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1、JOURNALOFGEOPHYSICALRESEARCH,VOL.112,G04S60,doi:10.1029/2006JG000371,2007RecentchangesinnitrateanddissolvedorganiccarbonexportfromtheupperKuparukRiver,NorthSlope,Alaska12,3345J.W.McClelland,M.Stieglitz,FeifeiPan,R.M.Holmes,andB.J.PetersonReceived13November2006;revised8Februar
2、y2007;accepted16March2007;published8November2007.[1]Exportofnitrateanddissolvedorganiccarbon(DOC)fromtheupperKuparukRiverbetweenthelate1970sandearly2000swasevaluatedusinglong-termecologicalresearch(LTER)dataincombinationwithsolutefluxandcatchmenthydrologymodels.TheUSGSLoadEst
3、imator(LOADEST)wasusedtocalculateJune–Augustexportfrom1978forward.LOADESTwasthencoupledwithacatchment-basedlandsurfacemodel(CLSM)toestimatetotalannualexportfrom1991to2001.SimulationsusingtheLOADEST/CLSMcombinationindicatethatannualnitrateexportfromtheupperKuparukRiverincrease
4、dby5foldandannualDOCexportdecreasedbyaboutonehalffrom1991to2001.ThedecreaseinDOCexportwasfocusedinMayandwasprimarilyattributedtoadecreaseinriverdischarge.Incontrast,increasednitrateexportwasevidentfromMaytoSeptemberandwasprimarilyattributedtoincreasednitrateconcentrations.In
5、creasednitrateconcentrationsareevidentacrossawiderangeofdischargeconditions,indicatingthathighervaluesdonotsimplyreflectlowerdischargeinrecentyearsbutasignificantshifttohigherconcentrationperunitdischarge.Nitrateconcentrationsremainedelevatedafter2001.However,extraordinarilyl
6、owdischargeduringJune2004andJune–August2005outweighedtheinfluenceofhigherconcentrationsindeterminingexportduringtheseyears.Themechanismresponsiblefortherecentincreaseinnitrateconcentrationsisuncertainbutmayrelatetochangesinsoilsandvegetationassociatedwithregionalwarming.While
7、changesinnitrateandDOCexportfromarcticriversreflectchangesinterrestrialecosystems,theyalsohavesignificantimplicationsforArcticOceanecosystems.Citation:McClelland,J.W.,M.Stieglitz,F.Pan,R.M.Holmes,andB.J.Peterson(2007),Recentchangesinnitrateanddissolvedorganiccarbonexportfromt
8、heupperKuparukRiver,NorthSlope,Alaska,J.Geophys.Res.,112,G04S60,doi:
