外文翻译挖掘机开垦森林土壤与修正方案Word格式文档下载.docx

外文翻译挖掘机开垦森林土壤与修正方案Word格式文档下载.docx

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Inearly1994,aresearchprojectwasinitiatedtoevaluatethesuccessofseveraltechniquesaimedatrestoringproductivitytodegradedsoilsonlandingsnearVamaVamaCreek,44kmeastofPrinceGeorgeinCentralBritishColumbia.Soilsweredevelopedfrommorainalparentmaterials,theusualsurfacesoiltexturewassiltloam.Twoorganicamendmentswereusedinthisstudy,includingfreshlypreparedwoodchipsandoldsawdust.Anexcavatorequippedwithasitepreparationrakewasusedtotillthesoilstoadepthof0.50m.Organicamendmentsweresubsequentlyaddedtotheplots,andeitherleftasamulchorincorporatedintothesurface0.20mofthesoil.Nitrogenwasappliedtoallplotsatarateof225kgNha-1,whichrepresentsaboutone-thirdofthe500±

700kgha-1thatwasestimatedtoberequiredtocompensateforNimmobilizationduringdecompositionofthewoodyresidues.Survivalwasgoodforalltreatments,butafter3years,treesweregrowingbestinareasthatweretreatedwithtillagealone.Treesgrowingonareaswhereoldsawdustwasusedasanamendmenthadmorevolumethantreesgrowinginareaswherewoodchipshadbeenused.Controlplotswithnotreatmenthadintermediategrowth.Soiltemperatureandchemicalpropertieswereevaluatedfortheireffectongrowth.#2000ElsevierScienceB.V.Allrightsreserved.

Keywords:

Forestsoilrehabilitation;

BritishColumbia;

Soildisturbance;

Soilconservation;

Soilproductivity;

Landingandroadrehabilitation

1.Introduction

SoilsonforestlandingsincentralBritishColumbiaarefrequentlycharacterizedbycompactionandnutrientdepletion（Carr,1988a）.Degradedsoilsonlandingsandotherareaswheresoilshavebeendisturbedbyforestoperationsoftensupportonlymeagergrowthofplantedconifers（Arnottetal.,1988）.Inmanycases,soilconditionsaresodegradedthatplantingisnotattemptedonlandings.

Restoringsoilproductivityondegradedsoilsrequiresthatgrowth-limitingconditionsbealleviated（Bulmer,1998）.Tillageisfrequentlyemployedtodecompactsoilsandimprovesoilproductivity（AndrusandFroehlich,1983）.Oncoarse-texturedsoils,tillagealonemayprovidesignificantbenefitsforgrowthofconiferssuchaslodgepolepine,althoughthelong-termconsequencesofsoilnutrientdepletionmaybeofconcern.Onfine-texturedsoils,tillageresultshavebeeninconsistent（Carr,1988b;

McNabb,1994）,partlybecausethereisanarrowrangeofmoisturecontentwhereeffectivetillagecanbecarriedout,butalsobecausestableaggregatesarerequiredtopreventpuddlingandpoorphysicalconditionsfromreappearingshortlyaftertillage.Stablesoilaggregatesformwhensoilmineralgrainsestablishanintimateassociationwithsoilorganicmatter（TisdallandOades,1982）.

Severalapproachescouldbeemployedtore-establishstablesoilstructureaftertillageoffine-texturedsoils.Acovercropofdeeprootedgrassesandlegumescouldbeestablishedtoprovideorganicmatterandenhancebiologicalactivityintherootzone,therebyencouragingthedevelopmentofstablesoilaggregates.Anotherapproachthathasbeenproposedinvolvestheincorporationoforganicamendmentsintothesurfacesoillayertobringorganicandmineralsoilmaterialsincontactwitheachother,andpossiblyencouragetheformationofstableaggregates.

Thisprojectwasdevelopedinordertogainmoreinformationaboutmethodsforrestoringproductivitytocompactandnutrient-poorsoils.WeevaluatedtheeffectofseveralcombinationsoftillageandtheadditionoforganicamendmentsonsoilpropertiesandtheestablishmentandearlygrowthoflodgepolePine.

2.Materialsandmethods

2.1.Studysites

Thestudywascarriedoutonthreeforestlandings44kmeastofPrinceGeorge,intheSBSwk1biogeoclimaticsubzone.Soilsweredevelopedfrommorainalparentmaterials.Theusualsurfacesoiltexturewassiltloam,butinatleastonelocation,aclay-richBhorizonwasencountered.Coarsefragmentcontentvariedbetween15and40%.Thelandingswerelocatedonlevelorgentlyslopingareas.Priortotreatment,therewaslittlevegetationgrowthontheLandings.

2.2.Experimentaldesign

Ninetreatmentswereappliedto5m

6mplots,asdescribedinTable1.Twocontrolplotswereestablishedoneachlanding.Thetwoorganicamendmentsusedwerewoodchipsproducedaspartoftreatmentstoreduce®

rehazardontheadjacentcutblock,andwell-rottedsawdustfromanoldsawmillsite.Thesematerialsaretypicalofsoilamendmentsthatmaybeavailableatremoterehabilitationsites.Thechipshadtypicalparticlesizeof0.1m

0.05m

0.005m,whilethesawdustparticleshadalldimensionssmallerthan0.003m.

2.3.Treatments

Treatmentswerecarriedoutinthesummerof1994usinganexcavatorequippedwithafive-toothsitepreparationrake.Soilsweretilledtoadepthof0.50m,andorganicamendmentsweresubsequentlyshoveledontotheplotstoobtainanevendistributionofthematerial.Amendmentswereeitherleftasamulchorsubsequentlyincorporatedintothesurface0.20mofthesoil.

Pineseedlings（PSB313）wereplantedat1mspacingonallplots.Alegumeseedmixwasappliedinthesummerof1995,butverypoorestablishmentofthelegumecovercropoccurredduetodryweather.Grassandlegumecoverhasbeenmaintainedatalowlevelthroughouttheexperiment.Allplots,includingcontrols,werefertilizedinthesummerof1995,usingacombinationofurea（45-0-0）andacompleteNPKfertilizer（18-18-18）.Nitrogenwasappliedatarateof225kgNha-1,whichrepresentsaboutone-thirdofthe500±

700kgNha-1thatwasestimatedtoberequiredtocompensateforNimmobilizationduringdecompositionofthewoodyresidues.Theplotsreceived50kgha-1ofK2OandP2O5.

2.4.Soilanalysisandtreeproductivitymeasurements

CompositesoilsampleswerecollectedinOctober,1994fromtherecentlytreatedplots.Sampleswereairdried,passedthrougha0.002msieve,andanalyzedatthePacificForestryCentre.Soiltemperatureandmoisturewereevaluatedapproximatelyeverytwoweeksduringthesummerof1995byobtainingthreereadingswithahand-heldthermometerthatwasinserted0.15mbelowthemineralsoilsurface.Treesurvivalandearlygrowthwasmonitoredafterone,two,andthreegrowingseasons.Treeheightandcaliperwasdetermined,alongwithanassessmentofthetreecondition.Treevolumewasdeterminedasthevolumeofacylinderwithbasediameterequaltothecaliper,andheightequaltotheseedlingheight.

3.Resultsanddiscussion

3.1.Soilproperties

SoiltemperatureresultsarepresentedinFig.1.Eventhoughnoanalysiswasdoneonthedata,andreplicationwaslimited,generalconclusionsappeartobejustified.Daytimesoiltemperaturestendedtobelowerformulchtreatmentscomparedtosoilswithoutaddedamendments.Plotswhereorganicamendments

hadbeentilledintothesurfacehadintermediatesoilTemperatures.

ThesawdusthadamuchlowerC:

Nratiothanthewoodchips（Fig.2）,reflectinghigherNconcentrationsforwoodymaterialsthathaveexperiencedseveralyearsofdecomposition.P,Ca,MgandFeconcentrationsalsoappearedtobeslightlyhigherinthesawdustmaterial（datanotshown）.Concentrationsofotherelementsdidnotappeartovaryconsistentlybetweenthesawdustandwoodchipamendments.

C:

Nratiosofsurfacemineralsoilsrangedfrom16.5to72.9.IncorporatedsawdustincreasedtheC:

Nratioofthe®

nefractionofmineralsoilscomparedtoplotswithoutaddedamendments.IncorporatedwoodchipsalsoresultedinaslightincreaseinmineralsoilC:

N,eventhoughthewoodchipsweregenerallymuchlargerthan0.002m.Carbonconcentrationsofsurfacemineralsoilswereaffectedbyseveralfactors,includingthepresenceofburiedwoodandotherorganicmaterialsintheuntreatedlandings,andtheeffectoftheorganicamendmentsonsoilCconcentrations.UntreatedsoilsatoneofthelandingshadhighCconcentrationsinsurfacemineralsoils,probablyresultingfromthepresenceofburiedwoodandforestfloormaterial.

A0.05mlayerofwoodchipsisequivalenttoanadditionrateof500m3ha-1.Thechipshaddrybulkdensityof152kgm-3,sotheadditionrateisequivalentto76000kgha-1oforganicmatter,orapproximately44000kgha-1ofcarbon.Incorporationofwoodchipsatarateof44000kgha-1ofCintothesurface0.20mofahypotheticalmineralsoilwithabulkdensityof1200kgm-3,wouldincreasetheCconcentrationby1.8%.OnlyaportionofthisCwouldendupinthe®

nefractionofsoilinthefirstfewyearsaftertreatment,butallofitisexpectedtobecomepartofthesoilcarboncycle,andportionswilleventuallycontributetothe®

nesoilorganicmattercontent.Incontrast,sawdustincorporationwouldbeexpectedtoresultinsimilarchangestototalCconcentration,buttheCwouldappearinthefinesoilfractionsooner,becausetheinitialparticlesizeismuchsmallerforsawdustthanforwoodchips.Asexpected,Fig.2showsthattheplotswheresawdustwasincorporatedintothesurfacehadhigherorganicmatterlevelsinthesurfacemineralsoilsthanothertreatments.Concentrationsofothernutrientsinsurfacemineralsoilswerevariable,anddidnotshowobvioustrendsarisingfromthetreatments.

3.2.Treesurvivalandearlygrowth

Seedlingsonplotswithtillagealoneproducedthemostvolumeoverthe3yearperiod（Fig.3）.Treesgrowinginplotswheresawdustwasusedasanamendmenttendedtohavemorevolumeafter3yearsthantreesgrowingwherewoodchipswereusedastheamendment.Heavyapplicationsofwoodchipsleftasasurfacemulchresultedinthelowestvolumegrowth