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全球变化背景下, 泥炭地的碳累积及其碳库的源汇功能仍然存在较大不确定性。以长白山区泉阳和露水河泥炭地各2个深度约35 cm的剖面为研究对象, 在210Pb/137 Cs年代-深度模型基础上, 利用有壳变形虫定量重建了近百年来的古水位变化, 基于有机碳含量和容重构建了泥炭碳累积速率序列。研究表明, 长白山区泥炭地近百年来呈变干趋势, 其间存在数十年时间尺度的干湿波动; 公元1905~1950年、 1995~2010年泥炭地水位较高, 环境湿润; 1960~1990年水位下降, 相对干燥, 而2010年以来环境显著变干。两个泥炭地平均现代碳累积速率为63.99~100.24 g C/(m2·a)。泥炭地水位与碳累积速率记录的对比显示, 泥炭地水位上升/下降通常会促进/抑制泥炭地碳累积, 但水位下降引起的泥炭藓发育会促使泥炭地碳累积动态呈非线性的复杂变化。研究结果进一步深化了对泥炭地的碳-水循环机制的理解, 但泥炭地碳累积速率与碳汇效应对水位、 气候等多因素的非线性响应仍需要更深入的研究。 相似文献
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有壳变形虫是一类具外壳的单细胞原生动物,广泛栖息在泥炭藓表面、湿润的土壤和淡水湖泊环境中。它们对环境变化敏感,其壳体能够在沉积物中保存下来,因而记录了丰富的环境变化信息。近20年以来,有壳变形虫在生物多样性、生态指示和古环境重建方面得到了广泛应用。近年来,我国对有壳变形虫的研究不断深入,陆续发现了一些新种和中国新纪录种,极大地丰富了我国有壳变形虫的物种名录。在前期的研究中,在我国长江中游地区的神农架大九湖泥炭湿地发现了一个有壳变形虫的新物种：九湖梨壳虫（Nebela jiuhuensis Qin,Mitchell&Lara,2016）,本文对这一物种的形态特征、分类地位、生态习性和地理分布进行了详细的描述,该物种的壳体梨形,侧面观壳体扁平,两侧有龙骨结构环绕,个体相对较大,壳长为216±8.44 μm,壳宽为122±6.24 μm,壳体测量特征的变异范围较小,具有较为稳定的形态特征。九湖梨壳虫目前发现于我国神农架、华南地区中部和朝鲜半岛的泥炭湿地中水位较高的地带。本文还讨论了该物种在生态指示、古环境重建和生物地理学等方面的意义。
相似文献3.
Ombrotrophic mires can provide records of palaeoclimate over the mid- to late- Holocene in several areas of the world. Their potential is currently partly limited by difficulties with scaling indices based on plant macrofossils and humification, and the need to account for the internal variability of the mire system. This paper explores the use of testate amoebae analysis as a third technique and assesses the minimum within-site variability by comparing results from two closely spaced cores. Reconstruction of surface wetness changes was carried out on cores from the centre of an intermediate raised-blanket mire, Coom Rigg Moss, Northumberland, by analysis of testate amoebae, plant macrofossils and humification. Surface wetness changes were expressed as mean annual water table changes inferred from testate amoebae assemblages, two separate indices based on plant macrofossils and percentage transmission of humification extracts. Comparisons between the proxies suggest good agreement of general trends in Sphagnum peats but some differences in monocot and ericaceous peats. The magnitude of surface wetness changes also differs within Sphagnum peats. The records from the separate cores converge over time and replicability between cores is best in the last 1000 yr. Changes over this period are similar to those shown by estimates based on documentary sources. Good agreement is obtained between a normalised plant macrofossil index and normalised reconstructed water-table values and it is suggested that this approach could form the basis for improved composite, multiproxy records from peatlands. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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在黑龙江流域上游图强、中游友好和下游洪河湿地采集3个典型泥炭剖面,基于210Pb/137Cs法建立剖面年代学框架,利用有壳变形虫指标,借助转换函数法定量重建人类世以来流域湿地水位变化历史,并探讨其可能的影响因素。研究发现,黑龙江流域图强、友好和洪河湿地泥炭柱芯年代均涵盖了人类世的时间尺度,且不同区域湿地中有壳变形虫的物种组成呈现显著的空间差异。根据约束聚类结果,黑龙江流域湿地水位变化可划分为3个阶段：1）人类世早期（1915年左右）,黑龙江流域湿地生境较为湿润,有壳变形虫以喜湿物种为主,如附石/泥炭藓截口虫（Heleopera petricola/sphagni）、凤蝶茄壳虫（Hyalosphenia papilio）等,但水位埋深逐渐增加,湿地生境呈现变干的趋势。区域气候变化是影响湿地水位变化的主要因素。2）1915~1990年左右,黑龙江流域湿地水位变化呈现显著的空间差异,图强湿地水位埋深显著降低,喜湿物种增加,以指示湿润生境的凤蝶茄壳虫（Hyalosphenia papilio）、针棘匣壳虫类（Centropyxis aculeata type）为主;而友好和洪河湿地水位埋深逐渐增加,湿地持续变干,指示湿润环境的物种显著减少,指示干燥环境的顶足法帽虫（Phryganella acropodia）、小匣三角嘴虫（Trigonopyxis arcula）、苔藓鳞盖虫（Assulina muscorum）丰度增大。图强和友好湿地因人类活动影响较弱,区域气候变化仍然是湿地水位变化的主要驱动因素,而洪河湿地水位则受人类活动的显著影响。3）1990年以来,黑龙江流域湿地水位变化因受人类活动的显著影响,上游和中游湿地水位埋深增加,湿地生境持续变干,顶足法帽虫（Phryganella acropodia）、苔藓鳞盖虫（Assulina muscorum）和半空鳞盖虫（Assulina seminulum）占优势;而下游湿地因农田开垦,农田退水使其水位埋深呈现降低的趋势。黑龙江流域人类世以来湿地水位变化受区域气候变化和人类活动的共同影响,在上、中和下游呈现出显著的空间差异。
相似文献6.
Mariusz Lamentowicz Willem Van Der Knaap Łukasz Lamentowicz Jacqueline F. N. Van Leeuwen Edward A. D. Mitchell Tomasz Goslar Christian Kamenik 《第四纪科学杂志》2010,25(2):190-202
We present the first testate amoeba‐based palaeohydrological reconstruction from the Swiss Alps, and the first depth to the water table (DWT) calibration dataset for this region. Compared to existing models, our new calibration dataset performs well (RMSEP = 4.88), despite the length of the water table gradient covered (53 cm). The present‐day topography and vegetation of the study mire Mauntschas suggest that it is partly ombrotrophic (large Sphagnum fuscum hummocks, one of which was the coring site) but mostly under the minerotrophic influence of springs in the mire and runoff from the surrounding area. Ombrotrophic Sphagnum fuscum hummocks developed at the sampling site only during the last 50 years, when testate amoebae indicate a shift towards dry and/or acid conditions. Prior to AD 1950 the water table was much higher, suggesting that the influence of the mineral‐rich water prevented the development of ombrotrophic hummocks. The reconstructed DWT correlated with Pinus cembra pollen accumulation rates, suggesting that testate amoebae living on the mire and P. cembra growing outside of it partly respond to the same factor(s). Finally, temperature trends from the nearby meteorological station paralleled trends in reconstructed DWT. However, contrary to other studies made on raised bogs of northwestern Europe, the highest correlation was observed for winter temperature, despite the fact that testate amoebae would more logically respond to moisture conditions during the growing season. The observed correlation with winter temperature might reflect a control of winter severity on surface moisture during at least the first part of the growing season, through snow melt and soil frost phenomena influencing run‐off. More ecohydrological work on sub‐alpine mires is needed to understand the relationships between climate, testate amoebae and peatland development. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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A Holocene record of pollen, macrofossils, testate amoebae and peat humification is presented from a small montane bog. Sediment accumulation began before 9000 yr BP, but peat growth not until ca. 7000 BP. From 12 000 to 7000 yr BP, a shrub–grassland dominated under a dry climate, with increasing conifer forest and tall scrub from ca. 9600 yr BP. At 7000 yr BP a dense montane–subalpine low conifer forest established under a moist, cool climatic regime. Between 7000 and 700 yr BP the bog surface was shrubby, tending to be dry but with highly variable surface wetness. The catchment was affected by major fire at least four times between 4000 and 1000 yr BP. Both fire and bog surface wetness may have been linked to ENSO-caused variations in rainfall. Cooler, cloudier winters and disturbance by fire promoted the expansion of the broadleaf tree Nothofagus menziesii between 4000 yr BP and 1300 yr BP at the expense of the previous conifer forest–scrub vegetation. Polynesian fires (ca. 700 yr BP) reduced the vegetation to tussock grassland and bracken. Deforestation did not markedly affect the hydrology of the site. European pastoralism since ad 1860 has increased run-off and rising water tables in the bog have led to a Sphagnum-dominated cover. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Robert K. Booth 《第四纪科学杂志》2008,23(1):43-57
Peatland‐inhabiting testate amoebae are sensitive indicators of substrate‐moisture conditions and have increasingly been used in palaeohydrological studies. However, to improve accuracy of testate‐amoeba‐based hydrological inferences, baseline ecological data on rare taxa, a larger geographic network of calibration sites, and incorporation of long‐term estimates of water‐table depth are needed. Species–environment relationships at 369 sites from 31 peatlands in eastern North America were investigated. Long‐term estimates of water‐table depth were obtained using the method of polyvinyl (PVC) tape‐discolouration. Transfer functions were developed using a variety of models, and validated through jackknifing techniques and with an independent dataset where water‐table depths were directly measured throughout the growing season. Results indicate that mean annual water‐table depth can be inferred from testate amoeba assemblages with a mean error of 6 to 8 cm, although there is a slight systematic bias. All transfer function models performed similarly and produced similar reconstructions on a fossil sequence. In a preliminary effort towards development of a comprehensive North American calibration dataset, data from this study were combined with previous studies in Michigan and the Rocky Mountains (n = 650). This combined dataset had slightly larger mean errors of prediction (8–9 cm) but includes data for several rare taxa. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Walter Finsinger Kristian Schoning Sheila Hicks Andreas Lücke Tomasz Goslar Friederike Wagner‐cremer Heidi Hyyppä 《第四纪科学杂志》2013,28(2):152-164
We present a record of peatland development in relation to climate changes and human activities from the Palomaa mire, a remote site in northern Finland. We used fine‐resolution and continuous sampling to analyse several proxies including pollen (for vegetation on and around the mire), testate amoebae (TA; for mire‐wetness changes), oxygen and carbon isotopes from Sphagnum cellulose (δ18O and δ13C; for humidity and temperature changes), peat‐accumulation rates and peat‐colour changes. In spite of an excellent accumulation model (30 14C dates and estimated standard deviation of sample ages <1 year in the most recent part), the potential to determine cause–effect (or lead–lag) relationships between environmental changes and biotic responses is limited by proxy‐specific incorporation processes below the actively growing Sphagnum surface. Nevertheless, what emerges is that mire development was closely related to water‐table changes rather than to summer temperature and that water‐table decreases were associated with increasing peat‐accumulation rates and more abundant mire vegetation. A rapid fen‐to‐bog transition occurred within a few years around AD 1960 when the water table decreased beyond the historical minimum, supporting the notion that mires can rapidly shift into bogs in response to allogenic factors. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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天鹅洲长江故道近代环境变化的有壳变形虫记录 总被引：1，自引：0，他引：1
通过对天鹅洲长江故道近代沉积物中有壳变形虫的形态、生态特征和多样性组合变化的研究,重建了该地区30 a以来有壳变形虫的群落演替过程.沉积物中有壳变形虫和色素分析结果表明,天鹅洲长江故道的生态与环境在人类活动和河道变迁的影响下发生了较为深刻的变化,即:①1975～1987年,水位较低,接受较多的外源有机物质,营养水平上升;②1987～1994年,水体稳定,水质变得清澈;③1994～2001年,自然保护区建立以后,外源有机物输入减少,营养化程度降低;④2001～2005年,随着故道环境由开敞式过渡到封闭式,水体的生产力提高,富营养化加剧.初步研究表明,有壳变形虫作为一种环境指示生物在湖泊沉积与生态演化研究中具有重要的应用价值. 相似文献
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长江中游高山泥炭湿地在区域生态安全和生物多样性保护方面具有举足重要的地位,有壳变形虫是一类在泥炭湿地表面大量生活的原生动物,它们对环境变化敏感,是环境变化的有效指示器。泥炭湿地的现代生态学调查已经表明,有壳变形虫群落对泥炭的表面湿度和水文条件具有灵敏的响应,但是与其他环境条件如水化学因子的关系尚不明确。本文主要调查了长江中游高山泥炭湿地有壳变形虫群落特征及其对水化学因子的响应,发现Cr和Mn对有壳变形虫的群落组成具有较为明显的影响。有壳变形虫的群落组成在不同湿地间有一定差异,这种空间上的差异分布可能反映了湿地的不同类型、发育阶段和人类活动等信息。有壳变形虫可为湿地的科学管理、动态监测和可持续发展等方面提供有效的指示信息。 相似文献
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The vertical distribution of foraminifera, testate amoebae and diatoms was investigated in saltmarshes in the Taf estuary (south Wales), the Erme estuary (south Devon) and the Brancaster marshes (north Norfolk), to assess the use of multiproxy indicators in sea‐level reconstructions. A total of 116 samples were subjected to regression analyses, using the program calibrate, with duration of tidal flooding as the dependent variable. We found that the relationship between flooding duration and taxa was strongest for diatoms and testate amoebae and weakest for foraminifera. The vertical range of testate amoebae in saltmarshes is small. Their lower tolerance limit in present‐day saltmarshes occurs where tides cover the marsh less than a combined total of 7 days (1.9%) in a year. However, they are important sea‐level indicators because information for sea‐level reconstruction is best derived from sediments that originate in the highest part of the intertidal zone. Diatoms span the entire sampled range in intertidal and supratidal areas, whereas the upper limit of foraminifera is found very close to the highest astronomical tide level. Local training sets provide reconstructions with higher accuracy and precision than combined training sets, but their use is limited if they do not represent adequate modern analogues for fossil assemblages. Although analyses are time consuming, a regional training set of all three groups of micro‐organisms yields highly accurate (r2 = 0.80) and precise (low value of root mean square error) predictions of tidal level. This approach therefore could improve the accuracy and precision of Holocene sea‐level reconstructions. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Adeline A. J. Wall Michel Magny Edward A. D. Mitchell Boris Vannière Daniel Gilbert 《第四纪科学杂志》2010,25(6):945-956
We tested the response of lacustrine testate amoebae (thecamoebians) to climate and environmental changes for the Lateglacial–Holocene transition. The palaeoenvironmental history of the study site (Lake Lautrey, Jura Mountains, eastern France) was previously established based on high‐resolution multi‐proxy studies of the same core. The present study is characterised by a high taxonomic resolution (54 taxa), inclusion of small species (down to 25 µm) and high total counts (>500 individuals per sample on average). Changes in the composition of testate amoeba assemblages (dominant species and assemblage structure), as well as in the accumulation rate (tests cm?2 a?1), corresponded to major climatic phases (i.e. Oldest Dryas, Bølling–Allerød Interstadial, Younger Dryas, Preboreal) as well as changes in organic matter inputs. Furthermore, decreases in the accumulation rate characterised minor short‐lived cooling events, such as Older Dryas event or Gerzensee oscillation. However, the Preboreal oscillation, which was well registered by other proxies at Lake Lautrey, could not be recognised in the testate amoeba record. This work demonstrates that lacustrine testate amoebae can be used for palaeoclimatic and palaeoecological reconstructions. Nevertheless, a better understanding of the relation between climate, organic matter and lacustrine testate amoebae requires further high‐resolution studies based on multi‐proxy approaches and the development of appropriate modern analogues. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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This paper presents a Holocene pollen record from an ombrotrophic bog in Southland, New Zealand, together with multiproxy data (testate amoebae, peat humification and plant macrofossils) from the same core to establish an independent semiquantitative record of peatland surface moisture. Linkages between reconstructed peatland surface moisture and regional forest composition are investigated using redundancy analysis of the forest pollen data constrained with predicted bog water‐table depths. Over 32% of the pollen data variance can be explained by surface moisture changes in the bog, suggesting a common cause of water‐table and regional vegetation change. Water tables were higher during the early to mid‐Holocene when the forest was dominated by podocarp taxa. Water tables lowered after about 3300 cal. yr BP coevally with the expansion of Nothofagus species, culminating with the dominance of Nothofagus subgenus Fuscospora in the past 1200 cal. yr BP. This is in apparent opposition to the warm/dry to cool/wet trend suggested by subjective interpretation of pollen data alone, from this and other studies. We suggest that during the late Holocene, drier summers associated with shifts in solar insolation caused reduced surface wetness and summer humidity, which together with a trend to cooler winters, apparently favoured the regeneration of Nothofagus species. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Proxy climate data can be obtained from reconstructions of hydrological changes on ombrotrophic (rain‐fed) peatlands using biological indicators, such as testate amoebae. Reconstructions are based on transfer functions, relating modern assemblage composition to water table and moisture content, applied to fossil sequences. Existing transfer functions in Europe and elsewhere are limited geographically and there are often problems with missing or poor analogues. This paper presents a new palaeohydrological transfer function based on sampling raised mires from across Europe. Relationships between assemblages and hydrological variables are described using ordination analyses. Transfer functions are developed for depth to water table (n = 119) and moisture content (n = 132) with root mean squared errors (RMSEP) of 5.6 cm and 2.7% respectively. Both transfer functions have an r2 of 0.71, based on ‘leave one out’ cross‐validation. Comparisons with an existing transfer function for Britain show that the European transfer function performs well in inferring measured water tables in Britain but that the British data cannot be used to infer water tables for other European sites with confidence. Several of the key missing and poor analogue taxa problems encountered in previous transfer functions are solved. The new transfer function will be an important tool in developing peat‐based palaeoclimatic reconstructions for European sites. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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有壳变形虫(testate amoebae)是一种新的具有潜力的环境变化生物指标。对采集自长白山区哈泥(42°12′50″N,126°31′05″E)、金川(42°20′47″N,126°21′35″E)、赤池(42°03′16″N,128°03′22″E)和圆池(42°01′55″N,128°25′58″E)等4个泥炭地不同生境的75个有壳变形虫样品,采用冗余分析方法(RDA)研究有壳变形虫种类组合变化与7个环境变量的关系,所有采样点均以泥炭藓(Sphagnum)为优势植被。结果表明水位埋深(depth to water table),pH值和泥炭湿度是影响长白山区泥炭地有壳变形虫种类变化的主要环境因子,显著性检验达到p＜0.001的水平。这一结果与国外其他地区的研究结果相一致,这3个环境因子可以作为目标变量进行有壳变形虫－环境因子转换函数的构建。 相似文献
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Matthew Peros Kathleen Chan Gabriel Magnan Leila Ponsford James Carroll Terry McCloskey 《第四纪科学杂志》2016,31(5):512-525
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Matthew J. Amesbury Gunnar Mallon Dan J. Charman Paul D. M. Hughes Robert K. Booth Timothy J. Daley Michelle Garneau 《第四纪科学杂志》2013,28(1):27-39
Proxy reconstructions of climatic parameters developed using transfer functions are central to the testing of many palaeoclimatic hypotheses on Holocene timescales. However, recent work shows that the mathematical models underpinning many existing transfer functions are susceptible to spatial autocorrelation, clustered training set design and the uneven sampling of environmental gradients. This may result in over‐optimistic performance statistics or, in extreme cases, a lack of predictive power. A new testate amoeba‐based transfer function is presented that fully incorporates the new recommended statistical tests to address these issues. Leave‐one‐out cross‐validation, the most commonly applied method in recent studies to assess model performance, produced over‐optimistic performance statistics for all models tested. However, the preferred model, developed using weighted averaging with tolerance downweighting, retained a predictive capacity equivalent to other published models even when less optimistic performance statistics were chosen. Application of the new statistical tests in the development of transfer functions provides a more thorough assessment of performance and greater confidence in reconstructions based on them. Only when the wider research community have sufficient confidence in transfer function‐based proxy reconstructions will they be commonly used in data comparison and palaeoclimate modelling studies of broader scientific relevance. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
