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31,2JeffJ.Schoenau31333SukhadevS.Malhi4(1,730000;2,730070;3DepartmentofSoilScience,UniversityofSaskatchewan,51CampusDrive,Saskatoon,Saskatchewan,Canada,SK,S7N5A8;4NutrientCyclingResearchStation,AgricultureandAgro2FoodCanada,Melfort,Saskatchewan,Canada,SK,S0E1A0)(CalcaricCambisols,FAO)(HaplicGreyxems,FAO)(OrthicBrownChernozem)(SOC).5020cm77%,2.15thm-2yr-1,.4270%,0.961.06thm-2yr-1,.1960020cm11%,0.17thm-2yr-1.192044%,0.45thm-2yr-1.,.3(LFOC):LFOC73%90%,19201960LFOC74%70%.3LFOCHFOC..1001-9332(2003)12-2213-06S153.6AInfluenceofcultivationonorganiccarboninthreetypicalsoilsofChinaLoessPlateauandCanadaPrairies.WUTianyun1,2,JeffJ.SCHOENAU3,LIFengmin1,QIANPeiyuan2,SukhadevS.MALHI4(1StateKeyLabo2ratoryofAridAgroecology,LanzhouUniversity,Lanzhou730000,China;2SoilScienceandFertilizerInsti2tute,GansuAcademyofAgriculturalSciences,Lanzhou730070,China;3DepartmentofSoilScience,Univer2sityofSaskatchewan,51CampusDrive,Saskatoon,Saskatchewan,Canada,SK,S7N5A8;4NutrientCy2clingResearchStation,AgricultureandAgro2FoodCanada,Melfort,Saskatchewan,Canada,SK,S0E1A0).2Chin.J.Appl.Ecol.,2003,14(12):22132218.Thedynamicsoforganiccarbonin3soilsofChinaLoessPlateauandCanadaPrairieswassignificantlydifferent:inChina,theHuangmiansoil(CalcaricCambisols,FAO)lost77%oftotalorganiccarbon(020cm)within5yearsofcultivation,withadecreaserateof2.11tonsChm-2yr-1,whichwasmainlycausedbywatererosionandtillageerosion;andtheHuihesoil(haplicgreyxems,FAO)lost70%oftotalorganiccarbon(020cmlay2er)attherateof0.961.06tonsChm-2yr-1,becauseofwatererosionanddecompositionover42years.How2ever,theorthicbrownchernozeminCanadalost11%and44%ofthetotalsoilorganiccarbon(020cmlayer)after40and80yearsofcultivation,respectively,withacorrespondingrateof0.17tonsChm-2yr-1and0.45tonsChm-2yr-1.Theimprovementintillageandrotationsystem,whichpreventedsoilfromwinderosionandincreasedcurrentresiduesintosoil,wasresponsibleforthedecreaseofthelossrate.Thedynamicsofsoillightfractionorganiccarbon(LFOC)wassimilartothatoftotalorganiccarbon:HuangmianandHeilusoillost73%and90%ofLFOC,whileorthicbrownchernozemlost74%and70%ofLFOCafterbreakedin1920and1960,respectively.Amongthetestsoils,HuangmianandHuihesoilhadthefastSOCdepletionduetothedifferenceintheallocationoforganiccarbonbetweenLFOCandHFOC.KeywordsSoilorganiccarbon,Lightfraction,Heavyfractionorgniccarbon,Soilerosionorgniccarbon,LoessPlateauofChina,CanadianPrairie.3(G2000018603)(990005)SaskatchewanAgricultureDevelopmentFundStrategicResearch(R252B)InternationalFoundationforSciences(C/331321).33.2002-09-19,2003-02-26.15105km2,.,,.,2003121412CHINESEJOURNALOFAPPLIEDECOLOGY,Dec.2003,14(12)22132218©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved.[20].,.[20],.,,1%.1%10%[13].,,[16].[11],,,..,3,CO2,[13].,,.,,20.253020%[13],,,2050[18].????,[4]..,.2211(CalcaricCambisols,FAO)(HaplicGreyxems,FAO).()(OrthicBrownCher2nozem).3107hm2,50%(ChernozemOrder)[3].:1).0540100,1015..413.9mm,6.4..N2540kghm-2,P2O51525kghm-2,0.751.5thm-2.0.751.00thm-2.200m2,3.20,020cm,(1kg).2mm0.25mm.2000514.,02m5,.2).04102042,58..587.6mm,789,58.7%.7.4..N3570kghm-2,P2O52338kghm-2,.1.001.25thm-2..2000525.3).010204080CentralButte,13.318mm,2.6.,.P2O51720kghm-2,1.251.50thm-2..200144.31.1Table1Particle2sizegroupsinthesoils(020cm)Soil+OMSand+OM(50m)Coarsesilt(2050m)Finesilt(220m)Coarseclay(0.22m)Fineclay(0.2m)7.2060.185.4522.762.96Calcariccambisols,FAO9.7658.954.4921.993.40Haplicgreyxems,FAO40.5926.904.4220.825.79OrthicbrownchernozemOrganiccarboninparticleswasnoteliminated.212212110.150.20g0.2mm,LecoCR212Analyzer840[19].=.212122mm25g250ml,1.70gml-1NaI,200rpm1h.1000g20min,NaI0.45m412214©1995-2004TsinghuaTongfangOpticalDiscCo.,Ltd.Allrightsreserved..75ml0.01MCaCl2,75ml.()50ml,24h,6072h[9].2.260,0.020.05gLecoCR212Analyzer840C.,100ml,10min.5000g15min,.3.,.60,0.150.20gLecoCR12Analyzer840C.21213137Cs3:2mm120150g150mlMarinellis,137Cs[7].[8]:137Cs=[0.95137Cs-137Cs]/[0.95137Cs],=137Cs.213SASANOVA,(137Cs).3311,[5].3,,,3.()5020cm,5020cm77%,2.15thm-2yr-1.3:,;;.,:,,4523m90,,23m.137Cs,5020cm90%,218.90kgm-2(2).,.5,020cm90%,77%,.,2(020cm)Table2Totalorganiccarbon,lightandheavyfractionorganiccarboninsoils(020cm)ofchronosequencesandsoillossSoilsandcultivationyearsTotalsoilorganiccarbon(tChm-2)LightfractionDrymatter(gkg-1soil)Ccontent(Cgkg-1LF)LFOC(tChm-2)HFOC(tChm-2)137Cs137Cschangesandsoillosses137Csandloss(Bqm-2)Soilloss(kgm-2)Calcariccambisols,FAO0yr.13.9411.77112.032.59(18.58a)6.66(47.78b)729.745yr.3.187.6338.880.71(22.32)2.74(86.16)67.23(-90.3c)-218.9040yr.5.305.7677.090.97(18.30)3.80(71.70)148.23(-78.7)-175.16100yr.5.036.6387.161.37(27.23)3.70(73.56)193.16(-72.2)-156.83LSD0.052.342.2719.280.311.26--Pr.F0.0010.0010.00020.00010.0005--Haplicgreyxems,FAO0yr.56.7837.57175.0314.74(25.96)34.80(61.29)1948.754yr.46.0930.53141.109.88(21.07)32.88(70.12)1764.46(-4.7)-10.6010yr.27.8313.20124.003.45(12.40)19.01(68.30)1046.66(-43.5)-92.4920yr.22.568.83133.572.67(11.84)21.62(95.83)911.48(-50.8)-115.8542yr.16.666.8395.831.41(8.46)13.81(82.89)961.35(-48.1)-104.12LSD0.0514.0512.3557.657.679.11--Pr.F0.0040.00070.11340.0140.