Achieving sustainable management of boreal and temperate forests Edited by Dr John A. Stanturf Estonian University of Life Sciences, Estonia
BURLEIGH DODDS SERIES IN AGRICULTURAL SCIENCE
E-CHAPTER FROM THIS BOOK
http://dx.doi.org/10.19103/AS.2019.0057.09Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States: projections and implications for forest managementW. Keith Moser, USDA Forest Service, USA; Patricia Butler-Leopold, Michigan Technological University and Northern Institute of Applied Climate Science (NIACS), USA; Constance Hausman, Cleveland Metroparks, USA; Louis Iverson, USDA Forest Service and Northern Institute of Applied Climate Science (NIACS), USA; Todd Ontl, Michigan Technological University and Northern Institute of Applied Climate Science (NIACS), USA; Leslie Brandt, USDA Forest Service and Northern Institute of Applied Climate Science (NIACS), USA; Stephen Matthews, Northern Institute of Applied Climate Science (NIACS) and The Ohio State University, USA; and Matthew Peters and Anantha Prasad, USDA Forest Service and Northern Institute of Applied Climate Science (NIACS), USA
1 Introduction 2 Climateprojectionsandtheirinfluenceonforestlandtrendsinthe
medium term—the Northern Forests Futures Project 3 Methodsofprojectioninthelongterm:modelingprojectedchangesin
habitat and potential migration 4 Ecoregional vulnerability assessments 5 Management implications 6 Conclusionandfuturetrends 7 Acknowledgements 8 References
1 IntroductionForestsplayanessential role in thesocial,economic,andecological livesoftheinhabitantsofthenorthernUnitedStates.Forestscover69.6millionha,or42%of the landareaof this region,which isboth themostheavily forestedand themost densely populated quadrant of the United States (Fig. 1). Topreserve a full rangeof forest ecosystem services into the future,managersare working to identify and implement strategies and tactics that take into
The impact of climate change on forest systems in the northern United States
The impact of climate change on forest systems in the northern United States
Chaptertakenfrom:Stanturf,J.A.(ed.),Achieving sustainable management of boreal and temperate forests, BurleighDoddsSciencePublishing,Cambridge,UK,2019,(ISBN:9781786762924;www.bdspublishing.com)
The impact of climate change on forest systems in the northern United States2
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account thepotentially dramatic effects of a changing climate (Nagel et al.,2010).Theregionencompassesalmost30°oflongitudeand10°oflatitudeandextendsfromtheAtlanticOceanwesttotheGreatPlains,containing20states:Connecticut, Delaware, Illinois, Indiana, Iowa, Maine, Maryland, Massachusetts, Michigan,Minnesota,Missouri,NewHampshire,NewJersey,Ohio,Maryland,Pennsylvania, New Hampshire, New York, Rhode Island, and Wisconsin.
Managersplanatseveraldifferentscalesandoverlappingtimehorizons.Inthischapter,weintegratedifferentanalysesthatprovidearangeofprojectedoutcomes over the medium and long term. In this chapter, we use several case studiestosuggestsomepotentialpathwaysformanagersseekingtoalleviateor otherwise mitigate potential climate change impacts. The intention is toprovideexamplesofstudiesat several scalesofanalysis,usingvarious toolsofanalysisandreporting.Readerscanthenmovewithintheirscaleofanalysisor interest to pursue the details cited within these case studies. We start with characterizationsofmid-andlong-termprojectedclimatechangeimpactsfortrees and forests of the northernUnited States. Particular attention is drawntotheimpactsofmorefrequentandsevereprecipitationanddroughtevents.Wethenscaledownthediscussiontoexamplesfromthethree-stateCentralAppalachians region, and last provide local examples in rural and urban landscapes. We conclude with some lessons learned and recommendations thatmanagersmightconsiderastheycrafttheirownstrategies.
Figure 1 Distributionofforest-typegroupsinthenorthernUnitedStates,2010.Source:adaptedfromGoerndtet al.(2016).
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2 Climate projections and their influence on forestland trends in the medium term—the Northern Forests Futures Project
2.1 The modeling process
A multistep process and many datasets were used to explore the potential medium-termimpactofeconomics,demographics,andchangingclimateontheforestedlandscapeofthenorthernUnitedStates.Trendsinforestdynamicsandtheresultantchangesinforestattributesintheregionwereprojectedandanalyzedfortheperiod2010–2060usingtwocyclesofdatasetsfromtheUSDAForestService,NorthernResearchStationForest InventoryandAnalysis (FIA)program (Woudenberg et al., 2010). Future forest conditions were imputedfrom the Forest Dynamics Model (Wear et al., 2011), which was previouslyemployed in the national-level analysis of future conditions in ResourcesPlanningAct(RPA)assessments(USDAFS,2012a,c).Thedataweredownscaledso that theycouldbematchedupwith individualFIAplots (USDAFS,2011;Goerndtetal.,2016).TheIntergovernmentalPanelonClimateChange(IPCC)describedasetofemissionsscenariosor‘storylines’1basedonassumptionsofpopulationgrowth,economics,andtechnologicalchanges.TheIPCCcreatedfourfamilies(A1,A2,B1,andB2)ofscenarios(Nakićenovićetal.,2000),fromwhich 12 individual storylines were developed. By using assumptions about changes in land use, population, and climate, along with modeled disturbances causedbyharvestingofforestproductsandinsect(emeraldashborer;Agrilus planipennis)attack,threestorylineswerelinkedwithclimatemodelstoprojectclimate scenarios and the associated future forest conditions at the locallevel(Goerndtetal.,2016;ShifleyandMoser,2016).Theseanalysesresultedin 13 future scenarios, ofwhich sevenwere studied in depth and three arepresentedinthefollowingdiscussion.
Analyses for the RPA assessment projected the entire US populationto increasebetween2010and2060 from309millionpeople to397millionfor the B2 scenario, 447 million for the A1B scenario, and 505 million fortheA2scenario,or increasesof29%,45%,and64%, respectively (USDAFS,2012b; Zarnoch et al., 2010). These population estimates are based on the2004 Census population series for 2000–2050, which were extrapolated to2060(USDAFS,2012b).Usinghumanpopulationprojectionsincorporatedintothe2010RPAanalyses(USDAFS,2012b),theNorthernForestFuturesProject(NFFP)projectedpopulationforthenorthernUnitedStatesandthenallocatedtheexpectedpopulationtothestatesandtheircounties(Zarnochetal.,2010;USDAFS,2012c;Goerndtetal.,2016).Thepopulationofstatesinthenorthern
1‘coordinatedgroupsofassumptionsthatdescribefuturepopulation,economicactivity,landuse,bioenergyuse,andassociatedgreenhousegasemissions’Goerndtet al.(2016).
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UnitedStatesareexpectedtoincreasefrom125millionin2010to140million(B2scenario),158million(A1Bscenario),andto178million(A2scenario)by2060,or increasesof12%,25%,and39%, respectively (Fig. 2). States alongtheAtlanticOceanseaboardareprojected tohave thegreatest increases inpopulation(Fig.3)(Goerndtetal.,2016).
Scientists throughout the world have developed models that project and map changes in selected weather factors, such as precipitation andtemperature,basedoneachoftheindividualIPCCstorylines.Fromthesemanycombinations,NFFPselectedtwoversionsofa‘middle-of-the-road’model,theCanadianGlobalCirculationModel (CanadianCentre forClimateModellingandAnalysis2012a,b;ShifleyandMoser,2016).Theseversionsformthebasisforthecalculationsinthefollowingdiscussion.
TheNFFPusedtheForestDynamicsModel(Wearetal.,2013)toprojectchangesintreeandstandconditions.ProjectionsoffutureFIAplotconditionswere used to model future wood volumes, species groups, and a host ofecosystemservices(Goerndtetal.,2016;Moseretal.,2016;Taverniaetal.,2016). Plotswerepartitioned intogroupsbasedonbiophysical, standage,and climate factors, with growing stock volume per ha used as a point ofsimilarity.
Changes in landusearea functionofchanges inpopulation,economicactivity,andanypotentialclimatechangeinfluenceoverthe50-yeartimeperiod
Figure 2 Projected increases inpopulationof thenorthernUnitedStates,2010–2060.Source:adaptedfromGoerndtet al.(2016).
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ofthisstudy(Wearetal.,2013;Goerndtetal.,2016).TheNFFPusedlanduseprojections fromtheRPAassessment (USDAFS,2012c),whichassumedthattherewouldbenolandusechangesonfederalforestlandacrossthenorthernUnitedStates, and that nonfederal forest landwoulddeclineby two to fourmillion ha by 2060.
ProjectedharvestinglevelswereextrapolatedfromobservedharvestinginthepriorFIAinventoriesandtiedtovariablesoftreesize,age,species,density,stand diversity, site conditions, and previous harvest types (full or partial)(Wearetal.,2013;Goerndtetal.,2016).Modelalgorithmsreplacedinventoryplots affected by harvesting with suitable replacement plots representingthe postharvest conditions (e.g. a newly regenerated plot; Goerndt et al.,2016).Atransitionmodel,whichpredictedchangesinplotageandspeciescompositionovertime,determinedforestage,harvesting,andregeneration.Theseprojectedvalues,alongwithclimatevariables,wereappliedasinputstoan imputationmodel.Thismodel selecteda replacement (updated)plotfroma subset of observedFIAplots ‘thatbestmatches conditions that areprojectedforeachplotlocation’,basedonage,speciesgroup,climate,andproportionsofhardwoodandsoftwood.Thisnewplotbecame the startingpoint for the next 5-year projection. Results for all plots were summarizedat theendofeachintervalandusedasastartingpoint forthenext interval(Goerndtetal.,2016).
Projected population density change(people per square kilometer)
Under 1 1 to 10 11 to 58 Over 58
Figure 3 Patternofprojectedpercentageincreasesinpopulation(2010–2060)undertheA2storyline.Source:adaptedfromGoerndtet al.(2016).
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2.2 Northern Forest Futures Project results of the medium-term projections
According to the analyses for theRPA (USDAFS, 2012c), the areaof forestlandinthenorthernUnitedStateswilldecreasefrom70millionhain2010to66millionha(a6.4%decrease)undertheA1Bscenario,67millionha(a5.4%decrease)undertheA2storyline,and68millionhectares(a3.5%decrease)under theB2storyline (Fig.4).Thegreatestdeclinesareexpected tooccurnear urban areas and in states along the eastern seaboard, which are also highlyurbanized.Percapitaforest landareainthenorthernUnitedStates isexpectedtodeclinefromabout0.6hato0.4haasthepopulationincreasesand forest land areadeclines (Moser et al., 2016).Oak/hickory andmaple/beech/birchforest-typegroups,togethermakingup61%offorestlandareain2010,willcontinuetobethemostprominentforest-typegroupsunderallthreescenarios,withaprojected64%offorestlandareain2060(Table1).Despitethis prominence, oak/hickory is expected to decrease slightly in the area under allscenarios,alongwithelm/ash/cottonwood,spruce/fir,andaspen/birch.Themaple/beech/birchforest-typegroupisexpectedtoincreasesomewhatinthearea under all scenarios.
Figure 4 Forest land area, historical and projected, in million hectares, 1900–2060.Source:adaptedfromMoseret al.(2016).
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The extent of each forest-type group is expected to change over the50-year projection period (Table 1; Moser et al., 2016). The expectation oflimited current forest products harvesting being extended into the future(Shifleyetal.,2014)isexpectedtoimpedeestablishmentofearlysuccessionalforest-type groups, such as aspen/birch, thereby reducing their proportion.Anothernotablechangeistheprojectionthat5%ofthecurrentforestlandisconvertedtononforestusesby2060(Moseretal.,2016).
Approximately70%of forests in thenorthernUnitedStates in2010wasestimatedtobe40–100yearsold(Shifleyetal.,2012).Applyingslightlydifferentdefinitions of early and late successional forests, Pan et al. (2011) observedrelativelylowpercentagesofearlyandlatesuccessionalforestsintheregion.Region-wide, thecurrentproportionof forest stands in the40–100-yearagebracket isnotexpectedtochangemuch(except for thenaturalagingof thecohort)through2060(Fig.5;Moseretal.,2016;Taverniaetal.,2016).
Using calculations based on the FIA database and transition models(USDAFS,2012b;Goerndtetal.,2016),theNFFPfoundthat,particularlyinthewesternpartoftheregion,thecurrentsubstantialpercentageofyoungerageclasses isexpected todeclineover the50yearsof theprojection. Increasedbiomassharvesting(datanotpresentedhere)wouldincreasetheproportionofearlysuccessionalforestsinthefuture.Therelativelylowpercentagesofforestin the northernUnited States in 2010 that are in the 100+ year age classesare expected to change dramatically depending upon the scenario, barring substantialincreasesinharvestingorseveredisturbances(Fig.6;Moseretal.,2016;Taverniaetal.,2016).Severedisturbances,suchaswindstorms(Nelsonand Moser, 2007; Moser and Nelson, 2009) or attacks by eastern spruce
Table 1 Projectedarea,inhectares,byforest-typegroupin2060basedonforestlandareaof2010, A2 scenario
Forest-typegroup(scientificname) 2010(%) 2060(%)
Aspen/birch(Populus spp./Betulaspp.) 6 983 038 10 5 747 767 8Elm/ash/cottonwood(Ulmus spp./Fraxinus spp./Populusspp.)
4 915 592 7 4 033 138 6
Maple/beech/birch(Acer spp./Fagus spp./Betulaspp.) 18 203 541 26 18 872 550 27Nonforest - 0 3 817 506 5Oak/hickory(Quercus spp./Caryaspp.) 25 569 666 36 24 009 601 34Other 5 158 122 7 4 676 753 7Spruce/fir(Picea spp./Abiesspp.) 6 183 077 9 5 599 335 8White/red/jackpine(Pinus alba/P. resinosa/P. banksiana)
3 438 607 5 3 694 993 5
Total 70 451 643 70 451 643
Source:adaptedfromMoseret al.(2016).
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budworm(Choristoneura fumiferana)(Robertetal.,2018),couldalsoacceleratesuccession, but there were not enough historical incidents during the study periodtoaccuratelyprojectfutureoccurrences.
Density-andage-inducedmortalitywouldhaveasignificanteffectonthenumberofalllivetrees,withthetotalnumberdecreasingby10–17%(Fig.7a).Live-treevolumeonforestlandisprojectedtostayroughlythesame(Fig.7b;Moseretal.,2016).
2.2.1 Conclusions from the future forests of the northern United States project
Incontrast tothemorelong-termprojectionspresentedlater inthischapter,theexpectationsover theperiod2010–2060 focuson thedemographicandeconomic patterns behind the three climate storylines, not the changing climates themselves. Unless natural disturbance or anthropogenic activitiessuch as biomass harvesting increase considerably, the currentmiddle-agedforestcohortwillcontinuetoagewithtime(Shifleyetal.,2014).Withoutsuchdisturbances, young forests of all forest-type groups and early successionalforesttypessuchasaspen-birchwilldeclineasapercentageofthetotalforestedarea.Managers chargedwithmaintainingorenhancing thehabitat forearly
Figure 5 Distributionofforestlandageinyears,bystoryline,2010–2060.Source:adaptedfromMoseret al.(2016).
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successionalspeciesor large-scale forestbiodiversitywill face thechallengeof developing socially acceptable and economically viable approaches thatprovideforthesespeciesinanever-agingforestaswellasbuildingresiliencein response to projected changes in climate patterns.
Forest managers must deal creatively with the heightened challenges expectedinthecomingdecades.By2060,aprojected85%ofthepopulationin
Figure 6 Proportion of forest land in early successional (young; <20 years) and latesuccessional(old;>100years)habitats,2010and2060,bystorylinesandstates.Source:adaptedfromMoseret al.(2016).
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thenorthernUnitedStateswillbelivinginurbanareas(NowakandGreenfield,2016).Greaterpressurewillbeexertedonforestsasprivate forest landareadecreasesduetolandconversionsandtheaccompanyingfragmentation.Thegrowing population will put evermore pressure on forest systems tomeetdemands for consumption, such as timber and fuelwood harvesting, andnonconsumptiveusessatisfiedbyecosystemservices.Withincreasedhumancontact, nonnative invasive species are projected to expand into the forest,further reducing its capacity to provide goods and services into the future.Managementactivitiesmusttakeintoaccountincreasingtheresilienceoftheforeststocopewithahighlyvariableclimate.
Decreased utilization of forests for industrial uses will have cascadingeffectsonlocaleconomiesandemploymentinruralareas.Thecontinuationofcurrentlevelsofharvestingorotherhuman-causeddisturbancewillcontinuethetrendtowardagingofthecurrently60–100-year-oldforests,exacerbatinglowage-classdiversitylevelsandreducingcarbonsequestrationrates(Shifleyetal.,2014).
Localimpactsofclimatechangearelesscertainthanexpectedregionalandglobalimpacts.Theprojectionsofincreasedfrequencyandmorepronouncedswings in precipitation and drought cycles (IPCC, 2014; Clark et al., 2016)havethepotentialtoposechallengesforforestplanningactivitiesandplacestressontheregionalecosystem.TheexpectedchangesinthenorthernUnitedStates are not expected to be uniform and, at least for the 50-year periodunder discussion, will be more highly correlated with human demographic and invasivespeciesissuesthanclimaticinfluencesperse.
Facedwithsuchchallenges, forestmanagersmayaimtostrengthen theincreasinglyurbanpopulations’connectionswiththeir forests,helpingurbanvoters and taxpayers understand the value, the possibilities, and the limitations of their forests. At larger scales, cross-ownership collaboration—an ‘all lands
Figure 7 (a)Numberoftreesonforestland,bystoryline,2010–2060.(b)Live-treevolumeon forest land in thenorthernUnitedStatesbystoryline,2010–2060.Source:adaptedfromMoseret al.(2016).
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The impact of climate change on forest systems in the northern United States 11
approach’—is essential to counteract the decrease in ecosystem values thatthe remaining forest land area can support as greater human pressure andland fragmentation reduce forest landareaandconnectivity.Asexemplifiedin the discussion of oak decline (see Section 2.3), older forests, particularlythose composed ofmid-seral species, are oftenmore susceptible to insectand disease attack than their younger counterparts. Furthermore, a lack ofdisturbancewillresult inlimitedearlysuccessionalforests,affectingthesuiteofanimalsandplantsthatdependonearlyandmid-successionaltreespecies(Taverniaetal.,2016).
2.3 Precipitation variability and frequency and its effects on oak health
2.3.1 Background
Mostclimatemodelsprojecta futureclimateregimewhereadverseweathereventsare likely tobemore frequentandextreme (IPCC,2014;Clarket al.,2016). These weather events have the potential to exacerbate forest healthvulnerabilities by creating destructive disturbances such as severe drought events (Wehner et al., 2011; Clark et al., 2016), derechos (Pokharel et al.,2019),hurricanes (Dinan,2017),extremeprecipitationevents (Kirtmanetal.,2013), and tornadoes (Straderetal., 2017).Suchdisturbancesmay setbackthenormalpatternsof succession (Oliver andLarson,1996;Johnson,2004)or may accelerate changes to another ecological state (IPCC, 2014). Theseclimatic events can create novel conditions that the current ecosystem has not experienced before (Bauer et al., 2016) and towhich it is not adapted.The following example shows how a forest ecosystem has been subjectedto challenging current climatic conditions and suggests how future climatescenarios may exacerbate these issues.
2.3.2 Oak decline
Sinclair(1965)andManion(1981)presentedamodelofforesttreedeclinethatidentifiedthreecategoriesoffactors:predisposing,inciting,andcontributing.Thedeclinemodelforoakforestsdefinedpredisposingfactors,suchasage,long-termclimate,airpollution,orpoorsitequality,aslong-termfactorsthatstressoakforestsbyreducingtheirvigor,andhencetheaccumulationofexcesscarbohydrate reserves,of a tree.This combinationof responsesmakesoaksmorevulnerabletothesubsequenteffectsofincitingfactorssuchasdrought,defoliatinginsects,orfrost.Theseincitingfactorscreateahigherlevelofstressinatreeandcantriggertheforesthealthcomplexcalledoakdecline.Finally,contributing factorsmaybeanaccumulationofadditional inciting factorsor
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theintroductionofotherinsectanddiseasespecies.Contributingfactorsareoften the agents present during oakmortality and the oneswhich forestersfocusonthemost(Worrall,2019).
Oakdecline isa long-recognized foresthealthcomplex thatparticularlyaffectsspecies intheQuercus erythrobalanus (redoak)speciesgroup. IntheOzarkMountains ofMissouri andArkansas,Quercus species exist today on landthatwashistoricallymaintainedby frequentfireasshortleafpine (Pinus echinataMill.)forests(StarkeyandOak,1988;CunninghamandHauser,1989;Dwyeretal.,1995;Oaketal.,1996;Bateketal.,1999;GuyetteandSpetich2003).Thesepinewoodsweremostlycomposedoflarge,widelyspacedpinetreeswithanherbaceousunderstory(Schoolcraft,1821).Uponremovalofthepineoverstoryfortimberorconversiontofarmland,thesitesoftenregeneratedto Quercusspecies,suchasblackoak(Q. velutinaLam.),scarletoak(Q. coccinea Münchh.),blackjackoak(Q. marilandicaMünchh.),southernredoak(Q. falcata Michx.),andnorthern redoak (Q. rubra L.), frequently influencedbyhuman-causedfires(GuyetteandSpetich,2003;Voelkeretal.,2004).
ThislandusehistoryandsubsequentmanagementledtothedevelopmentoftheMissouriOzarkforestsintodensestandsofoaks.Standsofscarletandblackoaksbecameprevalentonridgetopsandsouth-andwest-facingslopes;sites with northern aspects containedmore northern red oak (Cunninghamand Hauser, 1989; Voelker et al., 2004). This dense stand structure createdadditional stresson the trees,which resulted instandsmoreprone to foresthealth problems than stands with widely spaced trees and high species diversity.Scarletoaks,inparticular,weremorepronetoforesthealthproblemsas they got older.
The principles of Manion’s (1981) decline complex can be applied inthis situation, where predisposing, inciting, and contributing factors are allmanifested. In theOzarks, theseveredroughtof1998–2002wasthe incitingfactor(Fig.8a).Thisextendeddroughtreducedthevigorofoaktreesandmadethemvulnerabletocontributingfactors,suchasArmillariarootrot(Armillaria spp.), hypoxylon canker (Hypoxylon spp.), two-lined chestnut borer (Agrilus bilineatus), and red oak borer (Enaphalodes rufulus; Lawrence et al., 2002;Voelkeretal.,2008).Armillaria root rot, particularly Armillaria mellea, was an especiallyseverepathogen,particularlywiththehighincidenceoftransmissionvia root-grafts between scarlet and black oaks (Jenkins and Pallardy, 1995;Bruhnetal.,2000).Byexaminingfirescars,Guyetteet al.(2007)suggestedthatmoderateorseveredroughtconditionsoccurredevery10–20years.Voelkeret al.(2008)describeda‘pulseofmortality’thatoccurredimmediatelyafterthe1999–2002drought,suggestingthatmortalitywastheresponsetotheincitingcondition(drought),inthiscaseactingasathinningagent.2
2Formorediscussion,seeGrantet al.(2013).
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Some climate scenarios project precipitation and drought swings ofincreasingfrequencyandseverity(Clarketal.,2016),hypotheticallyrepresentedby Fig. 8b.Two important effects result from such a new climate norm as itpertainstooak-hickoryforestsintheOzarkMountains:
1 The rapid and dramatic oscillation and the attendant forest healthimpactsdonotallowsufficienttimefortheoakforeststorecoverfromprevious disturbance cascades. In this case, drought increases tree andforestvulnerabilitytoinsectanddiseaseattack,whichprecipitatesdeclineandmortalitybeforethenextdroughtoccurs.Thisrelativelyrapidsequenceofdisturbancesvirtuallyguaranteesthatthetreeisweakened.Its response to the subsequent drought is less robust, increasing the probabilityofmortality.
2 As shown in Fig. 8b, theprecipitation from the rain events—bybeingmoresevere—arenotlikelytobecompletelyabsorbedbytheforestsoilecosystem.Theinfiltrationrate,eveninadrysoil,maynotaccommodatethe total volume of the rainfall, with the excess sheeting off into thesurface water system (Williams, 1991; Ritchie, 1998). Assuming abalanced, closed system where the total annual precipitation may not change (whichwill notnecessarilybe thecase), the forestecosystemwill not obtain the full benefit of the precipitation (surplus) but willexperiencethefullextentofthemoisturedeficit(i.e.drought).Forthetree,theaveragelong-termwateravailabilityisnotthenominalaverage
Figure 8 (a)Hypotheticalrepresentationofhistoricalprecipitationandwateravailabilityovera10-yearperiodintheOzarkMountainsofMissouri.Thehorizontalaxisrepresentstime.Theproportionsarenotnecessarilytoscale,butrepresentahypotheticalcycleofwaterabundanceandshortageoveraperiodoftime.Forthepurposesofthisdiscussion,thepoint in timewhere thewater availability linegoesbelow zero is1998–1999. It isgenerallybelievedthat thedroughtended in2003. (b)Hypothetical representationofpotential precipitation patterns under climate change scenarios projecting increased frequency and severity of weather events. For our purposes, each cycle representsapproximatelyhalfthetimeofthecycleinFig.8a.Thered-shadedareaatthetopofthecycle represents precipitation that comes down at an amount and rate such that not all canbeabsorbedbytheecosystemandthusleavesthesiteasoverlandsurfacewater.Theblue line represents the actual soil moisture available to the trees, which is less than the nominal total moisture.
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precipitationrate(theredlineinthegraph,Fig.8b),butratherthelower(blue) line, the effective average water availability. Coupled with thestressimposedbytheboom-and-bustcycleofprecipitationmentionedearlier,thislong-termreductioninavailablesoilmoisturemayresultinageneraldeclineinvigorinthecurrentOzarkoak-hickoryforeststands.Alikelyconsequenceisconversiontoasuiteofmoredrought-tolerant(xeric)speciesovertime.
2.3.3 Oak decline lessons for managers
Forestmanagershaveexperiencedtheimpactsofperiodicdroughteventsoverthelastcenturies.Theseeventsarebasedondecadalormulti-decadalcycles.Suchlongperiodsbetweensuccessivedroughtsallowedtheforestecosystemtorecoveratleastsomewhatundersufficientorevenabove-averagelevelsofsoilmoisture.Climatechangemakescurrentdroughtcyclesdifferentfromthecyclesoftherecentpast.Droughtsareexpectedtoberelativelymorefrequentandsevere(IPCC,2014;Clarketal.,2016;butseeSeageretal.,2009).Giventheprojectedincreasedvariabilityinrainfall,andtheepisodicnatureofmortality,managersmayfind it logical tomanage forests to sustain them through themorestressfultimesratherthanforlong-termaverageconditions.
Though standard stocking charts or measures of density are based onaverage climate conditions, managers could consider voluntarily forgoingmaximizingproductivityinordertoreducepotentialsusceptibilitytodrought-inducedmortality (D’Amatoet al., 2013;Gleasonet al., 2017).Voelkeret al.(2008)suggestedthatstandswithrelativelylowstockingandhencepotentiallyless inter-tree competition may provide more resilience to drought. Forestmanagers could deliberately keep stands below full stocking. They wouldsacrifice some volume production and possibly reduce tree quality due topersistent branching, but at the same time they potentially would make them more resilient under drought conditions. The benefit gained would be theexpectedvalueofthevolumelosttomortalitymultipliedbytheprobabilitythata decline would result in that mortality.
Intermsofdensityreduction,MoserandMelick(unpublishedmemo,2002)suggestedthatapathologicalrotationofspeciespronetooakdecline,suchasscarletoak,andareductionofoakstanddensitytotheC-line(representedbythe redarrows inFig.9;Gingrich,1967)—adensity levelnormally reservedforattemptstoregeneratethestand—wouldbothreducethemoisturestresson treesand reduce thenumberofvulnerable treeson thesite.Somehaveconsideredthisstockingleveltobetoolow(Johnson,pers.comm.,2002),andinstead recommendkeeping stand stockingnear theB-line (representedbythebluearrows)andharvestoakdecline-pronespeciesaround70yearsofage(Clatterbuck andKauffman, 2006).Others haveproposed a landscape-scale
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matrixofeven-anduneven-agedforests,dependingonlocalsiteconditions,and shifting forest composition to more drought-resistant species such asshortleafpine(Pinus echinata)andwhiteoak(Quercus alba),astechniquestoreducethevulnerabilitytoseveredroughtevents(Johnson,pers.comm.,2002;Guyetteetal.,2007).
For example, the prognosis for forest survival in the presence of gypsymoth(Lymantria dispar)dependsontheforeststand’sabilitytosurviveoneormultipledefoliations,throughreducingthenumberofsusceptiblespeciesorincreasingthevigorofthetreesonthesite,orboth(Gottschalk,1993).Aftera few years, thegypsymothpopulationmaydeclineormaymove to othersites(Davidsonetal.,1999).Suchamodel isagoodtemplateformanaging
Figure 9 Stocking tables for upland central hardwoods, portraying the relationshipbetween trees per hectare (horizontal axis), density (basal area per hectare, verticalaxis), and thequadraticmeandiameter (raysextending from lower left toupper rightofthediagram).Inthisfigure,adaptedfromGin(g)rich(1967),theareaabovetheA-linerepresents anoverstocked stand.Theareabetween theA- andB-lines represents fullstockingand theareabetween theB- andC-lines represents anunderstocked stand.TheA-lineisbasedonthefullystockedstandthathasneverbeenthinned.AstandontheB-lineisthoughttohavetreeswithnocompetition,yetthereisnounusedgrowingspace.TheC-line isestimatedbasedon thenormalyield tableof the loweststockingthatwillgrowtotheB-linewithin10years.Source:adaptedfromLarsenet al.(2010)andLarsen(2014).
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aforest’soverallvigor.Treeswithgreatervigorstoremorecarbohydratesandsugars over winter. Consequently, they have the resources to develop more extensiverootsystemsandproduceabundantcurrent-yearcarbohydratestosupportdefenseagainstinsectanddiseaseattacksevenbeyondrequirementsforgrowthoffinerootsandleaves,heightgrowth,andreproduction.
Optionsforenhancingorshapingspeciesdiversitydependoncurrentstandconditions.Olderforestswithlimitedspeciesdiversityofferfewoptions.Suchcases point toward improving tree vigor by thinning and perhaps preparing the stand for future regeneration where there aremultiple species capableofreachingandbeingmaintainedintheoverstory.Aftertheseconditionsareachieved, more management options present themselves.
3 Methods of projection in the long term: modeling projected changes in habitat and potential migration
Modeling potential changes in habitat, and the potential migration into such habitats,requiresamajorsimplificationofrealityinanuncertainandchangingworld.There is a great deal of complexity to consider, as evidencedby themanyintrinsic(e.g.physicalhabitatspecialization,successionalstage,fecundity,dependence on particular disturbances) and extrinsic (e.g. browsing, pest/pathogens, dispersal barriers, climatic extremes) factors thatmay increase aspecies’orpopulation’sriskofextinction,extirpation,orgeneticdegradation.For models to be useful (Box and Draper, 1987), they must enhance ourunderstandingofcurrentandpotentialfuturespeciesdistributions.
Totacklethesecomplexities,ourapproachhasbeentocombineaspeciesdistribution model (SDM; DISTRIB-II, an updated version of the RandomForestDISTRIBmodel[Petersetal.,2019;Iversonetal.,2019a]),forprojectingpotentialfuturesuitablehabitats),andamigrationmodel(SHIFT,forestimatingcolonization likelihoods based on historical migration rates into projectedsuitablehabitatwithin100years).Inaddition,weusealiterature-basedsetofmodification factors forassistance in interpretation (ModFacs),andacurrentforest inventory assessment (Forest Inventory and Analysis, FIA, www.fs.fed.us/fia) to better understand current tree species abundance for a particulargeographic unit (Iverson et al., 2008, 2019a, 2019b; Iverson andMcKenzie,2013;Prasadetal.,2006).
TheresultingoutputsoftheseindividualspeciesmodelsprovideawealthofinformationacrosstheeasternUnitedStates.Asabackgroundtoourmodelingframework,theresponsevariablesarederivedfromFIAandweuseahybridgrid(Petersetal.,2019)of10 × 10or20 × 20kmcellstoaccountforthedifferentialdensityofFIAplots.TheFIAplotdataweretabulatedandaveragedwithineachofthe55nationalforeststoyieldarankedlistoftreespecies,byimportancevalue (IV)derivedequally fromtotalbasalareaandnumberof stems.These
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 17
IV datawere also used in conjunctionwith 45 environmental variables (e.g.climate,elevation,andsoil)inastatisticalmodel(RandomForest,Prasadetal.,2016)togeneratemodeledestimates(DISTRIB-II)ofcurrentIVforeachspeciesacrosstheeasternUnitedStates.Then,byswappingcurrentclimaticvariableswith potential future climate variables according to three models (CCSM4,GFDL-CM3,andHadGEM2-ES)andtworepresentativeconcentrationpathways(4.5and8.5),for30-yearperiodsendingin2039,2069,and2099,projectionsweremaderegardingpotentialsuitablehabitatforeachspecies(Prasadetal.,2016; Iverson et al., 2019a). Usingmultiple literature sources, each specieswas also scored on nine biological traits and 12 traits related to resilience fromdisturbances(Matthewsetal.,2011)andgivenaratingastothespecies’adaptability to thechangingclimate.TheSHIFTmodel is alsoparamount tothiseffort,toassesscolonizationlikelihoodwithinthesuitablehabitatsbasedonhabitatsuitabilityandthestrengthofthesourceabundance(Prasadetal.,2013,2016).BycombiningDISTRIB-IIandSHIFTresults,wenotonly identifypotential changes in suitable habitat under various scenarios of climatechange,butalsoprovide,foreachspeciespresentcurrentlyorpotentiallyinthefuture,estimatesofcolonization likelihoodthroughthecurrently fragmentedlandscapes (Iversonetal.2019b).Weassumedagenerousmigrationrateof50km/centurywithin100years; thismigration rate represents thehighendofaverageestimatesofmigrationduringtheHoloceneperiodthroughextantforest(Davis,1981;DavisandShaw,2001;Schwartz,1993)althoughMcLachlanet al.(2005)havedeterminedfrommolecularstudiesthat25,oreven10 km,maybemorerealisticforsomespeciesthatwereassistedbyseedsourcesinclimaticrefugia.Wecontinuetouse50km/centurybecausewedonotassumefutureformationsofclimaticrefugia.
WiththecombinationofresultsfromDISTRIB-II,SHIFT,ModificationFactors,andcurrentFIAestimatesofIV,weareabletopresentadetailedpresentationof(1)speciesimportancecurrently,(2)thepotentialchangesinsuitablehabitatby2100,(3)theadaptabilityofeachspeciestothechangingclimate,(4)thecapabilityofeachspeciestocopewiththe2100climatebasedonadaptabilityandabundancecurrentlywithintheNationalForest(NF),(5)thelikelihoodofeach species to naturallymigrate into theNF, and (6) an assessment of thepotentialforthespeciestobeusedforplantingorotherwisepromotingwithinthe NF.
In order to facilitate comparisons and quantify potential risks andopportunitiesunderclimatechange,wefocushereonthecollectiveoutputsforthefollowinggeographicunits:state,1 × 1o grid, ecoregion, hydrologic unit, and NF.Thiscanbedone,andtabulatedormapped,foranygeographiclocationintheeasternUnitedStates,solongasitoccupiesanareaofatleast8000km2 to allowsufficientFIAplotsforanalyses.WebrieflyreporthereonDISTRIB-IIandSHIFToutputsforthreeanalyses:(1)DISTRIB-IIoutputsofchangesinsuitable
The impact of climate change on forest systems in the northern United States18
Published by Burleigh Dodds Science Publishing Limited, 2020.
habitatsfortheentireeasternUSregion;(2)DISTRIB-IIwithSHIFToutputsfor55nationalforestsinthisregion,withanemphasisonone,theChequamegon-NicoletNFinnorthernWisconsin;and(3)DISTRIB-IIwithSHIFToutputsfor4641 × 1ogridsacrossthissameregioneastofthe100thmeridian.
3.1 DISTRIB-II projections of suitable habitat by 2100
Weevaluated 125 tree species that had sufficient FIA samples formodeling.Results show potentially large impacts, especially under a high emissions trajectory (RCP8.5),on suitablehabitat for tree species in theeasternUnitedStates. Of the 45 variables used in the Random Forest modeling, the sevenclimate variables were ranked among the top nine variables, indicating an overall influenceof climateassociationswith capturingpatternsat the species rangeextent. Inserting new possible climates caused large changes in potential suitable habitat.Ouranalysisfoundthatabout88ofthe125specieswouldgainand26specieswouldloseatleast10%oftheirsuitablehabitat.Theprojectedchangeinthemeancenterforeachspeciesshowsageneralmovementtothenortheast,with thehabitatcenters for81speciespotentiallymovingover100kmunderRCP 8.5. For example, Quercus nigra(wateroak)showsapotentialmovementof377kmunderthemeanofRCP8.5scenarios(Fig.10).Overall,manytreespeciesare likely to have better success in tracking their suitable habitats under RCP 4.5 ascomparedtoRCP8.5.DetailsarepresentedinIversonet al.(2019a).
3.1.1 Chequamegon-Nicolet NF assessment
The resultsof combiningmodeloutputsofDISTRIB-II andSHIFT,alongwiththemodificationfactorsandcurrentFIAestimates,areallpresentedwithinaninformation-packed,buteasilyunpackedtable(Table2,seealsoIversonetal.2019bfor fullexplanationof tablevariablesandderivatives).Besidesasuiteofspecies-level informationrelatedtocurrentandpotential futurecapacitiesto cope with the changing climate, it also provides suggestions as to species thatare(1)rarenowbutgoodcandidatesforincreasingprominenceinfuture(Infill); (2) likely there now but missed by FIA plots (Likely); and (3) goodcandidatesforassistedmigrationbecausetheyarenearbywithgoodpotentialfornaturalmigrationintotheareawithin100years(Migrate). InourexampleChequamegon-NicoletNF,weshowsixspeciesforInfill,twoforLikely,andsixtonineforMigrate,dependingonRCP(Table2).
3.1.2 1 × 1-degree assessment
Eachofthe4641 × 1ogridswastabulatedinthesamewayasdescribedfortheChequamegon-NicoletNF.These tables allow anyone east of the 100thmeridian(easternhalfoftheUnitedStates)theabilitytodeterminetheircurrent
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 19
and potential tree species attributes during this century. All that is necessary is for theuser to knowhis/hergeographic coordinates (e.g. 41.334 latitudeand−82.201longitude)andthenameofthegridwill indicatethesoutheastcornerof thegrid for thefile touse,eitheronlineordownloaded(e.g.S41_E82.pdf,seewww.fs.fed.us/nrs/atlas).Theareaconsideredwithingridsvariesslightlynorthtosouthduetothecurvatureoftheearth,soeach1 × 1o cell was calibrated to equal 10 000 km2,whichrepresentsroughly10010 × 10kmcellsor2520 × 20kmcells(usuallysomecombinationofeach).
Bycollectivelyevaluatingall1 × 1ogrids,wecanmapthecountsofspecieswithinanyofthefieldsofthe464tables.Thesecanbeassimpleascountingthenumberof species recordedonFIAplotsor thenumberofoak speciesrecorded,tomoreadvancedqueriessuchasthenumberoftreespecieswith
Figure 10 Ellipsesofone standarddeviationandmeancenters for the currentdistri-bution and suitable habitat according to CCSM4 RCP 4.5, mean RCP 4.5, mean RCP 8.5, andHadGEM2-ESRCP8.5forwateroak(Quercus nigra).FIAActualreferstotheknownFIAplotlocationsofthespecies,whileCurrentreferstothemodeledcurrentdistributionofthespecies.
The impact of climate change on forest systems in the northern United States20
Published by Burleigh Dodds Science Publishing Limited, 2020.
Tabl
e 2 DISTRIB-II/SHIFToutputtableforChequam
egon-NicoletNationalForest,sortedindecreasingorderofcurrentspeciesabundance(FIAsum)
Com
mon
na
me
Scientificname
MR
FIAs
umFI
Aiv
Chn
gCl4
5C
hngC
l85Ad
apt-
Abun
dCa
pabi
l45
Capa
bil8
5SHIFT45
SHIFT85
N
Qua
king
as
pen
Popu
lus
trem
uloi
des
Hig
h64
1.22
16.7
6Sm
. dec
.Sm
. dec
.M
ediu
mAb
unda
ntGood
Good
1
Red
map
leAc
er ru
brum
Hig
h54
8.33
13.8
4N
o ch
ange
No
chan
geH
igh
Abun
dant
Very
Good
Very
Good
2
Suga
r map
leAc
er sa
ccha
rum
Hig
h48
5.17
13.6
5Sm
. dec
.Sm
. dec
.H
igh
Abun
dant
Good
Good
3Balsamfir
Abie
s bal
sam
eaH
igh
315.
428.
63Sm
. dec
.Sm
. dec
.Lo
wAb
unda
ntGood
Good
4Bl
ack
ash
Frax
inus
nig
raM
ediu
m22
1.35
6.96
Sm. d
ec.
Sm. d
ec.
Low
Abun
dant
Good
Good
5Re
d pi
nePi
nus r
esin
osa
Med
ium
176.
3310
.63
Sm. d
ec.
Sm. d
ec.
Low
Abun
dant
Good
Good
6Tamarack
(native)
Larix
laric
ina
Hig
h16
1.77
7.35
No
chan
geN
o ch
ange
Low
Abun
dant
Very
Good
Very
Good
7
Pape
r birc
hBe
tula
pa
pyrif
era
Hig
h15
9.6
4.41
No
chan
geN
o ch
ange
Med
ium
Abun
dant
Very
Good
Very
Good
8
Blac
k sp
ruce
Pice
a m
aria
naH
igh
124.
916.
47Sm
. dec
.Sm
. dec
.M
ediu
mAb
unda
ntGood
Good
9N
orth
ern
red
oak
Que
rcus
rubr
aM
ediu
m12
2.8
5.11
Sm. i
nc.
Sm. i
nc.
Hig
hAb
unda
ntVery
Good
Very
Good
10
Nor
ther
n white-cedar
Thuj
a oc
cide
ntal
isH
igh
113.
97.
16Sm
. dec
.N
o ch
ange
Med
ium
Abun
dant
Good
Very
Good
11
Amer
ican
ba
ssw
ood
Tilia
am
eric
ana
Med
ium
112.
454.
37Sm
. inc
.N
o ch
ange
Med
ium
Abun
dant
Very
Good
Very
Good
12
Bigt
ooth
as
pen
Popu
lus
gran
dide
ntat
aM
ediu
m10
6.74
4.85
No
chan
geSm
. dec
.M
ediu
mAb
unda
ntVery
Good
Good
13
Yello
w b
irch
Betu
la
alle
ghan
iens
isH
igh
105.
823.
51Sm
. dec
.Sm
. dec
.M
ediu
mAb
unda
ntGood
Good
14
East
ern
whi
te
pine
Pinu
s stro
bus
Hig
h96
.91
4.47
Sm. i
nc.
Sm. i
nc.
Low
Abun
dant
Very
Good
Very
Good
15
East
ern
hem
lock
Tsug
a ca
nade
nsis
Hig
h79
.45
3.85
No
chan
geN
o ch
ange
Low
Abun
dant
Very
Good
Very
Good
16
Jackpine
Pinu
s ban
ksia
naM
ediu
m77
.19
12.6
7Sm
. dec
.Lg
. dec
.H
igh
Abun
dant
Good
Good
17W
hite
spru
cePi
cea
glau
caM
ediu
m56
.88
2.4
No
chan
geN
o ch
ange
Med
ium
Com
mon
Good
Good
18
Blac
k ch
erry
Prun
us se
rotin
aM
ediu
m49
.63
1.81
Lg. i
nc.
Lg. i
nc.
Low
Com
mon
Very
Good
Very
Good
19
Amer
ican
elm
Ulm
us
amer
ican
aM
ediu
m44
.77
2.4
Sm. i
nc.
Sm. i
nc.
Med
ium
Com
mon
Very
Good
Very
Good
20
Whi
te a
shFr
axin
us
amer
ican
aM
ediu
m36
.96
1.95
Sm. i
nc.
Sm. i
nc.
Low
Com
mon
Very
Good
Very
Good
21
East
ern
hoph
ornb
eam
Ost
ryav
irgin
iana
Low
36.9
51.
48Sm
. inc
.Sm
. inc
.H
igh
Com
mon
Very
Good
Very
Good
22
Nor
ther
n pi
n oa
kQ
uerc
us
ellip
soid
alis
Med
ium
36.0
24.
63Sm
. dec
.Sm
. dec
.H
igh
Com
mon
Fair
Fair
Infill+
Infill+
23
Greenash
Frax
inus
pe
nnsy
lvan
ica
Low
24.2
21.
49Sm
. inc
.Sm
. inc
.M
ediu
mCo
mm
onVery
Good
Very
Good
24
Bur o
akQ
uerc
us
mac
roca
rpa
Med
ium
20.3
34.
29N
o ch
ange
No
chan
geH
igh
Com
mon
Good
Good
Infill++
Infill++
25
Amer
ican
ho
rnbe
amCa
rpin
us
caro
linia
naLo
w16
.52
1.28
Sm. d
ec.
Sm. d
ec.
Med
ium
Com
mon
Fair
Fair
26
Cho
kech
erry
Prun
us
virg
inia
naFI
A5.
460.
54Unknown
Unknown
Med
ium
Com
mon
FIAOnly
FIAOnly
27
Pin
cher
ryPr
unus
pe
nsyl
vani
caLo
w5.
450.
89N
o ch
ange
VeryLg.
dec
Med
ium
Com
mon
Good
Lost
28
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 21
Tabl
e 2 DISTRIB-II/SHIFToutputtableforChequam
egon-NicoletNationalForest,sortedindecreasingorderofcurrentspeciesabundance(FIAsum)
Com
mon
na
me
Scientificname
MR
FIAs
umFI
Aiv
Chn
gCl4
5C
hngC
l85Ad
apt-
Abun
dCa
pabi
l45
Capa
bil8
5SHIFT45
SHIFT85
N
Qua
king
as
pen
Popu
lus
trem
uloi
des
Hig
h64
1.22
16.7
6Sm
. dec
.Sm
. dec
.M
ediu
mAb
unda
ntGood
Good
1
Red
map
leAc
er ru
brum
Hig
h54
8.33
13.8
4N
o ch
ange
No
chan
geH
igh
Abun
dant
Very
Good
Very
Good
2
Suga
r map
leAc
er sa
ccha
rum
Hig
h48
5.17
13.6
5Sm
. dec
.Sm
. dec
.H
igh
Abun
dant
Good
Good
3Balsamfir
Abie
s bal
sam
eaH
igh
315.
428.
63Sm
. dec
.Sm
. dec
.Lo
wAb
unda
ntGood
Good
4Bl
ack
ash
Frax
inus
nig
raM
ediu
m22
1.35
6.96
Sm. d
ec.
Sm. d
ec.
Low
Abun
dant
Good
Good
5Re
d pi
nePi
nus r
esin
osa
Med
ium
176.
3310
.63
Sm. d
ec.
Sm. d
ec.
Low
Abun
dant
Good
Good
6Tamarack
(native)
Larix
laric
ina
Hig
h16
1.77
7.35
No
chan
geN
o ch
ange
Low
Abun
dant
Very
Good
Very
Good
7
Pape
r birc
hBe
tula
pa
pyrif
era
Hig
h15
9.6
4.41
No
chan
geN
o ch
ange
Med
ium
Abun
dant
Very
Good
Very
Good
8
Blac
k sp
ruce
Pice
a m
aria
naH
igh
124.
916.
47Sm
. dec
.Sm
. dec
.M
ediu
mAb
unda
ntGood
Good
9N
orth
ern
red
oak
Que
rcus
rubr
aM
ediu
m12
2.8
5.11
Sm. i
nc.
Sm. i
nc.
Hig
hAb
unda
ntVery
Good
Very
Good
10
Nor
ther
n white-cedar
Thuj
a oc
cide
ntal
isH
igh
113.
97.
16Sm
. dec
.N
o ch
ange
Med
ium
Abun
dant
Good
Very
Good
11
Amer
ican
ba
ssw
ood
Tilia
am
eric
ana
Med
ium
112.
454.
37Sm
. inc
.N
o ch
ange
Med
ium
Abun
dant
Very
Good
Very
Good
12
Bigt
ooth
as
pen
Popu
lus
gran
dide
ntat
aM
ediu
m10
6.74
4.85
No
chan
geSm
. dec
.M
ediu
mAb
unda
ntVery
Good
Good
13
Yello
w b
irch
Betu
la
alle
ghan
iens
isH
igh
105.
823.
51Sm
. dec
.Sm
. dec
.M
ediu
mAb
unda
ntGood
Good
14
East
ern
whi
te
pine
Pinu
s stro
bus
Hig
h96
.91
4.47
Sm. i
nc.
Sm. i
nc.
Low
Abun
dant
Very
Good
Very
Good
15
East
ern
hem
lock
Tsug
a ca
nade
nsis
Hig
h79
.45
3.85
No
chan
geN
o ch
ange
Low
Abun
dant
Very
Good
Very
Good
16
Jackpine
Pinu
s ban
ksia
naM
ediu
m77
.19
12.6
7Sm
. dec
.Lg
. dec
.H
igh
Abun
dant
Good
Good
17W
hite
spru
cePi
cea
glau
caM
ediu
m56
.88
2.4
No
chan
geN
o ch
ange
Med
ium
Com
mon
Good
Good
18
Blac
k ch
erry
Prun
us se
rotin
aM
ediu
m49
.63
1.81
Lg. i
nc.
Lg. i
nc.
Low
Com
mon
Very
Good
Very
Good
19
Amer
ican
elm
Ulm
us
amer
ican
aM
ediu
m44
.77
2.4
Sm. i
nc.
Sm. i
nc.
Med
ium
Com
mon
Very
Good
Very
Good
20
Whi
te a
shFr
axin
us
amer
ican
aM
ediu
m36
.96
1.95
Sm. i
nc.
Sm. i
nc.
Low
Com
mon
Very
Good
Very
Good
21
East
ern
hoph
ornb
eam
Ost
ryav
irgin
iana
Low
36.9
51.
48Sm
. inc
.Sm
. inc
.H
igh
Com
mon
Very
Good
Very
Good
22
Nor
ther
n pi
n oa
kQ
uerc
us
ellip
soid
alis
Med
ium
36.0
24.
63Sm
. dec
.Sm
. dec
.H
igh
Com
mon
Fair
Fair
Infill+
Infill+
23
Greenash
Frax
inus
pe
nnsy
lvan
ica
Low
24.2
21.
49Sm
. inc
.Sm
. inc
.M
ediu
mCo
mm
onVery
Good
Very
Good
24
Bur o
akQ
uerc
us
mac
roca
rpa
Med
ium
20.3
34.
29N
o ch
ange
No
chan
geH
igh
Com
mon
Good
Good
Infill++
Infill++
25
Amer
ican
ho
rnbe
amCa
rpin
us
caro
linia
naLo
w16
.52
1.28
Sm. d
ec.
Sm. d
ec.
Med
ium
Com
mon
Fair
Fair
26
Cho
kech
erry
Prun
us
virg
inia
naFI
A5.
460.
54Unknown
Unknown
Med
ium
Com
mon
FIAOnly
FIAOnly
27
Pin
cher
ryPr
unus
pe
nsyl
vani
caLo
w5.
450.
89N
o ch
ange
VeryLg.
dec
Med
ium
Com
mon
Good
Lost
28
(Con
tinue
d)
The impact of climate change on forest systems in the northern United States22
Published by Burleigh Dodds Science Publishing Limited, 2020.
Com
mon
na
me
Scientificname
MR
FIAs
umFI
Aiv
Chn
gCl4
5C
hngC
l85Ad
apt-
Abun
dCa
pabi
l45
Capa
bil8
5SHIFT45
SHIFT85
N
Serv
iceb
erry
Amel
anch
ier
spp.
Low
3.94
0.53
Sm. i
nc.
No
chan
geM
ediu
mRa
reGood
Fair
29
Silv
er m
aple
Acer
sa
ccha
rinum
Low
3.7
10.9
3Sm
. dec
.Sm
. dec
.H
igh
Rare
Poor
Poor
Infill+
Infill+
30
Butte
rnut
Jugl
ans c
iner
eaFI
A1.
741.
71Unknown
Unknown
Low
Rare
FIAOnly
FIAOnly
31Ba
lsam
pop
lar
Popu
lus
balsa
mife
raM
ediu
m1.
40.
83VeryLg.
dec
VeryLg.
dec
Med
ium
Rare
Lost
Lo
st32
Slip
pery
elm
Ulm
us ru
bra
Low
0.82
0.81
Sm. i
nc.
Sm. i
nc.
Med
ium
Rare
Good
Good
Infill++
Infill++
33Bi
ttern
ut
hick
ory
Cary
a co
rdifo
rmis
Low
0.45
0.66
Sm. i
nc.
Sm. i
nc.
Hig
hRa
reGood
Good
Infill+
Infill+
34
Whi
te o
akQ
uerc
us a
lba
Med
ium
0.43
0.63
No
chan
geN
o ch
ange
Hig
hRa
reFa
irFa
irInfill+
Infill+
35
Mou
ntai
n m
aple
Acer
spic
atum
Low
0.43
0.25
Lg. d
ec.
Lg. d
ec.
Hig
hRa
rePo
orPo
or36
Nor
way
sp
ruce
Pice
a ab
ies
FIA
0.27
0.8
Unknown
Unknown
NA
Rare
NN
ISN
NIS
37
Scot
ch p
ine
Pinu
s syl
vest
risFI
A0.
180.
52Unknown
Unknown
NA
Rare
NN
ISN
NIS
38Peachleaf
will
owSa
lix
amyg
dalo
ides
FIA
0.13
0.37
Unknown
Unknown
Med
ium
Rare
FIAOnly
FIAOnly
39
Rock
elm
Ulm
us th
omas
iiFI
A0.
090.
27Unknown
Unknown
Low
Rare
FIAOnly
FIAOnly
40Bo
xeld
erAc
er n
egun
doLo
w0
0N
ew
Hab
itat
New
H
abita
tH
igh
Abse
ntN
ew
Hab
itat
New
H
abita
tLikely+
Likely+
41
Swam
p w
hite
oa
kQ
uerc
us b
icol
orLo
w0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Likely+
Likely+
42
Blac
k oa
kQ
uerc
us
velu
tina
Hig
h0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate++
Migrate++
43
East
ern
redc
edar
Juni
peru
s vi
rgin
iana
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
tMigrate+
Migrate++
44
Amer
ican
be
ech
Fagu
s gr
andi
folia
Hig
h0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
Migrate+
45
Blac
k lo
cust
Robi
nia
pseu
doac
acia
Low
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
tMigrate+
Migrate+
46
Blac
k w
alnu
tJu
glan
s nig
raLo
w0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
Migrate+
47
Shag
bark
hi
ckor
yCa
rya
ovat
aM
ediu
m0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
Migrate+
48
East
ern
cotto
nwoo
dPo
pulu
s de
ltoid
esLo
w0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
49
Hac
kber
ryCe
ltis
occi
dent
alis
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Hig
hAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
50
Blac
kgum
Nys
sa sy
lvat
ica
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Hig
hAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
51
Pign
ut h
icko
ryCa
rya
glab
raM
ediu
m0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
52
Syca
mor
ePl
atan
us
occi
dent
alis
Low
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
t53
Yellow-poplar
Lirio
dend
ron
tulip
ifera
Hig
h0
0N
ew
Hab
itat
New
H
abita
tH
igh
Abse
ntN
ew
Hab
itat
New
H
abita
t54
Moc
kern
ut
hick
ory
Cary
a al
baM
ediu
m0
0N
ew
Hab
itat
New
H
abita
t H
igh
Abse
ntN
ew
Hab
itat
New
H
abita
t55
Tabl
e 2 (Continued)
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 23
Com
mon
na
me
Scientificname
MR
FIAs
umFI
Aiv
Chn
gCl4
5C
hngC
l85Ad
apt-
Abun
dCa
pabi
l45
Capa
bil8
5SHIFT45
SHIFT85
N
Serv
iceb
erry
Amel
anch
ier
spp.
Low
3.94
0.53
Sm. i
nc.
No
chan
geM
ediu
mRa
reGood
Fair
29
Silv
er m
aple
Acer
sa
ccha
rinum
Low
3.7
10.9
3Sm
. dec
.Sm
. dec
.H
igh
Rare
Poor
Poor
Infill+
Infill+
30
Butte
rnut
Jugl
ans c
iner
eaFI
A1.
741.
71Unknown
Unknown
Low
Rare
FIAOnly
FIAOnly
31Ba
lsam
pop
lar
Popu
lus
balsa
mife
raM
ediu
m1.
40.
83VeryLg.
dec
VeryLg.
dec
Med
ium
Rare
Lost
Lo
st32
Slip
pery
elm
Ulm
us ru
bra
Low
0.82
0.81
Sm. i
nc.
Sm. i
nc.
Med
ium
Rare
Good
Good
Infill++
Infill++
33Bi
ttern
ut
hick
ory
Cary
a co
rdifo
rmis
Low
0.45
0.66
Sm. i
nc.
Sm. i
nc.
Hig
hRa
reGood
Good
Infill+
Infill+
34
Whi
te o
akQ
uerc
us a
lba
Med
ium
0.43
0.63
No
chan
geN
o ch
ange
Hig
hRa
reFa
irFa
irInfill+
Infill+
35
Mou
ntai
n m
aple
Acer
spic
atum
Low
0.43
0.25
Lg. d
ec.
Lg. d
ec.
Hig
hRa
rePo
orPo
or36
Nor
way
sp
ruce
Pice
a ab
ies
FIA
0.27
0.8
Unknown
Unknown
NA
Rare
NN
ISN
NIS
37
Scot
ch p
ine
Pinu
s syl
vest
risFI
A0.
180.
52Unknown
Unknown
NA
Rare
NN
ISN
NIS
38Peachleaf
will
owSa
lix
amyg
dalo
ides
FIA
0.13
0.37
Unknown
Unknown
Med
ium
Rare
FIAOnly
FIAOnly
39
Rock
elm
Ulm
us th
omas
iiFI
A0.
090.
27Unknown
Unknown
Low
Rare
FIAOnly
FIAOnly
40Bo
xeld
erAc
er n
egun
doLo
w0
0N
ew
Hab
itat
New
H
abita
tH
igh
Abse
ntN
ew
Hab
itat
New
H
abita
tLikely+
Likely+
41
Swam
p w
hite
oa
kQ
uerc
us b
icol
orLo
w0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Likely+
Likely+
42
Blac
k oa
kQ
uerc
us
velu
tina
Hig
h0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate++
Migrate++
43
East
ern
redc
edar
Juni
peru
s vi
rgin
iana
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
tMigrate+
Migrate++
44
Amer
ican
be
ech
Fagu
s gr
andi
folia
Hig
h0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
Migrate+
45
Blac
k lo
cust
Robi
nia
pseu
doac
acia
Low
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
tMigrate+
Migrate+
46
Blac
k w
alnu
tJu
glan
s nig
raLo
w0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
Migrate+
47
Shag
bark
hi
ckor
yCa
rya
ovat
aM
ediu
m0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
Migrate+
48
East
ern
cotto
nwoo
dPo
pulu
s de
ltoid
esLo
w0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
49
Hac
kber
ryCe
ltis
occi
dent
alis
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Hig
hAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
50
Blac
kgum
Nys
sa sy
lvat
ica
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Hig
hAb
sent
New
H
abita
tN
ew
Hab
itat
Migrate+
51
Pign
ut h
icko
ryCa
rya
glab
raM
ediu
m0
0N
ew
Hab
itat
New
H
abita
tM
ediu
mAb
sent
New
H
abita
tN
ew
Hab
itat
52
Syca
mor
ePl
atan
us
occi
dent
alis
Low
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
t53
Yellow-poplar
Lirio
dend
ron
tulip
ifera
Hig
h0
0N
ew
Hab
itat
New
H
abita
tH
igh
Abse
ntN
ew
Hab
itat
New
H
abita
t54
Moc
kern
ut
hick
ory
Cary
a al
baM
ediu
m0
0N
ew
Hab
itat
New
H
abita
t H
igh
Abse
ntN
ew
Hab
itat
New
H
abita
t55
(Con
tinue
d)
The impact of climate change on forest systems in the northern United States24
Published by Burleigh Dodds Science Publishing Limited, 2020.
Com
mon
na
me
Scientificname
MR
FIAs
umFI
Aiv
Chn
gCl4
5C
hngC
l85Ad
apt-
Abun
dCa
pabi
l45
Capa
bil8
5SHIFT45
SHIFT85
N
Post
oak
Que
rcus
stel
lata
Hig
h0
0N
ew
Hab
itat
New
H
abita
t H
igh
Abse
ntN
ew
Hab
itat
New
H
abita
t56
Red
spru
cePi
cea
rube
nsH
igh
00
New
H
abita
tN
ew
Hab
itat
Low
Abse
ntN
ew
Hab
itat
New
H
abita
t57
Scar
let o
akQ
uerc
us
cocc
inea
Med
ium
00
New
H
abita
tN
ew
Hab
itat
Med
ium
Abse
ntN
ew
Hab
itat
New
H
abita
t58
Peca
nCa
rya
illin
oine
nsis
Low
00
Unknown
New
H
abita
tLo
wAb
sent
Unknown
New
H
abita
t59
Swee
tgum
Liqu
idam
bar
styr
acifl
uaH
igh
00
Unknown
New
H
abita
tM
ediu
mAb
sent
Unknown
New
H
abita
t60
Suga
rber
ryCe
ltis l
aevi
gata
Med
ium
00
Unknown
New
H
abita
tM
ediu
mAb
sent
Unknown
New
H
abita
t61
Flow
erin
g do
gwoo
dCo
rnus
flor
ida
Med
ium
00
Unknown
New
H
abita
tM
ediu
mAb
sent
Unknown
New
H
abita
t62
Bigleaf
mag
nolia
Mag
nolia
m
acro
phyl
laLo
w0
0Unknown
Unknown
Med
ium
Abse
ntUnknown
Unknown
63
MRistomodelreliability(seeIversonetal.,2019forexplanation).FIAivistheaverageimportancevalueforthespecieswhenpresentonFIAplots.ChngC
l45or85
presentsthechangeclasses(increase,decrease,ornochange)ofhabitatsuitabilityby2100,accordingtoRCP4.5(lowemissions)or8.5(highem
issions).Ad
aptis
aclassofadaptabilityofthespeciesaccordingtothemodificationfactors.Ab
undisanabundanceclassbasedonFIAsum
.Capabil45or85isthecapabilityofthe
speciestocopewiththeclimatesofRCP4.5or8.5at2100,basedonabundance,changeclasses,andadaptability.SHIFT45and85arederivedfrom
severaloutputsof
theSHIFTmodelincom
binationwiththesuitablehabitatfromDISTRIB-IItoderivetwolevelsofpotentialforthespeciestoInfill(+or++)forspeciesthatarecurrently
foundrarelyintheNFandlikelytoexpandinthenext100years,Likely(+or++)forspeciesthatarelikelyalreadypresentintheareabutnotfoundbyFIAplots,and
Migrate(+or++)forspeciesthatdidnotoccuronFIAplots,butSHIFT(RCP4.5or8.5)didindicatepotentialforcolonizationintheNFwithin100years.Finally,theN
columnsim
plyisacounter.FurtherdetailsarefoundinIversonetal.2019b..
Tabl
e 2 (Continued)
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 25
NewHabitatandwithat least somecolonizationpotentialby2100 (Fig.11).From these summaries, we can begin to address questions at the community levels where these data indicate that northern locations have more options in selectingspeciesforassistedmigrationascomparedtosouthernlocationsthatonlyhavetheGulfofMexicotothesouth(Fig.11).Byassistedmigration,wemeanthephysicalmovingofpropagulesnorthwardfrompointssouthastheclimatewarms(Dumroeseetal.,2015;IversonandMcKenzie,2013).Mapssuchas these allow regional planners, researchers, and interested publics to better understandtheforestresourcenowandpotentiallyintothefuture.
4 Ecoregional vulnerability assessmentsForest managers often seek the best available science to inform theirmanagement, and they could spend significant amounts of time sorting
Figure 11 Mapshowingthenumberoftreespecies,by1 × 1o grid, with both new habitat appearing(viaDISTRIB-II)andsomepotentialtobecolonizedwithin100years(viaSHIFT).
The impact of climate change on forest systems in the northern United States26
Published by Burleigh Dodds Science Publishing Limited, 2020.
throughanddigestingthevastnumberofresearchpublicationsonclimateanditseffectsonecosystems.However,muchofthisliteratureisstilltoobroadscaleforsite-levelmanagement,andthereforelackinginrelevancyandconfoundedby numerous climate models, climate scenarios or representative concentration pathways, downscaling algorithms, time scales, ecological models, and sources ofuncertainty.
The Climate Change Response Framework addressed this informationchallengeby creatinga seriesof forest ecosystemvulnerability assessmentswritten specifically for landmanagers.Eachassessmentwas informedat theoutsetbyregionalexperts,includingbothscientistsandmanagers.Theseriescovers several ecological provinces and uses the same climate models and scenarios, and forest impactmodels. Each assessment also follows a similarformat.Eachassessmentdescribesthecontemporarylandscapeandidentifieskeystressors thathaveshaped forestecosystemsover thepastcentury.Pastandprojectedtrendsinclimatearethensummarizedfromclimateobservationsanddownscaled global circulationmodels. This information is then used toparameterizeforestimpactmodelsthatprojectfutureforestchange.Theresultsfromseveralforestimpactmodels,alongwithpublishedresearchontheeffectof climate on ecosystemprocesses, are consideredby an expert panel thatreliesonlocalknowledgeandexpertisetoidentifythefactorsthatcontributeto the vulnerability ofmajor forest ecosystemswithin each assessment areathrough theendof thiscentury.Afinalchapter summarizes the implicationsof these vulnerabilities on a variety of forest-related ecological, social, andeconomic topics across the region.
Theprimarygoalof thisseriesofassessments is tosummarizepotentialchanges to the forest ecosystemsof each regionunder a rangeofpossiblefutureclimates,anddeterminethevulnerabilityofforestecosystemstothesechanges during the next century. Uncertainties in modeling and gaps inunderstanding are also addressed in each assessment.
Vulnerabilityisdefinedhereas‘thedegreetowhichasystemissusceptibleto and unable to cope with the adverse effects of climate change’. Forestecosystem vulnerability is defined here as susceptibility ‘to a reduction inhealth and productivity or a change in species composition that would alter its fundamentalidentity’.
Eachassessmentsummarizedstatisticallydownscaledclimateprojectionsforthreefuturetimeperiods,usingtwoclimatemodels(GFDLandPCM)undertwo contrasting greenhouse gas emission scenarios (A1FI: high emissionsandB1:lowemissions)fortheyears2070–2100.GFDLA1FIprojectsagreateramount of warming and hot, dry summers throughout the region. PCMB1 projects a lesser amount of warming and wetter summers with modesttemperature increases in summer.Thesemodel-scenario combinationswereselected because they had been used previously for projecting changes in
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 27
habitatsuitabilityfortreespeciesandrepresentedtheleastandmostamountofclimatechange,respectively.Bothdownscaledclimatescenarioswereusedasclimate inputs for threeforest impactmodels,whichwereusedtoprojectclimate-inducedimpactsonselectedtreespeciesorforestcovertypes.Eachassessment also synthesized published research on projected changes inforestproductivity;naturaldisturbanceregimes;forestcomposition;intensifiedstressors;sea-levelriseandsaltwaterintrusion;andinteractionsamongclimatechange and other ecosystem processes.
4.1 Impacts
Major impacts to system drivers and stressors were identified across eachassessment area. The most frequently identified impacts contributing toecosystemvulnerabilityinallassessmentareasincludedchangesinfireregime,soil moisture, pest and disease outbreaks, and nonnative invasive species. Someimpactswerespecifictocertaingeographicregions,suchassea-levelrise andhurricanes along theMid-Atlantic andNewEngland coastal areas.A recent analysisof adaptationplans across thenortheasternUnitedStatessimilarly identified changes in the frequency and amount of precipitation,and increasedvegetationmoisturestress,among themost-cited impactsofconcernamonglandmanagers.TheseregionalconcernsarealsoidentifiedbythemostrecentNationalClimateAssessment,whichconcludedthefollowing:
• Heavyrainfallhasincreasedinrecentdecades,andisexpectedtocontinuetointensify.
• Heatwaves have become more common, and annual temperatures are expected to continue to rise.
• Earlier spring melt and reduced snowpack contribute to changes in growing season hydrology.
Forest impactmodels projected significant changes in tree species’ habitatavailability, growth, and productivity within each of the areas, with differentspecies’responsesbetweenassessmentareas(specificresultsfortheCentralAppalachiansarediscussedlater).Generally,changesinclimateandhydrologytendtointensifymanyofthestressorsthatmayalreadyexistformanyspeciesand can increase their susceptibility to drought, pests, disease, or competition fromotherspecies.
4.2 Adaptive capacity
A review of ecosystem vulnerability assessments found that factors thatcontributed the most to adaptive capacity were generally consistent across
The impact of climate change on forest systems in the northern United States28
Published by Burleigh Dodds Science Publishing Limited, 2020.
the assessment areas. Systems with high adaptive capacity had one or more ofthefollowingtraits:highdiversityofnativespeciesinboththeunderstoryandthecanopy;distributiononavarietyoflandforms,soiltypes,andgeologicsubstrates; distributionwith a large extent; high genetic diversity; and highspecies richness and/or diversity. Systems with low adaptive capacity oftenexhibited traits such as low species diversity and/or richness; low geneticdiversity; systems where the natural disturbance regime has been alteredsignificantly; systems where past management or land use reduced thediversity of species, ages, or genotypes. Although forest management caninfluencesomeoftheseadaptivecapacityfactors,futuremanagementwasnotaddressedinthevulnerabilityassessment;onlythecurrentadaptivecapacityofthe ecosystem was addressed in each assessment.
4.3 Forest ecosystem vulnerability in the Central Appalachian Mountains3
TheCentralAppalachiansregioncovers117400km2fromtheshoresofLakeErietothepeaksoftheAlleghenyMountainsandspansthreestates:Maryland,Ohio,andWestVirginia.Thisregioncontainsamosaicofhigh-elevationborealforests,uplandforestsandwoodlands,riparian,andfloodplainforeststhatareanessentialpartofthelandscape.
AspartoftheCentralAppalachiansClimateChangeResponseFrameworkproject,morethan40scientistsandforestmanagerscollaboratedtoassessthevulnerabilityofforestecosystemsinthisregiontothelikelyrangeofprojectedclimate change.
Although the annual average temperature in the Central Appalachians has remained generally the same between 1901 and 2011, minimum temperatures have increased by 0.6°C. By season, minimum temperatures have warmedthemostduringsummerandfall.BothminimumandmaximumtemperaturesincreasedinAprilandNovember,thetwofastestwarmingmonths.Acrosstheregion,precipitationhasincreasedinthefallbyanaverageof5.8cm(8%)andhasdecreasedinthewinterbyanaverageof2.5cm.Extremeraineventsof7.6 cmorgreater havebecomemore frequent,while light rain events havedecreased.
All climate models project that average temperatures will increase in the Central Appalachians. For the low emissions climate scenario, the projected changerangesfrom0.6°Cto2.2°C.Forthehighemissionsclimatescenario,projectedchangeincreasesrangefrom2.2°Cto6.7°C.Bothmodelsagreethatprecipitation is projected to increase in winter and spring, more so under the
3This sectionwas adapted from Butler-Leopold et al. (2018). https://forestadaptation.org/sites/default/files/evas_technicalsummary_centralapps_June%202016_0.pdf.
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 29
highemissionsclimatescenario.Modelsdisagreeaboutthetimingofpossibleseasonaldecreasesineithersummerorfall,dependingonscenario.Theremaybe greater moisture stress later in the growing season, especially as increasing temperaturesleadtoincreasedwaterlossfromevaporationandtranspiration.Evidence also suggests rain may occur during heavier rain events interspersed among relatively drier periods.
Two climatemodels, three forest impactmodels, hundreds of scientificpapers, and professional expertise were combined to assess the effects ofclimatechangeonregionalforestecosystems.Basedonthisinformation,thereisalargeamountofevidencetosuggestthatthefollowingimpactswilloccurin the Central Appalachians region:
• Soil moisture patterns will change, with drier soil conditions in summer andfall.Duetopotentialdecreasesinsummerandfallprecipitationandincreases in winter and spring precipitation, it is likely that soil moisture regimeswillalsoshift.Longergrowingseasonsandwarmertemperaturesmay also result in greater evapotranspiration and lower soil water availability later in the growing season.
• Fireriskswillincrease.Nationalandglobalstudiesagreethatwildfireriskwill increase across the region, especially in drier areas. Fire is expected to acceleratechangesinforestcomposition,promotingchangesinspeciesfasterthantemperatureormoistureavailability.
• Early growth and advanced regeneration will be vulnerable to changes in moisture. Predicted changes in temperature, precipitation, growing season onset,andsoilmoisturemayalterthedurationorqualityofgerminationconditions.Afterestablishment,saplingsmaystillbemoresensitivethanmaturetreestodisturbancessuchasdrought,heatstress,frost,fire,andflooding.
• Suitability for southern species will increase. Forest impact modelsproject increases in suitable habitat and volume formany specieswithranges largely south of the region, including shortleaf pine, post oak,andblackjackoak.Habitat suitabilitymay increase for species currentlyplanted in the region, such as loblolly pine. Most species are not expected tomigratefastenoughtokeepupwiththeshiftinghabitat.Development,fragmentation,andotherphysicalbarrierstoseeddispersalmayfurtherslownaturalmigrationoftrees.
• Suitabilityfornorthernspecieswilldecline.Forestimpactmodelsprojectdecreases in habitat suitability for northern species such as easternhemlock (Tsuga canadensis), and red spruce (Picea rubens), which arecurrently limited to specific landscape positions where conditions arecool and moist. These microhabitats may provide some refugia forthese species, but their presence on the landscape may become rare.
The impact of climate change on forest systems in the northern United States30
Published by Burleigh Dodds Science Publishing Limited, 2020.
Populationsofsugarmaple(Acer saccharum)andothernorthernspeciesmaybeable topersist in southern refugia if newcompetitors from thesouthareunabletocolonize.
• Invasive plants, pests, and pathogens will increase or become more damaging. A warming climate has allowed some invasive plant species, insectpests,andpathogenstosurvivefurthernorth.Threatssuchasthesouthernpinebeetle (Dendroctonus frontalis),oakdecline,and invasiveplantssuchaskudzu (Pueraria spp.),bushhoneysuckles (Lonicera spp.),andcogongrass(Imperata cylindrica)mayincreaseinthefuture.
Climatechangewillnotaffectallforestspecies,communities,andpartsofthelandscapeinthesameway.Ofnineforestecosystemsassessed,thespruce/firandAppalachian(hemlock)/northernhardwoodforestswereconsideredhighlyvulnerable due to negative impacts on dominant species and a limited capacity toadapttodisturbancessuchasdroughtanddefoliation.Dryoakandoak/pineforestswereconsideredlessvulnerablebecausetheyhavemoredroughtandsuchheat-adaptedspeciesarebetterabletowithstandlarge-scaledisturbances.Riparianforestsarealsovulnerabletopotentialshiftsinflooddynamics.
Thesedeterminationsofvulnerabilityaregeneralacross theregion,andwillbeinfluencedbylocalconditions,forestmanagement,andlanduse.Thehighdiversityinlandforms,microclimates,hydrology,andspeciesassemblagesacrosstheregiongreatlycomplicatesassessmentofvulnerability.Itisessentialto consider local characteristics when interpreting vulnerabilities at local scales. Theassessmentdoesnotconsideradaptivemanagementactions,changesinlanduse,orothersocialoreconomicfactorsthatcouldaffectforesthealthorproductivity.
TheClimateChangeResponseFramework(https://forestadaptation.org/)alsodevelopedforestadaptationresources,withbothanadaptationworkbookandamenuofadaptationstrategiesandapproaches,tohelplandmanagersdevisehighlyrelevantadaptationactionsfortheirprojectsiteandobjectives.
4.4 Climate change adaptation at the local scale4
4.4.1 Climate-informed restoration in the Appalachian Mountains—Lambert Run Demonstration Project
ThehighelevationregionoftheAppalachianMountainswaslargelyinfluencedby over 4000 km2ofspruceforestover150yearsago.Atthattime,thehighvolumeofspruce in theoverstorywasadriverofabove-andbelow-groundecological processes. Strip coalmining and logging are local drivers of the
4This section is adapted from Butler et al. (online) https://forestadaptation.org/adapt/demonstration-projects/monongahela-national-forest-lambert-restoration-project.
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 31
degradationofspruce forests thathasgreatly impactedthe land,hydrology,andvegetationoftheprojectarea.
In May 2014, the Monongahela National Forest worked with the Northern Institute of Applied Climate Science to use a five-step adaptation workbookprocess (Swanston et al., 2016) to carefully consider near- and long-termrestorationgoalsanddemonstratehowmanagementactionscanenhancelong-termresiliencetoclimatechange.The1079-haprojectencompassestheLambertRun watershed and two small adjacent watersheds. In addition to the Lambert RunStripcoalmine, theprojectareacontainsapproximately405haof legacycoalmine lands (reclaimedaccording tomining lawsat the time).Theprojectis located8kmnorthwestofDurbin, inRandolphCounty,WestVirginia,USA.TheMonongahelaNationalForestworkscloselywithanumberofpartnersonthisprojectwhoprovidefundingandcollaboration,includingtheAppalachianRegionalReforestationInitiative,GreenForestsWork,CanaanValleyInstitute,theNatureConservancy,WestVirginiaDivisionofNaturalResources,USDA-NRCSPlant Materials Center, and the Central Appalachians Spruce Restoration Initiative.
Managementgoals(Step1):TheLambertRunStrip–abandonedcoalminelandswereminedinthe1970sandboughtbytheUSForestServiceinthe1980sasaportionofthe16380-haMowerTractacquisition.Rehabilitationeffortsinthe1970sconsistedofreshapingtheminedareastoamorestableconditionandplantingspecies,mostlynonnative,forerosioncontrol.Thecontemporaryresultislargeareasofheavilycompactedsoilwithlowwaterinfiltration,wherethepredominantcoverisnonnativeinvasivegrassesandNorwayspruce(Picea abies)plantedaspartoftheminingreclamationplan.Grass-dominatedareasremain inaconditioncalledarrestedsuccession.TheMonongahelaNationalForest is implementing the Lambert Restoration Project to essentially restore ecological function by improving watershed conditions, providing wildlifehabitat, and restoring native red spruce–northern hardwood ecosystems onLambert Run and adjacent lands.
Climate change impacts (Step 2): According to numerous climate andprocessmodelsandtheCentralAppalachiansForestEcosystemVulnerabilityAssessment (Butler et al., 2015), climate change impacts are expected tointensifyoverthenextcentury,including:
• Regional increase of roughly 1–4°C in mean annual temperature, withhigh-elevationareasprojectedtowarmlessthanlowelevationareas.
• Depending on the model, regional decrease of roughly 2.5–10 cm ofprecipitationinsummerorfall,withmoreseveredryinginhigh-elevationareas.
• Increasedfrequencyofintenserainevents,whichisexpectedtoincreaseerosion potential, especially on steep slopes and where hydrology has been altered.
The impact of climate change on forest systems in the northern United States32
Published by Burleigh Dodds Science Publishing Limited, 2020.
• Projecteddeclines in redspruce,sugarmaple,bigtoothaspen (Populus grandidentata),andothernativespecies.
Challenges and opportunities (Step 3): Red spruce is currently expandingonthelandscape,recoveringfrompast logging,acidification,andwildfiretoregainan importantecologicalniche.Current restorationeffortsare focusedonrestoringsiteecological functionsrelatedtosoilandwater,andrestoringnative tree, shrub, and herb species. Although climate impact models project severedeclinesforredsprucebytheendofthecentury,thesehigh-elevationareas provide the last remaining habitat that is cool and wet enough to support redspruce.Restorationofthesesitesnowmayincreasetheabilityofredspruceforesttocopewithfuturechangesinclimatebycorrectingarrestedsuccession,reconnectingforestedlandscapes,andprovidingagreatersuiteofredsprucesiteswiththepotentialtoserveasrefugia.
Adaptation actions (Step 4): Numerous adaptation approaches andtactics were identified for the project area (Table 3). Adaptation approach1.1was selected to restore and sustain the ecological function so that thehydrologyofthesystemwillbebetterabletowithstandfutureclimate-relateddisturbances (Swanston et al., 2016); the tactic to leave thinned wood onsite isdesigned to improvenutrient inputs.Adaptationapproaches5.1–5.3were selected to enhance species and structural diversity in the spruce-firforest; tactics included releasing red spruce by removing some mid-storyhardwoods, but specifically retaining underrepresented species such asblackcherryanddisease-resistantbeech.Anothertacticistomonitornativespecies at lower elevations in order to detect and monitor upward migration, allowingspeciestoestablishnaturally.Thesetacticsaredesignedtosetuptheecosystemtofunctionasbestaspossibleintheshorttermsothatitcanbetterwithstand future climate changes.Although red spruce is projectedto decline across the region due to climate, the red spruce in this region are currently occupying the best possible habitat. Restoring the ecological functionanddiverse forestsnowmaydelayorbuffer theeffectsofclimatechange locally.
Monitoring (Step 5): Information was also gathered in order toevaluate whether the selected actions were effective and could informfuture management. Because standard monitoring is detailed within themanagement plan for this area, and the restoration of this site requires ahigh level of flexibility, staff did not identify any additionalmonitoring thatis recommended at this time. However, several monitoring variables were chosen for future consideration, includingmonitoring streamflow,pH, anddissolved oxygen in order to detect the progress made in the hydrologic restoration.
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 33
Tabl
e 3 Ad
aptationapproachesandtacticsfortheLambertRunDem
onstrationArea
Site
sM
anag
emen
t obj
ectiv
esAd
apta
tion
appr
oach
Adap
tatio
n ta
ctic
Mix
ed h
ardw
ood
fore
stTheseforestsw
ereformerly
redspruceforest.Red
spru
ce is
exp
andi
ng o
n th
e landscape.Othernative
spec
ies i
nclu
de: r
ed m
aple
, bl
ack
cher
ry, c
ucum
ber t
ree,
an
d bl
ack
birc
h.
•Im
prov
e co
mpo
sitio
n by
in
crea
sing
red
spru
ce
com
pone
nt to
30%
•En
hanc
e gr
owth
rate
and
st
and
stru
ctur
e
6.2:
Mai
ntai
n an
d re
stor
e diversityofnativespecies
6.1:
Pro
mot
e di
vers
e ag
e cl
asse
s1.
1: R
educ
e im
pact
s to
soils
an
d nu
trien
t cyc
ling
6.3:
Ret
ain
biol
ogic
al le
gaci
es
•Releaseexistingredsprucebyremoval(herbicide)
ofmidstoryhardwoodsandcreatewildlifesnags
•Protectblackcherryanddisease-resistantbeech
(othernorthernhardwoodspeciesarenota
conc
ern
at th
is tim
e du
e to
cur
rent
abu
ndan
ce o
n thelandscape)
•Leave-thinnedwoodonsiteforw
oodymaterial
Min
e be
nch
Theseareasareeither
com
pact
ed b
are
soil
or a
re
cove
red
with
Nor
way
spru
ce
andaggressivegrasses.They
aretypicallyconvexpartsof
the
land
scap
e so
soils
are
drieralready.Thereislittle
tonoinfiltrationintothesoil,
butrunoffisbeingcaptured
by m
inin
g po
ols.
•Es
tabl
ish n
ativ
e sp
ecie
s •
Incr
ease
coa
rse
woo
dy
mat
eria
l •
Rest
ore
hydr
olog
ic
function
•M
aint
ain
and
rest
ore
diversityofnative
spec
ies
•Re
duce
land
scap
e fragm
entation
•Pr
even
t the
intro
duct
ion
andestablishmentof
inva
sive
plan
t spe
cies
an
d re
mov
e ex
istin
g in
vasiv
es •
Redu
ce im
pact
s to
soils
an
d nu
trien
t cyc
ling
•M
aint
ain
or re
stor
e hy
drol
ogy
•Pl
ant n
ativ
e tre
e sp
ecie
s and
her
bace
ous s
peci
es
fromlocalnurserystock
•Prioritizenativespeciesinthislocation,whichmay
serveaslong-termrefugia,andmonitorupw
ard-
mig
ratin
g sp
ecie
s •Removenonnativetreesmechanically(Norway
spruce)andherbaceousspecies(spotted
knapweed)
•Increaseinputofcoarsewoodymaterial(leave-
upro
oted
Nor
way
spru
ce, m
ulch
tree
s on
site,
and
importcleanmulchfrom
othersites)
•Priordeep-rippedslopeshavenotshownincreased
erosion.Increaseallowableslopeto<45%to
loosensoilsandincreaserainwaterfiltrationover
mor
e la
nd a
rea
•D
ecom
miss
ion
road
s tha
t are
impe
ding
hyd
rolo
gic
functionorrepurposeforrecreation
•As
sess
road
stre
am c
ross
ings
and
upg
rade
cul
verts
tohandlehigherpeakstream
flow
andallow
aqua
tic o
rgan
ism p
assa
ge
The impact of climate change on forest systems in the northern United States34
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Next steps: Climate change considerations are integrated into forestmanagement under the Lambert Restoration Project. At the time of thispublication, some areas have already been deep ripped and planted, while others are in progress. Wetland creation and road decommissioning is also ongoing. Native species will continue to be planted according to availability, with an emphasis on greater native species diversity.
4.4.2 Climate-informed development of LEAP regional biodiversity vision—Implementation project at Cleveland Metroparks
The Lake Erie Allegheny Partnership for Biodiversity (LEAP) is a consortiumof over 50 conservation-minded organizations (park districts, museums,consultants, watershed groups, state and local government agencies and nonprofits) dedicated to protecting and restoring the biodiversity of theGlaciatedLakeErieAlleghenyPlateauEcoregion.Thisincludesapproximately57000 km2oflandandwaterssouthofCanadafromSanduskyBayinOhiotothe Allegheny Mountains in Pennsylvania.
Theregion’snatural landscapewasprimarilyadeciduous forest (uplandandriparian)withextensivewetlandcomplexesreflectingtheimpactofthelastglacialretreat18000yearsago.Muchoftheregion’sforestswerecutoverandits wetlands drained over a century ago to allow industrial development and agriculturalexpansion.Today’sfragmentedlandscapecontinuestoreflecttheintersectionofurbansprawlandagriculturewithnaturalcommunitiessparselyconnectedthroughforestremnants,ripariancorridors,andrevertingfarmandpastureland.Theresultisaregionwithamosaicpatternofhumandevelopmentinterspersed with natural areas. LEAP collectively protects through ownership or easement ~126 140 ha scattered across the region.
In2018,LEAPworkedwiththeUSForestServiceandtheNorthernInstituteofAppliedClimateSciencetodevelopcustomizedclimateassessmentsfortheregion.Theseeffortswerebrokendowntocapturevariousspatialscaleswherechanging climate could affect differences in tree species distributions. Thespatialscalesinclude(1)LEAPregionalscale,(2)fiveecoregionalsubsections,(3) five largewatershed (HUC6) designations, (4) 13 smallwatershed (HUC8)5 designations, and (5) 11-1 × 1-degree grid cells. Breaking down theregional landscape into these functional units increases the likelihood thatthe fragmentedpatchesofprotected landswereaccuratelycaptured. ItalsoprovidesindividualLEAPandlocallandownersofthosevariousfragmentswithmodeledspeciesadaptationinformationtoconsiderastheylooktoimplementforestmanagementstrategies.
5The HUC stands for hydrologic unit code (HUC) consisting of two to eight digits based on the four levels ofclassificationinthehydrologicunitsystemdevelopedbytheUSGeologicalSurvey.https://water.usgs.gov/GIS/huc.html.
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 35
Climatechangeimpacts:Theprojectedregionalclimatechangeimpactsareexpectedtointensifyoverthenextcentury,andinclude:
• Regionalincreaseof3.7–6.1°Cinmeanannualtemperature. • Regional increase of 9.9–13.2 cm of precipitation with the greatestincreasesprojectedtooccurinNEOhio,NWPennsylvania,andSWNewYork.
• Planthardinesszones6:AshiftofonefullzonewithRCP4.5andtwofullzoneswithRCP8.5.
• Average number of days above 30°C are projected to increase by anadditional41–109daysannually.
• Projected declines in eastern hemlock, pin oak (Quercus palustris),bigtooth aspen, and others.
4.4.2.1 Management goals
Results from the climate data were integrated into the development of aregional biodiversity vision (Beach, 2018). This resource provides prioritiesfor protecting nature across theGlaciatedAllegheny Plateau. Five prioritieswere established such as (1) preserve large blocks of natural land, (2) linknatural areas, (3) reduce habitat fragmentation, (4) reduce other stressors(invasivespecies,pollution,overabundanceofwhite-taileddeer (Odocoileus virginianus)), and (5) prepare for a changing climate (see example project).Eachprioritycontributestoensuringsuitableopportunitiesforforestsacrosstheregiontoadapttoclimatechange(Table4).
4.4.2.2 Challenges and opportunities
While models provide possible climate scenarios with potential species range shifts, several factors should be considered when interpreting the outputs.Modelsrelyongeneralizations,andscaleresolutionmaynotbeadequatetocapture unique microsite variability or subtle landscape features that affectspeciesdistributions.Speciesrecommendationsforclimatetolerancedonotconsiderplantcommunityassemblages,andcarefulreviewbylocalexpertsisrequired fordeterminingmanagementactivities suitable foragivenhabitat.Finally,aforestmaybecompromisedbyexistingsiteconditionsandstressors(invasiveplantspecies, forestpestsorpathogens,browsepressure) thatcanbe exacerbated by climate change and mitigating those stressors are also as importanttomaintainingorincreasingforesthealth.
6Planthardiness zonesaredelineatedbyaverageannualminimumwinter temperature,divided into10-degreeFzones.https://planthardiness.ars.usda.gov/PHZMWeb/.
The impact of climate change on forest systems in the northern United States36
Published by Burleigh Dodds Science Publishing Limited, 2020.
4.4.2.3 Example implementation
ClevelandMetroparks(CM),innortheastOhio,isapartnerwithinLEAPandisusingtheclimatedatageneratedtoassistwithforestmanagement.Theparkdistricthasover9700haofprotectedlandpredominatelyinCuyahogaCountywhichservesapopulationof1.25millionpeople.Approximately80%ofthelandisundevelopedandcomprisedofvariousnaturalcommunities(forests,wetlands,meadowsetc.).Thecurrentforestedcommunities,however,reflectthechangescausedbyvariouslanduseactivitiesandhistoric impactsfromthespreadoftheChestnutBlight(Flinnetal.,2018).Asanexampleproject,CM identified a small forested track (~10 ha) to implement managementactivitiesthatenhanceforestresiliencetoclimatechange.Originallyclearedforpasturepriortothe1930s,thestandhassincebeencolonizedbyruderaltreespeciesdominatedbypoorlyformed(multi-stemmed),single-cohortredmaple(Acer rubrum)withminorrepresentationofwildblackcherry(Prunus serotina) and sugar maple (Acer saccharum). Based on climate models,northern red oak (Quercus rubra), yellow-poplar (Liriodendron tulipifera),bitternut hickory (Carya cordiformis), shagbark hickory (Carya ovata), andAmericanelm(Ulmus americana)areallspeciesprojectedtodowellunderclimateprojections.Thesetreespeciesarealsopartofthemixedforestthatoccursinthisareaandarelimitedlyfoundonorneartheprojectsite.Forestmanagementwilltargetareductionindensityanddominanceofredmapleandotherpoorlyformedtreespeciesonsite(Table4).Theharvestwillreducebasalarea,createsmallgapopenings,releasedesirablecroptrees(i.e.oaksandhickories), and increase light reaching the forestfloor. Largeexclosurefences will allow regenerating seedlings time to establish without deerbrowse pressure.
While no tree planting projects are immediately planned at the example forestproject,CMregularlyimplementstreeplantingstomitigatetheimpactsof climate change. Special attention is provided during planning of thoseprojectstotrackprovenancesourceofthetrees.Inthisway,sourcelocationisconsideredasignificantfactordeterminingpotentiallocalgeneticadaptationsthatmayaffectclimateadaptabilityandensuringsuitablegeneflowintoourarea.
5 Management implicationsGuidance on incorporating information on projected climate changes andimpacts to natural ecosystems into planning efforts can aid on-the-groundimplementationofforestmanagementactions(Keenan,2015;WoodruffandStultz,2016).Tohelpovercomebarrierstoimplementingclimateadaptationactions,planningeffortsmustbeabletodeployresourcesonclimatechange
Published by Burleigh Dodds Science Publishing Limited, 2020.
The impact of climate change on forest systems in the northern United States 37
Tabl
e 4 Ad
aptationapproachesandtacticsfortheClevelandMetroparks
Land
scap
e sc
ale
Man
agem
ent o
bjec
tives
Adap
tatio
n ap
proa
chAd
apta
tion
tact
ic
Gla
ciat
ed A
llegh
eny
Plat
eau
Thisecoregionishighly
fragm
entedandincludes
intactforestcom
munities
like
Beec
h/M
aple
and
successionalforestsfrom
la
nd u
se c
onve
rsio
n
•Preservelargeblockofnatural
land
•Li
nk n
atur
al a
reas
•Reducehabitatfragm
entation
•Re
duce
oth
er st
ress
es in
nat
ure
•Prepareforclim
atechange(see
below)
•Expandsizeofexistingoradd
newlargeforestedareasfor
refugia
•C
reat
e m
igra
tion
corr
idor
s by
link
ing
key
land
scap
e fragm
ents
•En
cour
age
tree
rege
nera
tion
•Identifyunprotectedland(public)and
determineeasementorfeepurchase
pote
ntia
l •Buildlinkagebuffersalongphysicaland
physiographicfeatures(ripariancorridors,
wat
ersh
ed d
ivid
es, L
ake
Erie
shor
elin
e andPortageEscarpm
ent)
•M
anag
e in
vasiv
e pl
ant s
peci
es
com
petit
ion
and
miti
gate
dee
r bro
wse
pressureonyoungseedlings(fence
protection,cullingorhunting)
Clev
elan
d M
etro
park
sEx
ampl
e Fo
rest
Pro
ject
: Fo
rmer
cle
ared
pas
ture
convertedtoforestand
dom
inat
ed b
y ru
dera
l treespecies-redmaple.
•Eliminatenon-nativewoody
plan
t com
petit
ion
•In
crea
se tr
ee sp
ecie
s div
ersit
y •
Enco
urag
e yo
ung
tree
rege
nera
tion
•Re
duce
inva
sive
plan
t po
pula
tions
•M
anag
e ex
istin
g in
vasiv
e sp
ecie
s po
pula
tions
. Com
bine
phy
sical
and
ch
emic
al c
ontro
l with
prio
r and
subsequenttreatmentsfollowingforest
man
agem
ent
•Reducestem
densityofred
map
le •
Sing
le tr
ee se
lect
ion
rem
oval
•Reduceim
pactsofdeer
brow
se •Installfencedexclosureareas
•Co
nsid
er im
plem
entin
g cu
lling
in c
ut
zone
•In
crea
se li
ght g
aps
•Re
mov
e de
ad/d
ying
ash
tree
s •Removepoorlyformed(double/triple
trunk)trees
•C
reat
e sm
all g
roup
ope
ning
s
The impact of climate change on forest systems in the northern United States38
Published by Burleigh Dodds Science Publishing Limited, 2020.
impacts and adaptation responses that are at the same spatial scales as those used in management decisions. For example, interviews with state agency land managers suggested that adaptation actions that were needed at a local scale were limited because adaptation planning tended to occur at a regional scale (Anhalt-Depies et al., 2016). The AdaptationWorkbook is astructured adaptation planning process designed to help managers consider thepotentialeffectsofclimatechangeinidentifyingmanagementactionsthathelp reduce risks and increase the ability to cope with changing conditions (Janowiak et al., 2014). Managers use resources such as ecoregionalvulnerability assessments to understand the broad-scale climate changesandecosystem impacts inorder to ascertain site-level impacts thatpresentimportant risks tomeetingmanagementgoals andobjectives forparticularprojects or parcels of land. The process of ‘stepping down’ regional-scaleinformationtothesalientclimate impactsallowsforestmanagersto identifyspecificandtangibleadaptationactionstominimizeclimateriskstoachievingmanagementobjectives(Swanstonetal.,2016).ManycasestudiesofclimateadaptationinforestmanagementhavebeendevelopedthroughtheClimateChangeResponseFrameworkusingtheAdaptationWorkbook.Theseserveasimportantexamplesofhowmanagersarerespondingtoachangingclimate.Theyprovide insights intohowadaptation in forestryandnatural resourcesmanagement is occurring and highlight similarities across regions and types oflandownershipsaswellasfactorsthatinfluencedifferencesinadaptationresponses.
Theoverarchingsimilarityacrossadaptationprojectsdevelopedthroughthe Climate Change Response Framework is that adaptation decision-making is significantly shapedbypeople’svaluesof the land theymanageand the conditions of the site that they are managing. The recognitionof the critical importance of the uniqueness of both people and place toadaptation planning emphasizes that adaptation is not a one-size-fits-allprocess.This is evident in thebroad array of landmanagers’ goals acrossthe various ownership types and the climate-driven changes with whichthey are primarily concerned. Despite this diversity, regional trends suggest thatadaptationprojectsandparcelsreflectthepredominant—aswellastheunique—ecosystems and resources of a place (Ontl et al., 2018). Similarly,the climate impacts that concern managers the most vary depending on siteconditions,but suggest the importanceof regional climate trendsandimpacts. For example, based on regional forest vulnerability assessments(Janowiak et al., 2018), forestmanagers in northernNewEngland showedthe greatest concern with declines in northern and boreal tree species, while managers working in southern New England were most concerned about the impactsonsoilmoisturestressforthehealthandregenerationofforestsontheir management units.
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Theseregionaltrendsareapparentinthegeneralpatternsofemphasisoneitherresistingclimatechange,enhancingresilience,ortransitioningforeststoconditions thataredifferent fromcurrentconditionsandbetteradapted toafutureclimate (Millaret al., 2007). In thecentralhardwoods region (southernMissouri,Illinois,andIndiana),thelowadaptivecapacityofforestsresultingfromtheencroachmentofmesicspeciessuchasmaplesandalteredforeststructurefromclosureofthecanopyintheabsenceoffire,combinedwithaconcernwithchanges in precipitation patterns, resulted in an emphasis on adaptation actions thataimtotransitionforeststowardamorehistoricalspeciescomposition(e.g.increasedcoverofoakandhickoryspecies)andstructuralconditions(increasedcanopyopenings;Ontletal.,2018).InnorthernregionsofboththeMidwestandNewEngland,recognitionofthegreateradaptivecapacityofforestsresultingfrom higher species diversity or reduced sensitivity to projected changes inmany forest typesseems tocontribute toanemphasisonadaptationactionsthatenhanceresilienceofforeststoimportantsystemstressors,suchasinsectpestsandforestdiseases.Whileactionsaimingtoenhanceresilienceofforestswere the most common in southern New England as well, there was a greater relativeemphasisontransitionactionscomparedtonorthernNewEngland.Thisdifferenceinemphasisisverylikelyaresultofdifferingrelativelevelsofconcernoverforesthealthimpactsfromclimatechangeandnonnativeinsectpests(e.g.gypsymothdefoliationandtreemortality;Kretchumetal.,2014)andclimateinfluencesonpotentialtreeregenerationfailuresintheregion.
Whiletheseadaptationcasestudieshighlighttheimportanceofregionaldifferencesinclimateconcernsandadaptationresponses,theyalsoillustrateimportantcommonalities in forestadaptation.Acrossalladaptationprojects,managersidentifiednumerousadaptationstrategiesappropriateforindividualprojectsthatspannedthecontinuumofresistingclimate impacts,enhancingsystem resilience, and transitioning systems to be better adapted to futureconditions (Ontl et al., 2018). Similar to diversifying an investment portfolioto spreadfinancial risk, thesemanagersmaybe seeing thevalue inusingamultitude of adaptation tactics that address both near-term challenges andlong-term climate impacts to enhance the capacity of the system to copewithchange. Identifyingan ‘adaptationportfolio’ that includesactionsacrossthis resistance-resilience-transition continuum may also reduce risk whenplanningforarangeofpossiblefutureconditionsataparticularsite.Despitethis diversified approach to adaptation planning, there were strong linksbetween concern about particular climate impacts and adaptation responses, assummarizedinthefollowingexamples:
• Identifying increased stressors associated with warming winters andgreater pest and disease pressures correlated with actions that aimed to increase species and structural diversity.
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• Concern over altered precipitation patterns and related impacts were linkedtotacticsthataimedtofacilitatespeciestransitions.
• Impactsofextremeprecipitationeventscorrelatedwithactionsthatincreasedlandscape connectivity, generally in streams and aquatic ecosystems.
• Increasedriskofwildfirewasassociatedwithafocusonactionsthatrealignsystemsfollowingdisturbance.
Theprecedingsectionsonclimatechangeandnear-orlonger-termimpactspointtohighertemperatureandincreasedpossibilityofdroughtasacommonprojectedoutcome.Withepisodesof loweramountsof rainfallapossibility,andhighertemperatures—whichcanfurtherreducesoilmoistureavailabilitydue tohigher transpiration (Clarket al., 2016)— therewouldbeperiodsofreduced growing space for trees and other plants.Although some speciesmay be more adaptable to these swings, the moisture stress can reduce the vigor of a tree andmake itmore vulnerable tootherdisturbances, such asinsectordiseaseattack.Treeswithreducedvigorstoreloweramountsofplantsugars over the winter, so the plant starts out the new year in an even more vulnerable state. As water becomes limiting, current stand densities are no longer adaptive.
Theongoingreductioninanthropogenicdisturbances,suchasharvesting,willperpetuatethedeclineintheproportionofforestsinanearlysuccessionalstage.Withthisdecreaseinearlytomid-successionaltreespeciescomesalossofhabitat for theanimals,birds, insects,andotherco-occurringspecies thatrely on them.
6 Conclusion and future trendsThischapter isdesigned to inform landmanagersandpolicymakersas theythink about what their forests might look like in the future and considerapproachestopreparingforthatfuture.Intheshortterm—thenextdecadeortwo—thehuman-causeddemographicandeconomicfactorsthatcontributetofutureclimatechangescenarioshavemoreinfluencethanachangingclimateontheextentandcompositionof forests.Theanthropogenicvariablesaffectforestextentandfragmentation.Meanwhile,thebiologicaltrendsofsuccessionandcompositionreflectthehistoricaldevelopmentandcurrentstructuretoagreaterdegreethandonear-termclimateinfluences.Eventually,however,thisecological momentum is projected to be overwhelmed by the outside abiotic influencesofalteredtemperatureandprecipitation.
The information in this chapter provides context for climate changeconsiderationsandlaysthefoundationforthemanagementactionsdiscussedin the case studies. While there is deserved attention paid to the potential impact of climate change on forest land extent, composition, and health,
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readersareurgedtobear inmind theother forces thathelp toshape theseaspects of forests. These other influences, such as land use change, maymagnifytheprojectedclimatechangeeffectormaysloworotherwisemitigateit.Theoutcomedependsontheattributesoftheforest.Inturn,thenatureandtimelineoftheeffectsdependnotonlyonforestcharacteristics,butalsoonthetypeofstressor.Forexample,nonnativeinvasivespecieshaveanimpactthatismore pronounced in the near term than over the long term, but they can also reducethelonger-termresilienceoftheforeststowithstandchangingclimaticconditions.
Thesocialandeconomicfactorsthatdriveclimatechangealsohaveadirecteffecton theextent,composition,andstructureof the forest. Insomecases,managerscanemploythesefactorstobringaboutthedesiredoutcomes,butthepotentiallonger-termimpactsofachangingclimatewillgraduallyincreasein importance.
Ecologists speakof resistanceand resilience in the faceofdisturbance,usually with the former being a more pre-disturbance response and thelatter being post-disturbance response. Such a model is predicated on adiscrete event or block of time.Whatmanagers are urged to comprehendgoing forward is that the future forests may face both kinds of influencessimultaneously. Managers need to consider both resistance and resilience in their management plans. Some disturbances will set back the successional clockwithinthecurrentecologicalprogression(OliverandLarson,1996).Giventherightcircumstances,however,thesamedisturbancemaysettheforestedlandscape on a new trajectory.
Resiliency in future forests depends upon the collective response ofindividual tree vigor. As mentioned in the oak decline section mentioned previously,treeswithadequateorevenasurplusofresourcesshouldbebetterable towithstandperiodsofdroughtor forest health attacks. Leaving someunoccupied growing space, some ‘slack’ in the system gives room for theforest to absorb temporary resource restrictions. Fromamanagementpointofview,modelsofproductivitybasedon full stockingoftendonotconsidertheexpectedimpactsofattacksonforesthealth(Moseretal.,2003).Ifamoredemandingclimatemakes recovery frommortalityeventsmorechallenging,expectationsoffutureproductivitymustbereducedandmanagementactionsmustreflectthisnewrealitybydeliberatelykeepingforestsbelowthehistorical,nominallevelsoffullstocking.Suchforestsareanticipatedtobeabletobetterwithstandclimateinfluencesthanmightthepreviousdenseforests.Regardlessof the extent of climate change impacts, the forests of the northern UnitedStateswillrequiremanagementtomaintaintheirvigorandhealth.Toolsandapproachesforguidingwisemanagementareavailabletodaytohelpensurethat forests continue to provide the values andbenefits that people expectfromthem.
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7 AcknowledgementsWethankDr.StephenR.Shifleyforhisvaluablecommentsonearlierversionsof this manuscript and Cynthia F. Moser for her wide-ranging editorialcontributions. We are grateful to both for giving their insight and time sogenerously. Reviewers of earlier versions of this chapter provided manyvaluable comments and suggestions.
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