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1.
青藏高原湖泊沉积与环境演变研究：现状与展望 总被引：5，自引：0，他引：5
从空间尺度、不同时间尺度、重大气候环境变化事件、与其他研究结果的对比以及代用指标与气候要素的定量关系研究等几个方面总结了近十余年来青藏高原湖泊沉积与环境演变研究的主要成果。目前在高原上开展的湖泊沉积与环境演变研究主要分布在三个较为集中的地区：高原东北边缘区、高原西部西昆仑山湖泊群和高原中南部湖泊群。已有的湖泊沉积记录主要是以中长时间尺度的研究为主，而短时间尺度高分辨率的研究稍显不足。与其他地区全球变化研究结果的对比表明，湖泊沉积所反映的高原气候环境变化既具有全球性，又具有区域性的特征。湖泊沉积重建的环境序列的定量化研究仍处于探索阶段。由于湖泊沉积的环境代用指标存在着相对多解性，因此在实际研究中多学科交叉、多指标分析的方法是必需的。当前和今后需要深入开展环境代用指标与气候要素之间定量关系的研究，进一步提高沉积物定年的精确性，发现新的更为敏感的环境代用指标，不断完善多学科多环境代用指标的综合分析，并注重填补不同区域不同时间尺度的研究空白，加强高原上不同区域之间的对比研究。 相似文献
2.
Anton Brancelj Milijan Šiško Gregor Muri Peter Appleby Andrea Lami Ewan Shilland Neil L. Rose Christian Kamenik Stephen J. Brooks John A. Dearing 《Journal of Paleolimnology》2002,28(1):47-58
Lake Jezero v Ledvici (NW Slovenia) is a 14 m deep mountain lake at an elevation of 1860 m, situated on limestone bedrock. It is an oligotrophic, alkaline and hard-water lake with a transparency of about 14 m and has suffered several times over recent centuries from strong earthquakes. In 1996 five sediment cores, between 35 and 45 cm long, were collected from the deepest part of the lake and analysed to reconstruct environmental changes over the last few centuries. The data indicate changes induced by pollution and climate change during the last two centuries similar to those in other European mountain and remote lakes. However, at this site earthquakes have also affected the lake and partly obscure the interpretation of the sediment record. From 1780 to 1890, sediment records show low abundance of diatoms and relatively high abundance of Cladocera. After 1890, the number of diatoms started to increase coinciding with a strong earthquake. From the beginning of the 20th century, concentrations of spheroidal carbonaceous particles (SCP), diatom valves and head capsules of chironomids gradually increased whilst in Cladocera the main difference observed was a change in the proportion of benthic taxa. After 1960, in parallel with a rise in air temperature, a further increase in accumulation rate of diatoms started, but there was a decrease in Cladocera. 相似文献
3.
ShiQiao Zhou 《寒旱区科学》2020,12(6):430-435
Tibetan lake levels are sensitive to global change, and their variations have a large impact on the environment, local agriculture and animal husbandry practices. While many remote sensing data of Tibetan lake level changes have been reported, few are from in-situ measurements. This note presents the first in-situ lake level time series of the central Tibetan Plateau. Since 2005, daily lake level observations have been performed at Lake Nam Co, one of the largest on the Tibetan Plateau. The interannual lake level variations show an overall increasing trend from 2006 to 2014, a rapid decrease from 2014 to 2017, and a surge from 2017 to 2018. The annual average lake level of the hydrological year (May-April) rose 66 cm from 2006 to 2014, dropped 59 cm from 2014 to 2017, and increased 20 cm from 2017 to 2018, resulting in a net rise of 27 cm or an average rate of about 2 cm per year. Compared to the annual average lake level based on the calendar year, it is better to use the annual average lake level based on the hydrological year to determine the interannual lake level changes. As the lake level was stable in May, it is appropriate to compare May lake levels when examining interannual lake level changes with fewer data. Overall, remote sensing results agree well with the in-situ lake level observations; however, some significant deviations exist. In the comparable 2006-2009 period, the calendar-year average lake level observed in-situ rose by 10-11 cm per year, which is lower than the ICESat result of 18 cm per year. 相似文献
4.
5.
Seggedim is a remote site in NE Niger where previous studies demonstrated the presence of Holocene paleolake deposits beneath an existing sabkha. In 2005, we retrieved a 15-m core that contains a high-resolution record of early to middle Holocene environmental change. Mineralogical, chemical and petrographic data were used to infer paleoenvironmental conditions recorded by successive lake stages. An exceptionally stable lake regime existed from 10.6 to 7.3 cal ka BP. This regime, reflecting moist conditions, was characterized by deposition of continuously laminated diatomite with high organic matter content, formed under meromictic conditions, with very low detrital input. A lake regime shift occurred at 7.3 cal ka BP, interpreted as the beginning of a transition to arid conditions. This shift was initially marked by a change to predominantly clastic sedimentation, followed by increased sand input during later stages, culminating in the onset of the sabkha stage. Because of the presence of reworked organic material in the deposits, reliable radiocarbon dating of the succession of lake stages could not be achieved. 相似文献
6.
Gaute Velle Richard J. Telford Oliver Heiri Joshua Kurek H. John B. Birks 《Journal of Paleolimnology》2012,48(3):545-558
Most calibration data sets used to infer past environmental conditions from biological proxies are derived from many sites. An alternative strategy is to derive the calibration data set from within a single site. Transfer functions derived from such intra-site calibration data sets are usually applied to fossil assemblages from the focal lake, but a recent development has been to apply these transfer functions to other sites. Transfer functions derived from intra-site calibration data sets can have impressive cross-validation performance, but that gives little indication of their performance when applied to other sites. Here, we develop transfer functions for lake depth from intra-lake chironomid calibration data sets in Norway and Alaska and test the resulting models by cross-validation and against known depth in external lakes. Lake depth is a statistically significant predictor of chironomid assemblages at all these lakes, and most intra-lake transfer functions perform reasonably well under cross-validation, but their performance against external data is erratic. Downcore reconstructions from transfer functions developed on different lakes are dissimilar. Ignoring the poorly performing transfer functions, only 3 of 14 downcore reconstructions are statistically significant. Few assemblages downcore had good modern analogues in the calibration data set, even when the core was from the same lake as the calibration data set. We conclude that intra-site calibration data sets can find site-specific rather than general relationships between species and the environment and thus should be applied with care and to external sites only after careful and critical validation. 相似文献
7.
金藻孢囊是金藻生殖过程的特有产物,在淡水环境中广泛存在,其硅质外壳易在沉积物中保存。金藻孢囊的孔、领、环带以及表面纹饰特征是其鉴定分类的主要依据。金藻孢囊对水环境变化响应敏感,因而被广泛应用于水环境变化研究中,包括古温度和古水文重建、水体富营养化和酸化评估等领域。已有的研究主要集中在北美和欧洲地区,其他区域研究相对较少。相比于其他生物指标,金藻孢囊鉴定相对复杂,不利于其广泛应用。因此,未来应优化金藻孢囊鉴定分类方法,提高鉴定统计效率。其次,加强金藻孢囊的现代过程调查,尤其在欧洲和北美以外的地区,以揭示全球不同地区金藻孢囊多样性及其生态属性。在此基础上,加强金藻孢囊在泥炭地环境演变、生物地理学等研究领域的应用。 相似文献
8.
This Special Issue was produced as an output from the EU Integrated Project Euro-limpacs which aimed to evaluate the impacts of global change on European freshwater ecosystems using a combination of approaches,
including monitoring, experiments, modelling and palaeolimnology. The papers focus on the last of these approaches. They examine
the role of lake sediment records in determining reference conditions for a range of environmental pressures including acidification,
eutrophication, metal pollution, organic carbon and sediment accumulation rates. The findings are especially relevant to the
European Union’s Water Framework Directive which requires an assessment of lake ecological status based on deviation from
reference conditions. The contributions consider a range of issues relating to the use of palaeolimnological data in defining
reference conditions and lake status including human versus natural variability, concepts of pristine and reference conditions,
shifting baselines, and quantification of degree of change. This introductory paper sets the context for the volume by briefly
describing how palaeolimnology has evolved as a science, able now to contribute uniquely to the understanding of lake ecosystem
change, especially with respect to the role of human activity over recent decades and centuries. 相似文献
9.
Yongbo Wang Ulrike Herzschuh Xingqi Liu Oliver Korup Bernhard Diekmann 《Journal of Paleolimnology》2014,51(2):303-312
Lacustrine sediments have been widely used to investigate past climatic and environmental changes on millennial to seasonal time scales. Sedimentary archives of lakes in mountainous regions may also record non-climatic events such as earthquakes. We argue herein that a set of 64 annual laminae couplets reconciles a stratigraphically inconsistent accelerator mass spectrometry (AMS) 14C chronology in a ~4-m-long sediment core from Lake Mengda, in the north-eastern Tibetan Plateau. The laminations suggest the lake was formed by a large landslide, triggered by the 1927 Gulang earthquake (M = 8.0). The lake sediment sequence can be separated into three units based on lithologic, sedimentary, and isotopic characteristics. Starting from the bottom of the sequence, these are: (1) unweathered, coarse, sandy valley-floor deposits or landslide debris that pre-date the lake, (2) landslide-induced, fine-grained soil or reworked landslide debris with a high organic content, and (3) lacustrine sediments with low organic content and laminations. These annual laminations provide a high-resolution record of anthropogenic and environmental changes during the twentieth century, recording enhanced sediment input associated with two phases of construction activities. The high mean sedimentation rates of up to 4.8 mm year?1 underscore the potential for reconstructing such distinct sediment pulses in remote, forested, and seemingly undisturbed mountain catchments. 相似文献
10.
遥感对地观测为理解陆地植被动态与全球环境变化规律提供了数据基础,基于卫星观测的全球植被遥感数据产品近年来层出不穷,但缺乏基于数据使用者视角的系统梳理。本文回顾了全球植被遥感数据产品的发展历程,梳理了相关卫星计划及对应数据产品,分析了从植被光谱指数到生物物理特征参量、传统光学遥感反演到叶绿素荧光及星载微波反演产品、从单一传感器生产到多数据源—多数据集融合产品的发展脉络,阐述了全球植被遥感数据产品的来源、特征与关联关系。认为当前全球植被遥感数据产品的生产与应用存在一定脱节,遥感产品精度制约了对地球系统的深入理解。全球植被遥感数据产品正从宏观状态监测向专业化、精细化、标准化转变,建议未来制备全球遥感数据产品应充分利用目前已积累的长时序观测数据,融合多源观测资料,提升现有数据集的时空分辨率、精度及连续性;注重提高特殊区域与特定类型生态系统的反演精度,加强多维植被特征的一体化监测;建立全球植被产品数据共享平台,提供标准的全流程数据处理与分发服务,将数据不确定性信息高效、清晰提供给用户。 相似文献
11.
Environmental controls on modern chironomid faunas from NW Iceland and implications for reconstructing climate change 总被引：1，自引：1，他引：0
Reconstructing climate change quantitatively over millennial timescales is crucial for understanding the processes that affect
the climate system. One of the best methods for producing high resolution, low error, quantitative summer air temperature
reconstructions is through chironomid analyses. We analysed over 50 lakes from NW and W Iceland covering a range of environmental
gradients in order to test whether the distribution of the Icelandic chironomid fauna was driven by summer temperature, or
whether other environmental factors were more dominant. A range of analyses showed the main environmental controls on chironomid
communities to be substrate (identified through loss-on-ignition and carbon content) and mean July air temperature, although
other factors such as lake depth and lake area were also important. The nature of the Icelandic landscape, with numerous volcanic
centres (many of which are covered by ice caps) that produce large quantities of ash, means that relative lake carbon content
and summer air temperature do not co-vary, as they often do in other chironomid datasets within the Arctic as well as more
temperate environments. As the chironomid–environment relationships are thus different in Iceland compared to other chironomid
training sets, we suggest that using an Icelandic model is most appropriate for reconstructing past environmental change from
fossil Icelandic datasets. Analogue matching of Icelandic fossil chironomid datasets with the Icelandic training set and another
European chironomid training set support this assertion. Analyses of a range of chironomid-inferred temperature transfer functions
suggest the best to be a two component WA-PLS model with r
2
jack = 0.66 and RMSEP = 1.095°C. Using this model, chironomid-inferred temperature reconstructions of early Holocene Icelandic
sequences show the magnitude of temperature change compared to contemporary temperatures to be similar to other NW European
chironomid sequences, suggesting that the predictive power of the model is good. 相似文献
12.
S. Murnaghan D. Taylor E. Jennings C. Dalton K. Olaya-Bosch B. O’Dwyer 《Journal of Paleolimnology》2012,48(2):433-448
Knowledge of natural variability in aquatic ecosystems is vital for assessing the nature and amplitude of human-induced change, and for predicting future anthropogenic impacts. Distinguishing between naturally and anthropogenically caused variability in lake sediment records can be problematic, however, because both drivers can produce similar ecological effects. Standard sediment-based approaches for reconstructing past environmental changes tend to focus on qualitative and quantitative variations in palaeoenvironmental indicators, with little significance attached to their complete absence. We used multiple variables in radiometrically dated sediment cores collected from two sites in Lough Mask, a lake in western Ireland. Results suggest that the Lough Mask sediment record has been a sensitive recorder of past climate variability, especially changing precipitation, since the middle Holocene. Variations in the presence of aquatic siliceous microfossils and calcareous macrofossils, and changing sediment lithology and geochemistry, indicate a quasi-cyclic response to oscillations in climate conditions that correspond generally with palaeoclimate findings from elsewhere in NW Europe, including other sites in Ireland. We conclude that during much of the middle to late Holocene, prolonged periods of relatively high rainfall in the catchment reduced nutrient inputs to the lake, particularly silica and calcite. Diatom productivity consequently declined, whereas dissolution of frustules was enhanced. During relatively dry climate periods, availability of these nutrients increased, diatom productivity was higher, and dissolution was reduced. Relatively early human impacts are evident in the sediment record beginning ca. 1,000?BP. The results highlight the aquatic and taphonomic effects of complex interactions among past variations in catchment conditions, climate and water chemistry. The complexity of these interactions and their effects, mediated through the characteristics of Lough Mask and its catchment, pose problems for conventional interpretation of palaeolimnological data and their use in computer-based simulations of future changes in stresses on aquatic ecosystems and their consequent impacts. 相似文献
13.
科尔沁沙地沙丘-草甸相间地区1986-2013年湖泊演变 总被引：1，自引：1，他引：0
湖泊变化敏感地记录着气候变化的信息。以科尔沁沙地沙丘-草甸相间地区为研究区,利用多时相TM/ETM+遥感影像,基于遥感和GIS技术提取研究区1986-2013年湖泊个数与面积信息,分析其变化规律及空间分异特征。在此基础上,联系降水量、蒸发量等气候要素和以人类活动影响为主的时间因子t,采用多元统计分析方法对研究区湖泊面积进行了模拟分析。结果表明:(1)研究区小型湖泊近30年间面积和个数均发生了不同程度的变化,其变化趋势与降水量呈现很强的正相关,与蒸发量呈较强的负相关,人类活动对小型湖泊面积的影响不太显著,随着时间的推移,研究区湖泊面积趋于萎缩,这种萎缩主要归因于气候的干化;(2)研究区t年湖泊面积At与前一年湖泊面积At-1、t年降水量Pt和蒸发量Et存在较强的相关关系;(3)1986-2013年研究区典型湖泊--王巴哈嘎湖泊总体上呈萎缩状态,但不同方向上既有萎缩也有扩张,Ⅰ、Ⅱ、Ⅴ、Ⅵ区域(以北向为0°,顺时针每45°一个区域,并顺序标记为Ⅰ~Ⅷ区域)萎缩,其他区域扩张,其中以Ⅱ、Ⅲ、Ⅷ、Ⅳ区域为主导变异方向,Ⅵ方向次之,其他方向变化缓滞。研究成果不仅为科尔沁沙地生态系统的健康维持提供技术支撑,对其他同类地区湖泊环境的研究也具有指导作用。 相似文献
14.
A diatom-conductivity transfer function for Spanish salt lakes 总被引：3，自引：0，他引：3
J.M. Reed 《Journal of Paleolimnology》1998,19(4):399-416
Diatom-salinity transfer functions for interpretation of palaeosalinity and palaeoclimate change have been developed successfully for parts of North America and North and East Africa, but there is a need for data-sets in other saline lake regions of the world. A data-set of 74 modern diatom samples and associated water chemistry data is described from Spain. The influence of conductivity and other environmental variables on diatom distribution is explored using canonical correspondence analysis (CCA) and partial CCAs. A transfer function is derived for conductivity (70 samples) whose apparent predictive ability is high (apparent r2 = 0.91). Performance under jackknifing is poor due to the heterogeneous nature of the data-set and poor coverage of the freshwater end of the salinity gradient. There is a lack of suitable low-salinity sites in Spain, and the accuracy of estimated salinity optima and tolerance ranges may be improved by merging this data-set with those of other regions. The Spanish transfer function has strong affinities with the African data-set and contributes important ecological data for diatom taxa which are absent or poorly represented in the modern flora of African lakes, and for which, in fossil material, there were previously no good modern analogues. 相似文献
15.
Reconstructing air temperature at eleven remote alpine and arctic lakes in Europe from 1781 to 1997 AD 总被引：3，自引：0，他引：3
Pristine and sensitive environments, such as remote alpine and arctic lakes, are particularly susceptible to the effects of climate change. However, these remote environments do not have sufficiently long instrumental climate records to support studies on contemporary climate change. The issue of the scarcity of instrumental climate data at remote regions is addressed by reconstructing monthly mean air temperatures from 1781 to 1997 AD at eleven remote alpine and arctic lakes in Europe, as part of the MOuntain LAke Research (MOLAR) project. Stepwise multiple regression is applied to establish linear transfer functions of temperatures between each of eleven upland records and twenty homogenised long lowland records. Twelve monthly transfer functions are obtained for each lake. The skill of these transfer functions is found to range typically between 60 and 99%. The lower skill values generally correspond to winter months. The temperature reconstructions obtained using the transfer functions need to be corrected with vertical temperature gradients. Air-temperature lapse rates were obtained for each lake region by spatial interpolation of radiosonde air-temperature data (1990–1997). The resulting reconstructions at each lake were checked using air-temperature data (1996–1997) from automatic weather stations installed at the lakes during the MOLAR project. We estimate the typical reconstruction errors to be about 1.3 °C for low-sun months and about 0.98 °C for high-sun months. Trend analyses on the reconstructed annual mean air temperatures at the lakes show two distinct types of trends for the 19th and 20th centuries. During the period 1801–1900, the western European lakes show no significant trend whereas annual mean air temperatures at the eastern European lakes decrease significantly. The period 1901–1997 presents a warming trend at all but the Fennoscandian lakes. Our results are in good agreement with previous studies on the spatial distribution and magnitude of temperature change in Europe. Principal component analysis performed on the reconstructed annual mean air temperature reveals two different regimes of trends for the past two centuries. It also allows a regional clustering of the inter-annual variability of air temperature at the lakes to be identified. 相似文献
16.
Laura S. Epp Kathleen R. Stoof Martin H. Trauth Ralph Tiedemann 《Journal of Paleolimnology》2010,43(4):939-954
Using molecular genetic methods and an ancient DNA approach, we studied population and species succession of rotifers of the
genus Brachionus in the Kenyan alkaline-saline crater lake Sonachi since the beginning of the 19th century as well as distribution of Brachionus haplotypes in recent and historic sediments of other lakes of the East African Rift System. The sediment core record of Lake
Sonachi displays haplotypes of a distinct evolutionary lineage in all increments. Populations were dominated by a single mitochondrial
haplotype for a period of 150 years, and two putatively intraspecific turnovers in dominance occurred. Both changes are concordant
with major environmental perturbations documented by a profound visible change in sediment composition of the core. The first
change was very abrupt and occurred after the deposition of volcanic ash at the beginning of the 19th century. The second
change coincides with a major lake level lowstand during the 1940s. It was preceded by a period of successively declining
lake level, in which two other haplotypes appeared in the lake. One of these putatively belongs to another species documented
in historical and recent Kenyan lake sediments. The analysis of plankton population dynamics through historical time can reveal
patterns of population persistence and turnover in relation to environmental changes. 相似文献
17.
18.
青藏高原是我国重要的生态屏障,也是重要的盐湖分布区。在青藏高原第一次综合科考时曾对青藏高原盐湖开展过系统调查。二次科考在一次科考的基础上,加强了对一些工作程度不够的极端困难区的补充调查,还重点开展了气候变化及资源开发双重影响下青藏高原盐湖资源与环境的变化趋势;现代盐湖关键元素迁移、富集规律;古钾盐成矿预测;盐湖资源开发的生态环境效应等研究工作。经过近3年的系统工作,专题获得了大量一手科考数据,已取得了一批有显示度的科学成果。研究系统介绍了盐湖专题科考方案的整体思路、研究内容、技术路线、前期获得的亮点成果及下一步工作计划等。 相似文献
19.
基于地表覆盖物光谱特征的土地覆被分类系统 ——以鄱阳湖流域为例 总被引：8，自引：1，他引：7
土地覆被主要表现为陆地表面的形态特性和动态变化特征,土地利用是其动态变化的外在驱动力,植被是土地覆被的“主要”而非唯一的组成部分,土地覆被也包含着它的功能特性。地表覆被物的光谱特征及其季节性变化规律是土地覆被的本质特征,也是土地覆被分类的基本依据之一;利用遥感资料所表达的地表覆被物特征值 (如以NDVI为指标的绿度值、始绿期、终绿期、波形、峰值、谷值等) 可以方便地对土地覆被分类标准进行量化处理;对于一些复杂的复合单元,应着重于它的组合 (包括组成成分和结构) 特性及其对地面过程的影响来赋予更确切的内涵。据此,构建了包含7个一级类别和20个二级类别的开放式 (open-end) 的鄱阳湖流域土地覆被分类系统,并且应用SPOT4-VEGETATION 的时序NDVI数据,对各类别的面积比重进行了分析,结果显示鄱阳湖流域的现状覆被主要由常绿覆被和作物-树-草混合覆被以及人工栽培植被 (作物) 等构成。 相似文献
20.
基于流量监测的西藏东南部然乌湖水量平衡季节变化及其补给过程分析 总被引：1，自引：0，他引：1
青藏高原分布着亚洲大陆最大的湖泊群,其湖泊变化对气候变化响应敏感。基于遥感数据的湖泊面积变化不足以反映外流湖对气候变化的响应,需借助湖泊水量平衡过程分析来进一步研究各补给要素的变化。本文利用2015年4月-11月然乌湖水文气象监测数据,通过建立流量—水位关系,依据连续的水位数据重建了观测期内然乌湖主要径流的水文过程线,并结合SRM模型分析了然乌湖的水量平衡过程及季节变化。结果表明,观测期内然乌湖入湖水量约为18.49×108 m3,其中冰川融水约为10.06×108 m3,冰川融水占然乌湖补给的54%以上,湖面降水、湖面蒸发对湖泊水量平衡过程影响微弱。流域降水对湖泊的补给具有明显的季节特征。春季受西风南支扰动影响,然乌湖地区降水量大,降水是春季然乌湖的主要补给源。夏季和早秋由于气温升高,冰川消融量大,冰川融水是湖泊补给的主控因素。在未来气候变暖的条件下,冰川融水将会在湖泊补给中占据更大比例,并可能使得流域内的冰湖水量增加,产生潜在灾害风险。 相似文献