the aspen mortality summit

The Aspen Mortality Summit

December 18 and 19, 2006Salt Lake City, Utah

United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

Proceedings RMRS-P-60WWW

April 2010

Bartos, Dale L.; Shepperd, Wayne D., comps. 2010. The aspen mortality summit; December 18 and 19, 2006; Salt Lake City, UT. Proc. RMRS-P-60WWW. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 21 p.

Abstract

The USDA Forest Service Rocky Mountain Research Station sponsored an aspen sum-mit meeting in Salt Lake City, Utah, on December 18 and19, 2006, to discuss the rapidly increasing mortality of aspen (Populus tremuloides) throughout the western United States. Selected scientists, university faculty, and managers from Federal, State, and non-profit agencies with experience working with aspen were invited. Participants were first asked to share information on recent aspen mortality. Subject matter working groups were then asked to determine factors associated with recent aspen mortality, recommend research needs, and organize those needs into testable questions and hypotheses. This report documents their findings, and will serve as a platform for Resource Managers to address the Sudden Aspen Decline issue.

Keywords: aspen, Populus tremuloides, Sudden Aspen Decline, aspen mortality, aspen diseases, aspen ecology

The Compilers

Dale L. Bartos is a Research Ecologist, with the U.S. Forest Service Rocky Mountain Research Station, and an Adjunct Assistant Professor in the Department of Wildland Resources at Utah State University, Logan, UT.

Wayne D. Shepperd (retired) is a recognized authority on aspen. Wayne published numerous scientific papers on aspen ecology and management during his 37-year career with the U.S. Forest Service.

Contents

Introduction ................................................................................................... 1

Issue ............................................................................................................. 2

Aspen Summit Meeting ................................................................................ 4

Forest Health Working Group Report ........................................................... 4

Forest Ecology Working Group Report ......................................................... 6

Wildlife Ecology Working Group Report ....................................................... 9

Genetics Working Group Report ................................................................ 10

Silviculture/Management Working Group Report ....................................... 12

Terminology ................................................................................................ 14

Overall Needs ............................................................................................. 16

Definition of Terms ........................................................................... 16

Role of Herbivores ........................................................................... 17

Role of Aspen Roots ........................................................................ 17

Genetics........................................................................................... 17

Rapid Assessment ........................................................................... 17

Recommended Actions............................................................................... 18

References ................................................................................................. 20

Appendix..................................................................................................... 21

1USDA Forest Service Proc. RMRS-P-60WWW. 2010

Introduction

Quaking aspen (Populus tremuloides) are the most widespread tree speciesthroughoutNorthAmericaand is found in theRockyMountains fromCanadathroughtheUnitedStatesandintonorthernMexico.InthewesternUnitedStates,aspenaremostabundantinColoradoandUtah.Acrossitswesternrange,aspenareamid-elevation,shade-intolerantspeciesthatoccupiesawidevarietyofsites. Aspenareoneofthefewbroad-leavedhardwoodtreesfoundinmanywesternforests.Itisavaluableecologicalcomponentofmanylandscapes,occurringinpureforestsaswellasgrowinginassociationwithmanyconifersandotherhardwoodspecies.Whileaspenprovidesdesirablescenicvalue,thediversityofunderstoryplantsthatoccurinthefilteredlightundertheaspencanopysupplycriticalwild-lifehabitat,valuablegrazingresources,andprotectionforsoilandwater.Aspenprovidescriticalbiodiversitywhereitoccurs. Aspenthrivewhereregularandfrequentdisturbance(typicallyfireinmanywesternlandscapes)promotesvegetativeregenerationthroughrootsuckersthatrisefromlateralrootsthatliewithin6inchesofthesoilsurface(DeByleandWinokur1985).Aspensproutprofusely(upto500,000stemsperacre)followingadisturbancethatkillsorremovesoverstorytrees.Thesehighnumbersofaspensuckerstypicallygrowveryrapidlyandself-thin followinganegativeexponentialdecaymodel.Mostlossesoccurinthefirstfewyears(Shepperd1993).ManagementactivitiesrelyonthisprocesstoregenerateandrestoreaspenforestsinthewesternUnitedStates.ThemostcurrentliteraturepertainingtoaspenecologyandmanagementwassummarizedbyShepperdandothers(2006)fortheSierraNevadaarea,butitwouldpertaintomostwesternaspen. Comparedtoconifers,aspenarerelativelyshort-lived.Theoldestknownaspenstemsareonlyabout300yearsofage(Shepperdandothers2006).Mostaspenwereunlikelytolivemuchbeyond100yearsunderthenaturalfireregimesthatexistedpriortosettlementoftheWest.However,duetotheabsenceoffireoverthepastcentury,aspeninmanyareasareoldertoday,havesucceededtomixedconifer/aspenforests,andaregraduallylosingmaturestemsasthestandsage.Additionally,heavygrazingfrombothnativeandwildungulateshasdamagedmanyaspenforestsbyeliminatingordamagingaspensuckersthatareproducedtoreplaceoverstorytreesastheyageanddie(DeByleandWinokur1985).Techniquestoidentifyandrestoreaspenintheseconditionshavebeendeveloped(Shepperdandothers2006)andarebeingputintopracticethroughouttheWest.

The Aspen Mortality Summit

December 18 And 19, 2006Salt Lake City, Utah


Issue

Recentreportsofdyingaspenhavecausedconcernaboutthefutureofsomeas-penforests.Thismortalitydiffersfromnormalaspenvegetativesuccession(fig.1)orage-relatedreductioninstocking.Maturetreesaredyingatanacceleratedratewithlittleornonewsproutsoccurring,indicatingthatthelateralrootsmayalsobeaffected(fig.2).Ifthisisthecase,thenaffectedaspenwillnotbeabletoproducenewsuckersandaspengrovesthathaveexistedforhundredsandperhapsthousandsofyearscoulddisappear(fig.3). Thisrapiddeathofaspentreesseemstobegininepicentersandspreadradiallythroughanaffectedaspenstand.Standsonalltopographicpositions,moisturere-gimes,andsoiltypesareaffectedandthephenomenonhasbeenreportedthroughouttheWest,fromArizonaintoAlberta,Canada.However,specificcausesofaspenmortalitymaydifferfromareatoareaandwedonotassume,atthispoint,thatauniformsyndromeisinvolvedeverywhere.Generally,therapidmortalitycanaf-fectoneaspengrove,leavingothersnearbyuntouched.Youngerageclassesandpre-existingsproutsareoftennotaffectedtothesameextentasmatureoverstorytrees.Cytosporacankers,poplarborers,andotherdamageorstressagentsareof-tenassociatedwithdie-offepicenters;however,thepossibilityofayet-unknowninvasivediseaseorinsectcausestillexists.

Figure 1. An aspen stand in southeast Idaho where mature aspen trees died but sufficient aspen regeneration exists to restore the stand.


Figure 2. Dying aspen stand in the summer of 1990 on Cedar Mountain in southern Utah (photo by James Bowns, see Ohms 2003).

Figure 3. Same stand as shown in figure 2 during the summer of 2002. Few living trees remain and no regeneration is present (photo by Seth Ohms, see Ohms 2003).

AcceleratedratesofaspenmortalityhavebeenreportedforseveralyearsinUtahandArizona,butonlyrecentlyhavetheseratesbecomeapparentinColorado.Aerialsurveys,conductedbyForestHealthManagement,USFSRegion2,indi-catedthatnearly140,000acreswereaffectedbyaspendeclineinColoradoin2006;andby2009,thatareawasinexcessof500,000acres(seehttp://www.aspensite.org/SAD/sad_faqs.pdf).Theapparentlackofasuckeringresponseinsomecasesisdisturbing,asaspenmustsproutbackifitistopersist.Mortalityofthismagni-tuderaisesconcernsaboutthefutureofaspenforestsinsomeareasandjustifiesacomprehensiveinvestigationintothephenomenon.


Aspen Summit Meeting

TheUSDAForestServiceRockyMountainResearchStationinvitedselectedscientists, university faculty, andmanagers fromFederal,State, andnon-profitagencieswithexperienceworkingonaspentoanaspensummitmeetinginSaltLakeCity,Utah,onDecember18and19,2006.Participantswereaskedtoshareinformationaboutrecentacceleratedaspenmortality.OveradozenparticipantsfromthroughouttheWestpresenteddescriptionsandexamplesofdyingaspen.Participantswerethenassignedtothefollowingsubjectmattergroups:

• ForestHealth(pathologists,entomologists) • ForestEcology • WildlifeEcology • Genetics • Silviculture/Management

Eachgroupwasaskedtodiscussthefollowingtopicoutlineandmakerecom-mendationstoaddresstheaspenmortalityphenomenon:

a.Determinefactorsassociatedwithaspendie-off. b.Determineresearchneeds—factorsandquestionsthatneedtobestudied. c.Organizeresearchneedsintotestablequestions/hypotheseswithbudgets.

Broadguidelinesweregiventothegroups;however,nouniversalprotocolwassuggestedastohowthevariousgroupsshouldreporttheirefforts.Eachsubjectmattergroupproducedoutlinenotesfromitsdiscussionsandpresentedthemtoallparticipants.Transcribednoteswerethenusedtoproducethenarrativereportspresentedbelow.

Forest Health Working Group Report

Clarification of Terminology

TheForestHealthgrouphadconcernsabouttheterminologyusedindiscuss-ingtheaspenmortalityproblem.Thefourtermsofmajorconcernwere:decline,die-back,die-off,andsuccession.Thesewordsmeandifferentthingstodifferentpeople.Thefollowingdefinitionsexistfromaforesthealthperspective:

• Declineistheresultofaforestdiseasethatinvolvesmultiplespecificallyordered,interchangeableandinteractingfactors(Manion1981).Theclassicdefinitionofaforestdeclinetypicallyinvolvespredisposing,inciting,andcontributingfactors(table1).

• Die-backisasymptomcharacterizedbydeathofpartsofaplant.Itisoftenpresentaspartofforestdecline.Thetermmaybeappropriatetodescribedeathofstemsinaclonalplant,suchasaspen,whenrootsremainaliveandareabletosucker.

• Die-offischaracterizedbymortalityofaspentreeswithnoregenerationtorestorethestand.


• Succession(asequenceofchangesinaplantcommunity)isaseparateprocessfromdecline.Forestsuccessioncouldplayaroleincausingtreestodecline,butforestdeclinecanoccurwithorwithoutsuccession.

Commonlyrecognizeddefinitionsareneededsothatparticipantscaneffectivelycommunicate(forexample,theSilviculture/ManagementWorkingGroupusedthetermsdie,die-off,anddie-backintheirsummarylaterinthissection).TheForestHealthWorkingGroupconstructedtable1toillustratehowfactorsaffectingaspenmightfitintothepathologicaldefinitionofdecline.

Research Needs

Thereisaneedtoidentifycausalagentsintheaspenmortalityphenomenonthatwearecurrentlyobserving.Tounderstandthisphenomenonandmakerecommen-dations,weneedtoknowwhatagentsandstressesareinvolved,(biotic,abiotic,andsitefactors)andtodistinguishvariousinteractionsthatareoccurring. Biotic Factors—Tofullyunderstandthismortality,specificbioticagentsthatare involvedneed to be identified.Thismay includevarious diseases, insects,andtheimpactsofungulates.Someofthesebioticfactorswillplaymajorrolesinaspenmortalitywhileotherswillbesuperfluous.The roleofungulateswillundoubtedlybeamajorfactorincertainareasoftheWest.Whatisthemaximumpopulationlevelofwildungulatesthatwouldallowustostillgrowanaspentreefromasucker?Whendodomesticlivestocknegativelyimpactaspenregenerationandcanwedevelopguidelinesforthemanagertoaddressthisproblem? Abiotic Factors—Thesefactorsareprobablythemostsignificantcontributorstotheaspenmortalityproblem.Themostprevalentfactorcouldbedroughtanditseffectsontheaspenclone.Howdoesdroughtimpacttheaspenoverstoryaswellastheregeneration?Doesdroughtactasastressortostimulateregenerationinadditiontokillingmaturetrees? Site Factors—Additionally, therolesofvarioussitefactorsneedtobebetterunderstood.Factorssuchaselevation,topography,andsoilsareallanintegralpartoftheaspenecosystem.Whatpartdothesefactorsplayandhowdotheyinteractinthedemiseoftheaspen?Worrallandothers(2008),inaquantitativestudyofnumerousaffectedaspensitesinwesternColorado,stated:“Ourdataareconsis-tentwithahypothesisthat(a)predisposingfactorsincludestandmaturation,lowdensity,southernaspectsandlowelevations;(b)amajorincitingfactorwastherecent, acutedrought accompaniedbyhigh temperatures, and; (c) contributingfactorsandproximateagentsofmortalityarethecommonbioticagentsobserved.”

Table 1—Factors potentially involved in aspen decline.

Predisposing Inciting Contributing

Marginal sites Frost Animal damageOld age Acute drought Canker fungiWater tables Sucker mortality from browsing BorersSuccession Defoliation event BeetlesGenetic mutationIncreased temperatures


Testable Questions

• WhatisthemagnitudeandextentofaspenmortalityintheRockyMountains? • Whatsiteandbioticfactorsareassociatedwithaspenmortalityinthewestern

UnitedStates? • Whatmeteorologicalfactorsareassociatedwithaspenmortality? • What are the long-term effects of diseases and insects on the aspen

ecosystem?

Partners

Long-termresearchisneededtoaddressvariousaspectsofaspenmortality.Thiswillallowforthedevelopmentofmonitoringprotocolsandmanagementtechniques. Numerouspartnershavebeenidentifiedtocontributetotheselong-termefforts:theForestRestorationInstituteatCSU,theproposedCenterofExcellence(sincemorphedintotheWesternAspenAlliance)atUSU,andtheU.S.ForestServiceFIA/ForestHealthMonitoring.

Forest Ecology Working Group Report

OurcurrentknowledgeofaspenecologyshouldbeusefulinunderstandingtheextensiveaspenmortalitythatisoccurringintheRockyMountains.However,thereismissinginformationconcerningtheecologyofaspenthatwouldhelpdecipherthismortality.Thisgroupapproachedtheirsubjectintwoparts:(1)suspectedfac-torscontributingtotheaspenmortality,and(2)significantquestionsthatneedtobeevaluated.

Mortality Factors

Arapidassessmentmethodologymustbedeveloped todefine themagnitudeandextentoftheaspenmortalityproblem.Thismethodmustbeusefultore-sourcemanagersandapplicablethroughoutthewesternUnitedStates.ThefirststepinachievingthisgoalmaybetoadaptthemodelspecifiedintheSilviculture/Managementbreakoutgroup. Inaddition,a remotesensing techniquecouldbecoupledwiththerapidassessmenttomorepreciselydeterminethismortalityandbetterdefinetheextentorpatchynatureoftheproblem. Droughthasprofoundimpactsonmostvegetationsystems.Doesdroughtcon-tributesignificantlytothecurrentaspenmortality?Howdoesthismoisturestressrelate toelevation,aspect,etc.?Recently,Worrallandothers(2008)foundthataspenmortality,orSuddenAspenDeath(SAD),wasmoreprevalentinsituationswheredroughtwasmorepronounced. Aspen are a sun-loving, disturbance-dependent pioneer species that quicklyre-colonizesasitefollowingfirebutwilleventuallybereplacedbymoreshadetolerantconifersifasuitableconiferseedsourceisavailable.Givenenoughtime,mostaspenwilleventuallysucceedtoaconiferdominatedsystem,butathirdoftheaspenintheWestcanbeconsidered“climax”orstableformanagementpur-poses(Mueggler1989),sincenoconifersarecurrentlypresent.SADiscurrentlyaffectingbothstableandsuccessionalaspen(fig.4)andwillundoubtedlyaffectthefuturecharacterofbothtypesofaspen.


Successionisusuallyaffectedbyfire.Historically,manysitesburnedonaregularbasis,soconiferregenerationwasremovedandthestandsrevertedtobeingaspendominated.Becausefirehasdiminishedinthesesystems,aspentreesarebecomingmatureorover-mature.Astressorsuchasdroughtwouldgiverisetothepossibil-ityofmoreincidencesofdiseasesandinsects.Inadditiontofire,numerousotherfactorscancontributetotherejuvenationof“stable”aspen. Aspenusually regenerates in thewesternUnitedStatesbyvegetativemeans.Seedlingsdooccurbutnotonalevelthatwouldmeanwideexpansionofaspenseedlingsacrossthelandscape.However,withrecentdevelopmentsinthefieldofgenetics,thereismoreincidenceofregenerationbyseedsthanwasoriginallythought(seeGeneticsgroupreport). IncertainareasoftheWest,thereishighincidenceofherbivoryofaspenbybothdomesticlivestockandwildungulates.Theseherbivorescanhaveasevereimpactonaspen regenerationandonmature trees in somecases.Someaspenclones/standshavebeeneliminatedfromthelandscapebyexcessiveungulateuse.Whatroledoungulatesplayinthecurrentmortalitybeingobserved?Isexcessiveusebyungulatesremovingtheregenerationfromfadingmatureaspenstandscausingsomeofthemortalityweareexperiencing? Quakingaspenin thewesternUnitedStatesoccursoverawideamplitudeofconditions,fromshrub/woodlandecotoneonthelowerendofitsrangetotreelineattheupperlimits.Willtheprojectedclimatechangehaveaprofoundchangeinaspendistribution?Itisbelievedthatclimatechangemightcauseaspentorecedefromdriersitesatthelowerextremesofaspen’soccurrence.

Figure 4. Mortality of mature aspen in a mixed conifer/aspen stand on the Gunnison National Forest 2006.


Aspen Ecology Questions

• Areaspenrootsdying?Ifso,why?Ifdiseaseorinsectsarepresent,aretheygirdlingtheparenttreeandcausingtherootsystemtodie?Aretherootsbeinggirdledandcausingtherootstodie?

• Does herbivory act as a vector for pathogens? Do herbivores transferpathogens?

• Terminologyneedstobeclarified.Howdoesdeclinedifferfromdie-off/die-back?Weshoulduselessconfusingtermsthatreferjusttoaspenmortality.Specificadditionalwordsneedtobedefined,suchasstableaspen,clone,stand(grove),succession,anddisturbancespecies.

• QuestionsattributedtoWayneShepperd(giveninhisopeningremarks): o Ismortality(die-off)anormalevent? o Aretherenewdiseasesorinsectspresent? o Canthismortalitybepredictedbystandage,growthrate,stocking,or

othermetrics? o Isclimateinvolved? o Howlongwillthismortalitycontinue? o Whatcan(orshould)bedoneaboutthismortality?

• Isthiscurrentphenomenonjustareturntohistoricconditions?Ifso,shouldwebeconcernedaboutit?

• Isthereameansto“age”clones(seeGeneticsgroupreport)?Doesdiseasebecomealargerplayerastrees(clones)age?

• Howcanwebuildpublicsupport(fortreatment)tostopthelossofaspenincriticalareas?Whataretheeconomicsassociatedwiththismortality?Whataretheimpactsonthepublicasaresultofdiminishedfallcolors?

• Shouldwemimicdisturbanceeffectsinordertopreventthelossofsomeaspenclones fromthe landscape?Should treatedsitesbeprotectedfromherbivores?What newand innovative techniques couldbeused to keepherbivoresfromeliminatingaspenregeneration(forexample,hinging,slashpiling,andharassinganimals)?

• Whathappensaftermortality?Whatarethelong-termimpactsofthismor-talityonaspenclones,understoryvegetation,soils,scenicandrecreationresources,andanimalhabitats?

• Whyaresomeclonesaffectedwhileadjacentonesarenot?Aresomeclonesgeneticallypredisposedtothismortalityorisitjustarandomoccurrence?

Specific Questions and Approximate Costs

• Quantifythemagnitudeandextentofthemortalityissue($200K). • Definetheproblemandterminology;reviewandsynthesizeliterature;com-

municate researchneeds; anddefinepertinentquestions tobe addressed($50K).

• Developadie-offriskassessmentandakey(decisiontree)toidentifystandsatriskandwhichwouldbemosteconomicaltotreat($50K).

• Determinecausesofdie-off($200K): o Areelevation,aspect,andinsectanddiseasestressesresponsible?


o Whatistheroleofstandage,drought,andherbivory? o Identifyprimaryversussecondaryagents,includinggenetics. o Isungulatesalivaavectorfordiseasetransmission?

• DeterminetheknownNaturalRangeofVariability(NRV)ofaspenandtestforaprecedenceofdie-off($50K).

• Determinetheregionaleffectsofaspenmortality($1.5M). o Inter-clonalinteractions o Successionaltrajectory o Erosion o Alleopathy o Pathogenaccumulation o Insectaccumulation o Wateravailability

• Identify and test techniques to protect regeneration and restore “fading”standsthataretreated($100K).

Wildlife Ecology Working Group Report

Key Questions

TheWildlifeEcologygroupidentifiedseveralkeyquestionstoaddresspotentialchangesinwildlifehabitatresultingfromthelossofaspen.First,thecurrentstatusandprojectedtrendsoftheaspenresourceneedtobedeterminedandhowthesechangesmightaffectwildlifeatdifferentscalesneedstobeestablished.

• Whatimplicationswill thesetrendshavefordifferentspeciesofwildlifeassociatedwithaspen?

• Whatspeciesmightbemostaffectedbylossofaspen? • Whateffectswouldthelossoflargeaspentreeshavecomparedtocomplete

lossofaspen? • Atwhatscaleswouldlossofaspenbecriticaltowildlifespecies? Understandingtheroleoffireinshapingtheaspenresourceofthefutureisalsocritical.Re-establishing thepredominanceof fireon the landscapemightofferopportunitiesforaspenre-colonizationthatcouldpotentiallycompensateforthecurrentlossofaspen,butitisunclearhowthesefuturescenariosmightplayoutforwildlifespecies.Changingthespatialandstructuraldistributionofaspenonlandscapeswillundoubtedlyaffectwildlifehabitat.Gainingspecificknowledgeofhowwildlifespeciesuseaspenhabitatwillhelpmanagersunderstandhowtominimizeconflicts,predicttheeffectsofcurrentaspenloss,andplanfutureman-agementactions. Determiningtheseriousnessofthecurrentlossofaspenandhowitwillaffectpopulationlevelsofelk(Cervus elaphus)andmoose(Alces alces)iscritical.Thesespeciesuseaspenforforageandcoverand,consequently,mayaffectthehealthandvigorofaspenpopulations.Gainingabetterunderstandingofthedynamicsofthisinteractionwillaidmanagersinunderstandinghowtheycanbuildprovisionsforsustainableaspenhealthintointegratedvegetationmanagementstrategies.


Thegoalsforthesestrategiesshouldbedesignedtoachievedesiredfuturecondi-tionsforaspen,wildlife,andotherresourceobjectives. Anothercriticalneedislearninghowtotransferknowledgeaboutaspen/wildlifeinteractionsfromoneregiontoanother.Thisrequiresdetailedinformationonthefeaturesthatarebothcommonanddifferenttotheseareas.Wealsoneedtounder-standhoweasilytheresultsobtainedfromspecificsitesandscalescanbeparlayedintobroaderscalevegetationmanagementgoalsandstrategies.Similarly,weneedtodeterminehowtoassembleandsynthesizeelementsoftheaspenproblemfromdifferentdisciplinesandassesstheknownandunknownsinfuturescenarios.

Actions Needed

TheWildlifeEcologygroupsuggeststhatseveralimmediateactionsareneededtodealwiththecurrentaspenmortalityissuewithrespecttowildliferesources.First,areviewandsummaryofstatewide(wildlifeandfish)comprehensiveplansandTheNatureConservancyeco-regionalassessmentsshouldbeconductedtomorecompletelyascertainspecificquestionsandneedsrelatedtoaspenandwildlife.Inaddition,theUSFSprojectplanningandappealsdatabaseScheduleofProposedActions(SOPA)shouldbereviewedtoidentifytrendsandcriticalissuesassociatedwithplanningandimplementingvegetationmanagementprojectsinvolvingaspenandwildlife.Thiscomprehensivedatabasedescribesproposedvegetationmanage-mentprojectsonForestServicelandsandwouldprovideameansofidentifyingpotentialprojectsthatcouldbemonitoredorstudiedtolearnmoreaboutwildlifeandaspeninteraction(aswellasgainknowledgeaboutotheraspectsoftheeffectsofmanagementactivitiesontheaspenresource). Thegroupalso recommends thatamulti-partnerworkshopbeorganized thatwould o increaseunderstandingofaspen, o identifyresearchneedsforaspen/wildlifeinteractions,and o developanactionplanforaspenconservationandmanagementthatcould

beusedtoguideforestplanningandintegratedvegetationmanagement.

Genetics Working Group Report

Overarching Need

Acriticalneedtounderstandingthecurrentaspenmortalityphenomenonistoconsidertheclone-specificeffectswheninvestigatingdie-offsandtreatmenteffectsandwhenconductingtrendmonitoring.Theneedtoclearlydefinephenomenaandtermsinthisprocessshouldbeemphasized.Forexample,thefollowingphenomenamaybetheresultofverydifferentprocessesoccurringinaspenstands:

• overstorytreemortalitywithoutregeneration, • mortalityofallageclasseswithoutregeneration, • displacementbyconifers, • overstorymortalityfollowedbyephemeralregeneration,and • overstorymortalityfollowedbyregenerationofdifferentgenets(clones).


It isalsocritical to identify thegenetic factorsand issuesassociatedwiththe current aspendie-off.Potential factorsat thegenet level includeageneticsusceptibilityand/orlowfitnessofparticulargenetsthatisnowbeingexpressedunderchangingclimates.Giventhesuspectedageofsomeaspenclones,anotherfactormightbetheaccumulationofdeleteriousmutationsinoldergenetsthathaveexistedon-siteformanyyears.Earlierresearchhasshowndifferencesingrowthanddevelopmentinaspenthatcanbeattributedtothegenderinthispredominatelydioeciousspecies.Gendercouldalsoplayaroleinthedistributionandoccurrenceofaspenmortality.Inbreedingdepressioncouldalsobeafactor,ascouldthelackofphenotypicplasticityinparticulargenets. Potentialfactorsthatmightbeoperatingateitherastandorlandscapescalemightincludelownumbersofgenetsinastand,lowgeneticdiversityamonggenetsinthestand,ahighdegreeofrelatednesswithinastand,andlowlevelsofsexualreproductioninsomegenotypesorunderspecificecologicconditions.

Research Needs

Geneticresearchneedsincludeestablishingtheclonalboundarieswithinstandsbeingstudiedsothattheexistenceofdifferentgenotypesisknownwithrespecttotheoccurrenceofaspenmortality.Suchgenotypemappingshouldaccompanyresearchintoaspenregenerationtreatmentsandassessmentstodetermineormea-suretheroleofgeneticsinobservedresponses.Thisshouldalsobeacomponentofinventoryandmonitoringofaspen. Identifyinggenetictraitsthatmightbeassociatedwithdie-offisimportantaswell.Thiscouldinvolvelearningwhattradeoffsmightexistamongtraits(forexample,chemicaldefenseversusgrowth)thatmightbecontributingtoaspenmortalityandidentifyingwhetherthesetraitsareheritableorplastic.Potentialtraitsofinterestpossiblyrelatedtodie-offsusceptibilityincludedifferencesincavitationpotentialamong genotypes and physiologywith respect to above- versus below-groundviability.Geneticdifferencesinrootdeathrateandsecondarychemistry(herbivoryresistance)couldinfluencesuckeringrateandsuckersurvivabilityand,therefore,mightaffectsusceptibilitytoandtheultimateoutcomeofmortalityevents.Theroleofgeneticsintreestructure,pathogenresistance,droughtresistance,andfloodingresistancemightalsoinfluencetheoutcomeofaspenmortalityevents. Otherusefulinformationmightincludedeterminingtheextentthatrootgraftingoccursamongdifferentgenetsandquantifyingwhetherlossesinaspencoveragearecongruentwithlossesinthenumberofgenetsinaspenpopulations.Determininghowaspenstandstransformfrommonotypictodiverseandback(inotherwords,clonaldynamics)mayalsobeveryusefulinexplainingtheaspenmortalityphenom-enon.Althoughitmaynotbedirectlyrelatedtothecurrentaspenmortalityissue,determiningtowhatextentgenetdiversityinfluencesthediversityofunderstoryplants,insects,andsoforthinanaspenpopulationcouldbeenlightening.Thisistheconceptof“extendedphenotype”describedbyWhithamandothers(2003). Inadditiontogeneticinformation,knowingwhatenvironmentalconditionsareassociatedwithdie-offsisalsoimportant.Factorssuchassoils,slope,aspect,grazing/browsing,othertree/shrubpresence,climatehistory,anddiseaseoccur-renceshouldalsoberecordedinanyaspenassessment.


Testable Hypotheses

Thefollowinghypothesesneedtobetestedwithrespecttoaspengeneticsandcurrentaspenmortality: Hypothesis 1: Thenumberofgenetsinwesternlandscapesisdeclining(aseparate

phenomenonfromdecreasesinspatialcoverage). Test by: Collectinggeneticsdatainconjunctionwithestablishingsampling

plotsforlong-termmonitoringinconjunctionwithFIAatabroadgeographicscale.

Hypothesis 2: Aspenmortality is genet-specificwithin stands (HA:Die-off isacrossgenets).

Test by: Establishingsamplingplotsandcollectinggeneticsdataforlong-termmonitoringatafine-scaleresolution(fewerplotsbutmoredensesamplingthanH1),focusingonareasexperiencingdie-off.

Hypothesis 3: Lossofaspenarerelatedtomaladaptationinthefaceofclimatechange.

Test by: Usingacommon“garden”approachtoassessfitnessofgenotypesfromdifferentenvironments(clone-specificeffects).

Additionalbasicresearchneedsthatdon’tfitneatlyintotheabovehypothesestestingincludedeterminingtheextentofsexualreproductionamongaspengenotypesandstudyingmutationaccumulationandfitnessamongaspen.Developingmoreefficientwaysofsexingandagingaspenclonesandquantifyingtheextentofrootgraftingwouldbeuseful,aswouldinvestigating“extendedphenotype”effectsortheecologicaleffectsofaspengeneticdiversitywithinlandscapes.

Silviculture/Management Working Group Report

Define and Clarify Terminology

There isacriticalneed todefineandclarify terminologyassociatedwith therapidmortalityofaspen.Afirststepistoidentifywhetherthecurrentmortalityistrulyacrisisorjustanormaloracceleratedmortalityofoldtrees.Identifyinganyrelationshipsbetweenrametageandoccurrenceofmortalityiscrucial.Second,thereisaneedtoidentifyandquantifyanydifferencesinmortalitybetweenaf-fectedstandswithconiferencroachmentandthosewhereconiferencroachmentisnotoccurring.Ifmortalityisindeedstressrelated,thenthepresenceofconifershouldcontributetoeithertherateorincidenceofmortality.Finally,anycommonfactorsthatmightberelatedtocausalityneedtobeidentified. TheSilviculture/Managementgroupidentifiedthreedistinctconditionsthatcanbeassociatedwithaspenmortality:

• Overstorymortalitywhereregenerationofaspenareoccurring • Overstorymortalitywithoutsuccessfulregenerationofaspen • Overstorymortalityofaspenwhereconiferregenerationispresent,but

aspenregenerationisnotorisinsufficienttomaintainthepresenceofaspenonthesite


TheSilviculturegroupconcludedthattherewasnocauseforconcern,fromanecologicstandpoint,ifsufficientaspenregenerationisoccurring,oralreadypresent,todevelopintoafullystockedaspenstand.Whilethelossofamatureoverstorymightberegrettablefromanaestheticorwildlifehabitatstandpoint,itiswithintheexpected rangeofnaturalconditions foradisturbance-dependent relativelyshort-livedtreespeciesthatvegetativelyregenerates.However,ifregenerationisnotoccurringthesituationbecomesmorecritical.Ifsproutingisoccurringbutnotsuccessful,thereasonsneedtobeidentifiedandcorrected.Ifsproutingisnotoc-curring,thereasonsneedtobeidentified.Ifrootshavedied,wehavetoacceptthelossofaspenonthesiteandconcentrateourmanagementeffortsonareaswherethepotentialtoregenerateaspenstillexists.

Critical Research Questions

Severalquestionsmustbeansweredinsituationswherematureaspentreeshavediedbutsuccessfulregenerationisoccurring: • Whenregeneration(aspen)isoccurringunderadeadoverstory,howoldis

theunderstory? • Doestheregenerationpre-datetheoverstorymortality(e.g.,wasthestand

regeneratingpriortotheonsetofoverstorymortality)? • Ifso,whatfactorstriggeredtheregenerationresponse? • Ifnot,whywerethesestandsabletoinitiateregenerationwhenotherswere

not? • Couldpressurefrombrowsinganimalsbeafactor? Severalquestionsmustbeansweredwherematureaspenstandshavediedandregenerationisabsent: • Didthestandsattempttoregeneratebutsomethingkilledthesprouts? • Wastheoverstorytooweaktosprout? • Hadtoomuchtimeelapsedsincethelastdisturbancetoinitiatesprouting? • Didlateralrootsdiewhenoverstorystemsdied(orconversely,didrootsdie

firstandcausetheoverstorymortality)?

Whereconifersarepresent inaffectedaspenstands, theircontribution to theconditionsleadingtoaspenmortalityneedstobeidentified: • Didtheyout-competetheaspenformoisture,nutrients,orlightandthus

initiateaspenmortality? • Didtheirpresencecontributetothelackofaspensproutingbyshadingthe

soils?

Sinceliverootsarethekeytotheaspensuckeringprocess,itiscriticalto: • identifyhowaspenrootsareaffected; • findwaysofassessingaspenrootconditionpriorto,during,andafterover-

storymortalityhasoccurred;and • relaterootconditiontoanyfactorsthatmightbeidentifiedascontributing

tothisrapidmortalityphenomenon.


Inadditiontoansweringtheabovequestions,itiscriticaltoidentifyIntermountainWestbiodiversityhotspotswheremaintenanceofaspeninlandscapesiscriticaltoecosystemsandtodevelopameanstoprioritizetheneedformanagementinterven-tion.Tofacilitatethisprocess,thefollowingterminologymightbeadoptedtohelpdifferentiatebetweenvariousaspectsofaspensuccessionandclonalturnover.

Terminology

Die:when≥80percentoftheoverstorystemsinaclonediewithin3to5years. Die-off:notenoughregeneration(suckering)toperpetuatestanddueto

a)aphysiologicalfailureoftheaspentorespond,or b)thevegetativereproductionsystemis“turnedoff.”

Die-back:regenerationissufficienttoperpetuatetheclone

a)withpriorregenerationpresent,or b)whenregenerationcoincideswithoverstorymortality,or c)whenthereisagradualoverstorydecreaseinstandswithorwithout

conifers.

Bothdie-offanddie-backcanbeapartofthepathologicdefinitionof“decline,”butbothoccurveryrapidly.Wepreferthattheterm“decline”beusedtorefertothegradualdeathofaspenoverstoryineitherpureaspenstands,orinconjunctionwithconifer invasioninmixedaspen/coniferstands,whichisdescriptiveofanecologicratherthanpathologicprocess1.

Additional Questions Associated With This Classification

• Is themechanismforoverstorymortality thesamewhetherornotaspenregenerationoccurs,orwhetherornotconifersarepresent?

• What are the patterns of mortality progression associated with rapidmortalityofaspen?

• Doesmortalityradiatefromacentralpointoroccursimultaneouslythrough-outthestand?

• Ismortalitylimitedtoonegenotypeataspecificsiteordoesitcrossclonalboundaries?

• Istheabovedefinitionofrapiddeathvalid(forexample,3to5yearsfromonsettocompleteoverstorymortality)?

Assessment Needs

Itisimportanttogatherconsistentinformationtoaccuratelyassesswhatishap-peningtoaspenthroughouttheWestandcompileconsistentdatathatcanbeused

1 Compilers Note: In the time since the meeting, the term “Sudden Aspen Decline” (SAD) has been used to describe conditions associated with the rapid mortality of aspen trees. Within this context, we feel the distinctions made by the “die-off” versus “die-back” definitions formulated by the Silviculture Working Group above are still valid and should be considered, regardless of the terminology used to describe the overall rapid aspen mortality process.


toanswertheabovequestions.Assessmentprotocolsshouldbedevelopedtosurveyaspenmortalitythatfallsintothecategoriespreviouslydescribed. Categoriestosurvey:

1)die-off(noregenerationpresent) 2)die-back a. priorregeneration(existedbeforemortalitystarted) b.coincidentalregeneration(initiatedbytheoverstorymortalityevent)

Thesurveyshoulddefinehowmanyacresofeachexistandlistotherfactorsthatmaybeassociatedwitheachcategory,suchas:

• insectanddiseaseoccurrence,especiallyCytospora, • elevation, • aspect, • ungulatepressure, • drought, • currentvegetation(habitattypes), • currentvegetation(soils),and • treatments (if any) used to dealwith aspenmortality and their apparent

effectiveness.

A template for providing consistent treatment application and monitoringthroughouttheWestshouldbedeveloped.Coincidentally,amechanismshouldbedevelopedtofacilitatecollaborationandcommunicationamongallaspenmanagersintheWest

Suggestions for Initial Research and Inventory

1.Ineachofthethreedie-off/die-backcategories,determinethenumberofacresinlandscapescontainingaspenthatareaffectedbyrapidaspenmortality.ThistaskcouldbedonebytheForestService’sForestInventoryandAnalysis(FIA)andForestHealthManagement(FHM)usingtheFIAdatabaseandexistingFHMinsectanddiseasesurveytechniques.

2.Quantifybioticfactorsandabioticstandcharacteristicsassociatedwitheachofthethreedie-off/die-backcategories.Thiswouldmostlikelyinvolvecol-laborationamongFHM,university,andForestServiceresearchers.

3.Determine the causal agents behind rapid aspenmortality (for example,theresponsiblemechanismsorfactors).Again,datasharingandamulti-disciplinaryapproachwilllikelybeneeded.

4.Todealwiththephenomenon,testmanagementactionsanddetermineaneffectivemanagementtimeframeforaction.Thiscouldbestbeaccomplishedbymanagersworkingcollaborativelywithuniversityand/orForestServiceresearchers.

Intheshort-term,thedevelopmentofacommonprotocolfortreatmentexecutionandmonitoringisessentialinboththeearlyandlatestagesofaspenmortality.Thiswouldincludeapre-treatmentstandassessmentinventoryprotocoltoassessandquantifytheconditionofthestandsbeforetheyaretreated,aswellascommonmetricstoassesstheeffectivenessoftreatment.


Anothercriticalshort-termneedistoestablishaclearinghouseoraleadorganiza-tiontoensurecollaborationandprovidefeedbackamongmanagersandresearchers.Thiswouldincludesharingofinventoryandmonitoringdataandpre-publicationsharingandreviewofresearchdata.Theclearinghouseshouldhaveanofficialdatastewardtobuildandmaintaindatasets,maintainanddisseminatewebsiteinfor-mation,andensuredatacompatibilityandsecurity.Theclearinghouseshouldalsohaveapointpersonorfacilitatorwhowouldinteractwithstakeholders(managers,universities,researchers)tosecureanearmarkforfundingtodealwiththeaspenmortalityissue.

Overall Needs

Definition of Terms

Severalcriticalneedsandthemeswereevidentacrosstheworkinggroups.Fore-mostwastheneedforclarificationoftheterminologyusedtorefertothetypesofaspenmortalitythathavebeenobservedandreported.Allgroupsemphasizedtheneedforclearandsuccinctdefinitionsofthephenomenaandthetermsusedtodefinethecurrentmortalityofaspen.Subsequently,weendorsetheexplanationandterminologypresentedbytheForestHealthWorkingGrouptodescribedeclineinorganisms.However,thismodelisstillinadequatetodescribethesituationoc-curringinaspenpopulationsatlandscapescales.Termspreviouslyusedtorefertoaspenmortalityarealsoinadequateandcausedconsiderableconfusionduringmeetingdiscussions.Duringhissummaryremarks,DavidCleaves,DirectoroftheUSDAForestServiceRockyMountainResearchStation[currentlyAssociateDeputyChief,WO],suggestedtheacronym“SAM”forSuddenAspenMortalitybeusedtoavoidthevalue-ladenconnotationsassociatedwith“die-off”and“die-back”andtheconfusionwiththeclassicpathologicdefinitionof“decline.”2

However,SuddenAspenMortalitydoesnotcoveralloftheconditionsreportedanddiscussedatthemeeting.Anadditionalclassificationisneededtodifferenti-ateamongspecificmortalityeventsthathavebeenobservedandreported.Twoalternativelistsofconditionsweresuggestedbytheworkinggroups.WesuggestadoptingthefollowingwordmodelmodifiedfromtheSilvicultureandManage-mentgroup.Itprovidesaframeworkfordistinguishingamongmortalityeventsandallowsameansofinvestigatingspecificquestionsrelatedtotheevents:

1.Overstorymortalitywhereregenerationofaspenareoccurring 2.Stand (clone?) mortality—Overstory mortality without sufficient aspen

regenerationtomaintainaspenonthesite. o Coniferregenerationislargelyabsent o Coniferregenerationispresent

2 Compiler’s note: In the time since the meeting this term has morphed into “Sudden Aspen Decline,” which is consistent with the pathologic definition of decline presented earlier.


ThismodelisconsistentwiththedefinitionsproposedbytheForestHealthgroup,as“die-back”couldrefertothedeathofapartofanaspengenotypeexistingonasite,andthemortalityofastandorclonecouldbeconsideredtobetheresultofa“decline.”Manycriticalknowledgeneedsandquestionsposedbytheworkinggroupscouldfitwithinthisclassification.Mostgroupscalledfortheneedtoidentifyandquantifysiteandbioticfactorsassociatedwithaspenmortality.Additionally,suggestionswereofferedtoquantifyclimaticandmeteorologicalfactorsassociatedwithmortality,includingsitefactorssuchassoil,physiographicposition,aspect,andassociatevegetation. Investigation isalsoneeded into therole thatclimatechangemightplayintheaspenmortalityphenomenon,specificrelationshipsbe-tweendroughtandmoisturestress,andlongtermdiseaseandinsecteffects.Betterknowledgeoftherelationshipsbetweenchangesinfireregimesandcurrentaspenmortalitywasidentifiedasyetanothercriticalneed.

The Role of Herbivores

Severalworkinggroupsdiscussedtheneedtolearnmoreabouttheroleofherbi-voresinaspenmortalityevents.Specificneedsincludeaspen/herbivoreinteractionsandinter-dependency,whetherherbivorescanbeavectorforpathogensthatcaninfectaspen,andidentificationofcircumstanceswhereaspenneedprotectionfromherbivores.Especiallyimportantistheneedtolearnatwhatscalesandunderwhatconditionsherbivoresbecomeproblematicinaspenforests.

The Role of Aspen Roots

Theneedtolearnmoreabouttherolethataspenrootsplayinthevariousmortal-ityscenarioswasmentionedrepeatedly.Areaspenrootsreallydeadinsituationswheresproutingdoesnotoccur?Ifso,aretheydyingbeforeoraftertheoverstorytreesdie?Doesrootgraftingplayaroleinavoidingorcontributingtocompletestandmortality?

Genetics

Alackofkeygeneticknowledgewasidentified.Whatroledoesgeneticsplayinthemortalityprocess?Cansusceptiblegenotypesthatarepredisposedtomortalitybeidentified?Iscloneage(theamountoftimeagenotypehasexistedonasite)relatedtomortalityoccurrence?Aremaleorfemaleclonesmoresusceptibletomortality?

Rapid Assessment

A theme common to allworking groups, and subsequent discussions by theentiregroup,istheneedforarapidassessmentofaspenthroughouttheWestto(1)determinethecurrentstatusandprojectedtrendsofaspenforestsand(2)moreaccuratelyquantifythemagnitudeandextentofmortality.Theneedtoestimatethedurationofmortalityandprojecttheeconomicandecologiceffectsassociatedwithitisespeciallycriticaltomanagers.Identifyingstockingmetricsassociatedwithmortalitywouldbeveryuseful,especiallyifaspenlosscouldbeassociatedwithage,growthrate,stockingconditions,orotherbioticfactors.


Recommended Actions

Althoughworkshopparticipantsidentifiedanumberofresearchandmanagementneedsthatcouldimproveourunderstandingoftheprocessesinvolvedinthecur-rentaspenmortalityevents,wesuggestthatthemostcriticalneedistodevelopacommonrapidassessmentprotocolthatcouldprovidecomparabledatathatwouldmeetbothmanagementandresearchobjectives.Withthatinmind,werecommendthefollowingactions:

• Formamulti-agencytaskforcetodevelopacommonrapidassessmentpro-tocolthatcombinesremotesensingandgroundbaseddataaboutthecurrentconditionofaspenforestsand includesmethodologyanddataneeded tomonitorandassessmortalityevents.Thetaskforce,afterconsideringspe-cificdataneedsoutlinedintheworkinggroupreports,shouldrecommendaspecificprotocoltemplatethatwillallowconsistenttreatmentapplicationandmonitoringoftheaspenresourcethroughouttheWestandprovideinforma-tiontoplanfuturemanagementandresearchactivities.Subsequentresearchhasusedsimilarprotocols;howevernouniversalonehasbeenadapted.

• Holdafuturemulti-partnerworkshopafterthe2007fieldseasontore-assessthecurrentstateofaspenresources throughout theWest.Thisworkshopshouldbeavehicle to share informationcollectedduring the2007 fieldseason, identify additional research needs, and recommendmanagementactionsbasedonthenewinformation.[Update:ASuddenAspenDecline(SAD)meetingwasheldFebruary12-13,2008,inFort.Collins,CO.ThismeetingreportedeffortsconcerningSADforthe2007fieldseason.Awidevarietyof studies and issueswerepresented anddiscussed.Anuneditedsummaryofthismeeting,compiledbyPaulRogers,canbefoundathttp://www.western-aspen-alliance.org/.Thesummarycanbefoundbyactivating“Links”ontheleftsidebarandopening“SummaryoftheSuddenAspenDeath(SAD)…2/08.”]

• Reviewstate-widewildlife and fishcomprehensiveplans andTNCeco-regionalassessmentstoidentifyaspen-relatedissues,trends,andneeds.TheForestServiceSOPAdocumentsdatabaseshouldbereviewedtoidentifyspecificsiteswherevegetationmanagementprojectsareplannedorhavebeencompleted inaspenforests.This informationwillbeveryuseful intargetingresearchandmonitoringtoascertainhowparticularmanagementactivitiesaffecttheaspenresource.

• DevelopamechanismtofacilitatecollaborationandcommunicationamongallaspenmanagersandresearchersinthewesternUnitedStates.Thiscouldtaketheformofauniversityoragencyfundedinstituteoraninformalcol-laborativeworkinggroupthatwouldserveasaclearinghouseforinforma-tionanddiscussionconcerningaspen.Anintegralpartofthisorganizationwouldbetoserveasaconduitofinformationbetweeninterestedparties,providing assistance, consulting services, and disseminating informationthroughtheinternetorotherinformaloutlets.[Update:AjointeffortbetweenRockyMountainResearchStation(RMRS)andUtahStateUniversity(USU)hasresultedintheWesternAspenAlliance(WAA)beingformed.AformalMemorandumofUnderstanding(MOU)hasbeenestablishedbetweenRMRS


andUSUtovalidatethisAlliance.TheWAAisaconsortiumofresearchersandmanagerswhowillcoordinateandfacilitateadvancesinaspenecologyinwesternNorthAmerica.TheWAAprospectus(fig.5)andwebsite(http://www.western-aspen-alliance.org/) contain additional information on theAlliance.]

Figure 5. Prospectus for the Western Aspen Alliance (WAA).


References

DeByle,N.V.;Winokur,R.P.,eds.1985.Aspen:EcologyandmanagementinthewesternUnitedStates.Gen.Tech.Rep.RM-119.FortCollins,CO:U.S.DepartmentofAgriculture,ForestSer-vice,RockyMountainForestandRangeExperimentStation.283p.

Manion,P.D.1981.Treediseaseconcepts.Firstedition.Prentice-Hall,EnglewoodCliffs,NewJersey.402p.

Mueggler,W.F.1989.AgedistributionandreproductionofIntermountainaspenstands.WesternJournalofAppliedForestry.4(2):41-45.

Ohms,S.R.2003.RestorationofaspenindifferentstagesofmortalityinsouthernUtah.M.S.Thesis.UtahStateUniversity,Logan,UT.99p.

Shepperd,W.D.1993.Theeffectsofharvestingactivitiesonsoilcompaction,rootdamage,andsuckeringinColoradoaspen.WesternJournalofAppliedForestry.8(2):62-66.

Shepperd,W.D.;Rogers,P.C.;Burton,D;Bartos,D.L.2006.Ecology,biodiversity,management,andrestorationofaspenintheSierraNevada.Gen.Tech.Rep.RMRS-GTR-178.FortCollins,CO:U.S.DepartmentofAgriculture,ForestService,RockyMountainResearchStation.122p.

Whitham,T.G.;Young,W.P.;Martinsen,G.D.;Gehring,C.A.;Schweitzer, J.A.;Shuster,S.M.;Wimp,G.M.;Fischer,D.G.;Bailey,J.K.;Lindroth,R.L.;Woolbright,S.;Kuskeet,C.R.2003.Communityandecosystemgenetics:Aconsequenceoftheextendedphenotype.Ecology.84(3):559-573.

Worrall,J.J.;Egeland,L.;Eager,T.;Mask,R.A.;Johnson,E.W.;Kemp,P.A.;Shepperd,W.D.2008.RapidmortalityofPopulus tremuloidesinsouthwesternColorado,USA.ForestEcologyandManagement.255:686-696.


Appendix

List of attendees at the Aspen Summit Meeting, Salt Lake City, Utah, December 18 and 19, 2006.

Name Organization

Bill Jacobi Colorado State UniversityBrian Kurzel Colorado State ParksCarl Edminster USFS - Rocky Mountain Research StationCindy Swanson USFS - Region 1Dale Bartos USFS - Rocky Mountain Research StationDarren McAvoy Utah State UniversityDave Cleaves USFS - Rocky Mountain Research StationDavid Burton Aspen Delineation ProjectHenry Lachowski USFS - Remote Sensing Applications CenterIngrid Aguayo Colorado State Forest ServiceJack Troyer USFS - Region 4James Hoffman USFS - Region 4James Worrall USFS - Region 2Janine Powell USFS - Rocky Mountain Research StationJim Long Utah State UniversityJohn Guyon USFS - Region 4John Shaw USFS - Rocky Mountain Research Station Julia Richardson USFS - Region 4 (Humboldt-Toiyabe NF)Karen Mock Utah State UniversityKen Hehr USFS - Region 2 (San Juan NF)Laura Moffitt USFS - Region 4 MaryLou Fairweather USFS - Region 3Melissa Jenkins USFS - Region 4 (Caribou-Targhee NF)Michael Wilson USFS - Rocky Mountain Research StationMike Duncan USFS - Region 4 (Dixie NF)Mike Kuhns Utah State UniversityPhillip Kemp USFS - Region 2 (San Juan NF) (Retired)Robert Campbell USFS - Region 4 (Fishlake NF)Ron Ryel Utah State UniversitySkip Smith Colorado State UniversitySteve Ambrose USFS - Rocky Mountain Research StationSteve Solem USFS - Rocky Mountain Research StationTim Garvey USFS - Region 2 (Grand Mesa, Uncompahgre & Gunnison NF)Tom Martin USFS - Region 4Valerie Hipkins USFS - Pacific Southwest Research StationVicki Berrett USFS - Rocky Mountain Research StationWayne Shepperd USFS - Rocky Mtn. Res. Station (Retired)


Rocky Mountain Research Station

The Rocky Mountain Research Station develops scientific information and technology to improve management, protection, and use of the forests and rangelands. Research is designed to meet the needs of the National Forest managers, Federal and State agencies, public and private organizations, academic institutions, industry, and individuals. Studies accelerate solutions to problems involving ecosystems, range, forests, water, recreation, fire, resource inventory, land reclamation, community sustainability, forest engineering technology, multiple use economics, wildlife and fish habitat, and forest insects and diseases. Studies are conducted cooperatively, and applications may be found worldwide.

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Research Locations

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the aspen mortality summit

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