内蒙古东南部季风气候尾闾区全新世降水量时空差异性的孢粉学证据

内蒙古高原东南部森林草原过渡带位于中国东部季风气候尾闾区,是全球变化研究的关键区域.这一地区降水量存在着明显的东南至西北(SE-NW)梯度.在现代植被和表土花粉分析的基础上,建立了内蒙古高原东南缘森林草原过渡带孢粉-降水量转换函数.将研究区森林草原过渡带内3个湖泊沉积剖面的孢粉分析结果代入转换函数,定量恢复了这一地区全新世降水量的变化过程.结果表明:3个剖面全新世以来降水量变化的过程存在明显的差异,北部的好鲁库剖面在1 100 a BP以前一直呈减弱的趋势,而南部的碌轴湾剖面和小牛场剖面降水量在分别在7 800-6 200 a BP和7 200-5 000 a BP出现降水量的峰值,作者推断这种时空差异性与西南季风的影响、地形条件的差异有关.     

成都平原4 000aBP以来的孢粉记录与环境变化

成都平原晚全新世以来沉积的泥质层发现丰富的孢粉。根据孢粉成分组合特征和生态类型可划分出5个孢粉组合带,结合剖面上6个14^C测年数据,提出在过去的4000a研究区植被类型及气候环境经历了5个阶段的变化：3800-3600aBP为亚热带常绿阔叶林,气候暖偏湿;3600-3400aBP为含常绿树种的落叶阔叶林,气候温暖湿润;3400-2600aBP为草／湿地,气温下降,环境更潮湿;2600-900aBP为落叶阔叶林,温度又开始逐渐回升,气候温和偏湿;900-300aBP再次变为草／湿地,偏干冷的气候环境。     

内蒙古大青山调角海了地区全新世气候与环境重建研究

以全封闭湖泊调角海子湖相沉积的高分辨率采样为基本分析材料,采用孢粉分析,沉积地球化学分析,14C测年等多种分析手段,对调角海子地区全新世气候与环境进行了综合研究,结果表明：全新世气候与环境演化可划分为5个阶段,其中后两个阶段又可分为3个亚段;全新世大暖期的时代为9400－3800aBP;全新世大暖期具有二分性;6900－6300aBP为全新世气候最适宜的鼎盛期,当时气温比现在高2－3度,降水量至少高于现代150－200mm,植被为针阔叶混交林。     

基于若尔盖高原湿地唐克剖面孢粉记录的古气候重建北大核心CSCD

对青藏高原东北部若尔盖高原湿地唐克泥炭剖面TK1采样点按10cm间距作孢粉分析,依据主要孢粉类型的百分比关系,以及加速器质谱(AMS)14C测年数据,将剖面孢粉组合大致分为上下两个带。在下带,莎草科均在65%—75%之间变化,表明了相当稳定的气候条件。结合若尔盖表土孢粉数据和唐克泥炭剖面孢粉数据,首次定量重建了唐克7940cal.aBP以来的古气候变化规律:7940—6420cal.aBP,年均温0.72—1.48℃,年降水量650.34—662.29mm;6420—3790cal.aBP,年均温0.56—1.62℃,年降水量647.79—662.34mm;3790—1580cal.aBP,年均温0.54—1.65℃,年降水量647.40—657.71mm;1580cal.aBP至现在,年均温1.45—1.73℃,年降水量661.86—666.41mm。相应于气候变化,沼泽发育也依次经历了4个时期变化,即沼泽化过程发展期—沼泽大发展期—沼泽发育波动期—沼泽再度大发展期。     

内蒙古高原东南缘森林草原过渡带景观的若干特征

内蒙古高原东南缘森林草原过渡带位于中国东部暖温带落叶阔叶林向温带草原过渡的区域,本研究区的范围为115°45′～117°45′E,42°00′～43°45′N。以群落分类和分布规律为主要依据,利用遥感影象,划分了研究区内的植被界线,并分析了过渡带内部植被的空间分异。结果表明研究区内森林带、过渡带和草原带的界线明显,过渡带内部由于地貌条件的差异可进一步划分为高原边缘山地森林草甸景观、高原森林草原景观和山地森林草原景观。从东南向西北做一条样带,可以发现,从森林到森林草甸,进而到森林草原和草原,物种的递变明显。森林带有大量的本带特有的种类,这些种类为暖温带落叶阔叶林北部的常见种类,说明本区的落叶阔叶林并没有处在落叶阔叶林带的气候边缘,而是由于地貌的变化才迅速向森林草甸进而向森林草原过渡;高原边缘山地森林草甸景观与高原森林草原景观的共有种类少,二者各自均有大量特有种。从森林带过渡到高原边缘山地森林草甸,水热组合由暖湿向冷湿方向发展,这种变化是由坝缘山地的迅速升高所引起的。从高原边缘山地森林草甸过渡到高原森林草原,温度状况逐渐好转而降水量呈逐渐下降的趋势,说明研究区内高原边缘山地森林草甸与高原森林草原的差异在很大程度上是由海拔高度的分异所引起的。由过渡带进入草原带,降水量逐渐下降而温度状况变化不明显,水分不足是限制森林生长的主要因素。森林草原景观的植被性质为森林和草原/草甸的镶嵌分布。群落调查的结果表明,研究区榆树疏林不属于森林草原,而是草原带的超地带性群落类型。     

黄土高原西部4万多年以来植被与环境变化的孢粉记录

采集甘肃静宁、定西、秦安等地晚更新世晚期以来几个黄土剖面的孢粉样品,分别以晚更新世每个样品分辨率200—300年,全新世20—200年,揭示了黄土高原西部4万多年以来古植被曾经历过草原、森林草原(或疏林草原)、针叶林以及荒漠草原或荒漠几种植被的多次快速变化。在44.2—11kaBP期间,静宁地区植被主要表现为森林和草原成分的相互消长,其中44—29kaBP期间(MIS3)气候以湿润为主,发育针叶林,温度低于现在;23kaBP之后,气候冷干,以稀疏草原为主,在末次盛冰期植被甚至演化为荒漠草原。全新世大部分时间内是以草原或森林草原(或疏林草原)植被为主。在全新世中期,约7.6—5.8kaBP有近1700年时间发育有森林植被,在这个时期当地自然植被覆盖度较高,而草原或疏林草原发育时期植被往往较稀疏,反映气候相对干冷。根据出现的不同类型植物的孢粉浓度及其生态环境特性,研究区早、中全新世,约8.8—5.8kaBP沉积环境较湿润;自3.8kaBP以后气候环境总的变化趋势是逐渐变干,植被开始向草原荒漠化演变。然而,研究区整个全新世气候环境存在多次干湿交替现象,据孢粉记录,其中可能存在11次气候干寒事件。     

新疆天山北坡地区中晚全新世古生物多样性特征

选择新疆天山北坡不同海拔高度、不同植被带和不同沉积年代的大西沟、桦树窝子、小西沟、东道海子和四厂湖剖面计算孢粉复合分异度指数,并根据已发表的有关文献中关于粒度、磁化率、烧失量等多项分析的数值整合结果探讨了本区中晚全新世以来生物多样性的时空变化和环境特征。森林草原过渡带的古生物多样性远高于高山、亚高山草甸带和荒漠带,孢粉复合分异度较高,鉴定的孢粉科属数较多。3600~3200 aB.P.、1700~1400 aB.P.、1000~600 aB.P.和450 aB.P.以来4个时段的生物多样性偏高。大西沟地区3600~3200 aB.P.期间和四厂湖地区中世纪期间气候均较湿润,其古生物多样性也较高,可见古环境演变和古生物多样性的动态变化具有相对一致性,孢粉复合分异度指数在一定程度上可以反映气候与环境的变化。但由于孢粉鉴定的精确度较差、受外来花粉的干扰等多种因素影响,使得孢粉多样性指数在反映生物多样性和古环境方面存在一定的偏差。     

宁波北仑全新世有孔虫群落变化及古环境意义*

通过对宁波北仑NBBL钻孔约6.5m长柱状样中的有孔虫进行分析及定量统计,结合AMS14 C测年结果,恢复了宁波北仑中晚全新世古环境变化历史。研究结果显示,该区在全新世经历了一个完整的海进-海退演变过程。早中全新世(~7 300Cal aBP以前),宁波北仑为陆地;自~7 300Cal aBP开始,海水开始影响北仑地区,该区域为滨岸沼泽相;~7 150—2 480Cal aBP演变为近岸浅海环境,此时段为海侵最盛期;~2 480Cal aBP以后,海水影响逐渐减弱;其后海水完全退出该地区,北仑地区变为陆地。     

花粉—气候因子转换函数建立及其对古气候因子定量重建

以中国北方215块表土孢粉样品分析结果中的13种花粉类型与4种气候参数为基础资料建立花粉-气候因子转换函数。同时选取内蒙中部调角海子DJ钻孔岩芯高分辨率孢粉分析结果为材料,定量重建该地区10000～2100 a BP古气候因子数值特征。研究结果表明:内蒙古调角海子地区进入全新世后温湿状况较前全新世有了明显好转,在中全新世形成最为良好的气候要素组合。最高年平均温度比现在高4℃左右,最低年平均温度比现在低2℃左右。7月份和1月份平均温度的分析结果表明,1月份平均温度变化趋势较7月份的更接近年平均温度的变化趋势,说明该地区冬季温度占主导地位。在气候转折时期,气温和降水随时间的变化梯度明显加强,波动幅度为4～5℃。     

河北迁安盆地中全新世以来的植被变化及人类活动的影响(英)

依据位于燕山南部迁安盆地蚕姑庙村和余家洼村具放射性碳年代测定支持的埋藏泥炭剖面的孢粉分析资料 ,揭示了迁安盆地 5 0 0 0aBP以来自然植被变化和人类活动对自然环境的影响。在 4 6 0 0～ 310 0aBP期间 ,迁安盆地曾经生长着以栎为主的落叶阔叶林 ,至 310 0aBP以后 ,森林中阔叶树成分显著下降 ,喜凉耐干的松树比例增加 ,16 0 0aBP后 ,迁安盆地人类农耕活动进一步加剧 ,森林遭受到大规模的破坏。孢粉分析资料揭示迁安盆地人类栽培板栗的历史可以追溯到 16 0 0aBP左右 ,种植水稻的历史可以追溯到 70 0aBP左右。     

The Dry Holocene Megathermal in Inner Mongolia

The paleoclimate since 14 kyr BP (¹⁴C age) was reconstructed based on a 16.22-m-long sediment core collected from Lake Yanhaizi, a saline lake located near the northern limit of the East Asian summer monsoon in Inner Mongolia. Coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated. These sediments have low organic carbon contents but high maturity indices, indicating that they were deposited in an arid environment. By contrast, based on high organic contents and low maturity indices, fine sediments were deposited during periods of high lake stand in a humid environment. It was in general dry between 8.0 and 4.3 kyr BP. The above dry and wet phases are consistent with those recovered from the arid-semiarid transition zone elsewhere, but are unlike the widely perceived humid Holocene Megathermal reported in east China and the newly reconstructed record in the alpine Retreat Lake in Taiwan. The discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon. On the other hand, much enhanced evaporation over higher monsoon precipitation at Lake Yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon. This also accounts for the fact the high-temperature Holocene Megathermal, as revealed in the Okinawa Trough and the northern South China Sea, is correlated to the dry phases at Lake Yanhaizi. Conversely, the 4-2-kyr BP coldest period in the Holocene corresponds to a wet phase at Lake Yanhaizi.     

New High Resolution Pollen Records from Two Lakes in Xizang (Tibet)

Studies on the pollen from cores of Lake Hidden (29~48.77' N, 92~22.37' E) and Ren Co (30%3.97'N, 96~40.97'E) in Southeast Xizang (Tibet) showed climatic changes and the evolution of vegetation since the last Glacial Maximum (LGM). Before 16 ka BP pollen assemblages were dominated by Chenopodiaceae (20% -50% ) and Artemidis (10% ~ 30% ) and pollen influx values were very low from Lake Ren Co in Basu county. The vegetation around the lake was probably a desert-steppe during the LGM. The data also suggest that the climate in the Basu area was cold and dry during the LGM and the last glacial time. The mean annual temperature was probably 4 ~ 6 ℃ colder than the present, and the mean annual precipitation was only 250 mm, about 40% of the present. The Southwest monsoon became stronger from 12 ka BP to 6 ka BP reaching its acme by 7 ka BP, but weakened gradually from 5 ka BP to the present. The paleovegetation was dominantly forest or forest-meadow around Lake Hidden and Ren Co during the 9.2 ~ 5 ka BP. The mean temperature in January was probably 2 ~ 3 ℃ higher than the present, and the mean annual precipitation was 100 mm more than the present. The timing of vegetational and climatic changes based on pollen records generally supports the results of global climatic-model experiments that predict a strengthened monsoon system during the early to middle Holocene followed by a weakened monsoon system.     

Character of a Nology and Changes of Monsoon Climate Over the Last 10000 Years in Gucheng Lake,Jiangsu Province

Systematic palynological research was conducted on more than 343 samples from a column or rock core obtained by drilling to a depth of 20 m in Gucheng lake. According to three assemblage zones and nine subzones of the sporo-pollen, and the dating of 14℃, we have explored the regularity of palaeoclimatic changes and palaeomonsoon activities since 15.0 ka BP. During 15.0 ～ 11.0 ka BP, the temperature had increased a little, but the climate was still cool and relatively dry, reflecting a weak wet monsoon and low precipitation at that time. In the period of 3～11.0 ka BP, it became cold and wet, with an increased effect of the dry monsoon, and the area was probably situated in a position of the frontal zone. Causing considerable effective humidity. Later than 11.0 ka BP, the temperature increased rapidly within 500 years with a subsquent, turn of the climate towards significantly warmer and wet and a further intensification of the monsoon effect. This rapid temperature increase corre-sponded to the increasing radiation of solar energy during 11.0～10.0 ka BP. From 10.5 to 6.4 ka BP, the wet monsoon was the priority climate of the region, albeit there were at least two or three spells of cooling, as well as decreasing of monsoon precipitation.     

Pollen-based quantitative reconstructions of Holocene climate variability in NW Romania

A modern analogue technique is applied to two high-resolution pollen sequences from NW Romania to provide the first quantitative evidence for winter, summer and annual temperatures and for precipitation across the Holocene in this region.

The pollen-based climate reconstructions allow the identification of four main intervals: i) an early, less stable period between 11,700 and 11,200 cal. yr BP; (ii) generally stable conditions between 11,200 and 8300 cal. yr BP with winter and annual temperatures and precipitation higher than at present, and summer temperatures about the same; (iii) lower winter and annual temperatures, and higher summer temperatures and precipitation between 8000 and 2400 cal. yr BP; (iv) warmer winter and annual temperatures and lower precipitation for the last 2400 years, whereas summer temperatures became cooler at Steregoiu and remained stable at Preluca Tiganului.

The pollen-based climate reconstructions at the two sites show similar patterns in annual and winter temperatures and precipitation changes during the Holocene, but the trends appear to be less consistent for summer temperatures.

Our pollen-based reconstructions revealed several short-term climatic oscillations during the Holocene, the strongest of which occur between 10,300–10,100, 8300–8000, 6800–6400, 5100–4900, 4000–3600 and 3200–3000 cal. yr BP.     

Vegetation history with implication of climate changes and human impacts over the last 9000 years in the Lake Nanyi area,Anhui Province,East China

Palynological analyses in combination with radiocarbon dating on a Holocene borehole from the Lake Nanyi, Anhui Province, East China demonstrate a well-documented local vegetation evolution since 9000 cal BP, which is the first record of Holocene climate change and human impact in this region. Since 9000 cal BP a mixed evergreen and deciduous broad-leaved forest dominated by Cyclobalanopsis and Quercus developed in this area, indicating a warm climate condition with enhanced insolation. A mixed evergreen and deciduous broad-leaved forest was fully developed between 6600–4500 cal BP, which corresponds to the Holocene Climate Optimum with the strong influence of East Asian summer monsoon (EASM). After 3000 cal BP the broad-leaved forest decreased rapidly, while land herbs and ferns increased. It seems that the climate condition in East China was similar to the present after Holocene Climate Optimum. Pollen results show a potential interface between environment changes and human activities. Pollen diagram demonstrates that human impacts on the natural vegetation remained weak at the early stage but significantly enhanced upwards. The distinctive fluctuations of the pollen contents among AP (trees and shrubs), and the possible agriculture indicators might infer the potential human behaviors for environment changes. Due to the enlargement of organized farming and increase in population, natural forest was eventually replaced by farmland since 3000 cal BP. This study would increase our knowledge of Holocene vegetation transition related to the monsoon dynamics on a long timescale in East China and provide an environmental background for more detailed studies on cultural developments in the middle and lower reaches of the Yangtze River region.     

Fire and Pinus mugo Turra communities in the western Alps (Susa Valley, Italy) during the Lateglacial-Holocene transition: an evidence of refugia area

In western Italian Alps, small distinct populations of Pinus mugo Turra raise some questions concerning its ecological status and dynamics in the occidental Alps. This note present new palaeobotanical data based on cone imprints of Pinus mugo, identified in travertine systems located in the Val di Susa and dated back to the Late Dryas (11506+/-66 BP) and the Early Holocene (10145+/-225 et 9475+/-670 BP). Heliophilous species and charcoal fragments were also identified, testifying to the oldness of wildfires in this region. The data support the hypothesis that this zone was a refuge area of this pine during the last glaciation. Here we discuss about the postglacial dynamics of the Pinus mugo in the occidental Alps.     

青藏高原东南部18ka以来气候与水文变化

青藏高原东南部众多封闭小湖的湖相沉积记录着重要的地理信息,是恢复当地晚更民以来古环境演变的理想材料。西藏海登湖和仁同分辨率的花粉组合,ＡＭＳ＾１４Ｃ测年及磁化率和有机质含量测定,揭示了研究区与鳊季风密切相关的古植被,古气候和古水文变化历史。高分辨率的花粉记录反映,在１６ｋａＢｍ,Ｐ,以前花粉组合以黎科（Ｃｈｅｎｏｐｏｄｉａｃｅａｅ）和蒿属（Ａｒｔｅｍｉｓｉａ）为主,花粉浓度很低,应为荒漠草原植被。     

太湖东部平原平望孔全新世环境演变地层记录

通过对太湖东部平原平望钻孔的年代、有孔虫和孢粉分析,探讨了该区域全新世植被变化与环境特征。结果显示全新世(11.5 kaBP)以来,太湖东部平原未受到广泛海侵的影响,主要是以淡水湖泊-沼泽沉积为主。该区域在4 kaBP以后,才有大面积的水稻种植。11.0—9.1 kaBP,以常绿-落叶阔叶林为主,花粉浓度较小,木本植物和水生湿生植物花粉含量增加,整体环境温凉偏干,但湿度逐渐增大,指示东亚季风逐渐加强。9.1—5.8 kaBP,花粉浓度最大,木本植物花粉含量略有减小,草本植物含量明显增加,主要是水生、湿生花粉的含量增加明显,平均达到32%,藻类含量为整个钻孔最大,其中在8—7 kaBP前后常绿类花粉含量较大,水生湿生花粉、淡水藻类的含量达到整个剖面最大,推测此时区域湿度最大,东亚夏季风最为强盛。5.8—1.3 kaBP常绿阔叶林百分比含量增加,落叶阔叶花粉含量减少,陆生草本植物的含量增加,水生湿生草本的含量减小,主要以常绿-落叶阔叶林为主,环境较前一带略干,东亚夏季风减弱。     

Role of wild plant foods among late Holocene hunter-gatherers from Central and North Patagonia (South America): an approach from dental evidence

This study evaluates the role of plant foods in the subsistence of hunter-gatherers that inhabited the Central East, Northwest, and Northeast Patagonia (Argentina) during the late Holocene (ca. 3,000-500 years BP). The goal of the present study is to assess the temporal variation of dental caries ratio and wear rate in skeletal samples to ascertain if the biological information supports the dietary shift toward greater consumption of wild plant foods around 1,500 years BP, suggested by other types of evidence. The authors registered caries, antemortem and postmortem tooth loss, and tooth wear from eight samples belonging to hunter-gatherers from Patagonia for which chronological sequences from early late Holocene (ca. 3,000-1,500 years BP) up to final late Holocene (ca. 1,500-500 years BP) are available. The results indicate that caries percentages in Patagonian samples fall within the range established for hunter-gatherers but there are significant geographical differences. In addition, caries ratio does not change significantly through time, so the amount of carbohydrates consumed seems to have remained fairly constant since 3,000 years BP. In contrast, there is a marked temporal trend toward the reduction of wear rates in the three areas, suggesting a faster rate in early late Holocene than in final late Holocene. These results would reflect a change to less hard and/or abrasive diets in the final late Holocene, probably owing to differences in food processing methods employed.