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1.
我国6ka BP植被变化的气候模拟研究   总被引:1,自引:0,他引:1  
于革  刘健  陈星  薛滨 《古生物学报》2002,41(4):558-564
根据花粉恢复的古植被表面中国森林区的常绿阔叶,和叶阔叶林以及针叶林在6Ka BP向北扩张,反映了6ka BP夏季和冬季均比现代温暖的气候特征,然而,根据地球轨道参数变化驱动的气候模式,由于6kaBP时北半球夏季太阳辐射高于现代,而冬季太阳辐射低于现代,模拟的6ka BP夏季温度比规划温暖,但冬季比现代寒冷,模拟得出的冬季寒冷与地 冬季增温不一致,说明6ka BP的气候和植被变化并不完全受到太阳辐射变化的控制,针对这一重大缺陷,我们利用具有陆面过程的全球大气环流模型(ACCM+SsiB),采用了外动力太阳辐射变化和古地表状史的强迫边界场进行了古气候模拟试验,模拟结果能够捕捉到亚洲季风地区6kaBP冬季气候变暖的气候特征,初步阐明6ka BP植被变化的气候动力学机制。  相似文献   

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egetation evolution in the northern South China Sea region since 40 500 a BP is reconstructed using biomization procedure based on pollen data from deep sea core 17940. The result shows that, it is feasible to reconstruct palaeovegetation using biomization procedure, when pollen, particularly Pinus pollen, transported by wind over long distance is excluded. Results from factor analysis suggest that humidity and temperature are the two main factors determining vegetation evolution on land around the northern South China Sea. From 40 500 a BP to 11 100 a BP, broad-leaved evergreen forest (WAMF), and montane conifers(MGRF) occurred on hills and low mountains; while steppe (STEP) predominated on the exposed shelf. The main feature of the vegetation evolution is the frequent alternation between MGRF (or WAMF) and STEP, implying abrupt changes in millennium scale between humid/cold and dry/temperate climate. All abrupt climate events could be broadly correlated with Henrich events and Dansggard-Oscherge events. One of the events around 12 700 a BP, sees the occurrence of MGRF, suggesting that climate turned humid and cold rapidly. This may be correlated with the Younger Dryas event; Broad-leaved evergreen (WAMF) predominates since 11 000 a BP. During the early Holocene and late Holocene tropical rainforest (TRFO) or tropical seasonal forest (TSFO ) occurred several times.  相似文献   

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天山乌鲁木齐河源区大西沟剖面孢粉鉴定结果表明:在3.6~3.2 ka BP,该区气候较今温暖湿润;在3.2~2.0 ka BP,气候变为寒冷干燥,这一时期乌鲁木齐河源地区曾出现一次冰进;在2.0~1.4 ka BP,气候又转为暖湿;在1.4~0.5 ka BP,出现了3.6 ka BP以来气候最适宜的时期.整个剖面自下而上都有一定量的淡水水生植物出现,这反映了该剖面3 ka BP以来一直处于淡水沼泽的环境中.通过对云杉属生态习性、传播特性等综合分析,认为剖面中的云杉丰值可能与林线上移、山谷风搬运以及冰川退缩等有一定的相关性.通过对孢粉样品中炭屑浓度统计以及磁化率测试结果的综合研究,提出在0.5 ka BP左右,该地区可能出现过多次火灾;炭屑的峰值可能与人类活动有关.  相似文献   

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《L'Anthropologie》2021,125(3):102905
New surveys were undertaken in Abbeville in 2016 and 2017 on the site of the Moulin Quignon discovered before 1850 by Boucher de Perthes, relocated thanks to the archival work carried out by MNHN researchers. This research led 150 years later to the rediscovery of this emblematic Paleolithic site. Test pits and extensive excavation have led to the discovery of alluvial levels in situ and a lithic series composed of 254 fragments, 15 cores and 5 bifaces. The cores and flakes attest to in situ debitage on flint nodules according mainly to unipolar and centripetal unifacial technology, except for one core, which indicates a management on several debitage surfaces. The bifaces are diversified morphologically and technically (shaping modes). They attest to a general management of the bifacial volume and geometry of the tool, to the care taken at the tip of the tool and to the regularisation of the often peripheral edges. They resemble those discovered by Boucher de Perthes in 1837–1868 and described in the past as “Abbevillian”. Stratigraphic and ESR age studies on quartz date human occupation between 670 and 650 ka. These artifacts belong to the earliest Acheulean occupation ever dated in the Somme basin and more generally north of the 50th parallel north. The lithic series discovered at Moulin Quignon is indisputable proof of the presence of human occupations dated at more than 650 ka in the Somme valley, a natural pathway to northern sectors, present-day Great Britain. This discovery thus ages (1) the age of the oldest occupation in the North of France (previously 550 ka) and (2) the age of the oldest bifaces for Northwest Europe (100 ka older than the bifaces in Great Britain).  相似文献   

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天山乌鲁木齐河源区大西沟剖面孢粉鉴定结果表明:在3.6~3.2ka BP,该区气候较今温暖湿润;在3.2~2.0ka BP,气候变为寒冷干燥,这一时期乌鲁木齐河源地区曾出现一次冰进;在2.0~1.4ka BP,气候又转为暖湿;在1.4~0.5ka BP,出现了3.6ka BP以来气候最适宜的时期。整个剖面自下而上都有一定量的淡水水生植物出现,这反映了该剖面3ka BP以来一直处于淡水沼泽的环境中。通过对云杉属生态习性、传播特性等综合分析,认为剖面中的云杉丰值可能与林线上移、山谷风搬运以及冰川退缩等有一定的相关性。通过对孢粉样品中炭屑浓度统计以及磁化率测试结果的综合研究,提出在0.5ka BP左右,该地区可能出现过多次火灾;炭屑的峰值可能与人类活动有关。  相似文献   

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Fossiliferous Quaternary sedimentary beds in the Santa Lucía Basin (southern Uruguay) are potentially useful for the study of the last occurrences of extinct taxa, as well as the environmental and climatic patterns in the late Pleistocene to the early Holocene. They have provided a chronological framework (AMS 14C and Optically Stimulated Luminescence dates), a mammalian diversity and interpretations of last occurrence, the climatic-environmental setting, and some associated biogeographic processes. The ages produced encompass the last 30 to 7 ka interval (latest Pleistocene-early Holocene). The mammalian assemblage (36 genera, 24 species) includes typical South American late Pleistocene mammals, extinct species of extant genera, and some extant species that still exist elsewhere on the continent. The preservation pattern includes articulated and semi-articulated skeletons of large and small mammals. The presence in the southern Uruguayan Pampean area of some mammals currently inhabiting Patagonia, northwest and central Argentina (Dolichotis, Galea, Microcavia, Chaetophractus, Lagostomus, and Vicugna) is explained by the predominance of open areas and cold climates associated with the Last Glacial Maximum. The mammalian record depicts local extinctions or shifting ranges occurring in latest Pleistocene or early Holocene. The sedimentary chronological framework and taphonomic features suggest the persistence into the early Holocene of Eutatus seguini, Morenelaphus brachyceros, Equus neogeus, Hemiauchenia sp., Lama sp., and Vicugna sp. Glyptodon and Glossotherium seem to persist at least to the latest Pleistocene. This pattern can substantiate the hypothesis that some megafauna and large mammals persisted for some millennia alongside people with extinction occurring before, during, and after human colonization.  相似文献   

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最近有研究表明改性HA双膦酸酯(BP)既具有HA中自愈性和粘附性强的优点,又拥有骨矿物质的靶向结合特性,有利于成骨再生。本研究主要研究改性HA双膦酸酯(BP)对股骨头坏死和缺损的骨再生促进作用。首先通过Cell Counting Kit-8试剂盒(CCK-8)方法测定了改性HA双膦酸酯(BP)的细胞生物相容性,并对成骨过程中的成骨作用因子进行了逐一检测。最后通过随机对照实验分析兔模型中成骨量以及成骨的胶原蛋白表达情况进行分析对比。本研究结果表明,HA双膦酸酯(BP)具有很好的细胞生物相容性,能够明显增加表达与成骨相关的生长因子。而在兔模型中发现该物质能够增加成骨量,且能够促进骨再生和骨分化过程。最后本研究认为HA双膦酸酯(BP)是一种理想的人体骨骼组织替代的材料,在组织工程中具有较大的临床应用价值。  相似文献   

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青藏高原东南部18ka以来气候与水文变化   总被引:4,自引:0,他引:4  
青藏高原东南部众多封闭小湖的湖相沉积记录着重要的地理信息,是恢复当地晚更民以来古环境演变的理想材料。西藏海登湖和仁同分辨率的花粉组合,AMS^14C测年及磁化率和有机质含量测定,揭示了研究区与鳊季风密切相关的古植被,古气候和古水文变化历史。高分辨率的花粉记录反映,在16kaBm,P,以前花粉组合以黎科(Chenopodiaceae)和蒿属(Artemisia)为主,花粉浓度很低,应为荒漠草原植被。  相似文献   

11.
Boron is an essential nutrient for plants, but it is toxic in excess. Transgenic rice plants expressing an Arabidopsis thaliana borate efflux transporter gene, AtBOR4, at a low level exhibited increased tolerance to excess boron. Those lines with high levels of expression exhibited reduced growth. These findings suggest a potential of the borate transporter BOR4 for the generation of high-boron tolerant rice.  相似文献   

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The Kalahari features a long-lived lacustrine system which may exist since the Early Pleistocene. The emergence of an extant cichlid fish radiation from this (palaeo-) lake during the Middle Pleistocene indicates an ancient lake character. The early history of the system remains speculative, but it is established that lake extensions matching modern Lake Victoria in size have occurred during the Late Pleistocene. It has been assumed that the hydrographical dynamics chiefly depended on the inflow from the Okavango River and thus on ITCZ-controlled precipitation. Our studies, which focused the hydromorphological and palaeolimnological development of the Makgadikgadi Basin during the last 50 ka, suggest that from c. 46–16 ka it did not receive water from the Okavango River but from palaeo-rivers located in the northern and south-western catchment. A northward shift of the winter rainfall zone during the Last Glacial Maximum sustained a high lake level for a period of c. 6 ka. During Heinrich Event 1 (17–16 ka) the lake probably desiccated abruptly and completely. Higher lake levels, controlled by water from the Okavango river system, were reached again during the Holocene before the lake dried up in the middle of the last millennium.  相似文献   

13.
Jonathan Wylie 《Ethnos》2013,78(1-2):26-45
In many cultures with male‐dominated religions, women are subject to illnesses which are attributed to spirit‐possession. Two main alternative therapies are usually available. Treatment is effected either by exorcism, or by domesticating the spirit ‐ a process which de Heusch calls ‘adortism’. In the latter case, women are recruited through illness into female‐centred ‘cults of affliction’, regarded as superstitious and subversive by men, who try to prevent their wives from becoming involved in these cults, preferring exorcism as therapy. Exorcism thus becomes an instrument of male power in the struggle to control women's incipient religiosity. The paper examines the interplay of exorcism and adorcism in relation to gender in Christian, Muslim and Buddhist settings. It concludes by considering the implications of women as well as men practising exorcism, and suggests that the consequences of the formal distinction between exorcism and adorcism may not always be as sharply opposed as appears at first sight.  相似文献   

14.
第三节祖国在防治疾病上的伟大成就这节课是在学生已掌握了传染病的基本知識的基础上来进行講授的,首先在教材里提出以血吸虫病、天花、瘧疾、黑热病、痳疯等传染病說明了新旧社会的对比;同时也说明了社会主义社会制度的优越性。我們的党和政府对于人民健康的关怀是无微不至的,并且对于各种疾病的积极防治工作加强了党的领导,及时提出了一系列的方針、政策和措施;建立了专业防治机构,培养了专业干部;結合生产发动了广大羣众来参加防治。因此在防治各种传染病的工作中取得了很大的成績。  相似文献   

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第五节大脑皮层的机能——高级神經活动本节是本章也是本書的高峯,是把过去学习过有关反射作用的知識进行总結和提高,使学生能从理論上理解神经对人的意义——保持內部各器官的协調,同外界环境的统一。  相似文献   

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A previous study on the genetics of mouse C4-binding protein (C4-bp) indicated the existence of a genetic polymorphism. Two genetic variants were reported and their segregation used to determine the mapping position of the C4BP locus to the H-2D-Qa interval of the mouse H-2 system. We show here, however, that purified C4-bp does not display the previously reported polymorphism. The mapping position of C4BP in the mouse therefore remains undetermined.  相似文献   

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Abstract

The molecular structure of poly (dT)·poly (dA)·poly (dT) has been determined and refined using the continuous x-ray intensity data on layer lines in the diffraction pattern obtained from an oriented fiber of the DNA. The final R-value for the preferred structure is 0.29 significantly lower than that for plausible alternatives. The molecule forms a 12-fold right- handed triple-helix of pitch 38.4 Å and each base triplet is stabilized by a set of four Crick-Watson-Hoogsteen hydrogen bonds. The deoxyribose rings in all the three strands have C2′-endo conformations. The grooveless cylindrical shape of the triple-helix is consistent with the lack of lateral organization in the fiber.  相似文献   

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Hall(1977)首次在新西兰的土壤中发现GlomusinjtequensHall。Ames和Schneider(979)在美国的加利福尼亚再次发现了这个种。他们认为该种与无梗囊霉(Acauloryora)有相似之处,抱子都是从泡囊发育而成,但无梗囊霉的抱于是在产抱囊的侧面形成,而该种的抱子则是在产抱囊柄的内部发育而成的。为此,Ames和Schneider(197)为这个种建立起一个新属——内养囊霉属(Entrophospora),把这个种改名为稀有内养囊霉Entrophoworam斤equens(HallAmesetSchnelder。SChellGk和Spain(1984)报道了这个属的另一个种哥伦比亚内养囊霉(Entro…  相似文献   

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Obituary

Robert (Robin) Hill (1899–1991)  相似文献   

20.
TheZhoukoudian(Choukoutien)Site(英汉对照)TheZhoukoudianSite,famous“home”ofPekingMan,liesapproximately50kilometressouthwestofthePe...  相似文献   

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