Effect of genetic sources on anatomical,morphological,and mechanical properties of 14-year-old genetically improved loblolly pine families from two sites in the southern United States

Treeimprovementprogramsonloblollypine(Pinustaeda)inthesoutheasternUSAhasfocusedprimarilyonimprovinggrowth,form,anddiseasetolerance.However,duetotherecentreductionofdesignvaluesforvisuallygradedsouthernyellowpinelumber(includingloblollypine),attentionhasbeendrawntothematerialqualityofgeneticallyimprovedloblollypine.Inthisstudy,weusedthetime-of-flight(TOF)acoustictooltoassesstheeffectofgeneticfamiliesondiameter,slenderness,fiberlength,microfibrilangle(MFA),velocityanddynamicstiffnessestimatedusinggreendensity(DMOEG)andbasicdensity(DMOEB)of14-year-oldloblollypinestandsselectedfromtwosites.Allthe184and204treesoftheselectedeighthalf-sibgeneticfamiliesonsites1and2respectivelyweretestedusingTOFacoustictool,andtwo5mmcoresamplestakenatbreastheightlevel(1.3m)usedtofortheanatomicalandphysicalpropertiesanalysis.TheresultsindicatedasignificantpositivelinearrelationshipbetweendynamicMOEs(DMOEGandDMOEB)versustreediameter,slenderness,andfiberlengthwhiledynamicMOEsnegativelybutnonsignificantcorrelatedwithMFA.WhiletherewasnosignificantdifferenceinDMOEBbetweensites;velocity2forsite1wassignificantlyhigherthansite2butDMOEGwashigherforsite2thansite1.Again,themeanDMOEGandDMOEBreportedinthepresentstudypresentsasnapshotoftheexpectedstaticMOEforgreenand12%moistureconditionsrespectivelyforloblollypine.Furthermore,thereweresignificantdifferencesbetweenfamiliesformostofthetraitsmeasuredandthissuggeststhatforestmanagershavetheopportunitytoselectfamiliesthatexhibitthedesiredfibermorphologyforfinalproductperformance.Lastly,sincethedynamicMOEbasedongreendensity(DMOEG),basicdensity(DMOEB)andvelocity2presentdifferenceconclusions,practitionersofthistypeofacoustictechniqueshouldtakecarewhenextrapolatingresultsacrossthesites.