North Dakota’s Forests

2005

Resource Bulletin

NRS-31

Forest

Service

United States 

Department of Agriculture

Northern 

Research Station
We thank the following people who contributed both to the inventory and

analysis of North Dakota’s forest resources. 

Tom Berg

James Blehm

Joseph Boykin

Gary Brand

Bill Burkman 

Tom Claeys

Michael Downs

Keb Guralski

Ron Hackett

Tracie Hamilton

Mark Hansen

Bob Harsel

Gary Inhelder

Marcus Jackson 

Barb Johnson

Dan Kaisershot

Barb Knight

Larry Kotchman

William Laubscher

Earl Leatherberry

Mike Long

Corey Magdiak

Mark Majewsky 

Dennis May

Ron McRoberts

Ryan Medo

Dacia Meneguzzo

Pat Miles

Adam Morris 

Keith Moser

Marc Much 

Kevin Nimerfro

Cassandra Olson

Charles Paulson

Ron Piva

Greg Pugh

Matthew Riederer

Douglas Rollins

Travis Rymal

Tony Schram

Jason Severe

Earl Sheehan

Willard Smith

Jim Solomakos

Nate Sterns

Brad Totten

Greg White

Lacey Whitehouse

Joseph Zeleznik

Acknowledgments

Cover: Little Missouri River corridor. Photo used with permission from the North Dakota Forest Service. 
1

Manuscript received for publication

August 2008

Published by:

USDA Forest Service

Northern Research Station

11 Campus Blvd, Suite 200

Newtown Square, PA 19073-3294

January 2009 

For additional copies:

USDA Forest Service

Publications Distribution

359 Main Road

Delaware, OH 43015-8640

Fax: 740-368-0152

Visit our website: 

www.nrs.fs.fed.us

David E. Haugen, Michael Kangas, Susan J. Crocker, Charles H. Perry,

Christopher W. Woodall, Brett J. Butler, Barry T. Wilson, Dan J. Kaisershot

North Dakota’s Forests

2005
We welcome you to read the latest results of our statewide forest inventory, North

Dakota’s Forests 2005. The inventory and report are the product of a cooperative

effort between the North Dakota Forest Service and the Forest Inventory and

Analysis program of the U.S. Forest Service. 

North Dakota’s 724,000 acres of forests provide wildlife habitat, recreational

opportunities, and wood products; stabilize river banks; filter water runoff from

adjacent agricultural lands; serve as seed sources for conservation tree production;

and contribute to the botanical diversity of the State.

Private landowners hold 70 percent of the State’s forest land, and State or Federal

agencies own the remaining 30 percent. Both ownership groups play an important

role in the State’s natural resource heritage.

North Dakota’s forests are robust, but threats to these important resources exist.

Invasive species, conversion of forests to other land uses, overmaturity of existing

stands, and suppression of natural disturbances essential in regenerating forests are

issues that will require attention. 

Society demands a wide array of goods and services from our forests. North Dakota’s

Forests 2005 provides a common set of statistically accurate estimates that can be

used to make sound forest management decisions. We invite you to read this report

of North Dakota’s Forests 2005 and participate in the discussions about the future of

forests and forestry in our State.

Larry A. Kotchman

North Dakota State Forester

Foreword

2
3

Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

On the Plus Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Areas of Concern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Issues to Watch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

A Brief Primer on Forest Inventory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Forest Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

North Dakota’s Forest Land Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

North Dakota’s Forests—Where are They?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Forest Tree Diversity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

The Size of It All—North Dakota’s Woods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

How Old?—Forest Stand Age in North Dakota. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

How Dense are the Woods? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Biomass: North Dakota’s Forest Weighing In . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Cottonwood—A Special Situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

The Aspen Resource. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Whose Woods Are These? Family Forest Owners . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Whose Woods Are These? Public Forests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Forest Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Crowns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

North Dakota Soils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Down Woody Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Contents
4

Ozone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Invasive Plant Species. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Emerald Ash Borer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Wildlife Habitat—Snags. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Forest Health Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Forest Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Growing-Stock Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Sawtimber Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Timber Product Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Data Sources and Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Forest Inventory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Sampling Phases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Timber Product Output Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

National Woodland Owner Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Ozone Bioindicator Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5

North Dakota forest lands represent 1.6 percent of the State’s total land area,

at 724,000 acres.

There is an average of 478 trees per acre on forest land in the State.

There is an average of 22.3 tons per acre of dry all live-tree biomass on

timberland in the State. 

Cubic-foot volume in all live trees on forest land was estimated at 719

million cubic feet in 2005. Over 77 percent of the cubic-foot volume in the

State is on private forest land.

The volume of sawtimber on timberland equaled just over 1.1 billion board

feet in 2005, with close to half of the volume coming from cottonwood.

Fuel loadings of down woody materials are less in North Dakota compared

to areas of high fire hazard in Western States.

No ozone damage was observed on indicator plants in North Dakota during

the inventory period.

North Dakota’s aging cottonwood forests lack cottonwood regeneration with

the 2005 inventory estimating no cottonwood forest in the 0- to 20-year

stand age category. 

Only 21 percent of all timberland acres in North Dakota are categorized as

small diameter stands (1- to 5-inch diameter).

The majority of sawtimber (71 percent) is in lower valued tree grades 3, 4,

and 5.

Aspen forests in North Dakota are in a general state of poor health. Lack of

fire disturbance and/or harvesting has resulted in older stands with minimal

natural regeneration.

Highlights

On the Plus Side

Areas of Concern
Eastern bottomland forests have been severely impacted by Dutch elm

disease. This disease has eliminated many of the American elms that once

made up a large portion of this forest type and has shifted the species

composition toward green ash and boxelder.

With over 78 million ash trees growing on forest lands throughout the State,

the emerald ash borer could have a dramatic impact on the North Dakota

forest landscape.

The decline of cottonwood forests along the Missouri River is largely

attributed to the absence of regeneration and the gradual senescence of

mature overstory trees. Encroachment of nonnative species such as Russianolive, buckthorn, and brome grass create additional management problems. 

In ponderosa pine forests, years of past fire suppression coupled with high

stand density have created conditions that may intensify fire behavior.

With the increased interest in biobased fuels, marginal farm land that was

once in set-aside conservation programs is being put back into crop

production, which might reduce total forest land area in North Dakota in

the future.

6

Issues to Watch
Background

7

Ponderosa pine forest. Photo by Cassandra Olson, U.S. Forest Service.
Trees are perennial woody plants that have central stems and distinct crowns. In general,

FIA defines a tree as any perennial woody plant species that can attain a height of 15 feet at

maturity. 

FIA defines forest land as land that is at least 10 percent stocked by trees of any size or

formerly having had such tree cover and not currently developed for nonforest use. The

area with trees must be at least 1 acre in size, and wooded strips, such as those along roads,

streams, and agricultural fields, must be at least 120 feet wide and 363 feet long to qualify

as forest land.

From an FIA perspective, there are three types of forest land: timberland, reserved forest

land, and other forest land. In North Dakota, almost 74 percent of the forested acreage is

timberland, 3 percent is reserved forest land, and 23 percent is other forest land.

• Reserved forest land is withdrawn from timber utilization through legislation or

administrative regulation. 

• Other forest land is land not capable of producing 20 cubic feet/acre/year at its peak; this

is often due to poor soil conditions. 

• Timberland is forest land that is not reserved and meets the minimum productivity

requirements that other forest land does not.

In prior inventories, FIA measured trees only on timberland plots and was unable to report

volume on all forest land. The implementation of the new annual inventory system allows

volume to be reported on all forest land, not just on timberland. As these annual plots are

remeasured in the years ahead, FIA will also be able to report growth, removals, and

mortality on all forest land. In this report, trend reporting is limited to timberland except

for the area of forest land where individual tree measurements are not required.

What is a tree?

What is a forest?

What is the difference

among timberland,

reserved forest land,

and other forest land?

A Brief Primer on Forest Inventory

8

BACKGROUND
Volume can be precisely determined by immersing a tree in a pool of water and measuring

the amount of water displaced. The method used by the Northern Research Station to

estimate volume is less precise but more logistically feasible. In this method, several

hundred cut trees were measured taking detailed diameter measurements along their

lengths to accurately determine their volumes (Hahn 1984). Regression lines were then fit

to this data by species group. Using these regression equations, FIA can produce individual

tree volume estimates based on species, diameter, and site index.

The same method was used to determine sawtimber volumes. FIA reports sawtimber

volumes in International 1/4-inch Rule board-foot scale. Factors for converting to Scribner

board-foot scale are also available (Smith 1991).

Building on previous works, the Forest Products Laboratory of the U.S. Forest Service

developed specific gravity estimates for a number of tree species (USDA FS 1999). These

specific gravities were then applied to tree volume estimates to estimate merchantable tree

biomass (the weight of the bole). Determining live-tree biomass is more complicated

because the stump (Raile 1982), the limbs, and the bark (Hahn 1984) must be added in as

well. FIA does not currently report the biomass in roots and foliage.

Forest inventory can report biomass as either green weight or oven-dry weight. Green

weight is the weight of a freshly cut tree; oven-dry weight is the weight of a tree with zero

percent moisture content. On average, one ton of oven-dry biomass is equal to 1.9 tons of

green biomass.

Data from new inventories are often compared with data from earlier inventories to

determine trends in forest resources. However, for comparisons to be valid, procedures used

in the two inventories must be similar. As a result of FIA’s ongoing efforts to improve the

efficiency and reliability of the inventory, several changes in procedures and definitions have

occurred since the last North Dakota inventory in 1994. Although these changes will have

little effect on statewide estimates of timberland, timber volume, and tree biomass, they may

have significant effects on plot classification variables such as forest type and stand-size

class. Some of these changes make it inappropriate to directly compare 2005 data tables

with those published for 1994.

The biggest change between inventories was the change in plot design. For consistency’s

sake, a new national plot design was implemented by all five regional FIA units in 1999.

How do we compare

data from different

inventories?

How much does a tree

weigh?

How do we estimate a

tree’s volume?

9

BACKGROUND
The old North Central plot design used in the 1994 North Dakota inventory consisted of

variable-radius subplots. The new national plot design used in the 2005 inventory used

fixed-radius subplots. Both designs have their strong points, but they often produce

different classifications for individual plot characteristics.

FIA does not attempt to identify which lands are suitable or available for timber

harvesting— especially since suitability and availability are subject to changing laws and

ownership objectives. Just because land is classified as timberland does not necessarily

mean it is suitable or available for timber production. Forest inventory data alone are

inadequate for determining the area of forest land available for timber harvest because laws

and regulations, voluntary guidelines, physical constraints, economics, proximity to people,

and ownership objectives may prevent timberland from being available for timber

production. 

10

BACKGROUND

A word of caution on

suitability and

availability
The Features, Health, and Products of

North Dakota’s Forests

11

Killdeer Mountains. Photo used with permission from the North Dakota Forest Service.

Forest Features

13

Ponderosa pine on Logging Camp Ranch. Photo by Cassandra Olson, U.S. Forest Service.
North Dakota is characterized primarily as a prairie state due to the topography, soils, and

climate that promotes perennial grasses and forbs. Forests are found scattered across the

State in woodlots, along streams and river bottoms, within wooded draws of the western

region, and in the hills of the north-central and northeastern regions.

The area of forest land in North Dakota was estimated at 724,000 acres in 2005 (Fig. 1).

Timberland, a subset of forest land, increased between inventories by an estimated 92,000

acres (441,000 acres in 1994 to 533,000 acres in 2005) (Fig. 2).

Although area of forest land is small compared to the entire land area of the State (roughly

1.6 percent), it is an important resource for multiple uses including recreation, wildlife,

water, and forest products. As we move forward with the annual inventory, we should gain

valuable trend data that will help in crafting management decisions in the future.

Background

What we found

What this means

North Dakota’s Forest Land Base

14

FEATURES
15

FEATURES

Figure 2.—Total timberland area 

and associated standard error in 

North Dakota, 1954 to 2005.

0

100

200

300

400

500

600

700

1954 1980 1994 2005

Inventory Year

Timberland Area (thousand acres)

Figure 1.—Total forest land and

timberland area and associated standard

error in North Dakota, 2005.

0

100

200

300

400

500

600

700

800

900

Forest Land Timberland

Total Area (thousand acres)
The natural forests of North Dakota occur in the water rich areas along streambanks,

lakeshores, and in the draws, gulches, and ravines of the hills. The frequency and intensity

of drought is the primary factor that restricts forest growth within the State. North Dakota

is one of the few states where both eastern and western forest types occur (Warner and

Chase 1956).

North Dakota’s forests can be separated into four geographical watershed units: Devils

Lake/James River, Missouri River, Red River, and Souris River (Fig. 3). An estimated

275,000 acres (38 percent) of forest land are found in the Missouri River watershed (Fig.

4). The Red River watershed and the Souris River watershed have an estimated 208,000 

(29 percent) and 196,000 (27 percent) acres of forest land, respectively. The Devils

Lake/James River watershed has only 44,000 acres (6 percent) of the State’s forest land area. 

Generally, forests are more abundant in the eastern half of North Dakota and less abundant

to the west as the soil and climate become less favorable for the growth and survival of

eastern forest tree species. Forests are primarily found along the streams and river bottoms

where they are better protected from the drying effects of winds and soil moisture is greater.

The Turtle Mountains, Pembina Hills, and the area around Devils Lake hold some of the

largest tracts of forest land in the State. The Missouri, Red, and Sheyenne Rivers and their

tributaries contain much of the riparian forest lands in the State. Forest land area is

scattered in the Little Missouri watershed and Killdeer Mountains of the western region.

Forests are found in the draws and ravines, in canyons, and on lower north-facing slopes

across the west.

Background

What we found

What this means

North Dakota’s Forests—Where are They?

16

FEATURES
17

FEATURES

Figure 3.—Forest area by major

watershed units, North Dakota, 2005.

Figure 4.—Total forest land by major

watershed unit and associated standard

error in North Dakota, 2005.

0

50

100

150

200

250

300

350

Devils Lake &

James River

Souris River Red River Missouri River

Watershed Unit

Forest Land (thousand acres)
18

FEATURES

The species composition of a forest stand can indicate the type of wildlife habitat, potential

for forest products, and future silvicultural activities.

North Dakota’s forest lands contain just over 346 million trees (Fig. 5), an average of 478

trees per acre. Deciduous trees occupy 94 percent of North Dakota’s forest area. Elm/ash

forests are the most abundant (Fig. 6) and are composed of green ash, American elm, bur

oak, and cottonwood. The elm/ash forest type is important in terms of acreage and volume.

It covers nearly 28 percent (202,000 acres) of the State’s total forest land area and accounts

for more then 22 percent of all live-tree volume in the State (Fig. 7). Although aspen trees

are found throughout North Dakota, the largest concentration of the aspen forest type is

found in the Turtle Mountains and Pembina Hills regions, occupying 116,000 acres (16

percent) of the State’s forest land area. The bur oak forest type occurs on 77,000 acres of

forest land and is found primarily in and around the Turtle Mountains, Pembina Hills, and

Devils Lake region. 

The cottonwood forest type covers just 8 percent of North Dakota’s forest area, but

represents more than 30 percent of the State’s total forest volume. Cottonwood is

commonly found growing in pure stands but also grows in other forest types such as

elm/ash. Conifer-dominated stands cover roughly 5.8 percent of the forest area in North

Dakota and are composed primarily of ponderosa pine and Rocky Mountain juniper. The

Rocky Mountain juniper forest type covers more than 5 percent of North Dakota’s forest

area and occurs in the western part of the State known as the Badlands. This species grows

best in moist draws and ravines and on northern and western slopes.

Although the State’s forest lands hold some potential for wood products, many of the

forested acres are more valuable for protecting watersheds and providing wildlife habitat

and recreational opportunities. 

Background

What we found

What this means

Forest Tree Diversity
Figure 6.—Area of forest land in North

Dakota by forest-type group/local group,

2005.

0 50 100 150 200 250

Rocky Mountain juniper

Bur oak

Mixed upland hardwoods

Cottonwood

Elm/ash/cottonwood

Hard maple/basswood

Elm/ash

Aspen

Balsam poplar

Willow

Other hardwoods

Exotic hardwoods

Forest-type Group

Area of Forest Land (thousand acres)

0 20 40 60 80 100 120

Rocky Mountain juniper

Boxelder

Green ash

Aspen

Bur oak

Choke cherry

American elm

Hawthorn

American plum

Cottonwood

Species Group

Number of Trees (million)

19

FEATURES

Figure 5.—Top 10 species groups in

terms of number of live trees occurring on

North Dakota’s forest land, 2005.
0 20 40 60 80 100 120 140 160 180 200

Bur oak

Elm/ash/cottonwood

Aspen

Elm/ash 

Cottonwood

All Live Volume (million cubic feet)

Forest-type Group

20

FEATURES

Figure 7.—All live volume on selected

forest-type group/local groups in North

Dakota, 2005.
21

FEATURES

Forests are composed of many tree species representing various sizes. Forest stands are

analyzed by size classes as a means to delineate the structure of a forest. Stand-size class is a

measure of the average diameter of the dominant trees in a stand. There are three stand-size

classes: sawtimber—large trees, softwoods at least 9 inches in diameter at breast height

(d.b.h.) and hardwoods at least 11 inches d.b.h.; poletimber—medium trees 5 inches d.b.h.

to sawtimber size; and sapling/seedling—small trees 1 to 5 inches d.b.h. Tracking change in

the distribution of stand-size class provides information about forest sustainability and

succession, and potential for wood products, wildlife habitat, and recreation opportunities.

Figures 8a and 8b show the distribution of forest land and timberland by stand-size class 

in the State. Since the first inventory in 1954, the area of sawtimber in North Dakota has

steadily increased and now covers more than 198,000 acres of timberland (Fig. 9), and the

acreage of poletimber-size stands also increased over the same period of time. Currently,

poletimber-size stands represent more than 214,000 acres. The area of sapling-seedling size

stands has decreased since 1954 and now represents 110,000 acres. Two percent of the

timberland area is considered nonstocked. Forest types with a majority of area in the

sawtimber-size class include the cottonwood and bur oak types (Fig. 10). 

The steady increase in sawtimber-size stands indicates maturing forests. The decline in

sapling-seedling-size stands over this time period is an area of concern. This decline is due

in part to the lack of either natural or human-induced disturbance in many of these forest

stands. 

Background

What we found

What this means

The Size of It All—North Dakota’s Woods
Figure 8b.—Area of timberland by standsize class, North Dakota, 2005.

22

FEATURES

Figure 8a.—Area of forest land by standsize class, North Dakota, 2005.

Nonstocked

2%

Sawtimber

34%

Poletimber

37%

Sapling-seedling

27%

Nonstocked

2%

Sawtimber

37%

Poletimber

40%

Sapling-seedling

21%
Figure 10.—Percentage of select forest

types on timberland by stand-size class,

North Dakota, 2005.

0

10

20

30

40

50

60

70

80

90

100

Aspen 1994Aspen 2005

Cottonwood 1994

Cottonwood 2005

Bur oak 1994

Bur oak 2005Elm/ash 1994

Elm/ash 2005

Forest Type and Inventory Year

Small diameter

Medium diameter

Large diameter

Percent

0

50

100

150

200

250

300

Sawtimber Poletimber Sapling-seedling Nonstocked

Stand-size Class

Timberland Area (thousand acres) 

1954

1980

1994

2005

23

FEATURES

Figure 9.—Area of timberland by standsize class, North Dakota, 1954-2005.
24

FEATURES

North Dakota’s forest stands are represented by numerous age classes. Age is estimated

based on core samples from dominant or codominant trees from the overstory of a stand.

Estimating age is an important tool that provides information about the successional

development of a State’s forest lands. For example, a mixed age class distribution in aspen

forest types provides ruffed grouse with nesting cover, feeding areas, and drumming sites

along with places to roost. 

North Dakota’s forests can be categorized into six broad age classes: 0 to 20 years old, 21 to

40 years, 41 to 60 years, 61 to 80 years, 81 to 100 years, and 100+ years (Fig. 11). Stand

age varies by forest types. In 2005, stands dominated by Rocky Mountain juniper, bur oak,

and cottonwood contained a greater proportion of area in the oldest age class (Fig. 12)

whereas stands dominated by aspen generally are younger. 

More than three-quarters of the forest stands in North Dakota are 40 years or older. Lack of

regeneration is an issue of concern for many forest types within the State. This is due in

part to the lack of disturbances that are required to create suitable seedbeds and/or promote

root suckering.

Background

What we found

What this means

How Old?—Forest Stand Age in North Dakota
Figure 12.—Distribution of proportion of

area for selected forest types by stand

age class, North Dakota, 2005.

0

10

20

30

40

50

60

70

80

90

100

Pinyon/juniper Bur oak Cottonwood Aspen Elm/ash

Forest Type

Forest Land (percent)

0-20 years

21-40 years

41-60 years

61-80 years

81-100 years

100+ years

0-20 years

21-40 years

41-60 years

61-80 years

81-100 years

100+ years

25

FEATURES

Figure 11.—Distribution of forest land by

stand age class, North Dakota, 2005.

10%

1%

17%

36%

12%

24%
The extent to which trees occupy forests, woodlots, and riparian areas can indicate the stage

of stand development. Stand density can indicate the need for harvesting trees or other

activities that promote forest growth.

We used three features of stands to derive measures of density: number of growing-stock

trees per acre of timberland, growing-stock volume per acre of timberland, and percentage

of timberland by stocking class. The average number of growing-stock trees per acre of

timberland increased slightly between 1980 and 1994 and decreased between 1994 and

2005 (Fig. 13). Although volume of growing-stock trees on timberland increased between

1994 and 2005 (11 percent), the average volume of growing stock per acre of timberland

decreased between inventories due to the increase in nonstocked timberland. (Fig. 14, 15a).

Stocking, a relative measure of tree density, is used to describe how fully trees occupy

stands. A stand is considered fully stocked when trees occupy the amount of space in a

stand that creates conditions for the best growth and form. Almost half of the timberland is

in the moderately stocked (30 percent of all timberland) or fully stocked (15 percent of all

timberland) categories (Fig. 15b). About one-third of North Dakota’s timberland area is

poorly stocked. Such stands contain insufficient numbers of growing-stock trees per acre.

Nonstocked timberland represents 18 percent of the State’s total and has less then 10

percent stocking of live trees.

These varying stand density estimates indicate the varying stages of stand development and

ranges of ecological niches and processes across North Dakota. For example, on more

favorable growing sites certain trees gain early dominance, thus reducing the number of

competing trees. The remaining trees grow more vigorously than those on poor sites and

add more volume over the same period of growth. In contrast, many forest and woodlots

are nonstocked or poorly stocked across the State. Factors that affect stand development on

these sites include (1) marginal agricultural lands reverting to forests—stocking densities

usually are low on these sites, (2) stocking reduced by livestock grazing, (3) extreme

environmental conditions—low rainfall amounts.

Background

What we found

How Dense are the Woods?

26

FEATURES

What this means
Figure 14.—Average volume of growing

stock per acre of timberland, North

Dakota, 1954-2005.

0

100

200

300

400

500

600

700

800

1954 1980 1994 2005

Inventory Year

Average Growing-stock Volume 

per Acre (cubic feet)

0

10

20

30

40

50

60

70

80

90

100

1980 1994 2005

Inventory Year

Average Number of Growing-stock 

Trees per Acre

27

FEATURES

Figure 13.—Average number of growingstock trees per acre of timberland, North

Dakota, 1980-2005.
Figure 15b.—Area of timberland by

stocking class and associated standard

error, North Dakota, 2005.

0

50

100

150

200

250

Nonstocked Poorly

stocked

Moderately

stocked

Fully stocked Overstocked

Stocking Class

Timberland Area (acres)

0

10

20

30

40

50

60

70

80

90

100

1994 2005

Inventory Year

Timberland Area (percent)

Overstocked

Fully stocked

Moderately stocked

Poorly stocked

Nonstocked

28

FEATURES

Figure 15a.—Area of timberland by

percent stocking class, North Dakota,

1994 and 2005.
29

FEATURES

In this report, tree biomass is defined as the total dry weight of all live aboveground

components of a forest tree including boles, stumps, tops, and limbs. In commercial timber

harvesting, the bole usually is the primary product because it contains wood used as

lumber, pulp, post, and other wood products. Estimates of biomass are becoming

increasingly important for analyses of carbon sequestration, fiber availability for fuel, and

fuel loading/wildfire risk assessments. As new biofuel industries emerge across the country,

residual biomass from forest thinning and harvest operations takes on added environmental

and economical importance.

Live aboveground tree biomass is estimated at 19.8 million dry tons, an average of about 27

dry tons/acre of forest area (Fig. 16). Total aboveground tree biomass on timberland

increased by 2.3 million dry tons between 1994 and 2005. The bole (main stem) of trees

accounts for nearly 7 of every 10 dry tons of aboveground tree biomass in the State (Fig.

17). Stumps, tops, and limbs account for 25 percent of aboveground biomass and small

trees (1-5 inches d.b.h.) account for the remaining 10 percent. More than 77 percent of the

state total for aboveground biomass (trees) is found on privately owned forest lands (Fig.

18). Only county and local government forest lands have a higher per acre tonnage of

biomass than private forests (Fig. 19).

North Dakota is steadily accruing tree biomass as the forests continue to grow and mature.

Although the live-tree biomass of the forests holds substantial amounts of carbon, other

forest pools such as soils, dead trees, roots, and non-tree vegetation also contribute to the

total carbon pool of the forest ecosystem.

Background

What we found

What this means

Biomass: North Dakota’s Forest Weighing In
Figure 17.—Components of live-tree

biomass, North Dakota, 2005.

Figure 16.—Area of aboveground

biomass by dry tons per acre, North

Dakota, 2005.

30

FEATURES

Stumps, tops,

and limbs

25%

All live trees

1-5 inches

10%

Boles

65%
31

FEATURES

Figure 19.—Per acre aboveground dry

weight of all live-tree biomass on forest

land by owner group, North Dakota, 2005.

0

5

10

15

20

25

30

35

40

45

50

Forest Service Other Federal State County/Local Private

Owner Group

Tons per acre

Figure 18.—Ownership of forest biomass

(dry tons) for growing-stock and nongrowing-stock trees on forest land, North

Dakota, 2005.

Forest Service

5%

Other Federal

10%

County/Local

3%

Private

77%

State 

5%
32

FEATURES

Cottonwood trees hold a special place in the history of North Dakota. The giant

cottonwood trees along the Missouri River near Washburn in Smith Grove are living

witnesses to the Lewis and Clark Corps of Discovery Expedition that explored the

Louisiana Purchase some 200 years ago (North Dakota Forest Service 2003). In 1873,

Congress passed the Timber Culture Act, which offered 160 acres to any settler willing to

plant 10 acres of trees (North Dakota Forest Service 1991). Many of the tree plantings

included cottonwoods that are still around today. Cottonwood has always been one of the

primary tree species harvested in the State. The potential loss of area in the cottonwood

forest type is a major concern for North Dakota.

To gauge the future status of cottonwood in North Dakota, we looked at the area of

cottonwood forest type by stand age over time. In 1980, there were an estimated 66,000

acres in the cottonwood forest type; by 2005 that had dropped to 55,000 acres, a decrease

of around 20 percent (Fig. 20). Over this 25-year period, the cottonwood forest type in the

stand age category of 0 to 20 years dropped to zero acres.

We also assessed the number of cottonwood trees by diameter between the 1994 and 2005

survey. Across all forest types in North Dakota, we estimate that the number of cottonwood

saplings in the 1.0- to 2.9-inch diameter range is zero and there are only 445,000 saplings

in the 3.0- to 4.9-inch diameter range. These estimates illustrate the lack of cottonwood

regeneration within the State (Fig. 21). 

The lack of young stands of cottonwood across North Dakota, along with the low rate 

of regeneration as expressed by the number of saplings across all forest types, illustrates 

the shifts in natural disturbance regimes required to perpetuate cottonwood forests.

Cottonwood seeds require a moist bare mineral soil seedbed in which to germinate.

Frequent flooding along streambanks helps prepare suitable seedbeds. Flood control

structures on many of the major rivers across the State have resulted in the loss of

suitable sites for cottonwood regeneration. If these trends persist across North Dakota,

the area and the number of cottonwood trees growing in the State will continue to

decrease.

Background

What we found

What this means

Cottonwood—A Special Situation
Figure 21.—Cottonwood trees per acre,

North Dakota, 2005.

0

20,000

40,000

60,000

Stand Age

Area of Cottonwood Forest Type 

1980 52,547 2,962 2,286 0 3,426 5,153

1995 18,022 5,600 19,178 2,293 80 6,545

2005 0 17,852 13,609 11,249 5,236 7,129

0-20 

years

21-40 

years

41-60 

years

61-80 

years

81-100 

years

100+ 

years

33

FEATURES

Figure 20.—Area of cottonwood forest

type by stand age and inventory year,

North Dakota, 1980-2005.
34

FEATURES

With the exclusion of fire, much of the aspen in North Dakota has become overmature and

is declining in health and vigor (North Dakota Forest Service 2004a). Second only to the

elm/ash forest type in area with 116,000 acres of forest land, the aspen forest type is an

important resource for wildlife, recreation, esthetics, and forest industry.

In 1980, there were an estimated 154,000 acres in the aspen forest type. By 2005, the area

of aspen had dropped to 116,000 acres, a decrease of around 25 percent (Fig. 22). Over

this 25-year period, the aspen forest type in the stand age category of 0 to 20 years

decreased by more than 35,000 acres, while 60 percent of aspen stands in the State in 2005

were 40 years or older.

All live volume of aspen across all forest types in North Dakota in 2005 was estimated at

just over 100 million cubic feet (Fig. 23), an increase of just over 5.9 million cubic feet or 6

percent between inventories. Taking a look at volume per acre just on aspen stands

between inventories, we note a decrease in aspen volume. In 1995, aspen volume per acre

was estimated at 761 cubic feet per acre. By 2005, aspen volume per acre had dropped to

632 cubic feet per acre.

The aspen forest type in North Dakota is in decline. Stands of aspen are at or near maturity

for this pioneer species. Without disturbances (e.g., fire or harvesting) the aging stands of

aspen will continue to deteriorate, succumbing to weather, insects, and disease. 

Background

What we found

What this means

The Aspen Resource

Aspen trees. Photo by U.S. Forest Service,

Northern Research Station.
35

FEATURES

Figure 23.—Aspen live volume per acre,

North Dakota, 2005.

Figure 22.—Area of aspen forest type by

stand age and inventory year, North

Dakota, 1980-2005.

0

20

40

60

80

100

120

140

160

180

Area of Aspen Forest Type 

(thousand acres)

Stand Age

1980 154 54 27 63 11 0 0

1995 118 22 25 37 29 4 0

2005 116 19 28 47 22 0 0

Total 0-20 years 21-40 years 41-60 years 61-80 years 81-100 

years 100+ years
36

FEATURES

FIA conducts the National Woodland Owner Survey (NWOS) to increase our

understanding of who owns the forest, why they own it, and what their management

objectives are. Data presented here are based on survey responses from 28 randomly

selected families and individuals who own forest land in North Dakota. Although this

sample size is relatively small, the trends for North Dakota are consistent with the trends

for the region as a whole, albeit with large sampling errors. The general trends appear to be

accurate. For additional information on the NWOS, visit: www.fs.fed.us/woodlandowners.

The majority of the forest land in North Dakota, 424,000 acres or 58 percent, is owned by

families and individuals (Fig. 24). An additional 86,000 acres are owned by other private

groups (e.g., corporations, tribes, etc.). Collectively, private owners possess 70 percent of

the State’s forests. An estimated 30,000 families and individuals collectively own 424,000

acres of forest land in North Dakota. They are the dominant forest ownership group in the

State. Although 76 percent of family forest owners have fewer than 10 acres of forest land,

86 percent of family forest land is owned by people with landholdings of 10 acres or more

(Table 1). Although most family forest owners in North Dakota plan to do little or nothing

with their forest land in the next 5 years, approximately 1 in every 3 acres is held by

owners who plan to either transfer their land to heirs or otherwise sell it within the next 5

years (Table 2). Land transfer is related, in part, to the age of the owners. Twenty-one

percent of the family forest land is owned by people 75 years or older, and an additional 38

percent of the family forest land is owned by people between 65 and 75 years old (Table 3).

This large-scale intergenerational shift will change the characteristics of the family forest

owners; influence how owners view, interact, and relate to their land; and, as a result, alter

future forest characteristics.

North Dakota’s family forest landowners are stewards of an important resource that

provides both personal and societal benefits. As stewards, landowners maintain their

woodlots and forests to protect and enhance their personal interests while providing

environmental and other benefits to the public. 

Background

What we found

What this means

Whose Woods Are These? Family Forest Owners
37

FEATURES

Table 1.—Area and number of family

owned forests in North Dakota by size of

forest holdings, 2005

Figure 24.—Forest ownership in North

Dakota, 2005.

Business

12%

Federal

22%

Local

2%

Family and Individual

58%

State 

6%

Acres Sampling error Number Sampling error 

Thousands % Thousands %

1-9 61 82 22 69

10-49 106 51 5 39

50-99 45 106 1 58

100-499 151 37 1 30

500+ 61 107 <1 100

Total 424 10 30 52

Size of forest 

landholdings (acres) Area Ownerships
38

FEATURES

Table 3.—Area and number of family

owned forests in North Dakota by age of

owner, 2005.

Table 2.—Area and number of family

owned forests in North Dakota by

landowners’ 5-year plans for their forest

land, 2005.

Acres Sampling error Number Sampling error 

Thousands % Thousands %

No activity 91 58 1 46

Minimal activity 136 41 6 57

Harvest firewood 151 37 9 45

Harvest saw logs or pulpwood 15 287 <1 100

Collect NTFPs b 42 118 1 38

Transfer all or part of land to heirs 151 37 4 59

Buy more forest land 15 287 <1 100

Land use conversion (forest to other) 45 106 <1 67

No current plans 30 151 <1 80

a Categories are not exclusive.

b NTFPs = non-timber forest products.

Future plans a Area Ownerships

Acres Sampling error Number Sampling error 

Thousands % Thousands %

<45 21 217 4 51

45-54 85 66 10 33

55-64 64 84 <1 28

65-74 148 42 13 34

75+ 85 66 1 28

No Answer 21 217 1 51

Age (years) Area Ownerships
39

FEATURES

Public forests are an important part of North Dakota’s natural resource heritage. Forests

provide access to outdoor education and recreational opportunities, provide wildlife habitat,

and play an important role in protecting watersheds. 

Roughly 30 percent (214,400 acres) of forest lands in North Dakota are publicly owned

(Fig. 25). The Federal government, primarily the U.S. Forest Service, is responsible for

managing 72,000 acres or 34 percent while the State of North Dakota manages just over

46,000 acres or 22 percent of the forest land. More than 39 percent of the public lands are

managed by other Federal agencies, which include the Fish and Wildlife Service, National

Park Service, and Bureau of Land Management.

Much of the land available for public outdoor recreation such as hunting, fishing, hiking,

camping, or bird watching is managed by State and Federal agencies. For example, the

North Country Trail, which runs from New York to North Dakota, travels through both

state forest and U.S. Forest Service lands in southeast North Dakota. The North Dakota

Parks and Recreation Department administers 19 state parks and recreation areas across the

State. The North Dakota Forest Service manages lands for multiple benefits including

recreation and forest products. Federal agencies like the U.S. Forest Service, National Park

Service, and Fish and Wildlife Service manage areas available for recreation, many of which

are forested.

Background

What we found

What this means

Whose Woods Are These? Public Forests
0 5 10 15 20 25 30 35 40

Bureau of Land Management

County/Local Government

National Park Service

Other Federal

Fish and Wildlife Service

State Government

US Forest Service

Percentage

Public Owners

40

FEATURES

Figure 25.—Distribution of public

ownership by percent, North Dakota,

2005.
Forest Health

41

Aerial view of forest tent caterpillar defoliation in the Turtle Mountains. Photo used with permission from the North Dakota Forest Service.

Aspen conk produced by the fungus Phellinus tremulae. Photo used with permission from the North Dakota Forest Service.
The overall condition of the tree crowns indicates the health of a forest stand. For example,

a forest suffering repeated insect infestation will have low crown ratios, high transparency,

low density, and signs of dieback. Because tree crowns form part of the basic structural

architecture of a forest ecosystem, they also influence the composition, process, and vigor 

of understory flora and fauna (Schomaker et al. 2007).

Crown indicator variables are collected only on a subset of forest land plots. The following

data are from seven Phase 3 plots or 150 trees. Dieback is measured as the percentage of

branch tips in the crown that are dead. The categories for the dieback indicator are none 

(0-5 percent), light (6-20 percent), moderate (21-50 percent), and severe (51-100 percent)

(Fig. 26). Most trees were found to be in the none or light categories. Boxelder (8.3 percent)

and aspen (7.1 percent) had the highest dieback ratios.

The crown ratio of a tree is defined as the portion of the tree height supporting live foliage.

Eastern redcedar has the highest mean crown ratio at 90 percent; quaking aspen has the

lowest mean ratio at just over 35 percent. Crown transparency is a measure of the

proportion of the crown through which the sky is visible. The willow and boxelder species

groups have the highest average crown transparency, approaching 32 percent; the eastern

redcedar has an average crown transparency of only 10 percent.

Means of the crown indicators by species group appear to indicate healthy crown

conditions in North Dakota. Crown ratio and crown transparency appear to be inversely

related: the higher the crown ratio the lower the transparency. Crown ratios are generally

higher for trees on the edge of the forest. With the baseline data collected, we will continue

to monitor crown health and will be able to detect trends as they develop.

Background

What we found

What this means

Crowns

42

HEALTH
43

HEALTH

Figure 26.—Percentage of dieback, mean

crown transparency, and mean

uncompacted crown ratio for selected

species groups, North Dakota, 2005.

0 10 20 30 40 50 60 70 80 90 100

American elm

Boxelder

Bur oak

Eastern redcedar

Green ash

Quaking aspen

Willow

Species Group

Percent

Dieback

Crown ratio

Transparency
Soils are vital to a tree’s survival. In addition to physically supporting the roots, and

therefore the rest of the tree, soils also provide essential water and nutrients to the tree

(North Dakota Forest Service 2004b). Inventory and assessment of the forest soil resource

provides critical baseline information on forest health and productivity.

Field data are available from 2001 to 2004. There are relatively few soil inventory plots in

North Dakota, but it is possible to make some very broad generalizations using data from

other Plains States (South Dakota, Nebraska, and Kansas). 

Forest floor accumulations under North Dakota’s forests are at or above the median forest

floor thickness observed in the region (Fig. 27).

Soil carbon content in the forest floor and mineral soil was calculated from laboratory

measurements. The forest floor under North Dakota’s forests stores as much or more

carbon than that in most samples from neighboring states, both within and across foresttype groups (Fig. 28). The same is true in the 0- to 10-cm layer of mineral soil (Fig. 29).

In the 10- to 20-cm layer, carbon storage is more consistent across the region.

The Soil Quality Index (SQI) is a new measure designed to combine the distinct physical

and chemical properties of the soil into a single, integrative assessment (Amacher et al.

2007). SQI values in North Dakota are generally higher than those observed in

neighboring states (Fig. 30). The high quality of the sampled soils results from several

factors: moderate soil pH, abundant calcium and magnesium, and low levels of

aluminum.

Soil carbon is significant for several reasons. First, carbon is the primary component of

soil organic matter, which has a number of important functions. These include increasing

water holding capacity, retaining some nutrients by cation exchange (e.g., Ca2+, Mg2+,

K+), releasing other nutrients as it decays (e.g., nitrogen, phosphorus, and sulfur), and

capturing potential toxic agents (e.g., mercury) (McBride 1994). Nationally and

internationally, carbon is also inventoried to track the sequestration of certain 

greenhouse gases.

Calcium and magnesium are essential elements for plant growth. Calcium is required for

cell wall formation, and magnesium is essential to photosynthesis as the central atom of

the chlorophyll molecule (Marschner 1986). High levels of aluminum reduce root growth

(Marschner 1986).

Background

What we found

What this means

North Dakota Soils

44

HEALTH
45

HEALTH

The soil indicator is in its infancy, but the existing data suggest that the forest soils of

North Dakota are of high quality and storing above average amounts of carbon. This may

indicate an opportunity for the State’s limited forests to play an important role in future

sequestration programs.

Figure 27.—Observations of forest floor

thickness, North Dakota and other Plains

States, 2001-2004.
46

HEALTH

Figure 28.—Observations of forest floor

soil carbon content, North Dakota and

other Plains States, 2001-2004. 

Figure 29.—Observations of mineral soil

carbon content, 0 -10 cm, North Dakota

and other Plains States, 2001-2004. 
47

HEALTH

Figure 30.—The Soil Quality Index

(Amacher et al. 2007) highlights

differences in the overall chemical and

physical condition of the soil.
Down woody materials, in the form of fallen trees and branches, fill a critical ecological

niche in North Dakota’s forests. Down woody materials provide valuable wildlife habitat in

the form of coarse woody debris, increase the diversity of forest structure, and are an

important determinant of forest fire behavior. 

Overall, the fuel loadings of down woody materials (time-lag fuel classes) are relatively low

for most classes in North Dakota (Fig. 31) (for time-lag definitions see Woodall and

Monleon 2008). For comparison, the combined loadings of 1-hr, 10-hr, and 100-hr fuels in

blowdown areas of the Boundary Waters Canoe Area Wilderness in Minnesota exceeded 16

tons/ac (Woodall and Nagel 2007), while North Dakota’s combined loadings were below 3

tons/ac. One exception is the 1,000+-hr fuels that averaged over 8 tons per forest land acre.

However, it should be noted that this 1,000+-hr fuel estimate has a standard error of 3

tons/acre, which indicates that it may not be statistically different from that of neighboring

states. The size class distribution of coarse woody debris appears to be heavily skewed (84

percent) toward pieces less than 8 inches in diameter at the point of intersection with plot

sampling transects (Fig. 32a). In the decay class distribution of coarse woody debris, there

appears to be a fairly uniform distribution of stages of coarse woody decay across the State,

except for decay class 3 logs (48 percent) (Fig. 32b). Decay class 3 coarse woody pieces are

typified by moderately decayed logs that are still structurally sound but missing most of

their bark with extensive sapwood decay. There is no strong trend in coarse woody debris

volumes/acre among classes of live-tree density (basal area/acre) (Fig. 33). 

The down woody fuel loadings in North Dakota’s forests are not significantly different from

those found in neighboring states. Therefore, only in times of extreme drought would these

low amounts of fuels pose a hazard across the State. Of all down woody components,

1,000+-hr fuels made up the largest amounts possibly due to windthrow events along the

numerous forest fringes in this Plains State. However, coarse woody debris volumes are still

relatively low and were represented by small, moderately decayed pieces. Overall, because

fuel loadings are not exceedingly high across North Dakota, possible fire dangers are

outweighed by the benefits of down woody material for wildlife habitat and carbon pools.

Background

What we found

What this means

Down Woody Materials

48

HEALTH
49

HEALTH

Figure 31.—Means and associated

standard errors of fuel loadings

(tons/acre, time-lag fuel classes) on forest

land in North Dakota and neighboring

states, 2001-2005.

0

2

4

6

8

10

12

14

1-hr 10-hr 100-hr 1,000+-hr

Fuel-hour classes

Fuel Loadings (tons/acre)

South Dakota

North Dakota

Minnesota
50

HEALTH

1

2

3

4

5

Decay Class

Figure 32 a and b.— Mean proportions

of coarse woody debris total pieces per

acre by transect diameter (inches) and

decay classes on forest land in North

Dakota, 2001-2005.

3.0-7.9

8.0-12.9

13.0-17.9

18.0+

Coarse Woody Debris 

(inches) 

48%

17%

5%

30%

0%

84%

5%

0%

11%
51

HEALTH

Figure 33.—Means and associated

standard errors of coarse woody debris

volumes (cubic feet/acre) on forest land in

North Dakota, 2001-2005.

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

0.0-30.0 30.1-60.0 60.1-90.0 90.1-120.0 120.1+

Basal Area (sq. ft./acre)

Coarse Woody Debris (cubic feet/acre) 
52

HEALTH

Bioindicator leaf injury surveys were initiated in North Dakota in 2002. North Dakota has

eight permanent biosites scattered across the State; no foliar injury symptoms have been

observed so far.

Ground-level ozone exposure in North Dakota has not been detected by our inventory

measurements:

North Dakota’s ozone levels are some of the lowest in the country (Fig. 34). Plant species

used in the ongoing study to detect ozone damage include skunkbush, mountain

snowberry, common milkweed, and western wormwood. Tree species studied include green

ash, quaking aspen, and ponderosa pine.

North Dakota’s forests appear to be at low risk of suffering ozone damage to ozone-sensitive

species. Still, baseline data are needed to develop trends for potential ozone damage in the

future.

Background

What we found

What this means

Ozone 

Number of biosites 8 8 8 8

Biosites with injury (%) 0 0 0 0

Number of plants evaluated 866 695 752 775

Number of plants with injury 0 0 0 0

Mean biosite index 0 0 0 0

Parameter 2002 2003 2004 2005
53

HEALTH

Figure 34.—Mean biosite index map for

North Dakota, 2000-2004. 
54

HEALTH

Invasive plants spread into intact ecosystems and cause economic or environmental harm

by developing self-sustaining populations and becoming dominant or disruptive to those

systems (Clyde 2002). Nonnative invasive plant species can compete with and replace

native forest plants, reduce wildlife forage and habitat, and increase forest management

costs through their impact on tree regeneration and growth. 

Between the 2001 and 2003 field seasons, we collected data on native and nonnative forest

plant species from our seven ground vegetation plots, a subset of our forest inventory plots.

In 2005, we began collecting data on a select list of nonnative invasive plants on all forest

inventory plots across the State (Fig. 35). The two most prevalent nonnative species were

nonnative bush honeysuckle and common burdock, both species found on 19 percent of

sampled plots. Leafy spurge was the third most common nonnative species found. Other

nonnative species found include common buckthorn, spotted knapweed, Canada thistle,

and bull thistle.

Nonnative plant species are an emerging forest health concern in North Dakota because

they compete with native plant species for resources and threaten ecological diversity by

altering natural plant communities. Nonnative plants can also cause economic problems by

lowering land values for agriculture, forestry, and recreation.

Background

What we found

What this means

Invasive Plant Species
55

HEALTH

Figure 35.—Nonnative invasive plants on

forest lands, North Dakota, 2005.
56

HEALTH

Since its discovery in North America in 2002, the emerald ash borer (EAB) has caused

extensive decline and mortality of ash trees in the central portion of the U.S. and in southcentral Canada (Poland and McCullough 2006). EAB is an exotic wood-boring beetle that is

a pest of all major species of ash, including green, white, black, and blue ash, and all ash

cultivars. Both healthy and stressed ash trees, ranging in size from 1 to 59 inches in

diameter, are susceptible (Cappaert et al. 2005). Trees infested with EAB generally die

within 1 to 3 years (Poland and McCullough 2006).

North Dakota’s forest land contains an estimated 78.1 million ash trees greater than 1 inch

in diameter. Almost all of the State’s ash trees (96 percent) are green ash, with only a minor

component of black ash (4 percent). Overall, green ash represents 22 percent of all of the

live-tree species on forest land. Green ash is the second most abundant tree species in

North Dakota by number of trees and is ranked third by estimate of total volume. The total

volume of ash, both green and black, is 132.2 million cubic feet, or 18 percent of the total

volume on forest land. Ash is found throughout the State, with high densities in the Turtle

Mountain region and in west-central North Dakota, area including the Theodore Roosevelt

National Park and Wilderness, the Fort Berthold Indian Reservation, and the Little Missouri

National Grassland (Fig. 36). Ash is present on 507,700 acres, or 70 percent of North

Dakota’s forest land (Fig. 37). Although it generally makes up less than 25 percent of total

live-tree basal area (BA), in many areas ash represents more than 50 percent of total stand

basal area.

Ash is a major component of North Dakota’s woodland forests. It is also found in

shelterbelts and riparian areas and it is widely planted in North Dakota communities.

Human transportation of infested ash materials increases the risk of EAB introduction to the

State and therefore the potential impacts to statewide forest resources and forest industries.

Because ash is so abundant throughout the State, EAB would have a significant impact on

the structure and composition of North Dakota’s woodland, riparian, and community

forests. 

Background

What we found

What this means

Emerald Ash Borer
57

HEALTH

Figure 37.—Presence of ash on forest

land, expressed as a percentage of stand

basal area (ash BA per acre/total live BA

per acre), North Dakota, 2001-2005.

0

50,000

100,000

150,000

200,000

250,000

No ash 0.1 - 25.0 25.1 - 50.0 50.1 - 75.0 75.1 - 100.0

Basal Area (percent)

Total Forest Land (acres) 

Figure 36.—Density of all live ash trees

on forest land in North Dakota, 2001-

2005.
58

HEALTH

Dead and dying standing trees are important to numerous wildlife species. More than 85

species of North American birds are cavity nesters, and several dozen mammals also use

holes in trees for burrows and rearing of young. Nearly 40 percent of birds found in

midwestern forested areas are cavity nesters. In some areas of the northern plains, such as

North Dakota, it may be even more (North Dakota Outdoors 1994).

The abundance of standing dead or snag trees varies across the different forest types of

North Dakota (Fig. 38). For example, the average number of snags per acre in the aspen

forest type is higher (29.5) than what we find in the bur oak forest type (12.3). Many

factors contribute to the number of snags per stand including stand age, stocking levels,

and disturbances like insects, diseases, and weather. On average, there are an estimated

19.0 snags per acre on forest land in the State. Snags per acre differ by ownership as well

across the State (Fig. 39). Factors mentioned above along with different forest management

strategies will affect the number of snags per acre. 

North Dakota’s inventory data indicate a rich abundance of snags across all forest types that

provide important habitat for birds and mammals. In addition to providing nesting habitat

for cavity nesting birds, dead trees are used by great blue herons, cormorants, hawks, and

eagles as secure above-the-ground nest sites. Bats readily use the spaces under loose bark of

dead trees as places to raise young and gain protection from the elements. Chipmunks,

squirrels, raccoons, and weasels all will use holes in trees for raising young, hibernating, or

getting protection from the weather (North Dakota Outdoors 1994).

Background

What we found

What this means

Wildlife Habitat—Snags
59

HEALTH

Figure 39.—Standing dead trees by

ownership, North Dakota, 2005.

0 10 20 30 40 50 60

National Grassland

National Park Service

Bureau of Land Management

Fish and Wildlife Service

Other Federal

State

County and Municipal

Private

Ownership

Standing Dead Trees per Acre

Figure 38.—Standing dead trees by

select forest types, North Dakota, 2005.

0 5 10 15 20 25 30 35

Aspen

Cottonwood

Elm/ash

Elm/ash/cottonwood

Rocky Mountain juniper

Bur oak

Mixed upland hardwoods

Standing Dead Trees per Acre

Forest Type
60

HEALTH

The following summaries provide information on the general conditions of North Dakota’s

native forests. These narratives depict the factors that have led to the current condition of

these resources; they do not necessarily describe specific causal agents of tree/forest decline.

The information presented in this section was compiled from various sources and methods

including site visits, forest surveys, and personal communication with natural resource

professionals.

The elm/ash/cottonwood forest type is one of the most abundant of all native forest land

and is found along rivers throughout North Dakota. These forests have changed

significantly over the past decades due to damage caused by Dutch elm disease,

overgrazing, altered water flows, and conversion to nonforest.

Since Dutch elm disease was first detected in 1969, the disease has spread throughout

North Dakota. The American elm once was a major component of the State’s riparian forests

and occupied a wide range of sites. However, Dutch elm disease spread aggressively and

decimated the elm population that once made up a large portion of the riparian forests

along the Red, James, Sheyenne, and Pembina Rivers. In addition, the disease continues to

kill elms that grow in the wooded draws of western North Dakota. Although the American

elm has not been eliminated entirely from these forests, the species primarily persists as a

small understory tree, occupies a small proportion of the total stand basal area, and often

dies before reaching maturity. The loss of American elm dominance in these systems has

shifted the species composition toward green ash, boxelder, and other species. 

In addition to the impacts of Dutch elm disease, many riparian forests have been converted

to nonforest through agricultural and residential development particularly along the Red

River of eastern North Dakota. Other damaging factors include overgrazing and water flow

changes that can gradually reduce the vigor of existing trees and destroy understory woody

vegetation. Such forest changes and conversions adjacent to watercourses have important

implications for water quality, flood control, wildlife habitat, and recreation opportunities. 

The cottonwood forests that occur within the Missouri flood plain from Garrison Dam to

Lake Oahe are in a poor condition that has resulted from progressive mortality of mature

trees and the absence of natural regeneration to replace those that have died. Before flood

mitigation, the Missouri flood plain was periodicly inundated as high spring water flows

deposited sand in low-lying areas. These moist sandbars serve as seedbeds for cottonwood

and are critical for natural regeneration of the species (Burns and Honkala 1990). This

historical disturbance regime of periodic flooding drove the succession, distribution, and

age class structure of cottonwood forests along the flood plain (Ball 1997).

Riparian Forests

Forest Health Summary
61

HEALTH

In the absence of flooding and subsequent sandbar formation, there is limited cottonwood

regeneration to replace the overmature trees that have succumbed to old age and senescence.

As a result, the flood plain that once persisted as a fluctuating mosaic of backwater wetlands,

sandbars, and cottonwood forests now exists as a xeric, fire-prone flood plain bisected by a

channelized river. The cottonwood component of the Missouri flood plain may eventually die

out and give way to other tree species (both native and nonnative) with the exception of a few

isolated sites adjacent to the ever-deepening river channel.

Aspen/birch forests are abundant in the Turtle Mountains region and represent the State’s

largest concentration of forest land. Quaking aspen is the dominant species in these stands,

but paper birch, bur oak, and green ash can also be common on these sites.

A significant portion of this aspen resource can be characterized by low productivity, stem

decay, and large stem mortality that is associated with stand overmaturity. In the absence of

stand-replacing disturbances to encourage vigorous aspen regeneration, aspen stands age

and deteriorate over time as the result of numerous inciting, predisposing, and contributing

factors. These may include frost injury, drought, hail damage, windstorms, and several

forest pests. 

Forest pests such as defoliating insects, wood rotting fungi, and canker diseases also

contribute to the deterioration of these aspen stands. The Turtle Mountains are prone to

periodic defoliation episodes caused by the forest tent caterpillar. Defoliation reduces growth,

predisposes trees to other damaging agents, and exacerbates the senescence of aging aspen

stands. Internal decay of live aspen trees is common within mature aspen stands, particularly

those older than 60 years. Stem decay caused by the fungus Phellinus tremulae reduces the

amount of usable wood within a stand in addition to increasing the probability of stem

breakage. The wood volume loss due to this stem decay has been increasing as the aspen

resource continues to age in the Turtle Mountains. Similarly, mortality of large diameter trees

due to Hypoxylon canker contributes to the deterioration of older stands. 

The damage caused by these pests should not be perceived as unnatural but rather as a

reflection of a disturbance regime shift. Without disturbance (whether by fire, harvesting,

bulldozing, or other means) to encourage vigorous aspen regeneration, pests and

environmental factors deteriorate the aging aspen and give way to other species. Throughout

its western and eastern range, aspen is a pioneer species that is often succeeded (replaced) by

shade-tolerant conifer species in the absence of disturbance. However, many aspen forests of

the northern prairie regions of North America convert to shrubland where shade-tolerant

conifers do not naturally occur (Harniss 1981, Perala 1990). This successional scenario is

Aspen Forests
apparent within some areas of the Turtle Mountains where beaked hazel dominates the

understory of deteriorating aspen stands and prevents the establishment of other tree

species. 

In addition to the senescence of the aspen resource, many areas within the Turtle Mountains

have been converted to pastureland. This conversion may be driven in part by reduced

productivity and vigor of the stands coupled with a lack of harvesting opportunities for

private landowners. As a result, some private landowners are inclined to clear lowproduction forests and use the land for agricultural purposes that generate marginal

economic benefits. 

Fortunately, forest land owners have had a renewed interest in harvesting aspen in recent

years. Although clearcutting may look unappealing at first, the vigorous regeneration of

aspen that soon follows is important for the long-term perpetuation of this unique forested

resource. The young aspen stands that regenerate following harvest are beneficial to many

wildlife species.

Several animals, insect pests, and pathogens are found in the native ponderosa pine stands

of southwestern North Dakota. Of these, animal damage caused by deer and porcupines is

most apparent. Additionally, shoot death and branch dieback caused by western gall rust,

Diplodia shoot blight and canker, and pine pitch nodule maker are commonly encountered.

Such pests may lead to tree mortality if conditions favor repeated infections/infestations

over several years. Many pines weakened by these pests and other factors die following

colonization by pine engraver beetles or turpentine beetles. Despite the presence of pests,

these isolated pine stands are quite resilient and the level of tree mortality has remained low.

Perhaps the greatest concern in these areas has been wildfire. Years of past fire suppression

coupled with high stand density create conditions that may intensify fire behavior. These

wildfire concerns were realized when a large prairie fire spread into portions of the native

ponderosa pine stands of Slope County, ND, in September 2004. The fire (known as the

Deep Creek Fire) burned through approximately 800 acres of privately owned forest.

Mortality may reach 100 percent in stands that experienced high fire intensity with severe

needle scorching and stem charring, but estimations of tree mortality are uncertain in areas

that had less intense fires. The dense stocking and general low vigor of these stands suggest

that tree mortality could be significant within the following years. Survey plots were created

on these sites to assess delayed tree mortality during the following years. 

Ponderosa Pine

Forests

62

HEALTH
Forest Products

63 Wood chips. Photo by U.S. Forest Service.
Growing-stock volume is a measure of the amount of wood available for use in the

manufacturing of products such as lumber and paper. The definition of growing-stock

volume is the net volume of a growing-stock tree, 5.0 inches or greater d.b.h., from 1 foot

above the ground to a minimum 4.0-inch top. In other words, growing-stock volume is

wood volume in standing trees that are healthy, sound, reasonably straight, and have 

a diameter of at least 5 inches. Estimating volume is important when determining the

potential availability of wood for harvest (economic planning) and is an important 

measure when evaluating forest sustainability (forest management planning).

Growing-stock volume has increased steadily in North Dakota since 1980 and currently is

estimated at 366 million cubic feet (Fig. 40). Five species account for 95 percent of all

growing-stock volume in North Dakota: cottonwood, green ash, bur oak, quaking aspen,

and American elm (Fig. 41). Between 1994 and 2005, four of the top five species (all but

quaking aspen) increased in volume. Growing-stock volume currently averages 687 cubic

feet per acre, down by about 9 percent from the 1994 survey (Fig. 42). The decrease is 

due in large part to the increase in nonstocked timberland across the State (Fig. 43). Much

of the increase in growing-stock volume can be attributed to the growth of larger trees 

(Fig. 44).

Even though the growth of larger trees is the main reason for the increase in growing-stock

volume since 1980, riparian forest restoration and the gain of forested acres in North

Dakota have also contributed to this increase. 

Background

What we found

What this means

Growing-Stock Volume

64

PRODUCTS
65

PRODUCTS

Figure 41.—Net volume of growing stock

by select species group, 1994-2005.

0 20,000 40,000 60,000 80,000 100,000 120,000

American elm

Quaking aspen

Bur oak

Green ash

Cottonwood

Growing-stock Volume

(thousand cubic feet) 2005

1994

Species Group

Figure 40.—Total volume of growing

stock on North Dakota’s timberland, 

1954-2005.

0

50

100

150

200

250

300

350

400

450

1954 1980 1994 2005

Inventory Year

Growing-stock Volume 

(million cubic feet) 
66

PRODUCTS

Figure 43.—Acres of nonstocked

timberland, North Dakota, 1994

and 2005.

0

20

40

60

80

100

120

1994 2005

Inventory Year

Nonstocked Timberland 

(thousand acres) 

Figure 42.—Average growing-stock

volumes per acre of timberland in North

Dakota, 1954-2005.

0

100

200

300

400

500

600

700

800

1954 1980 1994 2005

Inventory Year

Growing-stock Volume per 

Acre (cubic feet)
67

PRODUCTS

Figure 44.—Distribution of growing-stock

volume by diameter class in North Dakota,

1994-2005.

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

6 8 10 12 14 16 18 20 22-28 29+

Diameter Class (inches)

Growing-stock 

Volume (thousand cubic feet)

1994

2005
68

PRODUCTS

Sawtimber is the wood in the saw log portion of a tree (main trunk between the stump and

the merchantable top, measured in board feet). Sawtimber volume is a measurement used

to determine the monetary value of wood volume in a tree or the amount of usable product

that might be manufactured from a given tree(s).

Sawtimber volume between 1954 and 1980 remained relatively unchanged. Between 

1980 and 2005, sawtimber volume steadily increased to more than 1.1 billion board feet 

(Fig. 45). Average sawtimber volume per acre in 2005 was 2,102 board feet, an increase of

233 board feet since 1994. Virtually all sawtimber volume is in hardwoods (Fig. 46), with

cottonwood, bur oak, and green ash accounting for more than 81 percent of all sawtimber

volume in the State.

Sawtimber volume continues to increase, with cottonwood volume doubling between 1980

and 2005. Sawtimber volume on timberland should be able to supply the forest product

industry in the State for years to come.

Background

What we found

What this means

Sawtimber Volume
69

PRODUCTS

Figure 46.—Percentage of total

sawtimber volume by species/species

group on timberland in North Dakota,

2005.

Figure 45.—Total sawtimber volume on

North Dakota’s timberland, 1954-2005.

0

200

400

600

800

1,000

1,200

1954 1980 1994 2005

Inventory Year

Sawtimber Volume

(million board feet)

Quaking aspen

12%

American basswood

1%

American elm

4%

Softwoods

<1%

Other hardwoods

2%

Bur oak

22%

Cottonwood

45%

Green ash

14%
70

PRODUCTS

North Dakota’s wood products manufacturing industries employ more than 2,000 workers

with an output of approximately $355 million (U.S. Census Bureau 2005). Most of the

wood product manufacturers in the State are secondary manufacturers, such as cabinet and

mill works. Much of their wood material originates from out-of-state sources. Sawmills are

the primary wood-using industry in North Dakota and utilize local timber. To properly

manage and sustain North Dakota’s forests, it is essential to have information about the

location and species of timber that will supply these mills. 

A mill survey was conducted of all known primary wood-using mills in North Dakota in

2003. The study included the size of the industry, the amount of roundwood harvested,

and its uses. Questions about the generation and distribution of wood residues were also

asked. The top three hardwood species harvested in the State were cottonwood, aspen, and

bur oak; the top softwood species harvested was spruce (Fig. 47). 

By product, saw logs accounted for 60 percent of all the roundwood produced, with

pulpwood making up the remaining 40 percent. Wood material harvested for industrial

roundwood on North Dakota’s forests was more than 400,000 cubic feet in 2003: 73

percent used for products, 17 percent was logging slash, and 10 percent was logging

residues.

In 2003, 73 percent of the State’s saw log production was exported to mills in Minnesota.

The remaining 27 percent went to mills in North Dakota. Totals from saw log mill receipts

from the 2003 survey illustrate that 100 percent of the wood coming into the mills is grown

in North Dakota.

A comparison of the 1998 and 2003 timber products inventories shows a decrease in

industrial roundwood production of 29 percent, which may be due in part to the closing of

one mill in the State. Even though the total active mills in North Dakota dropped slightly,

production capacity was changed considerably with the loss of this one mill. 

Cottonwood is still the most commonly harvested species in the State, partly because the

elm/ash/cottonwood forest-type group covers an estimated 165,000 acres of forest land and

cottonwoods are some of the State’s largest trees. In addition, there is also strong interest

from Minnesota’s timber industry.

Background

What we found

What this means

Timber Product Output
71

PRODUCTS

Figure 47.—Saw log production by select

species/species group, North Dakota,

2003. Other

<.3%

Ash

0.7%

Bur oak

1.2%

Aspen

2.8%

Cottonwood

95.0%

Data Sources and Techniques

73

Field crew member on plot in western North Dakota. Photo by Cassandra Olson, U.S. Forest Service.
Haugen (2003) described the annualized inventory methods for North Dakota. Since the

1994 inventory, several changes in FIA methods have improved the quality of the inventory

and have met increasing demands for timely forest-resource information. The most

significant change between inventories has been the shift from periodic to annual

inventories. Historically, FIA inventoried each state on a cycle that averaged about 12 years.

However, the need for timely and consistent data across large geographical regions along

with national legislative mandates resulted in FIA implementing an annual inventory. This

system was initiated in North Dakota in 2001.

With the NRS-FIA annual inventory system, approximately one-fifth of all field plots are

measured in any single year. After 5 years, the entire inventory is completed. After this

initial 5-year period, NRS-FIA will report and analyze results using a moving 5-year

average. For example, NRS-FIA will be able to generate inventory results for 2001 through

2005 or for 2002 through 2006. 

Other significant changes between inventories include implementing new remote-sensing

technology as well as a new field-plot configuration and sample design, and gathering

additional remotely sensed and field data. The use of new remote-sensing technology allows

NRS-FIA to use classifications of Multi-Resolution Land Characterization data and other

remote-sensing products to stratify the total area of North Dakota and to improve estimates.

New algorithms were used in 2001-2005 to assign forest type and stand-size class to each

condition observed on a plot. These algorithms are being used nationwide by FIA to

provide consistency from state to state and will be used to reassign the forest type and

stand-size class of every plot in the 1994 inventory when it is updated. As a result, changes

in forest type and stand-size class will reflect actual changes in the forest and not changes

due to differences between algorithms. The list of recognized forest types, groupings of

these forest types for reporting purposes, models used to assign stocking values to

individual trees, definition of nonstocked (stands with a stocking value of less than 10

percent for all live trees), and names given to the forest types changed with the new

algorithms. As a result, comparisons between the published 2001-2005 results and those

published for the 1994 inventory may be invalid. Contact NRS-FIA for additional

information on the algorithms used in both inventories. 

Forest Inventory 

74
The 2005 North Dakota inventory was conducted in three phases. In the first phase,

satellite imagery was used to stratify the State and aerial photography was used to select

plots for measurement. The second phase entailed measuring the traditional suite of

mensurational variables; the third phase focused on a suite of variables related to forest

health.

Land that could not be sampled included private tracts where field personnel were unable

to obtain permission to measure a Phase 2 plot and plots that were inaccessible because of a

hazard or danger to field personnel. The methods used in preparing this report were

adjusted to account for such sites.

For the North Dakota inventory, FIA used a classification of satellite imagery for

stratification. The imagery was used to form two initial strata: forest and nonforest. Pixels

within 60 m (2-pixel widths) of a forest/nonforest boundary formed two additional strata:

forest edge and nonforest edge. Forest pixels within 60 m of the boundary on the forest side

were classified as forest edge and pixels within 60 m of the boundary on the nonforest side

were classified as nonforest edge. All strata were divided into public or private ownership

based on information available in the Protected Lands Database (DellaSala et al. 2001). The

estimated population total for a variable is the sum across all strata of the product of each

stratum’s area (from the pixel count) and the variable’s mean per unit area (from plot

measurements) for the stratum.

Phase 2 of the inventory consisted of the measurement of the annual sample of field plots in

North Dakota. Current FIA precision standards for annual inventories require a sampling

intensity of one plot for approximately every 6,000 acres. FIA has divided the entire area of

the United States into nonoverlapping hexagons, each of which contains 5,937 acres

(McRoberts 1999). An array of field plots was established by establishing a plot in each

hexagon. This array of plots is designated the Federal base sample and is considered an

equal probability sample; its measurement in North Dakota is funded by the Federal

government.

Fieldwork for this inventory was expedited through the cooperation and assistance of the

North Dakota Forest Service.

The total Federal base sample was systematically divided into five interpenetrating, nonoverlapping subsamples or panels. Each year the plots in a single panel are measured, and

75

Sampling Phases

Phase 1

Phase 2
panels are selected on a 5-year, rotating basis (McRoberts 1999). For estimation purposes, the

measurement of each panel of plots may be considered an independent random sample of all

land in the State. Field crews measure vegetation on plots currently classified as forest by

trained photointerpreters using aerial photos or digital orthoquads.

NRS-FIA has two categories of field measurements: Phase 2 and Phase 3 field plots. Both

types are distributed systematically geographically and temporally. Phase 3 plots are measured

with the full array of vegetative and health variables as well as the full suite of measures

associated with Phase 2 plots. Phase 3 plots must be measured between June 1 and August 30

to accommodate measurement of nonwoody understory vegetation, ground cover, soils, and

other variables. The complete 5-year annual inventory of North Dakota includes seven

forested Phase 3 plots. On the remaining plots, only variables that can be measured

throughout the entire year are collected. In North Dakota, the complete 5-year annual

inventory includes 164 forested Phase 2 plots. 

The national FIA four-subplot cluster configuration (Fig. 48) was first used for data collection

in North Dakota in 2001 and will be used in subsequent years. The national plot

configuration requires mapping all forest conditions on each plot. Due to the small sample

size each year, precision associated with estimates of components of change such as mortality

will be relatively low. Consequently, we report estimates of components of change only after

multiple annual panels have been measured. With completion of the annual inventory in

2010, the full range of change estimates will be available.

The overall plot layout for the new configuration consists of four subplots. The centers of

subplots 2, 3, and 4 are located 120 feet from the center of subplot 1. The azimuths to

subplots 2, 3, and 4 are 0, 120, and 240 degrees, respectively. The center of the new plot is

located at the same point as the center of the previous plot if a previous plot existed at the

location. Trees that are 5 inches and larger in d.b.h. are measured on a 24-foot-radius (1/24-

acre) circular subplot. All trees less than 5 inches d.b.h. are measured on a 6.8-foot-radius

(1/300- acre) circular microplot located 12 feet due east of the center of each of the four

subplots. Forest conditions on each subplot are recorded. Factors that differentiate forest

conditions are changes in forest type, stand-size class, land use, regeneration status, reserved

status, ownership, and density. Each condition that occurs on one of the subplots is identified,

described, and mapped so long as the area of the condition is at least 1 acre. Field-plot

measurements are combined with Phase 1 estimates in the compilation process and table

production. The number of tables presented here is limited, but others can be generated at

http://fiatools.fs.fed.us. 

76

Phase 3
Program Manager, Northern Research Station, Forest Inventory and Analysis, 1992 Folwell

Avenue, St Paul, MN 55108 or State Forester, North Dakota Forest Service, Molberg Center,

307 1st Street East, Bottineau, ND 58318-1100.

The timber products inventory study was a cooperative effort between the North Dakota

Forest Service (NDFS) and the Northern Research Station (NRS) (Haugen and Harsel

2005). The NDFS canvassed all primary wood-using mills within the State using mail

questionnaires supplied by the NRS and designed to determine the size and composition of

North Dakota’s primary wood-using industry, its use of roundwood, and its generation and

disposition of wood residues. The NDFS then contacted nonresponding mills through

additional mailings, telephone calls, and personal contacts until a nearly 100 percent

response was achieved. Completed questionnaires were forwarded to NRS for compilation

and analysis.

As part of data processing and analysis, all industrial roundwood volumes reported on the

questionnaires were converted to standard units of measure using regional conversion

factors. Timber removals by source of material and harvest residues generated during

logging were estimated from standard product volumes using factors developed from

previous NRS logging utilization studies. Data on North Dakota’s industrial roundwood

receipts were added to a regional timber removals database and supplemented with data on

out-of state uses of State roundwood to provide a complete assessment of North Dakota’s

timber product output.

77

For additional

information, contact: 

Timber Products Output Survey

Figure 48.—Current NRS-FIA field-plot

design.
National Woodland Owner Survey

The National Woodland Owner Survey is conducted annually by the USDA Forest Service

to increase our understanding of private woodland owners – the critical link between

society and forests. Each year, questionnaires are mailed to individuals and private groups

who own the woodlands where NRS-FIA has established inventory plots (Butler et al.

2005). Twenty percent of these ownerships (about 50,000 nationwide) are contacted each

year with more detailed questionnaires mailed in years that end in 2 or 7 to coincide with

national census, inventory, and assessment programs. The target accuracies of the data are

plus or minus 10 percent at the state level.

Several bioindicator species have been tested in both laboratory and field settings over

several decades and have proven to be reliable indicators of ground-level ozone stress.

These include white ash, black and pin cherry, dogbane, milkweed, big leaf aster, and

blackberry. In North Dakota, the annual ozone biomonitoring by FIA began in 2002.

Foliar injury can be related to seasonal exposures as well as peak concentrations. Seasonal

exposures measure ozone stress by summing hourly concentrations above a threshold

concentration over several months. 

78

Ozone Bioindicator Species 
79

Amacher, M.C.; O’Neil, K.P.; Perry, C.H. 2007. Soil vital signs: new Soil Quality Index

(SQI) for assessing forest soil health. Res. Pap. RMRS-RP-65WWW. Fort Collins, CO: U.S.

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 12 p.

Ball, J.J. 1997. Restoration of bottomland forests: challenges and opportunities.

Proceedings of the North Dakota Academy of Science. Vol. 51, supplement 1: 40-43.

Burns, Russell M.; and Honkala, Barbara H., tech. coords. 1990. Silvics of North America:

1. Conifers; 2. Hardwoods. Agric. Handb. 654. Washington, DC: U.S. Department of

Agriculture, Forest Service. Vol. 2. 877 p.

Butler, Brett J.; Leatherberry, Earl C.; Williams, Michael S. 2005. Design, implementation,

and analysis methods for the National Woodland Owner Survey. Gen. Tech. Rep. NE336. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern

Research Station. 43 p.

Cappaert, D.; McCullough, D.G.; Poland, T.M.; Siegert, N.W. 2005. Emerald ash borer in

North America: a research and regulatory challenge. American Entomologist. 51(3): 152-

165.

Clyde, M.E. 2002. What is an invasive plant and why should we care? Habitats.

University of New Hampshire Cooperative Extension. Vol. 18. (1):1-2 

DellaSala, D.A.; Staus, N.L.; Strittholt, J.R.; et. al. 2001. An updated protected areas

database for the United States and Canada. Natural Areas Journal. 21(2): 124-135. 

Hahn, J.T. 1984. Tree volume and biomass equations for the Lake States. Res. Pap. NC250. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest

Experiment Station. 10 p.

Harniss, R.O. 1981. Ecological succession in aspen and its consequences on multiple

use values. DeByle, N.V., ed. Symposium proceedings, Situation management of two

intermountain species: aspen and coyotes. Aspen. Logan, UT: Utah State University: 31-39.

Vol. 1. 

Haugen, D.E. 2003. North Dakota forest resources, 2001. Res. Note NC-387. St. Paul,

MN: U.S. Department of Agriculture, Forest Service, North Central Research Station. 7 p.

Haugen, D.E.; Harsel, R.A. 2005. North Dakota timber industry: an assessment of timber

product output and use in 2003. Resour. Bull. NC-252 St. Paul, MN: U.S. Department of

Agriculture, Forest Service, North Central Research Station. 18 p. 

Literature Cited
80

Marschner, H. 1986. Mineral nutrition of higher plants. London: Academic Press. 674 p. 

McBride, M. 1994. Environmental chemistry of soils. New York: Oxford University Press.

406 p. 

McRoberts, R.E. 1999. Joint annual forest inventory and monitoring system, the North

Central perspective. Journal of Forestry. 97(12): 27-31. 

North Dakota Forest Service. 1991. Forest resource plan. Bottineau, ND: North Dakota

Forest Service. 47 p. 

North Dakota Forest Service. 2003. Lewis and Clark historic cottonwoods for purchase.

Bottineau, ND: North Dakota Forest Service. The Prairie Forester. 17(2): 1. 

North Dakota Forest Service. 2004a. Management of declining aspen. Bottineau, ND:

North Dakota Forest Service. The Prairie Forester. 18(3): 4. 

North Dakota Forest Service. 2004b. Tree tips: soils 101—physical properties of soil.

Bottineau, ND: North Dakota Forest Service. The Prairie Forester. 18(1): 5. 

North Dakota Outdoors. 1994. Bare trees. Bismarck, ND: State Game and Fish

Department. http://www.und.nodak.edu/org/ndwild/ndmag.html. 

Perala, D.A. 1990. Quaking aspen. In: Burns, Russell M.; Honkala, Barbara H., tech.

coords.1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agric .Handb. 654.

Washington, DC: U.S. Department of Agriculture, Forest Service: Vol. 2, 555-561 

Poland, Therese M.; McCullough, Deborah G. 2006. Emerald ash borer: invasion of the

urban forest and the threat to North America’s ash resource. Journal of Forestry: April

May: 118-124. 

Raile, G.K. 1982. Estimating stump volume. Res. Pap. NC-224. St. Paul, MN: U.S.

Department of Agriculture, Forest Service, North Central Forest Experiment Station. 4 p. 

Schomaker, Michael E.; Zanoch, Stanley J.; Bechtold, William A.; Latelle, David J.;

Burkman, William G.; Cox, Susan M. 2007. Crown-condition classification: a guide to

data collection and analysis. Gen. Tech. Rep. SRS-102. Asheville, NC: U.S. Department of

Agriculture, Forest Service, Southern Research Station. 78 p. 

Smith, W.B. 1991. Assessing removals for North Central forest inventories. Res. Pap.

NC-299. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest

Experiment Station. 48 p.
81

U.S. Department of Agriculture, Forest Service. 1999. Wood handbook – wood as an

engineering material. Gen. Tech. Rep. FPL-113. Madison, WI: U.S. Department of

Agriculture, Forest Service, Forest Products Laboratory. 463 p. 

U.S. Department of Commerce. 2005. 2002 Census of manufactures. Geographic area

series-North Dakota. EC02-31A-ND. Washington, DC: U.S. Department of Commerce.

Economics and Statistics Administration. Bureau of the Census. 

Warner, J.R.; Chase, C.D. 1956. The timber resource of North Dakota. Sta. Pap. No. 36.

St. Paul, MN: U.S. Department of Agriculture, Forest Service, Lake States Forest Experiment

Station. 39 p.

Woodall, Christopher W.; Monleon, Vicente J. 2008. Sampling protocol, estimation, and

analysis procedures for the down woody materials indicator of the FIA program. Gen.

Tech. Rep. NRS-22. Newtown Square, PA: U.S. Department of Agriculture, Forest Service,

Northern Research Station. 68 p.

Woodall, C.W.; Nagel, L.M. 2007. Downed woody fuel loading dynamics of a large-scale

blowdown in northern Minnesota, U.S.A. Forest Ecology and Management. 247: 194-

199.

Woodall, Christopher; Williams, Michael, 2005. Sampling protocol, estimation, and

analysis procedures for the down woody materials indicator of the FIA program. Gen.

Tech. Rep. NC-256. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North

Central Research Station. 47 p.
82

About the Authors

David E. Haugen is a Forester with the Forest

Inventory and Analysis Program, Northern

Research Station, St. Paul, MN.

Mike Kangas is a Forest Health Specialist with the

North Dakota Forest Service, North Dakota State

University, Fargo, ND.

Susan J. Crocker is an Entomological Specialist

with the Forest Inventory and Analysis Program,

Northern Research Station, St. Paul, MN. 

Charles H. Perry is a Research Soil Scientist with

the Forest Inventory and Analysis Program,

Northern Research Station, St. Paul, MN.

Christopher W. Woodall is a Research Forester

with the Forest Inventory and Analysis Program,

Northern Research Station, St. Paul, MN. 

Brett J. Butler is a Research Social Scientist with

the Forest Inventory and Analysis Program,

Northern Research Station, Amherst, MA.

Barry T. Wilson is a Research Forester with the

Forest Inventory and Analysis Program, Northern

Research Station, St. Paul, MN. 

Dan Kaisershot is a GIS Specialist with the Forest

Inventory and Analysis Program, Northern

Research Station, St. Paul, MN.
Haugen, David E.; Kangas, Michael; Crocker, Susan J.; Perry,Charles H.; Woodall, Christopher W.;

Butler, Brett J.; Wilson, Barry T.; Kaisershot, Dan J. 2009. North Dakota’s forests 2005. Resour.

Bull. NRS-31. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern

Research Station. 

82 p.

The first completed annual inventory of North Dakota’s forests reports estimates of more than

724,000 acres of forest land. Information about forest attributes and forest health is presented along

with information on agents of change including changing land use patterns and the introduction of

nonnative plants, insects, and disease.

KEY WORDS: inventory, forest statistics, forest health

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

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status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for

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(202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th

and Independence Avenue, SW, Washington, DC 20250-9410, or call (202) 720-5964 (voice or TDD). USDA is an equal

opportunity provider and employer.
“Capitalizing on the strengths of existing science capacity

in the Northeast and Midwest to attain a more integrated,

cohesive, landscape-scale research program”