United States

Department of 

Agriculture

Forest Service

Pacific Northwest

Research Station

General Technical

Report

PNW-GTR-642

August 2005

Productivity of Western

Forests: A Forest 

Products Focus
TECHNICAL EDITORS

Constance A. Harrington, research forester, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research

Station, Forestry Sciences Laboratory, 3625 93rd Ave. SW, Olympia WA 98512, and Stephen H. Schoenholtz, associate 

professor, Department of Forest Engineering, Oregon State University, Corvallis, OR 97331.

Cover Photography by Constance A. Harrington, U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station, Forestry Sciences Laboratory, Olympia WA 98512

Graphic designer: Jenny Beranek, Beaverton, OR 97006

Papers were provided by the authors in camera-ready form for printing. Authors are responsible for the content and accuracy.

Opinions expressed may not necessarily reflect the position of the U.S. Department of Agriculture. 

The use of trade or firm names is for information only and does not imply endorsement by the U.S. Department of A g r i c u l t u r e

of any product or service.

PESTICIDE PRECAUTIONARY STATEMENT

This publication reports research involving pesticides. It does not contain recommendations for their use, 

nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered 

by appropriate state or federal agencies, or both, before they can be recommended. 

CAUTION: Pesticides can be injurious to humans, domestic and wild animals, and desirable plants if they

are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices

for the disposal of surplus pesticides and pesticide containers.
Productivity 

of Western 

Forests: A Forest

Products Focus

Constance A. Harrington 

and Stephen H. Schoenholtz, 

Technical Editors

U.S. Department of Agriculture

Forest Service

Pacific Northwest Research Station

Portland, Oregon

General Technical Report

PNW-GTR-642

August 2005
This page is intentionally left blank.
ABSTRACT

Harrington, Constance A.; Schoenholtz, Stephen H., eds. 2005. Productivity of Western forests: a forest products focus. 

Gen. Tech. Rep. PNW-GTR-642. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest

Research Station. 176 p.

In August 20-23, 2004, a conference was held in Kamilche, WA, with the title “Productivity of Western Forests: A Forest

Products Focus.” The meeting brought together researchers and practitioners interested in discussing the economic and

biological factors influencing wood production and value. One of the underlying assumptions of the meeting org a n i z e r s

was that management activities would be practiced within a framework of sustaining or improving site productivity; thus,

several papers deal with methods to protect or improve productivity or discuss new studies designed to test the effects o f

various practices. This proceedings includes 11 papers based on oral presentations at the conference, 3 papers based on

posters and 2 papers describing the Fall River and Matlock Long-Term Site Productivity study areas visited on the field

tours. The papers cover subjects on forest harvesting activities, stand establishment, silviculture, site p r o d u c t i v i t y, remote

sensing, and wood product technologies.

K E Y W O R D S: Site productivity, forest harvesting, stand establishment, silviculture, forest products, Western forests,

LIDAR, log quality, tree quality.
PREFACE

During September 20-23, 2004, we held a conference, “Productivity of Western Forests: A Forest Products Focus,” at the

Little Creek Hotel and Casino in Kamilche, Washington. The conference was sponsored by Oregon State University College

of Forestry, Pacific Northwest Research Station, Western Forestry and Conservation Association, and Northwest Forest Soils

Council. The primary goal of the conference was to bring together people interested in managing Western forests for the

production of forest products. Many conferences held in recent years have focused on managing forests for wildlife habitat,

b i o d i v e r s i t y, or other nontimber objectives, but there has been relatively limited current information available on (1) markets

for wood products, (2) contemporary harvesting operations, (3) silvicultural practices (especially for stand establishment),

and (4) emerging technologies for remote measurement of trees and determination of stand and log characteristics that

influence marketability.

The main members of the steering committee were: Stephen Schoenholtz, committee chair, Oregon State University;

Bernard Bormann, Pacific Northwest Research Station; David Briggs, University of Washington; Scott Chang, University 

of Alberta; Mike Curran, British Columbia Ministry of Forests; Randall Greggs, Green Diamond Resource Company;

Connie Harrington, Pacific Northwest Research Station; Tim Harrington, Pacific Northwest Research Station; Rob

Harrison, University of Washington; Ron Heninger, Weyerhaeuser Company; Bob Powers, Pacific Southwest Research

Station; Tom Te r r y, Weyerhaeuser Company; Eric Turnblom, University of Washington; Joanna Warren, Oregon State

University; and Richard Zabel, Western Forestry and Conservation Association. Additional input was provided by Debbie

Page-Dumroese, Rocky Mountain Research Station.

Conference organizers wanted to highlight potential effects of forest practices on short- and long-term productivity. This

was accomplished through a preconference tour of the Fall River Long-Term Site Productivity Study (west of Chehalis,

Washington) and a midconference tour of the Matlock Long-Term Site Productivity Study (west of Shelton, Wa s h i n g t o n ) .

The midconference tour also visited the Simpson Timber Company small-log mill at Dayton, Washington, and attendees

had the opportunity to participate in demonstrations of new equipment for testing wood quality in standing trees and logs.

The conference included 17 invited talks, 10 poster presentations, and 2 tours. Speakers were invited to submit a

paper; poster presenters and field-trip organizers were invited to submit an abstract or mini-paper. Eleven speakers, three

poster presenters, and two field-trip presenters responded to our invitation to contribute to this proceedings. The papers that

follow are organized by topic area in the order that they were presented at the conference, followed by the posters in alphabetical order, and then by summaries of the two field-trip stops at the Fall River and Matlock study sites.

We thank Grace Douglass and Joseph Kraft for assistance in preparing the manuscripts for publication.

This is a product of the Sustainable Forestry Component of Agenda 2020, a joint effort of the USDA Forest Service

Research & Development and the American Forest and Paper Association. Funds were provided by the Forest Service

Research & Development, Washington Office.

We hope you find the information to be timely and of interest.

Constance A. Harrington Stephen H. Schoenholtz

Pacific Northwest Research Station Oregon State University 
Productivity of Western Forests: A Forest Products Focus

CONTENTS

HARVESTING

Harvesting Effects on Soils, Tree Growth, and Long-Term Productivity 3

Michael P. Curran, Ronald L. Heninger, Douglas G. Maynard, and Robert F. Powers

Harvest Planning to Sustain Value Along the Forest-to-Mill Supply Chain 17

Glen Murphy and Paul W. Adams

STAND ESTABLISHMENT

Silvicultural Technology and Applications for Forest Plantation Establishment West of the 

Cascade Crest 27

Timothy B. Harrington and Jeff Madsen

State-of-the-Art Silvicultural Technology and Applications for Forest Stand Establishment in 

Interior British Columbia 39

John McClarnon and R. Allan Powelson

Stand Establishment and Tending in the Inland Northwest 47

Russell T. Graham, Theresa B. Jain, and Phil Cannon

SILVICULTURAL TOPICS

Linkage Between Riparian Buffer Features and Regeneration, Benthic Communities, and Water 

Temperature in Headwater Streams, Western Oregon 81

Michael Newton and Elizabeth C. Cole

Slenderness Coefficient Is Linked to Crown Shyness and Stem Hydraulics in Lodgepole Pine 103

Victor J. Lieffers and Uldis Silins

WOOD PRODUCTS AND EMERGING TECHNOLOGIES

Forest Measurement and Monitoring Using High-Resolution Airborne LIDAR 109

Hans-Erik Andersen, Robert J. McGaughey, and Stephen E. Reutebuch

Acoustic Testing to Enhance Western Forest Values and Meet Customer Wood Quality Needs 121

Peter Carter, David Briggs, Robert J. Ross, and Xiping Wang

Does Lumber Quality Really Matter to Builders? 131

Ivan L. Eastin

Assessing and Managing Stands to Meet Quality Objectives 141

David Briggs
PAPERS BASED ON POSTERS

Carbon Sequestration in Douglas-Fir Stands of the Coastal Coniferous Forest Region 

of Washington State 155

A.B. Adams, R.B. Harrison, M.M. Amoroso, D.G. Briggs, R. Collier, R. Gonyea, B. Hasselberg, 

J. Haukaas, and M.O. O’Shea

Volumetric Soil Water Content in a 4-Year-Old and a 50-Year-Old Douglas-Fir Stand 161

Warren D. Devine, Constance A. Harrington, and Thomas A. Terry

Factors Affecting Nitrogen Mobility: Organic Matter Retention and Variable-Charge Soils 165

Brian D. Strahm, Robert B. Harrison, Thomas A. Terry, Barry L. Flaming, Christopher W. Licata, 

and Kyle S. Petersen

OVERVIEW OF STUDY AREAS ON FIELD TRIPS

Fall River Long-Term Site Productivity Study 169

Constance A. Harrington, Thomas A. Terry, and Robert B. Harrison

Forest Productivity Responses to Logging Debris and Competing Vegetation: Effects of Annual 

Precipitation and Soil Texture 173

Timothy B. Harrington, Constance A. Harrington, and Stephen H. Schoenholtz

METRIC-ENGLISH EQUIVALENTS 176
HARVESTING
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1 Michael P. Curran, corresponding author, research soil scientist, B.C. Ministry of Forests, Forest Sciences Program, Kootenay Lake Forestry Centre, 

1907 Ridgewood Rd., Nelson, BC, Canada, V1L 6K1. (also adjunct professor, Agroecology, University of B.C.). Phone: 250-825-1100. 

E-mail: mike.curran@gems5.gov.bc.ca 

2 Ronald L. Heninger is a senior scientist, Weyerhaeuser Company, P.O. Box 275, Springfield, OR, USA. 97478-5781

3 Douglas G. Maynard is a research scientist, Natural Resources Canada, Canadian Forest Service, 506 West Burnside, Victoria, BC, Canada, V8Z 1M5 

4 Robert F. Powers is a program manager, USDA Forest Service, Pacific Southwest Research Station, 2400 Washington Ave., Redding, CA. 96001 

Productivity of Western Forests: A Forest Products Focus, Chapter One

HARVESTING EFFECTS ON SOILS, TREE GROWTH, 

AND LONG-TERM PRODUCTIVITY

Michael P. Curran1, Ronald L. Heninger2, Douglas G. Maynard3, and Robert F. Powers4

INTRODUCTION

For forest productivity, sustainable development can be

defined as ensuring the biological, chemical and physical

integrity of the soil remains for future generations. Sustainability must be addressed throughout all facets of forest

management including implementation of individual harvest

or stand-tending plans, development of agency or company

standards and best management practices (BMPs), and thirdparty certification. Sustainable development is promoted

through reporting procedures required by applicable sustainability protocols, and by having third-party certification

of forest practices and products.

ABSTRACT

Soil disturbance related to timber harvesting, reforestation, or stand tending is mainly a result of moving equipment 

and trees. Compaction and organic matter removal are of primary concern. Severity and extent of disturbance depend on

harvest system, soil and climatic conditions. On-site, long-term effects range from permanent loss of growing sites to roads,

to more subtle changes in soil properties that ultimately influence site productivity. Off-site effects may include erosion and

landslides. Soil disturbance during operations is regulated and monitored to minimize both on- and off-site effects, which can

take years or decades to appear. At national and international levels, sustainability protocols recognize forest soil disturbance as an important issue. At the regional level, continual monitoring and testing of standards, practices, and effects, is

necessary for the successful implementation of sustainable soil management. In western forests, few studies are old enough

to conclusively predict the long-term effects of harvest-induced soil disturbance on tree growth. Results from existing longand short-term studies have demonstrated a full range of possible productivity outcomes. The net effect depends on which

growth-limiting factors have been influenced by disturbance. Refinement of policies will occur as existing studies like the

Long-term Soil Productivity (LTSP) network reach critical, predictive stand ages. In the interim, some regional trends are

apparent: deeply developed, moderately coarse textured soils appear less sensitive to disturbance. Conversely, shallower

and/or finer textured soils appear more sensitive. 

KEYWORDS: Criteria and indicators, organic matter depletion, soil disturbance, soil compaction, sustainability protocols.

3

Sustainability protocols exist at international and national

levels. At the international level, the Montreal Process (MP)

includes a Working Group on Criteria and Indicators for the

Conservation and Sustainable Management of Temperate

and Boreal Forests (Montreal Process Working Group 1997).

Some countries have developed their own protocols and procedures designed to track and report progress toward meeting requirements of international protocols such as the MP.

For example, the Canadian Council of Forest Ministers

recently developed revised criteria and indicators for sustainable forest management (CCFM 2003).
Third-party (eco) certification of forest practices and

resulting wood products has arisen in response to sustainability protocols and the greening of the global market

place. Organizations such as Sustainable Forestry Initiative

(American Forest and Paper Association), Canadian Standards Association, Forest Stewardship Council (FSC), and

ISO 1400.1 all have documented review processes and procedures for certification. Protecting streams and natural

drainage patterns, maintaining slope stability, and regulating soil disturbance are common elements considered. In

addition, most require some adaptive management process

to ensure continuous improvement of practices on the

ground. Compliance with current soil disturbance standards

is often used as a proxy for ensuring sustainability. Some

call for more restrictive standards than others (e.g., FSC in

British Columbia calls for lower disturbance levels than

Provincial regulations). 

When managing harvest effects on soils, tree growth and

long-term productivity at the local level, managers usually

focus on reducing soil disturbance from mechanical operations. Soil disturbance occurring at time of harvest can have

negative, positive, or no detectable effect on growth or

hydrologic function. Soil disturbance at the time of operations is often an indicator used in regulating long-term productivity and hydrologic effects. This is because in many

North American ecosystems, we need at least 10 to 20 years

of data to draw conclusions about the effects of various

practices. In discussing evidence for long-term productivity

changes, Morris and Miller (1994) indicated slow-growing

stands require 20 or more years of growth before long-term

productivity consequences can be ascertained. Soil disturbance is the proxy that we can observe and regulate at the

time of harvesting, site preparation, etc. A common approach

is needed for describing soil disturbance so that results

achieved in different areas are comparable (Curran et al. 

in prep.).

In this paper, we discuss effects of harvest induced soil

disturbance on subsequent tree growth. Long-term productivity implications are explored along with some soil considerations in harvest planning and continuous improvement

schemes. More detailed discussion of these effects and

practical interpretations are provided in the literature that

has been cited, guidebook materials available from government agencies like the B.C. Ministry of Forests (http://www.

g o v.bc.ca/for), the USDA Forest Service (http://www. f s . f e d .

us/), various University extension websites, and related

products like the new Forestry Handbook for B.C. (soils

chapter by Krzic and Curran, in press).

HARVESTING EFFECTS ON SOILS

Soil disturbance can be defined as any physical, biological, or chemical alteration of the soil caused by forestry

operations. The examples of soil disturbance we provide

here are primarily related to harvesting activities. Effects

on tree growth may be inconsequential, beneficial or detrimental, depending on the net effect on growth-limiting

factors and hydrologic properties. Soil disturbance can be

considered in the context of: (1) the necessary permanent

access network and (2) disturbance that occurs within individual harvest areas that will be reforested and managed 

as forest land. 

Permanent Access Network (Roads, Trails, Landings)

The permanent access network is part of the infrastructure required to transport timber and manage forest land.

Standards are in place for transportation system development because it represents a permanent removal of growing

sites from the land base, and can have long-term effects both

on- and off-site. Effects can include drainage interception

and disruption, as well as erosion and sediment delivery 

to streams, which can affect other resource values, and can

also cause property damage and possibly loss of life in catastrophic events. These are all good reasons to minimize

the amount of forest land lost to permanent access.

In-Block Disturbance (Area to be Reforested)

Most in-block soil disturbance is the result of harvest

equipment and dragging logs. Effects of soil disturbance

depend on harvest method and season of operation. Groundbased harvesting typically creates more disturbance than

aerial or cable. Wet season harvest is typically more disturbing than dry season harvest, or winter condition harvest

(where that option exists). Severity and extent of in-block

disturbance can be controlled or minimized through careful

harvest planning and practices. Guidelines, regulations and

standards often limit types and extent of disturbance and

commonly focus on compaction and displacement.

Fully mechanized harvest activities, where fellerbuncher and grapple skidder operations are allowed off

main skidtrails, can result in high amounts of soil disturbance. Examples of the type and amounts of soil disturbance that can occur from this type of harvest are shown in

figure 1. Total machine traffic coverage on the soil ranged

from 49% to 62 %. The amount of concentrated disturbance

complied with the guidelines at the time of harvest. Repair

of concentrated disturbance is often possible with rehabilitation techniques; however, extensive off-trail disturbance

is more problematic if it has damaged the soil. The main

concern with off-trail traffic is compaction.

4
Compaction and Puddling

Compaction and puddling result in alteration and/or loss

of soil structure with the affected soil often appearing coarse

platy or massive (figure 2). Guidelines define thresholds for

compaction severity and spatial extent, beyond which it is

generally thought to have a long-term effect on forest productivity or hydrologic function. Compaction results from

the weight and vibration of heavy equipment and dragging

of logs. Important effects of compaction on forest soils are:

1. Soil density and strength are often increased,

2. Soil macro-porosity is often decreased, and 

3. Soil infiltration is often decreased.

Bulk density increases are often measured in terms of

total soil or fine fraction bulk density. Neither of these may

be a true measure of other effects (e.g., soil porosity and

penetration resistance) because trafficking sometimes incorporates considerable amounts of organic matter in the soil.

Incorporation of forest floor and other organic material into

a soil can result in increased puddling of soils due to claysized particles settling under wet conditions, or being

smeared by equipment traffic. 

Penetration resistance can be a good measure of relative

compaction and conditions of high soil strength can restrict

root growth. However, penetrometer readings are dependent

on soil moisture content at the time and observations are

affected by soil texture, and the amount of coarse fragments and roots. Figure 3 shows how compaction increases

soil strength as measured by penetration resistance. Soil

moisture content often varies between disturbance types due

to differences in hydrologic properties (discussed below).

However, while strength is affected by soil moisture and

clay content, soils in areas severly disturbed invariably test

higher than undisturbed soil, regardless of soil moisture.

Figure 3 also demonstrates that most compaction occurs in

the top 20 cm. Compaction increases with increasing traffic, and most compaction occurs during the first trips over

the same piece of ground; as few as three passes can result

in most of the compaction. 

Perhaps the most important compaction effect is alteration of soil porosity, due to the collapse or distortion of

large macro-pores. Soil compaction increased bulk density

on a loam soil resulting in an overall decrease in aeration

porosity and slight increases in available and unavailable

water (figure 4). Less biological activity occurs as aeration

porosity decreases. Once aeration porosity drops below 10%

(at 0.01 MPa tension in a standard laboratory test) gas

diffusion in the soil is essentially zero (Xu et al. 1992). T h i s

is thought to be a result of the tortuous nature of remaining

large soil pores and restrictions in the necks between pores.

Another potential result of soil compaction is altered

hydrologic function. Saturated hydraulic conductivity can

decrease substantially in compacted soils (fig. 5). Infiltration decreases in compacted soil can result in increased

surface runoff and consequently less water storage. Soil

compaction may or may not impact plant growth detrimentally. Gomez et al. (2002), Powers (1999) and Powers et al.

(in review) found that for sandy soils and drier sites, compaction actually improved growth by improving water

a v a i l a b i l i t y. Interestingly, soil microbial activity may be

u n a ffected by soil compaction. Unless soils are poorly

drained, microbial activity probably continues unabated in

5

Figure 1—An example of soil disturbance coverage from mechanized harvesting in the Southern Rocky Mountain Trench British Columbia, 1991

(Curran 1999). (LL = light traffic trails; HL = heavy traffic trails – main

skid roads; 1 = 5 & 10 cm deep ruts; L at Chain of Lakes includes both

LL and HL.)

Figure 2—Close-up of an example of significant compaction from a heavy

traffic trail at the Perry Creek site (see Fig. 1). Note the coarse platy structure that often results from heavy compaction of these study soils.
small soil pores and micro-aggregates that are not reduced

by compaction (Shestak and Busse 2005).

Severity and extent of compaction are determined by

both controlling and manageable factors (modified from

Lewis et al. 1989). 

Controlling factors are those inherent to the harvest site

and include: 

• texture, 

• coarse fragments, 

• forest floor depth/type, 

• soil depth, and

• mineralogy.

Manageable factors can be controlled through harvest

planning and include: 

• machine traffic, 

• machine type/dynamic loading, 

• seasonal soil conditions (wetness, snow,

frozen soil), and

• machine operator awareness, training, and skill. 

Various hazard, or risk (hazard times consequence) rating schemes have been developed to evaluate the susceptibility of soils to compaction. One example that focuses on

controlling site factors is the B.C. Ministry of Forests compaction hazard key (Curran et al. 2000).

6

Figure 4—Effect of soil compaction on pore size distribution

and water availability, Cohasset Loam studied by SiegelIssem et al. (2005).

Figure 3—Iron Canyon soil monitoring to determine disturbance severity following second harvest. Penetrometer

profiles by disturbance class, October 2002 (21% soil moisture), and January 2003 (45 % soil moisture) (Unpublished data on file at the USFS, PSW Research Station, Redding, California.)
Effects of soil compaction can persist for decades

(Froehlich et al. 1985), so concern about cumulative effects

is important when planning harvest activities. Figure 6

shows there are no trees growing in a heavily used skid

trail about 40 years following initial logging. Successive

harvest entries can add to already existing compaction and

displacement. Figure 7 shows changes from pre- to postharvest for the area shown in fig. 6. Skid trail coverage

nearly doubled, general disturbance increased nearly threefold, and undisturbed ground fell to one-third its previous

extent. Lacking careful supervision, cumulative impacts

will occur during ground-based operations.

Displacement

Displacement is the removal of mineral topsoil and forest floor layers from tree-growing sites. It is also a result 

of machine traffic or dragging of logs. Most organic matter

and nutrients needed to sustain plant growth are in the developed topsoil, which varies in depth depending on local soil

development. Displacement can result in a loss of available

nutrients and effective rooting volume. In addition, it can

expose subsoils that are less favourable growing sites (e.g.,

dense or coarse parent materials). Loss of water-holding

capacity, exposure of subsurface seepage, increased runoff,

and drainage diversion can also occur and affect off-site

7

Figure 5—Saturated hydraulic conductivity on soil disturbance types from the mechanized harvesting study shown

in Fig. 1 (Curran 1999). (U = undisturbed; VL = light

traffic trails; HT = heavy traffic trails – main skid roads;

1 = 5 & 10 cm deep ruts).

Figure 6—Photo of old 1960’s era skid trail in the Iron Canyon study site

before the recent harvest study. Note lack of tree growth on this trail.

Figure 7—Iron Canyon soil disturbance monitoring pre- and post-harvest

showing increase in disturbance following the second harvest entry (Unpublished data on file at the USFS, PSW Research Station, Redding, California.)
values as well. Thus, displacing topsoil an appreciable distance may lower site productivity through loss of available

nutrients and effective rooting volume. Dyck and Skinner

(1990) found that the overall productivity of a plantation

where topsoil had been windrowed was only two-thirds that

of an adjacent, non-windrowed plantation.

Severity and extent of displacement are also influenced

by controlling and manageable factors (modified from

Lewis et al. 1989). 

Controlling factors include: 

• slope, 

• topography,

• soil depth, and 

• subsoil type. 

Manageable factors include: 

• amount and extent of excavation, 

• machine size/type, 

• seasonal soil conditions (wetness, snow,

frozen soil), and

• machine operator awareness, training, and skill.

Few hazard or risk (hazard times consequence) rating

schemes are available to evaluate soil susceptibility to displacement. Examples that focus on controlling site factors

are the B.C. Ministry of Forests soil displacement and forest floor displacement hazard keys (Curran et al. 2000).

Best Management Practices Components: Harvesting

Effects on Soils

Careful planning is required to manage effects of harvest

activities on soils. Planning should be based on guidelines

and standards that limit specific kinds of soil disturbance

and reduce potential for cumulative effects on productivity

and hydrologic function. Disturbance from in-block disturbance is often regulated based on inherent sensitivity of the

site/soil, with corresponding disturbance criteria and limits

that are normally set for temporary access and soil disturbance in the area to be reforested. The most manageable

factor may be operator training, awareness, and skill. Managing soil disturbance requires the following best management practice (BMP) components:

BMP components include:

1. site characterization, 

2. detailed soil inventory,

3. harvesting strategies to meet soil disturbance 

standards based on the local soil susceptibility to 

disturbance,

4. considerations for climatic constraints (e.g., wet

soils), or opportunities (e.g., snowpack),

5. monitoring of resulting soil disturbance, 

6. restorative treatments for disturbance that is either

over prescribed limits or preferably, pre-planned 

for rehabilitation, and

7. communication and information exchange 

(feedback loops) amongst the various level above, 

to enable continuous improvement of standards 

and practices.

Each of these components is discussed below.

Site characterization (1), and soil mapping of the area

(2) are done either during the planning phase for the harvest cycle (e.g., methods in British Columbia described in

Curran et al. 2000), or as a ground-checked resource inventory of the entire management area (this is more commonly

done in the US Pacific Northwest area). With appropriate

interpretations, soil mapping alerts harvesters about the

amount of care needed to avoid excessive soil disturbance,

when to schedule operations, and what portions of an area

are most or least operable in wet weather.

Harvesting strategies (3) have been described for meeting soil disturbance standards under site conditions in western Washington and Oregon by Heninger et al. (1997) and

for Interior British Columbia by Curran (1999). The objective is to match equipment capabilities to site sensitivity to

disturbance, while providing considerations for climatic

constraints (4) (e.g., avoiding wet soils), or opportunities

(e.g., using a snowpack to reduce compaction and/or 

displacement).

Monitoring of resulting soil disturbance (5) follows

established methods of measuring the occurrence of specific disturbance types along transects. A working group of

the NW Forest Soils Council is currently working towards

common disturbance criteria to facilitate comparison and

exchange of soil disturbance information (Curran et al. in

prep.). Classification systems that are considered to meet

desirable criteria, including visually identifiable disturbance

types, have been successfully used by the British Columbia

Ministry of Forests (Forest Practices Code Act 1995) and

Weyerhaeuser Company (Scott 2000), and are currently

under developmental use in the U.S. Forest Service Region

6 (Pacific Northwest Region). These classification systems

are successfully combined in monitoring protocols to determine severity and areal extent of soil disturbance after opera t i o n a l harvesting (B.C. Ministry of Forests 2001, Heninger

et al. 2002). 

Restorative treatments for disturbance (6) are required

either when disturbance levels are over prescribed limits or

preferably, in areas that were pre-planned for rehabilitation.

8
On the right sites, and with appropriate technique, rehabilitation can be an economical and environmentally responsible way to achieve logging efficiency without compromising

long-term forest productivity or hydrologic function. (In

fact, it can be hard to tell a trail or road existed previously

without digging in the soil.) Techniques have been described

in the literature, and prescribed in standards or policy guidel i n e s (e.g., B.C. Ministry of Forests 1997), field cards and

videos (e.g., Curran 1998). Procedures for successful rehabilitation usually involve both construction and deconstruction phases. 

Construction usually includes:

• stockpiling of topsoil for later re-spreading, 

• construction of the structure involved out of 

the subsoil. 

Drainage control needs to be considered during 

construction, to control runoff during harvest but 

also during and after rehabilitation. 

Rehabilitation involves:

• removing large cribbed-in (incorporated) woody

debris, 

• de-compaction through some form of tillage 

(e.g., Fig. 8), 

• replacement of topsoil layers, 

• covering with logging slash similar to the 

surrounding cutblock area (Fig. 9),

• re-vegetation similar to surrounding cutblock 

area, and

• use of erosion control mulches or seeding if 

erosion or sedimentation are concerns.

Rehabilitation of disturbed soils can fully restore the

growth potential to that of undisturbed soil, provided the

rehabilitation activities are done at the right time. However,

not all soils, or all soil disturbances, are conducive to rehabilitation. For example, soil rehabilitation resulted in variable effectiveness in ameliorating compacted soils in a study

on Vancouver Island (Maynard and Senyk 2004). In deep,

well-drained soils, tilling reduced bulk density to below

levels of undisturbed soils and in the short-term improved

growth. In contrast, under wetter site conditions rehabilitation decreased survival and growth of seedlings. Other examples where rehabilitation is difficult or very costly include

wet clayey-textured soils or where extensive rutting covers

the entire harvest area. Rehabilitation is best used as a preplanned activity for main trails and other temporary access

like spur roads and landings that are not needed until the

next harvest cycle.

Communication and information exchange (feedback

loops) amongst the various levels above, should enable

continuous improvement of standards and practices (7 from

list on page 8) and be part of an adaptive management system used by each agency responsible for managing soil disturbance and its effects on site productivity and hydrologic

function. Strategic databases are needed where disturbance

types are tracked in relation to actual tree growth effects on

long-term monitoring and research sites. Components for

this process are discussed by Curran et al. (in prep.).

9

Figure 8—Decompaction of a logging trail before soil replacement during

rehabilitation treatment. (Weyerhaeuser example)

Figure 9—Re-spreading slash onto logging trail as final stage of rehabilitation. (Weyerhaeuser example)
RESULTING TREE GROWTH EFFECTS

Soil disturbance effects on tree growth depend on the

growth-limiting factors influencing trees on a given growing site. Disturbance may both positively or negatively influe n c e a tree’s growing environment, with the net result being

determined by which factor is most limiting to growth. 

Growth limiting factors that are often positively 

influenced by harvesting soil disturbance include: 

• competing vegetation, 

• soil moisture, 

• soil temperature, and/or 

• air temperature (frost). 

Growth limiting factors that are often negatively 

influenced include: 

• aeration, 

• soil penetration resistance, 

• soil moisture availability or storage, and/or

• soil nutrients (e.g., nitrogen falling below 

critical thresholds).

Tree growth effects reflect the tremendous variability 

of climates and growing sites in the Pacific Northwest and

it can be difficult to draw strong conclusions regarding specific types and severity of soil disturbances and tree growth.

It is often necessary to monitor sites across the range of

management and environmental conditions, and document

results in a database used to continually improve guidelines, standards and management practices. Some examples

are presented below to illustrate the above statements.

In a Weyerhaeuser study comparing tilled and non-tilled

skid trails, bulk density for logged-only, non-tilled, and tilled

skid trails by depth and areas (Washington and Oregon) are

plotted in figure 10 (Miller et al. 1996 and Heninger et al.

2002). Compared to the logged-only plots, the non-tilled

skid trails showed increased bulk density at both geographic

locations. The Oregon Cascades tilled skid trails were rehabilitated to almost the same bulk density as the logged-only

control for that area. Thus, tillage recovered the bulk density

to that of undisturbed soil. There are significant differences

between locations in undisturbed soil bulk densities. The

next question would be: does this affect tree growth?

In the Washington study, there were no significant diff e rences in Douglas-fir heights among any of the disturbance

classes from year 2 through 18 (Fig. 11) (Miller et al. 1996).

In the Oregon study, Douglas-fir (Heninger et al. 2002),

height growth was reduced on OR skid trails for about 7

years after planting (Fig. 12). Up to age 7 years, the total

heights were diverging between treatments. Seedlings on

the non-tilled skid trails averaged 15% less in total height.

Height growth (slope of line) from year 7 through 10,

showed fairly consistent growth rate among the treatments,

and was non-significant. Trees on non-tilled skid trail ruts

were always shorter than those on logged-only control plots.

Trees on tilled skid trails averaged 2% taller than those on

logged-only plots. Thus, soil productivity, as measured by

total tree height was recovered by tillage. Working through

the data, considering time to attain 1.4-m breast height: LO

= 4.0 years; NR = 4.7 years; an average difference of 0.7

years to attain breast height. Therefore, trees on the nontilled skid trails are about one year behind in total height

10

Figure 10—Net soil bulk density (Mg/m3) for a Weyerhaeuser study of tree growth on

tilled and non-tilled logging trails (Heninger et al. 2002)
and diameter, because it took them one extra year to attain

breast height. This difference has been maintained through

age 10. The Oregon site has a finer-textured soil than the

Washington site and has a longer summer dry period (the

e ffect of the summer dry period is exacerbated by soil compaction). Our hypothesis is that the roots have grown through

the compacted skid trail ruts, and are now growing in nondisturbed soil, thus growth rates are now equal. However,

the full extent of the impacts on site productivity will surely

be magnified if the area in skid trails increases appreciably.

Absolute growth will be depressed if roots have little access

to friable soil. So, we need to question how common this

trend is and hence whether disturbance criteria need to be

modified if longer-term data confirms these apparent trends

on these site conditions. 

LONG-TERM PRODUCTIVITY

Factors that limit early tree growth and establishment

are often different from those that influence long-term prod u c t i v i t y. Changes occur as a stand grows and matures,

particularly around the time of canopy closure, when the

11

Figure 12—Mean total height of Douglas-fir in Oregon for the Weyerhaeuser study of tree growth on

tilled and non-tilled logging trails (Heninger et al. 2002).

Figure 11—Mean total height of Douglas-fir in Washington for the Weyerhaeuser study

of tree growth on till and non-tilled logging trails (Miller et al. 1996).
trees are influenced less by microclimate and competing

vegetation, and more by regional climatic conditions and 

a site’s ability to provide adequate nutrients and moisture.

Effects that are initially positive or negative may reverse

over time. The time required to verify long-term effects on

productivity is probably longer in slower growing subalpine

or droughty areas. For example, on a relatively clayey site

in southeastern British Columbia, short-term growth was

enhanced on some disturbance types (Fig. 13). However,

in the longer-term (15 years), tree growth was poorer on all

soil disturbances compared to the undisturbed areas (Wass

and Senyk 1999). It is clear that validation takes time and

long-term monitoring/data is essential. 

Some trends are becoming apparent. Deeply developed

soils in humid climates appear to be less sensitive to disturbance whereas shallow, often younger and drier soils

are more sensitive. Volcanic ash-influenced soils are often

c o nsidered less sensitive than other soils, but data are still

forthcoming.

The actual effects of site disturbances on tree growth

depend on many factors, like texture. In British Columbia,

our longer-term data currently available are from older

studies such as that discussed for figure 13. Figure 14 contrasts 15-year Douglas-fir volume on the Gates Creek site

shown in Figure 13 with a less clayey site at Phoenix. Both

sites have sandy-loam textures, but clay content varies from

4% at Phoenix to 12% at Gates Creek. This also demonstrates the need for a database that covers the specific soils

within the operating area covered by the guidelines. In our

example, current compaction hazard ratings for the two sites

would be the same, but the soils clearly behaved diff e r e n t l y.

Figure 15 shows the importance of texture in the

results from the Long-term Soil Productivity (LTSP) sites

in California. In the clayey and loam textured study sites

there is clearly a negative affect of compaction on 10-year

biomass, whereas on the sandy sites there is actually a positive effect. This is considered to be due to compaction

increasing the water-holding capacity on the sandy sites. Te n -

year findings from the oldest LT S P sites in California, Idaho,

the Lake States, and the Southern Coastal Plain support the

conclusion that impacts of soil compaction on tree growth

depend mainly on soil texture and degree of soil drought

(Powers et al., in prep.). Studies like the LTSP are producing more long-term data every year. Over time, we will

have indicators of soil disturbance conditions that affect

tree growth under specific conditions.

Long-term productivity is dependent on the amount of

permanent access and the net effect of in-block disturbance

on future yield. Timber supply modeling takes into account

these two factors. However, we need to improve data upon

Figure 14—Fifteen-year volume of Douglas-fir seedlings growing in different disturbance types on the Canadian Forest Service Gates Creek and

Phoenix stumping trial sites in southern B.C., which are gravelly sandy

loam textured with 12% clay at Gates Creek and 4% clay at Phoenix

(adapted from Wass and Senyk 1999). 

Figure 13—Comparison of relative growth of Douglas-fir on a stump

removal trial in southern British Columbia at 3, 10 and 15 years since treatment. All data is relative to the undisturbed condition (adapted from Wass

and Senyk 1999.

12
which in-block soil disturbance projections are based. Many

tree growth studies are based on individual tree data from

specific disturbance types. Data are needed on an areal (or

extent) basis across a cut-block to fully integrate the net

e ffect of on-site disturbance. The LT S P study is an areabased controlled experiment on compaction and org a n i c

matter levels that ideally should be paired with operational

disturbance types and rehabilitation at each installation.

Powers et al. (1998) proposed operationally feasible soilbased indicators for weighing the likely impacts of managem e n t on potential site productivity. Among their recommendations were to develop: soil maps highlighting soil types

apt to be sensitive to disturbances, soil physical indic a t o r s

such as resistance to penetration, and chemical/microbial

indicators of nutrient supply, such as mineralizable nitrogen.

These indicators need testing and implementation through

continued testing, refinement and augmentation of existing

soil disturbance standards.

SUMMARY

Harvesting Effects on Soils

Most soil disturbance caused by machine traffic is in

the form of compaction and displacement. Compaction often

results in increase in bulk density and decreases in penetrab i l i t y, amount and size of pore space, aeration porosity,

infiltration, and hydrologic conductivity. Displacement

often results in loss of topsoil and exposure of subsoils.

Off-site effects from soil disturbance can include erosion,

sediment delivery and loss of life and property loss (not

discussed in detail in this paper).

Effects on Tree Growth 

Soil disturbance effects on tree growth depend on the

nature of the disturbance in relation to the inherent site conditions/sensitivity such as soil texture and climate. Results

can range from positive, through no-effect to negative,

depending on which growth-limiting factor is affected.

Effects on Long-Term Productivity

Growth-limiting factors change as a stand ages and

crown closure occurs. Early effects may reverse over time.

Studies like the LTSP will permit better prediction of longterm effects and development of indicators that can be used

in managing disturbance at the time of harvesting. 

Best Management Practices

A number of soil considerations are required in harvest

planning. An adaptive management approach needed to

continually improve understanding of management effects

on our soils. One needs to: 

1. Know the soils upon which operations are planned 

(through survey of site information), 

2. Know what practices should be planned (organize 

this knowledge based on a soil disturbance classifica

tion, and a soil risk rating system),

3. Understand potential effects of these practices 

(both on- and off-site), and

4. Adapt planned practices (BMPs) over time as more 

knowledge becomes available.

Site-specific knowledge needs to be part of an adaptive

management process for continual improvement of practices

(sustainability). A lack of data often results in more restrictive policies, erring on the conservative side. Overly conservative policies and practices cost in terms of economics

and social benefit from the forest resource. Conversely, polic i e s that are not conservative enough may cost us in terms

of environmental values and long-term productivity and

hydrologic function. We need to constantly refine and adapt

our guidelines, standards, practices and tools as more information becomes available. To meet these needs, linked

databases that track the results of implementation, effectiveness, and validation monitoring are essential.

ACKNOWLEDGEMENTS

We thank Steve Howes, U.S. Forest Service, and Chuck

Bulmer, British Columbia Ministry of Forests, for their

reviews that have improved this manuscript.

13

Figure 15—The importance of texture on the LTSP sites in California (C0

= no compaction, C1 = moderate compaction, C2 = severe compaction)

(Powers et al. in review).
LITERATURE CITED

British Columbia Ministries of Forests. 1997. Soil rehabilitation guidebook. Victoria, BC. Forest Practices

Code of British Columbia Guidebook. British Columbia

Ministry of Forests. http://www.for.gov.bc.ca/tasb/

legsregs/fpc/FPCGUIDE/soilreha/REHABTOC.HTM.

(January 2005)

British Columbia Ministries of Forests. 2001. Soil conservation surveys guidebook. 2nd ed. Forest Practices

Code of British Columbia Guidebook. Victoria, BC:

Forest Practices Branch, British Columbia Ministry of

Forests. 63 p. http://www.for.gov.bc.ca/tasb/legsregs/

fpc/FPCGUIDE/SOILSURV/soilconsurv.pdf.

(December 2004)

Canadian Council of Forest Ministers [CCFM]. 2003.

Defining sustainable forest management in Canada.

Criteria and indicators. Canada. http://www.ccfm.org/

2000pdf/CI_Booklet_e.pdf. (November 2003).

Curran, M.P. 1998. Skid trail rehabilitation. Includes: 

Field cards for summer and winder skid trail construction and rehabilitation. (video). Nelson, BC: British

Columbia Ministries of Forests (BCMOF) Research

Program. 53min.

Curran, M. 1999. Harvest systems and strategies to reduce 

soil and regeneration impacts and costs. FERIC Special

Report No. SR-133. In: Impact of machine traffic on

soil and regeneration: Proceedings of FERIC’s Machine

Traffic/Soil Interaction Workshop. Edmonton, AB. 

75-11.

Curran, M.; Davis, I.; Mitchell, B. 2000. Silviculture 

prescription data collection field handbook: interpretive

guide for data collection, site stratification, and sensitivity evaluation for silviculture prescriptions. [Includes

forms FS39A and B]. Land Management Handbook 

No. 47. British Columbia Ministries of Forests. 156 p.

http://www.for.gov.bc.ca/hfd/pubs/Docs/Lmh/Lmh47.

htm. (December 2004)

Curran, M.; Maynard, D.; Heninger, R. [et al.] [In 

preparation]. A strategy for more uniform assessment

and reporting of soil disturbance for operations, research,

and sustainability protocols. Discussion paper from:

Conference on Long-term Productivity of Forest Soils.

Submitted to Forestry Chronicle 2005.

Dyck, W.J.; Skinner, M.F. 1990. Potential for productivity 

decline in New Zealand radiata pine forests. In: Gessel,

S.P.; Lacate, D.S.; Weetman, G.F.; Powers, R.F., eds.

Sustained productivity of forest soils: Proceedings 

of the 7th North American Forest Soils Conference.

Vancouver, BC. Faculty of Forestry, University of

British Columbia. 318-332.

Froehlich, H.A.; Miles, D.W.R.; Robbins, R.W. 1985.

Soil bulk density recovery on compacted skid trails in

central Idaho. Soil Science Society of America Journal

49: 1015-1017.

Gomez, A.; Powers, R.F.; Singer, M.J.; Horwath, W.R. 

2002. Soil compaction effects on growth of young 

ponderosa pine following litter removal in California’s

Sierra Nevada. Soil Science Society of America Journal

66: 1334-1343.

H e n i n g e r, R.L.; Te r ry, T.; Dobkowski, A.; Scott, W. 1997. 

Managing for sustainable site productivity: We y e r h a e u s e r’s

forestry perspective. Biomass and Bioenergy. 13(4/5):

255-267.

Heninger, R.L.; Scott, W.; Dobkowski, A.; [et al]. 2002.

Soil disturbance and 10-year growth response of coast

Douglas-fir on non-tilled and tilled skid trails in the

Oregon Cascades. Canadian Journal of Forest Research

32: 233-246.

Krzic, M.; Curran, M.P. [In press]. Forest soils and tree 

nutrition. In: Forestry Handbook for British Columbia.

Vancouver, B.C: Faculty of Forestry, University of

British Columbia. 353-389

Lewis, T., and Timber Harvesting Subcommittee. 1991. 

Developing timber harvesting prescriptions to minimize

site degration. BC Min. Forests Land Management

Report No. 62.

Maynard, D.G.; Senyk, J.P. 2004. Soil disturbance and 

five-year tree growth in a montane alternative silvicultural systems (MASS) trial. Forestry Chronicle 80: 

573-582.

Miller, R.E.; Scott, W.J.; Hazard, W. 1996. Soil 

Compaction and conifer growth after tractor yarding 

at three coastal Washington locations. Canadian Journal

of Foresr Research. 26:225-236.

14
Montréal Process Working Group, 1997. First approximation report on the Montréal Process, 1997. Ottawa,

ON: The Montréal Process Liaison Office, Canadian

Forest Service.

Morris, L.A.; Miller, R.E. 1994. Evidence for long-term 

productivity changes as provided by field trials. In:

Dyck, W.J; Cole, D.W.; Comerford, N.B., comps., eds.

Impacts of Forest Harvesting on Long-Term Site

Productivity. London; Chapman and Hall: 41-48.

Powers, R.F.; Alban, D.H.; Miller, R.E. 1990. Sustaining 

site productivity in North American forests: problems

and prospects. In: Gessel, S.P.; Lacate, D.S.; Weetman,

G.F.; Powers, R.F., eds. Sustained Productivity of Forest

Soils: Proceedings of the 7th North American Forest

Soils Conference. Vancouver, BC: Faculty of Forestry,

University of British Columbia: 49-79.

Powers, R.F. 1999. On the sustainable productivity of 

planted forests. New Forests 17: 263-306.

Powers, R.F.; Scott, D.A.; Sanchez, F.G. [et al.] [In 

preparation]. The North American long-term soil productivity experiment. Findings from the first decade of

research.

Shestak, C.J.; Busse, M.D. 2005. Compaction alters physical but not biological indices of soil health. Soil

Science Society of America Journal 69:236-246.

Scott, W. 2000. A soil disturbance classification system. 

Internal Report Forest Res. Tech. Note, Paper #00-1,

Federal Way, WA: Weyerhaeuser Company. 12 p.

Siegel-Issem, C.M.; Burger, J.A.; Powers, R.F. [et al.] 

2005. Seedling root growth as a function of soil density

and water content. Soil Science Society of America

Journal 69: 215-226.

USDA Forest Service. [Draft] 2003. National report 

on sustainable forests – 2003. U.S. Department of

Agriculture, Forest Service FS-766. http://www.fs.fed.

us/research/sustain/ (November, 2003). 

Wass, E.F.; Senyk; J.P. 1999. Tree growth for 15 years 

following stumping in interior British Columbia.

Technology Transfer Note 13. Victoria, BC: Canadian

Forest Service, Pacific Forestry Center.

Xu, X.; Nieber, J.L.; Gupta, S.C. 1992. Compaction 

effect on the gas diffusion coefficient in soils. Soil

Science Society of America Journal 56: 1743-1750.

15
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1 Glen Murphy and Paul W. Adams are both professors, Forest Engineering Department, Oregon State University, Corvallis, OR 97331. 

Email contact for the corresponding author is glen.murphy@oregonstate.edu

Productivity of Western Forests: A Forest Products Focus, Chapter One

HARVEST PLANNING TO SUSTAIN VALUE 

ALONG THE FOREST-TO-MILL SUPPLY CHAIN

Glen Murphy and Paul W. Adams1

INTRODUCTION

Forest managers spend decades creating potential value

in each tree. At harvest time more costs are incurred, more

revenue is generated, and more environmental impacts can

occur than at any other time during the rotation. An important challenge for the harvest planner is to maximize current net value recovery, while sustaining future net value

17

recovery. We prefer to use net value recovery, rather than

productivity, as a performance measure in this paper since

it ties together the impacts of harvesting and management

activities on volume production, values and costs.

Net value recovery = Volume * (Gross Value – Costs)

Between seedling and sawmill, there are many ways in

which net-value recovery can be sustained or lost along the

ABSTRACT

During the relatively few days it takes to harvest a stand of trees in a forest, more cost is incurred, more revenue is earned,

and potentially greater environmental impacts occur than in all of its prior decades of management combined. Careful design,

management and follow-up of the harvesting operation can help to maximize current net revenues (gross revenues minus

costs) while protecting future timber productivity.

Net-value recovery from a given piece of land is a function of volume, gross value and costs. These can be affected by 

a wide range of factors that relate to stand, terrain, markets, company policies, harvest systems, operating conditions and

practices, etc.

Harvest planning is a design process aimed at matching equipment and crew capabilities to the operating environment

while meeting production goals–one solution does not fit all design situations. To do this effectively the planner needs information on such factors as topography, soil characteristics, tree characteristics, and areas to be preserved/protected. T h e

planner can specify such things as equipment selection, skid-trail layout, felling patterns, operating season, road spacing,

harvest opening size, utilization level, duff and slash management, delimbing/processing location, log suspension, postharvest treatments, and standing tree protection.

To effectively protect or enhance future productivity, a forest manager has to continuously improve current harvesting

practices based on lessons learned from monitoring the effects of past practices—sometimes over long periods. Where possible, the effects should be measured directly rather than indirectly, e.g., monitoring not only the soil disturbance but also its

effect on tree volume and quality. Such observations are likely to show that not all disturbance and soil changes from harvest operations are equal in their effects on site productivity and net value recovery, i.e., they can range from negative to

insignificant to positive.

KEYWORDS: Harvesting, value recovery, soil disturbance, costs, productivity.
forest-to-mill supply chain. Value recovery can be maximized through:

• improved inventory systems which allow better 

understanding of the resource in terms of quantity,

quality and location,

• optimal scheduling of stands and allocation of logs 

to markets,

• planning of harvest layout,

• selection and scheduling of appropriate equipment 

and practices,

• improved log segregation and processing practices,

• optimal truck scheduling and log stocks 

management,

• improved process manufacturing, and

• improved post-harvest monitoring and treatment.

In this paper we will briefly look at: is there a need for

harvest planning in the Pacific Northwest (PNW), what

factors affect gross value recovery and harvesting costs,

what is harvest planning, what information is needed, what

can the planner specify, and finally the importance of monitoring performance and continuous improvement.

Is There a Need for Harvest Planning?

Good harvest planning generally leads to greater productivity, reduced costs, improved worker safety, and fewer

environmental impacts. 

Today, many forest companies, including those in the

P N W, operate in a worldwide marketplace facing increasing

global competition from other timber producers. Competition

is coming, however, not only from other wood producers

but also from (1) other industries, such as steel, aluminum,

plastics, and composites that are competing successfully

with the forest industry in traditional markets, and (2) alternative uses for the investors’ dollars. To be globally competitive, forest companies need to control costs, sort and

allocate logs to the most appropriate markets, and maximize

the value of the forest at the time of harvest. Harvest planning is vital for meeting these economic requirements in

the short and long term.

Forest soil compaction has been studied for over 50 years

in the PNW (Garrison and Rummel 1951). It has been

found that most PNW soils are susceptible to compaction,

compaction occurs in both dry and moist soils, large areas

may be compacted, and compaction can persist for decades

(Wronski and Murphy 1994). Soil compaction sometimes,

but not always, leads to reduced tree growth, and effects may

vary with soil type and other site conditions. For example,

a study of compaction effects on seedling growth on three

sites in northern California with clay, loam, and sandy loam

soils found reduced, insignificant, and increased stem volume growth, respectively (Gomez et al. 2002). Causal factors for observed growth impacts have become clearer, e.g.,

Powers et al. (1998) found that sandy loam soils compacted

by mechanized thinning had soil strengths that were limiting to root growth during the summer months. They

conclude that such a seasonal soil strength increase may

effectively shorten the growing period for impacted trees. 

PNW forest managers are not alone in their interest in

the impacts of harvesting systems on the site. Research on

the impacts of soil disturbance on tree growth in radiata

pine plantations at four sites, with different soil characteristics, in New Zealand has shown that planted seedling survival was not affected, stem malformation was affected on

two of the sites, and selection for pruning and for final crop

was affected on all four sites. Volume growth was also

affected, particularly for the heavily disturbed areas (Firth

and Murphy 1989, Murphy and Firth 2004). Other New

Zealand research has shown that, while the impacts of

heavy soil disturbance (topsoil removal and subsoil compaction) on volume production may be large (e.g., up to a

40% reduction) the impacts on net value recovery are likely

to be even greater (e.g., up to 65% reduction) due to stems

having to be cut into lower value products because of size

and quality constraints (Murphy et al. 2004).

Even without planning, harvesting operations create a

mosaic of disturbance classes so these volume and value

reductions are not seen over the whole harvest site. However,

harvest planning can effectively reduce the impacts that do

occur. Moreover, economic analyses have shown that volume losses from compaction can justify a significant investment in planning and other measures to avoid or reduce

these impacts (Stewart et al. 1988, Murphy et al. 2004).

Factors Affecting Gross Value Recovery

Many factors affect the gross value recovery coming off

a given piece of land (Murphy et al. 1991, Conradie et al.

2004). These include among other things:

• the proportion of the land area allocated to timber 

production—land allocated to non-timber uses, such

as reserves, is likely to reduce gross value recovery

• the volume per hectare of productive area and the 

tree species planted on that area

• the tree size—usually, though not always, larger trees 

are more valuable than smaller trees both on a per 

tree basis and a unit volume basis

• the quality of the wood and the treatments the stand 

has undergone—stems with rot or malformation are 

less valuable than well formed, rot-free stems; pruned 

18
stems are generally more valuable than unpruned

stems; older, high density wood is usually more 

valuable than young, low density wood, etc.

• the markets available for the wood, the prices the 

markets are prepared to pay, and how well the wood

has been allocated to those markets

• the premium the markets are prepared to pay for 

“environmentally friendly” products—there are mixed

signals from consumers on how large a premium will

generally be paid for environmentally friendly products, ranging from nil to less than 10%

• gains or losses in productivity and stem quality due 

to soil disturbance related to forest operations

• thinning-damage—the few studies that quantify thin

ning damage in terms of value recovery indicate that

losses range from 1 to 2% of the value of the stand at

the time of final harvest

• felling practices—8% to 12% of the value of a stem 

can be lost through poor manual falling practicesextraction breakage—up to 1% of the potential value

may be lost through extraction breakage

• bucking tools and practices—bucking can have one of 

the largest impacts on value recovery. Losses of up to

30% of potential value recovery have been recorded

for manual operations and up to 70% for mechanized

operations.

• loading and transport damage—little research has 

been done on value recovery losses due to loading and

transport. Damage is likely to result in losses of less

than 1%. Mis-sorting and loading of logs for the

wrong destination sometimes is of bigger concern.

• harvest system selection—mechanized harvesting 

systems have value recovery advantages over conventional systems with mechanized felling (due to lower

stumps and less breakage) but tend to incur lower

value recovery during bucking.

• equipment selection—mechanized felling equipment 

that is too small for the tree size it is operating in can

result in unacceptable value losses from stem breakage, and butt damage. Soil disturbance can be high if

inappropriate equipment is selected.

• operator skills and training—studies of many types 

of operations indicate that a third of the variation in

performance is often related to the human factor.

Factors Affecting Harvesting Cost

Many factors affect the harvesting costs for timber

coming off of a given piece of land (Conway 1976). These

include among other things:

• the size of the harvest unit—all harvest units generally 

incur the same fixed move-in, move-out costs. Unit

volume costs are therefore likely to be greater for

small harvest units than large harvest units.

• harvest system selection (see Figure 1 for relative 

costs per unit of volume)

• harvesting equipment selection—even for the same 

harvesting system, differences in costs can result from

the type of equipment selected. Not all equipment has

the same features, purchase price, repairs and maintenance requirements, etc.

• piece size—harvesting can generally be classed as a 

piece handling problem; it takes a similar amount of

resources to handle a small piece as it does a big piece.

Harvesting small trees, or big trees cut into small

pieces, tend to result in higher costs than harvesting

bigger trees. Costs rise rapidly once piece size falls

below about 1 m3 (200 bf).

• stand treatment—thinning generally results in higher 

costs (~ 10%) than clearfelling for the same piece

19

Figure 1—Standing-tree-to-truck costs for a range of harvesting systems (costs are expressed

relative to costs of ground-based manual operations).
size. The size of this increase depends largely on the

number of stems per hectare removed.

• operating practices—for example, requiring a mechanized harvester to cover forwarder trails with a running bed of limbs and tops may lower harvester 

productivity and increase costs 

• operator skills and training—see comment on value 

recovery

• terrain and soil type—steep terrain is generally more 

expensive to harvest than gentle terrain. Some soil

types can limit harvesting activity, particularly when

they are wet, resulting in a shorter operating season.

Fixed costs, therefore, have to be spread across fewer

operating days. Some soils can result in significant

wear on harvesting equipment, e.g., sands or volcanic

ashes.

• weather conditions—can limit the length of the 

operating season or reduce productivity on days when

harvesting can be undertaken.

• extraction distance—generally harvesting costs 

increase as the distance the timber has to be extracted

increases. One of the exceptions to this is for cable

logging systems where very short extraction distances

can result in frequent shifting of cables and a lot of

unproductive time.

• market complexity—the more complex the market (as 

measured by the number of log sorts) the higher the

harvesting cost. This can be due to an increase in time

required for sorting, a reduction in average piece size,

larger landings required, etc.

• distance to markets—transport from landing to mill 

can account for up to 50% of stump-to-mill harvesting

costs. The greater the distance to the mill, the higher

the transport costs.

• environmental protection requirements—such as 

riparian area protection, use of designated/old skid

trails, etc.

What Is Harvest Planning and What Information 

Is Needed to Implement It?

Harvest planning is a process whereby equipment and

crew capabilities are matched to social, environmental and

economic requirements so that production goals can be

met. One solution does not fit all design situations. As

noted earlier, an important goal is to sustain net value

recovery along the forest-to-mill supply chain.

Information required by harvest planners to effectively

carry out their job includes among other things:

• data on the terrain–contour maps, digital elevation 

models, aerial photos,

• applicable rules and regulations related to the project

area,

• detailed information on existing infrastructure; e.g., 

road locations and conditions, bridge weight limits,

sortyard locations, etc.,

• harvest schedule for area-level tactical planning (e.g., 

how will this harvest area relate to past and future 

harvest areas?),

• soils maps and soil descriptions,

• location of problem areas; e.g., unstable slopes,

• special on-and off-site requirements; e.g., archeological sites, riparian zones, reserves, viewsheds,

• inventory data; volume per hectare, tree size and 

stem characteristics,

• markets; what log grades and lengths are stems 

likely to be cut into,

• available equipment and skills in the region.

What can the Harvest Planner Specify?

There are many things the harvest planner can specify

that will affect soil disturbance and net value recovery.

Some of these include:

1. System selection—the selection of the harvesting system

can affect costs, gross value recovery, and soil disturbance. A wide range of systems are available—helicopters,

single-span skyline, multi-span skyline, skidder logging,

excavator logging, cut-to-length systems, motor-manual

systems, fully mechanized systems, etc., —but only a

limited number of these will result in an economically

viable harvest operation for a specific unit.

2. Equipment selection—equipment design, track and wheel

size, and suspension type can all effect duff integrity and

soil disturbance. Murphy (1982) found that equipment

design could cause a two- to three-fold difference in the

number of passes made by ground-based extraction equipm e n t before topsoil removal and subsoil compaction

occurred on skid trails.

3. Skidtrail layout—planned skid trails can result in less

soil disturbance overall, compared with the logger’s

choice of travel, by designating where ground-based

equipment travels (Froehlich et al. 1981). Providing the

distance between skid trails is not too great (requiring

l a rge amounts of time to pull winch-line to hook on the

logs), costs can also be reduced because of faster travel

times from stump to landings.

4. Felling pattern—timber felling patterns can influence the

degree of soil disturbance generated, and the amount of

breakage and damage to the residual crop. Felling stems

20
parallel to each other, and in a herring-bone pattern in

relation to the extraction skid trail or skyline corridor,

helps to minimize disturbance, breakage and damage

(Garland 1983, Garland and Jackson 1997).

5. Operating season—limiting the operating season to times

when the soils are less susceptible to disturbance may

reduce the impacts of harvesting on future site product i v i t y. Identifying effective limits is challenging, howeve r, given the wide range of site conditions and soil

and machine types that exist. For example, loaded

machines and travel on slopes can result in much greater

vehicle ground pressures than the static values more often

r e p o r t e d (Lysne and Burditt 1983). Limiting the operating season will also result in higher harvesting costs as

fixed costs have to be spread across fewer operating

days and harvest volume production.

6. Road and landing location and spacing—as well as 

taking land out of productive use for timber production,

forest roads and skid trails can be important sources of

runoff and sediment. However, only a fraction of all

roads and skid trails usually cause problems. Some of

the key factors determining whether they are a problem

are their length, location, design, use and maintenance

history. Road spacing can also affect harvesting system

selection, harvesting productivity (closer road spacings

usually result in faster cycle times and lower extraction

costs), and road construction costs (Sessions 1992). 

7. Utilization level (bole-only or full-tree) and processing

location—short-term net value recovery can be increased

(or decreased) by increasing the level of biomass utilization (Murphy et al. 2003). Nutrient removal from the

site, however, may or may not have significant impacts

on long-term value recovery. Processing stems at the

stump versus at roadside can have different effects on

costs, value recovery, and nutrient concentration. (Murphy

1987, Smidt and Blinn 1995).

8. Standing tree protection—damage to standing trees

during thinning operations can result in future gross

value losses due to reduced growth and quality impacts

(e.g., scarring) (Han et al. 2000). The potential for damage can be greater near designated skid trails and skyline

corridors where traffic flow is concentrated. Providing

protection for standing trees comes at a cost but may

result in net value recovery gains.

9. Duff and slash management—delimbing at the stump

keeps nutrient resources dispersed. Slash on skid trails

acts as a cushion between heavy equipment and the soil.

Maintaining or increasing slash on skid trails has been

shown to help reduce compaction and disturbance (Allen

et al. 1997). 

10. Log suspension—harvesting operations can be designed

to reduce soil disturbance by providing greater log lift.

H o w e v e r, this sometimes has a negative impact on costs

and gross value recovery. Log suspension can be achieved

by providing greater lift (e.g., using helicopters, multispan systems, forwarders instead of skidders, etc.) or

by cutting the stem into shorter logs.

11. Post-harvest treatments—runoff and erosion can be

minimized by including water bars, or slash-filter and

sediment traps in the design of skid trails and roads.

Limbs and tops, removed at the landing, can be spread

out over the harvest unit.

12. Riparian area protection—delineation of riparian areas

can affect harvest system productivity, costs and net

value recovery as well as the amount of sediment

reaching streams.

13. Tillage of skid trails and large landings—is useful for

clearfell sites when compaction is unavoidable; tillage

of thinned sites may result in damage to the root system of the residual crop, but the impact of such damage

has not been widely studied. Various implements have

been used for tilling compacted forest soils, and costeffectiveness can vary significantly (Andrus and

Froehlich 1983). Where moisture is limiting, the tree

productivity benefits of tillage may be masked by lack

of weed control. Tillage can also be extended to treat

areas compacted by earlier machine operations.

Continuous Improvement and Monitoring

To effectively protect or enhance future productivity

and net value recovery, a forest manager has to continuously

improve current harvesting practices based on lessons learned

from monitoring the effects of past practices—sometimes

over long periods. For example, until quite recently it was

thought that soil compaction was invariably bad and was a

problem serious enough to merit major operational changes.

Where possible, the effects of harvesting practices

should be measured directly rather than indirectly; a detailed

study of the soil is not always needed to identify soil productivity concerns. Soil productivity is reflected directly in

tree growth, form and health. When coupled with indirect

monitoring of soil productivity (mapping and quantifying

the problem visually, with bulk density measurements, with

penetrometers, etc.), a much clearer picture of cause and

effect relationships and the situations that merit attention

should emerge. 

21
CONCLUSIONS

The impacts of soil disturbance on volume production

can range from negative to insignificant to positive. Productivity measures, however, need to include a quality

component and be long-term. Net value recovery is a useful

alternative performance measure to productivity.

Sustaining net value recovery along the forest to mill

supply chain means managing activities that affect not only

productivity (i.e. volume production) but also gross value

recovery and costs. To sustain net value recovery, future

impacts as well as current impacts need to be considered

when harvesting operations are being planned. Harvest

planners have a wide range of alternative solutions at their

disposal. One solution does not fit all design situations.

Forest managers looking to continuously improve their

practices, and their net value recovery, need to manage gross

value recovery and costs associated with their operations.

They also need to monitor and evaluate the impacts of

c u rrent operations on the trees, in addition to the soils. 

ACKNOWLEDGEMENTS

The authors acknowledge the valuable comments made

by Han-Sup Han and John Firth in helping to improve this

paper.

LITERATURE CITED

Allen, M.M.; Adams, P.W.; Kellogg, L.D. 1997. Soil bulk 

density and penetrometer cone index after harvester 

and forwarder traffic over different slash depths in the

Oregon Cascades. Weyer- haeuser Foundation Report.

Corvallis, OR: Forest Engineering Department, Oregon

State University. 42 p.

Andrus, C.W.; Froehlich, H.A. 1983. An evaluation of 

four implements used to till compacted forest soils in

the Pacific Northwest. Res. Bulle. 45. Corvallis, OR:

College of Forestry, Oregon State University. 12 p.

Conradie, I.; Greene, W.D.; Murphy, G.E. 2004. Value 

recovery with harvesters in southeastern USA pine

stands. Forest Products Journal 54(12): 80-84.

Conway, S. 1976. Logging practices. Miller Freeman 

Publications, USA. 416 p.

Firth, J.; Murphy, G.E. 1989. Skidtrails and their effect 

on the growth and management of young Pinus radiata.

New Zealand Journal of Forestry Science 19(1): 22-8.

Froehlich, H.A.; Aulerich, D.E.; Curtis, R. 1981.

Designing skid trail systems to reduce soil impacts from

tractor logging machines. Res. Pap. 44. Corvallis, OR:

Forest Research Laboratory, Oregon State University.

Garland, J.J. 1983. Designated skid trails minimize soil 

compaction. Extension Circ. 1110. Corvallis, OR:

Extension Service, Oregon State University. 6 p.

Garland, J.J.; Jackson, D. 1997. Felling and bucking 

techniques for woodland owners. Extension Circ. 1124.

Corvallis, OR: Extension Service, Oregon State

University. 16 p. 

Garrison, G.A.; Rummell, R.S. 1951. First-year effects 

of logging on ponderosa pine forest range lands of

Oregon and Washington. Journal of Forestry 49: 708-

713.

Gomez, A.; Powers, R.F.; Singer, M.J.; Horwath, W.R. 

2002. Soil compaction effects on growth of young ponderosa pine following litter removal in California’s

Sierra Nevada. Soil Science Society of America Journal

66: 1334-1343.

Han, H.-S.; Kellogg, L.D.; Filip, G.M.; Brown, T.D. 

2000. Scar closure and future timber value losses from

thinning damage in western Oregon. Forest Products

Journal 49(11/12): 9 p.

Lysne, D.H.; Burditt, A.L. 1983. Theoretical ground pressure distributions of log skidders. Transactions of the

American Society of Civil Engineers (ASAE) 26: 1327-

1331.

Murphy, G.E. 1982. Soil damage associated with production thinning. New Zealand Journal of Forestry Science

12(2): 281-92.

Murphy, G.E. 1987. An economic analysis of final log 

manufacturing locations in the steep terrain radiata pine

plantations of New Zealand. College of Forestry,

Oregon State University. Ph.D. thesis. 420 p.

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Murphy, G.E.; G.P. Cossens; 

Twaddle, A.A. 1991. How 

to improve value recovery from plantation forests:

research and practical experience in New Zealand. In:

Proceedings: Forestry operations in the 1990's: chal-

lenges and solutions. Namaimo, BC: Council on Forest

Engineering.

Murphy, G.E.; Siren, M.; O’Brien, S. 2003. Potential 

use of slash bundling technology is western US stands.

In: Proceedings: Council on Forest Engineering. Bar

Harbor, ME.

Murphy, G.E.; Firth, J. 2004. Soil disturbance impacts 

on early growth and management of radiata pine trees

in New Zealand. Western Journal of Applied Forestry

19(2): 109-116.

Murphy, G.E.; Firth, J.; Skinner, M.F. 2004. Long-term 

impacts of forest harvesting related soil disturbance on

log product yields and economic potential in a New

Zealand forest. Silva Fennica 38(3): 279-289.

Powers, R.F.; Tiarks, A.E.; Boyle, J.R. 1998. Assessing 

soil quality: practicable standards for sustainable forest

productivity in the United States. In: Davidson, E. and

others, eds. The contribution of soil science to sustain-

able forest management. SSSA Special Pub No. 53.

Madison, WI: Soil Science Society of America. 

Chap. 3.

Smidt, M.; Blinn, C.R. 1995.Logging for the 21s t c e n t u r y :

protecting the environment. FO-06518. Extension

Service, University of Minnesota. 

Sessions, J. 1992. Proceedings of Computer Supported 

Planning of Roads and Harvesting Workshop., ed.

IUFRO S3.05., S3.06. Feldafing, Germany: University

of Munich. 316 p.

Stewart, R.; Froehlich, H.; Olsen, E. 1988. Soil compaction: an economic model. Western Journal of

Applied Forestry 3(1): 20-22.

Wronski, E.B.; Murphy, G.E. 1994. Responses of 

forest crops to soil compaction. In: Soane, B.D.; van

Ouwerkerk, C., ed. Soil compaction in crop production.

Elsevier Science Publishers, Amsterdam: 317-342.

23
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STAND

ESTABLISHMENT
This page is intentionally left blank.
1 Timothy B. Harrington is Research Forester, USDA Forest Service, PNW Research Station, Forestry Sciences Laboratory, 3625 93rd Avenue, 

Olympia, WA 98512.

2 Jeff Madsen is Forestry Manager, Port Blakely Tree Farms LP, 8133 River Drive SE, Tumwater, WA 98501.

Productivity of Western Forests: A Forest Products Focus

SILVICULTURAL TECHNOLOGY AND APPLICATIONS 

FOR FOREST PLANTATION ESTABLISHMENT WEST

OF THE CASCADE CREST

Timothy B. Harrington1 and Jeff Madsen2

BACKGROUND

In western Oregon and Washington (i.e., the “We s t s i d e ” ) ,

nearly half of all timberland is publicly owned. The federal

government owns 38% and state agencies control 11% of

all timberland in this region. Remaining ownership is dominated by industrial (34%) and other private landowners

(17%), including various tribal ownerships (Bolsinger et al.

1997, Alig et al. 2003, Haynes 2003, Campbell et al. 2004).

Each of these landowner classes differs strongly in their

management philosophies and constraints. In the last decade,

federal forestry agencies have had to operate within a litigious environment, and as a result, their timber harvest

currently is focused on salvage from fire and insect disturbances (Malmsheimer et al. 2004). State-managed forest

lands work under a range of constraints and objectives includi n g those of a federal Habitat Conservation Plan for lands

of the Washington State Department of Natural Resources,

various land trust concerns, and economic mandates (Coyner

and Coyner 2004, OSDF 2004a, Washington DNR 2004).

ABSTRACT

Research and operational trials have identified methods of forest plantation establishment that promote high rates of 

survival and early growth of tree seedlings in the Pacific Northwest. Primary reasons for this success are the intensive control

of competing vegetation provided by herbicide treatments and the planting of high quality seedlings. This paper discusses

the current state of the art in forest plantation establishment in Oregon and Washington west of the crest of the Cascade

Range. It considers technologies developed in the last two decades that currently have widespread application on lands

managed primarily for wood products. The focus of this review is on even-aged silviculture of conifer seedlings, especially

coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. m e n z i e s i i), but other species, silvicultural systems, and

regions are considered where appropriate. 

KEYWORDS: Vegetation management, nursery technology, tree planting, Douglas-fir.

27

With the exception of tribal owners, private landowners

operate under state Forest Practices Laws, the federal Clean

Water Act, and the Endangered Species Act. The Sustainable

Forestry Initiative includes additional self-imposed regulations by forest industry (SFB 2004). As a result of these

various conditions and constraints, most of the timber harvest on the Westside comes from private land (87%). Only

2% of the harvest comes from federal lands with the remaining 11% from state-managed timberlands (Larsen and

Nguyen 2004, OSDF 2004b). 

The private forest industry faces increasing regulatory

restrictions as urban and suburban interfaces move ever

closer to its land. Increasing property values from real estate

development are shifting land investment away from traditional forestry practices in some areas (Alig et al. 2003).

Facing global competition for wood products, We s t s i d e

industrial landowners are pushed towards intensive silviculture and lower rotation ages as they continue to protect

public resources and control treatment costs (Talbert 2004).
PREDOMINANT LIMITING FACTORS

Much of the forest land on the Westside is classified 

as the Western Hemlock (Tsuga heterophylla (Raf.) Sarg.)

Zone because of the species’ potential to establish and ultimately dominate most forest plant communities (Franklin

and Dyrness 1973). Douglas-fir is the primary crop species,

with occasional planting of western hemlock, western redcedar (Thuja plicata Donn ex D. Don), and red alder (A l n u s

rubra Bong.) (Briggs and Trobaugh 2001). Forest site quality is determined largely by soil depth, soil texture and

rainfall (Steinbrenner 1981). Nitrogen is the macronutrient

most limiting to forest productivity (Heilman 1981).

Douglas-fir seedlings require moderate to high levels 

of sunlight for optimal development. Mailly and Kimmins

(1977) found that seedlings need at least 40% of full sunlight to ensure survival and continued morphological development, although maximum growth rate occurs under full

sunlight conditions (Drever and Lertzman 2001). In contrast, western redcedar seedlings require only 10% of full

sunlight to survive (Wang et al. 1994), and their maximum

growth rate occurs at 30% of full sunlight (Drever and

Lertzman 2001).

Experiments throughout the region testing two-aged and

uneven-aged silvicultural systems have identified significant reductions in conifer seedling growth from overstory

shade and other resource limitations (Brandeis et al. 2001,

Mitchell 2001, York et al. 2004). Such multi-cohort methods of regeneration can be challenging to establish and

maintain; thus, most of the wood-producing industrial

forests on the Westside are managed using even-aged silvicultural systems with clearcutting the dominant method of

regeneration (Smith et al. 1997).

Competing Vegetation

Perhaps the most important biological constraint to

establishment of Westside forest plantations is competition

for limited resources from competing vegetation. Intense

shade and early-season depletion of soil moisture occur

when development of competing vegetation goes unchecked.

For at least five decades, forest managers have been aware

of the competitive pressure that results from tall-growing

hardwoods and shrubs. Reductions in Douglas-fir height

growth have been directly related to the amount of shade at

or above half of the tree’s height (Ruth 1956, Howard and

Newton 1984, Wagner and Radosevich 1991a). In addition,

severe competition for soil water can result from as little 

as 20% crown cover of woody vegetation (Oliver 1984,

Shainsky and Radosevich 1986, White and Newton 1989).

About fifteen years ago, Westside foresters became

keenly aware of the importance of competition from herbaceous vegetation (Newton and Preest 1988, Petersen et al.

1988, White and Newton 1989, Hughes et al. 1990, Wagner

2000). Many of the common grass and forb competitors

invade recently harvested sites by wind dispersed seed.

During the first three years of plantation establishment they

compete strongly with conifer seedlings for soil water,

sometimes depleting available supplies early in the growing season (Newton and Preest 1988).

Invasive species of all types are a continual threat to

ecosystems throughout the United States (National Biological

Information Infrastructure 2004). Recent changes in Westside plant communities resulting from invasion by nonnative species may intensify the competitive pressure that

already exists for conifer seedlings during plantation establishment. Species such as Scotch broom (Cytisus scoparius

(L.) Link.), Himalayan blackberry (Rubus discolor Weihe

& Nees), and Japanese knotweed (Polygonum cuspidatum

Sieb. & Zucc.) establish soon after a site disturbance such

as clearcutting. Once established, their seed or bud banks

can survive for extended periods of time, making them

long-term residents of Westside forest communities. Other

species, such as English holly (Ilex aquifolium L.), English

ivy (Hedera helix L.), and false-brome (Brachypodium 

sylvaticum (Huds.) Beauv.), are shade tolerant and capable

of establishing in a wide range of light environments. Thus,

they may already be present in a forest community at the

time of timber harvest and able to quickly increase their

abundance in response to the disturbance.

Wildlife Damage

Damage to conifer seedlings from black-tailed deer

(Odocoileus hemionus columbianus Richardson), Roosevelt

elk (Cervus canadensis roosevelti Merriam), and mountain

beaver (Aplodontia rufa pacifica Merriam) can be particularly devastating during establishment of Westside forests

(Black et al. 1979). Their effects on early growth of Douglasfir seedlings are so significant that often silvicultural studies must be fenced to eliminate confounding of tree responses

from animal damage. Western redcedar is particularly vulnerable to browsing by deer and elk because of its high

palatability, whereas western hemlock is generally avoided.

Brandeis et al. (2002) found that, when browsed for three

consecutive years, cedar had only 56% of the stem volume

of non-browsed seedlings 

Root and Foliage Pathogens

The common root disease of Westside forests, laminated

root rot (Phellinus weirii (Murr.) Gilb.), is generally considered a site-specific problem that impacts yield but does

28
not destroy entire stands (Thies and Sturrock 1995). Since

1990, the foliage disease, Swiss needle cast (P h a e o c ry p t o p u s

gaeumannii), has reached epidemic status and caused significant growth losses in coastal Douglas-fir (Maguire et al.

2002). However, recent aerial surveys suggest that the Swiss

needle cast epidemic may be stabilizing or even subsiding

(Kanaskie et al. 2004). Sudden oak death (Phytophthora

r a m o ru m) is a potential future threat to forest stands because

of its wide variety of plant hosts and ability to invade through

either the stem or foliage, depending on the host.

Environmental Regulations

Although these biological constraints can pose some

unique challenges to plantation establishment, often the

overriding constraints to management activities are environmental regulations imposed by government agencies or

self-imposed by forest industry. National and state environmental protection laws impact reforestation activities sign i f i c a n t l y. In addition, a relatively recent development in

forest management is the emergence of an activist citizenry

that has the time and resources to challenge specific management activities of public and private landowners. National

Forests are often involved in years of administrative appeals

prior to final adoption of management plans (Teich et al.

2004; Malmsheimer et al. 2004). These laws and/or social

pressures can directly influence the entire range of forest

management activities.

For example, new forest practices laws for riparian zones

(to safeguard threatened fish species) have significantly

increased the area that is non-managed or managed at low

intensity. Adjacency constraints in the Sustainable Forestry

Initiative and state Forest Practices Laws can determine the

location of future timber harvests and even reduce a lando w n e r’s planned harvest levels. Adjacency constraints also

encourage managers to make large investments in silvicultural treatments to accelerate the development of young

stands so they will meet the “green-up” requirements that

enable the harvest of an adjacent stand. Air quality (“smoke

management”) rules have almost eliminated the use of

broadcast burning for site preparation on the Westside.

TECHNOLOGY APPLICATIONS

A wide variety of research programs within universities,

government laboratories, and private industry have developed successful approaches for regenerating Westside forests

given the challenges posed by competing vegetation, animal

damage, and pathogens. These techniques are contributing

to an ever-increasing intensity of silviculture that accelerates

the rate at which forest plantations become merchantable.

Vegetation Management

A considerable amount of research on plantation establishment has contributed to a conceptual framework of

“crop” seedling responses to vegetation management. Many

of these concepts have been borrowed from the agricultural

literature (Cousens 1987) and applied successfully to forestry.

The following are three major contributions to this conceptual framework.

(1) Competition thre s h o l d s -( Wagner et al. 1989, Monleon

1999) quantify the “breakpoints” in relationships of crop

seedling performance to abundance of competing vegetation.

The breakpoints signify large changes in seedling response,

and therefore, dictate the abundance at which competing

vegetation should be managed to ensure a reasonable return

on investment from vegetation management.

(2) Critical-period thre s h o l d s- ( Wagner et al. 1999, Wa g n e r

2000, McDonald and Fiddler 2001, Rose and Rosner 2004)

define the time period when competing vegetation should

be controlled (i.e., duration of weed control) in order to

prevent reductions in crop seedling performance.

(3) Minimum area of vegetation control-(Dougherty and

Lowery 1991, Rose et al. 1999) quantifies the portion of a

crop seedling’s growing space that must be kept free of

competing vegetation to maximize its performance. If the

minimum area is less than 100%, a spot treatment can be

prescribed that will potentially provide a cost-saving relative to a broadcast treatment. 

Intensive control of competing vegetation early in stand

establishment is being attempted on some forest sites as a

means of maximizing productivity and accelerating the rate

of stand development. Larg e r-scale use of backpack sprayer

crews is providing forest managers with the flexibility to

conduct vegetation management treatments in local problem

areas. Pre-harvest herbicide applications are being used

successfully in southwestern Oregon and northwestern

California to provide more effective control of everg r e e n

woody vegetation than from conventional post-harvest

methods (Fredricksen 2005). While herbicides are a critical

tool for Westside plantation establishment, all of the new

products now in use have much lower toxicity to mammals

and fish compared to older products. In addition, most of

the newer products are effective at extremely low application rates (e.g., sulfometuron herbicide typically is applied

at 3 ounces or less of active ingredient per acre).

29
Herbicide technology has improved considerably over

the last two decades. Experimental comparisons have demons t r a t e d the effectiveness of thinline applications of imazapyr

or triclopyr ester herbicides for controlling bigleaf maple

(Acer macrophyllum Pursh.), a rapidly growing and difficult-to-control competitor (Wagner and Rogozynski 1994).

When added to fall site preparation sprays of imazapyr or

glyphosate herbicides, sulfometuron provides effective 

control of herbaceous vegetation throughout the following

growing season (Ketchum et al. 1999), thus, eliminating

the need for an additional treatment in the spring. One of

the newer herbicides, clopyralid, provides selective control

of broadleaf herbs without injuring neighboring Douglas-fir

seedlings.

Pre-emergent herbicides have the potential to prevent

germination and suppress growth of shrub and hardwood

competitors. For example, a greenhouse study demonstrated

that hexazinone herbicide reduced germination and suppressed growth of varnishleaf ceanothus (Ceanothus velutinus Dougl.), deerbrush ceanothus (C. integerrimus H. &

A.), and thimbleberry (Rubus parviflorus Nutt.) (Rose and

Ketchum 2002b). Similarly, hexazinone reduced the survival and growth of seedlings of the invasive shrubs, Scotch

broom and Portuguese broom (Cytisus striatus Hill) (Ketchum

and Rose 2003). Figueroa (1994) found that sulfometuron

significantly reduced germination of red alder seedlings. 

Non-herbicide methods for controlling competing

vegetation also are being developed. After two decades of

research on methods for controlling red alder with cutting

treatments, Belz (2003) concluded that the greatest mortality occurred when trees were cut at six to seven years of

age and 13 to 15 weeks after budbreak, presumably when

carbohydrates reserves were at their lowest level. Tappeiner

et al. (1996) observed reductions in crown volume and area

of bigleaf maple sprout clumps if the parent trees were cut

at 1-ft height one or two years before stand harvest. Mulches

are being used successfully to both conserve soil water and

reduce abundance of competing vegetation adjacent to conifer

seedlings (McDonald and Helgerson 1990). Mulching is

most effective when the material has high longevity and is

applied early in the growing season before soil water has

been depleted.

The timing, intensity, and duration of competing vegetation control are essential features to consider for any vegetation management treatment because often they determine

treatment cost-effectiveness. Wagner et al. (1999) found

that the duration of vegetation control resulting in a continued increase in stem volume index varied among conifer

species from two to four years. Manually removing competing vegetation around ponderosa pine (Pinus ponderosa

Dougl. ex Laws.) seedlings provided similar tree growth

responses regardless of whether the treatment occurred in

years 1-3, years 4-6, or years 1-6 after planting (McDonald

and Fiddler 2001). Ten-year growth of Douglas-fir was

similar when grown with densities of varnishleaf ceanothus

of 0 to 2700 plants/acre, but it decreased by 41% when

density exceeded 6070 plants/acre (Monleon et al. 1999).

However, regardless of ceanothus density, Douglas-fir

growth increased following removal of herbaceous vegetation. Rose et al. (1999) found that Douglas-fir growth

increased with area of vegetation control, with maximum

values occurring when either 60% (one site) or 100% (two

sites) of growing space was treated. Reporting on a larg e

study that compared various levels of vegetation control in

western Oregon, Rose and Rosner (2004) found that increases

in stem volume were proportional to the total number of

years of control for all four conifer species tested. Seedling

growth after four years of control resulted in 3- to 18-fold

increases in stem volume relative to non-treated seedlings. 

Seedling Quality 

Quality of Douglas-fir planting stock has improved

greatly in the last two decades. These improvements have

been prompted by studies attesting to the benefits of large

planting stock (Wagner and Radosevich 1991b, Roth and

Newton 1996, Rose and Ketchum 2003). In addition, the

“ t a rget seedling concept,” which links specific morphological and physiological traits with field performance, has

improved methods of plantation establishment by defining

tangible seedling characteristics for nursery managers to

cultivate and for foresters to select (Rose et al. 1990). The

plug+1 and 1+1 bareroot stock-types are currently accepted

standards for plantation establishment on the Westside and

have replaced the mainstay of the 1980’s, the 2+0 bare root.

Exponential nutrient loading is a relatively new concept for

nursery fertilization regimes (Timmer 1996) in which fert i lizer is applied at an exponentially increasing rate to maintain

seedling nutrient content at a constant level, and therefore

free from nutrient stress. This approach has been used eff e ct i v e l y in forest productivity research to test the upper limit

of tree growth responses to fertilization (Powers and

Reynolds 1999).

Planting Techniques

Given the current focus on large seedlings, planting is

almost entirely done with a planting shovel, replacing the

former planting tool of choice, the hoedad. The shovel

enables planters to set the roots of large stocktypes in a

hole of adequate width and depth, thereby avoiding potential

problems associated with shallow planting and deformity

30
of the taproot. Although use of careful planting methods

continues to be recommended, (Rose and Morgan 2000),

taproot deformity at planting may not cause significant

problems to the developing plantation. Surprisingly, Haase

et al. (1993) did not find any differences in 10-year survival and growth of Douglas-fir seedlings planted with

straight, “L”-shaped, or “J”-shaped root systems. Planting

in the fall, as opposed to the winter or early spring, has

been used in coastal areas to take advantage of warm soil

temperatures in the fall that should translate into increased

root growth following planting; however, the authors are

not aware of any published research on the benefits of this

practice. 

Planting Density

Although planting density continues to be an item of

debate, most plantations are established at 400 to 500

seedlings/acre. Recent research has indicated that higher

planting densities (up to 1200 trees/ac) may stimulate

short-term increases in both diameter and height growth

of Douglas-fir (Scott et al. 1998; Flewelling et al. 2001).

This effect may be the result of a phytochrome response

that modifies seedling allometry (Ritchie 1997). Because

the growth stimulation associated with high initial densities

is relatively short-lived, and reverses after several years,

pre-commercial thinning must follow soon thereafter if

potential benefits are to be captured. It remains to be seen

if these early growth gains due to higher initial densities

justify the cost of planting more trees per acre and the need

for early pre-commercial thinning. 

Genetic Improvement

Possibly more resources have been directed towards

genetic improvement of conifers on the Westside than any

other yield-improvement treatment. Regional tree improvement cooperatives are now well into second generation

testing and breeding efforts. Nearly all large private lando w n e r s and some public agencies utilize various levels of

genetically improved seed in their regeneration efforts. A

recent realized genetic gain study in Oregon estimated a

28% stem volume gain for Douglas-fir (St. Clair et al. 2004).

Greater genetic gains than this may be achievable with

increased selection differentials (Jayawickrama and Ye 2004).

Current programs select for wood quality and stem form

factors in addition to increased growth rates. Although the

genetic source of seedlings can significantly contribute to

stand productivity, research on ponderosa pine indicates

this may only happen when they are grown without competing vegetation (McDonald et al. 1999). In the absence of

competing vegetation, full-sibling families averaged 1.3 ft

taller than “woods-run” families six years after planting;

whereas, their heights were not significantly different in the

presence of competing vegetation.

Seedling Fertilization

Seedling fertilization is being considered as a technique

for accelerating juvenile growth of Douglas-fir. New, slowrelease products have been developed that can be combined

with the soil medium of container stock or placed directly

into the planting hole. Rose and Ketchum (2002a) found

that fertilization of Douglas-fir seedlings resulted in increased

growth only on sites having adequate soil water. The growth

increases associated with fertilization were smaller and more

transient than those from control of competing vegetation,

probably because the latter is associated with increases in

both soil water and nutrients. Roth and Newton (1996)

reported decreases in Douglas-fir survival following fertilization with 200 lbs N/ac, a response they attributed, in part,

to N-stimulated increases in the abundance of competing

vegetation. Powers and Reynolds (1999) found that stem

growth responses of ponderosa pine to competing vegetation control and repeated fertilization varied according to

the inherent fertility and soil water availability of a given

site, with greater responses to fertilization occurring on the

less droughty sites.

Treatment Combinations

Various combinations of treatments have been tested

during plantation establishment to determine whether they

interact to produce synergistic, antagonistic, or simple additive responses of crop seedlings. Synergistic responses

indicate that the combined effect of two or more treatments

is greater than the sum of responses to the individual treatments applied alone. Antagonistic responses indicate that

the combined effect is less than the sum of individual treatment responses, while additive responses occur when the

combined effect is equal to the sum of the responses. For

example, the addition of repeated fertilization to a sustained

vegetation control regime caused neutral, additive, or synergistic responses of ponderosa pine growth, depending on

whether the dominant factor limiting tree growth was soil

water or fertility (Power and Reynolds 1999; R.F. Powers,

personal communication). Rose and Ketchum (2002a, 2003)

detected only additive responses of Douglas-fir growth to

combinations of seedling size, fertilization, and area of

vegetation control. Growth increases from fertilization were

greatest on sites with adequate soil moisture, similar to the

findings of Powers and Reynolds (1999), but these responses

were short-lived as opposed to the sustained responses to

vegetation control. Roth and Newton (1996) found that N

fertilization had no effect on first-year survival and growth

31
of Douglas-fir when the treatment was combined with control of competing vegetation, but in the absence of vegetation control it reduced seedling performance.

Alternative Crop Species

A wide range of factors are motivating forest managers

to consider alternative crop species to Douglas-fir. Among

many, these include development of new markets, declining availability of certain raw materials, and increased incidence of forest diseases. The widespread outbreak of Swiss

needle cast has prompted increased interest in planting

western hemlock on sites formerly planted with Douglas-fir.

A survey of all major Westside forest landowners conducted

by Briggs and Trobaugh (2001) showed the percentage of

western hemlock planted either in mixture with Douglas-fir

or by itself began a steady increase in 1999. 

Previous research has shown how Douglas-fir, a species

of moderate to low shade tolerance, tends to occur in the

upper canopy while western hemlock, capable of living in

lower light conditions, will occur in the lower canopy of

natural stands (Oliver and Larson 1996, Lewis et al. 2000).

The ability of these species to occupy different niches suggests that mixtures of them may be more productive than

pure stands (Vandermeer 1989). Recent research assessing

the differences between Douglas-fir and western hemlock

growing in pure and mixed plantations has shown that only

at high densities (700 trees/acre) will the cubic volume of

mixed stands exceed that of pure stands of either species.

Lower densities – 200 and 450 trees/ac – did not show productivity increases from the mixture (Amoroso et al. 2004). 

Red alder has become a viable species for plantation 

silviculture on the Westside. Seed collection, nursery, and

planting guidelines have been developed (Hibbs and Ager

1989, Ahrens et al. 1992). Recent interest has developed

for planting hybrid poplar (hybrid of Populus trichocarpa

Torr. & Gray and P. deltoides Bartr. ex Marsh.) on farmland in the Willamette Valley of Oregon because of its

rapid growth and high yield on poorly drained clay soils

(Hibbs et al. 2003). Such stands have produced up to 4000

f t3/acre in six years on soils considered poor for agriculture.

Minimizing Browse Damage

Although a variety of barrier products exist for protecting conifer seedlings from deer and elk browse (Schaap and

DeYoe 1986), many of these can restrict and deform shoot

growth if not maintained properly. Gourley et al. (1990)

compared growth of tall (2 ft) Douglas-fir seedlings following six methods of protection with or without control of

competing vegetation. Control of competing vegetation had

the dominant effect, increasing fifth-year height an average

of 1 ft regardless of method of protection. In plots where

vegetation was controlled, the methods of protection had

neutral or negative effects relative to seedlings receiving no

protection. It is likely that smaller seedlings, as well as

those growing under intense competition, may benefit from

protection because their smaller initial size may prolong the

time period when they are susceptible to being browsed.

Protecting Soil Productivity

A better understanding of the effects of soil disturbance

on forest productivity has been developed (Miller et al.

2004). For example, research in northern California has

shown that soil compaction effects on seedling growth can

be negative, neutral, or even positive depending on soil

t e x t u r e and soil water regime (Gomez et al. 2002). R e d u c t i o n s

in Douglas-fir growth from soil compaction following

ground-based harvesting have been shown to last as little

as two years in coastal Washington and up to seven years

in the Oregon Cascade Mountains (Heninger et al. 2002).

FUTURE NEEDS 

Many of the advances in Westside silviculture have been

the result of research aimed at providing greater understanding of the mechanisms of tree responses. In following

with this approach, areas of research likely to advance the

technology of Westside plantation establishment include:

(1) Species- and site-specific competition thresholdsHow do tree responses to competing vegetation vary with

species and site characteristics? Can models predicting

these responses be used to refine vegetation management

prescriptions and improve their cost-effectiveness?

(2) Seedling fertilization-What are the reasons for the 

limited responses of planted seedlings to fertilization, and

what are methods that can be used to overcome these 

limitations?

(3) Minimizing animal damage-While considerable

research has gone into developing various products and

practices that protect seedlings from animal damage, very

few have been shown to be cost-effective. Continued

research and development is needed in this area to develop

products or practices that reduce these growth losses.

(4) Silvicultural treatment interactions-Can treatment

responses be predicted according to the limiting factors on

a given site? A general model is needed that links seedling

resource needs with the resource supplying power of the

site and of specific silvicultural treatments. 

32
(5) Predicting young stand development-New yield 

models and plantation site index equations are needed to

forecast the differential growth rates resulting from various

silvicultural treatments during plantation establishment. 

(6) Plantation silviculture for alternative crop speciesAdvanced technology exists for establishing Douglas-fir

plantations, yet basic information on seedling responses to

treatment is still lacking for western hemlock, western redcedar, and red alder. These information gaps must be filled

if intensive management is to be applied to these alternative crop species.

ACKNOWLEDGMENTS

The authors are grateful to M. Newton, R. Deal, and 

K. Puettmann for reviewing an earlier version of this paper

and providing many helpful comments.

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This page is intentionally left blank.
1 John McClarnon is regeneration specialist, Silviculture Practices Section, British Columbia Ministry of Forests, PO Box 9513 Stn Prov Govt, 

Victoria, BC, V8W9C2.

2 R. Allan Powelson is forester/ecologist, ALTRA Forestry Ltd., P.O. Box 125 Pender Island, B.C. V0N 2M0.

Productivity of Western Forests: A Forest Products Focus

STATE-OF-THE-ART SILVICULTURAL TECHNOLOGY

AND APPLICATIONS FOR FOREST STAND ESTABLISHMENT

IN INTERIOR BRITISH COLUMBIA

John McClarnon1 and R. Allan Powelson2

INTRODUCTION

In British Columbia, where approximately 95% of the

forestland is publicly owned Provincial Forest, the government has the ultimate stewardship role and sets overall

resource management objectives. Under an overarching

legislative framework, harvesting rights and forest management responsibilities, including the mandatory achievement

of government approved free growing stocking standards,

are provided to the forest industry through an array of different agreements. In British Columbia, a “free growing

stand” is defined as a stand of healthy trees of a commercially valuable species, the growth of which is not impeded

by competition from plants, shrubs or other trees (BC Gov.

2004). The achievement of free-growing status is satisfied

by attaining pre-determined standards for crop trees within

a specified time period; height, height-above-competing

brush, density, inter-tree spacing, and species composition

(BCMOF 2000a).

39

Due to the intense pressure to remain competitive in

international softwood markets, one of the overriding

post-harvest stand management objectives for the British

Columbia forest industry has become the establishment of

acceptable free-growing stands at the lowest possible cost

in the shortest timeframe. In this context, critical issues

impacting even-aged stand establishment and management

of lodgepole pine (Pinus contorta Dougl. var. latifolia

Engelm.) in the Sub-Boreal Spruce biogeoclimatic zone

(SBS) and white spruce (Picea glauca [Moench] Voss) in the

Boreal White and Black Spruce biogeoclimatic zone (BWBS)

in interior British Columbia are reviewed.

PREDOMINANT LIMITING FACTORS

In the central and northern interior and higher elevations

of British Columbia, combinations of any of the following

limiting factors may be encountered; cold soil temperature,

wet soils in spring, over-winter damage, severe frost events,

very short growing seasons, late access to sites in the spring,

deep snow packs and snow press (Meidinger and Pojar

ABSTRACT

As part of the pressure to be competitive in international softwood markets, the British Columbia forest industries’ p o s t -

harvest management objective has become the establishment of acceptable free growing stands at the lowest possible cost in

the shortest timeframe. To achieve this objective, it is critical to understand, at a site-specific level, when and where to apply

any given silviculture intervention and how effective it will be. As well, it is important to understand the costs versus benefits

of different treatment options. Studies and operational experience in British Columbia, and especially in the sub-boreal spruce

and black and white boreal spruce zones, indicate that the survival and early growth of conifer seedlings can be substantially

improved through deployment of select seed, selection of appropriate species and stock type combinations, and through appropriate site preparation and brushing treatments.

KE Y W O R D S: Stand establishment, technology applications, limiting factors.
1991, Krasowski 1996). Damage from ungulates, hares,

voles, cattle, porcupine, spruce leader weevil, pine stem

rusts, and armillaria and tomentosus root diseases may be

locally significant limiting factors (Meidinger and Pojar

1991). To provide examples of the application of silviculture technology in interior British Columbia, this paper

focuses on sites within the SBS and BWBS zones where

the predominant growth limiting factors are either cold soil

temperature, spring soil saturation, summer drought conditions, a preponderance of vegetation competition from aspen

(Populus tremuloides Michx.), hard pine stem rusts such as

western gall rust (Endocronartium harkenssii (J.P. Moore)

Y. Hirat) or a combination of any of these (Meidinger and

Pojar 1991, McDowell 1998a, McDowell 1998b, Bedford

et al. 2000, Bedford and Sutton 2000). In order to manage

the impacts of these many limiting factors, forest practitioners in British Columbia have to use a variety of technologies and systems.

TECHNOLOGY APPLICATIONS

Biogeoclimatic Classification System 

Successful site management begins with accurate 

identification and description of site characteristics. T h e

Biogeoclimatic Ecosystem Classification (BEC) system,

which integrates climate, soil and site features, and indicator plant species to group ecosystems (Meidinger and Pojar

1991), provides a “common language” to describe forest

sites and is utilized by all forest practitioners throughout

the province as the basis for silviculture prescriptions

(http://www. for.gov.bc.ca/hre/becweb/). The classification

system provides ecosystem specific recommendations for

ecologically appropriate tree species rated on the basis of

productivity, feasibility and reliability. Region specific field

guides provide silviculture treatment recommendations,

predictions of competing vegetation potential, and ecosystem specific recommendations for site preparation. Local

hazards are communicated through ecological footnotes

as microsite limitations (e.g., elevated microsites are preferred), mesosite limitations (e.g., restricted to southerly

aspects), geographic restrictions (e.g., restricted to lower

elevations of biogeoclimatic unit), pest limitations (e.g.,

risk of heavy browsing by moose), and abiotic limitations

(e.g., risk of snow damage).

Improved Seed 

Legislation has mandated that improved seed (that which

has a genetic worth of five percent or greater and has desirable traits) must be used for reforestation when it is available and requires that all seed, either natural or improved,

must be used in compliance with seed transfer guidelines.

In British Columbia, the tree seed improvement program is

a provincially co-ordinated co-operative venture between

government and industry (FGC 2004). Program goals are

to increase the average volume gain of select seed used for

Crown land reforestation to 20% by the year 2020 and to

increase select seed use to 75% of total provincial sowing

by 2013 (FGC, 2004). In 2003, the deployment in British

Columbia of seedlings grown from improved seed included

planting 49 million interior spruce, 10 million lodgepole

pine, 4.3 million western larch, and 1.1 million western

white pine seedlings. Increasing genetic worth and the production of improved seed are leading to wider availability

of faster growing seedlings.

Site Preparation

In the past, site preparation was applied extensively in

interior British Columbia reaching a maximum of 101,009

ha in 1992/1993 (BCMOF 2000b). However, in recent

years as the amount of area site prepared in interior British

Columbia has dropped to 51,088 ha in 2002 (BCMOF 2003)

(table 1), direct planting into appropriate micro-sites in

undisturbed forest floor materials with minimal screefing

has become a widespread practice (Heineman 1998). The

suitability of this practice, however, depends on the sites

limiting factors. For direct forest-floor planting to be a success in interior British Columbia, planting should occur: as

soon after harvest as possible, on sites with adequate moisture throughout the growing season, on sites with reasonable soil temperatures, and only on sites that have low to

moderate levels of competing vegetation unless viable

options exist for vegetation management. (Heineman1998).

Site preparation to reduce planting shock and improve survival and early seedling growth remains critical on sites with

cold wet soils, very dry soils, growing season frost and/ or

significant competing vegetation particularly where herbicides are not an option (Krasowski 1996, Sutton et al.

2001). Mechanical site preparation accounted for 75% of

the 51,088 hectares treated in interior British Columbia in

2002. M o u n ding and disc trenching are the two most commonly employed site preparation methods. Other site preparation techniques include drag scarification to promote

lodgepole pine natural regeneration, prescribed burning,

and patch scarification.

In the SBS, direct forest-floor planting did not result

in significantly lower lodgepole pine seedling survival

(Bedford and Sutton 2000, Macadam et al. 2001). Similarly,

white spruce exhibited the same general trends in the BWBS

(Bedford et al. 2000) and the SBS (Sutton et al. 2001).

While there may be little improvement in seedling survival

with site preparation in the SBS and BWBS, there are significant early growth benefits (Krasowski, 1996, Bedford

and Sutton 2000, Bedford et al. 2000, Byman 2000, Sutton

40
et al. 2001). These growth performance differences attributed to site preparation, however, diminished with time

(Bedford and Sutton 2000, Bedford et al. 2000). Site preparation has also been shown to reduce the potential for overwinter injury resulting from freeze-desiccation (Krasowski

1996). Treatments that increased the root zone temperature

of young seedlings reduced the potential for over- w i n t e r

injury and damage (Krasowski 1996). As the root systems

of established seedlings expand and exploit areas outside of

the area of site preparation, growth of seedlings unimpeded

by competing vegetation, is largely independent of micro-site

and growth increments become uniform across treatment

types (Bedford and Sutton 2000).

Another beneficial aspect of site preparation is the

potential for uniformity of growth over the entirety of the

growing site. Seedling establishment is more likely to occur

on similar micro-sites after site preparation. This uniformity

of micro-site selection results in greater uniformity of

growth performance of seedlings across the growing site

(fig. 1).

Uniformity of seedling performance across the growing

site can result in earlier achievement of the seedling characteristics necessary for the statutory free growing obligations in British Columbia (table 2) (Bedford and Sutton

2000). 

This improved growth performance, however, should

not be expected to be maintained for extended time periods

into the rotation of the stand.

Seedlings

Due to significant reductions in the use of herbicides,

broadcast burning and mechanical site preparation, p r o m p t

planting of high quality seedlings has become the primary

41

Table 1—Preparing sites for planting and natural

regeneration on interior British Columbia Crown

land in 2002/2003 (BCMOF 2003).

Area in

Treatment hectares

Biological 48

Burn 5,917

Chemical - air 0

Chemical - ground 232

Grass seeding 77

Manual 5978

Mechanical 38,836

Not specified 18

Total 51,088 Figure 1—Height frequency distribution on unprepared vs. prepared sites.

Table 2—Effect of site preparation on time to free growinga condition and meeting 

green-upb requirements.

Treatment Species Years to free growing (2 m) Years to green-up (3 m)

Untreated Spruce 7 16

Herbicide Spruce 6 11

Breaking plow Spruce 5 10

Well stocked Minimum Stocking

Untreated Pine 7 11 9

Disc trench Pine 6 7 8

Burn Pine 5 7 7

a A free growing stand means a stand of healthy trees of a commercially valuable species, the growth of which 

is not impeded by competition. b Stands are required to meet “green up”, generally a height of 3 to 3.5 m of dominant trees of a commercial 

tree species, before adjacent stands or cutblocks can be harvested.
tool in addressing site-limiting factors. In British C o l u m b i a ,

approximately 85% of the harvested area is planted

( B C M O F, 2003). Regeneration is primarily focused t o w a r d s

conifers with the exception of the boreal region where

aspen and mixedwood stand regeneration is more c o m m o n .

Tree planting densities are usually in the range of 1200 to

1600 stems per hectare. Very low densities are prescribed

in some fire prone natural disturbance ecosystems or where

wildlife management objectives (e.g., continuous g r i z z l y

bear forage production) take precedence over timber objectives.

Development of container seedling techniques evolved

in British Columbia in the 1970s. Continuous improvement

since that time has resulted in large-scale production of

high quality seedlings in a diversity of stocktypes (BCMOF

1998). Lodgepole pine and interior spruce account for 47%

and 31%, respectively, of the approximately 234 million

seedlings sown in British Columbia in 2004 (SPAR 2004).

Greater than 90% of the sowing is to produce one-year-old

container stock and the 410-styroblock container size (cavity volume of 80 ml) accounts for 40% (SPAR 2004) of the

production. The majority of seedlings (80%) are planted in

the spring window (to June 21st), with close to 20% as

summer plant, and a small remainder as fall plant (SPAR

2004). While approximately 24% of the sowing (mostly

lodgepole pine) is in copper treated container stock (SPAR

2004), little to no gain in survival and growth has been

demonstrated from this treatment (Jones et al. 2002). The

microsite that healthy seedlings are placed into is more

important in affecting growth than the nursery treatment

they were subjected to prior to planting (Jones et al. 2002).

Vegetation Management 

Forest practitioners in the British Columbia interior

may encounter any one of a multitude of vegetation complexes. These include the fireweed (BCMOF 1997c), fern

(BCMOF 2002), ericaceous shrub and subalpine herb

(BCMOF 1997b), pinegrass (BCMOF 1997e), reedgrass

(BCMOF 2000c), dry alder (BCMOF 1997a), wet alder

(BCMOF 1997f), aspen, and mixed broadleaf shrub complexes (BCMOF 1997e). A web-based stand establishment

decision aid is now available to provide practitioners with

access to the latest available information on vegetation

management of different complexes. The key to minimizing and justifying expenditures is determining the appropriate situations, timing, and treatment types for vegetation

management.

Approximately 60% of the 53,637 hectares brushed

annually in interior British Columbia is done with manual

techniques, including brush saws, chain saws, girdling tools,

and manual stem snapping (table 3). Aerial spraying and

ground based herbicide application account for approximately 25 and 15% of the brushing program respectively

(BCMOF 2003). A widespread lack of public acceptance of

the use of herbicides in British Columbia has limited the

number of herbicides available, the situations where they

can be used, and the methods of application that can be

deployed.

In the SBS and BWBS, aspen is one of the main competitors limiting coniferous growth potential. Strategies to

reduce the impacts of aspen have been to leave it standing

during harvest and girdle some of the residual stems so that

approximately 5m2/ha remain to reduce sprouting, postharvest foliar spray, cut-stump, and hack-and-squirt applications of glyphosate; basal bark and cut-stump applications

of triclopyr; hand-snapping in mid-summer below the lowest live limb, cutting stems below the lowest live limb, and

2 entry manual brushings that retain sufficient aspen stems

in the first entry to maintain conifer tree growth but reduce

aspen coppicing.

Determining the amount of broadleaved basal area that

can be retained without significantly reducing growth performance of the target crop species is essential in developing effective mixed-wood management stand establishment

prescriptions and to determine acceptable levels of broadleaf

components in free growing coniferous stands to maintain

biodiversity and ecological functioning (Comeau et al. 1999,

Comeau et al. 2003.). Species dependant factors such as

leaf shape, size, orientation, and opaqueness impact light

availability below broadleaf canopies (fig. 2) and light

availability increases rapidly with height in a broadleaf

canopy, even in dense stands where understory light availability is low (Comeau et al. 2003). Interest by forest managers in retaining either crop or non-crop broadleaved stems

42

Table 3—Brushing on interior British Columbia 

Crown land in 2002 and 2003 (BCMOF, 2003).

Area in

Treatment hectares

Biological 1,858

Chemical air 14,204

Chemical Ground 6,276

Manual – not specified 1,515

Manual – non-motorized 17,996

Manual – motorized 13,052

Mechanical 5

Not specified 191

Total 53,637
in stands targeted for coniferous regeneration has led to the

development of predictive models for aiding in the determination of the amount of broadleaf stems to be retained

(Comeau et al. 2003).

Forest Health

Western gall rust is one of the significant growth limiting factors of lodgepole pine in both the SBS and BWBS

zones (Fink et al. 1993, Reich 2002). Conducting forest

health overview studies has identified fairly specific ecosystems where western gall rust will have a higher likelihood of impacting the regenerating stand (Reich 2002).

Current management strategies for minimizing the impacts

of hard pine stem rusts are the establishment and maintenance of high stand densities (Reich 2002). Stand establishment regimes being employed that can result in high

densities on these sites include the encouragement of high

natural regeneration levels (e.g. stump processing and chaindragging), direct seeding (e.g., aerial, hand, or direct spot

seeding), or high density planting (Reich 2002).

Costs

Cost of the technologies applied to achieve a free growing stand, as is legislatively required in British Columbia,

varies widely (table 4). While individually some treatment

costs may appear to be high, forest practitioners have to

weigh this cost against the potential reductions in time to

achieve the legislative growth obligations (table 2) that

may be possible with the various combinations of these

treatments. By fully understanding the growing site and its

limitations, the goal of maximizing growth performance

while minimizing total cost may be achievable.

Future directions

Future directions may include the development of

approaches to assessing the free growing requirement that

are linked to growth and yield objectives and assess achievem e n t of the free growing objectives at a landscape level

rather than at the individual cutblock level. Tools are

required to predict appropriate mixtures of broadleaves and

conifers for different crop objectives. Results in interior

British Columbia remain variable with respect to seedling

response following fertilization at time of planting or nutrient loading in the nursery and further work is required to

43

Figure 2—Light availability under broadleaf canopies.

Table 4—Range of current costs for silvicultural 

treatments in Interior British Columbia.

Cost Range

Treatment ($CAD/ha)

Broadcast burning 400 – 2000

Excavator mounding 700 – 900

Disk trench 180 – 220

Chain drag 180 – 250

Seed (B vs. A class) 16 – 84

Seedlings 186 – 545

Planting (no site prep.) 336 – 420

Planting (site prepared) 238 – 322

Direct seed/site prepared 400 – 550

Aerial herbicide spray 225 – 275

Backpack herbicide 300 – 700

Sheep grazing 260 – 400

Brush saw 450 – 500

Manually brush (1-m radii) 500 – 600

“Snap” aspen 250 – 350

Thinning 450 – 600

Pruning 550 – 900
improve consistency of response. Widespread loss of plantations to drought and fire in 2003 combined with largescale forest health outbreaks (e.g., mountain pine beetle)

suggests that climate change may become one of the most

significant factors influencing future stand establishment.

SUMMARY

Studies and operational experience in British Columbia,

including the SBS and BWBS zones, indicate that the survival and early growth of conifer seedlings can be substantially improved through deployment of select seed, selection

of appropriate species and stock type combinations, and

appropriate site preparation and brushing treatments. Choice

of treatments that do not improve survival or growth or

treatments that exacerbate the growth-limiting factors present on a site will fail to achieve the growth performance

objectives in a timely manner and will lead to higher

expenditures when trying to achieve the free growing obligations.

LITERATURE CITED

Bedford, L.; Sutton, R.F. 2000. Site preparation for establishing lodgepole pine in the sub-boreal spruce zone of

interior British Columbia: the Bednesti trial, 10 years

results. Forest Ecology and Management 126: 277-238.

Bedford, L.; Sutton, R.F.; Strodeur, L.; Grismer, M. 

2000. Establishing white spruce in the boreal white and

black spruce zone: Site preparation trials at Wonowon

and Iron creek, British Columbia. New Forests 20: 213-

233.

British Columbia Ministry of Forests [BCMOF]. 1997a. 

Operational summary of vegetation management: dry

alder complex. Victoria, BC: Forest Practices Branch.

11 p.

British Columbia Ministry of Forests [BCMOF]. 1997b.

Operational summary of vegetation management: ericaceous shrub complex. Victoria, BC: Forest Practices

Branch. 11 p.

British Columbia Ministry of Forests [BCMOF]. 1997c. 

Operational summary of vegetation management: fireweed complex. Victoria, BC: Forest Practices Branch.

11 p.

British Columbia Ministry of Forests [BCMOF]. 1997d. 

Operational summary of vegetation management: mixed

shrub complex. Victoria, BC: Forest Practices Branch.

11 p.

British Columbia Ministry of Forests [BCMOF]. 1997e. 

Operational summary of vegetation management: pinegrass complex. Victoria, BC: Forest Practices Branch.

11 p.

British Columbia Ministry of Forests [BCMOF]. 1997f.

Operational summary of vegetation management: wet

alder complex. Victoria, BC: Forest Practices Branch.

11 p.

British Columbia Ministry of Forests [BCMOF]. 1998. 

Provincial seedling stock type selection and ordering

guidelines. Victoria, BC: Forest Practices Branch. 

British Columbia Ministry of Forests [BCMOF]. 2000a. 

Establishment to free growing guidebook: revised 

edition [May]. Victoria, BC: Forest Practices Branch. 

British Columbia Ministry of Forests [BCMOF]. 2000b. 

Just the facts: a review of silviculture and other forestry

statistics. Victoria, BC: Forest Practices Branch. 

British Columbia Ministry of Forests [BCMOF]. 2000c. 

Operational summary of vegetation management: reedgrass complex. Victoria, BC: Forest Practices Branch. 

8 p.

British Columbia Ministry of Forests [BCMOF]. 2002. 

Operational summary of vegetation management: fern

complex. Victoria, BC: Forest Practices Branch. 8 p.

British Columbia Ministry of Forests [BCMOF]. 2003. 

2002/2003 Annual service plan report: detailed statistical tables for 2002/03. Victoria.

Byman, P. 2000. Response of lodgepole pine seedlings to 

Donaren mounding. Prince George, BC: University of

Northern British Columbia. M.S. thesis. 55 p.

Comeau, P.G.; Biring, B.S.; Harper, G.J. 1999. Conifer 

response to brushing treatments: a summary of British

Columbia data. Extension Note 41. Victoria, BC: British

Columbia Ministry of Forests, Research Branch. 12 p.

44
Comeau, P.; McClarnon, J.; Heineman, J.; Kazems, R. 

2003. Predicting light availability in broadleaf stands: a

tool for mixedwood management. Victoria, BC: British

Columbia Ministry of Forests, Forest Practices Branch.

22 p.

Fink, K.E.; Humphreys, P.; Hawkins, G.V. 1989. Field 

guide to pests of managed forests in British Columbia.

FRDA report 16. Victoria, BC: British Columbia

Ministry of Forests, Protection Branch. 188 p.

Forest Genetics Council of British Columbia [FGC]. 

2004. Forest genetics council of British Columbia

strategic plan 2004 – 2008. Victoria, BC: Forest

Genetics Council of British Columbia. 9 p.

Heineman, J. 1998. Forest floor planting: a discussion 

of issues as they relate to various site limiting factors.

Silviculture note #16. Victoria, BC: Forest Site

Management Section: British Columbia Ministry of

Forests, Forest Practices Branch. 11 p.

Jones, M.D.; Kiiskila, S.; Flanagan, A. 2002. Field 

performance of pine stocktypes: two-year results on

interior lodgepole pine seedlings grown in Styroblocks,

Copperblocks, or Airblocks. B.C. Journal of Ecosystems

and Management. Forest Research Extension Partnership.

British Columbia Journal of Ecosystems and Management.

Vol. 2 (online at http://www.forrex.org/jem/2002/vol2/

no1/art5.pdf) Vol. 2.

Krasowski, M.J. 1996. Measures to reduce overwinter 

injury to planted spruce in the boreal forest of British

Columbia. FRDA report 254. Victoria, BC: British

Columbia Ministry of Forests Research Branch,

Canadian Forest Service. 18 p.

Macadam, A., Sutton, R.F., Bedford, L. 2001. Site 

preparation for establishing lodgepole pine on backlog

sites in the sub-boreal spruce zone. Silviculture note

#27. Victoria, BC: Silviculture Practices Section, British

Columbia Ministry of Forests, Forest Practices Branch.

5 p.

McDowell, J.A. 1998a. The ecology of the sub-boreal 

spruce zone. Victoria, BC: British Columbia Ministry 

of Forests, Research Branch. 6 p.

McDowell, J.A. 1998a. The ecology of the boreal white 

and black spruce zone. Victoria, BC: British Columbia

Ministry of Forests, Research Branch. 6 p.

Meidinger, D.; Pojar, J. 1991. Ecosystems of British 

Columbia. Special Report Series 6. Victoria, BC: British

Columbia Ministry of Forests, Research Branch. 330 p.

Province of British Columbia [BC Gov.]. 2004. Forest 

and Range Practices Act. Victoria, BC.

Reich, R. 2002. Forest health issues: options and decision 

aids for managing hardpine stem rusts in F.L.A. 18162

of the Nechako forest. [place of publication unknown].

Seed Planning and Registry System [SPAR]. 2004. Seed 

planning and registry system on-line report. Victoria,

BC: British Columbia Ministry of Forests.

Sutton, R.F.; Bedford,L.; Strodeur, L.; Grismer, M. 

2001. Site preparation for establishing interior spruce 

in British Columbia: trials at Upper Coalmine and

Mackenzie. Western Journal of Applied Forestry 

16: 9-17.

45
This page is intentionally left blank.
1 Russell T. Graham, Theresa B. Jain are Research Foresters, USDA Forest Service, Rocky Mountain Research Station, 1221 South Main, 

Moscow, ID, 83843.

2 Phil Cannon is Corporate Silviculturist, Boise Corporation, 1111 West Jefferson Street, P.O. Box 50 Boise, ID 83728.

Productivity of Western Forests: A Forest Products Focus

STAND ESTABLISHMENT AND TENDING 

IN THE INLAND NORTHWEST

Russell T. Graham1, Theresa B. Jain1, Phil Cannon2

FORESTS OF THE INLAND NORTHWEST

The Inland Northwest (144.2 million ac) forest region 

is defined by the Bitterroot, Selkirk, Cabinet, Salmon River,

Lemhi, Steens, Purcell, Cascade, and Blue mountain ranges

with many having elevations over 5,000 ft. This rough and

complex topography results in a variety of forest settings

ranging from steep slopes in narrow V-cut canyons to gentle

rolling slopes in wide river valleys. During the Pleistocene,

alpine glaciers shaped many of the canyons and valleys

throughout the area. Now these glaciated landscapes are

ABSTRACT

The moist, cold, and dry forests of the Inland Northwest occupy approximately 144 million acres. Ponderosa pine, lodgepole pine, western white pine, western larch, and Douglas-fir are usually the preferred commercial species of the area.

These early-seral species are relatively resistant to endemic levels of insects and diseases. They tend to grow rapidly and 

in general produce commercial products at a young age, especially using focused management actions packaged in silvicultural systems that are documented in silvicultural prescriptions. Even-aged systems (clearcut, seed-tree, and shelterwood)

are the most appropriate for growing commercial products. In limited circumstances uneven-aged systems may be appropriate on sites where ponderosa pine is the late seral-species. Planting of improved, site adapted trees usually offer the greatest

control over the amount, kind, and establishment of plantations. The control of competing vegetation during the site preparation and tending phases of the silvicultural system is usually extremely beneficial in enhancing tree growth and product

development. The forest soils of the Inland West are generally deficient in nitrogen and, in some settings, also potassium

deficient. The organic and mineral surface layers, often containing ash and loess soils, are vulnerable to compaction, displacement, or damage from fires (prescribed and wild) or mechanical forest operations. Therefore, soil and its conservation

should be integral to all activities included in a silvicultural system. For production forestry, herbicides offer an alternative

that can maintain the soil resource yet control competing vegetation and most often yield excellent results when properly

applied. Cleanings, weedings and thinnings are integral parts of the silvicultural system. These and all parts of silvicultural

systems designed to produce commercial products can be readily quantified, displayed, and visualized (spatially explicit)

through time using the Forest Vegetation Simulator.

KEYWORDS: Forest products, silvicultural systems, regeneration, stand tending, fertilization, site preparation, 

forest management.

47

covered with a mantle of glacial till often compacted on the

valley floors. Much of the fine silt outwashed by the glaciers was redeposited by winds leaving deep layers of loess

deposits over many landscapes. Some 15,000 to 12,000

years ago, Glacial Lake Missoula repeatedly filled and

emptied, flooding much of northern Idaho and eastern

Washington removing topsoil and redistributing the surface

sand, silt, and gravels. The eruption of pre-historic Mt.

Mazama (Crater Lake, OR) about 7,000 years ago deposited

a fine textured layer of ash up to 25 inches thick across the

area. The granitic and metasedimentary rocks, ash, and
loess deposits throughout the area are continually being

modified by disturbance events giving rise to a wide variety

of soils (Jain and Graham 2005, Quigley et al. 1996).

Moist marine air originating from the Pacific Ocean

moderates temperatures within the Inland Northwest, while

continental dry and cold air from the east brings cold

weather in winter and hot weather in the summer. Dry

Arctic air brings damaging frosts in winter and cool periods

in summer and the interaction of the marine and continental masses brings convective precipitation and lightning in

summer and warm wet periods in the winter. These air

masses, along with the heterogeneous and rugged topography, create a highly variable climate, which in turn, supports mosaics of compositionally and structurally diverse

forests. Historically (1850 to 1900), 19 percent (27.4 million acres) of the Inland Northwest (144.2 million acres)

was covered by dry forests, with 30 percent of them occurring below 4,000 feet and the remainder occurring at higher

elevations. Moist forests covered 18 percent (25.9 million

acres) of the region. The cold forests historically made up

10 percent of the area with 99 percent of them growing at

elevations exceeding 4,000 feet (Hann et al. 1997).

Moist Forests

Moist forests of the Inland Northwest occur in two locations, the eastern Cascade Mountains (east of the Cascade

Crest in Washington and Oregon) and the Northern Rocky

Mountains (northeastern Washington and Oregon, northern

Idaho, and western Montana) (fig. 1). They grow at elevations ranging from 1,500 to 5,300 feet and occasionally

occur at elevations up to 6,000 feet (Foiles et al. 1990,

Graham 1990, Packee 1990, Schmidt and Shearer 1990,

Hann et al. 1997) (fig. 1). These forests are influenced by a

maritime climate with wet winters and dry summers. Most

precipitation occurs during November through May, with

amounts ranging from 20 to 90 inches (Foiles et al. 1990,

Graham 1990, Packee 1990, Schmidt and Shearer 1990).

Precipitation comes as snow and prolonged gentle rains,

accompanied by cloudiness, fog, and high humidity. Rainon-snow events are common January through March. A

distinct warm and sunny drought period occurs in July and

August with rainfall in some places averages less than one

inch per month. Soils that maintain these forests include,

but are not limited to, Spodosols, Inceptisols, and Alfisols.

A defining characteristic of the Northern Rocky Mountains

is the layer of fine-textured volcanic ash (up to 25 inches

thick) that caps the residual soils. 

For both locations, the vegetation complexes range from

early- to late-seral, and occur within a landscape mosaic

possessing all possible combinations of species and seral

stages. Potential vegetation type (PVT) is a classification

system based on the physical and biological environment

characterized by the abundance and presence of vegetation

in the absence of disturbance (Daubenmire and Daubenmire

1968, Hann et al. 1997, Smith and Arno 1999). They are

defined by and named for indicator species that grow in

similar environmental conditions (Hann et al. 1997). The

PVTs in the Northern Rocky Mountains include western

redcedar (Thuja plicata), western hemlock (Tsuga heterophylla) and grand fir (Abies grandis) with western white

pine (Pinus monticola), western larch (Larix occidentalis),

lodgepole pine (Pinus contorta), Douglas-fir (Pseudotsuga

menziesii) and ponderosa pine (Pinus ponderosa) as the

early- and mid-seral species (Daubenmire and Daubenmire

1968, Hann et al. 1997). The eastern Cascades PVTs include

western redcedar, western hemlock, grand fir, white fir

(Abies concolor), and noble fir (Abies procera). The earlyand mid-seral species include lodgepole pine, Douglas-fir,

and ponderosa pine while western white pine and western

larch are less abundant when compared to forests in the

Northern Rocky Mountains (Franklin and Dyrness 1973,

Lillybridge et al. 1995).

Lush ground-level vegetation is the norm in the moist

forests. The vegetation complexes are similar to those

occurring on the west-side of the Cascade Mountains and

in some Pacific coastal areas. Tall shrubs include vine maple,

(Acer circinatum), Rocky Mountain maple (Acer glabrum),

Sitka alder (Alnus sinuata), devil’s club (Oplopanax horridum), rose (Rosa spp.), gooseberry (Ribes spp.), huckleberry (Vaccinium spp.,) and willow (Salix spp.). Forbs

include baneberry (Actaea rubra), pathfinder (Adenocaulon

b i c o l o r), wild ginger (A s a rum caudatum), queencup beadlily

(Clintonia uniflora), bunchberry dogwood (Cornus canadens i s) , and golden thread (Coptis occidentalis) (fig. 2). 

Throughout the moist forests, native disturbances (snow,

ice, insects, disease, and fire) singly, and in combination,

created heterogeneity in patch sizes, forest structures, and

compositions. Ice and snow created small gaps and openings, thinning forest densities and altering species composition. Native insects (e.g., pine beetle [Dendroctonus spp.])

and diseases (e.g., root rots [A r m i l l a r i a spp.]), mistletoe

(A rc e u t h o b i u m spp.) infected and killed the very old or

stressed individuals which tended to diversify vegetation

communities (Hessburg et al. 1994, Atkins et al. 1999).

Fires played a role in creating a mosaic of forest compositions and structures. Non-lethal fires (low intensity and

severity surface fires that cleaned the forest floor, killed

and/or consumed small trees and shrubs, and killed lower

branches of overstory trees while leaving them alive)

occurred at relatively frequent intervals (15 to 25 yrs) in a

48
quarter of the area. Lethal fires (intense and severe crown

fires that killed and/or consumed the vegetation in all

canopy layers) burned about a quarter of the area at intervals of 20 to 150 years but occasionally extended to 300

years. The mixed-fire regime (a combination of lethal and

non-lethal fires) occurred across the rest of the moist forests

at 20 to150 year intervals. Fires typically started burning 

in July and were usually out by early September when the

weather changed (Hann et al. 1997). Although fire exclusion

played a role in altering the moist forests of the Northern

Rocky Mountains, introduction of a European stem rust,

white pine blister rust (C ro n a rtium ribicola) in 1910, caused

the greatest change (Neuenschwander et al. 1999, Fins et

al. 2001). The rust infects all five-needle pines, and subsequently decimated the abundant western white pine (fig. 3).

Because the rust killed so many trees, the majority of surviving pines were harvested under the assumption they too

would succumb to the rust (Ketcham et al. 1968).

Cold Forests

Within the Inland Northwest, cold forests occur at high

elevations occupying about 10 percent of the area. T h e y

occur primarily in northern Idaho, central Idaho, and in 

the Northern Cascades Mountains of Washington (fig. 1).

Growing seasons in cold forests are short, ranging from

approximately 90 days at the lower elevations to just a few

weeks at the higher elevations, and frosts can occur any

time of the year. These forests are limited by poorly developed soils, and limited by moisture in some areas. Nearly

49

Figure 1—Extent of the forests of the Inland

Northwest (144.2 million acres). The cold forests

containing subalpine fir and Engelmann spruce

potential vegetation types (PVTs) occupy 14.4 

million acres (10%) of the area, the dry forests 

containing ponderosa pine, Douglas-fir, and dry

grand fir PVTs occupy 27.4 million acres (19%),

and the moist forests containing the moist grand

fir/white fir, western redcedar, and western hemlock PVTs occupy 25.9 million acres (18%) 

(Hann et al. 1997). 

Figure 2—A young (100-year-old) stand of western white pine

exhibiting a lush layer of ground-level vegetation located north of

Wallace, Idaho. 
forests. Some of the most commonly occuring forbs include

beargrass (Xerophyllum tenax), round-leaved violet (Viola

orbiculata), and queencup beadlily (Cooper et al. 1991).

The PVTs dominating the cold forests include subalpine

fir and subalpine fir/Engelmann spruce (Picea Engelmannii) .

Western larch and lodgepole pine are early-seral species in

the subalpine fir/Engelmann spruce PVT, Douglas-fir and

western white pine are mid-seral species, and grand fir,

Engelmann spruce, and subalpine fir are late-seral species

(fig. 4). The mixes of these species occurring in the subalpine fir/Engelmann PVT are highly dependent on elevation (and associated climate), and disturbance frequency

and type.

Depending on the physical setting, the cold forests of

the Inland Northwest historically (1850-1900) burned at 25

to 100 year intervals. Approximately 10 percent of these

forests were burned by non-lethal surface fires, every 30 

to 100 years. Lethal crown fires burned 25 to 30 percent of

the cold forests every 30 to 100 years with the longer intervals occurring in moist areas. During the short fire season

(≈ 60 days), a mixed fire regime burned about 60 percent

of the cold forests at 25- to 100-year intervals, with occasional large fires occurring every 100 years (Hann et al.

1997).

all (99 percent) of the cold forests occur over 4,000 feet,

but cold air drainage allows some cold forests to extend

below 4,000 feet (Hann et al. 1997). 

On settings dominated by subalpine fir (Abies lasiocarpa), mean annual temperatures range from 25° to 40° F.

Precipitation generally ranges between 24 and 75 inches

with the majority falling in the form of snow and sleet. Snow

comes early and stays late and can reach depths over 500

inches on settings in the Cascade Mountains with lesser

amounts where lodgepole pine persists (central Oregon and

central Idaho) (Alexander et al. 1990). The soils supporting

the cold forest are relatively young. They were covered by

extensive mountain glaciers during the Pleistocene and

have been free of ice less than 12,000 years. At the higher

elevations, most soil parent material is alluvium or glacial

tills, but soil surfaces range from very weakly weathered

(cobbly with no organic layers) to thick soils composed

primarily of organic materials. 

Like the moist forests, lush ground-level vegrtation is

the norm for most settings in the cold forests. Tall shrubs

include false huckberry (Menziesia ferruginea) and Sitka

alder while the dominant medium and low shrubs are often

huckleberries. Pinegrass (Calamagrostis rubescens), bluejoint reedgrass (Calamagrostis canadensis), and elk sedge

(Carex geyeri) typify the graminoids occurring in the cold

50

Figure 3—Western white pine blister

rust (A), an introduced disease from

Europe, in the early 1900s devastated

much of the native western white pine.

However through breeding programs

and natural resistance, western white

pine is once again a viable commercial

species (B). This stand of first-generation blister rust-resistant pines is ≈ 50

years old, ≈100 to 120 feet tall, and ≈

18 to 22 inches in diameter.
Dry Forests

Dry forests occur across a wide range of elevations in

northeastern Washington, northeastern Oregon, central and

southern Idaho, and south-central Oregon (fig. 1) (Hann et

al. 1997). Soil parent materials include granites, metasedimentaries, glacial tills, and basalts. Vegetation in these

forests is usually limited by water availability and often is

subject to drought. Nutrient deficiencies develop in eroded

areas that can limit forest development. Douglas-fir, ponderosa pine, and dry grand fir/white fir (PVTs) dominate

these settings (Hann et al. 1997). When western larch is

present in dry forests it is always an early-successional

species (dominant after disturbance). Grand fir/white fir or

Douglas-fir are late-successional species that are usually

more shade-tolerant than the early-seral species they succeed, while ponderosa pine can play both roles, depending

on the PVT (Daubenmire and Daubenmire 1968, Hann et

al. 1997). Surface vegetation in the dry forests includes

shrubs (kinnikinnick (Arctostaphylos uva-ursi), Ceanothus

spp., snowberry (Symphoricarpos albus), ninebark [Physocarpus malvaceus]), grasses (pine grass) e.g., bromes

(Bromus spp.), and sedges (Carex spp.) (Foiles et al. 1990,

Hermann and Lavender 1990, Oliver and Ryker 1990)

(fig. 5).

51

Figure 4—A thinned stand of lodgepole pine (an early-seral species)

growing on a subalpine-fir potential vegetation type.

Figure 5—A young (70-year-old) ponderosa pine stand being maintained by a

low intensity surface fire. Note the presence of some ground-level vegetation.

Fire, insects, diseases, snow, ice, and competition

thinned these forests, and surface fires provided opportunities for plant regeneration (Pearson 1950, Foiles et al.

1990, Hermann and Lavender 1990, Oliver and Ry k e r

1990). In concert, these disturbances historically maintained a variety of structural and successional stages. Fire

exclusion, harvesting, and changes in fire regime altered

the composition and structure of the dry forests (Hann et

al. 1997). The area burned currently by non-lethal surface

fires is estimated to be less than 50 percent of the dry

forests and the mean interval of these fires is estimated to

be to 40 to 80 years. Mixed-fires are estimated to burn 35

percent of the dry forests with a mean interval of 45 to 60

years and lethal fires are estimated to burn 20 percent of

the dry forests at mean intervals of 45 to 60 years (Hann 

et al. 1997). 

FOREST SOIL

Soil is the foundation of a forest ecosystem and its

character is a major contributor to site productivity (Harvey

et al. 1987). In general, nitrogen (N) is the most limiting

nutrient in most forests (Moore 1988, Moore et al. 1991).

However, there is evidence that potassium (K) also plays 

a key role, especially in relation to disease and insect infestation (Moore et al. 1994). As stated earlier, much of the

Inland Northwest is covered by rich loess and ash soils.
These materials, along with the weathering of the parent

materials (granitics, basalts, meta-sediments), all contributed to the productivity of the forest. Therefore, conservation of the soil resource is essential to maintain and sustain

forest productivity.

The character of the litter, humus, soil wood, and surface

mineral layers of forest soils are critical when developing

silvicultural systems (Harvey et al. 1987, Jurgensen et al.

1997). These soil layers are most easily and commonly

d i sturbed by silvicultural activities, yet they are crucial to

forest productivity. Depending upon the setting, org a n i c

matter (OM) is generally concentrated near the soil surface.

O rganic matter maintains the nitrogen cycle in soils through

its decomposition and by facilitating N fixation (the process

of making elemental N into a form that plants can use) and

N storage of N (Jurgensen et al. 1979). Physical properties

and nutrition are very important soil attributes but the biological component is integral for maintaining forest productivity. In particular, ectomycorrhizae (fungi that have a

symbiotic relationship with the plants) and their environment are critical for maintaining soil productivity. Ectomycorrhizae establish on the root systems of trees and facilitate the uptake of both water and nutrients by the tree,

which in turn supplies nutrients to the fungi (Harvey et al.

1981, Harvey et al. 1987). 

Woody Residues

Although they are not a soil component, the quantity,

quality, and disposition of coarse woody debris (CWD) can

influence forest soils (Harvey et al. 1987, Jurgensen et al.

1997). The quantity of downed material can vary dramatically, depending on site, forest conditions, and forest treatments (Brown and See 1981). Physically, woody residues

protect soil from erosion, displacement and compaction.

Residues provide shade and protection from wind and snow

and can protect newly established seedlings from livestock

(Edgren and Stein 1974, Graham et al. 1992). However,

falling or rolling logs can damage regeneration and fuel

loadings can threaten forests by increasing the fire hazard

(Brown et al. 2003). Decaying logs, especially those with

the incipient and advanced forms of decay, are excellent

substrates for non-symbiotic nitrogen fixation and if nitrogen-fixing plants such as ceanothus (Ceanothus spp.), buffaloberry (Shepherdia canadensis), or leguminous forbs are

not present, non-symbiotic forms of nitrogen fixation can

be significant. 

In addition to CWD, organic input to forest soils comes

from many other sources. Grasses, shrubs, root turnover,

needle fall, etc. contribute to soil OM. In general, CWD

comes from tree boles and limbs over three inches in diameter (smaller material is usually considered a fire hazard).

Accumulation of CWD on the forest floor depends upon

the amount of decomposition occurring on a site and the

frequency and severity of wildfires that burn a forest (Brown

and See 1981, Brown 1983). In general, those forests that

were frequently burned by low intensity surface fires tended

to accumulate and use less CWD than the cold and moist

forests with long fire-return intervals (Graham et al. 1994a,

Hann et al. 1997). The amount of CWD suggested for

maintaining soil productivity ranges from 3 tons per acre

on ponderosa pine settings to over 30 tons per acre on

western hemlock settings in moist forests (fig. 6) (Graham

et al. 1994a). 

Litter

Unconsolidated and undecomposed litter directly provide both N and ectomycorrhizae habitat for soil function.

This material is composed of organic materials from trees,

shrubs, grasses, forbs, and other plant material. Litter is not

usually important for ectomycorrhizal activity, but if moisture is maintained in these layers, ectomycorrhizae can be

present (Harvey et al. 1987). However, through its decay,

litter becomes a greater soil contributor. Litter can vary

widely in amount, composition, and structure depending

on forest type and PVT, as well as fire-return interval and

decomposition rate. Litter protects the soil from erosion and

retains moisture in the lower layers (Pannkuk and Robichaud

2003.) and protects soils from compaction (Lull 1959).

Litter can be an impediment to both natural and artificial

tree regeneration. If the litter layer is thick, which often

52

Figure 6—The amount of coarse woody debris suggested by Graham et al.

(1994) for maintaining soil productivity in the forests of the Rocky Mountains.

A=Arizona, I=Idaho, M=Montana for the habitat types where the recommendations apply.
occurs in ponderosa pine forests where decomposition is

slow and fire has been excluded, tree seeds falling on this

layer germinate, but root elongation may not keep pace

with litter drying (Haig et al. 1941, Pearson 1950). On the

other hand, if litter remains moist during germination and

early seedling growth (a situation that may be found in

many moist forests), establishment of tree seedlings on

o rganic layers is quite common (Minore 1972). Because

this most often occurs in the moist and cold forests with

late seral species, the desired mix of species for commodity

production is not often realized. 

Humus

Even though the humus (decomposed material in which

plant parts are indistinguishable) soil layer may be very thin

(i.e. < 0.25 in), it can be a prime site for both N and ectomycorrhizae. For example, in the surface 12 inches of a

Douglas-fir/ponderosa pine forest soil, over 20 percent of

the total N can occur in the humus and over 30 percent of

the ectomycorrhizae (Harvey et al. 1987). In addition, it

often has high moisture contents and is rich in calcium,

potassium, and magnesium. This layer often represents the

transition between organic layers and the mineral soil and,

when it is burned over, it is a superb site for seed germination and seedling establishment (Haig et al. 1941).

Soil Wood

A component of forest soils that is often over looked is

soil wood which is highly decomposed wood incorporated

into mineral soil horizons and is usually in the form of

brown cubicle rot (fig. 7) (Harvey et al. 1987). As it ages

and further decomposes, it can take on a much finer texture.

As with the other organic components of soil, the quantity

and character of soil wood can be quite variable. For example, the amount of soil wood in the surface 12 inches of

a forest soil is 20 percent in cold forests, 22 percent in

Douglas-fir forests, and over 26 percent in moist forests

(Harvey et al. 1987). Soil wood does not usually occur as a

layer within soil but rather occurs in deep pockets created

by buried logs and decaying stumps (Reinhardt et al. 1991).

Soil wood protects soils from compaction, provides OM to

the mineral soil, is also an important source of N (≈20 percent of the amount in surface 12 inches of soil) and is an

excellent substrate for ectomycorrhizae (≈50 percent of the

amount in surface 12 inches of soil) (Harvey and others

1987). Because of its water-holding availability and nutritional, biological, and physical characteristics, soil wood is

often prime habitat for rooting. In the cold forests, these

materials, intermingled with exposed parent material, can

constitute the majority of the soil (Graham et al. 1994a).

Forests dominated by pines and Douglas-fir develop brown

cubical rotten wood products that are deposited on the forest

floor and are subsequently incorporated into the mineral soil.

These products can persist in soils for hundreds of years and

during that time provide soil structural and nutritional benefits. In contrast, grand fir/white fir develop white rotten

wood products that are dispersed in soil relatively rapidly

(decades), thus shortening their contribution to soil productivity (Larsen et al. 1980, Harvey et al. 1987).

Surface Mineral Soil

The surface 6 to 12 inches of mineral soil is derived from

the deposits and parent materials of the site, but is also h i g h l y

influenced by vegetation, surface organic layers and disturbance history inherent to the PVT. The OM incorporated

into shallow mineral horizons carries important properties

into the mineral soil. Mineral soil with robust OM amounts

has better nutrition, water-holding capacity, and structure

than soils with small amounts of OM. In addition, OM-rich

mineral soils are excellent sites for nitrogen fixation and

ectomycorrhizae (Harvey et al. 1987). Surface mineral layers are highly susceptible to compaction and displacement

and soils with high volcanic ash content are particularly

sensitive to forest operations (Harvey et al. 1989b).

53

Figure 7—A large accumulation of brown cubical rotten wood occurring

in a lodgepole pine stand near Butte, Montana. In these forests, this material can be a major component of the surface soil. 
Altered Forest Soils

Soils in many forests are different from those that

occurred historically. Soils have been altered through species

changes (within shrub, tree, or forb components), organic

material accumulation on the forest floor, and by soil compaction and displacement. These changes have been the

result singly, or in combination of fire exclusion, timber

harvesting, animal grazing, and climate shifts. There is a

gradual shift in the proportion of soil nitrogen reserves and

OM in mineral layers of pine forests to surface organic layers in fir forests. Accumulation of both above-and belowground biomass from roots, needles, and boles in fir forests

is accelerating activities of decomposers by increasing and

changing the basic substrate they utilize (Harvey 1994).

Associated with these changes in litter type and quantity is

a likely change in soil surface chemistry, including allelopathic substances with the potential to alter a variety of

microbial activities (Rose et al. 1983). Forests dominated

by grand fir tend to concentrate both nitrogen and potassium in their foliage; these forests often have live crowns

extend down to the soil surface (Mika and Moore 1990,

Moore et al. 1991). In general, this combination of a low

canopy structure with nutrients and microbial activities

concentrated in or near the soil surface make both of these

critical ecological resources susceptible to mechanical and

fire destruction (fig. 8). 

GROUND-LEVEL VEGETATION

In the forests of the Inland Northwest, ground-level

vegetation is highly diverse with the cold and moist forests

containing lush and diverse shrub, grass, and forb communities (fig. 2) (Daubenmire and Daubenmire 1968, Pfister

et al. 1977, Cooper et al. 1991). Each plant in these communities has a different strategy for reproducing and surviving disturbances (Noste and Bushey 1987). Ground-level

vegetation can also play many roles such as maintaining

nutrients on a site after a disturbance, providing OM to the

forest floor, protecting soils from erosion, and facilitating

nutrient cycling ( Yarie 1980, Pannkuk and Robichaud 2003).

These plants tend to turnover a greater percentage of their

biomass each year through litter fall than do trees. Therefore, they tend to cycle nutrients and OM more readily than

trees. 

54

Figure 8—When fires are excluded from ponderosa pine forests, organic layers tend to accumulate and tree roots, ectomycorrhizae,

and nutrients tend to concentrate in these layers. Note the contrast between the amount of organic material on the forest floor when

General Custer came through the Black Hills in 1874 and the amount that has accumulated around the rocks by 2000. Photos courtesy of Paul Horsted/custertrail.com (Grafe and Horsted 2002).
Ground-level vegetation often aggressively responds to

canopy openings and forest floor disturbances. Species that

may not be present before a disturbance can proliferate after

a disturbance. For example, canopy removal and prescribed

fire can facilitate robust development of C e a n o t h u s s p p .

especially in the cold and moist forests even though none

was present pre-disturbance. Seeds of C e a n o t h u s spp. lie 

in wait in the forest floor for scarification through heat to

germinate; these species can rapidly occupy a site after disturbance (Noste and Bushey 1987). Other ground-level vege t a t i o n , such as alder, willow, and maple, are aggressive

resprouters from the root crown, rhizome or above-ground

stem. Some species are exceptional at resisting or enduring

disturbances. For example, pine grass in the dry and moist

forests and bear grass in the cold forest readily survive

disturbances.

When it comes to producing forest crops, ground-level

vegetation often competes aggressively with the establishment and growth of conifers (Baumgartner et al. 1986,

Boyd 1982). In all forests, the forb, shrub, and grass layers

can present formidable competition for nutrients, water, and

light with tree seedlings. In addition, it can interfere with

conifer development by occupying sites with roots, even

though the area appears to be unoccupied and, even though

ground-level vegetation may be dead, its root systems can

interfere with tree planting. Also, ground-level vegetation

can be allelopathic, that is emitting toxins both when the

plant is alive and dead, interfering with seed germination

and tree development (Ferguson 1991). Indirectly, groundlevel vegetation can supply habitat for damaging animals,

facilitating trampling, browsing and girdling damage on

plantations (Kingery and Graham 1991, Graham et al.

1992, Ferguson 1999). 

SILVICULTURAL SYSTEMS

In general, silviculture can be defined as the art and science of controlling the establishment, growth, competition,

health, and quality of forests and woodlands to meet the

diverse needs and values of landowners and society on a

sustainable basis (Helms 1998). The processes silviculturists use to manipulate forest vegetation are included in a

silvicultural system and documented in a silvicultural prescription. A silvicultural system outlines a series of treatments over the life of a stand to fulfill a set of values or

interests for a particular landowner (Schlich 1906). T h e

prescription is the formulation of a silvicultural strategy

using biological, managerial, and economic knowledge to

meet stand management objectives (Smith et al. 1997,

Nyland 2002). This plan should ensure that future yields of

goods are conserved while harvesting or utilizing currently

available goods (Smith et al. 1997). Most often, the earlyand mid-seral species are the fastest growing and most

t o lerant of endemic diseases and insects and are readily

managed using well-honed silvicultural systems so, therefore, they are the preferred species for timber and fiber 

production. 

Even-Aged Silvicultural Systems

Even-aged silvicultural systems usually create and

maintain stands with trees representing one age class, or a

narrow range of age classes. Historically, lethal fires created

forests containing even-aged stands. In general, clearcut,

shelterwood, and seed-tree systems can emulate these

stand-replacing events but these tend to perpetuate earlyseral or relatively intolerant (e.g., shade, canopy closure,

competition) trees.

With the exception of the clearcut, the other even-aged

silvicultural systems (seed-tree and shelterwood systems)

include some high forest cover during a portion of the system development. Overstory density and the species prescribed in seed-tree and shelterwood systems depend on the

site and desired forest structure and composition. The number of overstory trees prescribed in a shelterwood depends

on how much shelter is required to successfully regenerate

a desired tree species. As canopy cover increases, the amount

of shade-tolerant (e.g., grand fir, hemlock) regeneration

will also increase.

Clearcut Method

The clearcut regeneration method is easy to apply and is

often well suited for situations where disease and/or insect

problems exist. Disposal of hazard fuels and site preparation can readily be accomplished using prescribed fire,

mechanical means, or chemical application. In addition, 

the planting of improved stock from tree improvement programs is facilitated by the clearcut method. Clearcutting is

most applicable on sites and PVTs in which biophysical

conditions present without canopy cover provide suitable

conditions for seedling establishment and development

(e.g., western hemlock and subalpine fir PVTs, northerly

slopes etc.) (fig. 9). The optimum size and orientation of

the clearcut is also predicated on the biophysical setting

and the species and kind of regeneration desired (Burns

1983). If natural regeneration is planned, then ample seed

and dispersal will need to be available from neighboring

seed walls (clearcut edge) or within the tops of the trees

left after harvesting.

55
Seed-Tree Method

The seed-tree method can be applied on all slopes and

aspects but needs to be tailored to the forest PVT and biophysical setting. Vigorous, wind-firm trees should be left as

seed trees and selected for their phenotypic traits (Hoff et

al. 1976). On most settings, four to six trees per acre are

adequate for seed production for most preferred species.

For example, 7 to 12 trees/acre might be prescribed for a

poor seed-producing species (western larch), whereas 3 to

7 seed trees/acre might be utilized with a prolific seed-producing species (western white pine). If possible, site preparation should coincide with a seed crop in the overstory.

The seed trees should be removed as soon as possible after

regenerationbecomes established. Stocking control is usually needed to maintain the desired number and species

composition in the regenerated stand (Schmidt 1988). The

seed-tree method is ideal where seed dispersal could be

problematic from adjacent seed walls if the clearcut method

was applied. This often occurs with ponderosa pine because

it has heavy seeds that are dispersed shorter distances

compared to some of the mid- and late-seral species such

as grand fir and Douglas-fir (Haig et al. 1941, Burns

1983) whose seeds disperse longer distances. 

Shelterwood Method

The shelterwood regeneration method is applicable on

all aspects and slopes, but is especially suited to steep, dry

slopes where regeneration would benefit from protection.

Dominant overstory densities used in this method range

from 15 to 40 trees per acre depending on species. T h e

greater the number of trees left in the overstory, the greater

the proportion and number of shade-tolerant species regenerated (Haig et al. 1941). Because of the wide range in fire

resistance of the species occurring on these sites, slash disposal and site preparation may be difficult and expensive

depending on species and slope. Vigorous trees should be

left in the overstory to withstand the shock of release, stand

through weather events (e.g., snow, wind) and act as good

seed producers. When an adequate regeneration is achieved,

the overstory should be promptly removed (Burns 1983). 

Application of Even-Aged Systems 

In the cold forests, the clearcut and seed-tree methods

are very appropriate for producing even-aged stands of earlyseral species (e.g., western larch, Douglas-fir). Lodgepole

pine is the most frequently managed species within the

cold forests because it readily germinates and develops

using clearcuts on the subalpine fir PVTs (Schmidt and

Alexander 1985) (fig. 4). Serotiny in lodgepole pine usually

ensures the presence of viable seed in the unopened cones

present in the slash left after harvesting. However, diligence

is needed when disposing of slash and preparing sites to

insure the seed stored in the cones is not removed or destroyed. Cone serotiny is variable in lodgepole pine; therefore the presence of unopened cones should be verified

prior to relying on this characteristic to supply seed for

regeneration (Lotan 1973). 

Western larch is often a preferred early-seral species in the

cold forests and it also regenerates and develops well using

the clearcut system (Schmidt and Shearer 1990). Douglasfir is more intermediate in response to clearcutting in these

56

Figure 9—A clearcut regenerated

with western white pine located 

near Coeur d’Alene, Idaho. Note 

the well-defined seed wall (clearcut

edge).
settings but it also responds better to the open conditions of

a clearcut than spruce and subalpine fir, species that are

late-seral associates in these cold forests. In portions of the

dry forests, especially those on the more moist PVTs such

as the drier grand fir/white fir settings, clearcutting has been

successfully used to perpetuate ponderosa pine (Ryker and

Losensky 1983).

Clearcutting is very applicable for use in the moist forests

(fig. 9). The preferred early-seral species, western white

pine, western larch, and Douglas-fir, all regenerate and

develop readily using this method. In addition, because of

the large amounts of fuel that can be created when harvesting, clearcuts facilitate the use of prescribed fire for preparing sites for both natural and planted regeneration which

will decrease the wildfire hazard (Haig et al. 1941, Graham

et al. 1983). Regeneration of late-seral western hemlock,

grand fir, and western redcedar is often prolific in the moist

forests; however, clearcuts tend to favor the early-seral

species over the late-seral species, particularly if the preferred species regenerate promptly after harvest (Haig et al.

1941, Graham et al. 1983, Jain et al. 2004). Moreover, some

suggest that clearcuts are the preferred method for managing rust-resistant western white pine (Fins et al. 2001).

Seed-tree methods are most applicable in the cold and

moist forests but also have been used successfully in the

dry forests on settings in which shelter is not a prerequisite

for successful regeneration (Ryker and Losensky 1983).

Very often this occurs on PVTs where ponderosa pine readily regenerates such as those occurring in the Black Hills

and some sites in Arizona and New Mexico (Pearson 1950,

Shepperd and Battaglia 2002). Seed-tree methods can be

used in the moist forests to regenerate western white pine,

D o u g l a s - f i r, and western larch (Haig et al. 1941). In the

cold forests, the seed-tree method can be used to regenerate

western larch and Douglas-fir and is very applicable in situations where lodgepole pine does not express cone

serotiny (Lotan 1973).

Shelterwood regeneration methods are most applicable

on settings in which the preferred species, usually an earlyseral species, benefits from the presence of shade. This can

occur on Douglas-fir and ponderosa pine PVTs in the dry

forests where ponderosa pine regeneration benefits from

some shade (Pearson 1950, Ryker and Losensky 1983,

Shepperd and Battaglia 2002) (fig. 5). In the moist forests,

western white pine readily regenerates with the shelterwood method and, in many settings, it prefers partial shade

for the first few years of its life (Haig et al. 1941) (fig. 10).

Ponderosa pine is often regenerated using one or two stage

shelterwoods (Pearson 1950). The preparatory cut favors

seed producing pine developing their wind firmness and

crown expansion, and the final seed cut provides growing

space for the seedlings to be established (Boldt and Va n

Deusen 1974). By providing these openings, ponderosa pine

has the greatest opportunity to become established and outcompete its late- and mid-seral associates such as Douglasf i r, grand fir, and white fir (fig. 5). However, in many settings

Douglas-fir would also be the preferred species especially

on the drier grand fir or white fir PVTs. 

A consistent drawback of using seed-tree and shelterwood regeneration methods is the possibility of perpetuating dwarf mistletoe (Arceuthobium spp.). Ponderosa pine,

Douglas-fir, western larch, and lodgepole pine, depending

on the location and PVT, are all susceptible to infection

from mistletoe. Trees without mistletoe can be selected for

retention but if the disease is prevalent in the overstory, the

clearcut method usually provides more satisfactory control

of the disease (van der Kamp and Hawksworth 1985). 

Trees in shelterwood and seed-tree systems can be

grouped or spaced based on species composition or other

designated criteria. The seed-tree and shelterwood component used in these systems can be short- (removed early in

the life of the regenerated stand, 30 yr or less) or long-l i v e d

(left on the site through the life of the regenerated stand).

H o w e v e r, for use in most production situations, p r o m p t

57

Figure 10—A shelterwood system was used to regenerate western white

pine. Rust-free shelter trees were chosen. The seedlings regenerated using

this method could exhibit up to 19% resistance to blister rust (Hoff et al.

1976).
removal of seed and shelter trees, once regeneration is establ i s h e d , is preferred. The longer the overstory remains, the

more likely tolerant species will develop and compete with

the preferred intolerant species.

Uneven-Aged systems

From a timber management perspective, uneven-aged

systems are most likely applicable only on limited sites in

which a frequent and continual flow of wood products would

be desirable. Uneven-aged systems, both in groups and

individual trees, have been used successfully in the ponderosa pine PVTs (Shepperd and Battaglia 2002). However,

because these systems perpetuate late-seral species or those

favored with closed canopy conditions, uneven-aged systems in most situations would not be preferred for production forestry. However, uneven-aged systems do not have

applicability on small scales such as for non-industrial private landowners (Graham and Smith 1983, Graham et al.

1999a) 

SITE PREPARATION

The most important component of site preparation is to

prepare sites to meet sound and well thought-out objectives.

A prescription provides the plan on the kind, composition,

and amount of regeneration desired. This plan includes

describing seedbed and/or planting site requirements along

with the amount, and species (kind) of competing vegetation inherent to the site and its expected response to fire,

mechanical, or chemical disturbance. Potential vegetation,

habitat types or similar vegetation classifications usually

offer excellent descriptions of ground-level vegetation and

the seral stage of forest development it in which it commonly occurs (Daubenmire and Daubenmire 1968, Pfister

et al.1977, Cooper et al. 1991). In addition, these classifications provide insight into species that may be absent

preharvest and their expected response to disturbance.

Ideally, silvicultural systems should be designed to 

minimize competing vegetation without using expensive

control measures. However, disposal of the slash left after

yarding also affects soil compaction and soil organic content (Harvey et al. 1987, Page-Dumroese et al. 1997).

Broadcast burning is commonly used to prepare sites

throughout the Inland Northwest but slash is also burned

after machine piling (fig. 11). Whatever method is used, the

objectives of site preparation commonly include reducing

fire hazard, providing planting access, and controlling 

competing vegetation (Baumgartner 1982 Lotan 1986). 

In cold, dry, and moist forests, the amount of moisture

available to young trees during the summer months is

almost always the single most important determinant of

whether a planted seedling will survive and the rate at

which this seedling will grow (Cleary and Greaves 1976).

Of course not all water in a soil profile will be available to

regenerated trees. Some will percolate out of the soil profile,

some will evaporate, and much will be used by comp e t i n g

vegetation. Effective site preparation can dramatically

increase plantation survival and development. Powers and

Reynolds (1999), for example, showed that by completely

removing competing vegetation, ponderosa pine volume

growth was 400 percent greater 10 years later when compared to tree growth on areas with competing vegetation. 

58

Figure 11 — A helicopter igniting a prescribed fire in a clearcut near Sandpoint

Idaho. The fire was ignited in the evening ensuring that moisture contents

in the lower duff were above 100% and the fine fuel moisture contents were

conducive for producing a low severity fire. 
Mechanical Preparation

Depending on soils and steepness of slope, timely and

proper site preparation most often can be accomplished by

using machinery. This usually assures excellent site preparation even with sprouting and herbicide resistant species.

For example, Ceanothus spp. is often effectively controlled

mechanically since this method does not heat scarify seeds

stored in the forest floor. Depending on equipment and soil

conditions, most machines (except cable machines) can

safely and effectively operate on slopes with gradients less

than 30 to 40 percent (Miller 1986a). Machine methods

include rakes pulled or pushed by tractors, special dozer

blades, and cable scarifiers to name a few (Lowman 1986).

Very often the site preparation is accomplished simultaneously with reducing the wildfire hazard. In general, machines

capable of separating slash of different sizes, often called

“grapple machines”, displace less soil than rakes attached

to the front of tractors; thus the use of grapple machines can

help conserve and protect soil layers (Graham et al. 1994a).

Competition from pine grass and other sod-forming

grasses present different germination and planting problems than shrub competition. A mechanical option that has

shown success for both planting and seed germination is a

tractor-mounted rake that exposes mineral soil and prepares

planting sites yet does not displace the soil. The machine

uses a plow shear blade that rolls the sod, exposes the grass

roots, and decreases its survivability, and exposes mineral

soil (MTDC 1988) (fig. 12).

In contrast to machinery in the form of tractors, excavators, and other machines, hand tools at the time of planting

are frequently used (Lowman 1986). Scalping or removing

competing vegetation using hoes, shovels, hodads, or other

hand-tools have been shown to be effective in grass communities. Scalps should be at least two feet in diameter and

preferably larger (Miller 1986a). Compared to machinery,

hand scalping offers more latitude for locating favorable

planting sites. That is, locating sites with deep organic rich

soil, away from aggressive competing vegetation, or behind

logs that can provide shelter and protection. Site preparation

(scalping) should be differentiated from clearing debris prior

to opening a planting hole. Clearing is requisite to ensure

that organic material (sticks, litter, etc) that may interfere

with root to soil contact does not fall into the hole during

planting. This can often be accomplished in situations in

which soil is covered by litter, which can be cleared, exposi n g soil often covered with rich humus and fermentation

layers. No matter which method of the site preparation used,

it is critical that the soil is protected and maintained. 

The use of machinery to prepare sites for regeneration

is always a compromise between creating soil conditions

for regeneration while maintaining and preserving soil productivity (fig. 12). The greatest limitations of mechanical

site preparation are slope angle, soil compaction and displacement. As stated earlier, most early-seral species easily

germinate and develop on the mineral soil that can readily

be exposed by mechanical methods (Haig et al. 1941). A

favored micro-site for natural regeneration or for artificial

regeneration is one that prepares a weed-free planting/germination spot yet is in proximity to or conserves the nutrient- and water-holding surface organic layers (Graham et

al. 1989, Graham et al. 1994a, Graham et al. 1995). 

Fire

Fire can reduce fine fuels, prepare germination surfaces,

reduce competing vegetation, preserve surface organic layers, and maintain appropriate amounts of coarse woody

debris (fig. 11). However, unless fuel and weather conditions are appropriate, fire can create conditions adverse for

regeneration and impair soil productivity (Debano 1991,

Hungerford et al. 1991). The amount of forest floor consumed by a fire is dependent on its moisture content, particularly in the lower humus and fermentation layers. If the

moisture content of these layers exceeds 100 percent when

a fire occurs, the majority of litter and fine fuels (≤ 3 inches) do not burn and thus, are generally conserved (Ryan

1982). Under these moisture conditions, nutrients (such as

P, N, K) can condense in the humus and fermentation layers and, therefore, are not lost from the site (Harvey et al.

1989). The temperatures at the mineral soil/organic layer

interface usually do not exceed 300° C, the temperature at

which N is volatilized (Hungerford et al. 1991). At this

temperature, water-repellent layers are also less likely to

59

Figure 12—A Salmon blade can be used to effectively prepare sites subject to pine grass competition yet still conserve the nutrient-rich surface

soil layers.
occur even in coarse-textured soils. Burning when the lower

humus layers are moist facilitates consumption of fine fuels,

maintenance of CWD levels, and often results in exposure

of micro-sites for planting and/or seed germination.

Some ground-level vegetation responds vigorously to

heat such as C e a n o t h u s spp. with its seed buried in the

f o rest floor. Also, many ground-level species resprout aggressively in response to fire (fig. 13). Therefore, the amount,

kind, and severity of fire used to prepare sites needs to be

applied with an understanding of the expected response of

competing vegetation for a given forest, PVT, and biophysical setting (Baumgartner et al. 1986, 1989). 

Chemical Preparation

Chemicals are a very viable technique for site preparation. In particular, herbicides can target specific species or

life forms and protect the surface soil layers that can be

harmed by both mechanical and fire site preparation techniques. The latitude of site and weather conditions for

applying herbicides may be less operationally restrictive

than either fire or mechanical methods and, depending on

the circumstance, the results may be more cost eff e c t i v e

than using either of the other two methods (Baumgartner et

al. 1986). 

For the optimum growth of plantations, control of competing vegetation is essential. In the dry forests particularly

(depending on the PVT), if ground-level vegetation is present before the regeneration harvest is applied, it will likely

compete with future seedlings. Therefore, approximately

two years prior to the harvest, an herbicide treatment an be

applied to target the shrubby vegetation. Growing in the

understory of a high forest canopy, shrubs tend to develop

in sun-flecks, be single stemmed, spindly, and weak, thus

making them highly susceptible to control by herbicide.

When the regeneration harvest is applied, the ground-level

vegetation will be absent providing ample planting sites. In

contrast, if the chemical treatment is applied after the harvest treatment, ground-level vegetation will most likely be

the risk of greater injury to the plantation, delaying the site

preparation benefits.

Herbicides used for shrub control in forests include 2,4-

D, glyphosate, imazapyr, picloram and triclopyr. To control

grasses and forbs, atrizine, 2,4-D, sulfometuron, and hexazinone are suggested (Coop 2004). However, specific time

of application and effectiveness of herbicide to affect targeted vegetation varies. Specific details on application and

target species are available through the Pacific Northwest

2004 Weed Management Handbook (Coop 2004). 

An area mechanically prepared or burned, may provide

an ideal setting for the germination, establishment, and

development of tree seedlings, but these same conditions

are an ideal habitat for weeds (fig. 13). Weeds will quickly

develop and compete with the planted seedlings for water,

nutrients, occasionally light, and under some circumstances

they may be allelopathic, which can further retard seedling

development (Ferguson 1991). Pre-emergent herbicides can

be applied to the surface of the planting spot such as hexazanone, sulfometuron, metsulfuron, and atrazine products

60

Figure 13—Shrubs can

respond vigorously to

prescribed fire. 
to control competing vegetation as it develops. It is very

important to use the right chemical and the right amount to

insure only the weed species and not the planted seedlings

are affected. For example, sulfometuron and atrazine are

poor choices to use when planting ponderosa pine and

western larch, respectively (see Baumgartner et al. 1986

and Coop 2004 for discussions on herbicides and their

appropriate efficient, and effective use).

REGENERATION

A requirement for the successful application of a silvicultural system is the timeliness of regeneration, its amount

and composition. Environments conducive to seedling establ i s h m e nt can be directly influenced by the amount and

composition of over-story retained (seed tree, shelterwood

selection) and the intensity and extent of site preparation

(mechanical, fire, chemical). 

Natural Regeneration

The early-seral and/or preferred species for production

f o r e s t r y, e.g., ponderosa pine, lodgepole pine, western larch,

Douglas-fir, and western white pine, readily regenerate naturally (Haig et al. 1941, Pearson 1950). Depending on the

forest type and the PVT, natural regeneration may be a

viable alternative in many settings using a variety of silvicultural systems. However, less control of the timing,

amount, density, and consistency of plantation establishment is possible with natural regeneration compared to 

artificial regeneration.

The cheapest and most site-adapted regeneration can be

achieved through natural regeneration. On ponderosa pine

and Douglas-fir PVTs, ponderosa pine and Douglas-fir can

be naturally regenerated if appropriate site preparation is

accomplished (Shearer and Schmidt 1991, Shepperd and

Battaglia. 2002). However, many factors such as seed crop

frequency and size, animal predation on the seed, weather

damage to seed, and the timing and proper seedbed preparation can make the accomplishment of successful regeneration easier said than done (Haig et al. 1941, Pearson 1950).

For example, if the site preparation is not well timed with

the production of seed, adequate germination substrate and

establishment sites may not be available when seed is produced by the desired species. Weather favoring the regeneration might not occur even if the site preparation and seed

crops were well coordinated. Western larch is a case in

point. A weather event such as a frost injuring flowers or

unexpected cold weather hampering germination can spoil

the best-laid plans (Graham et al. 1995a). 

Species vary widely in seed production and dissemination (Haig et al. 1941). Western redcedar and western

hemlock produce larger and more frequent seed crops than

most of their associates. For example, the interval between

good seed crops in western larch is highly variable and is

often greater than 10 years. The other tree species usually

produce good seed crops at less than 5 year intervals. For

all tree species, wind plays a major role in seed dissemination. Only lodgepole pine exhibits cone serotiny and the

degree of serotiny present is variable within the cold forests

(Lotan 1973). Mineral soil and burned-over surfaces tend to

supply good soil-to-seed contact, maintain moisture levels

conducive to seed germination, plus supply water to the

roots as they develop. In the Northern Rocky Mountains,

temperature tends to be one of the most critical factors for

germination. Minimum soil temperature of 51° F is needed

and temperatures between 71° and 81° F are preferred

(Haig et al. 1941). Organic seedbeds tend to lose soil moisture faster than roots can develop thereby restricting seedling

establishment. Douglas-fir, ponderosa pine, western white

pine, and lodgepole pine have intermediate germination rates

while western larch and grand fir have low germination

rates. In addition, western hemlock and western redcedar

usually have high seed germination rates and occasionally

reproduce by sprouting. Because these species regenerate

easily, they can interfere with the regeneration and development of preferred early-seral species.

In moist forests, it is critical to understand the role

b l i ster rust plays in stand development especially when

using natural regeneration. Shelterwoods can be used to

naturally regenerate western white pine and a large proportion of these seedlings would be susceptible to blister rust

(Graham et al.1994b). However, Hoff et al. (1976) reported

that over 19 percent of natural regeneration in stands suffering high losses from blister rust could be resistant to the

disease (figs. 3, 10). Therefore, when western white pine

regeneration is abundant (thousands of trees per acre), a

number of the seedlings is likely resistant to white pine

blister rust. Nevertheless, distinguishing rust resistant from

nonresistant seedlings becomes problematic when the stands

are cleaned (precommercial thinning to alter species composition or improve stand condition). The resistance level

will not approach that of trees produced in improvement

programs but there is an excellent chance that some of these

naturally regenerated trees will survive and grow well

enough to produce commercial products and provide

genetic diversity in western white pine (Graham et al.

1994b Fins et al. 2001) (See section on enhancing the survivability of white pine through pruning).

61
Artificial Regeneration

Because of the uncertainty of natural regeneration, 

artificial regeneration often provides more assurance and

options for timely stand establishment and species composition, micro-site selection, tree density, and horizontal tree

distribution. In addition, artificial regeneration offers opport u n i t i e s to plant improved stock. Currently (2005), improved

planting stock is available for western white pine, lodgepole pine, western larch, Douglas-fir, and ponderosa pine.

The improvement developed in breeding programs includes

improved tree growth, increased disease resistance, increased

cold hardiness, and improved tree form compared to trees

naturally regenerated. 

However, care needs to be exercised to ensure that trees

planted are ecologically adapted to the sites. For example,

the environmental interval in elevation in which ponderosa

pine populations show habitat specificity is approximately

1380 feet or 38 frost-free days (Table 1). In contrast, no

habitat specificity in elevation has been found for western

white pine and the habitat specificity interval in frost-free

days is 90. The narrowest habitat specificity for any Rocky

Mountain conifer occurs with Douglas-fir which has an

environmental interval of 650 feet in elevation or 18 frostfree days (Table 1) (Rehfeldt 1994). Therefore, Douglas-fir

is considered a specialist and western white pine a generalist in their species’ adaptability to sites. Beginning in the

early 1900s and in earnest during the 1930s during the

Civilian Conservation Corp era, a major ecological mistake

was planting off-site (seedlings not adapted to their environment) ponderosa pine seedlings throughout the We s t .

Today, these off-site plantings are often dying from insects

and disease and producing malformed trees. Unfortunately,

a maladapted forest is being propagated, thus showing why

it is critical that seedlings be ecologically matched to the

site on which they are planted (Rehfeldt 1994).

Probably no other species is more suited to artificial

regeneration than western white pine because of the good

nursery and planting practices that have been developed

over the last 100 years. With the introduction of blister rust

from Europe in the early 1900s millions of white pine were

killed. When all control efforts (e.g., killing the alternate

host Ribes spp., fungicide application) failed, the future of

western white pine management in the western United States

appeared bleak (Ketcham et al. 1968). By 1950, the Office

of Blister Rust Control, Northern Region of the USDA

Forest Service, USDA Forest Service Northern Rocky

Mountain Forest and Range Experiment Station, and the

USDA Forest Service, Pacific Southwest Forest and Range

Experiment Station began a program to develop rust-resistant western white pine. By 1985, seed orchards were producing a second-generation of western white pine that were

65+ percent resistant to the disease (a portion of the trees

do get infected but survive) (Bingham 1983). The goal of

the white pine tree improvement program was to increase

its’ resistance to blister rust and to accomplish this by using

multiple genes, thus minimizing potential disease mutations

(Fins et al. 2001). With this multi-gene approach the rust

may infect and even kill some trees, but many trees, even

if they become infected, continue to survive and grow to a

saw timber rotation of 60 to 80 years (Graham et al. 1994b)

(figs 2, 3, 9, 10).

In general, there are two types of seedlings that are

planted, bare-root and container grown, and both have their

place in production forestry. Bare-root seedlings are usually

lifted from the nursery beds in the early spring for planting

in the spring. Depending upon the silvicultural method and

site preparation, a different size and age of seedlings can be

specified. In addition, a key characteristic of a proper rootto-shoot ratio can be specified. Generally, seedlings less than

62

Table 1—The genetic differentiation among populations of tree species. Adaptation 

of species is based on the environmental interval by which populations must be 

separated before there is a reasonable assurance that the populations are genetically 

different (Rehfeldt 1994)

Environmental Interval

Species Elevation Range (ft) Frost Free Days Adaptation

Douglas-fir 650 18 Specialist

Lodgepole pine 720 20 Specialist

Engelmann spruce 1215 33 Intermediate

Ponderosa pine 1380 38 Intermediate

Western larch 1480 40 Intermediate

Western redcedar 1970 54 Generalist

Western white pine none ~90 Generalist
three years old can readily be planted. Large-sized seedlings

often offer a higher success of establishment compared to

smaller seedlings because of their ability to rndure competing vegetation, damage from animals, or harshness of site.

Seedlings with large diameters may be specified for areas

prone to vegetation, woody debris or snow potentially

pushing over small seed- lings (Schubert and Adams 1971,

Baumgartner and Boyd 1976, Cleary et al. 1978). 

Great strides have occurred in recent years in producing

container-grown seedlings that meet a wide range of specifications. This can be accomplished by controlled growing

conditions and by different sized and treated containers. In

addition to a variety of seedling specifications, seedlings

can be produced to plant during different planting cycles

determined by the site and management objectives. As with

most bare-root seedlings, container seedlings are most often

planted in the spring but they can also be grown for planting in the fall (Landis et al. 1990, Landis et al. 1992). 

Under special circumstances, seedlings can be planted

in the summer if they are properly conditioned. Such situations exist when high elevation areas are not available to

plant during the spring or fall because of snow. In the greenhouse, seedlings can be artificially moved through a growth

cycle from bud burst through shoot elongation and bud set

in a matter of weeks. By doing so, dormant seedlings can

be planted during the summer (Landis et al. 1990, Landis

et al. 1992).

Even though seedling production from seed collection

through planting has been investigated and refined for 100

years, the successful completion of the entire regeneration

process is often problematic. Seedlings well prepared in

the nursery/greenhouse need to be handled with utmost

care while in storage and on the planting site to ensure a

dormant seedling is planted (Schubert and Adams 1971,

Baumgartner and Boyd 1976, Cleary et al. 1978).

We suggest that choosing desirable micro-site positions

that offer protection, have organic matter rich soil, and are

free of competing vegetation is preferable to planting on a

rigid grid. In most production operations and to minimize

future tending operations, 200 to 250 trees per acre would

suffice. A preferred micro-site for planting trees includes:

places with adequate soil moisture, soil temperatures

exceeding 40° F, uniform root-to-soil contact, and no soil

impediments that would distort roots (e.g., produce J-rooted

seedlings). In high organic soils, container-grown stock

appears to do better than bare-root stock because root-tosoil contact can be more readily achieved (Schubert and

Adams 1971, Baumgartner and Boyd 1976, Cleary et al.

1978).

Animal Damage

A variety of animals (insects, rodents, omnivores, ungulates, and livestock) may damage tree seedlings by eating,

browsing, trampling, and breaking limbs. Animals including, but not limited to, porcupines (Erethizon dorsatum),

pocket gophers (T h o m o m y s spp.), cattle, sheep, hares (L e p u s

spp. and Sylvilagus spp.), black bear (Ursus ameri-canus),

deer (Odocoileus spp.), and elk (Cervus spp.) can damage

seedlings of most western tree species. The potential for

damage should be thoroughly evaluated prior to implementi n g the silvicultural system (Kingery and Graham 1991,

Knapp and Brodie 1992). 

A variety of preventive and remedial techniques have

been tested with mixed results. These have included providing an alternative food source or planting unpalatable

tree species (Black and Lawrence 1992), modifying habitat

to disfavor specific browsing animals, physically or chemically protecting tree seedlings, frightening browsers away,

and trapping or killing browsing threats. Unfortunately, one

method does not solve all browsing problems. Many recommend large planting stock because it typically is less

vulnerable to animal damage (Loucks et al. 1990, Cafferata

1992, Graham et al. 1992, Marsh and Steele 1992). Nolte

(2003a) suggested using a five-step process to reduce the

effects of animal damage: 1) assess the severity and potential damage if no action is taken, 2) evaluate the feasibility

of alleviating the problem, 3) develop a strategy prior to

browse damage prevention measures, 4) implement a program, and 5) monitor the consequences. The preferred

approach will depend on the results from site-specific monitoring and the most effective treatment may require integrating several methods within the silvicultural system. 

Physical protection of seedlings with polypropylene

mesh tubes is an option and appears to be successful in

some cases (Black and Lawrence 1992). Fencing areas to

keep livestock out can be effective, but expense limits its

use (Nolte 2003b). Other forms of physical deterrents

might be possible. Graham et al. (1992) noted that seedling

damage from livestock fell below 10 percent when coarse

woody debris (> 3.0 inches in diameter) was greater than

30 tons per acre. In some cases, minimizing disturbance

avoids creating habitat that may increase pocket gopher

populations (Marsh and Steele 1992). For example, the

grasses that exist on a site can be killed using hexazanone

(most commonly Ve l p a r®), and this, in turn, will dissuade

gopher use. Pocket gopher predation on planted seedlings

is highest the first summer that the trees are planted and the

first two winters (Ferguson 1999). Studies have shown that

controlling pocket gopher populations with strychnine baiting poses relatively little risk to non-target species (Arjo

63
2003) but the effects of removal may be short-lived since

replacement animals usually occupy the vacant habitat, thus

necessitating the repeated application of treatments for

maximum efficacy.

FOREST TENDING

The silvicultural system does not end with the regeneration treatment (i.e., clearcut, seed-tree, etc.). After a stand

is regenerated or entered, stand tending is generally warranted to ensure the desired stand structures and compositions are developed and maintained (Fisher 1988). Tending

activities (i.e., thinning, cleaning, weeding, liberation

(overstory removal), sanitation, and fertilization) can occur

at a variety of time intervals and intensities depending on

forest type, PVT, species present, and past stand development. Release of species after periods of crowding or suppression is directly related to the length and vigor of the

crown (McCaughey and Ferguson 1988, Ferguson 1994).

G e n e r a l l y, shade intolerant species respond well to release

after suppression and intolerant species respond poorly.

Lodgepole pine, which often regenerates prolifically, is

prone to stagnation early in its development, making later

release cuttings less effective (Johnstone and Cole 1988).

Therefore, stand tending is an integral part of both evenaged and uneven-aged silvicultural systems. Tr e a t m e n t s

can occur within all canopy levels and many intermediate

treatments can produce forest products (Graham et al.

1999b).

In contrast to not acquiring enough regeneration, the

issue in many forests is excessive regeneration that makes

weeding and cleaning plantations (natural stands) essential

for satisfactory development. For example, in the ponderosa pine forests of the Black Hills in South Dakota,

ponderosa pine regeneration is often so prolific it creates

a fire hazard and compromises future stand development

options (Shepperd and Battaglia 2002). Similarly, in the

cold forests, over-abundant lodgepole pine regeneration is

often the norm, again making tending operations imperative

if the stands are going to develop productively (Johnstone

and Cole 1988) (fig. 4). Within the moist forests, natural

regeneration is often plentiful making cleaning and weeding operations a necessity (Haig et al. 1941, Deitschman

and Pfister 1973 Graham 1988) (fig. 9). 

Weedings

Weedings occur during the sapling stage of stand development to remove competitive vegetation, such as specific

trees or shrubs, and other vegetation that may compete with

crop trees (Smith et al. 1997, Helms 1988). Weedings tend

to be applied before or simultaneously with cleanings (treatm e n t s aimed at redistributing stand growth to selected stems).

Most often weedings are essential in mixed-species stands

and those prone to robust development of mid– and late–

seral trees or when grass or shrub development interferes

with stand development (Deitschman and Pfister 1973,

Miller 1986b). In dry forests, this often occurs where grand

fir and/or white fir, Douglas-fir, ninebark, or C e a n o t h u s s p p .

tend to aggressively compete with ponderosa pine. Similarly,

in the moist forests, grand fir, western hemlock, and alder are

frequently removed to favor western white pine and western

larch. Weedings can be accomplished most often mechanically or chemically and, in rare situations, fire can be used

to weed a plantation of unwanted competing vegetation

(Saveland and Neuenschwander 1988). 

Chemical

Frequently, within a year or two after plantation establishment, even on settings where the competing vegetation

was removed during site preparation, weeds tend to return

and interfere with seedling development (Petersen 1986).

Weeding young stands with herbicides is a viable alternative on many settings. However, specific time of application and effectiveness of the herbicide to affect targeted

vegetation varies (specific details on application and target

species are available through the Pacific Northwest 2004

Weed Management Handbook (Coop 2004). The actual

timing of when weeds interfere with tree growth depends

on forest type, PVT (weed species present and their ability

to colonize or survive), type and success of the site preparation applied (Noste and Bushey 1987, Baumgartner et al.

1986). Herbicides that can be applied over the top of established seedlings and have been successful in controlling

weeds include several hexazanone products (e.g., Velpar®,

P r o n o n e®). These herbicides are effective in removing weeds

without damaging most conifers except western larch.

Sulfometuron (Oust®) also removes weeds readily but is

not preferred for use with ponderosa pine because of potential tree damage. Granular herbicides can be applied with a

“weedometer” that distributes herbicides within a 3 to 5

foot radius of seedlings. Glyphosate (Roundup®, Accord®)

can be directionally applied to weeds between trees and

shields (e.g., PVC-plastic) can be used to apply herbicides

within close proximity of seedlings.

Within 4 to 6 years on some PVTs, tall shrubs (e.g.,

maple, alder, willow) not controlled by a pre-harvest herbicide, readily sprout and often aggressively compete with

planted trees (Lotan 1986). Imazapyr (a compound in

Arsenal®, Chopper® and Onestep®) can be aerially (helicopter) or hand (backpack sprayer) applied to control this

high shrub competition. Glyphosate, applied as a directed

64
spray, can be used to control tall shrub competition as well

as hexazanone, applied in the form of Pronone®. In northeastern Oregon, Oester et al. (1995), found that hexazanone, applied as a spot or broadcast spray, increased both

survival and growth of planted ponderosa pine. It has been

found to be more effective (more toxic) at controlling weeds

when it is applied in conjunction with N fertilizers compared to applying the herbicide alone. When applied in this

fashion, Pronone® has been found to be toxic to conifers

even though the dose was believed to be safe. Presumably,

the addition of N makes both the conifers and weeds grow

later in the growing season thus making them both vulnerable to the herbicide. The most effective combination of N

fertilizer and Pronone® will probably use smaller herbicide

dosages, such as only 2 to w of the amount that would be

used when applied by itself. The combination of fertilization and weed control should enable stands to develop more

quickily than would occur after the application of a single

treatment.

Most conifers have a high tolerance for hexazanone and

i m a z a p y r, while most grasses and woody (dicot) species

are very susceptible. Western larch, however, is very susceptible to damage from both of these herbicides. In most

settings, a directed application of gyphosate using a backpack sprayer will control unwanted vegetation in western

larch stands. The exact weeding approach and chemicals

used will depend on the forest, PVT, biophysical setting,

and nature of the competing vegetation (e.g., life form,

species, size, distribution) (Coop 2004).

Precommercial Thinning (Cleaning)

Precommercial thinnings are applied during the sapling

stage of stand development where specific trees are kept

and others are removed so that growth of selected stems is

favored (Smith et al. 1997).

In general, all of the early-seral species (ponderosa

pine, lodgepole pine, western white pine western larch, and

Douglas-fir) respond positively to precommercial thinning

(Schmidt 1988). Of course, the magnitude of the response

is predicated on the PVT and the biophysical setting.

H o w e v e r, with judicial control of planting densities, the

need for thinning to redistribute growth to selected trees

should be minimized. In stands with prolific natural regeneration (such as may occur with western larch, western

white pine, lodgepole pine, and on some sites, Douglas-fir

and ponderosa pine), precommercial thinning is necessary

to distribute the site’s growth potential to a manageable

number of trees that will result in future tree sizes consistent with predicted markets for wood products (Schmidt

1988). 

Moist Forests

Within the moist forest, the most important period in

the life of either a plantation or a natural stand is between

10 and 30 years. Prior to this time, stand densities have

minimal impact on tree development. During this 10- to 30-

year period, species composition and future stand dynamics

are largely determined. Past this age, stand improvement

can be accomplished only at high expense and at a heavy

sacrifice to growing stock (Davis 1942). Western white pine

over 30 years old will respond to release, but the required

wide tree spacings will reduce stand yields (Deitschman

1966). Four hundred trees per acre at age 30 appear to be 

a good goal. These densities provide for good diameter

growth, good volume production, and future thinning opport u n i t i e s. The timing of cleaning a western white pine stand

is a compromise impacted by waiting as long as possible to

allow blister rust to be fully expressed, maintaining canopy

closure to discourage Ribes spp. and competing conifer

regeneration, and to treat stands early as possible so as to

not create an unmanageable fire hazard (abundance of fine

fuels) (Graham 1988). 

Western larch also readily responds to precommercial

thinnings at 10- to 15 –years of age (Schmidt and Seidel

1988). Though expensive, thinning of extremely dense

stands, containing 1,000 to 25,000 stems per acre, will

respond well to thinning. During these treatments. mistletoe

can also be removed from the stand. Western larch benefits

greatly from early thinning because it relieves overstocking

and allows larch to capitalize on its rapid juvenile growth.

Schmidt and Seidel (1988) suggest that stocking levels for

western larch range between 45 and 75 percent of normal

stocking or in the range of 400 trees per acre or less. Thinning dense stands transfers growth to fewer numbers of

rapidly growing trees, thus maintaining good vigor and

crown development, increasing resistance to wind, snow,

and insects, and permitting more uniform diameter growth.

Judicious thinning regimes can result in shorter rotations

and increased merchantable yields. Target Douglas-fir densities also fall in the range of 400 trees per acre in precommercial thinnings in the moist forests (Lotan et al. 1988). 

It appears that the greatest benefit from thinning in mixed

stands of western white pine and associates is to improve

stand and tree quality. Cleanings do not increase overall

volume production, but do increase future value of stands

by concentrating growth on fewer, selected better quality

trees.

Western White Pine Pruning—Most lethal blister rust

infections occur in the lower crown when trees are quite

young (≈15 years). Pruning the lower branches of white

65
pines to a height of 8 to 10 feet, but not reducing the livecrown ratio to less than 50 percent, appears to offer the tree

some protection from blister rust infection while not substantially reducing tree growth rates. In addition, removal

of any branches with cankers greater than 6 inches from

the bole greatly increases the chances of the tree surviving

to produce a commercial product. Schwandt et al. (1994)

showed that by cleaning western white pine stands (10 to

18 years old) to a spacing of approximately 10 feet by 10

feet and pruning the lower branches, the value (1992

prices) per acre (22 years later) of the white pine doubled

in the treated stands ($2000 per acre) compared to that of

untreated stands ($1000 per acre).

Cold Forests 

Natural stands of lodgepole pine, which commonly regene r a t e following wildfire, are frequently dense (Johnstone

1985, Johnstone and Cole 1988). Likewise, stands that

regenerate following harvest and site preparation (scarification and/or prescribed fire) often establish in dense clumps.

Even when lodgepole pine is planted or cleaned at an early

age, ingress of seedlings may result in denser stand conditions than desired. Lodgepole pine does not self-thin well

on any PVT; thus without treatment dense stands tend to

remain dense. In these situations, tree growth is suppressed

and stands are subject to heavy mortality from snow and

wind. Consequently, stand yields will be well below the

capacity of the site. 

Determining thinning densities for all species and, in

particular lodgepole pine, the optimum management density

is a tradeoff between tree size and stand volume objectives.

Young lodgepole pine responds more readily to density

reductions compared to old trees (Murphy et al. 1999).

Merchantable cubic volume production per unit area is

maximized at relatively high (≈1000 trees per acre) initial

stand densities. A single precommercial thin (≈400 trees

per acre) at age 20 on many sites would produce commercial yields by age 40 compared to never producing a commercial product by age 120 years without the treatment

(Cole and Edminster 1985). However, for most management

considerations, cutting cycles of 30 years seem feasible and

o ffer commercial yields at several points during the rotation

(≈ 120 years). 

Dry Forests

Within the dry forests, the upper level management

zone for Douglas-fir approaches ≈2000 trees per acre of 3

66

Figure 14—A precommercial thinning

(cleaning) in a sapling-sized ponderosa

pine stand. Note the large amounts of

fuel produced, which is a common

occurrence, and needs to be decreased

to protect the stand from severe wildfire. 
inch diameter trees. However, a more realistic precommercial thinning density would approximate 450 trees per acre

and, of course, these estimates would be predicated on the

future management options and product needs. A target of

140 to 220 ft2 of basal area and 60 to 100 trees per acre

would be the range of tree densities that would be preferred

for most Douglas-fir settings (Lotan et al. 1988). 

The upper management zone (tree density) for ponderosa

pine is, for the most part, roughly based on threshold levels

of risk for bark beetle attacks. The lower level of stocking

for ponderosa pine is largely determined on the stand density in which regeneration is likely to occur (fig. 14). The

highest stand densities for precommercial thinning would

be in the range of 700 trees per acre and the minimum

v a lues would be in the range of 200 trees per acre. Target

stand densities should not exceed 150 ft2 of basal area and

minimums in the range of 50 ft2 would suffice in most situations (Edminster 1988). As with other species, these

v a lues would be based on the PVT, biophysical setting,

management objectives, and the markets available for

products. Significant declines in volume production will be

realized with low residual stand densities. If rapid development of merchantable–sized material is a goal, than the

lower residual stand densities are desirable. On lower productivity sites, more than one precommercial thinning may

be required to maintain the desired stand structures. Low

initial stand densities, either through planting or cleaning,

may greatly influence thinning opportunities. 

Thinnings

Beyond the sapling stage, thinnings redistribute growth

potential to fewer trees leaving stands with the desired

structure and composition. Even though thinning from

below is the most common method, there are other methods

that have applicability depending on the forest, PVT, and

management objectives and desires of the landowner. Low

(thinning from below), crown (thinning from above), selection (diameter-limit thinning), free thinning, and mechanical thinning all have application in the moist, cold, and dry

forests of the Inland Northwest (Nyland 2002, Smith et al.

1997).

Low thinning is when trees are removed from the lower

canopy, leaving large trees to occupy the site. This method

mimics mortality caused by inter-tree competition or surface fires and concentrates site growth potential on dominant trees. Low thinnings primarily remove intermediate

and suppressed trees, but heavy thinnings can also remove

many in the codominant crown class. Low thinnings not

only remove understory canopies but can also alter species

compositions. Usually, different tree species have characteristic development rates that result in individual species

dominating specific canopy layers. For example, in dry

forests, ponderosa pine primarily occupies the dominant

canopy layers, whereas shade-tolerant grand fir, white fir,

or Douglas-fir occupy the intermediate and suppressed 

layers. A low thinning in these stands therefore favors the

development of the dominant and codominant ponderosa

pine. Depending on the desired stand structure, low thinnings can remove few to many trees. Also, thinnings need

not create regular spacings but rather can vary both the

number and degree of clumping of residual trees.

Crown thinning, or thinning from above, reduces crowdi n g within the main canopy. Dominant and codominant trees

are removed to favor residual trees in these same classes.

This method is used to remove selected trees in the dominant and codominant crown classes that are competing with

more desirable trees (Nyland 2002). Selection thinning

removes dominant trees to favor smaller trees. This method

is often applied by removing trees greater than a certain

diameter. Diameter-limit cuts that continually remove the

largest trees may well be dysgenetic and can be a disguise

for high grading (removing trees of high economic value

without concern for future stand development). By maximizing removal of the current value from a stand, future

options may be limited and the only recourse for the future

may be to regenerate. Stand structures and species compositions created by using selection thinning are limited and,

in general, favor shade-tolerant species or trees occupying

the intermediate and suppressed crown classes. Often the

stands created by selection thinnings are prone to epidemics

of insects and diseases. Compared to the other thinning

methods, selection thinning is less useful in these forests

because of the limited stand structures and compositions 

it creates.

Free thinning, sometimes called crop-tree thinning, primarily releases selected trees. This method favors specific

trees, whereas the remainder of the stand goes untreated.

Depending on what is presented in various portions of a

stand (tree spacing, species, vertical structure, etc.), the

thinning criteria can be highly flexible and produces stands

with large amounts of diversity. It can be used in any of the

crown classes for releasing specific trees. This method has

the most flexibility for creating various stand structures and

compositions.

Mechanical thinning removes trees based on specified

spatial arrangements (Nyland 2002). This method is often

applied in plantations where every other row or every other

tree in a row is removed. Such a rigid thinning prescription

67
is easy to apply, but the stands created often lack diversity

in either structure or composition. This method also resembles strip thinning, where a strip of trees is removed.

Mechanical thinning may be well suited for timber production on uniform sites but has limited value for producing

conditions that meet other resource values.

Use of herbicides following any form of thinning has

r a r e l y, if ever, occurred in an Inland Northwest forest.

Nevertheless, there are some situations where past heavy

thinning and/or patchy stocking have created stands with

substantial biomass in competing vegetation. In these situations some form of herbicide application might be appropriate to maintain the desired forest structure. The repertoire

of herbicides that might be considered at this point would

be very similar to those applicable for use in stand weeding.

Fertilization

As stated earlier, nitrogen (N) is the most limiting nutrient in the Inland Northwest and the greatest growth response

comes from the addition of N (fig. 15). The combination of

stand density control, along with the application of N, appears

to be the best approach for managing young stands and

accelerating their growth and crown development (Graham

and Tonn 1979, Weetman et al. 1985, Moore 1988, Moore

et al. 1991)

Within the dry forests, ponderosa pine shows a strong

linear response up to approximately 400 pounds of N per

acre. Plantations with weed control can show twice the fertilization response as unweeded plantations (Powers et al.

1988). Powers (1988) found that volume growth was nearly

four times greater with weeding than no treatment but the

combination of fertilization and weeding produced volume

growth nine times greater than untreated stands. Similarly,

Douglas-fir can be rather responsive to fertilization and

response varies by stand density, soil parent material and

pre treatment N. Two-hundred pounds per acre appears to

be a good treatment and the response appears to last about

6 years but most likely depends on stand density (Moore

1988). 

Within the cold forests, lodgepole pine grows on some

rather infertile sites making it respond dramatically to

improved nutrition, especially following precommercial

thinning (Weetman 1988). Some evidence suggests that

thinning, along with fertilization, increases lodgepole pine’s

resistance to attack by mountain pine beetle. Also fertilizing

in the spring prior to bud burst seems to provide the best

response. Hamilton and Christie (1971) showed that mean

annual increments of 172 to 214 ft3 per acre were achievable by fertilizing prior to crown closure. 

There is a shift of nutrients from soil to tree, once the

canopy is closed. As the tree’s demands on soil rapidly

decline following canopy closure, the nutrient cycles within the tree and through the tree-litter system are then fully

c h a rged (Weetman 1988). The cycle within the tree is based

on the recovery and reuse of nutrients prior to the death of

old tissues, including those of the leaf before abscission,

and can be up to 85 percent efficient. However, the slow

release of N from litter can lead to late-rotation (≈ 60-80

years) N deficiency. In Oregon, fertilization of a 40-yearold closed-canopy lodgepole stand with 600 pounds of N

per acre produced an 8-year volume response of 79 percent

over a control stand and 370 pounds of N per acre produced a 3-year volume response of 87 percent over a

control (Cochran 1979). 

68

Figure 15—Helicopters can be used to apply nitrogen fertilizer (urea 

pellets).
Within the moist forests, grand fir is very responsive to

fertilization. The other species appear to be well adapted

to the nutrition regime of the moist forests. This lack of

fertilization response could possibly be related to the prevalence of the nutrient-rich volcanic soils. It also appears that

western white pine has wide amplitude of N demand

(Graham and Tonn 1979).

Most conifers favorably respond to the application of 

N at the time of planting, especially in concert with competitive vegetation control and proper site preparation. One

option is to apply nutrients in the nursery which will provide robust root growth and enhance establishment when

the seedlings are planted. Another opportune time to apply

fertilizer is when a planting is about 5 years of age. Both of

these fertilizer applications tend to further plantation establishment and increase juvenile tree growth. 

STAND MANAGEMENT PLANNING 

In the Inland Northwest, stand density studies, in particular thinning and precommercial thinning (cleaning and

weeding), have been conducted for nearly 100 years. The

concept of yield tables and normal stocking was produced

from this research (Haig 1932). In some settings, the information in these yield tables are as valid today as the day

they were produced (1930s). The concept of site index and

the site index curves produced during that time are also

still very applicable (in 2005). 

However, today there are more precise and robust tools

available for stand management planning. In particular, the

Forest Vegetation Simulator (FVS), with variants available

for areas across the United States, can be calibrated to a

given site and species mix (Dixon 2002). FVS contains

three major components: regeneration establishment, small

tree development, and large tree development (Wykoff et

al. 1982, Ferguson et al. 1986). These components can be

related to the physical setting based on location, slope,

aspect, elevation, PVT (e.g., habitat type, plant association),

site index, and stand density index. The small-tree component can be calibrated to a specific site by inputting the

periodic height increment of seedlings and saplings and the

large-tree component can be calibrated by inputting the

periodic diameter increment of large trees (Dixon 2002). 

All three components work in concert to project stands

into the future by incorporating various management activities including harvesting, site preparation, planting, thinning, pruning, and fertilization to name a few. The influence

these and other stand treatments have on stand development

can be projected into the future and displayed using a variety of stand metrics. Some of these include: stand diameter,

height and species distributions, total and merchantable

volume distributions by species and diameter, volume

accretion and mortality by diameter and species, total and

merchantable removals by diameter and species, amount

and characteristics of regeneration by species and individual tree characteristics. Several extensions are available to

display attributes such as those related to wildfire and fuel

treatments, root diseases, blister rust, bark beetles (e.g.,

Douglas-fir beetle (Dendroctonus pseudotsugae), mountain

pine beetle (Dendroctonus ponderosae)), and defoliators

such as the spruce budworm (Choristoneura occidentalis)

and tussock moth (Orgyia pseudotsugata). The FVS output

can be customized for desired time intervals, readily linked

to economic analysis, and pictorially displayed using the

Stand Visualization System. And, most importantly, FVS

can be linked to geographic information systems making

the management tool both spatially explicit and providing

information at resolutions customized for each owner and

application (Dixon 2002).

SUMMARY

Silvicultural systems describe the planned treatments

through the life of a stand and are documented in a silvicultural prescription (Smith et al. 1997, Nyland 2002). By

doing so, all of the treatments and their expected outcomes

from stand establishment through tending activities are

integrated and designed specifically for the biophysical

environment presented and designed to meet the management objectives for that stand fulfilling the goals of the

land-owner. Developing silvicultural systems for specific

sites enables silviculturists to recognize the different vegetation complexes and successional pathways inherent to the

moist, cold, and dry forests. In other words, one prescription

does not fit all stands, especially for the different forests

and environments intrinsic to the Inland Northwest. 

In general, the early-seral species western white pine,

western larch, ponderosa pine, Douglas-fir, and lodgepole

pine, are the most resistant to native insects and diseases,

the fastest growing, and the most aggressive establishers 

on the given potential vegetation type (PVT) on which they

occur. For production forestry, the most appropriate regeneration method to apply in the cold forests is a properly

applied clearcut. Likewise, within the moist forests, clearc u t t i n g provides good results but seed-tree and shelterwood

regeneration methods are also applicable depending on the

desired species mix and the biophysical setting (potential

vegetation type, slope, aspect, current vegetation). Within

the dry forests and especially on the grand fir and/or white

fir potential vegetation types, clearcutting and seed-tree

regeneration methods are very appropriate for the production of ponderosa pine and Douglas-fir. However, on the

69
drier PVTs (e.g., dry Douglas-fir and ponderosa pine), a

shelterwood system offers protection for the seedlings during the establishment period and may provide better results

than the total or majority canopy removal of clearcutting

and seed-tree methods. Two-stage shelterwoods (preparatory cut followed by a seed-cut) are suitable on ponderosa

pine PVTs. Also, under most circumstances, selection systems are most appropriate for use on ponderosa pine PVTs

for the production of wood crops. 

The foundation of all forestry is the soil resource. The

soil and its management in all phases of the silvicultural

system need to be recognized. In many portions of the Inland

Northwest, the residual soils are covered with volcanic ash

and/or loess deposits enriching them and, more often than

not, contain the majority of the site’s productive potential.

Frequently the biological and nutrient capital of a forest

soil tends is near the surface of the mineral soil or integrated into surface organic layers. The humus, fermentation,

and buried rotten wood layers in forest soils especially

need to be recognized for their contribution to the nutrition

of a site. In some settings, a major contributor to the org a n i c

matter on a site is coarse woody debris and it should be

recognized and managed appropriately.

Because of the importance of soil and especially the

nutrient rich (e.g., N) surface layers, we hope that the role

these layers play in maintaining forest productivity will be

more widely appreciated and suggest that these soil layers

should only be scarified and/or scalped for a purpose. The

contributions of ground-level vegetation to maintaining 

forest productivity in many settings should also be recognized. In particular, many shrubs and forbs fix N and

ground-level vegetation can conserve both nutrients and

soil in the face of catastrophic disturbances such as wildfire. Prescribed fire is an excellent tool for preparing sites

for both natural and artificial regeneration, managing competing vegetation, and reducing the wildfire hazard. However,

prescribed fire needs to be integrated into the silvicultural

system and used judicially to produce desired conditions. 

Each conifer species is ecologically adapted to a site

and it is paramount that seedlings be adapted to the site on

which they are planted. The ramifications of planting maladapted seedlings may not become apparent until the stand

is developing disease and/or insect epidemics or the trees

are malformed. Because the forest sites are so variable on 

a fine scale, all planting and tending activities should take

advantage of the small differences inherent to a site and

multi-species, multi-spacing plantings, cleanings, weedings,

and thinnings should be considered and used where appropriate. 

The benefits of using appropriate herbicides are often

substantial when managing forests in the Inland Northwest.

However, herbicides can be costly and environmentally difficult to use. Research continues on herbicide alternatives.

For example, some research addresses herbicides that have

not yet been tried in the Inland Northwest, some focuses on

herbicide doses, some on formulation, and some on fertilizerherbicide combinations. No doubt, herbicide use will continue to be a viable alternative for managing many Inland

Northwest forests for wood production.

To facilitate stand and forest management planning, a

calibrated, spatially explicit version of the Forest Ve g e t a t i o n

Simulator (FVS) is an effective tool. FVS can be created

and adapted to particular settings and provide realistic

views of stand and forest management alternatives and t h e i r

impacts on forest development over time. Various extensions of FVS are available for evaluating and displayi n g

insect, disease, and wildfire impacts to a stand. Most import a n t l y, FVS is a very appropriate way of integrating all

aspects of stand establishment and tending into a silvicultural system and its use fosters documentation of silvicultural prescriptions. 

LITERATURE CITED

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Atkins, D.; Byler, J.; Livingston, L. [et al.]. 1999. Health 

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178 p.

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Baumgartner, D.M.; Boyd, R.J.; Breuer, D.W.; Miller,

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Schwandt, J.W.; Marsden, M.A.; McDonald, G.I. 1994. 

Pruning and thinning effects on white pine survival 

and volume in northern Idaho. In: Baumgartner, D.M.;

Lotan, J.E., eds. Proceedings: Interior Douglas-fir: the

species and its management. Pullman, WA: Cooperative

Extension, Washington State University. Pullman, WA:

Department of Natural Resource Sciences, Washington

State University. 167-172. 

Shearer, R.C.; Schmidt, J.A. 1991. Natural and planted 

regeneration of interior Douglas-fir in western Montana.

In: Baumgartner, D.M.; Lotan, J.E., eds. Proceedings:

Interior Douglas-fir: the species and its management.

Pullman, WA: Cooperative Extension, Washington 

State University. 217-226. 

Shepperd, W.D.; Battaglia, M.A. 2002. Ecology, silviculture, and management of Black Hills ponderosa pine.

Gen. Tech. Rep. RMRS-GTR-97. Fort Collins, CO:

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

Mountain Research Station. 112 p.

Smith, D.M.; Larson, B.C.; Kelty, M.J.; Ashton, P.M.S. 

1 9 9 7 . The practice of silviculture: applied forest ecology.

New York, NY: John Wiley & Sons, Inc. 537 p.

Smith, H.Y.; Arno, S.F. 1999. Eighty-eight years of 

change in a managed ponderosa pine forest. Gen. Tech.

Rep. RMRS-GTR-23. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Rocky Mountain Research

Station. 55 p.

van der Kamp, Bart J.; Hawksworth, F.G. 1985.

Damage and control of the major diseases of lodgepole

pine. In: Baumgartner, D.M.; Krebill, R.G.; Arnott, J.T.;

Weetman, G.F., eds. Proceedings: Lodgepole pine: the

species and its management. Pullman, WA: Cooperative

Extension, Washington State University. 125-131. 

Weetman, G.F.; Yang, R.C.; Beella, I.E. 1985. Nutrition 

and fertilization of lodgepole pine. In: Baumgartner,

D.M.; Krebill, R.G.; Arnott, J.T.; Weetman, G.F., eds.

Proceedings: Lodgepole pine: the species and its management. Pullman, WA: Cooperative Extension,

Washington State University. 223-232.

Weetman, Gordon F. 1988. Nutrition and fertilization of 

lodgepole pine. In: Schmidt, W., ed. Future forests of

the mountain west: a stand culture symposium. Gen.

Tech. Rep. INT-243. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Research

Station. 231-239. 

Wykoff, W.R.; Crookston, N.L.; Stage, A.R. 1982.

User’s guide to the stand prognosis model. Gen. 

Tech. Rep. INT-133. Ogden, UT: U.S. Department 

of Agriculture, Forest Service, Intermountain Forest 

and Range Experiment Station. 112 p.

Yarie, John. 1980. The role of understory vegetation in 

the nutrient cycle of forested ecosystems in mountain

hemlock biogeoclimatic zone. Ecology 61(6): 1498-

1514.

78
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CONTINUE
SILVICULTURAL

TOPICS
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1 Michael Newton is professor emeritus, and Elizabeth C. Cole is senior research assistant, Oregon State University Department of Forest Science.

Corvallis, OR 97331.

Productivity of Western Forests: A Forest Products Focus

LINKAGE BETWEEN RIPARIAN BUFFER FEATURES AND

REGENERATION, BENTHIC COMMUNITIES, AND WATER

TEMPERATURE IN HEADWATER STREAMS, WESTERN OREGON

Michael Newton1 and Elizabeth C. Cole1

INTRODUCTION

Some states have adopted regulatory best management

practices (BMPs) while other states use voluntary BMPs to

address the interface between streams and forests to protect

ABSTRACT

Riparian forests can be managed using a range of harvesting and regeneration methods to achieve multiple environmental and economic objectives. In this study, seven low-elevation second- or third-order streams were subjected to either

patch clearcutting with no buffers or one-sided narrow buffers divided by uncut reaches. Of these streams, four were sites 

of intensive regeneration experiments, and the other three evaluated only the effect of harvest pattern on water temperature.

Regeneration was successfully installed along four streams with intensive planting experiments in which three clearcuts on

each spanned the stream for distances of 90 or 180 m. Regeneration cutting in these drainages included clearcutting to the

water’s edge in openings amounting to 25% of 1,500-m reaches. Planting tests evaluated three species: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar

(Thuja plicata Donn). Douglas-fir was represented by two different stock types, bareroot plug+1 and 1+1 transplants on two

sites and bareroot 1+1 and 2+0 seedlings on the other two sites. All regeneration efforts are on a path that will eventually

result in conifer-dominated riparian zones, with degree of success influenced by choice of stock type, overtopping cover,

animal damage and frost. Damage from deer (Odocoilius hemionus columbianus Rich.), elk (C e rvus elaphus c a n a d e n s i s L . ) ,

beavers (Castor canadensis Kuhl.) and/or mountain beavers (Aplodontia ru f a Raf.) occurred on all four stream systems.

There were no patterns of beaver or mountain beaver damage among the stock types; browsing on hemlock was minor.

Growth status of the plantations at age four was a function of overtopping vegetation where there is low risk of frost damage;

freezing temperatures were limiting to seedling growth along one stream. All three of the primary tree regeneration species

studied exhibited decreased growth with overtopping. As has been found on upland sites elsewhere, size of seedlings had a

strong influence on their competitive ability in riparian zones. 

Aquatic insect communities displayed approximately a doubling of abundance with either unbuffered clearcuts or those

buffered on just the south side. Minor shifts occurred in insect community composition; none decreased and certain genera

increased markedly, with a net increase in abundance of food organisms that could be utilized by salmonids. Stream temperature increased in response to silvicultural clearing when all cover was removed. Warming and cooling trends on the four

streams with regeneration experiments were not definitive, but were within the range reported by Zwieniecki and Newton

(1999). In the three clearcuts along streams having narrow buffer screens on the south side only, no evidence of warming

was observed in uncut areas 300 m downstream of cut areas compared with pre-harvest temperature patterns.

KEYWORDS: Stream temperature, reforestation, aquatic macroinvertebrates, riparian management, buffer design.

81

water quality and maintain aquatic habitat. These state BMPs

must be sensitive to forest landowner needs to ensure that

the practices will benefit fishery resources, meet other

environmental objectives, and maintain landowner support

and interest in forest management (Hairston-Strang and
Adams 1997). Reports of potentially harmful elevations of

stream temperatures in some studies have raised concerns

about harvesting practices (Brown and Krygier 1970,

Caldwell et al. 1991), leading to eventual adoption of prescriptive BMPs. Although current riparian regulations in

Oregon allow for some harvesting within riparian areas,

such management is expensive and may not eventually be

appropriate for regeneration of desired species or for providing economic benefits to justify it. Berg (1995) explored

the notion that active management of riparian forests can be

both economically and ecologically beneficial. His analysis

relies on partial cutting of riparian stands and model projections of growth. In this report, we explore several physical and biological interactions associated with clearcut

harvesting adjacent to streams with a goal of providing

long-term renewal of desirable species while protecting

streams. 

Removal of riparian forest cover immediately over

streams can increase solar radiation and stream temperature

in the short term (Brown and Krygier 1970, Tait et al. 1994).

Even if vegetation removal is such that there are no direct

effects on fish, fish may be impacted by indirect effects on

aquatic invertebrates. Fish feed intensively on aquatic invertebrates as both nymphs and adults. Immature benthic

( b o ttom-dwelling) insects live primarily on in-stream substrates but actively and passively enter the water flow and

drift downstream, becoming highly vulnerable to predation

by fish. Temperature and solar radiation loads may affect

insects by altering food sources, life cycles, and habitat

(Newbold et al. 1980, Murphy and Hall 1981, Tait et al.

1994), with potential changes being either negative or positive, depending on organisms used for a response index.

Changes in stream temperature directly impact numbers,

fecundity, body size emergence phenology, metabolic rate

and diurnal patterns of insects (Merritt and Cummins 1984).

Temperature changes indirectly affect aquatic insects

through oxygen saturation levels, respiration rates, food

availability and nutritive value, and competition from other

insects (Sweeney 1984; Walsh 1996). Photosyntheticallyactive radiation levels affect the amount of primary production in the stream, and thus, influence the kind and amount

of food for benthic (bottom-dwelling) insects. Changes in

some species may occur independently of others, so relative

abundance of species as well as total species present are

both important indicators of change. High levels of primary

productivity can be achieved with high levels of diff u s e

radiation, whereas most energy leading to increased streamwater temperature is attributed to direct radiation (Brown

1969). In short, there are several elements of riparian habitat management where there can be legitimate debate about

whether a particular procedure enhances one element of the

stream environment or degrades another, and whether practices with consistent improvement in over-all fish habitat

are achievable.

Whether any given level of protection is needed depends

on status of resources to be protected. Of particular interest

for many forest settings is the interaction of water temperature and food supply for fish (Sullivan et al. 2000). States

evaluate stream water quality conditions using standards

that include temperature. Whether the desired temperature

criteria can be met with buffer design depends on whether

any given stream is in a desirable range of temperatures 

to start with, and whether forest management approaches

affect water quality just locally versus downstream. The

studies we undertook were designed to provide coarse-resolution answers to questions about managing for favorable

temperature and food supply while also setting up future

conifer-dominated stands for recruitment of large wood 

and other values. 

We begin with several assumptions. First, that findings

of Warren (1971) and Sullivan et al. (2000) relating to

interaction of food supply and tolerance of elevated temperatures are valid, and that short-term exposures of well-fed

fish to temperatures above 17.8°C (64°F) will not materially

harm most salmonids. Second, that future structural features of streams will be enhanced by long-term development of durable conifers suitable for either tree-fall or

placement in streams within the riparian management areas.

Finally, that abundance and diversity of benthic macroinvertebrates are indicators of potential food supply for fish

in the presence of adequate pool and riffle habitat and

moderate temperatures (Wilzbach et al. 1988). 

This report summarizes data from a series of experiments that integrates silvicultural manipulation of riparian

forests with three key elements of riparian habitat: future

riparian stand establishment, water temperature, and aquatic

macroinvertebrate abundance. These experiments evaluate

a series of reforestation techniques based on upland experience to facilitate rapid establishment of conifers and greenup of riparian systems following commercial harvest. They

were based on two approaches to clearcut harvesting: clearcutting to the water’s edge on both sides versus clearcutting with one-sided buffers. Harvests with no buffers were

combined with trials of several coniferous stock types with

and without weed control with the general approach outlined by Newton et al. (1993). The object of the one-sided

buffer was to manipulate streamside shade to gain protection from direct radiation while allowing maximum regeneration opportunity. The regeneration studies rely on

repeated measurements of several planted coniferous tree

82
species and competing hardwood and shrub cover, measurement of water temperatures along streams passing

through the various treatments (including data from

Zwieniecki and Newton 1999), and samplings of bottomdwelling macroinvertebrates to assess impacts on potential

abundance of aquatic insects well utilized by salmonids. 

Our specific objectives were to: 1) evaluate the regeneration success and growth of combinations of planting

stock species and size combined with and without overstory removal and shrub control in streamside environments,

2) determine how alternative approaches to removing tree

cover near streams influence abundance and diversity of

benthic insect communities, and 3) develop a coarse-resolution estimate of whether openings to facilitate forest rehab i l i t a t i o n affect downstream water temperature. Robison

and Beschta (1990) and others have reported that most

large wood contributing to stream structure originates within 15 m from the banks. The first objective specifically

addresses the problem of establishing conifers near streams

on low-elevation sites in the Douglas-fir (P s e u d o t s u g a

m e n z i e s ii (Mirb.) Franco var. m e n z i e s i i)Region where most

low-elevation streams are bounded largely by hardwoods.

The persistence of these species as functional large wood

in streams tends to be short compared to that of large conifers.

While there are reports that upslope or upstream sources

may provide much large wood for these streams (Reeves et

al. 2003), a local source is presumably a better guarantee

that a local supply of wood will be present when needed.

Thus, in the event incentives develop for establishing large

conifers, there is a need to understand the environments and

management approaches in which such trees may develop.

The other objectives address impacts of buffer design on

aspects of the stream system that might relate to fish.

METHODS

Layout

The studies occurred in two primary phases, both of

which utilized fish-bearing headwaters streams passing

through low-elevation, intensively managed forest ownerships. Precipitation for all creeks is between 1200 and 2000

m m / y e a r, of which roughly 85 percent occurs between

October and April. In Phase I, four second- or third-order

fish-bearing streams (Ames, Bark, Buttermilk, Mosby Creeks,

fig. 1) were scheduled for clearcut harvests, with coniferous reforestation according to hardwood conversion rules

(Oregon Forest Practices Act) that allowed clearcutting to

the streambank according to a written plan. These were the

streams on which all reforestation experiments were conducted. 

Each Phase I stream was laid out to provide a basis 

for both reforestation and study of effects of small clearcuts with no buffers on water temperature. In each, a 1500-m

reach was identified for study. Two creeks (Bark and

Buttermilk) are in the central part of the Oregon Coast

Range, and are bedded in sedimentary rock. Buttermilk

Creek drains a basin of 702 ha at a gradient of three percent, and Bark Creek drains 1560 ha with a gradient of less

than two percent in the study reach. The other two (Ames

and Mosby) drain lower slopes of the Oregon Cascade

Mountains, and are bedded in basalt bedrock and boulders.

Ames Creek drains a basin area of 1441 ha and has a gradient in the study reach of three percent. Mosby Creek

drains 26,022 ha with a gradient of five percent in the

study reach. 

Buttermilk and Bark Creeks flow between terraces

largely of deposits of medium-textured material from sedimentary rocks of the Tyee formation, a readily weathered

siltstone in this area. These soils are extremely productive

for either conifers or red alder (Alnus rubra Bong.). Except

in poorly drained depressions and gravel piles, all soils are

of good to excellent productivity, capable of growing a

Douglas-fir tree 38 m to 40 m tall in 50 years (King 1966).

Stands removed in the harvests were dominated by red

alder, with understories of salmonberry (Rubus spectabilis

Pursh.). Ames Creek soils are a mixture of alluvial gravelly

loam terraces with scattered wet depressions, and residual

83

Figure 1—Map of stream locations in western Oregon.
well drained Jory silty clay loam soils; site quality is heterogeneous, and estimated 50-year Douglas-fir site index

ranges from 33 m to 37 m (King 1996). The previous stands

were primarily hardwoods, mixtures of bigleaf maple (Acer

macrophyllum Pursh.) and black cottonwood (Populus trichocarpa T. & G.) with some willows (Salix [Tourn.] L.)

and Douglas-fir. Of the four Phase I streams, Mosby Creek

differed markedly from the others in having been subjected

to placer mining, probably more than 50 years previously.

The soil there was largely comprised of a thin layer of

o rganic litter on top of piles of gravel and boulders, with

occasional patches of original gravelly loam soil. Planting

was exceedingly difficult. The stand removed in preparation for this study consisted primarily of immature red alder

with intermixed conifers of assorted sizes and understories

of mixed shrubs, depending on degree of suppression.

Estimated 50-year site index for Douglas-fir at Mosby

Creek ranges from 30 m to 35 m (King 1996). 

The 1500-m study reach for each of the four Phase I

streams was divided in half so that one 750-m sub-reach had

25% of its length clearcut-harvested in one 180-m reach

and the other sub-reach had two 90-m openings (fig. 2).

The remainder of each 1500-m reach was uncut or remained

b u ffered according to pre-1994 Oregon Forest Practice

Rules (22 m or more both sides), and there was at least 200

m of uncut stand or standard buffer between any two clearcuts. Logging of all units was completed in late 1992.

Phase I included all reforestation experiments, for which

all clearcuts were made with no buffers.

Phase II streams evaluated only the influence of a onesided buffer design on water temperature and stream productivity. Each had a single clearcut installation, in late

1993, with a buffer represented by a “sun-sided” vegetative

screen on each of three similar-sized streams (East Brush,

Mill, and Scheele Creeks, figs. 1 and 3). East Brush Creek

drains about 1100 ha of basaltic foothills of the Cascade

Mountains. In the Coast Range, Scheele Creek drains 1743

ha of deeply weathered Siletz River basaltic rock, and is

bounded by Jory soil with negligible terrace areas. Mill

Creek drains about 440 ha of sedimentary rocks and deep

soils. In each, cutting was done on both sides of the stream

so that a 760-m to 800-m reach was exposed, but a vegetated screen 12-m wide remained between any point in the

stream and the path of direct solar radiation through the

summer. The screen consisted of whatever trees and shrubs

were present in the uncut condition so long as they were

within 12 m of the streambank. Where streams were eastwest in orientation, no buffer was left on the north side, but

the sun shining on open water between 9:00 AM and 6:00

PM PDT was intercepted to a major degree by a screen of

cover. The protection was provided in meandering streams

by leaving all cover in a 150-degree fan-shaped range of

directions between true azimuths of 120 and 270 degrees

for a distance of 12 m from the bank as shown in figure 3

(adapted from Newton 1993). 

All cutting units were laid out specifically for the study.

The methods used in these experiments were within the

bounds of Oregon Forest Practice Rules, with the exception

that buffer removal to the water’s edge and one-sided buff e r s

required specific written plans and research protocols.

Logging operations were conducted with equipment and

approaches according to cable or ground-based systems

normal for each owner with special priority for avoidance

of damage to streambanks.

Reforestation

In each clearcut established for Phase I, planting was

done with four stock types, including large and small

D o u g l a s - f i r, and plug+1 western redcedar (Tsuja plicata

Donn) and western hemlock (Tsuga heterophylla ( R a f . )

84

Figure 2—Schematic of unit layout for reforestation (Phase I) studies.
Sarg.). The seedlings were planted in clusters of four seedlings, one of each species or stock type, in five rows of

clusters 6 m apart parallel to the stream, beginning about

three m from the bank, overall approximating a 3 x 3-m

spacing in a 30-m strip on each side of the stream (fig. 2).

The rows extended 18 m into the uncut timber upstream

and downstream from each clearcut. Half of each planting

was treated with a broadcast site preparation application of

glyphosate herbicide so as to leave a 3-m wide untreated

zone along the stream at Bark and Buttermilk Creeks. Spottreated release applications of glyphosate were applied at

Ames and Mosby Creeks. For each cutting unit, spraying

left a 3-m buffer along both banks of the stream. Spraying

extended 20 m into understories of the uncut stands at the

sprayed end of the unit where seedlings were to be planted.

A total of some 12,000 seedlings were planted. For each

seedling, annual measurements during the first four years

recorded seedling diameter 15 cm aboveground, diameter at

breast height (137 cm, dbh) if seedlings were of sufficient

size, and current and previous-year’s height (for confirmation). If data did not match previous year’s data, the site

was revisited and measurements confirmed. 

At each seedling, visual estimates were made of competing cover of herbaceous plants, shrubs, and ferns within

a 1-m radius for years one and two, and of overtopping

(Howard and Newton 1984) by shrubs and residual trees

for all years; residual trees were present primarily in underplanted stands at the ends of each unit. Condition of seedlings, including animal damage from beavers (Castor canadensis Kuhl.), mountain beaver (Aplodontia rufa Raf.), and

deer (Odocoilius hemionus columbianus Rich.)/elk (Cervus

elaphus canadensis L.) and mortality, were recorded

separately.

Stock quality problems were encountered for the

Buttermilk and Bark Creek plantations, both of which had

ideal conditions for seedling survival and vigor; the same

lot of seedlings planted on good sites elsewhere also performed poorly. Survival was lower than expected (65%) at

Buttermilk Creek, but we determined that would be acceptable. Survival at Bark Creek was less than 50%, and we

replanted there and removed the original survivors. Thus,

for Bark Creek, we have only three years of measurement.

Freezing damage and severe elk browsing occurred at

Mosby Creek. Survival was below 40% after two years,

and the landowner elected to replant vacant spots with a

mixture of valley ponderosa pine (Pinus ponderosa Dougl.

ex Laws) 2+0 seedlings, grand fir (Abies grandis (Dougl.)

Lindl.) plug+1 transplants, western white pine (Pinus monticola Dougl.) 1+0 containerized seedlings and western

redcedar plug+1 transplants with 5-cm Vexar® tubes

installed before planting. This plantation (replants only)

was two years old at last measurement, and the residual

seedlings of the original planting reflected four growing

seasons under severe elk pressure. They are summarized

separately.

For the seedling data, two types of analyses were performed. The first set of analyses examined the relationship

between 1) seedlings planted in the clearcut areas and those

planted under the residual stands, 2) seedlings in weeded

and unweeded areas in the clearcuts, 3) browsed and

unbrowsed seedlings in the clearcuts, and 4) browsed and

unbrowsed seedlings in the weeded and unweeded areas in

the clearcuts. All stock types were analyzed separately, and

only those seedlings that were alive at the time of the last

measurement were included in the analyses. For these

analyses, we used PROC MIXED in SAS® and the analysis

of covariance for comparison of regression lines as outlined in Littell et al. (1996). The dependent variable was

85

Figure 3—Schematic of fan-projection method of implementing one-sided

buffer boundaries for fish-bearing streams. Buffer design places 12 m of

cover between stream and water between 9:00 am and 6:00 pm PDT

(azimuth of 120° to 270°).
stem volume index (an easily measured estimator of total

stem volume), calculated as height*basal diameter2* ! / 1 2

and the independent variable was year of measurement

(zero to three or four). For the second set of analyses,

equations for each species and site were developed relating

stem volume index in year three (Bark Creek) or four

(other sites) to different cover variables. For all species and

sites, the best equation was ln(volume index) = ß0+ ß1

ln(initial volume) + ß2 overtopping + ß3 overstory cover.

For Bark Creek cover, overtopping and overstory cover

were from year three, and for all other sites, from year four.

Benthic Sampling

The sampling design for insects was described by Wa l s h

(1996) and was first developed on the Phase I streams, then

extended to Phase II streams. Among the four Phase I

streams, Bark Creek was not sampled, because the bottom

was covered with fine sediments and organic detritus on

which few insects were observed, and the invertebrate biomass was dominated by snails. Initial insect sampling was

done on Phase I streams in the first season following harvest (1993), and was repeated in the second year to determine whether populations were still responding. Phase II

streams were sampled in July and September, 1995, two

years after harvest, and at this time Phase I streams were

re-sampled so the two groups of streams could be compared.

For both Phases we placed four sampling stations on each

stream, with one station upstream at least 20 m from cutting units, one 20+m below the cutting unit, and two within

the cutting unit representing the upstream half and downstream half of the cutting unit. All samples were taken in

riffles to minimize variance so as to increase sensitivity to

harvest effects. In each designated sampling area, all

stretches of riffle at least 4.5-m long were noted, and one

was randomly chosen for sampling. Fish also consume

insects washed down into pools, eddies, backwaters, and

the downstream edge of riffles; our sampling system did

not capture these drift organisms, and they are not reflected

in our findings. 

For each sampling station, a 4.5-m length of stream was

divided into 45 sample spots in a 3 x 15 grid pattern, each

being 1/3 of the channel width wide by 30 cm long (fig. 4).

Six of the sections were then sampled each date following

a systematic non-aligned design so that two samples were

randomly chosen from the 15 sections on each of left, middle, and right part of the stream on each sampling date.

These six subsamples were pooled for analysis. Sections of

the grid that were sampled in July were not resampled in

September.

A 30-cm X 30-cm Surber sample (sample collected

from a net into a jar) was collected on the stream bottom

within each sampled section with the following specifications. Every rock in the sample square to a depth of 8 cm

was cleaned while in the water upstream from the collection net. Variability between subsamples was examined by

Walsh (1996) and provided the basis for pooling and subsampling for eventual estimation of populations with 50%

of the original combined sample material. July samples

were sub-sampled again in the lab, to reduce identification

time. Identification of insects smaller than 1.1 mm was

extremely time-consuming and inexact, hence samples of

record were restricted to insects larger than 1.1 mm after

the first year. This resulted in small sample sizes, and seasonal comparisons were not attempted. Insects were identified down to the family and genus level where possible. 

It was extremely difficult to differentiate between genera 

in some families (e.g., Plecoptera, Perlidae), and a few of

the insects were damaged from handling. Genera were

assigned to functional feeding groups as per Merritt and

Cummins (1994). 

Data were analyzed for Phase I in 1993 and 1994 by

Walsh (1996) in substantial detail to show immediate

responses to clearcutting. Those analyses included only 

the three streams with reforestation experiments on them.

Briefly, influence of substrate composition, stream velocity,

temperature and estimated radiation load (evaluated by

estimating vegetative cover with a densiometer) were evaluated for their effects on both abundance and diversity of

genera, using regressions based on log-transformed insect

counts. Residuals from regression were subjected to repeated measures analyses of variance for tests of differences

between streams, stations within streams, and interactions.

In 1995, additional samples (third year) were run in

Phase I streams and compared to second-year samples in

Phase II streams. In view of the increased sample sizes

when analyzing 1995 samplings of Phase I and II installations

86

Figure 4—Schematic design of sample location grid used to randomize

collections at each benthic sampling station. 
together, a separate analysis was used with the primary

objective of comparing effects of treatment on large insect

populations. Sample data were first transformed to approximate normality in order to run parametric statistics.

Analyses of variance (ANOVAs) were performed for total

abundance, relative abundance, functional feeding groups,

and generic richness for all experimental streams together

combining Phase I and II experiments. Means were compared between treatment streams, cut and uncut reaches,

and stations. Relative abundance was calculated as the

percent of each order in each sample collected. Tu k e y ’s

Honest Significant Difference test (HSD) was used to

compare multiple means. Spearman’s rank correlations

were done for each of the insect variables with stream 

temperature and discharge. 

Stream Temperature

Stream temperatures were recorded for two years immediately following harvest treatments (Phase I) and one year

before and one year after for Phase II installations. Four 

to six thermistors (two-channel Omnidata Datapod Digital

Recorders) were placed in each Phase I stream to record

water and air temperature, including one or two thermistors

above the entire study reach, below the study, in one clearcut, and at one or more other locations in covered sections

between clearcuts. The thermistors recorded diurnal temperature fluctuations through the June-September season.

Reflecting the importance of temperature extremes, our

findings are presented in terms of the influence of treatment

on the means of the maximum temperatures occurring in the

seven consecutive days with the highest seven-day-mean

temperature in each year of record, the standard regulatory

criterion. We bring in data from Zwieniecki and Newton

(1999) reflecting temperature patterns before and after harvest in sixteen headwaters streams that include the three

Phase II installations with sun-sided cover screens. On the

other 13 streams they described, clearcut harvesting had

been done in which a portion were buffered according to

conventional harvest buffer rules (15-21-m buffers on both

sides), and half were done with hardwood conversion rules

(6-m no-touch buff e r s , with up to 180 m of stream length

per unit having all trees removed). 

RESULTS 

Reforestation

Each stream had unique features and events that force a

presentation of data separately for each. Bark and Buttermilk

Creeks, our Coast Range sites, had heavy mortality immediately after planting of all stock types. Because of the

replanting at Bark Creek, we only have three years of data

for those seedlings. In both Bark and Buttermilk Creek

studies, it will also be noted that the “large” and “small”

Douglas-fir seedlings were of similar size, but one was 1+1

and the other was plug+1 in nursery regimes, so differences

between stock types were minor initially. Ames Creek and

Mosby Creek differed from the Coast Range streams in

having been prepared too late for site-preparation herbicides,

necessitating the use of directed spot herbicide treatments

instead. Ames Creek had significant herbicide injury to a

number of seedlings. Unrelated to this, Mosby Creek plantings were devastated by frost, elk and rocky substrate

resulting from prior mining activity; hence there is great

uncertainty in evaluating their future growth.

Bark Creek: Although the large and small Douglas-fir

stock types were similar in size when planted, analyses

indicate that there was a difference in the volume trajectory

(p = 0.0495). Examination of the means for year three

(table 1) indicate that the small Douglas-fir continued to

be smaller than the large Douglas-fir when underplanted 

in unweeded areas. The volume growth from year two to

three (not shown) was three times greater for the larg e

Douglas-fir than the small Douglas-fir in these areas. Results

for the two stock types elsewhere along Bark Creek were

similar (table 1). Both stock types of Douglas-fir and redcedar were larger (p < 0.0022) in clearcut areas than in

underplanted areas.

Within the clearcut areas, the large Douglas-fir and

western hemlock did not show an increase in growth due to

weeding (p = 0.5041 and 0.1395, respectively). Spraying

did not consistently result in the low levels of cover that

are usually needed for major increases in growth (table 2).

Redcedar (p = 0.0024) and the small Douglas-fir (p = 0.0137)

did have greater growth in the weeded areas. Year three

stem volume for all species was negatively correlated with

both overstory cover and overtopping with similar patterns

to those shown for Ames Creek in figures 5 to 8.

Buttermilk Creek: Although initial size of the Douglasfir stock types did not differ, by the end of the fourth year,

there were differences (p < 0.0001) among the two stock

types especially where weeded (table 1). It is not known if

these differences are attributable to greater vigor at the t i m e

of planting, differences in root mass, or both. However, by

the end of the fourth growing season, the large Douglas-fir

(1+1) were over 35% larger in volume than the small

Douglas-fir (plug+1) in both the weeded and unweeded

clearcut areas. All species had greater volume in clearcut

areas than in underplanted areas (p < 0.0724). All stock

types were affected by competition (p < 0.0619). In the

clearcut areas, stem volume of weeded redcedar, hemlock,

and small and large Douglas-fir averaged 62, 79, 20, and

32% larger than the unweeded seedlings after four years.

87
88
89
Ames Creek: Differences between stock types (1+1 and

2+0 bare-root) of Douglas-fir were still apparent after four

years (table 1). The relative difference between the types

has been decreasing, but absolute differences are increasing.

I n i t i a l l y, the large 1+1 seedlings were seven times larg e r in

volume than the small 2+0 seedlings. At age four, larg e

seedlings were only three times larg e r, but had more

absolute growth for the first four years.

This installation was established too late to complete

broadcast site preparation sprays in the appropriate season,

and careful spot treatments during active conifer growth

were all that could be done. In the process some seedlings

were damaged despite care. There were no differences in

growth between weeded and unweeded areas for larg e

Douglas-fir seedlings (p = 0.2034), but the other stock types

had greater growth in the weeded clearcut areas (p < 0.0322).

Redcedar and hemlock seedlings averaged 39 and 75%

l a rger in volume, respectively, in weeded clearcut areas

than in the unweeded clearcut areas. Regression equations

indicated that for all stock types, level of competition

affected growth (fig. 5). 

Mosby Creek: A variety of sources of damage have

severely compromised the initial plantation at Mosby Creek.

In addition to the rockiness that was atypical of riparian

soils, the mining had relocated some water channels that

eventually flooded or buried some of the plantings. T h u s ,

success was limited by physical circumstances. Nevertheless,

the site remains fundamentally productive, as measured by

its initial condition when selected. In addition to the physical limitations of this site, problems with spring and fall

freezing damage occurred in both sprayed and unsprayed

portions of the study.

90

Figure 5—Stem volume index of (a) unbrowsed large Douglas-fir, (b) unbrowsed small Douglas-fir, (c) unbrowsed western redcedar,

and (d) unbrowsed western hemlock at age 4 as a function of overtopping by hardwoods and shrubs, Ames Creek. Note: Scale for z

axes is different for each species.
The large Douglas-fir stock type (1+1) continued to be

the largest seedlings on the units (table 1). In clearcut areas,

the large Douglas-fir averaged almost three times greater

volume than the small Douglas-fir. Both stock types of

Douglas-fir and redcedar had less growth in underplanted

areas (p < 0.0001). Hemlock averaged over twice the size

in clearcut areas than in underplanted areas, but differences

were not significant (p = 0.7869) in part due to low survival (14 %) in underplanted areas.

Although differences in average seedling size for

Douglas-fir and redcedar in the weeded and unweeded areas

were relatively small (p > 0.0984), competition reduced

seedling growth similar to that shown for Ames Creek in

figure 5, but with smaller volumes in general. Hemlock

seedlings were larger in the weeded areas (p = 0.0065).

For the “new” plantings, at the end of two years, the

grand fir and ponderosa pine were growing best (table 3).

Although redcedars were the largest initially, they were

exhibiting poor growth, as with the first planting. Although

relative growth between the two pines was similar, the

white pines were still very small, and survival was poor.

All Sites: Animal damage had a major impact on all plantations. Mountain beaver clipping occurred on three of the

sites (table 4), and beaver clipping occurred on two of the

sites. At least 50% of the seedlings that had been damaged

by beavers were dead. Although the overall percentage of

damage by beavers was low, the local impacts were severe.

As would be expected, the damage by beavers was concentrated within 15 m of streams, but damage was seen more

than 30 m from the stream. 

Hemlock was infrequently browsed on all sites. For the

other stock types, browsing impacts were related to location of the seedling (weeded or unweeded areas, clearcut or

underplanted areas), whether or not the browsing was done

by deer or elk, whether browsing reduced shrub cover adjacent to the seedling, and inherent productivity of the site.

Browsed Douglas-fir were reduced in stem volume at age

four by 23-45 percent at the various sites. Redcedar volume reduction from browsing was greater, ranging from

50-60 percent relative to unbrowsed seedlings. As overtopping increased, the absolute impact of browsing decreased;

the unbrowsed seedlings growing under high degrees of

overtopping do not grow as well as those with low amounts

of overtopping. The lesser impact is associated with loss of

potential, over all, as long as overtopping remains.

Insect Abundance

Phase I analyses for the first and second years of

response to harvest showed that stream substrate explained

more variation in absolute abundance, diversity and functional feeding groups than any other stream variable (p <

0.001). The order in which substrate had a positive eff e c t

on total abundance was cobble>bedrock>boulder=sand=

silt>gravel. Walsh (1996) provides details of this analysis by

genera showing which genera were favored by each substrate medium. Of the remaining environmental variables,

stream velocity explained the most variance, as would be

expected from the comparatively high velocities of riff l e s

compared with other substrates. Collector-filterers were

positively associated with velocity. Mayfly (Ephemeroptera)

and caddisfly (Trichoptera) genera were positively correlated

with stream velocity and also negatively correlated with

exposed bedrock; those which were negatively associated

with velocity were positively correlated with fine-textured

substrates. Radiation load, as estimated by densiometer, did

91

Table 3—Height, diametera, and stem volume for new plantings, age 2, at Mosby Creek

Overstory<=15% Overstory>15%

Height Diametera Volume Height Diametera Volume

(cm) (mm) (cm3) (cm) (mm) (cm3)

Unweeded Grand Fir 43 7.3 7.1 39 6.4 5.3

Redcedar 57 7.7 9.6 66 7.5 10.6

Ponderosa Pine 38 9.2 10.4 29 7.8 5.3

White Pine 19 5.0 1.5 16 4.5 0.9

Weeded Grand Fir 49 9.1 12.1 46 7.6 8.2

Redcedar 55 8.2 10.9 58 6.8 8.3

Ponderosa Pine 38 10.1 12.7 29 7.7 5.2

White Pine 21 5.9 2.1 17 5.0 1.3

a Diameter refers to diameter at 15 cm above ground for grand fir, redcedar, and ponderosa pine. Diameter is root collar diameter for 

white pine.
92
not significantly explain the variance of any mayfly or caddisfly groups or functional feeding group, nor did stream

temperature.

Absolute abundance of most genera increased between

the first and second years following harvest (p < 0.01) and

most genera responded positively to harvest, with the

strongest response being in the second year. Only one genus,

Drumella, displayed more abundance outside the cutting

unit than within it, in general, and was more abundant both

upstream and downstream from a clearing than within the

clearcut. All others showing a significant response were in

greater numbers within the harvest unit than above or below

it (p < 0.05). C y n i n g m u l a and R h i t h ro g e n a were more

abundant downstream from the harvest units than above 

the unit (p < 0.05). 

The analyses of abundance in cut versus uncut units of

Phase II data all reflected second-year responses, and they

are compared here with third-year responses in Phase I

experimental streams; both sets of data compare same year

cut versus uncut while total abundance following clearcutting versus one-sided buffered cuts are based on two versus

three years since cutting. Mean total abundance (per square

meter) of benthic insects in the two uncut reaches up and

downstream from each clearcut unit was half (82.6) the

mean abundance in the cut reaches (165.4, p = 0.002, fig. 6)

in both Phases I and II. Overall abundance between the

clearcut and one-sided streams did not differ (p = 0.18).

Upstream stations had lower abundance than the two stations within cuts (p = 0.004) (table 5, fig. 7), and there was

a general increase in insect abundance in a downstream

direction, as streams increased in size. Initial conditions in

streams were not identical, but numbers were comparable.

Within the uncut reaches, there appeared to be fewer insects

in streams scheduled for zero-buffer treatment than there

were in one-sided streams, but the difference is not significant (p = 0.132). Abundance was similar between the two

treatment types (one-sided buffers and clearcuts) in cut

reaches (p = 0.737). 

Different orders of insects displayed varying responses

to harvest, but three orders were more abundant in cut than

in uncut reaches. Diptera (true flies) displayed the greatest

differences in mean abundance between the cut plots (17.2)

and uncut plots (6.5, p = 0.009). Trichoptera displayed a

l a rge difference between cut (mean = 67.0) and uncut

(mean = 40.7) reaches (p = 0.025), and Ephemeroptera also

differed (22 versus 13, p = 0.09). 

Some, but not all, effect of clearing on caddisflies and

mayflies showed up a short distance downstream, where

numbers were greater than upstream densities. We were

unable to separate the effect of stream position from that

of increased light when combining up-and downstream

data for these orders with data from the clearings, but both

were generally less abundant in the upstream uncut plots

than in the cut plots (p = 0.017 and 0.09, respectively) (fig.

7). Plecoptera (stoneflies) and Coleoptera (beetles) did not

differ in overall abundance between cut and uncut reaches,

hence post-harvest species ratios were somewhat altered

although no order decreased with harvest. 

93

Figure 6—Total abundance of insects in each treatment type for Phase I and II studies.
94

Table 5—Total abundance, insects of all genera >1.1 mm long per composite 

sample taken from six low-elevation western Oregon streams. Ames, Buttermilk,

and Mosby Creeks were harvested both sides with no buffers in 90 or 180 m

patches; Brush, Mill, and Scheele were clearcut both sides with 12 m screen

south of stream for buffer on 805 m reaches

Within cuts

Upstream Downstream

Stream uncut Upstream Downstream uncut

Ames (CC) 114 392 258 163

Buttermilk (CC) 27 115 71 2

Mosby (CC) 100 194 312 142

Percent of all 

insects/reach, 

all streams 13 37 33 17

Brush (OS) 136 140 129 131

Mill (OS) 134 163 371 137

Scheele (OS) 132 185 283 101

Percent of all 

insects/reach, 

all streams 20 24 38 18

Figure 7—Total abundance of each taxonomic order for the four stations in the one-sided buffer (Phase II study).
Within cut reaches only, there appears to be 50% more

Ephemeroptera and 60% fewer Coleoptera in one-sided

streams than in clearcut reaches, but results were not significant (p > 0.10). Only five individuals of Odonata

(Gomphidae, dragonflies) were collected, thus they were

left out of analyses by taxonomic orders, but included in

the functional feeding group analysis. 

Total abundance was mildly and positively correlated

with both stream discharge (r = 0.36, p = 0.013) and the

seven-day maximum mean temperature (r = 0.31, p = 0.032).

Plecoptera and Ephemeroptera abundance were more

strongly correlated with discharge, with fewer insects when

discharge was low (r = 0.49, p = 0.0004 and r = 0.51, p =

0.0002, respectively). At the genus level, Baetidae Baetis

and Ephemerellidae Eurylophella in Ephemeroptera were

positively correlated to discharge. No individual genera

could be identified in Plecoptera. 

Abundances for some insects were positively related 

to temperatures of streamwater. Trichoptera abundance was

positively correlated with the seven-day maximum mean

temperature (r = 0.53, p = 0.0001), which may explain much

of the correlation for total abundance. Only two of the four

genera (with adequate numbers) within Trichoptera were

significantly correlated, and here the correlation was positive: Glossosomatidae Glossosoma (r= 0.39, p = 0.006) and

Limnephilidae Neophylax (r= 0.41, p = 0.004). The mayflies

in Ephemerellidae Euryophella/Ephemerella had a positive

correlation (r = 0.49, p = 0.0004). No other taxonomic

orders were generally correlated with temperature.

The relative taxonomic composition did not differ 

s u bstantially between cut and uncut reaches of diff e r e n t

streams (fig. 8). Only Diptera increased in relative abundance in cut stands (p = 0.03), and Plecoptera decreased

slightly (p = 0.07). Relative abundance of insects between

clearcut and one-sided streams differed for two insect orders.

Coleoptera were more abundant in the clearcut streams (p

= 0.052), both in the uncut (100% more) and cut (200%

more) reaches than in the streams with one-sided buffers.

The interaction was not significant (p = 0.42). Ephemeroptera

were more abundant in the one-sided streams (p = 0.09),

with 50% more in uncut reaches and 100% more in cut

reaches, reflecting both random differences between streams

independent of treatment, and also effect of treatment. 

The insect genera were divided into five functional

feeding groups (FFG): collector-filterers, collector- g a t h e r e r s ,

scrapers, shredders, and predators. Some genera or families

contain diverse species that belong in more than one type

of FFG, thus separate categories of collector- g a t h e r e r s /

scrapers and collector-gatherers/shredders were included.

Few genera in this sample fell into the collector-gatherer/

shredder category, so those were not analyzed statistically.

C o l l e c t o r-filterers, collector-gathers, and predators

responded similarly to harvest design (clearcut vs. onesided buffer), and types of harvest were pooled for analysis.

All functional feeding groups were more abundant in cut

reaches than uncut reaches in both clearcut and one-sided

streams (p = 0.009, 0.017, and 0.030, respectively). The

relative abundance of insect groups did not change markedly

after harvest (fig. 9). Although predators increased by

almost 50%, their percentage of all insects decreased due

to the overall increase in benthic insect of all kinds in cut

reaches. Shredders displayed an interaction effect, with more

specimens from uncut portions of one-sided streams and

more in the cut portion of clearcut streams (p = 0.037). At

least one of the clearcut streams (Buttermilk) had larg e

amounts of wood only in the cut portions, which may have

trapped significant detritus and attracted more shredders. 

95

Figure 8—Relative abundance of insect taxonomic orders in cut and uncut

reaches for Phase I and II studies.
Abundance of some FFGs varied by treatment type.

Within the uncut plots there were more shredders and predators in streams with one-sided buffers, and more collectorgatherers and collector-gatherer/scrapers in the clearcut

streams. Despite these apparent differences, within-cut comp a r i s o n s showed only the shredders differed between treatments, with twice as many insects in the clearcuts than in

the one-sided cuts. There were no differences in overall

abundance between streams of the two treatment types. 

The number of genera represented in each stream system

did not differ by treatment types (p = 0.743), or between cut

versus uncut (p = 0.122). The mean number of genera found

in the uncut portions of both sets of treatment was about

the same (9.3 for clearcut, 9.5 for one-side), and the means

in cut reaches were also similar (10.9 for clearcut, 11.4 for

one-side). East Brush Creek (one-side) had low generic

richness (2-4) at all stations in September, although the

number of individuals in the samples was normal.

Stream Temperature

Temperature of water was evaluated at the warmest part

of each summer, based on the moving maxima of water

temperatures for seven consecutive days with the warmest

mean temperatures. Temperature profiles in the four

unbuffered (Phase I) experimental streams were not consistent, either in their patterns of warming or in uniformity

from year to year. None appeared to warm significantly

more than would be expected for a 750-m-long reach less

than 8 km from the source, but lack of pre-harvest basinwide trends were not recorded for reference. Dent (1995)

indicated that there were some measurable impacts on

stream temperature, but she had not compensated for the

expected rate of warming in covered reaches of comparable

position in the basins, a procedure regarded as necessary

for estimation of net warming (Newton and Zwieniecki

1996, Zwieniecki and Newton 1999). 

Streams showed variation in the amount of temperature

change between clearcuts, both among streams and among

years of observations, as reported by Dent (1995). The first

two years of data following harvest reflected contrasts in

summer temperature, with 1993 being cool and wet, and

1994 being extremely hot and dry. In 1993, the first year

following harvest, water exiting the study reach ranged

from 0.2°C in Bark Creek to 1.2°C in Buttermilk (main

stem) warmer than water at the upper end of each study

reach, based on seven-day moving mean maxima. Nearly

all the net rise occurred in harvested units, as shown by

Dent (1995). In 1994 during the period of least discharge,

Bark Creek gained 0.6°C over all, representing gains in

clearcut units and losses between cut units, while Buttermilk

Creek gained about 1.6°C over all, with no consistent pattern between cut and uncut units even though the previous

year had shown maximum warming to occur in harvest

units. No stream gained more than 1.6°C in the length of a

study reach (Dent 1995), a rise typical of the natural downstream warming trends of several headwaters streams

reported by Newton and Zwieniecki (1996). Unfortunately,

without baseline measurements, we are unable to determine

if the observed trends represent a change from pre-harvest

conditions. 

The uppermost cut unit on Buttermilk Creek was actually on a major tributary rather than on the main stem. The

main stem was largely slack water behind beaver dams

above the confluence, hence unsuitable for study, but there

was a large temperature rise at the confluence reflecting the

warm water from the shallow beaver impoundments. This

accounted for much of the total increase in the study reach. 

Phase II streams were described in the report by Zwieniecki

and Newton (1999) which did have both pre- and post-harvest data. Their report showed that all three of the Phase II

96

Figure 9—Relative abundance of functional feeding groups in cut and

uncut reaches for Phase I and II studies.
streams (sun-side buffered) were at or below pre-harvest

rates of warming with downstream flow soon after water

re-entered uncut stands.

DISCUSSION

The reforestation experiments demonstrate the difficulty

in establishing conifers in the presence of overtopping shrubs

and animals that damage seedlings. Problems with low

temperature can likely be reduced or eliminated by choice

of frost-hardy species, but their suitability for long-term

growth in streamside environments remains untested.

H e r b i v o r y will remain a serious problem regardless of

species planted as long as beavers have unrestricted access

to streamside regeneration.

Robison and Beschta (1990) have identified sites within

15 m of the streambank as the potential sources for most

local tree-fall recruitment of large wood. Losses of regeneration attributable to beavers were most frequent in this

zone, and led to elimination of most regeneration in large

portions of both Bark and Buttermilk Creek experiments.

Beavers were not selective among species. In these streams,

beavers were not restricted in their locations by dams or

other obvious residence areas, and they appeared to travel

over the length of experiments and occasionally forage more

than 30 m from the streams. The long-term effects of this

are important, because the possibility of recruitment of

conifers by natural regeneration in these areas is low owing

to re-development of competing cover. Even if conifers did

occasionally regenerate naturally, new seedlings would

likely be damaged or killed unless the beaver pressure

decreased. Fencing to keep beavers in the stream and away

from the plantations worked at one site for a time. However,

flooding breached the fences in several places, and cattle

grazing in the units resulted in trampling of the fence. Fence

failure allowed the beavers to continue foraging on the

seedlings, and damage was often lethal.

Damage by deer and elk was generally not lethal, but

did reduce growth. Visual examination of these plantations

after ten years reveals good plantation development in

clearcuts except where mortality from herbivory created

l a rge gaps. Regeneration in uncut stands was ultimately

unsuccessful. The need to reduce competition for establishment and growth of conifers in riparian areas was noted by

Chan et al. (1998) and Emmingham et al. (2000) in their

reviews of riparian regeneration studies. They also noted

that both shade tolerant and shade intolerant species were

limited by overhead competitors, as we demonstrate with

illustrations of interactions between canopy cover and shrubs

in uncut stands, and with shrubs as overtopping where

unsprayed. We also confirm that use of large, vigorous

planting stock increases the likelihood of survival in both

browsing and competitive environments, provided overtopping is not extreme and seedlings can be adequately planted.

Howard and Newton (1984), Wagner and Radosevich (1991),

and Newton et al. (1993) demonstrated a general adaptability of very large conifer seedlings in areas subject to

herbivory and shrub competition in the Oregon Coast Range.

Some success has also previously been observed after planting wild seedlings averaging 1.5 m tall in untreated salmonberry in shrub-dominated riparian systems near the Oregon

coast (Newton, M., unpublished data, 1970, from cooperative experiments with the USDA Forest Service, Siuslaw

National Forest, Waldport, OR). At Mosby Creek, the rocky

soils made planting large seedlings difficult, and planting

large seedlings may not be feasible in such areas.

Differences between sprayed and unsprayed areas were

less than expected. Spraying with glyphosate soon after

logging is typically unreliable because leaf area of shrubs

has been removed to the extent that translocation to roots is

sub-marginal. Application of this herbicide at least a month

prior to late-summer harvest would likely have nearly eliminated shrub development except in the 3-m buffer required

under Oregon Forest Practice rules for hand application. T h e

spot treatments at Ames and Mosby Creeks were of inadequate size to be the equivalent of site preparation and were

applied in spring, which led to rapid resprouting of shrubs

and some damage to seedlings; treated and untreated areas

were almost indistinguishable on those streams. There was

also some suppression of shrubs in unsprayed parts of the

experiments by herbivory, as noted in Mosby, Buttermilk

and Bark Creeks where elk were abundant. 

Large openings created by clearcutting demonstrated

advantages in riparian management areas beyond those

associated with establishment of conifers, and extend

B e rg ’s (1995) analysis beyond that associated with thinnings. The increase in benthic macroinvertebrates is consistent, both qualitatively and quantitatively with earlier

reports from the Pacific Northwest. Murphy and Hall (1981)

noted increased insect abundance in stream riffles within

clearcuts with no residual overhead cover compared to 

r i ffles in streams dominated by old-growth stands; they

observed somewhat decreased abundance in pools. Diversity

was greater in clearcuts in their work, but we did not record

either increases or decreases at the species level. Murphy 

et al. (1981) noted roughly the same increase in aquatic

insects between uncut and clearcut reaches in summer, but

also noted that differences in autumn after leaf-fall were

not significant except for an increase beneath a hardwood

canopy after leaf-fall. Insect numbers in riffles were consistently greater in clearcuts than in streams under canopies.

97
They noted no differences in insect response in riffles of

high- vs. low-gradient streams although there were more

decreases in insect abundance in pools than increases within clearcuts, regardless of gradient. We did not determine

whether there was complete compensation by autochthonous sources for decreases in allochthonous inputs of food

substrates.

Favorable effects of clearcutting in terms of stream productivity and regeneration must be interpreted in the same

context as reported negative consequences. Concern has been

expressed with respect to temperature (Sullivan et al. 1990,

Brown and Krygier 1970) to the extent that the Environmental

Protection Agency recommends a temperature standard of

17.8°C (64° F) maximum for seven-day moving mean of

daily maximum temperatures in streams supporting salmonids. This level is exceeded in many streams under natural conditions of forest cover (Ice et al. 2004), suggesting

that silvicultural activities potentially leading to a warming

trend on such streams are likely to have negative effects on

stream biota. In the event clearcutting were to raise temperature to a harmful level, the practice would not be permitted;

under Oregon, Washington and California laws, clearcutting to the stream is either prohibited or tolerated only in

rehabilitation situations regardless of baseline temperature

patterns. The question remains open as to whether this limits

future net stream productivity by restricting creation of

openings with positive long-term effects.

Our streams did, on occasion, exceed 17.8°C briefly.

We have inadequate data to determine whether downstream

temperature was consistently raised or not raised as the result

of cutting, and data reported by Zwieniecki and Newton

(1999) suggest that increases in uncut areas downstream

were in a range to be expected high in headwaters basins.

In no case did reported temperatures rise enough to threaten

mortality or cause a persistent depression of metabolism of

fish or macroinvertebrates, according to current literature

(Sullivan et al. 2000). Beschta et al. (1987) and Sullivan et

al. (2000) have pointed out that fish can tolerate short-term

exposure to temperatures several degrees higher than optimum without injury. Their reviews pointed out that the

higher temperatures slow feeding rates while metabolism is

elevated in the warmer conditions, and that this results in

slower weight gain. Brett et al. (1969) describe maximum

growth as increasing with temperature up to 15°C so long

as food supplies are adequate. His data also indicate that

growth of sockeye salmon fingerlings is positive (although

not maximum) at temperatures well above 20°C. Data,

largely from laboratory studies, has shown that tolerance to

elevated temperatures is inversely related to duration or

exposure to elevated temperatures (Sullivan et al. 2000).

They reported that salmon can spend lengthy periods above

24°C without mortality or loss of vigor on return to cool

conditions. The temperature effects reported above were

from laboratory studies with temperatures held at constant

levels. McMahon et al. (2001) exposed bull trout and brook

trout to constant versus temperatures fluctuating plus or

minus 3°C with the same mean temperatures. They observed

that fish growth was slightly greater when water temperature was constant than when mean water temperature was

the same but fluctuating, reflecting that less time is spent

within the optimum range. These data indicate that it may

be possible for fish populations to tolerate some exposure

to temperatures above 17.8°C, but the impacts of fluctuating natural streams, repeated occurrences of such peaks

for several days, and duration of exposure under different

levels of food supply are unknown.

Inferences from this study pertaining to water temperature from the reforested reaches were limited in their ability

to determine specifically where warming took place under

variable canopies. Dent (1995) did show that most warming

occurred in complete clearings and that some warming but

more cooling occurred in shaded reaches. Data gathered in

the sun-sided buffered streams were more comprehensive.

None of the sun-sided buffers except Scheele Creek resulted

in a net rise in temperature within the cutting unit despite

the lack of buffer on one side. Scheele Creek showed slight

warming in the lower end of the treated reach, but that peak

was not observed immediately downstream from the cut unit.

The data from Zwieniecki and Newton (1999) from clearcuts

16 to 48 ha in size indicated that average maximum temperatures on 16 streams may or may not rise above baseline

maximum temperatures within harvest units. Their highest

seven-day moving mean maximum temperature 300 m

downstream from the harvest units never exceeded 2°C

more than baseline trends, and based on one year of baseline and one year post-harvest data, there were as many

streams cooler 300 m downstream from units as there were

streams warmer than the baseline trends. These data demons t r a t e d the pitfalls of reliance on single-year observations,

of looking only in clearcuts and immediately upstream areas,

and of failure to adjust for the expected downstream temperature rise before cutting. 

The “sun-sided” buffers accomplished what was predicted for them by Newton’s (1993) report regarding silvicultural prescriptions in riparian zones. The sun-screen on

the south side intercepted most incoming direct radiation,

and also presumably allowed outgoing radiation. Related

work on streams in California (Newton and Zwieniecki

98
1997) has shown that streams flowing with no cover whatever, as in large burns, fluctuate greatly in diurnal temperature. In those streams, warming during the day appeared to

be attenuated by streams becoming very cold at night, presumably reducing the stored heat in sediments and rocks so

as to reduce heating during the day in the direct sun. 

When streams absorb heat, as in a fully exposed clearcut

reach on a hot day, peak temperatures tend to decrease when

they re-enter a covered reach, but in an uneven pattern. The

degree to which cooling may occur downstream from cutting units in the cooler air provided by shade is variable,

depending on the individual stream system. It appears that

over all, stream temperature is determined by a downstream

temperature fluctuation pattern, or “signature” comprised

of combinations of discharge, velocity, points of cool-water

baseflow and confluences, coupled with patterns of gaps in

cover (direct radiation) and air temperature patterns with

decreasing altitude. Ye a r-to-year variation in air temperature could be expected to raise or lower the whole trend.

Radiation level does not appreciably vary from year to year

except through changes in interception of radiation attributable to changes in plant cover. The combination of increased

radiation and elevated air temperature on fresh slash adjacent to the stream would lead to energy loading on the

stream that would increase with regional air temperature.

Of significance is that the “sun-sided” buffers permitted the

streams to stay within their signature patterns with no persistent hot spots, as nearly as we can determine, and are

favorable to both regeneration and benthic insect productivity.

We have not addressed other impacts of clearcutting to

streams. These may include bank damage, loss of existing

trees with their woody debris recruitment potential, and

loss of sources of leaf-fall and other inputs of organic debris

used as food for aquatic invertebrates. We have also not

addressed whether increases in insect abundance affect fish

productivity and whether clearings affect insect abundance

and stream temperature at other times of the year. We close

with the caveat that logging needs to be done with care to

avoid soil and streambank disturbance. It also is likely advantageous to leave strips of shrubs several meters wide along

the banks both for shade and litter, regardless of other

features of buffer design. 

CONCLUSIONS

1. All three principal species of conifer—Douglas-fir,

western hemlock, and western redcedar—displayed potential for good growth in riparian environments. Larg e

seedlings grew better than small seedlings. Seedlings of

ponderosa pine and grand fir were frost-hardy, but we have

no measure of their long-term suitability for these types of

plantings.

2. For satisfactory seedling growth of all species, both

residual hardwoods and overtopping shrubs should be kept

at a low level, however, a screen of shrubs should be retained

along the bank to shade the stream and provide litter inputs.

3. Cover removal to the extent done in these experiments

(Phases I and II) did not appear to cause warming of water

by 300 m downstream of harvest units. In a companion

s t u d y, none of the streams gained or lost more than 2°C

compared to pre-harvest conditions when measured in

uncut units 300 m downstream of cut units, based on the

seven-day moving mean maximum for the seven consecutive warmest days. Clearcutting to the streambank facilitated

regeneration and increased benthic productivity.

ACKNOWLEDGEMENTS

Sites and financial support for this study were provided

by Starker Forests Inc, Corvallis, OR, Cascades Timber

Consultants, Sweet Home, OR, Georgia Pacific Co, Toledo,

OR, and Weyerhaeuser Co, Tacoma, WA. Financial assistance was provided by Oregon Department of Forestry,

Salem, OR. Assistance in collecting and analyzing benthic

insect samples and data was provided by Jennifer Walsh of

Monmouth OR and Kajsa Wing of Corvallis OR. A s s i s t a n c e

in monitoring and analyzing water temperature was provided

by Elizabeth Dent and Ruth Willis.

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and assessment in the Pacific Northwest Cascade

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Hofstra, T.D. 1987. Stream temperature and aquatic

habitat: fisheries and forestry interactions. In: Salo,

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forestry and fishery interactions Contribution 57.

Seattle, WA: University of Washington College of

Forest Resources. Chap. 6.

Brett, J.R.; Shelbourne, J.E.; Shoop, C.T. 1969. Growth 

rate and body composition of fingerling sockeye salmon

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Brown, G.W. 1969. Predicting temperature of small 

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Brown, G.W.; Krygier, J.T. 1970. Effects of clearcutting 

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Caldwell, J.E.; Doughty, K.; Sullivan, K. 1991.

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Chan, S.S.; Minore, D.; Owston, P.W.; Hibbs, D.W.

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Report. Corvallis, OR: COPE Program, Oregon State

University College of Forestry. 7 p.

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riparian areas on summer stream temperatures on

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P.; B i s h a w, B. 2000. Silvicultural practices for 

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Hairston-Strang, A.B.; Adams, P.W. 1997. Oregon’s

streamside rules: achieving public goals on private

lands. Journal of Forestry 95(7): 14-18.

Howard, K.M.; Newton, M. 1984. Overtopping by 

successional coast-range vegetation slows Douglas-fir

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Ice, G.G.; Light, J.; Reiter, M. 2004. Use of natural 

temperature patterns to identify achievable stream 

temperature criteria for forest streams. Western Journal

of Applied Forestry. 19(4): 252-259. 

King, J. 1966. Site index curves for Douglas-fir in the 

Pacific Northwest. Weyerhaeuser Forestry Paper No. 8.

Centralia, WA: Weyerhaeuser Company Forestry

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Littell, R.C.; Milliken, G.A.; Stroup, W.W.; Wolfinger,

R.D. 1996. SAS® system for mixed models. Cary, NC:

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McMahon, T.; Zale, A.; Selong, J. 2001. Growth and 

survival temperature criteria for bull trout. Annual

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Merritt, R.W.; Cummins, K.W., eds. 1984. An introduction to the aquatic insects of North America. 2n d e d i t i o n .

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logging on predators and their habitat in small streams

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Murphy, M.L.; Hawkins, C.P.; Anderson, N.H. 1981. 

Effects of canopy modification and accumulated sediment on stream communities. Transactions of the

American Fisheries Society 110: 469-478.

Murphy, M.L.; Meehan, W.R. 1991. Stream ecosystems. 

Influences of forest and rangeland management on

salmonid fishes and their habitats. American Fisheries

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Newbold, J.D.; Ermen, D.C.; Roby, K.B. 1980. Effects 

of logging on macroinvertebrates in streams with and

without buffer strips. Canadian Journal of Fisheries 

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Newton, M. 1993. Silvicultural alternatives in riparian 

zones: a management proposal, with technical background, for riparian forest management in the Douglasfir region. Report. Oregon Forest Industries Council. 

78 p.

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stock for enhanced growth and domination of brush in

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streamflow regulation by streamside cover. Final

Report, Oregon Department of Forestry. Corvallis, 

OR: Oregon State University, Forest Research

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Sources of large wood in the main stem of a fourthorder watershed in coastal Oregon. Canadian Journal 

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Robison, E.G.; Beschta, R.L. 1990. Identifying trees in 

riparian areas that can provide coarse woody debris to

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Sullivan, K.; Tooley, K.; Doughty, J.E.; Caldwell, J.E.; 

Knudsen, P. 1990. Evaluation of prediction models 

and characterization of stream temperature regimes in

Washington. Timber/Fish/Wildlife Rep. TFW-WQ3-90-

006. Olympia, WA: Washington Department of Natural

Resources. 224 p.

Sullivan, K.; Martin, D.J.; Cardwell, D.J.; Toll, J.E.; 

Duke, S. 2000. [Draft] An analysis of the effects of

temperature on salmonids of the Pacific Northwest,

with implications for selecting temperature criteria.

Portland, OR: Sustainable Ecosystems Institute, 0605

SW Taylors Ferry Road.

Sweeney, B.W. 1984. Factors influencing life-history 

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NY: Praeger: 56-100.

Tait, C.K.; Li, J.L.; Lamberti, G.A.; Pearsons, T.N.; Li, 

H.W. 1994. Relationships between riparian cover and

community structure of high desert streams. Journal of

the North American Benthological Society 13(1): 45-56.

Wagner, R.G.; Radosevich, S.R. 1991. Interspecific 

competition and other factors influencing the performance of Douglas-fir saplings in the Oregon 

Coast Range. Canadian Journal of Forest Research 

21: 829-835.

Walsh, J.B.S. 1996. Effects of streamside riparian forest 

management on Ephemeroptera and Trichoptera

community structure in four western Oregon streams.

Corvallis, OR: Oregon State University, Department 

of Forest Science. MS thesis.189 p.

Warren, C.E. 1971. Biology and water pollution control. 

Philadelphia, PA: W. B. Asunders Co. 434 p.

Wilzbach, M.A.; Cummins, K.W.; Knapp, R.A. 1988. 

Toward a functional classification of stream invertebrate

drift. Verhandlungen der Internationalen Vereinigung für

Theoretische und Angewandte Limnologie 23: 1244-

1254. 

Zwieniecki, M.; Newton, M. 1999. Influence of streamside cover and stream features on temperature trends 

in forested streams of western Oregon. Western 

Journal of Applied Forestry 14(2): 106-113.

101
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1 Victor J. Lieffers is professor and Uldis Silins is associate professor, Department of Renewable Resources, University of Alberta, Edmonton, Alberta,

Canada, T6G 2H1. victor.lieffers@ualberta.ca

2 An extended version of this paper was not submitted for the proceedings.

Productivity of Western Forests: A Forest Products Focus, Chapter Three

SLENDERNESS COEFFICIENT IS LINKED 

TO CROWN SHYNESS AND STEM HYDRAULICS 

IN LODGEPOLE PINE

Victor J. Lieffers1 and Uldis Silins1

SUMMARY2

Slenderness coefficient, i.e., the height/diameter ratio of

a tree, has long been linked to the biomechanical relationships of trees and wind stability (Ruel 1995). Trees with

stout stems will resist deflection in wind much more than

slender stems (fig. 1). This short paper briefly outlines how

the slenderness coefficient of trees may be important to the

development and maintenance of crown size, crown leaf

area (crown shyness) and the hydraulic supply of that leaf

area. Examples are given for lodgepole pine (Pinus cont o rta var. latifolia Engelm.).

Crown shyness is the empty space that develops around

individual crowns of trees in fully stocked, maturing stands

(Putz et al. 1984) (fig. 2). Some researchers believe that the

103

empty space develops as a result of shading of foliage

between crowns (Umeki 1995; Cescatti 1997), but in reality

there is usually less leaf area in older stands (Ryan et al.

1997) than in young stands, where there is little crown shyness. In contrast, there is increasing evidence that the space

between crowns develops as a result of abrasion of the

crown during movement of trees during wind (Long and

Smith 1992; Smith and Long 2001, Rudnicki et al. 2001).

Indeed, the crown of a 15-m tall lodgepole pine tree may

collide with neighboring trees more than 40 times per

minute when wind speed averages 5 m/s (Rudnicki et al.

2002). Similarly, crowns may oscillate more than 6 m in a

wind gust (Rudnicki et al. 2001), and reach velocities of >

7m/s (Rudnicki et al. 2002). Impacts in these conditions

would therefore have sufficient energy to cause serious

damage to twigs, and branches (Grier 1988) especially in

ABSTRACT

This paper outlines several studies on hydraulic limitations, crown size and leaf area development in lodgepole pine (P i n u s

c o n t o rt a v a r. l a t i f o l i a Engelm.). A central theme of this work is that the bole slenderness coefficient (height/diameter ratio) is

linked to productivity by means of two mechanisms. First, trees with slender boles are less stiff and thus are more likely to

move widely in wind. In taller stands, wide movement of trees in windstorm will result in violent collisions with neighboring

trees; this results in crown abrasion and narrow crowns with unoccupied space between crowns, i.e., crown shyness. Stout

trees, in contrast, have only small oscillations in wind and neighboring trees often have overlapping branches. Second, slender

trees develop narrow annual rings with reduce permeability of the wood for transport of water to crowns. Also, the reduced

strength of slender trees will results in increased bending of the bole, which is also likely to reduce the permeability of the

xylem. Bole slenderness, therefore, likely plays a role in stand productivity, the ability of trees to release following thinning,

and in the probability of trees remaining alive after canopy disturbance late in stand development. Managers can manipulate

bole slenderness by stand density management.

KE Y W O R D S: Lodgepole pine, thinning, crown slenderness, height/diameter ratio, xylem permeability.
cold weather where twigs are very brittle (Lieffers et al.

2001). As bole stiffness and the ability of the stem to resist

deflection is strongly related to bole diameter (Silins et al.

2001), stems with low slenderness coefficient are expected

to move less in wind storms than slender stems. As hypothesized, stands with slender stems had much wider movement of crowns than those with stout boles of the same

height (Rudnicki et al. 2002). In a second study, crown

shyness was estimated in small plots in wild stands of

lodgepole pine (Rudnicki et al. 2004). When stems were

less than about 12 m tall, there was little crown shyness in

fully stocked stands; in these short stands crown closure

was apparently driven by relative density. In stands > 12 m

high however, there was increasing crown shyness in plots

with trees of high slenderness coefficient. 

Water relations of trees are also likely to be related to

the slenderness coefficient. First, slender trees have narrow

annual rings. Sapwood of lodgepole pine with rings < 0.5

mm has reduced permeability to water flow compared to

sapwood with wide annual rings (Reid et al. 2004). Reduced

permeability to water flow is expected to become a limiting

factor in transport of water to foliage in crowns, thereby

limiting growth. Secondly, there is increasing evidence that

bending deflection of trees by wind damages the permeability of tree stems (Frederickson et al. 1994, Silins et al.

unpublished). In a study of juvenile lodgepole pine following thinning, stems were either tethered to reduce sway or

had sails added to increase deflection in wind (Liu et al.

2003). Sapwood permeability after thinning was related to

sway treatments; sapwood permeability was ranked control

(unthinned) > tethered (thinned) > untethered (thinned) >

sail added (thinned). 

Since managers can use stand density management to

manipulate the bole slenderness coefficient, we hypothesize

that a thinning regime where stems are kept at slightly lower

relative density than typically develops in self-thinning

stands will produce stems with stiffer boles that are more

resistant to deflection. Stems that flex less will maintain

larger crowns in the second half of the rotation. Stems that

resist bending will also suffer less damage to xylem sapwood during strong wind events and maintain their ability

to deliver water to crowns. Finally lodgepole pine stems

with wider rings (often produced after stand spacing) have

higher sapwood permeability.

ACKNOWLEDGEMENTS

We thank NSERC, Weldwood of Canada, Westfraser

Timber, Weyerhaeuser Company and the Sustainable Forest

Management Network for funding these projects. We thank

Mark Rudnicki, Doug Reid, Mike Liu, Heather Fish and

Simon Landhäusser for their work.

104

Figure1—Deflection from a gust of wind for trees of the same

height with slender and stout boles.

Figure 2—A fully stocked, 16-m tall lodgepole pine stand in the Yukon Territory. The

photograph was taken at 1.7 m above the ground with a 55-m lens.
LITERATURE CITED

Cescatti, A. 1997. Modelling the radiative transfer in

discontinuous canopies of asymmetric crowns. I.

Model structure and algorithms. Ecological Modelling

101: 263-274.

Fredericksen, T.S.; Hedden, R.L.; William, S.A. 1994. 

Effect of stem bending on hydraulic conductivity and

wood strength of loblolly pine. Canadian Journal of

Forest Research 24: 442-446.

Grier, C.C. 1988. Foliage loss due to snow, wind, and 

winter drying damage: its effects on leaf biomass of

some western conifer forests. Canadian Journal of

Forest Research 18: 1097-1102.

Lieffers, S.M.; Lieffers, V.J.; Silins, U.; Bach, L. 2001.

Effects of cold temperature on breakage of lodgepole

pine and white spruce twigs. Canadian Journal of 

Forest Research 31: 1650-1653.

Liu, X.; Silins, U.; Lieffers, V.J.; Man, R.Z. 2003. Wind, 

bending and thinning, affect the hydraulic conductivity

of conifer stems. Canadian Journal of Forest Research

33: 1295-1203.

Long, J.N.; Smith, F.W. 1992. Volume increment in Pinus 

contorta var. latifolia: the influence of stand development and crown dynamics. Forest Ecology and

Management 53: 53-62.

Putz, F.E.; Parker, G.G.; Archibald, R.M. 1984. 

Mechanical abrasion and intercrown spacing. American

Midland Naturalist 112: 24-28.

Reid, D.E.B.; Lieffers, V.J.; Silins, U. 2004. Growth and 

crown efficiency of height repressed lodgepole pine: 

are suppressed trees more efficient? Trees Structure 

and Function 18: 390-398.

Ruel, J.C. 1995. Understanding windthrow: silvicultural 

implications. Forestry Chronicle 71: 434-445.

Ryan, M.G.; Binkley, D.; Fownes, J.H. 1997. Age-related 

decline in forest productivity: patterns and process.

Advances in Ecological Research 27: 213-261.

Rudnicki, M.; Silins, U.; Lieffers, V.J. 2001. Measure of 

simultaneous tree sways and estimation of crown interactions among a group of trees. Trees-Structure and

Function 15: 83-90

Rudnicki, M.; Silins, U.; Lieffers, V.J. 2002. Stand 

structure governs the crown collisions of lodgepole

pine. Canadian Journal of Forest Research 33: 1238-

1244.

Rudnicki, M.; Silins, U.; Lieffers, V.J. 2004. Relative 

density, tree slenderness and tree height determine the

crown cover of lodgepole pine. Forest Science 50: 

356-363. 

Smith, F.W.; Long, J.N. 2001. Age-related decline in 

forest growth: an emergent property. Forest Ecology

and Management 144: 175-181.

Umeki, K. 1995. Modeling the relationship between the 

asymmetry in crown display and local environment.

Ecological Modelling 82: 11-20

105
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WOOD PRODUCTS

AND EMERGING

TECHNOLOGIES
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1 Hans-Erik Andersen is a research scientist, Precision Forestry Cooperative, University of Washington, College of Forest Resources, Seattle, WA 98195.

2 Robert J. McGaughey and Stephen E. Reutebuch are research foresters, USDA Forest Service, Pacific Northwest Research Station, Seattle, WA 98195.

3 LIDAR systems are typically classified into two types, depending upon the size of the “footprint” for the laser pulse. “Small footprint” systems have 

ground spot sizes from 0.1 to 1 m, whereas “large-footprint” systems have spot sizes from 5 to 100 m. Given that large footprint, continuous waveform

LIDAR systems are neither commercially available nor capable of providing high-resolution data, in this paper we restrict our discussion to the use of

small-footprint, discrete-return LIDAR data. The application of large-footprint LIDAR to forestry applications has been discussed in Harding et al. (2001)

and Lefsky et al. (2002).

Productivity of Western Forests: A Forest Products Focus

FOREST MEASUREMENT AND MONITORING 

USING HIGH-RESOLUTION AIRBORNE LIDAR

Hans-Erik Andersen,1 Robert J. McGaughey,

2 and Stephen E. Reutebuch2

I N T R O D U C T I O N

The development of high-resolution, active remote

sensing measurement systems has the potential to support

the development and application of highly site-specific to

forest management. One of the more promising forest

remote sensing tools to emerge in recent years is smallfootprint airborne laser scanning, or light detection and

ranging (LIDAR). LIDAR is an optical remote sensing

technology capable of providing direct three-dimensional

(3-D) measurements of forest canopy structure. The components of an airborne LIDAR system include a laser scanner, which emits from 7,000 to 100,000 laser pulses each

second, coupled with a precise airborne positioning system,

ABSTRACT

Airborne laser scanning has emerged as a highly-accurate, high-resolution forest survey tool, providing the opportunity

to develop and implement forest inventory and monitoring programs using a level of detail not previously possible. In this

paper, we will present results from several research studies carried out at a study area within Capitol State Forest in the state

of Washington, where we investigated the utility of LIDAR for measurement of terrain and forest structure characteristics.

Previous studies at this site have shown that LIDAR can be used to accurately measure terrain elevation even under dense

forest canopy. The results of another study have indicated that LIDAR can also be used to accurately estimate a number of

forest inventory variables, including basal area, stem volume, dominant height, and biomass. The laser-reflection intensity

information provided by LIDAR can also be used for species classification. Individual tree crowns can be recognized by

using computer vision algorithms applied to a detailed LIDAR-based canopy surface model. This approach can be used to

extract measurements of individual trees, including top height and crown base height. Preliminary results have shown that if

high-density LIDAR data are collected in different years, measurements of individual-tree height growth can be obtained

for an entire forest area, allowing for detailed, spatially explicit analyses of site quality and productivity.

KEYWORDS: Forest measurement, remote sensing, LIDAR, terrain mapping, canopy mapping.

109

which uses differentially corrected GPS (global positioning system) and an inertial measurement unit to accurately

determine the position and orientation of the scanner at

the moment each pulse is emitted3. Because the speed of

light is a known constant, the distance corresponding to

each laser reflection from the ground can be calculated

from the time delay between the emission and reception of

the laser pulse. This distance is used along with the position and orientation information to calculate the 3-D coordinates of each reflection. Most airborne LIDAR systems

designed for topographic mapping applications use lasers

with wavelengths in the near-infrared region of the electromagnetic spectrum. These sensors typically use a system of

oscillating or rotating mirrors to generate a scan pattern of

measurements in a swath beneath the aircraft (fig. 1). LIDAR
systems typically collect data at a density between 0.5 and

4 pulses per square meter and with a pulse diameter between

0.4 and 0.7 m, depending upon the specific system and

flight parameters for the project. Many LIDAR systems

also have the capability to detece several reflections from a

single pulse. In a forested area, LIDAR pulses reflect from

the canopy foliage, branches, understory vegetation, and

the terrain surface. The LIDAR point cloud therefore represents a detailed 3-D measurement of the spatial organization of canopy materials (foliage, branches, stems, shrubs,

etc.) down to the ground surface for the scanned area.

Quantitative metrics describing the spatial distribution of

these LIDAR returns will therefore be related to a wide

variety of critical forest structure metrics, including dominant height, basal area, stem volume, and biomass. A h i g h l y

detailed model of the canopy surface can be generated by

using the LIDAR returns from the surface of the canopy.

The application of computer vision (object recognition)

algorithms then allows individual tree crowns composing

the canopy to be isolated and measured. Furthermore, if

LIDAR data are acquired over the same area of forest in

different years, detailed measurements of forest change

(mortality and forest growth) can be obtained. In this paper,

we present the results of a study investigating the use of

LIDAR for forest measurement and monitoring in a conifer

forest within western Washington state.

STUDY AREA

The study area for this project was a 5.2 km2 area within Capitol State Forest in western Washington (fig. 2). This

forest is composed primarily of coniferous timber species,

including Douglas-fir (Pseudotsuga menziesii), western

hemlock (Tsuga heterophylla), and western redcedar (Thuja

110

Figure 1—Components of an airborne laser scanning (LIDAR) system. 
plicata), along with various hardwood species, including

red alder (Alnus rubra) and big-leaf maple (Acer macrophyll u m). This area is the site of an on-going silvicultural

trial investigating the effects of several different harvest

treatments designed to create a variety of residual stand 

densities (clearcut unit: 0 trees per hectare (TPH); heavilythinned unit4: 40 TPH; lightly-thinned unit: 175 TPH; and

control unit: 280 TPH). 

A total of 99 inventory plots were established within this

study area, extending over a range of stand types including

young stands (about 35 years) and mature stands (about 70

years) with variable stand densities. Plot sizes ranged from

0.02 to 0.2 ha. A variety of measurements were obtained at

each plot, including species and diameter at breast height

for all trees greater than 14.2 cm in diameter. Additional

measurements of total height and height-to-live-crown were

acquired for a representative selection of trees over the range

of diameters by using a handheld laser rangefinder. A d e t a i l e d

description of the plot measurement protocol can be found

in a previous report (chapter 3, Curtis et al. 2004). 

LIDAR DATA

High-density LIDAR data were acquired over the study

area in the spring of 1999 and the summer of 2003, a period that represented five growing seasons. The 1999 LIDAR

data were acquired with a SAAB5 TopEye system operated

from a helicopter platform in the spring of 1999 (leaf-off

conditions). The 2003 LIDAR data were acquired with a

Terrapoint A LTMS system operating from a fixed-wing

platform in September 2003 (leaf-on conditions). Both data

sets were acquired with a nominal density of 4 returns (or

reflections) per square meter. The vendor provided raw

LIDAR data consisting of XYZ coordinates and returnintensity information for all LIDAR returns in an A S C I I

text format. In addition, the vendor provided “filtered

ground” data representing ground returns isolated via a

proprietary filtering algorithm. The filtered ground returns

from the 1999 data set were used to generate a 1.52-meter

(5 ft) digital terrain model (DTM) over the entire study

area, using the Surfer software system (Golden Software,

Inc. 1999) with the inverse distance interpolation algorithm

and a 4-sector search with a radius of 60 m (fig. 3). The

same gridding algorithm was used to generate a 1-m DTM

from the filtered ground 2003 LIDAR data (fig. 4). 

LIDAR-BASED TERRAIN MEASUREMENT

In a previous study, the accuracy of the 1999 LIDARbased DTM was assessed via comparison to 347 high-accuracy topographic checkpoints collected using survey-grade

equipment (Reutebuch et al. 2003). This study showed that

the LIDAR-derived DTM had a mean error of +0.22 m

with a standard deviation of 0.24 m. This study showed

that the accuracy of the DTM is slightly reduced by the

presence of heavy canopy or near-ground vegetation. A

similar accuracy assessment of the 2003 LIDAR-based

terrain model showed that the DTM had a mean error of

+0.31 m with a standard deviation of 0.34 m. The diff e rence between the 1999 and 2003 DTM errors is statistically

significant (at α = 0.05), and may be attributed to the fact

111

Figure 2—Capitol Forest study site. Image courtesy of Washington State Department of Natural Resources.

4 The heavily-thinned unit is called the 2-aged stand in Curtis et al. 2004.

5 The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture 

of any product of service. 
that the 2003 LIDAR was acquired in leaf-on conditions

whereas the 1999 LIDAR was acquired in leaf-off conditions. In leaf-on conditions, it can be expected that fewer

LIDAR pulses will penetrate through deciduous t r e e

crowns. In addition, there was significant growth of the

n e a r-ground vegetation in the treated areas between 1 9 9 9

and 2003 that could also have an effect on DTM accuracy. However, the difference between the mean error of the

l e a f - o ff 1999 DTM and the leaf-on 2003 DTM is remarkably small, indicating that LIDAR is capable of measuring terrain under this predominantly coniferous forest

canopy at a very high accuracy in both leaf-on and leaf-off

conditions. 

LIDAR-BASED FOREST MEASUREMENT

Canopy Surface Measurement

LIDAR canopy surface measurements were extracted

by filtering out the highest return within each 1-m grid cell

area. These filtered “canopy-level” returns were then gridded into a canopy surface model again using an inverse

distance interpolation algorithm and a 3-sector search with

a radius of 3 m. The 1999 LIDAR canopy surface model is

shown in figure 5, and the 2003 LIDAR canopy model is

shown in figure 6. In a comparison to profiles and spot

height measurements acquired from large-scale aerial photographs, the difference between photogrammetric canopy

height and 1999 LIDAR canopy height measurements

112

Figure 3—1999 LIDAR digital terrain mode (UTM coordinate system).

Figure 4—2003 LIDAR digital terrain model.
(after accounting for tree growth) was found to be within

approximately 1 m (Andersen et al. 2003). The detailed

LIDAR-derived canopy surface model provides a rich

description of overstory canopy structure, including information on canopy cover, gap distribution, and individual

tree dimensions (Andersen, 2003).

Species Recognition

Several previous studies have shown that the intensity

information provided for each LIDAR reflection can be

used to classify by species type (Andersen et al., in prep.,

B r a n d t b e rg et al. 2003, Holmgren and Persson, 2004).

B r a n d t b e rg and others used summary statistics of the height

distribution and intensity values within individual tree crown

segments to classify tree species within an eastern deciduous forest in West Vi rginia (Brandtberg et al. 2003). In

another study carried out in Sweden, LIDAR-derived metrics describing structural and reflectance characteristics of

individual tree crowns were used to discriminate between

spruce and pine trees (Holmgren and Persson 2004). In

leaf-off conditions, the near-infrared reflectance from hardwood tree crowns (and dead trees) is significantly lower

than that from coniferous crowns (fig. 7). Preliminary results

indicate that leaf-off LIDAR can be used to accurately class i f y tree crowns into hardwood-softwood classes (Andersen

et al., in prep.). This capability may be particularly important in determining species composition for riparian zone

management. 

113

Figure 5 –1999 LIDAR canopy surface model.

Figure 6—2003 LIDAR canopy surface model.
Plot-Level Measurement

The vertical distribution of LIDAR data within a given

area provides a detailed description of forest structure (fig.

8). Regression techniques can be used to model the relationship between a set of metrics describing the vertical

distribution of LIDAR canopy returns within a plot area

(e.g., 0.1 ha) and stand structure variables derived from a

plot tree list. Given the allometric relationships between

canopy dimensions and biomass, governed by the laws of

proportional growth, there is a strong physical basis for the

quantitative relationship between the distribution of LIDAR

measurements, which are essentially characterizing the

density of canopy foliage, and stand variables such as biomass, stem volume, and basal area (West et al. 1997). The

metrics used to characterize the vertical distribution of

LIDAR measurements within a plot include various height

quantiles (e.g., 10th, 20th, ..., 90th percentile heights), as

well as other metrics such as mean height, maximum height,

coefficient of variation of height, and a LIDAR-derived

measure of canopy cover (calculated as the percentage of

LIDAR first returns that reflect from the canopy level [i.e.,

more than 2 m above the ground]). Once these regression

models are developed to establish the quantitative relationship between the LIDAR metrics and the inventory parameters, these predictive models can be used to generate maps

of various stand parameters over the entire extent of the

LIDAR coverage. With this approach, however, it is important to collect plot-level inventory data over the full range

of stand conditions present in the mapped area. If stand cond i t i o n s exist that fall outside of the plot types used to generate the predictive models, the estimates are in effect

extrapolations outside the range of data and will be unreliable. Because this approach relies only on the vertical distribution of LIDAR returns and is not dependent on accurate

measurement of individual tree crowns, it is particularly

u s eful when the LIDAR data density is relatively low

(<1 r e t u r n / m2). This approach uses LIDAR data acquired

throughout the full depth of the forest canopy, including

the understory layer, and therefore provides a more comprehensive estimate of stand parameters than the individual-tree approach described in the next section, which is

114

Figure 7—Species classification using LIDAR intensity data a) leaf-on orthophoto, b) leaf-off hardwoods and dead trees (brown),

conifers (green).

Figure 8—Distribution of LIDAR returns within a 0.8 ha (0.2 ac) plot

area, Capitol Forest study area)
limited to the overstory layer. This plot-level approach to

LIDAR-based forest inventory has been applied across a

variety of forest types by researchers in North America and

Europe (Means et al. 2000, Naesset 2002, Naesset and

Okland 2002). In a study done at the Capitol Forest study

area, strong regression relationships were found between

LIDAR-derived predictor variables and field-measure

inventory variables, including basal area (R2 = 0.91), stem

volume (R2 = 0.92), dominant height (R2 = 0.96), and biomass (R2 = 0.91) (fig. 9). This plot-level approach has also

been used to estimate canopy fuel variables, including

canopy height, canopy bulk density, and canopy base

height at the Capitol Forest study site (Andersen et al. 2005).

Individual Tree-Level Measurement

If LIDAR data are acquired at a high enough density,

details at the scale of individual tree crowns can be resolved

in the LIDAR-derived canopy surface model (fig. 5). A

previous study showed that individual tree attributes, including tree height and crown base height, could be accurately

115

Figure 9—Results of plot-level LIDAR-based estimation of forest inventory parameters at Capitol Forest study site. Scatterplots represent relationship

between predicted (x) and field-based (y) estimates at the individual plots for a) dominant height, b) basal area, c) stem volume, and d) biomass. Lines 

represent 1:1 relationship.
measured by using a software system (FUSION) that provides for interactive visualization and direct measurement

of the raw LIDAR point cloud (McGaughey et al. 2004). 

In fact, results from this study indicate that in open stands,

individual tree dimensions (especially crown width and

crown height) can be measured more accurately with LIDAR

than with traditional field methods (by using Criterion laser

instruments, etc.). LIDAR-based individual tree measurement can be automated through the application of computer

vision algorithms. One of the more effective computer vision

algorithms for automated individual tree crown recogn i t i o n

is the morphological watershed algorithm (Soille 1 9 9 9 ) .

Conceptually, this algorithm finds the boundaries of b a s i n s ,

or watersheds, within a surface model. If the LIDAR- based

canopy surface model is inverted, each tree crown is essentially a small basin, and after application of the watershed

algorithm, the boundary of each individual tree crown is

delineated. The output of this algorithm is a segmented

canopy-height model, where each segment represents the

area associated with individual tree crowns (fig. 10). A

limitation of this LIDAR individual-tree level measurement approach is that only trees in the overstory can be

accurately segmented and measured. However, in practice

this is not a serious limitation because overstory trees are

typically of most interest in the context of commercial forest

i n v e n t o r y. Several previous studies have shown that this

morphological computer-vision approach can be effective

in identifying tree crown structures and measuring individual tree crown dimensions (Andersen et al. 2001, Persson

et al. 2002, Schardt et al. 2002). Once the canopy height

model has been segmented into individual tree crowns, the

raw LIDAR data within each crown segment can be extracted

to acquire high-resolution measurements of individual tree

crown attributes, including tree height and crown base

height (fig. 11). If height-to- diameter or crown-diameter- t o -

stem-diameter regression models are available for the area,

these LIDAR-derived crown measurements can be used to

estimate other tree attributes, including diameter and stem

volume. In addition, because the near-infrared reflectance

from hardwood crowns is significantly lower than conifers

in leaf-off LIDAR data, the mean (or median) intensity of

the LIDAR returns within each crown segment can be used

to classify the tree segment into a species type (i.e., hardwood or softwood) (fig. 12). 

LIDAR-BASED FOREST MONITORING

Measurement of Individual Tree Growth

When high-density LIDAR data are acquired over the

same forest area in different years, the difference in the

individual tree height measurements acquired from these

multi-temporal LIDAR data sets represents an estimate of

the tree height growth over the intervening period. T h i s

approach allows for accurate measurement of overstory tree

116

Figure 10—a) Orthophoto of selected area, and b) individual tree-level segmentation of LIDAR canopy height model via morphological watershed 

algorithm (color-coded by height; black lines indicate boundaries of segments).
117

Figure 11—Use of LIDAR to measure individual tree crown dimensions: a)

raw LIDAR measurements extracted from tree crown segment, and b) vertical distribution of LIDAR returns for this crown, with estimate of tree height

and crown base height shown.

Figure 12—Use of LIDAR intensity to classify species: a) orthophoto of selected area with mixed hardwoods (bigleaf maple), and conifers, and (b) individual tree crown segments classified by species: conifer (green) and hardwoods (brown).

A B
height growth over an extensive forest area. In a study conducted at the Capitol Forest study area, high-density LIDAR

data acquired in 1999 and 2003 were used to extract individual tree height growth measurements. Preliminary results

of this analysis showed that small differences in growth

between thinning treatments can be detected even over this

relatively short period (five growing seasons). As expected,

height growth was less pronounced in the heavily-thinned

unit (approximately 0 to 2 m), where the primary response

to the treatment was increased crown expansion, than in the

control unit, where the height growth was in the range of 1

to 3 m (fig. 13). Not surprisingly, the height growth within

a younger (35-yr-old) stand was much higher (3 to 5 m)

than in the mature stands. The capability of LIDAR to

accurately measure the growth rates of individual trees across

an entire forest provides an opportunity for much more

detailed, and spatially explicit, analyses of site quality and

availability, and intertree competition.

CONCLUSIONS

The application of airborne laser scanning to forest survey has the potential to revolutionize our approach to forest

118

Figure 13—LIDAR-based measurement of individual tree growth, 1999-2003: a) Selected area within

Capitol Forest study area shown in LIDAR canopy

height model, and b) LIDAR-derived individual tree

height growth measurement. A significant difference

in height growth between stands is evident [control

(70-yr.-old, unthinned stand) ~ 1- to 3-m growth;

young (35-yr-old) stand ~ 3 to 5 m; heavily-thinned

(70-yr-old stand)~ 0 to 2 m]. Segments colored

white indicate hardwoods that were excluded from

the analysis. 
119

inventory and monitoring. LIDAR can provide very accurate measurements of terrain even under dense forest canopy

(in both leaf-on and leaf-off conditions), and will support

the implementation of more detailed hydrological models

and site-specific forest operations. LIDAR also provides

highly accurate, high-resolution measurements of forest

canopy structure that can be used to estimate important

inventory parameters at the plot level (dominant height, basal

area, stem volume, biomass) and individual-tree level (height,

crown area, crown base height). In addition, the intensity

information provided by LIDAR can be used to classify

forest species type, an important capability where information regarding forest composition, particularly hardwoodsoftwood mix, is required. It was also shown that the use

of LIDAR data acquired in different years allows for forest-wide analysis of growth at the scale of the individual

tree, which can potentially support highly detailed investigations of spatially variable site characteristics and growth

potential. Through the analysis of LIDAR data collected

before areas are cleared for plot establishment, differences

in local site index across plots in the same block could be

identified and accounted for in long-term plantation growthand-yield studies, thus removing a potentially confounding

effect that has been impossible to identify in most forest

experiments. 

ACKNOWLEDGMENTS

The authors thank the Precision Forestry Cooperative at

the University of Washington, the USDA Pacific Northwest

Research Station, the Washington State Department of

Natural Resources, and the Joint Fire Science Program for

their support in carrying out this project. 

LITERATURE CITED

Andersen, H.-E.; Reutebuch, S.E.; Schreuder, G.F.

2001. Automated individual tree measurement through

morphological analysis of a LIDAR-based canopy 

surface model. Proceedings of the First International

Precision Forestry Symposium, Seattle, WA. 

Andersen, H.-E. 2003. Estimation of critical forest structure metrics through the spatial analysis of airborne

laser scanner data., Seattle, WA: University of

Washington. Ph.D. dissertation.

Andersen, H.-E.; McGaughey, R.J.; Carson, W.W.; 

Reutebuch, S.E.; Mercer, B.; Allan, J. 2003. A comparison of forest canopy models derived from LIDAR

and InSAR data in a Pacific Northwest conifer forest.

International Archives of Photogrammetry and Remote

Sensing. Dresden, Germany: Vol. XXXIV, Part 3/W13.

Andersen, H.-E.; McGaughey, R.J.; Reutebuch, S.E. 

2005. Estimating forest canopy fuel parameters using

LIDAR data. Remote Sensing of Environment 94: 

441-229.

Andersen, H.-E.; Reutebuch, S.E.; McGaughey, R.J. 

[In preparation]. The use of high-resolution, active 

airborne remote sensing technologies to support digital

forestry. One file with: Hans-Erik Andersen, Precision

Forestry Cooperative, University of Washington,

College of Forest Resources, Seattle, WA 98195.

Brandtberg, T.; Wa r n e r, T.; Landenberger, R.; McGraw,

J. 2003. Detection and analysis of individual leaf-off

tree crowns in small footprint, high sampling density

LIDAR data from the eastern deciduous forest in North

America. Remote Sensing of Environment 85: 290-303. 

Curtis, R.O.; Marshall, D.D.; DeBell, D.S., eds. 2004. 

Silvicultural options for young-growth Douglas-fir

forests: the Capitol Forest study—establishment and

first results. Gen. Tech. Rep. PNW-GTR-598. Portland,

OR: U.S. Department of Agriculture, Forest Service,

Pacific Northwest Research Station. 110 p.

Golden Software, Inc. 1999, Surfer user’s guide. 

Version 7. Golden CO: Golden Software, Inc. 

Harding, D.J.; Lefsky, M.A.; Parker, G.G.; Blair, J.B. 

2001. Laser altimetry canopy height profiles: methods

and validation for closed-canopy, broadleaf forests.

Remote Sensing of Environment 76: 283-297. 

Holmgren, J.; Persson, A. 2004. Identifying species of 

individual trees using airborne laser scanner. Remote

Sensing of Environment 90: 415- 423.

Lefsky, M.A.; Cohen, W.B.; Parker, G.G.; Harding, D.J. 

2002. LIDAR remote sensing for ecosystem studies.

Bioscience 52(1): 19-30.

McGaughey, R.J.; Carson, W.W.; Reutebuch, S.E.; 

Andersen, H.-E. 2004. Direct measurement of individual tree characteristics from LIDAR data. Proceedings

of the annual ASPRS conference. Bethesda, MD:

American Society of Photogrammetry and Remote

Sensing.

Means, J.; A c k e r, S.; Fitt, B.; Renslow, M.; Emerson, L.;

Hendrix, C. 2000. Predicting forest stand characteristics with airborne scanning LIDAR. Photogrammetric

Engineering and Remote Sensing 66(1): 1367-1371. 
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Naesset, E. 2002. Predicting forest stand characteristics 

with airborne laser using a practical two-stage procedure and field data. Remote Sensing of Environment

80: 88-99.

Naesset, E.; Okland, T. 2002. Estimating tree height and 

tree crown properties using airborne scanning laser in a

boreal nature reserve. Remote Sensing of Environment

79: 105-115. 

Persson, A.; Holmgren, J.; Soderman, U. 2002. 

Detecting and measuring individual trees using an airborne laser scanner. Photogrammetric Engineering and

Remote Sensing 68(9): 925-932. 

Reutebuch, S.E.; McGaughey, R.J.; Andersen, H.-E.; 

Carson, W.W. 2003. Accuracy of a high-resolution

LIDAR terrain model under a conifer forest canopy.

Canadian Journal of Remote Sensing 29(5): 527-535.

Schardt, M.; Ziegler, M.; Wimmer, A.; Wack, R.; 

Hyyppa, J. 2002. Assessment of forest parameters by

means of laser scanning. Graz, Austria: International

Archives of Photogrammetry and Remote Sensing. 

Vol. XXXIV, part 3A: 302-309.

Soille, P. 1999. Morphological image analysis. New York, 

NY: Springer-Verlag. 

West, G.B.; Brown, J.H.; Enquist, B.J. 1997. A general 

model for the origin of allometric scaling laws in 

biology. Science 476: 122-126. 
1 Peter Carter is manager of resource technology and commercialization, Carter, Holt, Harvey Fibre-Gen, Auckland, New Zealand.

2 David Briggs is professor and director, Stand Management & Precision Forestry Cooperatives, College of Forest Resources, University of Washington, 

Seattle, WA.

3 Robert J. Ross is project leader, Condition Assessment and Rehabilitation of Structures, USDA Forest Service Forest Products Laboratory, Madison, WI.

4 Xiping Wang is research associate, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, MN and USDA Forest Products 

Laboratory, Madison WI.

Productivity of Western Forests: A Forest Products Focus

ACOUSTIC TESTING TO ENHANCE WESTERN FOREST

VALUES AND MEET CUSTOMER WOOD QUALITY NEEDS

Peter Carter1, David Briggs2, Robert J. Ross3, Xiping Wang4

INTRODUCTION

While a large body of research has focused on understanding and improving the productivity of western forests,

improving value in these forests must also consider wood

quality. As harvest age decreases and use of intensive silviculture increases, quality of stands, logs, and products is

becoming more variable. However, application of intensive

silviculture throughout the life-cycle of a stand also presents an opportunity to measure, manage and control quality

as well as tree size and volume. 

Product markets readily segregate into applications

where aesthetic appearance features, such as grain, color

and knottiness, predominate in defining quality and applications where mechanical properties, such as stiffness and

strength used by architects and engineers in designing structures, predominate in defining quality. In the US, about 52%

121

of the solid-sawn lumber consumed is used in new residential and nonresidential construction and another 30% is

used for repair and remodel of existing structures (Eastin

2005). Much of the veneer production is also used in products where stiffness and strength are critical quality characteristics. The dependence of western forests on markets for

softwood structural products is illustrated by the state of

Washington where 92% of the harvest is softwoods, of

which 71% is sawlogs for lumber and 17% is peeler logs

for veneer (Smith et al. 2001).

Tr a d i t i o n a l l y, quality of softwood trees, logs and products

has been assessed by human visual observation of surface

characteristics, such as knots, splits, and rings per inch, and

assignment to one of several possible grades based on simple, broad allowable ranges for the characteristics. A l t h o u g h

these grades may be sufficient where appearance is the primary consideration, the adequacy of visual grades for applic a t i o n s involving stiffness and strength is questionable since

ABSTRACT

Nondestructive testing (NDT) of wood products, such as lumber and veneer, for stiffness and strength evaluation has

been proven and commercialized for many years. The NDT concept has been extended and commercialized in the Director

HM-200TM tool for testing logs in advance of processing so manufacturers can make more informed log purchases and better

match logs to customer needs for product stiffness and strength. Further extension of the NDT concept to standing timber is 

a logical progression and a new commercial tool, the Director ST-300TM, has just been developed for this application. This

paper describes operating principles of both tools and presents examples of their use with various species. The potential

effects of wood density, moisture content, temperature, and age on results from these tools are also discussed.

KEYWORDS: Nondestructive testing, tree quality, log quality, modulus of elasticity, stiffness.
no measure of these properties is actually obtained. Indeed,

a concern over reliability and the broad, conservative design

values associated with visual grades for structural applications led to the development of machine-stress-rating (MSR)

technology for lumber that has been in commercial use

since the 1960s. MSR technology non-destructively measures the stiffness of lumber and uses a pre-established relationship between stiffness and bending strength to define a

set of strength-based grades. This provides a more refined

and flexible approach than visual grading for identifying

and sorting lumber into stress grades used in products such

as glulam (glued laminated timber) beams and engineered

trusses. With the development and rapid growth of new

engineered wood products such as laminated veneer lumber

( LVL), I-beams and I-joists, there has been a parallel growth

in non-destructive testing (NDT) for the stiffness and strength

of lumber and veneer used as components of these products.

In addition, concerns with design values of structural lumber graded with visual methods is creating momentum for

verification testing of visually graded structural materials. 

These trends have renewed interest of mills in nondestructive methods. Mills seeking to capture a price premium (Spelter 1996) by producing non-destructively tested

lumber and veneer, find that it is very expensive to process

logs or purchase timber stands that have low yield of product with the stiffness and strength levels desired by their

customers. Consequently, researchers have developed technology for applying NDT to measure stiffness of logs to

improve sorting and matching with desired levels of lumber

or veneer stiffness (Wang et al. 2002, 2004a). This research

has led to development and introduction of the Director

HM-200TM, a log-stiffness testing tool described later in

this paper. A logical and desirable extension is to apply the

N D T technique to measure stiffness of wood in standing

trees (Wang et al. 2001, 2003), thereby providing timber

sellers and purchasers with a means for improved harvest

scheduling and timber marketing based on the potential

yield of stress-graded products that can be obtained from

trees within a stand. A new tool, the Director ST- 3 0 0 TM ,

has been developed for evaluating wood stiffness in standing trees and is also described in this paper.

BASICS OF NDT ASSESSMENT

OF STIFFNESS

Stiffness of a piece of lumber, or a log, can be measured

by placing it in a suitable static bending test apparatus,

recording the deflection as load is applied, and calculating

the modulus of elasticity (MOE or E), which is a measure

of stiffness or resistance to deflection. Although this “static

bending” MOE can be measured without testing the piece

to failure, it is slow and involves expensive equipment that

is not very portable. Consequently researchers have been

exploring the use of the “dynamic” MOE, which is well

correlated with the static MOE. Dynamic MOE is obtained

by measuring the velocity of an acoustic wave through the

material and is expressed by the following formula

Ed = ρ V2 (1)

where

Ed dynamic modulus of elasticity (in lb/in2 or Pa)

ρ density of the material (in lb/ft3 or kg/m3)

g acceleration due to gravity (in 386 in/s2 or 9.8 m/ s2)

V velocity of the wave through the material (in ft/s or

m/s)

Recognizing that g is a constant and applying any conversions between units, the constant k can be introduced

and the equation becomes

Ed = kρ V2 (2)

In practice, the density of many materials is relatively

constant; hence the velocity of the acoustic wave can be

used as a direct indicator of the dynamic MOE, a measure

of the material’s stiffness.

ASSESSING STIFFNESS OF LOGS 

WITH THE DIRECTOR HM-200TM

Operating the Director HM-200TM

Figures 1 and 2 show use of the Director HM-200TM 

for evaluating logs. The user first enters the log length or

selects the length from a pre-loaded list and then presses

the Director HM-200TM against the log. A sensor head signals that it has contact and the user strikes the end of the

log with a hammer. The sensor picks up the acoustic wave

signal as it passes back and forth along the length of the

log at a rate of a few hundred passes per second. Software

in the Director HM-200TM processes the signal and displays

the velocity in either feet or meters per second, depending

on whether the unit has been set for metric or imperial units.

The same velocity will be displayed regardless of which end

of the log is chosen or where on the end the sensor head is

placed and the hammer blow is struck. This is because the

Director HM-200TM software obtains the weighted average

velocity for the log from its analysis of the whole wave

signals received. The user can program the Director HM200TM to recognize up to 3 grade categories based on the

displayed velocity. These are signaled to the operator by a

color code in the display and by a unique sound signal. The

operator can then suitably color spray or otherwise mark

the log for subsequent sorting. 

122

g
Velocity, Stiffness of Product Within Log, and

Economic Benefit

Figure 3 illustrates the correlation between the acoustic

velocity (km/s) of green radiata pine (lower curve) and

southern pine (upper curve) logs and static bending MOE

of the dry boards sawn from the logs. Each data point

represents a log batch. A high correlation (R2=0.98) was

observed for both species. Figure 4 illustrates the relationship between acoustic velocity for log batches (10 percentile groups from log sample) for southern pine and the

average ultrasound propagation time (UPT) of veneer from

the logs. Ultrasound propagation time is the elapsed time

for ultrasound to travel between fixed roller wheel points

on a MetriguardTM veneer tester. Although a linear regression seems adequate to represent the relationship, a power

regression model (model in the form of y = axb) was found

to best fit the trend, with a coefficient of determination (R2)

value of 0.99.

Figure 5 shows the increasing yield of structural grades

of lumber with increasing acoustic velocity of logs processed,

as measured with the Director HM-200TM at two New

Zealand radiata pine sawmills. Assuming a price diff e r e ntial of NZ$200/m3 on lumber, an increase of 0.1 km/s in

logs sorted with the HM 200 produces a gain in structural

lumber yield of about 5%. This translates into a gain of

123

Figure 1—The Director HM-200TM in use in a log yard. Figure 2—Operating principle of the Director HM-200TM.

Figure 3—MOE (kPa) of dry lumber from a log verses Director HM200TM velocity of the log (km/sec) for Southern pine (upper line, R2 =

0.9779) and radiata pine (lower line, R2 = 0.9792).

Figure 4—Ultrasound propagation time (UPT) of veneer from a log vs

Director HM-200TM velocity of the log (km/sec) 10 percentile log batches

from a Southern pine trial.
about NZ$6/m3 on log volume or about NZ$1.8 million for

a mill processing 300,000 m3 of logs per year. A s i m i l a r

analysis for veneer for LVL production in the US resulted

in a gain of about US$16/m3 on log volume (about $80-

$100/MBF Scribner log scale).

Variation With Log Position and Age

As trees grow in height, they produce new cambium

along the shoot. This young cambium forms growth rings

with low wood density and a large microfibril angle which

together result in wood of low stiffness and strength. As the

cambium ages, it eventually produces denser, lower microf i b r i l angle wood which then is stiffer and stronger. Thus a

tree typically has a core of “juvenile” wood, depending on

species from about 7 to 20 or more rings wide, that becomes

surrounded by later rings of “mature” wood. More rings,

hence more mature wood, occur in the butt log of a tree

whereas the top log has fewer rings and has not yet undergone the transition to mature wood formation. T h e r e f o r e ,

one can expect that stiffness and acoustic velocity would

decrease as the percentage of juvenile wood increases from

the butt log to top log position in a tree. With the exception

of the butt log, this pattern is borne out as shown in figure

6 for Douglas-fir and ponderosa pine logs (Wang et al.

2004b). It appears that the butt log does not follow the

expected pattern. Researchers have found that the lower bole

has mature wood with lower density and higher microfibril

angles leading to lower stiffness (Megraw et al. 1999).

Since logs in the upper stem of a tree have both fewer

rings and a higher percentage of low stiffness juvenile wood,

one would expect low acoustic velocity in these low age

logs. This is also borne out and leads to a generally rising

trend of average acoustic velocity of logs from a stand as

stand age increases (figure 7). Figure 8 shows 21 radiata

pine stands in order of increasing average log acoustic velocity as measured by the Director HM-200TM. The mean as

well as 2 standard deviations is displayed for each stand

(log source). This demonstrates that there is much greater

variability within, rather than between, stands. Since some

younger stands contain logs with much greater velocities

than logs in older stands; the Director HM-200TM provides

a more reliable means for identifying and sorting the logs

with better stiffness characteristics than would be obtained

using age or other misleading appearance features. A l t h o u g h

sorting logs with the Director HM-200TM at a landing or log

yard provides obvious advantages, it would be desirable to

have counterpart technology for standing trees to help find

the best stands.

ASSESSING STIFFNESS OF STANDING

TREES WITH THE DIRECTOR ST-300TM

Operating the Director ST-300TM

Figure 9 shows the components and set-up of the Director ST-300TM. Transmitter and receiver probes are driven

through the bark into the outer wood of the lower stem.

They are vertically aligned along the stem approximately

1.3 meters apart and it does not matter which probe is the

higher or lower unit. A laser guided ultrasound rangefinder

measures the exact distance between the probes. An acoustic

wave is imparted into the tree stem through the transmitter

probe by a hammer blow. The receiver probe picks up the

acoustic signal passing through the tree and determines the

time-of-flight of the acoustic wave. The distance and time

124

Figure 5—Yield of structural lumber grades verses Director HM-200TM

log velocity (km/sec) for two New Zealand radiata pine sawmills.

Figure 6—Acoustic velocity of logs in relation to log position in a tree

stem.
are sent by wireless communication to a PDA (personal

digital assistant) that calculates the acoustic velocity and

also allows the user to enter other tree and stand data. Unlike

the Director HM-200TM, which obtains the weighted average velocity by analyzing whole wave signals transmitted

between the ends of a log, the Director ST-300TM measures

time-of-flight for a single pulse wave to pass through the

outer wood of the tree from transmitter probe to receiver

probe. Given this difference in how velocity is measured

and the fact that the Director ST-300TM only measures

velocity along a short distance along what will become the

base of the butt log from the tree, the most obvious and

immediate question is: “What is the relationship between

velocities obtained with the Director ST-300TM and those

from the Director HM-200TM?” Figure 10 provides evidence that the answer is there is a very strong linear relationship between acoustic velocity measured in trees and

acoustic velocity measured in logs (Wang et al. 2004b). 

Figure 11 shows tests in radiata pine of the effect of

misaligning the probes, i.e., keeping the receiver probe at

X and moving the source probe further and further out of

alignment (XA vs. XE). Since time-of-flight is measured

through the outer wood between the probes, figure 11 also

shows that moving the probes to a different location around

the circumference of the stem has a minor effect on velocity

(XA vs. YE). Finally, figure 11 shows the effect of lengthening the distance between the probes; including a knot

w h o r l with associated deviant grain slightly lowers the

velocity and thus, the predicted value of stiffness. Results

shown in figure 11 imply that correlations between Director

S T-300TM and Director HM-200TM velocities will be

125

Figure 7—Director HM-200TM velocity (km/s) verses average log age in

New Zealand radiata pine stands

Figure 8—Mean and variation in Director HM-200TM velocity (km/s) 

for logs from New Zealand radiata pine stands. Log sources (stands) are

sorted by mean acoustic speed.

Figure 9—Components of the Director ST-300TM.
improved as one acquires and averages more samples

around the stem circumference with the Director ST-300TM.

The issue of whether or not one should acquire more samples within each tree or sample more trees within the stand

of interest depends on the objective of the assessment

p r o ject.

EXPERIENCE WITH THE DIRECTOR 

ST-300TM IN DOUGLAS-FIR

A test of the Director ST-300TM was conducted in September 2004 in an unthinned and a thinned plot in the Stand

Management Cooperative’s (SMC) Type II Installation 803,

Beeville Loop, located near Shelton, WA. This thinning trial

was placed in a stand that was planted with 2-0 Douglas-fir

seedlings in 1955 on site class II (122 feet based on King

1966). In 1987, the SMC established five plots, a control

that had 320 trees per acre and would receive no future treatments and four plots of similar initial stocking that w o u l d

u n d e rgo thinning regimes. A crew of three measured 63

trees in the unthinned control (plot 2) and 50 trees in a plot

that was thinned in 1987 from a Curtis relative density

(Curtis 1982) of 55 to a relative density of 35 (plot 1). At

the time of the test, breast height age was 43, stand age

was 49 and age from seed was 51. Time to locate and walk

between trees, set up the test, and measure dbh averaged 

1 minute per tree.

Figure 12 presents the cumulative mean and standard

error for each plot as more trees were measured; by the time

35 trees were sampled, the difference between the plots

became apparent. The thinned plot, with faster growing and

larger diameter trees, has higher average acoustic velocity

and hence would be expected to produce greater yield of

products with higher stiffness. We speculate that this site

may experience water stress in summer, thus, the unthinned

stand, with more competing trees, may stop growing earlier

thereby truncating formation of dense latewood. The reduced

production of latewood would result in lower overall wood

d e n s i t y, which would translate into slower velocity and

lower stiffness. This is atypical of what would be expected

on sites where moisture is not limiting. In a wood quality

study conducted on young-growth western hemlock and

Sitka spruce, Wang examined the effects of thinning treatments on both stress wave velocity and wood stiffness. The

results revealed that highest stress wave velocity and stiffness were mostly found in unthinned control stands whereas the lowest values were found in stands that had received

heavy and medium thinning (Wang et al. 2001). This indicated that lower density stands exhibited a trend toward

decreased stress wave velocity and decreased stiffness. 

Figure 13 shows weak negative trends of velocity with

tree diameter in each plot. The unthinned plot trend is lower

than that for the thinned plot although the trends converge

for the larger diameter trees that were presumably in the

dominant crown class. Figure 14 shows similarly weak

126

Figure 10—Relationship between measurement of acoustic speed of logs

with the Director HM- 200TM and measurement of acoustic speed of parent trees with the Director ST-300TM.

Figure 11 — E ffects of Director ST-300TM probe location in relation to knot

inclusion and displacement from vertical on velocity in a radiata pine stem.
relationships between velocity and rings per inch5 for trees

on the plots. RPI is often viewed by mills and others as a

good indicator of strength and stiffness and often prefer

“slower growing” trees and logs. Does sorting by acoustic

velocity improve on sorting by RPI? Trees averaging 6 RPI

or greater had an average V2 (see Equation 1), a direct

measure of MOE, of 16.66 km2/ s2 whereas the mean V2

of all of the trees in both plots was 18.09 km2/s2, a gain of

2.3%. Note that roughly half of the trees with less than 6.0

RPI have V2 greater than 18.09 km2/ s2 and many trees with

more than 6.0 RPI have V2 less than 18.09 km2/s2. Using

the preceding economic analysis data, this 2.3% gain from

acoustic sorting would translate to about $8/m3 ($40-

48/MBF Scribner). 

127

Figure 12—Effect of increasing sample size on mean and standard error of Director ST-300TM acoustic velocity in

Douglas-fir trees in thinned and unthinned plots at the Stand Management Cooperative Beeville Loop installation.

Shown is cumulative mean plot velocity (±1 standard error) as number of trees sampled increased.

Figure 13—Relationship between tree DBH and Director ST-300TM velocity

for Douglas-fir trees in thinned, R2 = 0.2527, and unthinned, R2 = 0.0906,

plots at the SMC Beeville Loop installation.

Figure 14—Relationship between rings/inch and Director ST-300TM velocity

for Douglas-fir trees in thinned, R2 = 0.2333, and unthinned, R2 = 0.0604,

plots at the SMC Beeville Loop installation.

5 RPI = rings per inch, which is calculated as breast-height age divided by stem radius in inches (radius = diameter at breast height / 2)
OPERATIONAL CONSIDERATIONS

At a given time of year in a given stand, one can assume

that the density, ρ in Equation (1), which is simply weight

divided by volume, is reasonably constant and that the eff e c t

of changes in temperature would be minimal. Although for

many materials density is constant, it is variable for wood;

hence there may be seasonal and other effects to consider.

In the case of fresh, wet “green” wood, density can be 

calculated as follows:

ρ = ρH20SGg (1 + MCod ) (3)

Where

ρ = density (in lb/ft3 or kg/m3)

ρ H20 = density of water (62.4 lb/ft3 or1000 kg/m3)

SGg = wood basic density6 (also referred to as 

specific gravity or relative density) 

MCod = wood moisture content (oven-dry basis, in 

decimal form)

The basic density of wood varies by species and has 

a systematic pattern of change from pith to bark and from

base to top of tree that is associated with the formation

processes of juvenile and mature wood. These patterns are

part of the explanation of why acoustic velocity changes

with log position within a tree (figure 6) and why acoustic

velocity is correlated with log age (figure 7). 

It should be apparent from equation (3) that density

increases as wood moisture content increases; this is simply

a result of the fact that water in wood cells weighs much

more than the air which replaces the water during drying.

Consequently, one can expect lower velocities in wet wood

as compared to dry wood. In living trees and freshly-cut

logs, lumber, and veneer, wood moisture content often varies

between sapwood and heartwood. For example, moisture

content for softwood species ranges from 98 to 249% for

sapwood and from 31 to 121% for heartwood (Forest

Products Laboratory 1999). The moisture content of a log

whose velocity is being measured by the Director HM-200TM

is a weighted average of sapwood and heartwood moisture

contents. The moisture content of the outer wood of a tree

whose velocity is being measured with the Director ST- 3 0 0 TM

will be that of sapwood. Fortunately, it has been found that

when moisture content is above 40%, there is little effect

on acoustic velocity (Ross et al. 2004). However, for logs

from species with low heartwood moisture contents, for

dead timber, and for logs that may have undergone some

drying since harvest, an adjustment for the effect of moisture content may be needed. Continuous monitoring of

moisture content of a sample of logs will be useful to gain

an understanding of the effect of moisture content and

make appropriate adjustments, if necessary. Figure 15 illustrates the typical directions that changes in moisture content and basic density have on deviation of samples from

an established trend line.

128

6 Based on oven dry weight and green volume.

Figure 15—Relationships between 10th percentile classes of average board

MOE, and Director log speed for radiata pine. Arrows indicate shift of the

relationship with changes in basic wood density and moisture content.

Figure 16—Effect of seasonal change in temperature and moisture content

on log density and log velocity in radiata pine. Log density is based on

JAS log scale.
In addition to the effects of basic density and moisture

content, large seasonal changes in temperature may also

require the user to make an appropriate adjustment on

acoustic measures. Figure 16 illustrates the effects of seasonal changes in temperature and moisture content on

acoustic velocity of radiata pine. In-depth research is still

needed to further explore the influence of seasonal weather

change on acoustic measurements on trees and logs. 

CONCLUSIONS

Nondestructive testing of logs for stiffness with the

Director HM-200TM offers a new reliable and flexible

approach for sorting and matching logs to manufacturer

and customer demands for stiffness and strength of products they contain. It may also provide a new means by

which landowners and loggers can grade and market logs.

The nondestructive testing concept has been extended

to standing trees with Director ST-300TM which provides an

indicator of stiffness over an approximate 1.3 m distance in

the lower stem; lower portion of the butt log. This will provide a new means for assessing mature stands for marketing,

for harvest planning and scheduling, and has the potential

for assisting in planning silvicultural operations in immature stands.

LITERATURE CITED

Curtis, R.O. 1982. A simple index of stand density for 

Douglas-fir. Forest Science 28: 92-94.

Eastin, I. 2005. Does lumber quality really matter to 

builders? In: Harrington, C.A.; Schoenholtz, S.H., eds.

Productivity of Western Forests: A Forest Products

Focus. Proceedings of a meeting held June 20-23,

2004, Kamilche, WA. Gen. Tech. Rep. PNW-GTR-642.

Portland, OR: U.S. Department of Agriculture, Forest

Service, Pacific Northwest Research Station: 131-139.

King, J.E. 1966. Site index curves for Douglas-fir in the 

Pacific Northwest. Weyerhaeuser Company Forestry

Paper No. 8. Centralia, WA. 

Megraw, R.A.; Bremer, D.; Leaf, G.; Roers, J. 1999. 

Stiffness in loblolly pine as a function of ring position

and height, and it’s relationship to microfibril angle and

specific gravity. In: Proceedings of the 3rd Workshop

Connection Between Silviculture and Wood Quality

Through Modeling Approaches. La Londe-Les-Maures,

France: IUFRO Working Party S5.01-04: 341-349.

Ross, R.J.; Brashaw, B.K.; Wang, X.; White, R.H.; 

Pellerin, R.F. 2004. Wood and timber condition assessment manual. Madison, WI: Forest Products Society.

73 p.

Smith, W.B.; Vissage, J.S.; Darr, D.R.; Sheffield, R.M. 

2001. Forest resources of the United States, 1997. 

Gen. Tech. Rep. GTR-NC-219. St. Paul, MN: U.S.

Department of Agriculture, Forest Service, North

Central Research Station. 190 p.

Spelter, H.; Wang, R.; Ince, P. 1996. Economic feasibility 

of products from Inland West small-diameter timber.

Gen. Tech. Rep. FPL-GTR-92. Madison, WI: U.S.

Department of Agriculture, Forest Service, Forest

Products Laboratory. 17 p.

Forest Products Laboratory. 1999. Wood handbook: 

wood as an engineering material. Gen. Tech. Rep. 

FPL-GTR-113. Madison, WI: U.S. Department of

Agriculture, Forest Service, Forest Products Laboratory.

Wang, X.; Ross, R.J.; McClellan, M. [et al.] 2001. 

Nondestructive evaluation of standing trees with a stress

wave method. Wood and Fiber Science 33: 522-533.

Wang, X. Ross, R.J.; Mattson, J.A. [et al.] 2002. 

Nondestructive evaluation techniques for assessing

modulus of elasticity and stiffness of small-diameter

logs. Forest Products Journal 52(2): 79-85.

Wang, X.; Ross, R.J.; Punches, J. [et al.] 2003.

Evaluation of small-diameter timber for value-added

manufacturing - a stress wave approach. In:

Proceedings, The Second International Precision

Forestry Symposium. Seattle, WA: College of Forest

Resources, University of Washington: 91-96.

Wang, X.; Ross, R.J.; Green, D.W. [et al.] 2004a. Stress 

wave sorting of red maple logs for structural quality.

Wood Science Technology 37: 531-537.

Wang, X.; Ross, R.J.; Carter, P. 2004b. Assessment of 

standing tree quality – from baseline research to field

equipment. In: Forest Products Society 2004 Annual

Meeting – Technical Forum. Grand Rapids, Michigan,

USA.

129
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1 Ivan L. Eastin is professor of forest products marketing and the Acting Director of the Center for International Trade in Forest Products (CINTRAFOR),

College of Forest Resources, Box 352100, University of Washington, Seattle, WA 98195.

Productivity of Western Forests: A Forest Products Focus

DOES LUMBER QUALITY REALLY

MATTER TO BUILDERS?

Ivan L. Eastin1

INTRODUCTION

H i s t o r i c a l l y, residential housing has been the single larg e s t

market for softwood lumber in the United States (Joint C e n t e r

for Housing Studies 2001). While there has been a close

relationship between housing starts and softwood lumber

consumption and production in the past, domestic supply

constraints and the emergence of the repair and remodel

market in the late 1980s have tended to relax this relationship (fig. 1). Currently about 40 percent of U.S. lumber

consumption can be attributed to residential construction

ABSTRACT

Understanding the ways in which residential builders perceive and use softwood lumber and substitute structural materials

is essential to the success of any forest products manufacturer. This research represents the third in a longitudinal study and

describes trends in material substitution in the residential construction industry in 2001. This study looks at material substitution in structural framing applications and provides a benchmark for structural panel usage in exterior wall sheathing, subflooring and subroofing applications. The results of this research suggest that the pace of material substitution in the residential

construction industry has moderated since 1998. To a large degree this might be attributed to lower lumber prices, less

volatility in lumber prices, and the fact that builders have become more accepting of the perceived decline in softwood lumber quality that has been attributed to the younger, faster grown plantation resource and improved scanning and processing

technologies in the sawmill industry. The exception to this trend is in floor framing applications where wood I-joists continue

to expand their market share at the expense of softwood lumber. The most troubling result is the continuing misperception

among residential builders that when compared to alternative (non-wood) materials, softwood lumber is the least environmentally friendly material. This result could have serious implications for the forest products industry in the future as green

building programs become more prevalent and home buyers become more assertive in demanding that environmentally

friendly materials be used in building their homes. This misperception suggests that further research is needed to determine

the basis for the misperception and that strategies need to be developed to ensure that information regarding the positive

environmental benefits of using wood relative to non-wood substitutes is effectively communicated to home builders and

home buyers.

K E Y W O R D S: Material substitution, softwood lumber, marketing, attributes, residential construction.

131

while the repair and remodeling sector accounts for an

additional 30 percent of lumber consumption (fig. 2). 

Following the imposition of timber harvest constraints

in the Pacific Northwest in the late 1980s, the price volatility of softwood lumber increased dramatically, figure 3.

The timber harvest constraints occurred just as the residential construction industry entered a period of dramatic

growth. The combination of sustained growth in the housing industry, declining lumber production, timber harvest

constraints and the softwood lumber trade dispute between

the US and Canada all contributed to increased price
132

Figure 1—The relationship between housing starts and the consumption and production of softwood lumber in

the US.

Figure 2—Major end-use markets for softwood lumber (Western Wood Products Association 2002).
single-family homebuilders as well as the top 100 homebuilders in the United States. A stratified, random sample

of 2,400 homebuilders was obtained from a database of US

homebuilders maintained by Cahners Direct Marketing

Services located in Des Plaines, IL while a census of the

top 100 homebuilders was obtained from Builder Magazine

(May 2001 edition).

The database obtained from Cahners was specifically

designed to include an equal number of builders (600

builders) in each of the four regions in the US. In addition

to the regional specification, the sample frame was further

stratified to include an equal number of small, medium and

large sized firms within each region.

A cover letter was mailed to each survey recipient stating

the goals and purpose of the survey. In addition, each

homebuilder received an eight page survey and a self

addressed stamped envelope in which to return the completed survey. The results of this survey were offered free

to any builder that participated in the survey. As an additional incentive, the names of all survey respondents were

entered into a drawing for five Porter Cable 10-AmpQuick

Change Reciprocating Saws. Two follow up letters were

sent to non-respondents at intervals of two and four weeks

following the initial mailing. A total of 189 valid responses

were received which correlates to a final response rate of

9.0% (taking into account undeliverable surveys).

133

volatility. Sensitive to the dramatic effect that volatile lumber prices can have on their profit margins, builders began

to look at using more price-stable materials as substitutes

for softwood lumber (Shook et al. 1998; Fell 1999; Eastin

et al. 2000; Eastin et al. 2001; Shook and Eastin 2001; Fell

1999).

Understanding the ways in which residential builders

purchase and use softwood lumber and lumber substitutes

is essential to the success of any forest products manufacturer. The Center for International Trade in Forest Products

(CINTRAFOR) completed its first study on material substitution in 1995 (Eastin et al. 1996), providing a benchmark

for softwood lumber use in structural applications in residential construction. In 1998, a second study by CINTRAFOR found that softwood lumber was slowly losing market

share to engineered wood products and non-wood substitutes (Fleishman et al. 2000). The 1998 CINTRAFOR study

also provided a benchmark for material usage in residential

decking applications (CINTRAFOR Working Paper No. 78).

A third study conducted in 2002 describes the trends in

material substitution in the residential construction industry

in 2001 (Garth et al. 2004).

STUDY METHODS

Studies in this field rely primarily on survey instruments.

The sample population for this survey consisted of 2,400

Figure 3—Price changes for softwood lumber dimension lumber over time.
continues to grow even as the prices of softwood lumber

have moderated in recent years.

Material Use in Specific End-Use Applications

Survey participants were asked to estimate the percentage (on a volume basis) of material usage during the past

year in specific structural end-use applications (tables 1

and 2). These structural applications included wall framing

(including both load bearing and non-load bearing walls),

floor joists, roof framing and headers. The designation of

non-load bearing wall and load bearing wall applications

were a new addition to the 2001 survey. Material use in

header applications was also a new category in the 2001

survey.

The softwood lumber usage changes since 1998 are

minor but interesting. Softwood lumber used in wall framing and wood I-joists in used flooring both gained ground

slightly. The change in wall and roof uses was less than 1

percentage point. This differs from the results of the 1998

survey when softwood lumber lost considerable ground to

virtually every other substitute material identified in the

s u r v e y. Low and stable softwood lumber prices appear to be

a major factor in explaining the stabilization of the market

share of softwood lumber between 1998 and 2001.

Steel has seen a moderate decline across all structural

end-use applications. Table 1 provides a clearer picture of

steel use in wall framing. The underlying message is that

steel, though used by builders in some applications in some

SURVEY RESULTS

Builders Use of Substitute Materials

The total number of substitute materials used by residential builders in 2001 was very similar to that found in

the 1998 survey. A cumulative percentage graph comparing

the three survey results of 1995, 1998, and 2001 is presented in figure 4. Almost half of the respondents in 2001 have

used seven or more substitute materials; this is very similar

to results in 1998. In addition, almost a quarter of the respondents have used nine or more substitute materials. In

1998, only 15% of builders had tried nine or more substitutes. The further shift of the usage curve to the right indicates that builders are using more substitute materials over

time.

As was mentioned in previous survey results, the trend

of higher substitute usage can be partially explained by

b u i l d e r s ’ dissatisfaction with several softwood lumber

attributes, particularly with respect to overall price, price

s t a b i l i t y, and softwood lumber quality. As a traditionally

conservative group, particularly with respect to the trial a n d

adoption of new substitute materials, the shift by builders

toward using a broader range of structural materials should

be seen as an indication of their continued dissatisfaction

with softwood lumber. This shift should also be seen as an

indication that builders are more willing to try new products

as a result of their past experiences with substitute materials.

This explains why the aggregate use of substitute materials

134

Figure 4—Number of substitute products used by residential builders.
regions of the US, has not been successful in offering a total

framing system that builders are willing to adopt. Builders

remain reluctant to use steel to frame the entire house and

as a result, its overall market share has declined. In addition, low softwood lumber prices are seen as a significant

factor in the declining use of steel framing.

The share of softwood lumber used in header applications is less than that observed in wall framing, although it

still exceeds 70%, table 2. Builders reported using LVL

(laminated veneer lumber) for about 20 percent of header

construction. The survey data indicates that builders reported large increases in their use of LVL and while some LVL

is used in wall, floor and roof framing applications, the

largest volume was used in header applications which often

require the higher stiffness of LVL to bridge large window,

door and garage door openings.

135

Table 2 segments the wall framing data into load bearing and non-load bearing wall applications. Steel framing

is used significantly more in non-load bearing walls than 

in load bearing walls. LV L shows the opposite trend and

is used significantly more in load bearing walls than in

non-load bearing walls. Interestingly, the use of softwood

lumber is relatively consistent between both types of wall

applications, suggesting that most builders prefer to use a

single structural material rather than switch between materials depending on the end-use application.

Builder Importance Ratings for Softwood 

Lumber Attributes

Builders were asked to rate the importance of a broad

range of structural softwood lumber attributes in their mater i a l purchase decisions. The average importance ratings summ a r i z e d in table 5 are virtually identical to those obtained

in the two previous CINTRAFOR surveys and there are

two important inferences to be made regarding this observation. First, attitudes of builders toward the importance of

specific structural lumber attributes have remained relatively

constant since 1995. Second, the builders surveyed in 2001

are similar to those surveyed in the 1995 and 1998 studies.

These results are notable because, given the fact that residential construction framing technology has remained fairly

constant over time, we would not expect the relative import a n c e of specific purchase criteria to change much over

time.

Builder Satisfaction Ratings for Softwood 

Lumber Attributes

The satisfaction ratings for the softwood lumber attributes are summarized in table 6. It is important to note that

although the satisfaction scores have generally increased,

straightness and lack of defects in softwood lumber continue to be the material attributes with the lowest satisfaction

Table 2—Material use in load bearing and 

non-load bearing walls in 2001

Wall Framing End-Use

Application

Load Non-load

bearing bearing 

- - - - - - Percent- - - - - - -

Softwood lumber 83.4 83.9

Finger-jointed stud 5.5 5.5

Steel framing 6.6 8.5

LVL 2.7 0.4

Wood truss 1.1 0.8

Wood I-joist 0.4 0.4

Table 1—Product usage in specific framing applications

in 1995, 1998, and 2001. LV L = laminated veneer l u m b e r.

1995 1998 2001

- - - - - - - -Percent - - - - - - - -

Wall framing

Softwood lumber 93.0 83.1 83.4

Finger-jointed stud 4.0 5.3 5.5

Steel framing 0.0 8.8 6.6

LVL 0.0 0.8 1.6

Wood truss 0.0 1.1 1.1

Wood I-joist 0.0 0.4 0.4

Floor framing

Wood I-joist 23.0 38.8 43.2

Softwood lumber 59.0 41.8 38.6

Wood truss 16.0 10.4 12.7

LVL 0.0 3.0 2.3

Steel framing 2.0 2.2 1.7

Finger-jointed stud 0.0 0.3 0.3

Roof framing

Wood truss 46.0 47.7 49.7

Softwood lumber 51.0 40.0 40.9

Wood I-joist 2.0 3.4 3.0

LVL 0.0 2.7 2.7

Steel framing 1.0 2.9 1.7

Finger-jointed stud 0.0 1.3 0.1

Headers

Softwood lumber n/a n/a 71.9

LVL n/a n/a 20.4

Steel framing n/a n/a 3.8

Wood truss n/a n/a 1.6

Wood I-joist n/a n/a 1.2

Finger-jointed stud n/a n/a 0.2
ratings. Straightness and lack of defects are reported to be

two of the most important lumber attributes and yet they

are the two attributes with the lowest satisfaction ratings.

Considering the low satisfaction ratings provided for the

straightness and lack-of-defects attributes of softwood 

lumber, it appears clear that builders remain critical of the

quality of softwood lumber, a result that has remained fairly

consistent over the 1995-2001 period. In contrast, the satisfaction ratings for price and price stability continue to

increase as softwood lumber prices and price volatility

continue to moderate.

136

Figure 5—Survey respondents average importance ratings for softwood lumber attributes.

Figure 6—Survey respondents average satisfaction ratings for softwood lumber attributes.
Comparison of Importance and Satisfaction 

Attribute Rating Scores

A gap analysis highlights the observation that builders

appear to be more satisfied with softwood lumber. Table 7

quantifies the difference between the importance and satisfaction ratings for each of the 13 softwood lumber attributes.

These gaps were calculated by subtracting the satisfaction

rating from the importance rating for each material attribute.

Strength was the sole attribute for which an increase in the

importance-satisfaction gap was reported. For the remaining 12 attributes, either a decrease in the gap or no change

was reported. This is certainly good news for softwood

lumber manufacturers. However, substantial gaps were

observed for the straightness and lack of defects attributes

and, although the magnitude of these gaps was slightly

lower than observed in the previous surveys, this gap

remains problematic for softwood lumber manufacturers.

Similar to the 1998 survey, builders were asked to list the

three most important lumber attributes that they consider

when purchasing softwood lumber. The softwood lumber

attributes of strength, price, and straightness remained the

top three attributes.

Perceptions of Environmental Performance 

for Substitute Building Materials

Another objective of this research was to assess builders

perceptions of the environmental impacts associated with

the use of each substitute material relative to softwood

lumber. Survey respondents were asked to compare each

substitute material to softwood lumber with respect to its

impact on the environment using a Likert-like scale where

a rating of 1 indicated that the substitute material had a

much less favorable impact on the environment relative

to softwood lumber, a rating of 4 indicated that it had the

same impact and a rating of 7 indicated that the substitute

material had a much more favorable impact on the environment relative to softwood lumber. The average scores for

this and previous surveys are summarized in figure 8. All

of the materials identified in the survey saw an increase in

average ratings with the exception of wood I-joists. T h e

biggest increase was seen in steel, followed by concrete

blocks, SIPs (structural insulated panels) and wood/steel

trusses.

Clearly builders still perceive softwood lumber as having a poor environmental image, which may be due to recent

e fforts to position substitute materials as being environment a l l y f r i e n d l y. For example, much of the marketing effort for

steel has been to position steel as an environmentally friendly

product relative to wood and this message seems to have

taken hold. However, environmental performance currently

ranks the lowest in importance during the purchase decision

as seen in figure 5. While there have been several efforts to

improve the environmental perception of wood recently, it

appears that these have been too limited in scale and scope

to have had any substantial impact on builders’ perceptions

of wood.

137

Figure 7—Average gap score between the importance and satisfaction attribute ratings.
CONCLUSIONS

The results of this research suggest that the pace of

material substitution in the residential construction industry

has moderated since 1998. To a large degree this might be

attributed to lower lumber prices, less volatility in lumber

prices, and the fact that builders have become more accepting of the decreased softwood lumber quality that has been

attributed to the younger, faster grown plantation resource.

The exception to this trend is in floor framing applications

where wood I-joists continue to expand their market share

at the expense of softwood lumber. The 2001 survey results

clearly show that material quality remains the most important set of attributes and that the largest gap between import a n c e and satisfaction is observed with the material quality

attributes. However, a closer review of the survey data suggests that builders may be more concerned with the overall

value of structural materials (defined as the ratio of quality

over unit price) as opposed to simply material quality.

The most troubling result is the continuing misperception among residential builders that softwood lumber is the

least environmentally friendly material. This result could

have serious implications for the forest products industry in

the future as green building programs become more prevalent and homebuyers become more assertive in demanding

that environmentally friendly materials be used in building

their homes. This misperception clearly shows that further

research is required to determine the basis for this misperception and to identify strategies to ensure that information

regarding the positive environmental benefits of using wood

relative to non-wood substitutes is effectively communicated

to home builders and home buyers.

LITERATURE CITED

Eastin, I.L.; Fleishman, S.; Shook, S.R. 2001. Softwood 

lumber substitution in the residential construction

industry: 1998. Forest Products Journal 51(9): 30-37.

Eastin, I.L.; Fleishman, S.; Shook, S.R. 2000. Change 

of plans: material substitution in the residential 

construction industry. Engineered Wood Journal.

2000(Fall): 34-37.

138

Figure 8—Respondent’s perceptions of environmental performance of substitute materials relative to softwood

lumber. LVL = laminated veneer lumber, TM = trademark, W/S = wood or steel, FJ = finger-jointed lumber,

WPC = wood-plastic composite lumber, RC = reinforced concrete, and CB = concrete block.
Eastin, I.L.; Simon, D.D.; Shook, S.R. 1996. Softwood 

substitution in the US residential construction industry.

CINTRAFOR Working Paper No. 57. Seattle, WA:

University of Washington. Center for International

Trade in Forest Products. 54 p.

Fell, D. 1999. Target engineered products to builders most 

likely to innovate. Wood Technology. 126(4): 22-25.

Fleishman, S.J.; Eastin, I.L.; Shook S. 2000. Material 

substitution trends in residential construction, 1995 vs.

1998. CINTRAFOR Working Paper No. 73. Seattle,

WA: University of Washington. Center for International

Trade in Forest Products. 76 p.

Garth, J., Eastin, I.L.; Edelson, J. 2004. Material 

Substitution Trends in Residential Construction, 2001

vs. 1998 and 1995. CINTRAFOR Working Paper No.

93. Seattle, WA: University of Washington. Center for

International Trade in Forest Products.

Joint Center for Housing Studies. 2001. The state of the 

nation’s housing. Cambridge, MA: Harvard University.

Shook S.R.; Eastin, I.L. 2000. A characterization of the 

US residential deck market: 1998. CINTRAFOR

Working Paper 78. Seattle, WA: University of

Washington. Center for International Trade in Forest

Products. 45 p.

Shook, S.R.; Eastin, I.L. 2001. A characterization of the 

US residential deck material market. Forest Products

Journal 51(4): 28-36.

Shook S.R.; Turner, W.R.; Eastin, I.L. 1998. Adoption, 

diffusion, and substitution of structural wood panels.

CINTRAFOR Working Paper 65. Seattle, WA:

University of Washington. Center for International

Trade in Forest Products. 32 p.

Western Wood Products Association. 2002. 2001 

Statistical yearbook of the western sawmill industry.

Portland, OR.

139
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CONTINUE
1 David Briggs is professor and director, Stand Management Cooperative; College of Forest Resources Box 352100; University of Washington; 

Seattle, WA. 98195.

Productivity of Western Forests: A Forest Products Focus

ASSESSING AND MANAGING STANDS 

TO MEET QUALITY OBJECTIVES

David Briggs1

INTRODUCTION

For a long time relatively simple, economical field tools

have allowed forest managers to measure geometric properties of trees in a stand for inventory, and growth and yield

analysis. This has also led to the development and use of

growth and yield, harvest scheduling and other forest planning models. Unfortunately, counterparts for measuring

quality properties of trees have lagged, hence quality has

not received as detailed treatment in inventories, analyses,

and models. If quality is treated at all, it is often through

assuming an implied relationship of increasing quality with

increasing tree diameter. Although a general association of

higher quality with increasing tree diameter may have been

reasonable for natural stands and minimally managed plantations, it breaks down in intensively managed plantations

where different cultural regimes can produce similar size

trees with great differences in knot size, percentage of juvenile wood, ring width, and other characteristics. An alternat i v e to the diameter association is to estimate the log grade

composition or tree grade of trees in a stand. Unfortunately,

these grading systems provide only broad, generalized indications of quality and may not be consistent with, or at the

ABSTRACT

Process capability analysis (PCA) is a statistical quality control technique which managers can use to assess the degree

of nonconformance of individual timber stands to specifications for quality properties such as knot diameter, rings per inch,

and wood stiffness (MOE). Examples from Douglas-fir (Pseudotsuga menziesii Mirb. Franco) plantations demonstrate applic a t i o n of PCA to a single property or a combination and show how PCA can be used to monitor nonconformance over time.

Managers can use the PCA information to assist in harvest planning and marketing mature stands and to assist in planning

silvicultural planning in immature stands. Purchasers can use PCA to assist in determining if a stand has sufficient conformance to their log quality requirements to justify a bid.

KEYWORDS: Log quality, tree quality, silviculture, statistical quality control, process capability analysis.

141

resolution needed by, current and emerging markets. For

example the official log grades for Douglas-fir in the Pacific

Northwest do not discriminate knot size until knot diameter

is at least 2.5 inches (NWLRAG 1998). Furthermore, these

grades have sometimes been found to produce illogical

results when applied to managed plantations. For example,

Sonne et al (2004) found that No. 3 Sawlogs from a 70-

y e a r-old Douglas-fir stand that had been thinned and treated

with biosolids had greater yield of high grade lumber than

from No. 2 Sawlogs; a reversal of customary expectations

from these grades. Forest product manufacturers have

become more specialized in their log quality preferences 

as evidenced by an unofficial system of logs sorts (Bowers

1997) that largely replaced the official system. The principal feature of the log sorts is use of a finer resolution of log

properties present in the official rules; primarily log diameter; rings per inch, knot diameter, and number of knots per

log face. Manufacturer concerns with juvenile wood, wood

strength and stiffness, dimensional stability, and other prope r t i e s are not addressed by the current log grading systems

and little has been done to formally translate desired log

characteristics into counterparts that can be assessed in

trees and stands.
Forest managers need improved approaches for quantifying

relevant quality characteristics both for marketing and

managing quality in intensively managed plantations. Techniques for rapid and economical field measurement of key

tree quality properties exist, including tools that use acoustic

wave transmission to non-destructively assess potential

modulus of elasticity (MOE) of products from logs and

trees (Carter et al. 2004). Techniques of statistical quality

control have been successfully implemented in many indust r i e s and manufacturing settings where properties of the

product from a process are measured and monitored with

the objective of maximizing conformance of properties to

specifications supplied by a customer, product designer, or

management. Combining these field and statistical techniques provides an opportunity to develop analytic methods

for assessing quality of trees and stands that can assist silviculturists, managers and planners with silvicultural and

marketing decisions.

This paper reviews a statistical quality control technique,

process capability analysis (PCA), useful for assessing the

degree of conformance of product properties to specifications issued by a customer or stated as quality objectives.

Next, some important log quality properties that can be

readily measured or estimated in standing trees for application of PCA are discussed. Several examples illustrating the

use of PCA on some of these properties, singly and in

c o mbination, are presented for some intensively managed

Douglas-fir plantations. Finally, management implications

of applying PCA to quality of timber stands are discussed.

PROCESS CAPABILITY ANALYSIS

Process capability analysis refers to techniques for

studying “process capability” or the uniformity of a process

at either a single point in time or over time through repeated

sampling (Montgomery 2001). More specifically, a sample

of product from the process is measured for a specific

property and process capability is usually estimated by

using a probability distribution with the shape, center

(mean, μ) and spread (standard deviation, σ) appropriate

for the property. If no suitable probability distribution model

can be found, process capability can be estimated from the

actual frequency histogram. Two contexts for expressing

process capability are presented in the following paragraphs.

First, process capability can be stated without reference

to external specifications for the property of interest. In this

case, process capability is stated as the six-standard-deviation spread of the distribution of the product property,

expressed as the upper and lower natural tolerance limits

(UNTL, LNTL); 

UNTL,LNTL = μ ±3σ

If a normal distribution is assumed for the property,

process capability can be stated by noting that 0.27% of the

product, or 2700 product items per million, will be outside

the UNTL – LNTL range for the property.

Second, process capability can be stated as the percentage of product falling outside, or not conforming to, external

specifications for the property. Upper and lower specification limits (USL, LSL) may be one sided or two sided and

may originate from product designers and engineers, management directives, product standards, or customers. A

manager can compare USL and LSL with the probability

distribution of the product property. Nonconformance is the

percentage of the distribution outside the bounds defined

by USL and LSL. Assuming that the property is normally

distributed, that the process is in statistical control as evidenced by control charts for the process, and that the mean

is centered between USL and LSL, process capability can

be expressed as a process capability ratio (Cp), formed from

the external specification limits and the natural limits of the

process as follows:

Cp =

Correct use and interpretation of Cp is dependent on the

validity of the assumptions. Cp will not be used here; more

experience with the distributions of timber quality properties and the effect of cultural practices on these distributions

will be needed to determine if the assumptions underlying

Cp are valid.

If the assumptions underlying Cp are not met, an alternative is to compare USL and LSL directly with the probability distribution or frequency histogram of the property.

Process capability can be stated as the percent non-conforming as estimated from the portions of the distribution

or histogram outside the specification limits. This approach,

using actual frequency histograms based on sampling trees

from the stand of interest, will be used in the following

examples. Future research will be needed to discover probability distribution models that are adequate for quality

properties of interest and can reflect impacts of cultural

practices that could radically alter the distribution of the

p r o p e r t y. Developing the frequency histogram of a quality

property requires sampling a sufficient number of trees

from the stand. In constructing histograms, Montgomery

(2001) suggests using between 4 and 20 bins, “choosing

the number of bins approximately equal to the square root

of the sample size.” Thus to have six bins describing a

quality property of trees in a stand, one should measure the

142

USL,LSL

6σ
property on at least 36 trees from the stand. This seems

reasonable considering the typical number and size of plots

one would place in a stand for inventory or appraisal. 

WHAT IMPORTANT LOG PROPERTIES

CAN BE EASILY MEASURED IN TREES

FOR USE IN PCA?

Consider a mill peeling logs into veneer for plywood

and laminated veneer lumber (LVL). Its log specifications

may include a maximum and minimum diameter, a growth

rate limit expressed as a lower bound on rings per inch, and

an upper bound on knot diameter. It may also pay a premium

for logs exceeding a lower bound on modulus of elasticity

(MOE), a measure of stiffness and a key characteristic for

veneer to qualify for LVL manufacture. Can these log quality properties be easily translated into measurements that

can be easily obtained from standing trees and subsequently

used in PCA? 

Log Diameter Range 

The dbh of the sample trees, combined with a taper

curve to predict diameters inside bark, can be used to estimate log diameters. Since dbh is customarily measured in

an inventory, measuring this property adds no new cost. If

forest growth models are used, most project the dbh of

individual trees and some produce log stock tables that

would provide a means for finding nonconformance to log

diameter range specifications. Additional accounting may

be necessary before a model could automate calculation of

nonconformance to user-defined log diameter specifications. 

Rings Per Inch (Rpi)

On permanent plots where trees are tagged and periodically measured for dbh, the change in dbh can be used to

estimate periodic rpi without new cost. One can expect that

rpi at breast height (bh) is highly correlated with rpi of the

first log in the tree, since bh is within that log, and should

be well correlated with rpi of upper stem logs. Increment

cores could be used as an alternative but this would add

expense in collecting the cores and measuring the rpi. If

forest growth models are used, rpi can be readily inferred

from dbh changes between projection periods. It may be

necessary to add some accounting procedures in the models

to automate and report rpi and to produce log stock tables

according to user-defined rpi specifications.

Knot Diameter

Ty p i c a l l y, each log grade or log sort has a maximum knot

diameter (Bowers 1997) and product recovery researchers

have found that largest limb average diameter (LLAD, Fahey

et al. 1991) also known as branch index (bix, Barbour &

Parry 2001), defined as the average of the largest diameter

knot in each of the four quadrants or faces of the log surface, is a good predictor of product grade recovery from a

log. One can hypothesize that the diameter of the largest

knot or LLAD, measured with a caliper on the lower bole,

would be highly correlated with the largest knot diameter

or LLAD of logs within the tree. The Stand Management

Cooperative and others (Ingaramo 2003) have measured

diameter of branches within a region centered on BH and

have found that this adds little to field time and cost. Examination of the hypothesized relationship between BH and log

knot diameter measures will be presented later in this paper.

Some growth models can estimate the diameter of branches

at each whorl position along the boles of trees (Hann et al.

1997, Mitchell 1975). With some further accounting, this

information could be used to estimate nonconformance to 

a knot diameter specification. 

Modulus of Elasticity (MOE)

The relationship between the MOE of a material, its

density and the speed of an acoustic wave through the mater i a l forms the basis for a method of nondestructive testing

of logs for MOE (Wang et al. 2000). This acoustic method

measures the “dynamic” MOE in contrast with the MOE

obtained by static bending. Researchers have demonstrated

excellent relationships between the dynamic and static bendi n g MOE of logs, and between the average static bending

MOE of products obtained from a log and the dynamic and

static bending MOE of the parent log (Ross et al. 1999, Wa n g

et al. 2004). This research has led to commercial tools for

nondestructive testing and sorting logs using acoustic signals and a related tool for nondestructive testing in standing

trees has just become available (Carter et al. 2005; this

p r oceedings). This new tool, which is used on the lower

bole of a tree, provides the opportunity for assessing the

degree to which trees in a stand conform to a specification

for MOE. Further research is underway to develop relationships along the chain from tree to product and to optimize

use of these tools in the field. 

This review indicates that properties important to product and log quality and value can be readily measured on

standing trees and many can be inferred from growth and

yield models, although this may require some refinements

in summary programming. During a stand inventory, sufficient trees are likely to be present on plots to gather these

data and pooled if necessary to develop frequency histograms

for use in PCA.

143
PCA OF DOUGLAS-FIR STANDS 

AT A SINGLE POINT IN TIME

A spacing trial located on the Pilchuck Tree Farm near

Stanwood, Washington will be used as an example. In May

of 1983, six acres of former cattle pasture was divided into

fifty square plots, each 73 ft x 73 ft covering 0.08 acres.

Site index is medium to high: 140 ft at 50 years (King

1966), corresponding to 98 ft at 30 years, using the new

curves for planted Douglas-fir stands (Flewelling et al.

2001). The plots were planted with two-year-old, unimproved, local origin Douglas-fir seedlings over six densities

ranging from 194 to 681 trees per acre; two densities had a

rectangular spacing, while the rest were square. The outermost row of trees in each plot was regarded as a buffer to

avoid edge effects from contiguous plots. On each plot,

trees inside the buffer were tagged and measured for DBH

in 1990 and 1998. In the winter of 2001-2002, six plots,

chosen at random from each spacing, forming a completely

randomized design with six replications of six stocking

treatments, were measured for detailed growth, yield, and

quality attributes (Ingaramo 2003). Using the 1998 DBH

distribution, 12 trees were sampled on each plot; the smallest, the largest, and 10 others selected at random. All sample

trees were measured for dbh and divided into N, S, E and W

quadrants or faces. In each quadrant, the diameter of a l l

branches greater than or equal to 1/3 inch, located within o n e -

foot above and below breast height (4.5 ft), was measured

with a caliper. Branch diameter was measured perpendicular

to the branch axis, in the direction of stemcircum ference,

just beyond the branch collar. Restricting branch measurement to those that were at least 1/3 inch diameter excluded

many small ‘whiskers’ that tend to self-prune very rapidly,

and have little, if any, effect on grading. A random sample

of four of the study trees was measured for total height and

height to the live crown defined as the average of the height

to live branches in the four quadrants. Table 1 summarizes

the tree characteristics according to stand density; at age 

18 (20 years from seed). 

In May 2003, the four height trees were climbed to 17.5

feet using a ladder and the largest diameter branch in each

of the N, S, E and W faces of the 16-foot butt log was

measured. It was assumed that the stump was 1 foot high

and that the log had 0.5 feet of trim allowance. The 16-foot

butt log was chosen since it is a preferred length for lumber,

closely approximates two peeler bocks for making veneer,

and is relatively fast and easy to measure with the ladder

method; a crew of five located and measured 136 trees in

about four hours. The owner had initiated thinning in some

plots and if the sample tree had been removed in the thinning, the standing tree most similar in DBH was used as a

replacement. Two plots had been heavily thinned and were

inaccessible for sampling due to the amount of felled material on the ground. With the exception of a single branch 

on the southern aspect of one tree at the lowest density, all

branches in the BH region of the sample trees were dead.

Furthermore, live crowns had receded above the top of the

log and during climbing it was noted that there were only 

a very small number of living but severely suppressed

branches within the 16-foot butt log. It is assumed that there

will be negligible additional growth on these few branches.

The hypothesis that there would be a reasonably good

correlation between branch diameters in the BH region and

on the 16-foot butt log was mentioned earlier. Figure 1

presents regressions between largest diameter branch and

LLAD in the BH region and on the 16-foot butt log. LLAD

of the 16-foot log produced a better regression than the

l a rgest diameter branch of the log. Also, the regressions

were poorer using LLAD of the BH region. Over the short

two-foot BH region, some quadrants had no branches (zero

branch diameter), which increased variation in BH region

LLAD and reduced its correlation with the log measures.

This is fortunate since it is easier for field personnel to find

and measure the largest branch in the BH region rather than

spend time locating quadrants and measuring the largest

branch in each quadrant. 

Applying PCA To Knot Diameter

A timber seller or purchaser would use one of the regress i o n s to translate a log specification for knot diameter into

a counterpart BH specification for standing trees. For example, if a sawmill places a 1.5-inch upper limit on LLAD of

logs, the equation in figure 1A yields a largest BH knot

diameter of 1.5 inches. After translating the log specification to a tree specification, the frequency histogram of

largest BH branch diameters from the trees in a stand can

be compared with the translated specification. Figure 2

shows such a comparison for the 194 tpa (15 ft x 15 ft)

density and shows that about 52% of the trees are nonconforming. A mill may decide to not make a purchase bid for

a stand with such high nonconformance. The seller, aware

of this poor non-conformance, can focus marketing efforts

on those who accept trees with relatively large knots. Some

may prefer to create cumulative frequency distributions

that may be visually easier for comparing multiple stands

with the specification limits in the same graph. Figure 3

shows cumulative frequency distributions for knot diameter

for all of the densities in the 18-year-old trial; the percentage of trees nonconforming to the BH knot-diameter specification ranges from only 3% in the 681 (8 ft x 8 ft) density,

to 52% for the 194 tpa (15 ft x 15 ft) density.

144
145

Table 1—Mean (and standard deviation) of tree characteristics by spacing in the 

Pilchuck Tree Farm spacing trial at age 18

Charachistic Density, trees/acre Spacing ft x ft

194 218 302 340 435 681

(15 x 15) (20 x 10) (12 x 12) (16 x 8) (10 x 10) (8 x 8)

Quadratic mean 11.1 10.7 9.8 9.4 8.8 7.5 

diameter, in (0.56) (0.37) (0.36) (0.26) (0.21) (0.18)

Total height, ft 52.5 50.8 53.5 53.2 56.1 54.1

(1.67) (4.69) (4.82) (3.19) (2.26) (2.07)

Crown ratio .68 .67 .56 .58 .52 .47 

(0.015) (0.021) (0.046) (0.054) (0.022) (0.031)

Crown base, ft 

(calculated) 16.8 16.8 23.5 22.3 26.9 28.7

Largest b.h. 1.54 1.41 1.25 1.24 1.21 1.01 

diameter, in (0.26) (0.23) (0.23) (0.21) (0.28) (0.22)

Figure 1—Knot diameter measures in the BH region of a tree verses knot diameter measures in its 1st 16-foot log.
146

Figure 2—Distribution of the largest diameter knot in the BH region of 18-year-old trees in a plot planted at 15-ft x 15-ft spacing.

Figure 3—Cumulative distributions of the largest diameter knot in the BH region of Pilchuck Tree Farm spacing

trial at age 18.
Applying PCA To Rings Per Inch

Mills often find that extremely fast growth is an undesirable characteristic for their products while tree growers

find that extremely slow growth is undesirable from a financial perspective. Suppose a mill’s log specification excludes

growth rates faster than four rpi while a landowner does not

wish growth slower than eight rpi. Figure 4 shows an LSL

of four rpi and a USL of eight rpi overlaid on the cumulative frequency distributions of rpi for the 18-year- o l d

spacing trial, calculated from the 1998 and 2001 dbh measu r e m e n t s ; nonconformance ranges from 49% at 435 tpa 

(10 ft x 10 ft) to 91% at 194 tpa (15 ft x 15 ft). 

Applying PCA To Knot Diameter and Rings 

Per Inch Simultaneously

Specifications must usually be considered jointly rather

than independently; trees must simultaneously satisfy having

the largest BH branch diameter not greater than 1.5 inches

and rpi not less than four and not greater than eight. Joint

specifications can be readily treated by a data plot or twovariable histogram. Figure 5 plots largest BH branch diameter vs rpi for the 194 tpa (15 ft x15 ft) density along with

specification limits for both quality characteristics; 98.3%

of the trees are nonconforming to both specifications. Figure

6 summarizes the results across all densities. Nonconformance to the joint specification ranges from 98% at 194

tpa (15 ft x 15 ft) to 56% at 435 tpa (10 ft x 10 ft). 

PCA OF DOUGLAS-FIR STANDS 

AT MULTIPLE TIME POINTS

Consider a 0.5-acre plot planted at 100 trees per acre

(21 ft x 21ft), one of the spacings in Stand Management

Cooperative (SMC) Type I Installations. This plot is part of

Installation 925 located near Belfast, WA on a moderately

poor site (SI 107). The installation was planted in 1990 with

2-0 Douglas-fir seedlings and has been measured every two

years starting in 1997. The SMC developed a BH branch/

knot assessment protocol that was first applied to the install a t i o n in 1999 hence this is one of few that has been measured with this procedure three times. The SMC BH knot

protocol for Douglas fir locates the first whorl of branches

above BH and the region from the point midway to the next

lower and next higher whorl. In this region, the diameter of

the largest branch is measured and the number of branches

that are at least 50% of this largest diameter are counted.

This procedure is applied to those trees on the plot that are

measured for crown and total heights. Table 2 summarizes

the plot at ages 9, 11, and 13. The base of the live crown is

below BH hence branches at BH are alive and growing in

147

Figure 4—Cumulative distributions of rings/inch of the Pilchuck Tree Farm spacing trial at age 18.
148

Figure 5—Largest diameter knot in the BH region at age 18 verses rings/inch of the 15-ft x 15-ft (194 tree/acre)

spacing at the Pilchuck Tree Farm.

Figure 6—Conformance of Pilchuck Tree Farm spacing trials to joint specifications at age 18 .
d i a m e t e r. Figure 7 presents cumulative distributions of

largest BH branch diameter as this plot has aged. It is easy

for management to monitor the progression of the stand

relative to a target specification for largest BH knot diameter and consider actions that may be taken to prevent

excessive nonconformance. 

Discussion and Management Implications

The examples presented above illustrate how producer

and consumer desires for quality properties can be converted into specifications for trees. For some properties such as

rings per inch, developing an acceptable tree specification

may involve trade-offs between the desires of the parties

that define a range of mutually acceptable values. PCA

allows managers to combine these specifications with sample-based frequency distributions from stands of interest to

estimate nonconformance. This provides important information on marketability of a stand and information that can

assist in choosing future management actions. Process capab i l i t y and conformance to specifications can be improved

by taking actions to shift the process mean and/or reduce

variation. Managers can monitor changes in process capability and the effectiveness of actions taken over time through

repeated sampling. The following paragraphs provide two

examples.

First, consider nearly mature or mature stands that are

being considered for harvest scheduling or are already

scheduled for sale. A producer, aware of the log specifications of potential consumers, can use PCA as part of sale

development to assess which consumers are more likely to

be interested in a stand and focus marketing efforts accordingly. Similarly, consumers can use PCA when they assess

a stand to decide if it is worthy of a bid. Organizations with

large timberland holdings may use PCA as a method for

assessing conformance of stands to alternative market specification sets. These market conformance options could be

included in harvest planning models to improve decisions

as to which stands should be harvested and when in order

to meet mill and other customer demands. For example, if

a company has a laminated veneer lumber (LVL) plant, it

149

Figure 7—Cumulative distributions of largest diameter BH knot verses age for 21-ft x 21-ft (100 tree/acre) spacing

at Stand Management Cooperarative Installation 925.

Table 2—Trees charasteristics by stand age at SMC installation 925, 21 ft x 21 ft 

(100 tpa) planting

Stand age

Charasteristics 9 11 13

D.b.h., in. 1.6 (0.54) N=49 2.6 (0.82) N=49 3.8 (0.89) N=49

Total height, ft 12.0 (2.72) N=49 15.6 (5.81) N=49 20.8 (7.31) N=49

Height to crown, ft 1.2 (0.54 ) N=49 1.2 (0.62) N=49 1.3 (0.91) N=49

Largest b.h. branch 

diameter, in 0.51(0.14) N=47 0.63(0.17) N=45 0.80(0.18) N=45
would like assurance that it’s harvest plan provides an adequate supply of timber with high potential to meet the needs

of the LVL plant product line.

Second, in immature stands, there are many ways that

P C A could assist in silvicultural planning. For example,

consider figure 8 where the plot of largest-diameter BH knot

and rings per inch has been segregated for trees larger and

smaller than 10 inches in dbh. This new detail shows how

well larger and smaller trees conform to the joint specification. This could assist in planning future silvicultural

activities such as deciding if a thinning should be done

and, if so, which trees to remove. A goal might be to try

to identify, retain and manage trees that maximize conformance of the final stand. As a different example, figure 7

showed the progression of largest diameter BH knot with

age in the SMC 100-tree-per-acre plot. Since the crown base

is very low on these trees, will the crown recede before too

many trees develop large branches and become nonconforming? If this is likely, is pruning justified? These examples

imply the need for a mechanism for projecting the results

of such actions and providing feedback. If growth and yield

models are being used to project the effects of alternative

actions, are they capable of tracking quality properties and

providing feedback in a PCA format? Silviculturists could

use such models to simulate various options and eliminate

those with poor conformance with anticipated future market

specifications. 

Although the applications of PCA presented in the examp l e s focused on knot diameter and rings per inch, the techniques could be easily extended to other properties such as

data gathered with the new Director ST-300TM technology

for non-destructive testing trees for MOE (Carter et al. 2005;

this proceedings). Figure 9 presents frequency histograms

of acoustic velocities obtained from an unthinned (n = 63

trees) and a thinned (n = 50 trees) plot in SMC Type II

Installation 803 at bh age 43 (Carter et al. 2005; this proceedings). If a mill specification stated that it prefers stands

with trees with velocities exceeding 4.3 km/sec, the thinned

stand, with 48% of trees above this threshold, is preferable

to the unthinned stand with only 27% exceeding this thresho l d . Furthermore, the mill may pay a premium for trees

exceeding 4.5 km/sec; 25% of trees in the thinned stand

meet this premium whereas only 12% of the unthinned

trees qualify. Combining tools such as the Director ST

300TM with PCA can provide landowners and mills with an

improved and more flexible method for matching timber

quality with market needs.

When using regression models to translate log values 

to tree values as done earlier with the conversion of LLAD

of logs to largest BH knot diameter, a consumer would note

that using the direct equation prediction of largest diameter

BH knot would result in a tree specification where some

trees with an acceptable largest diameter BH knot would

contain logs with an excessive LLAD (fig. 10). The consumer’s risk can be reduced by calculating a lower prediction limit, say 95%, which would reduce the largest diameter

BH knot specification from 1.5 to about 1.25 inches. The

use of lower limits is used in setting grades for machinestress-rated lumber. Note that this lower limit increases the

producer’s risk, as more trees with acceptable logs will be

rejected. Ultimately, the parties involved would negotiate 

a solution that strikes a balance between producer and

c o nsumer risks.

150

Figure 8—Largest diameter knot in the BH region at age 18 verses rings/inch by DBH of the 10-ft x 10-ft (435 tree/acre) spacing at the

Pilchuck Tree Farm.
CONCLUSIONS

Process capability analysis has been shown to be a useful technique for quantifying conformance of a variety of

quality properties of trees that are important to log consumers. Several important properties can be easily estimated

at or near BH with little additional cost. Requirements for

many log properties specified by consumers can be translated into counterpart values that can be easily measured on

the lower bole of trees in the field; these values appear to

be well correlated with the butt log. Sample size requirements appear to fit reasonably within the number of trees

that would be found in commonly used inventory plots. 

151

Figure 9—Cumulative frequencies of acoustic velocities measured by the Director ST-300TM in thinned and

unthinned plots at Stand Management Cooperative Installation 803.

Figure 10—Producer (grower) and consumer (mill) risks as influenced by maximum BH knot size and the largestlimb average diameter in the 16-ft butt log.
Given specifications for one or more tree properties,

management can use a suitable individual tree growth model

to make projections and estimate the degree of nonconformance when the stand becomes ready to harvest. Armed with

this information, cultural options such as density mana g ement, fertilization, and pruning can be forecast and evaluated in the context of how these options would influence

the proportion of the stand that would be nonconforming.

These projections would provide management planners and

harvest schedulers with improved insights concerning t h e

potential marketability of developing stands in their p o r tf o l i o and provide feedback with respect to the degree to

which remedial silvicultural options can reduce nonconformance.

LITERATURE CITED

Bowers, S. 1997. Key to Douglas-fir log grades. Forestry 

Extension. Corvallis, OR: Oregon State University.

Barbour, R.J.; Parry, D.L. 2001. Log and lumber grades 

as indicators of wood quality in 20- to 100-year-old

Douglas-fir trees from thinned and unthinned stands.

PNW-GTR-510. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research

Station. 22 p.

Carter, P.; Briggs, D.; Ross, R.J.; Wang, X. 2005. 

Acoustic testing to enhance western forest values and

meet consumer wood quality needs. In: Harrington,

C.A.; Schoenholtz, S.H. eds. Proceedings—Productivity

of Western Forests: A Forest Products Focus. Gen.

Tech. Rep PNW-GTR-abc. Portland, OR: U.S.

Department of Agriculture, Forest Service, Pacific

Northwest Research Station: GTR-642. 121-129.

Fahey, T.D.; Cahill, J.M.; Snellgrove, T.A.; Heath, L.S. 

1991. Lumber and veneer recovery from intensively

managed young-growth Douglas-fir. Res. Pap. PNWRP-437. Portland, OR: U.S. Department of Agriculture,

Forest Service, Pacific Northwest Research Station. 

25 p.

Flewelling, J.; Collier, R.L.; Gonyea, B. [etal.]. 2001. 

Height-age curves for planted stands of Douglas fir,

with adjustments for density. SMC Working Paper 1.

Seattle, WA: Stand Management Cooperative, College

of Forest Resources, Universiy of Washington. 25 p.

Hann, D.W.; Olsen, C.L.; Hester, A.S. 1997. ORGANON 

user’s manual: Edition 6.0. Corvallis, OR: Department

of Forest Resources, Oregon State University.

Ingaramo, L. 2003. Effect of initial density and planting 

design on growth and quality of young Douglas-fir: a

case study. Seattle, WA: College of Forest Resources,

Univesity of Washington. M.S. thesis. 87 p.

King, J.E. 1966. Site index curves for Douglas-fir in the 

Pacific Northwest. Weyerhaeuser Company Forestry

Paper No. 8. Centralia, WA: Weyerhaeuser Company,

Western Forestry Research Center.

Mitchell, K.J. 1975. Dynamics and simulated yield of 

Douglas-fir. Forest Science Monogram 17. 39 p.

Montgomery, D.C. 2001. Introduction to statistical quality 

control, 4th ed. Wiley. 796 p.

NWLRAG. 1998. Official log scaling and grading rules. 

Northwest Log Rules Advisory Group. 8th ed.

Ross, R.J.; Willits, S.W.; von Segen, W. [et al.]. 1999. 

A stress wave based approach to NDE of logs for

assessing potential veneer quality. Part 1. Small 

diameter ponderosa pine. Forest Products Journal

49(11/12): 60-62.

Sonne, E.; Turnblom, E.; Briggs, D.; Becker, G. 2004.

Log and lumber quality and value from a low site, 

55 year old Douglas-fir stand in western washington 20

years after thinning and biosolids fertilization. Western

Journal of Applied Forestry. 19(1): 1-8.

Wang, X., R. Ross, J.; McClellan, M. [et al.]. 2000. 

Strength and stiffness assessment of standing trees

using a nondestructive stress wave technique. Res. 

Pap. FPL-RP-585. Madison, WI: U.S. Department 

of Agriculture, Forest Service, Forest Products

Laboratory. 9 p.

Wang, S.; Ross, R.J.; Green, D.W. [et al.] 2004. Stress 

wave sorting of red maple logs for structural quality.

Wood Science and Technology 37: 531-537.

152
PAPERS BASED 

ON POSTERS 
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1 A.B. Adams, R.B. Harrison, M.M. Amoroso, D.G. Briggs, R. Collier, R. Gonyea, B. Hasselberg, J. Haukaas, and M.O. O’Shea are faculty and staff of the

College of Forest Resources, University of Washington, Box 352100, Bloedel Hall 292, Seattle, WA 98195.

Productivity of Western Forests: A Forest Products Focus

CARBON SEQUESTRATION IN DOUGLAS-FIR 

STANDS OF THE COASTAL CONIFEROUS FOREST

REGION OF WASHINGTON STATE

A.B. Adams, R.B. Harrison, M.M. Amoroso, D.G. Briggs, R. Collier,

R. Gonyea, B. Hasselberg, J. Haukaas, and M.O. O’Shea1

INTRODUCTION

There exist several ecosystem management strategies

directed toward enhancing carbon (C) sequestration through

forest management: 1) to partition C into longer-lived pools;

2) to increase the physical, chemical and biochemical protection of soil C; and, 3) to enhance C storage in living tree

biomass. The overall theme of our work is to relate management practices to soil organic carbon (SOC) partitioning

among alternative pools including dissolved organic carbon

(DOC) production and transport. Specifically, in this paper

we report on the storage of soil organic carbon (SOC)

based on texture, horizon, depth and fertilization with urea.

Gains in forest productivity have been shown with Douglasfir stands in the Pacific Northwest (Stegemoeller and

ABSTRACT

Quantifying the effects of urea fertilization on carbon (C) in the solid and solution phases of soils can aid forest management. We evaluated the effect of urea fertilization on pure second-growth Douglas-fir [Pseudotsuga menziesii (Mirb.)

Franco] stands growing in four soil series of the coastal coniferous forest region of Washington State. Our major objective

was to determine the range of carbon flux and sequestration for this region. This paper covers our results for soil organic

carbon (SOC) sequestration. Our soils were selected to give a range of texture from coarse-grained glacial to fine-textured

volcanic. We compared soil types, soil depths and fertilization treatments over 20-year intervals. There was no difference in

soil C in a coarse glacial outwash soil. By contrast, in a glacial sandy outwash soil all mineral horizons had more soil C and

the forest floor less C compared with the paired unfertilized plot. In two volcanic soils our results provide evidence that DOC

from the forest floor and A horizons was sequestered in both the epipedon and lower horizons. Differences between glacial

and volcanic soils suggest that mechanisms of C were different in the coarse-textured materials than the fine-textured volcanic material. Urea fertilization added nitrogen to soils at all installations with differences ranging from 1-3 Mg N ha- 1.

The 2 glacial soils had lower site indices. They had less SOC (mean of 87 versus 348 Mg ha- 1) but greater increases in

aboveground C (mean increase of 41 versus 8 Mg ha- 1). Although fine-textured sites were more productive overall, the

aboveground response to urea was limited in comparison to differences found in fertilized plots of the glacial sites. In

c o ntrast, SOC did increase with urea applications in fine-textured sites in excess of increases solely attributable to DOC.

KEYWORDS: Carbon sequestration, urea fertilization, managed Douglas-fir stands.

155

Chappell 1990). Increased aboveground biomass may

(Johnson 1992) or may not (Harding and Jokela 1994,

Canary et al. 2001) be accompanied by a gain in soil C. Urea

fertilizer can increase the movement of SOM (Kelly 1981).

Our initial hypothesis was that total C accumulation would

exceed C accumulation in wood plus roots in response to

nutrient management of fine-textured soil, but not on coarsetextured soils. This paper includes sequestration of SOC

and aboveground C, but does not cover root C.

The Regional Forest Nutritional Research Project

(RFNRP) (Stegemoeller et al., 1990) established installations in the Pacific Northwest to evaluate the response of

coastal Douglas-fir to urea-N fertilization. In 1991, this

project was combined with the Stand Management
Cooperative (SMC) in order to include research on integrated studies (SMC 1999). For this study we utilized the

stand database created by RFNRP and currently maintained

by the SMC at the University of Washington. The sites

[arranged in order from coarsest textured soil (Site 1) to

finest textured soil (Site 4)] used were Cedar River [RFNRP

#159 (a coarse glacial outwash soil)], Port Gamble [#196

(sandy outwash)], Radio Hill [#247 (coarse silty loam over

a compacted duripan)] and Mud Mountain [#235 (deep, silty

loam)]. These soils represent a regional association of parent material types from a very coarse skeletal matrix, to outwash sand and then to deep, silty loam. The skeletal matrices

of Sites 1 and 2 were derived predominantly from glacial

parent material and Sites 3 and 4 from tephra. The RFNRP

permanent plots revealed that following fertilization, the

periodic increment increased due to the N treatment, resulting in 49.9, 31.3, 6.4, and 9.7 Mg ha-1 additional C in the

four sites, respectively, for an average of 24.3 Mg ha- 1

additional C from a 16-year growth period (Adams et al.,

submitted). The largest aboveground tree responses were in

the glacial soils. This paper focuses specifically on the SOC

in relation to the aboveground live tree C compartments of

these stands.

METHODS

When the four installations were established (1972 to

1980), 224 kg ha-1 elemental N as urea fertilizer was added

to treatment plots. The same amount of fertilizer was then

again added at 8 and 16 years. In addition, Sites 1 and 2

received 224 kg ha-1 urea 12 years after installation. One

pit was dug and soils collected at each 0.1 ha plot (2 pits

per installation). Soil collections were made from the face

of pits using a hand trowel. Sampled layers were delineated

and measured based on color, texture and structure breaks.

All soils with texture < 25 mm and rocks ≥ 25 mm were

weighed as two separate components in the field. A 1 kg

sub-sample of the < 25 mm component was taken from

each field identified layer and used to determine field

moisture, particle size distribution (standard sieve procedures with dried samples), C and N content and pH. Mineral

soil was air-dried to constant weight. Forest floor material

was dried for 7 days at 70°C. The amount of C and N (in

Megagrams ha-1) were calculated for each layer based on

thickness, percent soil C or N, and bulk density (Db); then,

values for all layers were summed within each horizon.

Adams et al. (in prep.) contains a more detailed explanation

of the sites and methods.

RESULTS

The range of soil textures present was a function of

parent material. Although volcanic and glacial activity both

impact soils in the Pacific Northwest, the soil skeletal matrix

of the parent material is usually dominated by one of the

two processes. Our study found (fig. 1) that the two coarsetextured installations (Sites 1 and 2) were dominated by

glacial outwash with mixed mineralogy, whereas Sites 3 and

4 were volcanic in nature (ashy, silty loam). Rocks dominated Site 1, while sand dominated Site 2. Tephra dominated

Sites 3 and 4. Clay (which can play a role in C stabilization

and sequestration) (Brady and Weil 2002) was almost absent

from Site 1, but present on the other three sites where it

ranged from 5% to 9% by dry weight. 

There was a marginally significant difference in total

SOC between unfertilized and fertilized paired plots (p <

0.1, paired Student’s t-test analysis, n = 4 (fig. 2). There

was a significant difference in N between fertilized and

unfertilized plots (p < 0.05) and both N and C in glacial

soil were significantly less than N and C of volcanic soils

(p < 0.05, ANOVA, n = 8). A regression of the means of

soil C from the two pits at each site compared with percent

silt was significant (R2 = 0.91, F = 19.2, P < 0.05; Y =

4.3X +20.2, n = 8). 

When profiles for these soils are compared with respect

to C (fig. 3), forest floor C is less in fertilized compared to

unfertilized plots. In the sandy glacial outwash plots (Site

2), C is higher in all horizons; interestingly, the E and B

horizons show two or three times as much C as the same

horizons in the unfertilized plot. In the volcanic installations, the higher soil C content is due to larger amounts of

C in the A and AB (Site 3) or just the AB (Site 4) horizons.

Much of the SOC is found below the A horizon. This difference is due to larger volumes of soil included in the calculations to a one m depth as well as the increase in Db of

the < 2 mm fraction that was measured.

At all installations fertilized plots have less C in the forest floor than paired unfertilized plots (fig. 4), but this difference was negligible (< 1 Mg ha-1) at Site 1. In contrast,

mineral soil of fertilized plots at Sites 2, 3, and 4 had more

soil C relative to paired unfertilized controls. The differences in C sequestration between paired plots were mainly

attributable to larger amounts of soil C in fertilized plots

between 10 and 60 cm depths (Adams et al. in prep.). The

three sites with greater mineral soil C were more acidic and

had higher C/N ratios than paired unfertilized plots. T h e

greatest increases in C sequestration occurred between 5

and 60 cm and at C/N ratios between 20 and 35.

156
DISCUSSION AND CONCLUSIONS

Our results provide evidence that in fertilized coarsetextured soils (as manifested in glacial parent materials) C

sequestration is mostly in aboveground living trees, whereas fine-textured soils (in this case, products of volcanic parent

materials) have more C sequestered in soils. The mechanisms

for coarse-textured soils appear to be different than those

of fine-textured ones. The idea of mechanistic differences

is supported by lower pH values, higher C/N ratios and solubilization of fertilized forest floors. In the Central Puget

Sound, the proportion of silt in soil may play a major role

in the amount and nature of C sequestered. Besides texture,

mineralogy is undoubtedly playing a role in shaping the

results because the silt source in our study area is volcanic

as opposed to the mixed mineralogy from the glacial parent

material. The benefit to using texture as a criterion of C

sequestration and forest productivity is that it can be easily

and quickly determined in the field. Mineralogy, on the

157

Figure 1—Particle size distribution taken at 25 cm mineral soil depth for each site. Site 1 (Cedar River) had many large rocks and 

gravel with only 12% < 2mm. Site 2 (Port Gamble) was mostly sandy outwash. Site 3 (Radio Hill) was coarse loamy silt with some

rocks and Site 4 (Mud Mountain) was mostly silty loam with no rocks.

Figure 2—Distribution of C and N by site and treatment in 2001. All previously fertilized plots still had more nitrogen several years after cessation

of urea applications. Volcanic soils and treated soils had more carbon, but

this difference was only significant with volcanic versus glacial soils.

Please note that the Y axis is a log scale.
158

Figure 3—Distribution of C by site and soil profile. In all cases the fertilized O horizon had less C than did the unfertilized plot. There

was no difference between treated and control of Site 1, but the A, E and B fertilized horizons of Sites 2, 3 and 4 had much more C than

did their respective controls.

Figure 4—Forest floor (O horizon) C versus mineral soil C. Fertilized plots have more C in

the mineral soil, but less C in the forest floor relative to paired controls.
other hand, requires complicated analyses that are expensive in terms of time and money. The fact that volcanic soil

holds more C is not surprising. What is interesting is the

idea that C sequestered above ground varies with soil type;

in particular, the less productive sites sequester more C in

trees when N fertilizer is applied. 

ACKNOWLEDGMENTS

Research supported by the U.S. Department of Energy’s

Office of Science, Biological and Environmental Research

funding to the Consortium for Research on Enhancing

Carbon Sequestration in Terrestrial Ecosystems (CSITE).

Oak Ridge National Laboratory is managed by UT-Battelle,

LLC for the U.S.Department of Energy under contract

DE-AC05-00OR22725. Additional support came from the

PRISM program (Jeff Richey, University of Washington).

C . T. Garten and Bob Luxmoore helped to initiate and superv i s e the project. We are grateful to Weyerhaeuser Company,

The Campbell Group, The Hancock Co., Champion Pacific

Timberlands, Inc. and the City of Seattle for access to their

property.

LITERATURE CITED

Adams, A.B.; Harrison, R.B.; Sletten, R.S.; Jensen, 

C.M.; Strahm, B.D.; Turnblom, E.C. [in preparation]. Carbon movement and sequestration in managed

Douglas-fir stands in the coastal coniferous forest

region of Washington State.

Brady, N.C.; Weil, R.R. 2002. the nature and property of 

soils. 13th ed. [city unknown], NJ: Prentice Hall. 960 p.

Canary, J.D.; Harrison, R.B.; Compton, J.E.; Chappell, 

H.N. 2001. Additional carbon sequestration following

repeated urea fertilization of second-growth Douglas-fir

stands in western Washington. Forest Ecology

Mangement 138: 225-232.

Crane, W.J.B. 1972. Urea-nitrogen transformations, soil 

reactions, and elemental movement via leaching and

volatilization in a coniferous forest ecosystem after 

fertilization. Seattle, WA: University of Washington. 

Ph.D. dissertation. 250 p.

Harrison, R.B.; Adams, A.B.; Licata, C.; Flaming, B.; 

Wagoner, G.W.; Carpenter, P.; Vance, E.D. 2003.

Quantifying deep-soil and coarse-soil fractions: avoiding sampling bias in estimating carbon in Pacific

Northwest forest soils. Soil Science Society of 

America Journal 67: 1602-1606.

Johnson, D.W. 1992. Effects of forest management on soil 

carbon storage. Wa t e r, A i r,and Soil Pollution 64: 83-120.

Kelly, J.M. 1981. Carbon flux to surface mineral soil after 

nitrogen and phosphorus fertilization. Soil Science

Society of America Journal 45: 669-670.

Stand Management Cooperative [SMC]. 1999. What is 

the Stand Management Cooperative? SMC Fact Sheet,

No. 1. Seattle, WA: College of Forest Resources,

University of Washington. 10 p.

Stegemoeller, K.A.; Chappell, H.N. 1990. Growth 

response of unthinned and thinned Douglas-fir stands to

single and multiple applications of nitrogen. Canadian

Journal of Forest Research 20: 343-349.

Stegemoeller, K.A., Chappell, H.N., Bennett, W.S., 1990. 

Regional forest nutrition research project analysis hist ory: objectives and achievements. RFNRP Report No.

12. Seattle, WA: College of Forest Resources,

University of Washington. 33 p.

159
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1 Warren D. Devine and Constance A. Harrington are research foresters, USDA Forest Service PNW Research Station, Olympia Forestry Sciences 

Laboratory, 3625 93rd Ave SW, Olympia, WA 985122.

2 Thomas A. Terry is senior scientist, Weyerhaeuser Co., PO Box 420, Centralia, WA 98531.

3 Textures are apparent field textures as assessed by Darlene Zabowski, University of Washington.

Productivity of Western Forests: A Forest Products Focus

VOLUMETRIC SOIL WATER CONTENT

IN A 4-YEAR-OLD AND A 50-YEAR-OLD 

DOUGLAS-FIR STAND

Warren D. Devine1, Constance A. Harrington1, and Thomas A. Terry2

INTRODUCTION

Silvicultural practices can influence soil water in forest

stands (Langdon and Trousdell 1972). For example, modification of the forest canopy affects stand evapotranspiration

rates, which in turn may affect soil water content. In the

Pacific Northwest, removal of overstory conifers will quickly

result in increases in soil water (Keppeler and Ziemer 1990;

Adams et al. 1991; Gray et al. 2002). Thus, in compared

to that available in an unharvested area, clearcutting will

increase the amount of soil water available to the subsequently regenerated stand. Our objective in this study was

to compare growing-season volumetric soil water content

(VSWC) in two conifer stands: a young Douglas-fir plantation established after a clearcut and an adjacent 50-year-old

Douglas-fir/western hemlock [Tsuga heterophylla (Raf.)

Sarg.] stand.

METHODS

We investigated two adjacent stands, one established 

in 1953 and one in 2000, on a highly productive site in the

161

Coast Range of southwestern WA, USA. Mean annual precipitation is 2260 mm, but an average of only 241 mm

occurs from 1 June through 30 September (USDA 1 9 9 9 ) .

Topography is gently sloping, and soil is of the Boistfort

series (medial over clayey, ferrihydritic over parasesquic,

mesic Typic Fulvudands), with a silt loam A horizon (12- to

17-cm thick) underlain by a silt loam AB horizon (19- to

24-cm thick) and a silty clay loam Bw horizon (to >140

c m )3. Soils are derived from basalt, with volcanic ash influe n c e , and are well drained, low in bulk density, and high in

available water capacity.

Until 1999, the entire study area was occupied by

Douglas-fir planted in 1953 and western hemlock that

established naturally (Terry et al. 2001). In 1999, a portion

of this stand was harvested, removing a volume of 914 m3

ha-1 (55% Douglas-fir; 45% western hemlock). In the harvested area, the Fall River Long-Term Site Productivity

study (LTSP) was established, and 1+1 Douglas-fir seedlings

were planted at a 2.5- x 2.5-m spacing in March 2000.

Although the LTSP study examines a range of treatments,

we collected data from a single treatment: a bole-only harvest of the previous stand and no vegetation control. We

ABSTRACT

We compared growing-season soil water content in a young Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] plantation

(established in 2000 with no vegetation control) to that of an adjacent 50-year-old conifer stand on a highly productive site in

southwestern WA. Soil water content in the older stand was slightly greater than that of the younger stand at soil depths of 10

and 30 cm during the 2003 and 2004 growing seasons. At 100 cm, soil water content was similar between stands. During the

2003 growing season, when precipitation was below average, soil water content declined by a similar amount in both stands.

K E Y W O R D S: Soil water, Douglas-fir, regeneration, evaporation, transpiration.
chose the treatment without vegetation control because we

considered it analogous to the understory conditions of the

stand established in 1953.

Using a Profile Probe® ( D e l t a - T Devices Ltd., Cambridge,

UK), we measured volumetric soil water content (VSWC)

at six depths (10-100 cm) at 3- to 4-week intervals during

the 2003 and 2004 growing seasons. In 2003, we sampled

12 locations in the 2000 stand and 4 locations in the 1953

stand; in 2004, the number of locations was increased to 21

and 6 in the 2000 and 1953 stands, respectively. Data were

recorded in millivolts (mv) and subsequently converted to

VSWC using a soil-specific calibration [% VSWC = (0.057

* mv) + 21.67]. We calculated VSWC loss during the

2003 growing season by subtracting values recorded on 4

September from those recorded on 1 May. Because data

presented here were not part of the randomized block design

of the LTSP study, we did not use analysis of variance.

RESULTS AND DISCUSSION

Growing-season fluctuations in VSWC varied between

2003 and 2004 due to large differences in precipitation (fig.

1). Precipitation during the 2003 growing season was 50%

of the long-term average, while in 2004 it was 134% of

162

Figure 1—Volumetric soil water content (VSWC, ± standard deviation) at 10-, 30-, and 100-cm soil depths during

2003 and 2004 in two forest stands. Data missing for 25 September 2003 in the 1953 stand.
163

average. In 2003, VSWC decreased from May through early

September in both stands at 10- and 30-cm depths. In 2004,

VSWC decreased only from June through July at these

depths because of above-average precipitation earlier and

later in the growing season.

At shallow sample depths, particularly 10 cm, V S W C

was generally greater in the 1953 stand than in the 2000

stand. At greater depths, VSWC was similar between the

stands. Seasonal fluctuations in VSWC also were similar

between stands. There were no differences in VSWC loss

between the two stands during the 2003 growing season at

any of the sample depths (fig. 2).

The overall similarities in VSWC between the two

stands were unanticipated. We had hypothesized that during

the growing season, VSWC would decrease by a greater

amount in the 1953 stand than in the 2000 stand as a result

of greater transpiration by the larger trees. It has previously

been shown that growing-season soil water content was

lower in a closed-canopy Douglas-fir forest relative to forest openings (Gray et al. 2002; Lindh et al. 2003). However,

vegetation regrowth after clearcutting can have a strong,

negative effect on soil water content (Adams et al. 1991).

The contribution of understory vegetation to total transpiration was likely greater in the 2000 stand than in the

1953 stand. Total dry biomass of understory vegetation in

the 2000 stand (sampled in 2004) was much greater (2940

kg ha-1) than that in the 1953 stand (221 kg ha-1). Much 

of this vegetation in the 2000 stand consisted of generally

shallow-rooted herbaceous species that may have reduced

VSWC near the soil surface. Furthermore, the transpiration

rate of the vegetation in the 2000 stand was probably

greater than that of the vegetation in the 1953 stand because

of microclimate differences caused by the forest canopy.

For example, from June through August 2002, the temperature at the forest floor was, on average, 4.8° C higher in 

the 2000 stand than in the 1953 stand. Increased air temperatures result in greater transpiration rates due to a

greater vapor pressure gradient between leaves and air

(Kramer and Kozlowski 1979).

Processes other than transpiration may have differently

influenced the soil water content of the two stands in this

study. Evaporation at the soil surface may have been lower

in the 1953 stand relative to the 2000 stand due to less

solar radiation reaching the ground as well as the mulching

effect of the undisturbed forest floor (Hillel 1998). At a soil

depth of 5 cm, summer soil temperatures averaged 4.2° C

less in the 1953 stand than in the 2000 stand. Thus, cooler

soil temperatures may have led to greater VSWC in the

1953 stand, especially at shallow depths. It is also possible

that the soil water content in the measured profile of the

1953 stand was influenced by hydraulic redistribution from

deeper soil layers. Elsewhere in the region, it has been

shown that water is transported upward in the soil profile

as a consequence of water uptake by overstory trees (Brooks

et al. 2002; Unsworth et al. 2004); however, the soil water

contents in our soils were higher than the levels at which

this phenomenon is likely to be operating.

Figure 2—The loss in volumetric soil water content (VSWC, ± standard deviation) from 1 May to 4 September 2003 in two forest stands.
164

While the final harvest of the previous stand in 1999

probably caused a temporary increase in soil water, soil

water content by age four in the 2000 stand was similar to

or less than that in the adjacent 50-year-old stand. In the

younger stand, transpiration, and possibly evaporation at

the soil surface, were reducing soil water to an extent

similar to that of the overstory trees in the older stand.

ACKNOWLEDGMENTS

We thank our current and former coworkers at the

Olympia Forestry Sciences Laboratory for their field work

in this study and Douglas Waldren for instrument calibration. Funding was provided by an American Forest & Paper

Association-USDA Forest Service Agenda 2020 grant and

the USDA Forest Service PNW Research Station.

LITERATURE CITED

Adams, P.W.; Flint, A.L.; Fredriksen, R.I. 1991. Longterm patterns in soil moisture and revegetation after 

a clearcut of a Douglas-fir forest in Oregon. Forest

Ecology Management 41: 249-263.

Brooks, J.R.; Meinzer, F.C.; Coulombe, R.; Gregg, J.R. 

2002. Hydraulic redistribution of soil water during 

summer drought in two contrasting Pacific Northwest

coniferous forests. Tree Physiology 22: 1107-1117.

Gray, A.N.; Spies, T.A.; Easter, M.J. 2002. Microclimate 

and soil moisture responses to gap formation in coastal

Douglas-fir forests. Canadian Journal of Forest

Research 32: 332-343.

Hillel, D. 1998. Environmental Soil Physics. San Diego, 

CA: Academic Press. 771 p.

Keppeler, E.T.; Ziemer, R.R. 1990. Logging effects on 

streamflow: water yield and summer low flows at

Caspar Creek in northwestern California. Water

Resources Research 26(7): 1669-1679.

Kramer, P.J.; Kozlowski, T.T. 1979. Physiology of 

Woody Plants. New York, NY: Academic Press. 811 p.

Langdon, O.G.; Trousdell, K.B. 1978. Stand manipulation: effects on soil moisture and tree growth in southern pine and pine-hardwood stands. In: Balmer, W.E.,

ed. Soil moisture...Site productivity: Symposium proceedings. Atlanta, GA: U.S. Department of Agriculture,

Forest Service, Southern Region: 221-236.

Lindh, B.C.; Gray, A.N.; Spies, T.A. 2003. Responses 

of herbs and shrubs to reduced root competition under

canopies and in gaps: a trenching experiment in oldgrowth Douglas-fir forests. Canadian Journal of Forest

Research 33: 2052-2057.

Terry, T.A.; Harrison, R.B.; Harrington, C.A. 2001.

Fall River long-term site productivity study: objectives

and design. Forest Research Technical Note, Site productivity paper 01-1. Centralia, WA: Weyerhaeuser

Company, Western Timberlands R&D. 10 p.

Unsworth, M.H.; Phillips, N.; Link, T.; Bond, B.J.; 

Falk, M.; Harmon, M.E.; Hinckley, T.M.; Marks, D.;

Paw U, K.T. 2004. Components and controls of water

flux in an old-growth Douglas-fir—western hemlock

ecosystem. Ecosystems 7: 468-481.

USDA Natural Resource Conservation Service, 

National Water and Climate Center, and Oregon

State University Spatial Climate Analysis Service.

1999. Parameter-elevation regressions on independent

slopes model (PRISM). http://www.wcc.nrcs.usda.gov/

climate/prism.html
1 Brian D. Strahm, Robert B. Harrison, Barry L. Flaming, Christopher W. Licata and Kyle S. Petersen are members of a forest soils research team,

University of Washington, College of Forest Resources, Box 352100, Seattle, WA 98195.

2 Thomas A. Terry is research forester, Western Forestry Research, Weyerhaeuser Company, Centralia, WA 98513.

Productivity of Western Forests: A Forest Products Focus

FACTORS AFFECTING NITROGEN MOBILITY:

ORGANIC MATTER RETENTION AND 

VARIABLE-CHARGE SOILS

Brian D. Strahm1, Robert B. Harrison1, Thomas A. Terry2,

Barry L. Flaming1, Christopher W. Licata1, and Kyle S. Petersen1

ABSTRACT

Forest harvesting and organic matter management practices may affect the cycling of nutrients, particularly nitrogen (N),

through the removal of different organic matter components (e.g., branches, foliage, coarse-woody debris) from a site, and

the associated changes in carbon-source quantity and quality. Such practices may also alter microclimatic conditions that

influence N cycling processes, thereby affecting the rates at which N is made available to plants or is leached through t h e

profile. This study examined the influence of intensive harvesting and organic matter retention practices on soil N dynamics

on a highly productive (Site Index I-II+) coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) site in southwestern

Washington; the study results are from a time period when all competing vegetation was controlled. Additionally, this study

addresses the ability of the Boistfort soil series (Typic Fulvand) to retain nitrate (NO3) as a function of soil mineralogy and

solution concentration. The specific focus of this investigation was to determine the effects of bole-only (BO) harvesting

and total-tree harvesting plus coarse woody debris removal (TP) on soil-solution N concentrations and leaching rates (to a

depth of 1.0 m) during the third through fifth year following harvest. Additional comparisons were made between the harvested treatments and the adjacent non-harvested stand (FS) representative of the initial stand condition. Solution concentrations were then related to NO3- sorption isotherms generated using batch equilibration techniques to determine the quantity

of NO3- retained via sorption. 

Soil-solution monitoring from April 2001 through March 2004 indicated that the increased organic matter retention associated with BO harvesting treatment increased the total N concentrations and leaching flux to a depth of 1.0 m by roughly

two to three times that of TP harvest treatments. Nitrate comprised a majority of the 75, 29 and 4.5 kg ha-1 yr-1 of total N

leached in the BO, TP and FS observations, respectively. The annual nitrogen leaching rates to a depth of 1.0 m however,

are a small percentage of the 15 Mg ha-1 total soil N pool to a depth of 1.0 m (0.5, 0.2 and <0.03%, respectively). Similarly,

the amount of NO3

- sorbed to the mineral surface represents a small fraction of the total soil N pool, however, it comprises

41, 53 and 152% of the NO3

- leached from the BO, TP and FS observations, respectively.

KEYWORDS: Nitrogen leaching, nitrate sorption, organic matter retention, soil-solution.

165
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OVERVIEW OF

STUDY AREAS 

VISITED ON 

FIELD TRIPS
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1 Constance A. Harrington is research forester, USDA Forest Service, Pacific Northwest Research Station, Olympia Forestry Sciences Laboratory,

3625 93rd Ave SW, Olympia, WA 98512.

2 Thomas A. Terry is senior scientist, Weyerhaeuser Company, PO Box 420, Centralia, WA 98531.

3 Robert B. Harrison is professor of forest soils, University of Washington, College of Forest Resources, 218 Bloedel Hall, Box 352100, Seattle, WA

98195-2100.

Productivity of Western Forests: A Forest Products Focus

FALL RIVER LONG-TERM SITE 

PRODUCTIVITY STUDY

Constance A. Harrington1, Thomas A. Terry2, and Robert B. Harrison3

INTRODUCTION

Intensive forest management practices aimed at increasing the production of wood products have raised questions

regarding potential detrimental effects to sustained forest

p r o d u c t i v i t y. Management practices such as harvesting

mechanization, harvesting intensity, and vegetation control

can affect tree growth and site productivity by creating soil

disturbance, removing nutrients in biomass, changing seedling microclimate, and altering plant community composition and the distribution of nutrients and biomass between

trees and non-trees.

How these factors affect forest growth over the short as

well as the long term (multiple rotations) is not well understood. In addition, the ameliorative potential of practices

such as soil tillage and nitrogen fertilization for maintaining

ABSTRACT

The Fall River Long-Term Site Productivity study is a cooperative project designed to examine factors influencing shortand long-term productivity and how management practices affect both tree growth and soil characteristics. The study was

established after the existing Douglas-fir/western hemlock stand was harvested in 1999 and several levels of biomass retention were created as major treatments in the study. The study also includes fertilization, vegetation control, compaction, and

tillage. Douglas-fir seedlings were planted in spring 2000 and several tree and soil assessments have been made since then.

Early results indicate that biomass removals and compaction/tillage affected physical and chemical soil properties but vegetation control was the primary factor affecting tree growth.

KEYWORDS: Douglas-fir, site productivity, seedling growth, vegetation management, woody debris retention, biomass

removal, compaction, soil tillage, nitrogen cycling.

169

and enhancing forest productivity needs to be evaluated. T h e

Fall River study will begin to fill a data gap that exists in

the Pacific Northwest for the management of Douglas-fir

forests. Fall River is an affiliate site in the Long-Term Soil

Productivity Study coordinated by the U.S. Forest Service

in several major forest production regions of the U.S. and

Canada. Fall River investigators also coordinate with scientists working on other productivity studies in the Pacific

Northwest.

STUDY OBJECTIVES

The overall objective of this study is to examine the

impacts of a range of biomass removal/wood retention

treatments and forest management practices on long-term

p r o d u c t i v i t y. The experiment was installed in 1999-2000 

on a highly productive Douglas-fir site on We y e r h a e u s e r
C o m p a n y ’s McDonald Tree Farm in southwestern Wa s h -

i n g t o n . Fertile soils such as those present at the study site

cover extensive areas in western Washington and are managed intensively for Douglas-fir wood production. 

Specific research objectives are:

1) Evaluate effects of four levels of biomass removal on

soil and Douglas-fir growth over a 40-year rotation.

2) Develop nutrient budgets for various levels of harvest

and biomass removal.

3) Determine the impact of soil compaction and tillage on

soil properties and tree growth. 

4) Evaluate the need for fertilization and its effects on

nutrient supply and tree growth.

5) Assess the effects of vegetation control and fertilization

on tree growth, plant community composition, and soil

characteristics.

6) Evaluate differences in seedling physiology and microclimate associated with the treatments.

The study addresses one of the priority topics in AF&

PAAgenda 2020–-Achieve and Sustain the Full Productivity

Potential of Forest Soils. The study also addresses the

Pacific Northwest Research Station’s Priority Research

Area: Produce Wood within Sustainable Frameworks.

METHODS

Site Description

The study area is on a 20-ha, very productive, low-elevation (300 m), gently sloping (<10 to 15%) site in the Coast

Range Mountains located 60 km southwest of Olympia,

WA, USA (Terry et al. 2001). Mean annual precipitation is

2260 mm, falling mostly as rain from September through

M a y. Temperatures are mild (9.2°C mean annual) with mean

January low of only -0.1°C (USDA NRCS 1999). The soil

is a deep, well-drained silt loam over silty clay loam (Typic

Fulvudand in the Boistfort series) developed from highly

weathered basalt with ash influences in the upper horizons

(Steinbrenner and Gehrke 1973). 

Study Treatments

Study treatments were designed to look at factors of

interest to both scientists and managers. Some treatments

were operational while others were designed to “stretch”

the system, that is, to implement treatments that are not

operational but would provide valuable information on

long-term productivity (table 1). In addition, the study was

designed to include treatments that could ameliorate problems if there was a reduction in productivity in one or more

of the treatments. For example, fertilization was included

to determine if fertilizer additions could compensate for

o rganic matter removals and a compaction-followed-bytillage treatment was included to see if tillage could eliminate any deleterious effects on soil characteristics or tree

growth induced by compaction. 

The overall study design is a randomized complete block

with 4 blocks. Treatment plots are 30 X 80 m. Study measurements include: tree size, condition and nutrient content;

cover, species composition, biomass, and nutrient content

of non-tree vegetation; volumetric soil water by depth; N

in soil water; soil and air microclimate; and soil physical

properties. A complete meteorological station is maintained

onsite (fig. 1).

RESULTS

Seedling growth and non-tree vegetation 

for years 1-4 (fig. 2)

• Seedling growth was markedly lower in the treatment

without vegetation control 

• There was no significant difference in tree size associated

with amount of biomass removed

• Compaction associated with harvesting was not detrimental to seedling growth

• Cover of non-tree vegetation was negatively correlated

with soil moisture content and tree growth (for more information on tree responses, see Roberts et al. 2005).

Microclimate during growing season: 

• Soil moisture was a good predictor of seedling volume

both across and within treatments

• Without vegetation control, soil moisture was lower

(Roberts et al. 2005)

• With removal of residues, soil moisture was lower

• With compaction, soil moisture was higher

• Soil temperature during the growing season increased

with intensity of residue removal

• Warmer temperatures were beneficial to tree growth when

soil moisture during the growing season was high

Soil physical properties:

Soil compaction in traffic lanes affected soil properties

but they did not exceed critical levels (for more information on this topic, see Ares et al. 2005)

170
• Bulk density in the 0- to 30-cm depth was increased by

compaction from 0.63 to 0.82 Mg m-3

• Macroporosity at 10- to 20-cm depth decreased in compacted areas (0.36 to 0.19 m3 m-3) but did not drop below

0.10 m3 m-3, the level that is usually considered limiting

for tree growth

171

• Soil strength in traffic lanes increased at all depths < 55 cm

but never exceeded 1300 kPa; the critical value for impacting tree growth is usually considered to be >2000 to 3000

kPa

• Available water and early tree growth were both increased

in traffic lanes 

Nitrogen movement and cycling:

The adjacent uncut forest (50-year-old stand) and two

of the biomass removal treatments differed in the amount

of total N in soil solution at 100 cm: Bole only (BO) >

Total Tree plus (TT+) > Uncut forest (for more information

on soil chemistry, see Strahm et al. 2005a and Strahm et al.

2005b)

• Nitrate was the major form of N in soil solution at 100 cm.

• NO3 accounted for 92% of N in BO, 84% in TT+, and

57% in the adjacent uncut forest.

Average annual leaching of total N to 100 cm from

April 2001 through March 2004 was: 75 kg/ha/yr for BO,

29 kg/ha/yr for TT+, and 4.5 kg/ha/yr for the adjacent

uncut forest.

• Percent N in Douglas-fir foliage was lowest in the treatment without vegetation control (Roberts et al. 2005)

• Percent N in Douglas-fir foliage was similar across 

biomass removal levels (Roberts et al. 2005)

Table 1—Plot-level treatments at the Fall River Long-Term Site Productivity study

Vegetation

Biomass Removal1 Fertilization2 control Compaction Tillage

Total tree plus + + - -

Total tree plus - + - -

Total tree + + - -

Total tree - + - -

Bole only, 5-cm top + + - -

Bole only, 5-cm top - + - -

Bole only + + - -

Bole only - + - -

Bole only + - - -

Bole only - - - -

Bole only + + + -

Bole only + + + +

1 Total tree plus = removal of entire tree bole and branches with foliage attached plus removal of legacy

woody debris (old-growth logs); Total tree = removal of entire tree bole and branches with foliage attached;

Bole only, 5-cm top = removal of the tree bole to a 5-cm top diameter (non-merchantable material that met

this diameter limit was also removed); Bole only = removal of tree bole to normal merchantability standards

(10-cm top, no removal of broken, rotten or otherwise defective material).

2 Fertilization treatments have not yet been applied.

Figure 1—The weather station at the Fall River study site records information for many meteorological factors.
ACKNOWLEDGMENTS

Financial support for this project has been provided by

Weyerhaeuser Company, the Northwest Stand Management

Cooperative, the National Council for Air and Stream

Improvement, the Olympic Natural Resource Center, the

Pacific Northwest Research Station, and Agenda2020 (a

joint project of the USDA Forest Service, Research &

Development and the American Forest and Paper

Association).

LITERATURE CITED

Ares, A.; Terry, T.A.; Miller, R.E.; Anderson, H.W.; 

Flaming, B.L. 2005. [In press]. Ground-based forest

harvesting effects on soil physical properties and

Douglas-fir growth on a coastal Washington site. 

Soil Science Society of America Journal.

Steinbrenner, E.C.; Gehrke; F.E. 1973. Soil survey of 

the McDonald Tree Farm. Tacoma, WA: Weyerhaeuser

Company.

Strahm, B.D.; Harrison, R.B.; Flaming, B.L.; Terry,

T.A.; Licata, C.W.; Petersen, K.S. 2005a. [In preparation]. Soil-solution nitrogen concentrations and

leaching rates as influenced by organic matter retention

on a highly productive Douglas-fir site.

Strahm, B.D.; Harrison, R.B.; Flaming, B.L.; Terry,

T.A.; Licata, C.W.; Petersen, K. S. 2005b. Factors

affecting nitrogen mobility: Organic matter retention a n d

v a r i a b l e - c h a rge soils. In: Harrington, C.A.; Schoenholtz,

S.H., eds. Proceedings of Productivity of western forests;

a forest products focus. Gen. Tech. Rep. PNW- G T R - 6 4 2 .

Portland, Oregon: U.S. Department of Agriculture,

Forest Service, Pacific Northwest Research Station: 165.

Terry, T.A.; Harrison, R.B.; Harrington, C.A. 2001.

Fall River long-term site productivity study: objectives

and design. Paper #01-1, Forestry Research Technical

Note, Weyerhaeuser Company, Western Timberlands

R&D. 10 p.

Roberts, S.D.; Harrington, C.A.; Terry, T.A. 2005.

Harvest residue and competing vegetation affect soil

moisture, soil temperature, N availability, and Douglasfir seedling growth. Forest Ecology and Management

205: 333-350.

USDA Natural Resources Conservation Service, 

National Water and Climate Center; and Oregon

State University Spatial Climate Analysis Service.

1999. Parameter-elevation Regressions on Independent

Slopes Model (PRISM). http://www.wcc.nrcs.usda.gov/

water/climate/prism/prism.html.

172

Figure 2—Effects of treatments on year-4 volume index (calculated as basal diameter squared times total

height). Bars with the same letter above them do not differ at p < 0.05.
1 Timothy B. Harrington and Constance A. Harrington are research foresters, USDA Forest Service, PNW Research Station, Forestry Sciences Laboratory,

3625 93rd Avenue, Olympia, WA 98512.

2 Stephen H. Schoenholtz is associate professor, Department of Forest Engineering, Oregon State University, Corvallis, OR 97331.

Productivity of Western Forests: A Forest Products Focus

FOREST PRODUCTIVITY RESPONSES TO LOGGING 

DEBRIS AND COMPETING VEGETATION: EFFECTS OF

ANNUAL PRECIPITATION AND SOIL TEXTURE

Timothy B. Harrington1, Constance A. Harrington1, and Stephen H. Schoenholtz2

STUDY OBJECTIVES AND TREATMENTS

In 1998, the Fall River long-term site productivity (LT S P )

study was initiated to examine effects of logging debris

removal, competing vegetation control, fertilization, compaction, and tillage on soil characteristics and Douglas-fir

growth (Terry et al. 2001). The study is affiliated with the

national network of Long-Term Soil Productivity studies

(Powers et al. 1990). In 2002, the Agenda 2020 program,

members of forest industry, and the USDA Forest Service,

P N W Research Station provided financial support to initiate an expansion of the Fall River research. The new research

was designed to quantify potential effects of annual precipitation and soil texture on Douglas-fir responses to logging

debris manipulation and competing vegetation removal. Six

treatments have been replicated at two sites: Matlock WA

(Olympic Peninsula) and Molalla OR (Western Cascades).

The sites differ from Fall River and from each other in soil

texture, precipitation, and temperature (fig. 1). Each site is

an independent study.

173

The research will quantify stand establishment, early 

(1 to 5 years) and longer-term (5 to 20 years) growth of

planted Douglas-fir, and long–term site productivity. A

variety of pre-treatment and first-year measurements have

been taken at each site, including soil nutrient content, bulk

d e n s i t y, in situ net nitrogen mineralization and needle decomposition rates, logging debris mass and soil disturbance

i n t e n s i t y, competing vegetation abundance, microclimate

(air and soil temperatures and soil water content), and

Douglas-fir initial size. The specific research objectives

are to determine:

1. effects of logging debris abundance (retained vs.

removed) and spatial distribution (dispersed vs. piled) 

and competing vegetation (presence vs. absence) on 

selected soil factors.

2. influence of soil responses on early growth and 

nutrition of Douglas-fir seedlings.

3. whether soil and Douglas-fir responses vary between

sites differing in annual precipitation and soil texture.

ABSTRACT

Logging debris and competing vegetation are being manipulated at two sites to determine their potential influences on

selected soil factors and productivity of planted Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii). The

sites, located at Matlock WA and Molalla OR, were selected to differ in annual precipitation and soil texture. As part of the

field tour for the Forest Productivity Conference, participants visited the Matlock site to observe the various treatments and

vegetation responses in the first year since study initiation.

KEYWORDS: Long-term site productivity, soil properties, microclimate, plantations.
174

The following experimental treatments have been replicated four times at each

site in a randomized complete block design:

Competing

Logging debris treatment vegetation

control

1. Stem-only harvest: removal of merchantable logs

only (i.e., retention of logging debris) Absent Present

2. Stem-only harvest + piling: removal of merchantable 

logs plus moving of tops and limbs into piles (i.e., 

retention and piling of logging debris). Absent Present

3. Whole-tree harvest: removal of merchantable logs 

plus tops and limbs (i.e., removal of logging debris) Absent Present

Figure 1—Predicted average monthly values for (a) 

precipitation and (b) air temperature at three forest 

productivity study sites in Washington and Oregon.

Values were predicted from the PRISM model

(Spatial Climate Analysis Service 2005).
175

CURRENT FINDINGS

In the first 3 or 4 months after treatment, mass of logging debris varied nearly two-fold between the stem-only

(20.5 to 20.7 Mg ha- 1) and whole-tree (10.9 to 12.3 Mg

h a- 1) harvesting treatments at each site. In August 2004,

first-year cover of competing vegetation differed between

herbicide-treated and non-treated plots at Matlock (12%

vs. 20%, respectively) but not at Molalla (61% vs. 59%,

respectively) where trailing blackberry (Rubus ursinus

Cham. & Schlecht.) became dominant. The logging debris

treatments had no detectable effect on abundance of competing vegetation at either site. Additional herbicide treatments are planned to achieve vegetation-free conditions 

on 80% or more of the area within treated plots. Although

first-year measurements of the planted Douglas-fir have 

not yet been completed, field observations indicate that

survival will be more than adequate for long-term monitoring of forest productivity.

FUTURE DIRECTION

In 2004, additional funding was received from the

Agenda 2020 program to begin a new phase of research at

Matlock and Molalla. Abundance of logging debris will be

varied systematically to quantify the level at which it causes potential effects such as increased soil water conservation and thermal insulation, and shifting roles as a nitrogen

source vs. a nitrogen sink. Logging debris will be applied

to create 0, 40, or 80% covers (±10%) in 2- x 2-m areas

around individual Douglas-fir growing either with or without competing vegetation. This new phase of research will

identify some of the mechanisms by which logging debris

and competing vegetation influence Douglas-fir product i v i t y. In combination with the Fall River study, the research

will contribute to a regional database that will enable forest

managers to make more effective silvicultural prescriptions

for maintaining or enhancing productivity of Douglas-fir

plantations.

ACKNOWLEDGMENTS

This is a product of the Sustainable Forestry component

of Agenda 2020, a joint effort of the USDA Forest Service

Research & Development and the American Forest and

Paper Association. Research partners include Oregon State

University (OSU), University of Washington, Port Blakely

Tree Farms LP, Green Diamond Resource Company, and

Green Crow Ltd. Funds were provided by Pacific Northwest

Research Station, USDA Forest Service and OSU

(Agreements # PNW-JV-11 2 6 1 9 9 3 - 111 and PNW- C A -

11261993-137), and in-kind contributions (e.g., treatment

and equipment costs, field assistance, etc) were provided

by the members of forest industry cited above.

LITERATURE CITED

Terry, T.A.; Harrison, R.B.; Harrington, C.A. 2001. Fall 

River long-term site productivity study: objectives and

design. Paper #01-1, Forestry Research Technical Note,

Weyerhaeuser Company, Western Timberlands R&D. 

10 p.

Powers, R.F.; Alban, D.H.; Miller, R.E.; Tiarks, A.E.; 

Wells, C.G.; Avers, P.E.; Cline, R.G.; Fitzgerald,

R.O.; Loftus, N.S., Jr. 1990. Sustaining site productivity in North American forests: problems and prospects.

In: Gessel, S.P; Lacate, D.S; Weetman,G.F.; Powers,

R.F. (eds.), Proceedings: 7th North American Forest

Soils Conference on Sustained Productivity of Forest

Soils. Victoria, BC: University of British Columbia:

49-79.

Spatial Climate Analysis Service. Oregon State University,

h t t p : / / w w w.ocs.oregonstate.edu/prism/, [28 March 2005].
176

METRIC EQUIVALENTS

When you know: Multiply by: To find:

Degrees Fahrenheit (°F) (F-32) x 0.556 Degrees Celsius (°C)

Inches (in) 2.54 Centimeters (cm)

Feet (ft) .3048 Meters (m)

Acres (ac) .4047 Hectares (ha)

Trees per acre 2.471 Trees per hectare

Square feet per acre (ft2/ac) .2296 Square meters per hectare (m2/ha)

Thousand board feet (MBF) .0024 Cubic meters (m3)

Fluid ounces .0296 Liters (L)

Gallons 3.78 Liters (L)

ENGLISH EQUIVALENTS

When you know: Multiply by: To find:

Degrees Celsius (°C) (C*9/5) +32 Degrees Fahrenheit (°F)

Centimeters (cm) .3937 Inches (in) 

Meters (m) 3.2808 Feet (ft)

Kilometers (km) 0.6214 Miles (m)

Square meters per hectare (m2/ha) 4.3560 Square feet per acre (ft2/ac)
The F o rest Service of the U.S. Department of Agriculture is dedicated to the principle of 

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

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

private forest owners, and management of the national forest and national grasslands, it strives

—as directed by Congress—to provide increasingly greater service to a growing Nation.

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

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

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

political beliefs, reprisal, or because all or part of an individual’s income is derived from any

public assistance program. (Not all prohibited bases apply to all programs.) Persons with

disabilities who require alternative means for communication of program information (Braille,

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

and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil

Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-

795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and

employer.

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