30494.陜西定邊地區(qū)2400abp以來高分辨率的花粉記錄及環(huán)境變化

1、蘭州大學(xué)碩士學(xué)位論文陜西定邊地區(qū)2400aBP以來高分辨率的花粉記錄及環(huán)境變化姓名：蒙紅衛(wèi)申請學(xué)位級別：碩士專業(yè)：地質(zhì)學(xué)第四紀地質(zhì)學(xué)指導(dǎo)教師：馬玉貞20090501AbstractBasedonthechronologyofsevenAMS14C，two14Cdates，andthemodempollendata，adetailedhistoryofvegetationandclimatechangeduringthelast2400y

2、earsWasreconstructedbyahighresolutionpollenrecordfromGouchi，Dingbian，attheDesertLoesstransitioninNorthernChinaThestudyformodempollenshows：1)Eachvegetationcommunitycanbecharacterizedbyadistinctivemodernpollenassemblage；2)

3、thepollenofPinus，PiceaandArtemisia眥overrepresented；TheChenopodiaceaeexistsmainlyindesertsteppe；AlthoughPoaceaeisunderrepresented，higherpercentages(overl0％)maybefoundinthegrasslandwherethenaturalvegetationisbetterpreserve

4、d41familiesand57generaoffossilpollenwereidentifiedThreepollenassemblagezonesandsevensubzonesweredividedbasedonthevariationsofmainpollenpercentages，pollenconcentrationandtheresultofCONISSanalysisfromthebottomtothetopBased

5、onthemodempollendata，adetailedhistoryofvegetationandclimatechangesduringthepast2400calBPwasreconstructedbyahighresolutionpollenrecordfromDingbianItshows：between2400and1740aBPthevegetationwasforeststeppedominatedbyOakandt

6、heclimateWaswarmerandmoister；during17401610aBPthesteppeexpandedattheexpenseoftheforestregressionandtheclimateturnedtobedrier；during16101240aBParborealplantsincreased，openforeststeppedevelopedandtheclimatebecamemildandmoi

7、ster；12401010aBPtheforestretreatedwhilesteppeexpanded，suggestingadrierclimate；1010690aBPthesteppefurtherdevelopedandageneralwarmanddryclimateprevailed；690500aBPthedeciduousbroadleavedplantsincreasedandtheclimateWastemper

8、ate；500190aBPthevegetationwassteppeandtheclimatewasdrier；1900aBParborealplantsincreased，／ndicatingamoisterclimateTheclimatebypollenrecordshowsthreewarmperiodsinDingbianThewa_rlnerandmoisterperiod(24001740calBE)beinginacc

9、ordwithQin—HanDynastyWarmPeriod；themildandmoisterperiod(16101240calBE)correspondswithSuiTangDynastyWarmPeriod；andthedryperiod(1010690ealBP)c觚correlativewiththeMedievalWarmPeriodInaddition，theecosystemdegradationinterval(

10、500190calBE)maybebecomparewith“LittleIceAge”，thoughtheclimatefluctuationofwarm／coldrepresentnotobviouslyKeywords：DesertLoesstransitioninNorthernChina，Hiighresolution，Pollenrecord，Vegetationandclimatechange，duringthelast2