The Western Juniper Resource

of Eastern Oregon

David L. Azuma, Bruce A. Hiserote, and 

Paul A. Dunham

United States

Department of

Agriculture

Forest 

Service

Pacific Northwest

Research Station

Resource Bulletin

PNW-RB-249

October 2005
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.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and 

activities on the basis of race, color, national origin, age, disability, and where applicable, 

sex, marital status, familial status, parental status, religion, sexual orientation, genetic 

information, political beliefs, reprisal, or because all or part of an individual’s income 

is derived from any public assistance program. (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 1400 Independence Avenue, SW, 

Washington, DC 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). 

USDA is an equal opportunity provider and employer.

Authors

David L. Azuma is a research forester, Bruce A. Hiserote is an information 

technology specialist, and Paul A. Dunham is a forester, Forestry Sciences 

Laboratory, P.O. Box 3890, Portland, OR 97208-3890.
Abstract

Azuma, David L.; Hiserote, Bruce A.; Dunham, Paul A. 2005. The western 

juniper resource of eastern Oregon, 1999. Resour. Bull. PNW-RB-249. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station. 18 p.

This report summarizes resource statistics for eastern Oregon’s juniper forests, 

which are in Baker, Crook, Deschutes, Gilliam, Grant, Harney, Jefferson, Klamath, 

Lake, Malheur, Morrow, Sherman, Umatilla, Union, Wallowa, Wasco, and Wheeler 

Counties. We sampled all ownerships outside of the National Forest System; we 

report the statistics on juniper forest on national forest lands by using data from the 

national forest, Pacific Northwest Region inventory. Statistical tables summarize 

the area covered by juniper trees and juniper forest, wood volume, and numbers of 

trees, by ownership and juniper type. We found juniper on an estimated 6.5 million 

acres, a little more than half that was considered forest land. Evidence suggests that 

amount of forest land will continue to increase.

Keywords: Forest inventory, western juniper, resource statistics, eastern 

Oregon.
Summary

Western juniper exists across a large expanse of eastern Oregon, over 6 million 

acres. It generally grows in multiaged stands with crown cover of less than 50 percent. We classify juniper stands as forest or savanna based on stocking of 5 percent 

or greater as being forest. The majority of the juniper forest is split almost evenly 

between the Bureau of Land Management and other private owners. The volume 

is estimated to be 766 million cubic feet, which is a little less than half that of 

ponderosa pine (Pinus ponderosa Dougl. ex Laws.) outside of national forests.

The estimated acres of juniper forest and savanna in Oregon have increased 

dramatically since the 1930s from about 1.5 million acres to around 6.5 million 

acres. Area classified as juniper forest has increased from 420,000 acres to over 

3 million. Over 1 million acres of area classed as juniper savanna have more than 

25 trees per acre. Over one-third of the acres classed as savanna had seedlings. 

All indications are that the area of juniper forest will continue to increase. 

Preface

Forest Inventory and Analysis (FIA) is a nationwide program of the USDA Forest 

Service authorized by the Forest and Rangeland Renewable Resources Research 

Act of 1978. Work units, located at Forest Service research and experiment stations, 

conduct forest resource inventories throughout the 50 States. The FIA Program 

of the Pacific Northwest Research Station in Portland, Oregon, is responsible for 

forest inventories in Alaska, California, Oregon, Washington, Hawaii, and the 

Pacific Islands.

Contents

 1 Introduction

 3 Inventory Procedures

 4 Reliability of Inventory Data

 5 Juniper Forest and Savanna

 6 Juniper Area and Ownership

 9 Changes From the 1988 Inventory

 9 Juniper Volume

 12 Growth, Mortality, and Removals

 13 Discussion

 15 Metric Equivalents

 16 Names of Trees

 16 Literature Cited
1

The Western Juniper Resource of Eastern Oregon, 1999

Introduction

The Forest Inventory and Analysis (FIA) Program of the Pacific Northwest 

Research Station conducted a multiresource inventory in eastern Oregon’s juniper 

forests in 1999. This inventory included all lands except those administered by the 

USDA Forest Service. This report summarizes the resource statistics for eastern 

Oregon’s juniper forests. Some statistical tables include inventory data provided by 

the USDA Forest Service for juniper forests on their lands. Other resources sampled 

but not included in this report include understory vegetation, crown cover, coarse 

woody debris, and snags. These data will lead to further analysis of the status of 

eastern Oregon’s juniper forests.

The FIA unit has periodically reported statistics for eastern Oregon since the 

1930s, e.g., Cowlin (1942), Bolsinger and Berger (1975), Farrenkopf (1982), Gedney 

et al. (1989), and Azuma et al. (2002). Gedney et al. (1999) reported on the juniper 

forests inventoried in 1988. This report summarizes statistics from over 400 plots 

taken over the range of juniper conditions across eastern Oregon.

Western juniper1 grows on xeric lands across eastern Oregon with the majority 

of stands growing where precipitation is between 10 and 20 inches per year and at 

elevations between 3,000 and 5,000 (Gedney et al. 1999) (fig. 1). Crown closure in 

juniper stands ranges from 60 percent to very sparse with only one to a few trees 

per acre. Many juniper stands contain trees that range in age from 1 to over 100 

years. Juniper successfully competes against other native plants like sagebrush 

(Artemesia spp. Nutt.) and grasses. Sometimes sagebrush serves as a shrub, with 

juniper establishing in the protected areas directly beneath (Eddleman 1986). As 

juniper stands age, they tend to exclude other native species through moisture 

competition (Evans and Young 1987).

The expansion of western juniper over the last 120 years has been well documented (Eddleman 1986, Gedney et al. 1999, Miller et al. 2000, Young and Evans 

1984). Overgrazing by domestic livestock, fire suppression, and climatic shifts 

(Burkhardt and Tisdale 1976, Knapp and Soule 1998, Miller and Rose 1995, Young 

and Evans 1984) are believed to be the causes of juniper’s phenomenal expansion. 

The hypothesis is that overgrazing has reduced the amount of fuel available to carry 

fire, and fire suppression has reduced the occurrence of fires that would have killed 

smaller juniper in sparsely populated stands. This coupled with a warmer, wetter 

climate conducive to seedling establishment has created favorable conditions for 

juniper to establish and expand its range. In 1936, Cowlin et al. (1942) estimated 

1 See “Names of Trees” for nomenclature.
2

RESOURCE BULLETIN PNW-RB-249

the area of juniper forest in eastern Oregon to be around 420,000 acres. In 1999, 

Gedney et al. estimated the acreage at about 2.2 million acres by using aerial 

photography. 

Western juniper was inventoried in 1999 as part of the eastern Oregon inventory conducted by the FIA Program of the Pacific Northwest Research Station. 

This inventory was initiated to supplement the timberland inventory conducted in 

1998 and as a follow-on to the 1988 juniper inventory. Many of the area statistics 

Figure 1—Plots with western juniper in eastern Oregon with 1936 vegetation type map.

Plots with juniper

Juniper

Other forest

Nonforest

Water
3

The Western Juniper Resource of Eastern Oregon, 1999

calculated in the juniper 1988 inventory were based on the cover that could be estimated from 1:40,000-scale aerial photos. In some circumstances, there were enough 

smaller juniper trees on a plot to qualify it as juniper forest; however, the smaller 

trees would not have been visible on the aerial photo, and would have been missed 

in the 1988 inventory. The 1999 inventory established ground plots on areas that 

were expected to have up to 9 percent cover as well as areas where juniper cover 

had been previously evaluated as greater than this threshold. 

The expansion of juniper forest over a large area of eastern Oregon has had 

a pronounced effect on the landscape. Several researchers have reported that the 

increasingly abundant juniper will outcompete other native vegetation, making the 

land less productive for grazing (Gholz 1980). Others have hypothesized that juniper uses more water than other range vegetation, thereby reducing flow (Miller et 

al. 1987, Miller and Shultz 1987). Juniper can also reduce through-fall precipitation 

by interception and subsequent evaporation and sublimation reducing the amount 

of moisture actually reaching the soil (Young and Evans 1984). Still others have 

looked at the amount of perch sites available for raptors in relation to the prey species. A study in Oklahoma evaluating decreases in the population of avian species 

dependent upon an open sage/grassland habitat (Coppedge et al. 2004) offers parallels for the juniper encroachment occurring in eastern Oregon.

The vast expansion of juniper has led landowners to attempt a variety of 

control measures, including cutting, chaining, and burning. All are relatively expensive, and most involve subsequent treatments (Evans and Young 1987). 

Inventory Procedures

The 1999 inventory of juniper in eastern Oregon sampled all lands with juniper 

present outside national forests. It also included a sample of plots where juniper 

was in proximity as judged from aerial photos, but not actually on the plot. The 

sampling scheme used the photointerpreted categories in the 1988 inventory as an 

initial stratification scheme. The 1988 photointerpretation classified sample points 

as to the percentage of cover but excluded some areas that were believed to have 

no juniper. In 1998, every secondary sample location that was excluded in the 1988 

photo work was evaluated by aerial reconnaissance. Using a global position system 

receiver to locate the point on the ground, an observer estimated the juniper cover 

and proximity to offsite junipers for these plots. These plots were subsequently 

included in the set of plots to be considered for ground sampling.

The juniper land of eastern Oregon was inventoried by using double sampling 

for stratification (Cochran 1977). The sample of ground plots was determined by 

choosing a random sample from the possible ground locations within categories 
4

RESOURCE BULLETIN PNW-RB-249

of juniper cover as determined from aerial reconnaissance or photointerpretation. 

Plots with juniper cover of at least 10 percent were sampled at a rate of about 50 

percent, plots with estimated cover between 1 and 9 percent at 20 percent, and plots 

with no estimated juniper cover at 5 percent.

Sample plots were located on a permanent systematic grid producing an even 

geographic distribution of both the field and photointerpreted locations. Ground 

plots were installed by using the FIA national program’s 4-point, mapped design. 

On the 57 co-located plots that had been previously established in the 1988 inventory as a 5-point design, field crews assessed all previously measured trees for 

mortality, harvest, and growth before installing a new national-design (4-point) 

plot centered on the same location. 

The new plot design consisted of a cluster of four 24-foot-radius subplots, 

totaling one-sixth of an acre, each with an annular ring extending to 59 feet covering about 2.1 acres in total (USDA 1999). All juniper trees regardless of size were 

sampled in the 24-foot-radius plot. Because larger trees tend to be rare in juniper 

forests, trees larger than 20 inches were sampled on the 59-foot-radius plot. The plot 

design also accounted for different land classes within the plot, known as condition 

classes. Condition classes were mapped on the plot delineating different situations 

that could occur such as, roads, pastures, and other forest and nonforest conditions. 

When multiple forested conditions existed on a plot, the data for each condition 

were processed separately.

The information collected on the plot included tree attributes (diameter, height, 

species, crown ratio, crown diameters, and terminal and lateral leader growth category); size and abundance of down wood; understory vegetation species, cover, and 

height; and various stand characteristics (e.g., age, size, and forest type). Individual 

tree crown area was computed as an ellipse with the perpendicular crown diameter 

measurements defining the axes. Woody biomass for individual trees was computed 

as total aboveground biomass, including bole, bark, and branches.

The area and volume statistics reported for national forests are based on the 

data collected by the USDA Forest Service, Pacific Northwest Region Continuous 

Vegetation Survey Program (Max et al. 1996) 

Reliability of Inventory Data

Inventories are designed to provide sampling errors consistent with national standards set by the USDA Forest Service. The target sampling errors for area of lowproductivity forest land such as juniper is 10 percent per million acres. 

The sample design for this inventory provides the highest precision when estimates are aggregated for all eastern Oregon. As the sample is divided into smaller 
5

The Western Juniper Resource of Eastern Oregon, 1999

units, the confidence intervals increase as a proportion of the estimate. Standard errors for marginal totals are included for most of the tables. Confidence intervals are 

quantitative expressions of the variability inherent in the sampling and estimation 

procedures. The tabulation below indicates, for instance, a 68-percent (one standard 

error) chance that the true forest or savanna area (estimated at 3,339,000 acres) is 

within the range of (3,173,000 and 3,505,000). 

Area and volume estimates and standard errors for juniper forest and savanna, 

by owner class, are displayed below:

Area Volume

Owner Forest Savanna Forest Savanna

Thousand acres Million cubic feet

Other public 472 ±22 174 ±50 96 ±9 17 ±3

BLM 1,534 ±156 1,196 ±168 328 ±42 21 ±5

Other private 1,556 ±154 1,869 ±319 247 ±33 35 ±10

All owners 3,339 ±152 3,227 ±340 671 ±45 73 ±12

Confidence intervals vary with the size of the estimate and the amount of variance associated with the estimate. As estimates get small, the standard errors will 

come close to 100 percent of the estimate, although a small estimate means that the 

attribute existed (i.e., is nonzero), we cannot be confident in the actual number. 

Juniper Forest and Savanna

The definition of juniper forest for the 1988 inventory was 10 percent or greater 

crown cover on the plot interpreted from aerial photography. The crown cover 

definition was a surrogate for the area occupancy of juniper or other trees. Because 

of their relative size, the seedlings and saplings contribute almost nothing to a 

definition that considers only crown cover. The persistence of juniper seedlings and 

saplings suggests that these junipers should be accounted for when defining forest 

land. We used stocking of 5 percent or greater (meaning 5 percent of full stocking), which includes the contribution of the seedlings and saplings, to define juniper 

forest. Juniper tends to grow on less productive sites than ponderosa pine, where a 

stocking level of 10 percent or greater defines forest land. As the capability of the 

land to support trees decreases, the stocking that will occupy the resources of the 

site decreases. Gedney et al. (1999) hypothesized that lateral root extension of as 

few as nine mature juniper trees per acre could fully occupy an acre. The Forest 

Service (USDA 1999) uses a definition of 40 trees per acre to define forest land for 

pinyon juniper lands to intermountain West. Applying this definition yields almost 

the same number of acres as the 5-percent-stocking rule.
6

RESOURCE BULLETIN PNW-RB-249

We defined juniper savanna as land with juniper trees growing on it but less 

than 5 percent stocking. Despite their low current stocking, such lands may well 

transition to juniper forest (Gedney et al. 1999). At least some of the savanna lands 

will continue to increase in canopy density, as evidenced by the proportion of the 

estimated total number of trees that are seedlings: 68 percent for savanna and 53 

percent for juniper forest (table 1). We estimated 695,000 acres of juniper savanna 

that had more than 25 seedlings per acre. The numbers of seedlings found suggests 

that these lands are still increasing in tree density.

Juniper forest is characterized by open-grown sparsely stocked stands. About 

30 percent of juniper forest has greater than 50 percent crown cover. Approximately 

48 percent of the juniper forest acres have crown cover between 10 and 40 percent 

(table 2). An interesting point is the occurrence of 8 percent of the juniper forest 

acres that have less than 10 percent crown cover but still have more than 25 trees 

per acre. This suggests that under steady-state conditions, over 50 percent of the 

juniper forest land could have 10 to 40 percent cover in the relatively near future. 

About 15 percent or 460,000 acres of the juniper forest land has more than 75 trees 

per acre but less than 20 percent crown cover. One might expect that on these lands, 

as the trees grow in size, cover would continue to increase to somewhere between 

20 and 40 percent cover.

Juniper Area and Ownership

With the exception of the ponderosa pine type, which covers 4.9 million acres 

(Campbell et al. 2003), juniper forests occupy more area than any other forest type 

in eastern Oregon, over 3.5 million acres (table 3). If the crown density of juniper 

trees continues to increase on these savanna lands, juniper forests may become 

the forest type with the most acres in eastern Oregon. The average percentage of 

juniper area, forest or savanna, across the counties with juniper is 20 percent. 

Crook County has the greatest percentage of its area in juniper with over 58 

percent, followed closely by Wheeler and Jefferson Counties with 46 and 34 

percent, respectively.

Most juniper forest and savanna lands (52 percent) are privately owned. The 

BLM manages about 43 percent (table 3). The private ownership category contains 

individuals, corporate owners, and native American tribes. When considering only 

lands classified as forest, the percentages of ownership are very close between the 

private sector and the BLM, 47 and 46 percent, respectively. The remaining proportion, totaling about 7 percent, is National Forest System and other public lands.
7

Table 1—Estimated number of western juniper trees by forest type class, owner, and diameter class for eastern Oregon, 19

Diameter class (inches) 

Owner Seedlings 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

Thousand trees

Juniper forest: Bureau of Land 79,282 16,718 12,288 16,825 14,659 13,001 5,815 3,497 3,023 1,772 1,363 

 Management Other public 4,876 4,619 2,601 2,109 1,447 861 302 96 112 112 15  Private 131,755 19,121 16,031 17,266 11,829 9,085 4,010 3,799 1,780 1,185 688  National forest 14,847 3,835 3,145 3,002 2,231 1,519 1,386 619 515 379 250  Total 230,760 44,293 34,065 39,202 30,166 24,466 11,513 8,011 5,430 3,448 2,316 3 Standard error (23,118) (4,170) (3,131) (3,391) (2,423) (2,191) (993) (799) (587) (512) (336) Juniper savanna: Bureau of Land 17,252 1,884 2,395 1,042 966 1,048 420 451 149 155 112  Management Othe public 949 193 461 193 193 465 32 125 — 32 —  Private 31,979 4,495 1,339 2,273 1,353 1,813 498 400 208 281 16  National forest 420 157 171 102 93 110 53 47 25 6 10  Total 50,600 6,729 4,366 3,610 2,605 3,436 1,003 1,023 382 474 138  Standard error (6,472) (1,891) (1,146) (869) (703) (831) (237) (288) (109) (134) (70) 
8

RESOURCE BULLETIN PNW-RB-249

Table 2—Estimated acres of juniper forest by tree-per-acre class and percentage 

of crown cover, eastern Oregon, 1999a

Crown cover percentage Standard

Trees per acre 0–5 5–10 10–20 20–30 30–40 40–50 50+ Total error

Thousand acres

1–24 — 12 70 — — — — 82 (40)

25–49 27 4 122 124 79 48 16 420 (96)

50–74 14 — 96 40 108 96 32 386 (85)

75–99 — 32 93 86 30 97 48 385 (90)

100–149 80 41 80 80 94 163 240 777 (116)

150–199 44 — 48 — 48 48 207 396 (79)

200+ 16 — 32 112 110 80 390 741 (120) 

 Total 181 89 541 441 470 532 932 3,187

 Standard (64) (39) (111) (98) (94) (99) (111) (169)

 error

— = less than 500 acres. a Does not include National Forest System land. Standard error in parentheses.

Table 3—Estimated area of western juniper forest by forest type class, county, and owner class for eastern 

Oregon, 1999a

Bureau of

National forest Land Management Other public Private Total County

County Forest Savanna Forest Savanna Forest Savanna Forest Savanna Forest Savanna 1936b

 area

Thousand acres

Baker 11 2 32 — — — 80 294 123 (53) 295 (149) 20 1,964

Crook 42 2 287 107 32 — 424 242 785 (118) 351 (121) 509 1,907

Deschutes — — 176 88 16 32 32 13 224(69) 133 (54) 329 1,932

Gilliam — — — — — — 16 32 16 (16) 32 (23) — 771

Grant 76 5 32 94 — — 257 373 365 (78) 472 (119) 41 2,898

Harney 43 5 460 496 15 32 19 142 537 (105) 675 (141) 189 6,486

Jefferson 112 1 32 — — — 218 142 362 (66) 142 (57) 63 1,140

Klamath 38 10 109 3 — — 118 — 265 (67) 13 (3) 106 3,804

Lake 42 5 214 279 16 29 80 182 352 (69) 495 (130) 222 5,207

Malheur — — 96 81 16 48 26 80 138 (52) 209 (69) 34 6,328

Morrow 4 — — — — — — — 4 (1) — (—) — 1,301

Sherman — — — — — — — 16 — (—) 16 (16) — 527

Wasco — — — 32 — — 48 202 48 (36) 234 (117) 2 1,524

Wheeler 6 2 96 16 — — 238 151 340 (85) 169 (58) 50 1,097

 Total 377 33 1,534 1,196 95 141 1,556 1,869 3,559 3,227 1,520 38,899

 Standard (18) (5) (156) (168) (39) (61) (154) (319) (152) (340)

 error

 — = less than 500 acres. a Totals may be off owing to rounding. Standard error in parentheses.

b Estimates of juniper extent based on a 1936 vegetation map from Oregon Department of Forestry.
9

The Western Juniper Resource of Eastern Oregon, 1999

Changes From the 1988 Inventory

In 1988, the population of plots to be sampled was drawn from photointerpreted 

points that had 10 percent or greater crown cover. Points that were determined to 

have less than 9 percent cover were not sampled on the ground. Plots representing 

nearly 800,000 acres of the 3 million acres determined to have less than 10 percent 

cover in 1988 had greater than 5 percent stocking when sampled on the ground in 

1999. This represents the majority of the change from 2.2 million acres of juniper 

forest estimated in 1988 to the 3.3 million estimated in 1999. We estimated that over 

2 million acres that had juniper present in 1999 were determined from aerial photos 

to have no juniper cover in 1988. Ninety percent of these acres were classified as 

juniper savanna in 1999.

Juniper Volume

The majority of the juniper volume is found on juniper forest lands, about 90 percent of the 744 million cubic feet. The BLM manages almost half of the total volume with private owners owning most of the rest (table 4). The volume for juniper 

in eastern Oregon is still relatively small, about half that of ponderosa pine outside 

of national forests of 1.51 billion cubic feet (Azuma et al. 2002). Juniper forest land 

is characterized by relatively low volumes per acre with greater than 64 percent of 

the area having less than 200 cubic feet per acre. The National Forest System lands 

are somewhat of an exception, where only 56 percent of the area falls into the 0 to 

200 cubic feet classes (table 5). Gedney et al. (1999) described these areas as transitional forests where forest types are transitioning from pine/fir to juniper types. 

In these areas, the juniper tends to grow taller and with more volume per tree than 

in other juniper forests; however, these areas represent a small proportion of the 

juniper forest. The transitional areas are probably best described by their elevation; 

as elevation increases, juniper tends to give way to ponderosa pine and Douglas-fir.

Juniper forests tend to have few other tree species intermingled within them, 

except in these transitional zones. The volume of other species within juniper forest 

is estimated to be 80 million cubic feet with ponderosa pine accounting for 65 million and curlleaf mountain mahogany, Douglas-fir, and quaking aspen making up 

the remainder (table 6). 
10

RESOURCE BULLETIN PNW-RB-249

Table 4—Estimated gross volume of western juniper by type class, county, and owner class for eastern 

Oregon, 1999a

Bureau of Land

National forest Management Other public Private Total

County Forest Savanna Forest Savanna Forest Savanna Forest Savanna Forest Savanna Total

Million cubic feet

Baker 4 1 6 — — — 7 4 17 (7) 5 (3) 21

Crook 14 1 56 3 4 — 59 4 133 (25) 8 (4) 139

Deschutes — — 49 1 3 3 2 — 54 (20) 4 (4) 57

Gilliam — — — — — — 3 1 3 (3) 1 (1) 4

Grant 24 3 7 2 — — 55 6 86 (18) 11 (3) 93

Harney 16 3 83 7 2 2 4 2 105 (26) 14 (4) 114

Jefferson 3 — 3 — — — 23 3 29 (9) 3 (2) 30

Klamath 6 1 32 — — — 31 — 69 (21) 1 (1) 69

Lake 7 1 54 6 6 — 23 10 90 (21) 17 (9) 109

Malheur — — 28 1 2 3 10 — 40 (19) 4 (2) 44

Wasco — — — 1 — — 5 4 5 (4) 5 (5) 10

Wheeler 2 — 9 — — — 28 1 38 (11) 1 (1) 38

 Total 78 10 328 21 18 7 247 35 671 73 744

 Standard error (5) (1) (42) (5) (8) (4) (33) (10) (45) (12) (44)

 — = less than 500,000 cubic feet. a Volume equations for juniper were developed by Chittester and MacLean 1984. Standard error in parentheses.

Table 5—Estimated acres of juniper forest by volume per acre class and owner 

class, eastern Oregon, 1999a

Volume Bureau of Land National Other Standard

per acre Management forest public Private Total error

Cubic feet - - --- - - - - - - - - - - - - - - Thousand acres - - - - - - - - - - - - - - - - -

0–99 350 150 — 683 1,183 (142)

100–199 470 64 80 462 1,076 (135)

200–299 421 67 — 205 693 (98)

300–399 128 49 — 64 241 (57)

400+ 166 47 16 141 370 (71)

 Total 1,535 377 96 1,556 3,563

 Standard error (156) (18) (39) (154) (153)

— = less than 500 acres. a Standard error in parentheses.

Table 6—Estimated volume of other species in juniper forest lands by 

owner class and species, eastern Oregon, 1999

Bureau of Land National

Species Management forest Private Total

Million cubic feet

Ponderosa pine 15 28 12 65

Douglas-fir — 5 — 5

Curleaf mountain mahogany 3 — 3 6

Quaking aspen — — 4 4

 Total 18 33 19 80

 — = less than 500,000 cubic feet.
11

The Western Juniper Resource of Eastern Oregon, 1999

Biomass of juniper may be of more importance than the cubic foot volume. 

Biomass is calculated as dry weight of bole, branches, and bark and is given in table 

7, by owner. Acres of juniper forest land by biomass class is given in table 8. A 

general rule-of-thumb relationship between percentage of crown cover and tons 

of dry weight biomass for trees greater than 5 inches in diameter at breast height 

(d.b.h.) was developed from FIA plot data and is given by the following equation:

Biomass = -0.258 + 16.42 × percent crown cover.

R2 = .63

Standard error = 1.98.

Table 7—Estimated biomass of western juniper trees greater than 5 inches in diameter by type class, county, 

and owner class for eastern Oregon, 1999a

Bureau of Land

National forest Management Other public Private Total

County Forest Savanna Forest Savanna Forest Savanna Forest Savanna Forest Savanna Total

Thousand tons

Baker 62 14 180 0 0 0 88 0 330(128) 14(11) 344

Crook 318 18 1,017 48 118 0 1,287 86 2,740(501) 152(60) 2,892

Deschutes 0 0 585 9 71 11 19 7 675(272) 27(16) 702

Gilliam 0 0 0 0 0 0 55 5 55(55) 5(5) 60

Grant 476 30 65 15 0 0 897 45 1,438(232) 90(24) 1,528

Harney 279 22 1,223 62 55 32 20 33 1,577(352) 149(44) 1,726

Jefferson 35 0 51 0 0 0 341 79 427(124) 79(41) 506

Klamath 161 27 590 0 0 0 715 0 1,466(414) 27(19) 1,493

Lake 227 9 924 52 48 0 473 96 1,672(345) 157(90) 1,829

Malheur 0 0 235 7 65 4 156 0 456(214) 11(8) 467

Wasco 0 0 0 6 0 0 41 61 41(32) 67(37) 108

Wheeler 20 0 244 0 0 0 670 10 934(279) 10(10) 944

 Total 1,578 120 5,113 199 357 47 4,763 421 11,811 788 12,599

 Standard error (139) (32) (732) (52) (148) (34) (678) (120) (750) (114) (769)

a Biomass estimates are dry weight including bole, bark and branch estimates. Foliage is not included. Standard error in parentheses.

Table 8—Estimated acres of juniper forest by biomass class and owner class, 

eastern Oregon 1999a

Bureau of Land National Other Standard

Biomass per acre Management forest public Private Total error

Tons - - - - - - - - - - - - - - - - Thousand acres - - - - - - - - - - - - - - - -

0–1 455 90 — 564 1,109 (104)

1–2 307 31 — 270 608 (107)

2–4 306 52 64 344 766 (98)

4–6 227 47 32 128 405 (71)

6–8 112 52 — 78 242 (44)

8+ 128 104 — 172 404 (51)

 Total 1,535 376 96 1,556 3,534

 Standard error (156) (18) (39) (154) (153)

— = less than 500 acres. a Standard error in parentheses.
12

RESOURCE BULLETIN PNW-RB-249

Figure 2—Eleven-year diameter growth increment on remeasured juniper trees.

Figure 3—Eleven-year height increment on remeasured juniper trees.

Growth, Mortality, and Removals

Juniper tends to be a slow-growing species although some trees, especially in the 

transitional zone, can grow quite rapidly. Of the over 500 trees that were remeasured from the 1988 inventory, no juniper trees were harvested, and only 4 had 

died. The sample of trees is too small to get an accurate estimate of removals and 

mortality. Eighty-nine percent of the remeasured trees had an 11-year diameter 

increment of less than or equal to 2 inches and 65 percent have a height increment 

of less than or equal to 2 feet (figs. 2 and 3). The majority grew less than 1.5 feet.
13

The Western Juniper Resource of Eastern Oregon, 1999

Both the terminal and lateral leaders of juniper trees were evaluated for growth 

in the last growing season and grouped into three classes: slow growing (less than 

1.9 inches per year), medium (1.9 to 3.9 inches per year), and (fast 3.9 inches or 

greater per year). Table 9 shows numbers of trees in terminal and lateral leader 

growth classifications by diameter class. Trees in the smaller diameter classes, 

mostly younger trees, show a greater proportion with fast-growing terminal leaders 

than trees in the largest diameter class (greater than 20 inches). The same pattern 

does not hold for lateral leaders with the small trees having a relatively even distribution across all growing classes; however, the largest diameter still has the greatest 

proportion of the trees in the slowest growth class.

Table 9—Number of trees by terminal and lateral leader growth class 

and diameter class, eastern Oregon, 1999

Growth rate

Diameter class Slow <1.9 Medium 1.9 to 3.9 Fast 3.9 + Total

Inches

Terminal growth

 Less than 5 680 825 1,295 2,800

 5 to 9 54 93 356 503

 9 to 20 218 244 489 951

 Greater than 20 182 78 51 311

Lateral growth

 Less than 5 911 981 908 2,800

 5 to 9 104 159 240 503

 9 to 20 302 332 317 951

 Greater than 20 217 64 30 311

a Diameter taken at breast height, 4.5 feet. Growth in inches for the latest year.

Discussion

Juniper forests generally grow in an environment where moisture is the limiting 

factor in the potential of a site to be occupied by trees. The occupancy of the site 

can be hypothesized to be the limit of the lateral extension of roots (Hall 2004). 

As stands develop, they will slowly outcompete other vegetation including smaller 

junipers, sagebrush, and other understory vegetation. Because juniper tends to grow 

in multiaged stands, which makes computing an average stand age problematic, 

we used average stand size (tree d.b.h.) as a surrogate for stand age: as stand size 

increases, the average number of seedlings per acre tends to decrease and amount 

of crown cover tends to increase (table 10). In some cases, there can be stands with 

juniper over 100 years old that have no seedlings at all. 
14

RESOURCE BULLETIN PNW-RB-249

Table 10—Average number of seedlings per acre and cover in square meters of 

juniper trees by stand size class, eastern Oregon, 1999

 Standard Standard

Stand size class Seedlings deviation Cover deviation

Large (greater than 9 inches d.b.h.) 31.8 35.6 125.8 137.5

Medium (5 to 9 inches d.b.h.) 45.6 50.4 134.1 109

Small (less than 5 inches d.b.h.) 108.1 91.7 106.6 92.8

Nonstocked 25.3 38.8 13.8 16.9

d.b.h. = diameter at breast height.

The area of land classed as juniper forest has increased over the last 60 years 

from 420,000 acres in 1936 (Cowlin et al. 1942) to 3.3 million acres in 1999. In 

figure 1, 1936 vegetation cover layer shows juniper type, which includes what we 

define as savanna and forest, covering about 1.5 million acres. Our current estimate, 6.5 million acres, is over four times as much. Some of the changes may be 

accounted for by definitional changes, but certainly there has been an enormous 

increase. These increases can have a profound effect on the landscape, lowering 

grazing carrying capacities, intercepting precipitation, and changing the available wildlife habitat. Although some of the forest acres we inventoried do not have 

much crown cover, they will continue to increase in cover percentage as trees grow. 

As forest canopy cover becomes increasingly dense, the carrying capacity of rangelands will continue to decrease owing to moisture competition. 

The clearing of juniper is expensive. Young et al. (1982) reported costs of $31 

to $832 per acre for treatments ranging from chemical treatment to wood harvesting and slash removal. Common treatments for clearing juniper include cutting 

and leaving stems, mechanical clearing, and burning. To truly clear juniper land by 

using any of these treatments will likely require repeated treatments to eliminate 

new seedlings as they emerge. With private owners controlling over 50 percent of 

juniper forest and savanna lands, it is difficult to imagine substantial areas being 

cleared of juniper considering the cost of treatment and posttreatment followup. 

Juniper stands in eastern Oregon tend to be multiaged with small trees intermingled with larger trees, so we used diameter range as a surrogate for age differences in an examination of both juniper forests and savanna. An interesting difference shows up in the percentage of land by diameter range (table 11). Forty-four 

percent of the savanna lands have a diameter range of less than 5 inches, but forest 

land has only 5 percent in this class. Conversely, the juniper forests have 52 percent 

of the area with a range greater than 20 inches compared to only 8 percent for the 

savanna. This suggests that much of the savanna is still developing into juniper 

forest.
15

The Western Juniper Resource of Eastern Oregon, 1999

Table 11—Estimated acres of juniper forest and savanna by range of 

plot diameter and juniper type, eastern Oregon, 1999a

Range of diameter Forest Savanna

Inches Thousand acres Percent Thousand acres Percent

0 to 4.99 158 5 1,415 44

5 to 9.99 175 5 450 14

10 to 14.99 506 15 374 12

15 to 19.9 744 22 716 22

20+ 1,744 52 271 8

a Diameter taken at breast height, 4.5 feet.

The expansion of juniper forests will probably continue to occur on lands that 

are now classified as juniper savanna. We estimate that more than 1 million acres 

of juniper savanna land has more than 25 trees per acre. Furthermore, plots representing one-third of the estimated acres of savanna had more than two seedlings on 

them. The evidence of seedlings on these lands suggests that juniper is still in an 

establishment stage, and that the probability of these lands continuing to increase 

in tree density is larger than for areas that have a single old juniper standing on it. 

Gedney et al. (1999) speculated that if all the juniper savanna lands converted to 

forest, there might be as much as 5 million acres of juniper forest in the future. If 

only half of the savanna lands continue to increase in tree density, the 5-millionacre number is quite reasonable, making juniper the forest type with the greatest 

area in eastern Oregon.

Metric Equivalents

1 acre = 0.405 hectare

1 acre = 4046.86 square meters

1,000 cubic feet = 28.3 cubic meters

1 cubic foot per acre = 0.07 cubic meter per hectare

1 foot = 0.3048 meter

1 inch = 2.54 centimeters

1 mile = 1.609 kilometers

1 ton = 907 kilograms
16

RESOURCE BULLETIN PNW-RB-249

Names of Trees

Common name Scientific name2

Softwoods:

 Douglas fir Pseudotsuga menziesii (Mirb.) Franco

 Ponderosa pine Pinus ponderosa Dougl. ex Laws.

 Western juniper Juniperus occidentalis Hook.

Hardwoods:

 Quaking aspen Populus tremuloides Michx.

 Curlleaf mountain mahogany Cercocarpus ledifolius Nutt.

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17

The Western Juniper Resource of Eastern Oregon, 1999

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RESOURCE BULLETIN PNW-RB-249

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