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1、Chapter8VariabilityofWoodWithinaSpecies 木材株内变异 Chapter8VariabilityofWoodWithinaSpecies 同种树木的变异性 Woodproducedbytreesofthesamespeciesisoftenmistakenlyassumedtobeidenticalinallstructuralandphysicalcharacteristics Infact differentpiecesofwood evenfromthesameteeeareneveridenticalandaresimilaronlywithinbr
2、oadlimits Alldimensionalandphysicalcharacteristicsofwoodwithintreesarevarible i e theyexhibitarangeodvalues Thevariationswhicharepresentcanberelatedtoradicaloraxialpositionofthesampleeitherwithinanindividualgrowthincrementoroveraseriesofgrowthincrementswithinthetree SummationofPrincipalFactorsAffect
3、ingVariavilityofWoodPropertiesinIndividaulTrees 影响单株树木木材性质变异的主要因子 A VariabilityinCellularCharacteristics 细胞特性的变异 Thecurvesrepresentingvariationincelldimensionsfrompithtobarkshowgreaterconsistencythanthoseforanyotherwoodcharacteristicwithintrees Thegeneralshapeofthesecurvesshowsminimumvaluesatorclose
4、tothepith 髓心 Themagnitudeofthecelldimensionsincreasesintheearlyyearsnearthepithduringtheperiodinwhichmostofthecambialmaturation 形成层 occurs Asthecambiumbecomesphysiologicallymature theslopesofthecurvesrelatingcelldimensionstotheageofthecambiumbecomelesssteepormayshownochange Inoldagethsslopesofthecur
5、vesmaydeclinewhenthecambiumagainproducescellswithreduceddimensions Thisgeneraltypeofpith to bark 从髓心到树皮 variationisparticularlyevidentforthoseaxialelementswhichundergopostcambialelongation Wherepostcambialelongationisconsiderable asinsoftwoodtracheidsandhardwoodfibers thecurvesexhibitsteepslopesnear
6、thepith Fig7 5 Limitedpostcambialelongation asinvesselelements isreflectedintherelativelylowslopesofthecurvesnearthepith Tracheiddiameters 管胞直径 andcellwallthicknessinthesoftwoodsincreasefrompithtobarkbutwithmuchlesschangethanshownfortracheidlengths 管胞长度 Fig 7 8 Inthehardwoodsthepatternsofchangeinfib
7、erdiametersandwall thicknessaregenerallysimilartothoseinsoftwoodsbutarelessconsistent Tracheidandfiberlengthswithingrowthincrementsincreasesfromthegroupupwardreachingamaximunbelowthecrown Lengthoftracheidsandfibersthendecreasestowardthetopofthetreetoaminimunmtypicalofthenewlyformedcambiuminthecrownr
8、egion Themaxiumtracheidsorfiberlengthintrunkoccursintheoutermostlayersofwoodatapointrangingfromone thirdtoone halfthetotaltreeheightabovetheground asisapparentinFig 7 6forsoftwoodsandinFig7 10forhardwoods Withinindividualincrements 年轮 thegeneralpatternisthatofaregularchangeinthelengthsofsoftwoodtrac
9、heids 管胞 hardwoodfibers纤维 andvesselelements 导管 intheradialdirectionfromearlytolatewood Theminimumlengthsarefoundintheearlywood andthemaximumisreachedinthelatewood BVariabilityinSpecificGravityandRelatedProperties 密度及有关性质的变异 1 Theradialdirection 横向 Averagespecificgravityinthemajorityofsoftwoodsshowsa
10、generalincreasefrompithtobark Thisisrelatedtotheincreasingpercentageofdenselatewoodinsuccessiveincrementsfromthepithoutward Inthediffuse porous 散孔材 hardwoodsabouttwo thirdsofthespeciesstudiedexhibitincreasingspecificgravityfromthepithoutward whichappearstoberelatedtofibercharacteristics Inthering 环孔
11、材 andsemi ring porous 半环孔材 hardwoodsdecreasesingspecificgravityfrompithtobarkcanberelatedtoincreasingearly woodpercentageinthesamedirectioninabouthalfofthespeciesstudied 2 Thelongitudinaldirection 树轴方向 Averagespecificgravityinthemajorityofthesoftwoodsdecreasefromthegroundupward Variationofspecificgr
12、avitywithheightwithinthetreeinhardwoodsfollowsbyoneofthethreepatterns itmaydecreasesupward itmaydecreaseinthelowertrunkandincreaseinthuppertrunk oritmayincreasefromthegroundupward C JuvenileandMatureWood 幼龄材与成熟材 Thestemofthetreemaybedevidedintotworegionsonthebasisfundamenttaldifferencesinthestructur
13、eandpropertiesofwood Juvenilewood 幼龄材 formsinacylindricalcolumnacoutthepithastheresultofprolongedinfluenceoftheapicalmeristemsintheregionoftheactivecrownonwoodformationbycambium Asthetreecrownmovesfatherupwardinagrowingtree theinfluenceoftheapicalmeristemsonagivencambialregiondecreasesandmaturewood
14、成熟材 isformed JuvenileandMatureWoodmustbeconsideredastwodistinctpopulationsinthesametree Thematurewoodpossessescharacteristicswhichareconsiderednormalforthespeciec whiclejuvenilewoodhasstructuralcharacteristicsandphysicalpropertiesinferiortothoseinthematurewoodofthesametree Thisisevidentforfiberandtr
15、acheidlengthsinFigs7 5and7 10 Itshouldbenotedthattheprimarybasisfordefiningjuvenileisthecellstructureandpropertiesofthewood Juvenilewoodinplantation grown 人工林 treescanberelatedtofastgrowthnearthepith butwideringsarenotnecessarilyassociatedwithjuvenilewoodinalltrees VariabtlityinWoodPropertiesamongTr
16、eesoftheSameSpecies 同树种木株间材性的变异 Variabilityinpropertiesofnormalwoodamongtreesofthesamespeciesmaybegreaterorsmallerthanthatwithinindividualtreesbeingcompared Thenormal woodcharacteristicsmaybemoditiedastheresultoflong termgrowingconditionsexistingondifferentsites eveninrathersmallareas Thedifferentconditionsondifferentsites eveninrathersmallareas Thedifferencesmayalsoarisefrominherentcharacteristicstransmittedfromparenttrees EnvironmentalandGeographicalInfluencedonVariabilityamongTrees 环境及地理因素引起株
