秦安振开题报告.docx
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秦安振开题报告.docx
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秦安振开题报告
甘肃农业大学
硕(博)士研究生论文开题报告
所在院系农学院
学科专业作物栽培学与耕作学
学位级别博士
学生姓名秦安振
入学时间2007年9月
导师姓名黄高宝,柴强
课题名称不同间作模式的土壤
呼吸差异及其机理
甘肃农业大学研究生处制
2011年1月7日
一、立论依据(以下各项均可加页)
(包括课题的研究意义,国内外研究现状分析,附主要的参考文献)
1.SignificanceofTheResearch
NorthwesternaridareaisoneofthemostfragileecosystemsbutdeeplyinfluencestheotherregionsofChina.Theareaofaridregionis3.15×106km2,accountingfor33percentoftotallandareaofChina,cultivatedlandsofNorthwesternaridareaaccountfor12.5percentoftotaltillablearea.Oasisisconsideredasasortofspeciallandscapeterrain,playinganimportantroleonagriculturaldevelopmentinNorthwesternarea.OasisareaofChinaonlyaccountsfor3.3percentofaridarea,whilethecropproductivityofthisareafostersmorethan90percentoflocalpopulation,creating95percentofagriculturalproductionvalues(Zhangetal.,2004).OasisiswidelydistributedinHexicorridorwhosetotaloasisareais1.94×104km2,totalpopulationis4.76million,accountingfor18.8percentoftotalpopulationofGansuprovince.
IthasbeenalonghistoryforHexiaridirrigationareatodevelopintercroppingpatternsbecausesolarresourceandannualradiationareadequatelysufficient.Inthisarea,watersourceismainlyderivedfromtheriverofShiyangandHeihe,thusgivingsufficientundergroundwaterfortheloweraltituderegionlikeHexiirrigationarea.Nowadays,wehavetofacetheseriousproblemsofinsufficientflowingamountsofriverandloweringwatertable,thesnowlineofQilianMountainhasbeenshrinkinggraduallybecauseoftheclimatechange.Atthesametime,humanactivitiessuchasfossilfuelcombustion,farmlanddisturbanceandlandconversionhadelevatedtheatmosphericconcentrationofCO2(Matsonetal.,2002),thosepracticesexertedaninevitableimpactonCO2fluxesofterrestrialecosystem,givingrisetoincreasingofcarbonemissions.Landusechangesuchasconvertinglandfallowtoannualcoveringalsoinfluencedsoilcarbonstorage.Thesimilarreportshadbeenissuedbyscholarsintermsofeffectofstrawreturn,stubbleincorporatedandcropallocationetc.onCO2sequestrationinagroecosystem(Bolinetal.,1977;Ojimaetal.,1993;Rounsevelletal.,1999;Amundasonetal.,2001;IPCC,2001;Keelingetal.,2002).Reportofthe32ndsessionofIPCC(IntergovernmentalPanelonClimateChange)(2010,Busan,Korea)indicatedthatlandusechangeandmanagementwerethemostimportantfactorsimpactingCO2emissionsfromterrestrialecosystem,andtheappealsfordevelopinglow-carbonagriculturebecamestrongerthanwheneverelse.Howtoselectlow-carboncropsisoneofessentialaspectstoidentifylow-carboncroppingsystem.Inthisstudy,accordingtolocalplantingtraditionwechosefourmainlyintercroppingpatterns,namely,wheat//maize,wheat//soybean,maize//peaandmaize//rapeandfivecorrespondingmonocroppingtreatments(i.e.solewheat,solemaize,solesoybean,solepeaandsolerape),givingtotallyninetreatmentsfortheexperimentaldesign.Wemeasuredsoilrespirationofalltreatmentstosiftthroughmono-andinter-croppingpatternsforlow-carbontreatments.
UnderstandingofCO2sourceandsinkcharacteristicsofagroecosystemsisoneofthemostcriticalproblemsatpresent,buttillnow,moststudiesconcerningthenaturalterrestrialecosystemcarboncyclesareconcentratedontheforestandgrasslandecosystem.Notenoughattentionispaidtotheagroecosystem,especiallytothetemperatearidfarmland.Sofar,thespatialandtemporalvariationsinsoilrespirationanditsrelationshipwithbiophysicalfactorssuchassoiltemperatureandmoistureonfarmlandscaleofHexiirrigationregionremainedhighlyuncertain.Nevertheless,despiteitsglobalsignificance,aswellasconsiderablescientificcommitmentstostudiesinthisfieldoverthepastdecades,wewerestilllimitedbyunderstandingofthefactorscontrollingtemporalandspatialvariabilityofsoilrespiration(Zhang,2000;Zhouetal.,2003;Reichsteinetal.,2003).SoiltemperatureandmoisturearetwoofthemostimportantenvironmentalparameterscontrollingvariationsinsoilCO2efflux(RaichandSchlesinger,1992;FangandMoncrieff,1999;Davidsonetal.,2000;Liuetal.,2002;Reichsteinetal.,2003).However,therelationshipsbetweensoilrespirationandtheseenvironmentalfactorsvaryindifferentecosystems(Moiser,1998;Buchmann,2000;Rustadetal.,2000).Thisvariabilitycallsformoremeasurementsofsoilrespirationtoexploreitsenvironmentaldependenceonafarmlandscale.Inthisstudy,fieldexperimentswerecarriedouttoinvestigatetheeffectsofdifferentcroppingpatternsontemperatureandmoisturesensitivitytosoilrespirationbetweenAprilandSeptember,from2009to2011.Toexaminethesoilrespirationwithinthescopeoffarmland,comparisonofdifferentcroppingpatternsiseffectiveasthevariouskindsofcropsaretemporallyandspatiallyheterogeneous.TheobjectivesofthisstudyweretoestimatethelowestCO2releasingpatterns,topredictseasonalCO2fluxunderdifferentpatternspergrowthperiod,toquantifytheimpactsofsoiltemperatureandmoistureonsoilrespiration.
2.Currentresearchsituationathomeandabroad
Terrestrialecosystemisoneofmostactivesoilcarbonpools,theamountsoforganiccarbonatdepthof1misabout2×103Pg,thereare1/3ofthetotalcarbonstoragesequestratedinforestpedosphere,1/3inprairieandsavanna,1/3inwetland,farmlandandotherbioticorganism(Amundason,2001).Rounsevell(1999)estimatedthetotalorganiccarbonpoolofglobeis1288-1939PgC,andthestorageinuppersoillayersisaround500Pg.IPCC(2001)reportedthatexchangecapacityamongeachcarbonpoolwasvarious,carboneffluxfromthedecompositionofsoilorganicmattertoatmospherewas50PgC/yr,CO2effluxemittedbyterrestrialecosystemsis50PgC/yr,fixationofCO2fromatmospherebyplantphotosynthesisis102PgC/yr,fossilfuelcombustionandforestlogginggaveaCO2effluxof5PgC/yrand2PgC/yr,respectively.Observationandtheoreticalresearchprovedthathumanactivitieswerethemainfactorcausingtheincreasingconcentrationofgreenhousegasviafuelburningandlandusechange.
2.1Organiccarbonstorage
Soilorganiccarbonpool(SOCP)referredtototalamountsofglobalsoilorganiccarbon.Photosyntheticproductionswerereallocatedintofourcarbonpoolsofagroecosystemi.e.biomasscarbonpool,soilorganiccarbonpool,leafandlittercarbonpoolandsoilanimalcarbonpoolinthecarboncyclesandenergyflowprocesses.Biomasspoolhadstoredlargeamountsoforganiccarbon,generallyspeaking,0.45-0.50wastheconversioncoefficientbetweenbiomassandcarbon.Soilcarbonpoolwasthelargestcarbonpool,consistedofleaves,litter,bioticdetritusandexcrementswhichweretransformedintoorganicmatterbymeansofhumification.Generally0.58wasdefinedasconversioncoefficientbetweensoilorganicmatterandorganiccarbon.
Bolin(1977)calculatedtotalcarbonstorageatadepthof100cmas710GtaccordingtoninedifferenttypesofsoillayersinUSA;Ojima(1993)simulateduppersoillayer(20cm)carbonstorageon31representativespotsoutof7grasslandecosystemsusingCENTURYmodel,theresultsindicatedthatsoilorganiccarboncontentandtotalstorageoftemperateprairiewerehigherthanthoseoftropicalsavanna.Carbonexchangebetweensoilandotherecosystemsprovidedbasisofcalculatingsoilcarbonchanges,soilrespirationandsoilsolublecarbonwerethemainpathwaysforcarbonexchangesamongpedosphere,atmosphereandhydrosphere,whichweredrawnmuchattentioninstudiesonglobalclimatechange.ByusingaBiogeochemicalModeldrivenbyclimatic,edaphicandvegetationaldata,Li(2002)etalreckonedsoilcarbonstorageinChinawas82.65Gt,accountingfor4percentofglobalcarbonstorage,generallycarbonstorageofSoutheasternChinawasgreaterthanthatofNorthwesternsemiaridareas,carbondensitywasgreatestinNortheasternChinaandsoutheasternedgesofQinghai-TibetPlateau,indicatingsoilcarbondensitywasinfluencedbyvegetationalandclimaticfactors.Zhangetal(2007)observedspatialdistributionofsoilorganiccarbonandtherelationshipbetweensoilorganiccarbonandsoilproperties&climaticconditionsinmiddlereachesofHeiheRiverinNorthwesternaridareas,resultsshowedthattotalsoilorganiccarbonstorageofHeiheRiverBasinwas94.72Tg,activatedorganiccarbonstoragewas45.12Tg,inertcarbonstoragewas49.60Tg.
2.2Soilorganiccarbonbalance
Theamountsofcarbonsequesteredinagroecosystemsequatestothebalanceofcarboninputsandlossesovertime,andisrelatedtobothbiotici.e.substratequalityandabiotici.e.temperatureconditions.Carbonsequestrationofagroecosystemdependedontwocontrastiveprocessesi.e.inputandoutputofcarbon.Theinputofcarbonwasmainlyvianetphotosynthesisofplants,whiletheoutputofcarbonmainlyreferredtosoilandbioticheterotrophicrespirationandmineralizationoflitters,inaddition,variousdisturbancescouldalsoimpactcarbonoutputofecosystems(Yangetal.,2005).
Agroecosystemwasoneoftheecosystemsthatweregreatlyinfluencedbyhumanactivities.CO2fixationbyplantphotosynthesismadelargeamountsoforganiccarbontransfertoplantresides,cultivationpracticessuchasplowing,tillage,irrigationandfertilizationetc.accelerateddecompositionandturnoverofsoilorganiccarbonafterplantresideswereputintosoils,resultingindynamicsofsoilcarboncontent.Inthemeantime,changesoforganiccarboncontentcouldalsoaffectandcontrolothermaterialandnutrientprocesses,toresearchorganiccarbontransformationand
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