ecology and ecophysiology - ctahr.hawaii.edu symposium 2016... · restored areas. sakai (1988)...

AcaciakoainHawai‘i:FacingtheFutureProceedingsofthe2016Symposium,Hilo,HI:www.TropHTIRC.org,www.ctahr.hawaii.edu/forestry

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ECOLOGYANDECOPHYSIOLOGY

INFLUENCEOFRESTOREDKOAINSUPPORTINGBIRDCOMMUNITIES

RichardJ.Camp (Hawai‘iCooperativeStudiesUnit,UniversityofHawai‘iatHilo),

EbenH.Paxton,Ph.D.(U.S.GeologicalSurvey,PacificIslandEcosystemsResearch

Center),andStephanieG.Yelenik,Ph.D.(U.S.GeologicalSurvey,PacificIsland

EcosystemsResearchCenter)

PaperTitle:Forestrestorationforwildlife:Acaciakoa inHawai‘i

ExtendedAbstract

DeforestationofHawaiianforestshasadverselyimpactednativewildlife,includingforestbirds,

batsandarthropods.Restorationactivitieshaveincludedreforestationwiththenativekoa(Acacia

koa),adominantcanopytreespeciesthatiseasytopropagate,hashighsurvivorship,andhasfast

growthrates.Wereviewrecentresearchdescribingtheecologicalbenefitsofkoarestorationon

wildlifecolonization/use,plantdispersal,andnativeplantrecruitment.Ingeneral,planting

monotypickoastandscanprovideforesthabitatsforspeciesthatneedthembutdoesnot

automaticallyleadtonaturalregenerationofadiverseforestspeciesassemblageandmayrequire

additionalrestorationactivitiessuchasoutplantingofothernativeplantsandaliengrasscontrolto

achievemorenaturalforestsystems.Althoughearlysignsofforestandwildliferecoveryhavebeen

encouraging,thegoalsofrestorationforwildlifeconservationversuscommercialgradeharvesting

requiredifferentrestorationmethods.

ThefloraofHawai‘ilacksmanyplantgroupscommontootherislandandcontinentecosystems;

thusthenaturalvegetation,whichservesashabitatforwildlife,islargelymadeupofrelativelyfew

dominanttreeandshrubspecies(PrattandJacobi2009).Themontanemesicforestsaredominated

bykoaand‘ōhi‘a(Metrosiderospolymorpha),andtypicallyoccurbetween1,000and2,000m

elevation(3,200and6,600ft,respectively).EarlyHawaiiansextractedselectkoatreesfromthese

forestsbutotherwisethereislittleevidencethattheyalteredthishabitat.AfterWesterncontact,

peopleexpandedintotheseforestswheretheyestablishedpermanentagriculturefieldsthat

resultedindeforestation,erosionandconversionofmanyoftheseforeststograsslandsbyexotic

grasses.Koawasthepreferredwoodfortimber,anditsextractionwastypicallyconcurrentwith


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forestclearingforpastureimprovement.AsnotedbyPrattandJacobi(2009:146)“today,almost

treelesspasturesofaliengrassescovertheuplandslopesofwindwardMaunaKeaandWaimea,

Hawai‘iIsland,aswellasthewestslopeofHaleakalā,Maui,”wherekoa-andkoa/’ōhi‘a-dominated

forestswereconvertedtopasturesforlivestockgrazing.Itisinmanyoftheseareasthatforest

restorationforconservationisfocused.

Althoughhistoricforestswereamixofkoaand‘ōhi‘a,restorationofwildlifehabitathasfocusedon

koa(Priceetal.2009)becauseitisaneasyspeciestopropagatebyseed,hashighsurvivorship,can

survivemildfrost,andgrowsmorequicklythan‘ōhi‘a(Yelenik2016).Koaforestrestoration

methodshavetakenthreegeneralapproachesthataredependentontheseverityofdegradation.

Thefirstisapassiveapproachthatreliesonthenaturalregenerationofnativespecies,particularly

koa,afterungulatesandselectalienplantshavebeenreducedorremoved.Anexampleofthis

approachisthefencingandremovalofungulatesintheStateofHawai‘iDepartmentofLandand

NaturalResources’KahikinuiForestReserveandadjacentNakulaNaturalAreaReserve,Maui

(note:thestatehasrecentlyincludedoutplantingofnativeplantsinthisareatoboostrestoration).

Thesecondapproachinvolvesscarificationwhereabulldozerisusedtoscrapethesurfacesoilto

removethedensegrasscover,whichleadstohighdensitykoarecruitmentwhereseedspersistsor

vegetativelyfromadjacentlivingtrees(McDanieletal.2011).Thisapproachhasbeensuccessfully

appliedonKamehamehaSchool’sKeauhouRanchandtheKahukuUnitofHawai‘iVolcanoes

NationalPark,Hawai‘i.Finally,inareasthathavebeenheavilydegraded,theplantingofseedlings

ofcanopytreesandunderstoryspeciesisrequired.Thisistheapproachtakenintheformer

pasturesoftheU.S.FishandWildlifeServiceHakalauForestNationalWildlifeRefuge,Hawai‘i.An

alternativeobjectivehasbeentoreplantandmanagekoaasasilviculturalspeciesfortimber

productionfollowingtimberharvestorcattlegrazingonprivatelands.

Throughanumberofsurveysweareseeingtwogeneralpatternsemergeasbirdsandinsects

respondtokoarestoration.Thecolonizationrate,orprocessbywhichaspeciesspreadsinto

restoredareas,isdependentontimesincereforestationanddistancetointactforest.Therateis

speciesspecificwithsomebird/insectspeciesabletomoveintotherestoredarearapidlywhenkoa

arestillsmall—moreshrub-likethantree-like.Astimepassesandthekoadevelopintotrees,the

restoredareassupportmorespeciesandgreaternumbersofindividuals,presumablybecause

largertreesarebetterhabitatforwildlife.AtbothHakalauandKeauhouweseeafewnativebird

speciesusingyoungkoa,suchasHawai‘i‘amakihi(Chlorodrepanisvirens)and‘apapane(Himatione

sanguinea),butastimepassesthenumberofspeciesandindividualsincrease(Campetal.2010,


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Paxtonetal.inreview).ThispatternismostclearlyseenintheendangeredbirdsatHakalauwhere

theyareabsentduringthefirst10to15yearsafterkoaplantingbeforeeventuallymovingintothe

restoredareas.Sakai(1988)notedthatnobirdswerepresentintherestor8ed,scarifiedkoaareaat

Keauhouforthefirstseveralyears,buttwodecadeslatertherewereapproximatelyequalnumbers

ofbirdsintherestoredareaasintheadjacentintactforest(Campetal.2010).AtHakalau,

Goldsmithetal.(2007)observedthatthenumbersoflonghornedbeetles(Plagithmysusspp)in

youngerkoa(3-8yrsold)wereaboutaquarterofthenumberfoundinolderkoa(12-15yrsold).

However,beetlescollectedinolderkoaintherestorationareawereonlyslightlylessabundant

thanthosecollectedintheadjacentintactforest.Thus,forsomespecies,koareforestationareascan

supportsimilarnumbersasadjacentintactforest,butotherspeciesstilllagandmaytakemuch

longertocolonize.

Inadditiontoatimelagforthehabitattobecomesuitable,thedistancefromadjacentintactforest

playsarole.ThispatternwasmorepronouncedatHakalauthanatKeauhouduetothesizeand

configurationoftherestoredareas.Forexample,duringthefirstdecadeafterplantingkoa,Hawai‘i

‘elepaio(Chasiempissandwichensis)venturednofurtherthan1-km(0.6mi)upslopefromtheforest

atHakalau.However,25yearsaftertheinitialkoawereplanted,Hawai‘i‘elepaiohadmovedmore

than2.5-km(1.6mi)upslope(Paxtonetal.inreview).Hawai‘i‘amakihiand‘apapanealso

demonstratedthispatternandnowoccurthroughoutthereforestedarea.

Toddetal.(2016)showedthatHawaiianhoarybatsoccurredinremnantkoaforestclearedof

understoryforpastureinKahikinuiFRandNakulaNAR,Maui.Interestingly,aftertheareawas

fencedandungulateswereremoved,koastartedtoregeneratebutbatoccupancydeclined.

Gorresenetal.(2013)observedasimilarpatternatHakalau,whereHawaiianhoarybatswerenot

commoninthekoarestorationarea.Theyalsoobservedthatbatoccurrencewaslowerinintact

forestsiteswherekoawasadominantorco-dominanttree,eventhoughkoahoststhekoamoth

(Scotorythrapaludicola),anendemicmoththatisapreyofHawaiianhoarybats.Gorresenetal.

speculatethat“koadoesnotoffersufficientshadecoverforday-roosts,andmaynotbesufficiently

importantinaffectingoverallpreyavailabilityotherthanforbriefperiodsandepisodickoamoth

outbreaks.”Thus,Hawaiianhoarybatsappeartorequireamorediversehabitatthanprovidedby

koadominatedforests.

Animportantgoalofhabitatrestorationforwildlifeistherapidprogressionfromyoungpurekoa

standstoadenseforestconsistingofanunderstoryofnativeshrubs,andasubcanopyandcanopy

ofkoaandothernativetrees.Thisforestcompositionandstructurewouldoffervariedresources


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(nestingandforagingsites,prey,fruits,etc.)thatcansupportwildlifespeciesdiversityand

abundance.Yelenik(2016)showedthatforestsuccessionfromanearlyrestorationcommunitycan

stallwhenkoaistheonlycanopytreeandtheunderstoryconsistsofexoticpasturegrassesand

scatteredshrubs.Recentdatahasshownthatthereisequivalentseedrainundertreesinkoa

restorationstandsasintheadjacentforest.Inaddition,birds,suchasthenative‘ōma‘o(Myadestes

obscurus),aredispersingseedsfromfruitingshrubsandtreesintothesekoarestorationareas

(USGSunpublisheddata).Therewas,however,almostnonativeseedlingemergencewithinkoa

stands.Thus,theunderstoryofexoticgrassesmaystiflesuccessionbyprohibitingnativeseedlings

fromestablishingandgrowing.

Inconclusion,anumberoffactors—lagtimesincerestorationstarted,distancefromadjacentforest

edge,andcompositionofreplacementplantcommunity—influencethediversity,abundanceand

timingofwildlifecolonization.Thereisageneraltrendtowardincreasingwildlifespeciesdiversity

andabundanceaskoastandsmatureandinsitesclosetoexistingforest.Seedrainsurveysindicate

thatamplepropagulesarebeingdeliveredbybirdstorestorationstands,butnativeplant

regenerationmayeventuallybelimitedbyweeds,especiallyexoticgrasses.Toadvancerestoration

beyondasimplekoa-grasssystem,weedmanagementundertreescouldpromotethe

establishmentofunderstoryspeciesbeingdispersedbybirds.Forestryandecosystemrestoration

goalsmaynotalwaysbeinlinewitheachother.Forexample,koatreesthatareprofitablefor

timberproductiondonotnecessarilybenefitwildlife,and,conversely,gnarledandtwistedtrees

thatbenefitwildlifearenotnecessarilymarketable.Intheend,managementobjectivesshould

driverestorationmethods.


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Figure1:OutplantingofAcaciakoaseedlingsinabandonedpastureareassuchasthisoneatthe

HakalauForestNationalWildlifeRefugeisonlypartlysuccessfulinrestoringwildlifehabitat.Atthis

sitevolunteersalsooutplantednativeunderstoryspeciessuchasnaio(Myorporumsandwicense),

‘ōlapa(Cheirodendrontrigynum),and‘akala(Rubushawaiiensis)toprovideunderstorycoverand

foodforfrugivorousbirds.


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Acknowledgements

WethankPaulC.Banko,FrankJ.Bonaccorso,JamesJacobi,SteveJ.Kendall,RobertW.Peck,Corinna

A.PinzariandEliRosefordiscussionsoftheirresearch,andprovidingdata,summariesandphotos.

WethankP.BankoandJ.Jacobiforthoughtfulcommentsthatimprovedthismanuscript.

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