United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

August 2012

Forest Resources of the Idaho 

Panhandle National Forest

Joshua C. Holte
About the author __________________________

Joshua Holte is a Forestry Technician with the Interior West Forest Inventory and 

Analysis Program, Rocky Mountain Research Station in Coeur d’Alene, Idaho. 

Contents___________________________________

Page

Description of the Idaho Panhandle National Forest....................................... 1

Forestland highlights of the Idaho Panhandle National Forest......................... 2

Roaded timberland highlights of the Idaho Panhandle National Forest ........... 9

The inventory methods................................................................................. 11

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

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

Rocky Mountain Research Station

240 West Prospect Road 

Fort Collins, CO 80526-2098
1

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 Idaho Panhandle National Forest (IPNF) using a nationally 

standardized mapped-plot design (for more details see “The 

inventory methods” section). This report presents the highlights 

of the 2001 inventory using variables and summaries commonly requested by IWFIA users. 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 IPNF 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. 

Forest Resources of the Idaho Panhandle 

National Forest 

Joshua C. Holte

Description of the Idaho 

Panhandle National Forest

The IPNF is an administrative unit combining most of the 

Kaniksu, Coeur d’Alene, and St. Joe designated National 

Forests. This report does not address designated forest areas 

outside the administrative boundary of the IPNF. The IPNF 

administers 2,506,649 acres (USDA 2000) of which 97 percent is nonreserved forest land, 2 percent is nonforest or 

water, and less than 1 percent is reserved (fig. 1). This report 

describes the characteristics of the forest land sampled on 

the IPNF. Forest land is at least 1 acre in size and 120 feet 

wide as well as being at least 10 percent stocked (or formerly 

stocked) with live tree species. Based on tree species present, 

forest land is subdivided into either timberland or woodland. 

Timberland areas are stocked mostly with tree species commonly used for wood products (such as Douglas-fir and ponderosa pine.) In woodland areas most trees have a multi-stem 

growth form and are not typically used for industrial wood 

products (such as Rocky Mountain maple.) On the IPNF, 

97.3 percent of the total forest land is timberland and 2.5 percent is woodland. It is important to note that in the next 

inventory Rocky Mountain maple, which is the major woodland component in this area, will be considered a shrub 

rather than a woodland tree (USDA 2004.) The ‘maple 

woodland’ forest type will be dropped causing a change 

in the classification of these areas. The revised forest type 

classifications will be based on the remaining non-maple tree 

species. 

97.3% 

0.2% 2.5% 

Nonreserved forest land 

Reserved forest land 

Nonforest and water 

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

Panhandle National Forest, 2001.
2

Less than one percent of the total area on the IPNF is in a 

reserved designation. Reserved lands have been withdrawn 

from management for production of wood products. These 

reserved lands are located in the Salmo-Priest Wilderness 

area of Washington. The reserved sample size is too small 

for a valid characterization in this report. 

The first part of this report focuses on forest resources of 

the forest land administered by the IPNF, including all types 

of land classification. The subsequent section addresses the 

roaded areas. The roadless designation used comes from the 

2008 Roadless Rule (USDA 2008) and does not include lands 

defined as wilderness. Characterizations of the five varieties of 

roadless areas defined in the 2008 rule are beyond the scope 

of this report. Roadless is an evolving classification, most of 

the land area covered in the 2008 designation was considered 

roadless under the earlier 1987 IPNF forest plan and the 2000 

Roadless Rule (USDA 2003.)

Forestland highlights of the 

Idaho Panhandle 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 (the most abundant tree species.) Stocking is an 

expression of the extent to which growing space is effectively 

utilized by live trees. 

Forest types are dynamic and may change slowly through 

forest succession, or rapidly due to a disturbance such as 

logging, fire, or insect and disease epidemics. Figure 2 

summarizes the distribution of forest land area on the IPNF by 

forest type. The Douglas-fir forest type is the most common 

at 25 percent, followed in abundance by Engelmann spruce/

subalpine fir (spruce-fir) at 18 percent. The grand fir forest 

type comprises 13 percent of the forest land area; western 

hemlock, 9 percent; lodgepole pine, 9 percent; western 

redcedar, 6 percent; western larch, 6 percent; mountain 

hemlock, 4 percent; Engelmann spruce, 3 percent; Maple 

woodland, 3 percent; and ponderosa pine as well as western 

white pine each comprise 2 percent. 

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

indicator of structural diversity. Figure 3 displays the distribution of the 1.4 billion live trees on the IPNF 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 limited resources.

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 show evidence of having supported stocked stands 

in the past but have been recently disturbed by tree cutting, 

forest fire, or other large-scale disturbances. 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 IPNF by area and stand-size 

class. Seventy-four percent of the stands on the IPNF have a 

majority of stocking from large trees, while 1.5 percent are 

nonstocked. 

0% 5% 10% 15% 20% 25% 30% 

Western white pine 

Ponderosa pine 

Engelmann spruce 

Maple woodland 

Mountain hemlock 

Western larch 

Western redcedar 

Western hemlock 

Lodgepole pine 

Grand fir 

Spruce-fir 

Douglas-fir 

Percent forest land 

Forest type 

Figure 2—Percent of forest land area by forest type, Idaho Panhandle National Forest, 2001.
3

Figure 5 shows the area of forest land by forest type and 

stand-size class on the IPNF. The two most common forest 

types in the large tree class are the Douglas-fir and spruce-fir 

forest types, which together make up 47 percent of large tree 

stands. The lodgepole pine forest type makes up forty-two 

percent of the stands in the medium tree class. The small 

size class is much more evenly distributed. Douglas-fir and 

spruce-fir together make up 36 percent of small stands.

0 

100 

200 

300 

400 

500 

600 

700 

800 

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 3—Number of live trees on 

forest land by 2-inch diameter class, 

Idaho Panhandle National Forest, 

2001.

Figure 4—Forest land area by 

stand-size class, Idaho Panhandle 

National Forest, 2001.

600 

500 

400 

300 

200 

100 

0 Douglas-fir

Spruce-fir

Grand fir

Lodgepole pine

Western hemlock

Western redcedar

Western larch

Mountain hemlock

Maple woodland

Engelmann spruce

Ponderosa pine

Western white pine

Thousand acres 

Forest type 

Large (>= 9 or 11 inches) 

Medium (>= 5 and < 9 or 11 inches) 

Small (< 5 inches) 

Nonstocked 

Figure 5—Area of forest land by 

forest type and stand-size class, 

Idaho Panhandle National Forest, 

2001.

0 200 400 600 800 1000 1200 1400 1600 1800 2000 

Thousand acres 

Stand size class 

Large (>= 9 or 11 inches)

Medium (>= 5 and < 9 or 11 inches)

Small (< 5 inches)

Nonstocked
4

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 characterizes the 1.4 billion 

live trees by species in three diameter-size classes. Seventy 

percent of all live trees on the IPNF are from 1.0 to 4.9 inches 

diameter, 21 percent are from 5.0 to 8.9 inches diameter, and 

10 percent are 9.0 inches diameter and greater. Rocky Mountain maple and grand fir each make up 16 percent of the total 

number of trees; western redcedar and subalpine fir, 12 percent each; Douglas-fir, and western hemlock, 10 percent each; 

lodgepole pine, 7 percent; mountain hemlock, 5 percent; 

western larch and western white pine, 3 percent each; pacific yew, 1 percent; ponderosa pine, 1 percent; and the remaining four species in figure 6 comprise the final 1 percent. 

The hardwoods category includes quaking aspen, black cottonwood and paper birch. Species that are scarce may not be 

well represented with the extensive sampling strategy used 

for this inventory. 

Figure 7 displays 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 dryer-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 IPNF displays distinct elevation 

patterns in tree distribution: subalpine fir and mountain hemlock do well at higher elevations, while Douglas-fir and grand 

fir are most common at middle elevations. Low elevations 

show a less defined gradient with no individual tree species 

dominating. High levels of precipitation allow a relatively 

high species diversity, masking the generally well defined 

species gradation seen on more xeric forests. 

Number and weight of dead trees—Standing and down 

dead trees are important for wildlife habitat and in fire 

1.0"-4.9" 

5.0"-8.9" 

9" and greater

250 

200 

150 

100 

50 

0 

Million trees

Rocky Mountain maple

Grand fir

Subalpine fir

Western hemlock

Lodgepole pine

Engelmann spruce

Douglas-fir

Western larch

Western redcedar

Mountain hemlock

Western white pine

Pacific yew

Ponderosa pine

Hardwoods

Whitebark pine

Species

0 20 40 60 80 100 120 140 

1,000-1,900 

2,000-2,900 

3,000-3,900 

4,000-4,900 

5,000-5,900 

6,000-6,900 

Million trees 

Elevation class (feet) 

Grand fir 

Subalpine fir 

Western larch 

Engelmann spruce 

Whitebark pine 

Lodgepole pine 

Western white pine 

Ponderosa pine 

Douglas-fir 

Western redcedar 

Western hemlock 

Mountain hemlock 

Hardwoods 

Figure 6—Number of live trees 1.0 inch 

in diameter and greater on forest land 

by species and diameter class, Idaho 

Panhandle National Forest, 2001.

Figure 7—Number of live 

trees 5.0 inches diameter 

and greater on forest land 

by species and elevation 

class, Idaho Panhandle 

National Forest, 2001.
5

ecology, as well as acting as nutrient/carbon sinks and 

erosion controls. Approximately 88 million standing dead 

trees (snags) and 83 million down dead trees 5.0 inches 

diameter and greater occur on forest land on the IPNF. If 

trees 1.0 inch diameter and greater are included there are 

approximately 231 million standing dead trees and 263 million 

down dead trees. 

 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 dead trees are generally scarce relative to smaller 

trees. Figure 8 shows the number of snags by forest type for 

three diameter classes. Of the total number of snags, the 1.0-

4.9 inch diameter size class accounts for 62 percent with an 

average of 58.6 trees per acre (TPA); the 5.0-10.9 inch class 

accounts for 27 percent with an average of 25.2 TPA; and the 

11.0 and greater inch class makes up 11 percent with an average of 10.7 TPA. 

The amount of dead tree material is a component of forest 

fuel loads. On the IPNF, about 22.6 million tons of standing 

dead trees and 18.1 million tons of down dead trees occur 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 

most dead material at 8.8 tons per acre, followed by the medium class at 4.3 tons per acre and the small at 3.5 tons per 

acre. For all stand-size classes combined, the western redcedar type has the highest weight at 17.2 tons per acre, followed 

by western hemlock and western larch at 9.7 and 8.6 tons 

per acre, respectively. Some class breakdowns in figure 9 

such as the Rocky Mountain maple and ponderosa pine 

classes may not be representative due to small sample size.

Stand age—Stand age 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 fewer trees. 

Figure 10 displays the percent of forest land area by 

forest type and stand-age class on the IPNF. 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 

81- to 100-year and 1- to 20-year age classes.

30 

25 

20 

15 

10 

5 

0 Douglas-fir

Grand fir

Lodgepole pine

Spruce-fir

Western hemlock

Western larch

Western redcedar

Maple woodland

Mountain hemlock

Western white pine

Engelmann spruce

Ponderosa pine

Million snags 

Forest type 

1.0"-4.9" 

5.0"-10.9" 

11.0" 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

Tons per acre 

Forest type 

Medium (>= 5 and < 9 or 11 inches) 

Large(>= 9 or 11 inches) 

Small (< 5 inches) 

Small (< 5 inches) 

Douglas-fir

Grand fir

Lodgepole pine

Spruce-fir

Western hemlock

Western larch

Maple woodland

Mountain hemlock

Western redcedar

Western white pine

All types

Engelmann spruce

Ponderosa pine

Figure 8—Number of standing dead 

trees 1.0 inch diameter and greater 

on forest land by forest type and 

diameter-class, Idaho Panhandle 

National Forest, 2001.

Figure 9—Weight of down dead 

trees 5.0 inches diameter and 

greater on forest land by forest 

type and stand-size class, Idaho 

Panhandle National Forest, 2001.
6

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 crosssectional 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 IPNF is estimated to be in excess of 7.9 billion cubic feet. Total biomass 

is estimated at 142 million tons, and the total basal area is 

estimated to be about 315 million square feet. Table 1 is a 

breakdown of volume, biomass, and basal area by species.

0% 

5% 

10% 

15% 

20% 

25% 

Percent of forest land area 

Douglas-fir 

Spruce-fir 

Grand fir 

Lodgepole pine 

Western hemlock 

Western redcedar 

Western larch 

Mountain hemlock 

Maple woodland 

Engelmann spruce 

Ponderosa pine 

Western white pine 

Nonstocked

1-20

21-4041-6061-80

81-100

101-120121-140141-160161-180181-200201-220221-240

>240

Stand age class

Figure 11 displays the percent net cubic-foot volume of live 

trees by diameter class. Eighty-seven percent of this volume 

is in trees 9.0 inches and greater diameter class. By species, 

100 percent of black cottonwood, 98 percent of ponderosa 

pine and 93 percent of mountain hemlock volume is in trees 

9.0 inches diameter and greater. Common species with low 

percentages of volume in trees 9.0 inches diameter and 

larger include paper birch at 54 percent and Rocky Mountain maple at 33 percent.

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

which estimates per acre can be computed along with basal 

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

by species, Idaho Panhandle National Forest, 2001.

Volume Biomass Basal area

(million (million (million

Species cubic feet) tons) square feet)

Douglas-fir 1,625.6 32.1 60.8

Grand fir 1,486.3 24.4 44.0

Western redcedar 754.7 11.7 29.9

Lodgepole pine 739.4 12.1 24.9

Western hemlock 733.8 14.7 26.3

Subalpine fir 714.1 11.8 29.9

Western larch 625.3 12.2 20.9

Engelmann spruce 556.9 8.5 17.9

Mountain hemlock 398.9 7.8 16.3

Western white pine 164.9 2.9 5.0

Ponderosa pine 76.3 1.5 2.7

Rocky Mountain maple 32.1 1.5 2.2

Paper birch 12.7 0.3 0.5

Quaking aspen 7.1 0.1 0.2

Black cottonwood 6.0 † 0.2

Whitebark pine 2.2 † 0.1

Pacific yew 0.1 † †

Total (not exact 7,936.5 141.8 281.9

 due to rounding)

† Less than 100,000.

Figure 10—Percent of forest 

land area by forest type 

and stand-age class, Idaho 

Panhandle National Forest, 

2001.
7

area (table 2). These numbers include the many different species that can occur together in each forest type. The highest 

volume, biomass and basal area per acre on the IPNF is in 

the western redcedar forest type. Volume 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. 

0% 

2% 

4% 

6% 

8% 

10% 

12% 

14% 

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 29.0-30.9 31.0-32.9 

>33.0 

Percent of total volume 

Diameter class (inches) 

Figure 11—Percent net cubic foot volume of live trees on forest land by diameter class, Idaho Panhandle National Forest, 2001.

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 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 IPNF were 

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, Idaho Panhandle National Forest, 2001.

Net cubic-foot Biomass Basal area

volume per acre tons per acre sq. ft. per acre Number of Condition

Forest type (5” dia.) (>1” dia.) (>5” dia.) conditionsa proportionsb

Western redcedar 5,297 84 185 30 23.3

Western hemlock 4,283 81 144 39 34.3

Grand fir 4,200 70 131 63 52.6

Mountain hemlock 4,032 78 160 18 16.9

Douglas-fir 3,122 60 114 106 98.0

Western larch 2,977 57 106 25 22.8

Lodgepole pine 2,780 48 102 39 34.2

Spruce-fir 2,701 45 104 77 71.3

Engelmann spruce 2,436 42 85 12 11.2

Western white pine 1,446 26 51 8 6.4

Ponderosa pine 1,092 23 45 10 7.1

Maple woodland 235 8 12 13 12.3

Total: 3,247 58 115 440 390.4

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

estimated using FIA plot data, and formulated specifically 

to match the procedure used by FIA to calculated 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, 66 percent of all forest 

stands on the Idaho Panhandle National Forest were 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 IPNF is estimated to be 217 million cubic feet, and net annual growth is 

Percent of maximum stand density index

Western white pine

Western redcedar

Western larch

Western hemlock

Spruce-fir

Ponderosa pine

Mountain hemlock

Maple woodland

Lodgepole pine

Grand fir

Engelmann spruce

Douglas-fir

<25 25.0-34.9 35.0-59.9 >60.0

1000

900

800

700

600

500

400

300

200

100

0

Thousand acres

0 10 20 30 40 50 60 

Grand fir 

Douglas-fir 

Western hemlock 

Subalpine fir 

Western redcedar 

Lodgepole pine 

Engelmann spruce 

Western larch 

Mountain hemlock 

Western white pine 

Rocky Mountain maple 

Ponderosa pine 

Million cubic feet 

Species 

Mortality 

Gross growth 

177 million cubic feet. Gross annual growth is compared to 

mortality for twelve high volume species in figure 13. Mortality on all forest land on the IPNF is about 18 percent of gross 

annual growth. Mortality is about 53 percent of gross annual 

growth for lodgepole pine, 46 percent for black cottonwood 

and 31 percent for ponderosa pine. In 2001 no species on 

the IPNF displayed a net loss of growth. 

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 2001, 39.7 million cubic feet of wood from live 

trees (5.0 inches diameter and greater) died on the IPNF. 

About 43 percent of the mortality was caused by disease, 

26 percent by weather, 17 percent by insects; fire and animal damage each account for 0.5 percent. The following are 

the top five tree species accounting for about 82 percent of 

Figure 12—Area of forest land by forest type and percent stand density index, Idaho Panhandle National Forest, 2001.

Figure 13—Gross annual growth of live trees 5.0 inches diameter and greater compared to mortality for twelve highvolume species on all forest land, Idaho Panhandle National Forest, 2000.
9

overall mortality on the IPNF: Douglas-fir (25 percent), 

lodgepole pine (22 percent), western hemlock (14 percent), 

subalpine fir (12 percent), and grand-fir (9 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 

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

Western white pine 

Western redcedar

Western larch

Western hemlock

Subalpine fir

Spruce-fir

Ponderosa pine

Mountain hemlock

Lodgepole pine

Grand fir

Engelmann spruce

Douglas-fir

Average percent cover

Forest type 

Tree 

Shrub 

Forb 

Grasses 

Mountain maple is the most abundant understory seedling/

sapling species, followed by grand fir. The most abundant 

understory shrubs are big huckleberry, mock azalea and 

mountain lover. Bear grass, broadleaf arnica, and goldthread are the most abundant forbs; and pinegrass, various 

sedge and wheatgrass species are the most abundant understory graminoids on the forest. 

Roaded timberland highlights of 

the Idaho Panhandle National 

Forest

Reserved lands are those that have been withdrawn from 

management for production of wood products, such as 

wilderness areas, wild and scenic rivers, and national parks. 

The nonreserved portion of the IPNF contains over 99 percent of the forest land on the forest, 97 percent of which is 

defined as timberland. The nonreserved portion of the 

IPNF is further divided by roadless designation. Currently, 

approximately 856,958 acres of nonreserved timberland, or 

35 percent, is designated as roadless area, which limits management for wood products production. There are 1.03 billion live growing-stock trees on nonreserved timberland, 684 

million in roaded portions and 348 million in roadless areas.

Forest type—Douglas-fir was the most common forest 

type on nonreserved timberland on the IPNF at 22 percent of 

nonreserved timberland, followed by spruce-fir (16 percent) 

and grand fir (14 percent). On the roadless portion, Spruce-fir 

was the most common at 26 percent, followed by Douglas-fir 

Figure 14—Average percent cover of four major understory plant groups on forest land by forest type, Idaho Panhandle National 

Forest, 2001.
10

(21 percent) and lodgepole pine (16 percent). The Douglasfir forest type was the most abundant on the roaded portion 

of the nonreserved timberland at 23 percent, followed by 

grand-fir (18 percent) and western hemlock (15 percent).

Dead trees and fuels—There are approximately 87 million 

standing dead trees (snags) and 82 million down dead trees 5.0 

inches diameter and greater on nonreserved timberland, with 

56 million standing dead and 55 million down dead occuring 

on the roaded portion. The merchantable bole and bark of all 

dead trees at least 5.0 inches in diameter on nonreserved 

timberland was equal to about 22.4 million tons in standing dead (15.0 million tons in the roaded portion) and 17.9 

million tons in down dead (12.1 million tons in the roaded 

portion). The weights per acre of down dead trees on nonreserved roaded timberland were similar for those on all forest 

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

(large tree class at 9.2 tons per acre, medium tree class at 

4.5 tons per acre, seedling/sapling class at 4.1 tons per acre) 

and by forest type for all size classes combined (western redcedar at 17.1 tons per acre, Engelmann spruce at 11.8 tons per 

acre and western larch at 8.8 tons per acre.) 

Stand age—Stands were generally very similar on nonreserved roaded timberland when compared to all nonreserved 

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). 

Roaded areas show more area in the 1- to 20- year age class 

and roadless areas show a relative increase in the 121- to 

140-year age class. 

Wood volume, biomass, and basal area of growing-stock 

trees—Table 3 displays a breakdown of net cubic volume, 

tons of biomass, and square foot basal area for growingstock trees 5 inches diameter and greater by species on 

nonreserved roaded timberland for the IPNF. The total net 

cubic-foot volume on nonreserved timberland was over 7.8 

billion cubic feet, with 65 percent (5.1 billion cubic feet) of 

the volume in the roaded areas. Douglas-fir and grand fir 

together account for 43 percent of the volume on roaded 

timberland. Total biomass was estimated at 131.5 million 

tons, 66 percent of it on the roaded portion of the forest. 

Forty-six percent of the biomass on roaded timberland 

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

estimated at 275.8 million square feet, with 64 percent 

of it in roaded areas. Douglas-fir and grand fir comprise 

43 percent of basal area on roaded timberland. Roughly 74 

percent each of the growing stock volume, biomass, and 

basal area of Douglas-fir and 73 percent each of grand fir 

on nonreserved timberland were in roaded portions of the 

forest.

The net volume of sawtimber trees (sawtimber volume) 

on nonreserved timberland was estimated to be 21.9 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 

nonreserved timberland by diameter class and roadless 

designation. The 15.0 to 16.9-inch diameter class had the 

most volume at 13.2 percent, followed closely by the 13.0 

to 14.9-inch class at 12.3 percent. Twenty-one percent of 

the total sawtimber volume on the Idaho Panhandle National Forest was from Douglas-fir (16 percent in roaded 

areas), with 20 percent from grand fir (15 percent in roaded areas), 10 percent from western hemlock (7 percent in 

roaded areas), and 9 percent from western redcedar (5 percent in roaded areas). Overall, 65 percent of the sawtimber 

volume was on the roaded portion of the forest.

Percent of nonreserved timber land 

Stand age class

Roadless

Roaded

16%

14%

12%

10%

8%

6%

4%

2%

0%

Nonstocked

1-20

21-4041-60

61-80

81-100

101-120

121-140

141-160161-180181-200

200+

Figure 15—Percent of 

nonreserved timberland by 

roadless designation and standage class, Idaho Panhandle 

National Forest, 2001.
11

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

on nonreserved roaded timberland, Idaho Panhandle 

National Forest, 2001.

Volume Biomass Basal area

(Million (Million (Million

Species cubic feet) tons) square feet)

Douglas-fir 1,203.4 23.1 44.2

Grand fir 1,073.1 16.7 32.4

Western hemlock 559.4 10.3 19.9

Western larch 488.0 9.3 15.9

Western redcedar 475.5 6.8 19.3

Lodgepole pine 424.6 6.7 13.9

Subalpine fir 288.4 4.3 11.9

Engelmann spruce 259.6 3.7 8.3

Western white pine 123.3 2.0 3.6

Mountain hemlock 107.6 2.0 5.1

Ponderosa pine 65.0 1.2 2.3

Quaking aspen 6.9 0.1 0.2

Paper birch 6.6 0.1 0.3

Black cottonwood 4.3 † 0.1

White bark pine 0.6 † †

Pacific yew 0.1 † †

Total (not exact 5,086.5 86.4 177.4

 due to rounding)

† Less than 100,000

Stand density index—Sixty-nine percent of the roaded timberland stands on the Idaho Panhandle National Forest were 

at 35 percent or more of SDI maximum, or considered to be 

fully occupied. One hundred percent of mountain hemlock 

stands, 89 percent of western redcedar stands, and 74 percent of grand fir stands were fully occupied. Western white 

pine had the least fully occupied stands with 23 percent 

reaching that level. 

Components of change: growth and mortality—Gross 

annual growth of growing-stock trees on nonreserved timberland on the IPNF was estimated at 212 million cubic 

feet, while mortality was an estimated 39 million cubic feet. 

Sixty-six percent of the growth and 71 percent of the mortality occurred on the roaded portion of the nonreserved 

timberland. Gross annual growth is compared to mortality 

of growing-stock trees for eight high volume species in figure 17. Mortality was 18 percent of growth on nonreserved 

timberland, 20 percent on the roadless portion, and 16 percent on the roaded areas. Mortality volume was highest in 

Douglas-fir and lodgepole pine. No species experienced net 

negative growth on the IPNF. A major difference between 

growing-stock mortality on roaded timberland and live tree 

mortality in all forest land was the much lower mortality to 

growth ratio on roadless timberland for western hemlock and 

western white pine.

The 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 two-phase sampling procedure for all inventories. Phase one is based on 

a grid of sample points systematically located 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 sub-sample 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. 

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

5,000 

Million board feet 

Diameter class 

Roadless Roaded 

9.0-10.9

11.0-12.913.0-14.9

15.0-16.9

17.0-18.919.0-20.921.0-22.923.0-24.9

25.0-26.9

27.0-28.9

29.0-30.9

31+

Figure 16—Net volume of sawtimber 

trees (International 1/4” rule) on 

nonreserved timberland by 2-inch 

diameter class and roadless 

designation, Idaho Panhandle National 

Forest, 2001.
12

Phase two plots were sampled using the mapped-plot 

design (see next section). There were 403 field plots on the 

IPNF, 3 of which were determined to be inaccessible. A total of 373 field plots sampled only forest conditions, 22 

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), and 1 was entirely in a nonforest condition. A total of 440 forest conditions were sampled on 398 plots that contain 390.4 forest, 

9.1 nonforest, and 0.5 water condition proportions.

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.

Figure 17—Gross annual growth 

of growing-stock trees 5.0 inches 

diameter and greater compared 

to mortality for nine high 

volume species on nonreserved 

timberland, Idaho Panhandle 

National Forest, 2000.

0 5 10 15 20 25 30 35 40 

Western white pine 

Western larch 

Engelmann spruce 

Lodgepole pine 

Western redcedar 

Subalpine fir 

Western hemlock 

Douglas-fir 

Grand fir 

Million cubic feet 

Species 

Roadless mortality 

Roadless growth 

Roaded mortality 

Roaded growth 

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

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, 

Idaho Panhandle National Forest, 2001.

Land class or Percent 

Type of trees Attribute Area or volume standard error

Total forest land (acres) Area 2,444,544 ±0.6

Total forest land Volume 7,936,478,247 ±3.8

 (all trees cubic feet) Growth 177,646,924 ±5.2

Mortality 39,679,794 ±13.5

Nonreserved timberland (acres) Area 2,360,866 ±1.1

Nonreserved timberland Volume 7,839,665,512 ±3.8

 (growing-stock trees cubic feet) Growth 173,591,299 ±5.3

Mortality 38,700,934 ±13.8

Conditions were separated, or mapped, based on differences 

in any of five attributes: forest/nonforest, forest type, standsize 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

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 evenaged 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.

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

Idaho Panhandle National Forest

Supervisor’s Office

808 Meadow Lane

Cody, Wyoming 82414-4549

Phone: 307-527-6241

FAX: 307-578-1212

World Wide Web: http://www.fs.fed.us/ipnf/

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://fia.fs.fed.us/tools-data/

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/

arizona/az_nfs.html (also available on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Ogden, UT).

U.S. Department of Agriculture, Forest Service. 2003. Technical Report: Analysis of the Management Situation for Revision of the Kootenai and Idaho Panhandle Forest Plans. 

U.S. Department of Agriculture, Forest Service, 2004. Forest 

Survey field procedures, 2004. Ogden, UT: USDA Forest 

Service, Rocky Mountain Research Station.

U.S. Department of Agriculture, Forest Service. 2008. Roadless Area Conservation, National Forest System Lands in 

Idaho.

Van Dyck, M.G. 2002. Keyword reference guide to the Forest Vegetation Simulator. WO-Forest Management Service 

Center, Fort Collins, CO.

Federal Recycling Program Printed on Recycled Paper
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.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, 

national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases 

apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, 

large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD).

	 To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice or TDD). USDA is an equal opportunity provider and 

employer.