简介：Themethaneconcentrationprofilefrom-1.5mdepthinsoilto32mheightinairwasmeasuredinalpinesteppelo-catedinthepermafrostarea.Methaneconcentrationsshowedwidelyvariationsbothinairandinsoilduringthestudyperiod.Themeanconcentrationsinatmospherewereallhigherthanthoseinsoil,andthehighestmethaneconcentrationwasfoundinairattheheightof16mwiththelowestconcentrationoccur-ringatthedepthof1.5minsoil.Thevariationsofatmosphericmethaneconcentrationsdidnotshowanyclearpatternbothtemporallyandspatially,althoughtheyexhibitedamoresteady-stablestatethanthoseinsoil.Duringtheseasonalvariations,themethaneconcentrationsatdifferentdepthsinsoilweresig-nificantlycorrelated(R2>0.6)witheachothercomparingtotheweakcorrelations(R2<0.2)betweentheatmosphericconcentra-tionsatdifferentheights.Meanmethaneconcentrationsinsoilsignificantlydecreasedwithdepth.Thiswasthecompositiveinfluenceofthedecreasingproductionratesandtheincreasingmethaneoxidationrates,whichwascausedbythedescentsoilmoisturewithdepth.Althoughthemethaneconcentrationsatalldepthsvariedwidelyduringthegrowingseason,theyshowedverydistincttemporalvariationsinthenon-growingseason.Itwasindicatedfromtheliteraturesthatmethaneoxidationrateswerepositivelycorrelatedwithsoiltemperature.Thehighermethaneconcentrationsinsoilduringthewinterweredeter-minedbythelowermethaneoxidationrateswithdecreasingsoiltemperatures,whereasmethaneproductionrateshadnoreactiontothelowertemperature.Relationsbetweenmethanecontributionandotherenvironmentalfactorswerenotdiscussedinthispaperforlackingofdata,whichimpulseustocarryoutfurtherandmoredetailedstudiesinthisuniquearea.

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简介：PermafrostdegradationisprevalentontheQinghai-TibetPlateau.Thismayleadtochangesinwaterandheattransitioninsoilsandthusaffectthestructureandfunctionofecosystems.Inthispaper,usingthemeasureddataofalpinesteppeinWudaoliangassessedthemodelperformanceinsimulatingsoilfreezingandthawingprocesses.Comparisonofthesimulatedresultsbysimultaneousheatandwater(SHAW)modeltothemeasureddatashowedthatSHAWmodelperformedsatisfactorily.Basedonanalyzingthesimulatedandpredictedresults,twopointswereobtained:(1)freezingandthawingoftheactivelayerproceededbothfromthesoilsurfacedownward.Comparedwiththefreezingprocess,thethawingprocesswasslower.Thefreezingperiodpersistedinthesurfacelayer(4cmdepth)forabout5months;(2)inthenext50years,frozenperiodwouldbeshortenabout20daysinthetop100cmdepthwhilethethawingwouldstartearlier40daysthanpresent.Soilwaterstorageinthe0-60cmwoulddecreaseby22%averagely,especiallyfromJunetoAugustwhenthevegetationisatthedominatingwaterconsumedstage.Therefore,thiskindofpermafrostdegradationasactivelayerfreezingandthawingprocesseschangeswillreducesoilwatercontentandthusinfluencethoseecosystemsaboveit.

简介：Themainobjectiveofthisstudyistosimulatethepotentialvegetationtypesonthebasisofenvironmentalparameters.ThepapertookBarkamCountyinamountainousregionoftheEasternTibetanPlateauasthestudyarea.Thevegetationdistributionwasmappedin1994and2007basedonTMremotesensingimagesbyobject-orientedinterpretationmethod.Weoverlaidthetwomapstofindoutthevegetationpatcheswhichhavenotchanged,andtookthemasstabletypes.Fiftypercentofthestablepatcheswererandomlysampledtooperatethelogisticregressionwithrelatedenvironmentalparameters;otherswereusedastestdataofsimulatedresults.Sevenenvironmentalparametersweremapped,includingelevation,slope,aspect,surfacecurvature,solarradiation,temperatureandprecipitation,basedonDEMdataandmeteorologicalsitedatabyGIStechnology.Therelationshipbetweenthespatialdistributionofvegetationandenvironmentalvariableswerequantifiedbylogisticregression.Thedistributionprobabilitiesofeachvegetationtypewerecalculated.Finally,thespatialdistributionofpotentialvegetationwassimulated.Thisresearchcanprovideascientificbasisforvegetationrestorationandecologicalconstructioninthisarea.