东北地区湿度梯度下的表土植硅体的空间分布规律

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。     

河北坝上地区植硅体空间分布特征及其环境意义

了解不同区域表土植硅体组合特征及其对气候环境的响应过程，是利用植硅体指标恢复古植被和古气候的基础。本文通过对河北坝上地区103块表土植硅体的分析鉴定，共统计出棒型、尖型、帽型、鞍型、哑铃型、齿型、块状、扁平状、扇型、三棱柱型、锥骨状、导管型、弓型和特殊型14种植硅体类型，其中植硅体类型主要以棒型和尖型为主，而短细胞植硅体的含量较少。通过研究区相对暖湿区、暖干区、冷湿区和冷干区的表土植硅体组合特征对比发现，在相对较冷的区域棒型量含量较高，在相对较暖的区域扇型、扁平状和鞍型含量较高，在相对较湿的区域尖型含量较高，在相对暖湿的区域块状含量较高，在相对冷湿的区域齿型含量较高，这表明研究区表土植硅体组合特征对气候环境响应较为敏感。本研究成果可为重建坝上地区古植被和古气候提供基础资料。     

长白山区湿地表土植硅体特征及其环境意义*

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。     

Phytolith reference study for identifying vegetation changes in the forest−grassland region of northeast China

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.     

Assessing modern arboreal phytolith sensitivity to vegetation variations in temperate forest regions

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.     

Simultaneous thin section and phytolith observations of finely stratified deposits from Neolithic Çatalhöyük,Turkey: implications for paleoeconomy and Early Holocene paleoenvironment

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.     

长白山北坡垂直植被带表土植硅体组合研究

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。     

长白山泥炭湿地主要植物植硅体形态特征研究

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。     

植硅体化学组成研究进展

现代植物植硅体化学组成研究有利于揭示植硅体的化学组成与细胞形态、植物种类及植物生长环境之间的关系,认识植硅体形成机制、植物分类及生态意义。植硅体化学组成测试方法多种多样,主要涉及植硅体化学元素组成及Si、O和C元素同位素组成测定,研究表明植硅体主要含二氧化硅和水,封闭有少量的有机成分及多种矿质元素。在植硅体封闭有机成分存在形式,部分元素的形成、迁移等循环机理,稳定碳同位素组成、分布及其生态指示意义以及^14C测年研究等方面取得一定认识。植物种类、组织部位、细胞微环境以及植物生长的环境因子能够影响植硅体的化学组成。植硅体化学组成研究对植硅体形成机制及碳、硅等元素循环具有重要意义,植硅体部分化学元素、植硅体稳定同位素组成及^14C测年具有较好的古环境及考古研究潜力。现代植物植硅体化学组成及其与环境因子的关系,以及植硅体电子探针微区研究有待于进一步深入开展。     

棕榈科植硅体形态分析及其环境意义

植硅体分析在古环境、古生态、环境考古、植物分类等众多领域研究中逐渐显示出其重要的作用,其应用潜力依赖于现代植硅体形态基础研究工作的深入。文章主要针对我国热带、亚热带地区常见的棕榈科15个属20个种植物进行了植硅体形态鉴定和多项形态参数(大小、突起等)的测量分析,同时对旅人蕉科的白花扇芭蕉、蝎尾蕉科的黄芭蝎尾蕉、苏木科的无忧树进行了对比研究。结合聚类分析方法把植硅体形态分为5个大的类型,棕榈科植硅体主要包括刺球形、水母形和草帽形3种形态。白花扇芭蕉植硅体呈褶球形,黄芭蝎尾蕉植硅体呈飞梭形,无忧树不含有植硅体。同时,给出了不同类型形态参数的大小和范围,为利用棕榈科植硅体等进行古环境研究提供了基础。     

Effect of fire on phytolith coloration

Dark‐colored phytoliths are often found preserved in paleosols and archaeological sediments. Some practitioners believe these darkened phytoliths provide evidence of fire histories, while others suggest alternative reasons for their occurrence. This study examines the effect of fire on phytolith appearance and discusses the extent to which color may be used as proxy evidence for fire. The results of this study demonstrate that under oxidative conditions of openair fire, the color of phytoliths can be altered, although dark‐colored phytoliths also occur naturally in some unburned plant species. Despite some overlap observed between burned and unburned color in phytoliths, clear differences are apparent in the way this color appears optically. In particular, transparent and opalescent qualities were found to occur in nature as opposed to a dull opaque appearance of charred phytoliths. Although fire‐induced color change is probably limited to a portion of the phytolith assemblage, phytolith color remains a tool that can be confidently used to indicate the presence of fire in various sedimentary contexts. © 2006 Wiley Periodicals, Inc.     

Estimating phytolith influx in lake sediments

So far, no phytolith extraction protocols have been tested for accuracy and repeatability. Here we aim to display a phytolith extraction method combining the strengths of two widely used protocols, supplemented with silica microspheres as exogenous markers for quantifying phytolith concentrations. Phytolith concentrations were estimated for samples from two sedimentary sequences in which numerical age–depth models make it possible to calculate phytolith influxes (phytolith numbers per cm²per yr). Analysis of replicates confirmed the statistical robustness, the repeatability and the very few biases of our extraction technique for small phytoliths, since the relationship between grass silica short cells and microspheres was kept stable. Furthermore, we demonstrated that silica microspheres are robust exogenous markers for estimating phytolith concentrations. The minimum number of items (i.e., phytoliths plus silica microspheres) that must be counted to estimate phytolith concentrations and thus influxes depends on the ratio of phytoliths to microspheres (R) and is minimized when R = 1. Nevertheless, we recommend using ratios R ≤ 1 in order to avoid having the counting process become excessively time-consuming, because microspheres are easier to identify and count than phytoliths.     

Macro- and micro-ecological reconstruction using plant opal phytolith data from archaeological sediments

Phytolith analysis is rapidly maturing into a robust and powerful paleobotanical data system. Many plant groups can be identified to family or subfamily, and even species identification has been suggested. Distinctive phytoliths occur abundantly in members of the grass family and are also found in several other groups including rushes, sedges, palms, conifers, deciduous trees, and other dicotyledonous plant taxa. Soil phytolith assemblages have provided paleobotanical data on the order of thousands to millions of years ago. Moreover, as test cases for analysis in soil have increased, an emerging pattern indicates that phytolith populations are stable decay-in-place residues following deposition in sediments. Phytolith studies reflect both macroecological as well as subtle microecological, ecotonal differences, and/or very specific ethnobotanical and cultural activities. Phytolith analysis is a superlative source of botanical information in narrowly defined contexts of archaeological sediments.     

Aqueous reactivity of phytoliths and plant litter: Physico-chemical constraints on terrestrial biogeochemical cycle of silicon

Quantification of silicon recycling by plants is hampered by the lack of physico-chemical data on reactivity of natural phytoliths and plant litter. In this study, we used an experimental approach for determining the silica release rates of phytoliths from tropical and temperate plants (bamboos, horsetails). Results are compared with litter degradation of horsetails and pine needles. Silica release rates suggest that the reactivity of phytolith surface does not depend on topology and geometry of local structures, and does not support the existence of preferential dissolution sites on surface. Litter degradation results suggest that the silica release rate is independent of cellulose hydrolysis that implies the presence of phytoliths in an “inorganic” pool not complexed with organic matter.     

Phytolith analysis of an archaeological site (longshan period) in Zhumadian City,Henan Province,China: Paleoenvironmental and cultural implications

With phytolith analysis of an archaeological site (Longshan Culture Period, 4800-4000 B. P.) in Zhumadian City of Henan Province, environmental and cultural information have been obtained. Phytolith assemblages both from the site and from a nearby ancient lake deposit of the same period indicate a warm and wet climate. Since this area is in an environment outside the natural distribution of wild rice, abundant “scooped” bilobate and special glume epidermal phytoliths found in all of the cultural layers and two samples of the lake deposits suggest that rice was cultivated in this region by the local people. © 1994 John Wiley & Sons, Inc.     

植硅体14C测年研究:过去、现在与未来

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。     

粟类作物稃片植硅体形态研究回顾与展望

中国是粟、黍的起源地,但受植物遗存保存状况及研究方法的限制,对粟类旱作农业起源与驯化的时间、地点、种类、过程等的认识仍然存在不同观点。植硅体分析为准确鉴定粟、黍及其野生祖本和亲缘物种提供了新的途径。本文总结了近几年来针对粟、黍种子稃片植硅体研究取得的新进展,获得以下认识:1)进一步明确了稃片表皮长细胞植硅体的形态特征、大小、数量是鉴定考古文化堆积中粟、黍及其野生祖本和亲缘野生物种的可靠指标;2)通过对比我国北方常见的狗尾草属稃片植硅体,发现了ΩⅢ型仅发育于粟和青狗尾草的稃片中部,且其大小与狗尾草属野生植物差异显著;3)分析和说明了稃片植硅体鉴定流程和方法、重点强调了稃片Ω/η类型的鉴定特征和应用范围,以及植硅体统计量等关键问题;4)讨论了粟类稃片植硅体产量与农作物产量的关系以及植硅体埋藏学问题,最后对深化粟类植硅体形态学研究提出了初步建议。希望通过本文的总结与讨论,能够使植硅体分析方法在粟类作物起源和传播的研究中得到更准确、更广泛的应用。     

Phytolith assemblages as a promising tool for reconstructing Mediterranean Holocene vegetation

The reliability of phytolith assemblage analysis for characterizing Mediterranean vegetation is investigated in this study. Phytolith assemblages are extracted from modern and buried Holocene soils from the middle Rhône valley (France). The relation between modern phytolith assemblages and the surrounding vegetation, as well as between fossil assemblages and contemporaneous vegetation, already reconstructed through other proxies, is discussed. We demonstrate that the main northwestern Mediterranean biomes are well distinguished by soil phytolith assemblage analysis. In particular, the density of pine and nonconiferous trees (densities expressed relatively to the grass cover) and the overall degree of opening of the vegetation appear well recorded by three phytolith indexes. North Mediterranean vegetation changes during the Holocene period, mainly tree line shifts, pine wood development and deforestation are poorly documented, due to the scarcity of proxy-preserving sites. Phytolith assemblage analysis of soils, buried soils, and sediments appears to be a promising technique to fill this gap.     

Phytoliths as indicators of pedogenesis and paleoenvironmental changes in the Brazilian cerrado

This paper presents the preliminary results of phytolith analyses of a peat located in the cerrado of the Uberaba municipality, State of Minas Gerais, Brazil. The phytolith soil sequence is discussed by comparison with phytolith assemblages extracted from dominant plants (Cyperaceae and Poaceae). Increasing mean age of phytolith assemblages with depth is assumed. Poaceae Cuneiform bulliform cell, Parallelepiped bulliform cell and Elongate smooth long cell types dominate up to 80 cm, rapidly drop to 42% at 80 cm and regularly decrease from 42% to 2% upwards. Cyperaceae Rondel concave type shows the inverse trend, being dominant in the upper part of the profile. This pattern can be assigned to increasing selective dissolution of the Cyperaceae phytolith type with depth, or/and to a decrease of water stress suffered by the grasses, leading to a decrease of bulliform cell silicification. Soil processes and paleo-environmental changes hypotheses are discussed.     

植硅体在河流硅输送中的作用

高等植物产生的植硅体是古气候和古环境研究的重要手段,也是陆地硅循环中重要的硅的储库;植硅体通过河流的跨区域输送在全球硅的生物地球化学循环中起着重要作用,是区域硅循环研究的重要载体,然而这方面的关注却很少。河流输送的生物硅大致分为自源和异源两种类别。"自源"生物硅主要包括河流水体本身自生浮游植物(主要是淡水硅藻)产生的硅质颗粒;"异源"生物硅主要由流域土壤的侵蚀输出到河流的植硅体所构成。流域地表过程是使得部分土壤中的植硅体进入河流的主要途径,并成为河流生物硅输送中重要的形式,这对河流-河口水循环体系的硅生物地球化学循环过程产生了重要的影响,但人们对河流输送的植硅体在硅循环中的作用的研究还不够。文章着眼于陆海相互作用研究,以河流中水体携带的植硅体为中心,总结了河流植硅体输送在地表水体硅循环系统中贡献的研究进展,分析了长江与黄河植硅体入海通量与河口行为及对近海海洋环境的影响。最后,对未来河流输送的植硅体参与硅循环研究可能需要加强的科学问题提出了建议。