Holocene deglaciation of Marie Byrd Land,West Antarctica

Surface exposure ages of glacial deposits in the Ford Ranges of western Marie Byrd Land indicate continuous thinning of the West Antarctic Ice Sheet by more than 700 meters near the coast throughout the past 10,000 years. Deglaciation lagged the disappearance of ice sheets in the Northern Hemisphere by thousands of years and may still be under way. These results provide further evidence that parts of the West Antarctic Ice Sheet are on a long-term trajectory of decline. West Antarctic melting contributed water to the oceans in the late Holocene and may continue to do so in the future.     

The ecology of early man in southern Africa

It is not possible at present to demonstrate hominid occupation of southern Africa prior to the middle or late Pliocene, perhaps 3 million years ago. It may be the case that much, if not most, of the subcontinent was in fact uninhabited before that. The earliest hominid known to have lived in southern Africa is Australopithecus africanus. It was apparently replaced by Homo (?evolved into Homo) by 2 million years ago, at approximately the same time as A. robustus is first recorded locally. Homo and A. robustus then coexisted until perhaps 1 million years ago, after which Homo survived alone. There is no solid evidence that either of the southern African australopithecines made tools or accumulated bones. In fact, at the known sites, it now seems more likely that the bones, including those of the australopithecines themselves, were accumulated by carnivores. The known archeological record of southern Africa begins 2 million to 1.5 million years ago and the oldest stone tools may belong to the Oldowan Industry. Far better documentation exists for the succeeding Acheulean Industrial Complex, which was present in southern Africa almost certainly before 1 million years ago and persisted with modifications probably until sometime between 300,000 and 130,000 years ago. Although it is known that Acheulean peoples made handaxes, cleavers, and other stone tools, very little else is known about the activities of Acheuleans in southern Africa. Far more is known about their Middle and Later Stone Age successors. Southern African MSA peoples were perhaps among the earliest anywhere to take systematic advantage of aquatic resources for their subsistence, although they apparently did so far less effectively than did the LSA peoples who followed them. There are also contrasts between the ways in which MSA and LSA peoples dealt with terrestrial prey and between the contents of MSA and LSA artifact assemblages. The LSA peoples, for example, seem to have made much more extensive use of bone as a raw material, and they were the first to manufacture articles that are clearly interpretable as ornaments or art objects. From an evolutionary perspective, the LSA may represent a quantum advance over the MSA, perhaps correlated with the replacement of an archaic human physical type by the modem one. However, this must remain only a working hypothesis until much more is learned about the earliest LSA, dating to 35,000 to 40,000 years ago or more, and until there are adequate samples of well-provenienced MSA and early LSA physical remains. The later LSA, postdating 20,000 to 18,000 years ago, is reasonably well known. Later LSA peoples were probably at least partly responsible for the extinction of several large mammals in southern Africa about 10,000 years ago. By that date or shortly thereafter, at least some LSA peoples established basic hunting-gathering adaptations, which continued until the introduction and spread of agriculture and pastoralism, beginning roughly 2000 years ago. Thereafter, hunters and gatherers became progressively restricted in numbers and distribution, such that today only a very few exist, restricted to some of the most marginal environments of the subcontinent. It remains a major goal of southern African archeology to shed more light on the evolution and operation of hunting-gathering cultures during the vast time span when they covered all of southern Africa.     

Climate Change During the Last Deglaciation in Antarctica

Greenland ice core records provide clear evidence of rapid changes in climate in a variety of climate indicators. In this work, rapid climate change events in the Northern and Southern hemispheres are compared on the basis of an examination of changes in atmospheric circulation developed from two ice cores. High-resolution glaciochemical series, covering the period 10,000 to 16,000 years ago, from a central Greenland ice core and a new site in east Antarctica display similar variability. These findings suggest that rapid climate change events occur more frequently in Antarctica than previously demonstrated.     

舟山群岛野生木本观赏植物资源及分布

通过对舟山群岛野生植物资源的调查，筛选出野生木本观赏植物350种，隶属于75科183属。部分种类蕴藏量大，群落面积大于50hm^2的有14种。其中海岛特有植物12种，滨海特有植物16种，国家级珍稀濒危植物4种，浙江省省级珍稀濒危植物11种。资源在各海岛的分布从南到北逐渐递减，其中在舟山备县（区）普遍分布的有92种，分布在岱山岛、长涂岛及以南岛屿的50种，分布在舟山岛及其以南以东岛屿的94种，仪局限在该区域个别岛屿的多达160余种；生长环境以丘陵山坡为主，基岩海岸次之，少数种类见于沙砾质海岸和淤泥质海岸，表现出分布区域不平衡，生态幅度差异大，生境多样化等特征。     

Photosynthetic Mechanisms and Paleoecology from Carbon Isotope Ratios in Ancient Specimens of C4 and CAM Plants

Carbon istotope ratios of modern, 10,000-year-old, and more than 40,000-year-old Atriplex confertifolia (C(4)) material from Nevada caves indicate that the C(4) photosynthetic pathway was operating in these plants over that period. Samples of a plant with crassulacean acid metabolism, Opuntia polyacantha, were also measured, and a shift in the 8(13)C value from -21.9 per mil (more than 40,000 years ago) to -13.9 per mil (10,000 years ago) was observed. This provides unique physiological evidence to support the hypothesis that the late Pleistocene pluvial climate in the region already had become drier about 10,000 years ago.     

Quebrada jaguay: early south american maritime adaptations

Excavations at Quebrada Jaguay 280 (QJ-280) (16 degrees30'S) in south coastal Peru demonstrated that Paleoindian-age people of the Terminal Pleistocene (about 11,100 to 10,000 carbon-14 years before the present or about 13,000 to 11,000 calibrated years before the present) in South America relied on marine resources while resident on the coast, which extends the South American record of maritime exploitation by a millennium. This site supports recent evidence that Paleoindian-age people had diverse subsistence systems. The presence of obsidian at QJ-280 shows that the inhabitants had contact with the adjacent Andean highlands during the Terminal Pleistocene.     

厚荚相思对风沙地土壤性状的改良

在滨海风沙地对厚荚相思 (A.crassicarpa)的生长情况、土壤性状进行研究 ,研究结果表明 :厚荚相思树能够适应沿海风沙地的恶劣环境条件 ,与木麻黄 (Casuarina equisetfolia)相比 ,厚荚相思树生长迅速 ,干形较通直 ,其土壤养分贮量及供应能力较强 .可望成为继木麻黄 ,湿地松 (P.elliotlii)之后 ,营造沿海海防林 ,改良林地立地条件的又一先锋树种     

Rapid thinning of parts of the southern greenland ice sheet

Aircraft laser-altimeter surveys over southern Greenland in 1993 and 1998 show three areas of thickening by more than 10 centimeters per year in the southern part of the region and large areas of thinning, particularly in the east. Above 2000 meters elevation the ice sheet is in balance but thinning predominates at lower elevations, with rates exceeding 1 meter per year on east coast outlet glaciers. These high thinning rates occur at different latitudes and at elevations up to 1500 meters, which suggests that they are caused by increased rates of creep thinning rather than by excessive melting. Taken as a whole, the surveyed region is in negative balance.     

Ocean warming and sea level rise along the southwest u.s. Coast

Hydrographic time-series data recorded during the past 42 years in the upper 500 meters off the coast of southern California indicate that temperatures have increased by 0.8 degrees C uniformly in the upper 100 meters and that temperatures have risen significantly to depths of about 300 meters. The effect of warming the surface layer of the ocean and there by expanding the water column has been to raise sea level by 0.9 +/- 0.2 millimeter per year. Tide gauge records along the coast are coherent with steric height and show upward trends in sea level that vary from about 1 to 3 millimeters per year.     

Postglacial change in sea level in the Western north atlantic ocean

Radioactive carbon determinations of the age of peat indicate that at Bermuda, southern Florida, North Carolina, and Louisiana the relative sea level has risen at approximately the same rate, 2.5 x 10(-3) foot per year (0.76 x 10(-3) meter per year), during the past 4000 years. It is proposed tentatively that this is the rate of eustatic change in sea level. The rise in sea level along the northeastern coast of the United States has been at a rate much greater than this, indicating local subsidence of the land. Between Cape Cod and northern Virginia, coastal subsidence of 13 feet appears to have occurred between 4000 and 2000 years ago and has continued at a rate of about 1 x 10(-3) foot per year since then. On the northeastern coast of Massachusetts, subsidence of 6 feet occurred between 4000 and 3000 years ago; since then sea level has risen at about the eustatic rate. Between 12,000 and 4000 years ago, sea level rose at an average of about 11 x 10(-3) foot per year. The part played by local subsidence or temporary departures from the average rate during this period is uncertain.     

Late quaternary environmental history of lake valencia, Venezuela

Chemical, paleontological, and mineralogical analyses of a 7.5-meter core from the middle of Lake Valencia, Venezuela, have provided information on the paleoclimatic history of this low-elevation, low-latitude site for the last 13,000 years. The data show that dry climates existed in this region from 13,000 years before present (B.P.) until about 10,000 years B.P. The Lake Valencia Basin was occupied by intermittent saline marshes at that time. About 10,000 years B.P., a permanent lake of fluctuating salinity formed and arboreal plant communities replaced the earlier dominant xeric herbaceous vegetation and marsh plants. By 8500 years B.P., Lake Valencia reached moderate to low salinities and discharged water; the modern vegetation became established at that time. After 8500 years B.P., the lake twice ceased discharging as a result of reduced watershed moisture. The second of these drying episodes is still in progress and has been aggravated by human activities in the watershed.     

Geomorphic reconstructions in the environs of ancient troy

Sea level rise, deltaic progradation, and floodplain aggradation have changed the landscape in the vicinity of ancient Troy during the past 10,000 years. With the waning of the last major world glaciation and resultant sea level rise and fluctuation, a marine embayment protruded nearly 10 kilometers south of the site of Troy at Hisarlik in the Troad of northwest Turkey. As the sea approached its present level approximately 6000 years ago, fluvial and marine deposition caused a northerly migration of the delta and floodplain of the Scamander and Simois Rivers past the site of Troy toward the present-day coast about 6 kilometers north of the site. In view of these major changes in morphology, interpretations of ancient geographies related to historical or historical-mythological settings must be changed. A number of paleogeographic maps have been reconstructed with the use of subsurface data that records the continuing landscape change since the first occupancy of the site at Troy 5000 years ago. These show that ancient Troy was located on an embayment of the sea. If the Trojan War occurred, then the axis of the battlefield and associated events must be relocated to the south and west of Troy.     

中国胎生植物的种类和地理分布

初步研究表明：中国胎生植物有15科24属51种(含亚种、变种、变型)。种子胎生类型的种类较少,主要集中分布在南方热带海岸的潮间带上;营养体胎生类型的种类较多,散布于全国各地。     

Ascent of dinosaurs linked to an iridium anomaly at the Triassic-Jurassic boundary

Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years.     

Late pleistocene faunal extinctions in southern patagonia

Major environmental changes recorded in pollen records from various sites in southern Patagonia and Tierra del Fuego are also reflected in pollen and cuticle data from dung of the late Pleistocene groundsloth. The most prominent change was the large-scale reduction of steppe environment about 10,000 years ago, which coincides with the latest dates for extinctions of many large grazers such as the giant groundsloth. Stress on food resources for all the large grazers may well have hastened their extinction. Hunting pressure by paleoindians may have been the final blow.     

Leaf pubescence: effects on absorptance and photosynthesis in a desert shrub

The presence of leaf pubescence (leaf hairs) in Encelia farinosa, a desert species of the Composite family, reduces the absorptance of photosynthetically active radiation (400 to 700 nanometers) by as much as 56 percent more than a closely related but nonpubescent species, E. californica, a native of the relatively moist southern California coast. Pubescence in E. farinosa, which increases through the growing season, modifies the leaf energy balance and dramatically reduces the photosynthetic rate. The reduction in the photosynthetic rate is caused by decreased light absorption rather than decreased carbon dioxide conductance through the boundary layer.     

A 10,000-year record of Arctic Ocean sea-ice variability--view from the beach

We present a sea-ice record from northern Greenland covering the past 10,000 years. Multiyear sea ice reached a minimum between ~8500 and 6000 years ago, when the limit of year-round sea ice at the coast of Greenland was located ~1000 kilometers to the north of its present position. The subsequent increase in multiyear sea ice culminated during the past 2500 years and is linked to an increase in ice export from the western Arctic and higher variability of ice-drift routes. When the ice was at its minimum in northern Greenland, it greatly increased at Ellesmere Island to the west. The lack of uniformity in past sea-ice changes, which is probably related to large-scale atmospheric anomalies such as the Arctic Oscillation, is not well reproduced in models. This needs to be further explored, as it is likely to have an impact on predictions of future sea-ice distribution.     

Middle cambrian arthropod embryos with blastomeres

A phosphatized Middle Cambrian ( approximately 510 million years ago) fauna from Duyun, southern China, has yielded fossil embryos that may be of arthropod affinity and could belong to the co-occurring eodiscid trilobite Pagetia sp. The shell was most likely flexible and possessed at least two thin layers. Four embryos reveal blastomeres, and two embryonic stages are represented. These embryos demonstrate that the basic paradigm for the growth of the invertebrate embryo has not changed in more than half a billion years.     

Tough times at la brea: tooth breakage in large carnivores of the late pleistocene

One million to two million years ago, most of today's large, predatory mammals coexisted with larger extinct species, such as saber-toothed cats and giant running bears. Comparisons of tooth fracture frequencies from modern and Pleistocene carnivores imply that predator-prey dynamics and interspecific interactions must have been substantially different 36,000 to 10,000 years ago. Tooth fracture frequencies of four Rancho La Brea species-dire wolf, coyote, saber-toothed cat, and American lion-were about three times that of extant carnivores. Consequently, these findings suggest that these species utilized carcasses more fully and likely competed more intensely for food than presentday large carnivores.     

Precessional forcing of nutricline dynamics in the equatorial atlantic

Climate control of nutricline depth in the equatorial Atlantic can be monitored by variations in the abundance of the phytoplankton species Florisphaera profunda. A conceptual model, based on in situ evidence, associates high abundances of F. profunda with a deep nutricline and low abundances with a shallow nutricline. A 200,000-year record of F. profunda relative abundances, obtained from a deep-sea core sited beneath the region of maximum equatorial divergence at 10 degrees W, has 52 percent of its variance centered on the 23,000-year precessional band. Cross-spectral analysis between the signals of F. profunda and sea-surface temperature, independently derived from zooplankton species, shows their 23,000-year cycles to be coherent and nearly in phase. Abundance minima of F. profunda coincide with times of December perihelion, whereas abundance maxima coincide with June perihelion. These relations indicate that nutricline dynamics in the divergence region of the equatorial Atlantic are controlled by variations in the tropical easterlies, forced by the precessional component of orbital insolation, on time scales greater than 10,000 years.