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1.
Phytolith has been widely used as a tool to reconstruct the paleoenvironment, and the investigation of modern phytolith is very crucial to the accurate interpretation of phytolith data in ancient sediments. Studies of modern process of phytolith primarily include the morphological analysis of phytolith in modern plants, and the relationships between the formation and growth of phytolith and environmental factors, as well as the transportation and taphonomy of phytolith in modern soils and sediments. The formation of phytolith in plants is controlled not only by genes but also by environmental factors, such as humidity, precipitation, temperature, CO2 concentration, soil pH, and nutrient status, etc. The morphology, assemblages, 13C and 18O of phytolith in plants can respond sensitively to environmental variables. The phytolith assemblages can be affected by its taphonomy and transportation that may be different due to phytolith types and soils/sediments texture. It is necessary to investigate the phytolith morphology and types in modern plants, the relationship between its formation and environmental factors, and the impact of transportation and taphonomy on phytolith assemblages under different environmental conditions in order to promote the application of phytolith analysis to paeloenvironment reconstruction. 相似文献
2.
选取广西桂林市雁山碳酸盐岩红土剖面,对红土中的植硅体类型、分布及含量进行了定量分析。发现:(1)表土植硅体形态多样、含量丰富,含量从剖面表层向下迅速减少,20cm及其以下植硅体含量极少或没有;(2)除了0~0.1m内有植硅体富集外,其他深度再也没有发现新的植硅体富集层;(3)受淋滤和生物扰动作用影响,植硅体可能出现向下10~20cm的运移,但运移对其形态和大小没有明显的选择性,植硅体形态组合受运移影响不大,能够很好地反映上覆植被的组成和所处地区的气候总体特征;(4)研究区植硅体富集于红土表层,且为剖面中的唯一富集层,是红土形成过程植硅体运移的反映,支持了红土的碳酸盐岩风化成因;(5)植硅体运移选择性不明显的特点,为利用碳酸盐岩红土植硅体客观分析和重建古环境提供了基础和可能。 相似文献
3.
东北地区泥炭表层沉积中植硅体分布特征 总被引：2，自引：0，他引：2
表土沉积物中的植硅体分析是了解第四纪沉积物中植硅体组成的重要途径,也是重建第四纪古环境的基础。对东北地区跨越3个气候带、6个地区的41处泥炭地表土中的植硅体进行提取,鉴定出东北泥炭表土中主要发育哑铃型、扇型、鞍型、方型、长方型、梯型、尖型、帽型、齿型、棒型和其它等11种植硅体类型。分析显示,它们的分布与纬度、地形和温热条件具有明显关系,即哑铃型、鞍型、扇型、方型、长方型和梯型植硅体随纬度和海拔较高而含量较小,其余类型反之;较高温度条件对应扇型、哑铃型植硅体含量较高,较高湿度对应扇型植硅体含量较高。 相似文献
4.
Assessing modern arboreal phytolith sensitivity to vegetation variations in temperate forest regions
Gui‐Zai Gao Dong‐Mei Jie De‐Hui Li Nan‐Nan Li Li‐Dan Liu Hong‐Yan Liu Cheng‐Cheng Leng Jiang‐Yong Wang Bao‐Jian Liu Ping Li 《Boreas: An International Journal of Quaternary Research》2019,48(3):731-745
To assess the reliability of arboreal phytoliths for differentiating vegetation types in temperate forest regions, we systematically analysed arboreal leaf phytoliths from 72 arboreal plants and 49 modern soils from three forest types in northeast China. The arboreal leaf phytolith production and morphotypes were highly variable between species. The arboreal leaf phytolith assemblages could clearly distinguish between broadleaf and coniferous species, but they were much less successful in differentiating broadleaved trees into subtaxa. Coniferous leaf morphotypes were successfully used to differentiate coniferous trees into families and subtaxa, especially in the Pinaceae. Two diagnostic broadleaved and six coniferous phytolith morphotypes were recognized within the modern soil beneath forest ecosystems. These arboreal phytoliths comprised up to 10–15% of the total soil phytoliths, and were dominated by coniferous types. Arboreal phytolith concentrations and phytolith assemblages in the soils fluctuated substantially amongst the three forest types. Soil arboreal phytolith assemblages were successfully used to differentiate samples from Larix mixed forest, broadleaf forest and Pinus koraiensis mixed forest. In addition, the arboreal index quantitatively distinguished the three forest types, with B/BE values <0.4 for Larix mixed forest samples, values from 0.4 to 0.6 for broadleaf forest samples, and values from 0.6 to 0.9 for P. koraiensis mixed forest. Thus, our surface soil arboreal phytolith assemblages and arboreal index are a useful reference for differentiating forest ecotypes, and they also provide reliable analogues for arboreal phytoliths from palaeoecological contexts in temperate forest regions. 相似文献
5.
长白山北坡垂直植被带表土植硅体组合研究 总被引：3，自引：0，他引：3
长白山垂直分布的植被是欧亚大陆从温带到寒带植被水平地带性的缩影。对其北坡不同海拔高度植被带土壤中的植硅体进行初次研究,结果发现,该山北坡海拔700m到2630m的土壤中发育了形态和数量丰富的植硅体。不同植被带植硅体组合的含量各不相同,主要特征表现为随海拔升高示冷型的植硅体含量整体呈上升趋势,而示暖型的植硅体含量整体呈下降趋势。温泉附近土壤中的植硅体则表现出明显的与其上下相邻地点不同的特点。它对中国东北第四纪沉积物中植硅体组合的研究及第四纪古植被和古环境的重建可提供重要的基础性资料。 相似文献
6.
Gu Yansheng Zhuo Ying Zhang Zejun Faculty of Earth Sciences China University of Geosciences Wuhan 《中国地质大学学报(英文版)》2001,12(1)
INTRODUCTIONVermicular red earth is distributed widely in South China,significant for the research into Quaternary environment andglobal change. Huang (1993) discovered the evidence of human activities-popple tools in vermicular red earth of the middle-upper reaches of Hanshui Riverl Zhu et al. (1991 ) statedthat red earth was a good information carrier of global changeafter the research into tropic red earth and environment byweathered mineral and geochemistry. Zhao and Yang (1995)stud… 相似文献
7.
《Boreas: An International Journal of Quaternary Research》2018,47(2):481-497
To provide a basis for tracing changes in vegetation and tree cover density, we studied the phytoliths of 129 common temperate plant species, and extracted the phytoliths from 75 surface soil samples from sites in grassland, forest−grassland ecotone and forest habitats in northeast China. From the analysis of shapes and morphological parameters of the plant samples, we developed a reference data set of herbaceous and woody phytoliths, and subsequently identified 21 herbaceous and 13 woody phytolith types in the surface soil samples. To test the reliability of soil phytolith analysis for distinguishing forest, grassland and the forest−grassland ecotone, we used principal components analysis (PCA) and discriminant analysis (DA) to summarize the soil phytolith assemblage characteristics of the different ecosystems. The results show that the grassland and forest samples are characterized by abundant herbaceous and woody phytoliths, respectively; and that forest−grassland ecotone habitats are characterized by low abundances of blocky polyhedral, multifaceted epidermal and sclereid phytoliths. In general, the surface soil phytolith assemblages can reliably differentiate samples from forest, grassland and the forest−grassland ecotone, with up to 92% of the samples classified correctly. We also tested the reliability of phytolith indices (W/G (1), W/G (2), W/G (3)) for discriminating different vegetation types in our study area, and found that W/G (2) was the most reliable index and corresponded well with the species inventory data. The W/G values for grassland ranged from 0 to 0.3, from 0.3 to 0.6 for the forest−grassland ecotone, and exceeded 0.6 for forest. We conclude that our study provides reliable analogues for phytolith assemblages from palaeoecological contexts, which can be used to reconstruct shifts in forest−grassland ecotones and vegetation succession in temperate areas. 相似文献
8.
Benjamin A. Bell William J. Fletcher Henk L. Cornelissen Jennifer F. E. Campbell Peter Ryan Helen Grant Christoph Zielhofer 《第四纪科学杂志》2019,34(4-5):323-332
Quantitative climate reconstructions from pollen typically rely on empirical relationships between pollen abundances or assemblages and climate, such as the modern analogue technique. However, these techniques may be problematic when applied to fossil sequences, as they cannot separate anthropogenic from climatic influence on pollen assemblages. Here, we reconstruct Mid‐ to Late Holocene summer aridity in the Middle Atlas, Morocco, using stable carbon isotope analysis of isolated fossil Cedrus pollen. This approach is based on well‐documented plant physiological responses to moisture stress and is therefore independent of vegetation composition. We find that there has been a general long‐term trend of increasing summer aridity in the region during the last 5000 years to the present day. The gradual decline of Cedrus atlantica forest in the Late Holocene follows this aridity trend. Additionally, we show how isolating a specific pollen type for carbon isotope analysis yields a robust climate signal, versus using pollen concentrates or bulk sediment. Our findings indicate that climate has become drier in the region and confirms the Mid‐ to Late Holocene aridification trend observed more widely in the western Mediterranean, using a novel proxy for this region with good potential for wider application in other environments. 相似文献
9.
Lisa‐Marie Shillito 《第四纪科学杂志》2011,26(6):576-588
Simultaneous thin section and phytolith observations of finely stratified anthropogenic deposits from the Neolithic settlement of Çatalhöyük, Turkey, dated between 7400 and 6000 BC provide evidence for both the depositional context and phytolith assemblage of these deposits. Although extracted phytoliths provide a general picture of vegetation that supports existing evidence of a local wet marshland environment, comparisons with observations of phytoliths in situ indicate a diverse range of microcontexts, as well as depositional and post‐depositional processes that influence phytolith size. This has implications for studies that use conjoined phytolith size as a proxy for water availability and early agricultural practices. Observations indicate a significant background noise of phytoliths and micro‐charcoal in the deposits, linked to the frequent use of fire, which has implications for interpreting assemblages where phytolith counts are low, such as from floors of buildings. This study confirms the usefulness of phytoliths in providing information on human plant use and environment where the taphonomy of the deposits is clear, and provides new evidence for wet farming of at least some of the wheat found at the site. It also suggests there needs to be greater consideration of phytolith taphonomy, which can be provided to an extent by combining phytolith analysis with thin section micromorphology. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Donald Lee Johnson 《Quaternary Research》1977,8(2):154-179
The present Mediterranean climate of coastal California is unique in North America and reflects the interaction of several important synoptic controls, principally the North Pacific semipermanent anticyclone, and to a lesser extent the Aleutian low-pressure system and the cool California oceanic current. These synoptic climatic controls, key parts of the global air-sea circulation, were probably operative throughout late Quaternary time as shown by paleoecologic evidence. The thick accumulations of sediments in basins of offshore California indicate that while variable sedimentation regimes reflect changing climatic and oceanographic conditions, the Quaternary climate was probably semiarid as now, even during glacial maxima. Late Quaternary coastal dunes preserve former wind directions and show that prevailing late Quaternary winds were directionally equivalent to modern winds, which are controlled by the North Pacific anticyclone and by interactions between the North Pacific high and the interior basin low. These sand dunes contain buried, datable, carbonate-rich soils. Precipitation then, like the present rainfall regime, was not enough to leach the carbonates from the soils. Charcoal in buried dunes and soils shows that fire was environmentally important throughout the Quaternary, just as it is today. Fossil plants indicate that sclerophyllous vegetation and forest stands of conifers, adapted to a Mediterranean climate, were widely distributed during late Quaternary time. Fossil pollen in the Sierra Nevada indicates the influence of the North Pacific high. The historical precipitation record overlaps a late Holocene tree-ring record permitting extrapolation of the precipitation curve back nearly 600 years. Well-defined wet and dry trends in the precipitation pattern characterized this time span, and provide a possible analog to the earlier Holocene and Pleistocene precipitation regime. The paleoecologic record shows that the late Quaternary climate of coastal California was characterized by regimes similar to those prevailing today. The persistence of a Mediterranean climate in California during the last glaciation contrasts with dramatic climatic changes experienced in glaciated parts of North America. California thus was an Ice Age refugium for animals and cold-sensitive plants. 相似文献
12.
湿地在全球环境变化中扮演着十分重要的角色,湿地表土中的植硅体分析是恢复第四纪古环境的重要途径。文中选取长白山区的桦南到哈尼一线的6处湿地表土,并采用PCA和CA分析植硅体组合的环境指示意义,结果显示：温度因子是造成长白山不同湿地表土植硅体组合差异的第1环境因子,且植硅体的种类和含量与采样点上覆植被、湿度与海拔等环境条件都存在相关性。结合方差分析和植硅体大小变化趋势分析曲线可以看出,不同表土中符合方差分析条件的植硅体类型的大小随着温度的升高而增大。总体来看,长白山区6处湿地中,植硅体类型基本相同,但温暖指数和植硅体的大小差异较显著,说明植硅体大小及其组合对温度都有较敏感的响应。 相似文献
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植硅体的现代过程研究是恢复古环境的基础,探讨表土植硅体分布及组合特征对环境因子的响应尤为重要。沿中国东北地区年均温为4 ℃等温线采集70块表土样品,研究了单一温度因素控制下表土植硅体的空间分布规律,以期获得不同类型植硅体对降水的响应。研究结果表明:所有表土样品中植硅体丰富且数量较多,主要有棒型、尖型、块状、扇型、扁平状、短鞍型、帽型、哑铃型、齿型、三棱柱型、导管型、硅质突起、硅化气孔、弓型和多面表皮植硅体;且主要以短细胞、棒型、尖型为主,其平均百分含量之和高达80.77%,块状、扁平状、扇型次之,其他类型的植硅体含量较少。方差分析结果表明:棒型、三棱柱型、硅质突起、哑铃型和扁平状在大兴安岭、松嫩平原和长白山之间存在显著性差异,且棒型、三棱柱型、硅质突起的百分含量与年降水量具有极显著的正相关性,哑铃型的百分含量与年降水量具有极显著的负相关性。总之,年均温为4 ℃等温线上70块表土样品中植硅体类型基本相同,但不同类型植硅体的百分含量存在差异,说明本研究区域内表土植硅体组合特征对降水的响应较为敏感。 相似文献
15.
对长白山地区常见的泥炭地25个属31个种植物进行了植硅体形态鉴定统计,共发现植硅体类型15种,它们分别是硅化气孔、棒型、扇型、板型、硅质突起、尖型、导管型、帽型、齿型、哑铃型、鞍型、多边帽型、毛发型等。除禾本科和莎草科、菊科部分植物植硅体含量高外,木贼科、堇菜科、茜草科、蓼科等部分植物植硅体的含量也较高。禾本科植物的短细胞植硅体对植物分类有意义,但可能因采样环境和种类差异等原因,长白山泥炭湿地禾本科植物的植硅体在形态和数量上都与其他区域同类研究结果有所差异,如禾本科早熟禾亚科的菵草中新发现了含量丰富的枕木型植硅体,黍亚科的荩草和水稗中还发现少量帽型植硅体; 另外菊科兴安一枝黄花和齿苞风毛菊含有大量的特殊的尖形植硅体。硅化气孔宽度大小可指示环境湿度状况,对硅化气孔的数量和大小的深入研究将对古环境和古CO2浓度的恢复有一定帮助。长白山泥炭湿地植物的植硅体与植物的分类关系密切,湿地植物植硅体中硅质突起、棒型、哑铃型和尖型植硅体特征组合代表湿冷组合,本研究中的5块泥炭湿地植硅体的组合特征受纬度变化影响不明显。 相似文献
16.
文章回顾了植硅体14C测年发展的历史,对当前其研究的现状进行了全面的总结和评述,对近年来其研究的争议进行了梳理。植硅体测年研究中存在的问题(如污染和老碳效应等)在其他材料测年过程同样存在,不能基于少量现代植物植硅体测年的异常数据而完全否定其意义。大量的测年数据显示,并不是所有的植硅体年代都偏老,相反地层中的植硅体年代与同层位其他材料的年代重合或接近。因此,在一些缺少其他有机质测年材料的地层,植硅体14C测年仍然是一种极具潜力的年代学方法,在构建一些重要环境和考古文化时间标尺上将会发挥更重要的作用。 相似文献
17.
MATTHEW C. BATINA CARL A. REESE 《Boreas: An International Journal of Quaternary Research》2011,40(2):332-341
Batina, M. C. & Reese, C. A. 2010: A Holocene pollen record recovered from a guano deposit: Round Spring Cavern, Missouri, USA. Boreas, 10.1111/j.1502‐3885.2010.00186.x. ISSN 0300‐9483. Bat guano deposits have been the subject of relatively few palynological studies. The studies to date have focused on the most modern samples only, and therefore the full potential of bat guano as an archive for fossil pollen analysis remains unknown. In this paper we report the results of pollen analysis on an 88‐cm vertical profile of fossil bat guano from Round Spring Cavern, Missouri. Four AMS radiocarbon dates were in sequence and showed that the guano pile was active between 8155 and approximately 550 cal. yr BP. Pollen is well preserved throughout the profile, with most samples containing less than 10% indeterminable pollen. Wind‐pollinated taxa are better represented than insect‐pollinated taxa, and pollen concentrations range from 842 to 371 660 grains cm?3. As expected, the dominant vegetation types represented by the pollen assemblage are oak and pine, in accordance with the region's oak–hickory–pine forest. However, there are discrepancies between the guano pollen record and the results of a lake pollen study conducted in southern Missouri. We propose several possible factors that may be influencing the guano pollen record and provide direction for further investigation into the palaeoecological potential of bat guano. 相似文献
18.
O. D. Naidina 《Stratigraphy and Geological Correlation》2006,14(3):331-340
The Holocene paleogeography of the Laptev Sea eastern shelf is reconstructed based on mollusks, foraminifers, ostracodes, spores and pollen found for the first time. Environmental changes in the course of the postglacial (Holocene) transgression are detectable from quantitative analysis of three ostracod assemblages. Three phases of the transgression are established based on ostracode assemblages from the AMS 14C-dated core from the ancient valley of Yana River, central part of the Laptev Sea eastern shelf. After the first phase of coastal brackish-water environment (11.3–11.1 ka), shallow-water marine taxa appeared in the transitional phase (11.1–10.3 ka), and the third phase of modern sea conditions commenced 10.3 ka ago. Spore and pollen assemblages from the core indicate that the early Holocene land vegetation was dominated by tundra plant communities adapted to climatic conditions not warmer than at present. In the interval of 9.3–8.0 ka, climate was increasingly humid and warm, and forest-tundra vegetation occupied more favorable zones of the region. 相似文献
19.
依据长江三角洲古河谷区典型钻孔CSJA6孔中冰后期孢粉分布情况,结合有孔虫分析以及6个样品的AMS 14C年龄,自下而上初步建立了冰后期3个有时间标定的孢粉组合,分别为:Ⅰ. Quercus-Lipuidambar-Artemisia-Polypodiacea组合,时代属于早全新世;Ⅱ. Quercus-Castanopsis-Cyperaceae-Pteris组合,时代属于早-中全新世;Ⅲ. Quercus-Ulmus-Artemisia-Polypodiacea组合,时代属于中-晚全新世。3个孢粉组合带所反映的古气候演变过程为凉干—热湿—温干,这与中国的气候大环境较为一致,且与本区前人研究成果亦做了相应的对比,依然具有较好的可对比性。 相似文献
20.
Based on the pollen spectrum characteristics of 46 surface samples collected in the western Tianshan Mountains of Xinjiang and a plant community quadrat survey, we analyzed the relationship between pollen assemblages and modern climate and vegetation distribution in the region. The results showed the surface pollen assemblages were consistent with the distribution of modern vegetation. Based on the results of cluster analysis, the study area could be divided into three pollen assemblage zones（mountain steppe zone, desert vegetation zone and typical desert zone）. In general, pollen assemblage can roughly reflect the main characteristics of local vegetation, but there are significant differences in the percentage of some pollen types and the coverage of related plants. The pollen of Picea and Pinus in arbor plants, Ephedra in shrub plants, Chenopodiaceae and Artemisia in herb plants were high represented due to the influence of natural wind, water flow and their own pollen yield. While Rosaceae pollen in shrubs and Poaceae in herbs were less representative in a modern plant community with its own dominant species;The Artemisia and Chenopodiaceae（A/C）ratio can distinguish the desert zone from the mountain steppe zone, and could clearly reflect the aridity level. However, when using this indicator to reconstruct the climate environment, it is necessary to combine the characteristics of pollen assemblage and the influence of changes in vegetation composition and other factors to distinguish;Altitude, average annual precipitation, and average annual temperature all affect the distribution of surface pollen in the area. © 2022 The authors. 相似文献