上海青浦8.5kaB.P.以来植被演变与气候波动

Paleovegetation and paleoclimate fluctuations in Qingpu Area,Shanghai since 8.5 ka B.P.

钻孔取自上海青浦县赵巷镇 ,柱长 1 9.8m,5个14 C年龄 ( AMS测定 )年代跨度从 1 3 4 60± 60 a B.P.到 2 660± 60 a B.P,但缺失全新世早期沉积。对 1 5m以上 ( 8.5a B.P.)部分系统采集了 3 5孢粉样品 ,样品分辩率在 1 50 a左右 (少数样品除外 ) ;通过有序分割并综合图谱特征划分出 7个孢粉带和 2个亚带 ,据此恢复和重建了本区 8.5ka B.P以来植被变化和气候波动历史。具体结果为 :与现今气候相比 ,8.5a B.P.～ 8.2 ka B.P.为冷干期 ,但气候呈上升趋势 ,地带性植被为含常绿阔叶树种的落叶阔叶林 ;8.2 ka B.P.～ 8.0 ka B.P.为暖湿期、常绿阔叶林 ,气候处于峰值 ,温度高于现今 2℃左右 ,降雨量高于现今 4 0 0 mm左右 ;8.0 ka B.P.～ 7.6ka B.P.为冷干期、落叶阔叶和针阔混交林 ,气候处于谷值 ,温度低于现今 2℃左右 ,降雨量少于现今 4 0 0 mm左右 ;7.6ka B.P.～ 6.2 ka B.P.为暖湿期、常绿阔叶林或常绿、落叶阔叶混交林 ;6.2 ka B.P.～4 .0 ka B.P.为温干期、含常绿阔叶树种的落叶林或针阔混交林 ;4 .0 ka B.P.～ 3 .0 ka B.P.为温凉略湿期、含常绿阔叶的落叶阔叶林 ;3 .0 ka B.P.～ 1 .5ka B.P.为暖湿期、常绿阔叶林 ,但 2 .6ka B.P.以来又有变冷趋势。文中还对常绿阔叶木本孢粉与总木本孢粉的比值 (

A 19.8m long sediment borehole ZX 1 was recovered in Zhaoxiang of Qingpu County,Yangtze delta plain of eastern China.Five samples were selected from lower core section through upper core section for Accessory Mass Spectrum(AMS)dating.Dates obtained range from 13 460±60 a B.P.to 2 660±60 a B.P.Thirty five samples were taken from upper 15 m core sediment(since about 8.5 ka B.P.)and were analyzed for spore pollen.Seven spore pollen zones and two sub zones were distinguished by means of constrained cluster analysis and the spore pollen spectrum.Spore pollen records indicate that from 8.5～8.2 ka B.P.,climate warmed rapidly,but was cooler and drier than today.Landscape of the study area during that time was covered by the deciduous broad leaved forest with a few evergreen broad leaved species,such as Castanopsis and Cyclobalanopsis glauca. During 8.2～8.0 ka B.P.,evergreen broad leaved froest prevailed,implying hot and humid climate.Our survey suggests that the averaged temperature of the study area be 2℃ higher than today and precipitation be about 400 mm more than that of the present.By the time period from about 8.0 to 7.6 ka B.P., Pinus forest dominated the study area to indicate a cold and dry climate.Spore pollen climate of 7.6～6.2 ka B.P.was consindered as the optimum period in Holocene,as represented by the evergreen broad leaved,or the evergreen and deciduous broad leaved mixed forests.Climate was primarily warm and humid.From about 6.2 to 4.0 ka B.P., Pinus and Cupressaceae increased while Ephedra,Tsgua and Betula can still be present.This vegetation combination indicates a cool and dry climate.Between 4.0～3.0 ka B.P., Castanopsis and Cyclobalanopsis glauca prevailed again,while Tsgua,Larix and Betula occurred to reflect cool,but a somewhat humid as compared with the last period.From 3 0～2.6 ka B.P.,the evergreen broad leaved forest appeared as implying warm and humid climate setting.This climate was followed by cooler and drier climate after 2.6 ka B.P.