長白落葉松人工林樹冠結(jié)構(gòu)及生長模型研究

長白落葉松人工林樹冠結(jié)構(gòu)及生長模型研究一、本文概述Overviewofthisarticle本文旨在對(duì)長白落葉松人工林的樹冠結(jié)構(gòu)及生長模型進(jìn)行深入的研究和分析。長白落葉松是我國東北地區(qū)重要的造林樹種，具有極高的生態(tài)和經(jīng)濟(jì)價(jià)值。隨著人工林的大規(guī)模種植和管理，對(duì)其樹冠結(jié)構(gòu)及生長規(guī)律的認(rèn)識(shí)和掌握變得尤為重要。本文首先介紹了長白落葉松的基本生態(tài)特性及人工林的發(fā)展背景，然后從樹冠結(jié)構(gòu)的角度出發(fā)，詳細(xì)探討了其形態(tài)特征和空間分布規(guī)律。接著，本文構(gòu)建了長白落葉松的生長模型，旨在預(yù)測(cè)和評(píng)估其在不同環(huán)境和經(jīng)營措施下的生長情況。本文總結(jié)了研究結(jié)果，并提出了針對(duì)長白落葉松人工林管理的優(yōu)化建議，以期為我國人工林的可持續(xù)發(fā)展提供科學(xué)依據(jù)。Thisarticleaimstoconductin-depthresearchandanalysisonthecrownstructureandgrowthmodelofartificialforestsofChineselarch.ChangbailarchisanimportantafforestationtreespeciesinNortheastChina,withextremelyhighecologicalandeconomicvalue.Withthelarge-scaleplantingandmanagementofartificialforests,understandingandmasteringtheircanopystructureandgrowthpatternshasbecomeparticularlyimportant.ThisarticlefirstintroducesthebasicecologicalcharacteristicsofChineselarchandthedevelopmentbackgroundofartificialforests.Then,fromtheperspectiveoftreecrownstructure,itexploresindetailitsmorphologicalcharacteristicsandspatialdistributionpatterns.Subsequently,thisarticleconstructedagrowthmodelfortheChineselarch,aimingtopredictandevaluateitsgrowthunderdifferentenvironmentsandmanagementmeasures.Thisarticlesummarizestheresearchresultsandproposesoptimizationsuggestionsforthemanagementofartificiallarchforests,inordertoprovidescientificbasisforthesustainabledevelopmentofartificialforestsinChina.二、長白落葉松人工林概況OverviewofChangbaiLarchArtificialForest長白落葉松（LarixolgensisHenry），又稱黃花落葉松，屬于松科落葉松屬，是東北地區(qū)特有的重要造林樹種之一。由于其優(yōu)良的木材性能和較強(qiáng)的適應(yīng)性，長白落葉松在東北地區(qū)的人工林建設(shè)中占據(jù)了舉足輕重的地位。LarixolgensisHenry,alsoknownasyellowlarch,belongstothefamilyPinaceaeandisoneoftheimportantafforestationtreespeciesuniquetotheNortheastregion.Duetoitsexcellentwoodpropertiesandstrongadaptability,thelongwhitelarchoccupiesacrucialpositionintheconstructionofartificialforestsintheNortheastregion.長白落葉松人工林主要分布于長白山脈及其周邊地區(qū)，這里的氣候條件適宜，土壤肥沃，為長白落葉松的生長提供了得天獨(dú)厚的自然環(huán)境。人工林的建設(shè)始于上世紀(jì)五十年代，經(jīng)過幾十年的經(jīng)營與管理，已經(jīng)形成了規(guī)模龐大的林分。這些林分結(jié)構(gòu)多樣，包括純林、混交林等不同類型，不僅提高了森林覆蓋率，也有效地改善了當(dāng)?shù)氐纳鷳B(tài)環(huán)境。LarixolgensisplantationismainlydistributedintheChangbaiMountainsanditssurroundingareas.Theclimatehereissuitableandthesoilisfertile,providingauniquenaturalenvironmentforthegrowthofLarixolgensis.Theconstructionofartificialforestsbeganinthe1950s,andafterdecadesofoperationandmanagement,alarge-scaleforeststandhasbeenformed.Theseforeststandshavediversestructures,includingpureforests,mixedforests,andotherdifferenttypes,whichnotonlyincreaseforestcoveragebutalsoeffectivelyimprovethelocalecologicalenvironment.在長白落葉松人工林的經(jīng)營過程中，科研工作者對(duì)其樹冠結(jié)構(gòu)及生長規(guī)律進(jìn)行了深入的研究。樹冠結(jié)構(gòu)是樹木生長的重要特征之一，對(duì)于樹木的光合作用、抗風(fēng)能力等方面有著重要影響。而生長模型則能夠定量描述樹木的生長過程，為人工林的經(jīng)營管理提供科學(xué)依據(jù)。Inthemanagementprocessofartificiallarchforests,researchershaveconductedin-depthresearchontheircanopystructureandgrowthpatterns.Thecanopystructureisoneoftheimportantcharacteristicsoftreegrowth,whichhasasignificantimpactonthephotosynthesisandwindresistanceoftrees.Thegrowthmodelcanquantitativelydescribethegrowthprocessoftrees,providingscientificbasisforthemanagementofartificialforests.目前，對(duì)于長白落葉松人工林的樹冠結(jié)構(gòu)及生長模型研究已經(jīng)取得了一定的成果。通過實(shí)地調(diào)查、遙感監(jiān)測(cè)等手段，科研工作者對(duì)長白落葉松的樹冠形態(tài)、枝條分布、生長速度等方面進(jìn)行了詳細(xì)的觀測(cè)和分析。也建立了多種生長模型，包括基于數(shù)理統(tǒng)計(jì)的模型、基于生理生態(tài)過程的模型等，用于預(yù)測(cè)長白落葉松的生長趨勢(shì)和產(chǎn)量。Atpresent,certainachievementshavebeenmadeinthestudyofcrownstructureandgrowthmodelsofartificialforestsofChineselarch.Throughon-siteinvestigation,remotesensingmonitoringandothermeans,researchershaveconducteddetailedobservationsandanalysisonthecrownmorphology,branchdistribution,growthrate,andotheraspectsofChangbailarch.Variousgrowthmodelshavealsobeenestablished,includingmodelsbasedonmathematicalstatisticsandphysiologicalandecologicalprocesses,topredictthegrowthtrendandyieldofChineselarch.然而，隨著全球氣候變化和人工林經(jīng)營管理水平的不斷提高，長白落葉松人工林的樹冠結(jié)構(gòu)和生長模型也在發(fā)生變化。因此，持續(xù)開展相關(guān)研究，深入了解長白落葉松的生長規(guī)律和適應(yīng)性，對(duì)于優(yōu)化人工林結(jié)構(gòu)、提高木材產(chǎn)量和質(zhì)量、維護(hù)生態(tài)平衡等方面具有重要意義。However,withthecontinuousimprovementofglobalclimatechangeandthelevelofartificialforestmanagement,thecrownstructureandgrowthmodelofartificiallarchforestsarealsoundergoingchanges.Therefore,itisofgreatsignificancetocontinueconductingrelevantresearchandgainadeeperunderstandingofthegrowthpatternsandadaptabilityofChineselarch,inordertooptimizethestructureofartificialforests,improvewoodyieldandquality,andmaintainecologicalbalance.三、長白落葉松人工林樹冠結(jié)構(gòu)研究AStudyontheCrownStructureofChangbaiLarchArtificialForest長白落葉松（Larixolgensis）是我國東北地區(qū)重要的造林樹種，其樹冠結(jié)構(gòu)對(duì)林木的生長和產(chǎn)量形成具有顯著影響。因此，對(duì)長白落葉松人工林的樹冠結(jié)構(gòu)進(jìn)行深入研究，對(duì)于優(yōu)化森林經(jīng)營管理、提高木材產(chǎn)量和質(zhì)量具有重要意義。LarixolgensisisanimportantafforestationtreespeciesinNortheastChina,anditscanopystructurehasasignificantimpactonthegrowthandyieldformationoftrees.Therefore,conductingin-depthresearchonthecrownstructureofartificialforestsofChineselarchisofgreatsignificanceforoptimizingforestmanagement,improvingwoodyieldandquality.本研究通過對(duì)長白落葉松人工林進(jìn)行系統(tǒng)的樣地調(diào)查和測(cè)定，分析了樹冠的形態(tài)特征、空間分布規(guī)律以及樹冠與林木生長的關(guān)系。結(jié)果顯示，長白落葉松的樹冠呈圓錐形或傘形，樹冠寬度隨林分密度的增加而減小，而樹冠高度則隨林分密度的增加而增加。這表明，在人工林經(jīng)營中，通過合理調(diào)控林分密度，可以有效調(diào)控樹冠結(jié)構(gòu)，從而實(shí)現(xiàn)林木生長的優(yōu)化。ThisstudyconductedasystematicsamplesurveyandmeasurementoftheartificialforestofChineselarch,analyzingthemorphologicalcharacteristics,spatialdistributionpatterns,andtherelationshipbetweenthecrownandtreegrowth.TheresultsshowedthatthecrownofChangbailarchwasconicalorumbrellashaped,andthewidthofthecrowndecreasedwiththeincreaseofstanddensity,whiletheheightofthecrownincreasedwiththeincreaseofstanddensity.Thisindicatesthatinartificialforestmanagement,byproperlyregulatingstanddensity,thecanopystructurecanbeeffectivelyregulated,therebyachievingoptimizationoftreegrowth.本研究還發(fā)現(xiàn)，長白落葉松的樹冠結(jié)構(gòu)與其生長量之間存在密切的關(guān)系。樹冠寬度越大，林木的胸徑和樹高生長量也越大；而樹冠高度與林木的材積生長量呈正相關(guān)關(guān)系。這一發(fā)現(xiàn)為我們?cè)趯?shí)際經(jīng)營中通過調(diào)控樹冠結(jié)構(gòu)來優(yōu)化林木生長提供了理論依據(jù)。Thisstudyalsofoundacloserelationshipbetweenthecrownstructureandgrowthoflarchtrees.Thelargerthewidthofthetreecrown,thegreaterthegrowthofthetree'sdiameteratbreastheightandheight;Theheightofthetreecrownispositivelycorrelatedwiththevolumegrowthoftheforest.Thisdiscoveryprovidesatheoreticalbasisforoptimizingtreegrowthinpracticaloperationsbyregulatingthecanopystructure.長白落葉松人工林的樹冠結(jié)構(gòu)具有顯著的形態(tài)特征和空間分布規(guī)律，且與林木生長量之間存在密切的關(guān)系。因此，在長白落葉松人工林的經(jīng)營管理中，應(yīng)注重樹冠結(jié)構(gòu)的調(diào)控，以實(shí)現(xiàn)林木生長的優(yōu)化和木材產(chǎn)量的提高。未來，我們將繼續(xù)深入研究樹冠結(jié)構(gòu)對(duì)長白落葉松生長的影響機(jī)制，為森林可持續(xù)經(jīng)營提供科學(xué)依據(jù)。ThecrownstructureoftheartificialforestofChangbailarchhassignificantmorphologicalcharacteristicsandspatialdistributionpatterns,andthereisacloserelationshipwiththegrowthofthetrees.Therefore,inthemanagementofartificiallarchforests,attentionshouldbepaidtotheregulationofcrownstructuretoachieveoptimizationoftreegrowthandincreaseinwoodyield.Inthefuture,wewillcontinuetoconductin-depthresearchontheimpactmechanismoftreecrownstructureonthegrowthoflarch,providingscientificbasisforsustainableforestmanagement.四、長白落葉松人工林生長模型研究AStudyontheGrowthModelofChangbaiLarchArtificialForest長白落葉松作為東北地區(qū)的主要造林樹種，其生長特性的研究對(duì)于人工林經(jīng)營和森林可持續(xù)發(fā)展具有重要意義。本研究針對(duì)長白落葉松人工林的生長特性，構(gòu)建了樹冠結(jié)構(gòu)和生長模型，旨在揭示其生長規(guī)律，為人工林優(yōu)化管理和撫育提供科學(xué)依據(jù)。AsthemainafforestationtreespeciesinNortheastChina,thestudyofgrowthcharacteristicsofChangbailarchisofgreatsignificanceforartificialforestmanagementandsustainableforestdevelopment.Thisstudyfocusesonthegrowthcharacteristicsofartificiallarchforestsandconstructsacanopystructureandgrowthmodel,aimingtorevealtheirgrowthpatternsandprovidescientificbasisforoptimizedmanagementandnurturingofartificialforests.本研究采用了多元線性回歸模型和非線性生長模型，結(jié)合長白落葉松人工林的實(shí)地調(diào)查數(shù)據(jù)，對(duì)樹高、胸徑、材積等生長指標(biāo)進(jìn)行了擬合。通過對(duì)比分析不同模型的擬合效果，最終確定了最優(yōu)的生長模型。結(jié)果表明，非線性生長模型能夠更好地描述長白落葉松人工林的生長過程，尤其是胸徑和材積的生長。Thisstudyusedmultiplelinearregressionmodelsandnonlineargrowthmodels,combinedwithfieldsurveydataofartificiallarchforests,tofitgrowthindicatorssuchastreeheight,diameteratbreastheight,andvolume.Bycomparingandanalyzingthefittingeffectsofdifferentmodels,theoptimalgrowthmodelwasultimatelydetermined.Theresultsindicatethatthenonlineargrowthmodelcanbetterdescribethegrowthprocessofartificiallarchforests,especiallythegrowthofdiameteratbreastheightandvolume.為了驗(yàn)證所構(gòu)建的生長模型的有效性和可靠性，本研究采用了獨(dú)立樣本數(shù)據(jù)對(duì)模型進(jìn)行了驗(yàn)證。驗(yàn)證結(jié)果表明，所構(gòu)建的生長模型具有較好的預(yù)測(cè)精度和穩(wěn)定性，能夠用于長白落葉松人工林的生長預(yù)測(cè)和管理決策。Inordertoverifytheeffectivenessandreliabilityoftheconstructedgrowthmodel,thisstudyusedindependentsampledatatovalidatethemodel.Theverificationresultsindicatethattheconstructedgrowthmodelhasgoodpredictionaccuracyandstability,andcanbeusedforgrowthpredictionandmanagementdecision-makinginartificialforestsofChineselarch.基于所構(gòu)建的生長模型，本研究進(jìn)一步分析了長白落葉松人工林的生長規(guī)律和影響因素。結(jié)果顯示，長白落葉松人工林的生長受到多種因素的影響，包括立地條件、林分密度、經(jīng)營管理措施等。通過優(yōu)化這些因素，可以有效提高長白落葉松人工林的生長速度和木材質(zhì)量。Basedontheconstructedgrowthmodel,thisstudyfurtheranalyzedthegrowthpatternsandinfluencingfactorsoftheartificialforestofChineselarch.TheresultsshowthatthegrowthofartificialforestsofLarixgmeliniiisinfluencedbyvariousfactors,includingsiteconditions,standdensity,andmanagementmeasures.Byoptimizingthesefactors,thegrowthrateandwoodqualityofartificiallarchforestscanbeeffectivelyimproved.本研究通過構(gòu)建和驗(yàn)證長白落葉松人工林的生長模型，揭示了其生長規(guī)律和影響因素，為人工林優(yōu)化管理和撫育提供了科學(xué)依據(jù)。未來研究可進(jìn)一步考慮不同環(huán)境因素對(duì)長白落葉松生長的影響，以及模型的動(dòng)態(tài)更新和優(yōu)化，以適應(yīng)不同生長階段和經(jīng)營管理需求。Thisstudyconstructedandvalidatedagrowthmodelofartificiallarchforest,revealingitsgrowthpatternsandinfluencingfactors,providingscientificbasisforoptimizingmanagementandnurturingofartificialforests.Futureresearchcanfurtherconsidertheimpactofdifferentenvironmentalfactorsonthegrowthoflarch,aswellasthedynamicupdatingandoptimizationofmodelstoadapttodifferentgrowthstagesandmanagementneeds.五、樹冠結(jié)構(gòu)與生長模型的關(guān)系研究ResearchontheRelationshipbetweenCrownStructureandGrowthModels樹冠結(jié)構(gòu)作為長白落葉松人工林的重要生態(tài)特征，對(duì)其生長模型具有顯著影響。本研究在深入了解樹冠結(jié)構(gòu)的基礎(chǔ)上，進(jìn)一步探討了其與生長模型之間的關(guān)系，以期為提高長白落葉松人工林的經(jīng)營管理水平和促進(jìn)可持續(xù)發(fā)展提供科學(xué)依據(jù)。Thecanopystructure,asanimportantecologicalfeatureofartificiallarchforests,hasasignificantimpactontheirgrowthmodels.Onthebasisofin-depthunderstandingoftreecrownstructure,thisstudyfurtherexploresitsrelationshipwithgrowthmodels,inordertoprovidescientificbasisforimprovingthemanagementlevelofartificialforestsofChineselarchandpromotingsustainabledevelopment.我們通過對(duì)不同林分密度下長白落葉松的樹冠結(jié)構(gòu)進(jìn)行分析，發(fā)現(xiàn)林分密度對(duì)樹冠形態(tài)、大小及空間分布等具有顯著影響。隨著林分密度的增加，樹冠呈現(xiàn)出向上生長的趨勢(shì)，樹冠投影面積和體積逐漸減小，而樹冠內(nèi)部的競(jìng)爭(zhēng)則愈發(fā)激烈。這種競(jìng)爭(zhēng)不僅影響了樹木對(duì)光、水、養(yǎng)分等資源的獲取，還進(jìn)一步影響了其生長速度和生長軌跡。WeanalyzedthecanopystructureofChineselarchunderdifferentstanddensitiesandfoundthatstanddensityhasasignificantimpactoncrownshape,size,andspatialdistribution.Withtheincreaseofstanddensity,thecanopyshowsanupwardgrowthtrend,andtheprojectedareaandvolumeofthecanopygraduallydecrease,whilecompetitionwithinthecanopybecomesmoreintense.Thiscompetitionnotonlyaffectstheacquisitionofresourcessuchaslight,water,andnutrientsbytrees,butalsofurtheraffectstheirgrowthspeedandtrajectory.我們?cè)跇涔诮Y(jié)構(gòu)分析的基礎(chǔ)上，建立了長白落葉松的生長模型。該模型綜合考慮了林分密度、樹冠結(jié)構(gòu)、立地條件等因素對(duì)樹木生長的影響，能夠較為準(zhǔn)確地預(yù)測(cè)長白落葉松的生長趨勢(shì)和生長量。通過對(duì)比分析不同樹冠結(jié)構(gòu)下樹木的生長情況，我們發(fā)現(xiàn)樹冠結(jié)構(gòu)對(duì)生長模型的精度和可靠性具有重要影響。具體來說，樹冠形態(tài)、大小及空間分布等因素不僅直接影響樹木的生長速度和生長量，還通過影響樹木對(duì)資源的獲取和利用效率來間接影響其生長。Onthebasisofanalyzingthecrownstructure,wehaveestablishedagrowthmodelforthelongwhitelarch.Thismodelcomprehensivelyconsiderstheeffectsoffactorssuchasstanddensity,canopystructure,andsiteconditionsontreegrowth,andcanaccuratelypredictthegrowthtrendandamountofChineselarch.Bycomparingandanalyzingthegrowthoftreesunderdifferentcanopystructures,wefoundthatcanopystructurehasasignificantimpactontheaccuracyandreliabilityofgrowthmodels.Specifically,factorssuchascrownshape,size,andspatialdistributionnotonlydirectlyaffectthegrowthrateandquantityoftrees,butalsoindirectlyaffecttheirgrowthbyaffectingtheirefficiencyinacquiringandutilizingresources.本研究還進(jìn)一步探討了樹冠結(jié)構(gòu)與生長模型之間的相互作用機(jī)制。我們認(rèn)為，樹冠結(jié)構(gòu)作為樹木生長的重要基礎(chǔ)，其形態(tài)、大小及空間分布等因素直接決定了樹木對(duì)資源的獲取和利用效率。而生長模型則通過綜合考慮各種因素對(duì)樹木生長的影響，來預(yù)測(cè)其未來的生長趨勢(shì)和生長量。因此，樹冠結(jié)構(gòu)與生長模型之間存在著密切的相互作用關(guān)系，二者共同影響著長白落葉松人工林的生長和發(fā)展。Thisstudyfurtherexploredtheinteractionmechanismbetweentreecrownstructureandgrowthmodels.Webelievethatthecanopystructure,asanimportantfoundationfortreegrowth,directlydeterminestheefficiencyoftreeresourceacquisitionandutilizationduetofactorssuchasitsshape,size,andspatialdistribution.Thegrowthmodelpredictsthefuturegrowthtrendandamountoftreesbycomprehensivelyconsideringtheimpactofvariousfactorsontheirgrowth.Therefore,thereisacloseinteractionbetweenthecanopystructureandthegrowthmodel,whichtogetheraffectthegrowthanddevelopmentoftheartificialforestofChineselarch.本研究通過對(duì)長白落葉松人工林的樹冠結(jié)構(gòu)進(jìn)行深入分析，并在此基礎(chǔ)上建立了其生長模型。研究結(jié)果表明，樹冠結(jié)構(gòu)對(duì)生長模型的精度和可靠性具有重要影響，二者之間存在著密切的相互作用關(guān)系。因此，在未來的經(jīng)營管理中，應(yīng)充分考慮樹冠結(jié)構(gòu)對(duì)樹木生長的影響，通過合理的經(jīng)營措施來調(diào)整和優(yōu)化樹冠結(jié)構(gòu)，以提高長白落葉松人工林的生長速度和生長質(zhì)量，促進(jìn)森林生態(tài)系統(tǒng)的可持續(xù)發(fā)展。Thisstudyconductedanin-depthanalysisofthecrownstructureoftheartificialforestofChineselarchandestablishedagrowthmodelbasedonit.Theresearchresultsindicatethatthecrownstructurehasasignificantimpactontheaccuracyandreliabilityofgrowthmodels,andthereisacloseinteractionbetweenthetwo.Therefore,infuturemanagement,theimpactoftreecrownstructureontreegrowthshouldbefullyconsidered,andreasonablemanagementmeasuresshouldbetakentoadjustandoptimizethetreecrownstructure,inordertoimprovethegrowthspeedandqualityofartificialforestsofChineselarch,andpromotethesustainabledevelopmentofforestecosystems.六、討論與結(jié)論DiscussionandConclusion通過對(duì)長白落葉松人工林樹冠結(jié)構(gòu)及生長模型的研究，我們獲得了深入的理解與認(rèn)識(shí)。本研究利用先進(jìn)的遙感技術(shù)和地面實(shí)測(cè)數(shù)據(jù)，詳細(xì)分析了樹冠結(jié)構(gòu)特征，并建立了生長模型，以期為長白落葉松人工林的可持續(xù)管理和優(yōu)化提供科學(xué)依據(jù)。Throughthestudyofthecrownstructureandgrowthmodelofartificiallarchforests,wehavegainedadeepunderstandingandrecognition.Thisstudyutilizedadvancedremotesensingtechnologyandgroundmeasurementdatatoanalyzethecharacteristicsoftreecrownstructureindetail,andestablishedagrowthmodel,inordertoprovidescientificbasisforthesustainablemanagementandoptimizationofartificialforestsofChineselarch.在樹冠結(jié)構(gòu)方面，研究發(fā)現(xiàn)長白落葉松人工林的樹冠形態(tài)多樣，受到林分密度、立地條件、樹種遺傳特性等多種因素的影響。隨著林分密度的增加，樹冠形態(tài)趨于緊湊，葉片分布更加密集。同時(shí)，立地條件如土壤養(yǎng)分、水分狀況等也對(duì)樹冠結(jié)構(gòu)產(chǎn)生顯著影響。這些發(fā)現(xiàn)有助于我們更好地理解長白落葉松人工林在不同環(huán)境條件下的適應(yīng)策略。Intermsofcrownstructure,researchhasfoundthatthecrownmorphologyofartificiallarchforestsisdiverseandisinfluencedbyvariousfactorssuchasstanddensity,siteconditions,andgeneticcharacteristicsoftreespecies.Astheforestdensityincreases,thecrownshapetendstobecompactandtheleafdistributionbecomesmoredense.Meanwhile,siteconditionssuchassoilnutrientsandwaterconditionsalsohaveasignificantimpactontreecrownstructure.ThesefindingshelpusbetterunderstandtheadaptationstrategiesofartificialforestsofChineselarchunderdifferentenvironmentalconditions.在生長模型研究方面，本研究基于大量的實(shí)測(cè)數(shù)據(jù)，建立了長白落葉松人工林的樹高、胸徑和材積生長模型。模型具有較高的擬合精度和預(yù)測(cè)能力，能夠較好地反映長白落葉松人工林的生長規(guī)律。這些模型不僅可用于評(píng)估林分生長狀況，還可為森林經(jīng)營管理提供決策支持。Intermsofgrowthmodelresearch,thi