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307 records – page 1 of 31.

A 300-million-year record of atmospheric carbon dioxide from fossil plant cuticles.

https://arctichealth.org/en/permalink/ahliterature95961
Source
Nature. 2001 May 17;411(6835):287-90
Publication Type
Article
Date
May-17-2001
Author
Retallack G J
Author Affiliation
Department of Geological Sciences, University of Oregon, Eugene 97403-1272, USA. gregr@darkwing.uoregon.edu
Source
Nature. 2001 May 17;411(6835):287-90
Date
May-17-2001
Language
English
Publication Type
Article
Keywords
Atmosphere - chemistry
Carbon Dioxide - metabolism
Cold Climate
Fossils
Ginkgo biloba - cytology - growth & development - metabolism
Greenhouse Effect
Ice
Methane - metabolism
Phylogeny
Plant Leaves - cytology - growth & development - metabolism
Plants, Medicinal
Pollen
Seasons
Water - metabolism
Abstract
To understand better the link between atmospheric CO2 concentrations and climate over geological time, records of past CO2 are reconstructed from geochemical proxies. Although these records have provided us with a broad picture of CO2 variation throughout the Phanerozoic eon (the past 544 Myr), inconsistencies and gaps remain that still need to be resolved. Here I present a continuous 300-Myr record of stomatal abundance from fossil leaves of four genera of plants that are closely related to the present-day Ginkgo tree. Using the known relationship between leaf stomatal abundance and growing season CO2 concentrations, I reconstruct past atmospheric CO2 concentrations. For the past 300 Myr, only two intervals of low CO2 (2,000 p.p.m.v.) concentrations. These results are consistent with some reconstructions of past CO2 (refs 1, 2) and palaeotemperature records, but suggest that CO2 reconstructions based on carbon isotope proxies may be compromised by episodic outbursts of isotopically light methane. These results support the role of water vapour, methane and CO2 in greenhouse climate warming over the past 300 Myr.
Notes
Comment In: Nature. 2001 May 17;411(6835):247-811357108
PubMed ID
11357126 View in PubMed
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A 700-year paleoecological record of boreal ecosystem responses to climatic variation from Alaska.

https://arctichealth.org/en/permalink/ahliterature85780
Source
Ecology. 2008 Mar;89(3):729-43
Publication Type
Article
Date
Mar-2008
Author
Tinner Willy
Bigler Christian
Gedye Sharon
Gregory-Eaves Irene
Jones Richard T
Kaltenrieder Petra
Krähenbühl Urs
Hu Feng Sheng
Author Affiliation
Institute of Plant Sciences and Oeschger Center for Climate Change Research, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland. willy.tinner@ips.unibe.ch
Source
Ecology. 2008 Mar;89(3):729-43
Date
Mar-2008
Language
English
Publication Type
Article
Keywords
Alaska
Climate
Diatoms
Ecosystem
Fires
Forestry
Fossils
Geologic sediments
Greenhouse Effect
Ice Cover
Plant Physiology
Pollen
Time Factors
Trees
Abstract
Recent observations and model simulations have highlighted the sensitivity of the forest-tundra ecotone to climatic forcing. In contrast, paleoecological studies have not provided evidence of tree-line fluctuations in response to Holocene climatic changes in Alaska, suggesting that the forest-tundra boundary in certain areas may be relatively stable at multicentennial to millennial time scales. We conducted a multiproxy study of sediment cores from an Alaskan lake near the altitudinal limits of key boreal-forest species. Paleoecological data were compared with independent climatic reconstructions to assess ecosystem responses of the forest tundra boundary to Little Ice Age (LIA) climatic fluctuations. Pollen, diatom, charcoal, macrofossil, and magnetic analyses provide the first continuous record of vegetation fire-climate interactions at decadal to centennial time scales during the past 700 years from southern Alaska. Boreal-forest diebacks characterized by declines of Picea mariana, P. glauca, and tree Betula occurred during the LIA (AD 1500-1800), whereas shrubs (Alnus viridis, Betula glandulosa/nana) and herbaceous taxa (Epilobium, Aconitum) expanded. Marked increases in charcoal abundance and changes in magnetic properties suggest increases in fire importance and soil erosion during the same period. In addition, the conspicuous reduction or disappearance of certain aquatic (e.g., Isoetes, Nuphar, Pediastrum) and wetland (Sphagnum) plants and major shifts in diatom assemblages suggest pronounced lake-level fluctuations and rapid ecosystem reorganization in response to LIA climatic deterioration. Our results imply that temperature shifts of 1-2 degrees C, when accompanied by major changes in moisture balance, can greatly alter high-altitudinal terrestrial, wetland, and aquatic ecosystems, including conversion between boreal-forest tree line and tundra. The climatic and ecosystem variations in our study area appear to be coherent with changes in solar irradiance, suggesting that changes in solar activity contributed to the environmental instability of the past 700 years.
PubMed ID
18459336 View in PubMed
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4200 years of pine-dominated upland forest dynamics in west-central Mexico: human or natural legacy?

https://arctichealth.org/en/permalink/ahliterature155658
Source
Ecology. 2008 Jul;89(7):1893-907
Publication Type
Article
Date
Jul-2008
Author
Blanca L Figueroa-Rangel
Katherine J Willis
Miguel Olvera-Vargas
Author Affiliation
Oxford Long-term Ecology Laboratory, Oxford University Centre for the Environment, School of Geography, South Parks Road, Oxford, OX1 3QY, United Kingdom. bfrangel@cucsur.udg.mx
Source
Ecology. 2008 Jul;89(7):1893-907
Date
Jul-2008
Language
English
Publication Type
Article
Keywords
Climate
Ecosystem
Fossils
Human Activities
Humans
Mexico
Paleontology
Pinus - physiology
Pollen
Population Dynamics
Soil
Time Factors
Trees - physiology
Abstract
The pine-dominated forests of west-central Mexico are internationally recognized for their high biodiversity, and some areas are protected through various conservation measures including prohibition of human activity. In this region, however, there is evidence for human settlement dating back to ca. AD 1200. It is therefore unclear whether the present forest composition and structure are part of a successional stage following use by indigenous human populations during the past, or due to natural processes, such as climate. We present a study reconstructing the vegetation dynamics of pine-dominated forest over the past 4200 years using paleoecological techniques. Results from fossil pollen and charcoal indicate that, in this region, pine-dominated forests are the native vegetation type and not anthropogenically derived secondary succession. The predominant driving mechanism for the expansion of pine-dominated forest appears to be intervals of aridity and naturally induced burning. A close association is noted between pine abundance and longer-term climatic trends, including intervals of aridity between ca. 4200 and 2500, 1200 and 850, and 500 and 200 cal yr BP and shorter-term trends. Evident periodicity occurs in pine and Poaceae abundance every 80 years. These short-term quasi-periodic oscillations have been recorded in a number of lake and ocean sediments in Mexico and are thought to be linked to solar forcing resulting in drought cycles that occur at approximately the same time intervals.
PubMed ID
18705376 View in PubMed
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Activity-induced dental modification in holocene siberian hunter-fisher-gatherers.

https://arctichealth.org/en/permalink/ahliterature100395
Source
Am J Phys Anthropol. 2010 Oct;143(2):266-78
Publication Type
Article
Date
Oct-2010
Author
Andrea Waters-Rist
Vladimir I Bazaliiskii
Andrzej Weber
Olga I Goriunova
M Anne Katzenberg
Author Affiliation
Department of Archaeology, University of Calgary, Calgary, Alberta, Canada, T2N-1N4. awaters@ucalgary.ca
Source
Am J Phys Anthropol. 2010 Oct;143(2):266-78
Date
Oct-2010
Language
English
Publication Type
Article
Keywords
Adult
Asia, Central
Chi-Square Distribution
Female
Fossils
Geography
History, Ancient
Humans
Male
Mandible
Microscopy, Electron, Scanning
Middle Aged
Occupations
Paleodontology
Sex Distribution
Siberia
Statistics, nonparametric
Tooth - anatomy & histology
Tooth Attrition
Abstract
The use of teeth as tools provides clues to past subsistence patterns and cultural practices. Five Holocene period hunter-fisher-gatherer mortuary sites from the south-western region of Lake Baikal, Siberia, Russian Federation, are observed for activity-induced dental modification (AIDM) to further characterize their adaptive regimes. Grooves on the occlusal surfaces of teeth are observed in 25 out of 123 individuals (20.3%) and were most likely produced during the processing of fibers from plants and animals, for making items such as nets and cordage. Regional variation in the frequency of individuals with occlusal grooves is found in riverine versus lakeshore sites. This variation suggests that production of material culture items differed, perhaps in relation to different fishing practices. There is also variation in the distribution of grooves by sex: grooves are found predominately in females, except at the Late Neolithic-Bronze Age river site of Ust'-Ida I where grooves are found exclusively in males. Occlusal grooves were cast using polyvinylsiloxane and maxillary canine impressions were examined by scanning electron microscopy (SEM) to determine striation patterns. Variation in striae orientation suggests that a variety of activities, and/or different manufacturing techniques, were involved in groove production. Overall, the variability in occlusal groove frequency, sex and regional distribution, and microscopic striae patterns, points to the multiplicity of activities and ways in which people used their mouths and teeth in cultural activities.
PubMed ID
20853480 View in PubMed
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Adaptive biological trends in the European upper palaeolithic: the case of the Sunghir remains.

https://arctichealth.org/en/permalink/ahliterature173463
Source
J Physiol Anthropol Appl Human Sci. 2005 Jul;24(4):425-31
Publication Type
Article
Date
Jul-2005
Author
Maria B Mednikova
Author Affiliation
Institute of Archaeology, Russian Academy of Sciences, Moscow, Russia. medma_pa@mail.ru
Source
J Physiol Anthropol Appl Human Sci. 2005 Jul;24(4):425-31
Date
Jul-2005
Language
English
Publication Type
Article
Keywords
Adaptation, Biological - physiology
Adult
Anthropometry
Bone and Bones - radiography
Child
Cluster analysis
Fossils
Human Development - physiology
Humans
Male
Principal Component Analysis
Russia
Abstract
Sunghir is one of the most important Upper Palaeolithic sites in the world because of its most Northern location, the extraordinary richness of the artifacts, and the state of human bone preservation. The skeletal finds give evidence for the study both of adult and subadult body builds in the group. For the reconstruction of patterns of postcranial morphology, total measurements of bones and X-ray observations have been used. We have determined the basic structural traits typical for Sunghirians: small corticalisation of adult postcranial skeletons; large volume of the bone marrow cavity relative to the general size; quick tempo of attainment in early ontogenesis of large adult size combined with late synostoses ensuring prolonged linear growth; macroskelia combined with extreme andromorphy in the shoulder belt structure; capacious chest. The above traits can be interpreted in terms of adaptation to such formative factors as low temperature stress, deficit of atmospheric oxygen, high protein nutrition, and mechanical loads.
PubMed ID
16079592 View in PubMed
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[A health-promoting approach to the study of morbidity with temporary loss of work capacity among oil workers in western Siberia]

https://arctichealth.org/en/permalink/ahliterature72829
Source
Probl Sotsialnoi Gig Istor Med. 1996 Nov-Dec;(6):16-9
Publication Type
Article
Author
E A Ovcharov
Source
Probl Sotsialnoi Gig Istor Med. 1996 Nov-Dec;(6):16-9
Language
Russian
Publication Type
Article
Keywords
Absenteeism
English Abstract
Female
Fossil Fuels
Health promotion
Humans
Male
Occupational Diseases - epidemiology
Petroleum
Risk factors
Siberia - epidemiology
Abstract
Social and economic instability induced a drastic increase in the incidence of diseases involving temporary disability among the oilmen of West Siberia in recent years. Multifactorial analysis disclosed the principal risk factors causing the formation of groups of subjects falling ill frequently and for a long time. The structure of risk factors in the multifactorial model of incidence of diseases with temporary disability has changed recently, reflecting the situation in Russia. The sanological approach to studies of morbidity helps effectively develop a system of complex measures aimed at primary prevention, which should be adapted to the local conditions. One approach is the creation of screening tests to be used in prophylactic check-ups, based on estimation of the threshold (critical) number of risk factors.
PubMed ID
9235262 View in PubMed
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Ammonium nitrate fertiliser production based on biomass - environmental effects from a life cycle perspective.

https://arctichealth.org/en/permalink/ahliterature95545
Source
Bioresour Technol. 2008 Nov;99(17):8034-41
Publication Type
Article
Date
Nov-2008
Author
Ahlgren Serina
Baky Andras
Bernesson Sven
Nordberg Ke
Norén Olle
Hansson Per-Anders
Author Affiliation
Swedish University of Agricultural Sciences, Department of Energy and Technology, P.O. Box 7032, SE 750 07 Uppsala, Sweden. Serina.Ahlgren@et.slu.se
Source
Bioresour Technol. 2008 Nov;99(17):8034-41
Date
Nov-2008
Language
English
Publication Type
Article
Keywords
Biomass
Environment
Eutrophication
Fertilizers
Fossil Fuels
Greenhouse Effect
Nitrates - chemical synthesis
Salix - growth & development
Abstract
Ammonium nitrate and calcium ammonium nitrate are the most commonly used straight nitrogen fertilisers in Europe, accounting for 43% of the total nitrogen used for fertilisers. They are both produced in a similar way; carbonate can be added as a last step to produce calcium ammonium nitrate. The environmental impact, fossil energy input and land use from using gasified biomass (cereal straw and short rotation willow (Salix) coppice) as feedstock in ammonium nitrate production were studied in a cradle-to-gate evaluation using life cycle assessment methodology. The global warming potential in the biomass systems was only 22-30% of the impact from conventional production using natural gas. The eutrophication potential was higher for the biomass systems due to nutrient leaching during cultivation, while the acidification was about the same in all systems. The primary fossil energy use was calculated to be 1.45 and 1.37MJ/kg nitrogen for Salix and straw, respectively, compared to 35.14MJ for natural gas. The biomass production was assumed to be self-supporting with nutrients by returning part of the ammonium nitrate produced together with the ash from the gasification. For the production of nitrogen from Salix, it was calculated that 3914kg of nitrogen can be produced every year from 1ha, after that 1.6% of the produced nitrogen has been returned to the Salix production. From wheat straw, 1615kg of nitrogen can be produced annually from 1ha, after that 0.6% of the nitrogen has been returned.
PubMed ID
18440225 View in PubMed
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Analysis of an early hominid ulna from the Omo Basin, Ethiopia.

https://arctichealth.org/en/permalink/ahliterature251291
Source
Am J Phys Anthropol. 1976 Mar;44(2):295-304
Publication Type
Article
Date
Mar-1976
Author
H M McHenry
S. Corruccini
F C Howell
Source
Am J Phys Anthropol. 1976 Mar;44(2):295-304
Date
Mar-1976
Language
English
Publication Type
Article
Keywords
African Continental Ancestry Group
Animals
Anthropometry - methods
Ethiopia
Female
Fossils
Haplorhini - anatomy & histology
Hominidae - anatomy & histology
Humans
Inuits
Male
Primates - anatomy & histology
Ulna - anatomy & histology
Abstract
The discovery (in 1971) of a nearly complete right ulna from the Shungura Formation of the Omo basin provides the opportunity to abalyze the forelimb structure of the Australopithecus boisei form of early hominid. Results from multivariate morphometric analyses show that this bone is unique in shape among the extant hominoids although it is most similar to Pan and Homo. Despite its long slender shaft and large distal articular surface the bone's overall morphology is quite unlike Pongo.
PubMed ID
816207 View in PubMed
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An articulated Late Triassic (Norian) thalattosauroid from Alaska and ecomorphology and extinction of Thalattosauria.

https://arctichealth.org/en/permalink/ahliterature307046
Source
Sci Rep. 2020 02 04; 10(1):1746
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Date
02-04-2020
Author
Patrick S Druckenmiller
Neil P Kelley
Eric T Metz
James Baichtal
Author Affiliation
University of Alaska Museum, 1962 Yukon Dr., Fairbanks, AK, 99775, USA. psdruckenmiller@alaska.edu.
Source
Sci Rep. 2020 02 04; 10(1):1746
Date
02-04-2020
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Keywords
Alaska
Animals
Biological Evolution
Extinction, Biological
Fossils - anatomy & histology
Reptiles - anatomy & histology
Abstract
Thalattosaurians are a cosmopolitan clade of secondarily aquatic tetrapods that inhabited low-latitude, nearshore environments during the Triassic. Despite their low taxic diversity, thalattosaurians exhibit remarkable morphological disparity, particularly with respect to rostral and dental morphology. However, a paucity of well-preserved material, especially leading up to their extinction, has hampered efforts to develop a robust picture of their evolutionary trajectories during a time of profound marine ecological change. Here, we describe a new taxon based on an articulated and nearly complete skeleton from Norian sediments of southeastern Alaska, USA. The holotype is the most complete North American thalattosaurian yet described and one of the youngest occurrences of the clade worldwide. We present a new hypothesis of interrelationships for Thalattosauria and investigate potential feeding modes in the Alaskan taxon. An integrated view suggests that the absence of pelagic lifestyles and restricted ecological roles may have contributed to thalattosaurs' eventual extinction.
PubMed ID
32019943 View in PubMed
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Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics.

https://arctichealth.org/en/permalink/ahliterature97786
Source
Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5675-80
Publication Type
Article
Date
Mar-23-2010
Author
Paula F Campos
Eske Willerslev
Andrei Sher
Ludovic Orlando
Erik Axelsson
Alexei Tikhonov
Kim Aaris-Sørensen
Alex D Greenwood
Ralf-Dietrich Kahlke
Pavel Kosintsev
Tatiana Krakhmalnaya
Tatyana Kuznetsova
Philippe Lemey
Ross MacPhee
Christopher A Norris
Kieran Shepherd
Marc A Suchard
Grant D Zazula
Beth Shapiro
M Thomas P Gilbert
Author Affiliation
Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, DK 1350 Copenhagen, Denmark.
Source
Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5675-80
Date
Mar-23-2010
Language
English
Publication Type
Article
Keywords
Animals
DNA - genetics - history
DNA, Mitochondrial - genetics - history
Extinction, Biological
Fossils
Genetic Variation
History, Ancient
Humans
Molecular Sequence Data
Phylogeny
Population Dynamics
Ruminants - genetics
Abstract
The causes of the late Pleistocene megafaunal extinctions are poorly understood. Different lines of evidence point to climate change, the arrival of humans, or a combination of these events as the trigger. Although many species went extinct, others, such as caribou and bison, survived to the present. The musk ox has an intermediate story: relatively abundant during the Pleistocene, it is now restricted to Greenland and the Arctic Archipelago. In this study, we use ancient DNA sequences, temporally unbiased summary statistics, and Bayesian analytical techniques to infer musk ox population dynamics throughout the late Pleistocene and Holocene. Our results reveal that musk ox genetic diversity was much higher during the Pleistocene than at present, and has undergone several expansions and contractions over the past 60,000 years. Northeast Siberia was of key importance, as it was the geographic origin of all samples studied and held a large diverse population until local extinction at approximately 45,000 radiocarbon years before present ((14)C YBP). Subsequently, musk ox genetic diversity reincreased at ca. 30,000 (14)C YBP, recontracted at ca. 18,000 (14)C YBP, and finally recovered in the middle Holocene. The arrival of humans into relevant areas of the musk ox range did not affect their mitochondrial diversity, and both musk ox and humans expanded into Greenland concomitantly. Thus, their population dynamics are better explained by a nonanthropogenic cause (for example, environmental change), a hypothesis supported by historic observations on the sensitivity of the species to both climatic warming and fluctuations.
PubMed ID
20212118 View in PubMed
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307 records – page 1 of 31.