United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

General Technical 

Report

PNW-GTR-828

October 2010

A Tale of Two Cedars:

International Symposium 

on Western Redcedar 

and Yellow-Cedar
_____________________________

U.S. Department of Agriculture

Pacific Northwest Research Station

333 S.W. First Avenue

P.O. Box 3890

Portland, OR 97208-3890

Technical Coordinator

Constance A. Harrington, research forester, U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station, 3625 93rd Ave. SW, Olympia, WA 98512-

9193

Credits

Cover photography by Constance A. Harrington and Joseph M. Kraft, U.S. Department 

of Agriculture, Forest Service, Pacific Northwest Research Station, 3625 93rd Ave. SW, 

Olympia, WA 98512-9193. Artwork on inside title page and section dividers by Jodie 

Krakowski, BC Ministry of Forests and Range, Research, Knowledge and Innovation

Management Branch, Cowichan Lake Research Station, Box 225, Mesachie Lake, B.C. 

V0R 2N0

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 names or firm names is for information only and does not imply 

endorsement by the U.S. Department of Agriculture of any product or service.

Pesticide Precautionary Statement

This publication reports on operations that may involve pesticides. It does not contain 

recommendations for their use, nor does it imply that the uses have been registered. All 

uses of pesticides must be registered by appropriate provincial, state or federal agencies, 

or both, before they can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, 

and fish or other wildlife – 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.
A Tale of Two Cedars 

International Symposium on 

Western Redcedar and Yellow-cedar

U.S. Department of Agriculture 

Forest Service 

Pacific Northwest Research Station 

Portland, Oregon 

General Technical Report 

PNW-GTR-828 

October 2010 

 
ABSTRACT 

Harrington, Constance, A., tech. coord. 2010. A tale of two cedars – International symposium on 

western redcedar and yellow-cedar. Gen. Tech. Rep. PNW-GTR-828. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 177 p. 

From May 24-28, 2010, an international symposium on western redcedar (Thuja plicata) and yellowcedar (Callitropsis nootkatensis [syn. Chamaecyparis nootkatensis]) was held at the University of 

Victoria on Vancouver Island in British Columbia, Canada. The symposium was entitled “A Tale of 

Two Cedars” and brought together local, regional, national, and international experts to present cultural, 

biological, management and economic information on the two species. Although some papers or posters 

focused on just one of the cedars, many of the presenters covered both species and discussed the 

similarities and differences between them. This proceedings includes abstracts or short papers from all 

of the formal presentations or posters presented at the symposium. 

KEYWORDS: Western redcedar, Thuja plicata, yellow-cedar, Callitropsis nootkatensis,

Chamaecyparis nootkatensis, Alaska yellow-cedar, cultural use, ecology, soils, nutrient cycling, 

physiology, forest health, climate, genetics, wood properties, silviculture and forest management.
PREFACE

From May 24-28, 2010, an international symposium on western redcedar and yellow-cedar was held at 

the University of Victoria, on Vancouver Island, British Columbia, Canada. The symposium was 

sponsored by the Centre for Forest Biology, University of Victoria; British Columbia Ministry of 

Forests and Range; and U.S. Forest Service, Pacific Northwest Research Station. The Organizing 

Committee consisted of: Paul Hennon, U.S. Forest Service, Pacific Northwest Research Station, Juneau, 

AK; John Russell, British Columbia Ministry of Forests and Range, Research, Knowledge and 

Innovation Management Branch, Cowichan Lake Research Station, Mesachie Lake, BC; Constance 

Harrington, U.S. Forest Service, Pacific Northwest Research Station, Olympia, WA; Barbara Hawkins, 

Centre for Forest Biology, University of Victoria, Victoria, BC; Diane Douglas, British Columbia 

Ministry of Forests and Range, Tree Improvement Branch, Victoria, BC; and Jodie Krakowski, British 

Columbia Ministry of Forests and Range, Research, Knowledge and Innovation Management Branch, 

Cowichan Lake Research Station, Mesachie Lake, BC. We also acknowledge the support and helpful 

suggestions of Charles Peterson, U.S. Forest Service, Pacific Northwest Research Station, Portland, OR, 

in the initial planning stages for the meeting.

Canadian and U.S. scientists and managers have accumulated substantial knowledge and experience 

with western redcedar and yellow-cedar but there have been few opportunities to exchange this 

information. The primary goal of the meeting was to bring together experts in a broad range of fields to 

share information and experience and, where possible, to synthesize knowledge on these two species. 

Both of these cedars are culturally, economically, and biologically important, but they have been 

relatively poorly studied compared to other species of comparable importance. In addition, by 

addressing only two tree species, we hoped to delve deeply into various scientific disciplines—

ethnobotany, ecology, soil science, physiology, entomology and pathology, climate, genetics, wood 

science, and silviculture. Many of the individual presentations in the sessions at the symposium 

addressed both cedar species and were multidisciplinary. We posed two related questions several times 

during the symposium: how are these two cedars similar, and how are they different? 

The 4-day meeting began with 4 keynote speakers to set the stage for the rest of the meeting -- one each 

on cultural roles of the cedars, nomenclature and relatedness within the Cupressaceae, and two on wood 

properties and market opportunities. Dr. Nancy Turner shared her understanding of the traditional 

knowledge and use of cedars by First Nations people. Many First Nations peoples living in western 

North America have access to one or both of the cedars. They recognized that each cedar has unique 

properties for various cultural and daily necessities of life, and they used them accordingly. Dr. Damon 

Little covered the evolutionary history, taxonomy, and nomenclature of yellow-cedar and western 

redcedar and outlined key taxonomic changes in the Cupressaceae. The two cedars may look similar, but 

their descendants emerged from different branches of an ancient plant family long ago and are actually 

only very distantly related. The taxonomic classification of western redcedar is stable, but not so for 

yellow-cedar: it is in considerable flux. Drs. Chris Gaston and Ivan Eastin rounded out the keynote 

presentations by discussing the wood properties and commercial value of the two cedars and their 

different domestic and international markets. Both cedars are consistently the most commercially valued 

wood where they grow, but their woods have distinct properties, and very different North American and 

Asian market niches.

Our keynote speaker session was followed by others which were organized around several broad 

themes. The ecological sessions built a foundation of where on landscapes the two cedars could be 

conserved or actively managed. Information on habitat preferences, soils and nutrient cycling, 

physiology, forest health, genetics, and wood properties gave guidance on where cedars are best-
adapted, both currently and in the future with a changing climate. This guidance came in the form of 

broad-scale patterns, such as physiological adaptation, climate envelopes, and the movement of 

populations to help ensure current and future adaptability. Speakers also addressed fine-scale features 

such as physiological plasticity in response to local climate, and ecological adaptation to wet soils 

through calcium and nitrogen uptake. Durable wood products from young-growth forests through 

silvicultural and genetic management are vital to the economic stability of our regions. Scientific 

information from related sessions outlined the progress that has been made to date as well as future 

research initiatives. These talks set the stage for the Friday management session which provided 

examples through field testing and operational experience of how cedars could be, and are being, 

managed with different silvicultural strategies and examined growth rates of these species with and 

without management. Our field trips reinforced many of the same themes. We experienced the beauty of 

old-growth forests and discussed the role of these cedars in forest management in areas within driving 

distance of Victoria. Population adaptation of the two cedars was witnessed first-hand, as were 

operational silvicultural successes and both ecologically rich and stressful environments. We thank: (1) 

Western Forest Products for providing staff to talk about their practices and for allowing access to 

multiple sites on a field trip where participants could view research installations, operational plantations, 

and natural stands of the species, and (2) Capital Regional District Watershed for allowing access to an 

exceptional old-growth stand. 

The symposium included a poster session (abstracts or mini papers are included from that session in this 

proceedings) which covered a wide range of topics. A related workshop was held the following week to 

document the progress that has been made in tree improvement, through breeding, testing, and selection, 

to develop clones which are resistant to browsing by deer and elk and to discuss opportunities for broadscale field testing. Information from that workshop is also included here. 

As mentioned above, one of our keynote speakers, Damon Little, The New York Botanical Garden, 

covered the systematics of the Cupressaceae family. Based on recent information from molecular 

markers and knowledge of the taxonomic rules used in assigning scientific names, he suggested that we 

use Callitropsis nootkatensis for the species also referred to in the literature as Xanthocyparis 

nootkatensis, Cupressus nootkatensis, and Chamaecyparis nootkatensis. Most participants adopted that 

nomenclature for this proceedings. Dr. Little did not have an opinion on a standard common name but 

the majority of the meeting participants felt that yellow-cedar was the best common name as that name 

refers to the bright yellow color of the tree’s heartwood and is widely used in British Columbia and 

Alaska where much of the range of the species exists. Other common names used include: Alaska 

yellow-cedar, Alaska cypress, Alaska cedar, Nootka false cypress, and yellow cypress. 

Species from the Cupressaceae family are distinct from other conifers (i.e., in the Pinaceae) in many

aspects that we addressed at the symposium. Our goal was to share information across topical and 

geographic barriers, and in this respect, the symposium was a resounding success. The symposium 

covered a wide range of topics and several participants expressed their enthusiasm at being exposed to 

subjects they might normally have thought little about. Discussion continued through the breaks, meals, 

and field trips and several attendees asked that a list of participants be included to facilitate future 

interaction (see the Table of Contents for this list). In addition, one of attendees, Bill Beese, wrote a 

song about the meeting and sang it, accompanying himself on the guitar, for the group (it was received 

with lots of laughter, clapping and cheers). He has graciously allowed us to print the lyrics from his song 

in the proceedings. 
We thank Joseph Kraft for his assistance in preparing the proceedings. Although we asked the authors 

for their papers as “camera ready,” we appreciate Joe’s tweaking to get them to the desired final format. 

Jodie Krakowski prepared the artwork (tree outlines, foliage and cones of western red cedar and yellowcedar) used on the inside front cover and section dividers in this document; her artwork was also used 

on meeting handouts and printed on cups and wooden coasters given to speakers and meeting 

participants, respectively. 

We hope that this printed proceedings will serve as a reminder of the topics covered for those who 

attended the meeting and as a synthesis of knowledge for these two important species. We closed A Tale 

of Two Cedars with the hope that a follow-on meeting will be held in 10 years to update our knowledge. 

The Organizing Committee – A Tale of Two Cedars 

2010 - A Tale of Two Cedars PNW-GTR-828

CONTENTS

SECTION A

KEYNOTE PRESENTATIONS 

Trees for life: The cultural roles of western redcedar and yellow-cedar for First Peoples of 

northwestern North America ........................................................................................................3

Nancy J. Turner

Western redcedar (Thuja plicata) and yellow-cedar (Callitropsis nootkatensis): Phylogeny, 

nomenclature, and organismal character evolution ..............................................................................4 

Damon P. Little

A tale of two markets: Opportunities for western redcedar and yellow-cedar in Japan and the U.S. ...............................5 

Chris Gaston and Ivan Eastin

PALEOECOLOGY, ECOLOGY, AND HABITAT PREFERENCES

Western redcedar and yellow-cedar distributions along elevation gradients in southeast Alaska: implications

for climate change......................................................................................................................6

John Caouette and Paul Hennon

Decline in western redcedar 1000 years ago at SGang Gwaay UNESCO World Heritage Site on southern

Haida Gwaii: Selective resource removal by Haida peoples ....................................................................7 

Terri Lacourse

Ecology and distribution of western redcedar and Alaska yellowcedar in northwestern Washington...............................13 

Robin D. Lesher and Jan A. Henderson

Nitrogen availability in forest floors of western redcedar: surprises, conundrums, solutions........................................19

Cindy E. Prescott

SOILS AND NUTRIENT CYCLING

The effects of excessive moisture on soil C and N mineralization and site productivity in coastal forests of 

British Columbia ....................................................................................................................25

Toktam Sajedi and Cindy E. Prescott

The biogeochemistry of cedar forests: the cedar-nitrate hypothesis.....................................................................26

Dave D'Amore and Paul E. Hennon

Decomposition and nutrient dynamics in western redcedar/hemlock and Douglas-fir/hemlock ecosystems

on the western Olympic Peninsula of Washington ..............................................................................27

Emily E.Y. Moghaddas, John G. McColl, Robert L. Edmonds, and Barbara Cade-Menun 

PHYSIOLOGY

Ecophysiological processes of western redcedar (Thuja plicata) and yellow-cedar (Callitropsis nootkatensis)..................33

Steven C. Grossnickle and John H. Russell

Stem water potential of western redcedar and Douglas-fir seedlings growing across a soil moisture gradient...................37 

Trevor Walter and Gregory Ettl
Foliage and light-use efficiencies of western redcedar (Thuja plicata) stands compared to western hemlock (Tsuga

heterophylla)..........................................................................................................................38

Roderick W. Negrave

SECTION B 

FOREST HEALTH

Determining the potential to reconstruct population dynamics of yellow-cedar in declining stands using 

dendrochronology....................................................................................................................41 

Amanda B. Stan, Thomas B. Maertens, Lori D. Daniels, and Stefan Zeglen

Phellinus weirii and other fungi causing decay in western redcedar and yellow-cedar ..............................................47 

Rona N. Sturrock, Kevin W. Pellow, and Paul E. Hennon

Traumatic resin duct formation in the phloem of western redcedar and other resistance mechanisms 

effective against Armillaria root disease...........................................................................................53 

Michelle R. Cleary

A landscape-level analysis of yellow-cedar decline in coastal British Columbia......................................................57 

Claire E. Wooton and Brian Klinkenberg 

CLIMATE

Bioclimatic envelopes, forest decline risk factors, and modeling suitable habitat for yellow-cedar conservation and

management..........................................................................................................................59

Paul Hennon, Dave D’Amore, Dustin Wittwer, and John Caouette

Managing western redcedar and yellow-cedar in a changing environment.............................................................64 

Laura Gray and Andreas Hamann

Yellow-cedar and western redcedar adaptation to present and future climates.........................................................65 

John H. Russell and Jodie Krakowski

Rates and causes of western redcedar and yellow-cedar mortality in old-growth forests of Mount Rainier National Park .....71 

Andrew J. Larson and Jerry F. Franklin

Comparisons of the cold tolerance and rooting depth of yellow-cedar, western redcedar, western hemlock,

mountain hemlock and Sitka spruce growing together in Ketchikan, Alaska................................................76 

Paul G. Schaberg, Paul E. Hennon, Dave V. D'Amore, Joshua M. Halman, and Gary W.T.F. Hawley

GENETICS

Genetic perspectives on the colonization history and population structure of western redcedar (Thuja plicata, 

 Cupressaceae)........................................................................................................................77 

Stacey Lee Thompson, Alison Dawn Scott, Lisa O’Connell, and Kermit Ritland

Correlates of clonality in western redcedar (Thuja plicata)..............................................................................78

Alison Scott, Jesse Granados, and Stacey Lee Thompson

Local and rangewide genetic structure of yellow-cedar...................................................................................79

Kermit Ritland, Terry Pape, and Stacey Lee Thompson

Development of markers for ungulate browsing resistance in western redcedar (Thuja plicata Donn ex D. Don)..............80 

Adam Foster, Leanne Mortimer, Dawn Hall, Regine Gries, Gerhard Gries, Aine Plant, Jörg Bohlmann, 

John Russell, and Jim Mattsson
SECTION C 

WOOD

Variation in western redcedar heartwood extractives ......................................................................................83 

John H. Russell and Bob Daniels

Reducing depletion of western redcedar extractives from wood in service..............................................................87 

Rod Stirling and Paul I. Morris

Durability of second growth versus old growth cedar lumber.............................................................................93 

Paul I. Morris, P. Laks, G. Larkin, and J.K. Ingram

Modelling the crown profile and branch size of western redcedar (Thuja plicata Donn) in coastal British Columbia ..........94 

Roberta Parish and James W. Goudie

SILVICULTURE AND MANAGEMENT

Western redcedar of the Rocky Mountains: ecology and management..................................................................95 

Russell T. Graham and Theresa B. Jain

Comparison of western redcedar and yellow-cedar growth under different silvicultural treatments...............................96 

William J. Beese and Dillon Chrimes

Growth of western redcedar and yellow-cedar...............................................................................................97 

Constance A. Harrington and Peter J. Gould

Effects of pruning severity on the growth of western redcedar after 12 years.........................................................103 

Louise E. de Montigny, Roderick W. Negrave, and Peter K. Ott

Growth of western redcedar with Douglas-fir in young plantations in western Oregon..............................................109

Doug Mainwaring and Doug Maguire

Survival and growth of western redcedar and Douglas-fir planted in a variable retention harvest unit

in the western Cascades, Washington............................................................................................115 

Andrew Cockle and Gregory Ettl

Ten-year performance of yellow cedar and interior spruce in southern interior British Columbia, Canada .....................121 

Clare Kooistra, Jonathan D. Bakker, and Patience Rakochy

20 years growing cedar: a silviculture forester’s experience............................................................................127

Rudi van Zwaaij, RPF

Size hierarchy development in juvenile western redcedar (Thuja plicata) stands compared to western hemlock (Tsuga

heterophylla)........................................................................................................................128

Roderick W. Negrave

Influence of N and P supply on rooting of yellow-cedar (Chamaecyparis nootcatensis) cuttings 

for planting stock production ....................................................................................................129

R. van den Driessche and J. Russell

SECTION D 

ABSTRACTS AND PAPERS BASED ON POSTERS

Silvicultural treatment effects on aboveground biomass growth and partitioning of western redcedar

(Thuja plicata Donn ex D. Don) stands compared to western hemlock (Tsuga heterophylla (Raf.) Sarg.)...........133

Roderick W. Negrave
Response of western redcedar to release and fertilization in a mixed-species stand.................................................139

Leslie Chandler Brodie and Constance A. Harrington

Sensitivity of western redcedar growth to climate and western hemlock looper in British Columbia’s

inland temperate rainforest.........................................................................................................145

Chris Konchalski

Ethanol synthesis by anoxic root segments from five cedar species relates to mesic habitat attributes but not their

vulnerability to Phytophthora lateralis root disease............................................................................146

Rick G. Kelsey, Gladwin Joseph, and Michael G. McWilliams

Characterization and biocidal activity of some yellow-cedar heartwood compounds...............................................147

Joe Karchesy, Rick Kelsey, Daniel Manter, Marc Dolan, Nick Panella, Javier Peralta-Cruz,

Mohammad Khasawneh, and Yeping Xiong

Vitality and defense mechanisms in bark-stripped cedar trees ..........................................................................148

Paul E. Hennon and Nancy Turner

The natural range of yellow-cedar: a photographic tour of diverse locations .........................................................149

Marshall D. Murray. 

Ancient yellow-cedar groves in the Olympic Mountains, Washington ................................................................153

Marshall D. Murray

Gene resource management for western redcedar and yellow-cedar...................................................................156

John Russell and Jodie Krakowski

Breeding and deployment for western redcedar deer resistance........................................................................156 

John Russell and Jodie Krakowski

Western redcedar (Thuja plicata) advanced regeneration response to variable retention harvesting in southwest 

Washington ........................................................................................................................157 

Florian Deisenhofer

Six-year western redcedar (Thuja plicata) height growth performance in southwest Washington................................158

Florian Deisenhofer and Chris Rasor

WESTERN REDCEDAR DEER BROWSE RESISTANCE WORKSHOP

Western redcedar browse resistance breeding and deployment material ..............................................................160

John H. Russell and Daniel C. Ferguson

Summary of western redcedar browse resistance research .............................................................................163 

John Russell and Bruce Kimball

FIELD TOURS

Capital Regional District Watershed: ......................................................................................................167

Don Harriott

Jordan River Western Forest Products Lands .............................................................................................168

Annette Van Niejenhuis

THE BALLAD OF TWO CEDARS ...........................................................................................171 

Bill Beese

MEETING PARTICIPANTS ....................................................................................................172 

METRIC-ENGLISH EQUIVALENTS ........................................................................................177
SECTION A

KEYNOTE PRESENTATIONS

PALEOECOLOGY, ECOLOGY AND HABITAT 

PREFERENCES

SOILS AND NUTRIENT CYCLING

PHYSIOLOGY

1
2
TREES FOR LIFE: THE CULTURAL ROLES OF WESTERN 

REDCEDAR AND YELLOW-CEDAR FOR FIRST PEOPLES OF 

NORTHWESTERN NORTH AMERICA 

Nancy J. Turner1

ABSTRACT

Western redcedar (Thuja plicata) and yellow-cedar (Chamaecyparis nootkatensis) are both trees of 

immense cultural importance for First Peoples in northwestern North America. Western red-cedar is the 

main type of wood used for dugout canoes, as well as the posts and planks of Northwest Coast big 

houses and bentwood boxes, as well as being used for numerous smaller items, from fire tongs to fishing 

lures. Yellow-cedar is a preferred wood for canoe paddles, and is also used for carving masks, bows and 

other items. The fibrous inner bark of both species is woven into baskets, hats, mats, blankets and 

clothing. The tough, fibrous roots and branches of western redcedar are also used in basketry and for 

cordage. Both species are also used for a variety of medicinal purposes. The importance of these two 

species in material culture is mirrored in their roles in ancient narratives and in their spiritual values as 

reflected First Peoples’ ceremonies and belief systems. First Nations have always used cedar trees with 

care and respect, often only partially harvesting cedar wood and bark to allow the trees to continue 

living – seen today in many places as culturally modified trees (CMTs). In many areas industrial logging 

has severely curtailed the availability of cedar for cultural purposes, but recent long-term management 

plans, and more widely adopted ethic of careful and caring use of these trees may help to alleviate this 

situation over time.

1 School of Environmental Studies, University of Victoria, Victoria, B.C., Canada

2010 - A Tale of Two Cedars PNW-GTR-828

3
WESTERN REDCEDAR (THUJA PLICATA) AND YELLOW-CEDAR 

(CALLITROPSIS NOOTKATENSIS): PHYLOGENY, 

NOMENCLATURE, AND ORGANISMAL CHARACTER EVOLUTION 

Damon P. Little1

ABSTRACT

I aim to summarize our current knowledge of cedar evolution and the expression of that knowledge 

through botanical nomenclature. Red (Thuja plicata) and yellow cedar (Callitropsis nootkatensis) are 

members of the subfamily Cupressoideae—by far the largest and most diverse subfamily in 

Cupressaceae. 

A number of organismal (anatomy, biochemistry, micromorphology, reproductive development, 

reproductive morphology, and vegetative morphology) and DNA sequence characters can be used to 

reconstruct the evolutionary (phylogenetic) history of Cupressoideae. Of particular interest are those 

characteristics that may be of adaptive significance. For example, wood secondary chemistry (the 

evolution of antimicrobial compounds), leaf architecture (the evolution of light tolerance), and 

transfusion tissue structure (the evolution of drought tolerance). 

Phylogenetic reconstructions usually position the species of red cedar (Thuja) and asunaro (Thujopsis 

dolabrata) as the earliest branch within Cupressoideae. The nomenclature of red cedar is 

uncontroversial. Yellow cedar is reconstructed, remote from red cedar, in a more apical position along 

with the junipers (Juniperus), Old World cypresses (Cupressus), Vietnamese cypress (Xanthocyparis 

vietnamensis), and New World cypresses (Callitropsis). The arrangement of these groups varies 

somewhat depending on the source of data utilized, but yellow cedar is consistently resolved alongside 

of the Vietnamese and New World cypresses. This phylogenetic reconstruction had led to recent 

nomenclatural changes for New World cypresses (controversial in some quarters). In literature, yellow 

cedar is known variously as Callitropsis nootkatensis, Xanthocyparis nootkatensis, Cupressus 

nootkatensis, and Chamaecyparis nootkatensis. Until the relationship between yellow cedar, Vietnamese 

cypress, and the New World cypresses are satisfactorily resolved, the most conservative nomenclatural 

treatment is to recognize a single genus—Callitropsis—for all three.

 

1 Cullman Program for Molecular Systematics, The New York Botanical Garden, Bronx, NY 10458-5126, dlittle@nybg.org.

2010 - A Tale of Two Cedars PNW-GTR-828

4
A TALE OF TWO MARKETS: OPPORTUNITIES FOR WESTERN 

REDCEDAR AND YELLOW-CEDAR IN JAPAN AND THE U.S.

Chris Gaston1 and Ivan Eastin2

ABSTRACT

This presentation will begin with an overview of the wood properties and markets for western redcedar 

and yellow-cedar. The specific attributes and properties of these two cedars will be covered from a 

supply, demand and competition perspective. Topics covered will include: BC/PNW production, 

shipments, international trade, end-uses, and market shares. This will provide a statistical overview of 

the opportunities for marketing these species. Our presentation will then focus in on two specific market 

opportunities. 

Market Opportunities in Japan

There are a number of potential market opportunities for cedar lumber in Japan. These range from rough 

green lumber to planed and kiln-dried lumber to glue-laminated yellow-cedar sill plates (dodai). The 

most promising opportunities include yellow-cedar dodai for the post and beam market, 2x4 and 2x6 

dimension yellow-cedar lumber for sill plates in the 2x4 market, yellow-cedar lamina for the gluelaminated beam industry, and rough, green or planed, kiln dried red or yellow cedar lumber for the shoji 

manufacturing industry. Strategic recommendations for selling cedar into Japan include: 1) develop 

comparative performance properties of species used for dodai, 2) develop a marketing campaign 

promoting the benefits of using yellow-cedar to homebuyers in Japan, 3) promote the idea of a yellowcedar foundation system for houses, 4) sawmills should carefully analyze market segments to ensure a 

good match with their production capabilities, and 5) investigate opportunities for WRC and YC in 

products targeted to the R&R, DIY, and outdoor use markets in Japan. 

Market Opportunities in Outdoor Decks in the US

The deck building industry is going through a period of rapid growth and dramatic change with respect 

to the types of materials available to build decks. To better understand material use and contractor 

preferences within the deck building industry, CINTRAFOR, with funding support from FPInnovations, 

recently completed a survey of deck builders and home builders across the US. The deck building 

industry is dominated by small to medium-sized firms. Just over 40% of deck builder projects were new 

(first time) decks built on existing homes while 25% were new decks built on new homes and almost a 

third were replacement decks built on existing homes. Material use in the substructure was dominated by 

treated lumber with a market share of over 90%. Material use in deck surface applications was 

dominated by wood-plastic composite products followed by treated lumber and western red cedar. 

Finally, approximately 30% of deck accessories were built using wood-plastic composites and treated 

lumber while an additional 18% were built from western red cedar. The results of the market research 

suggest that the target market for cedar should be deck builders located on the US west coast, comprised 

of California, Oregon and Washington. The survey results show that decks built in this market are 

larger, more expensive and more likely to use naturally durable woods. 

This study also investigated the potential for Profile Decking, a new treated whitewood decking product 

that has grown out of research conducted at FPInnovations. This product, along with cedars, is targeting 

solid wood alternatives to plastic wood decking.

1 FPInnovations, 2665 East Mall, Vancouver, BC, Canada V6T 1W5 chris.gaston@fpinnovations.ca 2 Center for International Trade in Forest Products, University of Washington, Seattle, WA.

2010 - A Tale of Two Cedars PNW-GTR-828

5
WESTERN REDCEDAR AND YELLOW-CEDAR DISTRIBUTIONS 

ALONG ELEVATION GRADIENTS IN SOUTHEAST ALASKA: 

IMPLICATIONS FOR CLIMATE CHANGE

John Caouette1 and Paul Hennon2

ABSTRACT

The coast Alaska rainforest is a large relatively intact forest, largely managed by a single entity (the US 

Forest Service), relatively low in tree species diversity, and not vulnerable to fire. The combination of 

these characteristics makes coastal Alaska an ideal setting for studying relationships between tree 

species distributions and climate. We conduct analyses of red and yellow cedar tree species and their life 

stages across elevation gradients in southeast Alaska. We conduct our analysis in a meta-replicated 

manner, emphasizing repeatable outcomes across multiple forest inventory datasets. We keep our 

explanatory factors simple (i.e., elevation classes), so as to better illustrate and measure complex 

relationships amongst tree species and within species attributes (e.g., dead, live and regeneration). 

Elevation is used as the primary explanatory factor because of its strong correlation with climate. Thus 

elevation becomes a pseudo-climatic gradient from which we can observe species niche differentiation

and migration. This type of analysis not only provides an additional perspective on forest-climate 

relationships, but also provides measurable indicators for tree species vulnerability assessments and 

monitoring programs related to climate change. Results show patterns of climatic niche differentiation 

for both red and yellow-cedar trees. Results also show climatic differentiation amongst dead, live, and 

regenerating for the yellow-cedar trees, but not for the redcedars. 

 

1 The Nature Conservancy, Juneau, Alaska

2 US Forest Service, Pacific Northwest Research, Juneau, Alaska

2010 - A Tale of Two Cedars PNW-GTR-828

6
DECLINE IN WESTERN REDCEDAR 1000 YEARS AGO AT

SGANG GWAAY UNESCO WORLD HERITAGE SITE 

ON SOUTHERN HAIDA GWAII: 

SELECTIVE RESOURCE REMOVAL BY HAIDA PEOPLES

Terri Lacourse1

ABSTRACT

SGang Gwaay village at the southern tip of the Haida Gwaii archipelago (Queen Charlotte Islands, 

British Columbia), with its many standing monumental poles and the remains of cedar-plank houses, is 

recognized as the greatest in situ example of Northwest Coast architecture and monumental art. The late 

Holocene vegetation history of Anthony Island and the potential ecological impact of Haida villagers 

were investigated by conducting pollen and plant macrofossil analyses on sediments from a small pond 

near the village. Fossil pollen and plant macrofossil assemblages reveal 1800 years of relatively stable 

temperate rainforest vegetation. However, Cupressaceae (cedar) pollen percentages and accumulation 

rates decline about 1000 years BP, coincident with radiocarbon-dated occupation of the island by Haida 

peoples, who use Thuja plicata Donn ex D. Don (western redcedar) almost exclusively for house 

construction, dugout canoes, monumental poles, and many other items. Selective resource removal by 

Haida peoples offers the most likely explanation for this local decline in western redcedar. Given the 

long lifespan of cedar and since many standing western redcedar remain on Anthony Island, it appears 

that harvesting was conducted at a sustainable rate. This research provides independent paleoecological 

evidence for local changes in forest composition attributable to Indigenous peoples on the Pacific coast 

of Canada.

KEYWORDS: pollen analysis, plant macrofossils, Thuja plicata, human impact, selective harvesting

INTRODUCTION

The village of SGang Gwaay, on the eastern 

shore of Anthony Island on the Pacific coast of 

Canada, was designated a UNESCO World 

Heritage Site in 1981. The remains of a large 

Haida village with collapsed cedar-plank houses 

and standing monumental poles make SGang 

Gwaay one of the best examples of prehistoric 

Northwest Coast architecture and art. Acheson 

(1998) determined that SGang Gwaay was 

settled by Kunghit Haida around 1590 ± 160 14C 

years before present (yr BP). Settlement 

occurred after late Holocene decreases in 

relative sea level of about 5 m exposed new land 

suitable for human habitation (Hebda and 

Mathewes 1986, Lacourse et al. 2010). 

This paper summarizes paleoecological 

evidence of prehistoric forest modification by 

Haida peoples on Anthony Island (Lacourse et 

al. 2007). Unlike archaeological and 

ethnobotanical remains, which are the direct 

products of human activities, paleoecological 

records offer independent data on the ecological 

impact of Indigenous peoples. Pollen and plant 

macrofossil analyses of a lake sediment core 

collected from SGang Gwaay Pond on Anthony 

Island are compared to the island’s 

archaeological record, which spans the last 1600 

years (Acheson 1998). We propose that 

localized selective harvesting of large Thuja

plicata trees by Haida is reflected in the pollen 

record from this site.

1 Dept. of Geography, University of Victoria, Victoria, BC V8W 3R4, tlacours@uvic.ca

2010 - A Tale of Two Cedars PNW-GTR-828

7
ENVIRONMENTAL SETTING

Anthony Island (52°05.75’N, 131°13.25’W) is 

located at the southern tip of the Queen 

Charlotte Islands (Haida Gwaii), an archipelago 

of about 150 islands on the edge of the 

continental shelf on the North Pacific coast. 

Anthony Island is small (~1.5 km2) and low in 

elevation (≤60 m a.s.l.). The island’s 

hypermaritime climate is characterized by cool 

summers and wet, mild winters.

Anthony Island lies within the Coastal Western 

Hemlock biogeoclimatic zone, which occurs at 

low to middle elevations along the coast of 

British Columbia (Meidinger and Pojar 1991). 

Forests in this zone are dominated by Tsuga

heterophylla (western hemlock) and Thuja

plicata with varying amounts of Picea sitchensis

(Sitka spruce), Chamaecyparis nootkatensis

(yellow-cedar), and Pinus contorta ssp. contorta

(shore pine). 

SGang Gwaay Pond is located on the southeast 

side of Anthony Island (5.3 m a.s.l.), about 700 

m south of the village. It is the only permanent 

body of water on the island and is very small 

(~0.3 ha), which suggests that most pollen 

deposited in the basin is of local origin. Picea

sitchensis, T. heterophylla, and P. contorta ssp. 

contorta grow immediately around the pond. 

Thuja plicata trees, some of which are culturally 

modified, are scattered on the island. 

METHODS

A 106 cm-long sediment core was retrieved 

with a Livingstone corer from SGang Gwaay 

Pond in 0.7 m of water (Hebda and Mathewes 

1986). Two radiocarbon ages were obtained 

from the core: one on peat at 95 cm (1750 ± 120

14C yr BP, WAT 1197 ) and one on a Picea twig 

at 40 cm (1110 ± 40 14C yr BP, BETA 201518). 

These 14C ages were calibrated to calendar ages 

(1665 and 1020 cal yr BP, respectively) using 

CALIB 5.0 (Stuiver and Reimer 1993). An agedepth model was then constructed using 

calibrated 14C dates and a cubic spline curve. 

Sediment samples were prepared for pollen 

analysis following standard methodology (Fægri 

and Iversen 1989). A minimum sum of 500 

terrestrial pollen grains was counted for each 

subsample. To calculate pollen concentrations, 

two tablets of Eucalyptus pollen (16,180 ± 1460 

grains; Batch 903722) were added to each 

sample. Pollen accumulation rates were 

calculated using pollen concentrations and 

sedimentation rates and were used to evaluate 

trends in population size, since they avoid the 

statistical interdependence of percentage data.

RESULTS AND INTERPRETATION

Sediment and Chronology

The base of the sediment core consists of gravel 

and coarse sand with fragments of marine shells 

(Fig. 1). The age-depth model predicted an age 

of 1780 cal yr BP for the core bottom. Marine 

shells occur below 98 cm i.e., ca. 1675 cal yr 

BP, which represents the minimum age for 

marine regression. The area near present sea 

level would not have been available for human 

occupation prior to this time (Hebda and 

Mathewes 1986, Lacourse et al. 2010). Marine 

sediments are overlain by dark brown limnic 

detritus (Fig. 1). 

Pollen Analysis

SGang Gwaay Pond pollen and spore 

percentages (Fig. 1) are dominated by Picea 

sitchensis, Tsuga heterophylla and Alnus crispa 

(Sitka alder). Cupressaceae (cedar), Alnus rubra

(red alder), and total herb pollen each do not 

exceed 5% of the sum. Ericaceae (heather; e.g., 

Gaultheria) and Rosaceae (rose; e.g., Rubus) 

pollen are consistently present at low levels. 

Polypodiaceae fern spores including 

Polypodium account for about 20% of the sum 

on average. Uncommon pollen and spores not 

shown in Figure 1 include Tsuga mertensiana

(mountain hemlock), Taxus brevifolia (Pacific 

yew), Gentiana douglasiana (swamp gentian), 

Lycopodium spp. (clubmoss), and Selaginella 

wallacei. Total pollen accumulation rates 

(PARs) are about 10,000 grains/cm2

/cal yr (Fig. 

1), similar to PARs in temperate rainforest 

elsewhere along the coast (e.g., Lacourse 2005). 

Cupressaceae pollen percentages and 

accumulation rates decline after 1000 cal yr BP 

8
9
(Fig. 1). Thuja plicata and Chamaecyparis

nootkatensis have indistinguishable pollen 

morphologies, but C. nootkatensis does not 

grow on the island, so T. plicata is likely the 

only contributor of Cupressaceae pollen. 

Furthermore, an abundance of T. plicata branch 

fragments, seeds, and scale leaves in the 

sediment core confirms the local presence of T. 

plicata over the last 1800 years (Lacourse et al. 

2007). 

DISCUSSION

Our data from Anthony Island show few 

changes in forest composition over the last 1800 

calendar years. The pollen record (Fig. 1) 

reflects closed rainforests dominated by Picea

sitchensis and Tsuga heterophylla with 

abundant Alnus crispa shrubs and 

Polypodiaceae ferns. The one exception to this 

relative stability is the near disappearance of 

Thuja plicata after 1000 cal yr BP i.e., after 

about 500 years of occupation at SGang Gwaay. 

The most likely explanation is selective 

harvesting of T. plicata trees by Haida for 

construction of houses, dugout canoes, and other 

items. The proof of this harvesting lies only 700 

m north of the pond in the cedar-plank homes 

and monumental poles of SGang Gwaay village.

These structures were constructed from large T. 

plicata trees, suggesting that harvesting would 

likely have focussed on mature trees. The 

removal of such large trees would have 

influenced the local pollen rain most strongly. 

Tc!u’uga village, which means “to go for 

cedar”, was established on the adjacent shore of 

Moresby Island around 980 ± 65 14C yr BP 

(~880 cal yr BP) (Acheson 1998) i.e., about 100 

years after the decline in T. plicata pollen at 

SGang Gwaay Pond. The precontact Haida 

population size is unknown but intensification in 

settlement and cultural activity and increases in 

site size in the southern Queen Charlotte Islands 

after 800 14C yr BP (~715 cal yr BP) suggest 

increased population at that time (Acheson 1998).

Paleoecological records from coastal British 

Columbia demonstrate that low elevation forests 

have been more or less stable in composition 

during the late Holocene, dominated by Tsuga

heterophylla, Thuja plicata, and Picea 

sitchensis (e.g., Brown and Hebda 2002, 

Lacourse 2005). A number of other pollen 

records from coastal BC show a slight decline in 

T. plicata pollen percentages over the last two 

millennia (Hebda and Mathewes 1984, Brown 

and Hebda 2002, Lacourse 2005), although 

some records show stable values and/or slight 

increases in T. plicata (e.g., Brown and Hebda 

2002). It is possible that a regional decline in T. 

plicata could be associated with climate 

variability. Temperatures inferred from varves 

in southern Alaska suggest relatively warm 

conditions during the Medieval Warm Period 

(AD 1000-1300) and cooler conditions during 

the Little Ice Age (AD 1500-1850) (Loso et al. 

2006). Tree-ring records from southern 

Vancouver Island suggest that precipitation has 

been relatively stable over the last 2000 years, 

with short periods of drought as well as 

increased precipitation, particularly during the 

Little Ice Age (Zhang and Hebda 2005). Other 

paleoclimatic records from the region also 

document climate variability over the last 2000 

years, but in general these changes would have 

been too low in amplitude to strongly influence 

the hypermaritime climate of Anthony Island. 

Climatic conditions remained within a range 

suitable for the growth of T. plicata. Also, the 

climatic preferences of T. plicata are more or 

less equivalent to other abundant species in the 

region such as Tsuga heterophylla (Thompson 

et al. 1999), which do not show a late Holocene 

decline in abundance. Climate variability may 

have facilitated a decline in T. plicata on 

Anthony Island, but the decline most likely 

reflects selective harvesting of T. plicata trees 

by Haida living on the island. 

The Haida have relied almost exclusively on T.

plicata for house posts and planks, dugout 

canoes, monumental poles, and smaller items 

such as storage boxes (Turner 1998). Thuja 

plicata bark was also used for clothing, mats, 

baskets, and cordage, and scars from barkstripping are apparent on several living T. 

plicata trees on Anthony Island. Given the long 

life span typical of T. plicata i.e., >1000 years 

(Waring and Franklin 1979) and since many 

10
standing T. plicata remain on the island, it 

appears that harvesting of T. plicata trees was 

conducted at a sustainable rate. Indeed, 

sustainable practices were often used by 

Indigenous peoples (Deur and Turner 2005). 

Pollen and plant macrofossil evidence indicated 

that Thuja plicata has been present in coastal 

British Columbia since about 9000 14C yr BP, 

although it was not abundant until after 6000 

14C yr BP, when the climate became cooler and 

more humid. On the basis of paleoecological 

and archaeological evidence, Hebda and 

Mathewes (1984) argued that the development 

of macro-woodworking technology on the North 

Pacific coast was linked to the mid-Holocene 

expansion of T. plicata in coastal forests. 

Specialized woodworking tools and large 

wooden structures do not appear in the 

archaeological record until about 5000 and 3000 

14C yr BP, respectively, i.e., only after T. plicata

became abundant and large trees became 

available (Hebda and Mathewes 1984). 

Our research highlights the contrast between 

prehistoric anthropogenic modification and 

disturbance of forests on the Pacific coast with 

the ecological impact of Indigenous peoples in 

parts of eastern North America, where largescale clearing and burning of the land 

dramatically altered regional forest composition 

and structure (Delcourt and Delcourt 2004). On 

Anthony Island, forest modification was 

primarily through selective resource removal 

and limited clearing for village areas. In general, 

the impact of Haida and other Indigenous 

peoples on Pacific coast rainforests involved 

subtle changes and diffuse terrestrial resource 

use compared to other regions, which is sensible 

given the marine focus of Northwest Coast 

cultures. Our research also demonstrates the 

value of conducting paleoecological analyses on 

non-cultural deposits from locations close to 

archaeological sites for expanding our 

understanding of the ecological impact of 

Indigenous peoples over long time periods. 

ACKNOWLEDGEMENTS 

We thank the Haida Nation for permission to 

conduct this study in their territory and for 

support through the Kunghit Haida Cultural 

History Project. Financial support was also 

provided by NSERC of Canada through 

research grants to T.L. and R.W.M. 

LITERATURE CITED

Acheson, S.R. 1998. In the wake of the 

ya’áats’xaatgáay [‘Iron People’]: A study of 

changing settlement strategies among the 

Kunghit Haida. British Archaeological Reports, 

International Series 711, Oxford. 

Brown, K.J.; Hebda, R.J. 2002. Origin, 

development, and dynamics of coastal temperate 

conifer rainforests of southern Vancouver 

Island, Canada. Can. J. For. Res. 32: 353-372. 

Delcourt, P.A.; Delcourt, H.R. 2004.

Prehistoric Native Americans and Ecological 

Change. Cambridge: Cambridge Univ. Press. 

Deur, D.; Turner, N.J. 2005. Keeping It 

Living: Traditions of Plant Use and Cultivation 

on the Northwest Coast of North America. 

Seattle, WA: Univ. Washington Press. 

Fægri, K.; Iversen, J. 1989. Textbook of 

Pollen Analysis. 4th Ed. Toronto, ON: John 

Wiley & Sons. 

Hebda, R.J.; Mathewes R.W. 1984. Holocene 

history of cedar and Native Indian cultures of 

the North American Pacific Coast. Science 225: 

711-713. 

Hebda, R.J.; Mathewes, R.W. 1986.

Radiocarbon dates from Anthony Island, Queen 

Charlotte Islands, and their geological and 

archaeological significance. Can. J. Earth Sci. 

23: 2071-2076. 

Lacourse, T. 2005. Late Quaternary dynamics 

of forest vegetation on northern Vancouver 

Island, British Columbia, Canada. Quat. Sci. 

Rev. 24: 105-121. 

Lacourse, T.; Mathewes, R.W.; Hebda, R.J. 

2007. Paleoecological analyses of lake 

11
sediments reveal prehistoric human impact on 

forests at Anthony Island UNESCO World 

Heritage Site, Queen Charlotte Islands (Haida 

Gwaii), Canada. Quat. Res. 68: 177-183. 

Lacourse, T.; Hebda, R.J.; Mathewes, R.W. 

2010. Cultural and noncultural deposits reveal 

human impact on late Holocene forests on 

Anthony Island, Haida Gwaii. In: R.M. Dean 

(ed.), The Archaeology of Anthropogenic 

Environments. Center for Archaeological 

Investigations, Occasional Paper No. 37, 

Southern Illinois Univ., Carbondale, pp. 54-74. 

Loso, M.G.; Anderson, R.S.; Anderson, S.P.; 

Reimer, P.J. 2006. A 1500-year record of 

temperature and glacial response inferred from 

varved Iceberg Lake, southcentral Alaska. Quat. 

Res. 66: 12-24. 

Meidinger, D.; Pojar, J. 1991. Ecosystems of 

British Columbia. BC Ministry of Forests, 

Victoria, BC.

Stuiver, M.; Reimer, P.J. 1993. Extended 14C 

data base and revised CALIB 3.0 14C age 

calibration program. Radiocarbon 35: 215-230. 

Thompson, R.S.; Anderson, K.H.; Bartlein, 

P.J. 1999. Atlas of relations between climatic 

parameters and distributions of important trees 

and shrubs in North America. USGS 

Professional Paper 1650A. USGS, Denver, CO. 

Turner, N.J. 1998. Plant Technology of First 

Peoples in British Columbia. Royal British 

Columbia Museum Handbook. Vancouver, BC: 

Univ. British Columbia Press. 

Waring, R.H.; Franklin, J.F. 1979. Evergreen 

coniferous forests of the Pacific Northwest. 

Science 204: 1380-1386. 

Zhang, Q.-B.; Hebda, R.J. 2005. Abrupt 

climate change and variability in the past four 

millennia of the southern Vancouver Island, 

Canada. Geophys. Res. Lett. 32, L16708, 

DOI:10.1029/2005GL02291.

12
1Robin D. Lesher is a plant ecologist and Jan A. Henderson is area ecologist (retired) with Pacific Northwest 

Region, Mt. Baker-Snoqualmie National Forest, 2930 Wetmore Ave, Suite 3A, Everett WA 98201. 

rlesher@fs.fed.us

ECOLOGY AND DISTRIBUTION OF WESTERN REDCEDAR AND

ALASKA YELLOWCEDAR IN NORTHWESTERN WASHINGTON

Robin D. Lesher and Jan A. Henderson1

ABSTRACT 

The ecology and distribution of western redcedar (Thuja plicata) and Alaska yellowcedar (Callitropsis 

nootkatensis, syn Chamaecyparis nootkatensis) were analyzed based on their occurrence and abundance 

on 5587 USFS ecology plots on National Forest lands in northwestern Washington. Western redcedar 

occurred on 40% of the plots, Alaska yellowcedar occurred on 10% of the plots. The ecology is 

described for these species relative to environmental gradients of elevation, temperature and moisture. 

Redcedar showed broad ecological amplitude, but was more frequent at lower elevations, warmer 

temperatures, and towards the drier end of the precipitation gradient, whereas yellowcedar was limited 

to cooler sites at mid to upper elevations and higher precipitation. The role of these cedars in forest 

succession and stand development is described based on their abundance and size-class distribution in 

different stand ages. 

KEYWORDS: ecology, distribution, succession, stand development, northwest Washington 

INTRODUCTION

This study provides baseline information on the 

current distribution and habitats of western 

redcedar and Alaska yellowcedar in 

northwestern Washington, their occurrence in 

different temperature and moisture regimes, and 

their abundance and size-class distribution 

during stages of stand development and 

succession. The Olympic and Mt. BakerSnoqualmie National Forests (NF) comprise the 

1 million ha study area. Beginning in 1979, a 

network of 5587 reconnaissance and permanent 

benchmark ecology plots were installed and remeasured to inventory and describe the 

vegetation on these two National Forests 

(Henderson et al. 1989, 1992). Data from 

ecology plots were used for results presented 

here; not all data were collected on every plot so 

sample size varies for the different analyses.

Western redcedar was well distributed across 

the study area, whereas yellowcedar was more 

limited in distribution (Fig. 1). Redcedar 

occurred on 2225 plots (40% of total) and 

Alaska yellowcedar occurred on 538 plots (10% 

of total). Large diameter trees (>1m dbh) are 

infrequent (Fig.1): 14.2% of the plots with 

redcedar had trees in this size class compared to 

8.7% for yellowcedar. Large diameter trees of 

both species tend to occur in moister sites and in 

older stand ages which is mostly related to the 

fire history of the area (Henderson et al. 1989). 

Environmental Distribution

The distribution of the two cedar species was 

analyzed for the environmental gradients of 

elevation, precipitation and temperature 

(Henderson et al. in review). Redcedar had 

higher average cover than yellowcedar, and was 

most abundant at elevations below 1000 m (Fig. 

2). Yellowcedar typically had low cover 

(averaging < 3%), with highest cover at middle 

elevations from 1200-1500 m. 

Spatial analysis of the elevation gradient for the 

study area in the Cascades (Fig. 3) showed the 

land area between 1000-1400 m was most 

abundant. However, redcedar plots were more 

frequent at lower elevations (400-1000 m),

2010 - A Tale of Two Cedars PNW-GTR-828

13
Figure 1 -- Western redcedar distribution (upper map) on ecology plots (n=2225) on National Forest lands of 

northwestern Washington, circles indicate plots with trees >1m dbh (n=316). Yellowcedar distribution (lower 

map) on ecology plots (n=538) on National Forest lands of northwestern Washington, circles indicate plots with 

trees >1m dbh (n=47). 

Redcedar

Alaska Yellowcedar

14
where yellowcedar plots were more frequent at 

mid elevations (800-1600 m). 

Figure 2 -- Mean cover of redcedar and yellowcedar 

by elevation for the western North Cascades.

The relationship of the frequency distribution 

for the species relative to the landscape displays 

ecological information on the importance of this 

complex variable (elevation) in the distribution 

of the species. If there was no relationship with 

elevation and redcedar, we would expect the 

distribution of redcedar to follow the 

distribution of the landscape (MBS NF) (Fig. 3). 

However, redcedar was more frequent at 

elevations below 1000 m (above the landscape 

(MBS NF) line), and less frequent above 1000 

m (below the landscape (MBS NF) line). 

Figure 3 -- Frequency distributions by elevation 

class of redcedar plots (n=1099) and yellowcedar 

plots (n=231) compared to the frequency distribution 

of pixels (n=900,000) for Mt. Baker-Snoqualmie 

NF.

A similar analysis was done for the precipitation 

gradient, where the frequency distribution for 

the landscape was compared to the distribution 

of the two cedar species (Fig. 4). Redcedar had 

a similar distribution as the landscape for the 

precipitation gradient, but was more frequent at 

the drier end of the precipitation gradient. The 

frequency for yellowcedar was highest between 

2000-4000 mm total annual precipitation. For 

the part of the gradient greater than 3200 mm 

precipitation, the frequency of yellowcedar was 

greater than the landscape frequency. This 

suggests that precipitation was an important 

predictor of the environment for yellowcedar for 

those areas on the landscape that receive more 

than 3200 mm of precipitation. 

Figure 4 -- Frequency distributions by precipitation 

class of redcedar plots (n=1099) and yellowcedar 

plots (n=231) and the frequency distribution of 

pixels (n=900,000) for Mt. Baker-Snoqualmie NF. 

The distribution of redcedar and yellowcedar for 

the gradient of mean annual temperature (MAT) 

were compared to the landscape (Fig. 5). The 

most common temperature classes for the 

western North Cascades were 4-5 deg C. The 

distribution of yellowcedar was centered on the 

MAT distribution for the landscape, and was 

most frequent from 3-6 deg C, where redcedar 

Figure 5 -- Frequency distributions by mean annual 

temperature class of redcedar plots (n=1099) and 

yellowcedar plots (n=231) compared to the 

frequency distribution (n=900,000 pixels) for Mt. 

Baker-Snoqualmie NF (western North Cascades).

0

10

20

30

0 500 1000 1500 2000 2500

Elevation (m)

Average Cover

Redcedar

Yellowcedar

0%

10%

20%

30%

40%

0 1000 2000 3000

Elevation (m)

Percent Frequency

MBS NF

Redcedar

Yellowcedar

0%

10%

20%

0 1000 2000 3000 4000 5000 6000

Total Annual Precipitation (mm)

Percent Frequency

MBS NF

Redcedar

Yellowcedar

0%

10%

20%

30%

40%

-10 -5 0 5 10 15

Mean Annual Temperature (deg C)

Percent Frequency

MBS NF

Redcedar

Yellowcedar

15
was most frequent at warmer temperatures (6-8 

deg C). The difference between the frequency 

curves for the landscape (MBS NF) and 

redcedar suggests that MAT was an important 

predictor of the environment for redcedar at 

temperatures above 5 deg C (Fig. 5). 

The occurrence and abundance of redcedar were 

analyzed by potential vegetation types (plant 

association groups). Plant Association Groups 

(PAGs) are units of potential vegetation 

(broader than plant associations and narrower 

than vegetation zones or series) that represent a 

complex environmental gradient. Redcedar had 

high constancy and a fairly even distribution 

throughout the western hemlock zone PAGs, 

which indicates broad ecological amplitude for 

this species. However, redcedar was rarely 

abundant and averaged about 20% cover. In the 

middle elevation forests of the silver fir zone, 

redcedar had lower frequency and cover, but 

there was little difference in constancy and 

cover between dry and wet vegetation types. 

Abundance of cedars and other tree species 

along age sequence 

The cover of redcedar and yellowcedar for 

different age classes was compared to other tree 

species to understand the contribution of tree 

species composition and abundance to stand 

development and succession in the western 

North Cascades. This analysis was done for the 

Western Hemlock/Swordfern-Mesic PAG 

(Tsuga heterophylla/Polystichum munitum) 

(Fig. 6). This PAG represents a relatively warm, 

mesic environment and is the most common 

PAG in the western hemlock zone in the study 

area. Cover of redcedar was fairly constant 

across the age classes and averaged about 20%. 

Most species showed a peak in cover between 

50-120 years; Douglas-fir (Pseudotsuga

menziesii) peaked early and declined in old 

stands; western hemlock increased over time 

and eventually dominated old-growth stands. 

Red alder (Alnus rubra) and bigleaf maple (Acer

macrophyllum) had the lowest cover and 

occurred throughout the age sequence but at low 

abundance; however, these early seral species 

may also occur in old stands where they can be 

found in canopy gaps. 

A similar analysis was done for the most 

common PAG in the middle elevation forests of 

the silver fir zone (Fig. 7). The Silver Fir/Alaska 

Huckleberry Moist PAG (Abies 

amabilis/Vaccinium alaskaense) occurs in cool 

moist environments with a persistent winter 

snow pack averaging 2-3 m. The cover of 

redcedar was fairly constant over time (Fig. 7), a

Figure 6 -- Averaged percent cover of major tree species by averaged stand age for the Western 

Hemlock/Swordfern-Mesic Plant Association Group, western North Cascades (n=403).

16
Figure 7 -- Averaged percent cover of major tree species by averaged stand age for the Silver Fir/Alaska 

Huckleberry-moist Plant Association Group, western North Cascades (n=813).

similar pattern to the western hemlock PAG 

(Fig. 6), but averaged about half the cover 

(10%) compared to the western hemlock zone 

PAG. Western hemlock and silver fir codominate in old forests, each averaged about 

50% cover. Yellowcedar occurred in the silver 

fir zone PAG, but was typically a minor 

component. Douglas-fir was also a minor 

species in these environments, and the young 

age classes with Douglas-fir were mostly 

plantations. 

Redcedar size class distribution by stand age 

The abundance (cover) of redcedar by size class 

and stand age was calculated for the Western 

Hemlock/Swordfern-Mesic PAG (Fig. 8). 

Redcedar cover peaked in the 80 and120 year 

age classes, and then was fairly constant into the 

oldest age class. Beginning in mature stands 

(120 year age class), all size classes for redcedar 

were represented but the relative abundance 

changed across the age sequence. Pole size trees 

dominated until the 200 year age class, when the 

3-10 dm dbh size class became more abundant. 

The cover of redcedar trees >1 m dbh was 

highest in the oldest stands. 

A similar analysis was done for the distribution 

and abundance (cover) of redcedar by size class 

and stand age for the Silver Fir/Alaska 

Huckleberry-Moist PAG (Fig. 9). In this cool 

moist environment, redcedar cover peaked in 

the 60 to 80 year age classes, and was fairly 

constant over time but at lower levels than warm 

mesic western hemlock PAG (Fig. 8). All size 

classes of redcedar were present in mature 

stands at about 80 years, but the relative 

abundance changed with age and larger 

diameter trees became more abundant over time. 

The silver fir zone is a colder environment than 

the western hemlock zone. Redcedar trees 

achieved larger diameters in younger age classes 

in the silver fir zone PAG compared to the 

western hemlock zone PAG (figs. 8, 9). This 

pattern may relate to competition with 

associated species, where the dominant tree 

species in the silver fir zone PAG have similar 

shade tolerance. There is a bigger range in shade 

tolerance of tree species in the western hemlock 

zone PAG where Douglas-fir was a major 

component of most stands. 

Alaska yellowcedar size class distribution by 

stand age

The abundance (cover) of yellowcedar by size 

class and stand age was calculated for the 

western North Cascades (Fig. 10). Most size 

classes of yellowcedar were represented in old17
growth stands beginning in the 300 year age 

class. Yellowcedar is a slow growing species, 

and the 3-10 dm dbh size class was not achieved 

until about 200 years. The oldest stands were 

dominated by yellowcedar in the 3-10 dm dbh 

and >1m dbh size classes, however the largest 

trees were uncommon until the oldest age class, 

which represented stands from 1000 to over 

1500 years of age. If this oldest age class didn’t 

exist on the landscape, there would probably be 

very few of these big old yellowcedar trees. 

Figure 8 -- Cover of redcedar by size class and stand 

age (n=157) for the Western Hemlock/SwordfernMesic PAG in the western North Cascades. Age 

represents the midpoint of the class. 

Figure 9 -- Cover of redcedar by size class and stand 

age (n=257) for the Silver Fir /Alaska HuckleberryMoist PAG in the western North Cascades. Age 

represents the midpoint of the class. 

Summary

Redcedar had broad ecological amplitude, 

tending somewhat to the dry end of the 

precipitation gradient. Redcedar was also more 

common at warmer temperatures and at lower 

elevations. The cover of redcedar was fairly 

constant over stand ages in both the western 

hemlock and silver fir zone PAGs. Larger 

diameter redcedar trees became dominant at 

younger stand ages in the silver fir zone PAG 

compared to the western hemlock zone PAG.

Figure 10 -- Cover of yellowcedar by size class and 

stand age for the western North Cascades (n=3837). 

Age represents the midpoint of the class.

Yellowcedar was less common on the 

landscape, and was limited to cooler sites at mid 

to upper elevations and with higher 

precipitation. The cover of yellowcedar was 

highest in the oldest stands. In the study area, 

the oldest trees were yellowcedar. It is a slowgrowing species, and trees >1m dbh were 

uncommon in forests less than 500 years old. 

LITERATURE CITED

Henderson, J.A.; Peter, D.H.; Lesher, R.D.; 

Shaw, D.C. 1989. Forested plant associations of 

the Olympic National Forest. Tech. Pap. R6-

ECOL-001-88. Portland, OR: USDA Forest 

Service, Pacific Northwest Region. 502 p. 

Henderson, J.A.; Lesher, R.D.; Peter, D.H.; 

Shaw, D.C. 1992. Field guide to the forested 

plant associations of the Mt. BakerSnoqualmie National Forest. Tech. Pap. R6-

ECOL-028-91. Portland, OR: USDA Forest 

Service, Pacific Northwest Region. 196 p. 

Henderson, J.A.; Lesher, R.D.; Peter, D.H.; 

Ringo, C.D. A landscape model for predicting 

potential natural vegetation of the Olympic 

Peninsula USA using boundary equations and 

newly developed environmental variables. In 

review.

0

2

4

6

8

10

12

14

16

18

20

3 15 25 40 60 80 120 200 300 500 850

Stand Age

Percent Cover

 < meter tall

<1 dm dbh

1-3 dm dbh

3-10 dm dbh

>10 dm dbh

0

1

2

3

4

5

6

7

8

9

10

15 25 40 60 80 120 200 300 500 850

Stand Age

Percent Cover

 < meter tall

<1 dm dbh

1-3 dm dbh

3-10 dm dbh

>10 ddm dbh

0

1

2

3

4

5

6

7

8

3 7 15 25 40 60 80 120 200 300 500 850 1250

Stand Age

Percent Cover

< meter tall

<1 dm dbh

1-3 dm dbh

3-10 dm dbh

>10 dm dbh

18
1

Cindy Prescott is Professor and Associate Dean, Faculty of Forestry, University of British Columbia, 2005-2424 

Main Mall, Vancouver, BC, Canada, V6T 1Z4 cindy.prescott@ubc.ca 

NITROGEN AVAILABILITY IN FOREST FLOORS OF WESTERN 

REDCEDAR: SURPRISES, CONUNDRUMS, SOLUTIONS 

Cindy E. Prescott1

ABSTRACT

Western redcedar (Thuja plicata Donn ex D. Don) is thought to be an indicator of nutrient-rich sites, to 

preferentially take up nitrate and to create N-rich forest floors. Higher concentrations or proportion of 

nitrate (relative to ammonium) are also commonly reported in cedar forest floors. However, rates of net N 

mineralization in cedar forests floors are usually not greater than other species; nor are N concentrations 

higher, indicating that cedar does not create particularly N-rich forest floors. This is consistent with cedar 

foliar litter consistently having high C:N ratio, high recalcitrant content, and slow decay relative to other 

tree species. This conundrum may be related to the high concentrations of Ca and high pH of cedar forest 

floors relative to other species. Cedar forest floors also have been reported to have higher bacteria 

biomass (including ammonium-oxidizing bacteria) and lower fungal biomass, probably as a consequence 

of the higher pH and Ca. Therefore, the greater proportion of nitrate in cedar forest floors is probably 

more reflective of higher pH and associated changes in microbial populations, rather than an indication of 

high N availability. There is also little evidence that western redcedar preferentially takes up the nitrate 

form of nitrogen.

KEYWORDS: Nitrate, litter decomposition, calcium, pH, common-garden experiment.

INTRODUCTION

Although it has long been recognized that tree 

species influence the properties of the soils and 

forest floors that develop beneath them, it has 

proven surprisingly difficult to generalize about 

the nature of particular tree species’ influences 

(Binkley 1995; Binkley and Giardina 1998). 

Western redcedar is no exception; in fact, recent 

evidence has called into question many of the 

ideas previously held about western redcedar and 

its influence on forest floor and soils. Cedar has 

traditionally been considered to be an indicator 

of nutrient-rich sites, and is thought to produce 

N-rich forest floors. These generalizations are 

based on cedar being generally associated with 

rich sites in ecosystem classification schemes 

(Klinka et al. 1989), evidence that cedar 

preferentially takes up nitrate (Krajina et al. 

1973), and the observation that cedar has 

arbuscular mycorrhizae, which tend to be 

associated with nitrate uptake and nitrate 

environments (Read and Perez-Mereno 2003). 

Cedar forest floors consistently have high 

concentrations of Ca and high pH relative to 

other species (Alban 1969; Turner and Franz 

1985; Prescott and Preston 1994) and higher 

concentrations of nitrate or proportion of nitrate 

(relative to ammonium) (Turner and Franz 1985; 

Harmer and Alexander 1986). These 

observations understandably led to the 

assumption that western redcedar is a 

nitrophilous species. 

Recent findings are not consistent with the 

conventional wisdom that western redcedar is an 

indicator of nutrient-rich sites, prefers nitrate and 

creates N-rich forest floors. On nutrient-poor 

cedar-salal sites on northern Vancouver Island, 

cedar grows better than other species, and 

responds less to fertilization with N and P 

(Bennett et al. 2003). There is also little evidence 

that cedar prefers nitrate – Bennett and Prescott 

(2004) found that cedar took up both nitrate and 

ammonium (Fig.1), and careful perusal of the 

early work of Krajina et al. (1973) does not 

2010 - A Tale of Two Cedars PNW-GTR-828

19
support the conclusion that cedar prefers nitrate 

any more than does Douglas-fir (Pseudotsuga 

menziesii (Mirb.) Franco) or lodgepole pine 

(Pinus contorta Dougl. ex Laws. var. contorta). 

Foliar litter of western redcedar consistently has 

high C:N ratio, high "acid-unhydrolyzable 

residue" (AUR) content, and decays more slowly 

than foliar litter of other west-coast tree species 

(Harmon et al. 1990; Prescott and Preston 1994; 

Prescott et al. 2004). Rates of net N 

mineralization in cedar forests floors are usually 

not greater than other species (Prescott and 

Preston 1994; Prescott et al. 1995); nor are N 

concentrations higher (Ovington 1954; Alban 

1969; Prescott and Preston 1994), indicating that 

cedar does not create particularly N-rich forest 

floors. In fact, at the Clonsast Bog trial in 

Ireland, cedar forest floors had the lowest rates 

of net N mineralization of 14 species, including 

Calluna (Prescott et al. 1995; Table 1).

THE CONUNDRUM

These observations lead to the question of how 

western redcedar can be associated with rich 

sites and nitrate, but also grow on N-poor sites, 

not respond to N addition, have recalcitrant litter 

and low-N forest floors, and not show a marked 

preference for nitrate.

A possible solution to this conundrum lies in the 

high calcium concentrations and pH that are a 

distinct characteristic of forest floors of western 

redcedar. Nitrifying organisms are known to be 

less active in acidic forest floors and soils, and so 

would be expected to be more active in cedar 

forest floors than other coniferous tree species. 

Cedar forest floors have been reported to have 

higher bacteria biomass (including ammoniumoxidizing bacteria) and lower fungal biomass 

(Turner and Franz 1985). The higher pH and Ca 

may also stimulate soil macrofauna, particularly 

earthworms. A positive association between Ca 

and pH in litter and forest floors, earthworm 

abundance and nitrate availability has been 

reported under certain broadleaf trees species 

(Reich et al. 2005; Hobbie et al. 2006; Laganiere 

et al. 2008). 

This leads to the hypothesis that the high 

proportion of nitrate in cedar forest floors is a 

Table 1 – Rates of net nitrogen mineralization and 

pH of forest floors under various species at the 

UBC Research Forest and Clonsast Bog (Ireland) 

field trials. Mineralization rates are based on 1-

mo lab incubations. From Prescott et al. (1995). 

Species N Mineralization pH

(μg N g-1 d-1)

UBC Research Forest

Douglas-fir 5.5 5.2

Western hemlock 3.2 4.2

Western redcedar 1.6 5.1

Clonsast Bog

Sissile oak 22.6 4.7

Sitka spruce 15.1 4.8

Grand fir 15.1 5.0

Douglas-fir 13.9 4.4

Norway spruce 12.7 4.9

Western hemlock 8.9 3.9

Scots pine 7.4 4.7

Monterey pine 5.3 4.1

Calluna 4.1 4.6

Western redcedar 1.2 6.1

consequence of higher pH and associated 

changes in populations of soil fauna and 

microorganisms, rather than an indication of 

high N availability. 

EP 571 SPECIES TRIAL

This hypothesis can be tested with data from the 

BC Ministry of Forests and Range Experimental 

Project (EP) 571 study sites on the west coast of 

Vancouver Island, British Columbia, Canada. 

Four installations were examined, each with two

plots of each of four tree species: western 

redcedar, western hemlock (Tsuga heterophylla

(Raf.) Sarg.), Douglas-fir and Sitka spruce 

(Picea sitchensis (Bong.)). The Upper Klanawa 

and Sarita Lake sites are near Franklin River; the

San Juan and Fairy Lake sites are near Port 

Renfrew. The installations are in the 

Submontane Very Wet Maritime Coastal 

Western Hemlock (CWHvm1) variant on the 

windward side of the Vancouver Island 

Mountains (Meidinger and Pojar 1991). The 

soils are Ferro-Humic or Humo-Ferric Podzols 

but soil moisture and nutrient regimes vary 

among sites. Fairy Lake installation soils are in 

the drier, less nutrient-rich range, Sarita Lake is 

20
moderate, and Upper Klanawa and San Juan are 

moister and more nutrient rich. The study area 

initially supported old-growth stands of western 

hemlock, western redcedar, amabilis fir (Abies 

amabilis [Dougl.] Forbes), and occasional 

Douglas-fir and Sitka spruce, and was logged 

between 1958 and 1960, slash-burned in 1961 

and planted in 1962. At each site, 81 seedlings 

were planted in each of two plots for each 

species at each of 2.7-m, 3.7-m, and 4.7-m 

spacing. In this study only the 2.7-m spacing 

plots were sampled, except at the Fairy Lake site, 

where one western hemlock plot failed so we 

sampled a 3.7-m spacing plot. Plots have been 

maintained since installation and volunteer 

conifers, (mostly western hemlock) have been 

periodically removed.

If the hypothesis is correct, then relative to the 

other tree species, cedar litter and forest floors 

will have higher pH and Ca, higher populations 

of bacteria, nitrifiers and soil macrofauna, and 

more available N in nitrate form, but will not 

have faster decay or greater N availability.

RESULTS 

Consistent with our hypothesis, cedar litter at the 

EP 571 sites had lower N and higher Ca and 

AUR concentrations than the other litters (Table

2). Cedar foliar litter decayed more slowly than 

litter of western hemlock or Douglas-fir (Fig. 2).

Table 2 – Nutrient and carbon concentrations (mg 

g-1) in foliar litter of western redcedar and other 

conifers at the EP 571 sites. AUR = acidunhydrolyzable residue (recalcitrant material, %). 

Adapted from Prescott et al. (2000).

Species N C/N P K Ca Mg AUR

cedar 5.46 

b

102 0.48 

b

0.6 

b

16.7 

a

0.8 

b

48

a

hemlock 5.26 

b

109 0.43 

b

0.6 

b

8.2 

c

1.2 

a

37

c

Douglasfir7.60 

a

75 0.53 

b

0.4 

b

6.9 

c

0.8 

b

39 

bc 

spruce 7.71 

a

73 0.80 

a

1.6 

a

11.6 

b

1.2 

a

42 

b

Values are means with SE given in parentheses of four samples per 

species or site. For each parameter, means followed by different letters 

are significantly different (p < 0.05) based on Duncan’s multiple range 

test.

Cedar forest floors also had higher pH, higher 

concentrations of Ca and Mg and lower N 

concentrations than the other species (Table 3). 

Table 3 – Mass (Mg ha-1), pH, and nutrient 

concentrations (mg g-1) in forest floors of western 

redcedar and other conifers at the EP 571 sites. 

Adapted from Prescott et al. (2000).

Species Mass pH N P K Ca Mg

cedar 59

 a 

4.8 

a 

8.6

a 

0.93 

ab

0.83 

c 

9.7 

a 

2.4 

a 

hemlock 36

ab

4.3 

b 

8.6 

b 

0.88 

b 

1.23 

ab

4.9 

b 

1.7 

a 

Douglasfir32

 b 

4.5 

a 

9.0 

ab

0.87 

b 

1.04 

bc

6.0 

b 

2.0 

a 

spruce 47

ab

4.8 

a 

10.3 

a 

1.06 

a 

1.50 

a 

8.7 

a 

2.1 

a 

Values are means with SE given in parentheses of eight samples per 

species or site. For each parameter, means followed by different letters 

are significantly different (p < 0.05) based on Duncan’s multiple range 

test.

Rates of net N mineralization and nitrification 

were highly variable within plots and differed 

greatly among sites, but average rates were 

slightly higher under cedar (Fig. 3). Lower 

fungal:bacterial ratios were found in cedar forest 

floors (Fig. 4). However, assessment of 

communities of soil invertebrates did not provide 

evidence for greater populations of earthworms, 

millipedes or enchytraeids in cedar forest floors 

(S. Berch, unpublished data). 

CONCLUSIONS

In conclusion, the evidence to date is consistent 

with the suggestion that western redcedar 

produces recalcitrant, low-N litter which 

decomposes relatively slowly, but has high Ca 

concentrations which stimulate nitrification. This 

creates the unusual situation in which the forest 

floor is N-poor but dominated by nitrate. It 

follows that the presence of nitrate is not 

necessarily an indication of high N availability. 

There is also little evidence that western redcedar 

preferentially takes up the nitrate form of 

nitrogen. 

21
Figure 4–Fungal:bacterial ratios of forest floors 

from four tree species at the EP 571 sites. 

Adapted from Grayston and Prescott (2005) 

Figure 3–Rates of N mineralization and proportion 

of ammonium and nitrate (μg g-1 25 d-1) produced 

during a 25-day laboratory incubation of forest 

floors from four tree species at the four EP 571 

sites. Error bars are standard errors (n = 2). Tree 

species abbreviations are as follows: Cw - western 

redcedar; Hw - western hemlock; Fd - Douglas-fir; 

Ss - Sitka spruce. Adapted from Prescott et al. 

(2000).

Figure 2–Mass loss of foliar litter of western 

redcedar and other conifers during 3 years at the 

EP 571 sites. Adapted from Prescott et al. (2000). 

Figure 1–Uptake of 15N-enriched solutions of

Ca(NO3)2, (NH4)2SO4 , glutamic acid, plant protein, 

and plant protein-tannin complex by cedar, hemlock 

and salal seedlings following injection into the forest 

floor at the beginning of the 20-day greenhouse trial. 

Adapted from Bennett and Prescott (2004).

22
LITERATURE CITED

Alban, D.H. 1969. The influence of western 

hemlock and western redcedar on soil 

properties. Soil Sci. Soc. Amer. Proc. 33: 453-

457. 

Bennett, J.N.; Prescott, C.E. 2004. Organic 

and inorganic nitrogen nutrition of western 

redcedar, western hemlock and salal in mineral 

N-limited cedar-hemlock forests. Oecologia 

141: 468-476. 

Bennett, J.N.; Prescott, C. E.; Barker, J.E.; 

Blevins, D.P.; Blevins, L.L. 2003. Long-term 

improvement in productivity and nutrient 

availability following fertilization and 

vegetation control on a cedar-hemlock cutover. 

Can. J. For. Res. 33: 1516-1524. 

Binkley, D. 1995. The influence of tree species 

on forest soils: processes and patterns. Pp. 1-33 

in: Proceedings of the Trees and Soil Workshop, 

Lincoln University. Edited by D.J. Mead and 

I.S. Cornforth. Agronomy Society of New 

Zealand Speical Publication # 10, Lincoln 

University Press, Canterbury, New Zealand. 122 

p. 

Binkley, D.; Giardina, C. 1998. Why do tree 

species affect soils? The warp and woof of treesoil interactions. Biogeochemistry 42: 89-106. 

Grayston, S.J.; Prescott, C.E. 2005. Microbial 

communities in forest floors under four tree 

species in coastal British Columbia. Soil Biol. 

Biochem. 37: 1157-1167. 

Harmer R.; Alexander, I. 1986. The effect of 

starch amendment on nitrogen mineralisation 

from the forest floor beneath a range of conifers. 

Forestry 59: 39-46. 

Harmon, M.E.; Baker, G.A.; Spycher, G.; 

Greene, S.E. 1990. Leaf-litter decomposition in 

the Picea/Tsuga forests of Olympic National 

Park, Washington, U.S.A. For. Ecol. Manage. 

31: 55-66. 

Hobbie, S.E.; Reich, P.B.; Oleksyn, J. 2006.

Tree species effects on decomposition and forest 

floor dynamics in a common garden. Ecology 

87: 2288-2297. 

Klinka, K.; Krajina, V.J.; Ceska, A.; Scagel, 

A.M. 1989. Indicator plants of coastal British 

Columbia. University of British Columbia 

Press, Vancouver. 330 p. 

Krajina, V.J.; Madoc-Jones, S.; Mellor, G. 

1973. Ammonium and nitrate in the nitrogen 

economy of some conifers growing in Douglasfir communities of the Pacific north-west 

of America. Soil Biol.Biochem.5: 143-147. 

Lageniere, J.; Pare, D.; Bradley, R.L. 2008.

Linking the abundance of aspen with soil faunal 

communities and rates of belowground 

processes within single stands of mixed aspenblack spruce. Appl. Soil Ecol. 41: 19-28. 

Meidinger, D.V.; Pojar, J. 1991. Ecosystems 

of British Columbia. B.C. Ministry of Forests, 

Victoria, B.C. Spec. Rep. Ser. 6. 

Ovington J.D. 1954. Studies of the 

development of woodland conditions under 

different trees. II. The forest floor. J. Ecol. 42: 

71-80. 

Prescott, C.E.; Preston, C.M. 1994. Nitrogen 

mineralization and decomposition in forest 

floors in adjacent plantations of western red 

cedar, western hemlock, and Douglas-fir. Can. 

J. For. Res. 24: 2424-2431. 

Prescott, C.E.; Thomas, K.D.; Weetman, G.F. 

1995. The influence of tree species on nitrogen 

mineralisation in the forest floor: Lessons from 

three retrospective studies. pp 59-68 in: Pp. 1-33 

in: Proceedings of the Trees and Soil Workshop, 

Lincoln University. Edited by D.J. Mead and 

I.S. Cornforth. Agronomy Society of New 

Zealand Speical Publication # 10, Lincoln 

University Press, Canterbury, New Zealand. 122 

p. 

23
Prescott, C.E.; Vesterdal, L.; Preston, C.M.; 

Simard, S.W. 2004. Influence of initial 

chemistry on decomposition of foliar litter in 

contrasting forest types in British Columbia. 

Can. J. For. Res. 34: 1714-1729. 

Prescott, C.E.; Vesterdal, L.; Pratt, J.; 

Venner, K.H.; de Montigny, L.M.; 

Trofymow, J.A. 2000. Nutrient concentrations 

and nitrogen mineralization in forest floors of 

single species conifer plantations in coastal 

British Columbia. Can. J. For. Res. 30: 1341-

1352. 

Read, D. J.; Perez-Moreno, J. 2003. 

Mycorrhizas and nutrient cycling in ecosystems 

– a journey towards relevance? New Phytol. 

157: 475-492. 

Reich, P.B.; Oleksyn, J.; Modrzynski, J.; 

Mrozinski, P.; Hobbie, S.E.; Eissenstat, 

D.M.; Chorover, J.; Chadwick, O.A. ; Hale, 

C.M.; Tjoelker, M.G. 2005. Linking litter 

calcium, earthworms and soil properties: a 

common garden test with 14 tree species. Ecol. 

Lett. 8: 811-818.

Turner, D.P.; Franz, E.H. 1985. The influence 

of western hemlock and western redcedar on 

microbial numbers, nitrogen mineralization, and 

nitrification. Plant Soil 88: 259-267. 

24
THE EFFECTS OF EXCESSIVE MOISTURE ON SOIL C AND N 

MINERALIZATION AND SITE PRODUCTIVITY IN COASTAL 

FORESTS OF BRITISH COLUMBIA

Toktam Sajedi1 and Cindy E. Prescott

ABSTRACT

Conifers regenerating on cutovers of cedar-hemlock (CH) forests exhibit slow growth and nutrient 

deficiencies (N and P) which are not observed on adjacent cutovers of hemlock-amabilis fir (HA) 

forests. The underlying causes of the nutrient deficiencies are not understood. Our field investigations 

indicate that CH soils are wetter, oxygen-limited and potentially more anaerobic than HA sites. We 

hypothesize that these conditions will be associated with lower mineralization of C and N, changes in 

prevalent N forms and lower forest productivity. Forest floor and mineral soil from 5 CH and 5 HA sites 

were incubated for 4 weeks in the laboratory at four moisture levels (field moisture and three levels up 

to saturation), and total N and C, dissolved inorganic and organic N (DIN and DON), microbial biomass 

and CO2 flux were measured.

Microbial biomass, C mineralization (CO2 efflux) and the SIN:SON ratio all declined under watersaturated conditions. SON was the most responsive N form to the changes in soil moisture and redox. 

SON concentrations increased with increasing moisture and decreasing redox potential. Ammonium 

concentrations were most closely related to total N concentration, and nitrate concentrations were 

correlated with pH. Concentrations of SIN (especially ammonium) increased with increasing moisture in 

HA soils, suggesting that excessive moisture did not inhibit N mineralization in HA forests. In contrast, 

in CH humus and soil, the SIN pool was small and decreased with increasing moisture. Our results 

indicate that the low N availability on CH sites results from synergistic effects of higher phenolic 

contents of the organic matter and greater frequency of waterlogging of soils on CH sites. 

Improving soil oxygen availability through the use of trenches can be an effective method to enhance 

timber growth by removing excess water from the rooting zone in wetland forests. The effects of 

drainage on site productivity and soil carbon stores was assessed by comparing tree growth, understory 

vegetation, soil C stores and C mineralization in drained and undrained areas in a cedar-swamp cutover 

that had been operationally drained 10 years earlier. Drainage improved tree growth and increased soil 

total C storage in the humus layer. However, laboratory incubation indicated that microbial biomass C 

and C mineralization (CO2) efflux were not affected. Our results indicate that drainage could be a useful 

silvicultural practice for improving the productivity of cedar-swamp ecosystems in coastal B.C. and that 

it may be possible to improve tree growth without stimulating loss of soil C. This requires that drainage 

improve aeration in the rooting zone while maintaining redox levels of less than +300 mV in the bulk 

soil, a condition where oxygen level may be sufficient for plant growth but not for aerobic microbial 

decomposition. 

1 Faculty of Forestry, 2424 Main Mall, University of British Columbia, Vancouver, BC, V6Z 1L1, tsajedi@gmail.com 

2010 - A Tale of Two Cedars PNW-GTR-828

25
THE BIOGEOCHEMISTRY OF CEDAR FORESTS: THE CEDARNITRATE HYPOTHESIS

David V. D’Amore1 and Paul E. Hennon

ABSTRACT

Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) and western redcedar (Thuja plicata Donn) 

are competitive in low productivity sites on wet, nearly saturated soils in forests of the Pacific 

Northwest, British Columbia and southeast Alaska. One means of surviving these marginal conditions is 

through exploiting a coupled calcium (Ca+2) and nitrate (NO3

-

) nutrient cycle where trees assimilate N as 

NO3

-

, but must accumulate a counter-ion to NO3

- such as Ca+2 to control their internal cell pH and 

provide electrochemical balance. This ‘cedar-nitrate hypothesis’ has been proposed as an explanation for 

the presence of yellow- and redcedar in ecotonal areas between open peatlands and well-drained soils. 

However, this process occurs preferentially near the soil surface where higher pH and aerobic soil 

promote nitrification leading to a potential susceptibility of the trees to freezing injury. Cedars must 

concentrate fine-root biomass near the soil surface to access Ca and NO3

-

 and this physiological 

adaptation that makes these cedars more competitive on marginal sites also creates a vulnerability to 

periodic root freezing injury that is leading to the decline of at least one of them – yellow-cedar. The 

proliferation of shallow fine roots to facilitate this nutrient acquisition strategy is consistent with the 

findings that yellow-cedar has been subject to fine root freezing injury leading to widespread decline. 

Cedars influence the soils under their canopy by enriching the forest floor with calcium compounds 

leading to increases in pH. The availability of NO3

- in cedar forests is favored by increased microbial 

activity and shifts in microbial community composition that is conducive to N mineralization and 

nitrification at higher pH. The cedar-nitrate process leads to fundamental shifts in the biogeochemistry 

of cedar forests. These biogeochemical changes have a potentially substantial cumulative impact on soil 

and streamwater that is incorporated into an entire watershed signal. We will provide evidence from a 

replicated yellow-cedar forest stand study to support the nutrient cycles associated with the cedar-nitrate 

hypothesis. We will also describe how the feedback mechanisms between the trees and soils of cedar 

forests impact watersheds. This information can be used to formulate management and adaptation 

strategies in the growing region of both yellow- and redcedar trees. We also explore the links to other 

cedars and the potential for the development of the cedar-nitrate acquisition strategy to guide the 

management and ecological understanding throughout the ‘cedar’ family. 

 

1 Forest Service, U.S. Department of Agriculture, Pacific Northwest Research Station, Juneau, AK 99801, U.S.A. 

ddamore@fs.fed.us (corresponding author), Tel: 907-586-7922, Fax: 907-586-7848; phennon@fs.fed.us

2010 - A Tale of Two Cedars PNW-GTR-828

26
1 Pacific Southwest Research Station, USDA Forest Service, Taylorsville, CA 95983

2 Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of 

California, Berkeley CA 94720 

3 School of Forest Resources, University of Washington, Seattle, WA 98195 

4 Agriculture and Agri-Food Canada, Swift Current, Saskatchewan, S9H 3X2, Canada 

DECOMPOSITION AND NUTRIENT DYNAMICS IN WESTERN 

REDCEDAR/HEMLOCK AND DOUGLAS-FIR/HEMLOCK 

ECOSYSTEMS ON THE WESTERN OLYMPIC PENINSULA OF 

WASHINGTON

Emily E.Y. Moghaddas1, John G. McColl2, Robert L. Edmonds3, 

and Barbara Cade-Menun4

ABSTRACT

Western redcedar and Douglas-fir are important tree species at lower elevations in the Pacific Northwest 

US and western Canada, but they differ ecologically. Despite these differences they grow together. 

Western hemlock is commonly associated with both species. This study was conducted to determine: (1) 

differences in soil between western redcedar/hemlock and Douglas-fir/hemlock stands on the western 

Olympic Peninsula of Washington, (2) differences in decomposition rates of a common woody substrate 

(birch sticks), (3) differences in nutrient immobilization and release, and (4) potential nutritional 

advantages for western redcedar and Douglas-fir to grow together. Stands ranged in age from about 75 

years to old-growth. Birch sticks were placed in three western redcedar/hemlock sites near Kalaloch and 

three Douglas-fir/hemlock sites near Forks, Washington in May 1998 and retrieved after 6, 12 and 16 

months. Sticks were analyzed for C, N, P, K, Ca, and Mg. Mass loss tended to be greater in sticks in 

Douglas-fir/hemlock than western redcedar/hemlock stands after 16 months (38% versus 34%), but not 

significantly (p<0.05). Temperature and moisture conditions in the stands were similar. Nitrogen and P 

were immobilized in sticks in both stand types, but to a lesser extent in western redcedar/hemlock than 

Douglas-fir/hemlock. Calcium, K, Mg were initially lost from the sticks and then slightly immobilized 

in both stand types. Soil pH in the upper 10 cm of mineral soil was similar in western redcedar/hemlock 

and Douglas-fir/hemlock stands (3.9 versus 4.0). There were no significant differences in concentrations 

of C and N and C/N ratios in the A horizon soil in the Douglas-fir/hemlock and western 

redcedar/hemlock sites. However, concentrations of total P and Ca were significantly higher in the 

Douglas-fir/western redcedar sites than the western redcedar/hemlock sites. The A horizon depth was 

also significantly greater in the western redcedar/hemlock stands. Nutritionally western redcedar might 

benefit from the higher P levels provided by Douglas-fir and Douglas-fir might benefit from the deeper 

rooting western redcedar which would aid in nutrient retention. 

KEYWORDS: Decomposition, nutrient cycling, western redcedar, Douglas-fir

INTRODUCTION

Western redcedar (Thuja plicata) and Douglasfir (Pseudotsuga menziesii) are important tree 

species at lower elevations in the Pacific 

Northwest US and western Canada. However, 

they differ considerably ecologically. Western 

redcedar is tolerant of shade and high soil 

moisture, while Douglas-fir is intolerant of 

shade and high soil moisture. Douglas-fir is fire 

tolerant and western redcedar is fire intolerant. 

Western redcedars also tend to live longer than 

Douglas-firs. Furthermore, western redcedar is 

an arbuscular mycorrhizal species while 

Douglas-fir is an ectomycorrhizal species. They 

also differ nutritionally, with western redcedar 

thought to be a Ca accumulator. Western 

redcedar has a wider range tolerance of nutrient 

availability, and grows better on extremely N2010 - A Tale of Two Cedars PNW-GTR-828

27
poor western redcedar-salal sites. Both species 

respond to N and P fertilization (Klinka and 

Brisco 2009). 

 

Despite these differences they grow together. 

Western hemlock (Tsuga heterophylla) is a 

common associate of both and all three can

occur together. Currently there is considerable 

interest in growing western redcedar with 

Douglas-fir in plantations instead of planting 

monocultures of Douglas-fir. However, western 

redcedar is heavily browsed by deer and is hard 

to establish.

Tree species can greatly influence litter 

substrate quality and have a large effect on the 

chemical and physical nature and decomposition 

of the forest floor (Prescott 1996, 2002; Prescott 

and Vesterdal 2005). Tree species also strongly 

influence the chemistry of throughfall and 

stemflow. Concentrations of PO4, SO4 tended to 

be higher in Douglas-fir throughfall and 

stemflow than western redcedar and hemlock in 

an old-growth rain forest on the Olympic 

Peninsula of Washington (Edmonds et al. 1991). 

Also stemflow had higher concentrations of Ca, 

K, Mg and Na in Douglas-fir. Ammonium 

concentrations tended to be higher in western 

redcedar throughfall and stemflow, but NO3 

concentrations were similar.

Few studies contrasting decomposition and 

nutrient dynamics of western redcedar and 

Douglas-fir have been conducted. Our specific 

objectives were to determine (1) differences in 

soil between western redcedar/hemlock and 

Douglas-fir/hemlock stands on the western 

Olympic Peninsula of Washington, (2) 

differences in decomposition rates of a common 

woody substrate (birch sticks), (3) differences in 

nutrient immobilization and release, and (4) 

nutritional advantages for western redcedar and 

Douglas-fir to grow together. The data 

presented here are part of a larger study 

involving determination of decomposition rates 

and nutrient dynamics at the mineral soil/forest 

floor interface under Douglas-fir and incense 

cedar (Calocedrus decurrens) in the California 

Sierra Nevada and Douglas-fir and western 

redcedar in the temperate rainforest of coastal 

Washington and the Mediterranean-type climate 

of California (Greinke 2000). 

STUDY SITES

Study sites were located within or near the 

lower Soleduck and Hoh River valleys of the 

Olympic Peninsula, Washington. Three western 

redcedar/hemlock sites near Kalaloch and three 

Douglas-fir/hemlock sites near Forks were 

selected. There is little difference in climate 

among the sites. Total annual precipitation 

averages about 300 cm, mostly falling from 

October to May. Mean monthly air temperature 

ranges from 4° C in January to 16° C in August 

(National Climate Data Center, U.S. Dept. of 

Commerce). The relatively young soils are 

classified as Dystrustepts and Ustorthents, with 

solum depths ranging from 30 to 110 cm. 

Douglas-fir, western redcedar, western hemlock 

and Sitka spruce were overstory species on the 

Douglas-fir/hemlock sites while only western 

redcedar, western hemlock and Sitka spruce 

occurred on the western redcedar/hemlock sites. 

Oxalis oregana, Gaultheria shallon and 

Vaccinium parvifolium were the dominant 

understory species on Douglas-fir /hemlock 

sites and Blechnum spicant, Gaultheria shallon, 

Vaccinium ovatum and Vaccinium parvifolium 

dominated on western redcedar/hemlock sites. 

MATERIALS AND METHODS

Soils

Forest floor depths and horizon depths were 

determined by digging soil pits at each site. 

Concentrations of C, total N, organic P, 

inorganic P, total P, available P, and Ca were 

determined in the A horizons. C/N ratios were 

calculated. 

Decomposition

Highly uniform, untreated white birch (Betula

papyrifera) craft sticks (2×18×130 mm) were 

obtained from Penley Corp, New Paris, ME. 

Sticks were linked together in sets of ten. In 

April, 1998, 15 sets of sticks were buried lying 

flat between the forest floor and mineral soil at 

each of the 6 study sites. Five sets were 

collected at each site in fall 1998, spring 1999, 

28
and fall 1999, corresponding to 6, 12 and 16 

months of decomposition, respectively. 

Sample processing and nutrient analyses

Sample processing and nutrient analyses were 

conducted at the University of California at 

Berkeley, with the exception of C and N, which 

were conducted at the Division of Agriculture 

and Natural Resources Analytical Lab, 

University of California, Davis. Sticks were 

oven dried to constant weight at 65° C. Stick 

weights were corrected for ash content and mass 

loss was calculated. Sticks were ground in a 

Wiley mill (Thomas Scientific, Swedesboro, 

NJ) to pass a 40-mesh screen. Total ash content 

was determined by incinerating at 600° C for 16 

h. A subsample was digested in nitric acid and 

analyzed for phosphorus (P), potassium (K), 

calcium (Ca), and magnesium (Mg) by ICP 

spectrometry. Carbon and total N were 

determined using a Nitrogen/Carbon Analyzer 

112-200-11 (Carlo-Erba, Milan, Italy).

Statistical analysis 

Student’s t tests (Microsoft Office Excel 2007) 

were used to determine differences in variables 

between western redcedar/hemlock and 

Douglas-fir/hemlock sites. Statistical differences 

were determined at p<0.05.

RESULTS AND DISCUSSION

Soils

The O horizon depth was not significantly 

different between the Douglas-fir/hemlock (5.0+ 

2.6 cm) and western redcedar/hemlock (7.0 + 

2.0 cm) sites. However, the A horizon depth 

was significantly deeper in western 

redcedar/hemlock (24.0+ 4.4 cm) than in 

Douglas-fir/hemlock (7.5+ 6.1 cm). 

 

There were no significant differences in 

concentrations of C and N and C/N ratios in the 

A horizon soil in the Douglas-fir/hemlock and 

western redcedar/hemlock sites (Table 1). 

Prescott and Vesterdal (2005) also found similar 

levels of total N in cedar forest floors relative to 

Douglas-fir and hemlock, but a higher 

proportion of nitrate relative to ammonium. 

They also found higher concentrations of Ca. 

However, we found that concentrations of Ca in 

A horizon soils were significantly higher in the 

Douglas-fir/hemlock sites than the western 

redcedar/hemlock sites. Total P concentrations 

were also significantly higher in Douglasfir/hemlock sites. Organic P, inorganic P, and 

available P concentrations also tended to be 

higher, but not significantly because of the high 

variation. Organic P tended to be the dominant 

form of P in the Douglas-fir hemlock sites, 

while inorganic P was the dominant form in the 

western redcedar/hemlock sites.

There were also no significant differences in the 

A horizon pH (Table 1). However, Prescott and 

Vesterdal (2005) found that western redcedar 

forest floors had higher pH (6.1) in comparison 

to Douglas-fir (4.4) and hemlock (3.9). 

Decomposition of birch sticks

There were no significant differences in 

decomposition rate of the birch sticks in the 

western redcedar/hemlock and DouglasTable 1-Average (+ SD) A horizon soil 

nutrient characteristics and concentrations in 

Douglas-fir/hemlock and western 

redcedar/hemlock sites. P concentrations are 

in mg/kg while Ca is in cmolc/kg. Averages 

with different letters are significantly 

different (p<0.05).

Douglas-fir/

hemlock

western 

redcedar/

hemlock

pH 4.0 + 0.3a 3.9 + 0.2a

C (%) 8.0 + 2.0a 8.8 + 1.7a

N (%) 0.4 + 0.1a 0.4 + 0.2a

C/N 21.7 + 0.3a 24.8 + 8.3a

Org P 1105 + 798a 43 + 20a

Inorg P 560 + 180a 375 + 220a

Total P 1665 + 650a 418 + 236b

Avail P 33.8 + 30.2a 2.8 + 2.0a

Ca 0.7 + 0.2a 0.4 + 0.1b

29
0

20

40

60

80

100

0 5 10 15 20

Percent 

Time (months)

Douglas-fir/hemlock

Cedar/hemlock

0

20

40

60

80

100

120

140

160

0 5 10 15 20

Percent 

Time (months)

Cedar/hemlock

Douglas-fir/hemlock 0

50

100

150

200

250

300

0 5 10 15 20

Percent

Time (months)

Cedar/hemlock

Douglas-fir/hemlock

fir/hemlock sites after 6, 12 and 16 months (Fig. 

1). However, decomposition tended to be faster 

at the Douglas-fir/hemlock sites after all time 

periods. Prescott and Vesterdal (2005) found 

that Douglas-fir and hemlock forest floors had 

faster decomposition than cedar forest floors. 

Also Graystone and Prescott (2005) found 

higher bacterial biomass and lower fungal 

biomass in cedar forest floors than Douglas-fir 

and hemlock forest floors. 

Nutrient immobilization and release

Changes in percent original N mass in birch 

sticks with times are shown Figure 2. Nitrogen 

was more rapidly immobilized in the Douglasfir/hemlock sites than the western 

redcedar/hemlock sites. However, N began to be 

released after 12 months in the Douglasfir/hemlock sites, but in the western 

redcedar/hemlock stand N continued to be 

immobilized for 16 months. The C/N ratio also 

decreased more rapidly with time in the 

Douglas-fir/hemlock sites than the western 

redcedar/hemlock stand. Like N, P was more 

rapidly immobilized in the Douglas-fir/hemlock 

sites than the western redcedar/hemlock sites 

(Fig. 3), and the C/P ratio fell more rapidly in 

Douglas-fir/hemlock sites. In contrast to N and 

P, Ca, K, and Mg were initially released from 

the decomposing birch stakes, but then began to 

be immobilized at both Douglas-fir/hemlock 

and western redcedar/hemlock sites. However, 

even after 16 months the percent of original Ca, 

K, and Mg was less than 100%. The nutrient 

mobility series after 16 months was similar in 

both western redcedar/hemlock 

(K<Mg<Ca<N<P) and Douglas-fir/hemlock 

(K<Mg=Ca<N<P) with K being most mobile 

and P being least mobile. 

Nutritional advantages for western redcedar 

and Douglas-fir to grow together

There may be a number of nutritional 

advantages for western redcedar and Douglas-fir 

Figure 1 -- Percent mass remaining of birch sticks at the 

western redcedar/hemlock and Douglas-fir/hemlock sites 

after 6, 12 and 16 months.

Figure 2 -- Changes in original percent N in birch 

sticks at the western redcedar/hemlock and Douglasfir/hemlock sites after 6, 12 and 16 months.

Figure 3 -- Percent P remaining in birch sticks at the 

western redcedar/hemlock and Douglas-fir/ hemlock 

sites after 6, 12 and 16 months.

30
to grow together along with western hemlock. 

Western redcedar and Douglas-fir in particular 

have quite different throughfall and stemflow 

chemistry (Edmonds et al. 1991). 

Concentrations of PO4, SO4 tend to be higher in 

Douglas-fir throughfall and stemflow than 

western redcedar and hemlock. Also stemflow 

has higher concentrations of Ca, K, Mg and Na 

in Douglas-fir than western redcedar. 

Ammonium concentrations tended to be higher 

in western redcedar throughfall and stemflow, 

but NO3 concentrations were similar.

We found that concentrations of P, particularly 

organic P, were much higher in the A horizon 

soil in Douglas-fir/hemlock sites than western 

redcedar/hemlock sites perhaps reflecting 

differences in throughfall and stemlow in 

western redcedar and Douglas-fir. The tendency 

for faster decomposition in the Douglasfir/hemlock sites might also indicate that the 

presence of Douglas-fir could make N and P 

more available to western redcedar when they 

grow together. In addition, western redcedar 

growing with Douglas-fir could result in deeper 

A horizons since western redcedar tends to root 

deeper than Douglas-fir (Bennett et al. 2002), 

more C storage, less nutrient loss below the 

rooting zone, and greater site occupancy. 

Western redcedar will also increase soil 

biodiversity since it has arbuscular mycorrhizal 

fungi and Douglas-fir and hemlock have 

ectomycorrhizal fungi. 

LITERATURE CITED

Bennett, J. N.; Andrew, B.; Prescott, C.E. 

2002. Vertical fine root distributions of western 

redcedar, western hemlock, and salal in oldgrowth cedar-hemlock forests on northern 

Vancouver Island.

Edmonds, R.L.; Thomas, T.B.; Rhodes, J.J. 

1991. Canopy and soil modification of 

precipitation chemistry in an old-growth 

temperate rainforest. Soil Sci. Soc. Am. J. 55: 

1685-1693. 

Graystone, S.J.; Prescott,C.E. 2005. Microbial 

communities in forest floors under four tree 

species in coastal British Columbia. Soil. Biol. 

Biochem. 37: 1157-1167. 

Greinke, E.Y.K. 2000. Wood decomposition 

and nutrient dynamics in California and 

Washington forests. MS thesis, University of 

California (Berkeley), Berkeley, CA. 

Klinka, K.; Brisco, D. 2009. Silvics and 

silviculture of coastal western redcedar: a 

literature survey. B.C Min. For. Range, For. Sci. 

Prog., Victoria, B.C. Spec. Rep. Ser. 11. 

Prescott, C. E. 1996. Influence of forest floor 

type on rates of litter decomposition in 

microcosms. Soil Biol. Biochem. 28: 1319-

1325. 

Prescott, C.E. 2002. The influence of the forest 

canopy on nutrient cycling. Tree Physiol. 22: 

1193-1200. 

Prescott, C. E. 2005. Decomposition and 

mineralization of nutrients from litter and 

humus. In:. BassirRad, H. (ed). Nutrient 

Acquisition by Plants: An Ecological 

Perspective. Springer-Verlag, Berlin: 125-41. 

Prescott, C. E.; Vesterdal. 2005. Effects of 

British Columbia tree species on forest floor 

chemistry. In: Binkley, D. ; Menyailo, O., eds. 

Tree species effects on soils: Implications for 

Global Change, Springer, Dordrecht, The 

Netherlands: 17-29. 

31
32
1 CellFor Inc., #4 6772 Oldfield Rd., Saanichton, BC, Canada V8M 2A3. sgrossnickle@cellfor.com

2 Cowichan Lake Research Station, BC Ministry of Forests and Range, Box 335, Mesachie Lake, BC, Canada V0R 2N0

ECOPHYSIOLOGICAL PROCESSES OF WESTERN REDCEDAR 

(THUJA PLICATA) AND YELLOW-CEDAR (CALLITROPSIS 

NOOTKATENSIS)

Steven C. Grossnickle1 and John H. Russell2

ABSTRACT

Each tree species has its own unique pattern of physiological response to field site environmental 

conditions. This presentation reviews the physiological performance of western redcedar (Thuja plicata

Donn) and yellow-cedar (Callitropsis nootkatensis (D. Don) Spach) in relation to environmental 

conditions. It must be recognized that environmental conditions change daily, seasonally and yearly. 

These two species show physiological responses to these changing environmental conditions. Their 

physiological performance in response to the environment ultimately determines these species 

subsequent performance in relation to field site conditions. This presentation is a synthesis of two 

decades of research by the authors and others. The first part of the presentation centers around the gas 

exchange processes of western redcedar and yellow-cedar in relation to atmospheric (i.e., light, 

humidity, temperature) and edaphic (i.e., soil temperature and water) conditions that occur in the field. 

Where available, information on these species growth is discussed in relation to these atmospheric and 

edaphic conditions. The second part of the presentation focuses on the seasonal patterns of freezing 

tolerance and drought tolerance of western redcedar and yellow-cedar. Where available, the talk will 

explore the dynamic nature of physiological responses and growth patterns that occurs for these species 

in a yearly cycle.

KEYWORDS: western redcedar, yellow-cedar, ecophysiology, gas exchange, freezing tolerance,

drought tolerance. 

INTRODUCTION

Each tree species has its own unique pattern of 

physiological response to field site 

environmental conditions. The physiological 

performance of western redcedar (Thuja plicata

Donn) and yellow-cedar (Callitropsis 

nootkatensis (D. Don) Spach) is driven by their 

response to environmental conditions. It must be 

recognized that environmental conditions 

change daily, seasonally and yearly. These two 

species show physiological responses to these 

changing environmental conditions. Their 

physiological performance in response to the 

environment ultimately determines these species 

subsequent performance in relation to field site 

conditions. The following sections briefly 

describe the major ecophysiological response 

patterns of these two species. Detailed 

discussions of the ecophysiological processes of 

western redcedar and yellow-cedar can be found 

in the list of publications by the authors (see 

attached list).

Photosynthetic Patterns 

Western redcedar and yellow-cedar have 

specific photosynthetic patterns in relation to 

atmospheric (i.e., light, humidity, temperature) 

and edaphic (i.e., soil temperature and water) 

conditions that occur in the field. Photosynthetic 

patterns of these species are only minimally 

affected by air temperatures >15 oC. Below 15 

oC there is a decline in photosynthesis with 

decreasing air and soil temperature, with 

western redcedar more sensitive of the species.

• Western redcedar declines at a faster rate 

(i.e. 46% greater decrease per 1 °C) than 

yellow-cedar.

• Yellow-cedar has greater photosynthetic 

capability at below freezing 

2010 - A Tale of Two Cedars PNW-GTR-828

33
temperatures (i.e. 68% higher @ -7.5 

°C).

Like air temperature, these species are only 

minimally affected by soil temperatures >15 oC. 

Below 15 oC there is a decline in photosynthesis 

with decreasing soil temperature, with western 

redcedar more sensitive of the species.

• Western redcedar declines at a faster rate 

(i.e. 58% greater decrease per 1 °C) than 

yellow-cedar.

• Yellow-cedar has greater photosynthetic 

capability at near-freezing temperature 

(i.e. 33% higher @ 0 °C).

Photosynthesis is at a maximum when western 

redcedar and yellow-cedar are exposed to wellwatered conditions (predawn water potential 

(ψpd) of -0.5 MPa). Photosynthetic capability 

declines with decreasing soil water availability 

with both species comparable in their response 

to drought. 

• Western redcedar declines to 20% of 

maximum photosynthetic capability at a 

predawn water potential (ψpd) of -1.4 

MPa (compared to photosynthesis @ a 

ψpd of -0.5 MPa) and 9% of maximum 

photosynthetic capability at a ψpd of -2.4 

MPa.

• Yellow-cedar declines to 32% of 

maximum photosynthetic capability at a 

ψpd of -1.4 MPa and 3% of maximum 

photosynthetic capability at a ψpd of -2.4 

MPa.

Photosynthesis is at a maximum when western 

redcedar and yellow-cedar are exposed to 

vapour pressure deficits (VPD) of <1.0 kPa. For 

both species their photosynthetic capability 

declines with increasing VPD. 

• Yellow-cedar is more sensitive to drying 

air with their photosynthetic capability 

declining at 11% to 19% greater 

decrease per 1 kPa increase in VPD than 

western redcedar.

Both species show a rapid increase in their 

photosynthetic capability as sunlight increases 

to 25% of full sunlight; thereafter both species 

have a continued gradual increase in 

photosynthesis as light level increase to full 

sunlight. Both species have a comparable 

photosynthetic response to light. However, 

under normal field conditions as light levels 

increase, VPD typically increases, thereby 

tempering the benefits of high light levels on 

these species photosynthetic capabilities.

GROWTH RESPONSE

Western redcedar and yellow-cedar growth 

patterns are responsive to critical seasonal 

environmental conditions. Both of these species 

are found to have optimum root growth at soil 

temperatures of ~22 °C. Low soil temperatures 

in the spring can limit root growth. 

• Western redcedar has an 8% decrease in 

root growth per 1 °C as soil temperature 

declines from 22 °C.

• Yellow-cedar has a 7% decrease in root 

growth per 1 °C as soil temperature 

declines from 22 °C.

During the spring, shoot flush for both western 

redcedar and yellow-cedar is initiated after they 

have received 700 thermal hours (hourly 

average >5 °C).

Shoot growth is at a maximum when western 

redcedar and yellow-cedar are exposed to wellwatered conditions (ψpd of -0.5 MPa). 

Availability of water is a major factor limiting 

shoot growth in the summer. 

• Western redcedar shoot growth 

decreases 4% per -0.1 MPa decline in 

ψpd (compared to growth @ a ψpd of -0.5 

MPa). 

• Yellow-cedar shoot growth decreases by 

7% decrease per -0.1 MPa decline in ψpd.

Shoot growth patterns of these species are only 

minimally affected by air temperatures >15 oC. 

However, there is a decrease in shoot growth 

when air temperatures are <15 oC in the fall.

• Western redcedar shoot growth slows by 

a rate of 17% decrease per 1 °C during 

the fall.

• Yellow-cedar has a decrease of 13% in 

shoot growth per 1 °C in the fall. 

For both species shoot growth and mitotic 

activity cease at 4 °C.

34
FREEZING TOLERANCE

Freezing tolerance of western redcedar and 

yellow-cedar has a seasonal shift; from a low 

level of freezing tolerance during the active 

summer-early fall growing season to maximum 

freezing tolerance in the middle of the winter. 

Freezing tolerance then declines from the mid 

winter maximum to a low level by early spring. 

The shift in freezing tolerance from these 

maximum and minimum levels is driven, in 

part, by how these species respond to seasonal 

temperature changes.

Freezing tolerance increases in the fall in 

response to decreasing air temperature. 

• Western redcedar has a 1.4 °C increase 

in freezing tolerance per 1 °C decline in 

average fall air temperature from 15 to 5 

°C. After shoot growth activity ceases 

freezing tolerance continues to increase 

by 2 °C per 1 °C decline in average air 

temperature from 5 to 0 °C. 

• Yellow-cedar also has a 1.4 °C increase 

in freezing tolerance per 1 °C decline in 

average fall air temperature from 15 to 5 

°C. However, after shoot growth activity 

ceases freezing tolerance increase by 5 

°C per 1 °C decline in average air 

temperature from 5 to 0 °C, more than 

double the acclimation rate of western 

redcedar.

Freezing tolerance decreases in late winter 

and early spring in response to increasing air 

temperature. 

• Western redcedar has a 1.9 °C 

decrease in freezing tolerance per 

100 thermal hours (from 0 to 500 

thermal hours). After shoot growth 

activity is initiated freezing tolerance 

continues to decrease by 4.0 °C per 

100 thermal hours. 

• Yellow-cedar has only a 0.7 °C 

decrease in freezing tolerance per 

100 thermal hours (from 0 to 500 

thermal hours). After shoot growth 

activity is initiated freezing tolerance 

continues to decrease by 3.1 °C per 

100 thermal hours. 

DROUGHT TOLERANCE

Drought tolerance of western redcedar and 

yellow-cedar also has a seasonal shift; from a 

low level of drought tolerance during the active 

growing season to maximum drought tolerance 

in the middle of the winter. This shift in drought 

tolerance from these minimum to maximum 

levels is driven, in part, by how these species 

respond to late summer drought conditions and 

fall seasonal temperature changes.

Drought tolerance is low when western redcedar 

and yellow-cedar are actively growing and 

exposed to well-watered conditions (ψpd of -0.5 

MPa). Drought tolerance increases in response 

to summer drought conditions. 

• Western redcedar osmotic potential at 

saturation (Ψsat) decreases by 1.7% and 

osmotic potential at turgor loss point 

(Ψtlp) decreases by 3.5% per -0.1 MPa 

decrease in ψpd (compared to wellwatered seedlings growing with a ψpd of 

-0.5 MPa). 

• Yellow-cedar Ψsat decreases 0.8% and 

Ψtlp decreases by 0.9% per -0.1 MPa 

decrease in ψpd (compared to wellwatered seedlings growing with a ψpd of 

-0.5 MPa). 

Drought tolerance is low when western redcedar 

and yellow-cedar are actively growing and 

exposed to air temperatures >15 oC. Drought 

tolerance increases with declining temperature. 

• Western redcedar Ψsat decreases by 7% 

and decreases by 13% for Ψtlp per 

temperature change of 1 °C (compared 

to well-watered seedlings growing at 15 

oC). 

• Yellow-cedar Ψsat only decreases 1% 

and Ψtlp decreases by only 3% per 

temperature change of 1 °C (compared 

to well-watered seedlings growing at 22 

oC).

Conclusion

This review briefly describes how the 

physiological performance of western redcedar 

and yellow-cedar are driven by their response to 

environmental conditions. Overall, western 

redcedar displays ecophysiological patterns that 

35
allow this species to respond to environmental 

conditions typically found in lower elevation 

forests that have potentially drier summer 

conditions and milder winter temperature 

conditions. Yellow-cedar generally shows 

ecophysiological patterns that allow this species 

to respond to environmental conditions typically 

found in high elevation forests that have 

potentially wetter summer conditions and colder 

winter temperature conditions. 

LIST OF PUBLICATIONS

Arnott, J.T.; Grossnickle, S.C.; Puttonen, P.; 

Mitchell, A.K.; Folk, R.S. 1994. Influence of 

nursery culture on growth, cold hardiness and 

drought resistance of yellow cypress. Can. J. 

For. Res. 23:2537-2547. 

Fan, S.; Grossnickle, S.C.; Russell, J.H. 2008.

Morphological and physiological variation in 

western redcedar (Thuja plicata Donn. Ex D. 

Don) populations under contrasting soil water 

conditions. Trees, 22:671-683. 

Folk, R.S.; Grossnickle, S.C.; Arnott, J.T.; 

Mitchell, A.K.; Puttonen, P. 1996. Water 

relations, gas exchange and morphological 

development of fall- and spring-planted yellow 

cypress stecklings. For. Ecol. Manage. 81:197-

213. 

Folk, R.S.; Grossnickle, S.C.; Major, J.E.; 

Arnott, J.T. 1994. Influence of nursery culture 

on western red cedar. II. Freezing tolerance of 

fall-planted seedlings and morphological 

development of fall- and spring-planted 

seedlings. New Forests, 8:231-247. 

Folk, R.S.; Grossnickle, S.C.; Russell, J.H. 

1995. Gas exchange, water relations and 

morphology of yellow-cedar seedlings and 

stecklings before planting and during field 

establishment. New Forests, 9:1-20. 

Grossnickle, S.C. 1992. Relationship between 

freezing tolerance and shoot water relations of 

western red cedar. Tree Physiol. 11:229-240. 

Grossnickle, S.C. 1993. Shoot water relations 

and gas exchange of western hemlock and 

western red cedar seedlings during 

establishment on a reforestation site. Trees, 

7:148-155. 

Grossnickle, S.C.; Fan, S.; Russell,J.H. 2005.

Variation in gas exchange and water use 

efficiency patterns among populations of 

western redcedar. Trees, 19:32-42. 

Grossnickle, S.C.; Russell, J.H. 1990. Water 

movement characterization of yellow-cedar 

(Chamaecyparis nootkatensis (D. Don) Spach) 

seedlings and rooted cuttings. Tree Physiol. 

6:57-68. 

Grossnickle, S.C.; Russell, J.H. 1991. Gas 

exchange processes of yellow-cedar 

(Chamaecyparis nootkatensis (D. Don) Spach) 

in response to environmental variables. Can. J. 

Bot. 69:2684-2691. 

Grossnickle, S.C.; Russell, J.H. 1993. Water 

relations and gas exchange processes of yellowcedar donor plants and cuttings in response to 

maturation. For. Ecol. Manage. 56:185-198. 

Grossnickle, S.C.; Russell, J.H. 1996. Changes 

in shoot water relations parameters of yellowcedar (Chamaecyparis nootkatensis D. Don) 

Spach) in response to environmental conditions. 

Can. J. Bot. 74:31-39. 

Grossnickle, S.C.; Russell,J.H. 2006. Yellowcedar and western redcedar ecophysiological 

response to fall, winter and early spring 

temperature conditions. Ann. of For. Sci. 63: 1-

8. 

Grossnickle, S.C.; Russell, J.H. 2010.

Physiological variation among western redcedar 

(Thuja plicata Donn ex D. Don) populations in 

response to short-term drought. Ann. of For. 

Sci. 67:506-517. 

Major, J.E. 1993. Influence of dormancy 

induction treatments on the photosynthetic 

response of field planted western hemlock and 

western redcedar seedlings. UBC MSc. Thesis. 

Major, J.E.; Grossnickle, S.C.; Folk,R.S.; 

Arnott, J.T. 1994. Influence of nursery culture 

on western red cedar. I. Measurement of 

seedling attributes before fall and spring 

planting. New Forests, 8:211-229. 

Russell, J.H. 1993. Genecology and genetic 

architecture in yellow-cedar. UBC PhD Thesis. 

36
STEM WATER POTENTIAL OF WESTERN REDCEDAR AND 

DOUGLAS-FIR SEEDLINGS GROWING ACROSS A SOIL 

MOISTURE GRADIENT

Trevor Walter1 and Gregory Ettl

ABSTRACT

Stem water potential of 2 year-old western redcedar (Thuja plicata) and Douglas-fir (Pseudotsuga 

menziesii) seedlings was measured across a range of volumetric water content. Western redcedar and 

Douglas-fir were planted in the winter of 2008 following a variable retention harvest of a 78 year-old 

Douglas-fir dominated stand at Pack Forest in the foothills of the western Cascades, WA. Stem water 

potential of 18 western redcedar and 18 Douglas-fir seedlings were measured on a hot day in August, 

2009 (~32°C) across a gradient of soil water moisture: 3-33% volumetric water content. Seedlings were 

selected to represent the microsite variability in water availability which ranged from dry convexities to 

moist depressions. Branches from seedlings were clipped, placed in aluminum foil pouches, and stored 

in plastic bags with a moist towel in a cooler until water potential measurements could be taken (within 

an hour). A Scholander type pressure bomb was used to measure water potential predawn, and then at 

9:30 AM, 1:00 PM (solar noon), 4:00 PM and 8:00 PM by clipping different branches off of each 

seedling throughout the course of the day. 

Water potential readings were more negative for Douglas-fir than western redcedar across all soil 

moisture levels. Western redcedar showed its greatest water stress (-1.9 MPa) by 9:30 AM on dry sites, 

but water stress (-1.6 MPa) was delayed until solar noon and was less severe on wetter sites. Douglas-fir 

showed the greatest water stress (-2.0 to -2.7 MPa) at solar noon regardless of soil moisture, however 

seedlings with greater than 16% volumetric water content showed greater water stress (< -2.5 MPa), 

than seedlings from lower soil moisture sites. The results suggest differences in water stress response 

and a greater ability of western redcedar to tolerate moist soils than Douglas-fir.

1 Center for Sustainable Forestry at Pack Forest, School of Forest Resources, College of the Environment, 

University of Washington, P.O. Box 352100, Seattle, WA 98195, ettl@uw.edu

2010 - A Tale of Two Cedars PNW-GTR-828

37
FOLIAGE AND LIGHT-USE EFFICIENCIES OF WESTERN 

REDCEDAR (THUJA PLICATA) STANDS COMPARED TO 

WESTERN HEMLOCK (TSUGA HETEROPHYLLA)

Roderick W. Negrave1

ABSTRACT

Intensive silvicultural treatments have been suggested to increase forest productivity and for carbon 

sequestration in Coastal British Columbia. Better understanding of the effects of these treatments on 

growth processes will improve the ability to manage these treatments and increase ecological 

understanding of the species involved. This study examined the effects of fertilization, planting density 

and site light-capture, light-use efficiency and foliar efficiency in juvenile western redcedar (cedar) and 

western hemlock (hemlock) stands on northern Vancouver Island. 

A factorial experiment was established in 1988 to examine the effects of: NPK fertilization versus nonfertilized; three establishment densities of 500 stems per ha (sph), 1500 sph and 2500 sph; the two 

species; and tree-size class. This design was replicated (4x) on two sites: Nutrient-poor cedar-hemlock 

(CH) and nutrient-medium hemlock-amabilis fir (Abies amabilis) (HA) sites. In 1997 and 2002, the 

experiment was measured for heights and diameters. Biomass estimation equations were developed 

through destructive sampling in 2002 and applied to plot data to produce estimates of total biomass and 

incremental biomass growth for each species. Photosynthetically-active light interception was assessed 

with hemispheric photography. Stand- and tree-level measures for growth efficiency were developed for 

foliage and intercepted light. Analysis was completed using PROC GLM in SAS (p<0.05). 

Fertilization did not improve foliar or light-use growth efficiency but increasing establishment density 

decreased these variables. Cedar had lower foliar growth efficiency than hemlock and this varied with 

tree size, tended to increase with tree size in cedar but decrease with size in hemlock. Light interception 

was increased by fertilization and increasing density. Growth increased exponentially with light 

interception. Results suggest that fertilization is a more efficient tool for increasing stand productivity 

compared to increasing density. If grown together, cedar will likely be at a disadvantage to hemlock 

during the early rotation and fertilization will amplify this disadvantage.

 

1 Coast Forest Region, Ministry of Forests and Range, 2100 Labieux Rd., Nanaimo, BC, V9T 6E9

2010 - A Tale of Two Cedars PNW-GTR-828

38
SECTION B

FOREST HEALTH

CLIMATE

GENETICS

39
40
1

Amanda B. Stan worked on this project while a postdoctoral researcher, 2Thomas B. Maertens is a Ph.D. 

candidate, and 3Lori D. Daniels is an Associate Professor, Department of Geography, University of British 

Columbia, 1984 West Mall, Vancouver, British Columbia V6T 1Z2, Canada 

4

Stefan Zeglen is a Forest Pathologist, Coast Forest Region, British Columbia Ministry of Forests and Range, 

2100 Labieux Road, Nanaimo, British Columbia V9T 6E9, Canada

DETERMINING THE POTENTIAL TO RECONSTRUCT 

POPULATION DYNAMICS OF YELLOW-CEDAR IN DECLINING 

STANDS USING DENDROCHRONOLOGY

Amanda B. Stan1, Thomas B. Maertens2, Lori D. Daniels3, and Stefan Zeglen4

ABSTRACT

Yellow-cedar (Callitropsis nootkatensis, syn Chamaecyparis nootkatensis (D. Don) Spach) forests of 

coastal British Columbia, Canada are experiencing decline in a manner similar to that observed in 

southeastern Alaska. In this pilot study, we use tree-ring data from live and standing dead yellow-cedar 

trees from four declining sites on the North Coast of British Columbia to assess some of the benefits and 

limitations of using tree rings to reconstruct population dynamics of yellow-cedar in declining stands. 

We found unique growth patterns between yellow-cedar trees from our sites and those from similar 

declining sites in nearby Alaska. Using outer-ring dates of increment cores, we were able to estimate 

time since death of decade to century old standing dead yellow-cedar trees, although the precision of the 

estimates was influenced by partial cambial mortality and erosion of outer rings. Our results provide 

valuable information for planning future studies that assess growth-climate relations of yellow-cedar and 

suggest potential for reconstructing long-term population dynamics of this species in declining stands.

KEYWORDS: dendrochronology, forest decline, Chamaecyparis nootkatensis, British Columbia. 

INTRODUCTION

Widespread mortality of yellow-cedar 

(Chamaecyparis nootkatensis (D. Don) Spach), 

referred to as yellow-cedar decline, occurs on 

more than 250,000 ha of coastal forests in 

Alaska and British Columbia, Canada (Lamb 

and Wurtz 2009; Westfall and Ebata 2009). Past 

research in Alaska suggested that biotic agents 

were not the primary cause of death of yellowcedar (Hennon and Shaw 1997). More recent 

hypotheses implicate factors related to climate 

change. In particular, increasing late-winter 

temperatures are leading to reduced snowpack 

and early dehardening of yellow-cedar, leaving 

this species susceptible to late-winter freeze 

events (Hennon et al. 2008). 

Research on the population dynamics associated 

with the decline of yellow-cedar is needed to 

begin to understand how stands have changed, 

and potentially will change, in response to this 

 phenomenon. In light of a shifting climate, this 

need is particularly pressing. Dendrochronology 

offers potential to assess the population 

dynamics of yellow-cedar and the decline 

phenomenon, as it can provide a means to 

reconstruct long-term trends in age structure, 

growth patterns, as well as recruitment and 

mortality rates.

In this pilot study, we explore the potential of 

dendrochronological techniques to reconstruct 

yellow-cedar population dynamics and decline. 

To do this, we use tree-ring data from live, 

asymptomatic and standing dead yellow-cedar 

trees from four declining sites on the North 

Coast of British Columbia. We compare our 

findings on crossdating quality, growth patterns, 

time since death, and partial cambial mortality 

of yellow-cedar to those of other studies in 

Alaska and British Columbia. Together, this 

information allows us to assess some of the 

2010 - A Tale of Two Cedars PNW-GTR-828

41
benefits and limitations of using tree rings to 

reconstruct population dynamics of yellowcedar in declining stands, providing a 

foundation for future studies that aim to better 

understand causes and effects of decline.

METHODS 

Field Procedures

We conducted this research at four sites near 

Prince Rupert, British Columbia (54o 19’ N, 

130o 20’ W). Sites consist of concentrated 

patches of dying and dead yellow-cedar trees 

(Fig. 1) and appear to have similar 

characteristics as those associated with the 

yellow-cedar decline phenomenon in 

southeastern Alaska (Hennon et al. 2005). 

Across all four sites, mean annual temperature is 

5.6o

C, with a mean of 12.9oC in August and -

0.7oC in January (very near the rain-snow 

temperature threshold), mean annual 

precipitation is 3793 mm, and mean annual 

growing season (May to September) 

precipitation is 982 mm (Wang et al. 2006). Site 

elevations range from 305 to 518 m a.s.l. 

At each site, we entered patches of dying and 

dead trees and systematically traversed them to 

locate and core 20 yellow-cedar trees in each of 

two status classes: live, asymptomatic and 

standing dead. We visually assessed the crowns 

and boles of trees (diameter at breast height ≥ 

10 cm) to separate healthy from declining and 

dead. Asymptomatic trees were those that had 

live and “healthy” crowns (i.e. green) and no 

obvious bole damage. Standing dead trees were 

assessed according to the six-class decay system 

for yellow-cedar described by Hennon et al. 

(1990). 

From each tree, we extracted two increment 

cores at approximately 30 cm above the ground. 

In most instances, the second core was taken at 

a location ≥ 90o from the first core. However, 

for standing dead trees, we took the second core 

through the face of basal scars that likely 

formed prior to the death of other parts of the 

bole and did not appear to be the result of 

abrasion. This sampling approach was aimed at 

capturing damage potentially associated with 

root death caused by freezing injury. By coring 

through these scars, we attempted to obtain data 

that maximized the difference in outer-ring 

dates between cores from the same tree to use in 

our analyses of partial cambial mortality.

Figure 1. Examples of declining yellow-cedar 

study sites near Prince Rupert, North Coast 

British Columbia, Canada. 

Laboratory Procedures

We prepared all cores following the procedures 

of Stokes and Smiley (1968). Ring-width series 

from live, asymptomatic trees were first visually 

crossdated (Yamaguchi 1991) and then 

measured to the nearest 0.001 mm using a 

stereozoom microscope and a Velmex slidingstage micrometer interfaced with MeasureJ2X 

software. We used the program COFECHA 

(Grissino-Mayer 2001) to detect crossdating 

42
errors and to calculate average mean sensitivity 

and average interseries correlation values, which 

we used to describe the crossdating quality of 

the ring-width series from each site. Ring-width 

series that could not be confidently crossdated 

were removed from the data set.

We used the program ARSTAN (version 41d 

for Windows XP; Cook 1985) to create a mean 

chronology for each site. First, we averaged the 

two ring-width series per asymptomatic tree, 

using only those years that were accurately 

dated and common to both series. Next, we 

detrended each resultant series by first fitting a 

negative exponential curve, line with a negative 

slope, or horizontal line, and subsequently 

fitting an 80-year cubic spline with a 50% 

frequency response. Finally, we created 

standard chronologies for the individual sites by 

averaging the index values of the series using a 

bi-weight robust mean (Cook et al. 1990). 

We measured the ring widths of all standing 

dead trees and used COFECHA to statistically 

crossdate individual ring-width series against 

the corresponding set of site-specific, dated 

series from asymptomatic trees. After statistical 

crossdating, we visually examined the ringwidth series from each standing dead tree and 

removed any that could not be accurately dated 

or that had broken or indiscernible outer rings. 

For each standing dead tree remaining in the 

data set, we first estimated its year of death 

using the most recent outer-ring date of the two 

ring-width series per tree and then calculated its 

time since death (i.e. 2007-year of death).

Data Analyses 

We compared crossdating quality of the ringwidth series from asymptomatic trees among the 

four sites and assessed growth patterns among 

the site chronologies. Growth patterns were 

examined both graphically, by comparing 

negative and positive marker rings (i.e. rings 

that differed from the mean tree-ring index by -

/+ 1 SD or more) and suppressions (i.e. multiyear periods of below-average growth) among 

all chronologies, as well as quantitatively, by 

calculating Pearson’s (r) correlation coefficients 

between individual chronologies. 

For standing dead trees, we combined 

individuals from all sites and used an ANOVA 

to test for differences in time since death among 

decay classes. Prior to analysis, time-sincedeath estimates were transformed using a 

natural logarithm. A Tukey’s HSD test was 

subsequently used to contrast means among 

decay classes. To estimate the frequency and 

minimum duration of partial cambial mortality 

in yellow-cedar, we compared the outer-ring 

dates of the two ring-width series from the same 

standing dead tree. Finally, we calculated 

Spearman’s (ρ) correlation coefficient to assess 

whether the difference in outer-ring dates 

between individual ring-width series from the 

same standing dead tree showed an increasing 

trend with increasing time since death.

RESULTS 

Crossdating quality of the ring-width series 

from live, asymptomatic trees at each site was 

similar among all four sites. Average mean 

sensitivity values were 0.24 ± 0.01 (mean ± SD 

here and throughout the text). Average 

interseries correlation values were 0.48 ± 0.02. 

Growth patterns of live, asymptomatic trees 

were similar among the four sites. The site 

chronologies ranged from 410 to 488 years. 

Between 1798 and 2006, the period in which all 

four chronologies had a minimum of 10 trees, 

there was an average of 32.0 ± 2.9 negative and 

25.0 ± 1.7 positive marker rings (Fig. 2). During 

that same period, all four chronologies had 

negative marker rings in seven years: 1811, 

1876, 1936, 1958, 1960, 1986, and 1987; three 

of the four chronologies had negative marker 

rings in an additional 16 years: 1810, 1812, 

1835, 1856, 1873, 1875, 1877, 1887, 1894, 

1896, 1917, 1918, 1920, 1926, 1972, and 1998 

(Fig. 2). Between 1798 and 2006, periods of 

suppressed growth lasting three to eight years 

occurred in all four chronologies in the late 

1800s through 1810s, 1870s, the late 1910s 

through the early 1920s, 1930s, 1950s, 1970s, 

and the late 1980s. Correlations between 

43
individual site chronologies ranged from 0.52 to 

0.78 (p < 0.001) between 1798 and 2006. 

Figure 2. Percentage of ring-width chronologies 

(n = 4) with a negative or positive marker ring in 

each year from 1798-2006, i.e. the period in which 

all four chronologies had a minimum of 10 trees. 

Marker rings are those that depart from the 

mean tree-ring index by -/+1 SD or more.

We successfully crossdated 121 of 158 (77%) 

ring-width series from standing dead yellowcedar and estimated the year of death of 70 of 

79 (89%) trees. Of the 37 remaining ring-width 

series, eight were too suppressed to confidently 

crossdate and 29 had broken or indiscernible 

outer rings. Except for two trees with outer-ring 

dates of 1903 (decay class IV) and 1728 (decay 

class V), all trees had outer-ring dates between 

1949 and 2006. Therefore, for 68 of the 70 trees 

assessed, time since death in 2007 ranged from 

1 to 58 years. 

Time since death increased significantly (F = 

78.65, p < 0.001) with advanced stages of 

decay. Standing dead trees in decay classes I (n 

= 21), II (n = 25), and III (n = 20) died 4.71 ± 

1.87, 12.56 ± 5.31, and 25.15 ± 9.87 years ago, 

respectively. Three trees in decay class IV (time 

since death = 40, 58, 104 years) and one tree in 

decay class V (time since death = 279 years) 

were not included in the analysis because of 

small sample sizes for those two classes.

The outer-ring dates of the two ring-width series 

from the same standing dead tree (n = 51) 

differed between 0 and 13 years. A total of 16% 

had the same outer-ring date. In contrast, 53% 

had dates that differed from 1 to 3 years, and 

31% had dates that differed by more than 3 

years. The difference in outer-ring dates 

between individual ring-width series from the 

same standing dead tree showed an increasing 

trend with increasing time since death 

(Spearman’s ρ = 0.56, p < 0.001).

DISCUSSION

Crossdating quality of the ring-width series 

from live, asymptomatic trees at each of our 

four sites is comparable to the crossdating 

quality of all other known yellow-cedar ringwidth series, which are from higher-elevation (> 

1000 m a.s.l.), non-declining sites in 

southwestern British Columbia (Laroque and 

Smith 1999; Kellner et al. 2000; Parish 2005) 

and lower-elevation (< 300 m a.s.l.), nondeclining and declining sites in southeastern 

Alaska (Beier et al. 2008). Our average mean 

sensitivity and interseries correlation values lie 

in the middle and upper end, respectively, of the 

range of all known values for yellow-cedar. 

Overall, these findings provide evidence of a 

moderately strong common signal and highquality crossdating among the individual ringwidth series at each of our four sites. 

Common marker rings and periods of 

suppressed growth, as well as strong 

correlations, indicate coherency in growth 

patterns of yellow-cedar trees among our four 

sites. Interestingly, our chronologies from 

declining sites on the North Coast of British 

Columbia have negative marker rings in 

common with chronologies from declining sites 

in southeastern Alaska (i.e. 1926, 1936, 1986, 

1987; Beier et al. 2008). Based on the 

resemblance of growth patterns between our 

yellow-cedar trees and those of trees in Alaska, 

similar growth-climate relations are plausible at 

declining yellow-cedar sites in British 

Columbia. 

44
Our results demonstrate the feasibility of 

estimating time since death by means of directly 

assessing dead trees using dendrochronological 

techniques. For yellow-cedar trees in decay 

classes I to III, Hennon et al. (1990) found 

similar, although slightly more variable, timesince-death estimates as ours. In that study, the 

authors used an indirect approach, in which 

time-since-death estimates of trees in different 

decay classes were determined using dates of 

radial-growth releases of nearby living hemlock 

trees. Although slight, the lower variability in 

our results demonstrates the value of directly 

sampling standing dead trees to attain more 

precise time-since-death estimates of individuals 

in different decay classes.

While direct dendrochronological dating can 

sometimes provide more precise time-sincedeath estimates, this approach does have its 

shortcomings. Besides the fact that directly 

sampling standing dead trees may not be 

possible because of erosion of outer rings, even 

when it is, the correspondence of an outer-ring 

date to the actual death date of a tree is 

complicated by the potential for a tree to 

produce partial or no annual rings as it dies. In 

this study, a difference in outer-ring dates 

between individual ring-width series from the 

same standing dead tree suggests evidence of 

partial cambial mortality at our sites, with a 

gradual cessation of radial growth around the 

circumference of individual yellow-cedar trees 

that tends to happen over just a few years, rather 

than decades. Collecting multiple increment 

cores per tree provides an estimate of the 

minimum duration of mortality of yellow-cedar 

in declining stands that represents the degree of 

error when determining year of death using only 

a single core. However, because this estimate 

increases with time since death, it may represent 

error from erosion of rings over time as well as 

error from partial cambial mortality.

CONCLUSIONS

Our pilot study provides a foundation for 

additional research in declining stands. For 

example, by identifying unique growth patterns 

between our yellow-cedar chronologies and 

those from comparable declining sites in 

Alaska, our study informs others that aim to 

assess the extent to which yellow-cedar in 

British Columbia is vulnerable to damage from 

similar climatic stressors as those documented 

in Alaska (see Beier et al. 2008). Furthermore, 

our study demonstrates the value of 

dendrochronology for providing information on 

time since death and partial cambial mortality of 

yellow-cedar that will be useful for 

reconstructing various aspects of this species’ 

population dynamics in declining stands. For 

example, estimating time since death of 

individual trees in different decay classes will 

facilitate reconstructing the frequency of 

yellow-cedar mortality through time and 

determining dead wood persistence in different 

classes. In addition, information on the 

frequency and duration of partial cambial 

mortality allows for a better understanding of 

tree decline and the use of less-intensive 

sampling procedures in the future. Future 

studies that assess growth-climate relations and 

reconstruct population dynamics of yellowcedar in declining stands will provide managers 

with information essential to project changes to 

stands and ecosystem reorganization in coastal 

forests. For additional details on this study, 

please refer to Stan et al. (in press).

ACKNOWLEDGEMENTS 

We thank Ron Diprose, Rachel Field, Harry 

Kope, Alex Marshall, Colin Nelson, and Mike 

Symons for assistance in the field, along with 

Kevin Johnstone, Jennifer Passmore, and Sonya 

Powell for assistance in the lab. Mike Grainger 

and the staff at the British Columbia Ministry of 

Forests and Range (BCMFR), North Coast 

Forest District, provided logistical support while 

in Prince Rupert. We are grateful to Colin Beier 

and Scott Sink for kindly supplying us their 

COFECHA outputs. The BCMFR provided 

funding for this project. 

LITERATURE CITED

Beier, C.M.; Sink, S.E.; Hennon, P.E.; 

D’Amore, D.V.; Juday, G.P. 2008. Twentiethcentury warming and the dendroclimatology of 

45
declining yellow-cedar forests in southeastern 

Alaska. Can. J. For. Res. 38:1319-1334. 

Cook, E.R. 1985. A time series analysis 

approach to tree-ring standardization. Ph.D. 

dissertation, University of Arizona, Tucson, AZ. 

Cook, E.R.; Shiyatov, S; Mazepa, V. 1990.

Estimation of the mean chronology. Pp 123-132 

in: Cook, E.R.; Kairiukstis, L.A., eds. Methods 

of dendrochronology: applications in the 

environmental sciences. Kluwer Academic 

Publishers, Dordrecht, The Netherlands. 

Grissino-Mayer, H.D. 2001. Evaluating 

crossdating accuracy: a manual and tutorial for 

the computer program COFECHA. Tree-Ring 

Res. 57:205-221. 

Hennon, P.E.; D’Amore, D.V.; Wittwer, 

D.T.; Caouette, J.P. 2008. Yellow-cedar 

decline: conserving a climate-sensitive tree 

species as Alaska warms. Pp. 233-245 in: Deal, 

R.L., ed. Integrated restoration of forested 

ecosystems to achieve multiresource benefits: 

proceedings of the 2007 national siliviculture 

workshop. Gen. Tech. Rep. PNW-GTR-733. 

Portland, OR: USDA For. Serv., Pac. NW Res. 

Stn. 

Hennon, P.E.; D’Amore, D.V.; Zeglen, S.; 

Grainger, M. 2005. Yellow-cedar decline in the 

North Coast Forest District of British Columbia. 

Res. Note. PNW-RN-549. Portland, OR: USDA 

For. Serv., Pac. NW Res. Stn. 16 p. 

Hennon, P.E.; Shaw III, C.G. 1997. The 

enigma of yellow-cedar decline: what is killing 

these long-lived, defensive trees? J. For. 95:4-

10. 

Hennon, P.E.; Shaw III, C.G.; Hansen, E.M. 

1990. Dating decline and mortality of 

Chamaecyparis nootkatensis in southeast 

Alaska. For. Sci. 36:502-515. 

Kellner, A.M.E.; Laroque, C.P.; Smith, D.J.; 

Harestad, A.S. 2000. Chronological dating of 

high-elevation dead and dying trees on northern 

Vancouver Island, British Columbia. Northwest 

Sci. 74:242-247. 

Lamb, M.; Wurtz, T., compilers 2009. Forest 

health conditions in Alaska – 2008. For. Heal. 

Protect. Rep. R10-PR-20. Juneau, AK: USDA 

For. Serv., Alaska Region 102 p. 

Laroque, C.P.; Smith, D.J. 1999. Tree-ring 

analysis of yellow-cedar (Chamaecyparis 

nootkatensis) on Vancouver Island, British 

Columbia. Can. J. For. Res. 29:115-123. 

Parish, R., 2005. Mount cain, Alaska yellowcedar tree-ring record (CANA175). In: GrissinoMayer, H.D.; Fritts, H.C., eds. International 

tree-ring data bank. IGBP PAGES/World Data 

Center-A for Paleoclimatology. NOAA/NGDC 

Paleoclimatology Program, Boulder, CO. 

Stan, A.B.; Maertens, T.B., Daniels, L.D.; 

Zeglen, S. In press. Reconstructing population 

dynamics of yellow-cedar in declining stands: 

baseline information from tree rings. Tree-Ring 

Res.

Stokes, M.A.; Smiley, T.L. 1968. An 

introduction to tree-ring dating. University of 

Chicago Press, Chicago, IL. 

Wang, T.; Hamann, A.; Spittlehouse, D.L.; 

Aitken, S.N. 2006. Development of scale-free 

climate data for western Canada for use in 

resource management. Int. J. Climatol. 26:383-

397. 

Westfall, J.; Ebata, T. 2009. 2008 Summary of 

Forest Health Conditions in British Columbia. 

Pest Management Rep. No. 15. Victoria, BC: 

BC Ministry of For. & Range, Forest Practices 

Branch 76 p. 

Yamaguchi, D.K. 1991. A simple method for 

cross-dating increment cores from living trees. 

Can. J. For. Res. 21:414-416.

46
1

Rona N. Sturrock is a research scientist, Pacific Forestry Centre, Canadian Forest Service, Natural Resources Canada, 506 

W Burnside Road, Victoria, BC V8Z 1M5 Rona.Sturrock@nrcan.gc.ca 1

Kevin W. Pellow is a research technician, Pacific Forestry Centre, Canadian Forest Service, Natural Resources Canada, 506 

W Burnside Road, Victoria, BC V8Z 1M5

2

Paul E. Hennon is a Research Forest Pathologist, Juneau Forestry Sciences Laboratory, Pacific Northwest Research Station, 

USDA Forest Service, 2770 Sherwood Lane, Suite 2A, Juneau AK 99801

PHELLINUS WEIRII AND OTHER FUNGI CAUSING DECAY IN 

WESTERN REDCEDAR AND YELLOW-CEDAR 

Rona N. Sturrock1, Kevin W. Pellow1, and Paul E. Hennon2 

ABSTRACT

In the forests of western North America, western redcedar and yellow-cedar are two long-lived 

coniferous species that have the rather anomalous distinction of having wood that is very resistant to 

decay in service but also frequently having extensive decay, especially in old-growth trees. More than a 

dozen different species of Basidiomycetous decay fungi occur on living western redcedar and yellowcedar. Despite the fungitoxic properties of the heartwood extractives in these two cedars, decay fungi 

can get established in trees just a few decades old and eventually cause significant cull or stem breakage. 

Decayed cedar stems that fail are also important agents of small-scale disturbance, altering the carbon 

budgets of coastal and inland forests. Research on how Phellinus weirii, one of the most important decay 

fungi occurring on living western redcedar, interacts with this cedar, is ongoing. Additional information 

is needed to identify the other major decay fungi in western redcedar and yellow-cedar and their 

infection biology. All such information will be useful to scientists producing carbon models and to 

professionals managing forests for timber and other resources. 

KEYWORDS: Decay fungi, heart rots, root rots, butt rots, western redcedar, Thuja plicata, yellowcedar, Chamaecyparis nootkatensis, Phellinus weirii

INTRODUCTION

In the forests of western North America, 

western redcedar (WRC; Thuja plicata Donn) 

occurs over a wide range of sites and elevations 

along the Pacific coast from California to 

southeast Alaska and along the interior wet belt 

from McGregor, British Columbia (BC) to 

western Montana and northern Idaho. Yellowcedar (YC; Callitropsis nootkatensis, syn

Chamaecyparis nootkatensis (D. Don) Spach) 

occurs predominantly at higher elevations along 

the Pacific coast from northern California to 

Prince William Sound in Alaska. In nature, both 

species reproduce sexually via seeds that mature 

in one year (WRC) or two years (YC) and also 

asexually by layering (Andersen 1959, Habeck 

1968). These two long-lived coniferous species 

have the rather anomalous distinction of having 

wood that is very resistant to decay but also 

frequently having extensive decay of live trees, 

especially in old-growth forests (van der Kamp 

1975, 1988). Thus, these cedars have high rates 

of internal wood decay as live trees, but slow 

deterioration as dead trees. The trait of decayresistant wood is a commercially valued 

property for these two species because of the 

long durability of wood in service. Individual 

WRC trees that were regenerated by layering 

are said to be more susceptible to fungal attack 

than those regenerated from seed (Klinka and 

Chourmouzis 2005). 

More than a dozen different species of 

Basidiomycetous decay fungi have been 

identified on living western redcedar and 

yellow-cedar trees. Many of these species have 

several synonyms, a fact that has 1) likely 

2010 - A Tale of Two Cedars PNW-GTR-828

47
created confusion about which decay organisms 

affect the two cedars and 2) made it challenging 

to find information on cedar decay in both 

historic and recent literature. The goal of this 

paper is to provide current information on the 

decay fungi affecting living WRC and YC trees.

Decay Fungi on Living Western Redcedar 

and Yellow-cedar

Decay fungi occurring on living WRC and YC 

trees cause either stem decay (= trunk or heart 

rots) or root and butt rot. The heart rots, which 

include Physisporinus rivulosus (Berk. & M.A. 

Curtis) Ryvarden, Perenniporia subacida (Peck) 

Donk, Phellinidium ferrugineofuscum (P. 

Karst.) Fiasson & Niemelä, Porodaedalea pini

(Brot.) Murrill, Ganoderma applanatum (Pers.) 

Pat., Fomitopsis pinicola (Sw.) P. Karst, 

Laetiporus conifericola Burds. & Banik, and 

Postia sericeomollis (Romell) Jülich, tend to be 

spread by wind-disseminated spores that likely 

gain entry to living trees through wounds, fire 

scars, and branch stubs. The root and butt rot 

fungi may also spread by wind-disseminated 

spores but more frequently spread vegetatively 

on roots and/or through the soil. These fungi, 

which include Armillaria solidipes Peck, 

Phellinus weirii (Murrill) Gilb., Heterobasidion 

occidentale Otrosina & Garbelotto, Onnia 

tomentosa (Fr.) P. Karst., and Phaeolus 

schweinitzii (Fr.) Pat., frequently kill and cause 

decay of cedar roots as well as causing decay in 

heartwood, sapwood, and cambial tissues. 

All of the decay fungi affecting western 

redcedar and yellow-cedar trees can be further 

categorized as causing either white rot or brown 

rot. White rot fungi digest all the components of 

wood tissue, including lignin, cellulose, and 

hemicellulose, and leave behind decayed wood 

that can be described as ranging from whitish to 

yellowish, spongy to stringy, and laminate to 

pitted. Brown rot fungi cannot digest lignin and 

so leave behind a distinctive brown cubical to 

brown crumbly wood decay which is composed 

of modified lignin. This material may be quite 

stable to further deterioration (Gilbertson and 

Ryvarden 1986) and thus would represent a 

sequestered form of carbon in the soil. Because 

most of the internal wood decay in live cedars is 

caused by white rot fungi, more of their carbon 

is likely to be released to the atmosphere as CO2

through the complete deterioration of wood. 

Although cedar trees are rarely killed by these 

decay fungi, infected trees may have extensive 

internal decay without any external signs of 

defect (Buckland 1946). More detailed 

information on each of these fungi and the 

diseases they cause can be found in publications 

such as Allen et al. (1996) and Sinclair and 

Lyon (2005). We thus present a list of fungi that 

cause wood decay of living western redcedar 

and yellow-cedar trees (Table 1). Currently, 

there is not enough information in the literature 

to identify with certainty which of these fungi 

are most important in particular regions, and 

which are minor species that are just 

occasionally found. 

Little is known about the infection biology of 

the decay fungi affecting WRC and YC. It is 

thought that a succession of early colonizing 

fungal ‘pioneers’, which presumably enter trees 

through trunk scars or root wounds, detoxify 

heartwood extractives sufficiently to allow 

activity by wood-rotting fungi (van der Kamp 

1986, Jin 1987, Jin et al. 1988). The principle 

fungitoxic extractives in WRC include alpha-, 

beta-, and gamma-thujaplicin, and betathujaplicinol (Rennerfelt 1948, Roff and 

Atkinson 1954), and plicatic acid (Stirling and 

Morris 2006, Stirling pers. comm. 2010). 

Biocidal extractives in YC (Barton 1976) 

include nootkatin, carvacrol, and other 

compounds (Rennerfelt and Nacht 1955, Kelsey 

et al. 2005). More research is needed on the 

suite of organisms involved in the decay 

processes in WRC and YC, including how and 

when they interact with heartwood compounds. 

Phellinus weirii Research – An Update

Phellinus weirii sensu stricto is considered to be 

the most important white rot fungus causing 

decay in western redcedar, particularly in the 

inland forests of its natural range (Buckland 

1946). This fungus also causes significant cull 

as a butt rot on yellow-cedar (Hennon 1991).

48
Table 1--A cast of characters: some of the principle decay fungi occurring on western redcedar (Thuja 

plicata) and yellow-cedar (Chamaecyparis nootkatensis). More research is needed to determine which of 

these fungi are important in particular regions and which are minor species just found occasionally.

Phellinus weirii was recently confirmed to be a 

closely related but different fungal species from 

P. sulphurascens Pilát (Lim et al. 2005), which 

causes laminated root and butt rot of Douglas-fir 

and several other coniferous species (Thies and 

Sturrock 1995).

Research on how P. weirii and western redcedar 

interact is ongoing at the Pacific Forestry, 

Centre, Victoria, BC, Canada. Using a technique 

that we developed, we have inoculated P. weirii

onto western redcedar roots in the field and have 

collected some preliminary data on the early 

stages of the infection process. To study P. 

weirii’s genetics as well as perform other 

research on this fungus, single spores are 

required. Since sporocarp formation in P. weirii

in the wild is not reliable and varies from year to 

year, depending on environmental conditions, 

we have developed a technique to induce 

formation of P. weirii fruiting bodies (Fig. 1), 

thus enabling the collection of single spores. 

Interestingly, although P. weirii is reported to 

fruit in the spring/mid-summer, we have 

observed fruiting in the fall as well, when 

conditions approximate those of the springtime. 

We are also actively collecting P. weirii isolates 

from throughout western North America and 

thus far have over 25 isolates in long-term 

storage. Using molecular techniques, we have 

sequenced several genes from P. weirii isolates 

collected from western redcedar over a large 

Pathogen

Disease Name

Synonyms Decay

Type

Western

Redcedar

Yellowcedar

Armillaria spp.

Armillaria root rot

Armillaria solidipes, A. ostoyae, A. obscura, A. 

mellea

Root,

White √ √

Phellinus weirii

laminated root rot

Poria weirii, Fomitiporia weirii, Fuscoporia 

weirii, Inonotus weirii, Phellinidium weirii

Root,

White √ √

Heterobasidion 

occidentale

annosus root rot

Heterobasidion annosum, Fomes annosus, 

Fomitopsis annosa, Polyporus annosus

Root,

White √

Onnia tomentosa 

Tomentosus root rot

Inonotus tomentosus, Polyporus tomentosus, 

Coltrichia tomentosa 

Root,

White √

Phaeolus schweinitzii

schweinitzii butt rot

Polyporus schweinitzii Root,

Brown √

Physisporinus rivulosus

white butt rot – white 

laminated rot

Ceriporiopsis rivulosa, Polyporus rivulosus, 

Poria albipellucida, Poria rivulosa, Rigidoporus 

rivulosus

Heart,

White √

Perenniporia subacida

stringy butt rot

Poria subacida, Polyporus subacida, Poria 

fuscomarginata

Heart,

White √

Phellinidium 

ferrugineofuscum

Phellinus ferrugineofuscus, Polyporus 

ferrugineofuscus

Heart,

White √

Porodaedalea pini

red ring rot

Phellinus pini, Fomes pini, Trametes pini Heart,

White √ √

Ganoderma applanatum

white mottled rot

Fomes applanatus, Polyporus applanatus Heart,

White √

Fomitopsis pinicola

brown crumbly rot

Fomes pinicola Heart,

Brown √ √

Laetiporus conifericola

brown cubical rot

Polyporus sulphureus Heart,

Brown √

Postia sericeomollis

brown cubical & pocket rot

Oligoporus sericeomollis, Polyporus 

sericeomollis, Poria asiatica, Poria 

sericeomollis, Tyromyces sericeomollis

Heart,

Brown √ √

49
geographic area. Results indicate regional 

differences between these isolates. Better, 

overall understanding of P. weirii behaviour and 

diversity will facilitate future management of 

this pathogen in North America’s changing 

forests.

Figure 1-Sporophore of P. weirii induced to form 

on blocks of treated red alder (Alnus rubra

Bong.). NRCAN, CFS photo.

IMPACTS AND OUTCOMES OF DECAY 

FUNGI

Decay fungi in general affect the quantity and 

quality of wood available for products. This 

issue led to research efforts in the 40s and 50s to 

document the amount of defect, or cull, in living 

conifers in the forests of the Pacific Northwest. 

One such study, conducted by Kimmey (1956), 

documented high rates of decay in live western 

redcedar in coastal Alaska. Most of the decay 

was apparently caused by two white rot fungi - 

Physisporinus rivulosus and Phellinus weirii 

sensu stricto - both of which do not typically 

form external indicators of defect.

Decay volumes in WRC are highly correlated 

with tree age. In BC, the total volume of 

accumulated decay in living trees is greater for 

WRC than for any other major conifer (Jin et al. 

1988). Kimmey (1956) found the same pattern 

in coastal Alaska, where western redcedar had a 

higher rate of internal decay at early ages than 

did the associated western hemlock and Sitka 

spruce. Less is known about the leading fungi 

that cause decay in living yellow-cedar, and the 

tree age – defect relationship.

The ecological roles of these wood decay fungi 

in old-growth forests have not received much 

attention. We have observed old, decayed 

western redcedar and yellow-cedar trees with 

boles that snapped to create canopy gaps (Fig. 

2). Thus, decay fungi are probably important 

mortality agents of old cedar trees that create 

small-scale disturbance (Hennon 1995) in oldgrowth forests.

Despite the cultural, economic, and ecological 

importance of western redcedar and yellowcedar, there is surprisingly little known about 

the fungi that cause so much defect in these live 

trees. More information is needed to identify the 

major decay fungi, resolve their infection 

biology, and determine at what tree and stand 

ages they become prevalent in different regions 

where the two cedars grow. Such information 

will be useful to scientists producing carbon 

models and to professionals managing forests 

for timber and other resources. 

Figure 2-Stem breakage due to decay in western 

redcedar creates canopy gaps and adds woody 

debris to the forest floor. USDA, FS photo.

50
LITERATURE CITED

Allen, E.A.; Morrison, D.J.; Wallis, G.W. 

1996. Common tree diseases of British 

Columbia. Victoria, BC: NRCAN, Can. For. 

Serv. 178 p. 

Andersen, H.E. 1959. Silvical characteristics of 

Alaska-cedar (Chamaecyparis nootkatensis). 

Station Paper 11. Juneau, AK: USDA For. 

Serv., Alaska For. Res.Center. 10 p. 

Barton, G.M. 1976. A review of yellow cedar 

(Chamaecyparis nootkatensis [D. Don] Spach) 

extractives and their importance to utilization. 

Wood and Fiber 8: 172-176. 

Buckland, D.C. 1946. Investigations of decay 

in western red cedar in British Columbia. Can. 

J. For. Res. 18: 158-181. 

Gilbertson, R.L.; Ryvarden, L. 1986. North 

American Polypores. Vol. 1. Fungiflora, Oslo. 

433 p. 

Habeck, J.R. 1968. Forest succession in the 

Glacier Park cedar-hemlock forests. Ecology 49: 

872-880. 

Hennon, P.E. 1991. Diseases, insects, and 

animal damage of yellow cypress. In: Lousier, 

J.D., ed. Yellow cypress: can we grow it? Can 

we sell it: Proceedings of a symposium. 

Nanaimo, BC: Richmond Inn, Richmond BC: 

36-43. 

Hennon, P.E. 1995. Are heart rot fungi major 

factors of disturbance in gap-dynamic forests? 

Northwest Science 69: 284-293.

Jin L. 1987. Detoxification of Thujaplicins in 

living western red cedar (Thuja plicata Donn.) 

PhD Thesis. University of British Columbia, 

Vancouver, British Columbia, Canada. 

Jin, L.; van der Kamp, B.J.; Wilson, J. 

1988. Biodegradation of thujaplicins in 

living western redcedar. Can. J. For. 

Res. 18: 782–786. 

Kelsey, R.G.; Hennon, P.E.; Huso, M.; 

Karchesy, J.J. 2005. Changes in heartwood 

chemistry of dead yellow-cedar trees that 

remain standing for 80 years or more in 

Southeast Alaska. J. Chem. Ecol. 31: 2653-

2669. 

Kimmey, J.W. 1956. Cull factors for sitka 

spruce, western hemlock and western redcedar 

in southeast Alaska. Station Paper 6. Juneau, 

AK: USDA For. Serv., Alaska For. Res.Center. 

31 p. 

Klinka, K; Chourmouzis, C. 2005. Ecological 

and silvical characteristics of major tree species 

in British Columbia. In: Watts, S.B.; Tolland, 

L., eds. Forestry handbook for British 

Columbia. Vancouver, BC: Faculty of Forestry, 

University of British Columbia: 326-347. 

Lim, Y.W.; Yeung, Y.C.A.; Sturrock, R.N.; 

Leal, I.; Breuil, C. 2005. Differentiating the 

two closely related species, Phellinus weirii and 

P. sulphurascens. Forest Pathology 35: 305-314. 

Rennerfelt, E. 1948. Thujaplicin a fungicidal 

substance in the heartwood of Thuja plicata. 

Physiol. Plant 1: 245-254. 

Rennerfelt, E.; Nacht, G. 1955. The fungicidal 

activity of some constituents from heartwood 

of conifers. Sven. Bot. Tidskr. 49: 419-432. 

Roff, J.W.; Atkinson, P.M. 1954. Toxicity 

tests of a water-soluble phenolic fraction 

(thujaplicin-free) of western red cedar. Can. J. 

Bot 32: 308-309. 

Sinclair, W.A.; Lyon, H.H. 2005. Diseases of 

trees and shrubs. New York: Cornell University 

Press. 660 p. 

Stirling, R. 2010. Rod Stirling, Wood Chemist, 

Building Systems Department, FPInnovations 

Forintek, 2665 East Mall, Vancouver, BC, 

Canada V6T 1W5. 

51
Stirling, R.; Morris, P.I. 2006. The influence 

of extractives in western redcedar’s equilibrium 

moisture content. International Research Group 

on Wood Protection . Document No. 

IRG/WP/06-40331. 12 p. 

Thies, W.G.; Sturrock, R.N. 1995. Laminated 

root rot in western North America. Gen. Tech. 

Rep. PNW-349. Portland, OR: USDA For. 

Serv., Pac. NW For. & Range Exp. Stn. 32 p. 

van der Kamp, B.J. 1975. The distribution of 

microorganisms associated with decay of 

western red cedar. Can. J. For. Res. 5: 61-67. 

van der Kamp, B.J. 1986. Effects of heartwood 

inhabiting fungi on thujaplicin content and 

decay resistance of western redcedar (Thuja 

plicata Donn.). Wood Fiber Sci. 18: 421-427. 

van der Kamp, B.J. 1988. Pests of western 

redcedar. In: Smith, N.J. ed. Western red 

cedar—does it have a future: Proceedings of a 

conference. Vancouver, BC: Faculty of 

Forestry, University of British Columbia: 145–

146. 

52
1 Michelle Cleary is a Forest Pathologist, BC Ministry of Forests and Range, Southern Interior Forest Region, 441 

Columbia Street, Kamloops, BC, V2C 2T3, Canada. 

TRAUMATIC RESIN DUCT FORMATION IN THE PHLOEM OF 

WESTERN REDCEDAR AND OTHER RESISTANCE MECHANISMS 

EFFECTIVE AGAINST ARMILLARIA ROOT DISEASE

Michelle R. Cleary1

ABSTRACT

Armillaria root disease is a significant forest health concern in the southern interior of British Columbia 

where the disease causes mortality in conifers and growth loss on trees that sustain non-lethal infections. 

One option to mitigate potential losses caused by Armillaria ostoyae is to plant conifer species that have 

a low susceptibility to killing by the fungus. A study of the pathological anatomy associated with 

different conifer species following infection by A. ostoyae revealed novel evidence of host reactions in 

western redcedar (Thuja plicata) characterized by traumatic resin ducts becoming included in the 

phloem. Other host reactions including necrophylactic periderm formation and barrier zone formation 

associated with compartmentalization of infected woody tissue impart increased resistance to the spread 

of A. ostoyae in host tissue. These results suggest that regenerating western redcedar on sites infested 

with Armillaria root disease may help alleviate some of the long-term impacts in second growth forests.

KEYWORDS: Armillaria ostoyae, western redcedar, resistance, host response, traumatic phloem resin 

ducts, necrophylactic periderm, British Columbia. 

INTRODUCTION

Armillaria ostoyae (Romagn.) Herink is the 

primary pathogen causing Armillaria root 

disease of conifers in British Columbia. The 

fungus is widespread across the southern onethird of the province and is almost universally 

present and damaging in mid-elevation forests 

located in the Interior Cedar-Hemlock (ICH) 

biogeoclimatic zone (Cleary et al. 2008). 

Much of the damage within this zone occurs in 

seral stages in plantations. The disease however 

goes unnoticed over time with only about onequarter of trees with belowground infection 

showing aboveground symptoms of Armillaria

(Morrison et al. 2000). In this zone, cumulative 

mortality in Douglas-fir (Pseudotsuga menziesii

(Mirb) Franco) plantations can be as much as 

20% by age 20-years and result in stands being 

serious understocked (Morrison and Pellow 

1994). 

Options to mitigate potential losses in new 

plantations include inoculum removal and 

planting species with low susceptibility to 

killing by A. ostoyae. Considering the latter 

however, there are no woody hosts that show 

complete resistance to the fungus.

In general, all conifer species less than about 15 

years of age are highly susceptible to killing by 

A. ostoyae and some conifers will start to show 

greater resistance to the fungus with age 

(Morrison et al. 1991, Robinson and Morrison 

2001). For example, western larch (Larix 

occidentalis Nutt.) becomes more tolerant of the 

fungus but only after it reaches about 20-25 

years of age. Before this age, western larch 

suffers very high mortality rates that are as 

much or sometimes greater than that observed in 

Douglas-fir (M.Cleary pers comm). Otherwise, 

very little is known about resistance in most 

other conifers in British Columbia. Hence, the 

aim of this study was to identify other useful 

species that show effective resistance against A. 

ostoyae. 

Western hemlock (Tsuga heterophylla (Raf.) 

Sarg.) and western redcedar (Thuja plicata

Donn ex D. Don) are two species that are 

2010 - A Tale of Two Cedars PNW-GTR-828

53
commonly found intermixed with planted 

conifers throughout the ICH biogeoclimatic 

zone in the southern interior of BC. Both are 

listed as being highly susceptible to killing by 

the fungus, but there is some indirect evidence 

from other studies that suggests western 

redcedar may in fact be less susceptible to the 

disease (Delong 1996, Morrison et al. 1988, 

Morrison et al. 2000). Knowledge of effective 

resistance mechanisms operating in other 

species would enable forest manager to explore 

new silvicultural options with respect to species 

mixtures in areas where root disease is of 

concern.

One means of assessing resistance in different 

conifers is to look for specific resistance 

mechanisms operating in trees that are effective 

against the fungus. When trees become infected 

by A. ostoyae, defense mechanisms in the bark 

and in the wood on root systems will determine 

the outcome of a particular reaction as being 

either susceptible or resistant. Several studies 

have shown necrophylactic periderm (NP) to be 

involved in resistant reactions in woody plants 

in response to mechanical injury or pathogenic 

invasion (Blanchette and Biggs 1992, 

Wahlström and Johansson 1992, Robinson and 

Morrison 2001). 

The overall objective of this study was to 

describe and compare host reactions to infection 

by A. ostoyae in the roots of western red cedar, 

western hemlock, and Douglas-fir; specifically 

necrophylactic periderm formation in the inner 

bark and barrier zone formation associated with 

the compartmentalization of infected woody 

tissue.

MATERIALS AND METHODS

Between 2002 and 2004, a series of 

geographically distinct field trials were 

implemented in ICH zone in the southern 

interior of BC to describe host response to 

infection by A. ostoyae on 20-30 year old 

Douglas-fir, western hemlock and western 

redcedar trees. In the field, root systems of trees 

were excavated and inoculated with A. ostoyae

that was previously grown on woody segments 

in the lab and then sampled after a period of 

weeks, months and 1 year post-inoculation. All 

roots were sectioned and examined for 

Armillaria lesions. Bark samples were collected, 

cryofixed and stored in liquid nitrogen. Woody 

samples showing compartmentalization were 

fixed in FAA and later sectioned on a rotary 

microtome to describe barrier zone anatomy.

In the lab, the cryofixed samples were sectioned 

in a cryostat maintained at -20°C and frozen 

sections were examined on a fluorescence 

microscope equipped with a freezing stage set at 

-35°C. Various histochemical staining 

techniques were used on thawed sections to 

detect lignin and suberin in some cells types. 

For each sample, host reactions and any 

anatomical changes in cells leading to the 

formation of these barriers in the bark and in the 

wood were described at the microscopic level 

and photographed. 

RESULTS 

Results showed noticeable differences between 

species in the ability to produce successful 

resistance reactions (either a NP in the bark or 

effective compartmentalization) to contain the 

fungus. 

In Douglas-fir and western hemlock, NP 

formation was relatively infrequent or was 

formed initially but then breached by the 

fungus. Western redcedar responded more 

efficiently by forming a NP to contain infections 

in the bark. Other unique reactions induced in 

cedar included a hypersensitive-type response 

consisting of rhytidome formation in the vicinity 

of a site of initial penetration by the fungus. 

This successive periderm extends for some 

distance proximally and distally along the length 

of the root eventually joining the pre-existing 

periderm.

Also during this study, novel evidence of a host 

reaction in western redcedar involving traumatic 

phloem resin ducts (TPRD) was observed 

(Cleary and Holmes 2010). These resin ducts 

appeared as small, circular zone of tissue above 

the vascular cambium and under or adjacent to a 

a newly differentiated periderm.

54
A comparative study looking at host response to 

abiotic wounding versus fungal infection by 

Armillaria showed that the intensity of the 

response involving TPRD formation was higher 

in roots inoculated with A. ostoyae than in roots 

that were abiotically wounded (Cleary and 

Holmes 2010). Deeper injuries to the bark, 

particularly with those caused by A. ostoyae, 

affected the intensity of the response by 

increasing the longitudinal expansion of resin 

canal formation in roots several centimeters 

beyond the margin of a newly differentiated 

periderm.

Compartmentalization of A. ostoyae infections 

following cambial invasion was also more 

frequent on western redcedar roots compared to 

Douglas-fir and western hemlock. This is due in 

part to anatomical and biochemical differences 

between the cedar and the other conifers.

DISCUSSION

In many conifers, the formation of resin ducts in 

the phloem, xylem, or both, is normal whereas 

in others it is considered a non-specific host 

response to biotic or abiotic injury. Western 

redcedar trees form neither normal nor traumatic 

resin canals in the xylem (Cleary and Holmes 

2010). Some reports exist describing traumatic 

resin duct formation in the phloem of species 

belonging to the Cupressaceae (namely 

Japanese cypress), however this study is the first 

to document the developmental anatomy and 

structure of traumatic resin canals in the phloem 

of western red cedar (Cleary and Holmes 2010). 

It is interesting that despite traumatic resin ducts 

being formed in the phloem, resinosus on the 

surface of the root was never observed. 

Precisely if or how oleoresin in cedar differs 

from that found in other conifers and the nature 

of the biochemical induction of resin ducts in 

the phloem with respect to its resistance against 

A. ostoyae warrants further investigation. 

Overall, the frequency of resistance reactions in 

western redcedar was on average 3-4 times 

higher than in Douglas-fir and western hemlock 

enabling most roots to effectively limit the 

extent of cambial invasion and/or girdling in 

roots. 

These results have practical implications with 

respect to reducing losses in new plantations. 

Planting western redcedar in higher proportions 

in mixtures with other conifers when 

regenerating sites infested with A. ostoyae can 

potentially reduced disease spread and tree 

mortality and help alleviate the long-term 

impacts of Armillaria to a more tolerable level.

ACKNOWLEDGEMENTS 

Very special thanks to Ms. Rona Sturrock for 

presenting this work at the ‘Tale of Two Cedars’ 

conference on my behalf. Funding for this 

research was provided by Forest Investment and 

Innovation Ltd. (FII), Forest Investment 

Account – Forest Science Program, Natural 

Science and Engineering Research Council of 

Canada, IMAJO Cedar Management Fund, and 

the Canadian Forest Service – Pacific Forestry 

Centre. I gratefully acknowledge D. Morrison, 

G. Jensen, B. van der Kamp, and T. Holmes for 

their help with various aspects of the work as 

well as the BC Ministry of Forests and Range, 

Tolko Industries, and Pope and Talbot Ltd. for 

their support. 

LITERATURE CITED

Blanchette, R.A. and Biggs, A.R. 1992.

Defense mechanisms of woody plants against 

fungi. Springer-Verlag, New York. 458 pp. 

Cleary, M.R. and T. Holmes. 2010. Formation 

of traumatic resin ducts in the phloem of 

western redcedar (Thuja plicata) roots following 

abiotic injury and pathogenic invasion by 

Armillaria ostoyae. IAWA Journal. [In press] 

Cleary, M., van der Kamp, B. and Morrison, 

D. 2008. British Columbia’s southern interior 

forests – Armillaria root disease stand 

establishment decision aid. BC Journal of 

Ecosystems and Management. 9:60-65. URL: 

http://www.forrex.org/publications/jem/ISS48/v

ol9_no2_art7.pdf

55
DeLong, D.L. 1997. A Retrospective 

Investigation of Advanced Western Redcedar 

Regeneration in the ICHwk1, ICHmw2, and 

ICHmw1 of the Nelson Forest Region – 

Experimental Project 1174. Res, Br., B.C. Min. 

For., Victoria, B.C. Work Pap. 25/1997. 

Morrison, D.J., Pellow, K.W., Norris, D.J., 

and Nemec, A.F.L. 2000. Visible versus actual 

incidence of Armillaria root disease in juvenile 

coniferous stands in the southern interior of 

British Columbia. Canadian Journal of Forest 

Research 30:405-414. URL: 

http://article.pubs.nrcnrc.gc.ca/ppv/RPViewDoc?_handler_=HandleIn

itialGet&Journal=cjfr&volume=30&calyLang=f

ra&articleFile=x99-222.pdf 

Morrison, D.J., Williams, R.E., and Whitney, 

R.D. 1991. Infection, disease development, 

diagnosis, and detection. In: Armillaria root 

disease. Edited by C.G. Shaw, III, and G.A. 

Kile. U.S. Dep. Agric. For. Serv. Agric. Handb. 

691. pp. 62-75. 

Morrison, D.J., Wallis, G.W., Weir, L.C., 

1988. Control of Armillaria and Phellinus root 

diseases: 20 year results from the Skimikin 

stump removal experiment. Pac. For. Res. Cent. 

Inf. Rep. BC-X-302, Can. For. Serv. 

Morrison, D.J. and Pellow, K. 1994.

Development of Armillaria root disease in a 25-

year-old Douglas-fir plantation. Eds: M. 

Johansson and J. Stenlid. Swedish University of 

Agricultural Sciences, Uppsala, Sweden. pp. 

560-571. 

Robinson, R.M. and Morrison, D.J. 2001.

Lesion formation in the roots of western larch 

(Larix occidentalis Nutt.) and Douglas-fir 

(Pseudotsuga menziesii) in response to infection 

by Armillaria ostoyae (Romagn.) Herink. For. 

Path. 31: 376-386. 

Wahlström, K.T. and Johansson, M. 1992.

Structural responses in bark to mechanical 

wounding and Armillaria ostoyae infection in 

seedlings of Pinus sylvestris. Eur. J. For. Path. 

22:65-76. 

56
A LANDSCAPE-LEVEL ANALYSIS OF YELLOW-CEDAR DECLINE 

IN COASTAL BRITISH COLUMBIA

Claire E. Wooton1 and Brian Klinkenberg1

ABSTRACT

Yellow-cedar (Chamaecyparis nootkatensis) is currently undergoing a dramatic decline in western 

North America, with concentrated areas of decline located in southeast Alaska and coastal British 

Columbia. Recent research suggests that a shift in climate is responsible for the decline and a working 

hypothesis concerning the role of climate and biophysical factors has been proposed. In our research 

project we have investigated the spatial pattern of yellow-cedar decline in British Columbia at the 

landscape scale. Our study aims to assess whether we can identify any significant relations between 

landscape-level biophysical variables and areas of decline. 

Our research questions are being addressed through a combination of remote sensing and GIS 

techniques. Sample points were distributed across the landscape according to a stratified sampling 

scheme and the presence/absence of decline at each point was determined using a forest cover dataset 

and aerial photograph interpretation. Spatial patterns of biophysical factors (e.g. elevation, slope, aspect) 

were derived from a 25 m digital elevation model of the province. In order to assess the strength of 

relations between the distribution of decline and the various environmental predictors, statistical and 

decision-tree models commonly used in predictive vegetation and species distribution modeling will be 

applied. Results from the optimal model will be presented, including maps of the probability of decline 

occurrence and binary presence/absence maps. 

Studying how the pattern of decline observed on the landscape relates to biophysical factors will assist 

in elucidating possible mechanism(s) of decline. Using multiple models in the analysis will allow a 

thorough investigation of the associations between the biophysical variables and decline. Knowledge of 

the determinants of the spatial pattern of decline will improve predictability and provide critical 

information for conservation and resource management. 

1 Department of Geography, University of British Columbia, Vancouver, BC, V6T 1Z2, Canada, 

cwooton@geog.ubc.ca

2010 - A Tale of Two Cedars PNW-GTR-828

57
58
1 Paul Hennon is research plant pathologist, and the corresponding author; 2 Dave D’Amore is research soil 

scientist, Forestry Sciences Laboratory, Pacific Northwest Research Station, 11305 Glacier Highway, Juneau, AK 

99801. 3 Dustin Wittwer is aerial survey specialist, Forest Health Protection, 11305 Glacier Highway, Juneau, AK 

99801. 4 John Caouette is statistician, The Nature Conservancy, Juneau, AK 99801

BIOCLIMATIC ENVELOPES, FOREST DECLINE RISK FACTORS, 

AND MODELING SUITABLE HABITAT FOR YELLOW-CEDAR 

CONSERVATION AND MANAGEMENT

Paul Hennon1, Dave D’Amore2, Dustin Wittwer3, John Caouette4

ASTRACT

Yellow-cedar (Callitropsis nootkatensis, syn. Chamaecyparis nootkatensis) has suffered an intensive 

mortality problem through the 1900s in coastal Alaska and adjacent British Columbia known as yellowcedar decline. Our research has investigated the cause of death through a series of coordinated studies 

that evaluate climate, site factors, and cedar physiology. Details from some of these studies will be 

shared in various sessions of this symposium. The occurrence of yellow-cedar decline in Alaska is found 

on a subset of the distribution of yellow-cedar, suggesting zones of maladaptation. The cause yellowcedar decline is complex, but can be reduced to two risk factors for landscape models – snow and soil 

drainage. We combine snow models using climate inputs with landscape models to identify portions of 

the landscape that are suitable and unsuitable to yellow-cedar as the climate warms. Examples of 

maladaptation and habitat suitability are given at several spatial scales. This partitioning of the 

landscape follows the bioclimate envelope concept as the basis for a regional conservation and 

management strategy. Management options for yellow-cedar in areas where it is maladapted (dead and 

dying) include salvage to recover valuable wood products. Utilizing dead yellow-cedar for wood 

products shifts some timber harvesting in other areas where it is thriving and serving conservation goals. 

More information is needed on successional trajectories in decline-impacted forests, whether or not 

salvage harvesting is conducted. Suitable current and future habitat for yellow-cedar includes drained 

soils that support deeper rooting and where snow persists past the last spring frost. Favoring yellowcedar through artificial regeneration and thinning in these suitable areas will help maintain yellow-cedar 

in forested ecosystems of Alaska and British Columbia. 

Key words: Chamaecyparis nootkatensis, yellow-cedar decline, climate, conservation strategy

INTRODUCTION

Yellow-cedar (Chamaecyparis nootkatensis) is 

an important tree along the Pacific coast. Our 

symposium highlighted the cultural, economic, 

and ecological values of this tree. Yellow-cedar 

has been dying on more than 250,000 hectares 

for the past 100 years in southeast Alaska and 

adjacent British Columbia. These patches of 

dead trees are conspicuous on the landscape as 

concentrations of long-dead, recently-dead, and 

dying trees. This forest problem is a leading 

example of a tree species negatively impacted 

by climate change. The goal of our research is to 

provide an understanding of the cause of 

yellow-cedar decline and to help develop a 

conservation and management strategy to ensure 

the long-term health of this valuable tree in 

Alaska’s forest ecosystems.

THE BIOCLIMATIC ENVELOPE 

CONCEPT

The bioclimate envelope (or climate profile) 

concept is useful in interpreting yellow-cedar 

decline and in formulating an adaptive strategy 

for forest management. The distribution of trees 

is shaped primarily by climate. When climate 

2010 - A Tale of Two Cedars PNW-GTR-828

59
shifts relative to a tree’s distribution, three 

spatial zones can be considered with respect to 

how well the tree is then adapted: “maladapted” 

and “stable” zones where the tree is growing,

 

Figure 1-- Left: a shifting bioclimatic envelope creates three theoretical zones of climate adaptation for yellowcedar: maladaptation where decline occurs, stability where the tree occurs but is not dying at an appreciable rate, 

and a migration zone where the climate has become suitable and is available for occupancy. Right: distribution of 

yellow-cedar decline (red) in Alaska represents the “maladapted zone”, the surrounding occurrence of yellowcedar (yellow) represents the “stable zone”. The “migration zone” is not shown. The speckled areas on the outer 

west coast represent the possible refugia where yellow-cedar survived the Pleistocene Epoch; these were likely 

epicenters from which Holocene migration occurred.

and a “migration” zone that represents new 

potential habitat (Fig. 1). The broad-scale 

occurrence of yellow-cedar decline (Fig. 1) can 

be interpreted as this maladapted zone, which is 

surrounded by areas where yellow-cedar grows 

but is not dying at an appreciable rate (i.e., the 

stable zone). Not shown on this map are areas 

that have a suitable climate, but where the tree 

does not yet occur (i.e., migration zone). Note 

that the migration zone does not imply that the 

tree will actually migrate there within some time 

frame; it simply suggests that the climate has 

become suitable. This concept is dynamic 

through time, and with inputs of climate 

forecasting, can indicate predicted suitable 

habitat into the future.

FOREST DECLINE RISK FACTORS

After evaluating a number of potential biotic and 

abiotic factors associated with yellow-cedar decline 

(Hennon et al. 2008), we formed a working 

hypothesis around the one vulnerability of yellowcedar—spring freezing injury. The cascading 

complex of factors that leads to fine root freezing 

injury in this scenario (Fig. 2) has become the 

framework for our research, with individual studies 

directed at testing each interaction of factors 

(Hennon et al. 2008).

Long-term climate or near-term weather events 

influence each of these steps. The cool, moist 

climate that developed in the late Holocene 

created the bog and forested wetland conditions 

that favored the abundance of yellow-cedar. 

Yellow-cedar was competitive on these wet sites 

60
through a unique ability to access nitrates with 

its habit of shallow fine roots (D’Amore et al. 

2009). The open canopy conditions on boggy 

soils allow a more extreme microclimate: 

greater warming, which appears to trigger cedar 

dehardening in late winter, and the lack of 

thermal cover, allowing cold temperatures to 

penetrate more deeply into soil during cold

Figure 2 -- Shallow root freezing as the leading 

hypothesis to explain yellow-cedar decline, and the 

predisposing and inciting factors that lead to it. 

weather (Hennon et al. 2010). Research on cold 

tolerance by demonstrates the vulnerability of 

yellow-cedar roots in early spring: soil 

temperatures below -5  ̊C are lethal (Schaberg et 

al. 2008). 

The presence of snow buffers soil temperatures, 

disrupting the progression of events leading to 

tree injury. Analysis of weather station data 

confirms the trend of warmer winters and 

reduced snow, but persistent early spring 

freezing events throughout the 1900s (Beier et 

al. 2008); these are all conditions necessary for 

yellow-cedar decline. Comparing snow models 

to the distribution of yellow-cedar decline 

further reveals the controlling influence of snow 

in the health of yellow-cedar forests. We are 

finding that yellow-cedar is healthy wherever 

snow persists past the last cold period, or where 

yellow-cedar is deep-rooted on better drained 

soils.

The complex interaction of climate, site, and 

forest structure can be reduced to two simple 

risk factors the purpose of landscape risk 

modeling for yellow-cedar decline: soil 

drainage and snow. These two risk factors play 

out at different spatial scales. Snow can be 

considered a broad- and mid-scale factor and 

modeled at the regional or small island spatial 

scale. Variation in soil drainage can be observed 

at every watershed in southeast Alaska; thus, it 

should be introduced into models at the fine 

spatial scale. Note that both risk factors, snow 

and soil drainage, are also important 

components in determining habitat features for 

live yellow-cedar.

A PROPOSED CONSERVATION – 

MANAGEMENT STRATEGY

Recommendations for the conservation or active 

management of yellow-cedar are based on 

current and future habitat suitability of this tree 

in the context of its vulnerability to climate. 

Partitioning the landscape into suitable and 

unsuitable areas is based on modeling risk 

factors and comparing those to the current 

distribution of the tree (Hennon et al. 2008). 

Snow modeling based on global circulation 

models helps predict habitat that will be suitable 

in the future. This highlights portions of the 

landscape where yellow-cedar is, or will be, 

dying, stable, and regenerating—an approach 

consistent with the shifting bioclimatic envelope 

concept (Hamann and Wang 2006). 

Planting or thinning is often needed to ensure 

the initial regeneration and competitive status of 

yellow-cedar; thus, there is a role for active 

management (Hennon et al. 2009). These 

activities are directed at higher elevation or on 

well drained soils where snow or deeper rooting, 

respectively, protects yellow-cedar roots from 

lethal cold temperatures. Recent studies have 

also demonstrated that dead cedar forests 

represent a surprisingly valuable wood resource 

for salvage recovery (Hennon et al. 2007) 

because the tree’s unique heartwood chemistry 

retains wood properties for up to a century after 

death (Kelsey et al. 2005). Salvage logging of 

dead cedar where it is now maladapted to 

climate can relieve pressure from other areas 

more suitable for long term conservation of 

yellow-cedar.

61
OPPORTUNITIES FOR 

COLLABORATIVE RESEARCH

Information gaps remain before a 

comprehensive conservation and management 

strategy can be fully implemented. These gaps 

in our knowledge represent opportunities to 

collaborate across international and discipline 

boundaries. Several examples are offered below.

Spatial and temporal aspects of yellow-cedar 

decline in British Columbia and Alaska should 

be contrasted. Research is underway in British 

Columbia to document the extent and timing of 

yellow-cedar decline. Recent findings reported 

in these proceedings suggest a continuation of 

decline occurring at higher elevation with 

decreasing latitude, as has been documented in 

Alaska. Integrating results from British 

Columbia and Alaska would cover a wide range 

of latitudes to strengthen this relationship. 

Research on the onset and development of 

decline in British Columbia should be compared 

to results on the epidemiology from Alaska.

Plant succession following intensive overstory 

yellow-cedar death needs to be documented in a 

variety of settings. The extent to which western 

redcedar benefits from yellow-cedar decline, 

and may provide similar ecosystem services, 

should be determined. Successional trajectories 

need to be assessed in forests that contain a 

variety of tree species (e.g., with and without 

western redcedar) and in different zones of 

productivity along the hydrology-soil drainage 

gradient. As above, this research should be 

conducted jointly between British Columbia and 

Alaska, or at least in a way that results could be 

compared.

Research on the yellow-cedar genetics is just 

beginning in Alaska but is more mature in 

British Columbia. The effect of yellow-cedar 

decline on the genetic structure of yellow-cedar 

populations has not been evaluated. Surviving 

yellow-cedar trees in stands impacted by decline 

have experienced intense selective pressure and 

thus may offer unique genetic material. Genetic 

conservation of yellow-cedar in the context of 

the widespread decline needs to be considered. 

The silvics of yellow-cedar in young-growth 

forests need research attention and more 

experience from management, especially in 

Alaska. Deer browsing on regenerating yellowcedar, and techniques to discourage it such as 

use of stock with high terpene concentrations, 

needs to be studied. The long-term ability of 

yellow-cedar to maintain its canopy status 

among competing tree species should be 

evaluated.

The unique way that cedars utilize calcium to 

alter nitrogen availability should be tested in the 

field. Selecting sites high in calcium, or 

fertilization with calcium on other sites, may 

provide a competitive advantage for yellowcedar over most other trees.

Developing a conservation and management 

strategy in British Columbia and Alaska will 

require more landscape and climate modeling. 

Higher resolution distribution maps are needed 

for yellow-cedar. Ideally, these would show 

both occupied and unoccupied suitable habitat. 

Climate projections, with an emphasis on snow 

models, could be combined with the other forest 

decline risk factor, soil drainage, to produce a 

dynamic yellow-cedar decline risk map.

The various values of yellow-cedar justify these 

efforts by research and forest management. A 

multi-disciplinary approach with science and 

management partners from British Columbia 

and Alaska working together is necessary to 

develop and implement a conservation and 

management strategy for yellow-cedar. 

LITERATURE CITED

Beier, C.M.; Sink, S.E.; Hennon, P.E.; 

D'Amore, D.V.; Juday, G.P. 2008. Twentiethcentury warming and the dendroclimatology of 

declining yellow-cedar forests in southeastern 

Alaska. Canadian Journal of Forest Research. 

38: 1319-1334. 

62
D’Amore, D.V.; Hennon, P.E. 2006.

Evaluation of soil saturation, soil chemistry, and 

early spring soil and air temperatures as risk 

factors in yellow-cedar decline. Global Change 

Biology. 12: 524-545. 

D’Amore, D.V.; Hennon, P.E., Schaberg, 

P.G., Hawley, G. 2009. The adaptation to 

exploit nitrate in surface soils predisposes 

yellow-cedar to climate change-induced decline 

and enhances the survival of redcedar. Forest 

Ecology and Management. 258: 2261-2268. 

Hamann, A.; Wang, T.L. 2006. Potential 

effects of climate change on tree spcies and 

ecosystem distribution in British Columbia. 

Ecology. 87: 2773-2786. 

Hennon, P.E.; D’Amore, D.; Wittwer, D.; 

Caouette, J. 2008. Yellow-cedar decline: 

conserving a climate-sensitive tree species as 

Alaska warms. In: Deal. R., ed. Integrated 

restoration of forested ecosystems to achieve 

multiresource benefits: proceedings of the 2007 

national silviculture workshop. Gen. Tech. Rep. 

PNW-GTR-733. Portland, OR: U.S. Department 

of Agriculture, Forest Service, Pacific 

Northwest Research Station: 233-245. 

Hennon, P. McClellan, M.; Spores, S., 

Orlikowska, E. 2009. Survival and growth of 

planted yellow-cedar seedlings and rooted 

cuttings (stecklings) near Ketchikan, Alaska. 

Western Journal of Applied Forestry. 24(3): 

144-150. 

Hennon, P.; Woodward, B.; Lebow, P.K. 

2007. Deterioration of wood from live and dead 

Alaska yellow-cedar in contact with soil. Forest 

Products Journal. 57(6): 23-30. 

Kelsey, R.G.; Hennon, P.E.; Huso, M.; 

Karchesy, J.J. 2005. Changes in heartwood 

chemistry of dead yellow-cedar trees that 

remain standing for 80 years or more in 

southeast Alaska. Journal of Chemical Ecology. 

31: 2653-2670. 

Schaberg P.G.; Hennon P.E.; D'Amore, D.V.; 

Hawley, G.J; Borer, C.H. 2005. Seasonal 

differences in freezing tolerance of yellow-cedar 

and western hemlock trees at a site affected by 

yellow-cedar decline. Canadian Journal of 

Forest Research. 35: 2065-2070. 

Schaberg, P.G.; Hennon, P.E.; D’Amore 

D.V.; Hawley, G. 2008. Influence of simulated 

snow cover on the cold tolerance and freezing 

injury of yellow-cedar seedlings. Global Change 

Biology. 14: 1282-1293.

63
MANAGING WESTERN REDCEDAR AND YELLOW-CEDAR IN A 

CHANGING ENVIRONMENT

Laura Gray1 and Andreas Hamann

ABSTRACT

Human-aided movement of species populations in large scale reforestation programs could be a potent 

and cost effective climate change adaptation strategy. However, while there is broad consensus that the 

habitat of many species generally shifts north and to higher elevations, we usually do not know if this 

applies to a particular population and where exactly appropriate target habitat would be under uncertain 

future climates. In a case study of western redcedar (Thuja plicata) and yellow-cedar (Chamaecyparis 

nootkatensis) in western North America, we report results from bioclimate envelope modeling that 

predicts suitable habitat for locally adapted genotypes under 18 climate projections from general 

circulation models for the 2020s, 2050s and 2080s, as well as under observed climate trends. We 

generally find maintenance and expansion (both northward and at higher elevations) of potential suitable 

habitat, however the scale of potential range expansion is different for the two species. Our results 

suggest that population-specific recommendations for assisted migration can be made with reasonable 

confidence over a 10 to 20-year planning horizon, but model uncertainty does not allow for long-term 

planning, which means forest management will lag behind prescriptions that would be optimal under a 

continued directional climate trend. 

1 Department of Renewable Resources, Faculty of Agricultural, Life, and Environmental Sciences, University of 

Alberta, 751 General Services Building, Edmonton, AB, Canada, T6G 2H1

2010 - A Tale of Two Cedars PNW-GTR-828

64
YELLOW-CEDAR AND WESTERN REDCEDAR ADAPTATION TO 

PRESENT AND FUTURE CLIMATES

John H. Russell and Jodie Krakowski1

ABSTRACT

Twelve range-wide yellow-cedar provenance trials and 23 western redcedar trials were assessed to 

quantify climatic influences on adaptive traits using regression analyses. Response variables were 

productivity (integrating height, survival and cold hardiness), and cedar leaf blight (CLB) infection on 

western redcedar. Climate change impacts by 2050 were modelled using the Canadian CGCM and the 

CSIRO models, B2 scenario. Range-wide productivity of yellow-cedar was weakly influenced by 

summer drought stress and growing season warmth (multiple R2 = 0.16). Stronger adaptive patterns 

were apparent on the harshest sites when individual sites were analyzed. California populations of both 

species were always maladapted. Yellow-cedar population productivity was highest on warmer, wetter, 

and less snowy sites than the location of origin. Climatic limits on productivity may shift from winter 

temperatures to summer maximum temperatures and drought by 2050. Seed transfer can be broad on 

ecologically suitable sites. Western redcedar had moderately strong species-wide relationships with 

climate variables, and pronounced differences among regions. Warm wet conditions during the growing 

season were the strongest drivers of productivity. CLB increased with site moisture and winter warmth. 

Populations from warmer, wetter low-elevation coastal sites had lower CLB than predicted, inferring 

evolved resistance. Coastal sites may have increased productivity in future on summer-cool sites where 

moisture is not limiting, but also higher CLB risk. Broad latitudinal seed transfer in the maritime region 

within the elevation band of origin would optimize productivity and minimize risk of CLB (above or 

below 500 m), and submaritime populations can be transferred broadly. More populations and test sites 

in warmer climates are needed to fully characterize interior redcedar genecology. 

KEYWORDS: Western redcedar, yellow-cedar, seed transfer, genecology, cedar leaf blight

INTRODUCTION

Yellow-cedar (Callitropsis nootkatensis) is 

primarily adapted to montane coastal sites with 

fluctuating water tables and winter snowpack. 

Western redcedar (Thuja plicata) typically 

occupies lower elevations and moist sites, 

overlapping with yellow-cedar, but its range 

extends broadly into interior wet forests. Studies 

have found no to weak clinal patterns for western 

redcedar in morphological and physiological 

traits (Cherry and Lester 1992; Fan et al. 2008; 

Grossnickle and Russell 2010), and no patterns 

in yellow-cedar seedlings (Russell 1998; 

Grossnickle and Russell 2010) despite significant 

population differences. 

Phenotypic plasticity facilitates physiological 

adjustment to environmental changes in these 

indeterminate species (Russell 1998; El-Kassaby 

1999). Many species with low population 

genotypic variation have phenotypic adaptive 

differences (e.g., Karhu et al. 1996). Coastal 

climates where western redcedar and yellowcedar occur are relatively homogeneous and 

expected to have minimal changes due to future 

climate impacts (Spittlehouse 2008). The interior 

range of western redcedar encompasses wider 

climatic extremes due to topographic diversity 

and continentality and is expected to change 

substantially in the future. 

1

John Russell and Jodie Krakowski are Research Scientists, B.C. Ministry of Forests and Range, Research and 

Knowledge Management Branch, Cowichan Lake Research Station, Box 335, Mesachie Lake, B.C. V0R 2N0 

2010 - A Tale of Two Cedars PNW-GTR-828

65
Cedar leaf blight (CLB) causes foliar mortality in 

western redcedar and plantation failure in severe 

cases. Caused by the fungal pathogen 

Didymascella thujina, field studies show western 

redcedar populations from coastal low-elevation 

sites were most resistant (Russell et al. 2007). 

Determining climatic factors associated with 

CLB severity is key to developing site hazard 

and seedling deployment guidelines. Although 

prevalent along the coast, CLB has been 

completely overlooked in forest management, 

but will likely gain importance as forest health 

becomes a priority management objective.

Climatic models are largely in accord over the 

cedar species’ ranges over the next 1-3 decades, 

after which they diverge considerably (Gray and 

Hamann, these proceedings). During the current 

management rotation, late- season drought is 

expected to become more severe in drier regions, 

earlier snowmelt will become more prevalent, 

and minimum and mean temperatures will 

increase. We explore the degree to which these 

factors influence the growth, survival, and health 

of western redcedar and yellow-cedar across 

their ranges. 

Objective

Our first objective was to determine for each 

species the climatic factors which most influence 

adaptive traits. Our second objective was to 

determine the extent of local population 

adaptation to guide incorporating climatic 

adaptation into seed transfer for each species 

considering current and future climate 

predictions. 

MATERIALS AND METHODS

Field trials

Seed for yellow-cedar trials was obtained from 

populations of three to 10 well-spaced trees from 

Alaska to California. Trials were established in 

1990 and 1991 with one year old seedlings 

planted in randomized complete blocks. Each of 

the 12 sites (Fig. 1) tested 19-40 populations in 

10 to 12 blocks and 5-tree row plots. 

Western redcedar seed was collected from 10 to 

50 trees per population range-wide, but primarily 

within British Columbia. Field trials were 

established between 1991 and 1998 with oneyear-old seedlings planted in randomized 

complete blocks with 9 to 26 populations in 10 to 

44 blocks and single tree plots at each site (Fig. 

1). Manual vegetation control was done as 

needed on all trials.

Figure 1 -- Locations of tested provenances and 

field trials. Cw is western redcedar; Yc is yellowcedar.

Data analysis 

Response variables assessed for both species 

were adaptability and height. Adaptability was 

scored as a binomial trait where dead or frost 

damaged trees scored 0 and healthy survivors 

scored 1. Height and adaptability were multiplied 

to yield a productivity index. Western redcedar 

CLB incidence was scored on a 0 to 6 scale 

indicating increased severity with a higher score. 

Individual western redcedar populations were 

analyzed for transfer functions, whereas response 

functions were based on grouping populations 

into 16 regions. 

 

66
To standardize results across years and trial 

designs, each trial was analyzed separately using 

a linear mixed model to generate best linear 

unbiased predictions (BLUPs) for each 

quantitative response variable (ASReml ver. 2.0). 

Population-site BLUPs for height and 

adaptability were added to best linear unbiased 

estimates of site to facilitate intra-site 

comparisons. 

Annual and seasonal regional climatic variables 

for each provenance origin and test site were 

estimated using ClimateWNA ver. 4.5.2 (Wang 

et al. 2010). Forward stepwise multiple linear 

regressions were used to identify for each species 

which combinations of climatic descriptors had 

the strongest influence on each response variable 

(SAS ver.9.1.3). To minimize the likelihood of 

spurious statistical relationships while capturing 

biologically significant differences α was set at 

0.10. Well-adapted populations were considered 

those with average or better performance at a 

site, or across multiple sites (i.e., well-adapted to 

a climatic range).

Methodology of Rehfeldt et al. (1999) was used 

to develop transfer and response functions to test 

population adaptation to climatic variables. 

Univariate quadratic regressions were analyzed 

across all sites, and at each site. Transfer 

distance is the value of a geographic or climatic 

descriptor at the origin site minus the value at the 

test site. A transfer function is a regression with 

climatic transfer distance as the independent 

variable, and the response as the dependent 

variable. Local populations were deemed 

maladapted to a given climate variable when the 

local mean (performance at transfer distance of 

zero) fell outside the 80% confidence interval at 

the quadratic function vertex. This provides an 

estimate of the climatic distance between the 

local and optimum. 

Response functions are regressions testing 

performance of a given population against a 

climate variable over multiple sites. Western 

redcedar populations were combined into 16 

regional groups for response function analyses 

based on preliminary analyses supporting broad 

adaptation patterns. Regional climate variables 

were the arithmetic mean of the maximum and 

minimum values of component populations. 

Current climate normals and two climate models, 

the Canadian CGCM and the CSIRO model were 

selected to model climate in 2050 using the B2 

scenario to provide predictive bound. The former 

model provides the best fit for the study area 

based on back-casting (Spittlehouse 2008) and 

the latter yielded the most divergent results. 

Population response patterns based on current 

climates were used to predict responses in 2050 

with the assumption that this span is too short for 

evolutionary effects. 

RESULTS AND DISCUSSION

Multiple regressions

Each species had only two significant climatic 

descriptors retained in the model for 

productivity. For yellow-cedar, 16.1% of 

variation in productivity was explained by 

maximum winter temperature and summer 

minimum temperature (cooler values were best). 

Western redcedar was more sensitive to climate 

with summer precipitation and maximum 

summer temperature explaining 29.1% of 

variation in productivity. CLB infection was 

associated with a complex set of environmental 

factors: summer precipitation accounted for 29%, 

while the best 2-variable combination of autumn 

precipitation and maximum summer temperature 

explained 38.5%. In total, a suite of 10 variables 

associated with warm, moist growing season 

conditions and warm winters accounted for up to 

62.5% of CLB incidence. 

Transfer functions

Yellow-cedar productivity had weak range-wide 

relationships with climatic factors (all R2 ≤ 0.03). 

Many local populations had better performance 

on on warmer, wetter, and less snowy sites than 

the location of origin. Productivity increased 

linearly as summer drought decreased, as the 

quadratic optimum was far beyond the range of 

habitat suitable for the species (Table 1). Future 

conditions predicted little change for yellowcedar, except the CSIRO model showed slightly 

weaker influence of snow due to warming. Both 

67
climate models indicated summer minimum 

temperatures would be less of an influence than 

currently.

Western redcedar productivity had significant 

relationships with a many climate descriptors 

(0.42 ≤ R2 ≤ 0.97), especially those associated 

with warm temperatures (Fig. 2). Populations 

were most productive on sites with a longer, 

wetter growing season, cooler summers, and 

warmer spring and fall than their locations of 

origin (Table 1), which corresponds in general to 

more southern climates. This may reflect 

adaptational lag from postglacial recolonization 

of its northern range from the south. Western 

redcedar productivity showed few range-wide 

differences from predictions based on current 

climate under expected future climates.

Under current conditions, significant amounts of 

variation in CLB were explained by almost all 

climatic variables (0.03 ≤ R2 ≤ 0.33), with 

maximum infection at temperate warm sites with 

wet, cool summers and mild winters. CLB 

incidence and severity may increase due to 

longer, milder growing seasons and warmer 

winters, since cold typically limits survival and 

spread of the pathogen. The CSIRO scenario 

(0.05 ≤ R2 ≤ 0.37) modelled warmer summers 

while the CGCM (0.03 ≤ R2 ≤ 0.36) predicted 

milder winters.

Individual sites expressed stronger relationships 

between yellow-cedar productivity and climatic 

indicators (0.12 ≤ R2 ≤ 0.52). Fall and winter 

maximum temperatures had the strongest 

influences, especially at environmentally 

stressful sites for this species. Western redcedar 

productivity at individual sites was most often 

Table 1 -- Climatic transfer distances (0 is local) for optimizing yellow-cedar and redcedar productivity and 

CLB under current and 2050 conditions from 2 climate models with the B2 scenario. Blank cells show no 

significant relationship. Bold values show local maladaptation across a species’ range. LP indicates linear 

patterns and thus no climatic optimum, or an optimum far beyond the climatic range of the species.

Yc productivity Cw productivity Cw CLB

current 2050 current 2050 current 2050

Variablea Units CGCM CSIRO CGCM CSIRO CGCM CSIRO

MAT °C -11 -9 -7 2 4 4

MWMT °C -1 0.5 1.5 LP LP -8 7 8 7

MCMT °C -6 -4 -4 5 7 8

TD °C 3 3 -4 -17 -14 -12

MAP mm LP LP -432 -2632 -2646 -2235

MSP mm LP LP LP 293 252 271 LP LP LP

AHM 13 11 13

SHM LP LP LP -1 6 7 66 67 67

PAS mm 1058 LP 761.2 830 903

EMT °C -7 0.4 42 30

TAV_wt °C -5 -6 -2 5 3 7

TAV_sp °C LP -3 LP 1 3

TAV_sm °C 21 -10 -14 6 7 7

TAV_at °C -8 LP -3 2 3 5

TMN_wt °C -6 -5 1 6 5 5

TMN_sp °C -5 -3 -3 2 10

TMN_sm °C -0.4 -0.6 LP LP -7 1 17 20

TMN_at °C -3 -4 -2 -0.1 2

TMX_wt °C -13 -12.9 -3.2 -5 -3 -7 3 8 10

TMX_sp °C 24 -21 9 17 4 4

TMX_sm °C -4 -2 -1 24 3 4

TMX_at °C 19 20.0 -72 -51 -24 4 5

PPT_wt mm 1046 1154.2 1454.3 -754 -707 -472 -516

PPT_sp mm -691 -764 -697

PPT_sm mm 427 435.8 479.3 164 158 159 LP LP LP

PPT_at mm 1679 1567.7 LP -1931 -2084 -1364 a MAT: mean annual temperature, MW(C)MT: mean temperature of warmest (coldest) month, TD: continentality, MWMT-MCMT, MA(S)P: mean annual 

(summer) precipitation, AHM: annual heat-moisture index, (MAT+10)/(MAP/1000), SHM: summer heat-moisture index, (MWMT)/(MSP/1000), PAS: 

precipitation as snow, EMT: extreme minimum temperature, TAV: average temperature, TMN: minimum temperature, TMX: maximum temperature, PPT: 

precipitation, wt: winter, sp: spring, sm: summer, at: autumn

68
Figure 2 -- Transfer functions showing optimal 

productivity of select western redcedar 

populations across mean spring temperature 

range.

influenced by summer precipitation (0.43 ≤ R2 ≤ 

0.93), and summer drought index (SHM: see 

Table 1; 0.22 ≤ R2 ≤ 0.94). Individual site CLB 

was most strongly influenced by maximum 

summer temperature (warmest had least CLB; 

0.46 ≤ R2 ≤ 0.65), continentality (more 

continental sites had least CLB: 0.28 ≤ R2 ≤ 

0.69), and precipitation during the growing 

season (driest had least CLB).

Response functions

Yellow-cedar populations had the strongest 

responses on sites that it was most maladapted 

to due to cold temperature stress. Productivity of 

all populations that had significant patterns was 

most influenced by winter temperatures, which 

reflects the cold hardiness component of this 

response variable. Spring and autumn 

temperatures were also strong drivers, being 

correlated both with growing season length and 

early and late frost damage. There were no 

latitudinal patterns, and California populations 

had low survival at all test sites. 

Twelve of the 16 western redcedar regional 

groups had significant relationships between 

productivity and growing season temperatures 

(warmer spring and fall, but cooler summers: 

Figure 3 -- Response functions showing 

productivity versus test site summer precipitation 

of selected regionally grouped western redcedar 

populations.

.40 ≤ R2 ≤ 0.97). Most regionally grouped 

populations, including those from the 

submaritime and high elevations, had 

significantly higher productivity at maritime test 

sites than continental sites. Populations from the 

coastal low elevation regions tended to 

outperform most others at a given site, except at 

the most continental and environmentally 

extreme sites (Fig. 3). 

Figure 4 -- Select western redcedar population 

responses to extreme minimum temperature 

relative to site mean CLB severity.

69
Population CLB responses showed major 

divergence between coastal low elevation and 

other populations with warming winters (Fig. 4: 

0.59 ≤ R2 ≤ 0.96). Populations from the maritime 

warmer regions with high CLB hazard had far 

less infection than average, indicating a potential 

coevolution of western redcedar with CLB. All 

other populations were more susceptible, with 

increasing infection severity on higher CLB 

incidence sites which were milder and wetter. 

Seed transfer

Seed transfer of yellow-cedar can be broad on 

ecologically suitable sites, but more restricted on 

sites with heavy snowpack as population 

adaptation to snow varied. As long as western 

redcedar populations are kept within the 

elevation band of origin to minimize risk of CLB 

(above or below 500 m), broader latitudinal seed 

transfer than currently allowed (±3° for natural 

stand seed) along the coast appears acceptable. 

Submaritime populations can be transferred 

broadly, with highest western redcedar 

productivity on milder sites. 

CONCLUSIONS

Yellow-cedar has very weak adaptive patterns 

associated with climate across its range, 

facilitating broad seed transfer. Productivity 

(combining height, survival, and frost hardiness) 

is most influenced by cool summer temperatures 

and summer moisture. Snowpack influences 

productivity primarily through frost damage, and 

likely by limiting early height growth. Western 

redcedar is much more sensitive to climate across 

its range. Productivity is highest on sites with 

long, wet growing seasons. Populations of both 

species have best productivity in climates that are 

warmer and with longer growing seasons than 

their locations of origin. CLB is most severe in 

coastal mild, cool sites with warm winters and 

wet summers; populations originating from 

above 500 m across the species range are highly 

susceptible, while coastal low elevation 

populations appear to have evolved resistance. 

CLB resistance as well as productivity should be 

considered when selecting western redcedar 

populations for reforestation. 

LITERATURE CITED

Cherry, M.L.; Lester, D.T. 1992. Genetic 

variation in Chamaecyparis nootkatensis from 

coastal British Columbia. West. J. Appl. For. 

7:25-29.

El-Kassaby, Y.A. 1999. Phenotypic plasticity in 

western redcedar. For. Genetics 6:235-240. 

Fan, S.; Grossnickle, S.C.; Russell, J.H. 2008. 

Morphological and physiological variation in 

western redcedar (Thuja plicata) populations 

under contrasting soil water conditions. Trees 

22:671-683. 

Grossnickle, S.C.; Russell; J.H. 2010.

Physiological variation among western redcedar 

(Thuja plicata Donn ex D. Don) populations in 

response to short-term drought. Ann. For. Sci. 67: 

506-517. 

Karhu, A.; Hurme, P.; Karjalainen, M.; 

Karvonen, P.; Kärkkäinen, K.; Neale, D.; 

Savolainen, O. 1996. Do molecular markers 

reflect patterns of differentiation in adaptive traits 

of conifers? Theor. Appl. Genet. 93:215-221. 

Rehfeldt, G.E.; Ying, C.C.; Spittlehouse, D.L.; 

Hamilton Jr., D.A. 1999. Genetic responses to 

climate in Pinus contorta: niche breadth, climate 

change, and reforestation. Ecol. Monogr. 69:375-

407. 

Russell, J.H. 1998. Genecology of 

Chamaecyparis nootkatensis. Pp. 82–89 in: 

Coastally restricted forests. A.D. Laderman, ed. 

Oxford Univ. Press, Oxford, U.K. 

Russell, J.H.; Kope, H.H.; Ades, P.; Collinson, 

H. 2007. Variation in cedar leaf blight 

(Didymascella thujina) resistance of western 

redcedar (Thuja plicata) Can. J. For. Res. 

37:1978-1986. 

Wang, T., A. Hamann, D. Spittlehouse. 2010.

ClimateWNA v4.52: A program to generate 

climate normal, annual, seasonal and monthly data 

for genecology and climate change studies in 

Western North America (WNA) region. CFCG, 

Dept. For. Sci., UBC, Vancouver, B.C. 

70
1 Andrew J. Larson, Assistant Professor of Forest Ecology, The University of Montana, College of Forestry and 

Conservation, Department of Forest Management, Missoula, MT 59812-0596. E-mail: andrew.larson@cfc.umt.edu 2 Jerry F. Franklin, Professor of Ecosystem Analysis, University of Washington, School of Forest Resources, Box 352100, 

Seattle, WA 98195-2100. E-mail: jff@uw.edu

RATES AND CAUSES OF WESTERN REDCEDAR AND YELLOWCEDAR MORTALITY IN OLD-GROWTH FORESTS OF MOUNT 

RAINER NATIONAL PARK

Andrew J. Larson1 and Jerry F. Franklin2 

ABSTRACT

We examined the rates and causes of mortality for Thuja plicata Donn ex. D. Don (western redcedar) 

and Chamaecyparis nootkatensis (D. Don) Spach (yellow cedar), and in contrast with co-occurring 

Pinaceae, using a three decade record of forest dynamics in old-growth forests of Mount Rainer National 

Park, WA, USA. All trees ≥15 cm dbh were tagged within 12, 1.00 ha permanent plots; trees were added 

to the study when they grew past the lower sampling size limit. Plots were censused every 4 to 10 years. 

Detailed observations of position, condition and causes of mortality were recorded for newly dead trees. 

The fates of 625 C. nootkatensis and 226 T. plicata were followed: a total of 58 C. nootkatensis and 13 

T. plicata stems died during the study. Mortality rates of T. plicata and C. nootkatensis were 

exceptionally low, with average annual rates of 0.1% to 0.2% and 0.2% to 0.3%, respectively. 

Mechanical processes--uprooting, stem breakage and crushing by falling macrolitter--accounted for 

69.2% of T. plicata mortalities; these same agents were responsible for 53.4% of C. nootkatensis

mortalities. In contrast, a smaller proportion (43.4%) of co-occurring Pinaceae species were killed by 

mechanical processes, suggesting a family-level tradeoff characterized by lower susceptibility to 

biological mortality agents and greater tolerance of competitive stress for the Cupressaceae, and 

relatively greater resistance to mechanical mortality agents by Pinaceae in old-growth forests of the 

Pacific Northwest. 

KEYWORDS: Old-growth, tree mortality, causes of mortality, permanent plots.

INTRODUCTION

Tree mortality directly regulates tree 

populations and forest community composition 

and structure, and mortality determines the 

upper bounds of tree size and age. In the oldgrowth forests of the Pacific Northwest, two 

Cupressaceae species (Figs. 1 & 2)—Thuja 

plicata Donn ex. D. Don and Chamaecyparis 

nootkatensis (D. Don) Spach—often attain 

greater ages than co-occurring Pinaceae. 

Empirical studies of rates and causes of tree 

mortality are the first step towards 

understanding how these two species attain 

great ages, and co-exist with typically more 

fecund Pinaceae.

Only direct long-term observations can reveal 

rates and causes of tree mortality in natural 

forests. Empirical documentation of the rates 

and causes of T. plicata and C. nootkatensis

mortality in old-growth forests of the Pacific 

Northwest is limited to just two studies 

(Franklin and DeBell 1988, Edmonds et al. 

1993), each from a single site. Consequently, 

mortality rates and causes for these species 

remain poorly understood in old-growth forests.

In this paper we report stem mortality rates for 

several populations of T. plicata and C.

nootkatensis studied over a three decade period 

at Mount Rainer National Park, in the western 

Washington Cascade Range, USA. We also 

report proximate causes of mortality for T.

plicata and C. nootkatensis, and contrast these 

causes of mortality with those of co-occurring 

Pinaceae.

2010 - A Tale of Two Cedars PNW-GTR-828

71
METHODS 

Study Forests and Field Procedures

Twelve, 1.00 ha permanent forest study plots 

were established in 1977 and 1978 in oldgrowth conifer forests in Mount Rainer National 

Park, WA, USA, an ecological reserve. The 

study sites represent the Tsuga heterophylla and 

Abies amabilis Zones (Franklin and Dyrness 

1988), the dominant lower and middle elevation 

forests of the western Cascade Range. Detailed 

descriptions of the physical and biological 

characteristics of the study sites are available 

online 

(http://www.fsl.orst.edu/lter/pubs/webdocs/perm

plot.cfm); additional details on the plant 

associations characteristic of each study plot is 

presented in Franklin et al. (1988).

In each plot all live trees ≥15 cm dbh (diameter 

at breast height, 1.4 m above ground level) were 

measured for diameter to the nearest 0.1 cm, 

identified to species and individually tagged. 

Plots were censused every 4 to 10 years, most 

recently in 2007 or 2008. 

Detailed information about tree position, 

condition and cause of mortality was recorded 

for newly dead trees at each census (excepting 

the first census when only the initial population 

of live trees was inventoried). Because 

proximate cause of mortality for intact standing 

dead trees can be difficult to assign when census 

intervals exceed 1 year field observations were 

summarized in three classes of proximate cause 

of mortality which can be unequivocally 

distinguished: biological/competitive stress (i.e., 

standing dead trees), mechanical mortality 

(uprooting and stem breakage), and crushing by 

falling trees or tree parts.

Data Reduction and Statistical Analysis

The annual mortality rate, m, was calculated as:

[ ( )] t m NM /1

01 −−= /11 (1) 

 

where N0 is the number of trees alive at the 

previous census, M1 is the number of trees dying 

between the previous and current census, and t

is the time between censuses in years (Sheil et 

al. 1995, Lutz and Halpern 2006). 

The null hypothesis of independence of family 

(Cupressaceae vs. Pinaceae) and frequency of 

mortality was evaluated with the randomization 

method. For each plot, simulations (n = 10000) 

in which the observed number of trees dying in 

the ith census interval were randomly selected 

(without replacement) from the empirical live 

tree list at the beginning of the ith census 

interval; variation due to census interval is 

accounted for in the simulations. Each 

simulation was summarized with the chi-square 

statistic. All n = 10000 simulation results were 

compiled into null distributions to which the 

observed chi-square statistic for the plot of 

interest, to which the chi-square statistic for the 

empirical data was compared using the 

randomization test (Roff 2006) with α = 0.05.

RESULTS 

Stem Mortality Rates 

The fates of 625 C. nootkatensis and 226 T. 

plicata were followed: a total of 58 C. 

nootkatensis and 13 T. plicata stems died during 

the study. 

Sufficient numbers of T. plicata and C. 

nootkatensis occurred in n = 4 plots (AB08, 

AG05, TO04, TO01) and n = 3 plots (AE10, 

AR07, AM16), respectively, to calculate 

annualized mortality rates. Mortality rates of

both species were exceptionally low. Annual 

mortality rates of T. plicata for all site X census 

combinations ranged from 0.0% to 0.8%; annual 

mortality rates for C. nootkatensis across all site 

X census combinations ranged from 0.0% to 

0.5%. Mean annual mortality rates (average of 

rates for individual census intervals within sites) 

for T. plicata ranged from 0.1% to 0.2%; mean 

annual mortality rates for C. nootkatensis

ranged from 0.2% to 0.3%. 

Randomization tests did not support rejection (P

> 0.1) of the null hypothesis of independence of 

family (Cupressaceae vs. co-occurring 

Pinaceae) and frequency of mortality for any of 

72
the 4 plots hosting populations of T. plicata or 

the 3 plots with C. nootkatensis populations. 

Causes of Mortality 

T. plicata and C. nootkatensis were more likely 

to be killed by stem breakage than species 

belonging to Pinaceae (Fig. 3). Mechanical 

processes--uprooting, stem breakage and 

crushing by falling macrolitter--accounted for 

69.2% of T. plicata mortalities; these same 

agents were responsible for 53.4% of C. 

nootkatensis mortalities. In contrast, a smaller 

proportion of co-occurring Pinaceae species 

were killed by mechanical processes, suggesting 

that lower susceptibility to biological mortality 

agents and greater tolerance of competitive 

stress may explain the low observed rates of T. 

plicata and C. nootkatensis mortality. This 

difference was complemented by a relatively 

lower proportion of standing deaths for T. 

plicata and C. nootkatensis relative to Pinaceae.

DISCUSSION

The low annual stem mortality rates for T. 

plicata and C. nootkatensis are exceptional, 

lower even than the 0.29% yr-1 reported for 

Sequoia sempervirens ≥10 cm dbh (Busing and 

Fujimori 2002). The results presented here, 

together with the other published data for Thuja

and Chamaecyparis, indicate that very low 

mortality rates are characteristic of these species

in old-growth forests of the Pacific Northwest. 

Franklin and DeBell (1988) reported mortality 

0.52% yr-1 for Thuja during a 36-year period in 

the southwest Washington Cascades; no Thuja

died and Chamaecyparis died at a rate of 0.68% 

yr

-1 in the western Olympics (Edmonds et al. 

1993). 

The divergent patterns of mortality causes for 

Cupressaceae and Pinaceae suggest a potential 

family-level tradeoff in demographic strategies. 

The mortality cause differences observed here—

lower susceptibility to biological mortality 

agents and greater tolerance of competitive 

stress for the Cupressaceae, and relatively 

greater resistance to mechanical mortality 

agents by Pinaceae—may correspond to 

differing strategies of resource allocation to 

secondary defense compounds and wood 

physical properties. The small number of 

Cupressaceae dying during this study limits the 

strength of this inference; this interpretation 

should be regarded as a hypothesis to be tested 

with additional observations. 

Improved understanding of the quantitative life 

history of tree species, including rates and 

causes of mortality, will require substantial 

investment—beyond current levels—in longterm research and monitoring of larger tree 

populations across a wider range of 

environmental and geographic gradients. Only n

= 58 C. nootkatensis and n = 13 T. plicata died 

during this three decade study (which included 

fully 360 hectare-years of observations); 

continued observations and additional study 

sites are necessary to understand mortality 

across the population size structure and 

environmental gradients. The importance of the 

data from long-term demographic studies cannot 

be overstated: such data constitute the primary 

means of testing predictions from basic 

ecological theory (e.g., Condit et al. 2006) and 

for developing forecasts for tree population 

structure in future climate scenarios (e.g., van 

Mantgem et al. 2009). 

ACKNOWLEDGEMENTS 

Many field workers contributed to this study 

three-decade study of tree mortality. The most 

recent census was only possible with help from 

Dan Underwood and his students at Peninsula 

College, the Lewis & Clark College Outdoors 

program, and James Freund and his field crews 

from the University of Washington. Fieldwork 

and data storage and management was made 

possible through funding and in king support 

provided by the National Science Foundation, 

the USFS PNW Research Station, the Wind 

River Canopy Crane Research Facility, Oregon 

State University, the University of Washington 

and the H.J. Andrews Experimental Forest 

LTER program. Permission to conduct this 

research within Mount Rainer National Park is 

gratefully acknowledged.

73
LITERATURE CITED

Busing, R.T.; and Fujimori, T. 2002.

Dynamics of composition and structure in an 

old Sequoia sempervirens forest. Journal of 

Vegetation Science 13: 785-792.

Condit, R.; and 39 others. 2006. The 

importance of demographic niches to tree 

diversity. Science 

313: 98-101. 

Edmonds, R.L.; Thomas, T.B.; and 

Maybury, K.P. 1993. Tree population 

dynamics, growth and mortality in old-growth 

forests in the western Olympic Mountains, 

Washington. Canadian Journal of Forest 

Research 23: 512-519. 

Franklin, J.F.; and Dyrness, C.T. 1988.

Natural vegetation of Oregon and Washington. 

Oregon State University Press, Corvallis, 

Oregon, USA.

Franklin, J.F.; and D.S. DeBell. 1988. Thirtysix years of tree population change in an oldgrowth Pseudotsuga-Tsuga forest. Canadian 

Journal of Forest Research 18:633-639. 

Franklin, J.F.; W.H. Moir; M.A. Hemstrom; 

S.E. Greene; and B.G. Smith. 1988. The forest 

communities of Mount Rainer National Park. 

Scientific Monograph Series No. 19. USDI 

National Park Service, Washington, D.C. 

Lutz, J.A.; and Halpern, C.B. 2006. Tree 

mortality during early forest development: A 

long-term study of rates, causes, and 

consequences. Ecological Monographs 76: 257-

275. 

Roff, D.A., 2006. Introduction to computerintensive methods of data analysis in biology. 

Cambridge University Press. Cambridge, UK. 

Sheil, D.; Burslem, D.F.R.P.; and Alder, D. 

1995. The interpretation and misinterpretation 

of mortality rate measures. Journal of Ecology 

83: 331-333. 

van Mantgem, P. J.; Stephenson, N.L.; 

Bryne, J.C.; Daniels, L.D.; Franklin, J.F.; 

Fulé, P.Z.; Harmon, M.E.; Larson, A.J.; 

Smith, J.M.; Taylor, A.H.; and Veblen, T.T. 

2009. Widespread increase of tree mortality 

rates in the western United States. Science 323: 

521-524. 

74
Figure 1 (above left). Large Thuja plicata individuals in Mount Rainer National Park, Washington, USA. Figure 2 (above 

right). T. plicata often attain greater age and size than co-occurring Pinaceae (primarily Abies amabilis and Tsuga 

heterophylla in the western Washington Cascade Range). Figure 3 (below). Proximate causes of mortality for 

Chamaecyparis nootkatensis, T. plicata and Pinaceae species in old-growth forests of Mount Rainer National Park.

0%

20%

40%

60%

80%

100%

Crushed

Snapped

Uprooted

Standing

75
COMPARISONS OF THE COLD TOLERANCE AND ROOTING 

DEPTH OF YELLOW-CEDAR, WESTERN REDCEDAR, WESTERN 

HEMLOCK, MOUNTAIN HEMLOCK AND SITKA SPRUCE 

GROWING TOGETHER IN KETCHIKAN, ALASKA

Paul G. Schaberg1, Paul E. Hennon2, David V. D’Amore2, Joshua M. Halman3

Gary W.T.F. Hawley3

and

ABSTRACT

It has been proposed that yellow-cedar decline is initiated by the freezing injury of roots when soils 

freeze during times of low snow cover. To explain the unique susceptibility of yellow-cedar to this 

damage, yellow-cedar roots would need to be 1) less cold tolerant, and/or 2) more concentrated in upper 

soil horizons than co-occurring tree species that are not declining. We measured the root cold tolerance 

and used ratios of foliar cations as an assay of rooting depth of five species growing together in one 

forest in Ketchikan, Alaska. Species evaluated were yellow-cedar (Chamaecyparis nootkatensis), 

western redcedar (Thuja plicata), western hemlock (Tsuga heterophylla), mountain hemlock (Tsuga 

mertensiana), and Sitka spruce (Picea sitchensis). Roots were collected in November 2007 and January, 

March and May 2008 to assess relative hardiness levels in fall through spring. Foliage was collected in 

January 2008. Yellow-cedar and redcedar roots were less cold tolerant than roots of other species on all 

dates. Yellow-cedar roots were slightly less cold tolerant than redcedar roots in November and January. 

Yellow- and redcedar foliage had significantly different concentrations of Ca (higher), Al (lower), Mn 

(lower), and ratios of Ca:Al and Ca:Mn (both higher) than foliage from other species. Yellow-cedar had 

higher foliar concentrations of Ca, and higher ratios of Ca:Al and Ca:Mn than did redcedar. Because 

concentrations of Ca are greatest in the upper soil horizons, whereas concentrations of Al and Mn are 

greater in the deeper soil horizons, the higher foliar concentrations of Ca, and ratios of Ca:Al and 

Ca:Mn, may indicate that the roots of yellow-cedar preferentially occupy higher soil horizons than the 

other species tested. Limited cold tolerance and shallow rooting may both contribute to the unique 

sensitivity of this species to freezing injury and decline. 

1

 Forest Service, US Department of Agriculture, Northern Research Station, South Burlington, VT 05403, 

pschaberg@fs.fed.us 2 Forest Service, US Department of Agriculture, Pacific Northwest Research Station, Juneau, AK 99801, 

phennon@fs.fed.us and ddamore@fs.fed.us

3

 The University of Vermont, Rubenstein School of Environment and Natural resources, Burlington, VT 05405, 

Joshua.Halman@uvm.edu and Gary.Hawley@uvm.edu

2010 - A Tale of Two Cedars PNW-GTR-828

76
GENETIC PERSPECTIVES ON THE COLONIZATION HISTORY 

AND POPULATION STRUCTURE OF WESTERN REDCEDAR 

(THUJA PLICATA, CUPRESSACEAE)

Stacey Lee Thompson1, Alison Dawn Scott1, Lisa O’Connell2, Kermit Ritland2

ABSTRACT

As knowledge of historical migration in response to climatic change allows insight into the dynamic 

nature of range shifts, patterns of post-glacial colonization were evaluated for the western redcedar 

(Thuja plicata). We sampled and genotyped 620 trees from 23 populations across its range, including 

disjunct coastal and interior mesic sites. Genetic variation at eight hypervariable microsatellite loci 

(mean alleles/locus = 10.30, mean expected heterozygosity = 0.755) was much higher than previous 

studies involving other markers, and inbreeding coefficients were predominantly positive 

(mean = 0.110). The two southernmost populations showed the greatest genetic distances, while 

remaining populations clustered into three distinct geographic groups, comprising northern/coastal, 

central, and southern/interior populations, respectively. Genetic diversity decreased with latitude, while 

genetic and geographic distances were strongly correlated (r = 0.788). Our findings are consistent with 

independent routes of relatively recent colonization from one major refugium, located south of the 

glacial maximum, rather than ancient vicariant events. Regional bottlenecks, detected in the south of the 

range, may have resulted from local extinctions as the range of western redcedar advanced northward. 

Combined with inbreeding and the evolution of inbreeding tolerance, this may have promoted 

homozygosity for most classes of genetic markers as observed in other studies of this species. The high 

heterozygosity for these microsatellite markers imply that there should be significant heritabilities for 

traits of concern for tree breeding programs, while the observed population clusters broadly delimit seed 

zones for reforestation.

1 Department of Biological Sciences, California State University, Los Angeles, 5151 State University Drive, Los 

Angeles CA 90032, staceylee.thompson@calstatela.edu and ascott3@calstatela.edu

2

 Department of Forest Sciences, University of British Columbia, Vancouver BC V6T 1Z4 kermit.ritland@ubc.ca

2010 - A Tale of Two Cedars PNW-GTR-828

77
CORRELATES OF CLONALITY IN WESTERN REDCEDAR (THUJA 

PLICATA) 

Alison Scott1, Jesse Granados, Stacey Lee Thompson

ABSTRACT

Asexuality has several evolutionary implications, including the reduction of genetic diversity, the 

creation of spatial genetic structure, the promotion of realized inbreeding through mating among clonemates, and the ultimate pace of adaptation. Western redcedar, a cornerstone of Pacific Northwest 

cultures, growing from California to Alaska, can reproduce both sexually and asexually through 

vegetative clones. Understanding environmental correlates of clonality in redcedar populations is 

critical, as the lack of recombination that accompanies asexuality could mean that certain natural stands 

may be less able to adapt to environmental change. To evaluate clonal reproduction in redcedar 

populations, we are genotyping seven highly polymorphic microsatellite loci in conjunction with spatial 

and climatic data. Foliage was sampled from ~60 trees in each of five natural populations that transect 

the coastal British Columbian range. In addition, spatial data were recorded and cores were taken from a 

subset of trees. Preliminary screening data from a test panel of 13 trees demonstrate the hypervariable 

nature of these loci (from 4-11 alleles per locus; observed heterozygosities from 0.538-0.846 per 

population). This high level of polymorphism across loci will allow us to genetically identify clones and 

determine the frequency of clonal reproduction. Field data indicate that sampling sites varied in stand 

density and age, moisture regime, temperature, and biogeoclimatic ecosystem. The integration of these 

data will allow us to better understand clonality in the species and how it correlates to environmental 

variability, which will be useful in maintaining genetic diversity when replanting of forested areas in 

British Columbia and to predict the impacts of a changing climate. 

1 Department of Biological Sciences, California State University Los Angeles, Los Angeles, CA, 

ascott3@calstatela.edu

2010 - A Tale of Two Cedars PNW-GTR-828

78
LOCAL AND RANGEWIDE GENETIC STRUCTURE OF YELLOW 

CEDAR 

Kermit Ritland1, Terry Pape1, Stacey Lee Thompson2

ABSTRACT

We describe two studies that document genetic structure at both local and regional scales in yellow 

cedar (Callitropsis nootkatensis). Based upon isozymes, the proportion of diversity among populations 

was considerable (Gst =0.139), and three major geographical groups were evident: (1) Vancouver Island 

– mid-north coast British Columbia (B.C.); (2) south coast B.C. – Washington state; (3) southeast 

Alaska. This may indicate the presence of multiple refugia during ice-age range contractions. The 

average inbreeding coefficient of adult trees was 0.18 suggesting considerable selfing (ca. 30%). In a 

second investigation into the effects of clonality on inbreeding and relatedness at small spatial scales, 

485 trees from nine populations were mapped to x-y coordinates and genotyped for 5 highly informative 

microsatellite loci (11-15 alleles per locus, ca. 75% heterozygosity). In accordance with expectations, 

substantial clonality was found. A “three-gene” analysis showed that clonality actually promotes 

inbreeding and spatial structure in most populations, probably through limited dispersal of outcrossed 

offspring and subsequent sib mating within cohorts derived from the same clone. Overall, the levels of 

geographic structure and selfing that we found in yellow cedar are quite high for a conifer (although 

other Cupressoideae species have comparable levels). Our results have implications for population 

conservation and breeding of yellow cedar.

1 Department of Forest Sciences, University of British Columbia

2 Department of Biology, California State University, Los Angeles

2010 - A Tale of Two Cedars PNW-GTR-828

79
DEVELOPMENT OF MARKERS FOR UNGULATE BROWSING 

RESISTANCE IN WESTERN REDCEDAR (THUJA PLICATA DONN 

EX D. DON)

Adam Foster1, Leanne Mortimer1, Dawn Hall2

Aine Plant1, Jörg Bohlmann2, John Russell

, Regine Gries1

, Gerhard Gries1, 3

, and Jim Mattsson1

ABSTRACT

Reforestation with Thuja plicata is severely hampered by extensive ungulate browsing of seedlings. 

High foliar monoterpenoid content correlates with reduced browsing, providing a target for resistance 

breeding. The most abundant terpenoids in T. plicata foliage are the monoterpenes α- and β-thujone, 

both of which strongly deter ungulate browsing. Here we present work towards the development of 

alternative markers, morphological and genetic, that may improve accuracy and possibly also reduce the 

cost and time to predict monoterpene content in breeding populations. T. plicata foliage contains glands 

that presumably stores resin. We found that monoterpenes are almost entirely stored in resin glands, 

suggesting that the foliar amount of glands may correlate with foliar monoterpene content. We have 

found initial evidence in support of this hypothesis and are currently expanding the analysis. The genetic 

basis of monoterpenoid biosynthesis in T. plicata is unknown; however it is suspected that the 

monoterpene sabinene is the precursor of thujone biosynthesis. With the aim of identifying a T. plicata

sabinene synthase, we sequenced a large number of expressed messenger RNA sequences from leaf 

foliage and compared the sequences to known monoterpene encoding genes. We identified several 

putative monoterpene synthase genes, one of which is expressed over 100-fold higher in foliage than the 

other genes. Expression of this gene is localized to the epithelium of foliar resin glands. In vitro enzyme 

assays showed that the corresponding protein converts geranyl pyrophosphate almost entirely into 

sabinene. In line with its expression in gland epithelium, the expression of this gene is very low in 

breeding lines lacking resin glands and high in breeding lines with large and many resin glands. In 

summary, we are well underway towards developing both morphological and genetic markers for foliar 

monoterpene content and indirectly also for ungulate browsing resistance. 

1 Department of Biological Sciences, Simon Fraser University, Burnaby, B.C.

2 Michael Smith Laboratories, University of British Columbia, Vancouver, B.C. 3 Cowichan Lake Research Station, Ministry of Forests and Range, Research and Knowledge Management 

Branch, Mesachie Lake, B.C. V0R 2N0

2010 - A Tale of Two Cedars PNW-GTR-828

80
SECTION C

WOOD

SILVICULTURE AND MANAGEMENT

81
82
1 Cowichan Lake Research Station, B.C. Ministry of Forests and Range, Box 335, Mesachie Lake, BC, Canada V0R 

2N0 John.Russell@gov.bc.ca 

2

 FP Innovations, Vancouver, BC, Canada

VARIATION IN WESTERN REDCEDAR HEARTWOOD 

EXTRACTIVES

John H. Russell1 and Bob Daniels2

ABSTRACT

Western redcedar heartwood contains the extractives α-thujaplicin (α-th), ß- thujaplicin (ß-th), γthujaplicin (γ-th) and ß- thujaplicinol (ß-thl) which are natural fungicides and are believed to be 

responsible for much of the woods natural resistance to fungal attack. Lignans such as plicatic acid (PA) 

and thujaplicatin methyl ether (TME), while much less toxic to fungi, are more abundant than the 

thujaplicins giving it the potential to play an important role in protecting the tree from decay. In this 

study four age classes of heartwood were sampled at breast height for extractives using high 

performance liquid chromatography: old-growth (OG; >200 years old), second growth (SG; five 

populations 50-115 years old), young trees (YT; 25-year-old clonal trials) and juvenile trees (JT; 10-

year-old progeny trials). All of the extractives increased with age except α-th which decreased relative to 

the other thujaplicins. Genetic parameters for individual extractives were significant, as were the 

positive genetic correlations among these compounds. Development of western redcedar durable breeds 

that incorporate important fitness traits for future climates, including cold-hardiness, growth, heartwood 

durability, deer browse resistance and cedar leaf blight resistance is discussed.

KEYWORDS: Western redcedar, heartwood extractives, phenotypic variation, age, breeding 

INTRODUCTION

Western redcedar is prized for its natural 

durability and is used in many exterior 

applications such as fencing, decking, roofing 

and siding. Traditionally, these products have 

come from old growth heartwood. The inevitable 

decrease of old growth stands available for 

harvesting raises the questions of second growth 

heartwood durability and the feasibility of the 

western redcedar coastal tree breeding program 

in British Columbia to develop durable 

phenotypes for inclusion in seed orchards. 

Harvesting pressures have resulted in an 

extensive regeneration program including the 

establishment of seed orchards for coastal British 

Columbia. Up to 10 million seedlings are 

planted annually in British Columbia, with over 

80% of the seed coming from managed orchards. 

The heartwood contains tropolones including αthujaplicin, ß-thujaplicin, γ-thujaplicin and ßthujaplicinol, which are all excellent natural 

fungicides and are believed to be responsible for 

much of the heartwood’s natural resistance to 

fungal attack (Maclean and Gardner 1956). 

Lignans such as plicatic acid, while much less 

toxic to fungi, can be up to ten times as abundant 

as the thujaplicins, indicating they may play an 

important role in protecting the tree from decay. 

The toxicity of ß-thujaplicin and γ-thujaplicin 

have been compared to that of 

pentachlorophenol, while plicatic acid has been 

compared to zinc chloride, which is only one 

tenth as effective as pentachlorophenol (Sterling 

et al. 2007) The roles of thujaplicatin methyl 

ether, thujic acid and methyl thujate in decay 

resistance are not yet known but they may also 

have some effects. 

In this study, we explore the effects of age, 

population and individual tree variation on 

expression of heartwood extractives in western 

redcedar.

2010 - A Tale of Two Cedars PNW GTR-828

83
MATERIALS AND METHODS

Heartwood was collected from four different age 

classes: old growth, second growth, saplings, and 

juvenile trees. All material was collected from 

breast height (except juvenile trees as described 

below) and separated into inner and outer 

heartwood to minimize within-tree variation.

Individual old growth trees: Six trees varying 

in age from 200-360 years old were selected

from British Columbia coastal low elevation

sites. Trees were felled and discs taken at breast

height. 

Second growth populations: Six to seven trees 

were selected from each of four populations; two 

from coastal and two from interior British 

Columbia. Discs at breast height were taken on 

all trees. 

Young clonal trial: Five-mm cores were taken 

at breast height from 2-4 copies each of 100 

clones. The trial, located on south Vancouver 

Island, was a randomized complete block design 

with single tree plots. Trees were 20 years old at 

time of sampling.

Juvenile progeny trial: Discs were taken at the 

base of ten-year-old trees from an openpollinated progeny trial. Samples were taken 

from 30 families with eight trees per family. The 

trial, located on south Vancouver Island, was a 

completely randomized block design. 

Extractives

A suite of known and unknown extractives were 

isolated using high performance liquid 

chromatography with a gradient elution (Daniels 

and Russell 2007). Volume weighted averages 

for each compound were calculated for inner and 

outer heartwood separately, assuming the tree 

was perfectly cylindrical. All extractive values 

are expressed as μg/cm3

 of heartwood. 

Data analysis

Simple statistics including means, variances and 

standard errors were estimated using SAS ver. 

9.1.3. Genetic analyses including heritabilities 

and correlations were done with ASREML ver 

2.0. Data analyses reported here focused on the 

known fungicidal compounds from the tropolone 

(α-, ß-, and γ-thujaplicin), and lignin (plicatic 

acid) groups. 

RESULTS 

Age Effects

There was a significant increase in the amount of 

α-thujaplicin compared to the other tropolones 

and plicatic acid at age 10 (P<0.05), but this was 

not evident at age 20. There were no significant 

differences among all four compounds at age 20; 

however, plicatic acid dramatically increased in 

the second growth trees and was seven-fold 

higher than the total thujaplicin concentration in 

old growth trees (Fig. 1). ß- and γ-thujaplicin had

similar in concentrations in second growth and 

old growth trees, and both were significantly 

greater than α-thujaplicin (P<0.05) which 

decreased dramatically in old growth trees (Fig. 

2).

Population effects

Interior British Columbia populations had 

significantly less α- and ß-thujaplicin than 

coastal populations (P<0.05). Plicatic acid and γthujaplicin concentrations were similar between 

the two geographic areas.

Genetic parameters

Coefficients of clonal variation were high, 

varying from 40% (α-thujaplicin) to 189% 

(plicatic acid). Estimations of coefficients of 

additive variation from the 10-year-old progeny 

trial were 69%, 86% and 159% for α-, ß-, and γthujaplicin, respectively. There was no detectable 

plicatic acid in the juvenile trees. Clonal mean 

repeatabilities varied from 0.62 (α-thujaplicin) to 

0.75 (γ-thujaplicin), and narrow-sense 

heritabilities were 0.55, 0.24 and 0.24 for α-, ß-, 

and γ-thujaplicin, respectively.

α -thujaplicin had significant positive genetic 

correlations (P<0.05) with ß-thujaplicin (0.56), 

γ-thujaplicin (0.66), and plicatic acid (0.48). 

There was a non-significant but positive genetic 

correlation between ß- and γ-thujaplicin (0.34). 

Plicatic acid had a significant positive genetic 

correlation with α-thujaplicin (0.48) and γ84
thujaplicin (0.49), but was there was no 

significant correlation with ß-thujaplicin. All of 

the extractives had positive genetic correlations 

with growth; the correlations for plicatic acid 

(0.42) and α-thujaplicin (0.44) were statistically

significant (P<0.05). 

IMPLICATIONS FOR BREEDING

Incorporating wood durability in the western 

redcedar breeding program is certainly feasible. 

Wood extractives that have fungicidal properties 

– lignans and tropolones – are present in 20-

year-old heartwood at significant concentrations 

and have high additive coefficients of variation 

and narrow-sense heritibilities. There are also 

favorable genetic correlations among the 

important extractives, as well as between 

extractive concentrations and growth. 

Managing the western redcedar gene resource for 

the future under a changing climate needs to 

address a number of challenges: growth and 

environmental related stress responses, ungulate 

damage, cedar leaf blight, as well as wood fungal 

rots. Ensuring a sustainable supply of durable 

products from future forests is the most 

economically important one; however, the other 

challenges cannot be ignored. If western 

redcedar forests are to remain adaptable in the 

long term, they must have positive growth 

responses to environmental stresses, as well as 

exhibit cold and drought tolerance. Deer browse 

and elk grazing pressures currently carry an 

annual economic cost of over $25 million just in 

seedling protection alone, and this pressure will 

most likely increase in the future, given an 

increasing trend in ungulate populations in 

redcedar habitat. As climate warms, favorable 

conditions for cedar leaf blight, a serious 

pathogen that causes decreased growth and 

mortality, will increase along the moist coastal 

areas of British Columbia and the Pacific 

Northwest. A gene resource management 

strategy that addresses these challenges is a 

necessity to ensure healthy future forests.

There are currently over 1000 parent trees in the 

western redcedar breeding program for the 

Maritime low elevation Seed Planning Zone 

(under 600 metres). Approximately 350 of these 

have been characterized for wood extractives. 

These same parent trees have also been progeny 

tested yielding breeding values for growth and 

cedar leaf blight. In addition, each parent tree has 

been characterized for foliar monoterpenes, an 

important secondary chemical in deterring deer 

browse. Genetic correlations among these traits 

have been near zero or moderately positive, 

allowing the selection of these traits through 

independent culling for future breeding 

populations. 

LITERATURE CITED

Daniels, B.; Russell, J.H. 2007. Analysis of 

western redcedar (Thuja plicata Donn) 

heartwood components by HPLC as a possible 

screening tool for trees with enhanced natural 

durability. J. Chrom. Sci. 45(5):281-285. 

Maclean, H.; Gardner, J.A.F. 1956.

Distribution of fungicidal extractives (thujaplicin 

and water-soluble phenols) in western red cedar 

heartwood. Forest Products Journal, 6(12):510-

16. 

Stirling, R.; Daniels, C.R.; Clark, J.E.; 

Morris, P.I. 2007. Methods for Determining the 

Role of Extractives in the Natural Durability of 

Western Red Cedar Heartwood. International 

Research Group on Wood Protection. Document 

No. IRG/WP/07-20356. 12p. 

85
Figure 1 -- Average plicatic acid and total thujaplicin concentrations across four age classes

Figure 2 -- Average α-, ß-, and γ-thujaplicin concentrations across four age classes 

0

2000

4000

6000

8000

10000

12000

14000

16000

juvenile sapling 2nd growth old growth

Extractives (ug/cm3)

plicatic acid total thujaplicins

0

100

200

300

400

500

600

700

800

900

juvenile sapling 2nd growth old growth

Thujaplicins (ug/cm3)

gamma thujaplicin

beta thujaplicin

alpha thujaplicin

86
1 Wood Chemist and Group Leader, respectively. FPInnovations 2665 East Mall, Vancouver, BC V6T 1W5 

rod.stirling@fpinnovations.ca

REDUCING DEPLETION OF WESTERN REDCEDAR 

EXTRACTIVES FROM WOOD IN SERVICE

Rod Stirling1 and Paul I. Morris1 

ABSTRACT

The natural durability of western redcedar depends on the presence of heartwood extractives. The 

depletion of these extractives by leaching or biological detoxification increases the wood’s susceptibility 

to decay. One potential way of reducing extractives leaching is to reduce their mobility by fixing them to

the wood. This could potentially reduce losses from leaching, reduce extractive staining, and enhance 

the service life of western redcedar products used in exposed applications. 

Twelve experimental fixative treatments were evaluated for their ability to prevent leaching in a 

laboratory test. A zirconium-based tannin-stain-blocking additive and several cationic polymers were 

found to significantly reduce the leaching of extractives, particularly plicatic acid. In a soil-block decay 

test some of the cationic polymers were associated with improved decay resistance of leached western 

redcedar heartwood samples, and no significant change in the durability of pine sapwood. This 

suggested that decay resistance was achieved through increased extractive retention, not inherent 

fungitoxic properties. Above-ground field tests have recently been initiated to evaluate the ability of the 

more effective fixative treatments to enhance service life and reduce extractive staining.

KEYWORDS: durability, extractives, fixatives, leaching, western redcedar

INTRODUCTION

One of western redcedar’s (Thuja plicata Donn 

ex D.Don) most important attributes is the 

natural durability derived from its unique set of 

heartwood extractives. The concentration of 

these extractives varies, with the highest 

concentration found in the outer heartwood and 

lower down the trunk (MacLean and Gardner 

1956). The heartwood of second growth trees 

tends to have higher concentrations than the 

same age rings on old growth trees due to 

extractive detoxification in these older trees (Jin 

et al. 1988). However, the outer heartwood of 

old growth trees is laid down by older trees and 

therefore contains even higher concentrations 

than second growth trees (Nault 1988). As a 

result there is a perception in the marketplace 

that second growth western redcedar (WRC) 

may not be as durable as old 

growth WRC. Recent laboratory (Freitag and 

Morrell 2001) and field tests (Laks et al. 2009) 

suggest heartwood from second-growth longrotation managed forests may be, on average, as 

durable as old growth. However, without 

selection of planting stock for durability 

(Daniels and Russell 2007), the best of the 

second growth will not be as durable as the best 

of the old growth due to shorter harvest 

rotations. Decay of old growth takes a 

considerable length of time and only proceeds 

rapidly after the loss of the extractives through 

biodegradation in the standing tree (Jin et al.

1988) or depletion in service (Johnson and 

Cserjesi 1980) likely due to leaching as well as

biodegradation (Chedgy et al. 2007). The 

durability of heartwood with initially low 

extractives content may be enhanced by 

treatments designed to reduce the loss of 

extractives. 

Properly selected, applied, and maintained 

coatings can slow the loss of extractives by 

leaching from wood in service (Stirling et al.

2006). However, extractives remain mobile 

2010 - A Tale of Two Cedars PNW-GTR-828

87
beneath the coating and can cause staining if an 

effective stain-blocking primer is not used. An 

alternative approach is to use a fixative agent to 

bind extractives to the wood and reduce their 

leaching. Fixative agents are used in the textile 

industry to bind functional chemicals to fabric, 

in the cosmetics industry to bind chemicals to 

hair and skin, and in the pulp and paper industry 

to bind fines to the sheet. Fixative treatments 

may also contribute to reduced extractive bleed 

and reduced extractive stain-lines caused by 

wetting at one end and drying further along the 

board. 

The present work describes the evaluation of 

fixatives agents for their ability to reduce 

extractive leaching, enhance resistance to decay 

fungi, and enhance service life of WRC 

products used in above-ground applications. 

MATERIALS AND METHODS

Second-growth WRC heartwood was obtained 

from the Malcolm Knapp Research Forest in 

Maple Ridge, BC. Straw-colored outer 

heartwood with no visible signs of fungal 

colonization was milled to provide test blocks of 

dimensions 19 x 19 x 19 mm. Ponderosa pine 

sapwood test blocks were prepared in parallel 

for use as a reference in soil block decay testing. 

WRC blocks were prepared for testing using 

eighteen replicates for each fixative agent, plus 

eighteen blocks for use as unleached controls in 

soil block testing. 

Test blocks were conditioned for 48 hours in a 

forced-draught oven at 60°C, weighed and then 

subjected to a vacuum/pressure impregnation 

with the fixative solution. The schedule was a 

15-minute vacuum at 26 inches of mercury 

followed by 30 minutes of pressure at 415 kPa 

(60 psi) and no final vacuum. Blocks remained 

submerged for a further 30 minutes, after which 

excess solution was wiped off and the blocks 

weighed. Blocks were then conditioned for 48 

hours at 60°C in a forced-draught oven prior to 

weighing, with the exception of the CCAtreated blocks which were stored at 60°C in 

sealed bags prior to conditioning. In addition to 

the chemical treatments, a set of water-treated 

control blocks, as well as a set of control blocks 

with no treatment, were prepared. 

All blocks were leached following the AWPA 

Standard E11 with the exception that more than 

four blocks were placed in an appropriatelysized container. Blocks were placed in 

containers, grouped by concentration, immersed 

in water (50 mL per block) and a vacuum of 26 

inches of mercury was pulled for 15 minutes 

followed by 30 minutes of pressure at 415 kPa 

(60 psi) and no final vacuum. The blocks 

remained immersed for a further 30 minutes. 

The restraining weights were removed from the 

waterlogged blocks and the water changed. 

Leach water was changed daily for a two-week 

period excluding weekends, using 50 ml/block. 

Samples of the leachate water were taken on a 

daily basis, excluding weekends, for extractive 

analysis. Leached blocks were then 

conditioning at 60°C in a forced-draught oven 

for 48 hours and weighed. 

Ten untreated, randomly selected WRC blocks 

were used to provide an extractives baseline. 

The blocks were cut and ground to pass through 

a number 20 mesh, and extracted and analyzed 

by HPLC according to the method outlined by 

Daniels and Russell (2007). Leachates were 

analyzed by HPLC based on the methods of 

Daniels and Russell (2007) using an external 

standard method. 

Sixteen leached and unleached WRC and 

ponderosa pine blocks from each treatment 

group were selected for soil-block testing. These 

blocks were sterilized by electron beam and put 

in a soil-block test with the brown rot fungus 

Coniophora puteana (Schum. ex Fr.) Karst., Ftk 

9G, and the white rot fungus Irpex lacteus (Fr.) 

Fr., Ftk 103B, based on AWPA standard E10. 

For each treatment group six blocks were 

exposed to each fungus and four blocks were 

left uninoculated as check blocks. 

The test method followed was generally as 

described in the AWPA E10-06 Standard for 

laboratory soil block testing (AWPA 2006).

Cylindrical glass jars were half-filled with soil 

adjusted to approximately 50% moisture 

88
0

10

20

30

40

A B C D E F G H I J K L M N O P

Extractive Leached (%)

PLICATIC ACID THUJAPLICINS THUJIC ACID

content. The soil was topped with two 3 x 29 x 

35 mm ponderosa pine sapwood feeder strips, 

the jar was closed, and the assembly sterilized 

by autoclaving. After cooling on a clean air 

bench, each jar was inoculated with one of the 

test fungi grown on 1.5% malt, 2.0% agar 

(Difco). White-rot infected jars were incubated 

for four and one half weeks at 25°C and 80% 

relative humidity, while brown-rot infected jars 

were incubated for three and one half weeks 

before the irradiated blocks were aseptically 

placed, two per jar, on top of the feeder strips. 

Jar assemblies were then incubated for a further 

12 weeks (brown rot), or 24 weeks (white rot). 

At the end of the incubation period, blocks were 

removed from jars, cleaned of any adhering 

mycelium, and weighed. Blocks were then 

conditioned at 60°C in a forced-draught oven 

and reweighed. Mass losses were corrected 

using non-inoculated treated check block results 

to compensate for any non-fungal mass loss or 

gains. Decay was confirmed by a visual 

inspection of the test blocks. 

RESULTS AND DISCUSSION

The average extractives content of each of the 

test blocks were consistent with previous 

analyses of WRC heartwood (Daniels and 

Russell 2007). Though some methyl thujate was 

detected in the extracted wood blocks, none was 

detected in the leachates so this extractive was 

not considered further. 

The concentration in the leachates decreased 

rapidly during the first week and leveled off in 

the second week. The percentages of total 

extractives leached from each fixative treatment, 

relative to the untreated, unleached control 

group are shown (Fig. 1). 

Plicatic acid, the most abundant extractive, was 

also leached in the greatest quantity. The 

leaching of plicatic acid was most strongly 

affected by treatment type. The treatments most 

effective at reducing leaching were CCA 

(treatment O), which was included as a 

reference since it was suspected to have fixation 

properties, and the tannin stain blocking 

additive (treatment L). Both of these are metalbased systems that likely reduced leachability 

through coordination with plicatic acid’s 

pyrocatechol group (Barton and MacDonald 

1971). It should be noted that treatment L was 

applied in much higher solution strength (as per 

manufacturer’s instructions) than the other 

compounds tested, so its efficacy may not be as 

good on an equivalent mass basis. Most of the 

cationic polymers tested (treatments H to K) 

performed well, reducing leaching by at least 

50%. The anionic nature of plicatic acid 

suggests that it could be bound well by cationic 

polymers. Some of the remaining treatments 

reduced extractive loss slightly but did not 

perform much better than the water-repellent 

coating (treatment N). 

Figure 1 -- Concentration of extractives leached 

relative to abundance in untreated, unleached 

WRC

Improved retention of plicatic acid is important 

as it has been implicated in WRC’s natural 

durability, both as a biocide (Roff and Atkinson 

1954) and as a radical scavenger and metal 

chelator (Stirling et al. 2007). Water-soluble 

phenolics, of which plicatic acid is the most 

abundant in WRC heartwood, have also been 

associated with lower equilibrium moisture 

content (Stirling and Morris 2006) and are some 

of the last extractives to be lost from WRC 

shakes and shingles (Stirling 2010). 

The leaching of the thujaplicins was less 

affected by treatment, though the metal-based 

systems (treatments L and O) were particularly 

89
-20

0

20

40

60

80

100

P M G H I J K L O

Mass loss (%)

WRC Leached WRC Unleached Pine Leached Pine Unleached

effective in reducing the amount of thujaplicins 

detected in the leachates. This is not surprising 

as the thujaplicins are well known metal 

chelators (MacLean and Gardner 1956). 

Mass losses for the pine blocks were high for 

the blocks treated with the polymeric fixatives 

(G – K), as well as the untreated control 

suggesting that the fixatives themselves were 

not directly toxic to C. puteana (Fig. 2). 

Fixative L, which contained zirconium 

compounds and was treated to a much higher 

retention than the polymeric fixatives, had a 

reduced mass loss that could indicate toxicity to 

C. puteana. As expected the CCA reference 

showed no mass loss in either the pine or WRC 

blocks, leached or unleached. 

Figure 2 -- Mass loss from Coniophora puteana in 

leached and unleached WRC and ponderosa pine 

blocks treated with selected fixative agents.

Untreated, unleached WRC blocks had a mass 

loss of 21% with C. puteana which would 

correspond to a rating of “resistant” (which is 

the book rating for WRC) in ASTM D2017-05, 

since untreated pine hit the target of 60% mass 

loss. Treatments G, I, J and K all had mass 

losses less than 10%, which would correspond 

to a “highly resistant” wood. Untreated, leached 

WRC blocks had a mass loss of 44%, only 

slightly lower than leached pine. Leached WRC 

blocks treated with fixatives G and I had mass 

losses of 17 and 24% respectively. Although 

these treatments did not completely prevent 

decay (like CCA) they were able to keep mass 

loss down to the same level as untreated 

unleached WRC. Such treatments could be 

useful in ensuring a more uniform durability in 

WRC and extending service life in applications 

where untreated WRC is used. These treatments 

may be even more effective in above-ground 

uses where spore germination, rather than 

mycelial attack is the main mode of infection. 

There were no significant mass losses from 

untreated WRC blocks exposed to I. lacteus

(data not shown). Data from this test can 

therefore not be used to evaluate fixative 

efficacy in WRC. However, I. lacteus did cause 

significant mass loss in the ponderosa pine 

blocks, indicating that untreated WRC is 

resistant to this fungus. Treatments G, H, I and 

L showed reduced mass loss in ponderosa pine 

samples, indicating some potential toxic effects 

towards I. lacteus. 

Field tests have been initiated to evaluate the 

performance of selected cationic polymers. 

Above-ground tests were set up to evaluate 

resistance to decay, and extractive staining. 

CONCLUSION

Pressure-treatment of WRC with CCA or a 

zirconium-based tannin blocking stain additive 

reduced the leaching of all quantified 

extractives.

Several cationic polymers were identified which 

reduced extractive leaching from WRC, largely 

by reducing the loss of plicatic acid. These 

polymers were also associated with reduced 

mass loss in a soil-block test. 

ACKNOWLEDGMENTS 

FPInnovations would like to thank its industry 

members, Natural Resources Canada (Canadian 

Forest Service); the Provinces of British 

Columbia, Alberta, Saskatchewan, Manitoba, 

Ontario, Quebec, Nova Scotia, New Brunswick, 

as well as Newfoundland and Labrador and the 

Government of Yukon for their guidance and 

financial support for this research. 

90
Thanks to Lisa McCuaig for conducting the 

leaching test, and Jean Clark for conducting the 

soil-block test.

LITERATURE CITED

American Society for Testing and Materials. 

2005. ASTM D2017-05 Standard Test Method 

of Accelerated Laboratory Test of Natural 

Decay Resistance of Woods. ASTM, West 

Conshohocken, PA. 5p. 

American Wood-Preservers’ Association, 

2005. AWPA E10-01. Standard Method of 

Testing Wood Preservatives by Laboratory 

Soil-Block Cultures. AWPA. Selma, AL. 11p. 

Barton, G.M.; MacDonald, B.F. 1971. The 

Chemistry and Utilization of Western Red 

Cedar. Can. For. Serv., Dept. Fish and For., 

For. Prod. Lab., Vancouver, BC. Publ. No. 

1023. 31p. 

Chedgy, R.J.; Morris, P.I.; Lim, Y.W.; 

Breuil, C. 2007. Black stain of Western red 

cedar (Thuja plicata) by Aureobasidium 

pullulans: the role of weathering. Wood Fiber 

Sci. 39(3): 472-481. 

Daniels, C.R.; Russell, J.H. 2007. Analysis of 

western red cedar (Thuja plicata Donn.) 

heartwood components by HPLC as a possible 

screening tool for trees with enhanced natural 

durability. J. Chromatographic Sci. 45: 281-

285. 

Freitag, C.M.; Morrell, J.J. 2001. Durability 

of a changing western redcedar resource. 

Wood Fiber Sci. 33(1): 69-75. 

Jin, L.; van der Kamp, B.J.; Wilson, J.; 

Swan, E.P. 1988. Biodegradation of 

thujaplicins in living western red cedar. Can. J. 

For. Res. 18: 782-786. 

Johnson, E.L.; Cserjesi, A.J. 1980.

Weathering effect of thujaplicin concentration 

in western red cedar shakes. For. Prod. J. 

30(6): 52-53. 

Laks, P.; Morris, P.I.; Larkin, G.M.; Ingram, 

J.K. 2008. Field tests of naturally durable 

North American wood species. Int. Res. Group 

Wood Protect. Document No. IRG/WP/08-

10675. 11p. 

MacLean, H.; Gardner, J.A.F. 1956.

Distribution of fungicidal extractives 

(thujaplicin and water-soluble phenolics) in 

western red cedar heartwood. For. Prod. J. 

6(12): 510-516. 

Nault, J.R. 1988. Radial distribution of 

thujaplicins in old-growth and second-growth 

western red cedar (Thuja plicata Donn.). Wood 

Sci. Technol. 22(1): 73-80. 

Roff, J.W.; Atkinson, J.M. 1954. Toxicity tests 

of a water-soluble phenolic fraction 

(thujaplicin-free) of western red cedar. Can. J. 

Botany. 32(1): 308-309. 

Stirling, R.; Morris, P.I. 2006. The Influence 

of Extractives on Western Redcedar’s 

Equilibrium Moisture Content. Int. Res. Group 

Wood Protect. Document No. IRG/WP/06-

40331. 12p. 

Stirling, R. 2010. Residual extractives in 

western red cedar shakes and shingles after 

long-term field testing. For. Prod. J. In press.

Stirling, R.; Morse, B.; Morris, P.I. 2006. The 

Effects of Various Coatings on Western Red 

Cedar Extractive Retention. Proc. Can. Wood 

Preserv. Assoc. 27: 14p. 

Stirling, R.; Daniels, C.R.; Clark, J.E.; 

Morris, P.I. 2007. Methods for Determining 

the Role of Extractives in the Natural 

Durability of Western Red Cedar Heartwood. 

Int. Res. Group Wood Protect. Document No. 

IRG/WP/07-20356. 12p. 

91
Table 1 -- Fixative agents

Treatment Description Concentration

(in water)

A Imidized poly (isobutylene-co-maleic anhydride) copolymer, personal care 

product fixative

5% + 0.2% 

triethanolamine

B Sodium polyvinylpyrrolidone, personal care product fixative 3%

C Anionic sodium polystyrene sulfonate, personal care product fixative 3%

D Modified corn starch, personal care product fixative 3%

E Acetyltriethyl citrate, personal care product fixative 5%

F Polyvinylpyrrolidone, personal care product fixative 3%

G Cationic polyethylene polyamine resin, dye fixative 2%

H Polymerized quaternary ammonium salt, dye fixative 3%

I Cationic polyethylene polyamine resin, dye fixative 2%

J Polyethyleneimine, pulp and paper cationic retention aid 3%

K Modified polyethyleneimine, pulp and paper cationic retention aid 3%

L Zirconium compounds in acetic acid solution, tannin stain blocking additive 18%

M Distilled water (control) -

N Water-repellent coating (reference) Brush applied

O Chromated copper arsenate (CCA, reference) 0.4%

P Untreated (control) -

92
DURABILITY OF SECOND GROWTH VERSUS OLD GROWTH 

CEDAR LUMBER

Paul I. Morris1, P. Laks2, G. Larkin2 and J.K. Ingram1

ABSTRACT

As harvesting shifts towards more second growth, questions increasingly asked about naturally-durableheartwood species include: 

“Is the lumber we are buying now as durable as the material we used to get?”

“What is the effect on service life of sapwood faces on lumber?” 

And, in new markets: “Is yellow cedar really as durable as western red cedar?”

There were plenty of textbook references and anecdotal evidence but little or no hard data on which to 

answer such questions. This paper reports on a collaborative field experiment designed to provide such 

answers, and develop basic data on the naturally durable species of northern North America. Old growth 

and second growth lumber of a range of species, with and without sapwood was installed in aboveground and ground-contact field tests in Maple Ridge, BC; Petawawa, Ontario; Gainesville, Florida; and 

Hilo, Hawaii. Ground-contact tests at all four sites and above ground tests in Florida and Hawaii were 

evaluated annually. Only the data on western red cedar and yellow cedar are reported here.

Contrary to expectations based on some previous work, second growth from long-rotation managed 

forests decayed at the same rates as old growth material in ground contact. While the sapwood parts 

clearly decayed faster than the heartwood the effect of small amounts of sapwood on the mean decay 

rating was negligible for old and second growth western red cedar, or old growth yellow cedar in ground 

contact. The exception was second growth yellow cedar where material with sapwood decayed faster at 

all four test sites. Yellow cedar and western red cedar showed similar decay rates in ground contact as 

expected from their textbook durability ratings. Above ground, only the Hawaii site showed some 

degree of separation among the various groups, thus it is too soon to draw firm conclusions. 

1 FPInnovations – Forintek Division, 2665 East Mall, Vancouver, BC, V6T 1W5 Canada, Paul.Morris@FPInnovations.ca

(correspondending author at Paul.Morris@FPInnovations.ca) 

2 Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49930-1295 USA

2010 - A Tale of Two Cedars PNW-GTR-828

93
MODELLING THE CROWN PROFILE AND BRANCH SIZE OF 

WESTERN REDCEDAR (THUJA PLICATA DONN) IN COASTAL 

BRITISH COLUMBIA.

Roberta Parish1 and James W. Goudie

ABSTRACT

Western redcedar (WRC,Thuja plicata Donn) is one of the most valuable timber species harvested in 

British Columbia. Despite its high timber, cultural and non-timber value, little modelling work has been 

done on the coast of British Columbia for this species. WRC often regenerates under the canopy in 

mixed stands, and emerges as dominant species when others have dropped out. As part of a project to 

expand the Tree and Stand Simulator (TASS) to complex stands containing multiple species and age 

classes, we began a two-year WRC sampling effort in 2009. Following modified protocols used with 

other species, we destructively sample 30 trees from three age classes (30, 60 and 90+ years) in each 

year. We measure crown characteristics (height growth, branch distributions, branch angle, branch size, 

and foliage biomass and leaf area) and bole attributes (ring growth, relative density and other ring 

variables). In this paper we report preliminary models predicting the crown profile, branching, and knot 

size characteristics of WRC from the first year’s data. These models will enhance TASS and other 

models in predicting the rate of crown growth, site occupancy and the wood quality characteristics of 

WRC, thereby improving forecasts of multiple stand values. 

1 BC Ministry of Forests and Range Research Branch, P.O. Box 9519 Stn. Prov. Gov., Victoria, BC Canada 

V8W9C2. Roberta.Parish@gov.bc.ca, Jim.goudie@gov.bc.ca

2010 - A Tale of Two Cedars PNW-GTR-828

94
WESTERN REDCEDAR OF THE ROCKY MOUNTAINS: ECOLOGY 

AND MANAGEMENT

Russell T. Graham1 and Theresa B. Jain

ABSTRACT

Western redcedar is a major component of the moist forests of the northern Rocky Mountains. As a late 

seral species it can be extremely long-lived (e.g., 1,000 years) with its major associates being western 

white pine, ponderosa pine, lodgepole pine, Douglas-fir, western larch, grand fir, and western hemlock. 

Very lush, robust, and complex forest structures and compositions often exist in these mixed conifer 

forests. The species has the ability to thrive and be climax in the wettest environments (wetter than 

western hemlock) and it is also the climax tree species on upland (drier than western hemlock) sites. As 

such, two potential vegetation classifications are determined by the regeneration and development of 

western redcedar. It has the ability to persist in the understory of early and mid-seral species for decades 

and when weather, fire, insects, or other disturbances thin the overstory, western redcedar can release 

and grow relatively well and in other situations trees succumb to diseases, sun- scald, and other 

damaging agents. Currently and historically, the species produced high value products such as shakes, 

siding, rails, and by far one of the most valuable products, utility poles. Nevertheless, the management 

of stands containing western redcedar has had mixed success, because of uncertainty in how it responds 

to weedings, cleanings, and thinnings. More often than not, western redcedar management is secondary 

to managing the early and mid-seral pines, western larch, and Douglas-fir. Even aged silvicultural 

systems have been used to manage stands containing western redcedar with limited success, however 

uneven-aged systems show promise. 

1 Forest Service, Rocky Mountain Research Station, 1221 South Main, Moscow, ID, 83843; 208.883.2325, 

rtgraham@fs.fed.us

2010 - A Tale of Two Cedars PNW-GTR-828

95
COMPARISON OF WESTERN REDCEDAR AND YELLOW-CEDAR 

GROWTH UNDER DIFFERENT SILVICULTURAL TREATMENTS

W.J. (Bill) Beese1 and Dillon Chrimes2

ABSTRACT

Western redcedar (Thuja plicata Donn ex D. Don) and yellow-cedar (Callitropsis nootkatensis (D. Don) 

Oerst.) are two of the highest valued native trees on the Pacific coast. On Vancouver Island, their natural 

ranges overlap between roughly 600m and 800m elevation; consequently, their relative performance 

under different silvicultural systems and treatments is of management interest. We present 15- to 20-

year results from two studies comparing the growth of redcedar and yellow-cedar and associated species 

in replicated experiments. The first study compared growth among low-severity and high-severity 

prescribed burns and unburned controls. Both cedars were planted in mixtures with Douglas-fir 

(Pseudotsuga menziesii (Mirb.) Franco) in randomized rows. The second study (MASS: Montane 

Alternative Silvicultural Systems) compared growth among clearcut (69 ha), patch cut (1.5 ha), 

dispersed retention (25 trees per ha) and shelterwood (25% basal area retention) silvicultural systems. 

Both cedars were planted in pure plots and were compared to Douglas-fir, western hemlock (Tsuga 

heterophylla (Raf.) Sarg.) and amabilis (Pacific silver) fir (Abies amabilis Douglas ex J. Forbes). 

On the fire study, both cedars had their best 20-year height growth on burned sites, where competition 

from ericaceous shrubs (Gautheria shallon Pursh, and several Vaccinium species) was reduced 

compared to unburned sites. Survival of both cedars was also improved with burning. Redcedar height 

and volume were equal to or greater than yellow-cedar on all treatments; this likely reflects the fact that 

the study areas (450m to 600m) are below the natural range of yellow-cedar in that area. Yellow-cedar 

survival, however, was typically better than redcedar. Foliar nitrogen was higher for yellow-cedar than 

redcedar across all treatments. Douglas-fir growth performance was greater on burned sites and 

exceeded both cedars in all treatments.

At the MASS study, 15-year conifer growth did not differ among the clearcut, green tree and patch cut 

treatments. Growth in the shelterwood was typically slower than in the other silvicultural systems. 

Although this was the trend for yellow-cedar and redcedar, differences in growth were not significant for 

yellow-cedar, and were only significant for some growth parameters for redcedar. Yellow-cedar outperformed redcedar in the shelterwood, but growth was similar for these two species in the clearcut. 

Douglas-fir and western hemlock had better growth in all treatments than both cedars. In some cases, 

growth of the cedars exceeded that of amabilis fir. 

These studies showed that both cedars grow best in open environments and respond positively to 

prescribed burning. Low levels of retention are not likely to have significant impacts on growth for 

either redcedar or yellow-cedar. Because of slower relative growth of cedars compared to commonly 

associated conifers, mixed regeneration must be planned carefully. The high value of both cedars for 

products and for wildlife habitat makes them highly desirable species despite slow growth rates. 

KEYWORDS: Silvicultural systems, prescribed burning, western redcedar, yellow-cedar. 

1 W.J. (Bill) Beese is a forest ecologist, Vancouver Island University, Forestry Department, 900 Fifth Street, Nanaimo, BC, 

V9R 5S5, Email: bill.beese@viu.ca

2 Dillon Chrimes has a PhD from the Swedish University of Agricultural Sciences, Department of Silviculture, Umea, 

Sweden and currently resides in Victoria, BC.

2010 - A Tale of Two Cedars PNW-GTR-828

96
1,2 Pacific Northwest Research Station, 3625 93rd Ave SW, Olympia, WA 98512-9193, USA. 1

Email: charrington@fs.fed.us

GROWTH OF WESTERN REDCEDAR AND YELLOW-CEDAR 

Constance A. Harrington1 and Peter J. Gould2

ABSTRACT

Western redcedar (Thuja plicata) and yellow-cedar (Callitropsis nootkatensis, syn Chamaecyparis 

nootkatensis) are important tree species in both ecological and economic terms but relatively little 

information has been available on their growth rates under different stand and site conditions. We took a 

“data-centric” approach to ask: (1) which environmental variables are most related to site index (for 

redcedar), (2) what are the limits to growth (size-density relationships) for both species, and (3) how is 

growth related to stand conditions and site quality? Data was analyzed for over 50,000 trees on more 

than 3,000 plots throughout the range of both species. A wide range in tree age and stand type was 

sampled. Results include a classification tree predicting site index for redcedar using climate variables, 

maximum size-density relationships for both species, and a model for redcedar diameter growth using 

site and stand variables. Less data was available for yellow-cedar than redcedar but where comparisons 

across species were possible it appears that although maximum growth rates appear to be lower for 

yellow-cedar than redcedar, both species respond similarly to stand density. 

KEYWORDS: redcedar, yellow-cedar, site index, height growth, diameter growth, size-density 

relationships 

INTRODUCTION 

Western redcedar and yellow-cedar are 

important species in northwestern North 

America but relatively little information is 

available on their growth rates (Klinka and 

Brisco 2009). We know that both species are 

tolerant of shade, have wide ecological 

amplitude, and are indeterminate in height 

growth (have no overwintered bud) (Minore 

1990, Harris 1990). Some information is 

available for redcedar on within-season height 

growth (Walters and Sooes 1963) and diameter 

growth (Reukema 1965), and a density 

management diagram has been available (Smith 

1989 and Farnden 1996 in Klinka and Brisco 

2009) but most past analyses have used small 

data sets which have been limited 

geographically. In addition, very little 

information has been available for redcedar on 

topics such as effects of climate on site quality 

or the effects of stand and site variables on 

height and diameter growth and almost no 

quantitative information is available for yellowcedar. For this project, we surveyed the 

literature, pulled together our own data sets and 

contacted several organizations to develop a 

data set of research and inventory plots where 

these species were present. We required 

measurements on fixed-area plots using 

standard protocols. Plots which had been 

remeasured were especially useful as they could 

be utilized to develop or evaluate growth 

functions, however, plots with only one 

measurement were also useful for a subset of 

our analyses. We compiled a data set with 3420 

plots with 73,406 trees for redcedar (75% of the 

plots were remeasured) and 739 plots with 5897 

trees for yellow-cedar (46% of the plots were 

remeasured). Although the two species occupy 

different ecological niches, we were hopeful 

that due to their shade tolerance and growth 

habits they might respond similarly for growth 

modeling. If so, this would allow us to develop 

information for redcedar based on a large data 

set and use it to guide stand management for 

both species. 

METHODS 

We analyzed climate variables associated with 

redcedar site index using a regression tree 

approach (De'ath and Fabricius 2000). There 

2010 - A Tale of Two Cedars PNW-GTR-828

97
were 1606 observations from a wide geographic 

area. Climate variables used were from

Crookston (2010) which included 15 variables 

that characterize monthly or seasonal 

temperature or precipitation; variables included 

monthly means, minimums, and maximum 

values as well variables related to time periods 

such as the frost free period. The classification 

tree was created using the “tree” package in R 

software for statistical computing (Ripley 2009). 

Density management diagrams (first proposed 

by Reineke 1933) are used by many foresters to 

look at tradeoffs between number of trees and 

tree size (QMD or stem volume) and 

information taken from these diagrams is used 

in growth models to predict mortality and 

regulate stand density (Drew and Flewelling 

1979). We developed maximum size-density 

relationships for both species by selecting plots 

where either redcedar or yellow-cedar was at 

least 50% of the basal area. We used this 

threshold for selecting plots to avoid reducing 

our data set too substantially. We plotted 

quadratic mean diameter (QMD) and number of 

trees per ha (in most cases only trees ≥ 2.5 cm 

DBH were measured) on a log-log scale. We fit 

the maximum density line to these points for 

redcedar using frontier analysis and compared 

the results to those for western hemlock (Tsuga 

heterophylla) and Douglas-fir (Pseudotsuga 

menziesii) by Weiskittel et al. 2009. Maximum 

Stand Density Index (Max SDI = number of 

trees on the line where QMD= 25 cm) was 

determined as first proposed by Reineke (1933). 

The Max SDI value and slope of the maximum 

density line were compared to the previous 

values for redcedar developed by Smith (1989) 

and Farnden (1996) (in Klinka and Brisco 2009) 

and recent values published for Douglas-fir and 

western hemlock (Weiskittel 2009), two 

common tree associates. We had to convert the 

earlier redcedar analyses from tree volume to 

QMD. We also plotted values over time for 

remeasured plots which experienced mortality 

in the BC Ministry of Forests and Range data 

set. In addition, the redcedar line was compared 

to the plot information available for yellowcedar. We did not fit a separate line for yellowcedar as we had insufficient remeasurement data 

to verify a separate line would be warranted.

ORGANON is a growth and yield model 

developed by David Hann and others at Oregon 

State University 

(http://www.cof.orst.edu/cof/fr/research/organo

n/). It models tree diameter growth as a function 

of tree diameter, basal area (BA), basal area in 

trees larger than the subject tree (BAL), crown 

ratio, and site index. Very few of our plots had 

crown data and only a subset had site index (SI) 

values. We predicted site index for our plots 

using the regression tree. We developed a model 

using an ORGANON-type growth equation (i.e., 

using the same equation form as in 

ORGANON) based on tree diameter, BA, and 

BAL, and SI. 

We did not model height growth but we did 

evaluate height increments for redcedar from 

remeasured plots by plotting them on the same 

scale as the commonly used site index curves 

for redcedar (Kurucz 1985). We determined the 

percentage of the plots which had height 

increments close to (± 25%), greater than 

(>25%) and less than (<25%) the predicted 

slope for that age and site index. This was done 

for two large datasets: the BC Ministry of 

Forests permanent sample plot network and the 

Continuous Vegetation Survey plots from 

national forests in WA and OR. There were very 

few plots with remeasured heights for yellowcedar so this comparison was only possible for 

redcedar.

We also determined years from 0.1 m to breast 

height (1.3 m) from stem analysis data from 10 

trees from each of the 19 naturally regenerated 

sites in BC, WA and OR sampled by Radwan 

and Harrington (1986) and compared those field 

values to the ones that would be predicted from 

the equations in Mitchell and Polsson 1988). 

RESULTS AND DISCUSSION

The most important climate variables in the 

regression classification for redcedar site index 

were: mean maximum temperature in the 

warmest month, minimum temperature in the 

98
coldest month, day of year to accumulate 100 

degree days > 5oC (a measure of how mild the 

winter is), and growing season precipitation

(Fig. 1b). These variables separated site index 

values into 6 classes. Looking at the plots 

spatially (Fig. 1a,c), we can see the sites with 

the lowest site index are mostly in southeast AK 

(which is not too surprising). However, the 

regression tree does provide interesting insights 

into the geographic separation of sites with 

moderate or high values for site quality. The 

greatest site index values were predicted for 

areas in OR, WA and southern BC that are 

moderately warm (winter and summer) and have 

relatively high growing season precipitation. 

Coastal sites in northwest Oregon, western WA, 

and BC appear to be limited in productivity by 

summer temperatures when compared to sites 

further inland. 

Comparisons of height growth increments 

against Kurucz (1985) site index curves 

indicated an interesting difference between the 2 

redcedar data sets (Fig. 2a,b). The BC data was 

relatively balanced in terms of the breakdown of 

percentage of plots with greater (21%) and 

lower (28%) slopes for the height increments 

than would be predicted for that age and site 

quality. On the other hand, in the OR-WA data 

set, the breakdown in percentage of plots (slopes 

of height increments compared to the SI curves) 

was 69% of plots with greater slopes and 15% 

with lower values. Since the curves underpredict growth for the majority of the OR and 

WA sites, this could indicate that the curves 

under predict height growth in warm 

environments and a future research topic could 

be the development of new curves for redcedar 

across a wider range of environments. 

The number of years to breast height for 

redcedar varied within sites (Fig. 3) but did not 

differ across our range of sampled site index 

(mean= 4.7 years). This compares to the mean 

value of 9.5 years as calculated from the 

equation in Mitchell and Polsson (1988); the 

M&P equation values differ by SI but the range 

is quite small. We assume the highest values in 

Figure 3 would represent trees which were 

damaged by browsing or other factors early in 

their life. The lowest values shown on the graph 

indicate that early height growth can be quite 

good under favorable conditions. 

We developed an ORGANON-type equation for 

predicting diameter growth of redcedar and 

compared it to an existing model for Douglasfir. We used moderate SI values for Douglas-fir 

(37 m) and redcedar (25 m). With these SI 

values, the models predict similar growth rates 

for redcedar and Douglas-fir (Fig.4a) when they 

are grown with minimal competition. Although 

the two species are well matched in this 

example, their growth rates could differ 

substantially if the SI for either species was 

changed. However, in all the comparisons we 

made growth rates are reduced much more 

sharply for Douglas-fir than redcedar when 

basal area is increased (Fig.4b). This trend was 

especially pronounced when BAL increased 

(Fig. 4c) as diameter growth of redcedar was 

predicted to be considerably greater than that of 

Douglas-fir in dense stands and when trees are 

in poor competitive positions. There was not 

enough remeasured plot data to fit a similar type 

of growth equation for yellow-cedar. On plots 

where both cedars were present (at least 2 of 

each species) and mean diameter for the 2 

species was ± 10 cm, mean growth of yellowcedar was about 25 to 30% slower than that of 

redcedar (but relative growth rates were 

variable, see Fig. 4). In the absence of more data 

for yellow-cedar, models developed for yellowcedar could be adjusted downward by 0.3 or 

could be adjusted based on local information. 

The maximum size-density relationship we 

developed for redcedar (n = 1688 plots) had a 

maximum density line with a lower slope (-1.29 

vs -1.77) and a higher Max SDI (2170 vs 1780) 

than that previously developed by Smith (1989), 

but our model was similar to more recent 

information (Farnden, 1996 as presented in 

Klinka and Brisco, 2009 had slope = -1.44, Max 

SDI = 2046) (Fig. 5a). We had a wider range in 

diameters and larger sample size than was 

available to Smith. Max SDI was higher than 

that reported for Douglas-fir (1462) and western 

99
hemlock (1582) (Weiskittel 2009). Reineke 

(1933) proposed a slope of -1.605; our slope of -

1.29 is significantly lower (95% confidence 

intervals = -1.34 to -1.24). The high Max SDI 

and lower slope may reflect the ability of this 

shade-tolerant species to grow in multilayered 

stands. Remeasured data from the BCMF data 

set fit the maximum size- density line very well 

(Fig. 5b). The data cloud for yellow-cedar 

appeared to fit the line developed for redcedar 

(Fig. 5c) and values associated with the redcedar 

line would probably be adequate for yellowcedar until more data is available to fit a 

separate line for each species.

CONCLUSIONS

In summary, redcedar productivity is quite 

sensitive to climate variables with the best sites 

having warm summers, mild winters, and high 

summer precipitation; thus, the factors which 

limit growth differ geographically. Redcedar 

and yellow-cedar have shared characteristics 

such as the capacity to develop very high stand 

densities and good survival in the understory. 

Although the species differ in their ecological 

niches, they appear to respond similarly in terms 

of stand density-tree size relationships. Most of 

our data was from natural stands and many of 

these stands were unmanaged. We recognize 

that management activities can have a major 

impact on tree growth (e.g., use of genetically 

improved stock, control of browsing, 

fertilization); however, until more data is 

available (e.g., genetic multipliers for growth 

models, juvenile height growth curves for 

managed stands), incorporation of our results 

into growth models and silvicultural guidelines 

should result in better management of these 

neglected species. The limited data available for 

yellow-cedar means managers will need to use 

relationships developed for redcedar or use 

knowledge based on local stand conditions. 

ACKNOWLEDGEMENTS 

We thank the following for their assistance: 

Tara Barrett, PNW Research Station, for 

assistance in processing FIA data (FIA = USFS 

Forest Inventory & Analysis program); Jim 

Menlove, Rocky Mountain Research Station, for 

providing FIA plot data for Idaho and Montana; 

Ron Planden, Forest Analysis & Inventory 

Branch, BC Ministry of Forests and Range, for 

providing data from the BC permanent sample 

plot network; Jane Reid, PNW Research Station, 

for providing FIA plot data for Alaska; Robin 

Lesher and Cindy McCain, US Forest Service, 

for providing data from Region 6 Ecology plots; 

and Bob Brown, USDA Forest Service Region 

6, for help with accessing the CVS data. 

Figure Captions

Figure 1 -- Regression tree to predict redcedar 

SI based on climate variables. The regression 

tree (b) divided the observations into two “cold” 

groups (a) and four “warm” groups (c).

Figure 2 -- Height growth increments of 

dominant and codominant trees from the BC 

and OR WA CVS datasets compared with the 

expected height trajectories from Kurucz (1978) 

site index curves. Height increments with slopes 

that are 25% greater than the site index curve (a) 

and 25% less than the site index curve (b) are 

color-coded by data source.

Figure 3 -- The average number of years to 

reach breast height across a range of site index 

for redcedar. Each grey point represents a single 

tree; the blue bars show the mean for each stand 

that was sampled. 

Figure 4 -- Comparison of new diametergrowth model for redcedar (red lines) with an 

equation used in ORGANON for Douglas-fir 

(blue lines). Diameter-growth rates were 

predicted to be about the same for both species 

when they are open-grown (a). Predicted growth 

was compared for stand basal areas of 10, 40, 

and 80 m2

/ha and for trees in superior 

competitive positions (b; 75% of basal area in 

smaller trees) and inferior positions (c; 75% of 

basal area in larger trees). 

Figure 5 -- Fit of a maximum stand density line

for redcedar (red) compared with lines presented 

by Smith (1989) and Farnden (1996). 

100
101
LITERATURE CITED

Crookston, N. L. 2010. Current climate data for 

western North America.

http://forest.moscowfsl.wsu.edu/climate/current

Climate.html (last accessed April 8, 2010).

De'ath, G.; Fabricius, K.E. 2000.

Classification and regression trees: a powerful 

yet simple technique for ecological data 

analysis. Ecology 81:3178-3192. 

Drew, T.J.; Flewelling, J.W. 1979. Stand 

density management: an alternative approach 

and its application to Douglas-fir plantations. 

For. Sci. 25: 518-532. 

Farnden, C. 1996. Stand density management 

diagrams for western redcedar. Silviculture 

Br.,B.C. Min. For. Data Source: TASSgenerated managed stand yield tables contained 

in the computer program WINTIPSY Version 

1.3. B.C. Min. For., Forest Productivity and 

Decision Support Section, Victoria, B.C. 

Harris, A.S. 1990. Chamaecyparis nootkatensis

(D.Don) Spach, Alaska-cedar. Pp 97-102 in: 

Burns, R.M.; Honkala, B.H., tech. coords. 

Silvics of North America, Vol.1, Conifers. 

USDA For. Serv. Agric. Handbk 654. Wash. 

D.C.

Klinka, K.; Brisco, D. 2009. Silvics and 

silviculture of coastal western redcedar, B.C. 

Min. For.& Rang, For. Sci. Prog., Spec Rep. 

Ser. 11. Victoria, B.C. 105 p. 

Kurucz, J.F. 1978. Preliminary, polymorphic 

site index curves for western redcedar – Thuja 

plicata Donn – in coastal British Columbia. 

MacMillan Bloedel Forest Research Note 3. 40 

p. 

Minore, D. 1990. Thuja plicata Donn 

ex.D.Don, western redcedar. Pp 590-66 in: 

Burns, R.M.; Honkala, B.H., tech. coords. 

Silvics of North America, Vol.1, Conifers. 

USDA For. Serv. Agric. Handbk 654. Wash. 

D.C.

Mitchell, K.J.; Polsson, K.R. 1988. Site index 

curves and tables for British Columbia: Coast 

ppecies. FRDA Report 37. 

Radwan, M.A.; Harrington C.A. 1986. Foliar 

chemical concentrations, growth, and site 

productivity relations in western red cedar. Can. 

J. For. Res. 16: 1069-1075. 

Reineke, L.H. 1933. Perfecting a stand-density 

index for even-aged forests. J. Agric. Res. 46: 

627–638. 

Reukema, D.L. 1965. Seasonal progress of 

radial growth of Douglas-fir, western redcedar 

and red alder. USFS Res. Pap. PNW-26. 14 p. 

Ripley, B. 2009. Tree: Classification and 

regression trees. R package version 1.0-27. 

http://CRAN.R-project.org/package=tree (last

accessed April 8, 2010). 

Smith, N.J. 1989. A stand-density control

diagram for western red cedar, Thuja plicata. 

For. Ecol. Mangmt. 27: 235-244. 

Walters. J.; Soos J. 1963. Shoot growth 

patterns of some British Columbia conifers. For. 

Sci. 9:83-85. 

Weiskittel, A. R; Gould, P.J; Temesgen, H. 

2009. Sources of variation in the self-thinning 

boundary line for three species with varying 

levels of shade tolerance. Forest Science 55:84-

93. 

 

102
EFFECTS OF PRUNING SEVERITY ON THE GROWTH OF 

WESTERN REDCEDAR AFTER 12 YEARS 

Louise E. de Montigny1, Roderick W. Negrave2 and Peter K. Ott3

ABSTRACT

It is assumed that pruning of western redcedar (Thuja plicata Donn ex D. Don.) may increase the 

proportion of high-value, knot-free wood and improve stem form characteristics. A pruning trial was 

initiated in a 14-year-old western redcedar stand on northern Vancouver Island in 1993 to investigate the 

effects of pruning severity on tree growth, taper, epicormic branching, and occlusion of pruning scars. 

The treatments consisted of an unpruned control and crown removal of 20, 30, 40, 50 and 60% of the 

total tree height. At the time of pruning, average tree height was 4.5–5.1 m. Initial tree size had a larger 

effect on growth than the pruning treatments after 12 years. Moderate pruning, up to 50% crown 

removal, did not reduce tree growth. Pruning only reduced taper at the highest severity (60% removal). 

The frequency and length of epicormic branches were not significant after 12 years of growth. Branch 

stub occlusion is not readily apparent in young trees. The financial returns of pruning western redcedar 

can be improved through the use of green-foliage pruning for floral boughs or the production of cedar 

oil. 

KEYWORDS: Western redcedar, silviculture, pruning, epicormic branching, branch occlusion. 

INTRODUCTION

Western redcedar (Thuja plicata Donn ex D. 

Don.) is an important commercial species in 

British Columbia (B.C.), Washington, and 

Oregon. The wood has low density and strength, 

but is aesthetically pleasing and has superior 

dimensional stability, durability, and insulating 

properties. The wood is highly desirable for 

decorative and specialty products, many of 

which require high-value clear wood that is 

currently obtainable only from large, old-growth 

logs. Second growth western redcedar (“cedar”) 

is commonly an understorey component of 

mixed stands with red alder (Alnus rubra

Bong.), western hemlock (Tsuga heterophylla

[Raf.] Sarg.), and/or Douglas-fir (Pseudotsuga 

menziesii [Mirb.] Franco) (Stubblefield and 

Oliver 1978). Cedar grows slowly under these 

conditions, with large living or dead branches, 

high stem taper, and fluting (Oliver et al. 1987). 

Trees in this environment take several hundred 

years to develop the high-quality wood 

characteristics of old-growth cedar. In contrast, 

cedar grown in even-aged, single-species stands 

at relatively close spacing can grow rapidly and 

produce trees of desirable form much sooner 

(Oliver et al. 1987). Cedar plantations have been 

established on over 150,000 hectares on 

northern Vancouver Island and the mid-Coast of 

B.C. A well-designed intensive silviculture

program may produce the wood quality 

characteristics of old-growth cedar in younger 

trees. For example, ensuring adequate spacing 

when trees are planted and pruned, and stand 

fertilization could improve rates of cedar growth 

and production of knot-free wood with better 

stem form and taper. There are still many 

unknowns: the growth response of cedar to 

pruning, its susceptibility to epicormic 

branching, rates of branch stub occlusion,

1 Louise de Montigny PhD, R.P.F. is Research Leader for Silvicultural Systems and Forest Dynamics, Research, Innovation and 

Knowledge Management Branch, B.C. Ministry of Forests and Range. P.O. Box 9519 Stn. Prov. Govt., Victoria, B.C. V8W 9C2 2 Roderick Negrave PhD, PAg, RPF is Research Team Leader, Research, Innovation and Knowledge Management Branch, B.C. Ministry 

of Forests and Range, 2100 Labieux Road, Nanaimo, B.C. V9T 6E9. 3 Peter Ott is a statistician, Research, Innovation and Knowledge Management Branch, B.C. Ministry of Forests and Range. P.O. Box 9519 

Stn. Prov. Govt. Victoria, B.C. V8W 9C2. 

2010 - A Tale of Two Cedars PNW-GTR-828

103
the susceptibility of pruned trees to disease, and 

the effects of pruning on wood quality. 

A pruning experiment was initiated in 1993 to 

examine the effects of pruning severity on 12-

year-old plantation cedar. Objectives of this 

study were to compare height and diameter 

growth, taper, the rate of occlusion of pruned 

branch stubs and epicormic branch development 

among pruning treatments. 

METHODS 

The study site is located near Port Hardy, B.C. 

(50°38'08" N, 127°17'54"), in Western Forest 

Products Ltd. Tree Farm License 25. The study 

area is classified as mesic, in the submontane 

variant of the very wet maritime subzone within 

the Coastal Western Hemlock biogeoclimatic

zone (CWHvm1/01 cedar—salal phase). The 

understorey is predominantly salal (Gaultheria 

shallon Pursh.) and deer fern (Blechnum spicant 

[L.] Roth.), with pockets of Vaccinium species. 

Soils are Humo-Ferric Podzols (Spodosols), 

often with a Duric horizon or other root- and 

water-restricting layers. The area receives 

approximately 1900 mm of precipitation 

annually, most of which falls as rain so there is 

typically no growing season soil moisture 

deficit. Average daily mean temperature ranges 

from 3.3°C in January to 14.1°C in August. 

The site was logged and broadcast burned in 

1980 and planted the following spring with 2-

year-old container-grown cedar at 1030 stems 

per ha. In December 1986, the stand was 

broadcast fertilized with urea and ammonium 

phosphate to deliver 225 kg/ha of N and 75 

kg/ha of P. 

Prior to plot layout, a reconnaissance survey 

was done to identify site differences and ensure 

homogeneity of treatment units. A randomized 

complete block design (RBCD) was used for 

this study, comprised of six pruning severity 

treatments and two blocks. Within each block, 

treatments were randomly assigned to a 

treatment unit that contained a single 0.1-ha 

core measurement plot with a surrounding 0.1-

ha buffer. There were 75–100 measurement 

trees in each core plot. The treatments consisted 

of an unpruned control and crown removal of 

20, 30, 40, 50, and 60% of the total tree height 

from the crown base, which was virtually 

equivalent to the tree base in this plantation. 

Pruning treatments were applied in the winter of 

1993–94. Heights were measured immediately 

before pruning to determine the height of 

foliage to remove using pruners and loppers. 

Immediately post-pruning and in 1995, 1997, 

2001, and 2005, we measured tree height, 

diameter at 1.3 m (or breast) height (DBH), 

pruning height, categorical measures of the 

number of epicormic branches (0, 1–10, 11–20, 

and > 20) and maximum vigour (length) of the 

epicormic branches (< 4 cm, 5–10 cm, and > 11 

cm), estimated branch stub occlusion, and 

assessed tree damage and condition classes. We 

also measured height to crown base in 1994 and 

diameter at 30 cm in 2006. 

We used a mixed-effects model to determine the 

significance of treatment and temporal 

differences on cedar height and DBH. We used 

Proc Mixed (SAS Institute Inc. 2004) to fit the 

following analysis of variance (ANOVA) 

model: 

Yijkl = μ + Bi + Pj + (BP)ij + Sk(ij) + Tl + (BT)il + 

(PT)jl + (BPT)ijl + (ST)kl(ij)

where Yijkl is the response of the k

th tree nested 

in both the i

th block and jth treatment level, 

measured at year l. The parameter μ denotes the 

overall experimental mean. Parameters Bi, Pj, 

Sk(ij), and Tl represent the effects of block, 

pruning treatment, tree (nested within block and 

treatment), and year of measurement, 

respectively. The trees measured within each 

plot represent subsamples within the 

randomized complete block design, and year 

was analyzed as a repeated measures effect 

(e.g., a split-plot factor). All factors and 

interactions except Pj, Tl, and (PT)jl were 

considered random, and were considered 

independent from one another, each with a 

normal distribution with zero mean and a unique 

variance component. The correlation between 

residuals from a tree measured at year tl and tl+m

104
was modelled as mll tt − + ρ , where |ρ| < 1. Custom 

contrasts were used to compare treatment levels 

with the control for each year. Comparisons of 

each mean with the control were adjusted using 

a simple Bonferroni-type correction (i.e., the 

level of significance was changed to α ÷ 5). 

Where there was a significant treatment × year 

(PT) interaction, simple main-effect tests were 

used to separately compare treatments for each 

year.

A yearly observation data point was eliminated 

if the height or DBH at the previous growth 

period was larger. Pearson and Studentized 

residuals were graphically examined for 

outliers, severe departures from normality, and 

heteroscedasticity. After removing a handful of 

obvious outliers, the residuals appeared to meet 

model assumptions for all dependent variables. 

A significance level of α = 0.05 was used for all 

tests unless otherwise indicated. 

For epicormic branching, wound occlusion, and 

tree condition, data were summarized for these 

variables in each treatment by year of 

measurement without performing any formal 

statistical tests.

RESULTS 

Height to Crown Base 

Total tree height averaged 4.5–5 m prior to 

pruning treatments. The height to crown base in 

the unpruned control was 40 cm, or about 10% 

of the total height. Pruning treatments increased 

the height to crown base by about 0.5 m with 

every 10% increase in pruning severity: from 

about 1.0 m for the 20% crown removal 

treatment to 3.0 m for the 60% removal 

treatment (Table 1). The variability in the total 

tree height by plot led to a range of heights to 

crown base within treatments, such that any

height to crown value was not exclusive to any 

one treatment.

Diameters

No significant difference developed for DBH 

between the control and the pruning treatments 

until 8–12 years after pruning (Table 1). By 

twelve years after pruning, only the 60% 

removal treatment was significantly smaller 

than the control. The estimate of the residual 

correlation parameter ρ was close to 1 (i.e., 

0.98–0.99) and highly significant in both cases, 

indicating that the DBH of the tree at the start of 

measurements strongly influenced the DBH of 

the tree after 12 years.

For diameter at 0.3 m, measured at year 12, 

none of the treatments were significantly 

different from the control, although the 60% 

removal treatment was the smallest (p = 

0.1006). 

Height

At the time of pruning, there were no significant 

differences in heights among treatments (Table 

1). None of the pruning treatments were 

significantly smaller than the control 12 years 

after pruning, but the 50% removal pruning 

treatment was significantly taller than the 

control. The estimate of ρ was 0.99 (highly 

significant), indicating that the initial tree height 

strongly influenced the height of the tree after 

12 years.

Branch Stub Occlusion 

One year after pruning, branch stubs were open 

on nearly 100% of trees in all pruning 

treatments. After 12 years, the branch stubs had 

occluded (healed over) in all pruning treatments, 

except that bark did not appear to grow over the 

wounds, but remained dimpled where the 

branch had been. It is unclear whether this will 

affect wood quality. 

Epicormic Branch Number and Vigour

Epicormic branching increased with pruning 

severity (Table 2). After two years, trees that 

received moderate to severe pruning treatments 

(40–60% crown removal) tended to have more 

epicormic branches than lightly pruned (20–

30% removal) trees. In the first two years, most 

epicormic branches were > 4 cm and their 

number and vigour tended to be slightly higher 

on the south side of the tree than the north side. 

There were generally ten or fewer epicormic 

branches per sample side (data not shown).

105
Table 1: Least-squares means (standard errors) and analysis for height, DBH, and volume at 0, 4, 8, and 12 

years after pruning; branch length at crown base and height to crown base at 0 and 12 years after pruning; and 

diameter at 30 cm.

Years since 

pruning

Crown removal treatment (%)a

pvalue NDFb DDFc

Control 20 30 40 50 60

DBH (cm)

0 7.49 

(0.76)

6.63 

(0.79)

8.82 

(0.79)

7.85 

(0.76)

8.50 

(0.76)

7.26 

(0.76) 0.379 5 15

4 9.82

(0.76)

8.87

(0.76)

11.67

(0.76)

9.84

(0.76)

10.50

(0.76)

8.30

(0.76) 0.080 5 15

8 11.52

(0.76)

10.46

(0.76)

13.79

(0.76)

11.79

(0.76)

12.64

(0.76)

9.75

(0.76) 0.022 5 15

12 13.03

(0.76)

11.80

(0.76)

15.58

(0.76)

13.38

(0.76)

14.51

(0.76)

11.05* 

(0.76) 0.008 5 15

Height (m)

0 4.81 

(0.24)

4.57 

(0.24)

5.01 

(0.24)

5.08 

(0.24)

5.15 

(0.24)

4.76 

(0.24) 0.536 5 15

4 6.17

(0.24)

6.01

(0.24)

6.76

(0.24)

6.65

(0.24)

6.83

(0.24)

5.96

(0.24) 0.064 5 15

8 7.04

(0.24)

6.74

(0.24)

7.83

(0.24)

7.55

(0.24)

7.78

(0.24)

6.64

(0.24) 0.008 5 15

12 7.86

(0.24)

7.48

(0.24)

8.70

(0.24)

8.43

(0.24)

8.78* 

(0.24)

7.41

(0.24) 0.002 5 15

HCBd (m) 0 0.40*

(0.05)

0.92*

(0.05)

1.51*

(0.05)

2.04*

(0.05)

2.59*

(0.06)

2.85*

(0.07) 0.0001 5 5 

D@30e (cm) 12 17.7

(1.12)

15.5

(1.12)

20.0 

(1.12)

18.0 

(1.12)

19.3

(1.11)

14.4

(1.13) 0.089 5 5 

a

Treatment levels with an asterisk are statistically significant from the control at α = 0.05 ÷ 5 = 0.01 b NDF – numerator degrees of freedom for F-test c DDF – denominator degrees of freedom for F-test. Tests of simple main effects from the full model (equation 1) will have more degrees of freedom (15) 

than tests based on a separate reduced model for each year (5) d HCB – height to crown base e D@30 – diameter at 30 cm

Twelve years after pruning, the proportion of 

trees that had developed epicormic branches 

increased to about 20–35% of lightly-pruned 

trees; approximately 45–55% of moderateseverity pruned trees, and 73% of severely 

pruned trees. Trees that developed new 

epicormic branches had 1–10 per tree (Table 2). 

The number of trees with 11–20 epicormic 

branches per tree decreased, suggesting this was 

likely due to mortality of these branches over 

the 12-year period. Twelve years after pruning, 

the proportion of trees with epicormic branches 

> 11 cm increased with pruning severity (Table 

2) from 6–9% in light pruning, 19–42% in the 

moderately severe pruning treatments, and 60% 

in the severe pruning treatments. 

DISCUSSION

Pruning may improve the growth and yield of 

western redcedar for several reasons: improved 

height growth, better stem form, and reduced 

knot size and number. Pruning did not 

significantly reduce height growth, which is 

consistent with other studies that found 

moderate pruning did not negatively impact 

height growth (reviewed by Maguire and 

Petruncio 1995); however our results suggest 

that cedar growth may be even less sensitive to 

pruning than other species. In our study, only 

the 60% treatment resulted in a mean DBH that 

was significantly smaller than the control. Other 

pruning studies found that one-third to one-half 

of live crown length can be removed before 

DBH is negatively affected (Gallagher 1984; 

Pentruncio 1994; de Montigny and StearnsSmith 2001a, 2001b). Although not significantly 

different, the average DBH of trees in the 30% 

removal treatment was larger than that of the 

control, likely because the pruned height was 

roughly equivalent to breast height (1.5 vs. 1.3 

cm, respectively), and because growth along the 

stem is largely controlled by relative proximity 

to the photosynthate source (Smith 1962). 

Several authors have suggested that pruning 

results in a reallocation of radial growth along 

the stem resulting in less taper (Larson 1965; 

Maguire and Petruncio 1995). A more detailed 

analysis of changes in stem form and volume

106
 

Table 2: Proportion of trees across treatments in categories for occurrence (count of) epicormic branches per 

tree and vigour (length) of the longest epicormic branch per tree.

Crown 

Removal (%)

Epicormic

Occurence 

(number per tree)

Vigour (length of epicormic branches)

1995 2006

< 4 cm 5–10 cm > 11 cm Total < 4 cm 5–10 cm > 11 cm Total

0 n/a n/a n/a 83.06 n/a n/a n/a 65.03

20 1–10 9.84 1.09 0.55 11.48 4.92 20.22 9.29 34.43

11–20 2.73 1.64 1.09 5.46 0.00 0.00 0.55 0.55

0 n/a n/a n/a 80.32 n/a n/a n/a 80.85

30 1–10 13.83 0.53 0.00 14.36 3.19 9.57 6.38 19.15

11–20 3.72 0.53 1.06 5.32 0.00 0.00 0.00 0.00

0 n/a n/a n/a 44.89 n/a n/a n/a 53.41

40 1–10 37.50 0.00 2.27 39.77 2.84 24.43 18.75 46.02

11–20 13.07 1.70 0.57 15.34 0.00 0.00 0.57 0.57

0 n/a n/a n/a 33.51 n/a n/a n/a 42.55

50 1–10 38.83 2.13 0.53 41.49 1.06 12.77 42.02 55.85

11–20 21.81 3.19 0.00 25.00 0.00 0.00 1.60 1.60

0 n/a n/a n/a 25.90 n/a n/a n/a 23.49

60 1–10 34.94 4.22 0.00 39.16 0.60 12.65 59.64 72.89

11–20 27.11 6.63 1.20 34.94 0.00 0.60 3.01 3.61

should be undertaken in future studies. 

Pruning can stimulate the growth of epicormic 

branches from dormant buds under the bark and 

from new buds that form in callus tissues as 

they respond to changes in heat, light, and/or in 

stem tissue hormonal balances (Collier and 

Turnblom 2001). Epicormic branching has been 

noted in other conifer species (Hingston 1990; 

Collier and Turnblom 2001; Waring and O’Hara 

2005). These studies typically find that the more 

severe the pruning, the more epicormic shoots 

develop, but they tend to die as residual crowns 

expand after pruning. Our results support that 

finding; after 12 years, the majority of trees 

have 0 to 10 epicormic branches per tree. The 

impacts of this epicormic branching on wood 

quality will be investigated using destructive 

sampling methods at a later date.

Occlusion of branch stubs is important because 

it is only after the branch stub has occluded that 

clear, high-value wood is produced by the tree. 

Any delay in occlusion reduces the volume of 

the clear wood and allows pathogens to enter. In 

cedar, the rate of occlusion was difficult to 

judge based on external appearances because the 

bark did not grow over the wound, even after 

twelve years. Since the pruned cedar trees 

remain healthy with no visible signs of decay, it 

indicates that the wound has likely occluded. 

Destructive sampling will allow a better 

evaluation of the branch stub occlusion below 

the cambium. 

Pruning as a silviculture investment has been 

shown to provide reasonable economic return 

only in stands with relatively high site indices 

that maintained rapid diameter growth over 

short rotations (Fight et al. 1987). This is 

typically not the case with cedar, which requires 

a long rotation age to achieve high quality, knotfree wood. However, the high initial investment 

for pruning could be offset by selling the pruned 

green foliage material for floral boughs or 

essential oil production, especially if 

entrepreneurs prune them at no cost to forest 

licensees. Such a situation has been documented 

by Western Forest Products Inc. in Tree Farm 

License 6 near Port McNeill (Western Forest 

Products 2003), where a local entrepreneur has 

pruned large areas of plantation-grown cedar for 

green foliage and has added almost $1.5 million 

to the community through cedar oil production. 

A well-designed intensive silviculture program 

that utilizes the foliage as a non-timber forest 

product may result in high-value cedar 

plantations with attractive financial returns.

CONCLUSION

Pruning may be a viable treatment to increase 

the value of wood produced in western redcedar 

plantations. We found that initial tree size had a 

107
greater effect than pruning treatment on growth 

12 years after pruning. Pruning up to 50% of the 

tree height in young cedar did not affect total 

height or DBH. Excessive epicormic branching 

and the inability of pruned branch stubs to 

occlude do not appear to be a concern at this 

time if pruning severity is kept below about 

50% of tree height. Continued measurement 

over a longer term and destructive sampling are 

necessary before conclusions can be made about 

the effects of pruning on wood quality. Despite 

long rotations and potentially high investment 

costs, the financial returns of pruning cedar can 

be improved entrepreneurs can prune the green 

foliage for non-timber forest products such as 

cedar leaf oil or floral boughs. 

ACKNOWLEDGEMENTS

Funding came from the Forest Investment 

Account–Forest Science Program, the B.C. 

Ministry of Forests and Range, and Western 

Forest Products Ltd. 

LITERATURE CITED

Collier, R.; E. Turnblom. 2001. Epicormic 

branching on pruned coastal Douglas-fir. W. J. 

Appl. For. 16(2):80-86. 

de Montigny, L.; S. Stearns-Smith. 2001a.

Pruning density and severity in coastal western 

hemlock: 4-year results. B.C. Min. For., Res. 

Br. Ext. Note 51. Victoria, B.C. 

de Montigny, L.; S. Stearns-Smith. 2001b.

Thinning and pruning coastal Douglas-fir near 

Chilliwack, B.C.: 8-year results. B.C. Min. For., 

Res. Br. Ext. Note 56. Victoria, B.C. 

Fight, R.D.; J.M. Cahill; T.D.Fahey; T.A. 

Snellgrove. 1987. Financial analysis of pruning 

coast Douglas-fir. Res. Pap.PNW-RP-390. 

Portland, OR: USDA For. Serv. Pac NW Res. 

Stn. 

Gallagher, G. 1984. To prune or not to prune? 

FWS Res. Br., Res. Note 2/84. Bray, Ireland. 

4p. 

Hingston, R.A. 1990. Chemical control of 

epicormic shoots on 4 year old Pinus radiata

D.Don Aus. For. 53(1):3-6. 

Larson, P.R. 1965. Stem form of young Larix 

as influenced by wind and pruning. For. Sci. 

11:413-424. 

Maguire, D.A.; M.D. Petruncio. 1995. Pruning 

and growth of western Cascade species: 

Douglas-fir, western hemlock and Sitka spruce. 

P. 179-215 in Hanley D.P. ed.. Proceedings, 

Forest pruning and wood quality of western 

North American conifers. For. Res. U. Wash. 

Seattle, WA. 403 p. 

Oliver, C.D.; M.N. Nystrom; D.S. DeBell. 

1987. Coastal stand silvicultural potential for 

western redcedar. P. 39-46 in N.J.Smith (ed). 

Proceedings, Western redcedar—does it have a 

future? Faculty of Forestry, Univ. B.C., 

Vancouver, B.C. 

Petruncio, M. 1994. Effects of pruning on 

growth of western hemlock (Tsuga 

heterophylla) and Sitka spruce (Picea sitchensis) 

in southeast Alaska. PhD dissertation, Univ. 

Wash, Seattle, WA. 160 p. 

SAS Institute Inc. 2004. The SAS system: SAS 

OnlineDoc® Version 9.1.3. Cary, N.C. 

Smith, D.M. 1962. The practice of silviculture.

7th ed. John Wiley and Sons. New York, N.Y. 

578 p. 

Stubblefield, G.W.; C.D. Oliver. 1978.

Silvicultural implications of the reconstuction of 

mixed alder/conifer stands. P. 307-320 in W.A. 

Atkinson, et al. (eds.). Utilization and 

management of red alder. Gen. Tech. Rep. 

GTR-PNW-70. Portland OR: USDA For. Serv., 

Pac NW Res. Stn. 

Waring, K.M.; K. L. O’Hara. 2005. Ten-year 

growth and epicormic sprouting response of 

western larch to pruning in western Montana. J. 

Appl. For. 20(4):228-232. 

Western Forest Products Ltd. 2003. Tree 

Farm Licence 6, 2003 Annual Report. 

Vancouver, B.C. 

http://www.westernforest.com/fstew/download/

TFL6-AR-2003.pdf

108
1 Doug Mainwaring is a Faculty Research Assistant, Oregon State University College of Forestry, 204 Peavy 

Hall, Corvallis, Ore., 97331.

2 Doug Maguire is a Professor and Director of the Center for Intensive Planted-forest Silviculture, Oregon State 

University College of Forestry, 204 Peavy Hall, Corvallis, Ore., 97331.

GROWTH OF WESTERN REDCEDAR WITH DOUGLAS-FIR IN

YOUNG PLANTATIONS IN WESTERN OREGON

Doug Mainwaring1 and Doug Maguire2

ABSTRACT

Basal area and height growth of western redcedar growing with Douglas-fir in 19-24-year-old 

operational plantations in western Oregon were measured four years after plot establishment. Plantations 

were established in stands infected with Phellinus sulphurascens, and contained mixes of planted 

western redcedar and natural Douglas-fir. 

Basal area and height growth of redcedar was determined by initial tree size and competitive position, 

with significant reductions in growth resulting from overtopping Douglas-fir. Where dense stands have 

resulted in significant stand differentiation, reductions in redcedar growth are significant. Relative to 

pure redcedar, individual tree basal area growth was reduced 30% for 20-year-old redcedar growing 

with as few as 125 Douglas-fir per ha. Depending on tree size, basal area growth was reduced 40-80% 

when redcedar was mixed with 500 Douglas-fir per ha. Reductions in height growth were significantly 

less, amounting to only 8% in the presence of 125 Douglas-fir/ha and 8-80% with 500 Douglas-fir/ha, 

depending on tree size. Four-yr mortality of redcedar decreased with size and increased with competitive 

position, reaching nearly 50% for 5 cm trees growing in a stand with 20m2

/ha of Douglas-fir. 

Where surrounding stands are nearly pure Douglas-fir, current stand trajectories imply that the number 

of naturally regenerating Douglas-fir must be controlled if redcedar is to remain a major overstory 

component to ameliorate Phellinus sulphurascens. 

KEYWORDS: western redcedar, Douglas-fir, mixed species, western Oregon

INTRODUCTION

In the last fifteen years, land managers in 

western Oregon have shown an increasing 

interest in growing and managing western 

redcedar. Although this change is primarily the 

result of high redcedar log prices relative to 

Douglas-fir (Pseudotsuga menziesii (Mirb.) 

Franco), the onset of a Swiss needle cast 

epidemic in Oregon Coast Range forests has 

also contributed. Swiss needle cast (SNC) is 

caused by a foliar fungus which causes 

premature needle abscission of Douglas-fir 

(Hansen et al. 2000). Resulting growth losses in 

SNC-infected 10-30 yr old Coast Range 

plantations were estimated to average 23% in 

1996 and were 52% in the most severely 

impacted plantations (Maguire et al. 2002). In 

stands where disease intensity is especially high, 

Douglas-fir is not considered a good candidate 

for reforestation (Filip et al. 2000). Managers 

have instead planted non-susceptible alternative 

species such as western hemlock (Tsuga 

heterophylla (Raf.) Sarg.), Sitka spruce (Picea 

sitchensis (Bong.) Carr.), and western redcedar 

(Thuja plicata Donn ex D. Don). 

Although high log prices make western redcedar 

the preferred species for new plantations where 

SNC presents a risk, managers have found 

establishment difficult and expensive, primarily 

due to deer and elk browse (M. Gourley, Pers. 

Comm.). The high cost of protecting seedlings 

2010 - A Tale of Two Cedars PNW-GTR-828

109
with barriers and high rates of seedling 

mortality have motivated managers to plant 

multiple species as a means of lowering costs 

and ensuring a full stocked stand. The slow 

height growth of redcedar relative to its 

associated species means that planting density, 

species proportions, and spatial distribution will 

have a large influence on differentiation and 

stand development,especially in Douglas-fir and 

redcedar mixes with faster initial height growth 

of Douglas-fir. The two are often mixed where 

SNC is of moderate or low intensity. Even 

where pure redcedar has been planted in root 

disease infected stands, Douglas-fir quickly 

regenerates naturally due to seedfall from 

surrounding stands. Although redcedar is shade 

tolerant, questions remain regarding what 

Douglas-fir densities will preclude overtopped 

redcedars from producing merchantable 

volumes at likely rotation ages. The objective of 

this analysis were to quantify growth and 

mortality of redcedar under the influence of 

Douglas-fir.

METHODS 

Sites

The study sites were located in the eastern 

foothills of the Oregon Coast Range, at 

approximately 44.7° N latitude, and with 

elevations ranging from 300-500m. All stands at 

the two sites had been planted to pure redcedar 

between 1986 and 1990 due to high levels of 

Phellinus sulphurascens root rot. Naturally 

regenerated Douglas-fir established shortly 

thereafter, with Douglas-fir and redcedar density 

varying by plot (table 1). Two of the plots were 

pure redcedar due to aggressive removal of 

Douglas-fir by the landowner. Douglas-fir site 

index is approximate 47m (Bruce 1981) and 

redcedar site index was ~33m (Kurucz 1978). 

Ten 0.2 ha plots were established in 1994 or 

1996 depending on site. On each plot, all trees 

were tagged and measured for DBH (nearest 0.1 

cm), and a subsample of 40 trees of each species 

was measured for total height and height to

lowest live branch (nearest 0.01 m). This 

subsample included the 10 largest by dbh, the 4 

smallest by dbh, and 26 additional trees 

distributed evenly across the diameter range of 

the plot. 

Analysis

Basal area and height growth of individual 

western redcedar trees was assessed over a four 

year growth period using non-linear regression. 

Many independent variables were used to 

quantify tree size, competitive position within 

the stand, and stand density, including dbh, 

height, stand basal area, Douglas-fir basal area, 

relative height (subject tree height relative to the 

largest 100 tph), basal area in larger trees, and 

various interactions. Mortality was assessed 

using logistic regression techniques and the 

same set of independent variables.

To estimate the implied effects of Douglas-fir 

on redcedar in different establishment mixes, 

five hypothetical stands of pure Douglas-fir 

were produced with SYSTUM-1, a young stand 

simulator (Ritchie and Powers 1993). These 

stands were assumed to have a site index of 45 

m (maximum allowed with SYSTUM-1). Five 

densities were projected to 20 years of age (62, 

125, 250, 500, and 750 tree per ha), and it was 

assumed that these projected trees would 

develop similarly with or without the presence 

of redcedar. Output from these hypothetical 

stands was used in combination with values 

from the measured plots to estimate from the 

constructed growth equations the effect of 

different establishment densities on the growth 

of western redcedar. 

Table 1—Per hectare density by plot and species

TPH BA (m2/ha)

plot WRC DF Total WRC DF Total

1 717 232 949 15.37 4.35 19.72

2 815 917 1732 16.47 5.92 22.39

4 539 534 1073 5.35 9.62 14.97

5 623 974 1597 5.59 13.67 19.26

6 524 890 1414 4.52 9.71 14.23

p1 519 677 1196 9.42 34.6 44.02

p2 499 756 1255 6.06 31.16 37.22

p3 766 376 1142 24.43 17.56 41.99

w1 801 801 17.93 17.93

w2 939 939 25.43 25.43

110
0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1

Relative height (ht/HT40)

Mult. effect of stand BA on WRC htgr

BA= 15 m2/ha

BA= 20 m2/ha

BA= 25 m2/ha

Figure 2—Multiplicative effect of stand BA on WRC 

height growth by relative height; relative to pure 

redcedar

RESULTS AND DISCUSSION

Basal area and height growth 

Redcedar basal area growth was described by 

the following equation: 

[1] BAGwrc

= α1*dbhβ2 *e(β3 *BAtot + β4 *bal -(exp (β5+BAdf) *relht β6 ))

 

where BAGwrc was redcedar basal area growth 

(cm2

/4 yrs), Dbh was diameter at breast ht 

(cm),BAtot was stand basal area (cm2/ha), BAL 

was basal area in larger trees (m2

/ha), BAdf was 

Douglas-fir basal area (m2/ha), and Relht was 

relative height.

Basal area growth of redcedar mixed with 

Douglas-fir was negatively correlated with total 

stand basal area and basal area in larger trees 

and positively correlated with dbh and relative 

ht (table 2). However, the positive correlation 

with relative height diminishes as the amount of 

Douglas-fir basal area increases (figure 1).

Redcedar height growth was described by the 

following equation: 

[2] Htgrwrc

= β1*htβ2 *e (β3 *bal -(e (β4 +BAtot)*relht β5 ))

where Htgrwrc was height growth (m/4-yr), ht 

was initial height (m) and BAtot, BAL, and relht 

are as defined above. 

Height growth of redcedar in mixed stands with 

Douglas-fir is negatively correlated with total 

basal area in larger trees and positively 

correlated with initial height and relative height 

(table 1). However, the positive correlation with 

relative height diminishes as total stand basal 

area increases.

Although not specifically tied to above 

canopy light levels, figure 2 is 

consistent with findings that redcedar 

height growth is relatively unaffected 

by shading until light levels become 

very low (Carter and Klinka, 1992, 

Drever and Lertzmann 2001). 

Mortality 

Redcedar mortality was described by 

the following equation: 

[3] log (p/(1-p)) = 

 β0 + β1*dbh + β2*BAL+ 

β3*BAdf

 

where p= probability of mortality over 

the 4-yr growth period and all other 

variables are defined as above. The probability 

of mortality was negatively correlated with dbh, 

and positively correlated with basal area in 

BAdf = 20 m2

/ha

BAdf = 0 m2/ha

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1

Relative height

Multiplicative effect of DF on BAwrc growth

BAdf = 15 m2

/ha

BAdf = 25 

2

BAdf = 10 m2

/ha

Figure 1—Multiplicative effect of BAdf presence on WRC BA 

growth, by relative height, relative to pure redcedar

111
larger trees and Douglas-fir basal area (table 2). 

Mortality was greatest for the smallest and most 

suppressed trees, and particularly where 

suppressed by Douglas-fir. The four year 

mortality rate of redcedar trees with dbh=5 cm 

in a stand containing 20 m2

/ha of Douglas-fir 

was nearly 50%.

 

In mixed stands of Douglas-fir and redcedar, 

Douglas-fir is generally assumed to overtop the 

redcedar the shade tolerant redcedar is assumed 

to persist. The results from this analysis do not 

support this generalization, even when stands 

are only 20-25 yrs old. Although mortality is 

still relatively low for the larger size classes of 

trees, as these stands continue to develop, 

greater mortality rates can be expected for the 

larger redcedar size classes. Furthermore, 

although some of these trees may persist, their 

chances of reaching merchantable size classes 

at the rotation age of the more dominant 

Douglas-fir is low, as is likely their ability to 

release successfully from suppression if left 

after an overstory harvest.

Growth under different establishment mixes

Using the growth equations [1] and [2], the 

negative effect of 20 yr old Douglas-fir on the 

concurrent dbh growth of similarly-aged 

redcedar was assessed for 5, 15, and 25 cm 

redcedar dbh classes, and on height growth for 

5, 10, and 13 m ht classes.

Independent variables used in equations [1] and 

[2] were calculated or estimated for each 

redcedar size class and specific to each of the 

Douglas-fir densities (0, 62, 125, 250, 500, and 

750 TPH). Average covariate values for the 

three size classes in a pure redcedar 

stand were based on the two pure 

redcedar study plots. Average covariate 

values for these different size classes in a 

750 TPH Douglas-fir stand were based 

on SYSTUM-1 output, and was similar 

to measured values on the two study 

plots with the greatest density of 

Douglas-fir. Covariate values on the 

intermediate Douglas-fir density 

simulations were generally linear 

interpolations between the values 

estimated for pure redcedar and high 

Douglas-fir density plots. However, for 

the large redcedar size classes (25 cm 

dbh, 13 m ht), linear interpolation was 

sometimes inappropriate. For example, 

because relative height is based on 

subject tree height relative to the largest 

100 TPH, and because low density Douglas-fir 

can be expected to be larger in diameter than 

slower growing redcedar, relative height for all 

redcedar will always be based on top height of 

the dominant Douglas-fir. Furthermore, because 

large redcedar at these stand ages remain free to 

grow even at the highest densities measured on 

these study plots, the relative height of a 25 cm 

redcedar growing with 125 DF per ha will be 

the same as the same tree growing with 750 DF 

per ha. In other words, subjectivity was applied 

Table 2 -- Parameter estimates for eqns 1-3

Parameter Eqn [1] Eqn [2] Eqn [3]

β0 -4.0452

β1 1.00196 1.5472 -0.6005

β2 1.383 0.2471 0.4605

β3 -0.0492 -0.0314 0.1864

β4 -0.1002 -22.3198

β5 -10.9885 -10.1395

β6 -2.8269

Figure 3—Four yr mortality by tree size and competitive 

position. Based on a stand with BAdf= 20 m2/ha.

dbh = 5 cm

dbh= 7.5 cm

dbh = 10 cm

0

10

20

30

40

50

10 15 20 25 30 35

Basal area in larger trees (m2/ha)

Four year mortality (%)

112
62 DF/ha

125 DF/ha

250 DF/ha

500 DF/ha

750 DF/ha

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25

BAdf (m2

/ha)

Mult. effect of DF on WRC BA gr 

d = 25 cm

d = 15 cm

d = 5 cm

Figure 4—Multiplicative effect of BAdf on BAwrc growth, 

relative to pure redcedar for 5,15, and 25 cm size classes

in estimating independent variable values for the 

largest redcedar size classes. 

Figure 4 implies that with a relatively low 

density of Douglas-fir (125 tph), the relative 

basal area growth loss is independent of size 

class, amounting to approximately 30% relative 

to a pure redcedar stand. As Douglas-fir density 

increases beyond 125 tph, the large size class 

experiences less relative growth loss. At 750 

tph, basal area growth loss of the 25 cm size 

class is 70% and trees in the 5 cm size class are 

implied to have stopped growing in diameter. 

As with basal area growth, the implied negative 

effect of 125 Douglas-fir per ha on redcedar 

height growth is independent of size class (Fig. 

5). All of the negative effect on the 25 cm size 

class is implied to result from the first 100 

Douglas-fir per hectare. Increased Douglas-fir 

density is implied to have no additional 

negative effect—large redcedar within a young 

and dense even-aged plantation of Douglas-fir 

exist because they have had sufficient sunlight 

and space for crown expansion. At the highest 

DF densities, height growth of the 15 cm size 

class is still 80% of that expected in a pure 

redcedar stand, though 5 cm trees are implied 

to have stopped growing in height. This is 

consistent with results shown in figures 2 and 

3. 

Broader application of these results to other 

sites or regions may not be appropriate. These 

sites are very productive with high site indices. 

Comparison of site curves corresponding to 

the calculated site indices for each species 

implies that the height of a dominant redcedar 

without overstory competition would be about 

70% that of its dominant Douglas-fir 

counterpart on these sites. If on other sites the 

relative height development rates were more 

similar, redcedar performance could be expected 

to improve. 

The fact that these stands have developed in 

harvest units originally considered worthy of P. 

sulphurescens sanitation with a rotation of 

western redcedar raises questions about the 

broad applicability of these results to healthy 

sites. Whether or not these plots were installed 

in areas specifically identified as root rot centers 

is unknown. At this time, the Douglas-fir has 

shown no obvious signs of infection (thin 

crowns, slow growth, or mortality), suggesting 

that the trees are growing normally, and that 

results of the analysis can be applied outside of 

P. sulphurescens infected stands. 

These results are also likely to be affected by 

the distribution of trees within a stand. On the 

study sites from which these equations were 

constructed, the two species were generally 

interspersed. Clumped distribution would 

improve the relative performance of redcedar. 

62 DF/ha 125 DF/ha 250 DF/ha 500 DF/ha 750 DF/ha

0

0.2

0.4

0.6

0.8

1

1.2

17.5 20 22.5 25 27.5 30

Stand basal area (m2

/ha)

Mult. effect of BAdf on WRC htgr

h = 13 m

h = 10 m

h = 5 m

Figure 5—Multiplicative effect of BAdf on BAwrc growth, 

relative to pure redcedar for 5, 10, and 13 cm size classes

113
LITERATURE CITED

Bruce, D. 1981. Consistent height-growth and 

growth-rate estimates for

remeasured plots. For. Sci. 27:711-725. 

Carter, R.E.; Klinka, K. 1992. Variations in 

shade tolerance of Douglas-fir, western hemlock 

and western redcedar in coastal British 

Columbia. For. Ecol. Manage. 55: 87–105. 

Drever, C.R.; Lertzman, K.P. 2001. Lightgrowth responses of coastal Douglas-fir and 

western redcedar saplings under different

regimes of soil moisture and nutrients. Can. J. 

For. Res. 31: 2124–2133. 

Filip, G.; Kanaskie, A.; Kavanagh, K.; 

Johnson, G.; Johnson, G.; Maguire, D. 2000. 

Silviculture and Swiss needle cast: Research and 

recommendations. Research Contribution 30, 

Forest Research Laboratory, Oregon State 

University, Corvallis.

Hansen, E.M.; Stone, J.K.; Capitano, B.R.; 

Rosso, P.; Sutton W.; Winton L.; Kanaskie 

A.; McWilliams, M.G. 2000. Incidence and 

impact of Swiss needle cast in forest plantations 

of Douglas-fir in coastal Oregon. Plant Disease. 

84: 773–779. 

Kurucz, J.F. 1978. Preliminary polymorphic 

site index curves for western redcedar

Thuja plicata Donn in coastal 

British Columbia. MacMillan Bloedel

Ltd., Vancouver, B.C. For. Res. Note 3. 

Maguire D.A.; Kanaskie A.; Voelker W.; 

Johnson R.; Johnson, G. 2002. Growth of 

young Douglas-fir plantations across a gradient 

in Swiss needle cast severity. West. Jour. of Ap. 

For. 17: 86–95. 

Ritchie, M.W.; Powers R.F. 1993. User's guide 

for SYSTUM-1 (Version 2.0): A simulator of 

growth trends in young stands under 

management in California and Oregon. General 

Technical Report. PSW-GTR-147. Albany, CA: 

Pacific Southwest Research Station, Forest 

Service, US Department of Agriculture; 45p. 

114
1 Andrew Cockle is a graduate student at the University of Washington’s School of Forest Resources, PO Box 352100, 

Seattle, WA 98195. andrew.cockle@gmail.com. 2 Gregory J. Ettl is an Associate Professor and the Director of the Center for Sustainable Forestry at Pack Forest, 

University of Washington, School of Forest Resources, PO Box 352100, Seattle, WA 98195. ettl@u.washington.edu.

SURVIVAL AND GROWTH OF WESTERN REDCEDAR AND 

DOUGLAS-FIR PLANTED IN A VARIABLE RETENTION HARVEST 

UNIT IN THE WESTERN CASCADES, WASHINGTON

Andrew Cockle1 and Gregory Ettl2

ABSTRACT

The effects of light, brush control, and simulated herbivory on the growth and survival of planted 

western redcedar and Douglas-fir were investigated under variable overstory retention; a factorial 

combination of two spatial patterns (aggregated vs. dispersed) and two retention densities (25 and 49 

trees per ha) was used to vary light. Seedlings were planted and measured for initial height and stem 

diameter. Prior to budbreak, half of all seedlings were clipped, removing their terminal bud and 

emulating natural browse observed in adjoining stands. Prior to the onset of summer drought, half of all 

seedlings were mechanically weeded within a 0.5 meter radius. Seedling mortality and change in height, 

diameter and volume were assessed after the first and second growing seasons. First-year mortality 

differed by species, as western redcedar experienced almost double the mortality rate of Douglas-fir. 

Overstory treatment also affected mortality, with the greatest mortality occurring in the most exposed 

treatment and the least mortality occurring in the shadiest treatment. Growth rates differed between 

species, as western redcedar displayed less mean height growth and greater diameter growth after two 

years, but volumetric growth was similar for the two species. Clipping reduced diameter growth in both 

species, with western redcedar experiencing a greater reduction in diameter growth than Douglas-fir 

when clipped. Seedlings were sensitive to total understory cover, displaying an increase in height growth 

and a decrease in diameter growth as understory cover increased. Results suggest that both species can 

survive and grow when underplanted in a variable retention harvest site and also exposed to herbivory, 

and that weeding provides no immediate advantage for seedling growth or survival. Both species 

experienced the least mortality in the overstory treatment that provided the greatest shade, suggesting 

some shelterwood benefit may be conferred by retaining more trees in a dispersed spatial pattern. After 

the earliest stages of stand regeneration following a variable retention harvest, it appears that 

establishing a two-species cohort is possible. 

KEYWORDS: Douglas-fir, seedling herbivory, variable retention harvest, weeding, western redcedar. 

INTRODUCTION

In the Pacific Northwest, variable retention 

harvest treatments are being increasingly 

utilized to balance ecological management 

objectives with timber extraction (Franklin et al. 

1997). However, the effect of shade provided by 

retained trees on underplanted seedling growth 

and mortality remains unclear. Seedling death

and impaired growth may be caused by varying 

species response to low light (Carter and Klinka 

1992), competition with understory vegetation 

(Brandeis et al. 2001) and herbivory (Stroh et al. 

2008), leading to delayed establishment. These 

complications can be exacerbated when planting 

multiple species with differing life history 

strategies. Western redcedar (Thuja plicata

Donn ex D. Don) and Douglas-fir (Pseudotsuga 

menziesii (Mirb.) Franco) are two species that 

naturally occur in mixed stands throughout the 

western slope of the Cascades (Franklin and 

Dyrness 1988), but they differ in shade 

tolerance. Western redcedar often outperforms 

Douglas-fir in lower light levels (Carter and 

Klinka 1992, Drever and Lertzman 2001) but 

concerns about western redcedar being 

preferentially browsed by ungulate herbivores 

2010 - A Tale of Two Cedars PNW-GTR-828

115
(Maas-Hebner et al. 2005) may lead managers 

to forgo planting the species in mixed stands. 

The objectives of this experiment were to 

determine rates and potential causes of seedling 

mortality, and to quantify the effects of light, 

understory competition and browse on the 

growth of Douglas-fir and western redcedar 

seedlings in a variable retention harvest system. 

METHODS 

Study area

The study was conducted at Charles L. Pack 

Forest (latitude 46° 50’ 11” N, longitude 122° 

15’ 55” W) located within the Puget Sound area 

of Washington. The study site is a 19 ha stand 

located on a moderately-dissected south-tosoutheast facing slope (mean aspect = 142°, 

mean slope = 21%). Elevation ranges from 390-

575 m, with a mean elevation of 496 m. Site 

topography is influenced by four perennial or 

intermittent streams that flow roughly from 

north to south on the site, with channels creating 

steep side-slopes. The site has Wilkeson series 

soil (gravelly silt loam, mixed, mesic Ultic 

Haploxeralfs, Anderson 1955). Data collected 

from a weather station at Pack Forest shows an 

average daily temperature of 9°C and average 

annual precipitation of 970 mm for the years 

1998-2008. 

The study site is located within the Tsuga 

heterophylla [Raf.] Sarg. Zone described by 

Franklin and Dyrness (1988). The upland forest 

is dominated by Douglas-fir, with black 

cottonwood (Populus balsamifera ssp. 

trichocarpa) and red alder (Alnus rubra) 

present. Understory vegetation is dominated by 

trailing blackberry (Rubus ursinus), salal 

(Gaultheria shallon) western sword fern 

(Polystichum munitum) and low Oregon grape 

(Mahonia nervosa). Weedy invasive species 

(native and non-native) such as stinging nettle 

(Urtica diocia) bull thistle (Cirsium vulgare) 

and foxglove (Digitalis purpurea) are present on 

the site, as well as rushes (Juncus spp.) and 

sedges (Carex spp.) on mesic portions of the site 

in local concavities (Pojar and MacKinnon 

1994). 

The stand is dominated by an 80 year-old cohort 

of Douglas-fir that was treated with biosolids in 

the 1980’s, commercially thinned, and harvested 

in 2007 for a regeneration cut leaving variable 

retention, with target residual densities of 25 

and 49 trees per hectare, in spatial arrangements 

of dispersed and aggregated. In December 2007, 

equal numbers of western redcedar and 

Douglas-fir seedlings were planted across the 

site at a density of 740 trees per hectare. Sixteen 

plots were subjectively established using a stem 

map to meet designated overstory densities (25 

and 49 trees per hectare) within the plot, and all 

seedlings were placed in Vexar® tubes (8 cm 

diameter × 80 cm height) to prevent natural 

browse from local populations of black-tailed 

deer (Odocoileus hemionus) and elk (Cervus 

elaphus).

Experimental Design 

The experiment utilized a factorial split-plot 

combination of four overstory treatments (high 

vs. low density, aggregated vs. dispersed spatial 

arrangement), within which four quarter-hectare 

(2500 m2

) plots were established, creating a 

total of sixteen plots. Within each plot, 92 

western redcedar and 92 Douglas-fir seedlings 

were tagged to track first-year growth and 

mortality (N = 2944). Additionally, within each 

plot, 20 western redcedar and 20 Douglas-fir 

seedlings were randomly selected to collect 

measurements of light, soil moisture, understory 

cover, and second-year growth at the seedling 

level (N = 640). 

All seedlings were randomly selected for a 

combination of two different treatment factors: 

clipping (to simulate natural browse) and 

weeding (to reduce competition with understory 

plants); weeding reduced mean understory cover 

by 35% (p < 0.0001). Seedlings were clipped in 

the spring of 2008 prior to budbreak to mimic 

natural herbivory by deer and elk observed in 

adjacent stands, removing 50% and 25% of the 

mean leader length for western redcedar and 

Douglas-fir respectively. Understory cover was 

assessed for a subsample (N = 640) of seedlings, 

with all species located within a 0.5 m radius of 

selected seedlings being identified and their 

116
Figure 1. Percent seedling mortality in the first year 

after planting by overstory treatment. White bars = 

western redcedar, hatched bars = Douglas-fir.

cover measured to the nearest 5% (after two 

years, weeding reduced mean understory cover 

by 6%, p = 0.014). 

Seedlings were assessed for growth and 

mortality in January 2009 (at the end of the first 

growing season) and October 2009 (at the end 

of the second growing season). Seedling height 

was measured from the root collar at ground 

level to the tallest living element of the plant to 

the nearest 0.5 cm. Seedling diameter was 

measured 7 cm above the root collar to the 

nearest 1.0 mm. From height and diameter, 

volume was calculated using the geometric 

formula for a cone: 

Hemispherical photographs taken above 

seedlings were used to determine total 

transmitted light in moles per m2

 per day when 

processed with Gap Light Analyzer software 

(Frazer et al. 1999). These photographs capture 

canopy architecture, and results indicate each 

overstory treatment has a unique light 

environment (p-values < 0.001 for all pairwise 

comparisons with Tukey HSD). The least mean 

transmitted light is found in the high 

retention/dispersed treatment (32.53 

moles/m2/day) and the greatest transmitted light 

found in the low retention/aggregated treatment 

(38.95 moles/m2/day).

Statistical Analysis

The effect of overstory treatment, clipping and 

weeding on mortality was analyzed with a logitlinked generalized linear model (GLM) 

incorporating species as a term in the model. 

Logit-linked GLMs assume that the models can 

be expressed as a linear function of the model 

parameters and that the errors are independent 

and from the binomial family of distributions.

The effect of treatments on growth was 

analyzed using a linear mixed model, with

overstory treatment, weeding and clipping being 

fixed factors and plot being a random factor 

nested within overstory treatment. In our study, 

seedlings can be expected to display within-plot 

correlation of response variables (height, 

diameter and volumetric growth) due to 

geographic heterogeneity naturally present 

within the study area. Linear mixed models 

account for the correlation of observations by 

presuming that the random effects (in this case, 

plot) are unknown but are randomly generated 

from some normal distribution with mean zero. 

Hypothesis tests were conducted using ANOVA 

with Type II sums of squares; change in height 

and change in volume were log-transformed for 

hypothesis testing.

RESULTS 

Mortality

There was a significant difference in first-year 

mortality between species, with western 

redcedar having a mortality rate of 27.8% and 

Douglas-fir having a mortality rate of 13.4% (p

< 0.0001). Overstory treatment had a significant 

effect on mortality (p = 0.0082), with greatest 

mortality in the low retention/aggregated 

treatment (30.9% for western redcedar, 16.2% 

for Douglas-fir, Fig. 1) and the least mortality in 

the high retention/dispersed treatment (24.3% 

for western redcedar, 4.8% for Douglas-fir). 

First year seedling mortality was unaffected by

117
weeding (p = 0.93) and clipping (p = 0.80). 

Second year mortality was very low (0 dead 

western redcedar, 4 dead Douglas-fir) but there 

was a significant difference in mortality rate 

between the two species (p = 0.0006). No 

statistical differences existed in mortality for 

overstory treatments, clipping, or weeding. 

Growth

There was a significant difference in two-year 

height growth between western redcedar and 

Douglas-fir (p < 0.0001) with western redcedar 

averaging 21.92 cm to Douglas-fir’s 24.73 cm. 

Overstory treatment (p = 0.0759), weeding (p = 

0.0519) and clipping (p = 0.1232) had no-tomarginal significance on seedling height 

growth, and there were no significant 

interactions between species, overstory 

treatment, clipping and weeding. First-year 

understory cover had a significant effect on twoyear height growth (p = 0.0260), with a slight 

positive correlation. 

Two-year diameter growth was significantly 

different between species (p = 0.0169) with 

western redcedar averaging 3.62 mm radial 

growth over two years and Douglas-fir 

averaging 3.23 mm. Overstory treatment had a 

significant effect on diameter growth (p = 

0.0241) and diametric growth in the high 

retention/aggregated treatment (average 2.96 

mm) was significantly different from growth in 

both the high retention/dispersed treatment 

(average 3.63 mm, p = 0.019) and the low 

retention/dispersed treatment (average 3.71 mm, 

p = 0.008). Clipping had a significant effect on 

two-year diameter growth (p = 0.0003), with 

both species showing reduced diameter growth 

when clipped. There was a significant 

interaction between clipping and species (p = 

0.0447), with clipped western redcedar showing 

an overall reduction of 0.96 mm in two-year 

diameter growth as opposed to unclipped 

western redcedar (Fig. 2). First-year understory 

cover had a significant effect on two-year 

diameter growth (p = 0.0154), with a slight 

negative correlation. 

Overstory treatment had a significant effect on 

volumetric growth (p = 0.0074) and volumetric 

growth in the high retention/aggregated 

treatment (average = 14.48 cm3

) was 

significantly different from both the high 

retention/dispersed treatment (average = 19.45 

cm3

, p = 0.0308) and the low retention/dispersed 

treatment (average = 19.94 cm3

, p = 0.0170, Fig. 

3). Clipping treatment also had a significant 

effect on volumetric growth (p < 0.0001) with 

clipped seedlings of both species averaging 

15.29 cm3 of two-year volumetric growth and 

unclipped seedlings averaging 20.00 cm3 of 

two-year volumetric growth. There was a 

significant interaction between clipping and 

species (p = 0.0213) with clipped western 

redcedar showing a marked decrease in volume 

(23.02 cm3

 unclipped, 16.39 cm3 clipped). There 

was no significant different in two-year 

volumetric growth between species (p = 0.8098) 

or by weeding treatment (p = 0.8131). 

DISCUSSION

Differences existed between Douglas-fir and 

western redcedar mortality, height growth and 

diameter growth, but not volumetric growth. In 

the first year following planting, western 

redcedar died at nearly twice the rate as 

Douglas-fir; however, by the second year, both 

species had mortality rates below 1%. From an 

operational perspective, mortality rates of 

27.8% for western redcedar and 13.4% for 

Douglas-fir seem to be high, it is not 

unprecedented. Brandeis, et al. (2001) reported 

a first year loss of 40-80% of Douglas-fir and 2-

15% of western redcedar when underplanted in 

evenly thinned stands, with mortality increasing 

for both species as overstory density increased. 

The authors attributed this high mortality to 

desiccation of roots due to cold, windy weather 

at the time of planting. 

The overstory treatments that provided the most 

shade/least transmitted light had the least 

mortality. Namely, the high retention/dispersed 

treatment had the lowest mean transmitted light 

and the least mortality for both species, while 

the low retention/aggregated treatment had the 

greatest transmitted light and the highest 

118
mortality rate for both species. There are two 

possible ways to interpret this: 1) reduced 

transmitted light leads to a shelterwood effect 

where overstory trees ameliorate site conditions, 

allowing for greater seedling survival, or 2) 

hydraulic redistribution from retained overstory 

trees assists in seedling survival during summer 

drought. 

When averaged across all treatments, western 

redcedar experienced less height growth and 

greater diameter growth than Douglas-fir, but 

there was no difference in volumetric growth. 

This could be attributed to the greater intensity 

clipping treatment given to western redcedar in 

order to mimic natural herbivory; however, in 

terms of volume growth, there is little difference 

between the two species after two years, as 

western redcedar allocated more carbon to 

diameter growth and less to height growth. 

Western redcedar were more sensitive to the 

clipping treatment, experiencing a significantly 

greater reduction in diameter and volume 

growth when clipped than Douglas-fir. So, 

while clipping does not statistically affect 

western redcedar mortality, clipped individuals 

grew less vigorously. 

Regardless of species, competition with 

understory plants had an effect on seedling 

growth. As first-year understory cover 

increased, seedlings tended to grow taller, with 

thinner stems. There was no effect of understory 

cover on volumetric growth, suggesting 

seedlings allocate more carbon to height growth 

as surrounding vegetation increases. There may 

be a competitive advantage in increased height 

growth as brush increases, allowing the seedling 

to overtop the understory vegetation. 

Western redcedar and Douglas-fir exhibit 

equally vigorous post-harvest growth after two 

years in a variable retention setting, albeit with 

differing growth patterns. While western 

redcedar experienced much greater initial 

mortality, second-year mortality was very low, 

and seedlings that survive in the post-planting 

environment should be expected to continue to 

live until density-dependent mortality begins to 

take effect. This experiment also demonstrates 

after two years, Douglas-fir can grow as well or 

better in shade than in open positions. Future 

monitoring of seedling mortality and growth in 

this site should continue to provide insight into 

relative growth rates of the two species in a 

varying light environment, as well as the 

potential for establishing a multi-species, multicohort stand. 

LITERATURE CITED

Anderson, W.W. 1955. Soil survey, Pierce 

County, Washington. Washington: US Govt. 

Print Office.

Brandeis, T.J.; Newton, M.; Cole, E.C. 2001.

Underplanted conifer seedling survival and 

growth in thinned Douglas-fir stands. Can. J. 

For. Res. 31: 302-312. 

Carter, R.E.; Klinka, K. 1992. Variation in 

shade tolerance of Douglas fir, western hemlock 

and western red cedar in coastal British 

Columbia. For. Ecol. Man. 55: 87-105. 

Drever, C.R.; Lertzman, K.P. 2001. Lightgrowth responses of coastal Douglas-fir and 

western redcedar saplings under different 

regimes of soil moisture and nutrients. Can. 

Jour. For. Res. 31: 2124-2133. 

Franklin, J.F.; C.T. Dyrness. 1988. Natural 

Vegetation of Oregon and Washington. Oregon 

State University Press. Corvallis, OR. 452 p. 

Franklin, J.F.; Berg, D.R.; Thornburg, D.A.; 

Tappeiner, J.C. 1997. Alternative Silvicultural 

Approaches to Timber Harvesting: Variableretention Harvest Systems. From: Creating a 

Forestry for the 21st Century: The Science of 

Ecosystem Management. Island Press, 

Washington D.C. 111-139 

Frazer, G.W.; Canham, C.D.; Lertzman K.P. 

1999. Gap Light Analyzer (GLA): Imaging 

software to extract canopy structure and gap 

light transmission indices from true-colour 

fisheye photographs, users manual and program 

documentation. Simon Fraser University, 

119
Burnaby, British Columbia, and the Institute of 

Ecosystem Studies, Millbrook, New York. 

Maas-Hebner, K.G.; Emmingham, W.H.; 

Larson, D.J.; Chan, S.S. 2005. Establishment 

and growth of native hardwood and conifer 

seedlings underplanted in thinned Douglas-fir 

stands. For. Ecol. Man. 208: 331-345. 

Pojar, J.; MacKinnon, A. 1994. Plants of the 

Pacific Northwest Coast. Lone Pine Publishing, 

Auburn, WA. 

Stroh, N.; Baltzinger, C.; Martin, J. 2008. 

Deer prevent western redcedar (Thuya Plicata) 

regeneration in old-growth forests of Haida 

Gwaii: Is there a potential for recovery? For. 

Ecol. Man. 255: 3973-3979 

Figure 2. Mean two-year change in height, diameter and volume (± 1 S.E.) for western redcedar and Douglas-fir 

by weeding and clipping treatment. Because there were no significant interactions for weeding and clipping, all 

values represent aggregate data for indicated treatment only.

Figure 3. Mean two-year change in height, diameter and volume (± 1 S.E.) for western redcedar and Douglas-fir 

by overstory treatment.

0.00

5.00

10.00

15.00

20.00

25.00

30.00

Not weeded Weeded Unclipped Clipped Not weeded Weeded Unclipped Clipped

western redcedar Douglas-fir

Change in Height (cm) Change in Diameter (mm) Change in Volume (cm3)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

high 

retention 

dispersed

low 

retention 

dispersed

low 

retention 

aggregated

high 

retention 

aggregated

high 

retention 

dispersed

low 

retention 

dispersed

low 

retention 

aggregated

high 

retention 

aggregated

western redcedar Douglas-fir

Change in Height (cm) Change in Diameter (mm) Change in Volume (cm3)

120
1 Clare Kooistra is a forest nursery and regeneration specialist with Conifera Consulting, 1-6916 Manning Place, Vernon, BC 

Canada, V1B 2Y5. Email: cmkooistra@shaw.ca. 2 Jon Bakker is an Assistant Professor in the School of Forest Resources, University of Washington, Box 354115, Seattle, WA 

98195-4115. 3 Patience Rakochy is a Nursery Services Forester with Nursery Services Interior (North), Ministry of Forests and Range, 2000 

South Ospika Blvd, Prince George, BC Canada V2N 4W5

TEN-YEAR PERFORMANCE OF YELLOW CEDAR AND INTERIOR 

SPRUCE IN SOUTHERN INTERIOR BRITISH COLUMBIA, 

CANADA 

Clare Kooistra1, Jonathan D. Bakker2, and Patience Rakochy3

ABSTRACT

Though common on the coast, yellow cedar (Chamaecyparis nootkatensis (D. Don) Spach.) (Yc) occurs 

naturally in two isolated pockets in the Slocan Valley of the BC Southern Interior. A trial was 

established in the Monashee Mountains to compare the survival and performance of Yc cuttings from 

one of these sources with that of interior spruce (Picea glauca [Moench] Voss, Picea engelmannii Parry, 

and their naturally occurring hybrids) (Sx) seedlings. Trees were planted in the spring of 1999 on a 1580 

m elevation site on Currie Ridge and tracked through their tenth growing season. Survival was initially 

lower for Yc, but after 10 years averaged 86% and did not differ between species. Although Sx seedlings 

were shorter at planting, they grew more rapidly. After ten years, Sx are larger than Yc in height, 

ground-level diameter, and stem volume. Yc exhibit more signs of browse and of stem damage, while Sx 

exhibit more signs of chlorotic foliage and insect damage to foliage. Whether one species is better than 

the other depends on the objectives for which a stand is being managed. Sx is a common species across 

the landscape, while Yc provides important diversity. Trends at this site are comparable to those at high 

elevation plantations on the BC Coast. Yc may provide another reforestation option to the moist ESSF 

zone of Southern Interior BC. 

KEYWORDS: Silviculture, survival, growth, reforestation, yellow cedar, interior spruce 

INTRODUCTION

Yellow Cedar (Yc) occurs in two isolated 

pockets in the Slocan Valley of the BC Southern 

Interior. The objective of this trial was to 

explore the possibility of increasing the role of 

Yc in silviculture and reforestation within the 

ICH and ESSF biogeoclimatic zones of southern 

interior BC. Yc cuttings were obtained from 

wild seed and cuttings obtained at one of these 

sites, Dago Creek. Yc performance was 

compared with that of Interior Spruce (Sx). This 

report focuses on performance during the first 

ten growing seasons after outplanting. 

METHODS 

The source material used in this study was Yc 

cuttings from cutting lot V0327 (cutting hedge 

established from wild seed and cuttings) and Sx 

seed from seedlot 06015 (1st generation seed 

orchard seed).

The trial was established at Currie Ridge 

(50o15’14” N 118o26’43” W) in the Monashee 

Mountains. The site is at 1585 m elevation, and 

is in the ESSF WC2 series 01 biogeoclimatic 

zone. 

Seedlings and cuttings were planted in Spring 

1999 in an alternating pattern within 4 four 

blocks. Each block contained 10 rows, and each 

row contained 50 trees (25 per species). In total, 

2000 trees were planted, 1000 Sx and 1000 Yc. 

In our analysis, we assumed that blocking 

occurred on the basis of blocks and rows (40 

block/row combinations). 

2010 - A Tale of Two Cedars PNW-GTR-828

121
Table 2—Proportion of live trees with chlorotic 

foliage (FC), vegetation / snow / debris press (VP), 

broken or dead top leaders (TD), insect-damaged 

foliage (FI), browse or broken branches (BR), and 

stem damage by unknown agents (SX) in Spring 

2009. Species data are averaged across blocks/rows.

Species FC VP TD FI BR SX

Sx 4 10 6 21 <1 3

Yc <1 6 3 1 17 7

Overall 2 8 4 11 2 5

122

Survival was measured in Fall 1999 and Fall 

2000, and tree survival and condition were 

measured in Fall 2003 (end of the fifth field 

season) and Spring 2009 (start of the eleventh 

field season). Stem and foliage faults (broken 

stems, chlorotic foliage, etc.) were recorded in 

Fall 2003 and Spring 2009. These categorical 

variables were analyzed using Cochran-MantelHaenszel tests to test for a relationship between 

the factor (species) and variable of interest after 

accounting for differences in another factor 

(block/row). Analyzed variables included 

survival, condition (live trees only), and various 

types of foliage damage and growth form 

differences, including the presence of multiple 

leaders (forks initiated during the year of 

measurement) and multiple stems (forks 

initiated two or more years earlier).

Growth data (stem height and ground-level 

diameter) were monitored at planting and in Fall 

1999, Fall 2000, Fall 2003, and Spring 2009. 

Four growth characteristics (height, groundlevel diameter (GLD), height:diameter ratio 

(HDR), stem volume) were analyzed. HDR was 

calculated as height/GLD, and stem volume 

using the formula for a cone. Height and stem 

volume increments were calculated as the value 

in one measurement minus the measurement in 

the previous measurement. Due to the large 

differences in diameter over time, diameter 

growth was calculated as the basal area 

increment between two measurements. 

Increments and final (Spring 2009) values were 

analyzed using ANOVA. All surviving trees 

were included in these analyses, with α = 0.05.

RESULTS 

Survival was higher for Sx than Yc after one 

(99.3 vs 93.6%), two (96.0 vs 90.8%), and five 

growing seasons (92.1 vs 87.8%). However, 

survival after ten growing seasons did not differ 

between species (86.1 vs 86.3%) (Table 1). 

Sx trees were in slightly better condition than 

Yc trees after five and ten growing seasons. 

However, these differences were diminishing; 

>90% of surviving trees of both species were in 

‘Good’ or ‘Average’ condition after ten growing 

seasons (Table 1).

Several types of foliage and stem damage 

differed between species in Spring 2009 (Table 

2). Sx exhibited more chlorotic foliage, 

vegetation press, dead or broken tops, and insect 

(aphid) damage to foliage. Yc exhibited more 

signs of browse and of stem damage by 

unknown agents. This stem damage often 

appeared to be due to branches being stripped 

off by snow and ice during the winter and/or to 

deer using the stems as rutting posts.

The proportion of trees with multiple leaders 

averaged < 1%, and the proportion with 

multiple stems averaged 3% (Table 3).

Yc cuttings were taller than Sx seedlings at 

planting, but did not grow as rapidly and were 

shorter by the end of the first growing season 

after planting. Sx continued to be taller 

throughout the trial, and this difference has 

increased over time (Fig. 1A). Height 

increments differed between species in all years 

except 2000. 

Sx seedlings had larger GLD at planting, and 

this difference increased during the first 10 

growing seasons (Fig. 1B). Basal area growth 

Table 1—Percent mortality and percentage of live 

trees in each condition class in Spring 2009. Species 

data are averaged across blocks/rows.

Species Live Trees Mortality

Good 

(4)

Average 

(3)

Poor 

(2)

Likely 

to Die 

(1)

Sx 44 50 5 <1 13.9

Yc 43 47 9 <1 13.7

Overall 44 49 7 <1 13.8
increments were larger for Sx than Yc in all 

measurement intervals. In terms of basal area, 

Sx seedlings were 11% larger than Yc cuttings 

at planting, 42% larger after 5 years, and 146% 

larger after 10 years. 

Sx seedlings had smaller HDRs (ie, were shorter 

for a given GLD) at planting, but higher HDRs 

after one and two growing seasons (Fig. 1C). 

HDR did not differ between species after five 

growing seasons, but Sx again had smaller 

HDRs after 10 growing seasons. 

Stem volume did not differ between species at 

planting, but Sx seedlings grew faster than Yc 

already in the first year and were larger 

throughout the first ten growing seasons after 

planting (Fig. 1D). Compared to Yc, Sx trees 

averaged 25% larger stem volumes after one 

growing season, 63% after five growing 

seasons, and 212% larger after 10 growing 

seasons.

DISCUSSION

After ten growing seasons in the field, the 

growth differences between Sx and Yc are 

increasing. Species are exhibiting different types 

of foliage and stem damage, and growth of Yc 

lags that of Sx considerably. However, ten-year 

survival does not differ between the species. 

Whether one species is better than the other 

depends on the objectives for which a stand is 

being managed. For example, Yc provides 

important diversity while Sx is a common 

species across the landscape. Since Yc is 

holding its own in terms of survival, it appears 

that it will be able to form crop trees at rotation 

0

30

60

90

120

150

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Date

A) Tree Height (cm)

Figure 1—Tree height, ground-level diameter, height: diameter ratio, and stem volume (mean ± SD) for 

Sx and Yc at planting and after one, two, five, and ten growing seasons.

0

2

4

6

8

10

12

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Date

Sx

Yc

C) Height: Diameter Ratio

0

10

20

30

40

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Date

B) Ground-level Diameter (mm)

0

100

200

300

400

500

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Date

D) Stem Volume (cm3

)

Table 3—Proportion of live trees with various 

numbers of leaders (shoots originating during 

previous growing season) or stems (shoots 

originating two or more growing seasons earlier, 

including basal forks) in Spring 2009. Species data 

are averaged across blocks/rows.

Number of Leaders Number of Stems

Species 1 2-3 ≥ 4 1 2-3 ≥ 4

Sx 99 <1 <1 98 2 <1

Yc 100 - - 96 3 <1

Overall 99 <1 <1 97 3 <1

123
age, although of a smaller log size than Sx. 

To determine if the performance differences that 

we observed are typical, we searched for other 

long term reforestation studies that involve Yc. 

We were unable to find published information 

from other trials in interior BC, though Yc is 

currently being tested in the ICH biogeoclimatic 

zone around Revelstoke (J. Russell and R. Mohr 

– personal communication). 

A few coastal trials have included Yc. Scagel et 

al. (1989) compared the ten-year performance of 

a number of high elevation species, including 

Yc and Engelmann spruce (Se; part of the Sx 

complex). The comparison is not ideal, as their 

four sites are located on the southern coast 

within the normal range of Yc, and are at lower 

elevations (1030-1200 m) than our site. In 

addition, their study involved spring and autumn 

planting dates along with a wide range of 

stocktypes (e.g., 2+0 Br, 2+0 PSB415, 1+0 

PSB211). Finally, some methodological details 

differed between studies; for example, we 

measured diameter at ground level while they 

measured it at 30 cm height. Nonetheless, it is 

instructive to put our results in the context of 

these sites.

Currie Ridge is less productive than the coastal 

sites (Fig. 2). Mortality is about equal between it 

and the furthest inland coastal sites (Railway 

and Chipmunk Creeks). Mean tree heights were 

taller for Sx than Yc at two coastal sites. Sx 

consistently had larger diameters than Yc. 

Coastal sites reported many more problems with 

multiple stems, particularly for Yc, though this 

diminished as elevation increased. Over all, it 

seems that Yc is performing as expected relative 

to Sx.

Scagel et al. (1989) concluded that Yc was 

questionable for regenerating high elevation 

sites because it was much more prone to faults, 

particularly stem sweep and forks. However, 

these differences between Yc and other species 

were less pronounced at the higher elevation 

(more inland) sites. In comparison, Currie Ridge 

is at a much higher elevation and has a shorter 

growing season but also experiences less snow 

Figure 2—Comparison of ten-year data from four coastal sites with our site at Currie Ridge: tree height, 

diameter, mortality, and percentage of trees with multiple stems. Sites are arranged in order of increasing 

elevation (increasing inland influence). Coastal site data were extracted from Scagel et al. (1989). Note that 

diameter was measured at 30 cm for the coastal sites but at ground level for Currie Ridge.

0

50

100

150

200

Mt.

Elphinstone

Statlu

Creek

Railroad

Creek

Chipmunk

Creek

Currie

Ridge

A) Tree Height (cm)

0

10

20

30

40

50

Mt.

Elphinstone

Statlu

Creek

Railroad

Creek

Chipmunk

Creek

Currie

Ridge

B) Diameter (mm)

0

10

20

30

40

50

Mt.

Elphinstone

Statlu

Creek

Railroad

Creek

Chipmunk

Creek

Currie

Ridge

Sx

Yc

C) Mortality (%)

0

10

20

30

40

50

Mt.

Elphinstone

Statlu

Creek

Railroad

Creek

Chipmunk

Creek

Currie

Ridge

D) Multiple Stems (%)

124
press, so these types of differences between 

species were minimal (Tables 2 and 3).

Another study compared the performance of Yc 

with other species (though not Sx) at multiple 

coastal sites for up to 20 years after outplanting 

(Arnott and Pendl 1994; Burgess et al. (2003) 

Yc outperformed other species at some sites, but 

was susceptible to breakage from heavy snows. 

Performance once again exceeded that at Currie 

Ridge.

A third study compared the performance of Yc 

and other species grown in different silvicultural 

systems, and concluded that Yc performed 

better in green tree and patch cut treatments than 

in clearcuts (Mitchell and Koppenaal 2006). 

The performance difference between Yc and Sx 

could also be due in part to the use of seedlings 

versus cuttings. Hennon et al. (2009) reported 

larger height and diameter in seedlings of Yc as 

compared to cuttings. 

Yc populations generally exhibit significant 

levels of inbreeding, and the interior population 

of Yc is genetically distinct from those on the 

coast (Ritland et al. 2001). This may also 

account for some lower performance in the Yc 

in our study, though a detailed genetic analysis 

of this population was obviously beyond the 

scope of this trial. Recently, the two interior 

populations of Yc have been crossed and new 

seed and cutting material are now available 

from these crosses. Use of this material is 

recommended.

CONCLUSIONS

The results of this 10-year study show that 

yellow-cedar is an interesting and acceptable 

species choice in the ESSF zone in southern 

interior BC. Older coastal stands of Yc in 

southern Alaska and northern BC have 

experienced severe decline (Hennon and Shaw 

1997). Therefore, use of Yc as an alternative 

species in reforestation in the BC southern 

interior and especially further north, should be 

tempered with some caution. At this time we do 

not know if it is appropriate to reforest areas 

outside the southern interior moist mountain 

environments with Yc.

This study should be followed for another 10 

years to track performance now that the stand is 

at free-growing and is reaching heights above 

the depth of the winter snow pack. In addition, 

the other Yc plantations in the BC southern 

interior should be examined for performance. 

While these may not have been planted in trial 

design, observations on them would be useful to 

determine the wider application of the results 

presented in this study. 

ACKNOWLEDGMENTS 

This trial was designed and installed by Sue 

Matovich of the Vernon Forest District, 

Ministry of Forests and Range; we are indebted 

to her for her efforts on this study in the early 

years. Wendy Clarke assisted with the repeated 

measurements of this trial. We thank Stephen 

Joyce for his direction and support to 

accomplish the latest measurement. Funding 

support for this study by the Ministry of Forests 

and Range, BC Timber Sales, Nursery Services 

Section is gratefully acknowledged.

LITERATURE CITED

Arnott, J.T.; Pendl, F.T. 1994. Field 

performance of several tree species and stock 

types planted in montane forests of coastal 

British Columbia. Information Report BC-X347. Victoria, BC: Natural Resources Canada, 

Canadian Forest Service, Pacific Forestry 

Centre. 45 p. 

Burgess, D; Mitchell, A. K.; Goodmanson, G. 

2003. Twenty-year assessment of four species 

planted in the mountain hemlock zone of coastal 

British Columbia. For. Chron. 79:280-284. 

125
Hennon, P. E.; Shaw III, C. G. 1997. The 

enigma of yellow-cedar decline: what is killing 

these long-lived, defensive trees? J. For. 95:4-

10. 

Hennon, P.E.; McClellan, M.H.; Spores, S.R.; 

Orlikowska, E.H. 2009. Survival and growth of 

planted yellow-cedar seedlings and rooted 

cuttings (stecklings) near Ketchikan, Alaska. 

West. J. Appl. For. 24:144-150. 

Mitchell, A.K.; Koppenaal, R. 2006.

Outplanting performance of western redcedar, 

yellow-cedar and Douglas-fir in montane 

alternative silvicultural systems (MASS). 

Technology Transfer Note 34. Victoria, BC: 

Natural Resources Canada, Canadian Forest 

Service, Pacific Forestry Centre. 4 p.

Ritland, C.; Pape, T.; Ritland, K. 2001.

Genetic structure of yellow cedar 

(Chamaecyparis nootkatensis). Can. J. Bot. 

79:822-828. 

Scagel, R.; Green, B.; von Hahn, H.; Evans, 

R. 1989. Exploratory high elevation 

regeneration trials in the Vancouver Forest 

Region: 10-year species performance of planted 

stock. FRDA Report 098. Victoria, BC: BC 

Ministry of Forests. 40 p.

126
20 YEARS GROWING CEDAR: A SILVICULTURE FORESTER’S 

EXPERIENCE

Rudi van Zwaaij1, RPF

ABSTRACT

My presentation will focus on 20 years of experience as a forester establishing and growing western 

redcedar on the upper Sunshine Coast in BC. The potential for increased yields of growing Yellow cedar 

will also be touched on briefly. Western redcedar is an exciting species that will be in short supply in the 

future and will fetch a substantially higher increase in log value over more common species

The presentation will include discussion on suitable ecosystems, considerations in the establishment of 

western redcedar, elk impacts and successful strategies in mitigating these impacts, and growth and yield 

data. The presenter will discuss that the potential for successfully growing western redcedar is affected 

by the lack of collaboration between government agencies and the lack of investment from government 

in forest management beyond the free growing declaration. 

1 Silviculture Forester, WFP, Stillwater Forest Operation, 201-7373 Duncan Street, Powell River, BC, V8A 1W6, 

rvanzwaaij@westernforest.com

2010 - A Tale of Two Cedars PNW-GTR-828

127
SIZE HIERARCHY DEVELOPMENT IN JUVENILE WESTERN 

REDCEDAR (THUJA PLICATA) STANDS COMPARED TO

WESTERN HEMLOCK (TSUGA HETEROPHYLLA) 

Roderick W. Negrave1

ABSTRACT

Size hierarchies describe size variability within populations and offer insight into inter-plant relations 

and factors influencing stand development. Factors influencing size hierarchy, including density and 

nutrient regime, are poorly understood but are important for understanding how diversity develops in 

stands. This study examined the effects of fertilization, planting density, and site on the development of 

size hierarchies in juvenile western redcedar (cedar) and western hemlock (hemlock) stands on northern 

Vancouver Island.

A factorial experiment was established in 1988 to examine the effects of: NPK fertilization versus nonfertilized; three establishment densities of 500 stems per ha (sph), 1500 sph and 2500 sph; the two 

species; and two sites: Nutrient-poor cedar-hemlock (CH) and nutrient-medium hemlock-amabilis fir 

(Abies amabilis) (HA) sites. The experiment was measured for heights and diameters seven times 

between 1988 and 2002. Predictive equations for biomass were developed to determine tree- and standlevel biomass estimates. Gini’s “G” coefficient was used to quantify size hierarchies (structural 

diversity) within stands. Development of size hierarch in treatments was analyzed over the 15-year 

period of stand development for size and biomass variables to determine the effect of site, fertilization 

and density. Analysis was completed using PROC GLM in SAS (p<0.05). 

Fertilization reduced size hierarchies i.e. made stands more uniform, by increasing the size smaller 

individuals, not by increasing their mortality, which is surprising. Density generally did not influence 

size hierarchy development, although there was a weak trend for more uniformity with increasing 

density. Size hierarchy varied with site and species: The species with the greater growth response had 

least diverse size structure on each site. Our results indicate that: Redcedar will tend to produce more 

structurally diverse stands than hemlock on sites with medium, but not poor, nutrient supply; 

fertilization reduces stand diversity; and increased soil resource availability does not promote structureincreasing competition.

1 Coast Forest Region, Ministry of Forests and Range, 2100 Labieux Rd., Nanaimo, BC, V9T 6E9 

2010 - A Tale of Two Cedars PNW-GTR-828

128
INFLUENCE OF N AND P SUPPLY ON ROOTING OF YELLOW 

CEDAR (CHAMAECYPARIS NOOTKATENSIS) CUTTINGS FOR 

PLANTING STOCK PRODUCTION

R. van den Driessche1 and J. Russell2

ABSTRACT

Yellow cedar is a valuable timber species, and reforestation is almost totally with rooted cuttings. 

Selected elite clones are used to provide cuttings to commercial nurseries where they are then grown 

into planting stock. Difficulties with rooting and growth of the cuttings encountered by the nurseries 

prompted work to see if changes in nutrient supply to the elite clones would influence the production of 

planting stock. 

Effect of amount and timing of N and P fertilizer applications to greenhouse grown hedged stock plants 

was examined in relation to size and survival of cuttings produced in two experiments. 

In the first experiment cutting production was from potted hedge plants of two kinds: (1) 2-year old 

hedges from 9-year-old serially propagated and selected material, and (2) 4-year old seedlings from wild 

stands. The peat vermiculite growth medium was uniformly fertilized when prepared, but during the 

experimental growing season applications of N (as Polyon 44-0-0, with a release time of 10 weeks) and 

P (as H3PO4) were made on 4 September (early) or on 1 November (late), or on both dates. Nutrients 

applied to each stock plant were 2 g N and 0.5 g P. Shoot and root dry mass of cuttings was greater in 

late applications, but with some differences between serial and wild stock plant sources. 

In the second experiment 12 serially propagated clones were subjected to 12 N and P fertilizer level 

combinations applied at three times during the growing season. Cutting number, survival, shoot dry 

mass and stem diameter were differently affected by different N and P combinations and application 

time, with later application times and higher N/P ratios often producing greater responses. 

This work showed that nutritional regimes of donor plants can be developed to increase faster rooting 

and growth of cuttings to produce larger planting stock. 

1 Dept. of Forest Biology, University of Victoria, P.O. Box 3020 STN CSC Victoria B.C. V8W 3N5, 

rvdd@telus.net

2 Cowichan Lake Research Station, Ministry of Forests and Range, Research and Knowledge Management 

Branch, Mesachie Lake, B.C. V0R 2N0, JohnRussell@gov.bc.ca

2010 - A Tale of Two Cedars PNW-GTR-828

129
130
SECTION D

ABSTRACTS AND PAPERS BASED ON POSTERS

WESTERN REDCEDAR DEER BROWSE 

RESISITANCE WORKSHOP

FIELD TOURS

THE BALLAD OF TWO CEDARS

PARTICIPANTS

METRIC-ENGLISH EQUIVALENTS

131
132
SILVICULTURAL TREATMENT EFFECTS ON ABOVEGROUND 

BIOMASS GROWTH AND PARTITIONING OF WESTERN 

REDCEDAR (THUJA PLICATA DONN EX D. DON) STANDS 

COMPARED TO WESTERN HEMLOCK (TSUGA HETEROPHYLLA

(RAF.) SARG.)

Roderick W. Negrave1 

ABSTRACT

An understanding of the production and allocation of biomass within forest stands is of interest in 

managing forests for carbon sequestration, managing for biomass-based energy production and increases 

our comprehension of ecological processes. This study examined the effects of silvicultural treatments 

and site influences on biomass accumulation and aboveground partitioning in juvenile western redcedar 

(cedar) and western hemlock (hemlock) stands on northern Vancouver Island. A factorial experiment 

was established in 1988 to examine the effects of: NPK fertilization versus non-fertilized treatments; 

three establishment densities of 500 stems per ha (sph), 1500 sph and 2500 sph; and the two species. 

This design was replicated (4x) on two sites: Nutrient-poor old-growth cedar-hemlock (CH) and 

nutrient-medium, second growth hemlock-amabilis fir (Abies amabilis (Dougl. ex Loud.) Dougl. ex

Forbes) (HA) sites. The experiment was re-measured after 15 growing seasons in 2002. Biomass 

estimation equations were developed through destructive sampling of 84 cedar and 41 hemlock saplings 

and applied to plot data to produce estimates of total stand biomass and biomass components for foliage, 

branches, wood and bark. Analysis was completed using PROC MIXED in SAS (p<0.05). Fertilization 

increased total and component biomasses compared to non-fertilized treatments and increased the 

proportion of wood in stands. The proportion of foliage in stands increased with establishment density. 

Proportionally, there was less wood in cedar stands on CH sites. On HA sites, cedar stands had 

proportionally more foliage than hemlock. Results suggest that: Both total biomass and wood production 

can be increased through fertilization; cedar responds less strongly than hemlock to fertilization; cedar is 

the preferred species in managing for both biomass and wood production on the poorer CH site; and 

return on fertilizer investment, in terms of biomass and wood volume (as opposed to value), is likely 

maximized by fertilizing hemlock on HA sites.

KEYWORDS: Western redcedar, western hemlock, fertilization, density, biomass, aboveground 

partitioning

INTRODUCTION

Management of forests for biomass and carbon 

sequestration has recently become of interest in 

British Columbia. These approaches to 

management differ from traditional views in that 

all of the biomass grown by a stand is of interest 

as a product, not just stem-wood. An 

understanding of how biomass is partitioned to 

stand structural components, foliage versus 

wood for example, can also further our 

understanding of how silvicultural treatment 

influence stand growth by how they affect 

allocation to these structural components 

(Gower et al. 1993, Retzlaff et al. 2001). 

In 1988, a silvicultural trial was established to 

study how fertilization and establishment 

density may be used to reforest former oldgrowth forest sites that were occupied by salal 

(Gaultheria shallon Pursh) on which it was 

difficult to establish viable conifer plantations 

1

Roderick W. Negrave is Research Team Leader and research silviculturist, British Columbia Ministry of Forests and 

Range, 2100 Labieux Road, Nanaimo, BC, V9T 6E9

2010 - A Tale of Two Cedars PNW-GTR-828

133
on. These treatments were also applied to 

nearby circum-zonal sites that supported 

acceptable conifer growth in comparison. 

We used this established experiment to study 

how silvicultural treatments during stand 

establishment might influence total stand 

biomass growth on different types of sites and 

the aboveground allocation to stem-wood, bark, 

foliage and branches.

METHODS

Study Sites

The study site was located on northern 

Vancouver Island (50o

 60’N, 127o 35’ W) in the 

Submontane Very Wet Maritime variant of the 

Coastal Western Hemlock Biogeoclimatic, or 

CWHvm1 zone (Green and Klinka 1994). The 

area receives approximately 1900 mm of 

precipitation annually, most of which falls as 

rain. Growing season soil moisture deficits 

typically do not occur (Lewis 1982). 

The experiment was conducted on two common 

CWHvm1 forest types. Hemlock Amabilis Fir 

(HA) sites are occupied by stands composed of 

western hemlock and amabilis fir. Cedar 

Hemlock (CH) sites are occupied by stands 

dominated by western red redcedar with lesser 

amounts of western hemlock and amabilis fir. 

CH sites support old-growth forests and 

canopies in these stands are irregular with 

frequent gaps and the understory is 

consequently well developed and dominated by 

salal. The HA sites in this study were secondgrowth forests that mostly originated from a 

major windstorm in 1906 (Prescott and 

Weetman 1994). These forests are more uniform 

in structure and are composed of younger trees. 

Canopies in HA forests are uniform and dense 

with little light penetration to the forest floor.

Nitrogen and P availability is lower on CH sites 

than on HA sites and the reasons for this 

phenomenon remain obscure. The wetter nature 

of CH humus and soil above concreted layers 

and resulting reduction of biological activity 

may be responsible for the lower N and P 

availability that characterizes these sites 

(Prescott and Weetman 1994, Prescott et al 

1996). 

Experimental design and treatments

Ninety-six square treatment plots, each 

containing 64 sample trees were established in 

1988. Treatments were arranged in a fullycrossed factorial combination with two levels of 

fertility (fertilized and unfertilized) and three 

levels of density (500, 1500 and 2500 stems per 

ha). The 2 x 3 combination of fertilizer/nofertilizer by densities was applied to each of 

redcedar and hemlock and duplicated on both 

CH and HA sites. The CH and HA sites used in 

this study were scattered throughout a 3-km2

area in close proximity to each other. Each 

fertilization-density-species combination was 

randomly assigned within four blocks on each 

site, with a single treatment level replicate per 

block. Thus, a total of 48 plots examined 12 

treatments with 4 replications per treatment 

level on each site. 

Fertilized plots received a 60 g dressing of 

NutricoteTM controlled-release fertilizer at time 

of planting. The fertilizer was raked into 15-cm 

radius areas around each seedling and provided 

10 g of N, 2.5 g of P and 5 g of K to each 

seedling. Total application rates per ha varied 

with density. All fertilized plots were refertilized before the beginning of the growing 

season in 1993 with a broadcast application of 

225 kg of N and 100 kg of P per ha as urea (46-

0-0) and triple superphosphate (0-45-0).

Measurements

Height and diameter of each living sample tree 

within core measurement areas were measured 

after the completion of growth in late 2002. 

Diameter was measured 1.3 m above the root 

collar. Regression equations were developed to 

predict individual tree total mass and mass of 

foliage, branch, bark and wood components. 

Saplings were destructively sampled after 

growth had ceased in the fall of 2001 and 2002. 

Dry mass conversion factors were determined 

for stem wood, stem bark, branch foliage and 

woody branch components for each sample tree. 

134
A total of 84 cedar saplings were destructively 

sampled compared to 41 for hemlock, due to the 

greater variability among mass components of 

cedar.

Mass Prediction Equations

Biomass estimation equations were developed 

from the destructive sampling data. These 

equations were ordinary least-square regressions 

of the allometric log-log transformed type e.g. 

Brix (1983). These regressions used height and 

diameter to estimate mass of stem wood, stem 

bark, branches, and foliage. Prediction equations 

were corrected for back-transformational bias. 

Separate equations were developed for each 

component for each species, along with 

equations to estimate total tree mass. All of 

these predictive equations were significant (p

<0.001) with r2 values ranging from 0.813 to 

0.981. The predictive equations were then 

applied to plot data to produce estimates of total 

stand biomass and biomass components. 

Proportional allocation of biomass to 

components within stands was then derived 

from these estimates.

Treatment effects on biomass growth and 

proportional allocation of biomass to 

components within stands were analyzed using a 

general linear model approach. Three factors 

including species, density and fertilization were

tested using a mixed-effects model with blockeffects assumed to be fixed. Variables analyzed 

included total stand mass, masses of stem-wood 

(wood), stem-bark (bark), branches and foliage, 

and the percentage of total stand mass contained 

in wood, bark, branches and foliage. Analysis 

was completed using PROC MIXED in SAS 

(p<0.05). 

RESULTS

Fertilization increased total stand mass and each 

of the masses of wood, bark, branches and 

foliage for both species on each site (p values 

ranging from <.0001 to 0.0225; Table 1). On 

CH sites, unfertilized cedar masses were greater 

that those of hemlock, however, hemlock 

responded more strongly to fertilization than did 

cedar and no differences existed between the 

species for masses when fertilized. Fertilization 

increased total stand and component masses by 

two to three times for most species-site 

combinations but up to a 15-times increase was 

noted for fertilized compared to unfertilized 

hemlock on CH sites (Table 1). Masses of 

hemlock exceeded those of cedar on HA sites (p 

<.0001; Table 1). 

On HA sites, total stand mass and the masses of 

bark and branches were least in the 500 sph 

treatments (p <.0001; Table 1). Total stand mass 

did not significantly increase with density on 

unfertilized CH sites (p = 0.0225; Table 1). The 

total, foliage, and wood masses of hemlock 

stands were less at 2500 sph than at 1500 sph on 

unfertilized CH sites, but these were not 

significant (Table 1). Although significant threeway treatment effects were present for masses of 

wood and foliage on CH sites, no clear pattern 

of effects was evident. Masses of bark and 

branches tended to be significantly least at 500 

sph than at the higher densities on CH sites (p 

values of 0.0186 and <.0001, respectively; Table 

1), although this effect was stronger for cedar 

and on unfertilized sites.

Fertilization increased the proportion of stand 

mass in wood for both species on both sites (p 

values from <.0001 to 0.0307; Table 2). On CH 

sites, hemlock had proportionally more stand 

mass in wood than cedar (p = 0.0008, Table 2). 

Fertilization decreased the proportion of stand 

mass in foliage for both species on both sites (p 

values from <.0001 to 0.0438; Table 2). On HA 

sites, unfertilized cedar had proportionally more 

mass in foliage than hemlock (p = 0.0438; Table 

2). Fertilization decreased the proportion of 

hemlock stand mass in branches on both sites (p

0.0024 to 0.0293; Table 2). Fertilization 

decreased the proportion of bark in both cedar 

and hemlock stands on CH sites and in cedar 

stands on HA sites (p values from 0.0002 to 

0.0003; Table 2). Cedar had proportionally more 

stand mass in bark than hemlock on CH sites (p

= 0.0002; Table 2). 

Increasing density reduced the proportion of 

stand mass in wood for both species on both 

sites (p values from <.0001 to 0.0307; Table 2). 

On CH sites, the proportion of stand mass in 

bark increased with density in cedar and the 

135
proportion of mass in branches increased with 

density in hemlock (p values of 0.0006 and 

0.0293, respectively; Table 2). On HA sites, 

proportional stand mass in bark was greater in 

the 2500 sph treatment compared to 500 sph (p 

= 0.0383; Table 2).

Table 1: Means of total stand mass and mass components with standard errors in brackets. 

Species Fert. Planting

Density

(Stems/ha)

Wood

(t/ha)

Bark

(t/ha)

Branches

(t/ha)

Foliage

(t/ha)

Total Stand

(t/ha)

CH Sites:

Cw F0 500 2.12(0.68) 0.35(0.09) 1.33(0.38) 1.10(0.25) 4.92(1.41)

Cw F0 1500 3.41(1.47) 0.66(0.22) 2.37(0.87) 2.25(0.63) 8.71(3.25)

Cw F0 2500 3.66(0.73) 0.78(0.13) 2.68(0.49) 2.74(0.43) 9.83(1.81)

Cw F1 500 5.04(1.03) 0.69(0.11) 2.85(0.51) 2.03(0.28) 10.66(1.92)

Cw F1 1500 11.86(3.61) 1.77(0.43) 7.05(1.88) 5.35(1.15) 26.22(7.08)

Cw F1 2500 10.56(4.77) 1.75(0.68) 6.68(2.78) 5.56(1.98) 24.74(10.35)

Hw F0 500 0.78(0.24) 0.12(0.03) 0.43(0.12) 0.41(0.10) 1.75(0.49)

Hw F0 1500 1.39(0.52) 0.23(0.08) 0.84(0.28) 0.86(0.26) 3.35(1.15)

Hw F0 2500 0.72(0.18) 0.13(0.03) 0.49(0.11) 0.54(0.12) 1.89(0.44)

Hw F1 500 6.96(2.37) 0.84(0.26) 2.99(0.92) 2.53(0.72) 13.18(4.17)

Hw F1 1500 9.44(3.57) 1.25(0.44) 4.52(1.58) 4.06(1.35) 19.31(6.92)

Hw F1 2500 14.52(7.86) 1.94(0.93) 7.00(3.30) 6.31(2.73) 29.83(14.68)

HA Sites:

Cw F0 500 2.79(1.40) 0.42(0.18) 1.66(0.76) 1.28(0.50) 6.18(2.84)

Cw F0 1500 4.89(1.99) 0.86(0.28) 3.21(1.16) 2.82(0.83) 11.85(4.32)

Cw F0 2500 6.17(6.18) 1.07(0.89) 3.99(3.61) 3.46(2.62) 14.74(13.44)

Cw F1 500 5.31(2.03) 0.70(0.22) 2.94(1.00) 2.03(0.56) 10.99(3.76)

Cw F1 1500 18.31(6.97) 2.42(0.73) 10.12(3.41) 6.99(1.89) 37.87(12.87)

Cw F1 2500 22.74(6.64) 3.18(0.74) 13.02(3.36) 9.42(1.94) 48.59(12.65)

Hw F0 500 6.32(3.97) 0.76(0.44) 2.71(1.54) 2.30(1.22) 11.95(7.00)

Hw F0 1500 15.05(11.04) 1.86(1.24) 6.65(4.39) 5.73(3.53) 29.09(19.82)

Hw F0 2500 21.06(19.38) 2.61(2.23) 9.34(7.92) 8.06(6.48) 40.80(35.50)

Hw F1 500 11.90(1.69) 1.34(0.18) 4.74(0.63) 3.84(0.49) 21.38(2.87)

Hw F1 1500 45.69(7.95) 5.08(0.82) 17.94(2.88) 14.41(2.21) 81.24(13.36)

Hw F1 2500 56.64(14.78) 6.48(1.52) 23.00(5.30) 18.84(4.02) 103.13(24.70)

Cw = Cedar, Hw = Hemlock, Fert. = Fertilization; F0 = Unfertilized, F1-= Fertilized

136
DISCUSSION

Fertilization was effective at increasing total 

stand mass and increasing the proportion of 

wood in stands. Increasing density was more 

ambivalent in this regard: the highest density 

did not always yield the greatest biomass, as 

with hemlock on CH sites. Increasing density 

also resulted in proportionally less wood in 

stands but more in branch and bark components.

Table 2: Mean mass component percentage of total stand mass with standard errors in brackets. 

 

Species Fert. Planting

Density

(sph)

Wood

(%)

Bark

(%) 

Branches

(%)

Foliage

(%)

CH Sites:

Cw F0 500 42.57(2.07) 7.11(0.30) 27.00(0.10) 22.66(1.83)

Cw F0 1500 38.52(2.08) 7.72(0.34) 27.20(0.11) 26.43(2.14)

Cw F0 2500 37.16(0.62) 7.95(0.12) 27.28(0.04) 27.96(0.78)

Cw F1 500 47.08(1.22) 6.51(0.14) 26.79(0.05) 19.14(0.78)

Cw F1 1500 44.93(1.57) 6.78(0.20) 26.88(0.07) 20.62(1.14)

Cw F1 2500 41.91(2.48) 7.21(0.39) 27.03(0.13) 23.23(2.49)

Hw F0 500 44.34(1.24) 6.65(0.05) 24.39(0.28) 23.77(0.81)

Hw F0 1500 41.33(1.26) 6.77(0.05) 25.09(0.31) 25.78(0.92)

Hw F0 2500 38.15(0.62) 6.91(0.03) 25.93(0.17) 28.42(0.54)

Hw F1 500 52.38(1.78) 6.37(0.06) 22.75(0.33) 19.36(0.82)

Hw F1 1500 48.49(1.52) 6.49(0.06) 23.48(0.32) 21.25(0.85)

Hw F1 2500 47.92(2.10) 6.51(0.07) 23.60(0.42) 21.56(1.12)

HA Sites:

Cw F0 500 44.16(2.98) 6.91(0.41) 26.93(0.14) 21.49(2.48)

Cw F0 1500 40.83(1.55) 7.36(0.24) 27.08(0.08) 24.17(1.48)

Cw F0 2500 39.45(3.60) 7.62(0.58) 27.17(0.19) 25.95(3.76)

Cw F1 500 47.77(2.42) 6.45(0.28) 26.76(0.11) 18.85(1.54)

Cw F1 1500 47.58(3.03) 6.47(0.36) 26.77(0.13) 18.95(2.00)

Cw F1 2500 46.39(2.17) 6.61(0.27) 26.82(0.10) 19.68(1.54)

Hw F0 500 51.58(2.85) 6.39(0.09) 22.91(0.53) 19.78(1.33)

Hw F0 1500 50.02(3.45) 6.45(0.12) 23.20(0.67) 20.55(1.73)

Hw F0 2500 48.54(4.94) 6.50(0.18) 23.52(1.02) 21.44(2.76)

Hw F1 500 55.61(0.908) 6.27(0.03) 22.19(0.15) 17.99(0.36)

Hw F1 1500 56.17(0.70) 6.25(0.02) 22.09(0.12) 17.77(0.27)

Hw F1 2500 54.69(1.28) 6.29(0.04) 22.34(0.22) 18.36(0.52)

Cw = Cedar, Hw = Hemlock, Fert. = Fertilization; F0 = Unfertilized, F1-= Fertilized

137
These results suggest that combined highdensity planning with fertilization will not 

always yield the greatest biomass and therefore 

both site and species factors need to be 

considered in management for biomass. 

Findings also suggest that the greatest return on 

fertilizer investment, in terms of biomass and 

wood mass production, is achieved by fertilizing 

hemlock on HA sites. 

Stand level results likely occurred via treatment 

effects on tree size and the mix of tree sized 

produced. Larger trees tend to consist of 

proportionally more wood and less foliage, bark 

and branches than smaller trees (Barclay et al.

1986, Newton and Jolliffe 1993). In our 

experiment, fertilization increased tree size, 

tended to favour the growth of smaller trees, and 

produced more uniformly-sized stands, while 

increasing density tended to decrease tree size 

but not affect size-distribution of individual 

trees within the stand (Negrave 2004, Negrave 

et al. 2007). 

LITERATURE CITED

Barclay, H.J., Pang, P.C. and D.F.W. Pollard. 

1986. Aboveground mass distribution within 

trees and stands in thinned and fertilized 

Douglas-fir. Can. J. For. Res. 16: 438 – 442. 

Brix, H. 1983. Effects of thinning and nitrogen 

fertilization on growth of Douglas-fir: relative 

contribution of foliage quantity and efficiency. 

Can. J. For. Res. 13: 167 – 175. 

Green, R.N. and K. Klinka. 1994. A Field 

Guide to Site Identification and Interpretation 

for the Vancouver Forest Region. British 

Columbia Ministry of Forests, Research Branch, 

Victoria.

Gower, S.T., Hayes, B.E. and K.S. Fassnacht. 

1993. Influence of fertilization on the allometric 

relations for two pines in contrasting 

environments. Can. J. for. Res. 23: 1704 – 

1711.

Lewis, T. 1992. Ecosystems of the Port McNeill 

block (Block 4) of Tree farm License 25. 

Western Forest Products Ltd., Vancouver, BC. 

75 p. 

Negrave, R.W. 2004. Nutrient and 

Establishment Density Effects on Structural 

Development and Growth Processes in Juvenile 

Western Redcedar and Western Hemlock Stands 

on Northern Vancouver Island. PhD Thesis, 

University of British Columbia, Dept. of Forest 

Sciences, Vancouver, BC. 289 p. 

Negrave, R.W., Prescott C.E., and J.E. 

Barker. 2007. Growth and foliar nutrition of 

juvenile western hemlock and western redcedar 

plantations on low- and medium-productivity 

sites on northern Vancouver Island: response to 

fertilization and planting density. Can. J. For. 

Res. 37: 2587 – 2599. 

Newton, P.F. and P.A. Jolliffe. 1993.

Aboveground dry matter partitioning, size 

variation and competitive processes within 

second growth black spruce stands. Can. J. For. 

Res. 20: 1720 – 1731. 

Prescott, C.E. and G.F. Weetman (eds.).1994. 

Salal Cedar Hemlock Integrated Research 

Program: A Synthesis. Faculty of Forestry, 

University of British Columbia, Vancouver, BC. 

 85 p. 

Prescott, C.E., Weetman, G.F. and J.E. 

Barker. 1996. Causes and amelioration of 

nutrient deficiencies in cutovers of redcedarhemlock forests in coastal British Columbia. 

For. Chron. 72: 293 – 302. 

Retzlaff, W.A., Handest, J.A., O’Malley, 

D.M., McKeand, S.E. and M.A. Topa. 2001.

Whole-tree mass and carbon allocation of 

juvenile trees of loblolly pine (Pinus taeda): 

influence of genetics and fertilization. Can. J. 

For. Res. 31: 960 – 970. 

138
1, 2 Leslie Brodie is a forester and Constance Harrington is a research forester with the Genetic and Silvicultural Foundations for 

Management team, PNW Research Station, 3625 93rd Ave SW, Olympia WA 98512. 1email address: lbrodie@fs.fed.us

RESPONSE OF WESTERN REDCEDAR TO RELEASE AND 

FERTILIZATION IN A MIXED-SPECIES STAND

Leslie Chandler Brodie and Constance A. Harrington2

ABSTRACT

Western redcedar (Thuja plicata Donn ex. D. Don) is of high commercial value, is considered highly 

shade tolerant and occurs more commonly in mixed-species, uneven-aged stands than in pure stands. 

Successful maintenance of redcedar as a component of mixed-species stands to enhance diversity or to 

overcome the difficulties of establishing redcedar regeneration is dependent on its response to release 

and other silvicultural treatments. To assess the response of western redcedar to release and fertilization 

in a mixed-species stand, 74 western redcedar trees were selected to represent a wide distribution of 

diameter and crown classes in a stand in which the overstory had been recently removed in Capitol State 

Forest near Olympia, WA. Three types of competition indices were calculated for each study tree in 

order to quantify the extent of the release treatment as well as to characterize the current growing 

conditions. Pre-treatment values for the competition indices were calculated retrospectively using the 

number and size of stumps present. Half of the study trees were fertilized with urea at the rate of 200 kg 

of N/ha. Percent DBH growth increased significantly in response to fertilization every year for 3 years 

following fertilization with the greatest effect the first growing season after application. Percent height 

growth was more affected by the presence of overtopping trees following the release treatment than by 

fertilization. Of the competition indices modeled, the percent overlap of influence areas (based on tree 

size) was the most consistently effective at predicting percent diameter and height growth at all years 

when measurements were taken up to year 15. Western redcedar responded positively to removal of 

overtopping trees; thus, this type of release should be considered a viable management option. Response 

to fertilization was positive but short lived. 

KEYWORDS: redcedar, release, fertilization, management, height growth, diameter growth

INTRODUCTION

Western redcedar (Thuja plicata Donn ex. D. 

Don) is a highly shade-tolerant tree species 

found in western North America and occurs 

more commonly in mixed-species, uneven-aged 

stands than in pure stands (Minore 1990, Klinka 

and Brisco 2009). Because of its shade 

tolerance, it can survive in the understory or 

midstory of forests, and thus, can be an 

important contributor to the structural diversity 

associated with old-growth stands (Old-growth 

Definition Task Force, 1986). It has been 

recommended that forest managers interested in 

wood production grow redcedar in relatively 

high density, pure-species stands because wood 

quality and growth will be reduced when 

redcedar is overtopped by faster growing trees 

(Oliver et al. 1988). Managers interested in 

wildlife habitat, biodiversity, accelerating the 

development of late successional characteristics, 

or maintaining visual quality, however, may be 

interested in managing redcedar as a component 

of more complex stands. Redcedar is difficult to 

regenerate in many locations due to browsing by 

deer and elk. For these reasons, it may be 

especially desirable to retain existing redcedar 

trees when harvesting the overstory, even if 

many of these trees may not be valuable for 

future timber harvest. 

Substantial information is available on the tree 

and site factors which influence response of 

2010 - A Tale of Two Cedars PNW-GTR-828

139
redcedar to release in the northern Rocky 

Mountains (Graham 1982) but very little has 

been reported for redcedar in the coastal portion 

of its range and some foresters have suggested 

that overtopped redcedar would not respond 

well to release as shade-formed leaves will not 

be able to function well in a higher light 

environment or root systems developed in a 

forest stand will not be adequate when the 

species is exposed to a more stressful

environment. Redcedar has been shown to be 

responsive to fertilization (Devine and 

Harrington 2009, Walker et al. 1955, Weetman 

et al. 1988, Prescott 1996) and could possibly 

respond more quickly to release if fertilized 

with nitrogen. In this experiment, we followed 

the fate of redcedar trees for 15 years in a stand 

near Olympia, WA after overstory removal and 

fertilization. Because the stand conditions were 

irregular, we evaluated competition indices for 

their efficacy in reducing variation in tree 

growth response and used release and

overtopping codes to further partition responses 

in a meaningful way.

MATERIALS AND METHODS

The study area is located in the northern portion 

of the Washington State Department of Natural 

Resources Capitol Forest near Olympia, WA, 

USA. It was in Unit 1 of the 'Poria' sale area 

(Fig. 1) which covered 11.3 ha; the unit is 

relatively flat and at an elevation of 180 m. The 

dominant soil type is Grove very gravelly sandy 

loam. In March 1995, the overstory was 

removed except for approximately 25 Douglasfir trees per hectare and all western redcedar—

primarily understory and midstory—was 

retained. We selected 74 western redcedar trees

for the study which were free from obvious 

logging damage and represented a wide range in 

stem diameter and crown position. Diameter at 

1.3 m (DBH) of selected study trees ranged 

from 0.8 to 24.8 cm and heights ranged from 1.6 

to 18.3 m. Half of the selected trees were chosen 

on the basis of crown class, diameter and 

distance to other selected trees to be fertilized 

with nitrogen such that fertilized trees were 

approximately the size and crown position as 

the non-treated trees and were well distributed 

throughout the stand. All study trees were 

measured for DBH, height, height to live crown, 

and crown width soon after logging in 1995 

(end of the 1994 growing season is year 0), prior 

to fertilization in the early spring of 1995 (year 

1), and at years 2, 3, 4, 5 and 15. 

We evaluated three competition indices (CI’s)

for their efficacy in reducing variation in tree 

growth response and to help quantify conditions 

pre- and post-release. The CI’s were calculated 

for each study tree both for past status 

(retrospectively, using stumps) and in their 

current status. The level of release was defined 

as the difference between the two values. Any

tree or stump with a diameter at 0.3 m greater 

than 15 cm and within 10.3 m distance from the 

study tree was considered a competitor. Trees 

and stumps with a basal diameter 5.0 cm to 14.9 

cm and located within a distance of 2.56 m were 

also considered competitors. In addition, study 

trees and surrounding trees and stumps were 

assessed post-harvest and used to estimate the 

tree’s crown position both before and after the 

harvest. As a result, study trees were coded as 

either ‘over-topped’ or ‘released’. 

The three competition indices (CI’s) used to 

quantify the extent of the release treatment and 

current growing conditions were ‘sum line 

length’, ‘area’, and ‘percentage overlap’. Their 

calculation and descriptions are presented in 

Table 1 (see Brodie and DeBell 2004 for 

additional detail). For ‘sum line length’, the 

length of each line is proportional to the ratio 

between the DBH of the 2 trees. The 

competition index ‘area’, is similar to ‘sum line 

length, but ‘area’ accommodates the differences 

in distribution of line lengths by going one step 

further to calculate the area enclosed by joining 

the endpoints of adjacent lines. For calculation 

of ‘percentage overlap’, each tree is considered 

to have a circular influence area estimated as 1⁄4 

of total height. The CI is the percentage of the 

study tree’s area of influence that is overlapped 

by those of competitors. 

In the early spring of 1996, urea at the rate of 

200 kg of N/ha was manually applied to 

140
individual trees in a circular area centered on the 

stem and with a radius equal to one-half of the 

tree height. 

Annual and periodic percent DBH and height 

growth were analyzed by a series of general 

linear models (GLM) using fertilization 

treatment, crown position, the CI’s and initial 

size class as covariates (SAS Institute Inc. 

2005). 

RESULTS AND DISCUSSION

Residual Stand Damage 

Selected study trees exhibited little or no 

damage from the removal of the Douglas-fir 

overstory either directly or as a result of the 

change in environment. Wind damage to the 

study trees during the course of the study was 

minimal. During the 15-year period, 4 trees 

were blown down or damaged by other blown 

down trees and two trees suffered broken tops. 

Excluding these trees from the study affected 

initial mean diameter and heights only 

minimally, so did not affect the overall study 

design. As a side note, in the months just prior 

to the last measurement, 3 of the study trees 

(and several others within the stand) were 

severely pruned by unauthorized bough 

harvesters. Generally, well over half of the 

crown was removed. The harvest of the 

overstory and subsequent crown development of 

the redcedar trees created a condition where the 

cedar boughs were not only more obvious, but 

more plentiful and may have subjected the stand 

to more damage of this type.

Response to Fertilization

Because of the wide range in initial diameter of 

study trees, growth response was expressed as 

percent DBH growth. Percent DBH growth 

increased significantly in response to 

fertilization every year for 3 years following 

fertilization with the greatest effect the first 

growing season after application (Fig. 2). 

Treated trees responded to fertilization with a 

44% increase in percent DBH growth the first 

year, a 97% increase the second year and a 60% 

increase the third year. Trees did not respond 

differentially by initial size class. Height growth 

(figure 3) was much more influenced by the 

presence of overtopping trees following the 

release treatment than by fertilization (height 

growth response to fertilization not statistically 

significant). Over the first 5 years of the study, 

trees with an over-topping crown grew a mean 

of 0.57 m while those without the presence of an 

over-topping crown grew 1.24 m—a 118% 

increase. Long-term (15-year) response to 

fertilization was not statistically significant for 

either diameter or height growth, nor was the 

interaction between CI and fertilization 

significant.

These findings concur with the findings of 

previous studies where western redcedar has 

been shown to be consistently responsive to 

nitrogen additions in relatively even-aged stands 

during the years immediately following 

treatment (as opposed to the more erratic 

response of western hemlock) (Harrington and 

Wierman 1985, Weetman et al., 1987, Weetman 

et al. 1989, Weetman et al., 1993, Devine and 

Harrington 2009). Significant differences were 

found in diameter and height growth (although 

in those studies the presence of over-topping 

trees was not a factor) and it was suggested that 

early response to thinning alone would be quite 

small in comparison to thinning and fertilization 

Table 1 -- Competition indices used in the study

Competition 

Index Name Definition/Description Representation

Sum Line 

Length

Area Area delineated by the endpoints 

of the lines defined by the CI 

‘Sum Line Length’

Percent 

Overlap

Where CIi =competition index of subject tree i, DBHi=diameter 

at 1.3 m of subject tree i, DBHj=diameter at 1.3 m of competitor 

j, DISTij = distance between trees i and j, and Oj=portion of the 

influence area of competitor j (radius=0.25 x height j) that 

overlaps influence of subject tree, and Ii = influence area of 

subject tree i .

141
combined, as this study suggests as well. Also 

similar to other studies, the increase in periodic 

growth rate produced by the addition of nitrogen 

was not sustained over a longer period of time 

(Weetman et al. 1989, Devine and Harrington 

2009), dissipating sometime between 4-10 years 

after treatment (Blevins et al., 2006).

Competition Index Evaluation 

For each measurement interval, an analysis of 

variance was performed for percent DBH and 

height growth using crown position, fertilization 

treatments, and 1 of the 3 CI’s as covariates. Of 

the 3 CI’s, ‘Percentage Overlap’ most 

consistently produced the highest R2 values and 

was used to quantify levels of competition in 

further analysis.

We believe that the other 2 CI’s did not perform 

as well in an unevenly spaced, mixed-species 

stand for several reasons. The CI ‘sum line 

length’ did not account for the spatial 

distribution of tree size in the area immediately 

adjacent to the study tree; in its calculation, it 

could not give value to a group of smaller trees 

to one side providing a gap for the study tree. 

Although the calculation of the CI ‘area’ did 

take the spatial distribution of competitor trees 

into account, it could not quantify the amount 

that competitors’ effects overlapped. By 

contrast, the value of ‘percent overlap’ has no 

upper limit. If a smaller competitor is slightly 

more distant from the study tree than a larger 

competitor, the influence of both is quantified. 

Although ‘sum line length’ and ’area’ may work 

well in evenly-spaced stands where trees are 

similar in size, the CI ‘percent overlap’, with its 

higher sensitivity, performed better as a 

modeling tool within this more variable stand. 

Response to Competition and Release

Percent DBH growth and percent height growth 

were both significantly increased by the release 

treatment (Figs. 4 and 5). Two factors 

contributed to the growth response to treatment. 

First, and most significant (p<0.05), was the 

reduction of competition within the immediate 

area (as quantified by ‘percent overlap’). Once 

percent overlap reached approximately 125, 

further increases in competition level had little 

or no effect on either DBH or height growth. 

The second factor contributing to response was 

crown position (over-topped or released). 

Although not as significant as ‘percent overlap’, 

crown position was significant at p<0.10. The 

response of released trees to their crown 

position was dependent on the level of 

competition present after treatment (Figs. 4 and 

5, inset graphs). If competition in the immediate 

area remained high (percent overlap greater than 

125), the trees did not respond to the removal of 

crowns directly above. If competition in the 

immediate area was low, there was greater 

differentiation in growth between those trees 

that remained over-topped in contrast to those 

that had been released. 

A related study in southwest Washington 

(Deisenhofer, 2010) found similar results 

although in that study, height growth response 

to release was slower and less pronounced than 

that of diameter growth. Redcedar’s response to 

release in the northern Rocky Mountains 

(Graham, 1982) was highly dependent on 

several site factors including aspect, initial tree 

size, and soil and foliar characteristics. 

Although this study did not evaluate all site 

factors, initial tree size was not a statistically 

significant predictor of response to release.

CONCLUSIONS

Anecdotal information suggests that western 

redcedar may suffer from 'thinning shock' as has 

been documented for Douglas-fir on poor sites 

resulting in short-term height growth reduction 

(Harrington and Reukema, 1983). Such was not 

the case in this study. The trees responded well 

to release from over-topping crowns and a 

reduction in the number of competitors in the 

immediate area, thus these treatments represent 

viable management options. Although diameter 

growth responded well to fertilization, the 

response was not sustained in the long-term, 

however, fertilization my still be a valuable 

silvicultural tool depending on the short-term 

management objectives.

142
Year

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Percent DBH Growth

0

2

4

6

8

10

Fertilized Over-Topped

Fertilized Released

Not Fertilized Over-Topped

Not Fertilized Released

(Not measured interim years)

 

F

Figure 2 -- Mean annual percent DBH growth by treatment and 

crown position.

Figure 3 -- Mean height growth from 1994-1999 

by treatment and crown position 

Percent Overlap 

0 50 100 150 200 250 300

Percent DBH Growth

0

100

200

300

400

500

600 Released

Over-topped

Level of Competition (Percent Overlap)

Low Medium High

Mean Percent DBH Growth

0

50

100

150

200

250

Figure 4 -- Percent DBH growth per tree by the CI, “overlap” 

and crown position. Note that the release was ineffective at high 

CI levels. Note: Percent Overlap may exceed 100% where 

multiple influence areas overlap.

Figure 5 -- Percent Height growth per tree by the CI, 

“overlap” and crown position.. Note: Percent Overlap may 

exceed 100% where multiple influence areas overlap.

Percent Overlap

0 50 100 150 200 250 300

Percent Ht Growth

0

50

100

150

200

250

Released

Over-topped

Level of Competition (Percent Overlap)

Low Medium High

Mean Percent Ht Growth

0

20

40

60

80

100

120

140

Figure 1 -- The study site in 2000 

(year 6 of the study). The overstory 

had been removed except for 

approximately 25 Douglas-fir trees 

per ha. 

Height Growth (m) 0.2

0.4

0.6

0.8

1.2

1.4

0.0

1.0

Fertilized

Released

 Fertilized

Over-topped

Not Fertilized

Over-topped

Not Fertilized

 Released

143
ACKNOWLEDGMENTS 

We thank the Washington State Department of 

Natural Resources for their cooperation and 

assistance with this study, particularly in the 

selection of the study site; Angus Brodie for his 

help in study establishment; and the former 

members of the Silviculture and Forest Models 

Team who assisted with data collection, 

particularly Mike Gloss, Chris Sato, and 

Jeanette Robbins. We also thank Dean DeBell 

and Florian Deisenhofer for their manuscript 

reviews.

LITERATURE CITED

Blevins, L.L., Prescott, C.E., and Van 

Niejenhuis, A. 2006. The roles of nitrogen and 

phosphorus in increasing productivity of 

western hemlock and western redcedar 

plantations on northern Vancouver Island. For. 

Ecol. Manage. 234: 116–122. 

Brodie, L.C.; DeBell, D.S. 2004. Evaluation of 

field performance of poplar clones using 

selected competition indices. New For. 27:201-

214. 

Devine, W.D.; Harrington, C.A. 2009. 

Western redcedar response to precommercial

thinning and fertilization through 25 years 

post treatment. Can. J. For. Res. 39: 619–628. 

Deisenhofer, F. 2010. Western redcedar (Thuja 

plicata) advanced regeneration response to 

variable retention harvesting in Southwest 

Washington. In: Gen. Tech. Rep. PNW-GTR828. Portland , OR: U.S. Department of 

Agriculture, Forest Service. Pacific Northwest 

Research Station. p.157.

Graham, R.T., 1982. Influence of tree and site 

factors on western redcedar's response to 

release: A modeling analysis. USDA Forest 

Service, Intermountain Forest and Range 

Experiment Station, Research Paper INT-296, 

Ogden ,UT.

Harrington, C.A.; Reukema, D.L. 1983. Initial 

shock and long-term stand development 

following thinning in a Douglas-fir plantation. 

Forest Sci. 29:33-46. 

Minore, D. 1990. Thuja plicata (Donn ex D. 

Don) Western redcedar. In Burns and Honkala 

(tech. coords.), Silvics of North America: 1. 

Conifers. Agricultural Handbook 654. USDA, 

For. Serv., Washington, D.C. vol. 1, 675 p. 

Old-growth Definition Task Group. 1986.

Interim definitions for old-growth Douglas-fir 

and mixed-conifer forests in the Pacific 

Northwest and California. USDA Forest 

Service, Pacific Northwest Research Station, 

Res. Note PNW-447. Portland, OR. 

Oliver, C.D.; Nystrom, M.N.; DeBell, 

D.S.1987. Coastal stand silvicultural potential 

for western redcedar. In N.J. Smith (ed.)Western 

redcedar - Does it have a future?. Conf. proc., 

Univ. of B.C., Vancouver, B.C., Canada. pp 39-

46. 

SAS Institute Inc. 2005. The SAS System for 

Windows. Version 9.1. SAS Institute Inc., Cary, 

N.C. 

Weetman, G.F., Fournier, R.; Barker, J.; 

Schnorbus-Panozzo, E. 1989. Foliar analysis 

of fertilized chlorotic western hemlock and 

western red cedar reproduction on salaldominated cedar-hemlock cutovers on 

Vancouver Island. Can. J. For. Res. 19:1512-

1520. 

Weetman, G.F.; McDonald, M.A.; Prescott, 

C.E.; Kimmins, J.P. 1993. Responses of 

western hemlock, pacific silver fir, and western 

redcedar plantations on northern Vancouver 

Island to applications of sewage sludge and 

inorganic fertilizer. Can. J. For. Res. 23: 1815-

1820. 

Weetman, G.F.; Radwan, M.A.; Kumi, J. 

Schnorbus, E. 1987. Nutrition and fertilization 

of western redcedar. In N.J. Smith (ed.)Western 

redcedar - Does it have a future?. Conf. proc., 

Univ. of B.C., Vancouver, B.C., Canada. pp 47-

59.

144
SENSITIVITY OF WESTERN REDCEDAR GROWTH TO CLIMATE 

AND WESTERN HEMLOCK LOOPER IN BRITISH COLUMBIA’S 

INLAND TEMPERATE RAINFOREST

Chris Konchalski1

ABSTRACT

Conflicting future predictions for British Columbia’s inland temperate rainforest under climate change 

scenarios make it an area of special concern for research, management, and conservation. The inland 

temperate rainforest results from a globally unique combination of humidity and continental climate, and 

is host to tree species that are normally considered coastal and rare lichens and bryophytes. 

Dendrochronology has the ability to describe and quantify the sensitivity of western redcedar (Thuja 

plicata), a dominant canopy tree, to climate and western hemlock looper by analyzing the annual growth 

increments. The influence of slope position, aspect, elevation, and biogeoclimatic subzone on the 

sensitivity of western redcedar to climate and western hemlock looper will be analyzed. One elevational 

transect consisting of three sites will be placed in the two available biogeoclimatic subzones in the study 

area, as well as one putatively sensitive climate site and one level, well drained site. Nine chronologies 

will be obtained during the field season. Understanding the sensitivity of western redcedar to climate 

and western hemlock looper in different areas will help predict future forest responses and processes in 

the inland temperate rainforest. 

 

1 MSc NRES (Forestry) Student, University of Northern British Columbia, 3333 University way, Prince George, 

British Columbia. V2N 4Z9

2010 - A Tale of Two Cedars PNW-GTR-828

145
ETHANOL SYNTHESIS BY ANOXIC ROOT SEGMENTS FROM 

FIVE CEDAR SPECIES RELATES TO MESIC HABITAT 

ATTRIBUTES BUT NOT THEIR VULNERABILITY TO 

PHYTOPHTHORA LATERALIS ROOT DISEASE 

Rick G. Kelsey1, Gladwin Joseph2, and Michael G. McWilliams3

ABSTRACT

Ethanol synthesis by anoxic root segments from yellow (Chamaecyparis nootkatensis), western red 

(Thuja plicata), Port-Orford (C. lawsoniana), Atlantic white (C. thyoides), and incense (Calocedrus 

decurrens) cedars were compared to determine whether ethanol released during anoxic stress from 

flooding could influence their vulnerability to the root pathogen, Phytophthora lateralis. Roots were 

incubated in water at 5, 15, 25, and 35 oC for 14 days. The water was periodically analyzed for ethanol. 

After a short 12 hour period of anoxia, Atlantic white- and yellow-cedar produced equal but 

significantly higher ethanol in about twice the amounts than the other three species that showed no 

differences. After an extended 14 days of anoxia, Atlantic white-cedar ethanol yields remained 

significantly higher, at about 2 to 3 times the other species, while incense-cedar produced the lowest 

quantities. Yellow, western red, and Port-Orford-cedar had intermediate ethanol yields, but only yellowcedar was significantly higher than incense-cedar by about 1.6 times. In general, root incubation 

temperature affected all species’ ethanol synthesis similarly. Anoxic root ethanol production did not 

correlate with the cedars vulnerability to P. lateralis. 

Anaerobic tolerance for all five cedars in this study has been estimated in the USDA PLANTS database, 

with Atlantic white-cedar rated high, yellow-cedar low, and the other three species as none. Ethanol 

synthesis is essential for roots to survive anoxia, but the quantities produced over time are not always a 

reliable indicator of a species tolerance to anoxic stress, as there are many contributing factors. 

However, the quantities of ethanol synthesized by detached roots over 14 days seems to align with the 

species associations with wet, mesic habitats and their likelihood of experiencing anaerobic stress from 

flooding. This suggests their ranking for anaerobic tolerance would be Atlantic white-cedar high, 

yellow, western red, and Port-Orford-cedar low to possibly moderate, and incense-cedar as none. 

1 USDA Forest Service, Pacific Northwest Research Station, 3200 Jefferson Way, Corvallis, OR, 97331, USA

2 ATREE, 659, 5th A Main Rd, Hebbal, Bangalore 560024, India

3 Oregon Department of Forestry, Salem, OR, 97310 USA, rkelsey@fs.fed.us.

2010 - A Tale of Two Cedars PNW-GTR-828

146
CHARACTERIZATION AND BIOCIDAL ACTIVITY OF SOME 

YELLOW-CEDAR HEARTWOOD COMPOUNDS

Joe Karchesy1

Javier Peralta-Cruz5, Mohammad Khasawneh1, Yeping Xiong1

, Rick Kelsey2

, Daniel Manter3, Marc Dolan4, Nick Panella4, 

ABSTRACT

The essential oil from yellow-cedar heartwood and its constituent compounds were investigated for their 

ability to control arthropods of public health concern and forest microbial pathogens. Comparisons were 

made for the activities of the essential oil, isolated compounds, and derivatives against mosquitoes 

(Aedes aegypti), ticks (Ixodes scapularis), fleas (Xenopsylla cheopis), and the microbe responsible for 

Sudden Oak Death (Phytophthora ramorum).

Laboratory bioassays showed that nootkatin and carvacrol are strong inhibitors of P. ramorum zoospore 

and sporangia germination and hyphal growth. Zoospore germination was reduced to 0% with 10 ppm of 

nootkatin, or 100 ppm carvacrol. Nootkatin instantaneously destroys the membrane surrounding 

zoospores and sporangia, but not the hyphae. 

Biocidal assays against arthropods showed that nootkatone, valencene-13-ol, and carvacrol were the 

most effective, while nootkatin was not effective. Nootkatone was the most effective against ticks (LC50

= 0.0029%) and valencene-13-ol the most effective against mosquitoes (LC50 = 0.0024%). Carvacrol 

showed activity against ticks, fleas, and mosquitoes with LC50 values after 24 hours at concentrations of 

0.0068, 0.0059, and 0.0051% (wt:vol), respectively. Residual activities were good for nootkatone and 

valencene-13-ol for up to four weeks. Repellency of yellow-cedar compounds against ticks compared to 

DEET showed that nootkatone and valencene-13-ol had repellent concentration (RC50) values of 0.0458 

and 0.0712% (wt:vol), respectively, compared to DEET (RC50 = 0.0728%). 

 

1 College of Forestry, Oregon State University, Corvallis, OR, 97331

2 USDA, Pacific Northwest Research Station, Corvallis, OR 97330

3 USDA, Agriculture Research Service, Fort Collins, CO 80526

4 Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases, Ft. Collins, CO 80521

5 Escuela Nacional de Ciencias Biologicas, Department of Organic Chemistry, Instituto Politecnico Nacional, 11340 D.F, 

Mexico

2010 - A Tale of Two Cedars PNW-GTR-828

147
VITALITY AND DEFENSE MECHANISMS IN BARK-STRIPPED 

CEDAR TREES 

Paul E. Hennon1 and Nancy Turner2

ABSTRACT

Native people of the Pacific Northwest Coast collect the bark from live Western redcedar (Thuja 

plicata) and yellow-cedar (Chamaecyparis nootkatensis) that results in large bole injuries. How do these 

culturally modified cedar trees appear so healthy, and live so long, after injury? This poster reviews 

studies on heartwood chemistry, deterioration in dead trees, and bole injuries caused by brown bears to 

propose a scenario that explains how static and active mechanisms in cedar trees compartmentalize 

wood decay and allows bark-stripped trees to survive for centuries. 

Cedars have defenses that are both passive (existing heartwood) and active responses (production of 

suberized layers, heartwood compounds in live sapwood, and callus growth. Many culturally modified 

trees are found on productive soils because this is where people find large trees free of lower branches. 

The long term viability of culturally modified trees may be explained by several defense mechanisms of 

trees growing on favorable sites...and the practice of never removing bark on too much of the tree’s 

circumference. 

1 Pacific Northwest Research Station, Juneau, Alaska, USA, phennon@fs.fed.us

2

 University of Victoria, Victoria, British Columbia, Canada 

2010 - A Tale of Two Cedars PNW-GTR-828

148
THE NATURAL RANGE OF YELLOW-CEDAR: 

A PHOTOGRAPHIC TOUR OF DIVERSE LOCATIONS 

Marshall D. Murray1

 

The natural range of yellow-cedar (Callitropsis nootkatensis) is along the Pacific Coast from northern 

California to Prince William Sound, Alaska. Within this range yellow-cedar occurs from sea level to 

2300 m elevation. Yellow-cedar is not ubiquitous throughout its total range and is absent from many 

areas where the habitat is suitable for this species. Yellow-cedar occasionally grows in pure stands but is 

usually found singly or in scattered groups mixed with other conifers. The purpose of this study was to 

locate and photograph yellow-cedar growing on diverse habitats throughout a subset of its natural range 

from northern California to southern British Columbia. Potential locations of yellow-cedar were found 

from range maps, hiking guides, personal observation and other reports. Yellow-cedar was found and 

photographed by using roads, hiking trails and by "bush whacking." Photographs were taken at a total of 

264 locations. This report shows a representative sample of 38 locations. Photographs illustrate the 

variation in stem and stand structure at locations from Memekay River, British Columbia to Elk Hole, 

California (the southern-most known occurrence of this species). The yellow-cedar trees photographed 

vary in size from krummholz to a tree 418 cm in diameter. The photographs show trees growing on 

bogs, shallow acidic soils, well-drained soils, rocky ridges, talus and along lake margins. Elevations 

ranged from near sea level to 1850 m. Four locations are east of the crest of the Cascade Mountains, 

Washington, with one location 35 km east of the crest. Yellow-cedar growing within this wide 

geographic and elevational range has value for ecological as well as genetic and seed source studies. 

Locations of these stands (Table 1) are being documented to share with other researchers.

KEYWORDS: Yellow-cedar, range, habitat, ecology, soils, British Columbia, Washington, Oregon, California. 

 

REFERENCES

Burns, R.M.; Honkala, B.H. 1990. Silvics of North America. Vol. 1, conifers. Agri. Handbook 654. 

USDA Forest Service, Washington, DC. 675 p. 

Griffin, J.R.; Critchfield, W.B. The distribution of forest trees in California. Res.Paper PSW-82/1972. 

Berkeley, CA: USDA Forest Service, Pac. SW For. & Range Exp. Stn. 114 p. 

 

ACKNOWLEDGEMENTS 

Many thanks to Joe Kraft for his assistance with the map and photographs and to Connie Harrington for 

her unwavering support. 

1 Marshall D. Murray is a volunteer forester, Pacific Northwest Research Station, Olympia WA.. Murray can be contacted at: 

3689 Cooks Hill Road, Centralia, WA 98531-9011. Email: skookum@localaccess.com

2010 - A Tale of Two Cedars PNW-GTR-828

149
Table 1 -- Photo locations for yellow-cedar stands sampled in British Columbia, Washington, Oregon and northern 

California. Numbers under Site name correspond to numbers on the photos in Fig. 1 and the map in Fig. 2.

Site name Lat. (N) Long. (W) Elev (m)

 1 - Bog forest, Pacific Rim National Park, BC 49.0200 125.6200 30

 2 - Memekay River, BC 50.0852 125.8627 1100 

 3 - Cypress Provincial Park, BC 49.3900 123.1900 880 

 4 - Mount Bolduc, BC 48.7130 124.3000 1120 

 5 - Forbidden Plateau, BC 49.7000 125.3000 1080 

 6 - Near Mt. Stickney, Mt. Baker-Snoqualmie NF 47.8980 121.6050 1200

 7 - Goat Creek, Goat Rocks Wilderness, Gifford Pinchot NF 46.4820 121.4850 1460 

 8 - Miners Ridge, Wenatchee NF1 46.9680 121.3470 1580 

 9 - Near Silver Star Mountain, Gifford Pinchot NF 45.7470 122.2000 1110

10 - Ipsut Creek, Mt. Rainier NP 46.9633 121.8374 1010 

11 - Duck Lake, Mt. Baker-Snoqualmie NF 46.6630 122.3300 970 

12 - Rat Trap Pass, Mt. Baker-Snoqualmie NF 48.2030 121.3750 1050

13 - Canyon Lake Community Forest, Whatcom County, WA 48.8220 122.0290 1320 

14 - Burnt Mountain, Wenatchee NF1 46.7130 121.1790 1850 

15 - White Pass, Highway 12, WA 46.6470 121.3850 1370

16 - Ridge above Kettle Lake, Wenatchee NF1 46.8800 121.3330 1850 

17 - Goat Creek, Mt. St. Helens National Volcanic Monument 46.4000 122.1350 1140 

18 - Windy Point, WA1 46.7035 120.9000 600

19 - Owyhigh Lakes, Mt. Rainier NP 46.8673 121.5822 1580 

20 - Granite Creek, North Cascades Highway, WA 48.5640 120.7760 1170 

21 - Echo Basin, Willamette NF 44.4130 122.0960 1380 

22 - Middle Pyramid, Willamette NF 44.4960 122.0760 1710 

23 - Thorn Mountain, Umpqua NF 43.3540 122.4150 1430

24 - Twin Lakes, Umpqua NF 43.2300 122.5920 1540 

25 - Pansy Lake, Bull of the Woods Wilderness, Mt. Hood NF 44.8900 122.1110 1210 

26 - Moss Mountain, Willamette NF 43.5780 122.2600 1690

27 - Opal Lake, Opal Creek Wilderness, Mt. Hood NF 44.7920 122.2200 1030 

28 - Pup Prairie, Rogue-Umpqua Divide Wild., Umpqua NF 43.0330 122.4700 1650 

29 - Elk Hole, Klamath NF 41.6083 123.7083 1530

30 - Frog Pond, Red Buttes Wilderness, Rogue River NF 41.9800 122.2600 1520 

31 - Mink Lake, Olympic NP 47.9474 123.8633 910 

32 - Near Wagonwheel Lake, Olympic NP 47.5293 123.3000 1160

33 - Matheny Ponds, Olympic NF 47.5640 123.8580 850 

34 - Buckhorn Mountain, Buckhorn Wilderness, Olympic NF 47.8260 123.0980 1550 

35 - Three Peaks, Olympic NF 47.4940 123.5600 960

36 - Big Creek Meadows, Olympic NP 47.6016 123.7133 880 

37 - Mt. Angeles, Olympic NP 47.9945 123.4583 1800 

38 - Royal Creek, Olympic NP 47.8540 123.2160 1430 1 -- East of the Cascade Crest.

150
1 2

3 4

5

6 7 8

9 10 11 12

13 14 15 16 

17 18 19 20 

21 22 23

24 26 25 27 28

29

30

31 32 33

34 35 36

37 38

Figure 1 -- Photographs of 

yellow-cedar sites. Numbers 

correspond to those on Table 1 

and Fig. 2. 

151
152 

Figure 2 -- Locations of yellow-cedar locations photographed for this study. Numbers correspond to those under 

“Site name” in Table 1 and on Fig. 1. 
ANCIENT YELLOW-CEDAR GROVES IN THE

OLYMPIC MOUNTAINS, WASHINGTON 

Marshall D. Murray1

 

Yellow-cedar (Callitropsis nootkatensis) grows throughout the Olympic Mountains, Washington at 

elevations of 500-2200 m. Recent surveys have found ancient yellow-cedar in this area range in size 

from a 365-cm diameter giant to shrubby krummholz at timberline. Eight groves of ancient yellow-cedar 

have been found on the windward side of the Olympic Mountains at elevations of 800 to 1000 m where 

precipitation is high and fire frequency is low (Fig. 1). These groves have not burned for more than 1000 

years and contain the oldest trees in Washington. Large yellow-cedar in the groves range in diameter at 

breast height from 150 to 365 cm. The actual age of the largest trees cannot be determined because of 

rotten centers and their large size. The 365-cm diameter tree, the largest yellow-cedar in the United 

States, has been estimated to be more than 2000 years old. Growth of these yellow-cedars is slow. Snow 

accumulation in the groves is often greater than 3 m per year and growth is affected by the short snowfree growing season. Large decadent trees continue to live and grow for a long time and paper-thin 

growth rings are common. A tree 180 cm in diameter had 922 annual growth rings on the outer 30 cm of 

its radius. Photographs from these ancient groves show the physical characteristics of the trees including 

large burls, rotten, hollow living trees, standing dead hollow trees, and dead trees that fall to the ground 

and leave a 3 to 5 m high hollow stump. The groves are accessible by road or trail, but most of the 

groves are not well known. Some visitors may not realize the significance of the large, old yellow-cedar 

or perhaps mistake them for western redcedar (Thuja plicata). The groves have a mystic aura of great 

antiquity and have important scientific and recreational value. This paper includes geographic 

coordinates for the eight major groves known to the author. 

KEYWORDS: Yellow-cedar, old-growth, ancient groves, Olympic Mountains, Washington. 

 

REFERENCES

Henderson, J.A.; Peter, D.H.; Lesher, R.D.; Shaw, D.C. 1989. Forested plant associations of the 

Olympic National Forest. R6 Ecol Tech. Paper 001-88. USDA Forest Service, Pac. NW Region. 502 p. 

Van Pelt, R. 2001. Forest giants of the Pacific Coast. Univ. Wash. Press, Seattle, WA 191 p. 

 

ACKNOWLEDGEMENTS 

Many thanks to Joe Kraft for his assistance with the map and photographs and to Connie Harrington for 

her unwavering support. 

1 Marshall D. Murray is a volunteer forester, Pacific Northwest Research Station, Olympia, WA. He can be 

contacted at: 3689 Cooks Hill Road, Centralia, WA 98531-9011 email: skookum@localaccess.com

2010 - A Tale of Two Cedars PNW-GTR-828

153
Table 1 -- Locations of ancient yellow-cedar stands visited on the Olympic Peninsula, Washington. 

Site name Lat. (N) Long. (W) Elev. (m)

Pine Mountain, Olympic NP 47.946 123.971 1000

3 - Lakes, Olympic NP 47.604 123.729 970

Big Creek Meadows, Olympic NP 47.602 123.692 800

3 - Peaks, Olympic NF 47.492 123.548 960

West Fork Humptulips River, Olympic NF 47.479 123.629 820

Quinault Ridge, Olympic NF 47.475 123.750 910

Matheny Ridge, Olympic NF 47.579 123.833 880

Matheny Ponds, Olympic NF 47.564 123.858 850

154
Pine Mountain

3 - Lakes

Big Creek Meadows

3 - Peaks

Matheny Ridge

Quinault Ridge Matheny Ponds

W. Fork Humptulips R.

Figure 1 -- Photographs 

of trees & locations of 

ancient yellow-cedar 

groves in the Olympic 

Mountains, WA.

155
GENE RESOURCE MANAGEMENT FOR WESTERN REDCEDAR

AND YELLOW-CEDAR

John Russell1 and Jodie Krakowski1

ABSTRACT

Conservation and management of tree populations in BC is based on the assumption of local adaptation, 

which is tested using long-term genecological research such as provenance and progeny trials. Since the 

climate at a given site is expected to change faster than the rate of population migration via seed and 

pollen, we need more proactive management and conservation to ensure adequate conservation of the 

genetic capacity to adapt to environmental stresses, provide ecosystem services, and withstand pests and 

diseases.

BREEDING AND DEPLOYMENT FOR WESTERN REDCEDAR 

DEER RESISTANCE

John Russell1 and Jodie Krakowski1

ABSTRACT

Ungulate browse damage to redcedar seedlings costs approximately $20-25 million in BC per year, at 

$5-6/tree to reach free-to-grow status. Browse damage levels were found to be directly related to foliar 

monoterpene concentrations which have high heritability. These naturally occurring chemicals increase 

as seedlings age. Western redcedar is unique since it can have a generation time as short as 2 years, and 

also is easy to successfully root cuttings, which allows for clonal testing and deployment, as well as 

deployment of material from older plants that cuttings can be taken from. Western redcedar shows no 

trade-off between high monoterpenes and height growth. Field trials in BC rely on natural deer 

populations to access a planted trial, and may be affected by adjacent stand composition and the design 

of the experiment in terms of the deer feeding behaviour. An important component of these ongoing 

studies is to determine how best to deploy resistant material. Planting 100% resistant redcedar stock 

would effectively force deer to forage on that, since no alternative food source is available, possibly 

applying selection pressure to the deer to overcome their aversion to high terpene concentrations. 

Studies are currently underway to determine appropriate levels and spatial distribution for deploying 

resistant redcedar while meeting stocking standards and other key objectives. 

1 Cowichan Lake Research Station, BC Ministry of Forests, P.O. Box 335 Mesachie Lake, BC, Canada, V0R 2N0

2010 - A Tale of Two Cedars PNW-GTR-828

156
WESTERN REDCEDAR (THUJA PLICATA) ADVANCED 

REGENERATION RESPONSE TO VARIABLE RETENTION 

HARVESTING IN SOUTHWEST WASHINGTON 

Florian Deisenhofer1

ABSTRACT

Western redcedar (Thuja plicata) is a disease resistant, valuable conifer species in the Pacific Northwest 

desirable for reforestation. In Southwest Washington many landowners are not planting western 

redcedar due to heavy ungulate browse. Using advanced regeneration of western redcedar may be a 

viable method of integrating this species into plantations at little cost, while adding economic value, 

diversity, habitat structure, disease resistance and resilience. 

The response of twenty eight western redcedar mid- and understory trees, ranging in diameter from 12 to 

38 cm and relatively free of logging damage on a site infected by Phellinus weirii, was studied after a 

variable retention harvest (20 trees per hectare, mostly scattered) in 2003. Trees selected for the study 

averaged 22 cm at DBH, 15 m in height with an average height-to-diameter ratio of 66 and an average 

live crown ratio of 73%. 

Within three years of harvest three of the 28 trees selected for the study died. All three trees had above 

average height-to-diameter ratios; two of the three trees had the greatest height-to-diameter ratios 

observed, 94 and 107 respectively. Over the six observed growing seasons post-release, average 

diameter growth has been accelerating from 1cm per year in 2004 to 2 cm per year in 2009. Average 

diameter increased from 22 cm at breast height to 31 cm over the six year period with trees in excess of 

75% live crown responding the most. Height growth in contrast has been slow with no measurable 

response in the first 3 post-release growing seasons and an average height growth response of 26 cm per 

year over the last 3 years. Average height-to-diameter ratios have decreased at an annual rate of 2.7.

Advanced regeneration of western redcedar with little or no logging damage responded well to release 

following variable retention harvesting. Diameter growth response was greater than height growth 

response thus reducing height-to-diameter ratios. Trees with initial height-to-diameter ratios of less than 

80, live crown ratios greater than 75% and free of logging damage are most likely to respond well. 

1 Washington Dept. of Natural Resources, 601 Bond RD, Castle Rock, WA 98611, 

Florian.Deisenhofer@dnr.wa.gov

2010 - A Tale of Two Cedars PNW-GTR-828

157
SIX-YEAR WESTERN REDCEDAR (THUJA PLICATA) HEIGHT 

GROWTH PERFORMANCE IN SOUTHWEST WASHINGTON 

Florian Deisenhofer1 and Chris Rasor1

ABSTRACT

Disease resistance, shade tolerance, and high economic and wildlife value make western redcedar (Thuja 

plicata) a desirable component of commercial forests in Southwest Washington. Due to heavy ungulate 

browse, achieving survival and tree heights above browse level (1.4 m) are major reforestation 

challenges. We studied the effects of two repellents, Plantskydd® and Deer Away Big Game 

Repellent® (BGR), applied to seedlings at the nursery on tree survival and subsequent six year height 

growth.

In 2003 five sites in southwest Washington were planted with adjacent 10-tree rows of Plantskydd, BGR 

and a control replicated five times at each site for a total of 150 trees per site. Both repellents kept 

browse levels low during the first growing season. Treated trees were on average 2-3 cm taller (5-7 cm 

more growth) than the control. Half of the repellent-treated trees were retreated with BGR in early 

December after the first growing season. After six growing seasons, there are no significant differences 

in survival with 80 to 83% of the trees still alive. Trees treated two times with repellents are 

significantly larger (73 cm) than trees treated once or the control (both 67 cm). Only 2.5% of all 

surviving trees have reached or exceeded 1.4 m in height and 14% are between 1 and 1.4 m. 22% of all 

surviving trees are shorter after six growing seasons than when they were planted. 

Three of the sites were chemically site prepared before planting. Regardless of treatment, trees planted 

on sites with chemical site preparation had higher survival (85% versus 77%), were significantly taller 

(71 cm versus 64 cm) and had a higher percentage of trees exceeding 1.4 m (3.7% versus 0.9%) than 

non-treated sites. 

Planting western redcedar without physical protection in southwest Washington will cause substantial 

reforestation delays. Management of competing vegetation and the repeated application of repellents 

significantly improve western redcedar growth. A combination of site preparation, physical protection or 

repeated application of repellants will most likely be required for success.

1 Washington Dept. of Natural Resources, 601 Bond RD, Castle Rock, WA 98611, 

Florian.Deisenhofer@dnr.wa.gov 

2010 - A Tale of Two Cedars PNW-GTR-828

158
WESTERN REDCEDAR DEER BROWSE RESISTANCE WORKSHOP

COWICHAN LAKE RESEARCH STATION

WEDNESDAY, JUNE 2ND, 2010

A post meeting satellite workshop on western redcedar deer browse resistance was offered at Cowichan 

Lake Research Station. The workshop involved presentations and field trips describing the current 

breeding program and deployment studies that have been ongoing for the last few years. The workshop 

was attended by over 50 people from Oregon, Washington and British Columbia including nursery 

growers, seed orchard managers, foresters and research scientists. At the end of the meeting the purpose, 

structure and function of a cooperative effort to deploy deer resistance material in operational trials 

across the landscape was discussed. The following two presentations describe the western redcedar deer 

browse resistant breeding program and a summary of deployment trials accomplished to-date.

159
1

Cowichan Lake Research Station, Ministry of Forests and Range, Box 335, Mesachie Lake, BC V0R 2N0. 

John.Russell@gov.bc.ca

WESTERN REDCEDAR BROWSE RESISTANCE BREEDING 

AND DEPLOYMENT MATERIAL

John H. Russell and Daniel C. Ferguson1

ABSTRACT

This presentation reviews progress of the British Columbia Ministry of Forests and Range deer browse 

resistant breeding program. Tremendous progress has been made in a short period of time selecting for 

foliar monoterpenes. We are currently in the third generation of breeding and testing. In addition, 

selected phenotypes have been bulked up through controlled crossing and vegetative propagation for 

future operational deployment trials.

INTRODUCTION

A breeding program for deer browse resistance 

was initiated mid-2000 after preliminary studies 

showed a linkage between foliar phytochemistry 

and deer preference, high genetic variation and 

heritabilities in these secondary chemicals that 

influence deer browsing, and the potential for an 

efficient and economically viable delivery 

program. The program has made tremendous 

progress in breeding and developing deployment 

material due to high selection efficiency and 

heritabilities, fast generation turnover, early 

seedling evaluation, ability to propagate 

vegetatively, and solid financial and institutional 

support. This report summarizes the progress to 

date for the western redcedar deer resistance 

breeding program.

FIRST GENERATION SELECTIONS

Initial observations at a southern Vancouver 

Island provenance trial at Holt Creek showed a 

causal relationship between deer browse 

preference and needle phytochemistry; high 

monoterpene trees were less likely to be 

browsed. We measured needle monoterpenes, 

browse severity and height on 2200 7-year-old 

trees at the Holt Creek provenance trial (60 

open-pollinated families from 14 BC range-wide 

populations) and multiple copies from 1000 

range-wide parent trees at Cowichan Lake 

research Station. Individual western redcedar 

monoterpenes had high additive genetic 

variations (21.2% to 30.7%) and narrow sense 

heritabilities (0.33 to 0.57). The genetic 

correlation between needle monoterpenes and 

height growth was 0.1. 

Selections were made from both sites for two 

populations: 1) preferred (30 selections: total 

monoterpenes less than 20,000 ppm) and 2) not 

preferred (120 selections: total monoterpenes 

greater than 30,000 ppm). Scions were taken for 

grafting from all selected trees. In addition, 

cuttings from the 7-year-old Holt Creek trees 

were rooted and subsequent rooted cuttings used 

for deployment trials at Olympia, WA and in the 

field on southern Vancouver Island. 

SECOND GENERATION 

BREEDING

Selected parents were crossed in partial diallels 

including selfs (there is minimal inbreeding 

depression in western redcedar – even from selffertilization), both on grafted selections in 

greenhouses at CLRS, as well as in the field, to 

help speed up the breeding process. Seed from 

the over 300 families was sown in 3 series

across five years. Foliage samples were taken 

for monoterpene analysis at the end of the first 

growing season. Selections were subsequently 

made for both preferred (<10,000 ppm total 

monoterpenes) and not-preferred (>65,000 ppm 

total monoterpenes) populations. Figure 1 

illustrates the frequency of individuals for total 

monoterpene classes from the first and second 

generation populations, as well as the notpreferred selections from each generation. Note 

2010 - A Tale of Two Cedars PNW-GTR-828

160
the high number of trees with foliar 

concentrations greater than the maximum class 

from the first generation. Vegetative material 

from the second generation selections was 

grafted for future breeding. 

THIRD GENERATION BREEDING

Limited third generation breeding has been 

undertaken. However, further breeding may not 

be necessary depending on results from 

deployment trials. It may be more important to 

integrate other correlated fitness traits including 

heartwood durability, growth, and cedar leaf 

blight resistance into the breeding population 

(Fig. 2).

MATERIAL FOR DEPLOYMENT 

TRIALS AND OPERATIONAL 

PLANTINGS

There are currently two populations available 

for operational deployment testing and eventual 

reforestation: preferred and not-preferred, both 

selected from the second generation 

populations. Vegetative material from second 

generation one-year-old select seedlings was 

grafted for seed production and rooted for clonal 

production. 

161
 

0

50

100

150

200

250

500

45008500

12500165002050024500285003250036500405004450048500525005650060500645006850072500765008050084500885009250096500

100500

# of trees

monoterpenes (ppm)

0

2

4

6

8

10

12

14

16

500

5500

105001550020500255003050035500405004550050500555006050065500705007550080500855009050095500

100500

# of select trees

monoterpenes (ppm)

1st generation not preferred selects

2nd generation not preferred selects

162

Figure 1 -- Foliage monoterpene classes and frequency of first (blue) and second (red) generation individuals 

from the main population and the select not preferred population.

Figure 2 -- Relationship between individual tree heartwood extractive effects (BLUPs) and total foliar 

monoterpene effects (BLUPs) from CLRS western redcedar parent trees. Shaded box indicates potential future 

selections for developing durable breeds.
1

Cowichan Lake Research Station, Ministry of Forests and Range, Box 335, Mesachie Lake, BC V0R 2N0. 

John.Russell@gov.bc.ca

SUMMARY OF WESTERN REDCEDAR BROWSE RESISTANCE 

RESEARCH 

John Russell1 and Bruce Kimball2 

ABSTRACT

This presentation reviews browse resistant field trials that have been conducted to measure deer 

responses to experimental manipulations of western redcedar foliar chemistry. Selective breeding was 

employed to produce planting stock of seedlings and cuttings with varying levels of monoterpenes. 

These studies examined black-tailed deer preferences among individual seedlings, how deployment of 

“browse resistant” seedlings influenced deer browsing behavior and the relative impacts of monoterpene 

content and tree maturation. Implications for future research and operational deployment of deer 

resistant material are discussed. 

INTRODUCTION

Deer browsing has a detrimental effect on 

productivity in managed plantations. Diversity 

may decrease when certain seedling 

characteristics are specifically targeted by 

foraging deer. Previous studies have suggested 

that much of the variability observed in deer 

preferences for individual conifer seedlings can 

be attributed to the phytochemical content of the 

plant tissues. Beginning in 2006, the USDAAPHIS-WS National Wildlife Research Center 

and British Columbia Ministry of Forests and 

Range jointly conducted a series of studies to 

measure deer responses to experimental 

manipulations of western redcedar foliar 

chemistry. Selective breeding was employed to 

produce seedlings (and cuttings) with varying 

levels of monoterpenes. These studies examined 

deer preferences among individual seedlings 

(tree selection) and also evaluated how 

deployment of “browse resistant” (notpreferred) seedlings influenced deer browsing 

behavior (plot selection) and assessed the 

relative impacts of monoterpene content and

tree maturation (ontogeny). 

METHODS 

Plant experimental material

Individual trees were selected from a 7-year-old 

Thuja plicata open-pollinated provenance trial 

with family structure established at Holt Creek, 

southern Vancouver Island, British Columbia 

(48° 45' N, 123° 53' W, elev. 212m). Selections 

were included from three browse potential 

categories based on foliar needle monoterpene 

and deer browse intensity observed in the 

provenance trial: not preferred (no browse and 

high monoterpene content), preferred (high 

browse and low monoterpene content), and 

intermediate (low browse and average 

monoterpene content). Selected trees were then 

cloned through propagation by cuttings and 

selfed/outcrossed using controlled crossing 

techniques. For trials using rooted cuttings, 

cuttings were taken from serial propagated 

clonal donors established from the original 

cuttings and for seedling trials. For seedlings, 

seed was sown from either selfed or full-sib 

families. Both rooted cuttings and seedlings 

were grown in greenhouses according to 

standard nursery protocol. The resultant oneyear-old rooted cuttings and seedlings of various 

ages were used for all subsequent experiments.

 

Trials

There were three studies as follows:

Tree selection. Multiple clones varying in foliar 

monoterpene concentrations were planted at two 

locations: USDA-APHIS-WS National Wildlife 

Research Olympia Field Station using penned 

2010 - A Tale of Two Cedars PNW-GTR-828

163
deer and a field plot at Fairservice, south 

Vancouver Island.

Plot Selection. Various percentages of not 

preferred seedlings and cuttings (33%, 66% and 

100%) were planted in large plots with preferred 

material at the Olympia Field Station. 

Ontogeny. Preferred and not preferred rooted 

cuttings and seedlings were outplanted together 

at the Fairservice field trial. At the Olympia 

Field Station, 1-, 2- and3-year-old preferred and 

not preferred seedlings were outplanted in 16 

tree plots.

RESULTS 

Tree selection

Browse damage varied significantly among 

three redcedar browse categories (preferred, 

intermediate, and not-preferred) that varied by 

monoterpene content. Similar damage 

observations were made in field and pen trials. 

Among the spatial parameters assessed, trees 

were more likely to be browsed in discreet areas 

where many surviving trees were available. 

Further, individuals near many not-preferred 

trees were very likely to be browsed themselves. 

Plot selection

Data from the initial experiments demonstrated 

that when deer are browsing in a patch, 

phytochemical content and spatial variables 

directly influence which individual trees are 

browsed. However, these data provide no 

information regarding factors that influence 

which patches are selected for browsing. When 

deer were required to select from distinct plots 

varying in distribution of not-preferred trees 

(33%, 66%, or 100%), browse damage 

decreased with increasing percentage of notpreferred seedlings: 33% > 66% > 100%. 

Within plots, deer did not eat higher proportions 

of preferred seedlings than expected by chance 

encounter – indicating that deer do not simply 

eat all the preferred trees in each plot, and then 

move on to the next (Fig. 1). 

Ontogeny 

Seedlings from both preferred and not preferred 

groups were significantly browsed more than 

rooted cuttings from either monoterpene group 

at the Fairservice field trial (Figure 2). The 

greatest browse resistance was observed in twoand three-year-old seedlings with high 

monoterpene content in the penned deer trials at 

Olympia Field Station. Although not explicitly 

evaluated in the plot selection trial, a dramatic 

decrease in deer browsing was observed when 

cuttings were employed (versus seedlings). 

These results suggest that chemical or physical 

characteristics of redcedar trees in addition to 

monoterpenes may dramatically influence deer 

foraging behavior. Results of field and pen 

studies indicate that both plant tissue 

development (ontogeny) and monoterpene 

concentration contribute toward reduced 

browsing by black-tailed deer. 

IMPLICATIONS

Phytochemical content of individual seedlings 

directly influences palatability and the 

likelihood of being browsed. However, once a 

patch has been selected, the presence of highly 

defended individuals may not confer significant 

browse protection to other seedlings in the 

patch. Deployment options should focus on 

aspects which influence patch selection.

Among-plot foraging behaviour observed in plot 

selection experiments suggests that increasing 

the distribution of high monoterpene-containing 

trees is desirable to promote patch avoidance. 

Thus, a management strategy should incorporate 

greater than 66%, but less than 100%, high 

monoterpene trees at a given location. Our 

results further indicate that a promising strategy 

for reducing browse damage to redcedar 

seedlings in reforestation operations should 

include both breeding for higher monoterpene 

defenses and exploiting tree maturation in the 

nursery. Ultimately, successful deployment of 

browse resistant redcedar requires further study. 

Among the questions left unanswered are: 1) 

importance of different age distributions, 2) 

critical spacing and plot sizes, and 3) 

importance of species diversity. 

164
 33% not-preferred 66% not-preferred 100% not-preferred

Figure 1 -- Number of trees receiving no damage (blue), minor damage (light blue), significant damage (green), 

or complete loss (light green) in 3 plot mixtures of preferred and not preferred seedlings. 

Figure 2 -- Survivability curves of 1-year-old seedlings and rooted cuttings with both stocktypes categorized as 

having high or low monoterpene content. 

-

0.100 

0.200 

0.300 

0.400 

0.500 

0.600 

0.700 

0.800 

0.900 

1.000 

0 2 4 6 8 10 12 14 16

survival function estimate

survival time (weeks)

preferred seedlings preferred cuttings not preferred seedlings not preferred cuttings

165
166
FIELD TRIP 1 – MAY 25: CAPITAL REGIONAL DISTRICT 

WATERSHED

Don Herriott1

The public is not permitted access to the watershed, except on guided scheduled tours. Access 

restrictions and careful stewardship has preserved unique pockets of pristine old-growth right in the 

backyard of Victoria. Forest harvesting ceased in the watershed in the 1990s. The focus has shifted to 

water quality, ecosystem restoration, forest health, and fire hazard abatement. 

Stop 1: Old-growth forest in the dry maritime coastal forest

Old-growth western redcedar (Cw) stands like this are extremely rare so near to an urban centre and 

represent some very unique intact old growth remnants of Coastal Douglas-fir and very dry Coastal 

Western Hemlock forests. This forest contains Douglas-fir (Fdc) and Cw with some western hemlock 

(Hw). Average age is estimated under 250, but there are many older veterans. Heights average 60-64 m, 

with a site index (bh age 50) of 32 m. 

Stop 2: Western redcedar used to mitigate Phellinus weirii

The original Fdc stand was harvested with mini tower and rubber tired skidder in 1993 using a variety of 

selection systems including strip shelterwood (60-200 residual stems per ha), group selection (in root rot 

pockets), and single stem selection. It was fall planted in 1994 and 1995, with Cw and western white 

pine (Pw) in the root rot pockets. Planting stock was: Fdc 1+1, Cw 1+2, Cw 1+1 bareroot, Pw 2+0 

styroblock, and Pw 3 year old stock in 6” pots. Since planting, the area experienced windthrow in 1995, 

1996 and 1999 and periodically since then. 

1 Senior Supervisor, Watershed Operations, CRD Integrated Water Services, Watershed Protection

2010 - A Tale of Two Cedars PNW-GTR-828

167
FIELD TRIP 2 - MAY 27: JORDAN RIVER WESTERN FOREST 

PRODUCTS LANDS 

Annette Van Niejenhuis1

Western Forest Products Ltd. (WFP) holds harvesting rights to 3.1 million hectares of Crown land on the 

BC coast under a variety of renewable forest tenures granted by the provincial government. These 

tenures allow the sustainable harvest of approximately 7.5 million cubic metres of high quality first- and 

second-growth logs each year. WFP also holds 30,000 hectares of private lands. The main species 

harvested are western hemlock and Pacific silver fir (Hem-Fir), western redcedar, Douglas-fir and Sitka 

spruce.

Principal activities conducted by WFP include timber harvesting, reforestation, sawmilling logs into 

lumber and wood chips, and value-added remanufacturing. WFP’s operations, employees and corporate 

facilities are located in coastal BC, while its products are sold in more than 20 countries worldwide. The 

company has a lumber capacity in excess of 1.5 billion board feet produced from 8 sawmills and 4 

remanufacturing plants.

Our Timberland Operations staff manage the company’s forestry program from initial inventories, 

assessments and plans, through road building and harvesting, to reforestation and second-growth stand 

management. Company and contract crews carry out these activities at more than 30 locations.

All timberland activities are governed by an Environmental Management System registered to ISO 

14001 standards. The majority of WFP’s harvested volume is also certified to CSA standards as coming 

from sustainably managed forests. Both ISO registration and CSA certification are verified annually 

through a program of internal and independent third-party audits. 

WFP plants approximately 8 million trees each year, with a third of these grown at WFP’s nursery near 

Victoria and the balance contracted out to other private nurseries. Of these, 2.5 million are western 

redcedar, and 0.7 million are yellow-cedar.

Jordan River Operations occur on Tree Farm License (TFL) 25, Block 1, and associated private lands on 

the southwest coast of Vancouver Island. It has a total area of 32,200 ha of which 30,477 ha are 

productive forest and a Timber Harvest Land Base (THLB) area of 25,562 ha comprised of 16,754 ha of 

Crown land and 8,808 ha of privately owned land. These Operations extend from sea level to the height 

of land on Loss and San Juan Ridges. This area has been managed as a separate, sustained yield unit 

within the TFL since its inception in 1958. The original TFL 25 was granted to a WFP predecessor 

company, Alaska Pine and Cellulose, on May 21, 1958. 

Recently, the Capital Regional District (CRD) has entered into agreement to purchase three parcels of 

the private lands (2,350 ha) previously managed by Jordan River Operations. These include the lands 

adjacent to the Sooke Potholes Regional Park, the lands adjacent to the CRD water supply, and the 

shorefront properties from Jordan River to Sandcut Beach. Additional parcels of these private lands 

remain on the real estate market. 

1

 FIA Coordinator, Western Forest Products Inc., 118-1334 Island Highway, Campbell River, BC V9W 

8C9, Canada 

2010 - A Tale of Two Cedars PNW-GTR-828

168
Stop 1: Yellow-cedar and western redcedar provenance trials

Populations from the entire range of both species were planted on multiple sites throughout each 

species’ range in British Columbia. Regional population differentiation can be observed for both 

species. Adaptability, productivity and health information from these studies has been used to develop 

breeding zones and operational seed transfers for current and future climates.

There are four provenance trials in Jordan River: two in this low elevation, productive site (150 m; 

Cwhxm1/01) and two at a high elevation, low productivity site (1000m; MHmm1/01). This yellowcedar (Yc) provenance trial is 20 years old, and the western redcedar (Cw) trial is 18 years old.

The local populations of both Cw and Yc have low mortality and good height growth here, compared to 

other test sites around B.C. However, local populations are not always the best. California populations 

showed severe maladaptation for both species at all sites. Interior Cw populations did best at the high 

elevation site. Yc populations were better adapted (better survival, less mortality) at the high elevation 

site, but this low elevation site had better height growth on average than the nearby high elevation site.

Cedar leaf blight (CLB) incidence is high on Cw across the coastal low elevation region, allowing us to 

test for resistance. Although populations from the local region (south coast low elevation) were more 

resistant than average, the most resistant population was from the wet northern Coast-Interior transition. 

Local populations had the best survival and height at the low elevation site. 

Stop 2a: Mature second growth forest of Douglas-fir, western redcedar, 

western hemlock, Sitka spruce in the transition between drier and wetter 

maritime habitats

This area is typical of the transition between the Coastal Western Hemlock very dry maritime western 

(CWHxm2) and the Coastal Western Hemlock very wet maritime submontane (CWHvm1) 

biogeoclimatic units. The site is characterized as CWHxm2/05(01), slightly richer than typical, with 

some zonal areas. This mature stand is approximately 70 years old with a site index of 32 (age 50). 

Thinning has occurred in these stands in the past. 

Stop 2b: Mixed species plantings in the transition between drier and 

wetter maritime habitats

The Hw/Fdc/Sitka spruce (Ss)/Cw (65/25/5/5) forest was logged in 2002 and 2003, slashburned, and 

planted in 2004 with a mix of Fdc and Cw seedlots with improved growth, wildstand seedlots of grand 

fir (Bg) and Pacific silver fir (Ba), blister rust-resistant western white pine (Pw), and weevil-resistant Ss. 

Minor fill planting was done in 2005. Target stocking is 900 stems per ha. This nutrient-rich ecosystem 

has a site index of 32. Western hemlock (Hw) has regenerated naturally. There is a 1st

-generation Cw 

progeny trial on the site that will yield information for improving the species’ productivity, and a 1st

generation Ss trial testing seedlings for white pine weevil resistance.

Stop 3: Western redcedar plantation on a nutrient-poor ecosystem

This ecosystem is classified as CWhvm1/01/06s, a nutrient- poor to -very poor “salal phase” which 

occurs in subdued terrain. The site index is 20. The original stand was harvested in 1990 and replanted 

in 1992 with 90% Cw and 10% Hw. It was declared free-growing in 2000 with no silvicultural inputs. 

Hw ingress is abundant. 

169
Stop 4: Plantation including yellow-cedar and western hemlock on a 

poorly drained site

This nutrient-poor and poorly drained ecosystem, classified as CWhvm1 (T. Lewis series 04) has a site 

index of 16. It is dominated by species that indicate acidic soils such as salal, Vaccinium 

membranaceum, V. ovalifolium, and V. parvifolium. The original stand was harvested in 1995, replanted 

in 2 sections in 1996 with 70% Yc rooted cuttings and 30% Hw; and 100% Yc. It was declared freegrowing in 2006 with no silvicultural inputs. There is substantial ingress of Pacific silver fir (Ba). 

Stop 5: Old-growth yellow-cedar and western redcedar forest

This moderately productive old-growth forest is typical of montane coastal sites, with substantial 

snowpack, classified as CWHvm2/01(06). Major species include Yc, Cw, Ba, Hw, and mountain 

hemlock (Hm). Note the abundant natural regeneration of all species present in the overstorey stand. 

170
THE BALLAD OF TWO CEDARS

Come listen to a story ‘bout a cedar that is red

The native folk say that it kept their family fed

Even though they didn’t use the cedar tree for food

They used the bark for baskets, and made houses from the wood

Long houses, sturdy walls, totem poles

Well the next thing you know those burly loggers came

The locals said, “Weyerhaeuser is to blame!”

They said “California is the place you ought’a be”

But they cut a lot of cedar and they left woody debris

Coarse woody, rotten logs, habitat

Well red cedar has a cousin and its wood is kind’ a yellow

Most folks say he’s a mighty handsome fellow

They say Callitropsis is the name we ought’a use

Don’t say Chamaecyparis or folks will be confused

Alaska cedar, Nootka cypress, Cupressaceae

Now folks did some retention and they left some scattered trees

Franklin and Bunnell said it’s good for birds and bees

Along came the wind and it blew some cedars down

But they’ll still have a life just lying on the ground

[If the salvagers don’t get ‘em!] Shake cutters, chainsaws

So now you’ve heard the story of the yellow and the red

Yellow is declining and a lot of trees are dead

They’re worth a lot of money making houses in Japan

And we want them in the future so we’re doin’ what we can

Research, management, conservation

Yes, we love both of these cedars

So we’re doin’ all we can.

<Da dada da da, da da>

Bill Beese, 26 May 2010

Written for the “Tale of Two Cedars” International Workshop, Univ. of Victoria, BC

Tune: The Ballad of Jed Clampett (Beverly Hillbillies theme), Lester Flatt & Earl Scruggs

2010 - A Tale of Two Cedars PNW-GTR-828

171
INTERNATIONAL CEDAR SYMPOSIUM PARTICIPANTS

Kim Allan, RPF

District of Mission

Director of Forest Management

Box 20, 33835 Dewdney Trunk Road 

Mission, BC V2V 4L9 

604.820.3764 Work (Direct) 

604.302.4082 (Mobile) 

604.826.8633 (Fax) 

kallan@mission.ca 

Bryce Bancroft RPBio.

Symmetree Consulting Group Ltd. 

6301 Rodolph Road 

Victoria, B.C. Canada V8Z 5V9 

250.652.6509 

http://symmetree.ca

BryceB@telus.net

Bill Beese

Professor, Forestry Department

Faculty of Science and Technology 

Vancouver Island University 

900 Fifth Street, 

Nanaimo, BC V9R 5S5 

Bill.Beese@VIU.ca

John Caouette

Forest Statistician

The Nature Conservancy

416 Harris Street, Suite 301 

Juneau, AK 99801 

907.523.1983 (Phone) 

907.586.8622 (Fax) 

jcaouette@tnc.org

Andy Cockle

University of Washington

Home address: 401 14th St. 

Bellingham, WA 98225 

360.393.4347 (Home Phone) 

andrew.cockle@gmail.com 

David D'Amore

Research Soil Scientist

Pacific Northwest Research Station

11305 Glacier Highway 

Juneau, Alaska 99801 

Phone: 907-586-7955 

Fax: 907-586-7848 

ddamore@fs.fed.us

Florian Deisenhofer

Region Silviculturist 

Pacific Cascade Region

Washington Department of Natural Resources (DNR) 

360.666.6005 / 666.9400 (Work center) 

360.773.5724 (Cell) 

360.577.2025 (Main office) 

Florian.Deisenhofer@dnr.wa.gov

Louise de Montigny, Ph.D., RPF 

Research Leader, Silvicultural Systems and Forest 

Dynamics

Research and Knowledge Management Branch 

B.C.Ministry of Forests and Range

PO Box 9519 

Stn. Prov. Govt., 

Victoria, BC V8W 9C2

250.387.3295 (Phone) 

250.387.0046 (Fax) 

Louise.demontigny@gov.bc.ca

Diane Douglas

Tree Improvement Branch

British Columbia Ministry of Forests and Range 

2nd Floor - 727 Fisgard Street 

Victoria BC V8W 9C1

250.356.6721 

Diane.L.Douglas@gov.bc.ca

Ivan Eastin

Professor/Director, CINTRAFOR

Center for International Trade in Forest Products

University of Washington

Seattle, WA

206.543.1918 

eastin@u.washington.edu

2010 - A Tale of Two Cedars PNW-GTR-828

172
Robert L. (Bob) Edmonds, Denman Professor in 

Sustainable Resource Sciences, and

Interim Director, The Water Center

School of Forest Resources 

Box 352100 

University of Washington

Seattle, WA 98195 

Office - 264 Bloedel Hall 

206.685.0953 (Phone) 

206.685.3091 (Fax) 

bobe@u.washington.edu

Gregory J. Ettl, 

Associate Professor, Ridgeway Chair, and Director

Center for Sustainable Forestry at Pack Forest

School of Forest Resources 

University of Washington

Box 352100 

Seattle, WA 98195-2100 

206-616-4120 

Shalima Devi Ganesan Meenakshy

PhD student 

Faculty of Forestry, UBC 

Dept. Of Forest Sciences

3041-2424 Main Mall

University of British Columbia

Vancouver, BC V6T1Z4

shalimag@interchange.ubc.ca

Chris Gaston

FPInnovations

2665 East Mall

Vancouver, BC V6T 1W5

chris.gaston@fpinnovations.ca

Rolf Gersonde

Silviculturist

Watershed Services Division

Seattle Public Utilities

19901 Cedar Falls Way SE 

North Bend, WA 98045 

206.233.1513 (Phone) 

rolf.fersonde@seattle.gov

Laura Gray

PhD Student 

Forest Conservation 

Department of Renewable Resources

815 GSB (SIS Lab)

780.492.2540 

lkgray@ualberta.ca

Steven C. Grossnickle, Ph.D.

CellFor Inc.

Senior Manager, DownStream - Development & 

Quality

250.544.3073 (Phone) 

250.889.3187 (Cell) 

SGrossnickle@cellfor.com

Joshua Halman

University of Vermont

705 Spear St. 

South Burlington, VT 05403 

802.656.0567 

jhalman@uvm.edu

Kevin J. Hardy, RPF 

Growth and Yield Forester 

Ministry of Forests and Range 

Coast Forest Region 

2100 Labieux Rd. 

Nanaimo, B.C. V9T 6E9 

250.751.7093 (Phone) 

250.751.7190 (Fax) 

Kevin.Hardy@gov.bc.ca

Constance A. Harrington

Research Forester

Pacific Northwest Research Station 

Forestry Sciences Laboratory

3625 93rd Avenue SW 

Olympia, WA 98512-9193 

360.753.7670 (Phone) 

360.753.7737 (Fax) 

charrington@fs.fed.us 

http://www.fs.fed.us/pnw/olympia/silv/

173
Dr. Barbara J. Hawkins

Centre for Forest Biology

University of Victoria

PO Box 3020, STN CSC 

Victoria, BC, CANADA V8W 3N5

250.721.7117 (Phone) 

bhawkins@uvic.ca

Paul Hennon 

Resilience and Ecosystem Disturbance Team 

PNW Research Station 

11305 Glacier Highway 

Juneau, AK 99801 

907.586.8769 (Phone) 

907.586.7848 Fax 

phennon@fs.fed.us

Clare M. Kooistra, RPF

Forest Nursery and Regeneration Specialist

Conifera Consulting 

1-6916 Manning Place

Vernon, BC V1B 2Y5 

250.549.2322 

cmkooistra@shaw.ca

Jodie Krakowski

Research Scientist

British Columbia Ministry of Forests and Range 

Cowichan Lake Research Station

Box 335 

Mesachie Lake, BC V0R 2N0

250.749.6811 ext. 43 (Phone) 

Jodie.Krakowski@gov.bc.ca

Terri Lacourse

Department of Geography 

University of Victoria

Victoria, British Columbia

V8W 3R4 

tlacours@uvic.ca

Joe LeBlanc, RPF 

Senior Forester, Coastal Woodlands 

International Forest Products Ltd. 

1250A Ironwood Street 

Campbell River, B.C. V9W 6H5 

250.286.5148 (Phone) 

604.422.3259 (Fax) 

joe.leblanc@interfor.com

Robin Lesher

Ecologist, Western Washington Ecology Program 

Mt. Baker-Snoqualmie National Forest 

rlesher@fs.fed.us

Thomas J. Link

District Silviculturist

Newport/Sullivan Lake R.D's, Colville N.F. 

U.S. Forest Service

Sullivan Lake Ranger Station

12641 Sullivan Lake Rd 

Metaline Falls, WA 99153 

509.446.7527 (Phone) 

tjlink@fs.fed.us

Damon Little

Cullman Program for Molecular Systematics

The New York Botanical Garden

Bronx, NY USA 10458-5126

dlittle@nybg.org

Thomas Brian Maertens

PhD student 

Tree Ring Lab, Department of Geography 

University of British Columbia

1984 West Mall

Vancouver, BC V6T 1Z2 

maertens@forestmail.com

Doug Mainwaring

Oregon State University

Dept of Forest Engineering, Resources, and 

Management

204 Peavy Hall 

Corvallis, Ore. 97331 

541.737.8107 

doug.mainwaring@oregonstate.edu

Brian Marcus

Western Forest Products

Port Alberni, BC 

BMarcus@westernforest.com

174
Carol McKenzie

Regional Silviculturist, Alaska Region

USDA Forest Service

P.O. Box 21628 

Juneau AK 99802-1628 

907.586.7915 (Phone)

cmckenzie@fs.fed.us

Rick Monchak RPF

Operations Forester

TimberWest Forest Corp.

Box 2500 Campbell River BC V9W 5C5 

250.286.7364 

MonchakR@TimberWest.com

Paul I Morris PhD

Group Leader - Durability and Protection 

FPInnovations - Wood Products Division 

2665 East Mall 

Vancouver, BC 

604.222.5651 (Phone) 

604.222.5690 (Fax) 

paul.morris@FPInnovations.ca 

www.fpinnovations.ca 

www.durable-wood.com

Roderick Negrave PhD, PAg, RPF 

Research Team Leader 

Coast Forest Region 

Ministry of Forests and Range 

250.751.7160 (Phone) 

Roderick.Negrave@gov.bc.ca

Victor Nery

Forest Engineer - Masters Candidate

2625E Forest Sciences Centre 

2424 Main Mall

UBC, Vancouver BC V6T 1Z4

604.866.5952 

victornery@gmail.com

Elisabeth Pittl

Department of Forest Sciences

3621-2424 Main Mall

University of British Columbia

Vancouver, BC V6T 1Z4 

lisa.pittl@gmail.com

Dr Cindy Prescott

Professor and Associate Dean, Graduate Studies and 

Research 

Faculty of Forestry 

University of British Columbia

2005-2424 Main Mall

Vancouver, BC, V6T 1Z4 

604.822.4701 

Cindy.Prescott@ubc.ca

John Russell

Research Scientist, Coastal Forest Genetics

British Columbia Ministry of Forests and Range 

Cowichan Lake Research Station

Box 335 

Mesachie Lake, BC V0R 2N0

250.749.6811 Ext.26 

John.Russell@gov.bc.ca 

Toktam Sajedi

PhD candidate 

Department of Forest Sciences

3621-2424 Main Mall

University of British Columbia

Vancouver, BC, V6T 1Z4 

tsajedi@gmail.com

Brian Saunders

Area Forester 

Island Timberlands 

Ph: 250 468 6838 

bsaunders@Islandtimberlands.com

Paul G. Schaberg, Ph.D.

Research Plant Physiologist

NRS-10-Burlington 

Northern Research Station

Forest Service, U.S. Department of Agriculture

705 Spear Street 

South Burlington, VT 05403 USA 

802.951.6771 Ext.-1020 (Phone) 

802.951.6368 (Fax) 

pschaberg@fs.fed.us

Mel Scott

250.598.7228 

melscott@shaw.ca

175
Ted Stevens, RPF, AScT

Forestry Coordinator, Gwa’sala-‘Nakwaxda’xw Nation 

and General Manager, Gwa’Nak Resources Ltd.

PO Box Port Hardy BC V0N 2P0 

250.949.8393 (Phone) 

250.949.8301 (Fax) 

250.949.0344 (Cell) 

forestry@gwanak.info

Rod Stirling

FPInnovations 

2665 East Mall

Vancouver, BC V6T 1W5 

604.222.5712 (Phone) 

604.222.5690 (Fax) 

rod.stirling@fpinnovations.ca

Rona Sturrock

Research Scientist

NRCAN-CFS

Pacific Forestry Centre

506 West Burnside Road 

Victoria BC V8Z 1M5

250.363.0789 (Phone) 

250.363.0775 (Fax) 

Rona.Sturrock@nrcan.gc.ca

Kwang-IL (Leo) Tak

ISEE (International School For Environmental 

Education, Korea)

7305 Rossiter Ave. 

Lantzville, B.C. V0R 2H0 

250.390.3711 (Phone) 

leotak@i-see.or.kr 

leotak@kookmin.ac.kr

Mark Tressel, RFT

Tamihi Logging Co. Ltd. 

42255 Arnold Road 

Chilliwack, B.C. V2R 4H8 

604.823.4830 ext.109 (Phone) 

604.823.7150 (Fax) 

mark.tamihilog@shaw.ca

Robert van den Driessche

2361 Queenswood Drive 

Victoria, B.C. V8N 1X4 

(Ret.) Research Branch, BC Min Forests

New Dendrology Inc. 

robtvdd@telus.net 

Annette van Niejenhuis RPF

FIA Coordinator 

Western Forest Products Inc.

118-1334 Island Highway 

Campbell River, BC V9W 8C9

250.286.4109 (Phone) 

AVanniejenhuis@westernforest.com

Rudi van Zwaaij, RPF

Area Forester

WFP Stillwater Forest Operation

604.485.3110 (Phone) 

RVanZwaaij@westernforest.com 

Dave Weaver RPF

Silviculture Survey Specialist

BC Ministry of Forest and Range 

Forest Practices Branch

Box 9513 Stn Prov Govt 

Victoria, BC VW 9C2

250.387.4768 (Phone) 

David.Weaver@gov.bc.ca 

Craig Wickland, RPF 

Silviculture Forester 

Coast Forest Region, Nanaimo. 

250.751.7094 (Phone) 

Craig.Wickland@gov.bc.ca 

Ralph Winter

Stand Mgmt Officer

Harvesting and Silvicultural Practices

Forest Practices Branch

Ministry of Forests and Range 

9th Floor - 727 Fisgard Street 

Victoria, BC V8W 9C2

250.387.8906 (Phone) 

Ralph.Winter@gov.bc.ca 

Claire Wooton, MSc. Student

Department of Geography 

University of British Columbia

1984 West Mall

Vancouver, BC V6T 1Z2 

604.822.6212 (Phone) 

cwooton@geog.ubc.ca 

http://www.geog.ubc.ca/~brian/cwooton 

176
METRIC - ENGLISH EQUIVALENTS

When you know: Multiply by: To find:

Degrees Celsius ( °C) ( °C * 9/5) + 32 Degrees Fahrenheit ( °F)

Centimeters (cm) 0.3937 Inches (in)

Meters (m) 3.2808 Feet (ft)

Square meters per hectare (m2/ha) 4.36 Square feet per acre (ft2 /ac)

Cubic meters per hectare (m3

/ha) 14.30 Cubic feet per acre (ft3 /ac)

Kilograms per hectare (kg/ha) 0.89 Pounds per acre (lb/ac) 

Kilometers (km) 0.6214 Miles (mi)

Hectares (ha) 2.470 Acres

2010 - A Tale of Two Cedars PNW-GTR-828

177
Pacific Northwest Research Station

Web site http://www.fs.fed.us/pnw 

Telephone (503) 808-2592 

Publication requests (503) 808-2138 

FAX (503) 808-2130 

E-mail pnw_pnwpubs@fs.fed.us 

Mailing address Publications Distribution

Pacific Northwest Research Station

P.O. Box 3890 

Portland, OR 97208-3890

The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of multiple use 

management of the Nation’s forest resources for sustained yields of wood, water, forage, wildlife, and 

recreation. Through forestry research, cooperation with the States and private forest owners, and 

management of the national 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) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider 

and employer. 
U.S. Department of Agriculture

Pacific Northwest Research Station

333 SW First Avenue

P.O. Box 3890

Portland, OR 97208-3890

Official Business

Penalty for Private Use, $300