Silvics and Silviculture of Coastal Western Redcedar : a Literature Review / Karel Klinka and David Brisco

Home , Didymascella thujina, Mayetiola, Thuja plicata

SPECIAL REPORT SERIES

Silvics and Silviculture of Coastal Western Redcedar A LITERATURE REVIEW

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Ministry of Forests and Range Forest Science Program SPECIAL REPORT SERIES

Silvics and Silviculture of Coastal Western Redcedar

A Literature Review

Karel Klinka and David Brisco

Ministry of Forests Ministry of Forests and Range Forest Science Program The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the Government of British Columbia of any product or service to the exclusion of any others that may also be suitable. Contents of this report are presented as information only. Funding assistance does not imply endorsement of any statements or information contained herein by the Government of British Columbia.

Library and Archives Canada Cataloguing in Publication Main entry under title: Silvics and silviculture of coastal western redcedar : a literature review / Karel Klinka and David Brisco. (Special report series, issn 0843-6452 ; 11) Includes bibliographical references. isbn 978-0-7726-6110-4 1. Western Redcedar - British Columbia. 2. Forests and forestry - British Columbia. 3. Forest management - British Columbia. I. British Columbia. Ministry of Forests and Range. II. Title. III. Series: Special report (British Columbia. Ministry of Forests and Range) ; 11. sd397.w46k55 2009 634.9'756509711 c2009-900862-9

Citation: Klinka, K. and D. Brisco. 2009. Silvics and silviculture of coastal western redcedar: a literature review. B.C. Min. For. Range, For. Sci. Prog., Victoria, B.C. Spec. Rep. Ser. 11. www.for.gov.bc.ca/hfd/pubs/Docs/Srs/Srs11.htm

Prepared by Karel Klinka Forest Sciences Department University of British Columbia 3041 – 2424 Main Mall Vancouver, BC v6t 1z4 David Brisco Ecotope Consulting Services 269 Gordonhorn Crescent Kamloops, BC v2e 1g5

When using information from this or any Forest Science Program report, please cite fully and correctly.

Copies of this report may be obtained, depending upon supply, from: Crown Publications, Queen’s Printer PO Box 9452 Stn Prov Govt 563 Superior Street, 2nd Flr Victoria, BC V8W 9V7 1 800 663-6105 www.crownpub.bc.ca

For more information on Forest Science Program publications, visit: www.for.gov.bc.ca/scripts/hfd/pubs/hfdcatalog/index.asp Executive Summary

This report has been produced at the given in consideration of possible changing request of B.C. Forest Service staff interest- climatic conditions, as well as details regarded in the future of western redcedar on the ing the first study on redcedar dieback on coast of British Columbia, and provides a eastern Vancouver Island. summary of current knowledge regarding The silviculture section includes this species. In response to their concerns, management-related topics such as growth we have brought together all pertinent and yield, regeneration strategies, and information related to the establishment intensive silviculture options. When the and growth of redcedar scattered in various decision to establish redcedar has been publications and journals, supplemented made, we propose several principles to with visuals to express the statements and guide management strategies. This subsec- support the inferences made in this report. tion is followed by growth and yield infor- The first three sections introduce our mation indicating potential productivity approach to the report and summarize of redcedar. Considering the impact of well-known information about the red climate change, we updated the list of cedar resource and the uses of redcedar coastal site series by including only those products. The fourth, silvics section sites that are thought to provide for a reli- describes morphological and reproduction able growth as a timber crop. Suitable characteristics, tolerance, damaging agents, methods of cutting to promote the regen- growth development patterns, and genetics. eration of redcedar, including site prepara- In this section, we include summaries of tion, potential for natural regeneration, several studies investigating redcedar stem and aspects of planting are described. The form and root characteristics. Survival and stand management subsection discusses growth of redcedar in relation to light spacing options, pruning, and thinning, availability has a direct connection to its and introduces the stand density manage- growth development patterns. ment diagram. The fertilization subsection The ecology section describes climatic is based primarily upon the results amplitude of redcedar, its occurrence within achieved in the Salal–Cedar–Hemlock biogeoclimatic units, edaphic amplitude, and Integration Research Program (SCHIRP). associated tree species. A review of vegeta- Three prominent and ongoing redcedar tion and site classification of redcedar eco- research initiatives are summarized in the systems is presented in a tabular format. The last chapter of this document: Imajo studies subsequent discussion describes the ecologi- funded through the University of British cal role of redcedar, which includes the pos- Columbia Forest Program, the SCHIRP sible modification of soil properties, increase Program funded co-operatively through of community diversity, self-pruning of the Ministry of Forests and Range and overstorey crop tree species, and suppression Western Forest Products, and the HyP3 of understorey vegetation. We also attempt Project funded through the Ministry of to elucidate the origin and perpetuation of Forests and Range Forest Science Program. old-growth redcedar stands, and conclude For this first initiative we provide only a list that in the CWH zone the species may have of recent studies supported by the Imajo a polyclimax role. General succession trends fund. However, the other two research pro- after disturbance of old-growth redcedar grams merit additional attention and dis- stands by clearcutting and windthrow are cussion because they convey applicable described, and the origin of many of these information about salal-dominated and stands in southern coastal British Columbia is low-productivity sites found throughout attributed to fire disturbance. Site selection the northern portion of the redcedar range recommendations for coastal redcedar are of coastal British Columbia.

iii Preface

The intent of this report is to present the other topics. We have aimed to present the most current and available information available knowledge in a manner compre- concerning establishment and growth of hensible to those determined to restore redcedar in the coastal region of British redcedar to the role it deserves in the Columbia. The report represents a synthe- coastal forests of British Columbia. We sis of selected information from several hope that those users will find this report major sources, such as Minore (1983, a practical and useful tool, facilitating 1990), Smith, N.J. (1988), Wiggins (1999), their promotion of redcedar as a key and Klinka et al. (2000), and from several component of our future forests. recent research studies carried out at the It should be noted that any mention of Forest Sciences Department, University of particular manufacturers or brands are British Columbia. The report is not a com- solely intended for simplicity for the reader. prehensive review because we have No products described within this docu- focused on the information pertinent to ment are explicitly endorsed by the regeneration and growth of redcedar, and authors to the exclusion of other suitable have limited the information related to products.

Notes on Taxonomy and Nomenclature

Thuja is a small genus limited to six species common name of western redcedar (just worldwide, with only two species native to two words, abbreviated to redcedar in the North America: eastern white cedar text) is preferred to western red cedar, and (T. occidentalis) and western redcedar the full scientific citation is Thuja plicata (T. plicata). Following Little (1979), the (Donn ex D.Don in Lamb.).

Acknowledgements

The authors thank Louise de Montigny, are noted and appreciated. Thanks are Hal Reveley, and Alan Banner of the also due to Katrine Evans of the Dean’s B.C. Ministry of Forests and Range for office, Faculty of Forestry, University of their interest and support of this project. British Columbia, for preparing the list of Additional credit must go to Christine Imajo-supported studies, and to all Forest Chourmouzis, who significantly improved Service personal who reviewed earlier early drafts of this report with her thor- drafts of this report. Unless otherwise ough editing, suggestions, and comments. noted, all photographic images were pro- The contributions and suggestions from vided by Karel Klinka. Gordon Weetman and Jaroslav Dobry

iv Contents

Executive Summary...... iii Preface...... iv Notes on Taxonomy and Nomenclature...... iv Acknowledgements...... iv 1 Introduction...... 1 2 A Prized Resource...... 6 2.1 Wood Properties...... 6 2.2 Wood Products...... 6 2.3 First Nations Usage ...... 8 2.4 Spiritual and Aesthetic Aspects...... 9 3 Silvics...... 11 3.1 Morphological Characteristics...... 11 3.2 Reproduction ...... 15 3.3 Tolerances...... 16 3.4 Survival and Growth of Redcedar Seedlings under Varying Light Conditions. 17 3.5 Damaging Agents...... 19 3.6 Growth Development Patterns...... 23 3.7 Genetics...... 24 4 Ecology...... 27 4.1 Climatic Amplitude...... 27 4.2 Occurrence in Biogeoclimatic Units...... 27 4.3 Edaphic Amplitude...... 28 4.4 Associated Tree Species ...... 30 4.5 Vegetation and Site Classification...... 31 4.6 Ecological Role...... 34 4.7 Succession...... 39 4.8 Dendrochronology ...... 46 4.9 Redcedar Dieback on Eastern Vancouver Island ...... 47 5 Silviculture and Management...... 52 5.1 Management Strategies ...... 52 5.2 Growth and Yield...... 54 5.3 Site and Species Selection...... 57 5.4 Cutting and Regeneration of Redcedar Stands...... 62 5.5 Stand Management...... 69 6 Large-scale Redcedar-focussed Research Initiatives...... 78 6.1 Imajo Studies...... 78 6.2 Salal–Cedar–Hemlock Integrated Research Program (SCHIRP) ...... 80 6.3 HyP3 Studies...... 82

v 7 Recommendations for Future Research...... 85 Literature Cited...... 90

Appendix 1 Site index curves and tables for coastal western redcedar ...... 86 2 Levels and symptoms of nutrient deficiency ...... 89

Tables 1 Mortality of planted redcedar seedlings according to study sites, growing seasons, and light classes...... 18 2 Relative occurrence of redcedar in subzones of the Costal Douglas-fir, Coastal Western Hemlock, and Mountain Hemlock zones ...... 27 3 Vegetation units of the most productive coastal Redcedar – Salmonberry order and their occurrence ...... 31 4 Site series in the subzones of the CDF and CWH zones where redcedar is considered a significant or potential climax species...... 35 5 Means of selected growth characteristics of 17 studied redcedar stands examined for site quality and by stem analysis...... 54 6 Site index of redcedar in CWHdm subzone and CWHvm subzone in relation to actual soil moisture and nutrient regime...... 55 7 Comparison of site index estimates of Kayahara et al. and SIBEC for redcedar for selected CWHdm and CWHvm site series...... 56 8 Generalized edatopic grid showing actual soil moisture regime and nutrient regime of the upland sites, floodplain, and sites with fluctuating water table that are suitable for growing redcedar as a reliable crop species ...... 60 9 Reliability ranking of TIPSY yield output, by species...... 69 10 Interpretations of foliar macronutrient concentrations for redcedar...... 75 11 A summary of projects funded by the Imajo Cedar Management Fund 1997/98 to 2006/07 ...... 78 12 Redcedar site index estimates from old-growth and second-growth stands from the CWHvh2 subzone...... 83

Figures 1 The range of redcedar in British Columbia...... 1 2 Second-growth, western hemlock in the Malcolm Knapp Research Forest...... 2 3 An undisturbed forest on upland rocky sites in the CWHvh subzone consisting of western hemlock, mountain hemlock, lodgepole pine, redcedar, and yellow-cedar ...... 2 4 As with Douglas‑fir, large, sound, clear, old-growth redcedar trees have been most sought after in harvesting the coastal forest...... 2 5 A dense, immature, naturally regenerated stand of redcedar in the Malcolm Knapp Research Forest...... 4 6 One of the managed, older-immature, experimental stands of redcedar in Great Britain...... 4 7 A fragment of a log cut 80 years ago in the Malcolm Knapp Research Forest showing negligible decay...... 7 8 Salvaged wood of yellow-cedar and redcedar from leftover logs after past cutting, stored in Sechelt and awaiting further processing...... 7

vi 9 Decay class III downed redcedar log in an old-growth stand, estimated to be 120 years old...... 7 10 An unfinished canoe from a redcedar log amidst advance regeneration, abandoned for unknown reasons some years ago ...... 8 11 Culturally modified trees in varying degrees of decompostion are often found in the coastal rainforest...... 8 12 One of several totem poles in Kitwanga village, west-central British Columbia. . . 9 13 This scenic drive through an old-growth redcedar stand in the Coquitlam watershed resembles the experience from a visit to MacMillan Park on Vancouver Island or Stanley Park in Vancouver...... 9 14 Redcedar makes an attractive ornamental tree especially when grown alone or in small groups...... 10 15 A redcedar hedge in Vancouver...... 10 16 Forked or candelabra crowns in an old-growth redcedar stand, often characteristic of old growth...... 11 17 Interestingly, not all trees in a stand will develop these forked crowns...... 11 18 One of the distinguishing features of redcedar can be extensive fluting at the base, as seen on a burned snag and a sound log ...... 12 19 Long, coarse, and persistent branches at the lower stem in a low-density stand. . . 13 20 An excessively high number of long, coarse, and persistent upper and middle crown branches in a low-density stand...... 13 21 The dense root system of an old redcedar established on a rock outcrop...... 13 22 The very dense and profuse system of an old redcedar tree established in a shallow soil over bedrock...... 13 23 Root density of fine, medium, and coarse roots in the forest floor and two mineral soil layers in hemlock, hemlock–redcedar, and redcedar stands...... 14 24 In redcedar, a developing branch is often taller than a terminal...... 15 25 Redcedar veglings rising from branches on a downed tree and fallen branches. . . 16 26 Scattergram and regression line of total biomass and specific leaf area of harvested redcedar seedlings on percent of above-canopy light three growing seasons after planting...... 18 27 A healthy and vigorous redcedar seedling 2 years after planting, protected by Vexar tubing...... 22 28 Relationship between total needle monoterpenes and percent browsing by clone in western redcedar grown at Fairservice Main, south Vancouver Island. . . 22 29 Distinctly developed fluting in a redcedar tree that had established on a downed, above-ground log...... 23 30 Examples of dense, immature, naturally regenerated, pure redcedar stands established after clearcutting and burning...... 24 31 Generalized edaphic amplitude of redcedar in the CWH zone in relation to actual soil moisture and nutrient regimes...... 28 32 Skunk cabbage – redcedar communities typically occupy margins of coastal lakes and depressions, forming a transition from non-forested wetland to upland communities ...... 29 33 A very dry, rock outcrop site on Bowen Island...... 29 34 A chlorotic redcedar plantation on an N-deficient, salal-dominated, old-growth cutover on northern Vancouver Island...... 29

vii 35 A markedly stratified structure is typical for mixed-species stands of Douglas-fir and redcedar...... 30 36 A stratified structure is typical for mixed-species stands of hardwoods and redcedar...... 30 37 A low-density, old-growth stand of Sitka spruce, redcedar, western hemlock, and Pacific silver fir on a lower, steep, seepage slope in the central coastal mainland ...... 32 38 A high-density, naturally regenerated, second-growth stand of western hemlock and redcedar on a zonal site in the CWHvm subzone...... 32 39 An unmanaged mixed-species stand of redcedar and Pacific silver fir on a moist, nutrient-rich site in the CWHvm subzone...... 33 40 The bark of old redcedar trees is calcium-rich, often supporting corticolous fern and bryophyte communities ...... 34 41 Redcedar stands on rocky sites can lessen erosion of shallow soils during heavy rains ...... 37 42 Redcedar stands, along with red alder, frequently occupy stream-edge sites and help stabilize streambanks ...... 37 43 A fully stocked, uniform forest with a preponderance of old redcedar on a second-order drainage in the Seymour watershed...... 40 44 One of the many old redcedar stands in the Capilano watershed maintaining high density and uniform appearance...... 40 45 Natural regeneration of redcedar amidst bryophytes on a well-decayed downed log near Tofino, Vancouver Island...... 41 46 Abundant advance regeneration of western hemlock in the shrub layer under the canopy of redcedar in the Seymour watershed ...... 41 47 A dense, naturally regenerated stand of redcedar with some western hemlock and lodgepole pine on a burnt, cutover area in the CWHvh subzone...... 42 48 Salmonberry – Red alder communities effectively prevent ingress of shade- tolerant conifers; winter aspect and summer aspect of the same stand ...... 42 49 Scattered saplings of redcedar and western hemlock in the understorey of a mid-seral Salmonberry – Red alder community...... 43 50 A windthrow-origin hemlock–Pacific silver fir stand on a zonal site in the CWHvm subzone on northern Vancouver Island ...... 43 51 An apparently truly old-growth western hemlock stand without redcedar on a near-zonal site, and an apparently truly old-growth redcedar–hemlock stand on a sloping zonal site in the CWHvm subzone on north Vancouver Island ...... 44 52 Chronology of redcedar age peaks and fire disturbance in the Pacific Northwest...... 45 53 Redcedar occupying coarse talus deposits in the CWHvm subzone ...... 46 54 Responses function of redcedar residual chronology of ring-width indices on 34 climatic parameters...... 46 55 Redcedar dieback observed from highway near Qualicum Beach, Vancouver Island...... 49 56 Understorey of Douglas-fir–dominated stand on a zonal site near Qualicum Beach, Vancouver Island...... 49 57 Root rot on redcedar, exposed by recent windthrow in association with Douglas-fir and bigleaf maple...... 49

viii 58 Vigorous saplings established as a pure stand on a water-surplus site south of Bowser, Vancouver Island...... 49 59 An advanced regeneration stage of a redcedar plantation on a poor, CWHvm1/01 HwCw–Salal site in the Suquash basin ...... 53 60 A naturally regenerated, seral redcedar–hemlock stand on a water-deficient, rocky crest after cutting and fire; old-growth redcedar–hemlock stands on rocky slope ...... 58 61 Dieback of redcedar under prolonged very wet conditions at the lake margin in the CWHvm subzone...... 59 62 An open-canopy, old-growth stand of redcedar, yellow-cedar, and western hemlock on a moist site in the CWHvh subzone ...... 59 63 Projection of the zone of minimum growth suppression for western redcedar under a canopy of 10-year-old black cottonwood for both black cottonwood and redcedar and growth rates characteristic of the CWHxm/08 site type...... 61 64 Height–age relationship for redcedar saplings stratified into two growing zones at the 10-year-old cottonwood on moist and rich sites in the CWHdm subzone ...... 61 65 A pure, immature stand of redcedar that originated following fire on a colluvial slope in the CWHvm subzone is one of many corroborating adaptations of redcedar regeneration to fire disturbance ...... 64 66 Dense natural regeneration of redcedar on the exposed mineral soil of a roadcut...... 65 67 Standard stocktypes available for western redcedar and yellow-cedar, with associated characteristics, coded designations, average height, and root collar diameter...... 66 68 Canopy of a dense, naturally regenerated, fire-origin, immature stand of western hemlock and redcedar on a sloping zonal site in the CWHvm1 variant.. . 69 69 Scattergram and fitted regression line of estimated shrub cover on estimated canopy cover...... 70 70 Stand density management diagrams for both natural and planted stands of redcedar ...... 71 71 A half-shade crown and three-quarters shaded crown of immature redcedar trees showing long, coarse, and persistent branches on the unshaded portion of the stem...... 74 72 Excellent stem form and high, narrow live-crowns of redcedar trees that have developed in high-density conditions ...... 74 73 A dense ericaceous shrub layer on one of the many salal- and blueberry-dominated cedar-hemlock cutovers in the CWHvh subzone ...... 76 74 A low-productivity, open-canopy, old-growth western hemlock–redcedar mixture on very moist, nutrient-poor sites ...... 80

1 iNTRODUCTION

Western redcedar is an important species 1983, 1990). The region of optimal growth that has become dominant in our provin- is near Washington’s Olympic Peninsula cial coastal forests relatively recently, in (Burns and Honkala 1990). contrast to its many coniferous associates Redcedar is the only Thuja species as they re-colonized the coastal regions native to western North America. Hebda following the last glaciation. Redcedar, a (1999) notes the fossil evidence of redcedar western North American species, grows existing in the Pacific Northwest over in the Pacific as well as the Cordilleran 30 000 years ago, and proposes the possi- regions, with the larger coastal population bility that redcedar populations may have separated from the smaller interior popu- survived the severe conditions found along lation (Figure 1) (Klinka et al. 2000). The the margins of the ice sheets in refugia on Brooks Peninsula on the west coast of Vancouver Island, allowing the re-establishment and expansion of redcedar populations approximately 6000 years ago. However, recent genetic evidence (O’Connell et al. 2008) suggests that the current distribution of redcedar (both coastal and interi- or) is the result of northward migration and colonization from a single population located south of the maximum glacial extent. It is one of the major tree species in old-growth and second-growth forests of the Pacific Northwest. It grows on a wide range of sites, and under certain stand conditions it can be a very productive and valuable timber species owing to the unique colour, texture, durability, and longevity of its wood. Redcedar trees can grow to enormous proportions. The Big Tree Registry of British Columbia (housed at the B.C. Conservation Data Centre in Victoria, B.C. [www.env.gov.bc.ca/bigtree/docs/ BigTreeRegistry.pdf]) lists a redcedar as Canada’s largest tree. This individual, known as the “Cheewhat Lake Cedar,” figure 1 The range of redcedar in British Columbia (Klinka et al. 2000). towers more than 55 m in height, has a breast height diameter of over 4.8 m, and is estimated to be over 450 m3 in volume. current natural range of western redcedar At one time, high-volume, old-growth extends along the Pacific coast from redcedar stands occurred across much California (40° N) to southeastern Alaska of the Lower Mainland, mainland coast (56° N) and along the interior wet belt (except the outer central and northern from McGregor River, B.C. (54° N) to coast where lower-productivity redcedar- western Montana and northern Idaho dominated stands are widespread), (45° N) (Boyd 1965; Little 1979; Minore Vancouver Island, and eastern Queen

1 Charlotte Islands (Haida Gwaii). Today, British Columbia forest industry), the tar- productive old-growth stands are rare and geted harvesting of this species, often at largely confined to ecological reserves, the individual tree level, has been leading parks, and protected areas (Figure 2). The towards an unsustainable removal of the most notable and accessible example is Vancouver’s Stanley Park, which is enjoyed by thousands of people from Vancouver and abroad. Along the north and central outer coast there are still large tracts of undisturbed old-growth forests of red cedar, western and mountain hemlock, yellow-cedar, and lodgepole pine. However, on the nutrient-poor soils of this hypermaritime environment (CWHvh subzone), productivity levels are often below operability thresholds, and these forests have generally not been harvested (Figure 3). Large old-growth redcedar trees have been highly sought after throughout coast- figure 3 An undisturbed forest on upland al history, as wood from these trees is used rocky sites in the CWHvh subzone consisting of for premium products (Figure 4). In con- western hemlock, mountain hemlock, lodgepole sequence, such trees have been harvested pine, redcedar, and yellow-cedar. over much of their natural range, resulting in considerable depletion and often an inadequate replacement of the resource (Figure 2) (Schmidt 1955). With the current economic pressures found in coastal British Columbia (and throughout the

figure 2 Second-growth, western hemlock in the Malcolm Knapp Research Forest. Large, often hollow yet remaining figure 4 As with Douglas‑fir, large, sound, sound, scattered redcedar stumps are long-lasting remnants clear, old-growth redcedar trees have been of the previous, old-growth, redcedar-dominated stands cut most sought after in harvesting the coastal in the 1930s. forest.

2 largest and highest-quality stems. Essent severe browsing damage to new planta- ially, the practice of “high grading” has tions, redcedar remains a relatively low- been occurring at greater levels, as coastal frequency species selected for regeneration companies attempt to keep their opera- (minor component of new plantations), tions active in spite of many negative eco- and is almost never established with the nomic conditions (remote locations, high intention of producing a pure stand. Due harvesting costs, relatively high Canadian to the inherent value (both cultural and dollar value, low international market economic) of coastal western redcedar, the demands). The targeted removal of high- selective establishment of pure stands on value redcedar stems, known as “high appropriate sites should become a higher- retention harvesting,” has become such an priority consideration for silviculturists. issue for the long-term economic value of Most of the provincial redcedar volume the managed coastal stands that the pro- is located in the coastal region. Quenet and vincial Forest Practices Board has recently Magdanz (1988) report that 81% of the total issued a special investigation report on the mature volume of 824 million m3 is in the subject (FPB 2008). This topic is described coastal region and the remaining 19% is in further detail in section 5.4 (Cutting found in the interior. Losses associated and Regeneration of Redcedar Stands). with decay, waste, and breakage increase Due to the targeted harvesting of this with increasing age and diameter, and range valuable species and perceived risks to its from < 6% for older immature to > 50% for re-establishment (such as deer browse), old-growth trees. The total volume of red- redcedar has not been replaced in the cedar in coastal Alaska, Washington, and regenerating stands at the levels it has Oregon is only 153 million m3, with 47% been historically removed (Nelson 2004). of that located in western Washington Banner and LePage (2008) have docu- (Gedney and Oswald 1988). mented the decreasing redcedar composi- Currently, > 20% of the harvested tion in second-growth stands, and suggest Annual Allowable Cut (AAC) of the pro- that without substantially more active vincial coastal regions is redcedar (Reveley management of redcedar (including both 1996). These inventory data, however, improved establishment and maintenance) may be outdated, and there is a call for a this important tree species will be reduced review and implementation of the British to only a minor component of our future Columbia forest inventory (Moss et al. coastal forests. The reduced presence of 2006). One of the recommendations is to redcedar has been a consistent (and his- determine the specific location of stand torical) trend, but policies within the types, defined by species, stand structure, coastal Forest Districts have been devel- height, density, and other stand data. oped in an attempt to improve the situa- Pure second-growth redcedar stands tion. Policies on the Queen Charlotte are relatively rare in unmanaged forests. Islands now require more explicit stocking However, there are stands of this type levels for this species, reversing the trend scattered throughout the mid and central away from redcedar. In the early 1990s, coast, likely the result of burning by less than 30% of planted seedlings were aboriginals (A. Banner, pers. comm., redcedar. By the mid-1990s, redcedar 2008). A few extensive and easily located made up 37% of seedlings sown on the examples of young, pure, naturally regen- Queen Charlotte Islands (Reveley 1996), erated stands can be found in the Lower and this proportion continues to increase Mainland, predominantly in the Greater within the North Coast Timber Supply Vancouver Regional District watersheds Area (Winter 2008). However, due to the (Capilano, Seymour, and Coquitlam),

3 Malcolm Knapp Research Forest, and tion about redcedar: its range, abundance, Mission Tree Farm (Figure 5). uses, silvics, ecology, dendrochronology, Redcedar is often grown inside and and silviculture, and an extensive list of outside its natural range either as an orna- references. Many of these topics can be mental in arboretums and parks and as a found in general reference texts such as hedge tree in northeastern United States Silvics of North America, by Burns and and Europe, or as a minor timber crop Honkala (1990). However, we have species in western Europe (Minore 1983; focussed on the most recent and relevant Hermann 1987). Redcedar was introduced knowledge and research, particularly in to Great Britain from Oregon about 150 the context of coastal issues, organizing years ago. Due to its many desirable quali- this report in three main sections: Silvics, ties, the extent of (industrial) redcedar in Ecology, and Silviculture. To facilitate the Britain has increased from 300 ha of plan- comprehension of this report, we have tations prior to 1950, to over 5000 ha of supplemented the text with many visuals plantations established by 1995 (Rollinson to illustrate key points. 1988) (Figure 6). The best-performing Although redcedar will always be part provenances originated from the northern of the timber harvest, and despite its rela- slopes of the Olympic Mountains, Shuswap tively rapid radial growth rate and shorter Lake, Sooke, and Ladysmith; the poorest- rotation to obtain sawlog values (Gedney performing provenances were from the and Oswald 1988), management practices Queen Charlotte Islands and near Terrace in the Pacific Northwest tend to favour (Lines 1987). other species. This report is written pri- We have included the following informa marily for field silviculturists who wish to

figure 5 A dense, immature, naturally figure 6 One of the managed, older- regenerated stand of redcedar in the Malcolm immature, experimental stands of redcedar in Knapp Research Forest. Note the development Great Britain. Note the low cover of the of clear, low-taper boles. understorey vegetation.

4 increase the component of redcedar in growth stands will provide satisfactory second-growth stands in response to con- wood quality and aesthetics comparable to cerns about its natural regeneration, surviv- old-growth stands. He foresees the major al, growth, browsing, stand management, contributors to price are aesthetics; much and health issues in view of predicted cli- of the value might even be cultural or tra- mate change. We have made a reserved ditional. Adams and McKetta (1988) also attempt to accommodate the impacts of predict that redcedar will remain a valu- climate change by selecting reliable sites able species in the future, even as second for future growth of redcedar. This can growth. be viewed as a contribution to the Future Understanding redcedar ecosystems Forest Ecosystems Initiative, focussing on requires knowledge of how redcedar is one of the key tree species. established and how it grows in pure Reviewing silvics, pest susceptibility, stands or in mixed-species stands in dif- growth and yield, and value aspects of ferent environmental conditions. Despite redcedar in relation to alternative coastal incomplete silviculture experience and tree species including Douglas-fir, yellow- lacking knowledge about the silvicultural cedar, western hemlock, Sitka spruce, and potential of redcedar in comparison to amabilis fir, Handley 1988( ) predicts red- Douglas-fir and western hemlock, we cedar to be the “future star” in coastal believe that it is possible to increase the forest industry considering the core of its diminishing supply of redcedar in the distribution in British Columbia. He based coastal forests if there is the willingness his prediction on taking into account silvi- and the means to do it. The retention of cal characteristics, such as easy regenera- this cultural keystone species across the tion and shade tolerance, resistance to coastal landscape is essential to the con- pests, growth and yield performance as servation of historical biodiversity levels good as its competitors, and unique wood and habitat features within these fragile properties. Handley believes that second- ecosystems.

5 2 a PRIZED RESOURCE

2.1 wood Wood properties of redcedar with respect plicins into less toxic compounds (Jin Properties to physical (structure and anatomy, density, et al. 1987), thus providing for their own seasoning, and strength) and chemical increased rates of heartwood colonization. properties are reviewed in detail by Swan This inherent natural resistance to decay et al. (1988). The wood is light, soft, easy makes redcedar wood desirable for lumber to work, relatively weak but dimensionally in weather-affected projects (exterior pan- stable and straight-grained; it has a high els, trim) as well as an important natural insulative value, and a very characteristic component of coarse woody debris for odour. However, much of the high market streamside structure and riparian habitat value is associated with its resistance to (Gray 2000). decay (DeBell et al. 1999). Redcedar is a As the supply of redcedar shifts from preferred wood for nearly all purposes old-growth to second-growth timber, where attractive appearance or resistance there are questions and concerns regarding to weather is important. Compounds wood quality, particularly in regard to the found in the heartwood, known as extrac- characteristics that make it so desirable. tives, act as a natural preservative and fungal Preliminary analysis suggests that second- repellant. The principal extractives respon- growth lumber will have lower density sible for the decay resistance include tro- than old-growth products; however, tro- polone compounds and water-soluble polone extractive content appears to be phenolics. The concentration of tropolones, highest in the most vigorous trees with which are the most effective decay-limit- rapid growth (Marshall and DeBell 2002). ing extractives (β-thujiplicin, γ-thujiplicin, Taylor et al. (2006) suggest that intensive and β-thujiplicinol), increases with distance silviculture treatment such as thinning and from the pith, making the outer regions of fertilization did not significantly affect the heartwood the most resistant to decay. average extractives concentrations. Lower This differential in concentration may be wood density would not be a significant due to their degradation over time—pith concern for redcedar wood products that wood is oldest (Hillis 1987). Significant value lightness over density. If vigorous variation in several extractives (including trees produce more decay-resistance– β-thujiplicin) has been detected between inducing extractives, silvicultural practices coastal and interior redcedar populations enhancing the growth and yield of young (Daniels and Russell 2007). Certain fungi managed redcedar stands could improve found in the heartwood of redcedar have or maintain this characteristic. demonstrated the ability to degrade thuja-

2.2 wood Because of their longevity and resistance paper products requiring high density, Products to decay, redcedar products have been air resistance, opacity, and exceptional important since prehistoric times. Redcedar smoothness, such as computer and medi- is widely used today for boat construction cal papers (Hatton 1988). Redcedar leaf (hull planking and cabin sides), log houses, oil, extractives, and residues are used in exterior siding, shingles, sashes, cabinetry, several non-wood products (Minore 1983, doors, window frames, interior finishing, 1990). utility poles, pilings, fence posts, chests, Shingles, shakes, and sawn siding caskets, crates, boxes, beehives, and gut- constitute the most important special ters. Redcedar is not regarded as a prime products of redcedar wood. Appearance, pulpwood species, but it is suitable for durability, lightness, and insulation quali-

6 ties are responsible for its popularity as a in old-growth stands in the CWHvm sub- roofing material. The heartwood of red zone. They sampled 15 logs in decay classes cedar (as well as of yellow-cedar) is very I (recent) to IV (old) and 17 snags in decay robust. Redcedar has such slow decay classes III (recent) to VI (old). Aged by rates that snags, downed trees, and log- radiocarbon dating, analysis revealed that ging residues that have lain on the ground the oldest logs (IV) were from trees that for decades may still produce resilient, died approximately 550–1200 years ago, large-dimension wood, such as used for and the oldest snags were still standing shakes and beams (Figures 7 and 8). after 276 years. This study demonstrated Using dendrochronological techniques that redcedar decay rates are dramatically and radiocarbon dating, Daniels et al. slower than for western hemlock and (1997) investigated the year of death and Douglas-fir. The persistence of redcedar rates of decay for redcedar logs and snags coarse woody debris is in agreement with its chemical properties (fungi-resistant extractives) and slow rate of decay. Thus, large-diameter logs can take centuries to fully decompose (Figure 9).

figure 8 Salvaged wood of yellow-cedar figure 7 A fragment of a log cut 80 years (right) and redcedar (left) from leftover logs ago in the Malcolm Knapp Research Forest after past cutting, stored in Sechelt and showing negligible decay. awaiting further processing.

figure 9 Decay class III downed redcedar log in an old- growth stand, estimated to be 120 years old (year of death was 1881). Note the negligible decay even on the roots.

7 2.3 first Nations There is evidence of western redcedar being Usage used by coastal First Nations over 3000 years ago (Nelson 2004). Due to the many advantageous properties and characteristics of redcedar wood, bark, and foliage, it became a cornerstone of the cultural and spiritual identity of these peoples, and is regarded as a prime example of a “cultural keystone species” (Garibaldi and Turner 2004). It is suggested that the expansion and appearance of redcedar in coastal forests 5000 to 2500 years ago is what permitted the cultural development and rapid evolution of woodworking technology that occurred in native communities during the later Holocene (Hebda and Mathewes 1984). Both redcedar and yellow-cedar have been exceptionally useful trees to the First Nations people of the coastal region, performing fundamental roles in their culture. From these two species, the materials for shelter, clothing, tools, transportation, and figure 11 Culturally modified trees CMT( s) in other artifacts were obtained (for more varying degrees of decompostion are often detailed accounts see Stewart 1984; Pojar found in the coastal rainforest. and McKinnon 1994; and Wiggins (1999). Redcedar formed the contextual under- pinnings of many coastal cultures, often almost all aspects of First Nations existence featuring prominently in the language, earned redcedar the status of the “tree of ceremonial, spiritual, and even common life”—arborvitae (Figures 10, 11, and 12). everyday practices of these peoples. Use of Often, First Nations would harvest its stem wood, branches, roots, and bark in products from redcedar trees without cutting them down, sustainably removing large planks, or strips of bark. Trees utilized in this way can still be observed alive today, bearing the marks of these historical harvests (Figure 11). These living cultural artifacts are known as “culturally modified trees” CMT( s), and are protected under current forest practices legislation. The reduced presence of redcedar, due to historical harvesting levels and poor rates of regeneration, is a serious concern for many First Nations groups located along the provincial coastline. In particular, the reduced availability of large old- growth trees is very concerning for those peoples attempting to carry on their traditional practices. These great trees were figure 10 An unfinished canoe from a redcedar log amidst advance used for the construction of traditional regeneration, abandoned for unknown reasons some years ago. longhouses, totems, and large canoes that

8 could handle volatile, open-ocean voyages. 100 years there might not be anything the The Haida peoples of the Queen Charlotte right size and shape that is needed for their Islands (Haida Gwaii) have most unequiv- use.” He emphasized that the Haida “do ocally voiced their alarm about the current not look at trees as just money; we look state of redcedar. In Wiggins (1999), Gitsga, at them as part of our freedom and we Guujaaw, White, Davidson, and Churchill- would like this to continue.” Guujaaw Davis express a sincere frustration with acknowledged the deer problem on Haida the considerable and focussed depletion of Gwaii (see Pojar 1999) but argued that the redcedar resource and its inadequate “the biggest changes that have happened replacement. on the Islands and are happening now are Gitsga and Guujaaw “are against being made by man.” exploitation of these trees that they treasure The challenge now is to improve the so much” and are greatly disturbed, “seeing current situation of poor redcedar estab- millions of dollars of logs going by their lishment, by promoting and encouraging village.” White acknowledged that “there the successful, productive, and efficient are not many large old redcedar trees left regeneration of this species on appropriate on the Islands; if there are, they are in sites. Only through the sustainable imp smaller and smaller pockets, and within rovement of the proportion of valuable redcedar within the coastal forests can either the economically important forest figure 12 One of several totem poles in industry or the cultural identity of First Kitwanga village, west-central British Columbia. Nations survive in these regions.

2.4 Spiritual and “Oh, the cedar tree! If mankind in his Grove, people drive treacherous roads to Aesthetic Aspects infancy had prayed for the perfect substance visit the “Three Sisters” in the Carmanah for all material and aesthetic needs, an valley, or board float planes or boats to indulgent god would have provided nothing visit the “Hanging Garden Cedar” on better.” Meares Island. The value of forests and (Bill Reid, from Out of the Silence, 1971) large trees, particularly in urban areas, is clearly evidenced by the millions of dollars While valued for millennia by First donated to help “restore” Stanley Park after Nations peoples, it probably was not until after Emily Carr captured its haunting dignity and splendour nearly a century ago that it became iconic in western culture. Because of the species’ significance, both culturally and ecologically, redcedar was officially adopted in 1988 as the provincial tree of British Columbia. Old- growth redcedar stands such as those in found in provincial and national parks, camping grounds, and preserved areas provide for recreational and spiritual values. Today, people from around the world visit the west coast to see these majestic figure 13 This scenic drive through an old- trees and our giant Douglas-fir and Sitka growth redcedar stand in the Coquitlam spruce (Figure 13). Raging Grannies lie watershed resembles the experience from a visit across logging roads to protect old-growth to MacMillan Park (Cathedral Grove) on forests, RVs clog the roads to Cathedral Vancouver Island or Stanley Park in Vancouver.

9 it was hit by a major windstorm in the winter of 2006/07. Redcedars, especially old trees, are aesthetically pleasing either grown alone or in groups. The large and long crown, drooping evergreen branches, fibrous bark, and flat sprays of scale-like leaves make redcedar an attractive ornamental tree (Figure 14) for use along roadways, in golf courses and parks, and around homes, both locally and abroad. When properly and consistently trimmed, redcedar makes excellent hedges (Figure 15).

figure 14 Redcedar makes an attractive ornamental tree especially when grown alone or in small groups.

figure 15 A redcedar hedge in Vancouver.

10 3 Silvics

3.1 morphological 3.1.1 Crown and stem form On productive and less planar with the smallest shoots Characteristics sites, redcedar can be > 60 m tall, > 200 cm upturned. When young, redcedar has a in diameter at breast height, and > 1000 thin, shiny, reddish brown bark. With age years old. The crown is long, symmetrical, the bark becomes shredded and grey- and narrowly conical. Older trees can have brown, and forms long, flat, narrow ridges an irregular shape, and for unknown rea- (Farrar 1995). sons sometimes develop a candelabra or Stem form of redcedar can vary greatly, spike-like crown (Figures 16 and 17). strongly dependent upon the development Redcedars main branches are spreading, pattern of stand growth, stand density, and drooping, and upturned at the ends. The canopy position. In either mixed-species pendent branchlets are arranged in planar stands (typically with red alder, Douglas‑ sprays, with each spray representing 1–2 fir, or hemlock), where redcedar is a years of growth. In open-grown trees, live common, slow-growing, understorey com- branches can extend to the ground. The ponent, or in low-density pure stands, the shiny yellowish green scale-like leaves are stems appear to be highly tapered and 1–2 mm in length and arranged in alter- fluted, maintaining a large number of nating pairs. Foliar morphology differs large and long-lived branches—all leading between sun and shade foliage: shade to undesirable wood quality (Figures 18, leaves are scale-like and decurrent, where- 19, and 20). In marked contrast, pure, as sprays of sun foliage are more flexible even-aged, high-density, second-growth redcedar stands can be fast growing and have high wood quality with little taper or fluting, and a small number of fine branches restricted to the upper crown. Klinka et al. (1996a) examined site quality and stand conditions in 35-year-

figure 16 Forked or candelabra crowns in an old-growth redcedar stand, often characteristic figure 17 Interestingly, not all trees in a stand of old growth. will develop these forked crowns.

11 a b

figure 18 One of the distinguishing features of redcedar can be extensive fluting at the base, as seen on a burned snag (a) and a sound log (b). old, experimental stands of grand fir, featured fluted boles, and high taper. Pacific silver fir, redcedar, western hem- Klinka et al. (1996a) attributed these lock, Douglas‑fir, Port-Orford cedar, and undesirable features to low stand density Sitka spruce located within the Hyper (a result of low initial spacing, high mor- maritime and Very Wet Maritime CWH tality, and failure of early crown closure). subzones on Vancouver Island. The pure More information regarding the develop- redcedar stands were found to have con- ment of good and poor growth forms in sistently open canopies, a history of initial redcedar stands is found in section 3.6 and continued mortality (deer browsing), (Growth Development Patterns). and slower initial growth (competing vegetation). The mean canopy cover was only 3.1.2 Roots The root networks of redcedar 40%, and live-crown length was 85% of are extensive. The taproots may be poorly the total tree height. The trees had poor defined or nonexistent, but fine roots stem form and/or undesirable branching develop a profuse, dense network (Figures characteristics, reducing their future 21 and 22). Root grafting between trees is merchantable value. The live crowns were common (Eis 1972). The root systems of long and conical, and showed continued understorey redcedars, even older trees, growth of lower lateral branches. The con- can respond dramatically in size and den- spicuous and unusual features were many sity when overstorey trees are removed large, long (up to 5 m), sparsely foliated, (Koenigs 1969). upward-sweeping live-branches on the Wang et al. (2002) examined rooting lower stem (Figures 19 and 20). The stems 60-year-old, naturally regenerated, western

12 figure 21 The dense root system of an old redcedar established on a rock outcrop. Note the dense system of medium and coarse, lateral roots covering the outcrop. figure 19 Long, coarse, and persistent branches at the lower stem in a low-density stand.

figure 22 The very dense and profuse system of an old redcedar tree established in a shallow (< 40 cm) soil over bedrock.

They investigated the hypothesis that mixed-species stands may be more productive because soil resources are used more completely and in a non-competitive way. They found that mixtures of hemlock- redcedar had the highest root density. Pure hemlock stands had intermediate root densities and pure redcedar stands had the lowest (Figure 23). In all stand figure 20 An excessively high number of long, types the highest concentration of fine coarse, and persistent upper and middle crown roots was in the forest floor (particularly branches in a low-density stand. in the humic forest floor layer [Green et al. 1993]) and decreased with increasing hemlock and redcedar in single- and depth of soil profile. In contrast with the mixed-species stands located on zonal sites hemlock stands, redcedar had more con- in the Lower Mainland with a disturbance centrated rooting and a higher proportion history of clearcutting and slashburning. of its coarse and medium roots in the

13 Fine roots as in the above study), rooting can be con- FF Medium roots Coarse roots centrated in the forest floor rather than in the underlying soil. MS1 Hemlock-redcedar mixtures showed MS2 Hemlock root characteristics of both hemlock and redcedar stands, as their root densities were nearly equal to the sum of those in FF r the forest floor ff( ) and ms1 layers (Figure MS1 23). This indicates the presence of overlapping and intermingling root systems of Soil laye Soil MS2 Hemlock–Redcedar these two species. Wang et al. (2002) concluded that hemlock and redcedar do not FF utilize soil resources in a selective, spatial- ly non-competitive way. As such, the MS1 resulting competition may negatively affect the growth of one or both species. MS2 Redcedar Most species of woody plants will 0 10 20 30 40 50 develop mutually beneficial relationships Root density (g • dm-3) with mycorrhizae of various types that facilitate the absorption of soil nutrients.

-3 Redcedar have vesicular-arbuscular figure 23 Root density (g • dm ) of fine (< 3 mm), medium (3–10 mm), and coarse (> 10 mm) roots in mycorrhizae, associated with the exterior the forest floor and two mineral soil layers (MS1 0–10 of the fine root sheaths (Minore 1979). cm, MS2 10–20 cm) in hemlock, hemlock–redcedar, Beese (1987) found that redcedar nursery and redcedar stands (Wang et al. 2002). stock was generally not mycorrhizal until after planting. The level of mycorrhizal colonization of the seedlings and their root uppermost mineral (ms1) layer. Both systems was not significantly affected by Bennett et al. (2002) and Wang et al. various site preparation treatments; howev- (2002) have documented redcedar rooting er, trends suggest a slight increase in more deeply within the soil profile than mycorrhizae colonization following mod- hemlock. For any given stand type and erate burning and possible detrimental layer, coarse roots formed the highest effects after heavy burning. proportion of all roots, followed by medium and fine roots. Redcedar expressed the 3.1.3 Leader growth The height growth highest proportion of fine and medium of redcedar is indeterminate. There is no roots relative to coarse roots in relation to terminal bud, and the developing topmost associated species. branches may often exist at a higher level Mixed hemlock-cedar stands showed than the terminal itself. Due to its method root characteristics of both single-species of indeterminate growth, redcedar lacks stands (i.e., overlapping and intermingling vegetative buds and does not exhibit shoot root systems) (Figure 23). Wang et al. dormancy as observed in other bud-forming (2002) concluded that the higher produc- conifers (El Kassaby 1999). Shoot growth tivity of mixed species was not due to the is controlled solely by temperature, with partitioning of underground resources. It no growth or mitotic activity occurring at should be noted that when thick forest temperatures of 4ºC or less (Grossnickle floors are present (i.e., not on zonal sites and Russell 2006).

14 Due to the lack of terminal buds, the measurement of the last growing-season height increment in redcedar is difficult. However, a simple, non-destructive tech- nique for aging redcedar terminals was developed by Parker and Johnson (1987) (Figure 24).

figure 24 In redcedar, a developing branch is often taller than a terminal. The main stem is distinguished by exhibiting a greater number of leaf pairs between branches than a lateral. To determine previous year’s height increment, one must identify the over-wintering point (*) usually 1–2 cm above branch junction. The distinction between annual increments is made based on difference in colour and texture or presence of the stem leaves (Parker and Johnson 1987).

3.2 reproduction Depending upon canopy conditions and 2. Rooting of fallen, live branches in soil moisture in the upper soil layer, red contact with moist soil; and cedar can reproduce successfully by either 3. Rooting along the trunk of a fallen, sexual or asexual means (Habeck 1968). living tree. Sexual reproduction appears to be more Low branches of a tree can touch the prevalent on areas disturbed by wildfires soil, often aided by snow or the weight of and on slashburned clearcuts (Schmidt fallen trees. These will develop (adventitious) 1955; Parker 1979; Feller and Klinka 1998). roots, turn upward, and form a new tree. In undisturbed areas, germination success Eventually, connection to the parent tree and survival is low (seeds succumb to is severed through the effects of decay. drought or to other agents), and regenera- Veglings then develop as independent tion is largely vegetative (Edwards and plants, but frequently with incipient stem Leadem 1988). decay. Shaded, slower-growing trees have longer lower branches, and are more 3.2.1 Asexual reproduction Asexual prone to produce vegetative regeneration (vegetative) reproduction involves the (Parker and Johnson 1988). development of new individual stems Artificial rooting of stem cuttings of (“veglings”) directly from the parent plant, redcedar is easy, inexpensive, and reliable and not from a germinating seed (Figure 25). (Edwards and Leadem 1988). Vegetative Schmidt (1955), Habeck (1968, 1978), and propagation is routinely utilized for the Dyrness et al. (1974) described three types production of seedlings by both the B.C. of vegetative reproduction. Ministry of Forests and Range and indus- 1. Rooting of attached live branches. trial suppliers. Complete redcedar plants Layering occurs when adventitious roots have been also regenerated by tissue develop after low-hanging branches culture (Edwards and Leadem 1988). come into contact with moist soil;

15 a b

figure 25 Redcedar veglings rising from branches on a downed tree (a) and fallen branches (b).

3.2.2 Sexual reproduction Thereproductive seeds per hectare, with heavy crops every cycle of redcedar has been described in 3–4 years (Schmidt 1955; Eis and Craigdallie detail by Owens and Molder (1984). Stobili 1983). The small seeds are adequately dis- are usually produced on alternate years persed within 100 m of the parent tree with production beginning as early as (Minore 1990). The rates of self-fertilization 10 years of age on open-grown redcedar. are very high relative to associated conifers, Redcedar is monoecious; the reddish male but redcedar does not suffer from inbreed- strobili develop on the lower branches and ing depression (O’Connell et al. 2001). For the green female strobili form on the upper more information, see section 3.7 (Genetics). branches, typically further from the trunk For more detailed information on the (Owens and Pharis 1971). Anthesis and biology of redcedar reproduction, please pollination occur during March and April refer to Edwards and Leadem (1988). They on the south coast, and during May and cover phenology of flowering, seed matu- June in coastal Alaska and the interior ration, cone-crop periodicity, seed-crop stands (Schopmeyer 1974). forecasting, cone harvesting, cone and Redcedar is a prolific seed producer seed processing, seed yields, seed dorman- (much greater than its associated species), cy and storage, and preparing seed for and rarely has poor cone crops. Annual sowing in the nursery. seed crops vary from 250 000 to 150 million

3.3 tolerances 3.3.1 Low light Redcedar can be highly highest in warmer and drier climates tolerant of low light conditions, compara- (and on warmer and drier sites in wetter ble to Pacific silver fir and yellow-cedar climates), and relatively lower in cooler (Krajina 1969; Minore 1979, 1983, 1990; and wetter climates (and on cooler and Wang et al. 1994), but the degree of toler- wetter sites in warmer and drier climates) ance is dependent upon climatic and site (Krajina 1965; Klinka et al. 1990). An conditions (see section 3.4: Survival and investigation into relative mortality among Growth of Redcedar Seedlings under eight canopy species of the Interior Cedar- Varying Light Conditions). Tolerance is Hemlock (ICH) zone in northwestern

16 British Columbia along a light gradient 3.3.3 Water deficit and surplus Tolerance identified redcedar as the most tolerant to water deficit is rated as medium, as red of low light conditions (Kobe and Coates cedar likely requires protection from open- 1997). area climate on warm, water-deficient sites Drever and Lertzman (2001) suggest that in the driest and warmest mesothermal a minimum of 30% of above-canopy light is climates. Its susceptibility to water deficit necessary to ensure maximal radial and has been linked to the apparent dieback of height growth in redcedar saplings. In con- redcedar on the east coast of Vancouver trast, at least 60% of above-canopy light is Island (see section 4.9: Redcedar Dieback required to achieve maximum growth rates on Eastern Vancouver Island). Its tolerance with Douglas‑fir. This low amount of full to water surplus, be it flooding or high or sun required to produce maximum growth strongly fluctuating water table, is high, in the redcedar saplings allows a relatively but it does not tolerate very wet sites well high degree of retention of forest structure (see section 4.3: Edaphic Amplitude). without substantially compromising the Although unable to grow productively on growth rates of young trees, once established. these sites, redcedar tolerates stagnant water to a greater degree than most British 3.3.2 Heat and frost The tolerance of Columbia conifers. redcedar to heat and frost varies from low to medium across its range. Redcedar 3.3.4 Nutrient deficiency and pH foliage is not protected from excessive Tolerance to nutrient-deficient soils is transpiration by cutin or wax layers. It did high. Redcedar has been shown to survive not demonstrate drought resistance in the and grow on nutrient-poor soils over physiological and anatomical investigations much of its natural range (Krajina 1969; conducted by Oppenheimer (1967). On Minore 1979, 1990). Redcedar can tolerate warm, water-deficient sites in the drier a wide range of pH conditions from acid to and warmer mesothermal climates (i.e., alkaline, and in Great Britain it has grown CDFmm), redcedar requires protection quite well on shallow soils over chalk from open-area climate by an overhead (Rollinson 1988). It is intolerant of ocean canopy. Coastal redcedar is not very spray and saline soils (e.g., tidal flats) frost-resistant, and is easily damaged by (Krajina 1969). early and late frosts.

3.4 Survival and Redcedar has always been considered a nearly optimum growth conditions in the Growth of shade-tolerant species, but scientific evi- CWHvm subzone in southern coastal Redcedar dence for interspecific and intraspecific British Columbia. On each site, the seed- Seedlings under variation in shade tolerance is poor. lings were planted on transects extending Varying Light Contemporary rankings of tree species are from the interior of an old-growth, Conditions based on qualitative field observations in redcedar-dominated stand (± 5% of above- which light was the “assumed” determinant canopy light) to a clearcut (100% of of both its natural regeneration and result- above-canopy light), and protected from ing structure in mature stands (Klinka browse. After three growing seasons, seed- et al. 1990). ling mortality, growth, and other charac- To better understand light–growth ters were compared across five light classes response relationships, Wang et al. (1994) and between study sites (Table 1). grew redcedar seedlings on three environ- Three-year seedling mortality was mentally equivalent sites, representing < 27%, with most occurring during the

17 table 1 Mortality of planted redcedar seedlings according to study sites, growing seasons, and light classes. The five light classes indicate percent of above-canopy light received by the seedlings (I = 1–20%, II = 21–40%, III = 41–60%, IV = 61–80%, and V = 81–100%) (Wang et al. 1994).

Growing season mortality (%) Light class (% total mortality) Site Planted seedlings 1990 1991 1992 3-year total I II III IV V

Eastcap Creek 490 3 22 2 27 96 1 1 1 1 Alpine Creek 497 2 14 0 16 85 10 1 2 2 Cedar Creek 494 1 15 2 18 99 0 0 0 1

80 200 (a) (b) 70 )

150 -1 60 • g 2

m 50

100 40

ve total biomass (%) biomass total ve 30 Relati 50 Speciﬁc leaf area (c 20

0 0 0 20 40 60 80 100 0 20 40 60 80 100 Percent above-canopy light Percent above-canopy light

figure 26 Scattergram and regression line of total biomass (a) and specific leaf area (b) of harvested redcedar seedlings on percent of above-canopy light three growing seasons after planting (from Wang et al. 1994).

second growing season (14–22%) and round and root biomass increased with under the lowest light conditions (light increasing light, with a slightly greater class i) within the forest understorey response in the aboveground biomass. (Figure 26a). Wang et al. (1994) suggest After three growing seasons, seedlings < 5% of above-canopy light as the likely demonstrated substantial reductions in threshold for survival of redcedar specific leaf area as light increased regeneration. (Figure 26b). Using a fitted regression line, Seedling growth improved with specific leaf area of 55 cm2 • g-1 in low light increasing light; however, growth response decreased to 35 cm2 • g-1 (37% decrease in at > 40% of above-canopy light was ext specific leaf area) under full light, indicating remely variable (Figure 26a). This variabil- a high degree of plasticity of redcedar foli- ity in growth suggests that other factors are age, responsive to varying light conditions. influencing seedling survival as light avail- Seedlings were able to acclimate ability becomes less limiting. Both aboveg- morphologically to changes in light condi-

18 tions by three strategies: 1) specific leaf area, clearcut expressed 4–8 times greater stem 2) height-to-caliper ratio, and 3) above- volume growth rates than those found in ground-to-root biomass ratio. These adap- thinned stands, without vegetation con- tations to low light are commonly associated trol, although deer browse on the redcedar with other shade-tolerant species. Despite was also highest in the clearcut. Highly these adaptations for survival when light is visible seedlings must have preventative limiting, redcedar in the study area cannot measures installed to protect seedlings be considered a truly shade-adapted species from browse. This study also confirmed in this climate, as it tolerates exposure to that redcedar is more tolerant of shade open-area climate, achieving its most and root competition than is hemlock. productive growth at full solar insolation. In a study investigating the effects of In a similar study, seedlings of redcedar shading due to overtopping brush, red and some associated coastal species were cedar seedlings were found to exhibit planted within clearcut, shelterwood, or nearly 3 times greater height growth when thinned Douglas‑fir stands, each type overtopping vegetation was completely expressing different light and understorey removed from the study site; much greater conditions. The greatest redcedar seedling performance than when the competing growth was found in the clearcut site, vegetation was simply tied back from the which in combination with vegetation redcedar (Adams and Mahoney 1991). control produced the absolute greatest This suggests that transpirational or nutri- growth response (Harrington 2006). Light ent/root competition plays a very signifi- and root competition were thought to be cant role in determining seedling growth the primary growth-limiting factors for in these conditions, perhaps even having a study seedlings. Redcedar seedlings in the greater influence than light availability.

3.5 damaging Redcedar is less susceptible to most obviously be more windthrow-prone than Agents damaging agents than other coastal species. other, less exposed, upland sites. On west- Most damaging agents are restricted to ern and northern Vancouver Island and stressed or dying trees, or are so rare that the central and northern mainland coast, their damage is insignificant and generally wind is the major disturbance factor, and unnoticed. Young redcedar is usually high-velocity storm events are common. healthy, making it a promising species in In this environment, windfirmness is a very coastal forest systems (van der Kamp 1988). desirable characteristic in a commercial timber species. 3.5.1 Snow As a submontane and montane Redcedar is considered moderately species, redcedar has low resistance to resistant to windthrow, ranking higher heavy, wet snowpack. Snow damage than western hemlock and Pacific silver results in stem and branch breakage in fir, and expressing similar resistance as saplings and high-density, immature Douglas‑fir (Minore 1979, 1983). In Great stands (Scagel et al. 1989). With increasing Britain, redcedar is also considered fairly elevation (and snowfall), the proportional windfirm (Savill 1991). This resistance is stand composition of redcedar within likely due to an extensive but less spread- zonal stands progressively diminishes, ing root system that varies with site quality replaced by yellow-cedar (these two spe- and stand conditions. On sites expressing cies may grow together on the same site) high water tables, its wind resistance until in the lower limits of the MH zone is dramatically lessened due to shallow where redcedar becomes absent. rooting. The buttress-like fluting of the lower bole is thought to add structural 3.5.2 Wind Wind-exposed sites will stability, as there appears to be a higher inci-

19 dence of fluting on exposed (wind-affected) attacks than other associated timber species. sites. A recent study at the Malcolm Knapp In the coastal region, the most important Research Forest (Byrne and Mitchell 2007) root and butt rots attacking redcedar are indicates a similar degree of windfirmness Phellinus weiri, Armillaria obscura, and between redcedar and western hemlock; Poria subacida, and the common trunk however, the study site had a water table rots are Poria asiatica and P. albipellucida that restricted rooting depth to approxi- (Boyd 1965; Hepting 1971; van der Kamp mately 1 m. As noted in section 3.1.2 1988). Armillaria obscura girdles and kills (Roots), a relatively greater proportion of young trees, but older trees are not so redcedar roots can be found in the deeper readily destroyed. Poria subacida can cause mineral soil layers than observed with west- extensive butt rot in pole-sized trees, the ern hemlock on mesic sites (i.e., no water damage apparently associated with table constraints to rooting depth). thinning (van der Kamp 1988). Following persistent attacks by Phellinus 3.5.3 Fire The fire resistance and resilience weiri or Armillaria spp., the heartwood of redcedar is low. Like western hemlock, extractives that provide decay resistance redcedar it is severely damaged by crown are eventually detoxified by a series of and surface fire (Minore 1983). Its foliage invading fungi (Jin et al. 1988). As a result, is very flammable and trees with long live the volume of accumulated decay found in crowns are killed by crown and surface living trees can be substantial, and hollow fires. The extensive fine roots in the surface old-growth trees are common. Relative to organic layers and thin bark are also easily the coast, natural redcedar stands in the scorched by surface fires. Risk of fire varies interior feature abundant advance regen- from very low in hypermaritime and wet eration, but the majority are veglings with maritime mesothermal climates to high in incipient stem decay. This raises the ques- dry maritime mesothermal climates. tion as to whether rot-free plantations can be established without the removal of veg- 3.5.4 Insects Redcedar is affected by few etatively established natural regeneration insect pests, but is a host for several eco- (Weetman et al. 1988). nomically important insect species (Furniss In one study, the release of overtopped and Carolin 1977). The gall midge Mayetiola( and dense redcedar stands (approximately thujae) can sometimes cause serious seed 80 years old), in combination with thin- damage. Several defoliators are known ning (performed in the 1940s), caused a but none of them causes serious damage. substantial increase in the incidence of Similarly, several species of bark beetle laminated root and butt rot 20 years later (Phloeosinus spp.) may occur on stressed (Koenigs 1969). The most common species or dying trees. The ambrosia beetle of infection were Armillaria obscura, (Gnathotrichus sulcatus) attacks the wood Corticum galactinum, Phellinus weirii, and of recently killed trees, forming small gal- Fomes annosus. Rots were present in the leries and introducing a staining fungus, unthinned stands but restricted to very degrading salvaged timber (van der Kamp small pockets several inches in length on 1988). The flatheaded borer (Trachykele the roots of infected trees. Conversely, blondeli) is a more serious concern, and root clusters in the thinned stands were can attack healthy trees (van der Kamp extensively decayed throughout. Koenigs 1988). The larvae enters and invades the (1969) postulated that the large amount of trunk, mining principally in the heartwood, residual inoculum (in the form of stumps causing considerable commercial, and from the removed overstorey and under- possibly structural, defect. storey trees) provided the resources neces- 3.5.5 Fungal disease – Roots Redcedar is sary for the large increase in fungal attack. less susceptible to pathological fungal Higher soil temperatures were also consid-

20 ered a factor. These were not young trees, as Phomopsis (Diaporthe lokoyae) can and were healthy when attacked, counter- develop on stressed or damaged trees ing some of the assumptions regarding (Allen et al. 1996). root rot resilience of redcedar, which obviously can be infected and killed if enough 3.5.7 Mammals Browsing from deer and inoculum is present. elk at the seedling and sapling stages is In contrast, Nelson and Sturrock (1993) likely the most serious issue concerning planted seedlings of many species around the regeneration of redcedar (Curran and stumps infected with Phellinus weirii to Dunsworth 1988), although bears are also determine their relative susceptibility to known to damage stands of redcedar when this fungus. After 17 years, there was no alternative food supplies are low (Sullivan evidence that the P. weirii killed any red- 1993). Low-elevation, low-snowpack, and cedar seedlings (0% mortality), unlike warm-aspect sites are the most prone to grand fir 30( %), Douglas‑fir 20( %), Sitka browsing. spruce (7%), or western hemlock (5%). Fencing, physical barriers, and chemi- However, deer browse was an issue com- cal repellents are the main methods of promising redcedar height growth in this seedling protection. Barriers are the pre- study. ferred method, but the costs associated with their installation and maintenance 3.5.6 Fungal disease – Foliage and bark over time are quite high. The physical bar- Redcedar germinants may be damaged riers include: 1) mesh type (degradable by damping-off due to fungal infection, plastic or Stucco wire), 2) shelter types, or although larger seedlings are less suscepti- even 3) the complete fencing of the planta- ble. In addition, redcedar may be attacked tion. For a more detailed account of these by several foliar diseases, most severely by barrier types, see Henigman (1999). cedar leaf blight (Didymascella thujina), Yerbury (1999) noted that the costs per which can induce complete defoliation of seedling can range from slightly over one young trees, or the lower crown of older dollar to over three dollars for the installa- trees (van der Kamp 1988). Also known as tion of mesh-type protection, excluding Keithia blight, cedar leaf blight prevalence the costs of the seedling itself. Including can be most severe in dense stands where annual maintenance costs can increase the humidity is highest (Allen et al. 1996; Kope cost to almost six dollars per seedling over and Sutherland 1994a). The prevalence of 5 years. In addition to protection by physi- cedar leaf blight infestation under high cal barriers, Henigman (1999) recom- humidity conditions makes this disease an mended planting with large vigorous ongoing challenge for seedlings grown at seedlings and fertilization. Those seedlings high densities in a nursery environment. that have been protected from browse Modifying seedling densities and styro have generally performed exceptionally block configuration may reduce infesta- well, with rapid, vigorous growth tion rates (Kope and Sutherland 1994b). (Figure 27). Natural resistance to this disease can vary In some areas of the province, most between different redcedar populations, notably on the Queen Charlotte Islands with coastal, low-elevation populations (Haida Gwaii), the regeneration of red exhibiting greater resistance than those cedar is seriously compromised by browsing. found at higher elevations in the interior Overbrowsing by the introduced Sitka of the province (Russell et al. 2007). black-tailed deer on Haida Gwaii has radi- Although relatively uncommon in cally altered the forests and natural vegeta- redcedar, canker diseases of the bark, such tion communities, severely reduced shrub

21 and herb layers, and nearly eliminated in taste). Work in this area is ongoing but redcedar regeneration (Pojar 1999). The it appears that monoterpene production effects of the deer and other animal intro- may be related to historical browse pres- ductions are cascading through plant, sures and the post-glacial re‑colonization animal, and insect communities (Allombert of British Columbia timberlands. Certain et al. 2005a, 2005b; Stockton et al. 2005), populations of redcedar appear to have seriously threatening the survival of higher concentrations of these distasteful endemic and rare plants and animals. (to deer) compounds, and the incorpora- Because of the major ecological damage tion of a large proportion of seedlings from that an extensive and uncontrolled deer popu these populations that are either similarly lation can inflict upon the resources of an or less palatable than the surrounding veg- island location, other more direct methods etation within harvested areas may make of controlling deer populations under con- it possible to regenerate redcedar without sideration include possible culls, the intro- other intensive (and expensive) measures, duction of predators (i.e., wolf), or even such as physical barriers. the use of contraceptives (Garrott 1995). In addition, it appears that there is a The recent discovery of preferential connection between the production of deer browsing on Haida Gwaii (Vourc’h monoterpenes and troponoid (extractive) et al. 2001, 2002a,b,c, 2003) and the substances. Current research is exploring the subsequent redcedar breeding/selection identification of those clones of redcedar efforts (Russell 2006) hold much promise. with higher production of these terpenoid It was determined that deer prefer redce- compounds, including monoterpenes dar with lower foliar concentrations of (browse resistance) and tropolones (decay monoterpenes (Figure 28). These sub- resistance) (Mattsson and Russell 2007). stances make the foliage much less palat- The ability to identify and select for these able (this is not a subtle difference—the important characteristics may yield future authors easily distinguished the difference redcedar plantations that are both less palatable to deer and express greater resistance to fungal colonization.

5 otal needle monoterpenes (000 ppm) T

0 0 10 20 30 40 50 60 Browse (%)

figure 28 Relationship between total needle figure 27 A healthy and vigorous monoterpenes and percent browsing by clone in redcedar seedling 2 years after planting, western redcedar grown at Fairservice Main, south protected by Vexar tubing. Vancouver Island (Russell 2006).

22 3.6 growth Redcedar trees often possess a rapidly tion, it has been noted that the incidence Development tapering stem, highly fluted lower bole, and severity of fluting increases with Patterns and persistent coarse branches in the decreasing stand density (Oliver 1988) lower crown. Based upon their knowledge and with higher growth rates (DeBell and as researchers and silviculturists, Oliver Gartner 1997; Singleton et al. 2003). et al. (1988) discuss in detail the physio- However, this postulated explanation of logical and morphological characteristics fluting and stem development has not been of redcedar that lead to the development verified by careful observation and subse- of possibly undesirable morphological quent research. DeBell and Gartner (1997) characteristics. Determining the causes of could find no relationship between the loca- these morphological traits can assist field tion of dying or dead lower branches and the silviculturists in management decisions development of flutes. Fluting was always that can reduce the incidence of these found to be deepest at the base of the tree, characteristics, and induce the develop- the opposite of what would be expected if ment of more desirable growth forms. flute development was influenced by dying Redcedar has a rapidly tapering stem, branches. In fact, DeBell and Gartner (1997) which Oliver et al. (1988) suggest is a detected minor flutes developing from the result of the high shade tolerance of the base of all studied trees, although most lower crown. The longevity of lower sup- were to a very minor extent and unlikely pressed branches on sub-canopy redcedar to be noticed by casual observation. Flutes trees is similar to those on trees grown in appear aligned with spaces between major the open or in low-density stands. One roots (DeBell and Gartner 1997; Singleton explanation for the taper is that the lower et al. 2003), suggesting that fluting devel- branches contribute photosynthate down- ops as a response to mechanical stresses ward from the stem and allow the lower acting upon the stem. Fluting appears to be stem to grow (radially) at relatively higher more prevalent on those stems growing in rates than those species that shed their locations where rooting substrates may be lower branches more frequently. less structurally sound, such as on decaying Redcedar can also develop a buttressed logs (Figure 29), wet sites, or where or fluted base. Fluting is the development exposed to frequent wind forces. of longitudinal grooves and ridges on the lower bole, resulting from uneven radial growth (Figure 18). For unknown reasons, radial growth stops at one or more locations around the circumference of the stem while the rest of the stem continues to grow at the same or higher rates. Oliver et al. (1988) believe that fluting may be caused by the restriction of cross-transport (lateral) in the phloem of the lower-bole due to the influence of very suppressed branches. Because a suppressed branch provides little photosynthate to the area below it, an indented flute will result in these locations where the tree grows radially very little, relative to surrounding cambium that is fed by more vigorous limbs higher in the canopy. Fluting may also result from unusual figure 29 Distinctly developed fluting in a rooting conditions such as downed, decay- redcedar tree that had established on a ing logs and wet sites (Figure 29). In addi- downed, above-ground log.

23 Clearly, the growth of redcedar within es and increased stem taper often develop its climatic and edaphic amplitude varies and stay alive such as in low-density stands greatly depending on light conditions—its or suppressed (below-canopy) trees. growth increases with increasing irradiance. However, redcedar will continue to survive even under low light conditions due to its high shade tolerance (Klinka et al. 2000), albeit growing slowly and with poor form (heavy branching and tapered bole). After the release of sub-canopy redcedar through thinning, Oliver et al. (1988) suggest that much of the increased growth following release would be directed to branches in a spreading crown, and less to the stem wood. If suppressed for a significant period, the lateral branches do not appear to be controlled by the terminal any longer and begin spreading out and growing upward. Even-aged redcedar stands growing under high-density conditions have their crowns in full light, with the terminal maintaining strong epinastic control; that is, the terminal exerts control over the length and direction of branches resulting in the development of a cone-shaped crown, with relatively short lateral branches (Oliver figure 30 Examples of dense, immature, et al. 1988) (Figures 5 and 30). Fluting is naturally regenerated, pure redcedar stands much less pronounced and taper is less of established after clearcutting and burning. a concern. In contrast, large, long branch- Note the desirable stem form.

3.7 genetics Evidence of genetic variation in redcedar environment (Sakai and Weiser 1973). has been shown in leaf blight resistance Bower and Dunsworth (1988) found no (Soegaard 1956; Russell 2007), frost resis- significant differences in survival and tance (Sakai and Weiser 1973), and prove- growth among three Vancouver Island nance performance (Lines 1987), but these provenances (low, mid, and high elevation) studies did not detect the substantial vari- in plantations near each collection site; ation in genetic expression between indi- however, there were differences among viduals commonly observed in other species. locations. Lack of isoenzyme variation in Across its range, redcedar characteristics newly germinated seedlings from British seem to vary less than all other northwest- Columbia, western Oregon, and eastern ern conifer species, indicating that it is rel- and western Washington indicates that atively genetically uniform (von Rudloff and redcedar populations contain little genetic Lapp 1979; Bower and Dunsworth 1988; polymorphism (Copes 1981; Yeh 1988). El‑Kassaby 1999; Glaubitz et al. 2000). Leaf oil terpene composition is similar in Seedlings from different seed sources usu- populations at both low and high elevations ally have remarkably similar forms and in British Columbia, Washington, Oregon, growth rates when grown in the same Idaho, and Montana; and only small

24 differences between coastal and interior impacts of inbreeding (homozygous populations have been detected (von recessive expression of lethal and sublethal Rudloff and Lapp 1979; von Rudloff et al. genes) (Woods et al. 2002). However, in 1988). Similarly, Grossnickle et al. (2005) contrast to other species, redcedar seems identified minor differences in foliage car- relatively immune to the typical negative bon isotope discrimination and foliage effects of self-fertilization (Wang and conductance between some redcedar popula- Russell 2006), and does not appear to suf- tions, but measures of gas exchange response fer significant losses in productivity due to and water use efficiency among redcedar inbreeding depression. Apparently, the populations demonstrate very little varia- species is extremely plastic in its morpho- tion across a longitudinal transect/precipi- logical development and response to site tation gradient—coastal to interior (in conditions (El‑Kassaby 1999), offsetting spite of large differences in environmental the relative homogeneity of its genetic conditions of seed source location). Fan makeup. If fact, redcedar resistance to leaf et al. (2008) also detected very little varia- blight and frost (obviously beneficial traits) tion in water use efficiency across similar has been shown to be homozygously populations, indicating no substantial recessive (Soegaard 1969). genetic adaptation to the climatic precipi- Based upon the reduced genetic variability tation conditions of the parent populations. of the species, Bower and Dunsworth (1998) The apparent lack of variation across this suggest that: 1) intensive breeding programs climatic gradient is surprising, considering may not be justified, 2) greater gains may the absolute differences in precipitation be captured from management practices, and seasonal drought. and 3) seed transfer rules can be simplified El‑Kassaby et al. (1994) postulate that a relative to other commercial species. population size bottleneck due to droughts In spite of these comments regarding occurring 6000–10 000 years ago may be the utility (or lack thereof) of redcedar responsible for these low levels of hetero breeding programs, current genetic research zygosity. Additional genetic research has demonstrated much potential to (Glaubitz et al. 2000; O’Connell et al. reduce the palatability of foliage to deer 2008) provides evidence that the current (Vourc’h et al. 2002b; Russell 2006a), and distribution of redcedar (from the possibly even to improve in the concentra- Alexandra Archipelago in Alaska to tions of heartwood extractives, providing northern California) is a result of migra- more fungi-resistant redcedar wood prod- tion and colonization from a single popu- ucts from second-growth timber (Mattsson lation that survived the most recent and Russell 2007). (Wisconsin) glacial period (80 000– A provincial breeding program for 18 000 years ago) in a refuge located to the redcedar exists, although still relatively south of the maximum glacial extent, pos- immature in comparison to programs sibly even south of its current range. No focussed upon other valuable conifers of genetic evidence suggests populations of the province (Russell 2006b). Using an redcedar existing in coastal refugia within accelerated breeding cycle experimental the glacial ice sheets. program, Russell and Ferguson (2008) were Redcedar exhibits the highest level of able to produce five generations of progeny self-fertilization reported of all coniferous in only 10 years. Due to the relatively low species (El‑Kassaby et al. 1994; O’Connell impact (negative) of self-fertilization upon et al. 2001), with the degree of “selfing” subsequent stand productivity, the use of increasing with the size of the individual self-fertilization techniques may facilitate tree (O’Connell et al. 2004). Typically, high a continued and rapid expansion of the rates of self-fertilization may lead to reduced provincial redcedar breeding program. levels of productivity due to the long-term With the importation of redcedar as a

25 potential timber crop on the British Isles, height growth and for resistance to the British Forestry Commission estab- Didymoscella thujina. Recommended lished provenance tests in the early 1970s provenances for British climatic condi- using 13 seed origins from British Columbia, tions are from the north slopes of the Washington, and Oregon. Significant differ- Olympic Mountains and from Ladysmith ences among provenances were found for (Rollinson 1988).

26 4 Ecology

4.1 climatic Redcedar is adapted to climates with falling as rain in the spring and autumn, Amplitude abundant precipitation and high humidity. and the remaining half falling as winter It is most common in montane continen- snow (Boyd 1965). tal cool temperate (the interior wet belt) Where precipitation is sufficient, low and cool and cold mesothermal climates temperatures appear to be the most limit- (coastal), and less frequently in the mari- ing climatic factor. Minore (1983) estimat- time subalpine boreal climates (higher ele- ed that the northern limits of redcedar vations on the coast) (Krajina 1969; Klinka follow the 11.5°C mean summer tempera- et al. 2000). ture isotherms in southeastern Alaska. The coastal population of redcedar tol- Krajina (1969) estimated absolute mini- erates extremes in annual precipitation, mum temperatures experienced by redce- ranging from less than 800 mm on south- dar in British Columbia to be between ern Vancouver Island to more than 4000 -10° and -30°C for coastal populations, mm (mostly as winter rainfall) on western and between -14° and -47°C for interior Vancouver Island (Meidinger and Pojar populations. Redcedar grows from sea 1991). Interior populations receive about level to about 1200 m in southern coastal 700 mm to more than 1200 mm, with half British Columbia.

4.2 occurrence in On the coast, redcedar occurs most abun- Meidinger and Pojar 1991; Klinka et al. Biogeoclimatic dantly in the Coastal Western Hemlock 2000). The relative occurrence levels of Units (CWH) zone, and is sporadic in the redcedar within the subzones (i.e., cli- Coastal Douglas-fir (CDF) and Mountain mates) of the CWH, CDF, and MH zones Hemlock (MH) zones (Krajina 1969; are shown in Table 2.

Table 2 Relative occurrence of redcedar in subzones of the Costal Douglas-fir (CDF), Coastal Western Hemlock (CWH), and Mountain Hemlock (MH) zones. Occurrence classes are: low (sporadic to infrequent), medium (common or frequent), and high (very frequent or abundant) (Banner et al. 1993; Green and Klinka 1994).

Subzone Occurrence Comment

Moist Maritime CDF (CDFmm) Low Sporadic; restricted to non-water-deficient sites Wet Hypermaritime CWH (CWHwh) Medium to High Infrequent in second-growth stands Very Wet Hypermaritime CWH (CWHvh) High Abundant; infrequent in second-growth forests Very Dry Maritime CWH (CWHxm) Low Absent on water-deficient sites Dry Maritime CWH (CHWdm) Medium Absent on very dry sites Moist Maritime CWH (CWHmm) Low to Medium Decreasing with increasing elevation (snowpack) Wet Maritime CWH (CWHwm) Low Sporadic to absent Very Wet Maritime CWH (CWHvm) High Decreasing with increasing elevation (snowpack) Dry Submaritime CWH (CWHds) Low to Medium Decreasing with increasing continentality Moist Submaritime CWH (CWHms) Low Decreasing with increasing continentality Wet Submaritime CWH (CWHws) Low Rare to absent Moist Maritime MH (MHmm) Low At the lowest elevation limits Wet Hypermaritime MH (MHwh) Low At the low elevation limits

27 The climate on the coast varies along region are generally cooler and have grow- the longitudinal gradient (west to east) ing-season water surplus compared to the from hypermaritime to submaritime; and southern coastal region. These climatic along the latitudinal gradient (south to differences are reflected in vegetation and, north) as temperature and evapotranspira- therefore, in zonal (Table 2) and plant tion decrease. Precipitation remains high community classification (see section 4.5: throughout the whole region. In conse- Vegetation and Site Classification). quence, the soils in the northern coastal

4.3 Edaphic Redcedar has a broad edaphic amplitude moisture regime (SMR) wet sites (Figure Amplitude (Figure 31). It tolerates a wide range of soil 32), which typically are nutrient-medium moisture and nutrient conditions within to -rich, but not on SMR very wet. It toler- its climatic range, but the most productive ates water-deficient sites to some degree, growth occurs on fresh to moist, nutrient- but does not tolerate the driest sites in dry rich soils. It tolerates water surplus and and warm coastal climates (Figure 33). flooded soils, and nutrient-deficient soils It can grow on sites too dry for western (Krajina 1969; Minore 1990; Klinka et al. hemlock presumably because it has deeper 2000). Redcedar can be abundant on soil root penetration (Franklin and Dyrness 1973; Klinka et al. 2000). Redcedar frequently occurs on nutri- Soil nutrient regime ent-poor soils, but natural regeneration VP P M R VR and planted seedlings often grow poorly and are chlorotic, such as those on salal- VD dominated sites on northern Vancouver Island (Figure 34). MD Redcedar grows on soils derived from a variety of parent materials. Krajina (1969) characterized redcedar as calciphilous, SD growing best on very slightly acidic to neutral, Ca-rich soils. On Vancouver Island, productive growth of redcedar is F found on limestone and limestone-derived soils. In Great Britain, redcedar grows well M on chalk-derived soils but tolerates both

tual soil moisture regime moisture soil tual acid and calcareous soils (Rollinson 1988).

Ac Krajina (1969) also stated that redcedar VM requires very high nutrient levels for optimum nutrition. However, it is not nutri- W ent-demanding, as it commonly grows on poor sites (Weetman et al. 1988). Krajina (1969) and Krajina et al. (1973) Figure 31 Generalized edaphic amplitude of described soil conditions for the most pro- redcedar in the CWH zone in relation to actual ductive (optimum) growth as rich in Ca, soil moisture and nutrient regimes. Light green Mg, and nitrate N. Based on sand culture indicates absence or infrequent occurrence and experiments, soil analyses, and field obser- marginal productivity, medium green indicates vations, they concluded that redcedar frequent occurrence and low productivity, and requires nitrate-N for its growth and can- dark green indicates very frequent occurrence not tolerate the complete replacement of and medium to high productivity. nitrate-N by ammonium compounds.

28 Based on its distribution in southwestern Oregon, Imper (1981) and Imper and Zobel (1983) suggest that redcedar is tolerant of soils high in Ca, N, and Ca:Mg ratios. Krajina et al. (1973) also demonstrated that redcedar seedlings require more N for optimum growth than Sitka spruce, western hemlock, or Douglas-fir. Additional information regarding the foliar nutrition of redcedar can be found in section 5.5.4: Fertilization.

Figure 32 Skunk cabbage – redcedar communities typically occupy margins of coastal lakes and depressions, forming a transition from non- forested wetland to upland communities.

Figure 33 A very dry, rock outcrop site on Bowen Island. Common tree Figure 34 A chlorotic redcedar plantation on species on such sites are more drought-tolerant than redcedar: Rocky an N-deficient, salal-dominated, old-growth Mountain juniper, Douglas-fir, and/or lodgepole pine. cutover on northern Vancouver Island.

29 4.4 associated Redcedar is present in early, mid-, and pole pine, yellow-cedar, black cottonwood, Tree Species late-succession stages in uneven- (less red alder, and bigleaf maple (Minore 1990; often in even-) aged stands. It is most Klinka et al. 2000). common in mixed-species stands and less Throughout its range along the coast, frequently occurs in pure stands. Mixed- the presence of redcedar has been shifting species stands of shade-intolerant tree spe- in favour of western hemlock and Douglas- cies with redcedar are typically layered, fir (in the south). The dominance of red- with the shade-tolerant and slower-grow- cedar populations is decreasing due to ing redcedar relegated to below-canopy, poor establishment success (both natural subordinate crown positions (Figures 35 and artificial regeneration) and to its and 36). In the coastal region, redcedar relegation to the lower tree stratum and commonly associates with many species: resulting slower growth rates in sub-cano- Douglas-fir, western hemlock, Sitka py environments. spruce, grand fir, Pacific silver fir, lodge-

Figure 35 A markedly stratified (two-storeyed) structure is typical for mixed-species stands of Douglas-fir and redcedar. It is not apparent whether such mixtures are even- or uneven-aged. In the absence of disturbance, redcedar will replace shade-intolerant Douglas-fir. Figure 36 A stratified (two-storeyed) structure is typical for mixed-species stands of hardwoods (here of black cottonwood) and redcedar. In the absence of disturbance, redcedar will replace a short-lived, shade- intolerant black cottonwood.

30 4.5 vegetation 4.5.1 Vegetation classification Mature species on those nutrient-rich sites with- and Site and old-growth stands on the coast that out a significant and prolonged soil mois- Classification have or are predicted to have a significant ture deficit. Therefore, edaphic climax component of redcedar at the final (cli- stands are characterized not only by the max) stage of secondary succession (see presence of redcedar, which may be absent section 4.7: Succession) were classified by in early- and mid-succession stages, but Krajina (1969), Nuzsdorfer and Klinka also by climatic and edaphic site qualities. (1988), and Klinka et al. (1996b). We are These environmental relationships are aware of the elusiveness of explicitly defin- reflected in the site classification for the ing the climax concept, and of the difficul- coastal region (Banner et al. 1993; Green ties in recognizing or predicting the and Klinka 1994). composition of climax stands. Moreover, At the highest categorical level, the the distinction between minor and major most productive actual and potential red- components in stand composition is arbi- cedar stands are classified in the Redcedar trary, for redcedar often occurs as a persis- – Salmonberry (Thuja plicata – Rubus tent component in many old-growth spectabilis) order, which is comprised of coastal stands, even if only in the under- five alliances, each consisting of two or storey. In view of its high shade tolerance, more associations (Table 3). The sampled edaphic adaptations, natural regeneration stands of this order are found on slightly capacity, and longevity, Krajina (1969) dry to wet moisture regimes, and medium considered redcedar an edaphic climax to very rich nutrient regimes within the

Table 3 Vegetation units of the most productive coastal Redcedar – Salmonberry (Thuja plicata – Rubus spectabilis) order (simplified from Klinka et al. 1996b) and their occurrence

Alliance Association Occurrence

Thuja plicata – Tiarella trifoliata (Slightly dry), fresh to moist sites Alnus rubra – Rubus spectabilis CDF, CWH; submontane sites; floodplains Thuja plicata – Oemleria cerasiformis CDF; floodplains, mainly on Vancouver Island Thuja plicata – Achlys triphylla CWH; submontane and montane sites, Vancouver Island Thuja plicata – Polypodium glycyrrhiza CWH, steep-rocky sites Thuja plicata – Acer circinatum Mainland CWH, submontane and montane sites Thuja plicata – Rubus spectabilis Mainland CWH, submontane and montane sites Picea sitchensis – Tiarella trifoliata Fresh to moist sites (infrequent on mainland) Picea sitchensis – Tiarella trifoliata Mainly hypermaritime CWH; submontane sites, floodplains Picea sitchensis – Rubus spectabilis Mainly hypermaritime CWH; submontane sites, floodplains Picea sitchensis – Oplopanax horridus Mainly hypermaritime CWH; submontane sites, floodplains Chamaecyparis nootkatensis – Tiarella trifoliata Fresh to moist sites Chamaecyparis nootkatensis – Tiarella trifoliata CWH; upper montane sites Thuja plicata – Vaccinium ovatum Hypermaritime CWH; Vancouver Island Abies amabilis – Tiarella trifoliata Fresh to moist sites Abies amabilis – Achlys triphylla CWH; montane sites, Vancouver Island Abies amabilis – Streptopus amplexifolius CWH; montane sites Abies amabilis – Oplopanax horridus CWH; montane sites Thuja plicata – Lysichitum americanum Wet sites Alnus rubra – Lysichitum americanum CDF, CWH; submontane and montane sites Abies grandis – Lysichitum americanum CDF; submontane sites on Vancouver Island Picea sitchensis – Lysichitum americanum Hypermaritime CWH, submontane sites Thuja plicata – Sphagnum Hypermaritime CWH; submontane and montane sites

31 CDF, CWH, and (marginally) MH zones. of the Yellow-cedar – Foamflower The Redcedar – Salmonberry stands are (Chamaecyparis nootkatensis – Tiarella known for the majestic stature of all asso- trifoliata) alliance are confined to sub- ciated tree species, including Douglas-fir, montane to montane, very moist sites in grand fir, Pacific silver fir, and Sitka spruce. similar climates as those of the Sitka The Redcedar – Foamflower (Thuja pli- spruce – Foamflower alliance (Figure 38). cata – Tiarella trifoliata) alliance repre- Communities of the Redcedar – Skunk sents the central concept of the order cabbage (Thuja plicata – Lysichitum (Figure 13), while other alliances repre- americanum) alliance are observed in sent climatic and/or edaphic variations. submontane and montane wet sites Communities of the Sitka spruce – throughout the CDF and CWH zones. Foamflower (Picea sitchensis – Tiarella Communities of the Pacific silver fir – trifoliata) alliance are confined to sub- Foamflower (Abies amabilis – Tiarella tri- montane, seepage water–receiving sites foliata) alliance are confined to the and fluvial terraces in the hypermaritime distributional area of Pacific silver fir; that and wetter maritime CWH subzones on is, predominantly high-elevation, cool and the Queen Charlotte Islands, Vancouver snowy climates (Figure 39). Island, and the central coast of mainland The floristic composition of stands in British Columbia (Figure 37). Communities the Redcedar – Salmonberry order are

Figure 37 A low-density, old-growth stand of Sitka spruce, Figure 38 A high-density, naturally regenerated, second- redcedar, western hemlock, and Pacific silver fir on a lower, growth stand of western hemlock and redcedar on a zonal site steep, seepage slope in the central coastal mainland. in the CWHvm subzone.

32 diverse and their structure is multi-lay- T. laciniata, and Trillium ovatum. The ered. The tree layer of old-growth stands moss layer can be somewhat sparse, usually has variable proportions of west- including notably Kindbergia praelonga, ern hemlock and redcedar. Depending on Leucolepis menziesii, and Plagiomnium climate, location, history of disturbance, insigne. The associated soils include and succession stage, Douglas-fir or Sitka Brunisols, Gleysols, Podzols, and spruce may also be present. The shrub Humisols (SCWG 1998), with Moder or layer is well developed, and includes: Acer Mull humus forms (Green et al. 1993). circinatum and A. macrophyllum (in the Typically, Redcedar – Salmonberry south), Oplopanax horridus, Ribes lacustre, stands occur on lower, seepage slopes Rubus parviflorus, R. spectabilis, and (Krajina 1969; Klinka et al. 2000, 2005). Sambucus racemosa. Athyrium filix-femi- When the contribution from both soil and na, Adiantum pedatum, Gymnocarpium seepage is considered together, the supply dryopteris, Dryopteris expansa, and of available nutrients is high. As a result, Polystichum munitu are common ferns. vegetation is rich in all macronutrients Herb species include: Achlys triphylla (in and the biogeochemical cycle counteracts the south), Galium triflorum, Streptopus the processes of soil podzolization charac- amplexifolius, S. roseus, Tiarella trifoliata, teristic of the CWH zone.

Figure 39 An unmanaged mixed-species stand of redcedar and Pacific silver fir on a moist, nutrient-rich site in the CWHvm subzone.

33 4.5.2 Site classification The purpose of were framed by Banner et al. (1993) and site classification in the system of biogeo- Green and Klinka(1994) (Table 4). We climatic ecosystem classification BEC( ) is consider these sites as excellent candidates to organize local ecosystems according to for growing redcedar as the primary com- similarities in climate, edaphic conditions mercial species. Several additional site and, eventually, other environmental fac- series in the CWHvh, CWHwh, and tors that strongly influence vegetation CWHvm subzones that feature a signifi- development (see Pojar et al. 1987 and cant proportion of redcedar in old-growth Meidinger and Pojar 1991). The resulting stands other than nutrient-rich were also site units are characterized and identified identified. Most importantly, this suggests using environmental features that are that redcedar is likely a variable climax linked to potential vegetation. component on a wider range of sites with- Site units, specifically site series, cir- in the wetter, maritime portion of the cumscribing plant communities of the CWH zone than originally described by Thuja plicata – Rubus spectabilis order Krajina (1969).

4.6 Ecological As a nurse species, redcedar provides sev- species, 5) suppression of understorey veg- Role eral beneficial ecological effects within the etation, and 6) wildlife habitat. These ecosystems in which it grows. These bene- items are discussed briefly below: fits include: 1) potential improvement of soil quality, 2) increases of plant and 4.6.1 Soil quality amendment Relative to structural diversity (Figure 40), 3) soil sta- associated tree species, redcedar is thought bilization, 4) self-pruning of timber crop to have the highest foliar requirements for N, K, Ca, and Mg to achieve optimal nutrition (Minore 1983), and yet is known to have the lowest percent composition of N in its foliage (Minore 1979). Redcedar is also known to accumulate Ca and Mg in its foliage (particularly in older branchlets), promoting the cycling of these nutrients within the forest floor (Alban 1969; Radwan and Harrington 1986; Collins et al. 2001). Radwan and Harrington (1986) considered redcedar a Ca-accumulator in excess of its nutrient requirements rather than requiring Ca-rich soils, thereby acting as a “Ca-pump” to the site (Kimmins 1997). Redcedar litterfall can have a dramatic impact upon forest floor chemistry and nutrient cycling activity. Alban (1967, 1969) found substantial differences in the soils under western hemlock and redcedar in eastern Washington and northern Idaho. More locally, Collins et al. (2001) examined forest floors in single- and Figure 40 The bark of old redcedar trees is mixed-species, second-growth stands of calcium-rich, often supporting corticolous fern western hemlock and redcedar on zonal and bryophyte communities. sites in the CWHvm1 variant in southern

34 Table 4 Site series in the subzones of the CDF and CWH zones where redcedar is considered a significant (major) or potential climax species (Banner et al. 1993; Green and Klinka 1994).

Subzone Upland sites Floodplain sites Fluctuating water table sites Moist Maritime CDF 05 CwFd-Kindbergia Cw-Snowberry 12 Cw-Vanilla-leaf (CDFmm) 06 CwBg-Foamflower 13 Cw-Indian plum 11 Cw-Skunk cabbage 14 Cw-Slough sedge Dry Submaritime CWH 05 Cw-Solomon’s seal Redcedar may be a These sites have not been (CWHds) 07 Cw-Devils’s club Minor species found 12 CwSs-Skunk cabbage Moist Submaritime CWH 04 BaCw-Oak fern Redcedar may be a These sites have not been (CWHmm) 06 BaCw-Devil’s club minor species found 11 CwSs- Skunk cabbage Wet Submaritime CWH 04 BaCw-Oak fern Redcedar is probably These sites have not been (CWHws) 06 BaCw-Devil’s club absent found 11 CwSs-Skunk cabbage Very Dry Maritime CWH 05 Cw-Sword fern Redcedar may be a Cw-Salmonberry (CWHxm) 06 HwCw-Deer fern minor species Cw-Black Twinberry 07 Cw-Foamflower Cw-Slough sedge 12 CwSs-Skunk cabbage Dry Maritime CWH 05 Cw-Foamflower (CHWdm) 06 HwCw-Deer fern 07 Cw-Lady fern 12 Cw-Skunk cabbage Moist Maritime CWH 04 CwHw-Sword fern Redcedar may be a These sites have not been (CWHmm) 05 BaCw-Foamflower minor species found 07 CwYc-Goldthreada 07/08 Cw-Salmonberryb 10/12 CwSs-Skunk cabbageb Wet Maritime CWH redcedar is not a major Redcedar is absent These sites have not been (CWHwm) component in any site series found Very Wet Maritime CWH 03 HwCw-Salalc No floodplain site These sites have not been (CWHvm) 04 CwHw-Sword fernc series have been found 05 BaCw-Foamflowerc described; redcedar 07 BaCw-Salmonberryc may be a minor 09/12 CwYc-Goldthreadc species in low 11/14 CwSs-Skunk cabbagec elevations Wet Hypermaritime CWH 02 CwHw-Salald No floodplain site These sites have not been (CWHwh) 03 CwSs-Sword fern series have been found 05/03 CwSs-Foamflowerd described; redcedar 06/04 CwSs-Conocephalumd may be a minor 10/05 CwYc-Goldthreadd species in low 12/06 CwSs-Skunk cabbaged elevations Very Wet Hypermaritime 01 CwHw-Salal Redcedar may be a These sites have not been CWH (CWHvh) 03 CwYc-Salal minor species found 05 CwSs-Sword fern 06 CwSs-Foamflower 07 CwSs-Devil’s club 11 CwYc-Goldthread 13 CwSs-Skunk cabbage a In the CWHmm2 variant. b In the CWHmm1 and CWHmm2 variants, respectively. c Historically in both Vancouver and Prince Rupert Forest Regions; now all Coast Forest Region. d In the CWHwh1 and CWHwh2 variants, respectively.

35 British Columbia with respect to soil acid- ent availability, Prescott et al. (2004) dem- ity (pH), and concentrations of total C, onstrated that redcedar litter is actually total N, mineralizable-N, and total Ca, one of the slowest to decompose of the Mg, K, P, and S. Forest floor pH and con- major British Columbia tree species (hard- centrations of mineralizable-N, total Ca, woods and softwoods). Prescott and and K increased, while concentrations of Versterdal (2005) suggest that the higher total C and S decreased in order from levels of nitrate and microbial activity hemlock to hemlock-redcedar to redcedar found in forest floor under redcedar are stands. These results are consistent with merely a result of higher pH, and do not previous studies suggesting that forest reflect an elevated level of nitrogen avail- floor decomposition and nutrient availability. N-mineralization rates have been ability increase with increasing presence found to be relatively low, and are as likely of redcedar. Redcedar forest floors are controlled by site factors as they are by consistently observed to have very high species composition (Prescott et al. 2000). pH (~6.0) and Ca concentrations relative Prescott and Versterdal (2005) also suggest to other species (Prescott and Vesterdal that the tendency of redcedar occurring 2005). on richer sites (in spite of its tolerance of Acid, mycogenous Mor humus forms nutrient-poor conditions) is likely more commonly develop in hemlock stands, associated with its tolerance of wetter while less-acid, more-zoogenous Morm moisture regimes (often found at the base oder, Moder, or even Mull humus forms of slopes receiving nutrient-rich seepage) are more often found under redcedar than its ability to improve site quality stands (Krajina 1969; Green et al. 1993; through its litterfall. Finally, Prescott and Collins et al. 2001). Vesterdal and Raulund- Vesterdal (2005) state that redcedar “nei- Rasmussen (1998) suggest that forest floor ther prefers N-rich conditions, nor does it characteristics and nutrient availability create them.” can be modified by the selection of appropriate crop trees. Harmer and Alexander 4.6.2 Plant and structural diversity (1986) have even hypothesized that the Including a component of redcedar can Ca-rich litter that undergoes nitrification increase plant and structural diversity. might give redcedar a competitive advan- Most forests do not have uniform micro- tage in nitrogen-poor soils, possibly topography or ground surface material improving the relative vigour and growth composition, but rather feature mounds of redcedar over time in contrast to other and depressions, with a variety of different species on similarly nutrient-poor sites. materials on the forest floor (e.g., litter, However, the degree to which redcedar decaying wood, exposed mineral soil, litterfall may “improve” the inherent qual- coarse fragments, and surface water). The ity of a site is in dispute. Although there is pattern and quality of microsites is reflect- no doubt regarding the influence of redce- ed in the understorey vegetation. A domi- dar litter upon several key chemical prop- nance of ericaceous plants can be found in erties of the forest floor (pH and base the presence of acid Mor humus forms saturation in particular), there is some and/or a high cover of decaying wood. In recent controversy regarding the contrast, the dominance of herbs and “improvement” of soil quality and result- ferns can reflect the presence of friable ing stand productivity. Redcedar is not Moder and Mull humus forms and higher like Alnus species, which actually add concentrations of plant-available nutrients. nitrogen to the system through the actions Once established, redcedar litterfall may of their associated nitrifying bacteria. By modify forest floor properties, promoting challenging some basic assumptions the development of less acid Mor and involving litter decomposition and nutri- Mormoder humus forms. Although the

36 presence of redcedar may not directly increase the nutrient availability of a site, it may lead to an increase in microsite complexity, and in turn, the presence and diversity of understorey vegetation (as permitted by level of available light). Tree-size diversity has been used successfully as a proxy for structural diversity. Using tree height and diameter, Varga et al. (2005) investigated variation in tree-size diversity between single- and mixed-species stands (50–120 years old) on intermediate sites in western Canada. They found that single- and mixed-species stands of shade-tolerant species (western hemlock and redcedar) had similar structural diversity. When mixtures were composed of shade-intolerant species (lodgepole pine and western larch) or shade-intolerant and -tolerant species (lodgepole pine and black spruce), the mixed-species stands were more structurally diverse than the single- Figure 41 Redcedar stands on rocky sites can species stands. Mixing redcedar with lessen erosion of shallow soils during heavy shade-intolerant species such as Douglas- rains. fir or with tree species with a greater height growth rate than redcedar could improve stand structural diversity (e.g., development of multi-layered stands). This could be considered as a means to provide for biodiversity and other wildlife values in future stands. The longevity of redcedar snags will add greatly to future biodiversity and habitat values of the stand.

4.6.3 Soil stabilization With its wide edaphic amplitude, tolerance to flooding, and profuse root system (Figures 21 and 22), redcedar stands can occupy rocky, seepage slopes, high-bench floodplains, and stream-edge sites. This vegetative cover provides excellent protection for sensitive sites, lessening soil erosion potential during high rainfall and flood events (Figures 41 and 42).

4.6.4 Self-pruning In stratified stands where redcedar grows uniformly in the lower canopy stratum, it will shade the Figure 42 Redcedar stands, along with red lower live branches of taller, shade-intoler- alder, frequently occupy stream-edge sites and ant crop trees in the upper stratum, thus help stabilize streambanks.

37 hastening their foliage mortality. As a coastal old-growth forests, but the fre- result, these branches become shorter and quency of nesting activity is negatively smaller in diameter and take less time to correlated with the increasing composi- fall off. In these situations redcedar will tion and density of redcedar (Burger and accelerate the rate of self-pruning and self- Bahn 2004). The marbled murrelet is thinning of other crop species (thus known to prefer western hemlock mistle- improving timber quality). toe platforms for nesting (A. Banner, pers. comm., 2008). 4.6.5 Understorey vegetation suppres- Coarse woody debris from redcedar sion Under the stand conditions as produces valuable habitat for wildlife long described above, a uniform layer of sub- after the tree dies. Its coarse woody debris canopy (intermediate) redcedar can pro- adds significantly to long-term fish habitat vide substantial interception of light development within riparian areas, and reaching the forest floor, thereby limiting provides excellent shading capacity to the development of understorey vegeta- enhance conservation of stream tempera- tion. In some situations, this may be an tures, improving both fisheries values and effective tool to limit growth of moderate- structure for terrestrial species. The long- ly shade-tolerant shrubs, reducing compe- lived and durable hollowed-out cores of tition for nutrient resources on potentially redcedar snags can provide a key feature limited sites. This is a particularly impor- for bear hibernation dens. Also, in the tant factor in managing salal competition coastal regions, bears preferentially feed on northern Vancouver Island. upon fresh cambium of redcedar (bark stripping), relative to other associated 4.6.6 Wildlife features Redcedar pro- conifers. It can be an important early-sea- vides many resources important to wild- son food source in the spring (Mason and life. Conifers in general offer necessary Adams 1989). protection for birds that nest in the early Finally, redcedar also acts as an impor- spring, and many species utilize redcedar tant source of winter browse for several seeds as a source of food in winter. Cavity ungulates. Unfortunately, one of the spe- nesters also find excellent habitat in the cies most influencing the regeneration of many redcedar snags. redcedar is the Sitka black-tailed deer Several squirrel species are known to (Odocoileus hemionus sitkensis). This spe- reside in stands with redcedar as a major cies arrived from the mainland to Haida species (Ransome and Sullivan 2002). Gwaii in the early 1900s, and has prolifer- Many bat species prefer snags for day- ated ever since in the absence of predators roosts in older redcedar stands along the or other natural enemies (Sharpe 1999). coast, particularly those with high solar Due to the very high population of this radiation exposure (Waldien 2000). deer on Haida Gwaii, this forager has been Pileated woodpeckers (Dryocopus pileatus) negatively affecting both the regeneration have also been shown to prefer redcedar potential of redcedar (high rates of selec- for roosting (diameters > 150 cm), over tive winter and spring feeding) and the associated species such as Pacific silver fir populations of rare endemic plant species and hemlock (Aubry and Raley 2002). (Pojar 1999). The impact of this extreme Conversely, the endangered marbled mur- browse pressure upon rates of redcedar relet (Brachyramphus marmoratus) is regeneration is discussed in section 3.5.7: known to be strongly associated with Mammals.

38 4.7 Succession The importance of natural disturbance in maintenance of old-growth structure and maintaining and revitalizing healthy for- character through fine-scale single-tree ests is well recognized today, and people gap disturbance is a dynamic ecological are generally more inclined to mimic dis- process (Daniels 2003). One species or turbance regimes rather than prevent group of species is not necessarily expect- them (Geils et al. 1995). Fire, insects, and ed to continually dominate the stand, but pathogens are now recognized to be per- long-lived, shade-tolerant tree species are forming valuable ecological functions in expected to maintain some presence directing the natural successional develop- (Oliver and Larson 1996). Redcedar has ment of a forested landscape. the capability to regenerate successfully Disturbances can be classified as minor (either vegetatively or from seed) on vari- or major depending on the magnitude of ous substrates (particularly on forest floor change they impose on ecosystems. Minor and decaying wood) under low light con- disturbances that can affect all or only ditions, and as such “should be” a consis- certain ecosystem components are not tent component of coastal climax forests. considered to have dramatic, ecosystem- (Refer to section 5.4.2: Natural regenera- altering effects. In contrast, a major dis- tion for more seedbed substrate informa- turbance has the potential (depending on tion.) the resilience of a system) to radically alter Perhaps the most extensive, majestic, a system, causing a shift to a different suc- old redcedar-dominated forests in the cessional stage. How various disturbance Lower Mainland are found north of types can affect the presence or regenera- Vancouver in the Capilano, Seymour, and tion of redcedar is discussed below. Coquitlam watersheds. Daniels (1994, 1996, 2003) and others (Daniels et al. 1995, 4.7.1 Minor disturbance – Stand main- 1996, 1997) intensively studied the struc- taining Oliver and Larson (1996) charac- ture and dynamics of these old redcedar- terized the true old-growth stage in stand dominated forests (CWHvm subzone) development as exhibiting great variation (Figures 43 and 44). The stands were con- in horizontal and vertical structure. Old- sidered to be in the old-growth develop- growth forests were also characterized as ment stage, probably within the transition self-replacing and as being maintained variation (as evident by the presence of through single-tree gap dynamics. They shade-intolerant Douglas-fir, fire scars, emphasized that tree mortality and growth and distinct cohorts). In spite of the rela- of understorey trees in old-growth stands tive scarcity of redcedar seedlings, sap- is achieved when trees regenerate and lings, and low canopy trees relative to grow without the influence of external western hemlock and Pacific silver fir, it disturbances. Dead overstorey trees are was concluded that redcedar populations replaced by understorey trees from the would likely not diminish due to episodic stand re-initiation stage of development. small-scale disturbance and re-establish- Oliver and Larson (1996) avoided the term ment. The predominance of peak age “climax” because of its fuzzy and elusive classes suggested that redcedar establish- concept, while others have considered cli- ment was related to past disturbances max stands to be conceptually similar to caused by fire, climate, or climate–fire true old-growth stands. interactions. The question remains In climax stands, dead canopy trees are whether redcedar can be replaced within a (assumed to be) replaced by sub-canopy stand in the absence of large-scale distur- individuals of the same species mixture. bance (i.e., if redcedar-dominated stands The mixture (i.e., tree species composi- are permanent features in the landscape). tion) is not expected to change dramati- Western redcedar has the potential to cally, but may fluctuate over time. The germinate on a variety of substrates

39 Figure 43 A fully stocked, uniform forest with a preponderance of old redcedar on a second-order drainage in the Seymour watershed.

(Figure 45) and grow in low light. In these Figure 44 One of the many old redcedar stands, Daniels (1994) found established stands in the Capilano watershed maintaining redcedar seedlings (mostly on windthrow high density and uniform appearance. mounds and decaying wood), but their numbers were low compared to western hemlock (Figure 46) and Pacific silver fir. These substrates provide elevated micro- demands a revised successional descrip- sites, reducing the influence of competitive label for redcedar, such as a polycli- tion from tall understorey vegetation. max species. Shade-tolerant but shorter-lived western hemlock and Pacific silver fir both exhibit 4.7.2 Major disturbance – Stand replac- greater regeneration potential under their ing Large-scale disturbance events in old- own canopy (Franklin and Dyrness 1973; growth redcedar stands are discussed in Minore 1983, 1990; Daniels 1994) and are the context of the four generalized stages thought to be favoured in old-growth of stand succession: initiation, stem exclu- stands with heavy accumulations of decay- sion, understorey re-initiation, and old ing wood. The low abundance of redcedar growth (Oliver and Larson 1996). Further was not interpreted by Daniels as an indi- discussion outlines stand development cation of its eminent exclusion. Redcedar and renewal in relation to redcedar fol- can withstand lengthy periods of suppres- lowing major disturbance due to clearcut- sion (50 years or more [unpublished data ting, windthrow, fire, and (to a lesser from the HyP3 project]) in the understo- extent) landslides. rey before release, and chances remain high (or high enough) that established Clearcutting Clearcutting by itself does saplings can be recruited to the canopy not prevent regeneration of exposure-tol- layer. Although not explicitly studied, it erant redcedar. Clearcutting followed by appears that redcedar has the capacity to planting or natural regeneration of the be a persistent, albeit variable, component desired species results in the development in old-growth stands. This situation of even-aged or single-cohort stands.

40 When species other than redcedar are established, redcedar may regenerate naturally during the initiation stage, depending on seed availability, site disturbance, site quality, and vegetation developed in response to disturbance. On salal-dominated and “high brush hazard” sites, the ingress of redcedar will likely be severely restricted due to competing vegetation. Provided the existence of an available seed source, redcedar may regenerate later during the understorey reinitiation stage, resulting in the development of stratified (uneven-aged or multi-cohort) stands (Figure 35). Redcedar may successfully regenerate naturally on some clearcut sites Figure 45 Natural regeneration of redcedar amidst bryophytes on a but it is not clear under which circum- well-decayed downed log near Tofino, Vancouver Island. stances the greatest success occurs (i.e., with or without post-cutting site disturbance) (Figure 47). Clearcutting on some water-surplus, nutrient-rich sites is followed by the rapid development (or re-growth after site disturbance) of understorey vegetation, notably salmonberry, which forms dense shrub thickets preventing natural regeneration of shade-tolerant conifers (Figures 48a and 48b). Easily exposed mineral soil is invad- ed typically by red alder, bigleaf maple, or willows. Thus, quite often, brushy, poorly stocked, open-canopy stands develop under these site conditions (Figure 49). These seral hardwood communities allow only sporadic establishment of the most shade-tolerant conifers, usually western hemlock and redcedar, which grow slowly and are visibly distinct from the canopy stratum. The possibility and benefit of growing redcedar under hardwood canopies as a management strategy is discussed in section 5.3: Site and Species Selection.

Windthrow Wind has been the primary Figure 46 Abundant advance regeneration of natural disturbance agent throughout the western hemlock in the shrub layer under the outer coast. Wind most often creates a canopy of redcedar in the Seymour watershed. minor disturbance, but fierce storms can affect large areas. Apart from fine and coarse woody debris, windthrow creates mound-depression microtopography with a highly variable composition of materials

41 across the ground surface. While depres- organic (either accumulation of forest sions usually have a shallow surface floor materials or decaying wood), miner- organic layer, mounds can be entirely al, or a mixture of both. Windthrow by itself does not prevent regeneration of exposure-tolerant redcedar, but the rate of its ingress will depend upon seed availability, site quality, and vegetation developed in response to disturbance. The landscape of northern Vancouver Island, particularly the Nahwiti Lowlands, features a pattern of relatively young, closed-canopy, hemlock–amabilis fir (HA) stands (Figure 50) and open-canopy, salal- dominated, old-growth, hemlock and redcedar–hemlock (CH) stands (Figure 51). Windthrow has been credited for improving forest productivity, because moss- dominated HA stands are more productive than salal-dominated CH stands. Lewis (1982, 1985) considered these stand types as two different seral stages within the Figure 47 A dense, naturally regenerated stand of redcedar with some same site-specific chronosequence, based western hemlock and lodgepole pine on a burnt, cutover area in the upon differences in stand history. He pre- CWHvh subzone (Tofino flats, Vancouver Island). dicted that windthrow-origin HA stands

a b

Figure 48 Salmonberry – Red alder communities effectively prevent ingress of shade-tolerant conifers; winter aspect (a) and summer aspect (b) of the same stand.

42 will develop over time into CH stands. turbances, they will develop into salal- While it is evident that HA stands can dominated CH stands. First, HA stands originate following windthrow events, it is seem to currently occupy somewhat drier not clear whether, in absence of major dis- and nutrient-richer sites than CH stands; therefore, technically, they cannot be two stages of the same chronosequence (McWilliams and Klinka 2005). Second, HA stands are virtually without advance regeneration of redcedar. A consistent, albeit variable, presence of redcedar in HA stands was observed only on those sites affected by fire or windthrow and always in close proximity to redcedar seed source. (Klinka 2006). Third, according to Weber et al. (unpublished): 1) in the absence of stand-replacing disturbance, both HA and CH stands are self-replacing, featuring reverse-J size distributions, and 2) the soil inoculation potential for redcedar in ectomycorrhiza-dominated stands may account for the virtual exclusion of redcedar seedlings from HA stands. Redcedar Figure 49 Scattered saplings of redcedar and western hemlock in the seedlings require arbuscular endomycor- understorey of a mid-seral Salmonberry – Red alder community. rhizal fungi–root relationships for successful establishment, and have difficulty establishing in arbusculae-sterile soil conditions (Minore 1979).

Fire Fire has been a major disturbance factor of coastal forests since the retreat of the last glaciation, particularly in southern British Columbia. The ecological role of fire is reviewed by Oliver and Larson (1996) and Kimmins (1997). Because redcedar does not regenerate well (compared to other species) in the understorey of established stands, it has been assumed that fire has played an important role in establishing the redcedar-dominated forests on the coast. There have been relatively few studies of fire history in the CWH zone. Based on the distribution of shade- intolerant Douglas-fir, Schmidt (1970) reported extensive fires occurring nearly every century over the past 1000 years, with the most extensive fires occurring in Figure 50 A windthrow-origin hemlock– the past 300–800 years (Green et al. 1998). Pacific silver fir stand on a zonal site in the Examining ages and Douglas-fir occur- CWHvm subzone on northern Vancouver rence, Eis (1962) considered fire origin for Island. many extant redcedar stands in the

43 Seymour and Coquitlam watersheds. tality of redcedar has been variable but Arsenault (1995), Daniels (1995), and episodic for over 800 years. It appears that Green et al. (1998) have all studied and regeneration peaks were synchronized attempted to reconstruct fire history of the with the major recognized fire episodes Vancouver watersheds. Arsenault (1995) (Figure 52). identified fire as the most important large- Although it is difficult to speculate as to scale disturbance on warm slopes in the the origin of the old-growth redcedar Eastcap Creek area, which currently sup- stands in these watersheds, it is likely that port extensive redcedar stands. Daniels et a significant portion of these stands, par- al. (1995) and Daniels (1996) examined the ticularly those featuring old Douglas-fir, disturbance history of old-growth redce- established following large-scale fires. In dar stands mixed with Douglas-fir. Based view of the long return interval of large- on the distribution of Douglas-fir and the scale fires in these climatic zones (estimat- presence of charcoal in the soil, they pre- ed at about 350 years), these stands are dicted that a large number of these stands now self-replacing by small single-tree- originated following partial to complete level disturbances. Undoubtedly, cata- stand-replacing fires. These fires occurred strophic fires affected other coastal forests between 500 and 900 years ago, possibly as well, which is consistent with the related to past climatic variations. They regional nature of these fires (Green et al. (Daniels et al. 1995, Daniels 1996) deter- 1998). mined the mean age of old redcedar trees The results of the recent study by in the watershed to range from 450 to 890 Daniels and Gray (2006) provide a some- years. The age structure of the stands was what different story. Through an extensive irregular with one or more peak age class- dendrochronological investigation, they es, indicating that establishment and mor- demonstrated that large-scale fires occur-

a b

Figure 51 An apparently truly old-growth western hemlock stand without redcedar on a near- zonal site (a), and an apparently truly old-growth redcedar–hemlock stand on a sloping zonal site (b) in the CWHvm subzone on north Vancouver Island.

44 Thuja regeneration: Thuja age peaks (this study)

Fire episodes: Olympic Peninsula WA (Henderson et al. 1989) Deer Site OR (Morrison and Swanson 1990) Cook-Quentin Site OR (Morrison and Swanson 1990) Fire events: Mainland BC (Eis 1962) Vancouver Island BC (Schmidt 1970) Desolation Peak WA (Agee et al. 1990) Mount Rainier WA (Hemstrom and Franklin 1982)

1400 1500 1600 1700 1800 1900 2000 Calendar years

Figure 52 Chronology of redcedar age peaks and fire disturbance in the Pacific Northwest. The left column identifies study areas and sources. Peak periods of redcedar regeneration are represented by solid bars bounded by the vertical broken lines. Fire episodes >1 year are represented by solid bar. Open squares show single year during which fires burned (Daniels 1995).

ring at 250- to 350-year intervals are not be greater following fire, but this remains the dominant disturbance force within the to be determined. Two forest types wet coastal temperate rainforest. Their evi- observed on the central and north coast dence suggests that widespread stand-ini- tend to substantiate the positive effect of tiating fires were much less frequent than fire on cedar regeneration (A. Banner, previously thought, and largely restricted pers. comm., 2008): 1) redcedar stands to low- and mixed-severity events. The 150–200 years old located on the central authors identify fine-scale gap dynamics and north coast near historical First as the dominant disturbance regime con- Nations Villages, which suggests that trolling the structure and successional burning by aboriginals resulted in redce- development of most unmanaged forests dar-dominated second-growth stands; and in these areas. Obviously, both large- and 2) redcedar-dominated stands established small-scale disturbances play a role, and, in the early 1980s on logged and burnt in either case, redcedar has maintained its sites of the north coast. Redcedar’s ability presence on the landscape. It is able to to regenerate on fire-created seedbeds is regenerate following wildfire and remain addressed in section 5.4.2: Natural regen- in its absence, being replaced through gap eration. phase dynamics. Replacement levels may

45 Landslides In addition to large-scale disturbance, redcedar can also be observed playing a minor role in primary succession on colluvial materials where it may establish in the spaces between stones and boulders filled with friable organic materials (Klinka et al. 2005) (Figure 53). Other species, such as bigleaf maple and red alder, are also observed scattered across these sites. These talus communities are low-density, discontinuous, and dominated by tall shrubs such as vine maple and salmonberry, and by ericaceous shrubs.

Figure 53 Redcedar occupying coarse talus deposits in the CWHvm subzone.

4.8 Dendro Dobry et al. (1996) studied tree-ring logical investigations. The negative pointer chronology sequences from old-growth redcedar and (a much narrower ring than the previous Pacific silver fir trees in the CWHvm sub- one) was 1876, a year that was also observed zone, near Vancouver, B.C., to improve in the redcedar cores from Bella Coola, understanding of past climatic fluctuations and probably a response to the cold and and climate-related events. Their study dry summer of 1875 (the year of major showed that ring widths of coastal redce- fires in the Pacific Northwest), the very dar on submontane and montane sites respond to variation in temperature and

precipitation. 0.4 x – Temp Sig 0.95 Response functions for the period – Precip 0.3 x – Temp from 1893 to 1990 demonstrate a stronger growth response to temperature but a 0.2 weaker response to precipitation. The 0.1 temperature in the previous fall and in

February of the current year had a positive value eﬃcient Co 0 effect on ring growth; the late-summer -0.1 precipitation of the current year had a negative effect on ring growth (Figure 54). -0.2 M J J A S O N D J F M A M J J A S These responses indicate that mild previ- 17 months, May prev. – Sept. current year ous fall and winter temperatures, but not late-summer precipitation, have a favour- Figure 54 Responses function of redcedar able effect on (subsequent) redcedar radial residual chronology of ring-width indices on 34 growth. climatic parameters. Variation explained by Dobry et al. (1996) identified 1876 and climate is 42%. The February temperature of 1959 as the best crossdating rings in redce- the current year is significant for diameter dar ring-width series for dendrochrono- growth (Dobry et al. 1996).

46 cold summer of 1876, and perhaps the and hot summer temperatures (i.e., tem- cold winter of 1875–1876. perature extremes) have a negative effect The negative pointer of 1959 was a on redcedar growth in the coastal region. response to the climatically extreme year This conclusion is in agreement with that of 1958 in which both the average temper- of Seebacher (2007), who found reduced ature in July and the yearly average tem- ring-width related to hot and dry sum- perature reached the highest values in the mers, confirming drought as a contribut- 99 years of available climatic records ing factor for observed redcedar dieback (investigated prior to 1996). on the east coast of Vancouver Island. These findings could mean that cold

4.9 redcedar Nearly 10 years ago, apical crown dieback her 16 study sites (four in each subzone) Dieback on of second-growth redcedar trees was included redcedar with dieback. Study Eastern Vancouver observed on east Vancouver Island. Hebda sites in the CDFmm near Qualicum Beach Island (1999) linked it to climate change, suggest- expressed the highest level of dieback (15 ing that the south and central portions of trees). Most dieback trees exhibited mild eastern Vancouver Island would be out- symptoms of thinning foliage. No dieback side the climatic amplitude of redcedar in was observed in the CWHmm2 variant. the near future. This drought-changing Supported by water-balance modelling, climate hypothesis has not been tested, Seebacher (2007) found reduced ring- and drought could be either a predispos- width apparently related to warm and dry ing, inciting, or contributing factor to the summers on only a few sites. Similarly, dieback. growing-season temperature and precipitation were found to significantly influ- 4.9.1 Dieback study Seebacher (2007) ence the radial growth of redcedar on a studied the extent and potential causes of limited number of sites. Residual ring- the dieback using dendrochronological width of redcedar decreased with increas- techniques and water-balance modelling. ing June temperatures; conversely, residual The main objective of her study was to ring-width increased with increasing determine occurrence of the dieback and spring and early-summer precipitation. to explore potential causes. Seebacher (2007) concluded that cli- Her 16 low-elevation, intermediate matically induced summer drought may (near-zonal or zonal) study sites were be the primary cause of redcedar dieback; located along the east coast of Vancouver however, she considers complete loss of Island from Victoria to Campbell River. redcedar from Vancouver Island unlikely. The sites were located on zonal units with- She showed that the dieback is less exten- in the CDFmm and CWHxm subzones, sive than one would assume based on and CWHxm2 and CWHmm2 variants, observations made travelling along the representing a gradient of decreasing tem- Island Highway, which features recently perature and increasing precipitation exposed redcedar trees and altered soil (Green and Klinka 1994). All units are moisture conditions. located within the rain shadow of the However, not all her study sites appear Vancouver Insular Mountains and to be zonal or near-zonal; for example, the Olympic Mountains and are relatively dry Qualicum Beach site was associated with compared to other CWH subzones. sandy soils; and high water table condi- Using a transect sampling method, tions were associated with Fluxnet, Seebacher (2007) detected only 27 dieback Shawnigan Lake, and Cowichan Lake sites. trees of the 512 trees sampled. Only four of Her study also raises a number of corol-

47 lary questions related to summer drought, was noted that other species (such as such as: why is there no observed dieback Douglas-fir and hemlock) had also been of the more drought-sensitive western killed, presumably by the raised water hemlock? Why is there virtually no redce- tables. The relatively rapid decomposition dar dieback on low-elevation sites along of those snags made them less obvious to the Sunshine Coast, where climate is simi- observers outside the stands. It is possible lar to the CWHxm subzone? It is not sur- that in this situation (altered moisture prising to find drought-induced dieback regime), redcedar was able to survive lon- in water-deficient sites in the CDFmm ger than its associates and thus became subzone, where redcedar is likely requir- more visually obvious as vigour decreased. ing protection from the overhead The redcedar snags have much less decay (Douglas-fir) canopy. When exposed to and are more visible from afar. open-area climates in this dry subzone, A few zonal sites were investigated. redcedar could be subjected to acute mois- These sites commonly experience grow- ture stress, resulting in partial or total die- ing-season water deficit, with deep, back. relatively coarse soils. The stands were dominated primarily by Douglas-fir in the 4.9.2 Field investigation During the overstorey, with redcedar often detected in development of this manuscript, the red- the subcanopy layers. Redcedar individu- cedar dieback issue (Seebacher 2007) on als observed growing in the canopy of eastern Vancouver Island became of great these stands generally expressed symp- interest to us. To witness and explore this toms of dieback, often severe (Figure 55). issue we visited areas north, west, and Understorey redcedar (sheltered) was south of Qualicum Beach. The areas were very healthy in appearance, and helped predominantly within the CDFmm sub- to shade out competing salal, which was zone and occasionally in the adjoining abundant in these stands (Figure 56). On CWHxm1 variant to the north and west. some of the driest sites investigated, hem- In this section we present several of our lock snags were identified even with anecdotal observations for consideration. healthy redcedar in the understorey. The dieback became immediately One productive site was found in a apparent upon leaving the Nanaimo ferry depression near the Island Highway, con- and driving north on the Island Highway. taining redcedar, Douglas-fir, bigleaf Dead-top and dead individuals and small maple, and hemlock. A cluster of three groups of redcedar were observed scat- redcedar with full or partial dieback was tered along the highway. Ten sites were observed. On this moist productive site, investigated where redcedar dieback was it is difficult to attribute the dieback to noticed from the road. The sites ranged drought. Adjacent was a downed redcedar from drier and poorer sites (with scattered with obvious root rot (recent windthrow lodgepole pine, hemlock, and sub-canopy with still-green foliage) (Figure 57). With redcedar in second-growth Douglas-fir this observation, it seems that root- and stands) to wetter and richer sites (with butt-rot sources of mortality in relation to Sitka spruce, Douglas-fir, redcedar, red dieback need to be investigated further. alder, and hemlock). Dieback or mortality was not observed Several of these sites had obviously in every stand in the CDF. A young regen- been affected by the relatively recent erating stand of pure redcedar was found development of the new highway. on a fresh to moist site along the side of Drainage flows had changed, and some the Old Island Highway near Bowser. The sites were experiencing strong fluctuating 3- to 4-m saplings expressed no dieback, water tables where (presumably) none had or mortality of any sort, and the stand existed before. Once inside the stands it appeared very healthy and vigorous

48 (Figure 58). Also, as we moved west into stratum of the CWHxm stands showed the CWHxm subzone, redcedar individu- good vigour. als on zonal sites could be seen growing 2. On some driest sites, canopy hemlock well in exposed, dominant positions. snags were also observed. 3. On some wet sites where dieback was Key observations from eastern Vancouver observed, there was evidence of recent Island disturbance and increases in water 1. Redcedar dieback in the CDFmm table. stands was infrequent; redcedar in any 4. All recently dead redcedar trees in the

Figure 55 Redcedar dieback observed from highway near Figure 57 Root rot on redcedar, exposed by recent windthrow Qualicum Beach, Vancouver Island. (still with green foliage) in association with Douglas-fir and bigleaf maple. All photos this page David Brisco David page this photos All

Figure 56 Understorey of Douglas-fir–dominated stand on Figure 58 Vigorous saplings established as a pure stand on a zonal site near Qualicum Beach, Vancouver Island. Note a water-surplus site south of Bowser, Vancouver Island healthy redcedar in subcanopy. (CDFmm)

49 areas investigated appear to be in domi- (albeit limited) of the “redcedar dieback” nant crown positions, or have been left found within the CDFmm near Qualicum exposed to open-area climate following Beach, the situation does not appear to some recent disturbance. indicate the occurrence of events beyond 5. Redcedar trees in the understorey were the “normal” expectations for this subzone always healthy and vigorous with no (i.e., no dieback was observed in the adja- evidence of dieback, even in those cent CWHxm). However, if widespread stands with dieback of dominant redce- “dieback” of redcedar was observed on dar trees. zonal sites in the CWH, that would be a 6. Redcedar snags last a long time. These much stronger indicator of possible cli- snags become more visually apparent as mate change, and of much greater con- the snags of other species (which may cern. The expressed apprehension over have died at the same time) rot and dis- dieback in the particular area near integrate. Snags of other species may be Qualicum Beach appears to be due pri- more readily attacked by fungi/insects marily to a combination of historical fire and associated woodpecker activity. suppression, recent occurrence of periodi- 7. Some dieback could be attributed to a cally severe drought, high traffic, and vegetative mode of origin and conse- widespread disturbance due to the con- quential development of root rot. struction of the 'new' Island Highway. Will climate change decrease the preva- 4.9.3 Conclusions The CDFmm subzone lence of redcedar on the British Columbia of southeastern Vancouver Island is mar- coast? Possibly, but, at the same time, ginal for redcedar growth, as redcedar warming climates are expected to increase is exposure-intolerant in this climatic the frequency of fires (decreased interval regime, and droughts are historically com- lengths) in many of these same areas. Fire mon. Under this climatic regime, redcedar disturbance is considered one of the pri- cannot grow successfully in the canopy mary factors contributing to establishment except on water-surplus sites. Due to of redcedar-dominated stands, so in cer- recent summer droughts, redcedars on tain locations a warming climate may water-deficient (including zonal) sites, actually benefit and promote the presence are prone to death, particularly if in an of redcedar. Alternatively, a warming and exposed situation. The redcedar stands drying climate may prevent redcedar from observed in these areas of dieback were dominating the canopy on certain sites allowed to develop and exist due to fire (e.g., the zonal sites of eastern Vancouver suppression. Under natural conditions, the Island). However, on water-surplus sites climatic regime would have produced fires and in the understorey of zonal stands in the understorey during extremely dry (Douglas-fir dominated), where redcedar years, removing redcedar from the under- is protected from exposure, it shall remain storey and selecting for Douglas-fir as the a significant component. dominant canopy species. Some climate models (Hamman and This is not to say that climate change Wang 2006) predict the CDF zone to will not influence the distribution of red- increase in area by 300% over the next 70 cedar on the eastern side of Vancouver years. If this occurs, then many locations Island and elsewhere. We have devoted a that currently support healthy redcedar in large component of this report to the a dominant and exposed crown position planning and selection of appropriate sites (CWH zone) can expect to witness major for the reliable establishment of redcedar dieback, particularly in those areas cur- in the context of climate change, and the rently adjacent to the CDF zone. However, associated rationale of these recommenda- our short field investigation gave us no tions. However, based on our observations indications of this trend yet occurring, at

50 least not in terms of redcedar mortality. by Pritchard (PPxh2 variant), redcedar Much more work is needed to properly was absent as a common component of examine this topic, possibly establishing forested sites. benchmark sites to detect any shifts in cli- The only evidence of any recent redce- mate that would jeopardize the distribu- dar dieback along the described corridor tion of this valuable softwood species. similar to that observed on Vancouver Island was located slightly northwest of Supplementary observations from the Salmon Arm in the ICHmw2 variant Interior Cursory observations were also before reaching Tappen. Several patches made upon the health and vigour of red- of redcedar showing crown dieback were cedar along the corridor from Revelstoke observed in exposed positions near the to Salmon Arm to Kamloops. This tran- highway. However, as these trees were on sect presents a transition through several private lots, their disturbance history is zones, from the ICHmw3 variant in the unknown. Even on the steep rocky site east (considered climatically suitable for further west, yet still east of Sorrento, dominant redcedar) to the BGxw1 variant where dieback would be expected (in the in the west (climatically unsuitable). This face of a warming and possibly drying cli- transition provides an opportunity to mate), no obvious mortality was detected. observe the possibly parallel dieback of The “dieback” of other species was redcedar on those sites that are marginal observed in several locations along this to its climatic tolerances. Proceeding from corridor, with both hemlock and Douglas- optimal to unsuitable climates (east to fir snags identified in many locations, even west), redcedar moves from a dominant within stands containing dominant redce- position in the canopy to complete dars. absence near Kamloops. In those areas where one would expect Healthy redcedars were observed in even mild drought to have an impact exposed and/or dominant canopy posi- upon redcedar survival, no dieback situations on zonal sites as far west as Sorrento tion was observed. The presence of redce- (IDFmw2 variant), with diminishing dar shifted as expected between zones, but occurrence progressing further west. In there was no explicit evidence that recent the transition to the IDFxh2 variant west climatic changes had made previously of Squilax, redcedar could be seen only in suitable sites unsuitable (and had induced the understorey and on wetter sites, and mortality).

51 5 Silviculture and Management

Although most forest management prac- 1999). Because of this key feature, silvicul- tices were developed with the goal of tural decisions made regarding the estab- enhanced wood production (Curtis and lishment and tending of this species will Carey 1996), many silvicultural practices dramatically influence the quality of final can be readily modified to meet a broad crop products, perhaps more so than any range of multiple objectives (Curtis et al. other North American conifer. 1998), including commodity products, The focal point of this section is on wildlife habitat, and recreational values. growing redcedar as a reliable crop species Redcedar exhibits very little genetic vari- for future wood production; however, its ability (Bower and Dunsworth 1988), and other uses (such as a nurse species) may yet is known to be an extremely “plastic” also be important silvicultural consider- species in terms of the expression of its ations (see section 4.6: Ecological Role). morphological characteristics (El-Kassaby

5.1 management While the decision to establish and grow on high brush-hazard sites, irregular spac- Strategies redcedar is site-specific (i.e., at the stand ing, and potential difficulties in site prepa- level), this decision should not be made ration), planting redcedar is the most without considering landscape-level man- viable and reliable of regeneration meth- agement goals. Only after the geographic ods. Even though silvicultural costs are pattern of suitable sites is determined can higher (planting, and potentially vegeta- redcedar regeneration plans be developed. tion or browse control), it will provide the An industrial strategy for redcedar regen- security of stand regeneration and a more eration on the Queen Charlotte Islands rapid arrival to free-growing status. has been proposed by Lackey (1999). There are two contrasting approaches Unlike some other coastal conifers, all to growing redcedar as a crop species in available evidence suggests that redcedar even-aged stands: either close or wide will grow as a productive and valuable spacing. Naturally established redcedar crop species in even-aged pure stands, can be observed growing successfully at even-aged cohorts in mixed-species both spacing densities (section 5.5: Stand stands, or even-aged cohorts in uneven- Management). The most appropriate aged stands. These multiple options will approach will depend upon the desired influence the choice of reproduction cut- nature, quality, and quantity of the wood ting methods and appropriate regenera- products to be obtained from the man- tion methods. The rationale for growing aged stand. redcedar in even-aged assemblages is dis- In general, the management of even- cussed in section 3.6 (Growth aged, pure redcedar stands is considered Development Patterns). Oliver et al. (1998) simpler, less expensive, and more profit- emphasize that wood quality and growth able than the management of mixed- rate of redcedar are reduced whenever it is species stands. Examples of young, pure, overtopped by faster-growing species. In immature redcedar stands successfully these situations, redcedar trees will devel- established over a large area can be op long, dense crowns with large branch- found in the Suquash Basin, Port McNeill, es, and fluted, tapered stems. within Western Forest Products TFL 6 In consideration of the unpredictable (Figure 59). success of natural regeneration (including We have listed pertinent silvical and sil- regeneration delay, which may be critical vicultural characteristics of redcedar to

52 guide its regeneration and tending (from • Self-pruning capacity is high, providing Klinka et al. 2000): a high initial stand density. • Reproduction capacity is high; seed- • Crown spatial requirements are low to producing at an age of 10 years; heavy medium. seed crops are frequent. • Windfirmness on upland sites is medi- • Seed dissemination capacity is medium; um (higher than hemlock and lower adequate dissemination within 100 m than Douglas-fir). from source. • Light conditions beneath closed-canopy, • Potential for natural regeneration from mature stands are low and restrict the seed in low light is low, but higher if development of competing understorey vegetative reproduction is considered. vegetation. • Potential for natural regeneration in the • Potential productivity is high; site index open is high, providing the presence of (50 yr @ bh) up to 32 m on the most exposed mineral soil or burnt forest productive sites. floor. • Longevity is high, frequently > 1000 • Potential initial growth rate (≤ 5 years) years. is high, may be as high as for the associ- • There is reduced susceptibility to vari- ated tree species commensurate to site ous root and butt roots, making this a quality. good alternative species on sites with • Response to spacing and thinning is these risk factors. high.

Figure 59 An advanced regeneration stage of a redcedar plantation on a poor, CWHvm1/01 HwCw–Salal site in the Suquash basin.

53 5.2 growth and The available growth and yield informa- Redcedar site index, years to breast Yield tion for coastal western redcedar is very height, and density in studied stands var- limited in comparison to the amount ied with site quality (soil moisture and existing for other associated coastal spe- nutrient conditions). Site index decreased cies such as Douglas-fir and western from the drier CWHdm to wetter hemlock. The following information is CWHvm subzone, and increased in each compiled from local sources, Washington subzone from drier and poorer to moist State, and Great Britain. The most current and richer sites, and then decreased on site index estimates utilized in British wet, skunk cabbage sites (Table 5). Actual Columbia (Mitchell and Polsson 1988) measured site index values (determined by originate from equations developed nearly stem analysis) were lower than predicted three decades ago by Kurucz (1979, 1985). from the tables. The density of stands In spite of their age, these equations still ranging from 50 to 60 years at breast height appear to be reasonably accurate for esti- appeared comparable between the two mating the growth of both managed and subzones, and tended to decrease from natural stands, and are still widely used 1200 sph on salal or flat moss and blueber- (i.e., TIPSY-provincial silvicultural plan- ry sites to 700 sph on lady fern, salmon- ning software). berry, and skunk cabbage sites. Years to Omule (1988) found early height breast height (measured from 0.3 to 1.3 m growth in 28-year-old redcedar planta- discs) ranged from 3 to 9 years, with the tions on moist and nutrient-medium actual number of years estimated at 6–10 (zonal) sites in the CWHvm and CWHvh years. The density range of 642–775 stems subzones on western Vancouver Island to per hectare is similar to, albeit slightly be similar to the published height curves higher than, the density of managed red- of Kurucz (1979) and Hamilton and cedar stands on intermediate sites in Great Christie (1971). See Appendix 1 for the Britain (Hamilton and Christie 1971). site index curves and tables produced by The Research Branch of the B.C. Mitchell and Polsson (1988) using the Ministry of Forests and Range provides Kurucz equations. site index estimates for crop tree species To quantify relations between redcedar according to BEC site units. The 2006 esti- site index and categorical measures of site, mates (Site Index Estimates by Site Series) Klinka (1994) sampled 17 immature, are available on the Ministry of Forests unmanaged, naturally regenerated, pure and Range SIBEC website (www.for.gov. redcedar stands in the CWHdm and bc.ca/hre/sibec). For some species such as CWHvm subzones in the Malcolm Knapp western hemlock and Douglas-fir, site Research Forest (Table 5). index estimates have been developed from

Table 5 Means of selected growth characteristics of 17 studied redcedar stands examined for site quality and by stem analysis. Bias was measured according to Mitchell and Polsson (1988) (from Klinka 1994).

Years to Density Site index (m @ 50 yr bh) breast (stems/ Stand BH Age Measured Predicted Bias (m) height ha)

CWHdm/03 FdHw-Salal 51.7 24.4 24.8 -0.4 8.7 1250 CWHdm/01 Hw-Flat moss 56.5 29.0 29.4 -0.4 4.5 1144 CWHdm/07 Cw-Lady fern 59.9 30.7 31.8 -1.2 2.4 775 CWHvm1/01 HwBa-Blueberry 53.6 22.5 22.5 0.0 3.8 1225 CWHvm1/07 BaCw-Salmonberry 55.8 27.0 27.7 -0.7 2.9 642 CWHdm-vm1/12-14 CwSs-Skunk cabbage 54.1 23.8 24.7 -0.9 2.8 712

54 a large sample size. However, most redce- index decreased outside this “green” dar SIBEC productivity estimates remain edaphic region, slightly dry through very as the 1997 approximations, because the moist sites and poor through medium natural stands required for sampling are sites still support productive redcedar rarely found across the landscape. growth (indicated by light brown colour in Kayahara et al. (1997) investigated vari- Table 6). ation in site index with site quality in the There were no major differences CWHdm subzone and CWHvm1 variant, observed between selected site series near Vancouver, studying naturally regen- in site index estimates computed from erated, immature, pure or mixed stands Kayahara et al. (1997) and those given in with western hemlock (Table 6). Their SIBEC (2006) (Table 7). All the differences estimates also revealed trends of site index were < 1 m, except for the CWHvm1/07 variation in relation to soil moisture and and CWHvm1/14 site series, for which the nutrient levels, and confirmed the validity differences were > 1 m and site index was of SIBEC productivity estimates. greatly underestimated. The highest site index of redcedar was Kayahara et al.’s (1997) study and SIBEC found on sites with no moisture deficit estimates suggest a wider range of sites and high nitrogen availability (indicated suitable for growing redcedar as a timber by light green colour in Table 6). The crop than indicated by the synopsis of pre- mean site index was significantly lower in ferred sites (Table 4), particularly within the warmer and drier CWHdm subzone the wetter maritime and hypermaritime than in the cooler and wetter CWHvm portions of the CWH zone, in which most subzone. We predict a progressive sites are without a prolonged water deficit decrease in site index in the CWHvm sub- (see section 4.5: Vegetation and Site zone from south to north. Although site Classification and section 4.7: Succession).

Table 6 Site index of redcedar in (A) CWHdm subzone and (B) CWHvm1 variant in relation to actual soil moisture and nutrient regime. Mean site index (m @ 50 years, 95% confidence interval in parentheses), and sample size are given for each edatope studied. Blank cells indicate absence of redcedar stands in the study area for those specific combinations of SMR and SNR (Kayahara et al. 1997).

SMR/SNR Very poor Poor Medium Rich Very rich (A) CWHdm subzone Very dry 13.4 (5.4) n = 2 Moderately dry 22.2 (7.2) n = 2 Slightly dry 24.4 (0.6) n = 5 26.7 (1.4) n = 4 Fresh 29.7 (0.8) n = 9 Moist 30.3 (2.7) n = 3 32.2 (3.5) n = 3 29.0 n = 1 Very moist 29.1 (1.5) n = 3 32.0 n = 1 Wet 16.5 n = 1 25.4 n = 1 (B) CWHvm1 variant Very dry Moderately dry Slightly dry 20.9 n = 1 22.0 (6.3) n = 2 24.8 (0.5) n = 3 Fresh 23.0 (0.06) n = 5 24.7 (0.8) n = 6 26.6 (0.7) n = 7 Moist 26.3 (0.6) n = 5 28.3 (0.5) n = 16 Very moist 21.8 n = 1 25.2 n = 1 27.9 (1.6) n = 7 27.7 (0.6) n = 5 Wet 17.8 (1.9) n = 7 22.5 (0.5) n = 3 26.2 n = 1

55 Table 7 Comparison of site index estimates of Kayahara et al. (1997) and SIBEC (2006) for redcedar for selected CWHdm and CWHvm site series

Kayahara SIBEC Site series et al.(1997) (2006)

CWHdm/01 Hw-Flat moss 26.9 27.6 CWHdm/07 Cw-Foamflower 30.6 30.8 CWHdm/12 CwSs-Skunk cabbage 20.9 20.0 CWHvm1/01 HwBa-Blueberry 22.7 22.6 CWHvm1/07BaCw-Salmonberry 28.0 24.0 CWHvm1/14 CwSs-Skunk cabbage 22.2 19.4

Relatively little is known about the Yield tables of Edwards and Christie growth of redcedar, particularly in mixed- (1981) indicate that height growth of dom- species stands. When grown in pure, inant redcedar trees is generally slower even-aged stands, its site index will usually than that of other major crop species. be lower than Douglas-fir, Sitka spruce, However, both Hamilton and Christie and even western hemlock. This does not (1971) and Edwards and Christie (1981) necessarily mean that it has a lower vol- demonstrate that shade-tolerant tree spe- ume. It can yield volumes higher than or cies can grow productively at higher den- comparable to Douglas-fir because of sities than shade-intolerant-species, higher stand densities (basal area) compensating for shorter average heights. (Hamilton and Christie 1971; Kurucz 1978; On medium sites, cumulative volume pro- Edwards and Christie 1981; Curran and duction at age 50 is comparable between Dunsworth 1988; Oliver et al. 1988). redcedar, Douglas-fir, and western hem- Oliver et al. (1988) observed the slow lock. For 80-year-old stands on medium volume growth of redcedars in mixed- sites, cumulative volume production of species, second-growth stands in western redcedar and western hemlock is similar, Washington, where redcedars were sup- and greater than for Douglas-fir. A pressed by faster-growing, shade-intoler- yield model on medium sites in British ant species. When not suppressed by Columbia indicates yields of 70 m3 ha-1 at faster-growing species, such as in pure, age 40, 350 m3 ha-1 at age 115, and 595 m3 even-aged stands, redcedar grows quite ha-1 at age 270; maximum current annual rapidly. They suggested that pure, even- increment occurs at 82 years and maxi- aged redcedar stands on upland sites in mum mean annual increment at 130 years western Washington produce volumes (Nakoe 1978). similar to or greater than pure, even-aged In Great Britain, the total cumulative Douglas-fir stands by 50 years on similar volume produced by redcedar stands on sites due to higher basal areas. Standing poor sites is 50 m3 ha-1 at age 20 and 953 volumes of 379- 825 m3 ha-1 were mea- m3 ha-1 at age 80; on good sites, the cumu- sured in 40- to 60-year-old, pure, second- lative volume produced is 232 m3 ha-1 at age growth stands on good sites in western 20 and 1839 m3 ha-1 at age 80 (Hamilton Washington (Nystrom 1980). SIBEC stud- and Christie 1971). Interestingly, redcedar ies have often reported second growth as apparently grows faster than Douglas-fir more productive than estimates from the in Great Britain on moist sites, and historical growth data of old-growth becomes increasingly more productive stands. than Douglas-fir on higher-quality sites.

56 5.3 Site and Crown land in British Columbia is man- this challenge, existing forests must be Species Selection aged for many different purposes (timber, assessed for their vulnerability to climate range, recreation, water, fisheries, wildlife), change, expectations of forest use must be each requiring different management revised, research and educational needs strategies. Most forest sites can support a must be clarified, and forest policies to variety of tree species, providing a range facilitate adaptation must be developed of possible options for the silviculturist. (Spittlehouse 2005). Needs, objectives, and climate will change Recent studies have explored the over time; therefore, management strate- potential impacts of climate on British gies and silvicultural information must be Columbia’s future forests (Hamann and continually updated to reflect the most Wang 2006; Hebda 2006a, 2006b), basing current knowledge. To achieve a viable their predictions upon ecosystem history, and appropriately regenerating plantation, ecosystem response to climate changes, all of these factors must be considered and climate impact models. The Royal during the evaluation of potential site British Columbia Museum models (Pacific species. Climate Impacts Consortium [online] Species selection and the choice of www.pcic.org) predicts the disappearance stocking level, combined with prompt and of climate suitable for redcedar in much of effective establishment, are crucial ele- the southern lowland British Columbia ments in creating a desired stand (B.C. and an increase in northern British Ministry of Forests 2000). For the purpos- Columbia by 2080. In general, there is es of producing a timber crop of redcedar, consensus that the future climate of the potential sites must have suitable attri- coastal region will be warmer, possibly butes that provide for: 1) productive with increased precipitation but with growth, 2) a reliable crop, and 3) feasible stronger summer droughts. It is not our silvicultural management (Klinka and intent to elaborate or postulate on possible Feller 1984). Selected sites must be clearly outcomes of various climate-change sce- within the major edaphic region of redce- narios at this time; all that can be done is dar (Table 2) and reflect the recommended to make redcedar crops reliable by reject- site classification of Banner et al. (1993) ing drought-prone sites in all submontane and/or Green and Klinka (1994) (Tables 4 and montane coastal biogeoclimatic sub- and 8) (see section 4.5: Vegetation and Site zones. After some deliberations, we have Classification). not considered sites within the present Although climate and species composi- lower limits of the Mountain Hemlock tion are known to have slowly changed zone for expanding the “reliable range” of over time, forest management decisions redcedar, due to the inherent risk of snow have been traditionally based upon the damage. Keep in mind that care is needed assumption that climate will remain rela- when applying simulation-model-derived tively stable. The predicted rapidity of cli- predictions of climate change at the local mate change over the next 100 years will level. The microclimate of small-scale top- require species compositions to shift at ographic features (e.g., frost pockets and rates much greater than could be accom- rivers and lakes) may significantly modify modated by natural seed dispersal and larger-scale climatic trends, and local con- regeneration. Although climate change ditions will not be correctly represented could lead to higher levels of forest pro- into the future (Wang et al. 2006). ductivity in some cases (Sohngen and In view of the predicted temperature Sedjo 2005), adaptation of current man- increases, sites on eastern Vancouver agement strategies is necessary to con- Island (CDFmm, CWHxm, and CWHmm serve possibly vulnerable species and subzones) and in the coast-interior transi- secure commercial plantations. To meet tion (CWHds, CWHms, and CWHws

57 subzones) are considered to be less reliable We suggest that reliable sites would be than those on central and west Vancouver fresh, moist, very moist, and wet sites, Island (CWHvm and CWHvh subzones), high-bench floodplain sites, and some the Queen Charlotte Islands (CWHvh and fluctuating water table sites, all preferably CWHwh subzones), and the coastal main- with adequate nitrogen availability (Table land (CWHdm, CWHvh, and CWHvm 8). In view of the future potential for subzones). Due to its intolerance of ocean increased summer drought, we reject very spray, shoreline and ocean spray–affected dry, moderately dry, and slightly dry sites sites are excluded from Table 8, as are sites regardless of the contemporary presence in the CWHwm, where redcedar is an of redcedar (Figure 60). We anticipate that insignificant component (Banner et al. fresh sites (no growing-season water defi- 1993). In some of these less reliable sub- cit) will become drier, likely slightly dry, zones, modification of local climate due to and possibly experience water deficits dur- topography (such as north-facing lower ing the growing season. With expectations slopes) may alleviate the impacts of pre- of increased precipitation, it is possible dicted warming to some extent, but these that certain wet sites may become very sites will need to be carefully assessed wet (i.e., with a water table at or above the (local climatic as well as edaphic condi- ground surface during winter). Excess tions) on an individual basis. Therefore, water availability may extend into the when evaluating suitable sites for future growing season due to unbalanced season- redcedar crops, it is imperative to consider al precipitation. Such soil moisture condi- local climatic as well as edaphic conditions may result in redcedar dieback tions. (Figure 61). As a result, some skunk cab-

a b

Figure 60 A naturally regenerated, seral redcedar–hemlock stand on a water-deficient, rocky crest after cutting and fire (CWHvm2/03 HwCw–Salal) (a); old-growth (climax) redcedar–hemlock stands on rocky slope (CWHvh/03 CwYc–Salal) (b).

58 Figure 61 Dieback of redcedar under prolonged very wet conditions at the lake margin in the CWHvm subzone.

bage sites could become unreliable for redcedar growth as well as for other associated tree species on these sites, such as Figure 62 An open-canopy, old-growth (climax) Sitka spruce. stand of redcedar, yellow-cedar, and western As with other associated species, redce- hemlock on a moist site in the CWHvh subzone. dar site index is estimated to be low on moist to very moist, nutrient-poor to medium (often salal-dominated) sites, In contrast, selecting moist to very particularly in the hypermaritime sub- moist, nutrient-rich sites on upland and zones (Figure 62). These types of sites floodplain sites will result in regeneration occupy a large area of the outer coast and difficulties and high costs associated with are considered at or below thresholds for the management of competing vegetation. economic operability (see section 6.3: These costs would be encountered with HyP3 Studies). However, there is good evi- many other crop species. dence that present site index estimates When mixed-species stands are desired, derived from existing stands may not western hemlock, Pacific silver fir, or yel- reflect the true productivity potential of low-cedar with similar growth rates, or redcedar on these sites (Banner et al. faster-growing grand fir, Douglas-fir, or 2005) (refer to Table 11). Taking into Sitka spruce could be appropriate species account the prediction of a warming cli- depending on site quality. On richer, mate, we believe that new, managed stands brush-hazard sites, hardwood species (e.g., regenerated to redcedar could be more black cottonwood, red alder, or bigleaf productive than existing natural stands. maple) could be utilized as temporary On those sites with adequate plant-avail- nurse species if regenerated in the spatial able nutrients, an increasingly warmer and arrangement as proposed by McLennan drier climate should allow for the improv- and Klinka (1990) (Figure 63). Using rap- ing reliability of these sites for the produc- idly growing black cottonwood or red tion of valuable redcedar crops. alder as a nurse species to shade out

59 Table 8 Generalized edatopic grid showing actual soil moisture regime and nutrient regime of the upland sites, floodplain, and sites with fluctuating water table that are suitable for growing redcedar as a reliable crop species. The site series names are given as numerical codes and abbreviated names. Current SIBEC estimates of site index (m @ 50 years breast height) are given in parentheses for each subzone or site series.

SMR/SNR Very poor–Poor Medium Rich–Very rich

Very dry Not suitable Not suitable Not suitable Moderately dry Not suitable Not suitable Not suitable Slightly dry Not suitable Not suitable Not suitable Fresh CDFmm/05 Cw-Kindbergia (24.0) CDFmm/06 CwBg-Foamflower (28.0) CWHxm/06 HwCw-Deer fern (not given) CWHdm/05 Cw-Tiarella (28.0) CWHdm/01 Hw-Flat moss (27.6) CWHvm1,vm2/05 BaCw-Foamflower (24.0, 24.0) CWHvm1,vm2/01 HwBa-Blueberry (22.6, 20.0) CWHwh1/03 CwSs-Sword fern (20.0) CWHwh1,wh2/01 HwSs-Lanky moss (21.4, 16.0) CWHvh1,vh2/05 CwSs-Sword fern (24.0, 24.0) CWHvh1,vh2/04 HwSs-Lanky moss (20.0, 22.8) CWHvh1,vh2/01 CwHw-Salal (16.0, 19.7) Moist - CWHds/06 Hw-Queen’s cup (24.0) CWHds/07 Cw-Devil’s club (28.0) Very moist CWHms1,ms2/05 HwBa-Queen’s cup (20.0, 16.0) CWHms1,ms2/06 BaCw-Devil’s club(24.0, 24.0) CWHws1,ws2/05 HwBa-Queen’s cup (16.0, 16.0) CWHws1,ws2/06 BaCw-Devil’s club (24.0, 20.0) CWHdm /06 HwCw-Deer fern (32.0) CWHxm/07 Cw-Foamflower (28.0) CWHmm1,mm2/06 HwBa-Deer fern (24.0, 20.0) CWHdm/07 Cw-Lady fern (30.8) CWHmm2/07 CwYc-Goldthread (16.0) CWHmm1,mm2/07-08 BaCw-Salmonberry (28.0, 24.0) CWHvm1,vm2/06 HwBa-Deer fern (23.3, 20.0) CWHvm1,vm2/07 BaCw-Salmonberry (24.0, 24.0) CWHvm2/09 CwYc-Goldthread (12.0) CWHvm1,vm2/08 BaSs-Devil’s club (22.1, 24.0) CWHwh1,wh2/04-02 CwHw-Salal (16.0, 16.0) CWHwh1,wh2/05-03 CwSs-Foamflower (20.0, 16.0) CWHwh1,wh2/10-05 CwYc-Goldthread (12.0, 8.0) CWHwh1,wh2/06-04 CwSs-Conocephalum (20.0, 12.0) CWHvh1,vh2/11 CwYc-Goldthread (12.0, 12.0) CWHvh1,vh2/06 CwSs-Foamflower 24.0, 24.2) CWHvh1,vh2/07 CwSs-Devil’s club (24.0, 22.0) Wet Not suitable CDFmm/11 Cw-Skunk cabbage (16.0) (water-collecting CWHds/12 CwSs-Skunk cabbage (20.0) sites) CWHms1,ms2/11 CwSs-Skunk cabbage (20.0, 20.0) CWHws1,ws2/11 CwSs-Skunk cabbage (16.0, 12.0) CWHxm/12 CwSs-Skunk cabbage (16.0) CWHdm/12 CwSs-Skunk cabbage (20.0) CWHmm1,mm2/10-12 CwSs-Skunk cabbage (20.0, 18.0) CWHvm1,vm2/14-11 CwSs-Skunk cabbage (19.4, 16.0 CWHwh1,wh2/12-06 CwSs-Skunk cabbage (12.0, 8.0) CWHvh1,vh2/13 CwSs-Skunk cabbage (16.0, 16.0) Floodplain sites High bench Not suitable CDFmm/07 Cw-Snowberry (28.0) CWHds/08 Ss-Salmonberry (28.0) CWHms/07 Ss-Salmonberry (24.0) CWHws/07 Ss-Salmonberry (20.0) CWHxm/08 Ss-Salmonberry (24.0) CWHdm/08 Ss-Salmonberry (32.0) CWHmm1,mm2/08 Ss-Salmonberry (28.0, 24.0) CWHvm1/09 Ss-Salmonberry (24.0) CWHwh1/07 Ss-Lily-of-the-valley (20.0) CWHvh1,vh2/08 Ss-Lily-of-the-valley (24.0, 24.0) Fluctuating water table sites Fresh - Not suitable CDFmm/13 Cw-Indian plum (28.0) Very moist CDFmm/14 Cw-Slough sedge (20.0) CWHxm,dm/13 Cw-Salmonberry (28.0) CWHxm,dm/14 Cw-Black twinberry (28.0) CWHxm,dm/15 Cw-Slough sedge (24.0)

60 shade-intolerant shrubs provides marginal redcedar under the cottonwood or red growth conditions for the shade-tolerant alder understorey can be profitable if redcedar. Following the mixed planting employed on appropriate sites. layout design of Figure 63 with the redce- Alternatively, if a mixed-species stand dar and hardwoods spaced at 2.5 m mini- is desired on a site with lower brush haz- mizes the suppressing impact of the black ard, it is possible to use redcedar as a cottonwood while maximizing crop tree means of shading out lower branches of stocking levels. The concept behind this Sitka spruce or Douglas-fir, thereby pro- approach is to create mixed plantations moting the rate of self-pruning on the that mimic cottonwood–redcedar commu- lower branches of those species. Due to its nities that develop in the course of succes- high shading capacity, once established on sion on the high-brush sites. moderate brush hazard sites, redcedar can Figure 64 illustrates the improved red- reduce the impact of the brush competi- cedar growth established in the way tion, and possibly reduce costs of vegeta- shown in Figure 63. The hardwood sap- tion control. To achieve this intended lings could be removed at any time after effect, larger stock would be essential, with 10 years or when the redcedar has reached seedling establishment required immedi- the height of > 4 m without the risk of ately following harvesting. shrubs overtopping the crop trees. Given It has been demonstrated that mixed the relatively low level of management stands of western hemlock and redcedar effort (compared to chemical or mechani- do not exhibit aboveground productivity cal brush control) and ecologically benign levels greater than single-species stands nature of the nurse tree method, growing (Chen and Klinka 2003). For the best

6 Zone of minimum growth suppression Cw

4 Height (m) of

2 Zone of maximum growth suppression Zone of maximum Zone of minimum growth suppression growth suppression Black cottonwood Western redcedar 0 0 5 10 Age (years) Figure 63 Projection of the zone of minimum growth suppression for western redcedar under a canopy of 10-year- old black cottonwood (based upon 2.5-m spacing) for both Figure 64 Height–age relationship for redcedar saplings black cottonwood and redcedar and growth rates stratified into two growing zones at the 10-year-old characteristic of the CWHxm/08 (Ss – Salmonberry/coarse- cottonwood (based on 2.5-m spacing) on moist and rich skeletal) site type (McLennan and Klinka 1990). sites in the CWHdm subzone (McLennan and Klinka 1990).

61 results as a crop species, redcedar should distribution pattern) should be group- be grown in even-aged, pure stands at random or -non-random to prevent over- high densities or with other species of topping of redcedar by faster-growing similar shade tolerance (such as western species, with the area of groups > 0.05 ha. hemlock) at relatively low spacing. In In the end, the decision to regenerate red- mixed-species stands, irrespective of shade cedar will remain a mix of subjective but tolerance of other species, arrangement of experienced judgement and objective fac- trees in the horizontal space (i.e., tree tual evidence.

5.4 cutting and A regeneration cut is a timber harvest > 0.05 ha) (Klinka et al. 1994). These Regeneration of designed to promote the establishment of methods will facilitate planting and pro- Redcedar Stands a particular tree species. Choosing an vide for the productive growth of redcedar appropriate regenerating cutting method in even-aged cohorts. Prior to any regen- will depend on the species of choice, the eration cut, seed trees must be clearly site, the management objectives, and the identified to ensure survival through har- desired products. For redcedar there are vesting operations. Leave trees must be several options, although the manager windfirm, which should be a realistic must first consider if a pure redcedar expectation with redcedar due to its exten- stand is desired, or redcedar mixed with sive root system. other species. Even when a mix with other If they survive, suppressed redcedars species is desired, redcedar must be estab- that are released during partial cuttings lished immediately with larger stock to (shelterwood, release, and selection cut- avoid it being overgrown by western hem- tings) will likely have developed large, lock advanced or seeded natural regenera- long branches, spreading crowns, and tion. tapered stem form (Oliver at al. 1988). Burns (1983) suggests that clearcutting, Releasing suppressed advance regenera- variable retention cutting, patch-cutting, tion may not provide acceptable levels of shelterwood, and selection cuttings are wood quality. Also, if evidence of root rot all appropriate for the establishment and is observed in the area, a release could growth of redcedar. Clearly, the choice of allow any resident rots to build up to high the harvest methodology will depend on levels (using residual stumps as inocu- site and management objectives, as it will lum) and overwhelm the remaining stand influence the silvicultural feasibility, utili- structure. Even “fungi-resistant” redcedar ty, productivity, and appearance of future cannot long survive a concentrated root redcedar stands. Detailed accounts of rot attack (Koenigs 1969). these various regeneration-cutting meth- At present, redcedar stands harvested ods can be found in Smith (1986) and in the coastal region are generally old and Nyland (1996). often located on slopes and rugged terrain. What are the appropriate regeneration The trees are large, and often decayed, and cutting methods that promote the estab- have large branchy tops. Wellburn and lishment of redcedar? In consideration of Peterson (1988) described harvesting of the selected management strategy (section old-growth redcedar as difficult and 5.1) and the relatively poor viability of nat- expensive. Felling of large trees is danger- ural regeneration (section 5.4.2), the ous, and often results in stem breakage. appropriate cutting options are clearcut- Large machinery is needed for yarding, ting (area > 1 ha), variable retention cut- loading, and sorting, and more breakage ting (containing clearcut areas > 0.05 ha), occurs during these operations. In conse- patch-cutting (area 0.05–1.0 ha), and quence, costs of harvesting old-growth group selection (containing clear areas redcedar stands are high and lumber

62 recovery is low. Such difficulties would be trees representative of the species (and much reduced when harvesting second- value) profile. Unfortunately, the harvest- growth stands. ing practices observed in the remaining It is because of these high costs that 66% (n = 36) of blocks surveyed in the minimal investment has been historically course of the investigation generated placed upon the regeneration of redcedar, residual stands severely reduced in eco- particularly in consideration of the easily nomic value and severely limited in terms regenerated but low-value hemlock, which of future harvest opportunity. A serious is also considered an acceptable species for secondary consideration is that residual restocking most coastal redcedar sites. The stands may contain a significant propor- combination of current poor economic tion of dwarf mistletoe infestation, render- conditions and the relatively high value of ing any potential seedling regeneration redcedar has led to the targeted harvesting prone to continued infection and reduced of this species. The targeted harvesting of value. any high-value species at the expense of An additional difficulty (one of many) long-term economic operability and struc- with the high-retention harvesting meth- tural diversity can only be identified as odology is that the residual stands are high grading. often still considered fully stocked under The occurrence of operational high current provincial policy, and so there are grading (termed euphemistically as “High no specific replanting requirements. What Retention Harvesting”) has become little regeneration there is in these har- enough of an issue within the coastal for- vested locations is limited to the natural est industry that the BC Forest Practices establishment of western hemlock or Abies Board (FPB) has issued a special report species. Furthermore, the complexity of detailing an investigation into the matter. the stands resulting from retention har- (The FPB is an independent public watch- vesting will require the development of dog that reports to the public about indus- new tools to adequately assess productivi- try compliance with the Forest and Range ty and predict future growth (FORCOMP Practices Act.) Their investigation FPB( 2008). 2008) describes a systematic shift (in cut The removal of the largest stems while profile) away from lower-value species retaining much of the canopy substantially (overmature hemlock with significant reduces the standing volume of the post- decay) towards high-value redcedar, thus harvest stand, and provides no avenue for shifting the residual stands to higher pro- recovery of this volume. The site occupan- portions of lower-value species. The very cy and high shading reduces the potential small openings created by this style of growth and vigour of any understorey sap- harvest severely limit the ability to re- lings. Although high-retention harvesting stock the harvested areas with redcedar or practices may meet certain environmental other valuable species. In spite of stated and social objectives (visual, limited cano- intentions of replanting redcedar detailed py disturbance), they do not provide for a in the approved cutting permits, the oper- long-term ecologically or economically ators instead often rely on natural regen viable forest industry. eration, which typically results in the establishment of western hemlock or ama- 5.4.1 Site preparation Site preparation for bilis fir. Alternatively, the openings may be redcedar includes options for slashburning small enough that no restocking is and mechanical preparation, with both required. decisions being site-specific (section 5.4.2: The FPB investigation determined that Natural regeneration). Slashburning would only 33% (18 of 54) of the surveyed high- be undesirable on shallow, high coarse retention harvested stands had removed fragment, nutrient-poor soils, and

63 mechanical site preparation would be on sites in the Capilano and Coquitlam undesirable on poorly drained, very moist watersheds, north of Vancouver. They or wet soils or fine-textured soils. Parker found high seedfall years in 1990/91 and and Johnson (1988) state that disturbance 1994/95, and an ample supply of viable is a major requirement for seed regenera- seed reaching the forest floor (200–1000 tion of redcedar. Fire may aid the natural seeds/m2). They also scattered 100 seeds in regeneration of redcedar by creating different sample plots (0.5 2m ), and after burned forest floor or exposed mineral three growing seasons found that an aver- soil seedbeds (Feller and Klinka 1998) age of only two seedlings per plot sur- (Figure 65). Broadcast burning may not be vived. It is because such large quantities feasible in partially cut sites or in small of seed are required to obtain adequate cleared areas. In these cases, burning piled stocking levels (Minore 1983) that planting slash would be more appropriate. seedlings is generally more strongly encouraged. 5.4.2 Natural regeneration The success In terms of germination substrate, of natural regeneration of redcedar is not Minore (1990) and Haig et al. (1941) con- limited by low seed production. When sider mineral soil to be the best seedbed regeneration failures occur, they are often (Figure 66). In old-growth stands, decay- due to mortality during germination ing wood is the most common (Parker (Gashwiler 1967) and are related to seed- and Johnson 1988), but produces the low- bed quality and microenvironment, par- est survival rates. Germinant survival may ticularly microclimate (Minore 1983). be highest on mineral seedbeds, such as Direct seeding in the fall may yield the root mounds (Parker 1986) but subsequent greatest success (Minore 1983). seedling growth was better on decaying To investigate the notion of a regenera- wood (Boyd 1959, 1965). Similarly, burned tion peak after fire disturbance, and to sites with exposed mineral soil favoured verify seedfall, germination, and seedling initial redcedar regeneration, yet growth on various substrates, Feller and unburned sites expressed better rates of Klinka (1998) carried out a 5-year study long-term survival (Soos and Walter 1963). Feller and Klinka (1998) also found the highest germination success on burned plots, followed by exposed mineral soil, and then forest floor. Feller and Klinka (1998) determined that the highest growth rates occurred on burned forest floor, followed by unburnt forest floor; the lowest growth rate was observed on mineral soil seedbeds. In terms of exposure, shaded seedbeds are associated with the best germination (Garman 1955); however, seedlings may fail due to poor root penetration (Sharpe 1974). Feller and Klinka (1998) also found higher germination success in protected understorey conditions compared to clearcuts, but growth rates were highest in clearcuts. Partial shade may protect seed- Figure 65 A pure, immature stand of redcedar that originated following lings and enable survival in moist condi- fire on a colluvial slope in the CWHvm subzone is one of many tions. However, once cover is removed, corroborating adaptations of redcedar regeneration to fire disturbance. shallow depth of rooting may limit a seed-

64 ling’s ability to tolerate exposure and testing, and storage of seed are given by drought. Schopmeyer (1974). The seeds of redcedar In undisturbed areas and in stands are particularly prone to viability losses in which redcedar as a minor species is during long-term storage, although non- growing in the intermediate and sup- destructive methods to determine seed pressed canopy positions, it reproduces deterioration are being developed and largely vegetatively (see section 3.2.1: implemented (Terskikh et al. 2008). A Asexual reproduction). The occurrence variety of containerized and bareroot of veglings is quite common in second- seedlings is available and used for planting growth as well as old-growth stands, and on the coast (Figure 67). Containerized is particularly abundant in the interior wet nursery seedlings, which can be produced belt. Generally, trees that originated as in 7 months, survive as well or better than veglings do not develop into desired crop bareroot stock when planted in coastal trees, as fungi infect them (typically butt Oregon, Washington, and British rot fungi) at an early growth stage. Columbia (Curran and Dunsworth 1988). Typical seedling stock planted varies 5.4.3 Artificial regeneration When natu- from 1+0 (315–615) styroblock plugs to ral regeneration is not a feasible option, 0.5+1.5 bareroot, ranging from 25 to 45 cm redcedar can be easily established by average heights. Most (~60%) planted planting. Vegetative propagation from cut- stocktype is 410–415 PSB (Brown 1999), tings (following procedures described by with the largest plugs (615 PSB) and bare- Brix and Barker 1973, 1975) was routinely root plug transplants making up 7% of the used by the B.C. Ministry of Forests and total planted materials (3.5% each). The Range and industry as it was more cost- largest stock is planted on those sites with effective and reliable than reproduction regeneration difficulties due to high brush from seed. Currently, propagation by seed competition, browse concerns, or possibly has become the primary method for water deficits. Also, larger and sturdier regenerating redcedar due to improved stocktypes minimize the levels of Keithia selection and storage methodologies. fungal infection (in nurseries). A bi-week- Techniques for collection, processing, ly application of the fungicide Mancozeb through the growing season controls the spread of this disease in the nursery environment (Trotter et al. 1994). Unless inoculated, redcedar seedling plugs directly lifted from a nursery express almost no association with mycorrhizal fungi. Within one growing season, most of these seedlings will have developed symbi- otic relationships with vesicular-arbuscular mycorrhizae (VAM), primarily on newly formed (non-plug) roots (Berch et al. 1993). The degree of colonization of seedling roots by VAM was slightly influenced by the severity of burning of cutover during site preparation. The incidence of VAM inoculation was slightly reduced with greater burn severity. It has been noted that very high rates of Figure 66 Dense natural regeneration of redcedar on the exposed self-fertilization are observed in redcedar, mineral soil of a roadcut. and the genetic variability of this species is

65 extremely low (section 3.7: Genetics). This Brush hazards On many of the most pro- combination of factors can lead to reduc- ductive sites for redcedar establishment tions in productivity (up to 8%) relative to (moist and richer), brush hazard ratings out-crossed (non-selfed) stands (Wang are high. Redcedar has the ability to sur- and Russell 2006). Fortunately, many vive and slowly grow through high brush poorer performing individuals are natu- due to its shade tolerance (see section 3.3: rally purged due to competition as crown Tolerances); however, this leads to poor closure is achieved. Wang and Russell growth form, heavy initial branching, and (2006) recommend planting at higher ini- slow capture (crown closure) of a site. tial densities to intensify the selection Studies of planted redcedar seedling pressures and further reduce the negative performance on Vancouver Island indicate effects of self-fertilization upon final stand a 3- and 5-year survival of 65% and 95%, productivity. respectively, with most of the mortality resulting from drought stress during 5.4.4 Establishment risks The establish- the first growing season (Curran and ment of any plantation can be a risky ven- Dunsworth 1988). Height growth ranged ture, requiring careful consideration of from 35 to 80 cm over five growing sea- costs and benefits for any decisions made sons. Two-year-old bareroot stock was regarding species selection and stocking found to be most effective for minimizing levels. The impact of these decisions must establishment costs; however, larger con- be borne for many years, during the full tainers were more effective at achieving rotation of that stand, and possibly longer. initial rapid height growth. Planting as Redcedar in particular, if established at early as possible has been most successful high densities as recommended for maxi- strategy. Survival is usually highest on mum productivity (> 1600 sph) can be an upland sites and lower on wet sites. To (initially) expensive investment. The two ensure the maximum likelihood of estab- greatest risks to that investment are brush lishment success in brush-hazard sites, and deer browse. Curran and Dunsworth (1988) suggest a five-rule protocol for planting: 1. Bareroot or container planting stock should have a shoot/root ratio < 2.5 50 and a caliper > 3 mm (> 412 PSB con- Western redcedar Yellow cedar 40 tainer stock). 30 2. Planting stock should not be stored for 20 longer than 30 days. 10 3. Spring planting should occur as soon 0 ntimetres Ce 5 as possible after lifting from contain- 10 15 ers. 20 25 4. Use barriers (or chemicals) against browsing. CW PSB CW PSB CW PSB CW PSB CY PSB CY PSB 5. Plant immediately after harvesting 410 412A 512A 615A CW PBR 410 412A 112/80 77/125 60/220 45/340 0.5+1.5 112/80 77/112 operations are complete. avg. ht. 25 cm 30 cm 35 cm 40 cm 45 cm 25 cm 30 cm Shade-intolerant trees, shrubs, and tall herbs, especially on moist and nutrient- avg. root 3.0 mm 3.6 mm 4.3 mm 5.0 mm 6.0 mm 3.0 mm 3.6 mm collar diam. rich sites, easily overtop smaller redcedar seedlings. It has long been demonstrated Figure 67 Standard stocktypes available for western redcedar and that planting larger seedlings will increase yellow-cedar, with associated characteristics, coded designations, average survival, height, and/or volume produc- height, and root collar diameter (Pacific Regeneration Technologies Ltd. tion in numerous coastal species (Long [online] www.prtgroup.com/products/CWCY.html). and Carrier 1993; Newton et al. 1993; Rose

66 and Ketchum 2003). Planting larger stock Salal (Gaultheria shallon) is a common can be more effective than herbicide or brush species on a wide range of sites that mechanical treatments on high brush-haz- can compromise redcedar seedling growth ard sites, and is often more economic. The throughout northern Vancouver Island. impact of larger stocktypes on plantation While salal does not affect redcedar to the growth is often long term, increasing even same degree as western hemlock (Fraser more over time. Larger bareroot stock et al. 1995), it has been shown to negative- was shown to attain a height of 6 m up to ly affect height and root collar growth. 8 years sooner than comparable smaller Reduction in herbaceous competition stock on the same brush-hazard site leads to much more rapid initial height (Newton et al. 1993), thereby producing growth. Salal is an oxylophytic species, merchantable volumes more reliably, and and very high application rates of nitrogen in substantially shorter timeframes. fertilizers (without phosphorus) have been Potential delays in plantation establish- shown to significantly reduce the vigour of ment due to the overtopping of undersized its re-establishment (Bennett et al. 2004). stock will increase costs by requiring Unfortunately, fertilizer applications at either multiple replants and/or herbicide these levels (1000 kg N/ha) are expensive applications to release suppressed seed- and can induce mortality in the seedling lings. The more quickly crown closure is crop trees. achieved, the more rapidly site resources are secured for the desired crop species. Browse damage Excessive deer browse This is particularly true for redcedar due can have a negative impact upon natural to its very high shading capacity. The use forest ecological systems and has been of “teabag” fertilizers at time of planting implicated in regeneration difficulties for has also been demonstrated to improve many species (Trembley et al. 2007). initial height growth, similarly reducing the Browse of redcedar seedling and saplings need for intensive weed control measures. in plantations by deer is a major manage- Similarly, weed removal or chemical ment issue throughout its range. Sitka control has also demonstrated substantial black-tailed deer (Odocoileus hemionus increases in seedling growth response sitkensis) was introduced to Haida Gwaii (Brisco 2004; Rose and Rosner 2005). in the late 19th century, and the heavy Rosner and Rose (2006) examined the browsing behaviour of this species has combined effects of seedling size and made redcedar in particular an especially weeding for redcedar and some associated difficult species to regenerate. It is almost crop species, with the following results. uneconomic to replant this species in The combination of larger seedling size many locations. and weed control produced the greatest Many deer repellents have been tested volume growth rates. Redcedar growth in for their efficacy in reducing deer browse particular was most responsive to the ini- damage. Deer repellents work by fear, con- tial seedling size. Rosner and Rose (2006) ditioned aversion, pain, and taste. Scent suggest that less competitive (more shade- capsules use odours (simulated or real) tolerant) species may be more responsive derived from deer predators, either canine to the use of larger seedling stock to keep (wolf) or feline (cougar/tiger). BGR-P is a them from being overtopped by compet- common scent product used by timber ing vegetation. Douglas-fir did not exhibit companies. Wolfin® capsules, a synthetic strong growth response relative to initial compound simulating wolf urine, was seedling size. Also, larger seedling stock tested as a repellent against ungulate requiring less intensive weed controls are browsing (Nolte et al. 2001) but did not likely a more economically sound silvicul- protect crop species from browsing. tural decision. Anecdotal evidence suggests a very strong

67 aversion to plantations inoculated with cally require repeated maintenance, but lion excrement (Pigott 2006), but this is are cost-prohibitive. In particular, com- hardly a realistic or economic alternative. plete fencing is extremely expensive and Products that affect palatability and/or interferes with the natural movement pat- induce pain often have capsicin as the terns of resident forest-dwelling creatures. active ingredient. One of these products, However, even with excellent fencing or Hot Sauce®, was evaluated as a mammal other effective protective measures, it deterrent by Wagner and Nolte (2000). A could take up to two decades for undam- 6% Hot Sauce® solution applied to redce- aged redcedar seedlings to achieve a size dar seedlings was found to be effective necessary to be immune to deer browse against black-tailed deer (Odocoileos (Stroh et al. 2008). hemionus) browse for 2 weeks; however, In addition to ungulates, bears can Big Game Repellent Powder® (BGR-P) was cause significant damaging to juvenile effective for the full 6 weeks of the study. stands of redcedar. Feeding bears (both BGR-P is a common product used by tim- black and grizzly) preferentially “barked” ber companies, promoting a fear response redcedar over western hemlock and in the herbivores by mimicking predator Pacific silver fir (Sullivan 1993). Bears scents—using putrescent egg solids (sul- remove the bark and scrape their lower phur). The mountain beaver (Aplodontia jaw against the exposed newly formed rufa) was not deterred from food by any wood tissue, effectively girdling the tree. chemical repellent. Barking damage mostly occurs is in the Garlic was evaluated and found to be a spring when the bark is easiest to remove very poor repellent (Nolte et al. 1995). It and the vascular tissues most succulent. lasted only for 2 days, whereas BGR-P Redcedar trees are most frequently dam- reduced feeding damage for a period of 8 aged when grown at wider spacings and/ or more weeks. In a large study that com- or on productive sites, where their radial pared 20 different products (Wagner and growth increments are high (thicker layers Nolte 2001), the most effective were those of tasty new wood). The more vigorous that included sulphurous odours and were the trees, the higher the percentage of bear directly applied to seedlings. Again, BGR-P attack. For example, Douglas-fir stands was the most effective, keeping browse fertilized with urea experienced 4 times damage to minimum levels for over 12 the feeding damage observed in controls weeks, although its effectiveness is depen- (Nelson 1989). Sullivan (1993) found the dent upon weather exposure and repeated greatest damage on redcedars at the widest applications. spacing and on trees ranging from 12 to 20 Some recent research indicates that an cm in diameter. Up to 70% of redcedar alternative non-commercial product was affected by age 33 years. (hydrolyzed casein—a milk product) can In a separate study, thinned stands were be prepared at various concentrations for found to be 5 times more susceptible to significant cost savings relative to com- bark stripping and sapwood feeding by mercial products, and may provide similar bears than adjacent stands (Mason and levels of seedling protection (Kimball and Adams 1989). This study within the interi- Nolte 2006). Also, the identification of or found that western larch and lodgepole monoterpenes as a natural agent making pine were preferentially damaged, whereas redcedar foliage less palatable to deer redcedar and Douglas-fir were not (Russell 2006) is another discovery that attacked. Damaged trees were predomi- may facilitate the less intensive re-estab- nantly in the 10–20 cm diameter class. On lishment of redcedar the coast and in the interior, widely spaced Fencing or other barriers are long-term young vigorous trees are most likely to solutions to deer browse that do not typi- suffer bear damage.

68 5.5 Stand Relative to other tree species and when density plantations, Smith, J.H.G. (1988) Management growing in pure stands, redcedar planta- suggests that faster-growing trees of tions should be regenerated at higher den- acceptable quality can be grown at wide sities, with intermediate trees removed in spacing if their lower boles are pruned. a light thinning at about age 25. Stands of However, he notes that percentages of about 400 crop trees per hectare at time latewood will be significantly decreased. of harvest may allow maximum diameter Regarding tools for the management growth without causing poor form (Ham and prediction of redcedar growth and ilton and Christie 1971; Nystrom 1980). yield, there are very limited updated The rationale for maintaining a nearly options. TIPSY® is a software product pro- closed canopy at all times is to encourage duced by the provincial government to the development of desirable stem form assist in the evaluation of managed stands (Figures 5, 38, and 68). In contrast to high- of known densities under different silvicultural regimes. Using TIPSY, a manager can evaluate the effects of different silvicultural treatments upon the final stand condition, and determine the most appropriate treatments to achieve desire stand product objectives. Unfortunately, TIPSY (and the TASS yield tables from which TIPSY results are interpolated) is considered fairly unreliable for redcedar (see Table 9). This unreliability stems from the poor representation (sample numbers) of redcedar stands within the provincial database and a lack of local knowledge regarding the response of redcedar to various cultural treatments.

5.5.1 Spacing and pruning A density of approximately 2400 trees per hectare (about 2-m spacing) appears to allow for unimpeded growth to 15 cm in diameter Figure 68 Canopy of a dense, naturally regenerated, fire-origin, (McArdle et al. 1961; Minore 1983; Oliver immature stand of western hemlock and redcedar on a sloping zonal site at al. 1988). The trees can grow to minimal in the CWHvm1 variant. Note the good stem form, absence of large merchantable diameters before the onset branches, and narrow, short live-crown. of competition with adjacent redcedar

Table 9 Reliability ranking of TIPSY yield output, by species (www.for.gov.bc.ca/hre/gymodels/tipsy/)

Species** Fdc Hwc Ss Cw Pl Sw Fdi Hwi Dr At Site Index* Reliability ***

High G G M P G M M P P M Average M M M P G M M P P G Low P P P P M P P P P P * Site Index: for coastal species High =35, Average =25, Low=15; for interior species High=20, Average=15, Low=10. ** Species: Fdc (coastal Douglas-fir), Hwc (coastal western hemlock), Ss (Sitka spruce), Cw (western redcedar), Pl (lodgepole pine), Sw (white spruce), Fdi (interior Douglas-fir), Hwi (interior western hemlock), Dr (red alder), At (trembling aspen). *** Reliability: G = Good, M = Moderate, P = Poor.

69 saplings for resources, allowing the first plantation will directly influence the thinning to be a commercial operation. development of the understorey shrub and The provincial stocking standards (B.C. herb community. As canopy cover increas- Ministry of Forests 2000) specify a target- es, light conditions in the understorey will ed range of 800–900 well-spaced crop deteriorate. On sites in the CWHvh and seedlings per hectare for the sites listed in vm subzones, the cover of both salal and Table 5. These are very low densities, and salmonberry was found to be inversely unlikely to produce high-quality redcedar related to canopy cover (Figure 69), with stands. In consideration of the current both species shaded out when the canopy “Results-Based” focus on regeneration cover was approximately > 85% (Klinka et standards, forest companies have the al. 1996a). option to develop their own stocking standards, detailing them in their Forest 5.5.2 Stand density management diagram Stewardship Plans. However most still rely Using data from natural stands and plan- on these Forest Practices Code Free- tations, N.J. Smith (1989) constructed a Growing Guidelines developed by the B.C. stand density diagram framework that Forest Service in the mid 1990s. Individual relates net standing volume to stem sur- growth rates may be higher at wider spac- vival. This was updated by Farnden (1996) ings, but crown and stem form will be (Figure 70). Height and diameter isolines negatively affected (Oliver at al. 1988; are overlain on the diagram, as are appro- DeBell and Gartner 1997; Singleton et al. priate points of crown closure, maximum 2003). current annual increment, and mean The influence of initial spacing, site annual increment. The diagram is entered quality, and stand density on growth and by determining the density (stems per yield of redcedar was studied intensively hectare) and quadratic mean diameter of by J.H.G. Smith (1980, 1988) in stands the stand. On average, a stand will tend to grown near Vancouver—in the Malcolm follow the survival isolines, moving from Knapp Research Forest and in Pacific the lower right to the upper left over time. Spirit Park. He concluded that the best If young trees are expected to suffer means of ensuring the development of high-quality timber was by pruning the lower boles of planted trees. The costs of pruning may be offset by the improve- 100 ments in timber quality and a higher-value end product. N.J. Smith (1988) argues 80 that natural pruning will be so slow that only 1 or 2% of clear lumber could be grown in a typical rotation. His projec- 60 tions suggest that such widely spaced redcedar stands (about 4.5 m) would produce 40 very high yields with large piece sizes. At age 100, predictions of merchantable vol- cover) ground (% layer Shrub 20 ume per hectare ranged from 1460 to 2651 m3 ha-1 depending on initial spacing (Smith, J.H.G. 1988). Projected volumes 0 0 20 40 60 80 100 for redcedar were lower than for Douglas- Tree layer (% ground cover) fir at the closest spacing, but greater at the widest spacing of 4.5 m (approximately Figure 69 Scattergram and fitted regression 485 trees per hectare). line of estimated shrub cover on estimated The establishment density of a redcedar canopy cover (Klinka et al. 1996a).

70 a) WESTERN REDCEDAR STAND DENSITY MANAGEMENT DIAGRAM 10.0 (NATURAL STANDS) 8.0 m 5 80 c 0 m 6.0 4 70 cm 6 m Quadratic Mean Diameter 4.0 Top Height 0 cm 6 38 m 3.0 Density Range For Maximizing CAI

2.0 30 TASS - Predicted Mortality Curves 50 cm m Mean and Lower Limits of the 26 m 40 cm Zone of Imminent Competition Mortality 1.0 24 m 0.8

0.6 cm 30 20 m 0.4

0.3 25 cm

1 0.2 6 m

) 20 cm 3 m (

M 0.1 U

L 0.08 15 cm O V 0.06 E E

R 12 m T

0.04 N

A 0.03 10 cm E M 0.02

0.01 8 m 0.008

0.006 5 cm 0.004 C ro w 0.003 n C lo s u 0.002 re

6 m 0.001 200 300 400 600 800 1000 2000 3000 4000 6000 8000 10000

DENSITY (trees per hectare)

Produced by Craig Farnden R.P.F., May 31, 1996. Data Source: TASS generated managed stand yield tables contained in the Produced for Silviculture Practices Branch, B.C. Ministry of Forests computer program WINTIPSY version 1.3 (B.C. Ministry of Forests, Forest Funding provided by Forest Renewal B.C. Productivity and Decision Support Section)

Figure 70 Stand density management diagrams for both natural (a) and planted (b, next page) stands of redcedar (from Farnden 1996).

71 b) WESTERN REDCEDAR STAND DENSITY MANAGEMENT DIAGRAM 10.0 (PLANTED STANDS) 8.0 4 8 m Quadratic Mean Diameter 6.0 0 cm 44 7 m Top Height 4.0 Density Range For Maximizing CAI 0 cm 36 3.0 6 m 3 TASS - Predicted Mortality Curves 2 m 2.0 2 Mean and Lower Limits of the m 8 m 50 c Zone of Imminent Competition Mortality

1.0 40 cm 24 m 0.8

0.6 20 m

m 0.4 30 c 16 m 0.3 25 cm

0.2 ) 3

m 20 cm (

M 0.1 U

L 0.08 12 m O 15 cm V 0.06 E E R T

0.04 N

A 0.03

E 10 cm M 0.02 8 m

C ro w 0.01 n C 0.008 lo s u 0.006 re

5 cm 0.004 6 m 0.003

0.002 200 300 400 600 800 1000 2000 3000 4000 DENSITY (trees per hectare)

Figure 70 Continued

72 competition from understorey vegetation Christie (1981). It is generally assumed that (e.g., from moderately shade-tolerant the method of thinning is an intermediate salal), it would be prudent to achieve full type that removes subordinate trees and crown closure as soon as possible. This encourages the growth of the selected, not would be of particular importance on necessarily dominant, crop trees. If the marginal sites, especially those prone to management intent is to grow clear wood water deficit and/or nutrient deficiencies for poles and high-quality sawlogs, then a Full crown closure is parallel to, and higher stand density should be retained slightly above, the 78% crown closure line well into mid-rotation age to promote shown in Figure 70. The slope of the line self-pruning. The effect of side-shade on is steep, suggesting that crown closure branch growth and self-pruning is illus- occurs at a much lower relative density in trated in Figures 71 and 72). stands with initially more stems per hect- Harrington and Wierman (1985) deter- are. Dense natural regeneration or planta- mined that, in natural stands on poorly tions would be desirable in this effect but drained sites, redcedar was more respon- they will require future density control to sive in height and diameter growth to ensure maximal growth increment and fertilization than to early thinning. Com high-quality timber production. bined thinning and fertilization increased growth significantly more than either 5.5.3 Thinning Selection of a thinning treatment in isolation. regime for a particular redcedar stand is When planning for the thinning of a decision that will depend upon specific redcedar stands, consideration should be stand, site, and management factors, par- given to the stem form of the dominants ticularly on the overarching management relative to the codominant trees. If many objectives and desired end products. As it of the largest trees are expressing high is impossible to account for all potential degrees of taper (and possibly fluting), variations in these factors and in consider- DeBell and Gartner (1997) suggest remov- ation of limited regional knowledge on ing a portion of the dominants with the growth and yield of redcedar, prescribing greatest degree of taper. Codominant indi- thinning regimes for pure or mixed-spe- viduals with better stem form and smaller- cies redcedar stands must remain a local, diameter branches should be left for and largely personal, decision. However, release. A high degree of fluting results in certain guidelines may be provided. wood waste during processing. Once the Oliver et al. (1988) recommend delay- high costs associated with defects, debark- ing thinning until lower branches are dead ing, and peeling highly fluted stems are to keep lower branches from surviving. accounted for, it may be more economic They suggest that a large portion of to leave the less tapered or fluted trees of improved growth following release is smaller diameter for a future harvest of added to large branches and not to stem higher-quality wood. wood. Depending on site quality, Ham ilton and Christie (1971) and Nystrom 5.5.4 Fertilization When soil moisture (1980) recommend light thinning as early deficits are not a factor limiting growth, as 21 years and as late as 30 years with the redcedar growth (like most agricultural aim of 350–750 crop trees per hectare on crops) can be consistently improved by high- and low-productivity sites, respec- fertilization. The available literature sug- tively. gests that young redcedar, even on poorly Thinning policies (i.e., intensity of thin- drained sites, responds in a conventional ning, thinning cycle, and thinning type), way to additions of nitrogen (Harrington for redcedar are discussed by Hamilton and Wierman 1990). However, specific and Christie (1971) and Edwards and characteristics of the site will dictate the

73 a b

Figure 71 A half-shade crown (a) and three-quarters shaded crown (b) of immature redcedar trees showing long, coarse, and persistent branches on the unshaded portion of the stem. ability of a stand to respond to any nutrient amendments. Weetman et al. (1988) pointed out that only with an understanding of nutrient requirements of tree species and the interaction of site quality, foliar nutrient concentration, and species growth can one identify possible nutritional problems and prescribe appropriate silvicultural treatments. In spite of its wide edaphic tolerances and ability to grow on nutrient-poor sites (section 4.3: Edaphic Amplitude), redcedar growth can be severely limited by deficiencies in certain macro- and micronutrients (Radwan and Harrington 1986). Stands experiencing specific nutritional deficiencies may exhibit symptoms that can be visually identified in the field (Walker et al. 1955; Ballard and Carter 1986). These visual symptoms of deficiency with their interpretations are listed in Appendix 2: Levels and symptoms of Figure 72 Excellent stem form and high, nutrient deficiency. However, diagnosis of narrow live-crowns of redcedar trees that have nutrient deficiencies solely by the inter- developed in high-density (fully shaded) pretation of visual symptoms may not be conditions.

74 exact or reliable. For more precise nutrient al. 1988; Weetman et al. 1988), and may diagnoses, chemical analyses should be produce a longer-term effect (Harrington performed upon collected foliage. Note and Wierman 1990). Urea is the most that foliar collection requires the observa- cost-effective product of the two, as it tion of particular protocols to ensure that has a much higher concentration of nitro- data are consistent with available inter- gen than ammonium nitrate, thereby pretations. The nutrient interpretations decreasing the amount of product applied presented in Table 10 from Ballard and to achieve a desired rate of nitrogen. In Carter (1986) were based upon a green- addition, urea has other desirable char- house seedling study performed by Walker acteristics (reduced volatility and ease et al. (1955), and it has been suggested that of handling) in contrast to ammonium their applicability to older stands is ques- nitrate. Fall applications of fertilizers tionable (Harrington and Wierman 1990). typically yield the most consistent results, Concentration ranges of foliar nutrients and allow for easier scheduling/timing of vary between interior and coastal popula- application. tions (Radwan and Harrington 1986) and Harrington and Wierman (1985) were strongly correlated with productivity. determined that in naturally established As operational fertilization of forest stands 20-year-old stands on poorly drained sites, is becoming more commonplace, and redcedar was more responsive in height because foliar concentrations are so and diameter growth to fertilization than valuable for evaluating stand nutrient to early thinning. Combined thinning and deficiencies, updating these 50-year-old fertilization increased growth significantly interpretations is strongly recommended. more than either treatment in isolation. Nitrogen was found to be the most Among other treatments, thinned stands growth-limiting nutrient for redcedar were treated with both urea and ammoni- seedlings, followed by phosphorus (Walker um nitrate, and no differences in response et al. 1955). With the application of appro- were detected between the two nitrogen priately tailored fertilizer compositions, sources in this study. Further analysis of redcedar has the ability to respond with these same study stands (Harrington and impressive growth results. When grown in Wierman 1990) revealed that unthinned, well-watered soil fertilized with nitrogen, high-density redcedar responded much phosphorus, and potassium, redcedar more strongly than expected to the fertil- seedlings will outgrow seedlings of izer treatment, likely due to the high shade Douglas-fir, grand fir, Sitka spruce, pon- tolerance of the species and its ability to derosa pine, and western hemlock. increase growth even under low light con- Using urea as the source of nitrogen ditions. The authors suggest that this may appears to be similarly effective to, or be the best treatment to consider for the more effective than, ammonium nitrate production of high-quality sawlogs. in stimulating growth in redcedar Perhaps the most extensive fertilization (Harrington and Wierman 1985; Oliver et efforts in redcedar plantations were car-

Table 10 Interpretations of foliar macronutrient concentrations for redcedar (from Ballard and Carter 1986)

N P K Ca Mg (Concentrations in percent, dry mass basis) Very severely or severely deficient <1.15 <0.10 <0.35 <0.07 <0.05 Severely or moderately-severely deficient <1.50 <0.13 <0.40 <0.10 <0.06 Moderately to slightly deficient <1.65 <0.16 <0.80 <0.20 <0.12 Possibly deficient, or adequate >1.65 >0.16 >0.85 >0.25 >0.14

75 ried out on northern Vancouver Island both inorganic and organic fertilizers, under the Salal–Cedar–Hemlock Int with or without the physical removal of egrated Research Project (SCHIRP). The salal. objective of these efforts was to accelerate In the first SCHIRP research update, crown closure of slowly growing (checked) Prescott (1996a) reported that: 1) the redcedar plantations on salal-dominated growth check of conifers on CH cutovers cutovers formerly supporting old-growth can best be relieved by N and P fertiliza- cedar–hemlock (CH) stands by alleviating tion or the application of fish silage and low nutrient availability (Figure 73). More sewage sludge, 2) growth response is details regarding other areas of SCHIRP correlated with foliar N concentrations, research can be found in section 6.2 and 3) Sitka spruce and western hemlock are online at www.forestry.ubc.ca/schirp/ more responsive to supplemental nitrogen homepage.html. than is redcedar, and 4) mechanical site In the early stages of SCHIRP develop- preparation or vegetation control are not ment, Weetman et al. (1988) reported that effective at alleviating the growth check in the checked trees responded immediately isolation from other nutritional treat- to NPK (nitrogen, phosphorous, potassi- ments. um) fertilizer treatment, with a 4- to In the second SCHIRP research update, 8-year temporary increase in leader length, including the results from 12 key silvicul- and that repeated fertilization may be tural trials, Blevins and Prescott (2002) required to obtain crown closure on these concluded that: salal-dominated sites. Prescott (1996a) 1. mechanical scarification and vegetation reported positive growth responses of red- control alone have little effect on tree cedar and hemlock on CH cutovers to growth on salal-dominated CH cutovers; however, the greatest response to fertilization occurs when it is combined with some form of vegetation control, 2. redcedar is less responsive than Sitka spruce and hemlock to fertilization, but produces the most volume on unfertil- ized, salal-dominated CH cutovers, 3. fertilization at time of planting combined with scarification on salal-dominated CH cutovers increases the growth of redcedar and hemlock, 4. urea and ammonium nitrate fertilizers produce similar growth response in treated conifer stands/plantations, 5. growth responses to organic fertilizers are similar to growth responses to inorganic fertilizers, and 6. fertilization of salal-dominated CH cutovers with very high rates of nitrogen inhibits the growth of salal but also reduces survival and growth of seedlings. Figure 73 A dense ericaceous shrub layer The field guide of Prescott (1996b) on one of the many salal- and blueberry- addressed operational application by dominated cedar–hemlock cutovers interpreting many SCHIRP studies and tri- in the CWHvh subzone. als and proposing silvicultural strategies

76 and possible treatments for creating closed than the redcedar on both sites. The canopies in young stands on salal-domi- growth improvements to both species due nated CH cutovers. Recommendations for to fertilization continued to be observed regenerating CH sites included clearcut- after 15 years for both the CH and (more ting, site preparation, a higher planting importantly) the HA sites. On the CH density preferring redcedar, and fertiliza- sites, the hemlock is becoming chlorotic tion with or without salal removal. after 15 years, whereas the redcedar Prescott (1996b) recommends nitrogen remains relatively productive with a great- (urea) and phosphorus application for the er long-term response to the fertilization best growth response, corroborating the treatment. On HA sites, the response of findings of Walker et al. (1955). both species to fertilization is much great- After 11 years, Prescott and Blevins er and remains strong over the long term. (2005) report that longer-term redcedar In particular, the redcedar growth response continues to remain similar for response (in terms of volume development both chemical fertilizers and biosolids, and periodic annual increment [PAI]) is doubling stand volume over that time rel- more than double that observed on the ative to controls. Hemlock is also recom- CH sites. The authors recommend that the mended as a mixed species on fertilized most appropriate management strategy for sites as it may provide a long-term these two site types is to establish moder- improvement in nitrogen availability ate-density redcedar plantations on the (improving overall site quality) due to the CH sites, with fertilization investment dol- rapid decomposition rate of its nutrient- lars best applied to redcedar plantations rich foliage. Bennett et al. (2003) have also established on the HA sites. documented the long temporal response Alternatively to seedling response, of young stands on CH sites to fertiliza- recent observations of fertilized stands tion (> 10 years), particularly in combina- near Gold River suggest that pole-sized tion with initial vegetation (salal) control. (23–36 years breast height) redcedar may They note that hemlock in particular not be as responsive to additions of nitro- had excellent long-term height growth gen (Van Niejenhuis 2004) as documented response, but do not mention diameter or in younger stands, or in the 20-year-old volume increment (where redcedar gener- stands of Harrington and Wierman (1985). ally demonstrates greatest relative growth) Testing of an application rate of 225 kg/ha (Harrington and Wierman 1990). Fifteen nitrogen (urea sourced) upon partial to years after treatment, fertilized redcedar completely closed canopy stands demon- stands continue to exhibit volumes more strated no strong response after 3 years. than double that of controls, with addi- This is disappointing in light of other tional applications of phosphorus having studies that indicate a strong fertilizer no greater effect than nitrogen (urea) response in younger redcedar plantations. alone (Blevins et al. 2006). It is difficult to interpret these results con- In the most recent analysis of SCHIRP clusively as there is little information pro- redcedar and western hemlock fertilized vided regarding the foliar nutrient status plantations, Negrave et al. (2007) make of the pre-treatment stands. The response note of some specific long-term trends of pole-sized redcedar stands to fertilizer observed 15 years following establishment requires further investigation for the of a trial paired across both the CH and development of appropriate management HA (hemlock–amabilis fir) site types. guidelines. Overall, the fertilized hemlock stands experienced substantially greater mortality

77 6 large-scale Redcedar-focussed Research Initiatives

6.1 imajo Studies The Imajo Cedar Management Fund was jects as compiled by Katrina Evans from established by Yoshihisa Imajo, President the Dean’s office (study details from of Sanki Corporation/Panabode the years prior to 1997/98 and the year International in the early 1990s. For over 2001/02 are missing) is presented in Table 15 years, this fund has supported research 11. Results of the listed studies are either studies intended to provide additional found in unpublished internal reports, as knowledge of the redcedar species and its publications in non-refereed or refereed ecological role in the British Columbia journals, or incorporated into graduate environment, and to promote redcedar theses on file at the Faulty of Forestry. establishment and sustainable manage- Please contact the listed recipient/ ment. The fund is administered by the researcher for details concerning the indi- Faculty of Forestry at the University of vidual project. British Columbia. A list of all funded pro

Table 11 A summary of projects funded by the Imajo Cedar Management Fund 1997/98 to 2006/07

Year Recipient Project description

1997–98 K. Klinka Two studies were conducted: (1) Relationship of site index to estimates of soil moisture and nutrients for western redcedar in southern British Columbia. In Scientia Silvica Extension Series No. 5 1997. (2) The relationship of site index to synoptic estimates of soil moisture and nutrients for western redcedar in southern coastal British Columbia. In Northwest Science 71:167–173 1997–98 K. Ritland Study of inbreeding in western redcedar. To date, he has identified six “good” microsatellite loci using advanced molecular genetics techniques. These loci will be used to study the degree of inbreeding of natural populations of western redcedar. 1997–98 Malcolm Knapp P. Sanders reported that work was well under way on a multi-species spacing trial that Research Forest included western redcedar among paper birch and red alder. The work was reported at (MKRF) a conference of over 20 experts from government, industry, and academia assembled in 1997 to discuss the design required to meet research objectives for this study. The trial was planted in 1997. 1998–99 Malcolm Knapp Funds were used to assist with the set-up of a long-term Multi-species Spacing Trial at Research Forest the forest. Specifically, these funds were used to purchase several thousand western redcedar, paper birch, and red alder seedlings needed to set up this trial. 1998–99 A. Weber Two studies were conducted: (1) Mycorrhizal relationships of western redcedar on three different substrates, and (2) The relative shade tolerance of cedar and hemlock. 1998–99 D.B. Collins Support for study on forest floor nutrient properties in single- and mixed-species stands of western hemlock and western redcedar in southern coastal British Columbia. 1999–00 Malcolm Knapp Study on the use of “teabag” fertilizer to facilitate seedling growth on brush sites at the Research Forest forest. 1999–00 J. Bennett Study on the nitrogen nutrition of western redcedar, western hemlock, and salal on cedar–hemlock sites on northern Vancouver Island. 1999–00 D. MacKillop Study on the development of old-growth stands and structural attributes in the moist Interior Cedar-Hemlock zone. 1999–00 A. Bal Study on the endophytic bacteria found in the internal stem, foliage, and root tissue of western redcedar.

78 Table 11 Continued

Year Recipient Project description

2000–01 Malcolm Knapp Investigation into the regeneration of western redcedar under variable retention Research Forest harvesting systems in the CWHdm subzone. 2000–01 Joanne Belik Study on vegetation community development in riparian reserves. 2000–01 M.C. Feller Study into the contributions of western redcedar to forest fire hazard in Coastal Western Hemlock zone forest. 2000–01 C. Chanway Study into the possibility of whether or not plant growth–promoting or nitrogen-fixing bacterial endophytes live in redcedar. 2002–03 I. Aron and Study on the use of salvaged western redcedar at the MKRF for producing signs for the P. Lawson Loon Lake Discovery Trail. 2002–03 A. Behennah Study on the surveying of western hemlock looper in the MKRF. 2002–03 N.J. Sutedjo Study on the detoxification of extractives of western redcedar wood in service. Fungal isolates on old western redcedar fences were isolated as potential white-rot fungi were confirmed. 2002–03 M. Cleary Study on the assessment of the resistance of western redcedar in the ICH zone to Armillaria ostoyae. This fieldwork included comparative descriptions of resistant reactions of western redcedar, Douglas-fir and hemlock to A. ostoyae. 2003–04 S.Mitchell and Study on the related variation in crown mechanical properties and drag for western S. Vollsinger redcedar. 2003–04 M. Cleary Study on the host responses of western redcedar to infection by Armillaria ostoyae in the southern interior of British Columbia. 2003–04 I. Aron and Extension of western red cedar research at the MKRF and development and testing of a P. Lawson high-density, high-value regime for management of a coastal mixedwood forest. 2003–04 G. Bull, R. Kozak, Study on the fibre supply issues of the British Columbia log home manufacturing and P. Thorny industry. 2004–05 C. Breuil and Study on detecting fungi in standing western redcedar trees. R. Chedgy 2004–05 I. Aron Extension of western redcedar research at the MKRF. 2004–05 B. van der Kamp Study on reducing the impact of Armillaria root disease via mixed-species plantations and M. Cleary including western redcedar. 2005–06 P. Perreault, Study on the cedar strategy workshop to develop a value-based management planning P. Lawson, and model for western redcedar, within the CWH zone, to ensure ecological, social, and S. Thuraismy economic sustainability of redcedar over a long-term planning horizon. 2005–06 S. Gergel and Study on the historical cedar inventory for Haida Gwaii to determine the original A. Pearson versus current extent of cedar, including monumental cedar, which will assist in land use planning, especially for traditional use. 2005–06 T. Seebacher and Study on western redcedar, climate change, and implications for forest management J.P. Kimmins on Vancouver Island; to determine the extent and cause of top-crown dieback in western redcedar on the east coast of Vancouver Island. 2006–07 C. Chanway Study on the visualization of western redcedar and lodgepole pine endophytic nitrogen-fixing bacteria and nif genes in situ. 2006–07 S. Gergel and Study investigating the possibility detecting and delineating large cedar crowns across N. Coops the landscape using high-resolution remotely sensed imagery. 2006–07 Paul Wood Study of the case for listing western redcedar in the Convention on International Trade in Endangered Species (CITES).

79 6.2 Salal–Cedar– Rarely have there been provincial research associated with acid substrates (Klinka Hemlock programs of such magnitude, duration, et al. 1989). On weakly acidic sites in the Integrated and operational significance as SCHIRP, CWHvm1 variant (e.g., nutrient-rich Research conducted in partnership between the 04 [Sword fern], 05 [Foamflower], and 07 Program Faculty of Forestry, University of British [Salmonberry] sites with Moder and Mull (SCHIRP) Columbia and Western Forest Products humus forms), salal growth is usually con- Inc. The purpose of this program was: fined to decaying wood (old stumps and 1) to understand the cause(s) of the poor large downed coarse woody debris). The forest regeneration on cedar–salal sites presence of salal appears to be limited by featuring a dense cover of salal (Figure 74), both higher nitrate concentrations (higher 2) to discover the ultimate causes of the pH) and reduced understorey light. It establishment/development of completely appears that salal strongly competes for different stand types (Cedar–Hemlock nutrients in the CH forest floor, greatly [CH] and Hemlock–Amabilis fir [HA]) on restricting its availability to other species. apparently “similar” sites, and 3) to deter- It should be noted that salal growth is not mine the best silvicultural practices for only restricted to CH sites. During their regenerating cedar–salal cutovers (Figures field investigations, McWilliams and 50 and 51). The study sites for the program Klinka (2005b) observed vigorous and were located on gently undulating terrain within the CWHvm subzone in Suquash Basin, near Port McNeill on northern Vancouver Island. The results of many SCHIRP studies are summarized in several major reports: Prescott and Weetman (1994), Prescott (1996a, 1996b), Blevins and Prescott (2002), and Prescott and van Niejenhuis (2005). Klinka (2006) reviewed 90 publications, including reports, journal articles, and graduate theses addressing the program that was initiated in TFL 6 on northern Vancouver Island in the early 1980s. In the initial synthesis report, Prescott and Weetman (1994) proposed four general hypotheses governing the development of SCHIRP studies for determining the underlying causes of poor regeneration on CH cutovers: 1) lack of disturbance, 2) the adverse effect of salal, 3) the adverse effect of redcedar litter and coarse woody debris on nutrient availability, and 4) site differences between CH and HA sites. Nearly all research focussed on the HA and CH sites as classified by Lewis (1982, 1985). The pri- Figure 74 A low-productivity, open-canopy, mary operational factor distinguishing old-growth (climax) western hemlock–redcedar these two site types is the difficulty in mixture on very moist, nutrient-poor sites regenerating productive plantations on (CWHvh2/11 CwYc-Goldthread sites). Note a harvested, salal-dominated CH sites. well-developed, ericaceous shrub layer. Salal is a moderately shade-tolerant, oxylophytic species; it tolerates and is

80 abundant salal on cutovers and within the program, excessive salal cover, low older stands found on the HA sites. site nutrient availability, and lack of Most salal roots are distributed in the windthrow/disturbance (protected, surface organic (forest floor) horizons, topographically-depressed sites) were with only minor proportions in the upper- considered the primary causes of poor most (usually Ae) mineral horizon. regeneration. After further investigation Bennett et al. (2002) found hemlock and into the effects of harvesting, age, tree spe- salal fine roots concentrated in the upper cies, salal cover, soil, and site characteris- forest floor, while redcedar fine roots were tics, Prescott and van Niejenhuis (2005) evenly distributed through the entire concluded that: soil profile. Based on fine root densities, 1. low nutrient supply is inherent to CH hemlock and salal probably compete for ecosystems (it is not an effect of har- resources in the upper forest floor, where- vesting); as redcedar is able to access nutrient res 2. HA and CH stands are not stages of ources in the lower organic and mineral the same chronosequence; soil horizons. This difference in vertical 3. redcedar litter is not contributing to root distribution may partly explain the the poor decomposition and N-status better performance of redcedar compared of the forest floor; to hemlock on CH sites. 4. salal is not causing the predicament Examining the SCHIRP installation (as it had been previously thought); plots, McWilliams and Klinka (2005a) 5. soil may not be the problem as no concluded that the primary factors con- large differences in mineral soil exist trolling the presence and growth of salal between HA and CH sites; and in these plots were: 1) light conditions— 6. CH sites are likely the cause of the ori- salal was absent in closed-canopy stands, gin of nutrient supply due to excess and 2) forest floor quality—salal prospers moisture (lower slope position) result- in very acid (pH < 4.0), carbon-rich ing in incomplete litter decomposition humus forms, such as Lignomors, Resimors, and N-immobilization. Hemimors, and Humimors, but avoids Prescott and van Niejenhuis (2005) weakly acid (pH > 4.0), friable, zoogenous imply that the low nutrient availability Moders and Mulls (Green at al. 1993). likely originates in the CH forest floor. The post-disturbance dominance of It could be argued that the low nutrient salal on CH sites appears to be due to its supply of the CH forest floor is the conse- ability to rapidly establish and effectively quence of thick, compacted (poorly compete both above and below ground permeable and aerated), colloidal Hh (from rhizomes present before distur- humus horizons, which very often develop bance). While understorey light condi- under water-surplus conditions. Further tions can be manipulated through density more, low temperature and aeration controls, thick acidic carbon-rich forest regimes of the CH mineral soils also likely floors in combination with a very high affect their nutrient availability. There is cover of decaying wood do not lend them- converging, yet still inconclusive, evidence selves to easy manipulation. in support of the site-difference hypothe- Prescott and van Niejenhuis (2005) sis; that is, CH and HA sites generally reviewed the problem of poor regenera- have different soil moisture, nutrient, tion on CH sites, various management temperature, and aeration qualities. This strategies, and the results of related assertion was corroborated by McWilliams SCHIRP studies. In the early stages of and Klinka (2005a, 2005b), who found HA

81 sites predominantly drier and nutrient- In examining possible application medium (corresponding to the of the BEC system for use in TFL 6, CWHvm1/01 HwBa-Blueberry sites), McWilliams and Klinka (2005b) suggest while the CH sites were predominantly that due to the large latitudinal range of wetter and nutrient-poor (corresponding the CWHvm subzone, the zonal classifica- to CWHvm/06 HwBa-Deer fern sites). tion should recognize two new variants— However, the effect of the nearly ubiqui- southern and northern—instead of the tous salal, as an element of vegetation single CWHvm1 variant. management, cannot be discounted, at For a summary of results from SCHIRP least in the early stages of plantation stand and site improvement studies, refer establishment. to section 5.5.4: Fertilization.

6.3 hyP3 Studies The HyP3 studies have important implica- ble results related to disturbance (type and tions for the potential regeneration of frequency) and productivity, operational redcedar on low-productivity sites in the trials, and the resulting management CWHvh1/CWHvh2 variants. interpretations. Banner et al. (2005) present an excel- Banner et al. (2005) consider forest- lent synthesis describing the patterns, floor dynamics of the hypermaritime for- processes, and productivity in the hyper- ests the primary determinant of forest maritime CWHvh2 forests that occupy productivity and succession. Natural dis- much of British Columbia’s outer coast. turbances typically mix organic material The hypermaritime forests of the central with mineral soil, increasing the rate and northern coast are distinctly different of organic decomposition and thereby from the maritime and submaritime for- improving forest productivity. Disturb- ests in the CWHvm subzones. Much of ance of this kind is rare in these forests. the landscape features large tracts of Without disturbance, moisture conditions undisturbed, low-productivity, old-growth facilitate the buildup of organic matter, forests of redcedar, western hemlock, resulting in soil paludification (lateral mountain hemlock, yellow-cedar, lodge- expansion of peatlands) and bog develop- pole pine, and abundant wetlands. The ment, conditions very detrimental to pro- predominance of the low-productivity for- ductive tree growth. ests (at or below operability thresholds) is Banner et al. (2005) constructed a sim- due to a combination of: 1) cool, perhumid ple model of ecosystem development and climate, 2) organic soils developed over productivity that includes three factors: severely glaciated, base-poor bedrock, and 1) bedrock geology, 2) soil drainage, and 3) cool, poorly aerated and poorly drained, 3) disturbance history. As most soils devel- water-surplus, nutrient-poor mineral soils op from the weathering of underlying (Figures 3 and 11). Banner et al. (2005) bedrock, sharp differences between soils focussed on forested sites series CWHvh2/ developed between slowly weathering 04 (HwSs-Lanky moss), CWHvh2/01 granodiorite (with relatively low amounts (CwHw-Salal), and CWHvh2/11 (CwYc- of nutrients) and easily weathered, nutri- Goldthread) (Table 8). ent-richer parent materials such as meta- The synopsis of the HyP3 projects by morphic rocks and limestone, producing Banner et al. (2005) is extensive. The focus distinct differences in forest communities of this report is the operationally applica- and potential site productivity.

82 Under conditions of surplus soil water, of suppression. This comparison clearly any variation in internal soil drainage indicates that the potential productivity of affects forest productivity. As long as soil redcedar may justify managing these sites water is free to drain, sites can support for wood production (with some special more productive forest growth, regardless considerations) as implied earlier in of slope position. Undisturbed sites with section 5.3: Site and Species Selection. poorly drained soils will accumulate Several research trials near Prince organic matter in the surface organic lay- Rupert investigated the effect of site prep- ers at a high rate. As a result, thick forest aration, including soil mixing, soil floors develop, creating continually cooler, mounding, and fertilization on seedling wetter, and nutrient-poorer conditions growth and nutrition. The preliminary yielding lower and lower levels of produc- results reported by Banner et al. (2005) tivity. In contrast, sites with a history of show that survival exceeded 90% (when disturbance show evidence of higher pro- the seedlings were protected against ductivity due to better drainage and high- browsing), and the average height growth er nitrogen mineralization rates. The of redcedar was marginally better on greater the inherent nutrient richness of mounded microsites. the underlying parent bedrock, the greater In the last chapter of the research syn- the history of disturbance; and the better thesis, Banner et al. (2005) presented the drainage, the higher the productivity management interpretations focussing on of the resulting hypermaritime forest. the ecological and operational feasibility Banner et al.’s (2005) study presented of sustainable practices on stands on zonal site index for redcedar derived from old- and near-zonal sites (CWHvh/01 CwHw- growth inventory estimates and from sec- Salal site series). As most of these unman- ond-growth SIBEC estimates for the study aged stands have very low merchantable area (Table 12). This comparison demon- volumes (< 300 m3 ha-1), stands on these strates that the former estimates signifi- sites currently exist outside of the operable cantly underestimated actual redcedar land base. By combining all research and productivity in open-grown conditions operational data, Banner et al. (2005) following a disturbance. In fact, these pro- developed a decision-making matrix to ductivity estimates derived from old- discriminate between potentially operable growth stands are exceedingly low, (suitable for redcedar crop production) suggestive of a long-lasting condition and inoperable stand sites.

Table 12 Redcedar site index (m @ 50 yr bh) estimates from old-growth and second-growth stands from the CWHvh2 subzone. Numbers in parentheses indicate range of site index (Banner et al. 2005).

Old-growth Second-growth Estimates Site series stands stands from

CWHvh/01 CwHw-Salal 3.9 17.8 19.7 (1.9–10.5) (13.5–22.3) CWHvh/04 HwSs-Lanky moss 5.2 22.7 22.8 (2.8–7.4) (17.0–34.3) CWHvh/11 CwYc-Goldthread 2.9 not given 8.0 (2.0–4.5) CWHvh/12 CwSs-Skunk cabbage 3.3 not given 16.0 (2.5–4.5)

83 The criteria in the matrix include: evapotranspiration and lead to increased depth and type of forest floor and mineral rates of paludification (Emili and Price soils, bedrock type, and stand composi- 2006). By investigating the use of slope tion. The inoperable sites are those identi- indices and topographical gradients fied as having the following characteristics: (including ground penetrating radar) to 1. transitional to very moist and wet sites predict forest type and productivity, Emili with the presence of Labrador tea, et al. (2006) determined that low slope crowberry, lingonberry, sedges, deer- index values derived from easily obtain- cabbage, Indian hellebore, Pacific able survey data correlated well with topo- reedgrass, and sphagnum, graphic high points. These high points had 2. peaty forest floor (organic surface layer) shallower organic horizons and deeper > 30 cm, water tables. Minor topographic gradients 3. mineral soil < 20 cm, produced large differences in site charac- 4. granodiorite, quartz diorite, diorite, teristics and potential productivity. and gnessic diorite underlying bedrock, Observed forest community types were a and function of the extent of organic matter 5. stand volume < 230 m3/ha. accumulation and water table depth as In addition, Banner et al. (2005) recom- constrained by topography. Accumulations mended specific terms for block layout, of organic matter decreased infiltration reproduction cuttings, harvesting meth- rates and drainage, resulting in higher ods, site preparation, and planting. water tables, which favours the invasion of However, there still remains some hydrophytic species such as Sphagnum uncertainty regarding the actual produc- mosses. By using simple survey data, this tivity of these sites once harvested and methodology reduces the need for inten- once a future reliable and productive crop sive hydrological investigations to deter- is required. In particular, there is concern mine suitability of a site for timber that once the original stand is removed, production. the water table will rise due to reduced

84 7 rEcommendations for Future Research

Based upon our review of current research, Vancouver Island to dieback instigated and the intention of promoting the estab- by root rot in relation to the mode of lishment of redcedar within our coastal origin. forests, we recommend the following 5. Update the foliar responsiveness and activities as priorities for research and nutrient interpretation for utilization policy development. in operational fertilization decision- 1. Review stocking standards and tree making. species selection guides for redcedar, 6. Continue genetic/breeding investiga- giving flexibility for establishing pure, tions into the development of seedlings high-density, crop-reliable stands. with elevated concentrations of terpe- 2. Monitor the health and vigour of coast- noid (deer and fungi repellency) com- al redcedar in the areas of marginal cli- pounds. matic range in relation to possible 7. Initiate further investigation into the climate change. A parallel investigation response of pole-sized and mature red- in similar marginal climates in the inte- cedar to operational fertilization. Study rior of the province may also provide new stand types not currently evaluated useful insights. by the ongoing SCHIRP trials, so that 3. Investigate the relationships between response across a wider range of stand climatic change, suitable climatic con- types and locations can be assessed. ditions for cedar leaf blight (including 8. Update the yield curves for redcedar. potential geographic expansion of Improve the reliability of key planning endemic cedar leaf blight infestation), tools such as TIPSY for redcedar stand and adaptive patterns of cedar leaf management and the application of blight resistance. The expanded genetic intensive silviculture. sampling of additional redcedar popu- 9. In consideration of the economic, eco- lations may provide further insight into logical, and cultural values of this spe- the adaptive patterns of cedar leaf cies, develop a formal redcedar strategy blight resistance. for coastal British Columbia to ensure a 4. Examine the susceptibility of second- continuing and sustainable supply of growth redcedar trees found on eastern old-growth and second-growth redcedar into the future.

85 Appendix 1 Site index curves and tables for coastal western redcedar

Coastal Redcedar Kurucz Top height (m) Top

Age at breast height (yr)

From: Mitchell and Pollson 1988. Based upon metric equations developed by Kurucz (1985).

86 * The broken line within the table(s) indicates the approximate age and site data used to develop the site index equations, and caution is recommended when using these curves and tables on stands 5 m site index or 20 years bha beyond this underlying data.

87 * The broken line within the table(s) indicates the approximate age and site data used to develop the site index equations, and caution is recommended when using these curves and tables on stands 5 m site index or 20 years bha beyond this underlying data.

88 Appendix 2 Levels and symptoms of nutrient deficiency

(From Walker et al. 1955; as detailed in Ballard and Carter 1986.)

Foliar concentrations Macronutrients (%, dry mass basis) Symptoms

Nitrogen < 1.5 Foliage yellowish; stems reddish in young seedlings; dying of older foliage conspicuous but little shattering; roots abnormally long in solution cultures; foliage sparse. Phosphorus 0.4 Stems and older foliage reddish or purplish during the first year, turning reddish brown and becoming necrotic in older seedlings; oldest foliage dies but does not shatter; youngest foliage retains good green colour. Potassium .39 – .78 Stems limber; foliage appears drooping, sparse; fourth-order branches apparently do not elongate; branch tips a good green, but older foliage necrotic or dying and any lower leaves and branches dead and brown. Calcium .10 – .20 Browning and drying at the tips of the leader and branch shoots; good green maintained in lower foliage; browning and dying of roots obvious in solution cultures. Magnesium .06 – .18 Good height growth; youngest foliage green, but older branchlets turn yellow or white then brown; a marked tendency to shatter, resulting in plants with a green tuft at the tip but bare branches below. (Other deficiencies do not seem to produce the white or yellow stage in necrosis characteristic of magnesium.) Sulphur .08 – .16 Foliage yellowish; older foliage paler than normal, although not so yellowish as younger portions of the plants.

Foliar concentrations Micronutrients (ppm, dry mass basis) Symptoms

Iron - Youngest foliage quite yellow, older foliage green; the difference more striking as the plants become older. Boron 15 Elongation in growing regions much restricted, so that needles are closely bunched, approaching the “rosette” in angiosperms; stems weak, upper parts of plant lop over; older foliage near normal; younger foliage “bronzed” in advanced stages; roots short with branches somewhat bulbous on the ends.

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