简介:Background:Volumeandtaperequationsareessentialforobtainingestimatesoftotalandmerchantablestemvolume.Taperfunctionsprovideadvantagestomerchantablevolumeequationsbecausetheyestimatediameterinsideoroutsidebarkatspecificheightsonthestem,enablingtheestimationoftotalandmerchantablestemvolume,volumeofindividuallogs,andaheightatagivendiameter.Methods:Usingdatacollectedfrom1218trees(1093Douglas-fir(Pseudotsugamenziesii(Mirbel)Franco)and125westernhemlock(Tsugaheterophylla)),weevaluatedtheperformanceofonesimplepolynomialfunctionandfourvariable-exponenttaperfunctionsinpredictingupperstemdiameter.SampletreeswerecollectedfromdifferentpartsofthestatesofOregon,Washington,andCalifornia.Wecomparedinside-barkvolumeestimatesobtainedfromtheselectedtaperequationwithestimatesobtainedfromasimplelogarithmicvolumeequationforthedataobtainedinthisstudyandtheequationsusedbytheForestInventoryandAnalysisprograminthePacificNorthwest(FIA-PNW)inthestateofCaliforniaandwesternhalfofthestatesofOregonandWashington.Results:Variableexponenttaperequationsweregenerallybetterthanthesimplepolynomialtaperequations.TheFIA-PNWvolumeequationsperformedfairlywellbutvolumeequationswithfewerparametersfittedinthisstudyprovidedcomparableresults.TheRMSEobtainedfromtaper-basedvolumeestimateswerealsocomparablewiththeRMSEoftheFIA-PNWvolumeequationsforDouglas-firandwesternhemlocktreesrespectively.Conclusions:ThetaperequationsfittedinthisstudyprovideaddedbenefittotheusersovertheFIA-PNWvolumeequationsbyenablingtheuserstopredictdiameteratanyheight,heighttoagivendiameter,andmerchantablevolumeinadditiontocubicvolumeincludingtopandstump(CVTS)ofDouglas-firandwesternhemlocktreesinthePacificNorthwest.ThefindingsofthisstudyalsogivemoreconfidencetotheusersofFIA-PNWvolumeequations.
简介:Background:Stemradialgrowthinforestsisnotuniform.Rather,itischaracterizedbyperiodsofrelativelyfastorslowgrowth,orsometimesnogrowthatall.Thesefluctuationsaregenerallyafunctionofvaryingenvironmentalconditions(e.g.wateravailability)and,importantly,willalsobeassociatedwithadjustmentsinpropertiesinthewoodformed.Standlevelconditionsandforestmanagement,particularlythinningandstanddensitywill,however,alsohaveamajorinfluenceonpatternsofgrowthvariation.Weexplorehowdifferentthinninghistoriesand/orstanddensitiesinfluencethesedynamicsoftreegrowthintheimportantcommercialplantationspeciesPinusradiotaD.Don.Methods:DailystemsizechangewasmeasuredusingelectronicpointdendrometersovertwogrowingseasonsonP.rodiatatreesattwosites,subjectedtodifferentthinningregimes.Timing,ratesandperiodicityofannualgrowthwerecalculatedfromthesedata.Results:Greateroverallcross-seaionalgrowthinthinnedplotswasdrivenmainlybytwodynamics.First,thecessationofseasonalgrowthoccurredatleast3weekslaterinthestandsinwhichthinninghadtakenplace.Therewasnodifferencebetweenthinned/unthinnedstands,however,inthetimingofgrowthonset.Second,withinthelongerseason,treesinthinnedplotshadmoregrowthdays(asmuchas20%more)thanunthinnedplots.Theratesofgrowthondayswhengrowthoccurredwerenotdifferent,however.Inthiscontext,itisnotablethatintreesintheunthinnedplotsexperiencingthemostseverecompetitiontherewerestrongMpulsesMofgrowthfollowingdrought-breakingrainfallevents.Unthinnedplotsathighstanddensitiesalsomaintainedasmaller(butconsistent)zoneofdividingcellsthroughouttheseasonthanthinnedplots.Conclusions:InPinusradiatogrowingunderconditionsasinourstudy,conditionslateinsummer,particularlydrought,haveanimportanteffectonthetimingofcessationofgrowth.Earlyseasontemperatureappearstohavenoeffectin
简介:地球是人类赖以生存、发展的惟一空间。人类为了活得更舒适、更繁荣,正以各种方式不断地推进工业化、现代化的进程。然而,越来越多的事实和血的教训证明人类这一行为是“搬起石头砸白己的脚”。看看我们的生存环境吧,森林覆盖率原来占陆地的70%,如今只剩下28亿hm^2、下降为30%,并且还在以每年损失2000万hm^2的速度减少。森林的减少,环境的恶化,便出现了土地沙化、水土流失、生物多样性锐减、城市居住环境恶劣,大气污染严重。实践证明,生产建设和生态平衡之间的关系是否协调,是经济建设中战略性、长久性的问题。国民经济比例失调,用几年的时间可以调整过来,而生态遭到破坏,没有几年几十年,甚至更长的时间是难以恢复的。诸如很多濒危的树种、动物一旦绝种,就意味着该类群从地球上彻底消失。在治理复杂的生态过程中,林业教育是其中一个重要环节。本文拟浅粗地探讨一下生态建设与林业教育之间关系。