Jennifer E.Tollefsonl, Department f Botany, nivers y of Vermont Bur ngton Vermont 5405 Ffederick . Swanson, USDA Forest ervice. ac c North\lest esearch tat n 3200 Jefferson Wa v Corva s Oregof 9733l an o John H. Cissel, Bureau f Land 4anagement O Box 10226, ugene. regon 7440 Fire Severity n Intermittent tream Drainages, estern Cascade Range, Oregon Abstract Wequantiiicd ir c severil\ prtterns $'irhin ntermittcnl strexm drainages n a recenrly bumcd,lrca of the cenral wencm Cascades. Ofegon. Aerial pholographs r ere used o estimate osl lr c live canopv cover vithin slrcamside nd upland zones on rhc soude.rst and south$e\I-facing slopcs of 33 \iatersheds. Live canopy colcr did not differ sigrrificanlh bclween streamside nd upland zones n the $aiersheds. Firc sc\crily dala obtained rom aerial pholographs were highl,v correlatcd $ith lire severiry data ob urined n the field in \ix of thc qalcrsheds. confirning that aerial pholognph esiimrte\ of live canopy cover reflecred acrual condilions on the ground. whilc prclious studies ndicate hat firc sc\crirv ma) be lo\\'er along percnnial sre.rnN. he fesults of thi\ \tud)_ suggest hat ilrc scvcritv n inknse event\ may be similar bet$een intermittent strea channels and adj.rcent pland areas. At the hndscapc scalc. dilGrences n fife se|eritl along slreams of different sizes nray nilucnce rhe mo\aic of post firc vegetation nd contribulc o o!crrll nructural di|eNity in forcns of mouDrainous andscapes. irc rcgime rfbrmation obtaincd l1 tiis and felated tudies nray bc used o guide fore\t managenrcnl cliliries that are modeled aftcr natural disturbance roccsscs and seek o balance comnrodily production and ecoslsten protection. Introduction Contemporary ecologists agree h t natural dis lurbancc vents ccurring over various spatial nd temporal scales arc ntegral components f eco- slslems White I979, Pickeu and White 1985. Sprugel 991,Whiteet l. 1999). nfbnnation bout the histoic l'rcqucncy. sevedty, and spatial cx- of such disturbance lents can be applied o landscapc management Agee 993. Huntcr 1993. Morgan et al. 1994, Swanson t al. 1994. Engstrom el al. 1999). Based on the assumption hat spe- cies have adapted o a certain range of ecosys- tem conditions reated y natural disturbance regimes. he concept f managing n ecosystem rvithin ts range of natural vadability s being erplored as a way to increase he potential for suslaining ative pecies cross broad ange f habitat ypes Morgan t al. 1994. Swanson t al . 199.1, ngstrom t al. 1999). ln thc Pacitic Northwest, ederal orest man- a-qcnent bjectives nclude both ecosystem ro rAuthor to who r corcspondence hould be addrc\scd. E mail: [email protected]. Cunent address: udronia t-ld. PO 8or 5000, Annandale. !'u YoR 1250,1 18 6 Northwest cience. ol.711. o. 3,2004 e.]1)rilli) rl,c\rahre!5fien!i.A*o.jrrdj,\llrighnrc\rned tection and timber production. Thc Norlhu'est Forest Plan employs a system of static reserves. corridors, andhabitat management rescriptions for matrix lands o protect an array of terrestrial species hought o depend upon ate successional forest habitat, o protect aquatic ecosystems. nd to provide sustainable upplv ftimber (USDA and USDI 1994). Riparian eserves. hich con- sist of zones of uncut orest along streams of all sizes. are an ntegral component fthc Nofthwest Forest PIan. These cserves. which are ntcnded to prolcct streamslde areas, concentrate lmber management n the upland areas etween buf'fers and esult n spatial segregation fold and young lbrest stands. An altemative strategy br meeling he broad objectives of the Northwest Forest Plan nvolves using atural isturbrnce egime nlonnrtion ,.r guide orest management ctivities Cissel et al. 1 999). n Douglas-fir .P eutlotsuga e nli e i ) dominatcd brests ofthe central wcstgrn Cascades of Oregon, ire has historically been the domi nant natural disturbance gcnt and a pdmary dc- terminant fforest stmcture nd composition Agee 1993.Weisberg 1998.Weisberg 1ir Prcss). Un- derstanding he ange ofnatural variabilitv within
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Fire severity in intermittent stream drainages in Western Cascade Range, Oregon
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8/3/2019 Fire severity in intermittent stream drainages in Western Cascade Range, Oregon
JenniferE.Tollefsonl,Departmentf Botany, niversy of VermontBur ngton Vermont 5405
Ffederick . Swanson,USDAForest ervice. ac c North\ lest esearch tat n 3200JeffersonWa v Corva sOregof9733l
an o
John H. Cissel,Bureau f Land 4anagement OBox 10226, ugene. regon 7440
FireSeverity n Intermittent treamDrainages, esternCascadeRange,Oregon
Abstract
We quantiiicd irc severil\ prtterns$'irhin ntermittcnlstrexmdrainagesn a recenrlybumcd,lrca of the cenral wencm Cascades.Ofegon.Aerial pholographsr ere used o estimate osl lrc live canopvcover vithin slrcamside nd uplandzoneson rhc soude.rstand south$e\I-facing slopcs of 33 \iatersheds.Live canopy colcr did not differ sigrrificanlh bclween streamside nd uplandzones n the $aiersheds.Firc sc\crily dala obtained rom aerialpholographswere highl,vcorrelatcd$ith lire severirydata oburined n the field in \ix of thc qalcrsheds.confirning that aerial pholognph esiimrte\ of live canopy cover reflecred acrualcondilions on the ground.whilc prclious studies ndicate hat firc sc\crirv ma) be lo\\'er alongpercnnialsre.rnN. he fesultsofthi\ \tud)_suggest hat ilrc scvcritv n inknse event\ may be similar bet$een intermittent strea channelsand adj.rcent plandareas.At the hndscapc scalc.dilGrences n fife se|eritl along slreamsof different sizesnray nilucnce rhe mo\aic of post firc
vegetation nd contribulc o o!crrll nructural di|eNity in forcns of mouDrainousandscapes. irc rcgime rfbrmation obtaincd l1tiis and felated tudies nraybc used o guide fore\t managenrcnl cliliries that are modeledaftcr natural disturbance roccsscsand seek o balancecomnrodilyproductionand ecoslsten protection.
Introduction
Contemporaryecologistsagree h t natural dislurbancc vents ccurringovervariousspatial ndtemporal scalesarc ntegralcomponents f eco-slslems White I979, Pickeuand White 1985.Sprugel 991,Whiteet l. 1999).nfbnnation boutthe histoic l'rcqucncy.sevedty,and spatial cx-tcntof suchdisturbance lents can be applied olandscapcmanagementAgee 993. Huntcr 1993.
Morganet al. 1994,Swanson t al. 1994.Engstromel al. 1999).Basedon the assumptionhat spe-cies have adapted o a certain range of ecosys-tem conditions reated y naturaldisturbanceregimes.he concept f managing n ecosystemrvithin ts rangeof naturalvadability s beingerplored as a way to increase he potential forsuslaining ative pecies cross broad ange fhabitat ypes Morgan t al. 1994.Swanson t al .199.1, ngstrom t al. 1999).
e . ]1 ) r i l l i ) r l , c \ ra h re !5 f ie n ! i .A * o . j r rd j , \ l l r i g h n rc \ rn e d
tection and timber production. Thc Norlhu'estForestPlan employs a systemof static reserves.corridors,and habitatmanagement rescriptionsfor matrix lands o protectan array of terrestrialspecieshought o dependupon atesuccessionalforest habitat, o protectaquaticecosystems.ndto provide sustainableupplv ft imber(USDAand USDI 1994).Riparian eserves. hich con-sist of zonesof uncut orest along streamsof allsizes.arean ntegralcomponent fthc Nofthwest
ForestPIan. These cserves.which are ntcndedto prolcct streamsldeareas,concentrate lmbermanagementn the uplandareas etweenbuf'fersand esult n spatialsegregation fold andyounglbrest stands.
An altemativestrategy br meeling he broadobjectivesof the Northwest ForestPlan nvolvesus ing a tura l i s tu rbrnceeg imen lonnr t ion , . rguide orest management ctivities Cisselet al.1999). n Douglas-fir .P eutlotsuga enli e i )dominatcd brestsofthe centralwcstgrnCascadesof Oregon, ire has historically been the dominant naturaldisturbance gcntand a pdmary dc-terminant fforeststmcture ndcompositionAgee1993. Weisberg1998. Weisberg1ir Prcss).Un-derstandinghe angeofnatural variabilitv within
8/3/2019 Fire severity in intermittent stream drainages in Western Cascade Range, Oregon
this andscapc,herelore.s coutingeirt pon antundcr . tand in !l l l re e ! ime har . re r i : l i c . .
Intcnnittcnt stlcam drainagesare a predomi
ni:urt tructurul lement f mountainousandscapes
in thc Pacitlc Northwest.Variation n fire severity at the scale of these small watershedsmaycontribute ignit icantlyo remnantrc cdcnsiti(]sand orerall habitatheterogeneity Ronme 1982.MorrisonandSwanson 990. urner t al. 199,1.
KushlaandRipple 1997, aylorandSkinner1998.Kccton 2000). Pattems of fire sevedt)' n thesesmallu'atersheds.owever. repoorlyunderstood.Th e central bjective f this studywas o quan-
tify fire sevedtypattems$,ithin the watershedsof internittent streamsn a recentlyburnedareain thc centralwestemCascades.
Documented re regimecharacteristicsbr thewatcrsheds l perennialsffeams uggest hat ireseverit)' s lower in riparianzones han in adja-
landtbrms ndvegetationonditions re hought1(r itigate fire severity Campet al. 1997,Impara1997,Kushlaan dRipplc 1997, aylorandSkin-ne r1998, eeton 000.Wimberly ndSpies 001.
Skinner2002, Lee and Smyth 2003).Higher hu-
midity, lower solarheating, he eft'ects fcold airdrainage. ydricsoils.abundant erbaceousnd
dce iJuouscge la l ion .ndh ighermoi \ tu re on-tent n both ivinganddeadwoody 'uelsmay allcontribute o apparently ower fire intensity and
severit),n these reasRomme1977.RommeaDdKni .eh t 981. gee t ;1 .2002 . Ber 'ausenter ' -mittcnt strcam channels n the study landscapearegenerally teeperandessoftenassociated,ith
humid riparian zonesand deciduous rees.ho\4-cvcr. wc predicted hat proximity to the steamchannel oesnot mitigate ire severity 'ithin hese
snall watelsheds.
StudyArea
We examincda portionol theWamerCreekFireon theWillametteNational Forest, 9 km eastof
Oakfidge n thc ccntralwesternCascade angeof Oregon. n this region, Iow summerraintall,castcrly winds. and lightning storms create a-vorablewildflre conditionsn latc summer nd
early fall. The Wamer Creek Fire was gnited b1'an arsonist n l0 October1991 ftera prolongcdperiodofhot, dry weatherand desiccatingwinds.
Dri\,enbl' a southwest 'ind. he ire raneastalong
the south aceofBunchgrassRidge.a north*estsouthcastrcnding idgc hat oughlybisccts hcfire arer.andnorth nto adjacent rainages. totalof 3,630 ha bumed befole rain showersslowedan dextinguishedhe ir eon 23 October. he irewas actively ought by the USDA ForestSerriceusing aerial etiLrdeurtropsand backlires USDA
Forest ervice 993). ecauseuppressionffbfts
were less ntensiveon the south side of Bulchgrass idgc, owcvcrwc think lrccffccls fsup-prcrs ion ct i r t i e . ' n i re .e rer i t r l l uern \n u fstudy areawere mininal.
The study area ncluded he watersheds f 33intermittentstreans nc;sed nto the steep. outh-southwcstaccof Bunchgrass idgc Fi-surc ).The averagewatershed ize s 16.2ha. andeler,a-tion ranges rom 800-1750m abovesea evel.Vegetationof the wcstcrn hemlock (fsir,qa
heten4 ryllu) zone s dominant n the study arca(Franklin ndDyrness 9lJll).Although vesternhemlockandwestem edcedarTlurjaplituttil are
common.shade-tolerantpecjesn this zone,Douglas-firmaintains ominanccn manystandsasa rcsultofits longevity elative o the requenc)offires thatcontinually esetsuccessionFianklin
an dHemstrom 91|]1).
Methods
Aerialphotographs erc used o quantifypattems
of fire severitywithin he ocalwatersheds.e-
causea fire of aparticular ntensity (e.g.,eoerg,vreleascdcrunitoffirc linc cngth)canhavcdiilcr-en teft-ectsn different lant peciesAgee1993).Wc quantified ire severity n tems of the eflectof the fire on Douglas fir, which is the dominant
canopyspeciesn the studyarea.Aerial photo-graphsof the Wamer Creek Fire area taker 1n1990. ne yearbefin the ire, nclicatcha t hewatersheds ad nearly complete orest co\,erbeforc Lhe um. Fire severiLywas herelbredelined
as he percentage f canopl' ffee cover hat sur-vived he ire.
Th e 33 sample trcams nd thcir watcrshcdboundarieswere drarvnon acetate hat overlaidI :12,000 oloracrialphotographsakcn n l99li.This photodate ndicates 'e sampled oth m-mediate reemo ality and nortalit.v of trees hat
occumed 7 yr atter he ire. Each watershedwasdividcd nto ourzones efined y andscapeo-
sition (sh'eamside r upland) and aspect south
eastor southwest-ti icing lope).The division
Fire Se\edty in lntenn ittent StreamDrainages 187
8/3/2019 Fire severity in intermittent stream drainages in Western Cascade Range, Oregon
bet$een he streamside nd uplard zoneswa sdrawn halfway between he strcamchannelandthe dg clinc so that th e zoneswould be largeenough o visuallv estimate ive canopycovt:ronthe 1 12.000 erial hotographs.his esultednindividual zones overingslopcdistances f-50-100 m. Using a Stratexprismnirror stereoscopewith,lx binoculars, ercent ost-t ireiv e
canopycover in each of the four \\,atelshed ones wasvisuallyestimated ithin l0cqual intervals angingfrom 0-1007c e.g.,0-10%, I l-207o,etc.).Th enid-point of each ntervalwasused n statisticalanalysese.g.. - 07c= 5a/cl1 20c/c l5%. etc.).The direct and interactiveetTectsof landscapeposition streamside.upslope) ndaspcct south-
east . southwcst-tacinglope) n Iivec,ulopv o\er$,ere estedusing t\\"o way analysisof variancc(ANOVA) on thearcsine quarc-rootranstbrnreddata Za r 1999,SAS nstitute 995). he evelolsignil icance asselat P = 0.05.
To test he accuracyof the aerialphotograph
interpretation, ire severitydataobtained rom aerialphotographs crc conrpared ith lire severity ataobtained n the tleld. Six of the studywate$heds(totaling 10 3 ha. or 197c f thc arcasanpled)werc randomlyselectedbr ground-truthing.Percent ive canopycover was calculatcd n the ieldusinga MoosehomdensitometerGarrison19,191.Each watcrshcdwa s divided nt o a l0 x l0 m
grid, and a canopy reading was taken at everygrid nterscction. t eachpoint, he canopywa sopen f l ivc canopy il led less ha n half ol thesquares isible n the Moosehon grid,andclosedif live canopv illed half or more of the squares.Fielddrta werecollapsed nto the our watcrshedzonesused n thc acrialphotograph nalysis,and
thepercentagefclosedcanopy ointswithin eachzone wascalculated o obtain an estimaLc f live
canopy cover within eachzonc. Wc tested br acoraelation etween ivc canopycovercalculatedfrom tield data and ive canopy cover estimatedfrom aerialphotographsbr eiichwatershed oneusing Pearson roduct-moment orelation (Zar
1999,SAS Institute1995). hc levelof signif i-cancewa sse tat P = 0.05.
Results
Aerial photographdata revealedno significant
differencc n Jivecanopycover betweensffeam-
side and upland zoneson either the soulheast rsouthwest-facinglopcs f the sarnpled atersheds(Figure2). Wc observeda significantcorelationbctween ive canopycover calculated rom fielddataand ive canopycoverestimated rom acrialphotographsn eachof the tbur watershed ones(Pearson roductmoment corelation: r = 0.95-0 . 9 8 . N = 6 , P < 0 . 0 0 5 ) .
Figure 2. Niean ivc canopy colcr (+ I srandarderor) estinated fionl aerial fhorographs n strcamsidc nd
adjacentupland Toncson sourhcaslrnd soulhwesl acing slopesu ithin the $arersheds f 33 i.lcrmit
tent streams n the WarnerCreekFire studv arca.Jul! 2000.
tr sbeamside
I upslope
45
4 4 0(D ^-
+g t ob 2 5
3 z o
3 t sc
3 r oo
0
wesl-tacingslopes east-hcing lopes
Fire Severityn Intcmrittent treamDrainages 18 9
8/3/2019 Fire severity in intermittent stream drainages in Western Cascade Range, Oregon
The watershedsncluded n this studyare ocatedin s teep. south-1acing. issected erain wherevegetationomposition nd environmentalon -ditions are similar along thc strcam and on the
rdjacent uplands. Solar radiation s high in thestud,varea and. by late sunmer, soil and fueJmoistureareextremely ow. The potential or ilr-termittent streamdrainages uchas hese o miti-gatc tirc scvcrity may be reducedby a lack ofnr i c roc i i t n r tend o l r r rn ro is lu rehr r i l c l (i \ l i (associated'ith riparianvegetation nd andfomscommonalongJarger,ower-gradienttreams.heextent o which fire severity s reducedalong streamdrainages n general. hcrcforc, mav dependonthe size of the streamand he degreeof differen-tiation betweendparian and upland fuel condi-tions. At the landscape cale.diflerences n fireseverityalong strcams f differentsizesare ikely
to nfluence he mosaicofpost fire vegetation ndcontribute o overallstructural iversity n for-estsof nountainous andscapes.
The conelation etweenlr e severity ataes -timated rom aerialphotographs nd ire severitydata obtained n the lield was signihcant, conllrming that acrial photographestimatesof livecanopy cover reflected actual conditions on theground.Although heremay have een orne e-la,ved o tality betweenhe ireyear 1991) ndtheycar hc acrialphotographs ere aken 1998),
u' eassumed osignitlcant hangen live canopycoverbctwccn1998and 2000.when ield sam-pling was conducted.
Potenta l\,4anagementmp cations
An alternative trategy1brmeeting he broadob-jectives f theNothwest ForcstPlan nvolves sing
Literature ited
Agee, J. K. 1991.Fire Ecologvof Pacific North$cn Forcsts.
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Canrp.A. . C. Oli\cr. P ilessburg.and R. E!crc[. 1997.Pre
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19 0 Tollefson, wanson. ndCissel
fire regime nformation o guide he ocation. iequency.and ntensity ol fbrest management ctivit ies Cissel t al. 1999). hisstrategvsbasedon the assumption hat species avc adaptedo acertain angeof ecosystcm onditions roughtabout by natural disturbance egimes,and thathumanactivities hat maintainecosystems ithin
this rangemay ncreasehe potential or sustain-in g ecological rocesses nd nativebiologicaldiversity. The resultsof this study demonstratethat some ire-relateddistuftance occurs n theriparian zonesof steep, ntermittent streamsonsouth-south\\,st facing slopes n thc western
Ca.cade.. tma) rherel-orce lpplopril le o.un-. idcr erm i t t i ngome uman i : l u rhrn . nsonre
riparian zonesof managed andscapesn this re-gion, providedother critical riparian zone unc-
tions, such as shading and large woody dcbrisinputs, are appropriatelydistributed n time andspaceat the andscapc cale.Modeling silviculturalpractices tier naturaldisturbance rocesses
maycontribute o andscape iversityand ncreascthe likelihood of balancingconmodity produc-
tion andbiodiversity onseruation.
Acknowledgements
Fundingandsupportwereprovidcdby the USDAForestService-PacificNonhwest ResearchSta-tion andWillametteNationalForest;OregonStateUniversity;he University f Vermont: he Conseryation nd Rescarch oundation:and he H. J.Andrews ExperimentalForest Long-Term Eco-logical Rcsearch rogram.sponsored y the National ScienceFoundationand he USDA Forest