祁连山青海云杉林不同海拔梯度土壤水分动态变化研究.docx

祁连山青海云杉林不同海拔梯度土壤水分动态变化研究.docx

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祁连山青海云杉林不同海拔梯度土壤水分动态变化研究

ResponseRelationshipbetweentheSeasonalFreezing-ThawingProcessofSoilandSpatialFactorChangesintheDayekouBasinoftheQilianMountains

Abstract

[Objective］Inthisstudy,theinfluenceandresponserelationshipbetweentheseasonalfreezing-thawingprocessofsoilandthespatialfactorchangesinthemanagementandutilizationofwaterresourceprocesseswereexplored.

[Methods]Themonitoringequipmentinthisstudywasarrangedatdifferentaltitudes,gradients,andslopedirections,suchasthetypicalforestsampleareaintheDayekouBasinoftheQilianMountains.Thespatialvariationcharacteristicsoftheseasonalfreezing-thawingprocessofthesoilwereanalyzed,andaregressionmodelwasestablished.

[Results]

（1）Theresultsofthisstudydeterminedthattherateofthesoil’sfreezingincreasedwiththealtitudeinatrendofvolatility.However,therateofthethawingofthefrozensoilwasfoundtohaveanoppositetrend.Thevariationdegreeofthefreezing-thawingprocessincreasedwiththealtitudeinatrendofvolatility.Theendtimeoftheapproximatesoilfreezingwithaltitudeincreasedinavolatilitytrendaheadofschedule.However,theoppositewasobservedinthethawingrateofthefrozensoil;

（2）Therateofthesoil’sfreezingunderthemossesofthespruceforestatanaltitudeof3,028mwasfoundtobethelowest.However,inthesub-alpinescrubforestatanaltitudeof3,300m,amaximuminthespatialorderingwasobserved,withanaverageof1.9cm·d-1.Thethawingrateofthefrozensoilinscrub-spruceforestatanaltitudeof3,300mwasfoundtobeminimal.However,inthesunnyslopegrasslandatanaltitudeof2,946m,amaximuminthespatialorderingwasobserved,withanaverageof1.5cm·d-1.Inthespatialorderingofthevariationdegreeoftheprocessoffreezing-thawingwithanaverageof1.2,thescrub-grasslandatanaltitudeof2,518mwasfoundtobethelowest,andthescrub-spruceforestatanaltitudeof3,195mwasalsolow;（3）ThesoilfreezingbeganonapproximatelyOctober20th,andtherateofsoilfreezinggraduallybecamereduced.Thearrivaltimeofthefrozensoilofupto150cmindepthinsub-alpinescrubforestwasfirstobservedatanaltitudeof3,028m.However,thescrub-spruceforestatanaltitudeof3,100mdidnotbecomefrozenuntilapproximatelyJanuary12thonaverage.Then,thethawingrateofthefrozensoilincreasedgradually.Theendtimeofthethawingwasearliestobservedinthesunnyslopegrasslandatanaltitudeof2,946m.However,thescrub-spruceforestatanaltitudeof3,100mwasfoundtobethelasttothaw,andaveragedapproximatelyJuly27th.Theaveragedurationsofthefreezingandthawingofthesoilwere77and121days,respectively,andtheaveragedurationoftheentireprocessoffreezing-thawingwas199days;（4）Thisstudy’sestablishedregressionmodelsofthedurationtimesoffrozensoil’sthaw,andtherateoffrozensoil’sthaw,allpassedtheRtestofgoodnessoffit,Ftestofvariance,andttest.

[Conclusions]Thecharacteristicsoftheseasonalfreezing-thawingprocessofthesoilwiththespatialchangeswereseasonal.However,thecharacteristicsunderthedifferentspatialfactorinfluenceswerenotthesame.

Keywords:

freezing-thawing;spatialfactor;seasonalfrozensoil;DayekouBasinoftheQilianMountains

Thefrozenearthchangesarethemainresearchcontentofacryosphere,andthefreezing-thawingprocessofsoildirectlyaffectsbasinrunoff.Itisknownthat,withinabasin,thefreezing-thawingprocessofsoiltendstobesensitivetospatialchanges.Therefore,inordertoexplorethebasinrunoffprocess,thespatialvariationattributesofthefreezing-thawingprocessofsoilshouldbeconsidered（Niuetal.,2014;Zhangetal.,2012）.Oneofthemostimportantanddifficultproblemsinfrozenearthresearchisthedeterminationofthespatialchangesofthefrozenearth,especiallythoseonabasinscale（Wangetal.,2014）.Thepreviousresearchregardingthespatialchangesoffrozenearthhasmainlyconcentratedonthreeaspects.Oneaspectistheassumptionofthefutureclimatescenarios,consideringthatplateauregionsaregenerallywarmingwiththesameamplitude,andpermafrostdegradationisknowntooccurnotonlyontheedgeofthepermafrostzone,butalsoaroundthevalleythawingarea,andthehighplainswampinthepermafrostregions（Lietal.,1999;Nanetal.,2004;NelsonFEetal.,2002）.Thesecondaspectisthespeculationofthespatialchangesofthepermafrostinthelimitedareasusingthedrillingorcuttingdataatlimitedpoints（Wang,2010）.Thethirdaspectofmainresearchcontentisthespatialchangesofthepermafrost,ortheseasonalfrozensoilintheQinghai-TibetPlateau（Wang,2008）.Theseresearchresultshaveimportantacademicandapplicationvalues.However,therehavebeenfewerexperimentsconductedregardingthemassivemeasureddataofthespatialvariationfactorsonabasinscalewhichcanbeutilizedforthestudyingofthefreezing-thawingprocessofsoil.

TheQilianMountainislocatedonanintersectionofthreeplateaus（i.e.theQinghai-Tibet,InnerMongolia-XinjiangandLoessPlateaus）,andhaveaveryimportantgeographicpositioninnationalforesthydrologyandecologyresearch.Acombinationofthesoil’sfreezing-thawinghydrologicprocessasaninevitablehydrologicalphenomenoninthisregion,andtheinsufficientrelatedresearch,hasmadeitverynecessarytocarryoutrelatedresearchinthisregion.DuringtheresearchregardingthespatialchangesofthefrozensoilintheQilianMountainsorupstreamoftheHeiheRiver,seventhermometerboreholeswereusedtosetthermometertubesforgroundtemperaturemonitoringforthepurposeofstudyingthefrozensoildistributioncharacteristics（Wang,2008）.Morethan40yearsoftemperatureandsoiltemperaturedataatadepthof5cmfrom11meteorologicalstationswereadoptedtosystematicallystudythemonthlyseasonalfrozensoildistributionfrom2000to2009,alongwiththespatiotemporalvariationcharacteristicsofthefreezingprobability（Peng,2013）.Basedonanelevation-responsemodel,thehigh-resolutionelevationdata（DEM）,longitudedata,latitudedata,annualaverageairtemperature（MAAT）,andverticallapseratedata（VLRT）wereappliedforanumericalsimulationofthefrozenearthdistributionintheQilianMountainsduringthelast40years（Zhang,2014）.RelatedresearchhasalsobeenconductedintheSidalong,Binggou,andPailugouBasinsoftheQilianMountainsbytheGansuResearchInstituteofWaterConservationForestintheQilianMountains（Wang,2001;Chang,2001;Jin,2011;Niuetal.,2014）.Thisresearchfocusedonthehydrologicalandinter-annualchangecharacteristicsofthefreezingandthawingprocessofsoil.

Insummary,therewerefewexperimentalresultsavailabletosetthedensersampleplotsandfrozensoiltubesinthebasinforthelong-termfieldmonitoringofthefrozensoilchanges.Therewasalsoonlyasmallamountofdataregardingthechangesinthespatialfactorssuchasaltitude,slopegradient,slopedirection,andcrowndensityfactors,bywhichtostudythefreezing-thawingprocessofsoil.Accordingly,themonitoringdevicesweresetintypicalsampleplotswithdifferentelevations,slopegradients,slopedirections,andforeststandsthroughouttheentirebasintoobtainthedataforthisstudy.Thespatialvariationcharacteristicsofthesoil’sfreezingandthawingprocesseswereanalyzedtofurtherresolvethestandstructureofthebasin,alongwithitsfunctionmechanismofwaterconservation,whichprovidedascientificbasisandreferencefortheecologicalhydrology.

1.Studyarea

TheQilianMountainsarelocatedattheintersectionoftheQinghai-Tibet,InnerMongolia-XinjiangandLoessPlateaus.Thismountainrangeisclassifiedasoneof50nationallyimportanteco-functionareas,andoneof25keyeco-functionareasbytheNationalEcologicalFunctionRegionalizationandtheNationalMajorFunctionAreaPlanning,andtherebypresentsaveryimportantecologicalniche.TheDayekouBasin（38°16'-38°33'N,100°13'-100°16'E）belongstotheZhongshanclimatezoneoftheQilianMountains,andextendseasttoMazongliang,westtoXigouliang,northtoZhengnangou,andsouthtoPailugou.ThisbasinoriginatedfromYeniuMountains,SunanCounty.Sixlargerbranches,namelyDongcha,Xicha,Toutangou,Xigouliang,GuantaigouandShengou,convergeattheDayekouReservoir,withanareaof80km2,andcontrol98%ofthebasincatchmentarea,whichindicatesatypicalclosedbasin（asshowninFig.1）.Duetogreatelevationvariationintervalsinthebasin,thehydrothermalconditionsdisplaylargedifferencesintheformofvegetationandsoiltypes,aswellasverticalandhorizontalgradientdifferences.Fromthelowesttohighestaltitudes,thevegetationtypescanbedescribedasmountaindesert,mountaingrassland,mountainforestgrassland,subalpinemeadow,andmountainsnowvegetation.Thesoiltypesincludemountainsierozem,mountainchestnutsoil,mountaingraycinnamonicsoil,subalpineshrubmeadowsoil,andalpinefrostdesertsoil.Amongallofthesoils,themountaingraycinnamonicsoilandthesub-alpineshrubmeadowsoilarethesoilsinvolvedinforestgrowth,andaredistributedintheregionswithaltitudesof2,400to3,300mand3,300to4,000m,respectively.Amongtheedificatories,theQinghaiPiceacrassifoliaisdistributedaspatchesorstripsontheshadedandhalf-shadedslopes,ataltitudesbetween2,400and3,300minthetestarea,staggeredwithgrasslandonthesunnyslopes.TheQilianSibinaprzewalskiisdistributedassmallblocksonthesunnyandhalfsunnyslopes.Theshrubswhichare