云南北海湿地沉积物记录的过去2050年气候演化及对区域人类文明的影响

Climate Variation during the Past 2050 Years Recorded in Sediments from Beihai Wetland,Yunnan Province,and Its Potential Influence on Civilization Evolution

过去2000年气候变化是深入了解过去全球气候演化机制、探索人类活动与环境演化相互关系的重要依据。我国西南地区是气候变化与人类文明研究的重要区域,获取更多记录资料对深入理解两者之间的相互关系尤为重要。本文以云南省腾冲县北海湿地沉积物为研究对象,利用AMS 14C测年建立年代学序列,利用烧失量、粒度分析结果建立了该地区过去2050年气候演变序列。结果表明:2050 cal.a B.P.~1400 cal.a B.P.期间尤其是最后阶段气候寒冷干旱;1400 cal.a B.P.~750 cal.a B.P.期间相对温暖湿润;750 cal.a B.P.~300 cal.a B.P.期间寒冷干旱;300 cal.a B.P.以来温暖偏湿。通过与云南地区人类活动记录对比发现,该地区人口的增长、社会政权的更替在一定程度上受自然气候环境演化的影响,南诏和大理民族政权的建立主要集中在相对温暖湿润的中世纪暖期;此外,云南地区近2000年来人口数量的变化与气候变化同样呈现出较好的一致性。

The variation of climate over the past 2000 years is the key to understanding the mechanism of past global changes,and for investigating the correlation between human activity and natural environmental evolution,especially in southwestern China which is directly influenced by the summer monsoon.A 2050⁃year continuous sediment core was recovered from the from Beihai Wetland,northwestern Yunnan province.Based on the age⁃depth model deter⁃mined by radiocarbon dating,grain size and loss on ignition(LOI)data was used to reconstruct regional climate variation.This showed distinct variations since 2050 cal.a B.P.The period between 2050 cal.a B.P.and 1400 cal.a B.P.was generally dry and cold,especially in the last 300 years of this stage.It then became warm and wet from 1400 cal.a B.P.to 750 cal.a B.P.,temporally consistent with the Medieval Warm Period(MWP).It was cold and dry during the Little Ice Age(LIA)from 750 cal.a B.P.to 300 cal.a B.P.,the last 300 years of which was characterized by increasing temperature and moisture.A comparison with historical records from Yunnan showed that the settlements of the Nanzhao and Dali Kingdoms existed mainly in the warm and wet conditions of the MWP.In addition,the variation in population of Yunnan also showed a close correlation with changes in the climate.Both aspects have confirmed the general influence of natural climate change on the evolution of civilization.