Forest Resources of the 

Umatilla National Forest

Glenn A. Christensen, Paul Dunham, David C. Powell, 

and Bruce Hiserote

United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

Resource Bulletin

PNW-RB-253

May 2007

DEPARTMENT OF AGRICULT URE
The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of 

multiple use management of the Nation’s forest resources for sustained yields of wood, 

water, forage, wildlife, and recreation. Through forestry research, cooperation with the 

States and private forest owners, and management of the National Forests and National 

Grasslands, it strives—as directed by Congress—to provide increasingly greater service 

to a growing Nation.

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opportunity provider and employer.

Authors

Glenn A. Christensen is an inventory analyst, and Bruce Hiserote is a forester, 

Pacific Northwest Research Station, 620 SW Main Street, Suite 400, Portland, OR 

97205; Paul Dunham is a forest health analyst, Forest Health Protection, Pacific 

Northwest Region, P.O. Box 3623, Portland, OR 97208; David C. Powell is a silviculturist, Umatilla National Forest, 2517 SW Hailey Avenue, Pendleton, OR 97801.

Cover: Umatilla National Forest, photograph by Paul Dunham.
Abstract

Christensen, Glenn A.; Dunham, Paul; Powell, David C.; Hiserote, Bruce. 

2007. Forest resources of the Umatilla National Forest. Resour. Bull. PNWRB-253. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 38 p.

Current resource statistics for the Umatilla National Forest, based on two separate 

inventories conducted in 1993–96 and in 1997–2002, are presented in this report. 

Currently on the Umatilla National Forest, 89 percent of the land area is classified 

as forest land. The predominant forest type is grand fir (26 percent of forested 

acres) followed by the interior Douglas-fir (25 percent) and ponderosa pine (17 

percent) types. The majority of net cubic foot wood volume (55 percent) comes from 

trees ranging in size from 11 to 23 inches diameter at breast height. The most commonly recorded cause of tree death was bark beetle (primarily Dendroctonus spp.) 

attack, with over half of the mortality volume attributed to these insects.

Keywords: Umatilla National Forest, forest inventory, Blue Mountains, Current 

Vegetation Survey. 
Summary

Updated resource statistics for the Umatilla National Forest are presented in this 

report. The last forest resource inventory information compiled for the Umatilla 

National Forest was completed in the early 1980s. Two relatively recent inventories 

(1993–96 and 1997–2002) using a grid-based sampling system prompted this 

analysis and report describing the current vegetation of the Umatilla National 

Forest. This report provides a broad overview of land status, forest structure and 

composition, and forest health and productivity. Key findings are:

• Currently on the Umatilla National Forest, 89 percent of the land area 

is classified as forest land.

• The predominant forest type is grand fir (26 percent of forested acres) 

followed by the interior Douglas-fir (25 percent) and ponderosa pine 

(17 percent) types.

• The most common tree species on the forest is grand fir (Abies grandis

(Dougl. ex D. Don) Lindl.); 32 percent of all trees (1.0 inch diameter at 

breast height [d.b.h.] and larger) are grand fir trees. The next most numerous tree species are lodgepole pine (Pinus contorta Dougl. ex Loud.) and 

Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) at 24 percent and 

15 percent, respectively, of all trees greater than 1.0 inch d.b.h.

• The majority of net cubic foot wood volume (55 percent) comes from 

trees ranging in size from 11 to 23 inches d.b.h.

• The current total net volume of wood in live trees on the forest is 

estimated to be in excess of 14.0 billion board feet (± 6 percent 

standard error).

• By species, grand fir, Douglas-fir, and ponderosa pine (Pinus ponderosa

P. & C. Lawson) contribute 76 percent of the total board foot volume. The 

two next most important species are western larch (Larix occidentalis

Nutt.) and Engelmann spruce (Picea engelmannii Parry ex Engelm.), contributing 11 percent and 10 percent, respectively, of the total volume.

• Overall, forest-land acreage averages 2.7 snags per acre greater than 20 

inches d.b.h. Within the grand fir forest type, snags this size average 5 

per acre with only 1 per acre in the “recent” decay class.

• On average, there are 3.7 down logs per acre greater than 20 inches 

diameter on forest land. Within the grand fir forest type, there are about 

5 down logs per acre this size.
• The most commonly recorded cause of tree death was bark beetle 

(primarily Dendroctonus spp.) attack, with over half of the mortality 

volume attributed to these insects.

• Wildfire risk assessment indicates that within the subalpine fir (Abies 

lasiocarpa (Hook.) Nutt.) and Engelmann spruce forest types more 

than half of the acres (64 percent for subalpine fir and 61 percent for 

Engelmann spruce) have a torching index that is less than 20 miles 

per hour of windspeed, indicating that a large proportion of these 

types are at high risk of wildfire torching.
Contents

1 Introduction

2 Methods and Inventory Procedures

4 Reliability of Inventory Data

5 Land Status

6 Forest Structure and Composition

6 Forest Type

9 Species and Size

10 Basal Area

11 Stand-Size Class

12 Forest Health and Productivity

12 Biomass

17 Wood Volume

20 Snags and Down Logs

23 Insects and Disease

28 Wildfire Risk Assessment 

31 Forest Growth and Mortality

34 Site Class

35 Common and Scientific Names 

35 Acknowledgments

35 Metric Equivalents

36 References
Forest Resources of the Umatilla National Forest

Introduction

Current forest resource statistics for the Umatilla National Forest (UNF) are 

presented in this report. The last forest resource inventory information compiled 

for the forest was completed in 1981 (Teply 1981). In the early 1990s, a grid-based 

sampling strategy was adopted for broad-scale inventory and monitoring of forest 

and range vegetation on National Forest System lands in the Pacific Northwest 

Region (Max et al. 1996).

Two relatively recent inventories (1993–96 and 1997–2002) using the new gridbased system prompted this analysis and report describing the current vegetation of 

the UNF. This report provides a broad overview of land status, forest structure and 

composition, and forest health and productivity as follows:

• Land status

• Forest structure and composition

• Acres of forest by forest type

• Numbers of trees by species and size

• Basal area by forest type

• Forest-land area by stand-size class

• Forest health and productivity

• Biomass of live, standing dead, and down logs by forest type and 

stand size

• Volume of wood by tree species

• Number of snags and down logs by forest type and tree species

• Insect and disease incidence by tree species and forest type

• Wildfire risk assessment 

• Forest growth and mortality by tree species

• Site class by forest type

The Umatilla National Forest, located in the northern portion of the Blue Mountains in northeastern Oregon and southeastern Washington, includes 1,406,513 

acres of National Forest System land (fig. 1). Over 20 percent of these lands occur 

in designated wilderness areas. The headwaters of three large drainage basins are 

within the forest: the Middle Columbia, the Lower Snake, and the John Day. The 

forest also has many rivers and streams including portions of the Grande Ronde, 

Umatilla, and North Fork John Day Rivers.

Topography of the northern Blue Mountains features thick basalt bedrock 

deposited during molten basalt flows originating from long fissure vents in the 

northeastern Blue Mountains (Clarke and Bryce 1997). This Columbia River basalt 
RESOURCE BULLETIN PNW-RB-253

Figure 1–Location of the Umatilla National Forest.

has weathered to create rugged mountains, steep canyons, and extensive ridges 

and plateaus (fig. 2) (Anderson et al. 1998).

Elevations within the UNF range from 1,700 to 7,900 ft. Natural disturbance 

processes on the forest include wildfire, insects, and disease. Owing to recent 

wildfires and insect outbreaks (table 1), the Blue Mountains have become a focal 

point of forest health issues (Johnson 1994, Mutch et al. 1993, Quigley 1992, 

Tanaka et al. 1995, Wickman 1992).

Methods and Inventory Procedures

The two most recent inventories on the UNF were conducted by using an inventory 

and monitoring system called the Current Vegetation Survey (CVS) (Johnson 1998, 

2001; Max et al. 1996). Land managers use CVS data to assess and monitor vegetation at known locations. The CVS plots are arranged on a regularly spaced grid at 

1.7-mi intervals across nonwilderness lands and 3.4 mi across wilderness lands. 

Each CVS plot contains five 0.05-acre subplots, with one subplot located at plot 

center, and the remaining four subplots 133.9 ft from center on cardinal directions. 

At the time of the first plot installation, the plot design was a 185.1-ft-radius circle 

Seattle

Portland Pendleton

O R E G O N

W A S H I N G T O N

Umatilla

 National Forest

I D A H O
Forest Resources of the Umatilla National Forest

Figure 2—Open stand of ponderosa pine on a steep canyon slope formed from 

weathered Columbia River basalt, Umatilla National Forest.

Table 1—Recent disturbance events on the Umatilla National Forest by causal agent

Bark beetles

Defoliators (budworm, (Douglas-fir beetle, Pine beetles Wildfires

Year tussock moth) fir engraver) (mountain, western) Other insects (≥100 acres)

Thousand acres

1970–1979 524 403 1,670 8 3

1980–1989 4,180 271 76 2 27

1990–1999 1,794 406 18 12 82

2000–2005 80 171 23 87 40

A note of caution when summing acreages: any individual acre is not exclusive to disturbance by only one causal agent, which means that 

areas affected by one agent may overlap with areas affected by other agents. An area can also be affected by the same agent in more than 

one year; for events such as budworm defoliation that often span a multiyear period, this means that the same acreage might be accounted 

for more than once in the decadal values shown in this table.

Species names: Budworm (Choristoneura occidentalis Freeman); tussock moth (Orgyia pseudotsugata McDunnough); Douglas-fir beetle 

(Dendroctonus pseudotsugae Hopkins); fir engraver (Scolytus ventralis LeConte); mountain pine beetle (Dendroctonus ponderosae

Hopkins); western pine beetle (Dendroctonus brevicomis LeConte).

Source: For defoliators, bark beetles, pine beetles, and other insects, the source was aerial detection survey data; for wildfires, the source 

was digital fire atlas records, U.S. Department of Agriculture, Forest Service, Umatilla National Forest. 2005. http://www.fs.fed.us/r6/

data-library/gis/umatilla/ (January 2007).

Umatilla National Forest
RESOURCE BULLETIN PNW-RB-253

containing the cluster of five subplots. Each of the five subplots consisted of nested 

circles of 51.1-ft, 26.3-ft, and 11.8-ft radii. At the time of remeasurement, the 26.3-ft 

plot was replaced with a 24-ft-radius plot.

The first inventory (first occasion) was conducted over several field seasons 

beginning in 1993 and ending in 1996. A total of 640 plots were installed. The 

second occasion was a remeasurement of first-occasion plots and conducted over 

a series of four panels, each panel consisting of about 25 percent of the plots. 

Remeasurement started with panel C in 1997, followed by panel D in 1999, and 

panel A in 2002 including all wilderness plots. Panel B plot remeasurements were 

completed in 2005, but the data have not yet been processed. The 490 remeasured 

plots in panels A, C, and D have been compiled for use as the second-occasion 

measurement for this report. Except where noted, broad forest overview estimates 

are based on this second-occasion information. Forest health estimates of growth, 

mortality, and causes of tree death given in the last part of the report are based 

on, except where noted, changes occurring between first- and second-occasion 

measurements of panels A and D. Panel C was not included in this comparison 

owing to an inability to determine if some trees were not remeasured because of 

a change in the subplot radius, or because they had fallen. In addition, the time 

between measurements for much of panel C was often less than 2 years. Estimates 

of dead wood are based on first-occasion measurements of all four panels; secondoccasion estimates of down dead wood had not been completed at the time of 

this report. All plot data were compiled by using the Pacific Northwest Research 

Station—Forest Inventory and Analysis Program’s integrated database (IDB) 

format (Waddell and Hiserote 2005).

Reliability of Inventory Data

The sample used for this inventory 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 standard errors along with standard error by forest 

type and species for various attributes are provided in each table. Standard errors 

for other estimates are available upon request. Results are based on the sums of plot 

data and represent conditions at the broader scale (UNF), and not any specific area 

or site except for the plot itself.
Forest Resources of the Umatilla National Forest

Land Status

The UNF can be broadly described by land cover and productivity. Land status is 

classified into the following categories, which are used throughout this report:

• Forest land—Land at least 10 percent stocked with live trees, or land that had 

this minimum tree stocking in the past and is not currently developed for nonforest use. The minimum area recognized is 1 acre.

• Timberland—Forested area capable of growing continuous stands of trees at a 

rate of 20 ft3/acre per year (at culmination of mean annual increment) and not 

reserved from harvest by law or statute such as in wilderness areas. This is a 

specific FIA subclassification for areas that are considered “productive forest 

land.” Throughout this report, all forest land is used when presenting summary data, not just forest land considered “productive.”

• Wilderness—Land protected from development or commodity production 

by the 1964 Wilderness Act.

• Nonforest—Land that has never supported forests or formerly was forested 

and currently is developed for nonforest uses. Included is land used for agriculture crops, Christmas tree farms, cottonwood plantations, improved pasture, residential areas, city parks, constructed roads, operating railroads and 

their right-of-way clearings, powerline and pipeline clearings, streams more 

than 30 ft wide, and 1- to 40-acre areas of water classified by the Bureau of 

the Census, U.S. Department of Commerce, as land. If intermingled in forest 

areas, unimproved roads and other nonforest strips must be more than 120 ft 

wide, and clearings or other areas must be 1 acre or larger to qualify as nonforest.

• Other forest land—Forest land that is not reserved or productive enough to 

be considered timberland.

• Other reserved—Forest land that is not productive enough to be considered 

timberland and not reserved from timber harvest by law or statute. This 

includes protected lands such as special interest areas, special botanical 

areas, wild and scenic river corridors, and wilderness study areas.

Currently, 89 percent of the UNF is classified as forest land (1.25 million acres), 

with 61 percent of the UNF classified as timberland (857,057 acres). On the UNF, 

there are three wilderness areas comprising 22 percent of the UNF acreage (281,684 

acres of forest land and 23,232 acres of nonforest). A total of 119,995 acres is defined 

as nonforest (9 percent of the total), and 77,825 acres (6 percent of the total) as other 

forest land (fig. 3). Throughout this report, the forest resource information pertains 

to all forest land (except where noted), including designated wilderness areas, and 

excluding areas classified as nonforest.

Currently, 89 percent 

of the Umatilla 

National Forest 

is classified 

as forest land.
RESOURCE BULLETIN PNW-RB-253

Forest Structure and Composition

Forest Type

Vegetation cover type is described here by using a forest type classification. Forest 

type is assigned by evaluating the relative proportions of live trees on the plot. The 

predominant tree species is based on plurality of tree stocking, and the plot area 

is classified as that forest type.1 Stocking is an expression of the extent to which 

growing space is effectively utilized by live trees. If total stocking is determined to 

be <10 percent, the area is assigned a nonstocked forest type. Table 2 shows how the 

forest is currently classified by forest type in acres.

On the Umatilla, grand fir and Douglas-fir are the most common forest types 

(fig. 4) by percentage of total forest-land area. Together these two types occupy 

slightly more than half of the total forest-land area with grand fir at 26 percent and 

Douglas-fir at 25 percent (fig. 5).2 Ponderosa pine is the next most common forest 

1Arner, S.L.; Woudenberg, S.; Waters, S.; Vissage, J.; MacLean, C.; Thompson, M.; 

Hansen, M. [N.d.]. National algorithms for determining stocking class, stand size class, 

and forest type for Forest Inventory and Analysis plots. Manuscript in preparation. On file 

with: G. Christensen, Pacific Northwest Research Station, 620 SW Main St., Suite 400, 

Portland, OR 97205. 

2

Douglas-fir growing on the Umatilla National Forest and as reported here is interior 

Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), not the coastal variety 

(Pseudotsuga menziesii var. menziesii) typically found growing west of the Cascade 

Mountain divide.

77,825

(6%) 119,995

(9%)

857,057

(61%)

281,684

(20%)

38,359

(3%)

8,360

(1%)

23,232 

(2%)

Timberland

Wilderness forest land

Wilderness nonforest

Other reserved nonforest

Other reserved forest land

Nonforest

Other forest land

Figure 3—Acres and percentage by land class, Umatilla National Forest, 2002 (occasion 2 data only).
Forest Resources of the Umatilla National Forest

Table 2—Forest-land acres by forest type, Umatilla National 

Forest, 2002 (occasion 2 data only)

Standard Number of plots with

Forest type Total error forest type present

Thousand acres (percent)

Grand fir 329 28 (8) 131

Douglas-fir 308 26 (8) 142

Ponderosa pine 213 23 (11) 109

Lodgepole pine 77 15 (19) 39

Western larch 75 16 (21) 29

Engelmann spruce 60 13 (22) 27

Subalpine fir 25 8 (32) 11

Western juniper 7 3 (43) 6

Nonstocked 160 18 (11) 100

 All types 1,254 17 (1)

Figure 4—Grand fir forest type. Grand fir and Douglas-fir are the most 

common forest types on the Umatilla National Forest.

Umatilla National Forest
RESOURCE BULLETIN PNW-RB-253

0

5

10

15

20

25

30

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Western juniper

Nonstocked

Forest type

Forest-land area (percent)

Figure 5—Percentage of forest-land area by forest type, Umatilla National Forest, 2002 (occasion 2 

data only).

Figure 6—Western juniper 

(foreground) is a minor forest 

type on the Umatilla National 

Forest.

type with 17 percent of the forest-land area. Other less common forest types include 

lodgepole pine (6 percent), western larch (6 percent), Engelmann spruce (5 percent), 

subalpine fir (2 percent), and finally western juniper at less than 1 percent (fig. 6).

Umatilla National Forest
Forest Resources of the Umatilla National Forest

Species and Size

One method to evaluate current forest composition is to look at the total number of 

trees by species. Figure 7 shows the estimated number of trees by species classified 

into three size classes: saplings (ranging in diameter at breast height (d.b.h.) from 

1.0 to 5.0 inches), larger pole-sized trees (ranging from 5.1 to 8.9 inches d.b.h.), 

and sawtimber-sized trees (all trees greater than 9.0 inches d.b.h.). The most common tree species on the forest is grand fir (see “Common and Scientific Names” 

section); 32 percent of all trees (1.0 inch d.b.h. and larger) are grand fir trees. The 

next most numerous tree species are lodgepole pine and Douglas-fir at 24 and 15 

percent, respectively, of all trees greater than 1.0 inch d.b.h. All other tree species 

each account for less then 10 percent of the total tree count. By size, sapling-sized 

trees are the most numerous at 66 percent of all trees greater than 1.0 inch d.b.h. 

Poletimber and sawtimber-sized tree counts are fairly equally divided at 16 percent 

and 17 percent, respectively. The species that have the majority (58 percent) of 

larger sawtimber-sized trees are grand fir (30 percent) and Douglas-fir (28 percent).

0

10

20

30

40

50

60

70

80

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Western juniper

Western white pine

Pacific yew

Species

Trees (millions)

Saplings (1.0–5.0 inches)

Poletimber (5.1–8.9 inches)

Sawtimber (≥9 inches)

Figure 7—Number of trees by species, Umatilla National Forest, 2002 (occasion 2 data only).

The most common 

tree species on the 

forest is grand fir.
10

RESOURCE BULLETIN PNW-RB-253

Basal Area

Tree count provides an estimate of how numerous trees are across the entire 

national forest, but it does not provide a good representation of the distribution 

or density of these trees for any “typical” acre of forest land. Basal area is the 

cross-sectional area of a single tree stem (including bark) at the point of diameter 

measurement (d.b.h. in this case), but it is usually expressed as the sum of the crosssectional area for all stems in a tree stand in square feet per acre. Figure 8 shows 

average basal area by forest type. Engelmann spruce and grand fir are the two forest 

types with the greatest tree densities when expressed as average basal area per acre. 

Each of these types carry more than 120 ft2/acre of basal area on average (130 and 

126 ft2/acre, respectively). The types with the next highest average densities are 

Douglas-fir, western larch, and subalpine fir. Each of these types has an average 

basal area of between 90 and 110 ft2/acre (Douglas-fir is 93 ft2/acre, western larch 

is 91 ft2/acre, and subalpine fir is 104 ft2/acre). All other forest types tend to have 

less than 80 ft2/acre of basal area on average.

0

20

40

60

80

100

120

140

160

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Western juniper

Forest type

A

verage basal area (ft2/acre)

Figure 8—Average basal area by forest type with standard error of the estimate, Umatilla National 

Forest, 2002 (occasion 2 data only).
11

Forest Resources of the Umatilla National Forest

Stand-Size Class

The distribution of tree sizes can also be evaluated by looking at stand-size class 

(rather than basal area, discussed previously). Stand-size class is a classification of 

forest land based on the predominant diameter of live trees contributing the majority of stocking for a plot. On the UNF, small sawtimber-sized stands (9.0 to 19.0 

inches d.b.h.) are predominant for 69 percent of forest-land acreage (fig. 9). Large 

sawtimber-sized stands (greater than 20 inches d.b.h.) occupy the next highest percentage of forest-land acreage at 21 percent. Together, seedlings and saplings (<1.0 

to 5.0 inches d.b.h.) and poletimber-sized stands (5.1 to 8.0 inches d.b.h.) occupy the 

remaining 10 percent of forest land. By forest type, 80 percent of the small sawtimber-sized stands are classified as grand fir, Douglas-fir, or ponderosa pine. For large 

sawtimber-sized stands, this increases to 95 percent of the forest land being classified as grand fir, Douglas-fir, or ponderosa pine types (fig. 10).

Figure 9—Forest-land area by stand-size class and forest type, Umatilla National Forest, 2002 

(occasion 2 data only).

0

50

100

150

200

250

Forest land (thousand acres)

Seedlings/saplings (<1–5.0 inches)

Poletimber (5.1–8.9 inches)

Small sawtimber (9.0–19.9 inches)

Large sawtimber (≥20.0 inches)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Western juniper

Forest type

On the Umatilla NF, 

small sawtimbersized stands (9.0 to 

19.0 inches d.b.h.) 

are predominant for 

69 percent of forestland acreage.
12

RESOURCE BULLETIN PNW-RB-253

Forest Health and Productivity 

Biomass

The distribution and characteristics of forest biomass are necessary for the assessment of important issues such as fire behavior, carbon and nutrient cycling, soil 

structure, and wildlife habitat. Inventory crews sampled both standing live and 

dead trees within circular plots. In addition, crews sampled down (dead) logs 

greater than 3 inches diameter on five, 51-ft transects at each plot (fig. 11). Standing live trees, standing dead trees, and down logs contribute to the biomass and 

account for the total biomass in the following discussion. Dead biomass consists 

of standing dead trees and down logs.

Figure 10—Ponderosa pine forest type, one of the three major forest types in 

the large sawtimber size class on the Umatilla National Forest.

Umatilla National Forest
13

Forest Resources of the Umatilla National Forest

It is not surprising that the distribution of biomass by forest type and by 

species on the forest is very similar to the distribution of forest-land acreage by 

forest type and volume by species. The forest types with the greatest biomass are 

the types with the most forest-land acreage: grand fir, Douglas-fir, and ponderosa 

pine. The grand fir forest type alone accounts for 38 percent of the total standing 

live, standing dead, and down log biomass (fig. 12). Douglas-fir is the next most 

important forest type with 24 percent of the total biomass, and the ponderosa pine 

type has 12 percent of the total biomass. All other forest types combined account 

for less than 30 percent of the total biomass on the forest.

Figure 11—Down logs in the lodgepole pine forest type; down logs were 

sampled on 51-ft transects on each plot.

Umatilla National Forest
14

RESOURCE BULLETIN PNW-RB-253

Table 3 provides total standing live, standing dead, and down log biomass in 

dry tons along with the associated standard error of each estimate. On the UNF 

there are about 40.1 million tons of live standing biomass, about 11.2 million tons 

of standing dead biomass, and about 9.1 million tons of down log biomass.

Engelmann spruce, grand fir, and western larch forest types were found to have 

the greatest average total biomass with over 60 tons per acre (fig. 13). Ponderosa 

pine forests typically had just over 30 tons per acre. Douglas-fir, lodgepole pine, 

and subalpine fir had intermediate amounts of biomass. With standing live tree 

biomass being the largest component of total biomass in all forest types, it is not 

surprising that the distribution of total biomass by forest type closely matches the 

distribution of volume by forest type. Ponderosa pine and Douglas-fir forest types 

have the lowest dead biomass to live biomass ratios at about 30 percent, while 

western larch, lodgepole pine, and nonstocked types have ratios over 80 percent.

The greatest amounts of dead biomass per acre (standing and down wood combined) were found in the Engelmann spruce, grand fir, lodgepole pine, and western 

larch forest types with over 23 tons per acre (fig. 13). The Douglas-fir, nonstocked, 

and ponderosa pine types had less than half the above value. Overall, standing dead 

Figure 12—Distribution of total biomass by forest type, Umatilla National Forest, 1996 (occasion 

1 data only).

Douglas-fir (24%)

Ponderosa pine 

 (12%)

Subalpine fir (3%)

Western 

larch (7%)

Other (<1%)

Nonstocked (4%)

Lodgepole 

 pine (6%)

Engelmann 

 spruce

 (6%)

Grand fir (38%)

On the Umatilla NF 

there are about 40.1 

million tons of live 

standing biomass, 

about 11.2 million 

tons of standing dead 

biomass, and about 

9.1 million tons of 

down log biomass.
15

Forest Resources of the Umatilla National Forest

Table 3—Total standing live, dead, and down log biomass by forest type, Umatilla 

National Forest, 1996 (occasion 1 data only)

Standing live Standing dead Down logs

Forest type Total SE(%) Total SE(%) Total SE(%)

Thousand tons

Grand fir 14,999 1,700 (11) 4,904 600 (12) 3,106 351 (11)

Douglas-fir 11,104 1,123 (10) 2,045 393 (19) 1,456 175 (12)

Ponderosa pine 5,284 745 (14) 876 219 (25) 915 158 (17)

Lodgepole pine 1,725 347 (20) 673 164 (24) 1,033 284 (27)

Western larch 2,480 564 (23) 1,188 448 (38) 836 240 (29)

Engelmann spruce 2,481 540 (22) 565 158 (28) 792 166 (21)

Subalpine fir 1,121 288 (26) 214 61 (29) 287 72 (25)

Other 64 28 (44) 6 4 (67) 2 1 (50)

Nonstocked 862 111 (13) 766 226 (30) 635 111 (17)

 Total 40,120 1,615 (4) 11,237 770 (7) 9,062 507 (6)

SE = standard error.

Figure 13—Average weight of live and dead biomass by forest type, Umatilla National Forest, 1996 

(occasion 1 data only).

0

10

20

30

40

50

60

70

80

Biomass (tons per acre)

Down logs

Standing dead trees

Live trees

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Nonstocked

Other

Forest type
16

RESOURCE BULLETIN PNW-RB-253

tree biomass tended to be greater than down log biomass (9.0 tons per acre versus 

7.3 tons per acre on average).

When analyzed by stand size, total biomass per acre is found to be higher in the 

larger stand size classes (fig. 14). The proportion of live biomass to dead biomass 

also increases in the larger stand sizes. The seedling-sapling and poletimber size 

classes have the largest per-acre values for down log biomass (12.8 and 10.8 tons per 

acre, respectively). This result probably reflects the result of historical disturbance 

processes where most of the previous tree cohort was killed and then fell over, and 

a new tree cohort became established and is now in the seedling, sapling, or pole 

size class (fig. 15).

Figure 14—Average biomass tons per acre by stand size, Umatilla National Forest, 1996 (occasion 1 

data only).

0

10

20

30

40

50

60

70

Biomass (tons per acre)

Down logs

Standing dead trees

Live trees

Seedlings/saplings

 (<1–5.0 inches)

Poletimber

 (5.1–8.9 inches)

Small sawtimber

 (9.0–19.9 inches)

Large sawtimber

( ≥20 inches)

Nonstocked

Stand size class
17

Forest Resources of the Umatilla National Forest

Wood Volume

The current total net volume of wood in live trees on the forest is estimated to be 

in excess of 14.0 billion board feet (±6 percent SE). This includes all live trees on 

forest land of sawtimber size. Sawtimber is defined as softwood species 9.0 inches 

d.b.h. and larger, and hardwood species 11.0 inches d.b.h. and larger. Table 4 is a 

breakdown of volume by species for both first and second occasions.

As was the case for forest type (fig. 5), the majority of volume comes from 

three species: grand fir, Douglas-fir, and ponderosa pine. These three forest types 

occupy 68 percent of the forest land. By species, grand fir, Douglas-fir, and ponderosa pine contribute 76 percent of the total board-foot volume (fig. 16). The next two 

important species are western larch and Engelmann spruce, contributing 11 percent 

Figure 15—A new tree cohort of lodgepole pine getting established after a 

stand-replacing disturbance event.

Umatilla National Forest

The current total net 

volume of wood in live 

trees on the forest 

is estimated to be in 

excess of 14.0 billion 

board feet.
18

RESOURCE BULLETIN PNW-RB-253

Table 4—Forest land live tree timber volume by species and measurement occasion, Umatilla National Forest, 

1996 and 2002 (occasions 1 and 2)

Occasion 1 Occasion 2

Species Total SE (%) Total SE (%) Total SE (%) Total SE (%)

Million board feet Million cubic feet Million board feet Million cubic feet

Grand fir 4,854 468 (10) 907 82 (9) 4,622 518 (11) 860 91 (11)

Douglas-fir 3,399 257 (8) 688 49 (7) 3,334 288 (9) 678 56 (8)

Ponderosa pine 2,342 219 (9) 438 38 (9) 2,773 282 (10) 517 50 (10)

Lodgepole pine 256 43 (17) 62 10 (16) 233 63 (27) 56 14 (25)

Western larch 1,378 140 (10) 268 27 (10) 1,505 203 (13) 291 38 (13)

Engelmann spruce 1,270 172 (14) 237 31 (13) 1,354 231 (17) 255 43 (17)

Subalpine fir 369 64 (17) 81 14 (17) 232 66 (28) 51 14 (27)

Western white pine 3 2 (67) <1 — 2 2 (100) <1 —

Black cottonwood 6 5 (83) 1 1 (100) — — — —

 Total 13,877 681 (5) 2,682 120 (4) 14,055 775 (6) 2,708 139 (5)

SE = standard error.

Figure 16—Forest-land live tree timber by species and measurement occasion with standard error of 

the estimate, Umatilla National Forest, 1996 and 2002 (occasion 1 and 2 data).

0

1,000

2,000

3,000

4,000

5,000

6,000

Tim

ber (million b

oard feet)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Species

Occasion 1

Occasion 2
19

Forest Resources of the Umatilla National Forest

and 10 percent, respectively, to total volume (fig. 17). Lodgepole pine and subalpine 

fir play a minor role, each adding 2 percent to the total board-foot volume on forest 

land. In terms of both forest type acreage and volume by tree species, grand fir is 

a major species on the forest. By forest type, both grand fir and Douglas-fir each 

occupy about 25 percent of the forest land.

Figure 17—Engelmann spruce forest type. Engelmann spruce 

is a minor forest type, and it contributes about 10 percent of 

the Umatilla National Forest’s total board-foot timber volume.

Looking at live tree volume by species, grand fir accounts for 33 percent of the 

sawtimber volume, whereas Douglas-fir accounts for 24 percent of the sawtimber 

volume. This suggests that not only is grand fir an important forest type but, as 

a species, it is occurring in many other forest types where it is not the majority 

species. There is no significant difference in board-foot volume by species between 

occasions when looking at all forest land on the forest (fig. 16).

In addition to understanding where the volume on the forest comes from by tree 

species, it is important to evaluate volume distribution by diameter class. Figure 

18 shows the percentage of total net cubic foot volume (gross cubic foot volume 

minus defect deductions) on forest land by diameter class; it illustrates that most of Umatilla National Forest
20

RESOURCE BULLETIN PNW-RB-253

the live tree volume is in smaller trees and that the contribution by diameter class 

tends to decline for trees larger than about 19.0 inches d.b.h. In fact, the majority 

of net volume comes from trees 11 to 23 inches d.b.h. These trees constitute 

approximately 55 percent of the total volume. Only about 5 percent of the total 

volume is from the largest trees (those larger than 40.0 inches d.b.h.).

Snags and Down Logs

The distribution and condition of standing dead trees (snags) are especially important to many bird species for nesting, roosting, and foraging. Down logs are also 

important for foraging and cover for many birds and mammals (Bull et al. 1997). 

In the context of wildlife habitat, the distribution, condition, and size of individual 

logs and snags is more important than the total biomass or volume of dead wood 

(snags and logs). 

Figure 18—Percentage of total net cubic foot sawtimber volume on forest land by diameter class, Umatilla National Forest, 2002 

(occasion 2 data only).

0

2

4

6

8

10

12

9.0–10.9

11.0–12.9

13–14.9

15.0–16.9

17.0–18.9

19.0–20.9

21.0–22.9

23.0–24.9

25–26.9

27–28.9

29–30.9

31–32.9

33–34.9

35–36.9

37–38.9

39–40.9

41–42.9

43–44.9

45–46.9

47–48.9

49+

Diameter class (inches)

Sawtim

ber cubic v

olume (percentage of total)
21

Forest Resources of the Umatilla National Forest

The western larch and lodgepole pine forest types were found to have the most 

snags per acre (fig. 19), but these snags also tended to be in the smaller diameter 

classes (fig. 20). The snags considered most useful for cavity-nesting birds are those 

greater than 20 inches d.b.h. (Bull et al. 1997). Overall, forest-land acreage averaged 2.7 snags greater than 20 inches d.b.h. per acre. Within the grand fir forest 

type, snags this size averaged 5 per acre with only 1 per acre in the “recent” decay 

class.

On average there were 3.7 logs greater than 20 inches d.b.h. per acre on forest 

land (fig. 21). Within the grand fir forest type, there were about 5 logs per acre this 

size. The lodgepole pine type averaged just one log larger than 20 inches d.b.h. per 

acre. Overall, forest land averaged 288 down logs per acre (all diameter classes). 

Figure 19—Young grand fir trees growing up through a mature western 

larch forest (dark stems) containing abundant snags.

Umatilla National Forest

The western larch and 

lodgepole pine forest 

types were found to 

have the most snags 

per acre.
22

RESOURCE BULLETIN PNW-RB-253

Although we cannot directly assess mortality before the first plot installations, 

measurement of standing dead trees at the time of plot installation can provide 

some insight about past mortality events. When standing dead trees were measured, 

inventory crews assigned each tree a “decay class” describing its stage of decomposition (Thomas et al. 1979). Trees in the first class generally have intact bark and 

limbs and have little decay of the bole. Trees in the second class will be losing 

limbs and bark and may have advanced decay of heartwood. Trees in the third 

through fifth categories have lost most of their bark and limbs and have progressively more decay and loss of the bole’s original form. Snags in the highest stages 

of decay are relatively uncommon, so for this report we have combined classes 

three through five. Snags in the first class are assumed to be relatively recent 

mortality, probably dying within the previous 5 years before plot measurement.

Overall, 36 percent of all snags sampled during the first occasion were assigned 

to the first decay class and are considered to have died within the previous 5 years. 

As can be seen in figure 22, the species with the highest proportion of snags in 

the recent mortality category are Douglas-fir and grand fir (41 and 45 percent, 

0

5

10

15

20

25

30

35

40

45

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

Douglas-fir Engelmann

spruce

Grand fir Lodgepole

pine

Other/

nonstocked

Ponderosa

pine

Subalpine

fir

Western

larch

Forest type

Snags per acre

Greatest stage of decay

Moderate stage of decay

Recent dead

Figure 20—Snags per acre by forest type, diameter class, and stage of decay, Umatilla National Forest, 1996 (occasion 1 data only).
23

Forest Resources of the Umatilla National Forest

respectively). All other species averaged 29 percent of their snags being classified 

as recent mortality. A pulse of Douglas-fir and grand fir mortality in the late 1980s 

and early 1990s would coincide with an outbreak of western spruce budworm 

(Choristoneura occidentalis Freeman) in northeastern Oregon (Powell 1994, 

Wickman 1992). Figure 23 shows areas where aerial survey reconnaissance flights 

detected spruce budworm defoliation between 1986 and 1992 where host trees 

had top-kill or complete defoliation. It should not be assumed that all defoliated 

trees within these areas died, but it is likely that many did die either directly from 

defoliation or were stressed to the point of succumbing to other insects or disease.

Insects and Disease

The actions of insects, diseases, and fire have always had a role in determining the 

condition of forest land in the Western United States (Sampson and Adams 1994). 

The remeasurement of plots across the UNF provides an opportunity to directly 

assess their impact over a 4- to 8-year period. Where trees that were alive at the 

first plot installation were found to be dead at the time of remeasurement, inventory 

Figure 21—Down logs per acre by forest type, diameter class, and stage of decay, Umatilla National Forest, 1996 (occasion 1 data only).

0

50

100

150

200

250

300

350

D

o

wn lo

gs per acre

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

3–4.9 inches

5–9.9 inches

10–14.9 inches

15–19.9 inches

≥20 inches

Douglas-fir Engelmann

spruce

Grand fir Lodgepole

pine

Other/

nonstocked

Ponderosa

pine

Subalpine

fir

Western

larch

Forest type

Greatest stage of decay

Moderate stage of decay

Recent dead

A pulse of Douglas-fir 

and grand fir mortality 

in the late 1980s and 

early 1990s would 

coincide with an 

outbreak of western 

spruce budworm 

(Choristoneura 

occidentalis Freeman) 

in northeastern 

Oregon.
24

RESOURCE BULLETIN PNW-RB-253

crews attempted to determine the reason for tree death. It was possible to determine 

the causes of death for trees on the 326 remeasured plots of panels A and D.

The most commonly recorded cause of death was bark beetle attack, with over 

half of the mortality volume attributed to these insects that feed on the cambium 

of living trees (fig. 24). Slightly more than one quarter of the mortality volume was 

attributed to trees that had fallen or been physically damaged. In addition to trees 

that were blown over during windstorms, this group likely includes those trees that 

had been killed by insects or diseases, but the exact cause of death could not be 

determined at the time of remeasurement. The remaining 18 percent of mortality 

was attributed to other insects, diseases, and fire.3

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

Snags (thousands) ...

0

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Other species

Engelmann spruce

Subalpine fir

Species

Greatest stage of decay

Moderate stage of decay

Recent dead

Figure 22—Number of snags by species and decay class, Umatilla National Forest, 1996 (occasion 

1 data only).

3

Determining cause of death is difficult owing to a lapse of time between tree death and 

observation by a field crew, and often more than one mortality agent is involved. Thus, 

these data should be used with other sources such as an aerial survey for a more accurate 

assessment of cause of death.
25

Forest Resources of the Umatilla National Forest

Umatilla National Forest

Spruce budworm defoliation:

1986 to 1992

Figure 23—Areas of spruce budworm defoliation detected by aerial survey, Umatilla National 

Forest, 1986–1992 (source: Oregon Department of Forestry, Washington Department of Natural 

Resources, USDA Forest Service-Forest Health Protection Cooperative Annual Aerial Survey).

Much of the bark beetle impact was related to a wide-ranging outbreak of 

western spruce budworm, a defoliating insect that primarily feeds on the foliage 

of grand fir and Douglas-fir (with lesser amounts of feeding on Engelmann spruce, 

subalpine fir, and western larch). Between 1980 and 1992, millions of acres in the 

Blue Mountains were affected by budworm defoliation. Tree stands weakened by 

successive years of budworm feeding are more susceptible to bark beetle attack. 

This situation commonly occurred on the southern half of the UNF (and south of 

there on the Malheur National Forest as well) (Powell 1994).

Although root disease was recorded as a cause of death for only 2 percent of the 

volume, root disease is common on the forest and likely predisposes trees to attack 

Tree stands weakened 

by successive years of 

budworm feeding are 

more susceptible to 

bark beetle attack. 
26

RESOURCE BULLETIN PNW-RB-253

by bark beetles and other insects or diseases.4 Root disease was found to be associated with 8 percent of the forest land overall, and with 12 percent of the grand fir 

forest type specifically (fig. 25). 

How is the presence of root disease related to bark beetle attack? Figure 26 

shows the percentage of trees ≥ 5-inches d.b.h. killed by bark beetles with and without root disease present. In grand fir, bark beetle-caused mortality appears to be 

higher when root disease was present. In other species, the difference is minor. The 

results displayed in figure 26 indicate that root disease might be predisposing grand 

fir stands to attack by bark beetles (fir engraver; Scolytus ventralis LeConte). A 

similar situation has been observed for Douglas-fir dwarf mistletoe (Arceuthobium 

douglasii Engelmann) and western spruce budworm in Douglas-fir stands: dwarf 

mistletoe parasitism was apparently predisposing Douglas-fir trees to budwormcaused mortality during the 1980–92 budworm outbreak (Powell 1994).

4

In addition to recording the occurrence of root disease on individual trees, inventory 

crews searched for root disease at each forested subplot and recorded its presence if found 

within 50 ft of the subplot center. For the purposes of this report, we assume that a subplot 

with root disease within 50 ft of subplot center will have its area influenced by the disease.

54%

27%

4%

4%

3%

3% 2% 2%

Bark beetles

Fallen or broken

Defoliators

Fire

Cut

Stem decays

Root desease

Other

Figure 24—Percentage of total mortality volume by cause of death, Umatilla National Forest, 1996 

(occasion 1 data only).

Root disease was 

found to be associated 

with 8 percent of the 

forest land.
27

Forest Resources of the Umatilla National Forest

Figure 25—Area associated with root disease by forest type, Umatilla National Forest, 1996 

(occasion 1 data only).

Figure 26—Bark beetle mortality with and without root disease present with standard error of the 

estimate, Umatilla National Forest, 1996 (occasion 1 data only).

7%

15%

12%

9%

11% 4% 10%

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Forest ty

pe (acres)

No root disease

Root disease present and

percentage of type affected

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Nonstocked

Forest type

0

5

10

15

20

25

30

35

Beetle-killed trees (percent)

Root disease present

No root disease

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Species
28

RESOURCE BULLETIN PNW-RB-253

Wildfire Risk Assessment

Several different models have been developed that allow an assessment of wildfire 

risk. For this analysis, we used the Fire and Fuels Extension (FFE) model (Reinhardt 

and Crookston 2003) to the Forest Vegetation Simulator (FVS) growth and yield 

model (USDA Forest Service 2005). All plot data from the first measurement occasion is used for estimates of fire risk with the Blue Mountain variant of the FVS-FFE 

model. We used first-occasion data, as all plot measurements including dead wood 

are available for modeling. To estimate wildfire risk, we use torching index and 

crowning index, two variables that have been used in recently published studies as 

a measure of wildfire risk (Fiedler and others 2004, Fried and others 2005, Scott 

and Reinhardt 2001). Torching index is the 20-ft windspeed (the average windspeed 

in miles per hour measured at 20 ft above the ground) at which a surface fire is 

expected to ignite the crown layer, and crowning index is the 20-ft windspeed (in 

miles per hour) needed to support an actively spreading crown fire (Reinhardt and 

Crookston 2003). The stands that are at greatest risk of torching are those with a 

torching index of about 20 miles per hour (mph) or less.

Within the subalpine fir and Engelmann spruce forest types, more than half of 

the area (64 percent for subalpine fir and 61 percent for Engelmann spruce) has a 

torching index that is less than 20 mph (fig. 27). The large proportion of area at high 

risk of torching within these types is likely due to lower crown base heights that create more opportunity for surface fires to ignite ladder fuels, allowing the fire to move 

up into the crown. For all forest-land area, 43 percent is at risk of a wildfire torching.

Figure 27—Percentage of area with a torching index less than 20 miles per hour, by forest type, as 

predicted by the FVS-FFE model, Umatilla National Forest, 1996 (occasion 1 data only).

0

10

20

30

40

50

60

70

Torching index <20 mph 

(percentage of forest type)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

All forest land

Forest type

Within the subalpine 

fir and Engelmann 

spruce forest types, 

more than half of the 

area has a torching 

index that is less than 

20 mph.
29

Forest Resources of the Umatilla National Forest

Figure 28—Percentage of area with a crowning index less than 20 miles per hour, by forest type, as 

predicted by the FVS-FFE model, Umatilla National Forest, 1996 (occasion 1 data only).

0

10

20

30

40

Crowning index <20 mph 

(percentage of forest type)...

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

All forest land

Forest type

Figure 28 shows the percentage of area with a crowning index less than 20 mph 

by forest type. As with torching index, those stands that have a crowning index of 

20 mph or less tend to be at the highest risk of an active crown fire. On the UNF, 

the forest type with the greatest percentage of acres that pose the highest risk for 

this type of wildfire is grand fir; 34 percent of the plots classified as grand fir forest 

type may be at risk of an active crown fire. For all forest land, 19 percent is at risk 

of a wildfire crowning (fig. 29). 

Figure 29—Aftermath of a crown fire on the southern Umatilla National Forest.

Umatilla National Forest
30

RESOURCE BULLETIN PNW-RB-253

Canopy bulk density (CBD) is another way to assess crown fire potential. The 

CBD is the mass of available canopy fuel per unit of canopy volume (Scott and 

Reinhardt 2001). It is usually expressed in kilograms per cubic meter and can range 

from zero where there is no canopy, to about 0.4 kg/m3 (0.025 lb/ft3) (Powell 2005). 

Powell (2005) provided three categories of crown fire potential based on a range of 

CBD values expressed as kilograms of canopy fuel (foliage and small branches) per 

cubic meter of canopy volume. With low CDB (<0.05 kg/m3 or 0.0031 lb/ft3), crown 

fire is impossible or unlikely; with high CBD (>0.10 kg/m3 or 0.0062 lb/ft3), a 

crown fire can be sustained; moderate (0.05 to 0.10 kg/m3 or 0.0031 to 0.0062 lb/ft3) 

CBD values occur between the upper and lower thresholds (Powell 2005). 

Simulation output from the FFE model includes estimates of CBD. Figure 30 

shows canopy fuel loading risk (as defined by CBD categories) by forest type. For 

the UNF, the forest type with the highest acreage at potential risk for a crown fire 

is grand fir (120,000 acres) followed by Douglas-fir (50,000 acres). There is a large 

acreage now classified with “moderate” crown fire risk in the grand fir, Douglas-fir, 

and ponderosa pine types (361,000 acres, 29 percent of forest land). Some of these 

acres may move into the “high” risk category as CBD increases over time. 

Figure 30—Canopy bulk density (CBD) by forest type as predicted by the FVS-FFE model, 

Umatilla National Forest, 1996 (occasion 1 data only).

0

20

40

60

80

100

120

140

160

180

Forest area (thousand acres)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Other

Forest type

Low (CBD<0.05)

Moderate (CDB 0.05–0.10)

High (CBD >0.10)

The forest type with 

the highest acreage 

at potential risk for a 

crown fire is grand fir 

(120,000 acres).
31

Forest Resources of the Umatilla National Forest

Figure 31—Average annual mortality and gross growth by species with standard error of the 

estimate, in millions of cubic feet for panels A and D only, Umatilla National Forest, 1996 to 2002 

(occasion 1 and 2 data).

0

5

10

15

20

25

30

35

M

ortality and

gro

wth (million cubic feet)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Other species

Species

Average annual mortality

Average annual growth

Forest Growth and Mortality

Trees with about 490 million cubic feet of volume died between the first and second 

plot measurements, balanced by 449 million cubic feet of gross growth.5 There is no 

statistically significant overall difference between mortality volume and gross growth 

volume. However, subalpine fir was found to have a mortality rate much higher than 

its growth rate. Conversely, ponderosa pine was found to be growing faster than it was 

dying (figs. 31 and 32). Figure 31 shows the relative cubic volumes of annual mortality 

and gross volume growth by tree species. Total mortality volume is predominately 

grand fir (39 percent) and Douglas-fir (23 percent) (fig. 33), roughly proportional to 

these species’ contribution to total live volume. Total gross growth is predominantly 

grand fir (38 percent) and Douglas-fir (23 percent). Ponderosa pine proved to be a 

relatively healthy species over the remeasurement period. Although ponderosa pine 

was 18 percent of the live volume, it accounted for only 8 percent of the mortality 

volume and 16 percent of the growth. Conversely, subalpine fir with 4 percent of the 

live volume contributed 10 percent of the mortality and only 2 percent of the growth.

Subalpine fir with 4 

percent of the live 

volume contributed 

10 percent of the 

mortality and only 

2 percent of the 

growth.

5

As mentioned in the “Inventory Methods and Procedures” section, mortality could be 

reliably assessed only on the 326 remeasured plots of panels A and D. The growth and 

mortality figures presented here were developed from this group of plots.
32

RESOURCE BULLETIN PNW-RB-253

Figure 32—Average annual mortality and gross growth by species as a percentage of live cubic foot 

volume with standard error of the estimate, for panels A and D only, Umatilla National Forest, 1996 

to 2002 (occasion 1 and 2 data).

0

1

2

3

4

5

6

7

8

Mortality and growth 

(percentage of live volume)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Other species

Species

Average annual mortality

Average annual growth

Figure 33—Percentage of total tree mortality volume, by species, Umatilla National Forest, 1996 to 

2002 (occasion 1 and 2 data).

0

5

10

15

20

25

30

35

40

45

M

ortality

v

olume (percentage of total)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Species
33

Forest Resources of the Umatilla National Forest

Most of the subalpine fir mortality was caused by the balsam woolly adelgid 

(Adelges piceae Ratzeburg), a small insect introduced from Europe more than 80 

years ago. Much of the subalpine fir component in the interior Pacific Northwest has 

been damaged or killed by this insect since the mid 1980s (Livingston et al. 2000). 

Damage caused by balsam woolly adelgid can be difficult for forest inventory crews 

to identify, and mortality may often be attributed to unknown causes. In 2000, a 

statewide ground survey was conducted by the Oregon Department of Forestry to 

specifically determine the extent and severity of balsam woolly adelgid infestation in Oregon (Overhulser et al. 2004). A total of 71 plots with subalpine fir were 

visited on the Umatilla National Forest. Balsam woolly adelgid was found on 53 of 

the plots, and 24 of the plots had mortality attributed to balsam woolly adelgid.

The growth-to-mortality ratio can be viewed as a coarse-scale estimate of 

forest sustainability: if growth matches or exceeds mortality (and timber removals), 

then the forests could be viewed as sustainable (O’Laughlin and Cook 2003). The 

remeasurement data indicate that overall mortality and growth are statistically not 

significantly different. These estimates include a recent dramatic decline in federal 

timber harvest levels for the Umatilla National Forest (fig. 34) and reflect the forest 

health issues discussed previously (Johnson 1994, Mutch et al. 1993, Quigley 1992, 

Tanaka et al. 1995, Wickman 1992).

Figure 34—Umatilla National Forest timber harvest volume by year, 1922 to 2006. Source: Powell, 

D.C. 2007. Unpublished data. On file with: USDA Forest Service, Umatilla National Forest, 2517 SW 

Hailey Ave., Pendleton, OR 97801.

0

50

100

150

200

250

1922

1926

1930

19341938

1942

1946

1950

1954

1958

1962

1966

1970

1974

1978

1982

19861990

1994

1998

2002

2006

Year

Harvest v

olume (million b

oard feet)
34

RESOURCE BULLETIN PNW-RB-253

Site Class

The distribution of site classes across the forest could be considered another 

measure of productivity. Site class is a measure of an area’s potential capability to 

produce woody biomass. It is determined by evaluating the mean annual increment 

(MAI) in cubic feet per acre (or other units of volume per area) per year, calculated 

by using published equations. Site classes on the forest range from site class 2, the 

most productive (MAI of 165 to 224 ft3/acre per year), to site class 7, the lowest 

productivity level of forest land (MAI of <20 ft3/acre per year). Figure 35 shows the 

distribution of site classes by forest type for the UNF. The greatest acreage (500,000 

acres) is in site class 5, about 40 percent of all forest land. The other common site 

classes are classes 4 and 6, accounting for 19 percent and 29 percent of forest land, 

respectively. By forest type, grand fir and Douglas-fir tend to occupy the greatest 

proportion of acres on higher site classes (site classes 2 to 4).

Figure 35—Forest land area by forest type and site class, Umatilla National Forest, 2002 (occasion 2 data only; MAI is mean 

annual increment).

0

20

40

60

80

100

120

140

160

Forest type

Forest land (thousand acres)

Site class 2 (MAI 165–224 ft3/acre per year)

Site class 3 (MAI 120–164 ft3/acre per year)

Site class 4 (MAI 85–119 ft3/acre per year)

Site class 5 (MAI 50–84 ft3/acre per year)

Site class 6 (MAI 20–49 ft3/acre per year)

Site class 7 (MAI <20 ft3/acre per year)

Grand fir

Douglas-fir

Ponderosa pine

Lodgepole pine

Western larch

Engelmann spruce

Subalpine fir

Nonstocked

Western juniper
35

Forest Resources of the Umatilla National Forest

This resource bulletin uses first- and second-occasion inventory data to 

describe forest conditions related to species composition, forest structure, stand 

density, woody biomass, and forest growth and mortality. Short-term trends for 

these condition indicators are interpreted in the context of forest health and productivity, including an assessment of how they were influenced by recent insect and 

disease outbreaks, and what they might represent in terms of future wildfire risk.

Common and Scientific Names

Common name Scientific name

Black cottonwood Populus trichocarpa Torr. & Gray

Douglas-fir Pseudotsuga menziesii (Mirbel) Franco

Engelmann spruce Picea engelmannii Parry ex Engelm.

Grand fir Abies grandis (Dougl. ex D. Don) Lindl.

Lodgepole pine Pinus contorta Dougl. ex Loud.

Pacific yew Taxus brevifolia Nutt.

Ponderosa pine Pinus ponderosa P. & C. Lawson

Subalpine fir Abies lasiocarpa (Hook.) Nutt.

Western juniper Juniperus occidentalis Hook.

Western larch Larix occidentalis Nutt.

Western white pine Pinus monticola Dougl. ex D. Don

Acknowledgments

The authors thank Alison Nelson, Glenn Fischer, Don Justice, Karen Waddell, 

and David Hatfield for their continued support and assistance in the preparation 

of this report.

The report was improved with critical reviews and suggestions made by 

Sally Campbell, Dave Azuma, Bill McArthur, Charlie Gobar, and Olaf Kugler.

Metric Equivalents

1 acre = 0.405 hectare (ha)

1 acre = 4046.86 square meters

1,000 acres = 404.7 hectares

1,000 cubic feet (ft3) = 28.3 cubic meter

1 square foot per acre (ft2/acre) = 0.229 square meter per hectare

1 cubic foot per acre (ft3/acre) = 0.07 cubic meters per hectare (m3/ha)

1 foot (ft) = 0.3048 meters (m)

1 inch = 2.54 centimeters (cm)

1 mile (mi) = 1.609 kilometers (km)

1 pound per cubic foot (lb/ft3) = 16.02 kilograms per cubic meter (kg/m3)

1 ton = 907 kilograms

1 ton per acre = 2.24 tonnes per hectare
36

RESOURCE BULLETIN PNW-RB-253

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