简介：Alaboratory-basedaerobicincubationwasconductedtoinvestigatenitrogen(N)isotopicfractionationrelatedtonitrificationinfiveagriculturalsoilsafterapplicationofammoniumsulfate((NH4)2SO4).Thesoilsampleswerecollectedfromasubtropicalbarrenlandsoilderivedfromgranite(RGB),threesubtropicaluplandsoilsderivedfromgranite(RQU),Quaternaryredearth(RGU),QuaternaryXiashuloess(YQU)andatemperateuplandsoilgeneratedfromalluvialdeposit(FAU).Thefivesoilsvariedinnitrificationpotential,beingintheorderofFAU>YQU>RGU>RQU>RGB.SignificantNisotopicfractionationaccompaniednitrificationofNH+4.δ15NvaluesofNH+4increasedwithenhancednitrificationovertimeinthefouruplandsoilswithNH+4addition,whilethoseofNO-3decreasedconsistentlytotheminimumandthereafterincreased.δ15NvaluesofNH+4showedasignificantlynegativelinearrelationshipwithNH+4-Nconcentration,butapositivelinearrelationshipwithNO-3-Nconcentration.TheapparentisotopicfractionationfactorcalculatedbasedonthelossofNH+4was1.036forRQU,1.022forRGU,1.016forYQU,and1.020forFAU,respectively.Zero-andfirst-orderreactionkineticsseemedtohavetheirlimitationsindescribingthenitrificationprocessaffectedbyNH+4inputinthestudiedsoils.Incontrast,Nkineticisotopefractionationwascloselyrelatedtothenitrifyingactivity,andmightserveasanalternativetoolforestimatingthenitrificationcapacityofagriculturalsoils.

简介：RemotesensingdatafromtheTerraModerate-ResolutionImagingSpectroradiometer(MODIS)andgeospatialdatawereusedtoestimategrassyieldandlivestockcarryingcapacityintheTibetanAutonomousPrefectureofGolog,Qing-hai,China.TheMODIS-derivednormalizeddifferencevegetationindex(MODIS-NDVI)datawerecorrelatedwiththeabovegroundgreenbiomass(AGGB)datafromtheabovegroundharvestmethod.RegionalregressionmodelbetweentheMODIS-NDVIandthecommonlogarithm(LOG10)oftheAGGBwassignificant(r2=0.51,P<0.001),itwas,there-fore,usedtocalculatethemaximumcarryingcapacityinsheep-unityearperhectare.Themaximumlivestockcarryingcapacitywasthenadjustedtothetheoreticallivestockcarryingcapacitybythereductionfactors(slope,distancetowater,andsoilerosion).Resultsindicatedthatthegrasslandconditionsbecameworse,withlowerabovegroundpalatablegrassyield,plantheight,andcovercomparedwiththeresultsobtainedin1981.Atthesametime,althoughtheactuallivestocknumbersdecreased,theystillexceededthepropertheoreticallivestockcarryingcapacity,andovergrazingratesrangedfrom27.27%inDarlagCountyto293.99%inBaimaCounty.Integratingremotesensingandgeographicalinformationsystemtechnologies,thespatialandtemporalconditionsofthealpinegrassland,trend,andprojectedstockingratescouldbeforecastedfordecisionmaking.