FAO Decline and diebackdieback FORESTRY of tretreess and forestsforests PAPER 120 A globalgIoia overviewoverview by William M. CieslaCiesla FADFAO Forest Resources DivisionDivision and Edwin DonaubauerDonaubauer Federal Forest Research CentreCentre Vienna, Austria Food and Agriculture Organization of the United Nations Rome, 19941994 The designations employedemployed and the presentation of material inin thisthis publication do not imply the expression of any opinion whatsoever onon the part ofof thethe FoodFood andand AgricultureAgriculture OrganizationOrganization ofof thethe UnitedUnited Nations concerning the legallega! status ofof anyany country,country, territory,territory, citycity oror area or of itsits authorities,authorities, oror concerningconcerning thethe delimitationdelimitation ofof itsits frontiers or boundarboundaries.ies. M-34M-34 ISBN 92-5-103502-492-5-103502-4 All rights reserved. No part of this publicationpublication may be reproduced,reproduced, stored in aa retrieval system, or transmittedtransmitted inin any form or by any means, electronic, mechani-mechani­ cal, photocopying or otherwise, without the prior permission of the copyrightownecopyright owner.r. Applications for such permission, withwith aa statement of the purpose andand extentextent ofof the reproduction,reproduction, should bebe addressed toto thethe Director,Director, Publications Division,Division, FoodFood andand Agriculture Organization ofof the United Nations,Nations, VVialeiale delle Terme di Caracalla, 00100 Rome, Italy.Italy. 0© FAO FAO 19941994 FOREWORD The periodic occurrence ofof lossloss ofof treetree vigour,vigour, branch diebackdieback andand treetree mortalitymortality for reasonsreasons unknown or difficult toto determinedetermine isis aa phenomenonphenomenon whichwhich has frustratedfrustrated resource managersmanagers andand intriguedintrigued scientistsscientists for manymany years.years. Referred toto as "dieback" or "decline", itit hashas becomebecome a subjectsubject ofof intensifiedintensified interestinterest asas forestforest scientistsscientists attemptattempt to achieve a better understanding ofof thethe dynamicsdynamics ofof forestforest ecosystems.ecosystems. ThereThere is also great concern onon thethe part of general public andand thethe scientific community that manymany instancesinstances of decline or diedieback back may bebe thethe result of human activities.activities. Most cases of decline have been reportedreported fromfrom Europe, NorthNorth AmericaAmerica,, Australia and thethe Pacific RegionRegion.. HoweverHowever decline is by no meansmeans restricted to these regions.regions. There areare reportsreports ofof treestrees andand forests forests affected affected byby declinedecline throughout throughout the the world.world. WhileWhile the symptoms of declinedecline may be strikingly similar, theythey can be the resultresult ofof manymany different abiotic and bioticbiotic factors,factors, oftenoften interactinginteracting inin aa complex complex manner.manner. Some declines are thethe resultresult ofof processes whichwhich areare anan integral integral partpart ofof thethe dynamicsdynamics ofof forestforest communities. OthersOthers maymay bebe relatedrelated toto humanhuman activitiesactivities includingincluding landland managementmanagement practices, emissions from motor vehiclesvehicles or industrial processes.processes. InIn manymany instancesinstances thethe causal factors responsible forfor decline are notnot known. The frequency of occurrence,occurrence, pattern and intensity ofof declinedecline oror diebackdieback maymay adversely affect the sustainablesustainable flow ofof goods goods andand servicesservices fromfrom forestsforests andand influenceinfluence forest management.management. DeclinesDeclines maymay alsoalso serve as indicatorsindicators of forest response toto climate change, an issueissue whichwhich isis currentlycurrently inin thethe forefrontforefront of scientific andand publicpublic interest. It is important.important, therefore, thatthat foresters,foresters, ecologists,ecologists, biologistsbiologists andand scientistsscientists fromfrom relatedrelated disciplines understand the mechanismsmechanisms and factorsfactors involvedinvolved in declinesdeclines so thatthat appropriate forest monitoring andand managementmanagement systemssystems cancan bebe implemented.implemented. The purpose of this paper, which is based onon surveyssurveys ofof thethe publishedpublished literature,literature, unpublished reports, correspondence, personalpersonal eexperiencexperience and review by aa numbernumber ofof specialists, drawn fromfrom developeddeveloped and developing countries worldwide, isis toto provide provide anan overview of declinesdeclines andand diebacks in a globalglobal context.context. Similarities and differences between decline events are examined,examined, as are the mechanisms whichwhich are believed to cause decline. ThisThis paperpaper isis intendedintended toto serveserve asas aa referencereference sourcesource whichwhich describesdescribes case histories of declines fromfrom most of the'World'sthe·world's forestforest regionsregions andand isis designeddesigned forfor use by foresters, forestforest scientists,scientists, policypolicy analysts analysts andand decisiondecision makers.makers. J.P. LanlyLanly Director, Forest ResourcesResources DivisionDivision Forestry Department ACKNOWLEDGEMENTS The constructive commentscomments and additional information kindly providedprovided byby thethe many people whowho reviewed the draft paper,paper, "Dieback"Dieback andand DeclineDecline inin Forests:Forests: A GlobalGlobal Overview (FAO MiscMisc.. F0/275)F0/2/5) are gratefully acknovvledged.acknowledged. TheyThey were;were; ARGENTINAARGENTINA - Jose LuisLuis Darraidou,Darraidou, AUSTRALIAAUSTRALIA -- R.C. Ellis, Glen Kyle and KennethKenneth M.M . Old,Old, BANGLADESH -- MohammedMohammed Abdur Rahman,Rahman, BURKINABURKINA FASO - Laurent Magliore Some,Some, CANADA -- JeanJean ClaudeClaude MercierMercier andand J.J. PeterPeter Hall,Hall, CHILECHILE -- HernanHernan Peredo,Peredo, COLOMBIACOLOMBIA­ - Cielo Orozco JaramilloJaramillo andand WendyWendy Arenas Arenas Wightman, Wightman, COMISSION COMISSION OF OF EUROPEAN EUROPEAN COMMUNITIES -- BernardBernard MalletMallet,, COSTA RICA - Felix E. Scorza Reggio,Reggio, GERMANYGERMANY­ - U. Hoenish and O. Kandler, ISRAEL -- O.O. Bonneh,Bonneh, KENYAKENYA - -Garry Garry Hill, Hill, MALTAMALTA - Joseph BorgBorg,, NEW ZEALAND -- P.G. Cannon andand GordonGordon Hosking,Hosking, PAKISTAN - Bashir Ahmed Wani, PHILIPPINESPHILIPPINES -- Emilio Rosaria, SEYCHELLESSEYCHELLES - W.W. Andre,Andre, SIERRA SIERRA LEONELEONE -- E.K.E.K. Alieu,Alieu, SPAINSPAIN -- SantiagoSantiago MarracoMarraco and and Fernando Fernando RobredoRobredo Junco,Junco, SWITZERLAND SWITZERLAND -- R.R. Volz, TRINIDADTRINIDAD -- S.S. Faizool,Faizool, UNITEDUNITED KINGDOMKINGDOM -- EricEric Boa,Boa, J.N. Gibbs,Gibbs, UNITEDUNITED STATESSTATES - Allan Auclair, DieterDieter Mueller-Dombois,Mueller-Dombois, PaulPaul Hennon,Hennon, PaulPaul Manion, A.J.A.J . RebertusRebertus andand C.G. Shaw Ill,III, ZAMBIAZAMBIA - -O.O. ShakaciteShakacite and and ZIMBABWEZIMBABWE -- G.D.G.D. Piearce.Piearce. Jim Ball,Ball, KlausKlaus Janz,Janz, MichelMichel Malagnoux,Malagnoux, ChristelChristel Palmberg-LerchePalmberg-Lerche andand PaulPaul Vantomme, FAO,FAO, ForestForest ResourcesResources Division,Division, ForestryForestry DepartmentDepartment in in RomeRome alsoalso providedprovided information, reviewreview commentscomments andand suggestions.suggestions. Shingo Shibata,Shibata, FAO,FAO, ForestryForestry Operations, AsiaAsia Desk,Desk, arrangedarranged for for the the acquistitionacquistition ofof photographs ofof firfir waves in JapanJapan.. ii TABLE OFOF CONTENTSCONTENTS FOREWORD . .. .. ........ • ..•..•.. • .. • .. .•.. .. •.... ......... ii ACKNOWLEDGEMENTS ..• . ..•..... • ..•..•..• . .. • ... .. •.. • ..•...... ii TABLE OFOF CONTENTSCONTENTS .......•........... ..•. .. ..•......... ...... iii LIST OF TABLES ........ ... • .. • . • . •. •. .•. • . ..•. • . .. .. .... vii LIST OF ILLUSTRATIONSIllUSTRATIONS ...... ... .... • ..•...•..•...•..•..•. ... viii CHAPTER 11 - INTRODUCTIONINTRODUCTION 1 CHAPTER 2 - DECLINE:DECLINE: WHAT ISIS IT?IT? .. .. .•. •..•......... .. .. .. ... .•... 3 2.1. DEFINITION OF TERMS . .. .. .. .... ......... ... 3 2.2. DIEBACK AND DECLINEDECLINE AS SYMPTOMSSYMPTOMS OFOF DISEASEDISEASE ......... •.... 4 2.3. DECLINE ASAS A CLASSCLASS OFOF DISEASEDISEASE .......... ..•..•.. ... .. 4 2.3.1. THETHE HOST, HOST, STRESS, STRESS, SAPROGEN SAPROGEN CONCEPTCONCEPT . .. ... .. • .. 5 2.3.2. THETHE PREDISPOSING, PREDISPOSING, INCITINGINCITING AND CONTRIBUTINGCONTRIBUTING FACTORSFACTORS CONCEPTCONCEPT .. ..• .. • . • . ... 6 22.3.3..3 .3 .DECLINES DECLINES AS AS DISEASES DISEASES OF OF POORLYPOORLY UNDERSTOOD AETAETIOLOGYIOLOGY . .. ....... •.........•... 6 2.4. DECLINE ASAS A PARTPART OFOF FORESTFOREST DYNAMICSDYNAMICS ... ...• . ... ..... 7 CHAPTER 3 -- EUROPEEUROPE ........ .. ... .. .. .......... • ..... ... .... 10 3.1. SILVER FIR DECLINEDECLINE . .. .•. .•.. • .......• . .•. •.. • . ... 10 3.2. HARDWOOD DECLINESDECLINES .. ............• . .... .•. .. ... 10 3.3. ACUTE YELLOWINGYELLOWING OFOF NORWAYNORWAY SPRUCESPRUCE ......... ...... ..... 13 3.4 REGIONAL DECLINE OF CONIFERS ANDAND HARDWOODS ..... .• .. •.. 14 CHAPTER 44 - NORTH AMERICA .. •. .. ... •. ..• ... • . .•. .... .. 18 4.1. BIRCH DIEBACK ....................... •.. .. ..• . ... .. 18 4.2.4.2. POLE