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首页 草被覆盖的影响在沙质土壤水文物理参数和水流的异质性.pdf

草被覆盖的影响在沙质土壤水文物理参数和水流的异质性.pdf

草被覆盖的影响在沙质土壤水文物理参数和水流的异质性.pdf

上传者: 紫幽 2013-02-23 评分 5 0 215 29 979 暂无简介 简介 举报

简介:本文档为《草被覆盖的影响在沙质土壤水文物理参数和水流的异质性pdf》,可适用于表格/模板领域,主题内容包含Pedosphere():–,ISSNCNPcSoilScienceSocietyofChinaPublishedbyElsevierBVandSc符等。

Pedosphere():–,ISSNCNPcSoilScienceSocietyofChinaPublishedbyElsevierBVandSciencePressGrassCoverInfluencesHydrophysicalParametersandHeterogeneityofWaterFlowinaSandySoilLLICHNER,,DJELDRIDGE,KSCHACHT,NZHUKOVA,LHOLKO,MSˇIRandJPECHOInstituteofHydrology,SlovakAcademyofSciences,Racianska,Bratislava(Slovakia)DepartmentofEnvironmentClimateChangeandWater,SchoolofBiological,EarthandEnvironmentalSciences,UniversityofNewSouthWales,Sydney,NSW(Australia)GeographyDepartment,RuhrUniversityBochum,Universitaetsstrasse,Bochum(Germany)MNodiaInstituteofGeophysics,Alexidzestr,Tbilisi(Georgia)InstituteofHydrodynamics,AcademyofSciencesoftheCzechRepublic,PodPatankou,Prague(CzechRepublic)InstituteofAtmosphericPhysics,AcademyofSciencesoftheCzechRepublic,BocniII,Prague(CzechRepublic)(ReceivedApril,revisedSeptember,)ABSTRACTVegetationcoverhasamajoreffectonwaterflowinsoilsTwosites,separatedbydistanceofaboutm,wereselectedtoquantifytheinfluenceofgrasscoveronhydrophysicalparametersandheterogeneityofwaterflowinasandysoilemergingduringaheavyrainfollowingalonghot,dryperiodAcontrolsoil(puresand)withlimitedimpactofvegetationororganicmatterwasobtainedbysamplingatcmdepthbeneathagladearea,andagrasslandsoilwascoveredinacmthickhumiclayerandcolonisedbygrassesThepersistenceofwaterrepellencywasmeasuredusingthewaterdroppenetrationtimetest,sorptivityandunsaturatedhydraulicconductivityusingaminidiskinfiltrometer,andsaturatedhydraulicconductivityusingadoubleringinfiltrometerDyetracerexperimentswereusedtoassesstheheterogeneityofwaterflow,andboththemodifiedmethodforestimatingeffectivecrosssectionandanoriginalmethodforassessingthedegreeofpreferentialflowwereusedtoquantifythisheterogeneityfromtheimagesofdyedsoilprofilesMosthydrophysicalparametersweresubstantiallydifferentbetweenthetwosurfacesThegrasslandsoilhadanindexofwaterrepellencyabouttimesthatofpuresandandthepersistenceofwaterrepellencyalmosttimesthatofpuresandWaterandethanolsorptivitiesinthegrasslandsoilwereand,respectively,ofthoseofthepuresandHydraulicconductivityandsaturatedhydraulicconductivitiesinthegrasslandsoilwereandofthoseofthepuresand,respectivelyDyetracerexperimentsrevealedastableflowwith“airdraining”conditioninpuresandandwelldevelopedpreferentialflowingrasslandsoil,correspondingtoindividualgrasstussocksandsmallmicrodepressionsThegrasslandsoilwassubstantiallymorewaterrepellentandhadtimesthedegreeofpreferentialflowcomparedtopuresandTheresultsofthisstudyreinforceourviewthattheconsequencesofanychangeinclimate,whichwillultimatelyinfluencehydrology,willbemarkedlydifferentbetweengrasslandsandbaresoilsKeyWords:dyetracing,grasslandsoil,hydrophobicity,infiltration,preferentialflowCitation:Lichner,L,Eldridge,DJ,Schacht,K,Zhukova,N,HolkoL,Sˇır,MandPecho,JGrasscoverinfluenceshydrophysicalparametersandheterogeneityofwaterflowinasandysoilPedosphere():–INTRODUCTIONGlobalchangesintheEarth’sclimateareknowntohavesubstantialandirreversibleeffectsonsoilandecologicalprocesses(Solomonetal,)ClimatechangeprojectionsforcontinentalEurope,forexample,suggestageneralincreaseinairtemperaturesandlargechangesinrainfallpatterns(Hardy,)LenderinkandvanMeijgaard()predictedthatthehourlyprecipitationextremescouldincreaseSupportedbytheSlovakScientificGrantAgencyVEGA(Nosand)andbytheMinistryoftheEnvironmentoftheCzechRepublic(NoVaVSPlab)CorrespondingauthorEmail:lichneruhsavbaskLLICHNERetalbyorevenmorebytheendofthiscenturyChangestothesummerprecipitationregimehaveimportantimplicationsforhydrologyManyareasofsouthernSlovakiaareexperiencingincreasesinthefrequencyandintensityofheavyrainsfollowinglonghot,dryperiods(Fasˇkoetal,),leadingtoincreasedsurfacerunoff,soilerosionanddepositionofsedimentwithinriversandstreams,aswellasanutrientwashout(Pekarovaetal,)Therelationshipbetweenrainfallintensity,runoffandinfiltrationcapacityofthesoilisclearlyanimportantconsiderationfordeterminingtheamountoftotalcatchmentrunoffanditscomponents(overlandflowversussubsurfaceflow)followinghighintensitystorms(eg,SˇandaandCıslerova,Holkoetal,)Runoffislikelytobeexacerbatedbywaterrepellency,asitdecreasesinfiltrationrates,enhancesoverlandflowandincreasestheriskofsoilerosion(Cerda`etal,Doerretal,)Waterrepellencyisatransientsoilproperty,whichtendstobebothspatiallyandtemporallyhighlyvariableItoftendisappearsafterperiodsofprolongedsoilwetting,butwillusuallyreemergeduringdrierperiodswhensoilmoisturefallsbelowacriticalthreshold(Dekkeretal,)Waterflowpaths,oncecreated,persistovertimeduringsummer,butoverannualcyclestheirspatialarrangementscanchangecompletely(Wessoleketal,)Slightreductionsinsoilwatercontentareknowntocausesubstantialreductionsinsoilwettability(Czachoretal,)Soilwaterrepellencyiscausedmainlybylongchainedamphiphilicmolecules,whichhavebothhydrophilic(withpolarfunctionalgroup)andhydrophobic(withnonpolarhydrocarbonchain)endsAmphiphilicmoleculesmaybereleasedfromawiderangeofplants,organisms,anddecayingorganicmatterOndrying,thehydrophilicendsbondmorestronglywitheachotherandsoilparticles,leavinganexposedhydrophobicsurface(Hallett,),leadingtothefluctuationsdescribedpreviouslyBoththepersistenceandseverityofwaterrepellencyareinfluencedbylanduseandplantcover,aswellassoiltemperature,texture,pH,watercontent,andbysoilorganiccarbon(SOC)andclay(mainlykaolinite)content(Doerretal,Dekkeretal,Lichneretal,Arceneguietal,Lachaczetal,Novaketal,Diehletal,)Wangetal()revealedthatthewettabilityinwaterrepellentsoilswasaffectedmorebySOCthanbysoiltextureandpH,whereasinwettablesoils,soiltextureandpHhadagreaterimpactIngrasslandsoils,wettabilityandinfiltrationcanbeaffectedconsiderablybyvegetationcover(Alaouietal,Kodesˇova`etal,)Infiltrationisacriticalprocessingrasslandswhereresourcessuchaswater,litter,nutrientsandbiologicalactivityaretypicallyscaledatthelevelofindividualplants(Schlesingeretal,)Ingeneral,theenhancementofinfiltrationduetoplantsandsoilanimalactivitycanbeexpectedinfinetexturedsoils,whereasplantsandbiologicalcrustsareknowntodecreaseinfiltrationincoarsetexturedsoils(Cerda`,Ravietal,Caldwelletal,Capuliaketal,Cerda`andDoerr,Eldridgeetal,)Grasscovercaninducewaterrepellencyinallsoiltypesrangingfromsands(Dekkeretal,)toclays(DekkerandRitsema,)bybothrootexudatesandthatch(thelayeroforganicmatterbetweenthemineralsoilandthegreengrass)Inwellstructuredsoils,rootsareoftenfoundintheinteraggregateporenetwork,andtherefore,waterrepellentsubstancesarefounduponthefacesofaggregatesandorlargerstructuralelements(GerkeandKohne,)Repellencyisgenerallyabsentwithinaggregatesandlargerstructuralelementswhererootsareabsent(DekkerandRitsema,)Aamlidetal()foundsandlayerstobemorestronglywaterrepellentthantheoverlyingorganicthatchlayerThiscouldbecausedbyleachingofamphiphiliccompoundsfromlitterandtheorganiclayer,bygrassrootexudates,andorbythehyphaeandexudatesofsoilfungi(Bond,)Theobjectiveoftheresearchwastoquantifytheinfluenceofgrasscoveronhydrophysicalparametersandheterogeneityofwaterflowinasandysoilemergingduringaheavyrainfollowingalonghot,dryperiodWehypothesisedthatsoilwaterrepellency,inducedbythethatchandmucilagesofgrasses,aswellasinfillingofvoidsbyorganicmatter,wouldreducesubstantiallysorptivity,andunsaturatedandsaturatedhydraulicconductivitySoilwaterrepellencyshouldalsoresultinanincreaseintheheterogeneityofwaterflow(fingeredflow)ThepracticalrelevanceofourresearchisinquantifyingtheinfluenceofgrasscoveronboththesoilpropertiesandtheheterogeneityofwaterflowinasandysoilMATERIALSANDMETHODSStudyareaThefieldsiteswerelocatedintheBorskanızˇinaLowlandofsouthwestSlovakiaThisareacoversaboutGRASSCOVERINFLUENCESSOILWATERFLOWkmandconsistsofaeoliansanddunesTheregionisintransitionzonebetweentemperateoceanicandcontinentalclimatesPrecipitationisseasonal,averagesmmperyearandismainlysummerdominantTheclimateinsummertendstoconsistoflonghotanddryspellsinterspersedwithintenserainfallAirtemperatureaveragesaboutCTemperaturesofConthesurfaceofbaresoilatagladelastedabouthoursadayduringahotsummer,asmeasuredonJuly,ThedailyprecipitationamountsandtemperaturemeasuredintheMeteorologicalStationoftheSlovakHydrometeorologicalInstituteinMoravskySvatyJan,atadistanceofaboutkmfromthestudysites,inJulyandareshowninFigThestudyareawaslocatedatMlakyIInearSekule(′′′N,′′′E)whichisaboutmaslTwosites,separatedbyadistanceofaboutm,formedthebasisofourstudyAcontrolsoil(puresand)withlimitedimpactofvegetationororganicmatterwasobtainedbysamplingatcmdepthbeneathagladeareaThiswascomparedtoagrasslandsoilthatwascoveredbyacmthickhumiclayerandcolonisedbygrasses(Calamagrostisepigejos,andAgrostistenuis)Thesandsoilatthegladesitesupportedasparsecoverofmosses(mainlyPolytrichumpiliferum)andlichens(mainlyCladoniasp),andoccasionally,grasses(mainlyCorynephoruscanescens)(Sˇomsˇaketal,)SomeareasinthegladehadexposedbaresoilBoththemacroscopicandmicroscopicsoilfungihavebeenrecordedatthissite(Lichneretal,)ThesoilwasaRegosolformedfromwindblownsand(IUSSWorkingGroupWRB,)andhadasandytexture(SoilSurveyDivisionStaff,)PhysicalandchemicalpropertiesofsoilsamplesarepresentedinTableIWiththeexceptionoforganiccarboncontent(responsibleforthedifferencesinsoilwettability),soilpropertieswerealmostidenticalThemineralogyoftheaeoliansandwasprimarilysiliceoussand(silicacontentupto),withalowcontentofprimaryminerals(feldsparsandmicas)(Kalivodovaetal,)Comparedwiththecmthickhumiclayeratthegrasslandsoil,athinhumiclayerafewmilimetersthickoccurredbelowthemosscoverinthegladesoilThesoilbeneaththisthinhumiclayeriswettableallyearroundThintexturaltransitionsaswellasanaccumulationofFeoxidesandFehydroxidesweredetectedina–cmthicklayerinthesoilprofilesduringexcavation(Lichneretal,)FieldmethodsSoilwatercontentwasestimatedbythegravimeFigMeandailyairtemperaturesanddailyprecipitationsmeasuredattheMeteorologicalStationoftheSlovakHydrometeorologicalInstituteinMoravskySvatyJan(southwestSlovakia)inJuly–AugustandLLICHNERetalTABLEIPhysicalandchemicalpropertiesofthesoilfromthestudiedsiteSiteDepthSandSiltClayCaCOCpH(HO)pH(KCl)cmgkgGrassland–<Puresand–<tricmethodafterdryingatC(KutilekandNielsen,)Thepersistenceofwaterrepellencywasmeasuredusingthewaterdroppenetrationtime(WDPT)test(Doerr,)Inthisstudy,µLdropsofdistilledwaterwereplacedontothesoilsurfacefromastandardheightofmmabovethesurface,andthetimerequiredforinfiltrationwasrecordedFieldmeasurementsofinfiltrationwereperformedusingaminidiskinfiltrometer(DecagonDevices,USA)underanegativetensionh=PaTheminidiskinfiltrometerhadadiameterofcmwithliquidtransportthroughsinteredstainlesssteeldiscatthebasethatwasincontactwiththesoilMeasurementsweremadewithwaterandethanol,withthelatterprovidinganinfiltrationmeasurementthatwasnotinfluencedbywaterrepellencyThecumulativeinfiltrationIwascalculatedbasedonthePhilipinfiltrationequation(Philip,):I=CtCtCtCt()whereC,C,C,C,arecoefficients,andtistimeZhang()proposedtoestimatethesorptivityS(h)andunsaturatedhydraulicconductivityk(h)atsuctionhfrom:I=C(h)tC(h)t()whereC(h)andC(h)arefunctionsofsuctionhThesorptivityS(h)andunsaturatedhydraulicconductivityk(h)atsuctionhcanbecalculatedfrom:S(h)=C(h)A()andk(h)=C(h)A()whereAandAaredimensionlesscoefficientsEqwasusedtocalculatethesorptivitiesofbothwater,Sw(Pa),andethanol,Se(Pa),fromthecumulativeinfiltrationvstimerelationshipstakenwiththeminidiskinfiltrometerduringearlytime(<s)infiltrationofwaterandethanol,respectivelyTheindexofwaterrepellencyRwascalculatedfrom(Hallettetal,):R=Se(Pa)Sw(Pa)()Eqwasusedtoestimatethehydraulicconductivityk(Pa)inthisstudy,usingA=forsandysoilandsuctionh=PafromTableIIintheMiniDiskInfiltrometerUser’sManual,Version(DecagonDevices,)InourformercalculationsweusedA=forsandysoilandsuctionh=PafromtheMiniDiskInfiltrometerUser’sManual,Version,publishedin,andthiscoefficientwaschangedtoA=inVersion,publishedinDohnaletal()modifiedtheoriginalZhang()formulatolowertherelativeerrorofthehydraulicconductivityestimatesGrassandcrustcoverwasremoved(scalped)beforethemeasurementsofWDPT,k(Pa),Sw(Pa),andSe(Pa)Scalpingcouldresultinanincreaseinsomeoftheseproperties,asobservedbyEldridgeetal()forsorptivityandsteadystateinfiltrationrateunderbothpondingandtensionFieldmeasurementsofinfiltrationunderasmallpositivepressureheadh=Pawerealsoperformedrepeatedlyatallsitesusingadoubleringinfiltrometerwithaninnerringdiameterofcm,bufferringdiameterofcm,andlengthofcmThefirsttwoandthreetermsofthePhilipinfiltrationequation(Eq)canbeusedtoestimatethesaturatedhydraulicconductivityKsThefirsttwotermsareapplicabletorelativelyshorttimesasfollows:ISwtmKst()whereSwisthesorptivityofwater,withcoefficientm=beingthemostfrequentlyusedvalue(KutilekandNielsen,)KutılekandKrejcˇa()proposedtousethreetermsofthePhilipinfiltrationequationtoestimatethesaturatedhydraulicconductivityKs:GRASSCOVERINFLUENCESSOILWATERFLOWKs(CC)C()EqsandwereusedtoestimatethesaturatedhydraulicconductivityKsinthisstudyThetracerexperimentatthegrasslandsitewascarriedoutatthecmcmplotusingthemethodsimilartoBachmairetal()andHomolaketal()First,thegrasswasmowed,andtheplotwaspartitionedintotwosmallersubplots(cmcmeach)toapplydifferentrainfallamounts(andmm)RainfallofmmwaschosentorepresentincreasedrainfallsexpectedasaconsequenceoftheclimatechangeBrilliantbluedyewasaddedataconcentrationofgLtothewaterusedtosimulaterainfallandthedyedwaterwasappliedatarateofaboutmmminThetracerapplicationwasconductedmanuallywithawateringcan,andittookandminutesforapplicationamountsmm(onthecmcmplot)andnextmm(onthecmcmsubplot),respectivelyThirtyminutesafterthefirstsprinkling,verticalsectionswereexcavatedatdistancesof,,,andcmfromtheedgeoftheplot,andcleansoilprofileswerephotographedwithadigitalcameraSimilarly,minutesafterthesecondsprinkling,verticalsectionswereexcavatedatdistancesof,,,,andcmfromtheedgeoftheplot,andcleansoilprofileswerephotographedThetracerexperimentinthepuresandwascarriedoutatthecmcmplot,wheremmofdyedwaterwasappliedThesoilsurfaceonthisplotwasflattenedtopreventuneveninfiltrationofwaterduetopondingThewaterdyedwithbrilliantbluewasappliedmanuallywithawateringcanatarateofaboutmmminSeventyminutesaftersprinkling,verticalsectionswereexcavatedatdistancesof,,,,andcmfromtheedgeoftheplot,andcleansoilprofileswerephotographedwithadigitalcameraAllthetwodimensionalpictureswerethendigitallycorrectedandgeoreferencedusingstandardGISsoftwareaccordingtothescalesprovidedTomakedyepatternscomparableamongsitesandrainfallamounts,twoparameterswerechosenforacharacterizationofverticalflowpatterns:theeffectivecrosssectionforwaterflow,ECS,andthedegreeofpreferentialflow,DPFECSwasusedtoquantifytheheterogeneityofwaterflowinsoilTheapproachpresentedinTaumeretal()wasmodifiedsothatthefractionoftotalwatercontentchangewasdeterminedfromthestainedareaThepictureofeachverticalsectionwasdividedintoi=verticalbandswiththewidthofcm,andthenumbersniofstainedcmcmpixelswerecalculatedineachbandThenumberofstainedpixelsisnotanintegerifalltheareaofpixelswasnotstainedThefractionoftotalwatercontentchangefi,whichistheratiobetweenthewatercontentchangeinbandiandthetotalwatercontentchangeinverticalprofile,wascalculatedforeachbandusingfi=nii=i=niwithi=i=fi=()Thefractionsfiwererankedindescendingorderandpresentedagainstthefractionofcrosssectionalarea,FCA(blackdotsinFigsbandb)Abetadistributionp(x,α,β)=Γ(αβ)Γ(α)Γ(β)x(α)(x)β(α>,β>,x)()wasfittedtothedataandtheLevenbergMarquardtalgorithm(thenonlinearleastsquarefitting)wasusedtooptimizetheparametersαandβTheLevenbergMarquardtmethodisapopularalternativetotheGaussNewtonmethodoffindingtheminimumofafunctionthatisasumofsquaresofnonlinearfunctionsThefittedcurveexpressestheshareofthewatercontentchangesasafunctionoftheareashareAccordingtothedefinitioninTaumeretal(),ECSwasthenestimatedasthefractionofthetotalareathatcorrespondstotheofwatercontentchangeinverticalsection(Figs

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