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The Present foraminiferal distribution (live + dead) in Freemansundet between Barentsøya and Edgeøya, Svalbard, has been compared with assemblages in raised marine Holocene deposits in Guldalen on Edgeeya. Four distinct foraminiferal assemblages were identified in Freemansundet, the Elphidium excavatum-Cassidulina reniforme assemblage, the Elphidium hallandense assemblage, the Cibicides lobatulus assemblage and the Elphidium incertum-Haynesina orbiculare assemblage. Four assemblage zones (Zones A-D) have been established in the glaciomarine to marine sediment sequence in Guldalen. Only two of the recent fauna! types were represented here. The Elphidium excavatum-Cassidulina reniforme assemblage, which reflects a proximal glacier environment, was found in the lowermost Zone A (the Elphidium excavatum Zone) and in Zone C (the Elphidium excavatum-Cassidulina reniforme Zone) in the Guldalen stratigraphy; the Elphidium incertum-Haynesina orbiculare assemblage, which reflects ameliorated shallow water conditions, was found in the uppermost Zone D in Guldalen. The marine sequence in Guldalen represents a relatively short period of time during the Early Holocene (ca 9700 to 8300 BP). The succession of the foraminiferal assemblages suggests that the deglaciation was interrupted by a cold period with glacial stagnation just after 9600 bp (Zone B. the Astrononion gallowayi-Nonionellina labradorica Zone). 相似文献
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150年来青藏高原南红山湖的介形类与环境变化 总被引：14，自引：1，他引：14
青藏高原西北部南红山湖2孔湖芯沉积物中的介形类动物群计有4属4种,据其分布特征划分出5个组合,各组合间的差异表现在介形类动物群丰度和每个种的丰度变化以及特征种的出现。通过分析介形类属种生态特征和组合变化对150年来的南红山湖环境变化进行了探讨。分析结果表明:1884年前为有缓慢水流注入的滨岸浅水期;1885～1970年间为湖水相对温暖期,在这期间湖泊环境仍有次一级的变化,其中,1885～1905年湖面迅速抬升,水深增大,水温也较高,1923～1944年为湖水温度另一个稍高期,1961～1969年湖面再次出现明显上升;1970年以来湖泊退缩、咸化。 相似文献
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Short sediment cores from two gulfs, Monche Bay and Kunchast Bay, of Lake Imandra (Kola Peninsula, northern Russia) were analysed for sediment chemistry and chironomid head capsule remains. Monche Bay has been receiving metals from the Severonikel copper-nickel smelter since the late 1930's. Kunchast Bay was selected in the remotest lake basin as an internal reference site. There were no pronounced changes in the chironomid assemblages with the beginning of slight metal contamination of Kunchast Bay. Based on the reconstructed environmental variables and chironomid assemblages, three developmental stages were distinguished from the chironomid fauna history of Monche Bay: (1) A natural development stage; (2) the early warning stage; and (3) the developing crises stage. During the first period, the changes in the chironomid fauna reflect an anthropogenically undisturbed assemblage, with Micropsectra insignilobus dominating (17–23%). The changes during the second period reflect the initial phase of anthropogenic succession associated with the beginning of metal pollution. The main species showed opposite distributional patterns in this period: the abundance of M. insignilobus decreased, whereas the abundance of Chironomus, Procladius and Sergentia coracina increased. At the same time, maximal numbers were attained for species richness (45) and Shannon-Weaver diversity (4.85) of chironomid assemblages, and the highest head capsule concentration (75 head capsules · g–1 of dry sediment). The third period was characterized by a major shift in the faunal assemblages, from M. insignilobus to other dominant species, including Chironomus (22–44%), Procladius (10–30 %) and S. coracina (15–18%). Besides fauna changes, assemblages of the third period are distinguished by the occurrence of mouthpart deformities in Chironomus head capsules. 相似文献
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Laurent Millet Boris Vannière Valérie Verneaux Michel Magny Jean Robert Disnar Fatima Laggoun-Défarge Anne Véronique Walter-Simonnet Gilles Bossuet Elena Ortu Jacques-Louis de Beaulieu 《Journal of Paleolimnology》2007,38(4):525-539
This study focuses on the response of lacustrine littoral chironomid communities to late glacial changes in limnological,
environmental and climate conditions in the Mediterranean context. Late glacial chironomid (Diptera: Chironomidae) assemblages,
organic petrography and geochemistry were analysed in a sediment core from the littoral zone of Lago dell’Accesa (Tuscany,
Italy), where the lake-level fluctuations and the vegetation history have been previously reconstructed. Comparison of the
chironomid stratigraphy to other proxies (pollen assemblages, organic petrography and geochemistry, lake-level) and regional
climate reconstruction suggested the predominant influence of lake-level changes on the littoral chironomid fauna. The main
lowering events that occurred during the Oldest and the Younger Dryas were followed by higher proportions of taxa typical
of littoral habitats. A complementary study of organic matter suggested the indirect impact of lake-level on the chironomids
through changes in humic status and habitat characteristics, such as the type of substrate and aquatic macrophyte development.
Several chironomid taxa, such as Glyptotendipes, Microtendipes and Cricotopus type patens, were identified as possible indicators of low lake-level in the late glacial records. Nevertheless, this study suggested
that parallel analyses of organic matter and chironomid assemblages may be needed to circumvent misinterpretation of littoral
chironomid assemblage stratigraphy. There was a weak response of the chironomid assemblages to small lake-level lowerings
that corresponded to the Older Dryas and Preboreal oscillations. A higher level of determination, e.g. to the species group
level, may be necessary to increase the sensibility of the indicators to lake-level changes. 相似文献
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Geoffrey Lemdahl 《Journal of Paleolimnology》2000,23(1):57-66
Thirty-six Coleoptera (beetle) taxa and other insects were identified from the late-glacial and early-Holocene sediments at Kråkenes Lake. Compared with other Scandinavian late-glacial sites, this is a rather sparse record. The water beetles found in the Allerod are characteristic of a poorly vegetated clear-water lake. The terrestrial fauna is indicative of dwarf-shrub and moss vegetation. A marked decline in the number of species at the start of the Younger Dryas was rather rapid, probably over less than 80 calendar yrs. No obligate tundra species replaced the Allerod fauna. Most of the Younger Dryas is virtually devoid of beetles. The increase in numbers and diversity of both aquatic and terrestrial species at the Younger Dryas/Holocene transition is very rapid. After an initial pioneer stage, beetles associated with dwarf-shrub heath and willow scrub appeared, but no obligate tree or forest taxa were recorded.Mutual Climatic Range (MCR) temperature reconstructions suggest that the Allerod was colder and more continental than present. The near absence of beetles in the Younger Dryas probably reflects very cold conditions. A rapid temperature rise at the start of the Holocene resulted in a warmer and more continental climate than present. 相似文献
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沙坡头昆虫区系初步研究 总被引：6，自引：3，他引：3
本项研究根据昆虫的生境, 把沙坡头昆虫区系分为流沙区(S区), 沙地人工植被区(M区)和沙地农业改良利用区(A区)。S区以拟步甲科(Tenebrionidae)昆虫为优势种; M区以象甲科(Curculionidae)、螟蛾科(Pyralidae)、草蛉科(Chrysopidae)、和蝗科(Acridiidae)等多科昆虫为特征; A区以金龟甲科(Scarabaeidae)等多科农业昆虫为优势种。分析沙坡头昆虫区系组成, 灰斑古毒蛾(Orgyia ercae)有大发生现象, 但其寄主——花棒(Hedysarum scoparium)在人工植被演替过程中的地位已不重要, 所以沙坡头昆虫区系的指示作用表明, 控制花棒在人工植被中的发展就可以达到昆虫区系改造的目的。 相似文献
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Testate amoebae are informative about palaeoecological conditions, but the methods generally used for their analyses in lake
sediments differ from those used for their analyses in peats, making comparisons difficult. This study examines how filter
mesh size and total number of individuals counted affect species richness, Shannon diversity, equitability, density and assemblage
structure. We analysed the complete testate amoeba contents of six sediment samples from Lake Lautrey, France. The abundance
of testate amoebae was high (1,403–10,870 shells cm−3), and species smaller than 63 μm in both length and width represented up to 89% of total abundance and 43% of species richness.
A simulation showed that using 47- or 63-μm mesh-size filters reduced inter-sample differences and changed the patterns of
abundance, species richness and assemblage structure, causing loss of information and leading to potential erroneous palaeoecological
interpretation. Rarefaction analyses suggest that although 170 shells are sufficient to assess the general structure of assemblages,
such small sample sizes can underestimate species richness by overlooking taxa with relative abundances <4%. Total counts
of 400 shells yield better estimates of assemblage structure and recover at least 50% of total species richness, although
species with absolute frequencies below 2% may still be missed. Higher counts are required to obtain reliable estimates of
species richness and assemblage structure in samples that have high testate amoeba densities but are dominated by a few small
taxa. Further studies should determine the bioindicator value and functional roles of small and/or rare species in lakes and
thus to what extent overlooking them affects palaeoecological interpretations. 相似文献
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Torkild Bakken Jon Anders Kongsrud Eivind Oug Sabine K.J. Cochrane Toril Loennechen Moen & Beata E.B. Solbakken 《Polar research》2010,29(1):1-21
A thorough literature review has been undertaken to establish the first complete account of polychaetes recorded from the area around the volcanic island of Jan Mayen. The annotated checklist lists 121 species-level taxa, representing an increase from the 75 species previously recorded. The checklist is based on existing records, supplemented with material sampled in 1999, from which 42 species new to the area were reported. Some previously reported species from the area have been excluded because of inadequate documentation. The polychaete fauna of Jan Mayen is comparable with that of the mainland Norwegian coast and the Svalbard area. No taxa unique to the island were found. However, knowledge of the marine invertebrate fauna in general at Jan Mayen is sparse because few surveys have been undertaken there. It is expected that future expeditions will reveal further new taxon records for the area. 相似文献
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本文记述了四川万县盐井沟和巫山大庙山原期夷平面上的喀斯特洞穴及其动物群。论证了山原期夷平面的剥夷时期为新第三纪;洞穴生成时期为上新世;其堆积为更新世。并对万县盐井沟动物群的时代及所属层位提出了讨论。 相似文献
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A small mammal collection from the Kolyma region in northeastern Siberia collected by the Norwegian trapper and naturalist Johan Koren between 1915 and 1917 comprises 152 specimens of 17 species. The collection was brought to Norway with Roald Amundsen's "Maud" expedition through the Northeast Passage and has been held by the Zoological Museum, University of Oslo.
When comparing the collection with the current distribution of small mammals in the region, it is not possible to detect changes in the small mammal fauna. As several species which are common today are missing in the collection, the collection apparently does not give a complete account of the small mammal fauna in the Kolyma region from 1915 to 1917. This discrepancy can largely be explained by the fact that Koren caught small mammals only in parts of the Kolyma region and not in those areas where the missing species are found in abundance. 相似文献
When comparing the collection with the current distribution of small mammals in the region, it is not possible to detect changes in the small mammal fauna. As several species which are common today are missing in the collection, the collection apparently does not give a complete account of the small mammal fauna in the Kolyma region from 1915 to 1917. This discrepancy can largely be explained by the fact that Koren caught small mammals only in parts of the Kolyma region and not in those areas where the missing species are found in abundance. 相似文献
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Habitat degradation in the Chaco has been intense and widespread since European settlement. Detailed knowledge about its effects on the Chaco fauna is scarce despite the critical importance of such information for biodiversity conservation. The effects of habitat degradation on the Arid Chaco lizard assemblage were evaluated by comparing species richness and abundance in four sites along a gradient of increasing vegetation degradation. Two undisturbed sites (primary forest and grassland), and two sites with different degrees of forest degradation (moderate and severe) were selected. Ten lizard species were recorded (nine were trapped and one was sighted), totaling 1122 captures. Abundance of Homonota fasciata, Leiosaurus paronae, Liolaemus chacoensis and Stenocercus doellojuradoi was highest in the primary forest, with significantly lower values in the remaining three sites. Teius teyou and Tropidurus etheridgei were more abundant in the moderately and severely degraded forests than in the primary forest. Management implications of our results in terms of lizard biodiversity in the Chaco are analyzed. 相似文献
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渤海湾北岸表层沉积中的有孔虫群及其生态环境 总被引：2，自引：0，他引：2
我们对渤海湾北岸177个表层沉积物样品进行了有孔虫分析。经鉴定,未发现浮游有孔虫,底栖有孔虫共计82种,其中包括一新种Jadammina planata He et Li sp.nov.根据不同的环境中沉积物内有孔虫群属种组合不同,大体可归纳为二种组合:一是河口、海滩、泻湖、滨海平原等滨海边缘环境组合,在南堡以东该组合称为厚壁转轮虫——显孔鼓室希望虫组合,南堡以西称为厚壁转轮虫——多变假小九字虫组合,二是分布在水深10米以内的近岸浅海环境组合,称为厚壁转轮虫——缝裂希望虫组合。在不同环境中,有孔虫壳体数量的变化是有规律的,一般在泻湖中有孔虫含量最多,滨岸沙坝处最少,沙坝脊部有时为零,向海方向至近岸浅海共含量又有逐渐增多的趋势。 相似文献
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南极乔治王岛长城湾活有孔虫和死有孔虫的比较分析 总被引：1，自引：0，他引：1
本文对中国首次南极考察队在长城湾采集的海底底质样品作了有孔虫分析,初步查明有孔虫属种,并揭示了长城湾有孔虫组合和分布规律。 相似文献
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E. Cuna E. Zawisza M. Caballero A. C. Ruiz-Fernández S. Lozano-García J. Alcocer 《Journal of Paleolimnology》2014,51(1):1-14
The Little Ice Age (LIA), AD 1350–1850, represents one of the most recent, persistent global climate oscillations. In Mexico, it has been associated with temperature decreases of 1.5–2 °C and mountain glacier advances, which are not accurately dated. We present new information about the nature of the LIA in central Mexico based on a decadal-resolution sediment sequence from high-altitude, tropical Lake La Luna, in the Nevado de Toluca volcano. We inferred past climatic and environmental changes using magnetic susceptibility, charcoal particles, palynomorphs, diatoms, cladoceran remains and multivariate statistics. The onset of the LIA corresponds with the beginning of a long-term trend to colder and drier climate ca. AD 1360–1910. The coolest and driest episode, ~AD 1660–1760, which corresponds with the Maunder Minimum in solar activity, was characterized by a cladoceran assemblage that showed the greatest dissimilarity to the modern one (no modern analogue), with the presence of cold-water species and Daphnia ephippia. The beginning of a warming trend ca. AD 1760, was identified by a diatom assemblage dominated by species with affinities for higher pH values (>6) and the greatest dissimilarity to the modern assemblage. This less cold, but still dry period, corresponds with historical reports of cattle and crop losses that predated the Mexican wars of Independence (AD 1810–1821) and Revolution (1910–1924). Modern conditions, established around AD 1910, resemble those during the Medieval Climate Anomaly (ca. AD 1200). No clear evidence of modern, human-induced environmental change was recorded, indicating that Lake La Luna is an ideal site in Mexico to monitor future impacts of global change. 相似文献
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Marianne Presthus Heggen Hilary H. Birks Oliver Heiri John-Arvid Grytnes H. John B. Birks 《Journal of Paleolimnology》2012,48(4):669-691
How representative of the whole-lake fossil assemblage are analyses from a single sediment core taken in the centre of a small lake? This question was addressed in five shallow Norwegian lakes that ranged in location from low-altitude, boreal-deciduous forest to mid-alpine environments. Surface-sediment samples were taken from the deepest part of each lake and in two transects running from the lake centre to shore, and analysed for mites, chironomids, and plant remains. Ordination techniques summarised patterns of variation between and within lakes. Correlations between whole-lake assemblages and water depth and sediment organic content (loss-on-ignition) were investigated. Representativeness of each sample of the whole-lake assemblage was determined by comparing Principal Components Analysis scores of the original data with those of Monte Carlo-simulated data sets, using the actual data as constraints in the simulations. The majority of samples are representative of the whole-lake assemblages. Littoral samples, however, are most frequently unrepresentative or poorly representative samples. Water depth is an important controlling variable. A sediment core from the lake centre has the highest probability of representing the whole-lake assemblage. It may, however, also yield the lowest concentrations of terrestrial remains. A sediment core from the slope is slightly more likely to be unrepresentative of the total plant macrofossil assemblage, but generally has higher concentrations of terrestrial remains. These site differences should be considered when choosing a core location. Overall, the three fossil types are deposited in similar patterns. Therefore they can be satisfactorily analysed using a single core. 相似文献
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松嫩草原土壤动物的分布格局受多种因素的综合影响,地形通过影响其他环境因素进而能够影响土壤动物的分布格局。本研究分别在松嫩草原固定沙丘和草甸选取5个生境,进行为期一年的土壤动物群落调查,分析土壤动物生态分布特征和多样性特征,探讨地形和时间对土壤动物分布格局的影响。结果显示,研究期间获得土壤动物密度为5144.62 ind·m-2,所获土壤动物隶属于4门8纲24类;不同生境土壤动物多样性指数随时间变化规律存在一定的差异性,方差分析发现,时间和地形对土壤动物数量特征和多样性特征具有明显的作用,但是地形和时间对土壤动物群落的交互作用不是十分明显。因此,地形分异能够显著地影响松嫩草原土壤动物的分布格局,这可能主要与生境的生物和非生物特征有关。 相似文献
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María Gabriela Mángano Luis Alberto Buatois Xiantao Wu Junmin Sun Guocheng Zhang 《Journal of Paleolimnology》1994,11(1):41-65
The Middle to Upper Triassic Tanzhuang Formation represents part of the infill of the early Mesozoic Jiyuan-Yima Basin. The upper part of this stratigraphic unit records deposition within prevailing shallow lake conditions. Well-developed sequences crop out near Jiyuan, western Henan Province, central China. Six sedimentary facies clustered into two facies assemblages were recognized in the lacustrine section. Facies assemblage 1 consists of stacked coarsening-upward sequences composed, from base to top, of organic-rich shales (facies E, type I), laminated siltstones (facies A) and current-rippled laminated sandstones (facies B). Units of assemblage 1 record progradation of small mouth-bar deltas within a perennial open lacustrine system under temperate and humid conditions. Facies assemblage 2 lacks a clear vertical pattern and consists of interbedded fine-grained carbonates and siltstones (facies C); deformed and wave-reworked sandstones (facies D); organic-rich shales (facies E, type II) and clayey mudstones (facies F). The assemblage also represents a perennial, hydrologically-open, shallow lacustrine system, but characterized by strong seasonal climatic control. Water stratification probably occurred in several periods of the lake history. Pangaean megamonsoonal influence is envisaged to explain the strong seasonality imprint evidenced toward the upper part of the Tanzhuang lacustrine column.This is the fourth paper in a series of papers published in this issue on Climatic and Tectonic Rhythms in Lake Deposits. 相似文献