Download pdf - ECOLOGY AND ECOPHYSIOLOGY - ctahr.hawaii.edu symposium 2016... · restored areas. Sakai (1988) noted that no birds were present in the restor8ed, scarified koa area at Keauhou for

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

56

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


57

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,


58

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


59

(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.


60

Figure1:OutplantingofAcaciakoaseedlingsinabandonedpastureareassuchasthisoneatthe

HakalauForestNationalWildlifeRefugeisonlypartlysuccessfulinrestoringwildlifehabitat.Atthis

sitevolunteersalsooutplantednativeunderstoryspeciessuchasnaio(Myorporumsandwicense),

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

foodforfrugivorousbirds.


61

Acknowledgements

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

A.PinzariandEliRosefordiscussionsoftheirresearch,andprovidingdata,summariesandphotos.

WethankP.BankoandJ.Jacobiforthoughtfulcommentsthatimprovedthismanuscript.

References

Camp,R.J.,J.D.Jacobi,T.K.Pratt,P.M.Gorresen,andT.Rubenstein.2010.Statusandtrendsof

nativebirdsintheKeauhouandKīlaueaforest,Hawai`iIsland.Hawai`iCooperativeStudiesUnit

TechnicalReportHCSU-016.UniversityofHawai‘iatHilo.

[http://www.uhh.hawaii.edu/hcsu/publications.php]

Goldsmith,S.,H.Gillespie,andC.Weatherby.2007.RestorationofHawaiianmontanewetforest:

endemiclonghornedbeetles(Cerambycidae:Plagithmysus)inkoa(Fabaceae:Acaciakoa)

plantationsandinintactforest.TheSouthwesternNaturalist52:356-363.

McDaniel,S.,R.Loh,S.Dale,andC.Yanger.2011.Experimentalrestorationofmesicandwetforests

informerpastureland,KahukuUnit,Hawai‘iVolcanoesNationalPark.PacificCooperateStudies

Unit,UHMānoa,TechnicalReport175:1-26.

Paxton,E.H.,S.G.Yelenik,T.E.Borneman,E.T.Rose,R.J.Camp,andS.J.Kendall.2017.Rapid

colonizationofaHawaiianrestorationforestbyadiverseaviancommunity.Submittedto

RestorationEcology.doi:10.1111/rec.12540

Pratt,L.W.,andJ.D.Jacobi.2009.Habitatloss,degradation,andpersistence.Pages137-158inT.K.

Pratt,C.T.Atkinson,P.C.Banko,J.D.Jacobi,andB.L.Woodworth,eds.,ConservationBiologyof

HawaiianForestBirds:Implicationsforislandavifauna.YaleUniversityPress,NewHaven,CT.

Price,J.P.,J.D.Jacobi,L.W.Pratt,F.R.Warshauer,andC.W.Smith.2009.Protectingforestbird

populationsacrosslandscapes.Pages381-404inT.K.Pratt,C.T.Atkinson,P.C.Banko,J.D.Jacobi,

andB.L.Woodworth,eds.,ConservationBiologyofHawaiianForestBirds:Implicationsforisland

avifauna.YaleUniversityPress,NewHaven,CT.

Yelenik,S.G.2016.LinkingdominantHawaiiantreespeciestounderstorydevelopmentin

recoveringpasturesviaimpactsonsoilsandlitter.RestorationEcology25(1):42-

52.doi:10.1111/rec.12377.