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中国阿尔泰山全新世气候变化的泥炭记录
张东良
Subtype博士
Thesis Advisor冯兆东 ; 穆桂金
2018-06-05
Degree Grantor中国科学院大学
Place of Conferral新疆乌鲁木齐
Degree Discipline理学博士
Keyword阿尔泰山 全新世气候 泥炭 孢粉 碳和氧同位素 Altai Mountains Holocene climate change Peat Pollen Carbon and oxygen isotope
Abstract阿尔泰山位于欧亚大陆中部, 横跨中国、 哈萨克斯坦、 俄罗斯和蒙古。 该山脉不仅是东亚季风系统和西风系统相互作用的地区, 也是东方文化和西方文化交融的重要地带。 近年来, 随着“草原丝绸之路” 沿线考古研究的兴起, 阿尔泰山以及周边地区的气候变化吸引着学术界的兴趣。 已有的古气候研究结果显示, 阿尔泰山及其周边地区全新世气候记录存在复杂性和不一致性。 这些记录的复杂性和不一致性意味着: 学界应在建立新的全新世气候记录的基础上,以更为广阔的视野重新审视和研究已有的全新世古气候序列, 以期揭示阿尔泰山及其周边地区全新世气候变化的时空规律及驱动机制。 为此, 本文首先在中国阿尔泰山建立三根泥炭-湖相序列(娜仁夏、 克拉沙子和三道海子) 的全新世植被和气候变化历史。 其次, 本文重新整理阿尔泰山及其周边地区的 31 个全新世孢粉序列, 并依据位点的分布将其划分为五个区域: 哈萨克丘陵(a) 、 西伯利亚南部(b) 、 阿尔泰山-萨彦岭区(c) 、 蒙古高原西部(d) 和新疆北部(e)。基于三个新序列的建立和区域资料的集成, 本文得出以下主要结论:(1) 娜仁夏序列孢粉资料揭示, 约 11,500 cal. yr BP 前该区域气候相当冷干, 裸露的基岩地形是当时的主导景观; 约 11,500 至 7000 cal. yr BP 时段泰加林快速扩张, 气候变得温暖湿润; 接下来的 3000 年(约 7000 至 4000 cal. yr BP),泰加林明显萎缩, 气候变得相对冷干; 约 4000 cal. yr BP 开始泰加林再次扩张,气候再次变得暖湿; 过去 1200 年气候变得相对冷干。 娜仁夏泥炭莎草纤维素碳和氧同位素(δ13Ccellulose 和δ18Ocellulose) 可能是区域湿度变化的代用指标, 它们揭示, 约 8000 年前之前是干旱的, 而 8000 年前之后逐渐变的湿润了。 与基于孢粉定量计算的干旱指数(RDI) 的对比显示, δ13Ccellulose 和δ18Ocellulose 记录的湿度变化趋势与 RDI 较为相似, 而 RDI 是基于孢粉定量重建的温度和降水的。 这种相似性暗示, 全新世以来湿度的持续增加是温度和降水共同作用的结果。(2) 克拉沙子序列孢粉资料揭示约 10,000 cal. yr BP 前植被为苔原或者冷沙漠草原, 气候相对寒冷干燥; 约 10,000 cal. yr BP 后泰加林开始扩张, 气候变得暖湿, 泰加林生物群落得分(biome score)的最大值出现在约 8200 至 5500 cal.yr BP 之间; 约 5500 至 3200 cal. yr BP, 泰加林萎缩, 草原植被扩张, 气候再次变得冷干。通过与基于孢粉定量重建的干旱指数相对比, 泥炭藓纤维素δ13Ccellulose和δ18Ocellulose 也应该被看做是区域湿度的代用指标。 泥炭藓纤维素δ13Ccellulose 和δ18Ocellulose 显示, 气候经历三个阶段: 低湿度出现在约 9600 至 7800 cal. yr BP 阶段, 高湿度出现在约 10,500 至 9600 cal. yr BP 和约 7800 至 3200 cal. yr BP 阶段。(3) 三道海子序列孢粉资料揭示约 8700 至 4200 cal. yr BP 植被是草原, 气候较为暖湿; 约 4200 至 2300 cal. yr BP 植被是高山草甸和苔原, 气候变得冷湿;约 2300 至 700 cal. yr BP 以莎草主导的草甸植被增加, 而蒿属和藜科主导的草原植被下降, 气候变得冷干。(4) 中国阿尔泰山泥炭植物(莎草和泥炭藓) δ13Ccellulose 和δ18Ocellulose 是区域湿度变化的代用指标, 整体揭示中国阿尔泰山气候经历了干旱的全新世早期(约 7000 cal. yr BP 前) 、 湿润的全新世中晩期(约 7000 cal. yr BP 以来) 。 此湿度重建得到周边其他代用湿度指标的广泛支持。 中国阿尔泰山全新世湿度变化主要受到西风急流南北移动的调控。 详细来说, 全新世早期暖阶段, 偏干的气候主要与偏北的西风急流输送的高纬度区域的远源的低水汽通量有关。 全新世中晚期随着气候的变冷, 西风急流南移。 南移的西风急流将更多来自中、 低纬区域(地中海、 黑海、 里海一线) 的水汽输送到阿尔泰山地区。 而西风急流的南移是与全新世以来偏负的北大西洋涛动(NAO) 和极地涛动(AO) 耦合在一起的。(5) 阿尔泰山及其周边地区孢粉资料的集成结果揭示, 集成的区域平均温度在约 12,000 至 9000 cal. yr BP 时段是持续增加的, 而随后自约 9000 cal. yr BP开始逐渐变冷了。 低海拔地区全新世温度敏感地响应了北半球的夏季辐射。 但是森林上限以上位点记录到的温度对太阳辐射有一定的延迟, 这种延迟可能是由高海拔的冻土融化引起的。 集成的区域平均干旱指数在低海拔地区(即哈萨克丘陵、 西伯利亚南部、 蒙古西部和新疆北部) 呈现持续变湿的趋势。 但高海拔区(即阿尔泰山-萨彦岭区)干旱指数变化在全新世早期(约 10,000 至 6500 cal.yr BP) 与低海拔地区明显不同。 再次, 如此的明显不同也可能与高海拔的冻土融化有关。 此外, 推导的全新世降水指数表明阿尔泰山及其周边地区全新世以来湿度的逐渐增加是下降的温度和增加的降水共同作用的结果。
Other AbstractThe Altai Mountains range, situated in the middle part of the Eurasian continent,is shared by China, Kazakhstan, Russia and Mongolia. The range is importantclimatologically because it might have been the conjunctional area between theWesterlies-dominated climate systems from the west and the Asian Monsoondominated climate systems from the east during the Holocene. The range is also abridge in the middle of the ‘Eurasian Steppe Silk Road’ that linked the orientalcultures from the east with the occidental cultures from the west. It should beparticularly noted that the Holocene climate change in the Altai Mountains hasrecently regained scientific attentions and the attentions were primarily stimulated byrenewed archaeological interests in understanding the relationship between climatechange and cultural evolution along the ‘Eurasian Steppe Silk Road’. However, theexisting data not only revealed a degree of climatological complexity but also datainconsistency. The complexity and the inconsistency call for establishing newHolocene climate records of high quanlity and also for re-examining the alreadypublished data in the Altai Mountains and the surrounding areas in the context of abroader geographic extent with the hope that our understanding of the climaticchange in the examined area (i.e., the Altai Mountains and the surrounding areas) canbe elevated.In this study, the Holocene vegetation evolution and the associated climatechanges were firstly reconstructed in the Chinese Altai Mountains. And then thevariations in the reconstructed temperature and aridity were compared with thereported variations in the already-published data at other sites in the Altai Mountainsand the surrounding areas. The reported variations were based on 31 pollensequences reviewed. According to the geographic locations of the 31 sequences, theexamined area were divided into five regions and they are Kazakhstan Hills (a),southern Siberia (b), Altai-Sayan region (c), western Mongolia (d) and northern Xinjiang (e). Following are major conclusions drawn from this dissertation research.(1) Pollen data from the Narenxia peat revealed that prior to ~11,500 cal. yr BP,the region was dominated by a barren terrain under a cold and dry climate and thatthe succeeding interval (~11,500 to ~7000 cal. yr BP) was a period of dramaticexpansions of taiga forests under a generally warm and wet climate. The periodspanning from ~7000 to ~4000 cal. yr BP was an interval of taiga forest shrinkageunder a considerably cooled and dried climate, followed by another expansion oftaiga forests under a resumed warm and wet climate between ~4000 and ~1200 cal.yr BP. The past ~1200 years have been relatively cool and dry. The δ13Ccelluose- andδ18Ocelluose-recorded warm-season moisture reconstruction in the Narenxia peat lendsa strong support to the widely-reported proposition that the climate was generally drybefore ~8000 cal. yr BP and experienced a wetting trend during the past ~8000 yearsin the Altai Mountains and the surrounding areas. The wetting trend since ~8000 cal.yr BP well resembles the increasing trend of the reconnaissance drought index (RDI)that was calculated on the basis of pollen-inferred temperature and precipitation datafrom the same core. The resemblance implies that the wetting trend of the past ~8000years resulted from the combined effect of temperature and precipitation.(2) Pollen data from the Kelashazi peat revealed that prior to ~10,000 cal. yr BPthe vegetation was dominated by tundra and steppe, suggesting a relatively cold anddry climate. Picea-dominated taiga forests expanded at ~10,000 cal. yr BP inresponse to a noticeable increase in precipitation and temperature. An expansion ofsteppe at the expense of taiga forest occurred after ~5500 cal. yr BP under a cold anddry climate. By rather comparable with the pollen-based aridity, Sphagnumδ13Ccellulose and δ18Ocellulose in the Kelashazi peat seem to indicate the variations inwarm-season moisture. The δ13Ccellulose and δ18Ocellulose results revealed that the climateexperienced two wet intervals intervened with one dry interval: a wet interval before~9600 cal. yr BP, a dry interval between ~9600 and ~7800 cal. yr BP, and a wetinterval between ~7800 and ~3200 cal. yr BP.(3) Pollen data from the Sandaohaizi peat revealed that the vegetation was dominated by a steppe between ~8700 and ~4200 cal. yr BP, suggesting a relativelywarm and wet climate. And then the period spanning from ~4200 to ~2300 cal. yr BPwas characterized by mountain meadow and tundra under a cold and wet condition.An expansion of Cypereance-dominated meadow at the expense of Artemisia- andChenopodiaceae-dominated steppe occurred after ~2300 cal. yr BP under a cold anddry climate.(4) The cellulose carbon and oxygen isotopes (δ13Ccellulose and δ18Ocellulose) ofpeat plants (sedge and Sphagnum) was proved to be an acceptable proxy of moisturein the Chinese Altai Mountains. The analytical result revealed that the climate wasdry in the early Holocene (since ~7000 cal. yr BP) and was turned to a wetting trendafterward in the Chinese Altai Mountains. This trend is well corroborated by othermoisture records in the Altai Mountains and the surrounding areas. The Holocenemoisture variations in the Altai Mountains and the surrounding areas have beenmainly modulated by the north-south swing of the westerlies. Specifically, the dryclimate in the early Holocene probably resulted from insufficient water vaporsupplies from long-distance sources associated with the northward-shifted westerlyjet. The wet climate in the middle and late Holocene probably resulted from sufficientwater vapor supplies from more proximal sources associated with thesouthward-shifted westerly jet. The southward-shifted westerlies jet is mainlyattributed to the negatively Arctic Oscillation (AO) and the negatively North AtlanticOscillation (NAO) phases in the middle and late Holocene.(5) The synthesized regionally-averaged temperature-index curve shows thatthe climate was consistently warming between ~12,000 and ~9000 cal. yr BP and hasexperienced a gradual cooling since ~9000 cal. yr BP. The Holocene temperaturetrend in low-altitude regions of the studied area has sensitively responded to the totalsolar irradiance. Nevertheless, the early-Holocene temperature inferred from the sitesabove the upper limits of forests appears to be a delayed response to the solarirradiance and the delay was probably resulted from permafrost thawing at higherelevations. The synthesized regionally-averaged aridity-index curve exhibits a persistent wetting trend during the Holocene in low-altitude regions (i.e., KazakhstanHills, southern Siberia, western Mongolia and northern Xinjiang). But, thesynthesized regionally-averaged aridity-index curve in high-altitude region (i.e.,Altai-Sayan region) was significantly different from that in low-altitude regionsduring early-middle Holocene spanning from ~10,000 to ~6500 cal. yr BP and thedifference was most likely associated with permafrost thawing at higher elevations.The deduced Holocene precipitation-index variations suggest that the Holocenewetting trend in the examined area resulted from a combined effect of temperaturedecreasing and precipitation increasing.
Subject Area自然地理学
Language中文
Document Type学位论文
Identifierhttp://ir.xjlas.org/handle/365004/14946
Collection研究系统_荒漠环境研究室
Affiliation中国科学院新疆生态与地理研究所
First Author Affilication中国科学院新疆生态与地理研究所
Recommended Citation
GB/T 7714
张东良. 中国阿尔泰山全新世气候变化的泥炭记录[D]. 新疆乌鲁木齐. 中国科学院大学,2018.
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