最近13ka以来长江中游古水文变化

长江中游是旱涝灾害频发区,但人们对该地区的古水文变化规律了解得很少.基于长江中游地区的大九湖泥炭沉积和 清江和尚洞石笋研究,综合集成4个古水文代用指标,重建了本地区13ka以来的古水文,探讨其变化规律,识别出持续时间 达千年以上的3个长时间尺度的较干时期(11.7~10.7kaBP、6.4~5.5kaBP、4.0~3.0kaBP)和3个长时间尺度的湿润期 (13.0~11.7kaBP、8.7~6.4kaBP、3.0~1.7kaBP).其中,8.7~6.4kaBP的长时间湿润期可能具有大区域性乃至全球性的特 点(全新世大暖期),对应于以定居的村落为规模的水稻种植发展.随后的6.4~5.5kaBP的长时间较干时期也具有大区域性 乃至全球性的特点,对应地出现了复杂的、具有国家性质的社会.长时间的湿润期之前或之后出现了长时间较干时期.此外,还 识别出5个短时间尺度的较干时期(9.8~9.2kaBP、9.0~8.7kaBP、5.0~4.2kaBP、1.7~1.1kaBP、0.7~0.0kaBP)与5个短 时间尺度的湿润期(10.7~9.8kaBP、9.2~9.0kaBP、5.5~5.0kaBP、4.2~4.0kaBP、1.1~0.7kaBP).长江中游地区大部分较 干时期表现出暖干的特点,这与北方的冷干现象不同.同时,湿润气候既可以出现在温暖时期,也可以出现在寒冷时期,水热配 置存在不稳定性.尽管古温度与古水文的关系比较复杂,但当温度从一种状态向另一种状态转变时,长江中游地区的干旱程度 加剧.长江中游古水文对古文化产生重要影响. 

Paleohydrological Variation since 13 ka BP in Middle Yangtze Region

MiddleYangtzeinSouthChinaiswellknownbythefrequentoccurrenceoffloodinginassociationwithdrought events.However,lessisknownaboutthehydrologicalvariationintheancienttimes.Hereweareabletoreconstructthepaleohydrologicalconditionssince13kaBPinthisregionbasedonthesynthesisof4proxiesextractedfromtheDa jiuhupeatlandand stalagmiteinHeshangcavenearQingjiangRiver.Threelong-termdrierperiods(11.7-10.7kaBP,6.4-5.5kaBPand4.0- 3.0kaBP)andthreelong-termhumid/floodingperiods(13.0-11.7kaBP,8.7-6.4kaBP,3.0-1.7kaBP),eachlastingover onethousandyears,wereidentifiedinthistimeinterval.Thehumidperiodat8.7-6.4kaBP(knownasHoloceneOptimum) isofabroadregionoronaglobalscale,whenthesedentaryvillage-basedricecultivationwasdeveloped.Thesubsequentdrier periodsat6.4-5.5kaBPisalsoofabroadregionorevenofglobalscalewhenthecomplicatestate-levelsocietystructurewas established.Thelong-lastingdrierperiodscouldbepresentedpriortoorpostthelong-lastinghumidperiods.Inaddition,5 short-termdroughtevents(9.8-9.2kaBP,9.0-8.7kaBP,5.0-4.2kaBP,1.7-1.1kaBP,0.7-0.0kaBP)and5shorttermhumidperiods( 10.7-9.8kaBP,9.2-9.0kaBP,5.5-5.0kaBP,4.2-4.0kaBP,1.1-0.7kaBP)werealsoidentified. InmiddleYangtzeregion,mostdrierperiodsoccurredatthewarmconditions,differentfromthecold-droughtassociationin NorthChina.Meanwhile,thehumidclimatecouldoccuratboththecoldandwarmconditions,indicatingthecomplicaterelationshipbetweentemperatureandhumidity.Itisnotablethatthearidityincreaseswhenthetemperatureshiftsfromonestateto another(i.e.,fromcoldtowarmorfromwarmtocoldconditions)inMiddleYangtze.Hydrologicalconditionsalsoplayanimportantimpactonhistoricalculturesinthisregion