靖边地区全新世气候变化及植被演替

Holocene climate and vegetation changes reflected by the pollen record from Sandaogou loess section,Jingbian area,northwest of Chinese Loess Plateau

靖边地区地处季风边缘区,对气候变化响应十分敏感。为研究其全新世以来的气候变化及植被演替,文中根据靖边地区孢粉代用指标,结合AMS^(14)C定年,重建了该地区全新世以来的气候变化及植被演替。结果表明:该地区在全新世以来的气候变化经历了温凉偏湿-温暖湿润-温暖干燥-温暖偏湿-凉爽干旱5个阶段,植被演替划分为疏林草原-典型草原-干旱草原-典型草原-干旱草原5种类型。与季风边缘区典型剖面对比,靖边地区气候变化存在夏季风增强时间晚,最大有效湿度结束时间早、持续时间短的特点。

The Jingbian area is located at the margin of the monsoon,so where is very sensitive to climate change.In order to study the climate change and vegetation succession of monsoon margin since the Holocene,a Sandaogou loess section from Jingbian area,northwest of Chinese Loess Plateau was selected.The precise geological age was determined by AMS^(14)C.Pollen-assemblage reflects the climate change and vegetation succession of the East Asian Monsoon margin during the Holocene.The results showed that steppe dominated the vegetation of Sandaogou section during the Holocene.The climate change of Jingbian area could be divided into five stages since the Holocene.Pine forests and steppe expanded from 8.96 to 8.2 ka BP,implying a cool and wet climate.Typical steppe dominated the loess sediment from 8.2 ka BP to 6.9 ka BP,suggesting a warm and wet climate.From 6.9 ka BP to 4.7 ka BP,the climate became warmer and more arid,dry steppe was the main vegetation.Typical steppe recovered during 4.7~3.0 ka BP,the climate became warm and wet again.Both temperature and precipitation decreased from 3.0 ka BP to1.74 ka BP,as indicated by decreased Artemisia and the development of Chenopodiaceae,so dry steppe became the main vegetation again.Compared with the typical section in the typical area of the monsoon margin,the climate change in Jingbian area were characterized by late summer monsoon intensification,early end of maximum effective humidity and short duration.