简介：TheblacksoilregionofnortheastChina,whichcoverstheProvincesofHeilongjiang,JilinandtheInnerMongoliaautonomousregionwithblacksoil,chernozemandmeadowsoil,hasexperiencedsoilerosionsinceintenseagriculturalreclamationbeganapproximately100yearsago.However,thesedimentdeliveryratio,definedasthefractionofgrosserosionthatistransportedfromagivenareainagiventimeinterval,isstillunclear.Inthisstudy,wecalculatedthedeliveryratioandanalysedchangesinerosiveprocesseswithinHebeicatchmentfrom1977to2007basedonananalysisofsedimentsoftheLiuduireservoir.Theoriginalvegetationlayerclearlyidentifiedthebottomofthereservoirwhenitwasconstructedin1977;thus,thereservoirsedimentscouldbepreciselydated.Thedeliveryratio,calculatedbycomparingthesedimentdepositioninthereservoirwiththetotalsoilerosionintheupstreamcatchment,wasfoundtobeexponentiallycorrelated(r~2=0.95,P<0.01)withdecreasinggrainsize,exceptforthefraction<0.002mm.Thedeliveryratiofortheclays(<0.002mm)waslow,averaging0.10duringthestudyperiod,whichindicatedpartialremovalofclaysfromthereservoir.Thechangesinthereservoirdepositionratereflectedthetemporalchangesintheerosionprocesses.Theexceptionallyhighrainfallin1998wasconfirmedbythedistributionsof~(137)Cs,~(210)Pb,andthegrain-sizeofthesediments.Beginningfromthepositionoftheoriginalgrasslayer,wedefinedthreeperiodsfrom1977to2007basedondepositionrates:2.40cmyear~(-1)from1977to1997,5.60cmyear~(-1)in1998duetounusuallyhighrainfall,and1.55cmyear~(-1)from1999to2007.Theoverallaveragedepositionratefortheentireperiodwas2.26cmyear~(-1).Precipitationwasfoundtobethemainfactoraffectingthesoilerosionofthestudyarea.