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T!   _  E!XX    %  EffectsofOzoneonForestTreesintheSouthernAppalachians:AnAssessmentoftheCurrentStateofKnowledge X6eX! EPreparedfortheSouthernAppalachianMountainInitiative(SAMI)October28,1996ArthurH._Chappelka_ԀandLisaJ.SamuelsonSchoolofForestryAuburnUniversityAuburn,Alabama368495418JohnM._Skelly_DepartmentofPlantPathologyPennsylvaniaStateUniversityUniversityPark,Pennsylvania168024507AllenS._Lefohn_ASL&AssociatesHelena,Montana596014144 }^XX6e#X6eX}^#   -() _}^XX6e8XXdXXd8EXECUTIVESUMMARY#X6eX}^,#  3 X` _ XX3  TheSouthernAppalachianMountainInitiative(SAMI)isamultiinstitutionalcooperative N establishedinresponsetoconcernsoverthepotentialadverseeffectsofairpollutantsonterrestrialandaquaticecosystemsinthesouthernAppalachianregion.Themainfocusofthisprojectistoprovideabalancedandunbiasedassessmentoftheeffectsoftroposphericozoneonforesttrees.PrimaryemphasisisonClassIareasintheAppalachianregionsofAlabama,Georgia,Kentucky,NorthCarolina,SouthCarolina,Virginia,andWestv v Virginia.v v Keyv v indicatorsusedintheevaluationofozonev v effectsv v onforesttreesv v are:visiblefoliarinjury,growthandproductivity,andphysiologicalv v function.v v Themajorobjectivesofthisreportare:0  1.0(#(#Summarizetheexistingstateofknowledgeontheeffectsofozoneonforesttreesin  theSAMIregion. (#(# 0  2.0(#(#Evaluatetheuseofavailableassessmentmethodologiesforpredictingfuturechanges  inozoneeffectstoforesttreesintheSAMIregion. 6(#(#  Themajorfindingsare:   VisibleInjury  n"   U XXGԀ*0  #XGX  U #Troposphericozoneairpollutionhasrepeatedlybeenshowntocausefoliarinjuryon  $ sensitivevegetationthroughoutmuchoftheSAMIregion.Onbroadleafspecies,foliarinjuryhasbeenobservedasamidtolateseasonadaxialstipple,leafreddening,andearlyleafsenescence.v v Underambientozonev v v v exposures,v v symptomsonconifersarelessevidentduetomanymimickingsymptoms,buthavebeennotedtoinvolveseasonlongchloroticspottingandmottle.Afewobservationsofanearlysummeruniformtipburnofnewlyemergingneedleshavebeenreported. (#(#   U XXGԀ ':#2   )%4 Ѐ*#XGX  U` # 0  Foliarinjuryhasbeeninducedfollowingexposurestoozonedeliveredwithinlaboratory,   greenhouseandfieldopentopchamberconditionsoffumigation.However,veryfewexposure/foliarsymptomresponsesaredefinedforsubsequentuseunderfieldconditions. (#(#   U XXGԀ*#XGX  U(# 0  Opentopchambershavebeenusedundernaturalfieldconditionsfortheprotectionof B  forestspeciesfromambientozoneexposuresonaseasonlongbasis.Cleardifferencesinsymptomexpressionareconsistentlyobservedfollowingsuchtreatments. (#(#   U XXGԀ*#XGX  U# 0  Withtheexceptionofonepreliminarystudy,noclearlydefinedassociationhasbeen  $  demonstratedbetweenfoliarinjuryandgrowthundernaturalgrowingconditions.Suchrelationshipshavebeenrecentlyobservedformeasuredphysiologicalchangesinleafperformance. (#(#  GrowthandPhysiologicalFunction *z  U XXGԀ*#XGX  Uf# 0  Growthandphysiologicalresponsestoozonehavebeenreportedforindividualtreesthat  occurintheSAMIregion.Mostofthesearewithindividualseedlings(95%)ofresearchwasconductedonloblollypine(majorityofallresearchregardingozoneeffects)andredspruce.Yellowpoplar,northernredoakandblackcherrywerebyfar,themostinvestigatedhardwoodspecies. (#(#  U XXG 򀀀*#XGX  U# 0  MaturetreeresponsesintheSAMIregionhavebeenreportedforsixspecies:black j#* cherry,redmaple,easternwhitepine,loblollypine,northernredoakandloblollypine.Threeofthestudieswerecorrelativeanduncontrolled.Onlyresearchwithnorthernredoakwascontrolled(causeeffect)innature. (#(#  U XXG 򀀀*#XGX  U# 0  Rankingofspeciessensitivitytoozone(growth,physiologyandvisibleinjury)ishindered ^)$2 byvariationinenvironmentalconditions,ozoneexposures,studydurationandobjectives, ,+|&4 treeageanddifferentialgeneticsensitivitywithinaspecies.Ofthefivespeciesmostintensivelystudied,blackcherryandloblollypineappearthemostsensitive,yellowpoplarandnorthernredoakintermediatetotolerant,andredspruceverytoleranttoozone.Resultswerequitevariable,fortheabovementionedreasons.Elicitingastatisticallysignificantgrowthresponseatambientozonelevelsisverydifficult.Thismaybetheresultofseveralfactors;thetreesexposedarenotsensitiveundermostambientconcentrations,notenoughreplicationtodetectstatisticaldifferences,theshorttermnatureofmoststudies(generallylessthan5%ofatreeslifespan),variabilityinozoneexposureregimes(temporallyandspatially)anddifferentialsensitivitywithinthespeciesexposed(ChappelkaandChevone1992,Teskey1995). (#(#  U XXG 򀀀*#XGX  U+# 0  Noconclusionscanbemadeatpresentregardingtheeffectsofozoneongrowthand   productivityoftheforestsintheSAMIregion.Thereareonlytworeportsofozoneeffectstomaturetreegrowthgrowinginaforestsituation.Oneisapreliminaryreportwithyellowpoplarandblackcherryandtheotherwithloblollypine.Therearesimplynotenoughdatatomakeany broadstatementsregardinggrowthandproductivity. (#(#  U XXG 򀀀*#XGX  U\# 0  Ozoneeffectscanbealteredbyotherenvironmentalandbioticfactorssuchaswater * status,temperature,light,relativehumidity,insectsanddiseases.Giventheinteractionbetweenozoneandthesefactors,itisunknownifanyreductionsinozonelevels(1020%)willresultinsubsequent,measurableincreasesingrowthandphysiologicalfunctionofforesttreesintheSAMIregion. (#(#  ExposureResponse "*  U XXGԀ*#XGX  U# 0  Fortheyears1983through1990,theozoneexposurekrigingestimatesresultedinmostof #D, thegridcellsfallingbetween23.866.5ppmhfortheW126index.In1988,11ofthe120cellshadW126estimatesgreaterthan66.5ppmh.Threecellsin1986and1989,andonecellin1990hadaW126estimateof5.923.7ppmh.Nocellswereclassifiedashaving lessthan5.9ppmh.)8%4(#(#   U XXGԀ*#XGX  U!# 0  Animportantobservationisthatusually,withintheSouthernAppalachianareaboundary,   ozonemonitorsexperiencedfewerthan40hoursinwhichthehourlyaverageozoneconcentrationwas0.10ppm(19831990).Theonlyyearthatdeviatedfromthispattern 0 was1988when11ofthe15ozonemonitorsintheareahadgreaterthan50hoursinwhichthehourlyaverageozoneconcentrationwas0.10ppm. (#(#  U XXG 򀀀* #XGX  U##0  ThecombinationofthePalmerhydrologicindexandtheozoneexposureresultsindicate  V  thatsoilmoistureconditionsmayaltertreegrowthresponsetoozoneexposures(Lefohnetal.1997).Combiningexposureinformationwithmoistureavailabilityandexperimental 6  exposureresponsedatahasidentifiedpossibleareasthat mayhavethegreatestpotential   forpossiblevegetationeffects. (#(#  Models     U XXGԀ*#XGX  U2&# 0  Severalmodelshavebeenusedtosimulategrowthand/orphysiologicalresponsesto &v ozonefortreesintheSAMIregion.Theseincludeasingletreemodel(TREGRO),severalcanopymodelsonozoneuptakeandcarbonfixation,aforestsuccessionmodel(FORET)andaloblollypinemanagementmodel(AIRPTAEDA).ThesemodelsallprovidesomeinformationonozoneeffectstospeciescommonlyfoundintheSAMIregion.Eachmodelhasadvantagesanddisadvantages,andtheyvaryintheirlevelofcomplexity.TREGROprovidesgoodinformationonozoneeffectsforasingle,opengrowntree.It,however,doesnotprovideinformationregardingforeststandgrowth.AccurateozonedoseresponsefunctionsareneededtomodeltreeresponsesusingTREGRO.Whilethesefunctionsareavailableforsometreespeciesattheseedlinglevel,theyarenotavailableformaturetrees.Giventhepaucityofmaturetreestudies,modelpredictionsusingexperimentalgrowthresponsesarenoteasilyvalidated.Inaddition,themodel(TREGRO)requiresdetailedozoneexposure,environmentalandphysiologicaldata.Thesev v dataarev v notpresentlyavailableformanyspecies.Thecanopymodelsallprovidegoodinformationonozoneuptakeandcarbonfixation.Theydonotprovideinformationonwholetreeresponses(rootgrowth,etc.).Inaddition,allassumethatozonelevelsandozone P+&6 responsesareequalwithinacrown.Thismayproduceerrorinthemodel.TheFORETmodelprovidessomeextremelyusefulinformationonozoneeffectstoaforeststand.Itcanprovideinformationonchangesingrowthandproductivityovertime.Thissimulatorneedstobereparameterizedspecificallyforozone.Itoriginallywasparameterizedforairpollutioneffectsingeneral,andthisassumptionneedstobev v modifiedspecificallyforozone.v v Also,themodelassumesozoneeffectstobeequalwithinaspecies,anderrorcouldresultduetothisassumption.AIRPTAEDAhaslimiteduseforanassessmentofthetreeswithintheSAMIregionatpresent,sinceloblollypineisaminorcomponentwithintheforestsoftheSAMIregion.Also,thismodelisbasedonagrowthandyieldmodelforplantationgrowntrees.Itdoes,however,accountfordifferentialgeneticvariabilitywithinaspeciestoozone. (#(#  AssessmentMethodologies  H   U XXGԀ*#XGX  U0# 0  Threeassessmentmethodologieshavebeenusedtodetectriskduetoozonev v forv v different  foresttypesintheSAMIregion.ThemethodproposedbyLefohnandcoworkers(1997)providesinformationofareasthatarepossiblyatrisk.ThemethodologyusesexposureresponseinformationwithozonekriginginformationandthePalmerhydrologicindextocreate areasofconcernmapsforozone.Thismethodologyisempiricallydrivenandisbasedontheassumptionthatmoisturestressinconjunctionwithozonecausesareductioninozoneinducedgrowtheffects.Limitedexposureresponsedatawereavailablefromwhichtheinvestigatorscouldchoose.Morerealisticexposureresponseexperimentswithdeciduoustreespeciesexperimentswouldbehelpful.ThesecondriskassessmentwasconductedbyHogsettetal.(1993).Thereappearstobeseverallayersofparameterization #, necessary(modellinkages)fortheassessmenttobeoperational.Forestgrowthscenariosarebasedonindividualseedlingdatafromonlyasmallnumberofstudies(similartotheonesusedbyLefohnetal.(1997),mostlywithseedlingsgrowinginpots,inopentop '"2 chambers.Otherconcernsarewiththeerrorassociatedwiththeestimationofozoneexposuresandspeciesdistribution.SimilartothelimitationsoftheworkdescribedbyLefohnetal.(1997),thereislittleozonemonitoringdataavailable.Hogsettetal.(1993) +$'8 estimateozonevaluesfortheregionusingactualdata,NOxemissionsinformation,and  meteorologicaldata.Theuncertaintyinusingcountybasedemissionsinformationasapredictorofozoneformationcanleadtopotentialerrorsinthedeterminationofexposurevalues.Regardingspeciesdistributionandamounts,theinventoryofparticularspeciesmaynotbeuptodate.Thethirdmethodology,proposedbyLuxmoore(1992)althoughaveryvalidtechniqueisprobablynotfeasibleinitscurrentform(assessmentonlyforloblollypine).However,itmaybepossibletomodifythistechniqueinthefuturetoencompassthemajortreespeciesgrowingintheSAMIregion. (#(#  Recommendations  "r    Itisouropinionthatanyofthethreeaforementionedassessmentmethodologieshavemerit,butitisuptoSAMItochoosewhichone(oramodificationofthem)thatbestsuitsitspurpose.Itisimperative,however,whenconductingassessmentexercises,thatwemustconstantlykeepinmindthetremendousvariabilitythatexistswithinnaturalsystems.Therefore,to"model"ozoneinducedexposure/responsesacrossthegeographicrangeofaspecies(evenwithinthelimitedrangeoftheSAMIregion)posesaformidabletask.Atthistime,wewouldconsidertheinfluenceofmicrositefactorstobemostimportantincontrollingresponsestoalteringthepotentialforozoneinducedexposures.Availablesoilmoistureappearsv v atv v v v presentv v tobeofgreatestsingleimportanceincontrollingozoneuptake,andsubsequenteffects,throughitsinfluenceonstomatalfunctionattheleaflevel.Thereforescalingofthissinglesite/physiologicalresponsephenomenonfromseedlingresearchtomaturecanopyresponsescontinuestoholdasignificantpositionofneedinfutureresearchefforts.Suchforestbasedresearchisnecessaryinsupportoftheassessmenteffortsatdeterminingregionwideozoneimpactswhenthesearesuggestedtobeoccurringaslargerscaleforestresponses.  Inaddition,assessmentsmustalsotakeintoaccounttherelativeinfluencesofinsectpests,bioticpathogensandabioticstressors(otherthanozone)andinterandintraspeciescompetitionforresourcesincontributingtothemeasured/modeledchangesinforesthealthand/orproductivity.Verycarefuldiagnosticsmustfirsttakeplaceatthespecificsitesandforthespeciesofinterestbeforeanozoneinducedresponsemaybeheldaccountableatthatspecificsite,oreven h+&8 forselectedspeciesatthatsite.Scalingresponsesacrossbroadregions(i.e.,SAMI)forthe  purposeofdeterminingozoneinducedeffectswithoutregardtogainingaclearunderstandingoftheinfluenceofmanyotherstressinducingfactorswouldpossiblypresentaskewedand,therefore,unrealisticscenariooftherelativeimportanceofambientozoneexposurestoforestsintheSAMIregion.  8  X (XXG t TABLEOFCONTENTS#XGX(YB#   K" X9` _ X X` _ XKExecutiveSummary""(#. %i  I.Introduction""(#.< < #1   9 ClassIAreas""(#.U U (1   9 ForestResources""(#. +2 t   9 NaturalStressors""(#. ,2 `   9 Objectives""(#.y y %3 L  II.VisibleFoliarSymptoms""(#.D D /4 8   9 DescriptionofSymptoms""(#.%%25 $ t   9  % BroadleafSpecies""(#. 05 `   9  % ConiferSpecies""(#.  . 7  8  L   9  % BioindicatorSpecies""(#. 38 8   9 VisibleFoliarOzoneSymptoms:TreeSpeciesintheSAMIRegion""(#.Y 9  8  $   9  % Aspen(Populustremuloides)""(#.AA:9    9  % Blackcherry(Prunusserotina)""(#.=9    9  % Blacklocust(Robiniapseudoacacia)`"`"(#.B10   9  % Honeylocust(Gleditsiatriacanthos)`"`"(#.eeB10   9  % Hybridpoplar(Populusmaximowiziixtrichocarpa)`"`"(#.IIP1 1  0  p  9  % Redmaple(Acerrubrum)`"`"(#.--611 \  9  % Redoak(Quercusrubra)`"`"(#.611 H  9  % Sassafras(Sassafrasalbidum)`"`"(#.}}<12 4  9  % Sweetgum(Liquidambarstyraciflua)`"`"(#.A12  p  9  % Sycamore(Platanusoccidentalis)`"`"(#.?12  \  9  % Whiteash(Fraxinusamericana),Greenash(F.pennsylvanica)`"`"(#.[1 3  2  H  9  % Yellowpoplar(Liriodendrontulipifera)`"`"(#.F13 4  9 UnderstorySpeciesSensitivities`"`"(#.));14    9 Conifers`"`"(#.#15    9  % Jackpine(Pinusbanksiana),Easternwhitepine(P.strobus)`"`"(#.[15   9  % Loblollypine(P.taeda)`"`"(#.715   9  % Pitchpine(P.rigida)`"`"(#. 516    9  % Redspruce(Picearubens)`"`"(#.qq81 7  6  l!  9  % GeneralConclusions`"`"(#. 217 X"  III.InteractionsofO3andOtherStressFactors`"`"(#.LLD17 D#!  9  % GeneralConclusions`"`"(#. 220 0$" IV.PhysiologicalEffects`"`"(#.h h -2 1  0  %l # М     9  % MechanismsofOz       oneToxicity`"`"(#.;2 1 0  @9   @%    0   &X!$    9  %  TreePhysiologicalResponsetoOzone:TreeSpeciesintheSAMIRegion`"`"(#.  d21 &D"%  9  %   Yellowpoplar`"`"(#. 02 2  1  '0#&  9  %   Northernredoakandwhiteoak`"`"(#.A22 ($'  9  %   Blackcherry`"`"(#.  /23 )%(  9  %   Sugarmapleandredmaple`"`"(#.<23 *%)  9  %   RedspruceandFraserfir`"`"(#.=24 +&*  9  %   Loblollyandshortleafpine`"`"(#.YY>24 |,'+  9  %   Easternwhitepine`"`"(#. 525 h-(,  9  % OzoneEnvironmentInteractions`"`"(#.QQ=2 6  5  T.)-  9  % OzoneUptake`"`"(#. +27 @/*.  9  % GeneralConclusions`"`"(#. 228 ,0|+/    V.GrowthResponses`"`"(#. '29   9 GreenhouseStudies`"`"(#.i i -30   9  % EasternHardwoods`"`"(#.Q Q 03 1  0    9  % ConiferousSpecies`"`"(#.  132 t  9  % Summary`"`"(#.  &33 `  9 ControlledFieldExposures`"`"(#.534 L   9  % EasternHardwoods`"`"(#.Q Q 034 8   9  % Pine`"`"(#.}}#36 $ t  9  % OtherConiferousSpecies`"`"(#.739  `  9  % Summary`"`"(#.  &39  L   9 UncontrolledFieldStudies`"`"(#.540  8   9  % Summary`"`"(#.  &42 $   9 GeneralConclusions`"`"(#. .42   VI.ExposureResponse`"`"(#.  )43    9 GeneralConclusions`"`"(#. .47   VII.Models`"`"(#.47    9 IndividualTreeModels`"`"(#.y y 14 9  8  p  9  % Summary`"`"(#.  &49 \  9 CanopyModels`"`"(#.! ! (50 H  9  % Summary`"`"(#.  &51 4  9 StandModels`"`"(#. '51  p  9  % Hardwoods`"`"(#. (52  \  9  % Summary`"`"(#.  &53 H  9 LoblollyPine`"`"(#.Y Y (5 4  3  4  9  % Summary`"`"(#.  &54    9 GeneralConclusions`"`"(#. .55   VII.MethodologiesUsedinAssessingOzoneEffects`"`"(#.@@F5 6  5   0 9 ApplyingExposureInformationforIdentifyingAreasofConcernLefohnetal.(1997)#`"`"(#.]!]!p9(#9(##56   9 RiskCharacterizationHogsettetal.(1993)`"`"(#.%%H 60  59    9 ScalingUpPhysiologicalResponsestoOzoneLuxmoore(1992)`"`"(#.X6 2  1  l  9 GeneralConclusions`"`"(#. .62 X  VIII.OverallConclusionsandRecommendations`"`"(#.A6 4  3  D!  9 Conclusions`"`"(#.  &6 4  3  0"   9 Recommendations`"`"(#. *6 9  8  #l! IX.References`"`"(#. #7 1  0  $X" X.ListofFigures`"`"(#.d d '8 9  8  $D #  9 Figures`"`"(#." 90  89  %0!$ Table1!!(#.10 2  1  &"% Table2!!(#.10 6  5  '#& Table3!!(#.11 5  4  (#' N" X` _ X X9` _ XN  |*%) X (XXG I.INTRODUCTION #XGX(f#  М  TheSouthernAppalachianMountainInitiative(SAMI)isamultiinstitutionalcooperativeestablishedinresponsetoconcernsoverthepotentialadverseeffectsofairpollutantsonterrestrialandaquaticecosystemsinthesouthernAppalachianregion.ThemissionofSAMIis throughacooperativeeffort,toidentifyandrecommendreasonablemeasurestoremedyexistingandtopreventfutureadverseeffectsfromhumaninducedairpollutionontheairqualityrelatedvalues(AQRVs)ofthesouthernAppalachians,primarilythoseofClassIparksandwildernessareas.  OzoneisconsideredasoneofthemostimportantairpollutantsaffectingvegetationintheSAMIarea(U.S.EPA1986,1996).Therefore,assessingtheimpactofthispollutantonterrestrialecosystemsoccurringwithintheregioniscritical.Themainfocusofthisprojectistoprovideabalancedandunbiasedassessmentoftheeffectsoftroposphericozoneonforesttrees.PrimaryemphasisofthisassessmentisonClassIareasintheAppalachianregionsofAlabama,Georgia,Kentucky,NorthCarolina,SouthCarolina,Virginia,andWestVirginia(Figure1).Keyindicatorsofozoneeffectstobeevaluatedare:visiblefoliarinjury,growthandproductivity,andphysiologicalfunctionsofforestvegetation.   ClassIAreas  n"   TheCleanAirAct,enactedin1970,wasamendedin1977toestablishClassIareasasnationalparksandwildernessareasgreaterthan2,400and2,000hectaresinsize,respectively.TheseareasareaffordedthegreatestdegreeofairqualityprotectionundertheCleanAirAct.AirpollutionisnotacceptableinresourcesinClassIareasifit1)diminishesthenationalsignificanceofthearea,2)impairsthequalityofthevisitorexperience,or3)impairsthestructureandfunctionoftheecosystem(USDADOI,1982).FederallandmanagersarerequiredtodetectairqualityinClassIareasandassesspossibleimpactsofairpollutantsonresources(AQRVs)withinthesedesignatedareas.OftheClassIareasshowninFigure1,TheShenandoahNationalParkandGreatSmokyMountainsNationalParkarebyfarthelargestareasthatarepotentiallyatriskintheSAMIregion. +&8 & & ForestResources     TheforestedareaswithintheSAMIregioncovermorethan50%ofthelandareaandareverydiverseinnature.Mostofthetreespeciesintheregionaredeciduoushardwoods'&nrԀwithvariousspeciesofoak,hickories,maplesandyellowpoplar(Liriodendrontulipifera)asthe & predominantspecies.Manyotherspeciesofhardwoodsdocommonlyoccurintheregion.Althoughnotasprevalentashardwoods(<30%ofthetotalwoodvolume)severaldifferentconiferousspeciescancommonlybefoundintheSAMIregion.Theseincludeeasternhemlock,Fraserfir,redspruce,pitchpine,Virginiapineandloblollypine.AmoredetaileddescriptionoftheforestedresourcesintheregionispresentedinTheSouthsFourthForest:Alternativesfor   theFuture(USDAForestService1988). "r   NaturalStressors  6   Besidesairpollutants,manyotherstressesaffectforestsintheSAMIregion.Thesecanbefoundinanyforestintheworldandincludeabioticagentssuchasmoistureandnutrientdeficiencies(Dougherty1995)andbioticstressessuchasinsectsanddiseases(Hepting1971,Skellyetal.1987). n   Commonlyfoundinsectsincludethebalsamwoolyadelgid(Adelgespiceae),gypsymoth    (Pothetriadispar),severalbarkbeetles(primarilyIpsspp.)inclusiveofthesouthernpinebeetle 2" (Dendroctonusfrontalis),anddiseasessuchassycamoreanthracnose(Gnomoniaveneta), $ Armillariarootrot(Armillariaspp.),numerouscankers,fusiformrust(Cronartiumquercuumf. F& sp.fusiforme),littleleafsyndrome(Phytophthoracinnamomi),andannosumrootrot X ( (Heterobasidionannosum).Althoughprimarilyendemicinnature,insectattacksanddiseasescan ! * reachepidemicproportionsintheSAMIregionasevidencedbythebalsamwoolyadelgid,gypsymoth,andthefungiwhichcausechestnutblight[Cryphonectria(Endothia)parasitica],dogwood ~$. anthracnose(Disculadestructiva)andbutternutcanker(Sirococcusclavigignenti %0!0 juglandacearum).Wildlifeactivitiesalsocauseseriouslossesintheforestwithparticularconcern B'"2 fordamagetoregenerationbythewhitetaildeer.Inaddition,numerousabioticstressorsinclusiveoflocaland/orregionalscalemajorandminorperiodsofdrought,rimeiceandmoreheavyaccumulationsoficeleadingtotopbreakage,freezingtemperaturesleadingtowinterinjury, h+&8 flooding,andofcoursefireareallpresentwithintheforestsoftheSAMIregion.MoistureandnutrientstressescanbelimitingfactorsinboththeproductivityandspeciescompositionofthevariousforesttypesintheSAMIregion.  Theinterrelationshipsofambientozoneexposurewithallofthesenaturalstressorsremainsvirtuallyunknown.Introducedinsectsandpathogensusuallyneedonlyasusceptiblehostspecie(s)andfavorablegrowingconditionsforrapidspeedandreproductionintoepizootic/epidemicproportions.Moreisknownaboutotherabioticstressorssuchaswithdroughtand/orotherpollutantinteractionsasreviewedlaterinthisdocument.ThesenaturallyoccurringandintroducedstressorsasmaybefoundthroughouttheSAMIregionaredescribedinmoredetailbySkellyetal.(1987),MeadowsandHodges(1995)andTainterandBaker(1996). Objectives  6   Thesynthesisdocumentwilluseinformationobtainedfromtheannotatedbibliography(alreadysubmittedtoSAMI)toassessthescientificevidenceconcerningozoneeffectsonforesttrees(primarilyClassIareas)intheSAMIregion.Theprimaryemphasisofthedocumentincludessevenitems:1)evaluationofozoneeffectsonvisibleinjury,growthandproductivity,andphysiologicalfunction;2)reviewandclassifyhistorictrends,statusandcontributionofozonetothesetrendsintheSAMIregion;3)evaluateozoneexposureresponserelationshipsderivedfrombothgreenhouseandfieldstudies;4)critiqueexistingozoneexposuredatasetsapplicablytoClassIareasandtheirpotentialforuseinassessingstatusofClassIareas;5)evaluateotherabioticandbioticfactorsthatmayinfluenceforestresponsetoozoneandassessthepotentialinfluenceofozonecomparedwithotherenvironmentalandplantfactors;6)reviewalternativeinterpretationsofexistingdata;and7)identifyinformationgapsthatlimitassessmentofcurrentandfuturestatusofforestresourcesintheSAMIregion.RecommendationsfromthisassessmentwillbeusedbySAMItoaddressthreepolicyquestions:0  1.0(#(#Whatisthecurrentstatusoftheresourcesrelativetoozoneeffectsonvegetation?(#4(#(#  0  2.0(#(#Whatistherelationshipbetweenozoneexposuresandvegetationresponse?*V%6(#(# 0  3.0(#(#Whatchangesinresourcestatusareprojectedtooccurfromchangesinexposuresdue   toimplementationofthe1990CleanAirActAmendmentsorotheremissionmanagementoptionsbeingconsideredbySAMIsPolicyCommittee? (#(# & b (XXGII.VISIBLEFOLIARSYMPTOMS#XGX(X# 8  М   Thisintroductorysection,asadaptedinlargemeasurefromSkellyetal.(1987),will  &  presentdescriptiveinformationonthevisiblefoliarinjuriesasinducedbyexposuresto'b8 IԀambientozoneundernaturalfieldconditionswithintheSAMIregion.Itisrecognizedthatprevisualphysiologicalchangesareinducedbeforethemanifestationofsuchvisiblesymptoms.Growthand/orproductivitychangesmayalsoprecedeorfollowvisiblesymptoms.Pleaserefertotherespectivesectionsthatreviewtheseformsofprevisualandproductivitychanges.      Visiblesymptomsresultingfromozoneexposurearegenerallyrecognizedasresulting "r fromeitheracuteorchronicexposuresasmanifestedonthefoliageofsensitiveplants.Injuryfromacute[unusuallyhighconcentrations(generally>0.10ppmintheSAMIregion),shortterm(generally<24hr)]exposuresnormallyinvolvesthedeathofcellsanddevelopswithinafewhoursordaysfollowingexposure.Injuryisexpressedastissuebleaching,leadingtobifacialnecrosis(fleck),andmayfollowexposuretounusuallyhighozoneconcentrations.Acuteozoneexposuresrarelyoccurinnature.  Foliarinjuryresultingfromchronicexposures[lowerconcentrations(generally<0.100ppmintheSAMIregion),longerterm(generallydays,weeks,ormonths)]maybemanifestedaschlorosis,pigmentation(stippling),generalleafreddeningand/orprematureorenhancedsenescence.Bothtypesofsymptoms(resultingfromacuteorchronicexposures),particularlythosefromchronicexposures,maybeconfusedwithsymptomsofotherconditions,suchasnormalsenescence,nutritionaldisorders,otherenvironmentalstresses,bioticpathogens,orinsectinfestation(Skellyetal.1987). &l!0   ~'"2 М&     DescriptionofSymptoms    BroadleafSpecies  b   Underconditionsofambientozoneexposuresseveralspecificsymptomsappearonbroadleafspeciesinthefield,themostcommonofwhichisstipple,definedasdiscreteareas'Sofpigmentationrestrictedtotheadaxialleafsurface.Theupperleafsurfaceofsensitiveplantsmayhaveatan,red,brown,purple,orblackstippling(asifpepperhadadheredtotheupperleafsurface)thatmayappearuniformlyovertheleafsurface,orrestrictedtocertainareasoftheleaf,ordiscretedotlikelesions.Thelowerleafsurfaceusuallyremainsuninjured,withonlythepalisadecellsunderlyingtheupperepidermisaffected.Veinsandveinletsareusuallynotinvolved,andsmallveinletsoftenboundtheinjuredareas,producingangularsectionsofaffectedtissue.Sometimesstipplingisbestobservedbyholdingtheleaftowardthesun;symptomsareoftenmoreintenseonleavesexposedtodirectlight.Recentevidencesuggeststhatshadedleavesmaybemoresensitiveearlierinthegrowingseasonandexhibittheearliestsymptoms(Fredricksenetal. H 1995).  Stipplinghasbeendescribedastheclassicsymptomofozoneinjuryonbroadleaftrees.Thecolorationofstipplingisusuallycharacteristicforaspecies,butcanvarywithenvironmentalorphysiologicalconditions.Theyoungestfullyexpandedleavesarenormallythemostsensitive,althoughallbuttheyoungestleavesmaybeaffected.Onyoungleaves,symptomstendtodevelopatthetips,onolderleaves,towardthebase.Theentiresurfaceofolderleavesmayexhibitsymptomswhenexposedtoozoneperiodicallyduringthegrowingseason.Althoughstipplingisusuallyinterveinal,followingrepeatedandcontinuallyhigherozoneexposures,extensiveinjurymayalsooccurtotheleafveinsthemselvesresultingingeneralizedchlorosis.Insomespecies,especiallysycamore,stipplingtendstoappearadjacenttothelargerveins.Chlorosis,orlossofchlorophyll,mayoccurasageneralizedconditionsimilartosenescence,indiscretepatchescalledmottle,orinpatternssimilartostippling.Chlorosisisoftenmoreprevalentontheupperleafsurfaceofspeciesthathavepalisadecells.Onplantswithpinnatelycompoundleaves,suchasash,hickory,andtreeofheaven,onlysomeleafletsatcertainpositionsalongthepetiolemaybeaffected.Becausestipplingisaphotosensitiveresponse,overlappingleafletsorleavesmaycreateasharplineofdemarcationbetweeninjuredanduninjured(shaded)tissue. h+&8   Onbroadleafspeciesthatareverysensitivetoozone,injuryisusuallyexpressedasafleckcharacterizedbysmall,discreteareasofdeadcells"usuallypalisadeparenchymaandsometimesassociatedepidermaltissues"leadingtotheformationofirregularlesionsthatalthoughfirstevidentontheadaxialleafsurfaceinjuryquicklybecomeevidentonbothleafsurfaces.Thelesionsareoftenbleached(unpigmented)butcanbecoloredasinstippling,andtheaffectedareasmaybeslightlysunken.Bifacialnecrosisresultswhenthetissuesconnectingtheupperandlowerleafsurfacesarekilled.Thetissuecolorationrangesfromwhitetoredorangetoblackandisoftencharacteristicsofaspecifictreespecies.Smallveinsareusuallyincludedinthenecrotictissue,butlargerveinsoftenremainalive.Theareaofdeadcellscollapses,andtheupperandlowerleafsurfacesadheretogethertoformapaperylesion.  Inbifacialnecrosis,theleafmarginsaresometimesthemostseverelyinjured.Prolongedexposurestoevenlowozoneconcentrationsmaycausecoalescenceofchlorotictissues,lightstippling,and/orproductionofabronzedappearance,especiallyonozonesensitivetreespecies.  Seasonlongexposurestoambientozonemayfurtherresultinprematureorenhancedsenescenceoftheolderleavesonsensitivespecies.Thismaybeaclassicsymptomofcumulativeozoneexposuresformanyspecies,butremainselusiveofdescriptionduetolackoffilteredaircontrolsforpurposesofphenologicalcomparisons.Forsensitivespeciessuchasblackcherry,notablestipplingandgeneralleafreddeningoftheolderleaveshasbeenobserved,withdefoliationoccurringseveralweeksbeforemoretolerantindividualsonthesamesite(Skelly,personalcommunication). Forothersensitiveindividualswithinspeciessuchasyellowpoplar F& (Liriodendrontulipifera,L.),whiteash(Fraxinusamericana,L.),orsassafras(Sassafras ^ ( albidumL.)prematuresenescenceischaracterizedmoresimplybytheyellowinganddroppingof !* theolderleaves.Whendefoliationissevere,leaveswithozoneinducedstipplemaycommonlybefoundontheforestfloorbelowsensitiveindividualsseveralweeksbeforefullautumncoloration.& &   ConiferSpecies  H'"2   Foliarinjuriesonconifersasmaybeinducedbyambientozoneexposuresarefarmoredifficulttoidentifyincomparisontothemoredistinctivesymptomsinducedonbroadleaf'&H'PԀspecies.Althoughozoneinducedsymptomswereoncethoughttobeeasilydiagnosed,recent n+&8 controversies(Skelly,personalcommunication)aboutthecausesofseveralneedleanomalieshaveaddedtotheconfusionofproperdiagnosis,especiallyunderambientforestconditionsandfollowingambientozoneexposures.Somanyothercausesmaybeinvolvedininducingthesymptomsdescribedbelowthatdeterminationofcause/effectrelationshipsduringfieldsurveysmayprovedifficult.  Usually,onconiferspeciesthetwomostcommonneedlesymptomsarechloroticmottleandtipburn(Skellyetal.1987).Overall,mottleofyoungandolderneedlesmaybeinducedby  L  lowozoneexposures,whiletipburnofyoungneedlesmaybeproducedbyhigher,earlyseasonexposures.Thereis,however,considerabledifferenceinsymptomexpressiondependingonspecies,withinspeciesvariation,timingofexposures,andenvironmentalconditions.Chronicsymptomsusuallyonlydevelopduringthelatesummerorearlyfallonthecurrentyearneedleswithchloroticmottleand/orspottingdevelopingassmallpatchesofyellowtissueinterspersedwithgreenareas(mottle),orasdiscreteyellowspotssurroundedbyapparentlyhealthytissue.Chronicsymptomsintwo,threeandolderyearneedlessimplyintensifywithcoalescingofsymptomaticareasleadingtomoregeneralneedlechlorosisandearlysenescence.Lossofsecondandthirdyearneedlesoneasternwhitepine(Pinusstrobus,L.)andloblollypine(Pinustaeda, n L.)followingadvancingchloroticmottle,spotting,andgeneralchlorosishasbeenreported(Skellyetal.1987,ChappelkaandChevone1992). 2" Ѐ  Symptomsonmostconiferspeciesoccurringastheresultofacuteexposuresarerareand $ usuallyoccurfollowingepisodiceventstoambientozoneearlyinthegrowingseason.Ifanozoneepisodeweretooccuratthissensitivetimeofneedlegrowth,thatportionexposedtothehigherozoneconcentrationsmaysubsequentlydevelopnecroticneedletipsresultingintipdiebackornecroticbanding.Tipnecrosisischaracterizedwithapinktoreddishcolorationthatfadesbrownwithage.Towardstheendofthegrowingseason,thesenecrotictipsmaybreakoff,makingaffectedneedlesappearmuchshorter.Thetipburnsymptom,especiallyineasternwhitepine,usuallyaffectsallneedlesinafascicleequallyfollowinganexposuretoepisodicozoneinthespringportionofthegrowingseason.Severelyaffectedindividualsareevidentwithinpopulations duetotheiroffcolorformuchofthegrowingseason. *V%6   Oneasternwhitepine,alateseasonphenomenonofbandinginthemidportionsof individualneedleswithinthecurrentyearfascicleshasalsobeenattributedtoepisodicozoneexposuresimmediatelybeforesymptomexpressions.Althoughshowntobeinducedbyhighozoneexposuresundercontrolledconditions,additionalcontroversyastotheroleoffungiincausingthissymptomleadstoalesscleardecisionofdeterminingthissymptomassolelybeingduetoambientozoneexposuresunderforestconditions(Skelly,personalcommunication).  Young,rapidlygrowingneedlesthataredirectlyexposedtosunlightarethemostsensitive,butolderneedlescanexhibitmottleandprematuresenescencefromprolonged,chronicexposures.Similartobroadleafspecies,symptomsonplantswithinasingleconiferspeciescanvaryconsiderably.    BioindicatorSpecies  6   Someparticularlysensitivebroadleaftreespeciesincludeblackcherry,whiteash,yellowpoplar,andsassafrashavebecomerecognizedasveryusefulbioindicatorsofozoneexposurebecauseofadistinctiveuppersurfacestipple,leafreddening,andalargeportionofthepopulationappearingassensitiveundervariedconditionsofexposureandenvironments(Chappelkaetal. n 1992).Clonallinesofeasternwhitepinehavebeensuggestedforuseasbioindicatorsofambientozoneexposures,butasdescribedabovethegeneraluseofthisspeciesunderfieldconditionsmayposedifficultiesindeterminingcause/effectrelationships.Otherforestspeciesthatmayserveasbioindicatorsofozonepollutionareblackberry,milkweed,dogbane,bigleafasterandpoisonivy.Blackberryandpoisonivyexhibitadarkpurpleredstipplingoftheupperleafsurfacethatoftencoalescesovermostoftheleafsurface.Thesymptomonmilkweedissimilartothatonblackberry,exceptthatthecolorationispurpleblack.Milkweedhasbeenreportedasacommonbioindicatorofozone(DuchelleandSkelly1981).& & VisibleFoliarOzoneSymptoms:TreeSpeciesintheSAMIRegion B'"2   CurrentknowledgeofvisiblefoliarsymptomsonforesttreespeciesgrowingintheSAMI (#4 regionislimitedtoonlyafewspeciesofhardwoodsandconifers.Onlythosespecies'&B'PԀthathavehadsymptomsconfirmedfromlaboratorystudies(forexample,CSTRs)orstudieswithopentop h+&8 chambersusingcharcoalfilteredaircontrols(CF)willbediscussed.Forpurposesofthissectiononlyopentopchamberstudiesandfieldsurveyswillbereviewed.   Aspen (Populustremuloides): &   Inacontrolledstudyusingopen-topchambersinSwitzerland,Keller(1988)observednovisiblesymptomsbutprematuredefoliationoccurredwhenozonewasgreaterthan20ug/m3hfor    sensitiveclonesandgreaterthan60ug/m3hfortolerantclones.Inamorerecentstudyofaspen  R  byKarnoskyetal.(1992),symptomsappearedasupperleafsurfacestipple,bifacialnecrosis,and d  prematureleafabscission.FoliarinjurybegantooccurbylateJulyandmorethan50%ofleavesofsensitiveandintermediatecloneshadsymptomsbytheendofAugust.Open-topchamberswereused,withcumulativeozoneconcentrationsof5.0,10.0,19.4ppm-hr(1988)and7.7,15.4,26.4ppm-hr(1989)for6hr/d,3d/wkduringbothyears.Treeswerealsogrowninambientair.   Blackcherry (Prunusserotina):    Blackcherrydevelopsverydistinctivesymptomsinthepresenceofelevatedambientozoneexposures.Verysensitiveindividualsrapidlydevelopanuppersurface(adaxial)stipplefollowedbyleafreddeningandearlyleafsenescence.InascreeningstudybyDavisandSkelly(1992a)thepredominantfoliarsymptomobservedconsistedofadarkadaxialstippleoftheoldestleaves;prematuresenescenceoccurredfollowingexposuresof12weeks.Ozoneconcentrationswere0.01,0.075,and0.150ppmfor6hr/d,2d/wk/12wks.Darkadaxialstippleonoldestleaveswasobservedwithconcentrationsof0.040or0.080ppmozonefrom0830-1530h/5d/wkfor8or12wks.  InafieldstudybyFredericksenetal.(1995)injuryonblackcherryfoliagewasgreateston (#x, seedlings,followedbysaplings,withleastinjurynotedonmaturetrees.Inlargertrees,symptomsweremoreprevalentinthelowercrown.  Symptomsofred/blackadaxialstippleandleafabscissionwerepositivelycorrelatedwithozoneexposureinastudybyNeufeldandRenfro(1993).NecrosisofolderleaveswasalsoobservedbyAugust.InastudyinTN(Samuelson1994a)exposedseedlingstoozoneinopen-topchamberswithCF,1.0,1.5,2.0AAexposuretreatments.Adarkadaxialstippling,characteristic t+&8 ofozoneinjuryoccurredontheoldestleavesofblackcherryexposedto2.0XAAfromApril-August1993.  Intwoseparatefieldsurveysduringthelatesummerseasonsof1991,1992,and1993,foliarsymptomsonblackcherrywereobservedatsitesofthreedifferentelevationseachinShenandoahNationalPark,Va.andGreatSmokyMountainsNationalPark,respectively.Black,red/black,andred/purplestipplewasobservedonblackcherryfoliage;symptomswereobservedtohaveincreasedwithincreasingozoneconcentrationandwithincreasingelevation.(Chappelkaetal.1992,Hildebrandetal.1996).Subsequentregressionanalysisshowedsymptomstobe ^  positivelycorrelatedwithSUM06andW126ozoneconcentrations,ie.,thehigherozone   concentrationswererelatedtothegreatestamountofvisiblefoliarinjury.(Hildebrandetal. "r  1996).   Blacklocust (Robiniapseudoacacia): H   Duringalateseasonsurveyofseveralspeciesforresponsestoambientozoneexposures,significantpositivecorrelationswereshownbetweenfoliarinjury(uppersurfacestipple),typicalofozonesymptomsforthisspecies(Duchelleetal.1992),andelevationinfieldsurveysin t ShenandoahNationalPark,VA.byWinneretal.(1989). &     Honeylocust (Gleditsiatriacanthos): $   SymptomswereobservedfromJunethroughSeptember,1981onhoneylocustseedlingsgrowninopenplotsunderconditionsofambientozoneexposuresinNewJersey.Symptomsincludedupperleafsurfacestipple,chlorosis,andprematureleafdrop.Therewasconsiderablevariationinresponseamongpredetermined,ozonesensitiveandtolerantselections,withozonetoleranttreesremaininggreenandfull-crownedthroughoutthegrowingseason(SmithandBrennan1984).   Hybridpoplar (Populusmaximowiziixtrichocarpa): ($4   DavisandMcClenahen(1993)reportedthatmoreozoneinducedinjury(stippling)wasobservedonhybridpoplarsestablishedalongridgetopthaninlowerelevationplots.Seedlings z+&8 wereplantedinopenplotsnearcoal-firedpowerplants.Morenecrosisoccurredincrosswindplotsandinjuryincidencewaspositivelycorrelatedwiththenumberofdayswhenozonewasgreaterthan0.040ppm.Hourlymeanswere0.040-0.050ppmthroughoutthesummer.Therewere36hrswithozoneconcentrationsgreaterthan0.080ppminJuneandJulyatonesite,morethan98hoursatanothersite.Themaximumconcentrationatthefoursitesrangedfrom0.124-0.155ppm.   Redmaple (Acerrubrum): ^    Inanearlystudy,TownsendandDochinger(1974)reportedredmapletoexhibitpalegreentoyellowishwhitechloroticareaswithintheinterveinalleaftissues.Ozonefumigationswereveryhighat0.750ppmfor7hr/d,3d/wk.Therewasmorefoliarinjuryinyoungerthaninolderseedlings,andmoreinjuryinseedlingsfromPAandMNstocks.TheleastinjurywasreportedforseedlingsgrownfromALsources.InalatercontrolledCSTRstudy,DavisandSkelly(1992a)reportedchlorosiswithinfourweekswhenwildtypePAredmapleseedlingswereexposedto0.150ppb.Ozoneconcentrationsinalltreatmentswere0.0,0.075,and0.150ppmfor6hr/d,2d/wkfor12wks.Samuelson(1994a)alsoobservedozoneinducedinjuryonredmapleaschlorosis,withmoreinjuryinthelowerportionsofthecrown.Seedlingplantswereexposedto2.0XAA,withcumulativeconcentrationsof29,38,41,33,32ppm-hforApril-August.   Northernredoak (Quercusrubra): L&   SamuelsonandEdwards(1993)reportedthatnovisibleinjurywasobservedonmaturetreesorseedlingsinopen-topchamberswithozoneconcentrationsof18,45,87ppm-h,or34,79,147ppm-hrand/orat37,95,188ppm-hr(0.03,0.060,0.090,0.120ppmfor7hr/d/5d/wkfor6,8,10wks).̀  Similarly,redoakwastheonlyoneofeighttreespeciesshowingnovisiblesymptomsof %0.160ppmproducedvisibleinjuryinallfamilies.Reductionsingrowth,however,werenotdirectlycorrelatedwithvisibleinjury,withcertainfamiliesexhibitinggreatersuppressionsingrowththanothers.TheseresultswereconfirmedinanindependentstudybyWinneretal.(1987). X (   Severalstudieshavereporteddecreasedbiomassproductionofloblollypinewithincreasedozoneexposure(Hortonetal.1990,McLaughlinetal.1993,Shaferetal.1993,Wiselogeletal. #l, 1991).Allplantcomponentpartsexamined(roots,foliage,stems)exhibiteddeceasesingrowth.Resultswerevariabledependingonfamilyandexposureconcentrationsused.TheseresultsaresummarizedinmoredetailinFlaglerandChappelka(1995).  Hortonetal.(1990)foundthatpottingmediahadalargeinfluenceonloblollypine (#4 responsetoozone.Theyfoundthatrootbiomasswasdecreasedmorethanabovegroundbiomassinresponsetoozoneexposuresof0.320ppm,6hoursperday,fourdaysperweekfortwo h+&8 months,buttheresponsevariedwiththegrowingmediaused.Thedecreaseinrootbiomasswasgreaterwhentheseedlingsweregrowninapeatvermiculitecommercialgrowthmediathaninmineralsoil.Thedecreaseinabovegroundbiomasswasnotsignificantlyaffectedbythegrowingmediaused.  Pitchpinewasmoderatelysensitivetoozonewiththegreatestreductionsingrowthoccurringatthehighestozoneconcentrations(0.200.30ppm)(ScherzerandMcClenahen1989,Schieretal.(1990).Adifferentialsensitivitytoozoneamongdifferenthalfsiblingfamilieswas  L  observed(ScherzerandMcClenahen1989)andozoneinteractedtocausesasignificantdecreaseinrootweightwasobservedathighlevelsofaluminumandozone(Schieretal.1989).     Otherconiferousspeciesexposedtoelevatedozoneconcentrationsexhibitedlittleifanygrowthresponses.Thesespeciesincluderedspruce(Leeetal.1990,Tayloretal.1987),white   pine(Reichetal.1987)andFraserfir(Seileretal.1994,Tsengetal.1988). 6    Summary     GrowthresponsestoozonehavebeenreportedforindividualtreesthatoccurintheSAMIregion.Mostofthesestudiesare,however,withindividualseedlings(<2yrsinage)undercontrolledconditions(CSTRs).Moststudieswereshortterm(0.039ppminteractingwithhightemperaturesandlowsoilmoistureresultedinashorttermdepressioninradialgrowth.Theinteractionofincreasedsoilmoisturedeficitwithincreasedozoneconcentrationsresultedinadecreaseinannualradialgrowthrates.Reductionsingrowthwerepredictedtovaryfrom7%inarelativelywetyearto30%inarelativelydrieryear.  Recently,thisreport(McLaughlinandDowning1995)hasbeenquestionedregardingthestatisticaltreatmentofthedata(Reamsetal.1995).Reamsetal.(1995)perceivethatthe 6 majorityofthewithinyearvariationobservedisexplainedbynaturalvariationsingrowthleavinglittlevariabilitytobeexplainedbyenvironmentalvariables,includingozoneandmoisturestress.Inreply,theauthors(McLaughlinandDowning)defendtheiranalysisandstatethatthediscrepancybetweentheiranalysisandtheoneconductedbyReamsetal.(1995)isthatReamset n al.(1995)onlyexaminedthevariabilityofthemostozonetoleranttree.Bothgroups,however,    feelthatthisisanimportanttopicandmoreresearchisneededinthisarea.  Basedonastudywherevisiblesymptomsofozoneinjurywerecharacterizedonlarge,matureyellowpoplarandblackcherrytreesinGreatSmokyMountainsNationalPark,Somerset F& al.(1997)comparedradialgrowthdifferencesamongtreesclassifiedassensitiveortolerantbased X ( ontheseverityofozonesymptomsobservedoverathreeyearperiod.Twentyfivetolerantand26sensitiveyellowpoplarand23tolerantorsensitiveblackcherrywerecoredandpatternsofradialgrowthdeterminedforthelast5(19901994)and10years(19851994).Variousindicesweretousedtoeliminatevariables(competition,etc.)thatmaybeconfoundingfactors.Althoughtheresultsareunpublishedandpreliminary,Somersetal.(1997)observedsignificantlymore B'"2 radialgrowthforboththelast5and10yearsfortheyellowpoplartreesidentifiedastolerantbasedonvisibleinjury.Thisrelationshipwasnotobservedwithblackcherry.Sincethiswasnotacontrolledexperimentandwaslimitedinthenumberoftreesused,thereisnowaytoprovea h+&8 causeeffectrelationshipbetweenvisiblesymptomsandradialgrowth.However,theseresultsdoindicatetheneedforfurtherresearch.  Summary  &   AlthoughseveralstudieshaveimplicatedozoneasapotentialcontributingfactortodecreasesinradialgrowthofafewforesttreespeciesnoconclusionscanbemadeatpresentregardingtheeffectsofambientlevelsofozoneongrowthandproductivityoftheforestsintheClassIareasoftheSAMIregion.Thereissimplynotenoughdatatomakeany broadstatements.Giventheinteractionamongozoneandotherenvironmentalfactors,itisunknownthatanyreductionsinozonelevelswillresultinsubsequentincreasesingrowthandphysiologicalfunctionofforesttrees. GeneralConclusions  H   ThecriticalassessmentofozoneeffectstoforesttreegrowthintheSAMIregionisverydifficultforseveralreasons:0  1.0(#(#Ozoneresearchisrelativelynewandthemajorityofearlyexperiments(19601970's    usedunrealisticconcentrationsandinstrumentcalibrationwasdifficult(Matysseketal. 2" 1995). (#(# 0  2.0(#(#Thenumbersofspeciesexposedincontrolledstudiestoambientornearambient F& ozoneexposuresintheSAMIregionislimited,especiallyregardingdeciduoustreespecies. (#(# 0  3.0(#(#Generally,studiesareshortterminnature(<1year)andinartificialgrowingmedia. #l, Thisdiscountsthecumulativenatureofozoneeffects(Reich1987,ChappelkaandChevone1992). (#(# 0  4.0(#(#Thereisapaucityofdataregardinggrowtheffectsonlargetreesandforeststands B'"2 (Matysseketal.1995,ChappelkaandChevone1992).Northernredoakistheonly (#4 specieswherelarge,maturetreeswereexposedtoozoneundercontrolledconditions(SamuelsonandEdwards1993).Allcontrolledexposurestudies,exceptone h+&8 preliminarystudywithloblollypine(Barboetal.1995)arewithindividualtreesina  noncompetitivesituation.Therearenogrowthstudiesregardingozoneeffectstomatureeasternhardwoods,exceptoneunpublished,uncontrolledfieldstudywithblackcherryandyellowpoplar. (#(# & b (XXGVI.EXPOSURERESPONSE    XGX(   Ozoneisanaturallyoccurringchemicalinboththeupperatmosphereandatsurfacelevels. 8   Ozoneisconsideredthepollutantofgreatestconcernwithrespecttopotential'b ԀregionalimpactstotreesinNorthAmerica(U.S.EPA1986,1996,NationalAcidPrecipitationAssessmentProgram1991).Ozoneisanomnipresentairpollutantthathascausedfoliarinjurytoagriculturalcropsandtrees(U.S.EPA1986,ChevoneandLinzon1988,KrupaandManning1988,Pye1988,SwankandVose1991,ChappelkaandChevone1992).Theeffectsofozoneonindividualplantsandthefactorsthatmodifyplantresponsetoozonearecomplexandvarywithspecies,environmentalconditions,andsoilandnutrientconditions.Factorssuchasgeneticsusceptibility,light,temperature,relativehumidity,soilnutrients,andsoilmoistureinfluencetheuptakeofozone.  Unfortunately,notenoughdataareavailabletoquantifytherelationshipbetweendoseandvegetationeffects(Fredericksenetal.1996).Furthermore,thelinkbetweenexposureanddosage  \  arenotstrong.Alternatively,researchershavefocusedondescribingtherelationshipsbetweenexposurecharacteristicsandplantresponse,recognizingthatexposureisnotnecessarilyanadequatesurrogatefordose(Lefohn1992,U.S.EPA1996).Althoughitwouldbehelpfulifonecoulduseactualozonedosemeasurementstopredictcauseandeffectrelationships,thecurrentstateofscienceislimitedmostlytorelatingozoneexposuremeasurementstovegetationeffects.Untilfurtherinformationisavailableonactualdosagesreceivedbyvegetationandtheirresultingeffects,thefocuswillcontinuetobeonexposure.  Airpollutionspecialistshaveusedexposureindicesassurrogatesfordose(Oshima1975,LefohnandBenedict1982,Lefohnetal.1988a,Leeetal.1988,Hogsettetal.1988,Leeetal. ~'"2 1991,Lefohn1992,U.S.EPA1986,1992,1996).Forselectingasetofexposureindicestorelatetointernaldose,someimportantconcernsthatneedtobeaddressedare: +&8   8  Whatistheeffectwearetryingtoprevent?""   8  Aretheresufficientexperimentaldatatolink"dose"withexposure?b""   8  Whatisthesensitivityvariationamongspeciesand/orcultivars?Whatarethe t causesofthesevariations? ""   8  Isthereaspecifictimeofdayorspecificmonththatvegetationismostsensitive?8 ""   8  Isthereaspecificthresholdorrangeofthresholdsbelowwhichnoeffectsoccur?  ""   8  Forassessingeffects,shouldallconcentrationsbetreatedinanequivalentfashion?  L  Aresomeconcentrationsmoreimportantthanothers? ""   8  Isconcentrationmoreimportantthanthelengthofexposureoramountof   exposure? ""   8  Whatarethespecificexposureregimesresponsibleforaffectingvegetation? ""   8  Whataretheimportantcomponentsofthoseregimesresponsiblefortheobserved 6 effects? ""   8  Aretheconcentrationregimesusedinresearchexperimentsmimickingthose  regimesexperiencedunderambientconditions? ""   Severaldifferenttypesofozoneexposureindiceshavebeenproposedassurrogatesfordose,andaresummarizedasfollows(adaptedfromLeeetal.1989): 2"   0  OneEvent:thesecondhighestdailymaximum1hconcentration(HDM2),the F& maximumof7h(P7)and1h(P1)maximumdailyaverages,andthe90th(PER90),95th(PER95),and99th(PER99)percentilesofhourlydistribution; (#(#   0  Mean:theseasonalmeanof7hdailymeans(M7),theseasonalmeanof1hdaily #l, peaks(M1),andtheeffectmean(EFFMEAN)(LarsenandHeck1984); (#(#   0  Cumulative:theseasonalsumofhourlyconcentrations(i.e.,totalexposure %0!0 (TOTDOSE).ThisissometimesreferredtoasSUM0; (#(#   0  ConcentrationWeighting:theseasonalsumofhourlyconcentrationsatorabove0.06 (#4 ppm(SUM06),0.07ppm(SUM07),0.08ppm(SUM08),0.10ppm(SUM10);theseasonalcensoredsumofhourlyconcentrationsatorabove0.08ppm(AOT08)or h+&8 0.10ppm(AOT10);thetotalimpact(TIMPACT)(Larsenetal.1983);the  ALLOMETRICinwhichthehourlyconcentrationswereraisedtoapowerandsummed;SIGMOIDorW126inwhichthehourlyconcentrationwasvariablyweightedusingasigmoidfunctionandsummed(seeLeeetal.1989,Lefohnetal.1988a);total & hourswithconcentrationsatorabove0.08ppm(HRS08),or0.10ppm(HRS10);thenumberofepisodes(anepisodewasdefinedasaneventwithhourlyO3concentrations    aboveathresholdlevel)ofthreshold0.08ppm(NUMEP08),or0.10ppm(NUMEP10);andtheaverageepisodelengthwiththreshold0.08ppm(AVGEP08),or0.10ppm(AVGEP10); (#(#   0  Multicomponent:indicesthatincorporateseveralcharacteristicsofexposure,including "r  thephenologicallyweightedcumulativeimpactindices(PWCI)(Leeetal.1987). (#(#   Apossibledisadvantageofapplyinganintegratedexposureindex,suchastheSUM06,isthattheuseofanartificialthresholdconcentrationasacutoffpointeliminatesanypossiblecontributionofthelowerconcentrationstovegetationeffects.Recognizingthis,LefohnandRuneckles(1987)suggestedamodificationtotheLefohnandBenedict(1982)exposureindexbyweightingindividualhourlymeanconcentrationsofozoneandsummingovertime.LefohnandRuneckles(1987)proposedasigmoidalweightingfunctionthatwasusedindevelopingacumulativeintegratedexposureindex.Thesigmoidfunctionwasoftheform:*"+[KGzx x 0 @Xdddddddd@E"xydG S' af"@ (#(#     (#(#here:  MandAarepositivearbitraryconstants &"*   wi= ` weightingfactorforconcentrationI (#,   ci= ` concentrationI |*%.  h+&/   Lefohnetal.(1988a)reportedtheuseofthesigmoidallyweightedindexwithconstants, b MandA,4403and126ppm1,respectively.TheauthorsreferredtotheindexasW126.The t valuesweresubjectivelydeterminedtodevelopaweightingfunctionthat1)includedhourlyaverageconcentrationsaslowas0.04ppm,2)hadaninflectionpointnear0.065ppm,and3)hadanequalweightingof1forhourlyaverageconcentrationsatapproximately0.10ppmandabove.Todeterminethevalueoftheindex,thesigmoidalweightingfunctionatciwasmultipliedbythe  L  hourlyaverageconcentration,ci,andsummedoverallrelevanthours.Theindexincludedthe ^  lower,lessbiologicallyeffectiveconcentrationsintheintegratedexposuresummation.  Usingvariousindices,severalinvestigatorshavedescribedozoneexposuresintheSAMIregion(e.g.,PinkertonandLefohn1986,1987,LefohnandPinkerton1988,Lefohnetal.1988b,   Winneretal.1989,LefohnandLucier1991,Anejaetal.1992,1994,Lefohn1992,Gilliamand 6 Turrill1995).  Lefohnetal.(1997)collectedhourlyaverageozoneconcentrationdatafromtheU.S.  EnvironmentalProtectionAgency(EPA)AerometricInformationRetrievalSystem(AIRS)databaseandfromthedataintheNationalDryDepositionNetworkprogramfortheperiod19831990.Usinga24hperiod,theW126cumulativeexposureindexwascalculatedforeachmonitoringsite.The7month(AprilOctober)W126exposureindexvaluewaskrigedforeach 2" $by$cellinAlabama,Georgia,SouthCarolina,NorthCarolina,WestVirginia,Tennessee, $ Kentucky,andVirginiaforeachyear.Atthistime,thereisinsufficientinformationavailableregardingoptimumgrowthperiodsfortreestolimitthedailyintegratedexposureperiodtoaminimumof12hours(e.g.,08001959h)ora3monthgrowthperiod.Itwasdecidedtointegrateoverthefull24hours,recognizingthatinmostcases,thelowelevationsiteswouldexperiencetheirhighesthourlyaverageconcentrationsduringthedaylighthours(i.e.,greaterthan12hoursbutlessthan24hours).Therefore,atthesesitesthecontributiontotheW126magnitudewouldmostlyconsistofhourlyaveragevaluesexperiencedduringthedaylighthours.Lefohnetal. B'"2 (1997)selectedthe7monthtimeperiodbecauseofgrowthpatternsassociatedwithmosttrees.Lefohnetal.(1987)andLefohnetal.(1992a)havediscussedtheapproachusedforkriging *V%6 ozone.Figures29illustratetheW126exposuresfortheareaduringthetimeperiod(19831990). h+&8 Ї GeneralConclusions     Manydifferentindiceshavebeenusedassurrogatesforozonedoseinexposureresponse b models.Apossibledisadvantageofapplyinganintegratedexposureindex,suchastheSUM06,isthattheuseofanartificialthresholdconcentrationasacutoffpointeliminatesanypossiblecontributionofthelowerconcentrationstovegetationeffects.Recognizingthis,LefohnandRuneckles(1987)suggestedamodificationtotheLefohnandBenedict(1982)exposureindexbyweightingindividualhourlymeanconcentrationsofozoneandsummingovertime(W126).  Fortheyears1983through1990,theozoneexposurekrigingestimatesresultedinmostofthegridcellsfallingbetween23.866.5ppmhfortheW126index.In1988,11ofthe120cellshadW126estimatesgreaterthan66.5ppmh.Threecellsin1986and1989,andonecellin1990hadaW126estimateof5.923.7ppmh.Nocellswereclassifiedashavinglessthan5.9ppmh.Generally,withintheSouthernAppalachianareaboundary,ozonemonitorsexperiencedfewerthan40hoursinwhichthehourlyaverageozoneconcentrationwas0.10ppm(19831990). H Theonlyyearthatdeviatedfromthispatternwas1988when11ofthe15ozonemonitorsintheareahadgreaterthan50hoursinwhichthehourlyaverageozoneconcentrationwas0.10ppm.  \   ThecombinationofthePalmerhydrologicindexandtheozoneexposureresultsindicatethatsoilmoistureconditionsmayaltertreegrowthresponsetoozoneexposures(Lefohnetal.    1997).Bycombiningexposureinformationwithmoistureavailabilityandexperimentalexposureresponsedatapossibleareasthat mayhavethegreatestpotentialforpossiblevegetationeffects $ maybeidentified. (XXGVII.MODELS #XGX(># !*   Asstatedintheabovesections,themajorityofthereportedgrowthandphysiologicalresponsesduetoozoneareforindividualtrees,primarilyintheseedlingorsaplingstageofdevelopment,andingreenhousesoropentopchambers.Thelackofinformationconcerningtreeresponseunderfieldconditionspresentsdifficultyinextrapolatingozoneeffectstoaforeststandorregionwideassessment.Onewaytoattempttousetheselaboratorydataisthroughtheuseofmodels.SeveralmodelsusedwithtreesspeciescommontotheSAMIregionaredescribedinthissection. +&8   Itisimperativewhenconductingmodelingexercises,thatforestbiologistsmustconstantlykeepinmindthetremendousvariabilitythatexistswithinnaturalsystems.To"model"ozoneinducedexposure/responsesacrossthegeographicrangeofaspecies(evenwithinthelimitedrangeoftheSAMIregion)posesaformidabletask.Atthistime,weconsidertheinfluenceofmicrositefactorstobemostimportantinalteringthepotentialforozoneinducedexposures.Availablesoilmoistureappearsatthepresenttimetobeofgreatestsingleimportanceincontrollingozoneuptakethroughitsinfluenceonstomatalfunctionattheleaflevel(Showman1991,Lefohnetal.1997).Scalingofthissinglesite/physiologicalresponsephenomenonfrom ^  seedlingtomaturecanopyresponsescontinuestonecessitatefutureresearch.Suchresearchisnecessaryinsupportofthemodellingattemptsatdeterminingregionwideozoneimpacts.  Modelingeffortsmustalsotakeintoaccounttherelativeinfluencesofinsectpests,bioticpathogensandabioticstressors(otherthanozone)incontributingtothemeasured(modelled)changesinforesthealthand/orproductivity.Verycarefuldiagnosticsmustfirsttakeplaceatthespecificsitesandforthespeciesofinterestbeforean ozoneinducedresponsemaybeheldaccountableatthatspecificsite,orevenforselectedspeciesatthatsite.Scalingresponsesacrossbroadregions(i.e.,SAMI)forthepurposeofdeterminingozoneinducedeffectswithoutregard n togainingaclearunderstandingoftheinfluenceofmanyotherstressinducingfactorswouldpossiblypresentaskewedand,therefore,unrealisticsenariooftherelativeimportanceofambientozoneexposurestoforestsintheSAMIregion.  Modelscanbeforindividualtrees,foreststandsorregions.Severalexamplesofeachwillbeincluded.Thisreviewwillnotbeexhaustiveinnatureregardingthemechanicsofthemodels.ForadetaileddescriptionofthisthereaderisreferredtothecriticalreviewofKickertandKrupa(1991).̜ IndividualTreeModels  Amodelhasrecentlybeendeveloped(TREGRO)toderivetheimpactofozoneon B'"2 individualwholetreeprocesses(Weinsteinetal.1991,WeinsteinandYanai1994).This (#4 simulationmodelcalculatestheflowofwater,carbonandnutrientsthroughaplantandtheinfluencesoflimitationsofeachoncarbonassimilation,allocationanduse.Atreeisdividedinto h+&8 thecanopy,branches,stemandcoarseandfineroots.Themodelthencalculatesphotosynthesis,dailycarbondistributionwithintheplant,andlossesofcarbonduetorespirationandsenescence.Themodelwasoriginallydevelopedtosimulatetheresponseofindividual,opengrownredsprucetreestoozonestress,withorwithoutnutrientstressovera10yearperiod(Weinsteinet & al.1991,Laurenceetal.1993,WeinsteinandYanai1994).A20%and40%reductionin 8  nutrientsinduceda19%and28%decrease,respectively,ingrowthafter10yearsofsimulation.Nutrientstressresultedinashiftincarbonallocationfromabovetobelowgroundplantparts.Elevatedozone(2X)causedasimulatedreductioninabovegroundandbelowgroundgrowthbyapproximately18%and20%,respectively,after10years(Weinsteinetal.1991).Laurenceetal.   (1993)comparedsimulatedresultswithactualresponsesinfieldgrownredspruce(1993).Resultsfromthesimulationmodelparrelledtheexperimentalfindings.Simulatedseedlingweightwaswithin8%oftheactualweightoftheexperimentaltrees.Over34yearsofsimulationcumulativephotosynthesiswasdecreasedby8%andtotalbiomassby6%inthe3Xambientozonetreatments.   Summary  n   AccurateozonedoseresponsefunctionsareneededtomodeltreeresponsesusingTREGRO.Whilethesefunctionsareavailableforsometreespeciesattheseedlingleveltheyarenotavailableformaturetrees.Giventhepaucityofmaturetreestudies,modelpredictionsusingexperimentalgrowthresponsesarenoteasilyvalidated.Inaddition,themodel(TREGRO)requiresdetailedozoneexposure,environmentalandphysiologicaldata.Thesearenotpresentlyavailableformanyspecies.̜ CanopyModels ~$.   Asimulationmodelofozoneimpactsonphotosyntheticcarbongainatthecanopylevel %0!0 wasdescribedbyReichetal.(1990).LeafandcanopylevelCO2exchangeratesofseveralforest B'"2 treetypeswerepredictedusingozoneconcentration,leafNconcentration,leafweight/area,lightintensity,VPDandwaterpotentialasthedrivingvariables.Thedatausedforthemodelwerecollectedfromamixedoakmapleforest.Themodelwasdevelopedfromasoftwarepackage h+&8 calledSTELLA(HighPerformanceSystems,Lyons,NH).Simulatedozoneconcentrationsusedinthemodelwere0.35,0.50,0.65or0.80ppm,12hr/d,for90consecutivedays.Thetreecanopywasdividedintofoursections,understory,lower,middle,anduppercanopy.Ozoneconcentrationscouldbesimulatedtobethesameorvariableamongcanopylayers.Ozoneeffectsonthematuretreecanopycarbonbalanceresultedfromeffectsonprimarilytheupperandmiddlecanopypositions.Eightysixpercentofthetotalcarbongainoccurredinthetoptwolayersofthecanopy.Ozone,however,wasfoundtoaffectcarbonbalanceofplantsinthelowercanopyorunderstorypositions.  Amodeldevelopedtopredictthefluxofcarbonfromtreecrownswithinaforestcanopy(MAESTRO,WangandJarvis1991)wasusedtoassesstheeffectsofozoneoncarbongainofmatureloblollypine(Doughertyetal.1992).Themodelfocusesonasingletreecanopyora   groupofcanopiesfromneighboringtrees.Photosyntheticallyactiveradiationandvaporpressuredeficitwerethedrivingvariables.Ozoneconcentrationswereassumedtobeconstantthroughoutatreecrown.Ozoneeffectsoncarbongainwereincorporatedintothemodelbymodifyingmesophyllconductanceasafunctionofcumulativeozoneexposure.Themodelingdatawerecloselylinkedtotheexperimentalresultswhereloblollypinebrancheswereexposedtoozoneatseverallevelsusingbranchchambers(Teskeyetal.1991).Fromthemodelitwasdeterminedthat    ozonecanaffectannualnetcarbonfixationfromapproximately29%fortolerantorsensitivetrees,respectivelycomparedwithtreesexposedtocarbonfilteredair.Ifozoneconcentrationsweredoubledtheamountofcarbonfixedperyearwoulddecreasebyapproximatelyarangefrom522%.  Anothercanopylevelmodelforeasternhardwoodtreespecieshasbeendevelopedusingozoneasapredictorvariable(Amthoretal.1994).Themodelisbasedonthe bigleafmodel #l, (Sinclairetal.1976),whereacanopycanbeconsideredanalogoustoasingle,largeleaf.Amthor ~$. etal.(1994)foundapositivecorrelation(r=0.76)betweenpredictedandmeasuredozoneuptake %0!0 ratesforamature,mixedoakmaplestandinMassachusetts.Themodelmoreaccuratelypredicteduptakeduringthemorninghourscomparedwithafternoon,indicatingthatthemodeloverpredictedstomatalconductance.Themodelcouldbeadaptedforpredictionsofcarbongaininrelationtoozoneexposureanduptake. h+&8 Ї   Summary     Allofthemodels(canopylevel)provideinterestingresultsregardingozoneuptakeandcarbonfixationwithinthecanopyoftreespeciescommontotheSAMIregion.Thesemodelsifcombinedwithstandlevelmodelscanpotentiallyprovideinformationoncarbonfixationandgrowthatatreeand/orstandlevel.  Themodels,inpresentform,allhavesimilarassumptionsthatcouldcauseerrorintheresults.Allassumedthatfoliageresponseinallcanopypositionswouldbeequal.Recentreports(Tjoelkeretal.1993,Fredricksonetal.1995,SamuelsonandEdwards1994,Chappelka ^  unpublished)withseveralhardwoodspecieshaveindicatedthatthismaynotbeavalidassumption.Itappearsthatfoliagegrowinginthelowercanopymaybemoresensitivivetoozoneinjurythat sunleavesgrowingintheuppercanopy.Thiswouldcauseagreaterreductionincarbonfixationthanpreviouslyestimated.  Anotherfactorthatinfluencesozoneuptakeandsubsequentlycarbonfixationisthefluctuationinozonedistributionwithinthecanopy.Allofthemodelsassumedthatozoneconcentrationsdidnotfluctuatewithinaforestcanopy.Ozoneconcentrationsdo,however,varydependingoncanopyposition(Nuefeldetal.1992,Fredricksonetal.1995,Samuelsonetal. n 1996)andwhetherornotthecanopyisclosedoropen(Neufeldetal.1992).    М   StandModels  Individualtreeandcanopylevelmodelsprovidevaluableinformationontreeresponseto F& ozone,however,translationofthesemodelstothestandlevelisverydifficultwithoutappraisementofthecomplexnatureofthesystem.Considerationhastobegiventointraandinterspecificcompetition,differentialsensitivitytoozoneanddifferencesingrowthhabitsandformofthemanydifferentspeciescomprisingtheforestsoftheSAMIregion.Reviewedbelowaretwomodels(oneforhardwoodsandoneforconifersthathavebeenusedtoexploretheresponseofforesttreesfoundintheSAMIregiontoozone.̜    h+&8    Hardwoods     Westetal.(1980)utilizedthesimulationmodelFORET(ShugartandWest1977)tostudy b thelongtermeffectsofairpollutiononforestcommunitygrowthanddynamics.TheFORETmodelisastochasticsimulationmodelthatgrowsaforestandfollowsstanddynamicsthroughtime(successionalmodel).Themodel(Westetal.1980)evaluated32foresttreespeciesnativeto 8  thesouthernAppalachian(SAMI)regionandsimulatedthegrowthofindividualtreesonacircular1/12haplot.Annualgrowthratesvarywithdegreedays,totalleafareaofthedominanttrees,andthenumberandsizeoftreesperplot.Theestablishmentandgrowthofeachspeciesarethendeterminedbyitssilviculturalcharacteristics.AschematicdiagramofthemodelisshowninFigure10.ForamoredetaileddescriptionofthemodelcharacteristicsthereaderisreferredtoShugartandWest(1977).  Toevaluateairpollutionstressontheforest,relativespeciessensitivityrankingsweredevelopedusedexistingliterature(upto1980).Therankingswerebasedonvisibleinjurytosulfurdioxideand/orphotochemicaloxidants.Theywerenotspecifictoanyonepollutant.Resistantspeciesidentifiedwereredmaple,sugarmaple,bitternuthickory,pignuthickory,shagbarkhickory,mockernuthickory,dogwood,persimmon,Americanbeech,whiteash,redcedar,blackgum,sourwood,whiteoak,chestnutoakandpostoak(16species).Intermediatetreespecieswerebuckeye,redbud,sweetgum,yellowpoplar,scarletoak,southernredoak,northernredoak,blackoak,sassafras,andbasswood(10species).Sensitivespeciesincludedblackwalnut,shortleafpine,whitepine,Virginiapine,blackcherryandblacklocust(6species).Theauthorsassumedthatreductionsinphysiologicalfunctionandgrowthwouldparrellvisibleinjuryeffects.Forestresponseswereexaminedbyimposingvaryingdegreesofstressonthetreesbasedontheirsensitivityranking.Twolevelsofstresswereimposed:high(20%,10%,0%)andlow(10%,5%,0%)forsensitive,intermediateandresistanttrees,respectively.Nodifferentialsensitivitywithinaspecieswasassumed.Thesimulatedforestwasgrownupto400years.Airpollutionstresswasimposedatvarioustimesduringthesimulation(age0,50and400).  Themodelshowedthatresponsetothestressvariedbyspeciesandbythetimewhenthestresswasimposed.Severalspeciesbasedontheirgrowthcharacteristics tookadvantageofthestressandgrewatmorerapidratesthanotherspeciesinthesamesensitivitycategory.Yellow h+&8 poplarandblackoakwerebothclassifiedasintermediate,however,yellowpoplargrewbetterovertimeandblackoakgrewlessunder10%stress.Thisisduetotheirsiliviculturalcharacteristicssuchasgrowthrates,tolerancetolight,etc.Blackcherrywasthemostsensitivespeciesobserved.Under20%stressthespeciesalmostdisappearedinolderstands(>100yearsold).Biomassproductionintheforeststandwasreducedunderthehighstresslevel,withthemaximumreductionoccurringat200years.& &   Summary ^    Althoughthemodelprovidesaninterestingtooltostudyairpollutioneffectsoverthelifespanofaforeststandseveraloftheassumptionsneedtobereevaluatedtomakethe'&^tԀmodelmoreamenabletoozoneeffectstoforestsintheSAMIregion.  1.0  Therelativesensitiviesofthevariousspeciesthatweregrownneedstobeupdated H andbasedongrowthreductions.Thecorrelationbetweenvisibleinjuryandgrowthreductionsisweekatbest.Sensitivityrankingneedtobespecifictoozone. (#(# 0  2.0(#(#Differentialsensitivitytoozonewithinaspeciesisareality.Thismaybeverydifficult n tosimulate. (#(# 0  3.0(#(#Isconstantadditionofastressappropriate?Variableadditionsmayprovidemore 2" meaningfulresults. (#(# ̜    LoblollyPine  X (   Anindividualtree,distancedependentmodel(AIRPTAEDA)thataccountsforstandcompetitionandmortalitywasdevelopedforloblollypine(WebbandBurkhart1988,Webbetal. #l, 1992).Themodelwasadaptedfromagrowthandyieldmodelforloblollypine(PTAEDA2)developedbyBurkhartetal.(1987).Themodelincludesonebasicassumption:ozoneimpactto %0!0 treeswithinastandisnotuniform.Basedonthisassumption,thesimulatorgeneratesoneoftwoscenarios:sensitivetreesarechosenatrandom,orthetallesttreesareconsideredthemostsensitive.Thepopulationoftreesisthenfurtherdividedintothreesensitivitycategories(low,medium,orhigh).Theproportionofindividuals fallingineachcategorycanbevaried.Ozone h+&8 effectscanonlybesimulatedstartingwiththeninthgrowingseason,basedontheinherentnatureoftheoriginalmodel,PTAEDA2(Burkhartetal.1977).Themodelsimulatesgrowthfor30 b years,whichisanaveragerotationageformostsouthernpines.Differentgrowthratereductionscenarioswereused,basedonexperimentaldata(ShaferandHeagle1989,Stowetal.1991, & Doughertyetal.1992). 8    Growthlossatthestandlevelwasdependentonseveralfactors:1)Theseverityofthegrowthloss.Themoreseverethegrowthlossthegreaterthereductioninstandvolume.2)Therelativefrequencyoftreesinthevarioussensitivitycategories.Thegreatertheproportionoftreesintheinsensitivecategorythegreaterthegrowthreductionneedstobetoelicitaneffect.3)Randomnessinsensitivity.Whensimulationswereconductedwithrandomlyselectedtreescomparedtotalltreesbeingthemostsensitive,standswherethelaterscenariowaschosenexhibitedlessergrowththanwhentreeswereselectedatrandom.  Averageannualreductionsaveragedfromapproximately12%peryearto1020%peryearbasedontheinputvariables.Themostseverecasewasbasedonreductionsincrownvolumeratherthandecreasesinheightordiametergrowth.  Summary      Thissimulationmodelprovidessomeinterestinginformationonozoneeffectstoloblollypinestands.Itaccountsfordifferentialsensitivitywithinaspecies.Theinputvariablesandsensitivityrankings,however,aredrivenbyexperimentaldata.Thismodelisadaptedforasinglespecies,loblollypine,growinginanevenaged,plantationsituation.Themodelalsorunsforonly30years,anddoesnotbeginintroductionofthevariousozonescenariosuntilagenine.Itsutilityinanassessmentofmixedhardwoodconiferousstandsandearlysuccessionalstagesofforestdevelopment,therefore,islimited. GeneralConclusions  B'"2   Severalmodelshavebeenusedtosimulategrowthand/orphysiologicalresponsestoozone.Theseincludeasingletreemodel(TREGRO),severalcanopymodelsonozoneuptakeandcarbonfixation,aforestsuccessionmodel(FORET)andaloblollypinemanagementmodel h+&8 (AIRPTAEDA).AllofthesemodelsprovidesomeinformationonozoneeffectstospeciescommonlyfoundintheSAMIregion.Eachmodelhasadvantagesanddisadvantages,andtheyvaryintheirlevelofcomplexity.TREGROprovidesgoodinformationonozoneeffectstoasingle,opengrowntree.Ithowever,doesnotprovideinformationregardingforeststandgrowth.AccurateozonedoseresponsefunctionsareneededtomodeltreeresponsesusingTREGRO.Whilethesefunctionsareavailableforsometreespeciesattheseedlingleveltheyarenotavailableformaturetrees.Giventhepaucityofmaturetreestudies,modelpredictionsusingexperimentalgrowthresponsesarenoteasilyvalidated.Inaddition,themodel(TREGRO)requiresdetailedozoneexposure,environmentalandphysiologicaldatathatarenotpresentlyavailableformanyspecies.  Thecanopymodelsallprovidegoodinformationonozoneuptakeandcarbonfixation.Theydonotprovideinformationonwholetreeresponses(rootgrowth,etc.).Inaddition,allofthecanopymodelsassumethatozonelevelsandleafresponsesareequalwithinacrown.Thismayproduceerrorinthemodel.  TheFORETmodelprovidessomeextremelyusefulinformationonozoneeffectstoaforeststand.Itcanprovideinformationonchangesingrowthandproductivityovertime.Thissimulatorneedstobereparameterizedspecificallyforozone.Itoriginallywasparameterizedforairpollutioneffectsingeneral,andthisassumptionneedstobemodified.Also,themodelozoneeffectstobeequalwithinaspecies,anderrorcouldensueduetothisassumption.AIRPTAEDAhaslimiteduseforanassessmentofthetreeswithintheSAMIregion,sinceloblollypineisaminorcomponent.Alsothismodelisbasedonagrowthandyieldmodelforplantationgrowntrees.Itdoes,however,accountfordifferentialgeneticvariabilitywithinaspeciestoozone.Thistechniquemaybeabletobemodifiedandusedinconjunctionwithothermodelsinanassessmentframework. (XXGVII.METHODOLOGIESUSEDINASSESSINGOZONEEFFECTS B'"2 М#XGX(#    EstablishingtherisktoforestsintheSAMIregionfromtroposphericozoneisadifficult (0$4  task.Itrequiresapproachesthatutilizeexistingdatabasesontheforestresources,ozone B*%6 monitoringinformation,realisticozoneexposuretreeresponseexperiments,modelinginformationtopredictchangesoveraspatialandtemporalscale,andintegrationofsocialvalues.   Inthissectionthreedifferentassessmentmethodologieswillbediscussed.AllthreemethodshavebeenutilizedfortreespeciesgrowingintheSAMIregion.Thefirstmethodologyinvolvedtheuseofkriging(ozoneconcentrations)combinedwithdataobtainedfromexperimentalresultsforfourtreespecies,blackcherry,northernredoakandyellowpoplar,growingintheSAMIregiontodetermineareasofpossibleconcern(Lefohnetal.1997).Since  L  environmentalfactorssuchassoilmoistureavailabilitymaypotentiallyinfluencetreeresponsetoozone,thePalmerhydrologicindex(Palmer1965,1967)wasusedtofurthersubdividetheseareasofconcern.  Eventhoughnotapplied,Hogsettetal.(1993)inthesecondapproachdiscussedtheuse   ofGISincombinationwithexperimentaldataandindividualandstandlevelmodelstodeterminepotentialgrowthlossesofseveralmajortreespeciesduetoozone.Atriskareascouldthenbeidentified.Theinvestigatorscombinedexposureresponsemodelsderivedfromdatacollectedinopentopchamberswithpredictedozoneexposurestopredictgrowthlosses.  AthirdproposedapproachusedinriskassessmentwasdevelopedbyLuxmoore(1992).Thisapproachisbeingdevelopedfortheassessmentofregionalresponsesofloblollypinetoozoneandotherclimaticfactors(variationinrainfall) scalingupfromseedlingstoforeststands 2" usingvariousphysiologicallybasedsimulationmodels.  $ ̜  ApplyingExposureInformationforIdentifyingAreasofConcernLefohnetal.(1997)  ^ (   Lefohnetal.(1997)describedtheprotocolsfortheidentificationofvegetationareasthat !* maybeatrisk,whichinvolvedcombiningexperimentalexposureresponseeffectsdatafordeciduousandconiferousseedlingsandtreeswith1)krigedcharacterizedO3ambientexposure $. datamentionedpreviouslyand2)soilmoisture.TheconclusionsofMusselmanetal.(1994)and %6!0 others(seeU.S.EPA1996),thatallhourlyaverageconcentrationshavethepotentialforimpactingvegetation,butthatthehighervaluesshouldbegivenagreaterweightingthanthemidandlowlevels,wereusedinthemethodologydescribedbyLefohnetal.(1997).Recentworkby  *\%6 Karnoskyetal.(1996)appearstoreinforcetheimportanceofhighhourlyaverageconcentrations. n+&8 Thecumulativetypeexposureindexperformsadequatelyinrelatinggrowthreductiontovegetationandozoneexposuresoccurringwithsingleexperiments(U.S.EPA1992,1996,Leeet b al.1991,Lefohn1992).However,whenattemptingtorelateaparticularsetofexposureresponse t resultstoambientconditionsorotherexperimentalresults,singleparametercumulativeindicesshouldbecombinedwithsomemeasureofthehighhourlyaveragevalues(e.g.,values0.10 8  ppm),whichoccurredinmanyoftheopentopexperiments(LefohnandFoley1992,1993,Lefohnetal.1992b,Lefohn1992).  L    Intheiranalysis,the24hsigmoidallyweightedexposureindex(LefohnandRuneckles1987),W126,wasusedovertheAprilOctoberperiodforthereasonsdescribedabove.Alternatively,a24hSUM06(thesumofallhourlyaverageconcentrations0.06ppm)exposure "r  indexcouldhavebeenused.BoththeW126andtheSUM06arehighlycorrelatedandprovidesimilarexposureresponseresultsineffectsmodelingefforts(U.S.EPA1996).TheW126wasselected,however,becauseitdoesnotuseasubjectivelydeterminedthresholdof0.06ppm,whichcannotbebiologicallysubstantiatedatthistime.Theindexincludesthelower,lessbiologicallyeffectiveconcentrations.TheW126cumulativeindexwasintegratedovera24hperiod.  ForestimatingtheexposureregimesthatrelatetogrowthreductionofvariousdeciduousandconiferoustreespeciesgrownintheSouthernAppalachianregion,Lefohnetal.(1997)    characterizedozoneexposuresfrombiologicalexperiments.Theinitialreviewoftheliteratureassociatedwiththisresearcheffortfocusedonexposureresponseinformationforthefollowingspecies:blackcherry;yellowpoplar,Virginiapine;redmaple,easternwhitepine,slashpine,pitchpine,loblollypine,northernredoak,whiteoak,sycamore,shagbarkhickory,Americanbeech,whiteash,andgreenash.  Usingtheexperimentalresults,fourbroadsensitivitycategoriesweredeveloped[i.e.,1) #l, minimal,2)level1(blackcherry),3)level2(yellowpoplar),and4)level3(northernredoak,Virginiapine,loblollypine,easternwhitepine,whiteoak,sugarmaple,redmaple,Americanbeech,andshagbarkhickory]weredefined.Forassigningtheresponsecategories,focuswasononlythosestudieswheregrowtheffectswerenoted.Theminimalcategorywasdefinedasalevelwhereexposureswerelessthanthosewhichcausedamagetoblackcherryorwheremoistureconditionswerenotfavorableforozoneuptake. h+&8   Theinitialapproachassumedthatthe1)environmentalconditionswerefavorableforozonetoentertheleafand2)totalcumulativeexposurewouldresultinagrowthloss.However,asmentionedabove,itisnecessarytoconsiderconditionsthataffectaplant'ssensitivity.Theexperimentalstudiesusedseedlingandtreeplantswhichweregrownunderoptimumconditions(e.g.,adequatemoistureandnutrients).Showman(1991),Jacksonetal.(1992)andKouterick 8  (1995)haveobservedsignificantlyfewerozonesymptomsonsensitivespeciesduringperiodsofdroughtthanduringyearswhenthegrowingseasonhadadequaterainfall.Unfortunately,atthistime,littleexperimentalinformationisavailablerelatingozoneexposure,droughtconditions,andtreegrowthreduction.  Each$by$gridcellintheSouthernAppalachianareawasassignedoneoffour "r  categories(Table3)mentionedabove.BecausethecriterialistedinTable3requiresthatboththeW126andnumberofhours0.10ppmbemet,itwasnecessarytopredictthenumberof 6 occurrencesofhighhourlyaverageconcentrations.Thereisapaucityofairqualitymonitoringdatawhichmakesitdifficult,atthistime,tospatiallypredictthenumberofhourlyaverageconcentrations0.10ppmaccurately.However,theauthorsfoundthatitwaspossibleto  \ separatetheareaintobroadexposurecategoriesduetotheoccurrencesofhourlyaverageconcentrations0.10ppmduring"high"and"low"ozoneexposureyears.Forexample,in1983    1986and19891990,thenumberofhourlyaverageconcentrations0.10ppmatallsitesinthe 2" geographicareawaslessthan51,whichisbelowtheLevel2sensitivitycategory.In1987,therewasonlyonesitethatexperiencedgreaterthan51occurrences0.10ppm.In1988,thehigh F& exposureyear,11of15monitoringsitesexperienced51ormorehourlyoccurrences0.10ppm. X ( Subjectively,itwasdecidedthatgridswhichhadtwoormoreozonemonitorswereclassifiedusingthehighestvalue;cellswhichdidnothaveamonitorwereclassifiedbyexaminingthepatternfrommonitorssurroundingthecellandselectingasitewhosevaluewasthesecondhighestnumberofhours0.10ppm. %0!0   ThePalmerhydrologicindexwasselectedasanindicatorofsoilmoisture(Palmer1965,1967).BecausePalmerhydrologicindexdatawereavailablefortheperiod19831990,thestudywaslimitedtothistimeframe.Theindexisamonthlyvalue,computedforaclimaticdivision,whichindicatestheseverityofawetordryspell. h+&8   CombiningthePalmerhydrologicindexandozoneexposuresallowedLefohnandcoworkers(1996)toidentifythoseareaswithintheregionwhere1)soilmoisturemayhavebeenadequateintheareaand2)ambientexposureregimescloselymatchedthoseexperimentswheregrowthlosseswereobserved.Areaswhichwereclassifiedasexperiencingadroughtwereassignedtheminimalcategory;otherwisethesensitivitycategoryvalueremainedthesameafterapplyingthecriteriapreviouslymentioned.  Usingavailablemonitoringdatafor19831990andexposureresponsedatabasedonseedlingsandtrees,Lefohnetal.(1997)identifiedgeographicregionswithintheareathatmay ^  haveexperiencedozoneexposures,whichincludehighcumulativevaluesaswellasthepresenceofsufficientnumbersofhighconcentrations,coupledwithsufficientsoilmoisture,thathavethepotentialforinhibitingvegetationgrowth.Asindicatedearlier,currentozoneexposuresarecausingvisiblesymptomsonthefoliageofsensitivespeciesandinjuryhasbeendocumentedinnumerouslocationsthroughouttheSouthernAppalachianarea.Theirresultsindicatedthatinasmallnumberofareaswithintheregion,ozoneexposuresandsoilmoistureavailabilitymightbesufficienttocausegrowthlossestosomesensitivespecies.Thenumberofhectareswherevegetationmaybeaffectedbyexposuresmayrepresentanoverestimateduetotheoptimumgrowthconditionsexperiencedintheexperimentalopentopchambersandthemannerinwhichtheinvestigatorscharacterizedtheambientozonedata(i.e.,overa7monthperiod).Inaddition,twootheritemsareimportant:1)thegrowingrangeofeachspeciesandamountsofspeciesineachcellwerenotusedinouranalysis;and2)theresolutionofthePalmerhydrologicindexisattheclimaticdivisionforeachmonthand,dependinguponthevariabilityofsoilsintheclimaticarea,theindexmayprovidelessthanoptimumpredictions.Itisclearthattherestillneedstobeverificationofactualgrowthlossesfortheareasofconcern. RiskCharacterizationHogsettetal.(1993)  %0!0   Toassesspotentialriskofsensitivetreespeciestoozone,Hogsettetal.(1993)appliedan B'"2 assessmentmethodologybasedontheuseofaGeographicalInformationSystem(GIS)combinedwithestimatedozoneexposures,simulationmodelsandexperimentaldata.Totestthismethod,theyusedtheeasternUS,includingtheSAMIregionasthestudyarea.Forthepurposesofthis h+&8 initial,preliminaryassessmenteighttreespecieswereused:quakingaspen,blackcherry,yellowpoplar,sugarmaple,redmaple,loblollypine,Virginiapine,andeasternwhitepine.AllspeciesoccurintheSAMIregion,however,quakingaspenandloblollypineareminorcomponentsoftheforesttypescommonlyfoundinthisregion.  Tocharacterizeriskoftheseforeststoozone,Hogsettetal.(1993)attemptedtointegrate 8  fourelementstoformthedatabasethatcomprisedthetwomajorcomponentsoftheassessment(exposurecharacterizationandcharacterizationofecologicaleffects).Thesefourelementsare:  1.0  Ozoneexposuresfortheregion. (#(#   2.0  Spatialdistributionoftheresources.Thedegreeofinterestcanbeatthespecies, "r  communityorecosystemlevel. (#(#   3.0  Thespatialdistributionofotherabioticorbioticfactorsthatmayinfluencetree 6 responsetoozone.Includedinthisisenvironmentalfactorsandexposuredynamics. @"  (#(#   4.0  Exposureresponsefunctionsfortheselectedmeasurementendpoints.(#(#   TheframeworkofthisassessmentisillustratedinFigure11.(Hogsettetal.1993). n Informationusedtodeveloptheresponsefunctions(ecologicaleffects)areenclosedwithinthecircles.Thesedataarederivedthroughexperimentaldataorliterature,thensimulatedovertimebyusingsimulation,processlevelmodels.Modelswereusedbecauseallofthedatausedinthepreliminaryassessmentwasfromindividualtreeseedlingdatagatheredoverashortduration(generallyoneyearorless).Theseresults(responsefunctions)werethenintegratedwithozoneexposureinformation,speciesdistributionsandotherenvironmentalfactorsusingGIStoderivethefinalriskcharacterization,ie.,thelikelihoodoftheoccurrenceofadverseeffects(biomassreductions,etc.)withozoneexposure(Figure11).  Sinceozonemonitoringdataarelimited,ozoneexposureswereestimatedforareaswithoutmonitorsusingamethoddevelopedbyHogsettandHerstrom(1991,Hogsettetal. B'"2 1993).ThemethodusesGIStogeneratepotentialozoneexposuresbasedonozoneprecursors (NOx),solarradiation,stagnatingairmassesandwinddirection.Theozoneexposurestatistic *V%6 usedwasthemaximum3monthSUM06value.Exposureresponseinformationwasdevelopedfromopentopfumigationexperiments.   Theresultsofthispreliminaryassessment(Hogsettetal.1993)indicatedawiderangeof t annualbiomasslosses(033%)dependingonspeciesandozoneexposures.Thetwomostsensitivespecieswereblackcherryandaspenwithannualpredictedgrowthlossesover20%forgreaterthan50%oftheirrange.Yellowpoplar,loblollypine,sugarmapleandwhitepinehadbetween512%annualbiomasslosseswithalargeportionortheirrangeexperiencingtheselosses.  Asmentionedbytheauthors(Hogsettetal.1993)thisassessmentwaspreliminaryin   natureandsubjecttoseveralsourcesoferror.Theseincludeuncertaintyassociatedwiththeuseofseedlingdatatoestimatematureforestresponse,climatedata,estimationofozoneexposures,andspeciesdistribution.Theauthorsdofeel,however,thatthisisavalidtechniqueanddeservesfurtherrefinement.OnekeydifferencebetweenthatbyHogsettetal.(1993)andLefohnetal. H (1997)isthatHogsettetal.(1993)didnotfocusonthepresenceofhighhourlyaverage  concentrations(i.e.,0.10ppm),whileLefohnetal.(1996)did.AsdiscussedinLefohnetal.  \ (1997),manyoftheexperimentsusedtodeveloptheexposureresponseinformationbyHogsettetal.(1993)werebasedonNCLANtypeexposures,whichexperiencenumerousoccurrences    0.10ppmintheexperimentaltreatmentswhereeffectswereobserved.Ignoringthepresenceofthehighhourlyaverageconcentrations,mayleadtooverestimatesofgrowthreduction.Inaddition,Hogsettetal.(1993)useda92daySUM06exposureindex.Therationaleforusinga F& thisexposureperiodisunclear.Thegrowingseasonformosttreespeciesisgenerallygreaterthanthisthreemonthperiod.̜ ̛ ScalingUpPhysiologicalResponsestoOzoneLuxmoore(1992)  ~$.   AnotherpotentialassessmentmethodologytoconsiderisoneproposedbyLuxmoore(1992)wheretheresponseofloblollypinevariationsinrainfallandozoneexposureswouldbescaledupfromaseedlingtoaforeststandandlongtermeffectsonloblollypineproductivity wouldbeassessed.TheframeworkforthisproposedmethodologyisshowninFigure4. *V%6   Inputvariablesarefirstenteredintoaphysiologicallybasedmodel[UnifiedTransport Model(UTM)].Thismodelconsistsoffivelinkedmodelsthatprovidedataatanhourlybasisoncarbon,nutrients,waterandpollutantfluxestotreesinauniformstand.DataarethenincorporatedintheFORETmodel(previouslydescribed)andtreesgrownovertime.ThisinturnislinkedtoPTAEDA2toprovidedifferentmanagementoptionsandstandmanipulations.Thesearethenincorporatedwithdifferentpolicyoptionswithdifferentpollutionandclimatechangescenarios(Figure12).  Thisassessmenttechniqueisstillinthedevelopmentstages,ie.,ithasbeentestedononly ^  onetreespecies(loblollypine).It,however,allowsfortheincorporationofpolicyoptionstoaphysiologicallybasedprocessmodel.Themodelallowsforthemanipulationofvariousedaphicandclimaticvariables,aswellasozoneandcarbondioxidelevels.̜   GeneralConclusions H    Allthreemethodologiesprovideinformationthatcanbeusedinanassessmentframework.  Eachofthesehasadvantagesanddisadvantagesorlimitations.Eachmethodispotentiallyapplicabletoaregionalassessment.  ThefirstmethodbydescribedbyLefohnetal.(1997)affordsatechniquewhereareasof    potentialriskcanbeidentifiedforseveraldifferenttreespecies.Manydifferentozoneexposurestatisticscanbeused,althoughtheauthorsforreasonsmentionedabove,prefertheW126accumulatedovera24h,7monthperiod.Italsoprovidesawaytocombineozonedatawithotherenvironmentalvariables,ie.,wateravailabilitythatarebelievedtobeimportantin X ( physiologicalfunctionandgrowthresponsetoozone.  Thereareseverallimitationsthatneedtoberecognized.Theexperimentaldatausedwerelimitedbecauseofdataavailabilityandprimarilywasforseedlingresponsetoozone.Becauseozonemonitoringinformationislimited,krigingwasusedasasurrogatetoozonemonitoringdatainmanyareas.Theerrorsassociatedwithusingkrigingtoestimateozoneexposureswasdeterminedforeachcell.ThePalmerhydrologicindexmanynotrepresentatrueaccountofwhetherornotaparticularspeciesisunderwaterstress.Somespeciesaremoreadaptedtoxericconditionsthanothers.Inaddition,arecentreportbyMcLaughlinetal.(1995)suggeststhe h+&8 possibilityofgrowthresponseofloblollypinetoozonebeingenhancedbydrought.ThiscontrarytothehypothesisproposedbyLefohnetal.(1997)andcitedintheU.S.EPACriteriaDocument b (U.S.EPA1996),anddeservesfurtherexploration.  Hogsettetal.(1993)proposedamethodologyfortheregionalriskassessmentofforest & responseduetoozoneexposureforsimilartreespeciesasdescribedbyLefohnetal.(1997) 8  growingintheSAMIregion.ThismethodtakesadvantageofthenewtechnologyassociatedwithGISandsimulationmodels,andprovidesinformationontheareaswithinaspeciesrangethatarepotentiallyatmoreriskthanothers.Thereappearstobeseverallayersofparameritizationnecessary(modellinkages)fortheassessmenttobeoperational.Forestgrowthscenariosarebasedonindividualseedlingdatafromonlyasmallnumberofstudies,mostlywithseedlingsgrowinginpots,inopentopchambers(Hogsettetal.1993,Neufeld1993,Karnosky1993,   Karnoskyetal.1993,Lefohnetal.1992,Qiuetal.1992).Otherconcernsarewiththeerror 6 associatedwiththeestimationofozoneexposuresandspeciesdistribution.Becausethereislittleozonemonitoringdataavailable,theexposuresareestimatedusingemissionsdata.Thiscanleadtoerrorindeterminationofexposurevalues(Hogsettetal.1993).Regardingspeciesdistribution,  \ theinventoryofaparticularspeciesmaynotbeuptodate.  Thethirdproposedassessmenttechnique(Luxmoore1992)maynotbeapplicableatpresentforanassessmentofmultipletreespeciesthatoccurintheSAMIregion.Thismethodwasdevelopedforasinglespecies,loblollypine,andwouldhavetobereparameterizedforanassessmentincludingmultiplespecies.Thistechniquereliesheavilyonphysiologicallybasedprocesslevelmodelsandagreatdealofparameteritizationandcomputertimewouldberequired.̜&  (XXG  VIII.OVERALLCONCLUSIONSANDXGX((XXGRECOMMENDATIONS#XGX( # #l,  Q% X` _ X X` _ XQӜ  Conclusions  $ . 1.0  Growthandphysiologicalresponsestoozonehavebeenreportedforindividualtreesthat &l!0 occurintheSAMIregion.Mostofthesestudiesare,however,withindividualseedlings'#Ԁ(<2yrsinage)undercontrolledconditions(CSTRsoropentopchambers).Moststudieswereshortterm(Lee,E.H.,Hogsett,W.E.andTingey,D.T.1991.Efficacyofozoneexposureindicesinthestandardsettingprocess.P.255271In:R.Berglund,D.LawsonandD.McKee(eds.).  TransactionsoftheTroposphericOzoneandtheEnvironmentSpecialtyConference.Airand  WasteMange.Assoc.,Pittsburgh,PA.XGXXXGԛ  Lee,W.S.,Chevone,B.I.andSeiler,J.R.1990.Growthresponseanddroughtsusceptibilityofredspruceseedlingsexposedtosimulatedacidicrainandozone.For.Sci. 36 :265275. h  ̜#XGXXXG#Lefohn,A.S.1992.Thecharacterizationofambientozoneexposures,Chapter3.P.3992In: D"  A.S.Lefohn(ed.).Surface-LevelOzoneExposuresandTheirEffectsonVegetation.Chelsea, 0#! MI.LewisPublishers,Inc.Lefohn,A.S.andBenedict,H.M.1982.Developmentofamathematicalindexthatdescribesozoneconcentration,frequency,andduration.Atmos.Environ. 16: 25292532. &0"% Lefohn,A.S.andFoley,J.K.1992.NCLANresultsandtheirapplicationtothestandard-settingprocess:Protectingvegetationfromsurfaceozoneexposures.J.AirandWasteManag.Assoc. 42: 1046-1052. *%)  +&* Lefohn,A.S.andFoley,J.K.1993.Establishingozonestandardstoprotecthumanhealthandvegetation:Exposure/doseresponseconsiderations.J.AirandWasteManag.Assoc. 43: 106  112.Lefohn,A.S.andLucier,A.A.1991.SpatialandtemporalvariabilityofozoneexposureinforestedareasoftheUnitedStatesandCanada:1978-1988.J.AirandWasteManag.Assoc.  P  41: 694-701. @  Lefohn,A.S.andPinkerton,J.E.1988.HighresolutioncharacterizationofozonedataforsiteslocatedinforestedareasoftheUnitedStates.J.AirPollut.ControlAssoc. 38: 1504-1511.  X  Lefohn,A.S.andRuneckles,V.C.1987.Establishingastandardtoprotectvegetation-ozoneexposure/doseconsiderations.Atmos.Environ. 21: 561-568.   Lefohn,A.S.,Laurence,J.A.andKohut,R.J.1988a.Acomparisonofindicesthatdescribetherelationshipbetweenexposuretoozoneandreductionintheyieldofagriculturalcrops.Atmos.Environ. 22: 12291240.  Lefohn,A.S.,Jackson,W.,Shadwick,D.S.andKnudson,H.P.1996.EffectofsurfaceozoneexposuresonvegetationgrownintheSouthernAppalachianMountains:Identificationofpossibleareasofconcern.Atmos.Environ.(inpress).Lefohn,A.S.,Knudsen,H.P.andMcEvoy,L.R.Jr.1988b.TheuseofkrigingtoestimatemonthlyozoneexposureparametersforthesoutheasternUnitedStates.Environ.Pollut. 53: 27-42. 8 Lefohn,A.S.,Knudsen,H.P.,Shadwick,D.S.andHermann,K.A.1992a.SurfaceozoneexposuresintheeasternUnitedStates(19851989).P.8193In:R.B.Flagler(ed.).  TransactionsoftheResponseofSouthernCommercialForeststoAirPollutionSpecialty  Conference.AirandWasteMange.Assoc.,Pittsburgh,PA.  Lefohn,A.S.,Knudsen,H.P.,Logan,J.L.,Simpson,J.andBhumralkar,C.1987.AnevaluationoftheKrigingMethodtopredict7hrseasonalmeanozoneconcentrationsforestimatingcroplosses.J.AirPollut.ControlAssoc. 37: 595602. 8#! Lefohn,A.S.,Shadwick,D.S.,Somerville,M.C.,Chappelka,A.H.,Lockaby,B.G.andMeldahl,R.S.1992b.Thecharacterizationandcomparisonofozoneexposureindicesusedinassessingtheresponseofloblollypinetoozone.Atmos.Environ. 26A: 287298.XGXXXG &<"% #XGXXXG#Lewis,E.andBrennan,E.1977.Adisparityintheozoneresponseofbeanplantsgrowninagreenhouse,growthchamberoropentopchamber.J.AirPollut.Contr.Assoc. 27 :889891.XGXXXG )%(  #XGXXXGƑ# *%) Luxmoore,R.J.1992.Anapproachtoscalingupphysiologicalresponsesofforeststoair pollutants.P.313322In:R.B.Flagler(ed.).Transactions:TheResponseofSouthern  CommercialForeststoAirPollution.AirandWasteMange.Assoc.,Pittsburgh,PA.  Mahoney,M.J.,SkellyJ.M.,Chevone,B.I.andMoore,L.D.1984.Responseofyellowpoplar(LirodendrontulipiferaL.)seedlingshootgrowthtolowconcentrationsofO3,SO2,andNO2. L  Can.J.For.Res. 14 :150153. 8  XGXXXGMatyssek,R.,Reich,P.,Oren,R.andWinner,W.E.1995.Responsemechanismsofconiferstoairpollutants.P.255308In:W.K.SmithandT.M.Hinckley(eds.).Ecophysiologyof  P  ConiferousForests.AcademicPress,SanDiego,CA.  <  #XGXXXG#McLaughlin,S.B.andDowning,D.J.1995.Interactiveeffectsofambientozoneandclimate   measuredongrowthofmatureforesttrees.Nature 374 :252254.   XGXXXG#XGXXXGɖ#McLaughlin,S.B.andKohut,R.J.1992.Theeffectsofatmosphericdepositionandozoneon   carbonallocationandassociatedphysiologicalprocessesinredspruce.P.338382In:C.Eagar x andM.B.Adams(eds.).EcologicalStudies:AnalysisandSynthesis,96:EcologyandDeclineof d RedSpruceintheEasternUnitedStates.SpringerVerlag,NewYork,NY. P ̜McLaughlin,S.B.,McConathy,R.K.,Duvick,D.andMann,L.K.1982.Effectsofchronicairpollutionstressonphotosynthesis,carbonallocation,andgrowthofwhitepinetrees.For.Sci. 28 :6070. P МMcLaughlin,S.B.,Layton,P.A.,Adams,M.B.,Edwards,N.T.,Hanson,P.J.,O'Neill,E.G.andRoy,W.K.1994.Growthresponsesof53openpollinatedloblollypinefamiliestoozoneandacidrain.J.Environ.Qual. 23 :247257.  McQuattie,C.J.andSchier,G.A.1993.Effectofozoneandaluminumonpitchpine(Pinus  rigida)seedlings:Needleultrastructure.Can.J.For.Res. 23 :13751387. | XGXXXGMeadows,J.S.andHodges,J.D.1995.Responseofloblollypinetomoistureandnutrientstress.P.244280In:S.FoxandR.A.Mickler(eds.).ImpactsofAirPollutantsonSouthernPine. D"  SpringerVerlag,NewYork,NY.#XGXXXG#ԛ̜Meier,S.,Grand,L.F.,Schoeneberger,M.M.,Reinert,R.A.andBruck,R.I.1990.Growth,ectomycorrhizaeandnonstructuralcarbohydratesofloblollypineseedlingsexposedtoozoneandsoilwaterdeficit.Environ.Pollut. 64 :1127. &0"% МMusselman,R.C.,McCool,P.M.andLefohn,A.S.1994.Ozonedescriptorsforanairqualitystandardtoprotectvegetation.J.AirandWasteManag.Assoc. 44: 13831390. )$(   *%) NationalAcidPrecipitationAssessmentProgram.1991.Changesinforesthealthand productivityintheUnitedStatesandCanada.P.186In:AcidicDepositionStateofScienceand  Technology,Vol.III.Report12.  Neufeld,H.S.andRenfro,J.R.1993.Sensitivityofblackcherryseedlings(Prunusserotina)to ` ozoneinGreatSmokyMountainsNationalPark.U.S.Dept.ofInterior,NationalParkService,Denver,CO,TechnicalReportNPS/NRTR93/112.Neufeld,H.S.,Lee,H.E.,Renfro,J.R.,Hacker,W.D.andYu,B.H.1995.Sensitivityofseedlingsofblackcherry(PrunusserotinaEhrh.):1.Exposureresponsecurvesforbiomass.  L  NewPhytol. 130 :447459.  8  Neufeld,H.S.,Renfro,J.R.,Hacker,W.D.andSilsbee,D.1992.OzoneinGreatSmokyMountainsNationalPark:dynamicsandeffectsonplants.P.594617In:R.L.Berglund(ed.).   Transactions:TroposphericOzoneandtheEnvironmentII.AirandWasteMange.Assoc.,   Pittsburgh,PA.Oshima,R.J.1975.DevelopmentofasystemforevaluatingandreportingeconomiccroplossescausedbyairpollutioninCalifornia.III.Ozonedosage"croplossconversionfunction"alfalfa,sweetCorn.IIIA.Proceduresforproduction,ozoneeffectsonalfalfa,sweetcornandevaluationofthesesystems.CaliforniaAirResourcesBoard,Sacramento,CA.Palmer,W.C.1965.MeteorologicalDought.U.S.WeatherBureauReportNo.45,p.58.U.S.DepartmentofCommerce,Washington,D.C.Palmer,W.C.1967.Theabnormallydryweatherof19611966inthenortheasternUnitedStates.P.3256In:Proc.ofConferenceonDroughtintheNortheasternUnitedStates,New  YorkUniversityGeophysicalResearchLaboratoryReportTR683.XGXXXGԛ̜Patton,R.L.,Jensen,K.F.andSchier,G.A.1991.Responsesofredspruceseedlingstoozoneandaciddeposition.Can.J.For.Res. 21 :13541359. \  ̜Paynter,V.A.,Reardon,J.C.andShelburne,V.B.1992.Changingcarbohydrateprofilesinshortleafpine(Pinusechinata)afterprolongedexposuretoacidrainandozone.Can.J.For.Res. $#t!  22 :15561561. $`" ̜Pell,E.J.1987.Ozonetoxicity"istheremorethanonemechanismofaction?P.229240In: %AA 9*.9C C9noeffectonPn,gs =*.:C C=Fosteretal.1990 L=%.;C   CLQuercusrubra 9*<C C92growingseasons 9*=C C9OTC,Norris,TN 9*>C C9CF(SUM00=35ppmh),AA(SUM00=100ppmh),AAx2(SUM00=190ppmh) 9*TBC C9noeffectonPn,gsofseedlings;Pnreducedby25%inAAand50%inAAx2inmaturetrees =*GC C=Hansonetal.1994 L=%HC   CL 9*IC C93growingseasons 9*JC C9OTC,Norris,TN 9*KC C9CF,AA,AAx2 9*LC C9greaterinfluenceofozoneoncarbonallocationandpartitioning,andnutritionofmaturetreesthanseedlings. =*vRC C=Samuelsonetal.1996;Samuelson1996 L=%*zUC   CL 9*PVC C97h/day,5d/week,10weeks 9*dXC C9CEC 9*PYC C90.03,0.06,0.09,0.12ppm 9*d[C C90.12ppmreducedPnby20% =*d]C C=Reichetal.1986 L=%P^C   CLLiriodendron >_ tulipifera 9*`C C96h/day,1month 9*>aC C9CSTR 9*>bC C9CF,0.07,0.15ppm 9*dC C9noeffectonPn,gs =*>eC C=Cannonetal.1993 L=%>fC   CL 9*C C94h/day,5d/week,6 weeks 9*dC C9CSTR 9*C C9<0.02,0.05,0.10,0.15ppm 9*dC C90.10ppmreducedgsby15% =*dC C=Chappelkaetal.1988 L=%d C   CL 9*> C C98h/day,3d/week,5months 9*x C C9CSTR 9*>C C90,0.05,0.10,0.20ppm 9*xC C9noeffectonPnorrootstarchπ =* C C=Jensenetal.1990 L=%>C   CL 9*d C C98h/day,3d/week,3months 9*( C C9CSTR 9*d C C90,0.05,0.10,0.20ppm 9*( C C90.10ppmreducedPnby24% =*( C C=Roberts1990 L=%d C   CL 9* xC C98h/day,3d/week,20weeks 9* <!C C9CSTR 9* x"C C90,0.05,0.10,0.20ppm 9* <$C C90.20ppmincreasedfoliarMnandFe =* <&C C=Schier1990 L=% x'C   CL 9* (C C918weeks 9* )C C9OTC,OakRidge,TN 9*d+C C9CF,AA,AA+60ppm 9* ,C C9noeffectonPn,gs;nointeractionbetweenO3andsoilnitrogen =*( /C C=TjoelkerandLuxmoore1991 L=%d1C   CLPicearubens 9*x 2C C94h/day,3d/week,10weeks 9*< 4C C9CSTR 9*x 5C C9<0.25,0.10ppm 9*x 6C C9noeffectonPn,gs =*x 7C C=Leeetal.1990a L=%x 8C   CL 9* 9C C96h24h/day,28weeks 9*d ;C C9CSTR 9* <C C9CF,0.15ppmfor6h/day,0.15ppmfor6/hday+0.07ppmfor18/hday 9*b@C C9greatestozoneexposurereducedsugarinneedlesandroots =*( CC C=Pattonetal.1991 L=% DC   CL 9*<EC C92growingseasons 9*<FC C9OTC,WhitetopMT.,VA 9*HC C9AAx0.5,AA 9*<IC C9noeffectonPn =*<JC C=Pieretal.1992 L=%<KC   CL 9*dLC C94h/day,2d/week,16weeks 9*(NC C9CSTR 9*dOC C9CF,0.12ppm 9*dPC C9noeffectonleaforwholeseedlingPn =*(RC C=Tayloretal.1986 L=%dSC   CL 9*xTC C91growingseason 9*xUC C9OTC,WhitetopMT.,VA 9*<WC C9CF,AA 9*xXC C9noeffectonPn =*xYC C=Thorntonetal.1990 L=%<[C   CL 9*\C C93growingseasons 9*]C C9OTC,WhitetopMT,VA 9*d_C C9CF,AA 9*`C C9noeffectonPn,seedlingnutrition =*dbC C=Thorntonetal.1992L=%ddC   CLPrunusserotina 9*C C91growingseason 9*C C9uncontrolledfield,centralPA 9*dC C9ambient 9*C C9foliarinjuryrelatedtoPn =*dC C=Fredericksenetal.1996 L=%d C   CL 9*> C C91growingseason 9*> C C9OTC,Norris,TN 9*> C C9CF(SUM00=35ppmh),AA(SUM00=89ppmh),AAx2(SUM00=173ppmh) 9* C C9AAx2reducedPnby23% =*xC C=Samuelson1994 L=%>C   CLPinusstrobus 9*d C C97h/day,3d/week,4months 9*( C C9CEC 9*d C C90.02,0.06,0.10,0.14ppm 9*( C C9linearincreaseinfoliarK,decreaseinrootCa =*( C C=Reichetal.1988 L=%d C   CL 9* xC C97h/day,3d/week,4months 9* <C C9CEC 9* x C C90.02,0.06,0.10,0.14ppm 9* <"C C9linearreductioninPn,20%declineinPnin0.14ppm =*N&C C=Reichetal.1987 L=% x'C   CL 9*( (C C91growingseason 9*( )C C9uncontrolledfield,OakRidge,TN 9*& ,C C9ambient 9*( -C C925yroldtreeswithgreatervisibleinjuryhadgreaterfoliarrespiration =*& 0C C=McLaughlinetal.1982 L=%b 2C   CL 9* 3C C94h/day,50days 9* 4C C9CSTR 9* 5C C90,0.10,0.20,0.30ppm 9* 6C C9photosyntheticreductiondependentoncloneandexposureduration =*L:C C=Yangetal.1983 L=% ;C   CLPinustaeda 9*&<C C912weeks 9*&=C C9OTC,OakRidge,TN 9*t?C C9CF,AA+0.08ppm,AA+0.16ppm 9*tAC C9AA+0.16ppmreducedcoarserootstarch =*8DC C=AdamsandO Neill &E 1991 L=%tFC   CL 9*GC C92growingseasons 9*HC C9OTC,OakRidge,TN 9*LJC C9CF,AA,AAx2 9*KC C9AAx2increasedfoliarN,P =*LMC C=Edwardsetal.1991 L=%PC   CL 9*tQC C92growingseasons 9*tRC C9OTC,OakRidge,TN 9*8TC C9CF,AA,AAx2 9*tUC C9noeffectoncarbonallocation =*8WC C=Edwardsetal.1992 L=%tXC   CL 9*YC C93growingseason 9*ZC C9OTC,OakRidge,TN 9*L\C C9CF,AA,AAx2 9*]C C9AAx2affectedcarbonallocation&partitioning =*L_C C=FriendandTomlinson1992 L=%LaC   CL 9*&bC C97h/day,5d/week,13weeks 9*tdC C9OTC,OakRidge,TN 9*tfC C90.014,0.170ppm 9*&gC C9reducedPnby25% =*&hC C=Hansonetal.1988 L=%&iC   CL 9*NjC C94h/day,3d/week,10weeks 9*lC C9CSTR 9*NmC C9CF,0.10ppm 9*NnC C9ozoneinducedgreatersensitivitytowaterstress =*LqC C=Leeetal.1990b L=%NrC   CL 9*C C95h/day,5d/week,12 weeks 9*dC C9CSTR 9*C C9CF,0.05,0.10,0.15ppm 9*dC C9linearreductionsinfoliarstarchandtotalplantcarbohydrates =*( C C=Meieretal.1990 L=% C   CL 9*x C C91growingseason 9*x C C9OTC,OakRidge,TN 9*<C C9CF,AA,AAx2 9*xC C9noeffectonseedlingnutrition =*<C C=SimmonsandKelly1989 N=%<C   CN ;* C C;18weeks ;* C C;OTC,OakRidge,TN ;*d C C;CF,AA,AA+60ppm ;* C C;AA+60reducedgs35%,nointeractionofO3withsoilnitrogen =*( C C=TjoelkerandLuxmoore19915+)d C  $  5   b ЛX^DXCXXXX^DTable2.0  SummaryofozoneeffectsongrowthandbiomassproductionofselectedtreespeciesfoundintheSAMIregion.Ozone  exposuresweredeliveredusingCSTRs(continuouslystirredtankreactors),CECs(controlledenvironmentchambers)orOTCs(opentopchambers).OnlyOTCfieldstudieslocatedintheSAMIregionwereincluded.Unlessnoted,studieswereconductedwithseedlings.#X^DXXXOL##CXX^D0L#t.. *$%d%djZ@jZ@jZ@@jZ@jZ@jj@..,jZ ,jZ ,jZ ,@jZ ,jZ ,jj +  & $ t & Treespecies %:  % Exposureduration %:  % Exposurefacility %:  % Ozoneconcentration %:   % Growthresponse %:   % Reference 8+!:      8Abiesfraseri % d  %4h/d,3d/wk,10wks % d  %CSTR % d %<0.02,0.05,0.10ppm % d %Noeffectonanygrowthvariablemeasured % ( %Tsengetal.1988 3) d   3 "  "4h/wk,3d/wk,10wkgrowthcycles  v  CSTR    0.025,0.70,0.15ppm    Noeffectonanygrowthvariablemeasured  v  Seileretal.1994 #   #Acerrubrum  P  1growingseason  P  OTC(treesinpots)Norris,TN  d  CF,NF,NFX2  P  Noeffectonanygrowthvariablemeasured  d ! Samuelson1994a &P "  & "> # "8h/d,3d/wkfor16weeks   % CSTR  > & 0.0,0.07,0.15ppm  > ' Slightdecrease(4%)inleafdryweightat0.15ppm  v * JensenandDochinger1989 & ,  & "P - "7h/d,5d/wkfor8or12wks  d / CSTR  P 0 0.04or0.08ppm  P 1 Sig.decreasesinstemdia.,twigdia.,andstembiomass;18%,18%and34%,respec.At0.08ppmcomparedwith0.04ppm  $t7 Davis&Skelly1992b &d 9  & "N: "1growingseason  N; OTC(treesinpots)GreatSmokyMount.Nat.Park  J? CF,NF,NFX1.5,NFX2,24h/d  A Sigdecreaseinrootbiomass(29%)andtotalbiomass(15%)at2Xcomparedwithambient.Noeffectonht&dia  ^F Nuefeldetal.1992&NG  &Acersaccharum % %8h/d,3d/wkfor16weeks %d %CSTR %d %0.0,0.07,0.15ppm % %Slightdecrease(4%)innewgrowthbiomassat0.15ppm %(  %JensenandDochinger1989 3)d    3 %x  %6h/dfor28consec.d %x  %МCSTR %x %0.0,0.05,0.1,and0.15ppm %< %12%,42%,31%and41%decreaseinheight,topwt.,rootwt.,andtotalbiomassat0.15ppmcomparedwith0.0ppm.Onlysig.treat.effect %  %Kress&Skelly1982 0&x   0Fraxinus t  americana  8 6h/dfor28consec.d  t  CSTR  t  0.0,0.05,0.1,and0.15ppm  8 Sig.decreasesintop,rootandtotalbiomass(9%,8%,13%)beginningat0.1ppm  6 " Kress&Skelly1982 &t #  & " $ "4h/d,5d/wkfor5wks  ^ & CSTR   ' 0.0,0.05,0.1,and0.15ppm  ^ ) Sig.lineardecreaseinroot,leafandtotalbiomass,totalheightandroot/shootratiowithincreasingozoneconc.  n/ Chappelka&Chevone1986 &^ 1  & "H2 "4h/d,5d/wkfor6wks   4 МCSTR  H5 М0.025or0.1ppm  H6 Sig.decreaseinleafarea(18%)andtotalbiomass(14%)athighconc.   : Chappelkaetal.Ϝ1988 # <  #F. n= pennsylvanica  2> 4h/d,5d/wkfor6wks  2@ CSTR  nA 0.025or0.1ppm  nB Sig.decreaseinhtgrowth(15%)at0.1ppm  lE Chappelkaetal.1988 &2G  & "FH "6h/dfor28consec.d  FI CSTR  FJ 0.0,0.05,0.1,and0.15ppm   L A24%decreaseinhtgrowthat0.1ppm   N Kress&Skelly1982 &FO  & "nP "2growingseasons  nQ OTC(treesinpots)ShenandoahNat.Park,VA  0U CF,NF,AA  nV 67%decreaseinhtgrowthinNFcomparedwithCF  lY Duchelleetal.1982 &nZ  &Liquidambar  styraciflua %d %8h/d,3d/wkfor16weeks %d %CSTR % %0.0,0.07,0.15ppm % %At0.15ppmtreeshadaslightreduc.inleaf drywt,leafareaandht(47%) %b  %JensenandDochinger1989 3)d    3 %<  %6h/dfor28consec.d %< %МCSTR %< %0.0,0.05,0.1,and0.15ppm %  %Reduc.inhtandbiomassoccurredat0.1ppm.Rootbiomasswasthemostsensitivevariablewitha48%decreaseat0.15ppm %  %МKress&Skelly1982 0&<   0Liriodendron t  tulipifera  8 6h/dfor28consec.d  t  CSTR  t  0.0,0.05,0.1,and0.15ppm  8 Nosig.effectcomparedwithcontrolsforgrowthvariables  r ! Kress&Skelly1982 /%t "  / +!L # +7h/d,5d/wkfor8or12wks   % CSTR  L & 0.04or0.08ppm  L ' A20%,35%decreaseintwigdiaandleafwt.and30%increaseindefoliationatelevatedozonelevel  \ , Davis&Skelly1982b /% .  / +!6/ +8h/d,3d/wkfor16weeks  1 CSTR  62 0.0,0.07,0.15ppm  63 Nosig.effectonhtgrowthorbiomass  5 JensenandDochinger1989 /%7  / +!^8 +4h/d,5d/wkfor6wks  ": CSTR  ^; 0.025or0.1ppm  ^< Nosig.diff.inplantgrowth  "> Chappelkaetal.1985 /%"@  / +!rA +4h/d,5d/wkfor6wks  6C CSTR  rD <0.02,0.05,0.1or0.15ppm  6F Nosig.diff.inplantgrowth  6H Chappelkaetal.1988 /%6J  / +!K +6h/d,7d/wkfor5wks  ^M CSTR  N 0.0or0.07ppm  O Nosig.diff.inplantgrowth  ^Q Mahoneyetal.1984 /%R  / +!8S +2growingseasons  8T OTC(treesinground)ϜShenandoahNat.ϜPark  X CF,NF,AA  8Y 41%decreaseinhtgrowthinNFcomparedwithCF  6\ Duchelleetal.1982/"8]  /Picearubens .! .4h/d,2d/wkfor4months %d %CSTRs % %CFor0.12ppm % %Noeffectsforanyvariablemeasured %d %Tayloretal.1986 <2   < +!>  +1growingseason  >  OTC(treesinpots)WhitetopMT,VA  <  CF,NF  > Noeffectsforanyvariablemeasured  x Thorntonetal.1990 /%>  / +!  +3growingseasons    OTC(treesinpots)WhitetopMT,VA  (  CF,NF    Noeffectsforanyvariablemeasured  d  Thorntonetal.1992 /"   /Platanus  x occidentalis .! < .6h/dfor28consec.d % x %CSTR % x %0.0,0.05,0.1,and0.15ppm % <  %Alineardecreaseinrootwt.andtotalwt.withincreasingconc.Totalbiomassdecreasedby69%at0.15ppmcomparedwith0.0ppm %L & %Kress&Skelly1982 <2 x'   < +!& ( +1growingseason  & ) OTC(treesinpots)GreatSmokyMount.Nat.Park  r - CF,NF,NFX1.5,NFX2,24h/d  t / IncreaseinleafdropandproductionatNFX2.Rootandleafbiomassdecreasedwithincreasingozoneconc.Totalbiomassreduced9%fromCFtoNF  H6 Nuefeldetal.1992 ,"& 7  ,Pinusechinata "8 ozoneadded12h/dfor28months  \: OTC(treesinground)Clemson,SC   = CF,NF,NFX1.7andNFX2.5  \? Sig.effectsonlyobservedatNFX2.5.Leafareareduc35%andleafbiomassdecrease30%fromCF  2D Shelburneetal.1993/"\F  /P.pungens .! .1growingseasoneachfor3consecgrowingseasons %( %OTC(treesinpots)GreatSmokyMount.Nat.Park %b %CF,NF,NFX1.5,NFX2,24h/d %d  %Noeffectongrowthortotalbiomassproduction %(  %Nuefeldetal.1992 <2   < +!< +2growingseasons  < OTC(treesinground)ShenandoahNat.Park    МCF,NF,AA  < A12%decreaseinhtgrowthatNFcomparedwithCF  N  Duchelleetal.1982 ,"<  ,P.rigida  b 6h/dfor28consec.d   b CSTR   b 0.0,0.05,0.1,and0.15ppm   & Ozoneeffectsobservedbeginningat0.10ppm.Totalbiomassreduced24%at0.15ppm  8" Kress&Skelly1982 /% b#  / +! $ +8h/dfor13wks   % CEC   & 0,0.05,0.1,and0.2ppm  L ( Increasingozonecauseddecreasesinneedle,stemandrootdrywt.Greatesteffectat0.2ppm  " - Schieretal.1990 /% .  / .!r / .Variable,24hfumg.or6h/d,3d/wkfor5wks %2 %CEC %r 3 %0,0.08,0.1,0.2or0.3ppm %65 %Noeffectswithinfamilies,butdiff.insensitivityamongfamilies %H9 %Scherzer&McClenehen1989 9/6;   9P.strobus "< 7h/d,3d/wkfor4months  \> CEC  "? 0.02,0.06,0.1or0.014ppm  \A Noeffectonseedlingbiomass  \C Reichetal.1987 /%"D  / +!6E +2growingseasons  6F OTC(treesinground)ShenandoahNat.Park,VA   J МCF,NF,AA  6K A20%decreaseinhtgrowthatNFcomparedwithCF  HN Duchelleetal.1982/"6O  /P.taeda .! .6h/dfor28consec.d % %CSTR % %0.0,0.05,0.1,and0.15ppm %d %Differentialsensitivityinresponse. Wildtypeseedlingsmoresensitivethanafullsibfamily %b  %Kress&Skelly1982 <2    < +!<  +3growingseasons  <  OTP(treesinpots)OakRidge,TN  N  CF,NF,NF+0.06ppm  < Noeffectsonanygrowthvariablemeasured  N  Adamsetal.1990 /%<  / +!(  +2growingseasons  (  OTP(treesinpots)OakRidge,TN   & CF,NF,NFX2  (  HtgrowthlowestinNF.Increasingozoneexposuresresultedindecreasedbiomassofallplantcomponentsafter2yrs  r  Edwardsetal.1991 /%( !  / +!L " +3growingseasons  L # OTP(treesinpots)OakRidge,TN  ^ & CF,NF,NFX2  L ' HtgrowthlowestinNF.DiagrowthgreatestinCF.Relativewooddensitydecreasedwithelevatedozone.Increasingozoneexposuresresultedindecreasedbiomassofallplantcomponents(8%decreaseintotalbiomass)after3yrs  ~2 Edwardsetal.1992 /%L 3  / .!X4 .2growingseasons %X5 %OTP(treesinground)Durham,NC %V8 %CF,NF,NFX1.5,ϜNFX2.25,NFX3 %: %Foliageretentiondecreasedwithincreasedozone.Familydiff.observed %> %Kressetal.1992 </X?   < .!~@ .6h/d,4d/wkfor12weeks %BB %OTC(treesinpots)OakRidge,TN %|E %CF,NF,NFX0.53,NFX1.1,NFX1.58,NFX2.15 %|H %NFtreatmentresultedina26%decreasedinhtand5%deceaseindiacomparedwithCF.Responsetoelevatedconchighlyvariable;dependentonfamily % O %McLaughlinetal.1994 <2BQ   < +! + 2growingseasons   OTC(treesinground)Durham,NC  ( CF,NF,NFX1.5,NFX2.25,NFX3  d ShootandfascicleelongationlongerinCFcomparedwithNFX3.Noeffectatintermediatelevels  &  Mudanoetal.1992 /%   / +!  +3growingseasons    OTC(treesinground)Raleigh,NC    CF,NF,AA,NFX1.25,NFX1.5,NFX1.75,NFX2  N  Differentialsensitivityinresponseobserved.Visibleinjurynotcorrelatedwithgrowth.Exposureresponsemodelspredictedabovegroundreductionsinbiomassatambientozonefrom019%aftertwoyrs.After3yrsgrowthlosswas13%formostsensitivefamily  0 ! Shafer&Heagle1989 /%N #  / +! $ +6h/d,4d/wk,for12Ϝwks  X& CSTR  X( 0,0.08,0.16,0.24,0.32ppm  X* Differentialsensitivityinresponseobserved.Usingaregressionmodeltotaldrywtwasreduced25%at0.32ppmcomparedwithcontrols  ,1 Shaferetal.1993/" 2  /P.virginiana .! .6h/dfor28consec.d % %CSTR % %0.0,0.05,0.1,and0.15ppm %d %Nosig.effectsforanygrowthvariablemeasured %( %Kress&Skelly1982 <2    < +!x  +2growingseasons  x  OTC(treesinground)ShenandoahNat.Park,VA  N  МCF,NF,AA  x A22%decreaseinhtgrowthatNFcomparedwithCF    Duchelleetal.1982 ,"x  ,Prunusserotina (  7h/d,5d/wkfor8or12wks   b CSTR  (  0.04or0.08ppm  (  A43%,37%,62%,45%,47%and54%decreaseinht,twigdia,stemdrywt,rootdrywt,leafdrywtandleavesproducedat0.08ppmcomparedwith0.04ppm   ! Davis&Skelly1982b /% b#  / +!^ $ +1growingseason  ^ % OTC(inpots)Norris,TN  " ' CF,NF,NFX2  ^ ( A29%and14%decreaseinhtandroot/shootratioand18%increaseinbranchwtat2X  n- Samuelson1994a /%^ .  / +!H/ +1growingseasoneachrepeatedfor2yrs   1 OTC(inpots)GreatSmokyMts.Nat.Park  F4 CF,NF,AA,NFX1.5,NFX2   6 InbothyrstheNFX2causedareducintotal,leaf,rootandstem+rootbiomass,andpresentdefol.Usingcombineddata,growthlossesrangedfrom12%inNFvs.CF  > Neufeldetal.1995/"H?  /Quercusrubra .! .7h/d,5d/wkfor8or12wks %d %CSTR % %0.04or0.08ppm % %A20%decreaseoccurredinrootdrywtanda6%increaseindefoliationat0.08ppm %b  %Davis&Skelly1982b <2d    < .!<  .1growingseason %<  %OTC(treesinground,seedlingsinpots)Norris,TN %  %CF,NF,NFX2 %< %Noeffectonseedlinghtorbiomass,canopyleafdrywtwasdecreasedatNFX2formaturetrees % L %Samuelson&Edwards1993 <2    < +! & +3growingseasons   & OTC(treesinground,seedlingsinpots)Norris,TN  r  CF,NF,NFX2   &  SeedlinghtincreasedatNFX2.Noeffectonbiomassordia.Noeffectsonfoliarbiomassorcanopystemgrowthformaturetrees   & Samuelsonetal.1996 ,"t (  ,Robinia ^ ) pseudoacacia " * 2growingseasons  ^ + OTC(inground)τShenandoahNat.Park,VA  \ . CF,NF,AA  ^ / An18%decreaseinhtgrowthatNFcomparedwithCF  \ 2 Duchelleetal.1982^ 3  6 М   3 TRY3'Letter (Portrait)P '3Letter (Landscape) 3' Letter '3 Letter LandscapeTX^DXCXXXX^DTable3.0  Ozoneexposurelevelsasafunctionoftreeresponsecategory.#X^DXXX$##CXX^D#(#(# * d7djZ jZ jZ @jZ jZ jj $%(#(#, dd ,td ,dd",dd +   ` TreeResponseCategory .! . 7*" 7Exposure 7*" 7 +!" + ! l !W126(ppmh) 7-0 " 7 7-l " 7Hours0.10 l  ppm .!0 " .Minimal .!8   .М0 .!8 U .Лand .!8  .0 +!8 U +Level1(onlyhighsensitivespeciesaffected(e.g.,blackcherry)  T  5.9  U and    6  U Level2(moderatelysensitivespeciesaffected(e.g.,yellowpoplar)  p  23.8  U and    51 % U %Level3(allspeciesaffected,eventhosenaturallynonsensitive(e.g.,redoak) 2!  266.6 2! U 2and 2!  2135/%# U   /