木材科学与工程专业英语

课程内容Chapter1

IntroductionChapter2

TreestemanditsgrowthChapter3

ThegrossfeaturesofwoodChapter4

ChemicalcomponentsofwoodChapter5

ThewoodycellwallChapter6

TheminutestructureofconiferouswoodsChapter7

TheminutestructureofporouswoodChapter8

BarkChapter9

ThephysicalnatureofwoodChapter10

MechanicalpropertiesofwoodChapter11

VariabilityofwoodwithinspeciesChapter12

DefectsinwoodChapter13

NaturaldurabilityofwoodChapter1Introduction/绪论Ⅰ.Characteristicpropertiesofwood/木材的特性Ⅱ.VariabilityofwoodProperties/材性变异Ⅲ.Woodasanindustrialrawmaterial/木材作为工业原材料Ⅳ.Woodasaconstructionmaterial/木材作为建筑材料Ⅴ.Knowledgeofwoodandbetteruse/木材知识与木材合理利用Acomprehensiveknowledgeofthecharacteristicsofanymaterialisessentialtoitsbestutilization.Thisisespeciallytruewithwoodbecauseofthemannerofitsformationanditscomplexcellularandcellwallstructure.全面掌握材料的特性对任何材料的合理利用都是非常重要的，对于木材来说更是如此，因为木材的细胞构成及其细胞壁结构非常复杂。Ⅰ.Characteristicpropertiesofwood/木材的特性Allwood,regardlessofitsbotanicalorigin,possessescertaincharacteristicsincommon.Thesearesummarizedinthefollowingparagraphs.所有木材，无论其植物起源如何，都会具有一些共有特征，以下对这些共有特征加以总结。1.Allwoodiscomposedofwoodcells/所有木材都是由木材细胞构成Allwoodiscellularinstructurewithcellwallscomposedofacharacteristicmixtureofpolymersofcellulose〔纤维素〕,noncellulosiccarbohydrates〔非纤维素碳水化合物〕,andlignin〔木素〕,organizedasareinforcedmatrix.Thisaccountsforacombinationofelasticandplasticresponsesofthecellwalltoappliedforces.2.Woodisanisotropicinnature/木材具有各向异性Woodexhibitsdifferentphysicalproperties〔物理性质〕whentestedalongitsthreemajordirectionalaxes.Thisbehaviorarisesfromthestructureandorganizationofcelluloseinthecellwalls,theelongatedshapeofthewoodcell,andtheirlongitudinal-radialarrangement〔纵向-径向排列〕resultingfromtheradialsymmetryofthetreetrunk.3.Woodisahygroscopicsubstance/木材是一种吸湿性材料Woodlosesandgainsmoisture〔水分〕asaresultofchangesintheatmospherichumidity〔空气湿度〕andtemperature.Becauseofitsanisotropicnature〔吸湿性〕thesemoisturevariationsproducedimensionalchanges〔尺寸变化〕inwoodwhichareunequalinthethreeaxialdirections;theyarequitesmallinthelongitudinalandappreciableintheradialandtangentialdirections〔弦向〕.Inaddition,thechangesinmoisturecontentanddimensionsaffectstrengthandanumberofotherphysicalpropertiessuchaselectricalconductivity.4.Woodisbiodegradable/木材可以被生物降解Woodmaybereducedtoitscomponentsimplesugarsandligninelementsthroughattackbyorganismssuchasfungi〔真菌〕,bacteria〔细菌〕,andcertaininsects〔昆虫〕,forinstance,termites〔白蚁〕.Itcanalsobedegradedbyhydrolysis〔水解〕andoxidation〔氧化〕resultingfromconditiontowhichitisexposed.5.Woodiscombustible/木材具有可燃烧性Thispropertymakeswoodoneofthemajorsourcesoffuelintheworldeconomybecauseoftherelativeabundanceandtherenewablenature〔可再生性〕ofthesupply.Italsoopensmanypossibilitiesforderivingbasicchemicalsfromwood,suchasalcoholsandgaseouscompoundsthatcanreplacesimilarmaterialsnowobtainedfromcrudeoil〔原油〕.Ontheotherhand,combustibility〔燃烧性〕ofwoodmustbetakenintoaccountwhenitisemployedinlightconstruction.6.Woodisremarkablyinerttotheactionofmostchemicals/木材对大多数物质具有化学惰性Forthisreasonitiswellsuitedformanyindustrialapplicationswhereresistancetothedisintegratingactionofchemicalsandtocorrosion〔腐蚀〕isimportant.However,whenwoodisexposedtoatmosphericconditions,itwillslowlyerodeundertheactionofweatherastherateofabout0.25inchpercentury.Thiscanbeeasilypreventedbypaintingthesurface;suchprotectioncarriestheaddedadvantagesofdecoration〔装饰〕andreductionofsurfaceporosity〔外表孔隙度〕.7.Woodisdurablewhenusedproperly/只要使用正确，木材非常耐久Woodissurprisinglydurablewhenusedunderconditionswhicharenotdeliberatelyfavorabletothewood-destroyingagencies〔木材败坏因子〕.Manyinstancesareknownofwood,protectedfromdampnessandfromattacksbyinsects,lastingcenturiesandevenseveralmillennia.Suchextremeexamplesoftheenduringqualitiesofwood〔木材耐久性〕werefound,forinstance,inthe2700-year-oldwoodbeamsinthetombofKingGordius,nearAnkara,Turkey.Soundbeams,manycenturiesold,haverecentlybeenremovedfromancienttemplesinJapan.Inthiscountry,perhapslessspectacularbutneverthelessimpressive,aretheoldcolonialhomesinNewEnglandandinSouth,withtheoriginalwoodexterior〔室外〕andinterior〔室内〕inawell-preservedstateafter200yearsormore.Thereisnoreasonwhy,ifproperlyused,woodshouldnotlastindefinitely.Decay〔腐朽〕andinsectdamagecanbelargelyeliminatedbyfollowingsoundmethodsofdesigninconstructionandbyusingproperlyseasonedwood.Insituationswherebiologicalwood-destroyingagencies〔木材的生物败坏因子〕areespeciallydifficulttocontrol,woodcanbemadetolastbyimpregnation〔浸渍〕withsuitablepreservatives〔防腐剂〕.8.Woodhasexcellentinsulatingproperties/木材具有很好的绝缘性Becauseofitsfibrousstructure〔纤维结构〕andthequantityofentrappedair,woodhasexcellentinsulatingproperties〔绝缘性能〕.Withtheexceptionofwood,thecommonbuildingmaterialsusedinhouseconstructionarenotgoodinsulators.Incomparisonwithwood,theheatlossthroughcommonbrickis6times,andthroughaglasswindow8timesasgreat.Concretemadewithsandandgravelaggregateis15timesasconductiveaswood,steel390times,andaluminummorethan1700times.Well-constructedwoodwindowsprovideaconsiderableadvantageoverhighlyheat-conductivemetalwindowsbyreducingheattransmissioninandoutofthebuildingandminimizingvaporcondensationincoldweather.Ⅱ.VariabilityofwoodProperties/材性变异Woodisaninherentlyvariablesubstancebecauseofitsoriginasaproductofmetabolism〔代谢产物〕ofthelivingtree.Asaresult,itspropertiesaresubjecttowidevariationsbroughtaboutbythephysiology〔生理〕ofthetreesandtheexternalfactorsaffectingitsgrowth.Therefore,woodcharacteristicsmayvaryindifferentpartsofthesametreeaswellasfromtreetotree.Furthermore,woodisaproductofnotonebutmanyspeciesoftreeswitheachkindofwoodexhibitingitsownanatomical〔解剖的〕,physical,andchemicalproperties.Inconsequencewehaveavailableamaterialwithanalmostinfiniterangeofpropertiesandcharacteristicsfromwhichtoselectforparticularuserequirements.Ⅲ.Woodasanindustrialrawmaterial/木材作为工业原材料Mostofcharacteristicsofwoodthatmakeitanoutstandingindustrialandconstructionmaterialaretraceabletooneormoreofitsbasicpropertiesandtoitsmanneroforigin.Converselyitsfaults〔缺陷〕arederivedfromthesamebasiccharacteristics.Acomprehensiveknowledgeofthestructureofwood〔木材构造〕,itschemicalandphysicalbehavior〔理化性能〕,andthecausesofitsvariability〔变异〕astheyaffectitsutilizationisthereforethebasisofpresentandpotentialutilization.Thesupremacy〔优势〕ofwoodasarawmaterialforpulp(纸浆〕andpaperisunquestioned.Thereisnoothernaturalsubstancethatcanmeettheever-increasingdemandsofmodernsocietyforpaperandotherpulpproducts.Atpresentitseemsunlikelythatasyntheticmaterialcouldbeproducedeconomicallytorivalwoodasasourceofpulp,especiallyinlightofthelimitedsuppliesofpetroleum〔石油〕,whichwouldhavetoprovidethechemicalsforproductionofcompetingmaterials.Infacttheincreasingcostofcrudeoiliscausingacriticalreevaluationoftheimportanceofwoodasapotentialsourceofbasicchemicals.Somemethodsofwoodconversionintochemicalssuchasreductionofwoodwastetoalcohols,havealreadybeendeveloped,andotherpotentialsexistforusingwoodasarawmaterialforproducingchemicalsthatarenowobtainedfrompetroleum.Ⅳ.Woodasaconstructionmaterial/木材作为建筑材料Whenwoodisemployedinitsbasicallyunalteredforminconstruction〔建筑〕,furniture〔家具〕,containers,powertransmissionlines〔高压电杆〕,transportation,andahostofotherapplications,itoffersthegreatestchallengeandopportunitytothedesigneranduser.Thisistruebecausewoodisuniversallyavailableinalargevarietyofshapesandsizeswithgreaterdiversityofuniquecharacteristicsthanarefoundinothermajorstructuralmaterials〔结构材料〕.1.Woodcanbeeasilycutandworkedintovariousshapes/木材容易切削加工成各种形状Woodmaybecutandworkedintovariousshapeswiththeaidofsimplehandtoolsorwithpower-drivenmachinery〔电动设备〕.Itthereforelendsitselfwellnotonlytoconversioninafactorybutalsotoon-the-sidefabrication〔现场加工〕.Itisthelatterfactthatlargelykeepsconventionalwood-frame〔木结构〕constructionfullycompetitivewithanymethodofcompleteprefabrication〔预制〕ofhousesyetemployed.Woodcanbejoinedwithnails,screw,bolts,andconnectors,allofwhichrequirethesimplestkindsoftoolsandproducestrongjoints.Woodcanalsobejoinedwithadhesives〔胶粘剂〕,whichcanproduceacontinuousbondovertheentiresurfacetowhichtheyareappliedanddevelopthefullshearstrengthofthewood.Thisuseofadhesivesprovidesameansoffabricatingwoodmembers〔木构件〕ofdifferingshapesandalmostunlimiteddimensions.Prefabricationoflargewoodtrusses〔桁架),laminatedbeams〔层积梁〕andarches〔拱门〕,andstressed-skinpanels〔表层受力板〕havemadewoodconstructioncompetitiveinbuilding.2.Woodhashighstrength-weightratio/木材的强重比高Flexuralrigidity〔抗弯强度〕inrelationtotheweightofthematerial,traceabletothenatureofthecellwallmaterialanditsdistributionasasystemofthin-walledtubes,isoneoftheoutstandingmechanicalpropertiesofwood.Forinstance,whenDouglas-fir[Pseudotsugamenziesii(Mirb.)Franco花旗松]iscomparedwithlow-carbonstructuralsteelonanequalweightbasis,evenifthedesignstressesarereducedtoallowforthepresenceofdefectsinwood〔木材缺陷〕,itisapparentthatDouglas-firissuperiortosteelinbendingbyaratioof2.6to1.Thehighflexuralrigidityofwoodismosteffectiveinmembersinwhichthelengthisfarinexcessofdepthofthecrosssection〔横切面〕,suchasinbeamsandlongslendercolumn.Forexample,an8×4inch“I”-sectionsteelcolumn20feetlongandaDouglas-firpolewithaneffectivecircularcrosssection10.5inchesindiameterwillhaveequalweights,butthewoodpolewillcarry32percentmoreloadascolumn.3.Woodisagoodenergy-absorbingmaterial/木材是一种很好的吸能材料Woodstructurescanbedesignedtocarryimpactloadsthataretwiceasgreatasthosetheycansustainunderstaticloading.Thiscanbecontrastedwithsteelandconcreteforwhichnoincreaseinloadsisallowedundersimilarconditions.Theexceptionalimpactstrengthofwoodgivesitaconsiderablemechanicalandeconomicadvantageforstructuresdesignedtoresistearthquakesorforsituationswhereabruptloadsareimposed,e.g.,inaircraftcarrierdecking,sincewoodisatleastninetimesasgoodanenergy-absorbingmaterial〔吸能材料〕assteel.Unlikesteel,woodalsopossessesexcellentvibration-dampingcharacteristics〔减震特性〕.Thispropertyisofutmostimportanceinbridgesandotherstructuressubjecttodynamicloads〔动载荷〕.4.Woodisdimensionallystabletotemperaturevariation/木材的热稳定性好Dimensionalchangesthatmaytakeplaceasaresultofriseintemperaturearelesssignificantinwoodconstruction〔木建筑〕thantheyareinconstructionutilizingmetalstructuralmembers.Whenheated,woodexpands〔膨胀〕acrossthegrain〔纹理〕asmuchasormorethanmetals,butonlylittleinthelongitudinaldirection〔纵向〕,whichisimportantinconstruction.Moreover,inwood,increaseindimensionswithriseintemperatureisfrequentlybalancedtoaconsiderabledegreebyshrinkage〔收缩〕causedbydrying,withacorrespondingincreaseinstrength.Thereisnosuchcompensatingeffectinmetalstructuralmembers,whichexpandandlosestrengthprogressivelywhenheated.

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Ⅴ.Knowledgeofwoodandbetteruse/木材知识与木材合理利用Certaincharacteristicsofwoodaresometimescitedasdetrimentaltoitsuseforparticularpurposes.However,whenitspropertiesarewellunderstood,thesesupposeddisadvantagesmaybeminimizedandinsomecaseseventurnedtoadvantage.Forinstance,theessentiallytaperedcylindricalshape〔尖削柱状〕ofthetreetrunkcausessomelossesinsawingstraight-grained〔直纹理〕,rectangularlumberfromlogs,butthisveryshapeoftrunk〔树干〕offersamaximumstressresistanceforaminimumofmaterialused.

Wemayusewoodwithintelligenceonlyifweunderstandwood.Chapter2TreeStemAndItsGrowth/树干与树干的生长Ⅰ.Theplantoriginofwood/木材来源于植物Ⅱ.Partsofatree/树木的各个局部Ⅲ.Howatreegrows/树木的生长Ⅳ.Orientationofthetissuesinayoungtreestem(twig)/幼树杆中各种木材组织的起源Ⅴ.Barkstructure/树皮的构造Ⅰ.Theplantoriginofwood/木材来源于植物Woodisplantorigin.Notallplants,however,possesswoodystems,andnotallthatdopossesswoodystemsproducetimber〔木材〕suitableforuseasanindustrialmaterial.Thefollowingcriteriaservetodistinguishwoodyfromnonwoodyplants:Woodyplants〔木本植物〕mustbevascularplants〔维管植物〕;i.e.,theymustpossessspecializedconductingtissues〔输导组织〕consistingofxylem(木质部)andphloem(韧皮部).Thexylemislignified〔木质化〕andisthewoodofthematureplant.Plantsdevoidofvasculartissue〔维管组织〕cannotproducewood.Theymustbeperennialplants〔多年生植物〕;i.e.,theymustliveforanumberofyears.Theymustpossessastemthatpersistsfromyeartoyear.Manyperennialsfailtobeclassedaswoodyplantsbecausetheirstemsdiebacktothegroundeachautumn,therootspersistingthroughthewinterandproducinganewstemthefollowingspring.Someplantspossesspersistentcreepingstemsandhencefallintothecategoryofwoodyplants,eventhoughtheyappeartobeherbaceous〔草本的〕.Typicalwoodyplants,whichincludeallthecommerciallyimportanttimbertrees,exhibitsecondarythickening〔次生加厚〕;i.e.,theyhaveameansofthickeningtheirstemsbysubsequentgrowthindiameter,nottraceabletoterminalgrowingpoints〔顶端生长点〕.Thisisachievedthroughtheactivitiesofagrowinglayers,calledcambium〔形成层〕,whichissituatedjustoutsidethelastformedlayerofwoodandbeneaththeinnerbark(phloem);newwoodandnewphloemarethusproducedyearlyandaredevelopedbetweenthepreviouslyformedwoodandbark.Inthismanner,inthecaseoftrees,thetrunkeventuallyattainsadiameterofsufficientsizetobeconvertedintolumberorotherusefulproducts.Ⅱ.Partsofatree/树木的各个局部Atreehasbeendefinedasaperennial,vascular,woodyplant〔多年生具有维管组织的木本植物〕whichattainsaheightatleastof20feetandusually(notalways)hasasingle,self-supportingstem.Althoughtrees,likeothervascularplants,exhibitasurprisingrangeofvariationinsize,form,andstructureandare,inreality,complexorganisms,theyareconstructedaccordingtoasimple,uniformplan.Theplantbodyconsistsofacontinuouscylindricalaxis,whichbearslateralappendages.Themainportionoftheaxisabovegroundisthestem,trunk,orbole;thisdividessuccessivelyintolimbs〔树丫〕,branches〔树枝〕,andbranchlets〔小枝〕,ofteninamannercharacteristicforthetreespecies.Theremainderoftheaxisisembeddedintheearth;liketheportionaboveground,itdividesagainandagain,andformstherootsystem〔树根系统〕.Thestemprovidesmechanicalsupportforthecrown〔树冠〕,servesasanavenueforconductionbetweenthecrownandtheroots,and,onoccasion,maystoreappreciableamountsofreservefood.Roots,incontrast,areorgansofanchorageandsupport,whichinadditionperformthefunctionsofabsorptionbymeansofroothairsormycorhiza〔菌根〕,ofconduction,andofstorage.Bothrootsandstemsexhibitradialsymmetrywhencuttransverselyi.e.,thevariouspartsarearrangedaroundacommoncenter.Treesaredifferentfromthehigheranimalsinwhichbilateral(rightandleft)symmetryistherule.Ⅲ.Howatreegrows/树木的生长Woodonacommercialscaleisobtainedonlyfromtreesofsomematurity.Sincetheprocessesofgrowthinlengthandinthicknessintreesareidenticalwiththosethattakeplaceintheproductionofseedlingsfromseeds,andtreesfromseedlings,adiscussionofthemannerinwhichgrowthproceedsinthematuretreewillservethepurposeofthistext.Atree,aspreviouslynoted,consistsofabranchedcylindricalaxistowhichappendagesofvarioussortsareattached.Thetrunkandmuch-branchedcrowncomposetheportionsofthisabovetheground;belowthesurfaceoftheground,theaxisdividesmoreorlessabruptlyintoawidespreadingrootsystem,whichinsizeandbulkcomparesfavorablywiththecrown.Untilthetreeattainsmaturity,enlargementofthecrownandrootsystemproceedsatafairlyrapidpace,inlateryearsundoubtedlymoresluggishly.Butelongation,atleastinsomepartsofthecrownandrootsystem,neverstopsduringsuccessivegrowingseasons,i.e.,aslongasthetreelives.Elongationofthebranchesoncylindricalaxisistraceabletoapicalgrowingpoints〔顶端生长点〕,andtothesealone.Throughgrowthproceedinginthese,theaxisincreasesinlength,branchesaccordingtotheplancharacteristicofthespecies,andaddsnewappendagesacropetally(towardtheapices),meanwhile(andsometimesinseason-leaves)castingitsolderappendages.Tissuesarisingfromsuchapicalgrowingpointsaretermedprimarytissues〔初生组织〕.Butlittlethickeningwouldoccurinthebranchedcylindricalaxisofthetreewereitdependentuponprimarygrowthalone.Obviously,thegrowingpoints,astheyforgeahead,leavetissuestotherear,whichaltertovaryingdegreeastheymature.However,thenumberofcellsthatcanariseinanapicalgrowingpointislimited,whichmeansinturnthatthevolumeoftissuederivedfromitmustberestricted,infact,toorestrictedtoinsurethenecessarystrengthtosupportthecrowofthetree.Intrees,growthinthicknessistraceabletoacambium(形成层)betweenthebarkandthewoodthroughoutthetree;thecambiumcontinuestoliveforagoodmanyyearsandannuallyproducesnewwoodandbarkbetweentheoldbarkandwood.Growthofthissortfromalateralcambiumisresponsibleformostofthethickeningofthestem;itisdesignatedassecondarygrowth〔次生长〕orsecondarythickening,todistinguishitfromgrowthinlengthtraceabletoapicalgrowingpoints.Tissuesoriginatinglaterallythroughsecondarythickeningareknownassecondarytissues〔次生组织〕.Suchtissuesaddtothebulkoftheplantbody,especiallyofthevascular(conducting)tissue,andstrengthenthestem;theydonot,however,fundamentallyalteritsstructure,norarenewtypesofcellsusuallyformed.Ⅳ.Orientationofthetissuesinayoungtreestem(twig)/幼树杆中各种木材组织的起源Themassivetrunkofatreeisbutamainsteminwhichprimarygrowth(growthinlength)hasensuedeachyearattheapexandinwhichsecondarygrowth(growthinthickness)hasproceededthroughitslength.Oncesecondarygrowthisinitiated,itcontinuesperiodicallyaslongasthetreelives.Hence,aproperunderstandingofthemannerinwhichatreeboleisbuiltup,yearbyyear,entailsknowledgeofthetissuespresentinayoungstemandtheirorientationasregardsoneanother,thispriortoandaftersecondarythickeningisunderway.Ⅴ.Barkstructure/树皮的构造Eventhelaymanisconversantwiththefactthatthetrunkofamaturetreeiscomposedofcoreofwoodcoveredbyalayerofbarkontheoutside.Themannerinwhichwoodaccumulatesinthebolethroughperiodicgrowthofalateralmeristem(cambium)hasalreadybeenexplained.Thesignificanceofbarkformationintreesnowdeservesattention.Forashorttime,theyoungstem(twig)isprotectedfromdesiccation〔脱水〕,andtosomeextentfrommechanicalinjury,bytheepidermis〔表皮〕.Theoutersurfaceofthisismoreorlesscutinized〔角质化的〕topreventunduelossofmoisture,anditisgenerallypiercedbystomatalopenings〔皮孔〕,whichensuretheproperaeration〔通气〕ofdeeperlyingtissues.Butinthegreatmajorityofwoodyplantnoprovisionismadeforthearealincreaseoftheepidermisasthetwigenlargesingirththroughsecondarythickening.Itsoonruptures(usuallyduringthefirstyear)andissloughedoff〔脱落〕promptlyinmostcases.Werethetwigleftwithoutaninsulatinglayerontheoutside,itwouldsoondryoutanddie,butthiscontingencydoesnot.Beforetheepidermisisruptured,anewprotectivelayer,thefirstperiderm,isformedunderit.Thisservestoprotectthestemdesiccationaftertheepidermisisruptured.Itisprovidedwithlenticels(breathingpores)inlieuofstomates.Structurally,aperidermconsistsofthreelayers:(1)thephellogen(corkcambium木栓形成层),(2)thephellem(木栓层)whichiscomposedoflayersofcorkcells〔木栓细胞〕,and(3)thephelloderm(栓内层)composedofoneormorelayersofthin-walled,nonsuberizedcells〔未木栓化细胞〕.Thephellogenoccupiesthemedialposition,andtheothertwolayersoriginatefromitthroughcelldivision.Instems,asarule,itarisesfrommature,livingparenchymatouscells〔薄壁细胞〕underlyingtheepidermisthathaveremainedthin-walledandbegindividing,cuttingoffcellsparalleltotheoutersurfaceofthetwig.Theinsulatingqualitiesoftheperidermaretraceabletothephellemlayer,whichisheavilysuberizedtopreventoratleastinhibitthepassageofmoistureandgases.Chapter3

TheGrossFeaturesofWood/木材的宏观特征Ⅰ.Thenatureofgrossfeatures/宏观特征的属性Ⅱ.Thegrossstructuralfeaturesofwoodofvalueinidentification/对木材识别有价值的木材宏观结构特征Ⅲ.Thephysicalpropertiesofwoodofvalueinidentification/对木材识别有价值的木材物理性质Ⅰ.Thenatureofgrossfeatures/宏观特征的属性Thistextisconcernedwiththeprinciplesinvolvedinteachingwoodidentification〔木材鉴定〕.Inapproachingthissubject,thelogicalprocedureisfromthegross〔宏观〕totheminute〔微观〕,especiallyfortheneophyte〔初学者〕inthisfield:featuresvisibleorevidentatlittleornomagnification〔放大〕thusreceiveattentionfirst;thoseevidentonlyatthestartarereserveduntilthelast.Thisplanhasbeenpursuedinthepagesthatfollow.Thegrossfeaturesofwood〔木材宏观特征〕are,ingeneral,oftwokinds:thosetraceabletoitsstructure,itsgrossstructuralfeatures〔宏观构造特征〕,andthosewhichfallinthecategoryofphysicalproperties〔物理性能〕as,forexample,color,odor,taste,weight,etc.Certainfeaturesofthefirsttype,suchasthefactthatthegrain〔纹理〕alwaysrunslengthwiseofthelog,holdforcommercialtimbersingeneral;othersarespecificforcertainwoodsandhenceareofdiagnosticimportanceasofferingabasisforseparationinKeys〔检索表〕.Whethergeneralorspecific,grossstructuralfeaturesarediscussedherebecausethehand-lensidentificationofwoodsrequiresanall-roundknowledgeoftheirgrossanatomy〔解剖〕.Thephysicalpropertiesofwoodare,ingeneral,lessreliableindistinguishingspeciesthanitsstructuralfeaturesbecausetheyexhibitgreaterfluctuation.However,accurateidentificationshouldseldombemadedependentupononefeaturealonebutonanumberofcharactersconsideredinunison〔同时〕.Here,certainofthenonmechanicalphysicalpropertiesarefrequentlyofvalue,whichrenderstheirinclusioninthisportionofthetextnecessary.ⅡThegrossstructuralfeaturesofwoodvaluableinidentification/对木材识别有价值的木材宏观结构特征A.Theplanesinwhichthestructuralfeaturesofwoodarestudied/木材的三个标准切面Beforeproceedingtothestudyofthegrossandeventuallytotheminutefeatures〔微观特征〕ofwood,thestudentmustorienthimselfastotheplanesinwhichwoodiscustomarilyexamined.Thefacethatisexposedwhenwoodiscutorsawedatrightangles〔垂直〕tothegrainisthetransversesurface(crosssection横切面).Theendgrainisvisibleinthisplane;itisthesurfacethatispresentedontheendofalog.Theradialandtangentialsurfaces(径切面和弦切面〕)ofthewoodareatrightanglestothetransversesurface;i.e.,theyextendalongthegrain.Thefirstissomadethatthecutfollowsaradiusofacrosssectionofthelog.Suchasurface,ifitwastrulyaccurateastodirectionandwascontinued,wouldpassfromthebarkthroughthepith(隨心〕ofthetree.Thetangentialfaceofwoodisexposedwhenthebarkispeeledfromatree.Thissurface,ofcourse,iscurved.Inpractice,whenwoodiscutorsawedtangentially,thesurfaceexposedisflatandisthenachordofthecurvedsurfaceunderthebark,soalignedthatitisapproximatelyatrightanglestothewoodrays〔木射线〕.B.Growthincrements/生长轮Growthincrementsaregenerallyprominentfeaturesofwoodsgrownintemperateregions〔温带地区〕andareusuallyvisible,atleastinthinsections,intimbersfromthetropics〔热带〕.Asstatedpreviously,intreeswithexcurrent〔贯顶的〕growthsuchaspine,theyapproachtheformofhollowconesorhollowparaboloids〔抛物面〕inthemainstem,onemountedaboveanother.Inbroad-leavedtrees〔阔叶树〕withdeliquescentbranching〔伞状分枝〕,theshapeisfarlessregular.1.Annualringsofnormaltype/正常年轮Theappearanceofnormalgrowthincrements〔正常生长轮〕,asseeninwood,dependsintheplaneinwhichtheyareviewed.Ontheendofalog,theyshowasasuccessionofgrowthringsaroundthepith.Whenonlyonesuchlayerisproducedayear,itiscalledanannualring〔年轮〕.Ringcountsonthestump〔树桩〕hencemayindicatetheapproximateageofatreebutnotitsactualagesincetheseedlingstages〔苗期〕arenotrecordedatthisheight.Inlongleafpine(PinuspalustrisMill.长针松),errorwouldresultnotonlybecauseofthisbutalsoforanotherreason;duringthe“grassstage”ofthisspecies,whichmaylastfrom4to12yearsormore,nodistinctannualringsareproducedinthestemandroot.Falserings〔假年轮〕anddiscontinuousrings〔不连续生长轮〕alsoleadtoerrorsinringcounts.Dendrochronology〔树木年代学〕,thecorrelationofannualringswithperiodsoftime,hasbeenaveryeffectivetool,particularlyinthearidSouthwest,indeterminingtheageofprehistoricruins.Onthefaceofboards,thefigures〔花纹〕resultingfromgrowthincrementsvaryaccordingtotheplaneofthewoodthatisexposed.Inedgegrained(quartersawn径切)stock,theincrementsassumetheformofparallelstrips.ConcentricandnestedUandVpatternsaretheruleinflat-sawnstock〔弦切板〕.2.Annualringsofabnormaltype/非正常年轮Ringsofabnormaltype,whenpresent,coursearoundthepithlikenormalrings.Thediscussionthatfollowsisdevotedtothevarioustypesoftheseabnormalities.Notinfrequently,particularlyinveryoldtreeswithone-sidedcrownsorintreesinwhichgrowth