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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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
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