青藏高原与黄土高原毗邻地区晚更新世以来孢粉植物群及沉积环境

本文对青藏高原与黄土高原毗邻地区近20个剖面(点)的黄土沉积进行了孢粉分析表明,自晚更新世以来,研究区黄土剖面中古土壤层的孢粉种类、数量以及木本植物花粉成分均比黄土中多得多,反映了该时期研究区的气候条件比现今要温和湿润,植被较繁茂,以后逐渐旱化,但并不连续。此阶段研究区主要植物群的演替规律是:针叶林→森林草原→草原。     

萨拉乌苏河地区地层中的碎屑矿物及其所反映的中更新世末期以来之气候环境变化

文章根据对萨拉乌苏河地区第四纪地层中的碎屑矿物分析结果,将重矿物按其抗化学风化的能力不同分为不稳定、较稳定、稳定和极稳定四种类型,不同层位的重矿物类型的百分含量不同,从而可求出重矿物的风化系数HW。不同时期地层的HW不同,而HW的大小变化与化学风化的程度有很大关系,一般来说,化学风化作用强,HW相应变小。而化学风化作用的强弱又主要受气候的影响,从而可推测该时期气候环境的变化。     

青海共和盆地达连海湖泊流域表土花粉-气候响应面分析

孢粉分析是研究过去全球变化的一种重要方法,而研究花粉与现代气候之间的相互关系是古气候定量重建研究中的前沿课题。要预测未来气候的中长期变化,必须从花粉记录中定量提取古气候信息,建立的多种孢粉-气候数学模型必须经过不同边界条件下的古气候数据检验校正才能应用到实际当中。花粉-气候响应面方法是考虑了花粉与气候间的非线形关系上,提出的将现代花粉丰度在地理空间的分布转换为气候空间的分布,并以提供定量的古气候数据,已被广泛应用于COHMAP等各种重要古气候研究项目。本文就是利用该方法,以青藏高原东北部共和盆地达连海湖泊流域54个表土样品中的花粉丰度及采样点的气候参数为基础数据,通过主成分分析选择了特征值高且指示意义明显的4种花粉类型,对其丰度与7月平均温度及年平均降水量两个气候参数进行多项式回归分析,其结果显示模型对数据拟合较好,为定量重建该区古气候变化提出了较为准确的数量指标。     

Vegetation and climate changes over the last 30 000 years on the Leizhou Peninsula,southern China,inferred from the pollen record of Huguangyan Maar Lake

A pollen record from Huguangyan Maar Lake documents regional palaeovegetation and palaeoclimate changes in southern China over the last 30 000 years. Huguangyan Maar Lake is located close to the South China Sea (SCS) coastline and is influenced by the East Asian Monsoon (EAM). The pollen assemblages show a succession of vegetation and climate changes. During the Last Glaciation, 30–15.8 cal. ka BP, the Huguangyan area was dominated by subtropical evergreen‐deciduous forest with grassland surrounding the lake, indicating a colder and drier climate than today. During 15.8–11 cal. ka BP, the study area experienced several climatic fluctuations. From 11 to 2 cal. ka BP, the climate shifted to warmer and wetter conditions. After the Holocene Optimum in the early Holocene, the temperature and precipitation decreased. The sediment record of the last 2000 years cannot be used to interpret natural palaeoclimate changes due to the intense anthropogenic influences. Overall, however, the Huguangyan pollen archive highlights the rapid responses of subtropical vegetation to insolation changes in southern China.     

上海东部地区全新世孢粉组合及古植被和古气候

通过对上海东部地区南汇鹤鸣Hm孔、东海Dh1井、高桥G2孔3口钻井全新世地层的孢粉研究,划分出5个孢粉组合带和3个亚带,恢复了本地区古植被演替和古气候波动的5个阶段：第1阶段为针阔叶混交林-草地,反映气候温凉略湿（前北方期）;第2阶段为含常绿阔叶树的针阔叶混交林,反映气候温和略干（北方期）;第3阶段为以常绿栎类、栲属、杨梅等为主的常绿阔叶林,反映气候热暖潮湿（大西洋期）;第4阶段是以栎、松、禾本科为主的针阔叶混交林,反映气候温暖略干（亚北方期）;第5阶段是以落叶栎类、常绿栎类、松为主的落叶阔叶、常绿阔叶、针叶混交林-草地,反映气候温暖湿润（亚大西洋期）。这为本地区的地层年代划分和对比提供了可靠的证据,为全新世古植被、古气候及古环境的重建提供了重要的孢粉学资料。     

冀西北坝上全新世堆积及环境演变特征

冀西北坝上全新世岩性四分性明显，早期堆积物为洪、冲积并存，分布较少，中期以冲积为主，分布较,后转为风积，晚期为洪积、洪冲积、沼泽堆积。相应的气候则由较暖较干、温暖湿润、温度较干到温凉较干四个主要变化过程。     

北京环境考古

人类居住场所和生活方式受环境的显著影响。30,000年以来北京环境演变可分作6个阶段。旧石器晚期在干寒的环境下,古人类依洞穴而居。到新石器时代之初,气候变暖,有人类活动于山间谷地。后来,直到商、周时期,气候暖湿,人类多在山前台地上生活。到战国至西汉,气候明显变干变凉,人类向泛滥平原转移。北京的先民居住场所迁移的总趋势是,由山地而平原,由台地而低谷。农业兴起于新石器时代早、中期的山前二级台地上,发达于历史时期的低谷地带。北京城的兴起,地利起了重要作用。     

Modern pollen assemblages from surface lake sediments and their environmental implications on the southwestern Tibetan Plateau

The relationships amongst modern pollen assemblages, vegetation, climate and human activity are the basis for reconstructing palaeoenvironmental changes using pollen records. It is important to determine these relationships at regional scales due to the development of vegetation under different climatic conditions and human activities. In this paper, we report on an analysis of modern pollen assemblages of 31 surface lake samples from 31 lakes (one sample per lake) on the southwestern Tibetan Plateau where the knowledge of modern pollen and their relationships with vegetation, climate and human activities is insufficient. The region includes five vegetation zones: sub‐alpine shrub steppe, alpine steppe, alpine meadow and steppe ecotone, mountain desert and alpine desert. The lakes span a wide range of mean annual precipitation (50–500 mm) and mean annual temperature (?8 to 6 °C). Modern pollen assemblages from our samples mainly consist of herb taxa (Artemisia, Cyperaceae, Poaceae, Chenopodiaceae, etc.) and some tree taxa (Pinus, Fagaceae, Alnus, etc.). The results indicate that modern pollen assemblages are able to reflect the main vegetation distribution. Redundancy analysis for the main pollen types and environmental variables shows that precipitation is the leading factor that influences the pollen distribution in the study area with the first axis capturing 13.7% of the variance in the pollen data set. The Artemisia/Chenopodiaceae ratio is valid for separating the desert component (<2) from the steppe and other vegetation zones (>2) but is unable to distinguish moisture variations. The Artemisia/Cyperaceae ratio is able to identify meadows (<1) and steppes (>1) and can be used as a moisture index on the southwestern Tibetan Plateau. Our results show that an appropriate range is needed for a modern pollen data set in order to perform pollen‐based quantitative climate reconstructions in one region. It is essential to perform modern studies before using pollen ratios to reconstruct palaeovegetation and palaeoclimate at a regional scale.     

孢粉证据揭示MIS5a以来福建东北沿海地区人类活动、海平面及气候变化

通过获取了位于福建省宁德市海岸带的两个钻孔,并使用孢粉分析的方法来重建古环境.光释光和放射性碳十四测年结果表明,钻孔中最老的沉积物来自于深海氧同位素(MIS5a)阶段.孢粉组合中,海相沟鞭藻出现在MIS5a,MIS3早期和早、中全新世阶段,反映了这些时段的海侵事件.MIS5a以来,孢粉组合受控于常绿栎(Quercus)...     

安徽巢湖湖泊沉积物孢粉-炭屑组合记录的全新世以来植被与气候演变

利用湖泊钻孔的孢粉及炭屑分析资料,探讨了安徽巢湖湖泊沉积物孢粉-炭屑组合记录的全新世以来植被与气候演变。孢粉-炭屑记录表明：本区9870-6040 cal.{a BP},植被是以壳斗科的落叶、常绿属种为主的落叶阔叶、常绿阔叶混交林,气候呈现温和略干的特点;6040-4860 cal.{a BP},植被是以落叶栎类、栗属、青冈属和栲/石栎属为主的落叶阔叶、常绿阔叶混交林,气候由前一阶段的温和略干变为温暖湿润,进入全新世最适宜气候期;4860-2170 cal.{a BP},植被是以落叶栎类占绝对优势的落叶阔叶、常绿阔叶混交林,气温逐渐降低、湿度下降,气候温和干燥,环境整体向着干旱趋势转化,2170 cal.{a BP}左右出现一次明显的干旱事件;2170-1040 cal.{a BP},森林退缩,落叶阔叶、常绿阔叶混交林迅速被破坏,演替成以禾本科为主的草地,气候处于转型时期,总体上温和湿润;1040-200 cal.{a BP},木本植物仅零星分布,可能存在针叶阔叶混交林植被,植被类型逐渐演替成以禾本科、蒿属和蓼属等为主的草丛,其中包括较多的农作物,气候温凉稍湿;200 cal.{a BP}以来,湖区周围零星分布有阔叶乔木,松林在远处可能有分布,植被仍是以禾本科、蒿属和蓼属等为主的草丛,气候相对温暖湿润,但也有若干变凉干的波动,湖泊富营养化水平逐渐增加,人类活动已经对环境变化产生了较大的影响。