通过对广东湛江湖光岩玛珥湖B孔顶部8～0.6m岩芯较高分辨率的孢粉分析,揭示了该区全新世植被、气候变化的历史:早全新世(约11600～7800cal a BP),木本植物花粉含量为56.0%,其中热带木本植物花粉含量占优势,最多的时期发生在9500～8000cal a BP左右,达到木本植物花粉的60.2%,反映气候热暖潮湿;中全新世(7800～4200cal a BP),热带-亚热带植物花粉含量明显下降,而草本植物和山地针叶植物花粉含量增加,指示了中全新世温度下降;晚全新世4200cal a BP开始,草本植物和山地针叶植物花粉明显增多,揭示出晚全新世湖光岩地区温度、湿度明显下降.研究结果表明,中国南方热带-亚热带地区高温湿润的全新世适宜期发生在早全新世(9500～8000 cal a BP),与全球低纬地区全新世气候变化格局一致.初步认为,全新世早期,在岁差周期的控制下,北半球较强的太阳辐射驱动了热带辐合带(ITCZ)和副热带锋面季风降水带同时向北推移,造成中国热带低纬度地区早全新世最适宜期.湖光岩地区中晚全新世气候干旱趋势和气候波动除了与北半球夏季太阳辐射强度减弱有关外,可能与该时期ENSO的活跃也有一定的联系.
A high-resolution pollen record of the past 13000 a from Huguangyan Maar Lake reveals the vegetation and environment changes in southern China during the Holocene. It shows that (i) pollen percentage of trees and shrubs reached 56% during the early Holocene (11600―7800 cal a BP), of which the pollen percentage of tropical trees reached a maximum at 9500―8000 cal a BP, reflecting a hot and wet envi- ronment; (ii) during the mid-Holocene (7800―4200 cal a BP), the pollen percentage of montane conif- erous trees and herbs increased, while the percentage of tropical-subtropical trees decreased, indi- cating lower temperature and humidity; (iii) in the late Holocene spanning from 4200 to 350 cal a BP, the pollen percentage of herbs and montane conifer increased significantly, indicating a marked decrease of temperature and humidity. Our pollen data reveal that the time period 9500―8000 cal a BP in south- ern China represents a climatic optimum for the Holocene characterized by hot and wet conditions. This is consistent with the Holocene optimum found in lower latitude regions globally. We speculate that strong insolation might cause the northward migration of the ITCZ and subtropical summer mon- soon front, which resulted in an early Holocene optimum in the Huguangyan area. The dry tendency and climate fluctuations of the middle and late Holocene could be associated with a decrease in solar insolation and frequent ENSO event.
WANG ShuYunLUE HouYuanLIU JiaQiJoerg F. W. NEGENDANK
