phytolith analysis for a wet tropics environment

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American Association of Stratigraphic Palynologists, Inc.

Phytolith Analysis for a Wet Tropics Environment: Methodological Issues and Implicationsfor the Archaeology of Garua Island, West New Britain, Papua New GuineaAuthor(s): W. E. Boyd, C. J. Lentfer, R. TorrenceSource: Palynology, Vol. 22 (1998), pp. 213-228Published by: American Association of Stratigraphic Palynologists, Inc.Stable URL: http://www.jstor.org/stable/3687629

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PHYTOLITHANALYSISFORA WETTROPICSENVIRONMENT:METHODOLOGICALSSUESANDIMPLICATIONS OR THEARCHAEOLOGYOF GARUAISLAND,WESTNEWBRITAIN,PAPUANEW GUINEAW. E. BOYDC. J. LENTFERSouthernCrossUniversityLismore,New SouthWalesAustraliaR. TORRENCEAustralianMuseumSydney,New South WalesAustralia

AbstractThearchaeologyfprehistoricccupationf the sland fGarua,WestNewBritain,s beginningo provide detailed icture fhumanadaptationo a highlyvolatileenvironmentn whichperiodicatastrophicestructionfvegetation,oilsand, resum-ably,human abitation,s countered,pparently,ythe humanabilityo recolonise ndadaptochangingircumstances.ow-ever,ourabilityofully dentifyhesehumanesponsess pres-entlylimitedby a lack of paleoenvironmentalata.Thiswettropicalregionpresents pecificproblemsn obtainingandanalysinguchdata. n hiscase heseproblemsre npart eingovercome ytheuseoffossilphytolithnalysis.However,oputthis echniquentouse,severalmethodologicalssueshavehad obe addressed. hispaper onsiderseveral f these,describingexperimentsesting reparationechniques,ntroducingeyele-mentsnfluencingssemblageompositionsnthisenvironment,andoutlininghe orm fstatisticalnalyses daptedndadoptedto nterrogatehe argemultivariateata et.Results redescribedfrom estsusingmodem nalogueamples,whichndicaterom-ise in the abilityof the analyticalechniqueso identifyanddifferentiateey ndicatorsf thecomplex nddynamicnviron-mentof prehistoricWestNewBritain.

INTRODUCTIONPaleoenvironmental ndArchaeologicalSettingGarua sland ies within hewettropics,some 5? southoftheequator,off theeastcoast of the WillaumezPeninsulain West New Britain,P.N.G. (Text-Figure1). The islandhas a documentedprehistoricoccupationfor some 6,000

Palynology,22 (1998): 213-228? 1998 by AASP Foundation ISSN 0191-6122

years(Torrence,1994;Torrenceet al., 1997);neighboringareasprovideevidence for humanpresencewell into thelastglacialperiod Spechtetal.,1988;PavlidesandGosden,1994;Spriggs,1997).Theoccupationappearso bereason-ably longterm,albeitwithpossibleshortperiodsof humanabsence.However, t is temperedby periodicnatural ata-strophicevents. The island is partof the volcanic regionalongthesouthernmarginof theBismarckSea,andassuchis tectonically unstable (Heming, 1974; Machida et al.,1996).It has beensubjected,during ateQuaternaryimes,to successive volcanic tephrafall events, and probablevertical ectonicmovements.Arecent ectonicupliftevent,forexample,is reflected n thepresenceof coralreef, of aradiocarbonmodem age, whose surface ies a littleabovepresenthightide. Thatuppersurface s now beingerodedand is supplyingcoral debris into the beach, inter-coralareasandbeachzone;there s similar edimentary videncefor thishavinghappenedduringatleast one mid-Holoceneperiodonthe island.There s alsogoodevidence for at east19majorvolcaniceruptions n theregion(Machidaet al.,1996)during heHolocene,at least four of whichresultedin the substantialdepositionof tephra ash)on the island,withdepositsfrom individualeruptionsbeingin excess of60 cm depth (probably originally much deeper) beingwidelydistributed cross heisland's andsurface.The twoprocesses of tectonic uplift and tephradeposition havecombined oeffectivelycreatealandscapehistory nwhichthe land surface of the island has been fluctuating inelevationin relation to the sea level. Independentof any


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Text-Figure. Locationmap howing amplingocationsn WestNewBritain.Note:Kaula ndGaralaslands renotshown.Theyaresmallrock slandsadjacentoGarua sland.Likewise,NaveRiver s ontheWillaumez eninsula etweenGaru ndGaruaIs.).

eustaticsea-levelchangesaffectingthiscoastalregion,theisland has, with periodic rises in its land surface,beenexposedto theequivalentof periodicsea-leveldrops.Boththe supra-tidal oastalplatformandlowercatchment andsurfaces n partsof this island aremantledwithsedimentsvariously deposited as sub- or inter-tidal tephras, andelsewhere there is sedimentaryevidence for the periodicdeposition of colluvium, derived from both tephraandweatheredrhyoliticbedrock, ndicatingthatdowncuttinghas occurred.The effects of these periodic events are still unclear,althoughprobablycomplex and inter-related. n general,however,there arethree mportantikely impacts.1. Soil erosionis a likely effect of the variousdisruptions

tobase level and andsurfacestability.Indeed, n many

placesthere s evidenceof thetruncationf thepaleosoilsdevelopedonthe former ephraandsurfacesor, nsomecases,theabsenceof distinctive ephra ayers ndicatingthe erosion and removal of this material.Researchiscontinuingto establishthe exact temporal,spatialandprocessualrelationships hatmay exist between whatappearto have been distinct and discrete periods ofcatchmenterosion andotherenvironmental actorsin-cluding land-sea-level fluctuations, climate, and thepossibly periodicpresenceof prehistoricpeople (BoydandTorrence,1996).2. Disruptionof the island's vegetation- naturallywettropicalrainforest,but probablyalso cultivationcom-munities andforestregrowthcommunities is prob-abledue to periodicdestructionor at leastpartialdam-age,andthesubsequent ecolonisationandformationof

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replacementcommunities. The degree and nature ofsuch disruptionwill reflect a complex of processes.These includetimingand ntensityof ashfall, thestruc-ture and composition of the pre-existing vegetation,prevailingweather onditions, ntensityanddistributionof soil erosion associated with the ash fall, and theavailabilityanddistribution f seed sourcesandcommu-nityremnants vailable o contribute otheregenerationof a new rainforest.Other han,atpresent,beingable tosuggest that each successive regenerating ainforest slikelyto have been different romthepreviousone,littlemore s able to be statedabout hevegetationresponsesto these events.3. Finally, it is very likely that both ash depositionandvegetationalchangehad importantmpactson the hu-man communitiesand theirabilityto survive heeffectsof thesecatastrophic vents. Natural oil andvegetationconditionsmay have predeterminedhe type, distribu-tion andextentof agricultural rhorticultural ractices,which in turnmayhaveresponded n differentways tosuccessive ash falls. The abilityto utilise volcanicallydisturbedareaswould thereforebe dependenton ratesandpatternsof reforestationand theprevailingsubsis-tence strategiespractisedatanyone time.The archaeological nterpretation f the island is pres-entlybasedonaninvestigationof alargenumber c.100)of

(usually) 1 m2 trial excavation pits representinga widerangeof the island'senvironments.From hese,apicture semergingof aperiodicoccupationcharacterized y chang-ing patternsof landscape usage (scatteredto nucleatedsettlement,andchanges in the coastalinland focus) plussome indicationof thenatural esourceusageof the islandand tsneighboringdistrict,especiallyin termsof access tomaterials for tool manufacture Torrenceet al., 1997).Furthermore,here is an emerging historyof widespreadregionalcontactandexchange(Torrence,1992).However,the archaeological nterpretations impeded by a lack ofunderstandingf thepaleoenvironmentalarameters ithinwhich to set the humanoccupation.Priorto this researchprogram,herewas nopaleoenvironmentalr environmen-taldataavailable.Fundamentalssuesregardinghe humanoccupationof this particular andscapecan only be ad-dressedby identifyingthe following:1. the natureof pastvegetationalconditions;2. theresponsesof thepast vegetationto thecatastrophiceffects of majorvolcanic eruptions;3. thedegreeof forestclearance mpactof thepasthumanoccupants;4. the form of agricultural r horticultural ractice;5. the formand distribution f settlement ypes;and

6. the extent and degree of soil erosion attributable ohumanactivity.Until these issues can be addressed, he archaeologicalinterpretation f the prehistoricoccupationof the regionwill remain ncomplete.

METHODOLOGICAL ONSIDERATIONSPhytolith Analysis as a Solution to PalynologicalConstraints

Given the archaeologicalproblems,the paleoenviron-mentalstudyof the islandis of paramountmportance ndthe issues above arecurrentlybeing addressedwithinthePrehistory of Garuaarchaeologicalprogram.This studyhas been, and will continue to link emerging analyticaltechniques,understandings f contemporarynvironmen-tal processes, and analysis of prehistoricsediments andtheirpalynologicalcontent,in addition o adopting radi-tionalarchaeological echniques.Severalapproachesarebeing adopted, ncludinga sedimentologicalandedaphicstudyof the archaeologicalsediments.This providesevi-dence of depositionanderosionhistoryand of soil devel-opment.To address hevegetational ssues, palynologicalmethods are seen as being most appropriate.However,thereare anumberof impediments.Theregion s typicallywet tropical,with a very high rainfall(4,000 - 5,000 mm/year)andseasonal luctuation f thewatertable verat eastseveralmeters.The island's sedimentscomprisestacksoftephras,whichhave toa argeextentbeendeeplyweatheredto stickyredclays.Thisprovidesan environmentn whichfossil pollen is poorlypreserved.Furthermore, therthanveryfew andsmallremainsof charcoal, here s littlein theway of macroscopicorganicremainsin any of the soils.There s, however,anddespitetheintensityof silica disso-lution in this wet tropicalenvironment,anabundant res-ence of fossil phytolithswithin these sediments; n somecases these may be up to 8%by weight.This providesanopportunity o investigatethe paleoenvironmental ondi-tions.However,adopting hisapproach rovidesa numberof methodologicalchallenges especially given the sedi-mentaryconditionsand the wet tropicalenvironmentofWestNew Britain.These include:1. adaptingsample preparationmethods to suit the de-mandsof extractingusablematerial romclay-richsedi-ments;2. developing a databaseof phytolithassemblagesfrommoder environmentsby which to compare assem-blagesderivedfrompaleoenvironments;

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3. developing an appropriatemorphotypecategorisationmethod opracticallymanage heextremelydiverseandlargeassemblageof phytoliths;4. overcoming he effects of differentialpreservation; nd5. developingan appropriatetatisticalprocedure o dealwithalargedatamatrixusuallycharacterisedyvariableswithlargevarianceandhighnumbersof zero values.Progress n the developmentof these technical areas sreportedhere. Since this is a pragmatic tatement,discus-sioncommenceswith he aboratoryxtraction fanalysablephytolith assemblages. Key interpretivetechniques arethen discussed; these techniques should not be seen asexhaustive, but are regardedas the key elements to thepaleoenvironmentalnterpretation f the region.The dis-cussion hereis basedon the analysisof moder analoguesrepresented y 29 soil samplescollected from a numberofdifferentenvironments beach,foreshore,closed forest,regrowth orest,oldgarden ites,newgarden ites,coconutplantation ites,villagesites andhouse sites- throughoutWest New Britain Text-Figure1).Habitatdescriptionsofsites areshownin Table 1.

Extractionof Phytoliths rom SoilsThere have been several methodologicalproblemstoovercome in this work. The first of these concerns theextraction of clean samples from extremely tenaceousclays which typify most of the sediments from GaruaIsland.To overcome this and dentifya suitableextractionprocedurean experimentwas conducted,in which com-parisonwas madebetween wotechniques fdeflocculationandclayremoval oneusingcentrifugationBrown1960;Batesetal., 1978)and heotherusingfinesieving (Cwynaret al., 1979;Dricot andLeroy,1989)- generallyused forpollen extraction(Lentferand Boyd, in press b). In theexperiment,methods used commonly for pollen extrac-tions were appliedto phytolithextraction.Residues ex-

tractedusing differentpreparationechniqueswere com-paredby referenceto severalattributes:1. the time andefficiency in the preparationmethod,2. the weightof residueresultingfrom each method;3. phytolithcomposition;4. clarityof thephytolithsand othersiliceous microfossilson the slides; and5. measuresof differential oss andselectionby phytolithshapeandsize.

The results were also discussed in relationto the stillsettling technique which is most commonly used for

phytolithextraction Piperno,1983; 1988;Lentferet al., inpress). It was concluded that centrifugingis a reliablemethodfor removalof clays from fine grainedsedimentsandsinceit cangreatlyreduceextraction ime t waschosenas thepreferredmethodfor the current esearch.Thesecondmethodological roblem oncerned hechoiceof a suitablepreparationechnique o maximise heconcen-trationof fossil phytolithsandproduceanoptimalcondi-tionforeffectiveexamination.There s anabundantitera-tureon phytolithextraction(see Piperno,1988; Pearsall,1989; Lentfer,1997).However,unlikepollen preparationfor which there is now a limited range of standardandwidely adopted techniques, there is some considerablediversityof opinionandpracticeregardingoptimalprepa-ration of samples for the extraction of phytoliths.Thisresults n theproduction fdatawhich nmanycases cannotbe directly compared.In this study, threemethodscom-monlyusedtoextract ossilphytoliths romsedimentswerecompared Lentfer,1997;LentferandBoyd, inpressa). Abasicprocedureusing heavyliquidflotationandoxidationwascomparedwith two otherproceduresacross arangeofsedimenttypes commonlyencountered n archaeologicalstudies. The threeproceduresare:1. a heavy liquid flotation method (HLF), similar toPiperno's(1988) and Pearsall's(1989) methods;2. a burningmethod (POW) adaptedfrom the method

describedby PowersandGilbertson 1987); and3. anotherheavy liquidflotationmethod HLFPol)similartoHLF,butadaptedoallow theextraction f pollenandsporesas well asphytolithswithin a single process(seeTable2).Comparisonof the resulting output using these threetechniques on the same group of samples showed thatdifferentmethodscan producedifferentresults, and fur-thermorehatbasictechniquesshouldbemodified accord-ingto thecharacteristics f the sediments or whichtheyareused. All the methods were shown to have advantages,

although ome wereclearlyunsuitable orcertain edimenttypes. While all the techniques showed similarities inassemblageresults, there were problemsassociatedwithdisaggregation nd effective separation f lightandheavyfractions, n particularwith the POWprocedure.The evi-dencesuggeststhatmorphotype election occurredwithinthis lattermethod, althoughit was difficult to suggest asolution to the problem. The results show clearly thatadvantages ainedbyusingthePOWprocedure re argelyoutweighedby theproblemsencounteredwith its use, andbecause of possible size/shape selection, it is not recom-mended orgeneralextractionprocedure.Theheavyliquidflotationprocedures,on the other hand, producedmore

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concentrated esidueswithhigher evels of clarityandhaveless potentialthan the POW procedure or sample bias.Therefore, incethe use of a non-toxicheavy iquid,sodiumpolytungstate,now allowstheprocesstobeusedin relativesafety, heavy liquidextractionprocedureswith chemicaltreatmentsspecific to sedimentrequirementshave beenadopted or West New Britain sediments.

PhytolithAssemblagesfrom Modem EnvironmentsThe ultimate intention of this researchprogram s toidentify prehistoric landscapes in terms of theirvegeta-tion communities and dynamic effects of human andnaturaldisturbance.Hence, if phytolith analysis is to be

used, it is necessary to assess its ability to differentiatebetween differentvegetation communities and levels ofdisturbance,and therefore it is considered essential toestablish a reference collection of modern analogues.This is the major focus of the researchpresentedhere.Analysis of modernmaterialcan:1. help determine he relative contributionsof species tophytolithassemblages;2. assess the relative importance of certain types ofphytoliths n assemblages;3. identifysignature pecies withincertainenvironments;4. identify pastenvironments epresentednmodemland-scapes;and5. allowdifferentanalyticalprocedures o be testedunderknown conditions before being applied topaleoenvironmentaleconstruction. uture esearchwillextend this analogue approach ocusing on interpreta-tion of paleoenvironmental ata.

Categorization f PhytolithsThere are some fundamentalproblemsin categorizing

phytolithdatasets. Unlikepollen, where there s a reason-ablylimitedtaxonlist, even in richsamples,becauseeachspecies producesonly one pollen type, andmanypollentypes may represent large groups of species or genera,phytolithassemblagescan be very large.Individualplantscanproducenumerousphytolithmorphological ypes de-termined by cell structuree.g. long cells, short cells,bulliformcells andtrichomes.This is referred o as multi-plicity. Also, the sametypes of phytolithscan often occurin differentplantsand thereforecannotbe used for differ-entiatingplants(redundancy).Phytolithscan thereforebecategorizedas individual ypes orgroupsof similar ypes,regardlessof plantderivation or they can be categorized

according o singularspecies, genera,families or broaderplantgroups.The firstapproach an be problematic spe-cially for very diverseassemblages,whereassignmentofphytolithsto types is open to high levels of subjectivityinvolving 'lumping'phytolithtypes into broadcategoriesor 'splitting' hem ntogroups(PearsallandDinan,1992).This can often lead to misleadingand unreliableresults.Assigningphytoliths oplantcategories s thereforeprefer-ablebutnevertheless, ecauseofmultiplicity ndredunancyit is oftennecessary o use a combinationof categorizationprocedures.Furthermore,uchanapproachs necessitatedsincecompilationof referencematerial s verylabor nten-sive andcostly and while several researchersaround heworld are in the process of compilingmaterialuseful forworld-wideapplication, e.g., Runge,1996;KealhoferandPiperno, in press) comprehensiveinformationfor mostregionsis not as yet available.

PhytolithPreservationAs analysis ntheexperimentprogressed,t becameclearthat preservationvariability of the phytoliths, even inmodemsoils, mayexerta controlonassemblagecomposi-tion. It is necessary for reliable assessment ofpaleoenvironmental onditions and vegetationalchange,therefore, o considerthe effects of weatheringanddiffer-

entialdissolutiononthe microfossilassemblages.Dissolu-tionof phytoliths s dependentuponsoil conditionsand hecharacteristics f the fossil types includingtheir relativedensitiesandmorphologies.Obviously hin,platytypesaremoreproneto weatheringand dissolutionthan solid types(Pipero, 1991) andthe resultantassemblages presentinsediments arelikely to be biasedtowardsthe solid types.Suchbias wouldbe accentuatedwithincreasingalkalinityandwould be expectedto increase withage. There s alsothe possibility that types with ornamentation, pines orotherprojectionsmay be misidentified,havinglost thesefeaturesthroughweatheringand dissolution. It is impor-tant, therefore, o establishbase-line data sets by way ofreference materialfrom both plantmaterial and modersoils withinarangeof environments.Potential ordissolu-tion of individualtypes within assemblagescan then beassessed. It is also important o investigatepresence ofothermicrofossilswithin each sedimentassemblageespe-cially as differentmicrofossils (e.g., pollen, spores andstarchgrains)can documenta differentspectrumof planttaxa and can be used to complementphytolithanalysis.This approachcan be particularlyuseful for identifyingerodedphytoliths.Forexample, highly weathered pheri-cal forms could either be derived from a range ofmagnoliopsid(dicotyledonous)trees and shrubs or from

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palms (the spines being worn smooth). The presenceofEuphorbiaceae ollen in the same assemblage,however,wouldsuggestthat hewornspherewouldberepresentativeof Euphorbiaceaeather hanpalms(Arecaceae).Since itisoften assumed thatpollen andsporesarenotpreserved ndryland ediments t is usefulto use extractionproceduresthat allow their presence to monitoredduringphytolithcounts.Adoptionof thistypeof opportunistictrategyneednot be detrimental o phytolithassemblagedata(Lentfer1997;LentferandBoyd, submitted)and can facilitatetherecognitionof pollen and sporesthatmightotherwise beoverlooked.

StatisticalMethodsGiven thecomplexityof atypicalphytolithassemblage,it is recognised hatmultivariate nalysis s the mostusefulanalyticalmethod for showing relationshipsbetween as-semblagedata(Pentice,1986;Birks, 1986;Baxter,1994).However,the applicationof this type of analysisto fossilphytolith assemblages that are usually characterizedbylargenumber f types(variables),with argevariances,owfrequenciesor zero values across a data set of multiplesamplescanbe problematicalor bothabsolutecounts andcompositional percentage)data.Forexample, nprincipalcomponentsanalysis (PCA), variables with the greatest

magnitudes and variances can dominate analyses, andovershadow ess commonvariables or variableswith theleast variance Baxter,1994). Therefore, o limitthe num-ber of PCs required o fully investigatepatternsof varia-tions withinassemblagesit is necessaryto treatdatain away thatdown-weightsabundant ndmorevariable ypesandup-weights ess common ypes.Forcompositionaldatathis can be achievedby eithertransforming ercentages osquare-root, rc-sinvaluesorlog ratiosandusinga covari-ance matrix or PCA orgiving variablesequalweightsbystandardising ata,therebyusing a correlationmatrixforPCA (Prentice,1986;Baxter, 1994;Lentfer,1997). Vari-ance-stabilizing ransformation anlikewise be applied oabsoluteconcentrationsalculatedby wayof marker rainsinassemblages.Datacanbetransformed singanumber fdifferent methods including logarithmictransformationsand arc-tan ransformationGordon,1982;Prentice,1986;Birks, 1986).The sametransformations an be appliedtocorrespondence nalysis(CA).Analysingdata nthis man-nerensures hat nterestingdifferences nassemblagescanbe detected in analysesrather than being overriddenbypatternsdominatedby types (variables)with the greatestvariance. This is particularly elevantto paleoecologicalstudies suchas this, wherethe most significant ndicatorsmay indeed be the occasional and low-value taxa which

would normally be omitted or overlooked in standardstatistical analyses. The choice of PCA, CA, or othermultivariateests foranalysisof datasets isdependentupontheabilityof anyone methodto best illustrate hepatternsof assemblagevariationandprovidethe means for mostreliable nterpretation.

RESULTS:EXPERIMENTALEVALUATIONTo evaluate the potentialfor resolution of the method-ologicalproblemsdiscussedabove,results romtheanaly-sis of the modernreferencesamples are describedhere.With the exception of the beach and foreshoresamplesfromGarala sland(G2 andG1), heavy liquidextraction,described above (see Table 2), produced phytolithrichresidues rommostof thetwenty-nine5g samples.Percent-ageresidueranged rom 1.3% o 8%by weightof bulksoil.Alnuspollenwas added o the residues andused for calcu-lation of absolutefrequencydata.Phytolithswere exam-ined at x400 magnificationand examples of types weredrawn o scale usinga CameraLucida at x600 magnifica-tion(seeText-Figure ). Over 500 phytolithswere countedfromallassemblageswith theexceptionof G1 andG2(seeTable 1). In the absence of a comprehensivereferencecollection for theregion,typeswerecategorizedprimarilyon thebasis of morphology,although,wherepossible typeswereassigned oplant amiliesusinginformation btainedfromreferencematerial rom otherregions(e.g., Piperno,1988;Kealhofer,1994;Runge, 1996).Initially,189 differentmorphological ypeswere identi-fied fromtheassemblages.These werecategorized nto 29majorgroups epresenting families(Poaceae,Cyperaceae,Arecaceae,ZingiberaceaendMusaceae)and8othergroupsthatcould not beassigned oany particular lantgroup seeText-Figures2 and3). PCA with Euclideandistancemea-sures using the correlationmatrix for both percentagecomposition and absolute abundancedata with arc-tantransformationecommended yBirks(1986)was usedfor

the initialanalyses.The employmentof PCA rather hanCA in this case allows the importanceof taxa in eachanalysis o bereadilyassessedbythe engthof theh-vectors(distancefrompointof originto variablesas depictedbyvectorplots- seeText-Figure4B). The same informationis notreadilyavailable ncorrespondence nalysisconfigu-ration(Gordon,1982).The resultsfromthe PCA using the absolutefrequencydata wereproblematical, nd arenotshown here. Cluster-ingof sitesusingthis datamayreflectvariation nphytolithassemblages attributable o geomorphologicaland soilformationprocessesmoreso thanvariationattributableothevegetationcontributingo theassemblages. t is consid-

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Phytolith ype(Code) Phytolithype(Code)Bilobateo >2.5:1 to lowerspecific gravityof >2.5:1 to lowerspecificsolutionto


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TABLE 3. Eigenvalues>1 and%variationexplained by the first 11principalcomponents.Eigenvaluesrelate to theproportionof varianceexplainedby the principal components. (e.g.: The sum of squaredvariableloadings for a principalcomponentequalstheeigenvalue.This numberdividedby thetotal numberof PCsrequired o explain 100%of theassemblagevariationand converted to a percentage is the percentagevariationexplained by thatPC).

Principalcomponent (PC) Eigenvaluescores > 1 % variationexplained by PC Cumulative %variation explained1 4.622 16.5 16.52 3.724 13.3 29.83 2.726 9.7 39.54 2.324 8.3 47.85 1.994 7.1 55.06 1.678 6.0 61.07 1.579 5.6 66.68 1.491 5.3 71.99 1.249 4.5 76.4

10 1.160 4.1 80.5L 11 1.033 3.7 84.2

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phytolith analysis for a wet tropics environment

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