简介：Twenty-threeprogressiveextractionswereperformedtostudyindividualhumicacids(Has)andhuminfractionsfromatypicalblacksoil(Mollisol)inHeilongjiangProvince,Chinausingelementalanalysisandspectroscopictechniques.After23HAextractionstheresiduewasseparatedintohighandloworganiccarbonhuminfractions.HAyieldwasthehighestforthefirstextractionandthengraduallydecreasedwithfurtherextractions.Organiccarbon(OC)ofthehuminfractionsaccountedfor58％oftotalOCevenafter23successiveHAextractions.Inaddition,theatomicC/HratiodecreasedduringthecourseofextractionwhileC/Oincreased;theE4/E6ratiofromtheUVanalysisdecreasedwithfurtherextractionwhileE2/Eaincreased;thebandassignedtoaliphaticcarbon(2930cm-1)inthediffusereflectanceinfraredFouriertransformspectroscopy(DRIFTS)spectragraduallyincreasedwithprogressiveextraction;thecalculatedratioofthesumofaromaticcarbonpeakheightstothatofaliphaticcarbonpeakheightsfromDRIFTSspectradeclinedwithextractions;andnuclearmagneticresonance(NMR)datasuggestedthatHAaliphaticcarbonsincreasedwithextractionswhilearomaticcarbonsdecreased.Thus,hydrophobicityandaliphaticityofHasincreasedwithextractionswhilepolarityandaromaticitydecreased.Thesedatashowedsubstantialchemical,structural,andmoleculardifferencesamongthe23Hasandtwohuminfractions.Therefore,theseresultsmayhelpexplainwhysoilandsedimenthuminfractionshavehighsorptioncapacityfororganiccontaminants.

简介：Availablewaterandfertilizerhavebeenthemainlimitingfactorsforyieldsofspringwheat,whichoccupiesalargeareaoftheblacksoilzoneinnortheastChina;thus,theneedtosetupappropriatemodelsforscenarioanalysisofcroppingsystemmodelshasbeenincreasing.ThecapabilityofCropSyst,acroppingsystemsimulationmodel,tosimulatespringwheatgrowthofawidelygrownspringcultivar,'Longmai19',intheblacksoilzoneinnortheastChinaunderdifferentwaterandnitrogenregimeswasevaluated.Fielddatacollectedfromarotationexperimentofthreegrowingseasons(1992-1994)wereusedtocalibrateandvalidatethemodel.Themodelwasrunfor3yearsbyprovidinginitialconditionsatthebeginningoftherotationwithoutreinitializingthemodelinlateryearsintherotationsequence.CropinputparametersweresetbasedonmeasureddataortakenfromCropSystmanual.Afewcultivar-specificparameterswereadjustedwithinareasonablerangeoffluctuation.TheresultsdemonstratedtherobustnessofCropSystforsimulatingevapotranspiration,abovegroundbiomass,andgrainyieldof'Longmai19'springwheatwiththerootmeansquareerrorsbeing7%,13%and13%oftheobservedmeansforevapotranspiration(ET),grainyieldandabovegroundbiomass,respectively.AlthoughCropSystwasabletosimulatespringproductionreasonablywell,furtherevaluationandimprovementofthemodelwithamoredetailedfielddatabasewasdesirableforagriculturalsystemsinnortheastChina.

简介：Thedynamicsofrhizospheremicrobialcommunitiesisimportantforplanthealthandproductivity,andcanbeinfluencedbysoiltype,plantspeciesorgenotype,andplantgrowthstage.ApotexperimentwascarriedouttoexaminethedynamicsofmicrobialcommunitiesintherhizosphereoftwosoybeangenotypesgrowninablacksoilinNortheastChinawithalonghistoryofsoybeancultivation.Thetwosoybeangenotypes,Beifeng11andHai9731,differinginproductivityweregrowninamixtureofblacksoilandsiliceoussand.Thebacterialcommunitieswerecomparedatthreezonelocationsincludingrhizoplane,rhizosphere,andbulksoilatthethirdnode(V3),earlyflowering(R1),andearlypod(R3)stagesusingpolymerasechainreaction-denaturinggradientgelelectrophoresis(PCR-DGGE)of16SrDNA.Theresultsofprincipalcomponentanalyses(PCA)showedthatthebacterialcommunitystructurechangedwithgrowthstage.Spatially,thebacterialcommunitiesintherhizoplaneandrhizosphereweresignificantlydifferentfromthoseinthebulksoil.Nevertheless,thebacterialcommunitiesintherhizoplaneweredistinctfromthoseintherhizosphereattheV3stage,whilenoobviousdifferenceswerefoundattheR1andR3stages.Forthetwogenotypes,thebacterialcommunitystructurewassimilarattheV3stage,butdifferedattheR1andR3stages.Inotherwords,somebacterialpopulationsbecamedominantandsomeothersrecessiveatthetwolaterstages,whichcontributedtothevariationofthebacterialcommunitybetweenthetwogenotypes.Theseresultssuggestthatsoybeanplantscanmodifytherhizospherebacterialcommunitiesintheblacksoil,andthereexistedgenotype-specificbacterialpopulationsintherhizosphere,whichmayberelatedtosoybeanproductivity.

简介：Soilaggregatestability,animportantindexofthephysicalcharacteristicsofasoil,canprovideagoodindicationofasoil’serodibility,anddeservesspecialconsiderationinregionswithcoldclimate.Theobjectiveofthisstudywastostudytheeffectoffreeze-thawonsoilwater-stableaggregatesintheblacksoilregionofNortheastChina.Samplesofatypicalblacksoilintheregionwerecollectedtomeasurewater-stableaggregatesafterfreeze-thawunderdifferentconditions(i.e.,initialmoisturecontents,freezethawcyclesandfreezingtemperatures)bywet-sievingintoeightparticlesizegroups(>10,10–6,6–5,5–3,3–2,2–1,1–0.5,and0.5–0.25mm).Freeze-thawhadthemosteffectonaggregatestabilitywhenthesampleshadaninitialmoisturecontentof400gkg-1.Thewater-stableaggregatesofthefourlargerparticlesizegroups(>5,5–3,3–2,and2–1mm)reachedapeakstabilityvalue,butthoseofthetwosmallerparticlesizegroups(1–0.5and0.5–0.25mm)reachedaminimumvaluewhenthesoilmoisturecontentwas400gkg-1.Water-stableaggregatesofthefourlargerparticlesizegroupsdecreasedwhilethoseofthetwosmallerparticlesizegroupsincreasedwiththeincreaseoffreeze-thawcycles.Astemperaturesfell,thewater-stableaggregatesofthefourlargerparticlesizegroupsdecreasedwhilethoseofthetwosmallerparticlesizegroupsincreased.

简介：在中国的黄土高原上，干燥土壤层可以由于过量蒸发形成，导致蝗虫(Robiniapseudoacacia)承受的黑色的降级。为了更好设法，预测包含黑蝗虫，这研究被打算调查黑蝗虫蒸发率的反应玷污在黄土高原上用二代表性的土壤(卢拇的泥土和沙的沃土)由气象学的因素影响了的水可获得性。四个土壤水内容为在开始户外的壶然后在一个控制气候的房间种的黑蝗虫幼苗被维持，由弄干或灌溉壶。在两环境，每日的蒸发率被力量功能与空气温度并且由逻辑功能有关引用土壤水分蒸发蒸腾损失总量(et0)。蒸发率比在卢拇的黏土更产生处于在沙的沃土的气象学的条件的变化。在浇得好的处理的蒸发率为比在卢拇的黏土在沙的沃土种的黑蝗虫是更大的。规范的蒸发率由et0是未受影响的直到土壤水内容的批评价值(c)被达到；c价值为卢拇的黏土显著地减少了，但是当et0增加了时，为沙的沃土土壤显著地增加了。这些建议黑蝗虫的蒸发特征上的气象学的条件的效果依赖于土壤质地。