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.
