clearwater National Forest, 1999.

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

Tons Per Acre 

Forest Type 

Large trees 

Douglas-fir

Engelmann spruce

Grand fir

Lodgepole pine

Maple woodland

Mountain hemlock

Paper birch

Spruce-fir

Western larch

Western redcedar

All types

Medium trees 

Saplings/seedlings 

Nonforest 

Figure 9—Weight of down dead trees 5.0 inches diameter and greater on forest land by 

forest type and stand-size class, Clearwater National Forest, 1999.
6

Figure 10 displays the percent of forest land area by 

forest type and stand-age class on the Clearwater National 

Forest. Stand age can indicate the duration since the 

last extensive disturbance of the forest overstory. This 

figure shows the 61- to 80-year class as the most common 

on the Forest, followed by the 1- to 20-year and 81- to 

100-year age classes.

Wood volume, biomass, and basal area of live trees—

Estimates of cubic-foot volume and basal area include 

all live trees 5.0 inches diameter and greater. Basal 

area is the cross-sectional area of a tree stem/bole 

(includes bark) at the point of diameter measurement. 

Biomass estimates include boles, bark, and branches 

of all live trees 1.0 inches diameter and greater. The 

net volume of wood on the Clearwater National Forest 

is estimated to be in excess of 5.9 billion cubic feet. 

Total biomass of wood is estimated at just over 99 million tons and the total basal area is estimated to be about 

199 million square feet. Table 1 is a breakdown of volume, biomass, and basal area by species.

Figure 11 displays the percent net cubic-foot volume of 

live trees by diameter class. Eighty-nine percent of this 

volume is in the 9.0- to 10.9-inch and greater diameter 

class. By species, 100 percent of black cottonwood, 

99 percent of ponderosa pine, 96 percent of mountain 

hemlock, 95 percent of western white pine, and 94 

percent each of western redcedar and western larch 

volume is in trees 9.0 inches diameter and greater. Common species with lower percentages of volume in trees 

9.0 inches diameter and larger include subalpine fir at 

78 percent, paper birch at 52 percent, whitebark pine at 

44 percent, and Rocky Mountain maple at 42 percent.

Another way to look at wood volume is by forest type, 

for which estimates per acre can be computed along with 

basal area (table 2). These numbers include the many 

0% 

5% 

10% 

15% 

20% 

25% 

30% 

Nonstocked

1-20

21-40

41-60

61-80

81-100

101-120

121-140

141-160

161-180

181-200

201-220

221+

Percent of forest land area 

Stand-age class 

Western redcedar 

Western larch 

Spruce-fir 

Ponderosa pine 

Paper birch 

Mountain hemlock 

Maple woodland 

Lodgepole pine 

Grand fir 

Engelmann spruce 

Douglas-fir 

Figure 10—Percent of forest land area by forest type and stand-age class, Clearwater 

National Forest, 1999.

different species that can occur together in each forest 

type. The highest basal area per acre on the Clearwater 

National Forest is in the western redcedar forest type, 

followed by mountain hemlock and ponderosa pine. 

Ponderosa pine is the highest volume per acre. Volume 

Table 1—Net volume, biomass, and basal area on forest 

land by species, Clearwater National Forest, 1999.

Volume Biomass Basal area

(Million (Million (Million

 Species cubic feet) tons) square feet)

Grand fir 1,438.4 23.5 41.4

Douglas–fir 1,035.9 20.2 37.6

Western redcedar 825.3 12.8 31.0 

Lodgepole pine 724.1 11.6 24.2

Engelmann spruce 632.6 9.4 19.4

Subalpine fir 541.5 9.0 22.3

Mountain hemlock 357.2 6.5 12.8

Western larch 125.4 2.4 4.1

Ponderosa pine 92.0 1.7 2.3

Western white pine 53.0 0.9 1.4

Rocky Mountain maple 15.4 0.7 1.1

Paper birch 14.5 0.3 0.7

Western hemlock 7.9 0.2 0.3

Whitebark pine 4.9 0.1 0.3

Black cottonwood 2.2 † 0.1

Pacific yew † † †

 Total (not exact 5,870.5 99.2 199.0

 due to rounding)

† – Less than 100,000
7

and basal area per acre for maple may not be representative due to the small sample size. One characteristic of 

the mapped-plot design is that a plot may sample more 

than one condition (last two columns of table 2). A forest condition is generally defined as an area of relatively 

homogeneous vegetative cover that meets the criteria for 

forest land. Forest type is one of several attributes that 

define and separate conditions identified on the plot. 

Stand density index—Many factors influence the rate 

at which trees grow and thrive, or die. As tree size and 

density increase, competition for available resources also 

increases. Stand density index (SDI), as developed by 

0% 

2% 

4% 

6% 

8% 

10% 

12% 

14% 

16% 

5.0-6.9 7.0-8.9 

9.0-10.9 

11.0-12.9 

13.0-14.9 

15.0-16.9 

17.0-18.9 19.0-20.9 21.0-22.9 23.0-24.9 25.0-26.9 27.0-28.9 

29+ 

Percent volume 

Diameter class 

Figure 11—Percent of total net cubic-foot volume of live trees by diameter class, 

Clearwater National Forest, 1999.

Reineke (1933), is a relative measure of quantifying the 

relationship between trees per acre and average stand 

diameter. The concept was developed for even-aged 

stands dominated by one or two related size classes 

(based on diameter and/or height), but can also be applied to uneven-aged stands composed of three or more 

size classes (Long and Daniel 1990; Shaw 2000). SDI is 

usually presented as a percentage of the maximum SDI 

for each forest type (Van Dyck 2002). Maximum SDI values for the forest types on the Clearwater National Forest 

were estimated using FIA plot data, and formulated specifically to match the procedure used by FIA to calculate 

Table 2—Net volume per acre, biomass per acre, basal area per acre, number of conditions, and condition proportions on forest land by forest type, Clearwater National Forest, 1999.

Forest Volume Biomass Basal area Number of Condition

type (cubic ft. per acre) (tons per acre) (sq. ft. per acre) conditionsa proportionb

Western redcedar 6,252 9.3 214 29 24.0 

Mountain hemlock 6,011 107.5 211 10 10.0

Ponderosa pine 6,854 124.9 171 2 2.0

Grand fir 3,920 65.7 118 63 55.3

Western larch 3,680 66.7 128 4 3.4

Engelmann spruce 3,472 53.3 113 14 11.4

Douglas-fir 3,311 60.9 116 67 61.5

Lodgepole pine 2,688 44.2 94 38 36.9

Spruce-fir 2,420 39.2 88 80 73.8

Paper birch 1,744 34.6 75 3 3.0

Maple woodland 231 5.3 12 10 8.3

Total 3,378 57.1 115 320 289.7

a Number of conditions by forest type that were sampled. These numbers are often greater than the total number of forested plots 

by forest type because a plot may sample more than one forest condition.

b Sum of the condition proportions of plots by forest type that were sampled. These numbers are often less than the total number 

of plots by forest type because of nonforest condition proportions (from plots containing both forest and nonforest conditions) that 

are not included here.
8

0 

100 

200 

300 

400 

500 

600 

700 

<25 

25.0 - 34.9 35.0 - 59.9 

60 + 

Thousand acres 

Percent of maximum stand density index 

Western redcedar 

Western larch 

Spruce-fir 

Ponderosa pine 

Paper birch 

Mountain hemlock 

Maple woodland 

Lodgepole pine 

Grand fir 

Engelmann spruce 

Douglas-fir 

Figure 12—Area of forest land by forest type and percent stand density index, Clearwater 

National Forest, 1999.

SDI (Shaw 2000). Resulting percentages were grouped 

into four classes (fig. 12), whose thresholds have ecological and management significance. A site is considered to 

be fully occupied at 35 percent of SDI maximum, which 

marks the onset of competition-related stresses and 

slowed growth rates (Long 1985). Based on FIA sample 

data, 58 percent of all forest stands on the Clearwater 

National Forest are considered to be fully occupied.

Components of change: growth—Another measure of 

forest vigor is net annual growth. Net annual growth is the 

difference between gross annual growth and losses due 

to mortality. Gross annual growth of live trees (5.0 inches 

diameter and greater) on all forest land on the Clearwater 

National Forest is estimated to be 154 million cubic 

feet, and net annual growth is 116 million cubic feet. Gross 

annual growth is compared to mortality for seven high 

volume species in figure 13. Mortality on all forest land 

on the Clearwater National Forest is about 25 percent of 

gross annual growth. Mortality is only about 2.6 percent 

of gross annual growth for western larch, 3.3 percent 

for Rocky Mountain maple, 8.8 percent for whitebark 

pine, and 11.5 for western redcedar, while mortality 

exceeds growth by 126 percent for western white pine. 

The leading cause of mortality for all species was disease 

(49 percent of mortality) and insects (20 percent of 

mortality).

0 10 20 30 40 50 60 

Mountain hemlock 

Lodgepole pine 

Subalpine fir 

Engelmann spruce 

Western redcedar 

Douglas-fir 

Grand fir 

Million cubic feet 

Species 

Gross growth 

Mortality 

Figure 13—Gross annual growth of all live trees 5.0 inches diameter and greater 

compared to mortality for seven high-volume species on all forest land, Clearwater 

National Forest, 1998.
9

Components of change: mortality—Field crews assess 

which trees have died in the past 5 years; these trees 

are used to estimate an average annual mortality. Based 

on this estimate, in 1999, 38.1 million cubic feet of wood 

from live trees (5.0 inches diameter and greater) died on 

the Clearwater National Forest. About 49 percent of the 

mortality was caused by disease, 22 percent by weather, 

20 percent by insects, 5 percent unknown, and 3 percent 

was fire–related. The following are the top five mortality 

species accounting for 83 percent of overall mortality: 

subalpine fir (20 percent), lodgepole pine (18 percent), 

Douglas-fir and mountain hemlock (15 percent), and 

grand fir (14 percent).

Understory vegetation—Understory vegetation provides forage and cover for wildlife, contributes to forest 

fuel load, and can be an indication of the successional 

stage of the forest community. On each plot, field crews 

visually estimated crown canopy coverage for four plant 

groups—tree seedlings/saplings, shrubs, forbs, and graminoids (See USDA 1999 for details). Figure 14 shows the 

average percent cover of plant groups on forest land by 

forest type. Forest wide, Rocky Mountain maple is the most 

abundant understory seedling/sapling species, followed 

by grand fir. The most abundant understory shrubs are 

mountain huckleberry, fools huckleberry, and snowberry. 

Twinflower and queencup bead-lily are the most abundant forbs; and pinegrass, elk sedge, blue-grass, and 

timothy are the most abundant understory graminoids 

on the forest. 

Nonreserved timberland 

highlights of the Clearwater 

National Forest

Reserved lands are those that have been withdrawn 

from management for production of wood products, 

such as wilderness areas and national parks. The nonreserved portion of the Clearwater contains nearly 86 

percent of the forest land on the National Forest. There 

are 542 million live, growing-stock trees on nonreserved 

timberland, 72 million in reserved areas.

Forest type—Grand fir is the most common forest type 

on nonreserved timberland on the Clearwater at 24 percent, followed by spruce-fir (22 percent) and Douglas-fir 

(19 percent). On the reserved portion, Spruce-fir is the 

most common at 61 percent, followed by Engelmann 

spruce (16 percent) and lodgepole pine (13 percent). 

Dead trees and fuels—There are approximately 35 million standing dead trees (snags) and 31 million down dead 

trees 5.0 inches diameter and greater on nonreserved 

timberland. Snags at least 11.0 inches diameter are found 

at densities of 8.2 per acre. There are 2.9 snags per acre 

19.0 inches diameter or greater. The merchantable bole 

and bark of all dead trees at least 5.0 inches in diameter 

on reserved timberland is equal to about 1.6 million tons 

in standing dead and 2.0 million tons in down dead. With 

the exception of the medium tree (poletimber) class at 

4.2 tons per acre on nonreserved timberland versus 0.0 

on reserved land, weights per acre of down dead trees 

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

Grand fir 

Douglas-fir 

Subalpine fir 

Western redcedar 

Lodgepole pine 

Spruce-fir 

Engelmann spruce 

Mountain hemlock 

Paper birch 

Ponderosa pine 

Western white pine 

Average percent cover 

Forest type 

Seedlings/saplings 

Shrubs 

Forbs 

Graminoids 

Figure 14—Average percent cover of trees (seedlings/saplings), shrubs, 

forbs, and graminoids on forest land by forest type, Clearwater National 

Forest, 1999.
10

and greater-inch diameter class has the most volume at 

15 percent, followed closely by the 13.0 to 14.9-inch class 

at 12 percent. Twenty-six percent of the total sawtimber 

volume on the Clearwater National Forest is from grand 

fir, with 22 percent from Douglas-fir, 17 percent from 

western redcedar, and 13 percent from spruce-fir forest 

type.

Stand density index—Sixty percent of nonreserved 

timberland stands on the Clearwater National Forest are 

at 35 percent or more of SDI maximum, or considered 

0% 

5% 

10% 

15% 

20% 

25% 

1-20 

21-40 

41-60 61-80 

81-100 

101-120 121-140 141-160 161-180 181-200 

201-220 

220+ 

Percent of timberland area 

Stand-age class 

Not reserved 

Reserved 

Figure 15—Percent of timberland by reserved designation and stand-age class, 

Clearwater National Forest, 1999.

Table 3—Net volume, biomass, and basal area of growingstock trees 5 inches diameter and greater by 

species on nonreserved timberland, Clearwater 

National Forest, 1999.

Volume Biomass Basal area

(Million (Million (Million

Species cubic feet) tons) square feet)

Grand fir 1,380.8 21.8 39.4

Douglas–fir 955.1 18.2 34.2

Western redcedar 754.3 10.6 27.4

Lodgepole pine 617.3 9.6 20.6

Subalpine fir 356.6 5.3 14.4 

Mountain hemlock 355.5 6.3 12.7

Engelmann spruce 350.8 5.1 11.4

Western larch 113.5 2.2 3.8

Ponderosa pine 91.4 1.6 2.3

Western white pine 53.0 0.9 1.4

Paper birch 13.3 0.2 0.6

Western hemlock 7.9 0.1 0.3

Black cottonwood 2.2 † 0.1

Whitebark pine 2.1 † 0.1

Pacific yew † † †

 Total (not exact 5053.8 81.8 168.7

 due to rounding)

† – Less than 100,000

on nonreserved timberland are similar for those on all 

forest land, both by stand-size class for all forest types 

combined (large tree class at 8.2 tons per acre and seedling/sapling class at 3.6 tons per acre) and by forest type 

for all size classes combined (mountain hemlock type at 

11.7 tons per acre, western redcedar at 11.4 tons per acre, 

and grand fir at 7.5 tons per acre).

Stand age—Stands are generally younger on nonreserved timberland than on all forest land, with the 61- to 

80-year age class being the most common, followed by 

the 81- to 100- year age class (fig. 15). The 61- to 80-year 

age class is also the most common in the reserved area. 

Fifty-five percent of all trees in reserved areas are 101 

years and greater in age, compared to 24 percent in nonreserved areas.

Wood volume, biomass, and basal area of growingstock trees—Table 3 displays a breakdown of net cubic 

volume, tons of wood biomass,and square foot basal area 

for growing-stock trees 5 inches diameter and greater by 

species on nonreserved timberland for the Clearwater. 

The total net cubic-foot volume is nearly 5.1 billion cubic feet. Grand fir and Douglas-fir together account for 

46 percent of the volume on nonreserved timberland. 

Total wood biomass is estimated at 82 million tons. Fortyfour percent of the biomass on nonreserved timberland 

consists of grand fir and Douglas-fir. Total basal area is 

estimated at 169 million square feet. Grand fir and Douglas-fir comprise 44 percent of basal area on nonreserved 

timberland. 

The net volume of sawtimber trees (sawtimber volume) on nonreserved timberland is estimated to be over 

26.1 billion board feet (International 1⁄4-inch rule). This 

includes all growing-stock trees 9.0 inches diameter and 

greater for softwoods, and 11.0 inches diameter and 

greater for hardwoods. Figure 16 illustrates the sawtimber volume on timberland by diameter class. The 29-inch 
11

Figure 17—Gross annual growth of growingstock trees 5.0 inches diameter and greater 

compared to mortality for seven high 

volume species on non reserved timberland, 

Clearwater National Forest, 1998.

0 

500 

1000 

1500 

2000 

2500 

3000 

3500 

4000 

4500 

Million board feet 

Diameter class 

9.0-10.9

11.0-12.9

13.0-14.9

15.0-16.9

17.0-18.9

19.0-20.9

21.0-22.9

23.0-24.9

25.0-26.9

27.0-28.9

29+

Figure 16—Net volume of sawtimber trees 

(International 1/4” rule) on nonreserved 

timberland by 2-inch diameter class on 

Clearwater National Forest, 1999.

to be fully occupied. Forty-four percent of Engelmann 

spruce stands, 53 percent of lodgepole pine stands, 61 

percent of Douglas-fir stands, and 79 percent of western 

redcedar stands are fully occupied.

Components of change: growth and mortality—Gross 

annual growth of growing-stock trees on nonreserved 

timberland on the Clearwater is estimated at 135.8 million 

cubic feet, while mortality is an estimated 29.5 million 

cubic feet. Gross annual growth is compared to mortality 

of growing-stock trees for seven high volume species 

in figure 17. Mortality is 22 percent of growth on nonreserved timberland. Mortality volume was highest in 

mountain hemlock and lodgepole pine.

Inventory methods

Forest Inventory and Analysis (FIA) provides a statistically based sample of forest resources across all ownerships that can be used for planning and analyses at local, 

state, regional, and national levels. IWFIA uses a twophase sampling procedure for all inventories. Phase one 

is based on a grid of sample points systematically located 

Mountain hemlock 

Engelmann spruce 

Subalpine fir 

Lodgepole pine 

Western redcedar 

Douglas-fir 

 Grand fir 

Million cubic feet 

Species 

Gross growth 

Mortality 

0 10 20 30 40 50 60

every 1,000 meters across all lands in a state. Phase one 

points are assigned ownership and vegetative cover attributes using maps and remotely sensed imagery. Field 

crews conduct phase two of the inventory on the subsample of phase one points that occur on forest land. The 

sampling intensity is one field plot every 5,000 meters, or 

about every 3 miles. Phase two plots are stratified based 

on phase one ownership and vegetation information, and 

weights are assigned to each stratum based on the proportion of phase one points in that stratum. 

Phase two plots were sampled using the mapped-plot 

design (see next section). There were 304 field plots on 

the Clearwater National Forest, no plots were completely 

hazardous or inaccessible. However, 11 plots contained 

portions that were inaccessible. A total of 272 field plots 

sampled only forest conditions, 23 sampled both forest 

and nonforest conditions, 3 sampled both forest and 

water conditions (rivers, reservoirs, lakes, etc. at least 

30 feet wide or 1 acre in area), 6 sampled only nonforest conditions, and none sampled only water. A total of 

320 forest conditions were sampled on 298 plots that 

contain 289.7 forest, 7.6 nonforest, and 0.7 water condition proportions.
12

Table 4—Percent standard error for area estimates on total forest land and 

reserved timberland; and percent standard errors for estimates of net 

volume, net annual growth, and annual mortality for live trees on total forest land and growing-stock trees (5.0 inches d.b.h. and greater) on nonreserved timberland, Clearwater National Forest, 1999.

Land class or Percent

type of trees Attribute Area or volume standard error

Total forest land (acres) Area 1,737,816 ±1.1

Total forest land Volume 5,870,533,579 ±4.9

(all trees cubic feet) Growth 115,679,252 ±8.4

Mortality 38,139,120 ±18.7

Nonreserved timberland (acres) Area 1,448,793 ±1.6

Nonreserved timberland Volume 5,065,033,126 ±5.4

(growing-stock trees cubic feet) Growth 106,327,470 ±8.8

Mortality 29,493,241 ±22.4

About the mapped-plot design—The mapped-plot 

design was adopted by FIA nationwide by 1995. Its predetermined subplot layout uses boundary delineation, 

when necessary, to classify differing conditions. Most 

plots sample one forest condition; therefore, delineating 

conditions is often not required.

Conditions were separated, or mapped, based on differences in any of five attributes: forest/nonforest, forest 

type, stand-size class, stand origin, and stand density. The 

condition proportion is the fraction of plot area sampled 

in each condition. The sum of all condition proportions 

for any given plot equals 1.00. Therefore, the number and 

relative size of plot conditions determines the weighted 

area used for sample expansion. 

Standard errors—The sample was designed to meet 

national standards for precision in state and regional 

estimates of forest attributes. Standard errors, which 

denote the precision of an estimate, are usually higher 

for smaller subsets of the data. Forest-level estimates 

and percent standard errors by land class or type of trees 

for various attributes are presented in table 4. Standard 

errors for other estimates are available upon request (see 

“For further information” section on the inside back cover). 
13

Federal Recycling Program Printed on Recycled Paper

For further information ________________

Interior West Forest Inventory and Analysis Program (IWFIA)

Rocky Mountain Research Station

c/o Program Manager

507 25th Street, Ogden, UT 84401

Phone: 801-625-5388

FAX: 801-625-5723

World Wide Web: http://www.fs.fed.us/rm/ogden

Clearwater National Forest

Supervisor’s Office

12730 Highway 12

Orofino, Idaho 83544

Phone: 208-476-4541

World Wide Web: http://www.fs.fed.us/r1/clearwater/

Selected data for this National Forest are part of a national data base that 

houses information for much of the forest land in the United States. This 

data base can be accessed on the Internet at the following web site:

http://ncrs2.fs.fed.us/4801/fiadb/fim17/wcfim17.asp

Documentation _______________

Long, James N. 1985. A practical approach to density 

management. Forestry Chronicle 61:23-27.

Long, James N., Daniel, Theodore W. 1990. Assessment of 

growing-stock in uneven-aged stands. Western Journal 

of Applied Forestry 5(3):93-96.

Reineke, L.H. 1933. Perfecting a stand density index for 

even-aged forests. J. Agric. Res. 46:637-638.

Shaw, John D. 2000. Application of Stand Density Index 

to Irregularly Structured Stand. Western Journal of 

Applied Forestry 15(1):40-42.

U.S. Department of Agriculture, Forest Service. 1999. Forest 

Survey field procedures, 1999. Ogden, UT: USDA Forest 

Service, Rocky Mountain Research Station.

U.S. Department of Agriculture, Forest Service. 2000. 

Land Areas of the National Forest System. FS-383. 

As of September 1999.

U.S. Department of Agriculture, Forest Service. 2002. 

Periodic mapped-plot design inventory terminology. 

[Online]. Available: http://fsweb.ogden.rmrs.fs.fed.

us/state_reports/wyoming/wy_nfs_main.html (also 

available on file at: U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research Station, 

Ogden, UT).

Van Dyck, M.G. 2002. Keyword reference guide to the 

Forest Vegetation Simulator. WO-Forest Management 

Service Center, Fort Collins, CO.
14

The Rocky Mountain Research Station develops scientific information and technology to improve management, protection, 

and use of the forests and rangelands. Research is designed to meet the needs of National Forest managers, Federal and State 

agencies, public and private organizations, academic institutions, industry, and individuals. 

Studies accelerate solutions to problems involving ecosystems, range, forests, water, recreation, fire, resource inventory, 

land reclamation, community sustainability, forest engineering technology, multiple use economics, wildlife and fish habitat, 

and forest insects and diseases. Studies are conducted cooperatively, and applications may be found worldwide.

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