a summary of western yew biology with … summary of western yew biology with recommendations for...

L A N D M A N A G E M E N T H A N D B O O K

A Summary of Western Yew Biology

with Recommendations for its Management

in British Columbia

1 9 9 5

Province of British ColumbiaMinistry of Forests Research Program

3 2

A Summary of Western Yew Biology

with Recommendations for its Management

in British Columbia

Province of British ColumbiaMinistry of Forests Research Program

Elizabeth Campbell andAlison Nicholson

Canadian Catalogue in Publication DataCampbell, Elizabeth, -

A summary of western yew biology with recommendationsfor its management in British Columbia

(Land management handbook ; )

Includes bibliographical references: p.ISBN ---

. Yew - Ecophysiology - British Columbia. . Yew -Genetics. . Yew - British Columbia - Management.I. Nicholson, A. C. (Alison C.), - .II. British Columbia. Ministry of Forests. ResearchBranch. III. Title. IV. Series.

SD.YC .' C--

Prepared by:Elizabeth Campbell and Alison NicholsonResearch BranchB.C. Ministry of Forests Bastion SquareVictoria, B.C. VW E

Province of British ColumbiaPublished by theResearch BranchB.C. Ministry of Forests Bastion SquareVictoria, B.C. VW E

Copies of this and other Ministry of Foreststitles may be obtained, subject to supply, from:Crown Publications Inc. Fort StreetVictoria, B.C. VW E

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E X E C U T I V E S U M M A R Y

Considerable interest in western yew (Taxus bre-vifolia Nutt.) has been sparked by the recently dis-covered anti-cancer properties of taxol, a chemicalextracted from the bark of this conifer. Clinicaltrials show that taxol is a successful treatment forapproximately % of women whose ovarian can-cers resist conventional therapies (Stone ).Taxol also shows promise in treating breast, head,and neck tumors (Stone ). These positiveresults have greatly increased the demand for taxolobtained from wild western yew trees. Scientists donot expect an alternative taxol source to be availableon a commercial scale for about three years.

Wild western yew trees are a limited resource andare not considered as an option for the long-termsupply of taxol. They are small, slow growing, anduncommon relative to other commercial tree spe-cies. Furthermore, large quantities of bark arerequired to produce small quantities of taxol. Thereis concern that continued reliance on naturally occur-ring western yew will diminish this resource, jeopar-dizing the supply of taxol and threatening the species.The effect of western yew harvest on ecosystem struc-ture, function, and diversity is also a concern.

Existing Ministry of Forests policy on resourcemanagement dictates that western yew can be har-

vested in designated areas (i.e., areas approved forharvesting, and other areas, with a free-use permit).The policy also provides procedures for the acquisi-tion of permits, transfer of harvesting authority,and recording amounts harvested, but does notaddress significant ecological issues like:• the landscape and stand-level management of

western yew;• the extent and method of harvest in management

areas subject to different silviculture systems; and• the appropriateness of harvest in particular

ecosystems.These deficiencies and increased pressure to

selectively harvest western yew in areas reservedfrom conventional harvesting have prompted theneed for more comprehensive management guide-lines in British Columbia.

More information about the distribution, abun-dance and genetics of western yew in BritishColumbia was needed to develop management rec-ommendations. In and , the B.C. Ministryof Forests initiated ecological and genetic studies ofwestern yew. This report summarizes the results ofthis research and data obtained from the literature.This information forms the basis for managementrecommendations also presented in this report.

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A C K N O W L E D G E M E N T S

We gratefully appreciate the many helpful sugges-tions provided by those who reviewed this report:Allen Banner, Greg Britton, Phil Comeau, DelMeidinger, John Russell and Alvin Yanchuk (B.C.Ministry of Forests, Research Branch); Russ Cozens(Timber Harvesting Branch); John Howe (Vancou-ver Forest Region, Timber Management Section);and Alan Mitchell (Natural Resources Canada,Pacific Forestry Centre).

Field assistance and technical advice were pro-vided by Frances Backhouse, Chris Clement ofShearwater Mapping, Brian Egan of Egan Ecologi-cal Consultants, and Andrea Lawrence. Don Piggothelped to locate some sampling areas. Dendrologi-cal assistance was provided by Bruce Bennett.

Del Meidinger and Greg Britton assisted in theacquisition of data from the B.C. Ministry of For-ests Biogeoclimatic Ecosystem Classification data-base. We greatly appreciate their help.

Alvin Yanchuk provided data on the taxol con-tent of western yew bark and needles collected fromsome of our sample sites. The National CancerInstitute in Bethesda, Maryland conducted chemi-

cal analyses of the samples collected by AlvinYanchuk and Don Piggot and his crew.

Paul Nystedt drew the illustrations that appear inthis report and David Izard produced the computergraphics. Susan Bannerman and Fran Aitkens edi-ted the text and Beth Collins typeset it. Shirley Mahand Rick Page used ecological data from this pro-ject to produce a range map of western yew using PAMAP.

Wendy Bergerud and Vera Sit provided advice onstatistical analyses and the use of the statisticalsoftware package SAS.

Don Mullet (Silviculture Branch) and PatrickDaigle (Research Branch) provided valuable insightinto silvicultural systems and the associatedterminology.

There were many other forest region and districtstaff who assisted in locating sampling areas andwho provided advice throughout this project. Weare grateful for their help.

This project was partially funded by the Canada-British Columbia Partnership Agreement on ForestResource Development (FRDA).

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C O N T E N T S

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iiiAcknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Existing Harvesting Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Western Yew Biology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Distribution and Abundance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Geographic range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Biogeoclimatic distribution and abundance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Site and soil conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Nutrient regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Moisture regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Determinants of Western Yew Occurrence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Growth, Development and Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Phenology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Seed production and dispersal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Seed viability and germination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Vegetative reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.6 Response to Disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Forest canopy removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Soil disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Wildlife Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Genetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Genetic variability of western yew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Maintenance of genetic diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Taxol Content and Site Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Recommendations for Western Yew Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Management Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Principles and Assumptions for the Management Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Management Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Management of western yew in landscapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. The link between landscape and stand-level management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Management of western yew in stands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.. Needle harvest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Appendices Sample Letter of Authorization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sample Shipping Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sample Western Yew Bark Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Biogeoclimatic occurrence of western yew in British Columbia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of site associations where western yew is found . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Diseases and insect pests of western yew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Environmentally Sensitive Area (ESA) summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tables Average western yew tree height by diameter class for coastal plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figures Foliage and bark of a western yew tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Range of western yew in British Columbia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Typical size distributions of western yew in m plots surveyed on the coast and in theinterior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mean taxol content of western yew bark and foliage by site type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 I N T R O D U C T I O N

Western yew (Taxus brevifolia Nutt.) has been ofnegligible commercial importance in BritishColumbia because of its small size and rarity rela-tive to other commercial tree species. Use of thewood has been restricted to the making of archerybows, canoe paddles, fence posts, musical instru-ments, carvings, and other miscellaneous noveltyitems (Bolsinger and Jaramillo ). Until recently,only aboriginal peoples of the Pacific Northwestused decoctions of western yew bark for medicinalpurposes (Taylor and Taylor ; Bolsinger andJaramillo ; Turner et al. ).

Through widespread screening of natural prod-ucts in the late s, the United States NationalCancer Institute found the chemical taxol in west-ern yew bark to have significant anti-cancer proper-ties (Wani et al. ; Fuchs and Johnson ).Clinical trials show taxol to be a successful treat-ment for approximately % of women whoseovarian cancers resist conventional therapies (Stone). Taxol also shows promise in treating breast,head, and neck tumors (Stone ).

T.P.L. Phytogen, the pharmaceutical companyproducing taxol in British Columbia, estimates thatthey will need kg of western yew bark toextract taxol for research, testing, and clinical trialsover the next two years (J. Kapitany, T.P.L. Phy-togen, pers. comm., ). Fifty thousand kilo-grams of bark will produce about kg of taxol andrequire the harvest of almost western yewtrees each year for the next two years. This sixkilograms of taxol should be sufficient to treatapproximately Canadian cancer patients.

In British Columbia and the United States, thebark of wild western yew trees has been the primarysource of taxol. Several alternative sources of taxol,however, are currently under development. Theseinclude: large-scale domestic cultivation of western

yew, yew cultivars and exotic yew species (N.Wheeler, Weyerhaeuser, pers. comm., ); anewly discovered species of fungus called Tax-omyces andreanae (Stone ); and tissue cultures.Taxol and taxol analogues can also be obtainedthrough partial (Gueuritte-Voegelein et al. ) ortotal synthesis (Wender ; Holton et al. a,b; Nicolaou et al. ). While much progresshas been made with respect to alternative taxolsources, none are able to provide taxol on a com-mercial scale at this time.

Until an economically viable alternative is avail-able, we will continue to rely on wild western yewas a source of taxol. These trees, however, are fre-quently small, slow growing and relatively uncom-mon. Furthermore, large quantities of bark arerequired to produce small amounts of taxol. Thereis growing concern, therefore, that continuedreliance on wild trees will diminish this resource,jeopardizing the supply of taxol and threatening thespecies. Whole-tree harvest may also have adverseeffects on the structure, function and diversity ofwestern yew ecosystems.

The dependence on this forest-based source oftaxol has emphasized the need for a managementstrategy that will preserve western yew and its asso-ciated ecosystems, as well as provide moderateamounts of bark for extraction purposes.

This report provides recommendations for west-ern yew management in British Columbia. Theserecommendations are based on recently collectedbiological information. In , the B.C. Forest Ser-vice embarked on an ecological survey and a studyof western yew genetics (El-Kassaby and Yanchuk). The results of this research and informationobtained from the literature are summarized here.A glossary of terms used in this report is providedin Appendix .

Based on western yew harvest statistics provided to the Ministry of Forests, Vancouver Region in .

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2 E X I S T I N G H A R V E S T I N G P O L I C Y

Existing policy regarding western yew harvest iscited in the Ministry Policy Manual on ResourceManagement (B.C. Ministry of Forests ). Thispolicy dictates that western yew harvest on Crownland can occur in the following areas:• in areas approved for harvesting under an exist-

ing agreement, with the consent of the agreementholder;

• in areas where approval for harvesting is immi-nent under an agreement, with a free-use permitissued by the District Manager;

• in areas reserved from conventional harvesting,with a free-use permit issued by the DistrictManager that will authorize the harvest of west-ern yew bark but require a minimum number ofstems to be left in a range of age and size classes;

• in young stands, with a free-use permit issued bythe District Manager that will authorize the har-vest of yew bark but require a minimum numberof stems to be left.The harvesting of western yew needles is admin-

istered in the same manner. Needles may be har-vested from % of western yew trees by diameterclass and no more than % of the foliage shouldbe harvested from any one tree.

In areas approved for harvest operations underconventional agreements (i.e., tree farm licence,forest licence, or timber sale licences, etc. with validcutting permits), the licencee may extend cuttingauthority to permit harvest of western yew by asecond party. This permission must be issued inwriting and should explicitly identify the areas (ona map) where harvest is authorized. It should alsoincorporate any specific instructions from the For-est Service (District Manager) or the licencee. Free-use permits are issued by the Forest Service (Dis-trict Manager) as indicated above. Copies of eithera Letter of Authorization (Appendix ) or a free-usepermit should be readily available for viewing bythe proper authorities (i.e., the Forest Service or theRCMP) when harvesting and transporting westernyew bark. Authority to harvest western yew onprivate land may be obtained through written per-mission of the landowner.

To transport special forest products from site ofharvest, a Shipping Notice is required (Appendix ).A copy of this shipping notice should be given to theperson authorizing western yew harvest. This docu-

ment, together with the above mentioned permis-sion documents, will attest to the legitimacy ofwestern yew harvesting operations.

A Western Yew Bark Register (Appendix ) willbe kept by collectors and should be submittedannually to the Forest Service (Regional Manager)to document the extent and location of western yewharvest.

The current approach to western yew harvest onapproved sites includes removal of western yewbefore primary harvesting (similar to poling opera-tions) and post-logging salvage of western yew logs.Bark is usually stripped from the trees on the site. Iflogs are removed from the site, however, they mustbe scaled and a stumpage will be charged. Toencourage regeneration, current policy requiresthat western yew stumps, at least cm high withthe cambium intact, be left to resprout.

The harvest of western yew in the provinceyielded approximately kg (dry weight) ofbark; most of this bark was exported to the UnitedStates for taxol extraction. In , when a Cana-dian facility (T.P.L. Phytogen Inc.) developed themeans to extract taxol, the B.C. Ministry of Forestsceased granting bark export permits. T.P.L. Phy-togen estimates that they received 40000 kg of barkin and kg in . They expect torequire kg of bark over the next two years.

Current western yew harvest policy may not beadequate to accommodate the future need for barkand to ensure sustainable western yew populations.While current policy identifies areas of harvest andrequirements for harvest permits, shipping, andrecord keeping, it does not address significant eco-logical issues like:• landscape and stand-level management of west-

ern yew;• the extent and method of harvest in managed

areas subject to different silvicultural systems(e.g., clearcutting, seed-tree and selective sys-tems); and,

• the appropriateness of the harvest in particularecosystems.

These current policy deficiencies and the increasedpressure to selectively harvest western yew in areasreserved from conventional harvesting haveprompted the need for a more comprehensivemanagement strategy.

3 W E S T E R N Y E W B I O L O G Y

. Description

Western yew is a long-lived conifer whose growthhabit varies from a small tree to a low spreadingshrub. The tree form often exhibits a twisted andfluted trunk that may be multi-stemmed. Youngtrees frequently have a square to rectangular profilebecoming more conical with age. Branches are longand slender and tend to stand out straight, droop-ing only slightly. On trees growing partly or whollyin the open, numerous drooping branchlets formon the branches creating a weeping effect.

Needles are flat, characteristically pointed at thetip and − cm long. They are spirally arranged onbranchlets but have the appearance of being two-ranked. Fruits are produced at the terminal end ofbranchlets in early fall. The bark on mature trees is− mm thick, scaly and dark reddish brown(Figure ).

FIGURE Foliage and bark of a western yew tree.

. Distribution and Abundance

.. Geographic rangeOn the coast, western yew occurs as a sub-canopytree and constitutes a minor component (−%) offorested sites. Its range in British Columbia extendsalong the coast from the United States border northto Portland Inlet (approximately °N) and inlandto moderate elevations of the coastal mountains(Figure ). Western yew also occurs on the QueenCharlotte Islands, Vancouver Island, on the islandsof the Strait of Georgia, and at the extreme south-eastern tip of Alaska. South of the border, the rangeof western yew on the coast extends into northernCalifornia.

East of the Cascade Mountains, western yewgrows below the main canopy as a small tree orshrub, also forming a minor component (−%) offorests in the interior wet belt. It occurs on thelower slopes of the Columbia Mountains in south-eastern British Columbia and extends south tonorthern Idaho and northwest Montana. At it'seastern limit, western yew is found on the westernside of the continental divide near Sparwood andFernie.

Western yew grows at low to moderate elevationsand only rarely occurs in subalpine ecosystems inBritish Columbia. On the coast, it is typically foundfrom sea level to approximately m but has beendocumented on sites up to m in altitude. Inthe interior it is found at altitudes ranging from− m... Biogeoclimatic distribution and abundanceThe climate throughout the range of western yew ischaracterized by long growing seasons, high precip-itation and high relative humidity (Taylor and Tay-lor ). On the coast, most of the precipitationfalls as winter rain. Western yew is found almostexclusively in the low-lying Coastal Douglas-fir(CDF), Coastal Western Hemlock (CWH), and theInterior Cedar−Hemlock (ICH) biogeoclimaticzones. It also occurs, albeit rarely, in the InteriorDouglas-fir (IDF) zones, and the higher elevationMontane Spruce (MS), Mountain Hemlock (MH),and Engelmann Spruce−Subalpine Fir (ESSF)zones (see Appendix 4).

Biogeoclimatic classification of British Columbia is described in Meidinger and Pojar (editors) .

3

FIGURE Range of western yew in British Columbia.

Coastal subzones Western yew is present in mostsubzones/variants of the CWH zone, with exceptionof CWHwm, CWHws1, CWHws2, CWHmm2, andCWHds2. The CWHwm and CWHws subzones,north of Portland Inlet, have the coldest winter tem-peratures and heaviest snowfall of all subzones in theCWH zone. Mean winter temperatures range from-. to -°C (Meidinger and Pojar [editors] ). It islikely that western yew is excluded from these sub-zones because cold temperatures, combined withexposure to winter sun and dry winds, inflict foliardamage (N. Vance, U.S. Dep. Agric. For. Serv., pers.comm., ) or prevent seed germination.

Western yew is most prevalent in the warmerCWHvm1 and CWHvh1 on Vancouver Island andcoastal mainland British Columbia, the CWHwh1

and CWHvh2 on the Queen Charlotte Islands, theCWHms2 in the Squamish area, and the CWHds1,which is restricted to a small portion the southernmainland. Western yew is also prevalent in theCDFmmÐa subzone confined to southeasternVancouver Island, the Gulf Islands and the lowermainland. This subzone has the warmest and driestcoastal climate. Crown cover is typically about %on forested sites in subzones of the CWH and CDF.

Western yew occurs rarely in subalpine ecosys-tems of the MH zone, which is characterized byshort, cool summers and long, wet, snowy winters(Meidinger and Pojar [editors] ). It is found inall subzones except the leeward MHmm2 which isthe coldest, driest climate in this zone. Crown coveris typically % in MH subzones.

See Appendix for definitions of the alphabetic symbols used to designate subzones.

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Interior subzones In the interior, western yew isconcentrated in the Interior Cedar−Hemlock(ICH) zone. It is most prevalent in ICHmw2,ICHdw, ICHwk1,2 and ICHvk1 where the regionalclimates are relatively warm. Crown cover is typ-ically about % in the ICH zone.

Western yew is absent from the coldest sub-zonesof the ICH including the ICHdk near Canim Lake,the ICHmk2 near the Thompson River, theICHwk3 and ICHwk4 in the upper Cariboo Riverarea, the ICHvk2 in the Slim Creek area, and theICHvc and ICHmc subzones in the Nass Basin.

Western yew is rare in the Montane Spruce zone,occurring exclusively in the MSdk. It is also rare inthe Engelmann Spruce−Subalpine Fir (ESSF) zonewhere it occurs only in the warmest subzone,ESSFmw.Site associations Site associations are groups ofrelated ecosystems that are similar enough in sitequality and productivity to produce similar vegeta-tion types at climax. Western yew has been docu-mented in site associations defined within theB.C. Ministry of Forests Biogeoclimatic EcosystemClassification System. These site associations arelisted in Appendix .

Western yew is most prevalent on site associa-tions dominated by Douglas-fir (e.g., Fd−Salal,Fd−Oregon grape), western redcedar (e.g.,Cw−Skunk cabbage, CwSs−Skunk cabbage), westernhemlock (e.g., HwCw−Deer fern) and interior westernredcedar/western hemlock (e.g., CwHw−Devil’sclub−Lady fern). It is more rare in coastal amabilis firand Sitka spruce stands, as well as western hemlock-dominated stands of the interior. Western yew does notoccur on dry site associations dominated by shore pine(e.g., Pl−Kinnikinnick), but does occurs in wet (e.g.,Pl−Sphagnum and PlYc−Sphagnum) site associations.

A pilot inventory conducted in the CWHvm andCWHvh subzones of northern Vancouver Island showsthat western yew attains greatest average densities(trees/ha) in mature ecosystems of Yellow-cedar−Shorepine−Sphagnum (µ=., Std. Err.=.); Western red-cedar−Western hemlock−Salal (µ=., Std.Err.=.); and Western redcedar−Skunk cabbage(µ=., Std. Err.=.) (R. de Jong, Natural ResourcesCan., pers. comm., ).

Western yew is absent from stands dominated bydeciduous species such as Garry oak, red alder, andblack cottonwood.

. Habitat

.. Site and soil conditionsWestern yew grows on a wide variety of forested sitetypes, from upper rocky sites to lower slopes, moistdepressions, and ravines. In warm, dry climates likethe CDFmm, it is often restricted to cool, moisthabitats. Western yew can also form dense thicketson non-forested talus slopes and lower elevationavalanche chutes.

Because of its slow growth rate, western yew ismost frequent in the later successional stages of aforest. Large trees are prevalent in mature and old-growth stands. However, western yew does notapparently require mature or old-growth forests, assuggested by the U.S. Forest Service, (U.S. Dep.Agric. ), since it occurs, to a lesser extent, insome seral stages. Seral stands composed ofdeciduous species like big-leaf maple and red aldertend not to contain western yew. The distributionand abundance of western yew in seral ecosystems,however, requires further research.

Western yew grows on a variety of soil types (i.e.,from deep, fine-textured organic soils to shallow,coarse-textured regosols or folisols) but best growthoccurs on deep, moist, moderately well-drainedsoils (Taylor and Taylor ). Western yew is mostabundant on podzolic soils of the CWH and ICHzones and on brunisolic soils of the CDF zone. Itseems to adapt well to slightly acidic or alkaline soilconditions (Taylor and Taylor ; Krajina et al.)... Nutrient regimeLittle is known of the nutrient requirements ofwestern yew, but it grows best on sites with mediumto rich nutrient content. Average growth rates ofwestern yew are significantly greater (up to . cm/yr) on rich sites.

Western yew, however, occurs more frequentlyon poor to medium sites. An association of vesicu-lar-arbuscular mycorrhizae with the roots of west-ern yew (U.S. Dep. Agric. ) may contribute tothis tree’s ability to occupy less-than-optimal sites.Association of this fungus with plant roots permitsthe retrieval of phosphates and water from the soilmore efficiently than uninfected roots (Trappe andFogel ; Begon et al. ). Vesicular-arbuscularmycorrhizae are predominantly associated withangiosperm roots, but genera such as Thuja, Juniperusand Sequoia are also associated with this type offungus (U.S. Dep. Agric. ).

See Appendix for tree species abbreviations.

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.. Moisture regimeIn wet climates like that of the CWHvh, westernyew tolerates a wide range of soil moisture condi-tions, from dry to wet. In drier regional climatessuch as the CDFmm, CWHxm, and IDFww, lack ofsoil moisture confines western yew almost entirelyto relatively moist or wet sites.

In general, western yew does not occur on poorlydrained soils (Alaback and Juday ), and on poorlydrained Pl−Sphagnum or CwSs−Skunk cabbage sites,western yew is restricted to elevated microsites.

Western yew shows no significant increase inabundance on riparian sites at low to moderateelevations, especially in wetter regional climates.However, at higher elevations western yew appearsto be restricted to riparian areas or swampy depres-sions, and is often associated with yellow-cedar(Chamaecyparis nootkatensis) on the coast.

Despite a tendency to occur more frequently inriparian areas in dry regional climates, western yewis generally restricted to high bench positions onfloodplain sites. It is mostly absent on the morefrequently flooding medium and low bench sites.Mature western yew trees appear to tolerate theperiodic flooding on high bench sites. Western yewrarely occurs on sites with strongly fluctuatingwater tables (e.g., Cw−Swordfern, Cw−Indianplum).

Western yew is not usually found on ocean spraysites of the CWHvh and CWHwh. These sites occuralong the outer coast of Vancouver Island, the cen-tral mainland, and the Queen Charlotte Islands,and are dominated by Sitka spruce. Western yew isabsent from exposed rocky headlands, old beachplains, and marine terraces/scarps.

. Determinants of Western Yew Occurrence

Regional climate significantly influences the occur-rence of western yew in British Columbia (Appen-dix ). In the interior wet belt and on the coast,temperature defines the northern limit of the spe-cies, and a combination of insufficient moistureand high summer temperatures limit the extensionof western yew into the southern interior of BritishColumbia.

Western yew grows on a wide variety of site typesin seral and climax forests, but it occurs sporad-ically. While site factors such as soil moisture and

nutrient regimes have some effect on its distribu-tion within a regional climate, these factors do notappear to be the primary determinants of westernyew occurrence. Although western yew is morefrequent in some s i te associat ions (e .g . ,CwSs−Skunk cabbage, FdBg−Oregon-grape, andCwHw−Falsebox−Feathermoss), it still occurs inless than % of plots sampled on most of thesesites. Combinations of episodic wildfire or diseaseevents, poor seed crops and pollen or seed dis-persal, ungulate browsing, and competition withother species may have a greater effect on westernyew occurrence than ecological site factors.

In a forest history study conducted at MarionLake in southwestern British Columbia, Wainmanand Mathewes () suggested that western yewmay have been a larger component of forests beforethe arrival of western redcedar − years ago.

. Growth, Development and Reproduction

.. GrowthWestern yew occurs as both an upright tree and ashrub in British Columbia. The tree form is mostprevalent on the coast while the shrub form isfound most extensively in the interior (especiallyon steep slopes), as second growth in clearcuts, andon talus slopes. Taylor and Taylor () found thatthe shrub form is also prevalent on ecologicallymarginal sites.

Western yew trees are small compared to theircommon associates. Mature western yew treesmeaured on the coast average . m in height and. cm in diameter (at breast height). Table 1summarizes average western yew height by diame-ter class. The largest western yew trees measuredreach heights of − m and diameters (at breastheight) of − cm.

TABLE Average western yew tree height by diameterclass for coastal plots

Diameter class (cm)a Average height (m)

0−9 3.210−19 7.020−29 10.430−39 12.440−49 14.250 + 18 +

a Diameters were measured at breast height.

Large western yew trees occur most frequently onthe coast (Figure ). In the interior, the largest treesare found in the southern ICH zone and decrease insize, tending toward shrub form, further north. Lessprecipitation, and greater frequency and extent ofnatural fire disturbance in the interior compared tothe coast, may account for the observed differencesin size distributions... PhenologyWestern yew is dioecious (i.e., male and female repro-ductive structures occur on different trees). Mono-ecious trees can occur but they are rare. Male treesproduce small stalked pollen cones in clusters of six totwelve on the terminal underside of branchlets. Conesmature in April or May and the pollen is wind-dispersed. The female flower is also borne on theterminal underside of branchlets. In its earliest stagesit resembles a vegetative bud, but is easily distin-guished by an opening at the tip of the pointed,exposed ovule (Chadwick and Keen ). A greenfruit produced in the summer matures to a red aril inearly fall. The presence of female fruit in varyingstages of development suggests multiple pollinationevents or the absence of pollination in some cases.

Sex ratios of : reported by the U.S. Forest Ser-vice (U.S. Dep. Agric. ) were not substantiatedby ecological research conducted in British Colum-bia. The sex of many trees could not be determinedin the field because of the rarity or lack of repro-ductive structures... Seed production and dispersalIt is not known when western yew first begins to

produce seed but trees less than m tall and . cmin diameter rarely produce reproductive parts.Once mature, western yew produces some seedevery year and large seed crops at irregular intervals(Taylor and Taylor ). It is a prolific seed pro-ducer in open canopies. Small mammals and birdsgenerally disperse the seed... Seed viability and germinationWestern yew seed germinates slowly, usually notuntil the second year (Rudolf ; Bolsinger andJarmillo ). There is some indication that seedremains dormant for about three years (G.Edwards, Natural Resources Canada, pers. comm.,). Western yew seed is more difficult to germi-nate than the seed of its commonly associated con-ifers (e.g., Douglas-fir, western redcedar) (Rudolf; U.S. Dep. Agric. ). Cold stratification isnecessary to break seed dormancy. Exposure to sixmonths of °C day and °C night temperatures,followed by °C temperatures for six months wassuccessful at breaking seed dormancy (U.S. Dep.Agric. ).

While Rudolf () indicates that seed germina-tion does not require light, seedlings are more com-mon in open areas such as forest canopy gaps,clearcuts and roadcuts. Seedlings in densely shadedmature and old-growth forests are comparativelyrare. Increased soil radiation in open areas maycontribute to the breaking of seed dormancy. Seedgermination occurs mostly on organic soils but alsoon decaying wood and mineral soil (Crawford ;Bolsinger and Jarmillo ).

FIGURE Typical size distributions of western yew in 400 m2 plots surveyed on the coast and in the interior.Diameter classes (cm) are: 1 = 0−9, 2 = 10−19, 3 = 20−29, 4 = 30−39, 5 = 40−49, 6= 50+.

7


.. Vegetative reproductionWestern yew is capable of vegetative reproductionby layering and by the sprouting of stumps or liverootstocks. Vegetative reproduction is particularlyevident on clearcut sites and on steep slopes, espe-cially in the interior.

On unburned clearcut sites, western yew regener-ates well from live rootstocks. Stump sproutingdoes not appear to be as successful. When exposedto direct sunlight, stumps are prone to desiccationand therefore sprout best in partial shade. Stumpsprouts may be extensively browsed by ungulates.

Layering occurs when branches root after beingpressed to the ground for a prolonged period.Snowpress likely contributes to the extensive layer-ing observed on steeper slopes in the interior.

Using standard rooting practices, western yewmay be propagated vegetatively in a greenhousefrom cuttings. Genetic factors, as well as the healthand age of the parent tree appear to be importantinfluences on rooting ability. Rooting success in agreenhouse is variable, ranging from % to %,but is enhanced by partial shading of cuttings(J. Russell, B.C. Min. For., pers. comm., ).

. Response to Disturbance

.. Forest canopy removalWestern yew is able to grow in both open andshaded areas. Trees growing in the open have fullercrowns and produce more flowers and fruit thantrees growing in shaded forests. Canopy removalresults in extensive foliage production with exten-sive sprouting along branches and the tree trunk.Changes in shoot morphology and needle colourwith canopy removal suggest an ability of westernyew to acclimatize to increased light intensities(A. Mitchell, Natural Resources Can., pers. comm.,)... FireWestern yew is sensitive or intolerant to firebecause of its thin bark (Taylor and Taylor 1981;Crawford ). It is therefore associated with areashaving a low incidence of fire disturbance. Westernyew increased in frequency with decreasing inci-dence of wildfire in Washington and Oregon (Scherand Jimerson ).

In Idaho, a % mortality rate occurred in areasof low to moderately severe broadcast burns. Treessurvived burns only when insulated from radiant

heat (Crawford ). A study of post-logging forestsuccession in Oregon indicated that western yewregenerated most rapidly to pre-logging levels onunburned sites (U.S. Dep. Agric. ). In areaswhere western yew survived broadcast burns, thepresence of unburned slash and duff immediatelysurrounding the trees indicated low fire intensity orthe absence of fire. However, depending on the siteconditions, fire is not always fatal to western yew(Betlejewski ). Trees can survive on northaspects and near roads where heat from a burn isleast (U.S. Dep. Agric. ). The shrub form ofwestern yew seems to be particularly susceptible tofire (Stickney ).

On burned clearcuts in British Columbia, regen-eration occurs primarily through seed germination,whereas on unburned clearcuts, western yew regen-erates by a combination of stump and live rootstocksprouting and seed germination... Soil disturbanceLittle is known of the effects of soil disturbance onwestern yew. It returned to pre-logging levels mostrapidly, however, in the absence of soil disturbance(i.e., site preparation) in the H.J. Andrews Experi-mental Forest in Oregon (U.S. Dep. Agric. )... PestsDisease and insect pests of western yew havereceived little study. Until recently, this species wasconsidered essentially pest-free. Several potentialinsect pests and disease-causing organisms associ-ated with western yew in Canada and the UnitedStates are listed in Appendix .

. Wildlife Interactions

Western yew plays several important roles in eco-system functioning, one being its interaction withwildlife. In coastal forests and in the ColumbiaRiver drainage near Revelstoke, it is important for-age for black-tailed deer, elk, moose and caribou(Simpson et al. ; Nyberg and Janz [editors]). In areas of north-central Idaho, where itforms a sub-canopy beneath a mixed coniferousforest, western yew is the chief food of deer andmoose during the winter when deep snow pre-cludes the use of open areas (Pierce ; Peek et al.; Simpson et al. ).

Where forest management practices favourungulate habitat, over-browsing severely reduceswestern yew abundance (Crawford ); browsing


removes the reproductive parts on terminalbranchlets. Studies of Canadian yew (Taxus cana-densis) in eastern Canada indicate a decrease inpollen and seed production associated with ungu-late browsing (Allison ).

Several bird species such as thrasher, blackbirds,waxwings, and nuthatches, as well as many smallmammals feed on western yew fruit (Scher andSchwarzschild ). Birds presumably aid in long-distance seed dispersal since the seed remains viableafter passing through their digestive tracts (Bol-singer and Jarmillo ). Passed seed or seedcached by rodents and some birds (e.g., nut-hatches) probably account for the clusters of west-ern yew seedlings that are occasionally observed(Crawford ).

In northern California, sub-canopies of westernyew in riparian areas provide shade to maintain thecool temperatures required by salmonids and severalother anadromous fish (Scher and Schwarzschild).

. Genetics

.. Genetic variability of western yewA study of genetic variation in western yew revealedlow within-region genetic diversity relative to othertemperate conifers (El-Kassaby and Yanchuk ).Significant genetic differences, however, were foundbetween regions of the interior, Queen CharlotteIslands, and Vancouver Island. Western yew in theinterior exhibited the lowest levels of genetic diver-sity. Western yew on eastern Vancouver Island wassufficiently different from the rest of the speciesrange sampled to be considered genetically distinct.This area is an ecologically unique area of BritishColumbia because of its typically dry coastal envi-ronment. The results of this study suggest that mostof the genetic variation observed in western yewwill be preserved by maintaining representativepopulations throughout its natural range.

The capture of genetic variation is importantbecause it permits adaptation to long-term envi-ronmental changes and resistance to future chal-lenges by pests and pathogens (Ledig , ). Ifwestern yew is well represented throughout its nat-ural range, limited harvest should not adverselyaffect the genetic diversity of this species... Maintenance of genetic diversityGenetic conservation practices are classified as in

situ and ex situ. The B.C. Ministry of Forests isinvolved in both types of conservation programs.In situ conservation In situ gene conservationpreserves, via protected areas, trees (and theirgenes) in their natural habitat. Western yew wasincluded in a preliminary survey that estimated thelevel of protection for several conifers in BritishColumbia.6

Western yew appears adequately represented inprotected areas throughout its natural range withthe exception of populations occurring in the CWHzone on the mid-coast, and populations in the CDFzone. Peripheral and outlier populations may alsorequire further protection. More data, however, arerequired to confirm these findings.Ex situ conservation Ex situ gene conservationmakes use of botanical gardens, test plantations,seed storage banks, seed orchards, DNA libraries,tissue culture, and clone banks to preserve geneticvariation (Ledig ). In British Columbia, ex situgene conservation includes the preservation ofwestern yew genotypes in clone banks. From systematically selected stands, representing biogeo-climatic zones and latitudinal gradients, cuttingswere collected from − randomly selected westernyew trees per stand. These cuttings are now rootingat the B.C. Ministry of Forests Cowichan LakeResearch Station on Vancouver Island. The rootedcuttings will be incorporated into clone banks.

This collection, combined with the western yewpreserved in protected areas, will ensure that a largepercentage of the genetic variation of this specieswill be captured (A. Yanchuk, B.C. Min. For., pers.comm., ).

. Taxol Content and Site Type

On any given site, taxol concentrations in westernyew trees are variable (Wheeler et al. ). Despitethis variability, data from a small sample of westernyew show that bark collected from trees on moistsites contains greater concentrations of taxol onaverage than bark from dry sites (Figure ). There islittle difference in the taxol content in needles fromdifferent site types. Genetic and environmentalstudies in the United States also indicate significantdifferences in taxol content by ecological groupings(Wheeler et al. ). Trees from cool, moist siteshad more taxol on average than those from dry,warm sites.

Lester, D.E., E. Campbell, and A. Yanchuk. . A gene conservation strategy for B.C. conifers. Part I. A survey of protected areas forthe maintenance of genetic resources of conifers in British Columbia with recommendations. B.C. Min. For., Res. Br., Victoria, B.C.Unpubl. draft rep.

FIGURE Mean taxol content of western yew bark and foliage by site type. Samples were collected in British Columbia.

4 R E C O M M E N D A T I O N S F O R W E S T E R N Y E W M A N A G E M E N T

Western yew is not a threatened or endangeredspecies in British Columbia. Like any other forestresource, however, it must be managed to ensurethat sustainable populations are maintainedthroughout its natural range. Although conserva-tion and management issues are generallyaddressed in regional and provincial guide-books,, supporting the regulations of the ForestPractices Code, this handbook supplements thoseguidebooks by providing recommendations specificto western yew management.

The following sections provide recommenda-tions for western yew management in BritishColumbia, based on the biological information cur-rently available. The recommendations reflect theinterim management guidelines developed by theU.S. Forest Service (U.S. Dep. Agric. ), but havebeen modified to incorporate special considera-tions of western yew occurrence in British Colum-bia, new biological information, and forest

management in this province.These recommendations apply to all provincial

forests at the stand and landscape levels. Theyshould be flexible and adaptive and should formpart of an integrated approach to resource manage-ment. Changes to these recommendations willlikely occur as more biological and managementinformation becomes available.

. Management Objectives

The management objectives for western yew are:. To maintain ecologically and genetically diverse

populations of western yew throughout its natu-ral range;

. To describe a method of western yew harvestthat will preserve the biological diversity, integ-rity, and function of ecosystems where westernyew occurs; and

. To provide a sustainable short-term source ofbark and needles for taxol extraction.

B.C. Ministry of Forests. []. Biodiversity guidebook. B.C. Min. For., Victoria, B.C. In prep. . []. Riparian management areas guidebook. B.C. Min. For., Victoria, B.C. In prep. . []. Managing identified wildlife guidebook. B.C. Min. For., Victoria, B.C. In prep.

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. Pr inciples and Assumpt ions for theRecommendations

The impact of harvesting western yew is not fullyunderstood. The management recommendationstherefore rest on the following principles andassumptions:• Maintenance of a broad geographic distribution

of western yew ecosystems will sustain its geneticdiversity.

• Current information on distribution and abun-dance supports the assumption that some level ofwestern yew harvest is possible.

• Retention of % of western yew on partial har-vest sites will provide a sufficient seed source forfuture regeneration and connectivity betweenpopulations.

• Sex ratios do not significantly differ from : forboth the tree and shrub form.

• Western yew is sensitive to fire, and prescribedburning on clearcuts will significantly decrease thepotential for regeneration to pre-harvest levels.

. Management Recommendations

The following sections provide recommendationsfor landscape and stand-level management of west-ern yew. Sections .., .., and .. provide rec-ommendations for whole-tree (or shrub) harvest,and Section .. provides recommendations forharvesting western yew needles... Management of western yew in landscapesRECOMMENDATION :Ecosystems where western yew occurs should be repre-sented and maintained in landscapes. To maintainwestern yew viability, populations should be suffi-ciently dispersed or connected in the landscape.

For planning purposes, a landscape is generallydefined as a watershed or a series of interactingwatersheds up to ha in size.

A draft guidebook by the B.C. Ministries of For-ests () provides recommendations for main-taining biological diversity in landscapes and pro-poses the use of Forest Ecosystem Networks (FENs).Establishment of FENs will be part of a long-termmanagement approach to retain a network of repre-sentative ecosystems in managed landscapes. A FENmay consist of a variety of areas subject to timberharvesting constraints, including

existing protected areas (e.g., ecological reserves, wil-derness areas, and parks), sensitive areas (e.g., rip-arian areas, wildlife areas, and areas of unstableterrain) and Old-Growth Management Areas. Sincethe components of a FEN will remain relativelyundisturbed and will be designed to interconnectwith one another as much as possible, they will be auseful mechanism to achieve landscape-level man-agement goals for western yew.RECOMMENDATION :Western yew should not be harvested in special eco-systems, including the high-elevation ecosystems ofMountain Hemlock, Montane Spruce, andEngelmann Spruce−Subalpine Fir; dry sites inregional climates like the Interior Douglas-fir(IDFmw and ww); the Coastal Western Hemlock(CWHxm); and the Interior Cedar−Hemlock(ICHxw) biogeoclimatic zones.

Special ecosystems could include those exhibit-ing unusual geological, soil, vegetative, and climaticcharacteristics. For western yew, examples includesoils derived from calcareous and serpentine parentmaterials; populations found at elevations greaterthan m on the coast and m in the interior;and those on extremely dry sites.RECOMMENDATION :Western yew should not be harvested in outlierpopulations.

Small populations, disjunct from the main distri-bution of western yew, may be sufficiently isolatedto be identified as outliers. Populations in uniqueecological environments, as well as outlier popula-tions, possess the potential for the evolution of newand unique genotypes... The link between landscape and stand-levelmanagementA stand is an area of forested land which is rela-tively uniform in species composition, structure,age, arrangement, and site quality. While standssubject to timber harvesting constraints (e.g., thoseareas that may be FEN components) can be impor-tant for maintaining western yew populationsacross the landscape, more intensively managedstands in which silvicultural activities maintainstructural diversity, (generally the forested areasoutside FENs), can also, in aggregate, contributesignificantly to the goal of maintaining biologicallydiverse western yew ecosystems in a landscape.

Follows the recommendations put forth by the U.S. Dep. Agric. . Further research is required to determine if this level ofretention is satisfactory.

B.C. Ministry of Forests. []. Biodiversity guidebook. B.C. Min. For., Victoria, B.C. In prep.


.. Management of western yew in standsStand-level management focuses on the mainte-nance of stand attributes, and requires that particu-lar attention be given to the method and extent ofwestern yew harvest in stands.

General recommendationsRECOMMENDATION :Where inventory information is not available, itshould be obtained before harvesting occurs.

This information will allow for an evaluation ofthe effects of harvesting, site preparation, andstand-tending on future western yew populations.Some forest districts are already collecting inventorydata on western yew in their regular timber cruises.RECOMMENDATION :Western yew trees should be cut so that stumps are at least cm above ground level, with bark and cambium intact.

Stumps higher than cm provide more dor-mant sprout buds than shorter stumps (U.S. Dep.Agric. ). Damage to bark and cambium mayreduce the stump’s ability to resprout.RECOMMENDATION :Bark should be peeled from all harvested trees includ-ing branches with end diameters greater than . cm.

At present, the wood remaining after bark har-vest may be left as logging slash. If there is increasedinterest in using western yew wood in the future,however, this recommendation may require someadjustment.RECOMMENDATION :Alternatives to broadcast burning (e.g., spot burning,pile and burn, no burn) should be considered for siteswhere western yew grows. If burning is deemed essen-tial, and % of western yew trees or stumps cannotbe saved, then western yew in adjacent areas shouldnot be harvested.

Western yew bark is thin and is not fire-resistant.The use of prescribed fire to remove organic mate-rials from a site often kills stumps and rootstocks,reducing the rate of western yew regeneration.RECOMMENDATION :The success of western yew regeneration should beevaluated in regeneration surveys.

Protection of some western yew seedlings andsprouting stumps may be required in areas of heavyungulate browsing.

Areas subject to timber harvesting constraintsRECOMMENDATION :Western yew may be harvested in some areas subject

to timber harvesting constraints (e.g., riparian areas,wildlife areas, Environmentally Sensitive Areas, andOld-Growth Management Areas), but the extent andmethod of harvest should support the managementobjectives for these areas.a) In riparian areas, harvesting should incorporate

regulations and standards of the Forest PracticesCode and the recommendations presented in rip-arian management area and biodiversity guide-books. Western yew should not be harvested in the‘reserve zone’ of riparian management areas (For-est Practices regulations). In the ‘managementzone,’ when harvest is deemed ecologically suitable,not more than % of western yew in each diame-ter class (-, -, + cm) should be harvested.

Western yew is frequently restricted to streamedges especially in drier climates and higher ele-vation sites. The extensive root system of westernyew may provide for stream bank stability (Scherand Schwarzschild ). On Class A and Bstreams it may provide shading to stream fish.

The proposed Forest Practices regulations dic-tate that riparian management areas be estab-lished along all streams, lakes, and wetlands.Riparian management areas will comprise areserve zone (in which no harvesting is permit-ted) and a management zone (permitting har-vest, where ecologically suitable, by selection sil-viculture systems). The minimum size of reserveand management zones will depend on the sizeof the stream and/or water body.

b) In wildlife areas, western yew should be harvestedonly if removal would not have adverse effects onexisting wildlife populations. Wildlife biologistsshould be consulted to assess this risk. Western yewshould not be harvested in juvenile or maturestands where there is evidence that it is beingextensively utilized by wildlife.

Western yew in early seral and juvenile sec-ond-growth stands are a preferred food source,particularly for deer in summer. In the winter,western yew, in mature forests, is an importantsource of food when winter snow depths pre-clude access to open areas (Pierce ; Peek etal. ; Simpson et al. ).

c) In Environmentally Sensitive Areas (ESAs), west-ern yew harvesting could be considered, but thelevel of harvest should not exceed the netdownspecifications for that ESA.


In addition to their timber values, ESAs areareas that have high value for other resourceslike water, wildlife, fisheries, recreation, etc. Thecontribution of ESAs to timber harvest is lim-ited. Appendix 7 provides a summary of ESAsand their respective netdown limitations.

d) In Old-Growth Management Areas (OGMAs),western yew should not be harvested.

The biodiversity guidebook recommends theestablishment of Old Growth ManagementAreas (OGMAs) if the target old-growth objec-tives cannot be achieved within existing pro-tected areas or Sensitive Areas. OGMAs areintended to assist in the preservation of a rangeof ecosystems in mature and old-growthconditions.

Areas subject to more intensive forest managementRECOMMENDATION :In more intensively managed forests, western yewshould be harvested only in areas approved for log-ging operations (i.e., forested Crown Land with anapproved silviculture prescription and cutting permitin place) unless it would otherwise be destroyed (e.g.,road or landing construction). The method andextent of western yew harvest will depend on thesilvicultural system used for logging operations.

While the areas described in Recommendation are subject to timber harvesting constraints andmay form the components of FENs, the managedforest outside FENs may be subject to more inten-sive forest management.

Two classes of silvicultural systems direct themethod by which timber is harvested in BritishColumbia: even-aged (e.g., clearcut, shelterwood,and seed-tree silvicultural systems) and uneven-aged systems (e.g., selection systems) (Matthews; B.C. Ministry of Forests ).

Even-aged silvicultural systems may retainpatches of green trees (group reserves), or scatteredgreen trees (individual tree reserves), or both,throughout the rotation of a cutblock for theirbiodiversity value or to mimic natural disturbance.Group reserves may also be left in areas that poseproblems for harvesting, yarding, or regeneration(i.e., near gullies or rock outcrops).

Under uneven-aged silvicultural systems, matureand immature trees are harvested singly (i.e., par-tial cut or individual tree selection) or in groups(i.e., group selection).

Recommendations , , and address levels of

western yew harvest in areas scheduled to be loggedusing even-aged and uneven-aged silvicultural systems.Western yew may be removed before full-scale loggingoperations or may be salvaged following logging.RECOMMENDATION :In stands subject to even-aged management (e.g.,clearcutting, shelterwood silvicultural systems):a) Scattered, healthy western yew, of various sizes,

should be left as individual tree reserves in acutblock, and group reserves should contain awestern yew component. These trees will contrib-ute to the vertical diversity of future stands andwill also act as seed sources.

b) Western yew trees along a cutblock boundaryshould not be harvested. In addition to any west-ern yew retained within the cutblock, the treeson the cutblock edges will provide a seed sourcefor regeneration.

c) If stump sprouting is to be an important method ofregeneration on these sites, individual tree reserves(of any species) should be left to provide partialshading for western yew stumps. Western yewstumps sprout readily in selectively logged for-ests with moderate amounts of shading. Stumpssubjected to direct sunlight are prone to desicca-tion. Alternative methods of stump shadingshould be investigated.

RECOMMENDATION :In stands subject to uneven-aged management, usingindividual tree selection silvicultural systems:a) On sites where western yew occurs as a tree, no

more than % of each diameter class should beharvested. Areas should not be re-entered for addi-tional harvest until pre-harvest levels of westernyew are attained. This step will help to maintainwestern yew as an important structural compo-nent in these stands.

b) On sites where western yew occurs as a shrub (e.g.,young stands, talus slopes, and matures forests),no more than % of shrubs, with basal diametersgreater than . cm, should be harvested. Theremaining shrubs should mimic the original dis-tribution patterns in the harvest area, and shouldbe retained undamaged. Areas should not be re-entered for additional harvest until pre-harvestlevels of western yew are attained.

RECOMMENDATION :In stands subject to uneven-aged management, usinggroup selection silvicultural systems:a) Western yew should be harvested only from group

selection openings.


b) Some healthy western yew of various sizes shouldbe left as individual tree (or shrub) reserves ingroup selection openings.

c) Western yew should not be harvested from patchesof undisturbed forest remaining in the cutblock.

d) Except for individual tree (or shrub) reserves, barkmay be harvested from all usable western yew ingroup selection openings.

e) Individual tree reserves, of any species, should beleft in group selection openings to provide partialshading for resprouting western yew stumps.

RECOMMENDATION :If western yew is to be harvested in young stands, itshould be harvested essentially as a thinning opera-tion before treatments such as spacing, pruning, orbrushing occur. Some unburned, to -year-oldclearcut sites support extensive populations of theshrub form of western yew. Most of the westernyew on these sites regenerate vegetatively, primarilyby rootstock sprouting.a) Recommendations for maintaining biodiversity

during juvenile spacing should be followed. Areport providing guidelines to maintain bio-diversity during juvenile spacing (B.C. Ministryof Environment ) and the biodiversityguidebook should be consulted before westernyew is harvested in young stands.

b) Where western yew occurs in young stands, therecommended harvest levels for the shrub formapply (see Recommendation 12b).

c) Western yew should not be harvested from wildlifescreens (e.g., roadside buffers). It is often an inte-gral component of the screen and conceals wild-life from view.

.. Needle harvestAt present, western yew foliage is not extensivelyharvested in wild stands. Taxol extraction from

needles now focuses on harvesting needles fromdomestically cultivated English yew (Taxus bac-cata). Needles harvested from wild stands are notexpected to be a major source of taxol.

Where harvest of needles from trees and shrubsin the wild is practical, it may be appropriate toharvest needles in some areas where no or limitedwhole-tree (or shrub) harvest of western yewoccurs (e.g., sensitive areas, Old-Growth Manage-ment Areas, managed forests outside FENs that arenot approved for logging).RECOMMENDATION :In some areas where whole-tree (or shrub) harvest islimited, western yew needles may be harvested.a) Needles should be harvested from only % of

western yew trees by diameter class (−, −,+ cm) and from an equal number of male andfemale trees.

b) No more than % of foliage should be harvestedfrom any one tree (or shrub), evenly distributedthroughout the crown to preserve some sexualbuds on the new growth. Large main branchesshould not be cut.

c) Where browsing by ungulates is evident, foliageshould be retained up to m above the ground.

d) In areas where the shrub form predominates, nomore than % western yew crown cover, evenlydistributed throughout the stand, should be har-vested. The remaining % crown cover should beleft as undamaged shrubs.

e) Harvested areas should be re-entered only aftertotal foliage recovery, and the same trees (orshrubs) should be harvested at each re-entry.Repeated foliage harvest may reduce sexual repro-duction and natural regeneration. (Allison ,U.S. Dep. Agric. ). The unharvested treesremaining should provide sufficient seed source.


5 C O N C L U D I N G R E M A R K S

These recommendations are geared to both provid-ing bark (or needles) for taxol extraction and pre-serving the biological diversity of western yew andthe ecosystems in which it occurs. However, morebiological information is required to improve themanagement of western yew. Some specific areasthat require further research include:

• western yew population and stand dynamics(e.g., studies of seedling recruitment and sur-vivorship, growth and reproductive rates, andthe factors that affect these rates);

• the impacts of harvesting on western yew pop-ulations and ecosystems;

• the effects of natural disturbance (e.g., fire orpests) on western yew populations;

• various aspects of reproductive biology (e.g.,seed germination requirements, reproductivestrategies, growth, and development);

• general physiology, including studies of thenutritive requirements of western yew; and

• the distribution and abundance of westernyew in seral ecosystems.

While the recommendations presented in this report arelikely to change as new biological information becomesavailable, they provide an initial framework for develop-ing more comprehensive management guidelines.

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A P P E N D I X 1 Sample Letter of Authorizationa

Letter of Authorization−Western Yew

Date:

To whom it may concern:

As a designated agent of(licencee name)

I hereby authorize(name of person and address)

representing

(self or company name and address)

to harvest western yew(bark, wood, or bark and wood)

from the following areas which are currently approved by the Ministry of Forests for harvesting operations:

Tenure (Licence No.) Cutting Permit No. Cutblock No.

This authorization is only valid for the above noted areas. Operations on any other areas are illegal and mayresult in charges being assessed. All harvesting is subject to the requirements of the Forest Act and all of theconditions of the above-noted tenures. All shipments must be accompanied by a Shipping Notice which willserve the same purpose as load destination notices for minor forest products.

This authorization is valid for the following (time) period: , is not transfer-able, and may be revoked at any time. Unauthorized operations may result in charges being assessed by theMinistry of Forests.

Signed:(name)

(position)

(company)

a Extracted from the Ministry Policy Manual: Resource Management (B.C. Ministry of Forests 1993).


A P P E N D I X 2 Sample Shipping Noticea

Shipping Notice−Western Yew

This form is to be carried with the shipment and must be left with the buyer at destination as a permanentrecord.

Date of Shipment

Delivered from(Forest District) (Forest Region)

Producer(Name and Address)

Authorized by(Licencee) (Company Name[s])

(Name of Company Representative)b

(Signature of Company Representative)

Locale(s) of origin (Licence No.Cutting Permit No. Approximate weight ofCutblock No.) List No. of trees harvested bark (wet) −kg

Weight of bark (kg) Dry weight(according to payment)

Wet weight

Delivered to(Buyer’s, or Collector’s name)

Location

(Address)

a Extracted from the Ministry Policy Manual: Resource Management (B.C. Ministry of Forests ).b Company representative to retain a copy of this completed shipping notice.


A P P E N D I X 3 Sample Western Yew Bark Register

Western Yew Bark Registera

For:

(Collector’s Name, Address and Signature)

Collector’s or buyer’s record of purchases for the calendar year ended December 31, 19 .

Source (location) of Names and addresses

Weight of bark bark harvest (Licence of person issuing

Names and addresses purchased No., Cutting Permit Authorization to

Date of purchase of sellers (kg wet or dry) No., Cutblock No.) Harvest

a Extracted from the Ministry Policy Manual: Resource Management (B.C. Ministry of Forests ).Note: A photocopy of this record shall be submitted yearly by the wholesaler or buyer to the Regional Manager as an annual report.

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A P P E N D I X 4 Biogeoclimatic occurrence of western yew in British Columbia

TABLE A Western yew occurrence in coastal biogeoclimatic units

Biogeoclimatic zonea No. of plots reviewed Prevalenceb (%) Average crown cover (%)

Coastal Douglas-fir:CDFmm 396 19 3.8

Coastal Western Hemlock:CWHxm1 159 3 3.2CWHxm2 389 4 3.1CWHdm 306 12 1.0CWHds1 40 25 5.4CWHds2 23 0 0.0CWHmm1 98 10 2.4CWHmm2 45 0 0.0CWHms1 38 21 1.4CWHms2 112 7 3.7CWHwh1 197 20 2.0CWHwh2 79 9 0.8CWHwm 71 0 0.0CWHws1 92 0 0.0CWHws2 160 0 0.0CWHvh1 294 11 2.7CWHvh2 419 16 1.0CWHvm1 749 12 2.4CWHvm2 191 8 1.6

Mountain Hemlock:MHmm1 140 <1 2.0MHmm2 81 0 0.0MHwh1 18 <1 2.0MHwh2 19 5 0.2

a The lower-case alphabetic symbols used for subzones designate precipitation (x - very dry, d - dry,m - moist, w - wet, v - very wet) and continentality (h - hypermarine, m - maritime, s - submaritime).

b Percentage of plots reviewed that contained yew.


A P P E N D I X 4 (Continued)

TABLE A Western yew occurrence in interior biogeoclimatic units


Interior Douglas-fir:IDFxh1 137 0 0.0IDFxh2 91 0 0.0IDFxw 29 0 0.0IDFxm 39 0 0.0IDFdm1 89 0 0.0IDFdm2 34 0 0.0IDFdk1 118 0 0.0IDFdk2 130 0 0.0IDFdk3 45 0 0.0IDFdk4 33 0 0.0IDFmw1 74 4 3.2IDFmw2 78 3 0.8IDFww 84 1 1.0

Interior Cedar−Hemlock:ICHxw 6 17 2.0ICHdw 71 30 4.7ICHdk 34 0 0.0ICHmw1 37 24 7.5ICHmw2 206 41 4.7ICHmw3 88 19 5.0ICHmm 53 9 0.7ICHmk1 92 6 2.2ICHmk2 42 0 0.0ICHmk3 35 12 1.8ICHmc1 63 0 0.0ICHmc1a 15 0 0.0ICHmc2 175 0 0.0ICHwk1 158 36 2.1ICHwk2 67 40 4.2ICHwk3 56 0 0.0ICHwk4 51 0 0.0ICHvk1 71 41 1.8ICHvk2 64 0 0.0ICHvc1 16 0 0.0ICHvc2 8 0 0.0

Montane Spruce:MSxv 183 0 0.0MSdm1 172 0 0.0MSdm2 104 0 0.0MSdk 129 <1 1.5MSdc 50 0 0.0

Engelmann Spruce−Subalpine Fir:ESSFxc 66 0 0.0ESSFxv 2 0 0.0ESSFdk 59 0 0.0ESSFdc1 79 0 0.0


A P P E N D I X 4 (Concluded)

TABLE A (Continued)


ESSFdc2 45 0 0.0ESSFdv 70 0 0.0ESSFmw 40 <1 1.5ESSFmm 43 0 0.0ESSFmk 25 0 0.0ESSFmc 54 0 0.0ESSFmv1 30 0 0.0ESSFmv2 45 0 0.0ESSFmv3 109 0 0.0ESSFmv4 43 0 0.0ESSFwm 16 0 0.0ESSFwk1 97 0 0.0ESSFwk2 39 0 0.0ESSFwc1 16 0 0.0ESSFwc2 83 0 0.0ESSFwc3 41 0 0.0ESSFwc4 74 0 0.0ESSFwv 74 0 0.0ESSFvc 62 0 0.0ESSFvv 26 0 0.0

a The lower-case alphabetic symbols used for subzones designate precipitation (x - very dry, d - dry,m - moist, w - wet, v - very wet) and temperature (h - hot, w - warm, k - cool, c - cold, v - very cold).

b Percentage of plots reviewed that contained yew.


A P P E N D I X 5 List of site associations where western yew is founda

Amabilis fir forests(CWH; occasionally in the ICH along thecoast transition)

BaCw−Devil’s clubBaCw−FoamflowerBaCw−Oak fernBaSs−Devil’s club

Coastal western redcedar forests(CWH, CDF)

Cw−Indian plumCw- Sword fernCw-Skunk cabbageCw−Slough sedgeCw−Solomon’s-sealCw−Lady fernCwHw−BlueberryCwSs−Skunk cabbageCwSs−SalalCwYc−GoldthreadCwYc−Salal

Coastal western hemlock forests(CWH)

Hw−Flat mossHwBa−BlueberryHwBa−Deer fernHwBa−Pipecleaner mossHwBa−Step mossHwCw−Deer fernHwCw−SalalHwFd−Cat’s-tail mossHwFd−Kindbergia

Interior western redcedar−western hemlock forests(ICH and IDF)

CwFd−Devil’s club−Lady fernCwFd−FalseboxCwHw−HorsetailCwFd−FeathermossCwHw−Oak fernCwHw−Oak fern−FoamflowerCwHw−Oak fern−Spiny wood fernCwHw−Devil’s club−Lady fernHwCw−Falsebox−FeathermossHwCw−Falsebox−Step mossHwCw−Spruce−Step mossCw−Foamflower

Mountain hemlock−amabilis fir forests(MH)

BaHm−Oak fern

Mountain hemlock−yellow-cedar forests(MH)

HmYc−Goldthread

Sitka spruce forests(CWH, infrequent in MH)

Ss−Lily-of-the-valleySs−Slough sedge

Interior Douglas-fir forests(mainly IDF but also ICH)

FdCw−HazelnutFdCw−Falsebox−Prince’s pineFd−Pinegrass−Feathermoss

Coastal Douglas-fir forests(CDF and CWH)

Fd−SalalFdBg−Oregon grapeFdHw−FalseboxFdHw−SalalFdPl−Arbutus

Interior western redcedar−spruce forests(mainly ICH, often IDF)

CwSxw−Devil’s club−HorsetailCwSxw−Falsebox−Knight’s plumeCwSxw−Skunk cabbage

Shore pine forests(CWH and CDF)

Pl−SphagnumPlYc−Sphagnum

a Tree species codes: Ba - amabilis fir, Bg - grand fir, Cw - western redcedar, Fd - Douglas-fir, Hm - Mountain hemlock, Hw - westernhemlock, Pl - lodgepole pine, Ss - Sitka spruce, Sxw - spruce hybrid, Yc - yellow cedar.

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A P P E N D I X 6 Diseases and insect pests of western yew

Diseases

Foliage diseases: Snow blights caused by Pha-cidium taxicola Dearn. and House, and Her-potrichia juniperi (Duby) Petr. result inlocalized damage to foliage buried undersnow for prolonged periods (Farr et al. ).Hepting () also cites snow blights causedby Neopeckia coulteri (Peck) Sacc.

Macrophoma taxi (Berk.) Berl. and Vog. andDothiora taxicola (Peck) Barr. (Farr et al.) are reported to cause needle blights onwestern yew in British Columbia (Taylor andTaylor ). Herpotrichia juniperi (Duby)Petr., Dothiora taxicola, Mycosphaerella taxi(Cooke) Lind, and Phyllosticta concentricaSacc., were identified in the United States(Hepting ; Farr et al. ).

Stem diseases: Twig blights are attributed to Phy-salospora gregaria Sacc. (Funk ) and Phy-llosticta concentrica (Farr et al. ).Diploidia taxi (Sowerby) De Not. is reportedto cause stem cankers (Hepting ).

Root Diseases: Armillaria ostoyae (Romag.) Her-ink causes root rot (U.S. Dep. Agric. ).Phaeolus schweinitzii (Fr.:Fr.) Pat. was docu-

mented to cause root rot in Idaho. Phy-tophthora lateralis, which causes root diseasein Port Orford-cedar in southwestern Oregonand northern California, was isolated andidentified in several dying western yew trees(U.S. Dep. Agric. ).

Insect pests

Mites: Cecidophyopsis psilaspis Nel., the westernyew big bud mite, attacks buds, producingdistinctive morphological changes in foliage(A. Mitchell, Natural Resources Canada, pers.comm.). To date, these mites have beenobserved in coastal samples but not in sam-ples collected from interior populations. Spi-der mites (Tetranychidae) are also reported inassociation with western yew in BritishColumbia (Taylor and Taylor ).

Weevils: Otiorhynchus singularis L., the clay col-oured weevil, causes shoot dieback (B. Dun-can, Natural Resources Canada, pers.comm.).

Moths: Argtrotaenia citrana Fern., the orangetortrix, damages buds (B. Duncan, NaturalResources Canada, pers. comm.).

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A P P E N D I X 7 Environmentally Sensitive Area (ESA) summarya

Environmentally sensitive areas are shown on forestcover maps and have been used for harvest plan-ning and timber supply review and Annual Allow-able Cut calculations. ESAs will, however, bereplaced with designated sensitive areas.

Soils - Es

Es1 Areas having extremely fragile or unstablesoils. Harvesting is likely to be severelylimited in these areas because it would leadto unacceptable site deterioration. Net-down is usually %.

Es2 Areas having significantly fragile or unsta-ble soils but less than those designated Es1.Harvesting is conditional. This designationis for ‘‘red flagging’’ areas for further fieldexamination. Netdown is usually %.

Forest regeneration - Ep

Ep1 Areas where climatic conditions causesevere forest regeneration problems, mak-ing them unavailable for sustained timberharvesting. Netdown is usually %.

Ep2 Areas where brush, wildlife, or cattle causesevere forest regeneration problems. Sus-tained harvesting of these areas requiresspecial management of these biotic factors.Netdown is usually %.

Snow Avalanche - Ea

Ea This category is intended to protect con-structed and natural resources from snowavalanches. Resources include roads, rail-ways, industrial and residential areas, recre-ational sites, and forest land of medium tohigh site quality. Netdown is usually %.

Recreation - Er

Er1 Areas having exceptionally high value forrecreation or viewing, where harvesting islikely to be severely limited. Netdown isusually %.

Er2 Areas having high value for recreation orviewing, but less than Er1. Forest harvest-ing is conditional in these areas. Netdownis usually %.

Wildlife - Ew

Ew1 Areas of critical importance to wildlife for

food, shelter, and reproduction. Includedare habitat areas for endangered andthreatened species; deer, elk, and moosewinter ranges; and other special wildlifeareas identified by the B.C. Ministry ofEnvironment, Lands and Parks. Netdownis usually %.

Ew2 Areas where a significant portion of thetimber is important to wildlife.Included are deer winter ranges in lowsnowfall areas; grizzly bear habitat; Rip-arian Management Zones; areas for ForestEcosystem Network linkages; and areasunder short-term deferral to protect nest-ing sites for eagles, ospreys, or herons, andunder temporary deferral (until furtherdata are available) for marbled murreletnesting corridors. Netdown is usually%.

Watershed-Eh

Eh1 Areas where timber harvesting would havelong-term adverse effects on water quality,quantity, or the seasonal distribution of itsconsumptive use. Netdown is usually atleast %.

Eh2 Areas that have high water values for con-sumptive use and are sensitive to timberharvesting (though less sensitive than Eh1areas). Harvesting in Eh2 areas is subjectto special management conditions. Net-down is usually %.

Fisheries - Ef

Ef1 Areas along streams that have fish spawn-ing and highly productive rearing areas.These areas or buffers are known asStreamside Management Zones and arehighly sensitive to timber harvesting.Included are m buffers around lakes andestuaries. Netdown is usually at least %.

Ef2 Areas containing braided stream channelsand floodplains that are suitable for spawn-ing and fish rearing. These areas are knownas Fisheries Sensitive Zones. They are notas sensitive to timber harvesting as Ef1areas. Netdown is usually %.

a Extracted from: B.C. Ministry of Forests. []. Biodiversity guidebook (draft version). B.C. Min. For., Victoria, B.C. In prep.

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A P P E N D I X 8 Glossarya

abundance: in this report, abundance is expressedas the % cover of a plot in a defined area (i.e., m), or the number of tree stems con-tained in a hectare.

anadromous: pertaining to fish that migrate fromsalt water to fresh water streams to spawn(e.g., salmon).

angiosperm: a flowering plant.

biogeoclimatic zone: a geographic unit with abroadly homogeneous macroclimate.

Class A stream: a stream or portion of a streamfrequented by anadromous salmonids and/orresident sport fish or regionally significantfish species (i.e., a species designated in aspecial management plan or identified as rareor endangered); or a stream that has beenidentified for fishery enhancement in anapproved fishery management plan. Streamgradient is usually less than %.

Class B stream: a stream or portion of a streamthat is populated by resident fish not cur-rently designated as sport fish or regionallysignificant fish. Stream gradient is usually−%.

clearcutting system: an even-aged silviculturalsystem in which all trees are removed from anarea of forested land in a single cut.

climax: the mature or stabilized stage of naturalforest succession in which communites areself-perpetuating and species compositionremains relatively constant over time; ecosys-tems arrive at climax through a process calledsuccession.

clone: any of two or more individuals with identi-cal genetic makeup, propagated from a singleancestor or parent.

clone bank: a place of storage for clones; in for-estry, generally refers to the collection andstorage of rooted cuttings, from any tree spe-cies, outside their natural habitat in green-houses or common gardens.

Crown land: a category of land ownership underwhich provincial legislation, regulation, andpolicy set the guidelines directing managementand administration. Approximately % of landin British Columbia is Crown land.

cutblock: a forested area of land designated fortimber harvesting.

cutting permit: a permit, authorized under theForest Act, that provides a licencee with theright to harvest trees in areas with anapproved management plan.

duff: the litter and decomposed organic mattermaking up the forest floor.

endangered species: any species threatened withimminent extinction or extirpation through-out all, or a significant portion of, its BritishColumbia range (see also extirpated, extinct,threatened, and vulnerable species).

Environmentally Sensitive Areas (ESAs): includepotentially fragile or unstable soils that maydeteriorate after forest harvesting, and areasof high value to non-timber resources such asfisheries, wildlife, water, and recreation.

even-aged management: forest management prac-tices that create stands of trees of the same ageor of the same age class. Includes clearcutting,shelterwood, and seed-tree silviculturalsystems.

ex situ: with reference to gene conservation of for-est trees, the preservation of genetic materialoutside its natural habitat (e.g., in botanicalgardens, test plantations, tissue cultures, orclone banks).

extinct species: a species formerly indigenous toBritish Columbia that no longer existsanywhere.

extirpated species: a species no longer existing inthe wild in British Columbia but occurringelsewhere.

floodplain: the level or nearly level land that bordersa stream or river and is subject to flooding.

a Some of the definitions in this glossary have been extracted from the following publications: B.C. Ministry of Forests ;Environment Canada ; B.C. Ministry of Forests []. Biodiversity guidebook. B.C. Min. For., Victoria, B.C. In prep.


A P P E N D I X 8 (Continued)

Forest Ecosystem Network (FEN): a plannedlandscape zone that serves to maintain orrestore the natural connectivity within a land-scape unit. A FEN consists of a variety of fullyprotected areas, Environmentally SensitiveAreas, and Old-Growth Management Areas.

forest licence: a forest tenure administered by theB.C. Ministry of Forests that grants thelicencee the right to harvest a specific volumeof timber each year. The licence may requirethat the licencee be responsible for regenera-tion and stand-tending activities.

genotype: the genetic constitution of an organism.

green tree retention: the maintenance of live treesretained after harvest for various biodiversityvalues (e.g., for wildlife or as a source ofcoarse woody debris).

group selection silvicultural system: a silviculturalsystem in which clumps of mature trees areharvested continuously over short periods oftime, resulting in an uneven-aged stand struc-ture. Group selection openings resemble smallclearcuts but are generally not larger than oneor two tree lengths wide.

individual tree selection silvicultural system: asilvicultural system in which scattered, singletrees of various diameter classes are harvestedcontinuously or over short intervals, resultingin an uneven-aged stand structure.

in situ: with reference to gene conservation of for-est trees, the preservation of genetic materialin its natural habitat (e.g., in protected areas).

juvenile spacing: the reduction of tree density inpre-commercial stands.

landscape: in this report, a watershed or a series ofinteracting watersheds up to 100000 ha in size.

landscape-level management: a level of forestmanagement concerned with maintainingdiversity of age classes, species mix, and eco-systems over landscapes.

managed forest: that portion of the landscape out-side protected areas where forestry operationsoccur.

management zone: the outer portion of a riparianmanagement area situated adjacent to astream, lake, or wetland and established toconserve and maintain the productivity ofaquatic and riparian ecosystems when har-vesting is permitted.

morphology: shape and form.

mychorrizae: an association between a fungus andthe roots of a higher plant which may belocated on or in the root.

netdown: an estimate of the amount of timberreserved from harvesting.

protected area: permanent geographic areas thatare legally designated as protected from cer-tain specified activities.

poling operation: the removal of trees of a spe-cified diameter to produce special forestproducts such as fence posts, rails, or utilitypoles.

reserve zone: the inner portion of a riparian man-agement area situated adjacent to a stream,lake, or wetland and established to conserveand maintain the productivity of aquatic andriparian ecosystems when harvesting is notpermitted.

riparian area: an area adjacent to the high watermark that borders streams, rivers, lakes, orponds, and the surrounding portion of landinfluenced by the water body.

riparian management area (RMA): a classifiedarea of specified width surrounding or adja-cent to streams, lakes, riparian areas, and wet-lands. The RMA includes, in many cases,adjacent upland areas. It extends from the topof the streambank (bank full height) or fromthe edge of a riparian area or wetland, or thenatural boundary of a lake, outward to thegreater of: ) the specified RMA distance, )the top of the inner gorge, or ) the edge ofthe floodplain. Where a riparian area or wet-land occurs adjacent to a stream or lake, theRMA is measured from the outer edge of thewetland.


A P P E N D I X 8 (Concluded)

salmonids: pertaining or belonging to the Salm-onidae family of fishes, including Pacificsalmon and trout.

seed-tree silvicultural system: an even-aged sil-vicultural system in which selected standingtrees are left scattered throughout the cutblock after a harvest operation to act as seedsources for natural regeneration.

seral: pertaining to the stages of natural successionthat occur before the development of the cli-max community.

shelterwood system: an even-aged silvicultural sys-tem in which groups of trees in mature standsare removed in a series of − cuts. Trees thatremain standing provide openings and partialcover for the regenerating understorey.

silvicultural system: a process by which forests areharvested, regenerated, and tended.

slash: the residue left on the ground after felling andtending or that accumulates as a result of storm,fire girdling, poisoning, disease, or pests.

stand-level management: a level of forest manage-ment by which a relatively homogeneous geo-graphic unit can be managed under a singlesilvicultural prescription or set of treatments.Stands are rarely larger than ha.

succession: the progressive development of ecosys-tems towards a climax state where speciescomposition remains relatively constant.

threatened species: a species likely to becomeendangered in British Columbia if the factorsaffecting its vulnerability are not reversed.

tree farm licence: a form of forest tenure; a -yearlicence conveying exclusive rights to harvestby the licencee in a specific area of Crownland.

uneven-aged management: management practicesthat create stands of three or more inter-mingled age classes; many of the habitatattributes of mature forests may be main-tained with uneven-aged management.

ungulate: any hoofed wildlife (e.g., deer, moose,elk).

viability: with reference to populations, those thatare self-sustaining with a high probability ofsurvival despite effects of demographics,changing environments, and natural disasters.

vesicular-arbuscular: a type of mychorrizal fungithat have globular swellings (vesicles) andsmall, finely branched projections (arbuscles)that infect host cells.

vulnerable species: a species that is particularly atrisk because of low or declining numbers,small range, or for some other reason, but isnot a threatened species.

watershed: the entire basin area drained by astream or a lake.

SEQ 3462 JOB YEW-013-011 PAGE-0029 LIT CIT REVISED 06MAR00 AT 13:57 BY BC DEPTH: 61.04 PICAS WIDTH 42 PICAS COLOR LEVEL 1

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