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Atacama Desert (atacama + desert)
Selected AbstractsThe Dry Limit of Microbial Life in the Atacama Desert Revealed by Calorimetric ApproachesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2008N. Barros Abstract The Atacama desert in Chile is one of the driest and most lifeless environments on Earth. It rains possibly once a decade. NASA examined these soils as a model for the Martian environment by comparing their degradation activity with Martian soil and looking for "the dry limit of life". The existence of heterotrophic bacteria in Atacama soil was demonstrated by DNA extraction and by the isolation of microorganisms. So far, however, no data have been available about the metabolic activities in these soils due to the limitations of the existing methodologies when applied to desert soils. Calorimetry was used to obtain information on the metabolic and thermal properties of eleven soil samples collected at different sites in the Atacama desert. Differential scanning calorimetry and isothermal calorimetry were employed to determine the pyrolysis properties of the carbon-containing matter and to measure biomass and microbial metabolism. They were compared to other soil properties such as total carbon and nitrogen, carbon to nitrogen ratio and pH. There was measurable organic matter in nine of the eleven samples and the heat of pyrolysis of those soils was correlated to the carbon content. In five of the eleven samples no biomass could be detected and the existence of basal microbial metabolism could not be established because all samples showed endothermic activity, probably from inorganic reactions with water. Six samples showed microbial activation after the addition of glucose. Carbon content, nitrogen content and the microbial activity after glucose amendment were correlated to the altitude and to the average minimum temperature of the sampling sites calculated from meteorological data. The detectable microbial metabolism was more dissipative with increasing altitude and decreasing temperature. [source] PHYLOGEOGRAPHIC STRUCTURE AND CRYPTIC SPECIATION IN THE TRANS-ANTARCTIC MOSS PYRRHOBRYUM MNIOIDESEVOLUTION, Issue 2 2003Stuart F. McDaniel Abstract Many bryophyte species have distributions that span multiple continents. The hypotheses historically advanced to explain such distributions rely on either long-distance spore dispersal or slow rates of morphological evolution following ancient continental vicariance events. We use phylogenetic analyses of DNA sequence variation at three chloroplast loci (atpB-rbcL spacer, rps4 gene, and trnL intron and 3,spacer) to examine these two hypotheses in the trans-Antarctic moss Pyrrhobryum mnioides. We find: (1) reciprocal monophyly of Australasian and South American populations, indicating a lack of intercontinental dispersal; (2) shared haplotypes between Australia and New Zealand, suggesting recent or ongoing migration across the Tasman Sea; and (3) reciprocal monophyly among Patagonian and neotropical populations, suggesting no recent migration along the Andes. These results corroborate experimental work suggesting that spore features may be critical determinants of species range. We use the mid-Miocene development of the Atacama Desert, 14 million years ago, to calibrate a molecular clock for the tree. The age of the trans-Antarctic disjunction is estimated to be 80 million years ago, consistent with Gondwanan vicariance, making it among the most ancient documented cases of cryptic speciation. These data are in accord with niche conservatism, but whether the morphological stasis is a product of stabilizing selection or phylogenetic constraint is unknown. [source] Violence in the Atacama Desert during the Tiwanaku period: social tension?INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2004A. Lessa Abstract Tiwanaku influence significantly affected the lifestyle of the prehistoric peoples of the Atacama Desert as it represented an important period of social and economic change. Such intense changes as social stratification and new religious and ideological influences have always been characterized as peaceful ones. Palaeopathological studies based on the violence-induced traumatic lesions of 64 well-preserved human skeletons from an excavated funerary site named Solcor-3 have facilitated a comparison between Pre-Tiwanaku and Tiwanaku periods. Results show an increase in violence between males represented by low-intensity skull traumas, arrow wounds and a high mortality rate between 20 and 30 years of age during the Tiwanaku period. The interpretation of this data is contrary to the model of peaceful acceptance of the changes that followed the Tiwanaku influence into the Atacama. At least for Solcor-3, economic and political factors should be re-considered in order to explain the emergence of social tension during the Tiwanaku period. In the future, more detailed studies will probably help to clarify if conflicts had also extended to other sites in San Pedro de Atacama under Tiwanaku influence. Copyright © 2004 John Wiley & Sons, Ltd. [source] Palaeoindian occupation of the Atacama Desert, northern Chile,JOURNAL OF QUATERNARY SCIENCE, Issue 7-8 2005Martin Grosjean Abstract Palaeoindian occupation of the Atacama Desert in northern Chile has been found between 12,600 and 10,200,cal.,yr,BP. The new site at Salar Punta Negra (24°28,S/60°53,W/2976,m) includes about 1000 classifiable, mostly unifacial artefacts and, uniquely, three different diagnostic types of early projectile points. Two of the Lateglacial/early Holocene projectile types have wide distribution and are known from different geographical areas in South America: the Palaeoindian ,Fell' fish-tail point mainly from the southern cone of South America, and the triangular ,Tuina' points typical of the Puna of the south-central Andes in northern Chile and northwestern Argentina. In addition, we found a third type, a stemmed point typical for the Salar Punta Negra. Filling a large geographical gap of ,Fell' occupation, the site at Salar Punta Negra provides evidence for generally much higher mobility and diversity of early cultures, and supports an Andean-Pacific route for early human exploration of South America to the south through the desert at intermediate altitudes. Contemporaneous high-amplitude climatic changes were fundamental preconditions to provide adequate environments and habitats, and to make Palaeoindian hunting-gathering occupation possible in the Atacama Desert. Copyright © 2005 John Wiley & Sons, Ltd. [source] Oxygen isotopes in nitrate: new reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration,,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2003J. K. Böhlke Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO3, in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying ,18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO3) with low ,18O and USGS35 (NaNO3) with high ,18O and ,mass-independent' ,17O. The procedure used to produce USGS34 involved equilibration of HNO3 with 18O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO3, reference materials with a range of ,18O values and normal (mass-dependent) 18O:17O:16O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor (,) between [NO3,] and H2O decreases with increasing temperature from 1.0215 at 22°C to 1.0131 at 100°C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17O:18O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO3, isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO3, samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ±0.2,0.3,, 1,): IAEA-N3 has ,18O,=,+25.6, and ,17O,=,+13.2,; USGS32 has ,18O,=,+25.7,; USGS34 has ,18O,=,,27.9, and ,17O,=,,14.8,; and USGS35 has ,18O,=,+57.5, and ,17O,=,+51.5,. Published in 2003 by John Wiley & Sons, Ltd. [source] GEOCHEMICAL ANALYSIS OF VITREOUS ROCKS EXPLOITED DURING THE FORMATIVE PERIOD IN THE ATACAMA REGION, NORTHERN CHILE,ARCHAEOMETRY, Issue 1 2009A. SEELENFREUND Petrographic analysis and geochemical characterization studies were carried out on vitreous dacite and/or rhyodacite artefacts from Formative period archaeological sites in the upper Salado River Basin in the Atacama Desert, northern Chile. These were compared with samples taken from two source areas located within the subregion, named Linzor and Paniri. Source samples and archaeological specimens were analysed by inductively coupled plasma , mass spectrometry (ICP,MS) combined with optical emission plasma , mass spectrometry (ICP,OES) and atomic absorption spectroscopy (AAS). Results from the limited number of samples analysed indicate that the Linzor source seems to have been the primary source exploited during the Early and Late Formative periods in the Salado River Basin. [source] The Dry Limit of Microbial Life in the Atacama Desert Revealed by Calorimetric ApproachesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2008N. Barros Abstract The Atacama desert in Chile is one of the driest and most lifeless environments on Earth. It rains possibly once a decade. NASA examined these soils as a model for the Martian environment by comparing their degradation activity with Martian soil and looking for "the dry limit of life". The existence of heterotrophic bacteria in Atacama soil was demonstrated by DNA extraction and by the isolation of microorganisms. So far, however, no data have been available about the metabolic activities in these soils due to the limitations of the existing methodologies when applied to desert soils. Calorimetry was used to obtain information on the metabolic and thermal properties of eleven soil samples collected at different sites in the Atacama desert. Differential scanning calorimetry and isothermal calorimetry were employed to determine the pyrolysis properties of the carbon-containing matter and to measure biomass and microbial metabolism. They were compared to other soil properties such as total carbon and nitrogen, carbon to nitrogen ratio and pH. There was measurable organic matter in nine of the eleven samples and the heat of pyrolysis of those soils was correlated to the carbon content. In five of the eleven samples no biomass could be detected and the existence of basal microbial metabolism could not be established because all samples showed endothermic activity, probably from inorganic reactions with water. Six samples showed microbial activation after the addition of glucose. Carbon content, nitrogen content and the microbial activity after glucose amendment were correlated to the altitude and to the average minimum temperature of the sampling sites calculated from meteorological data. The detectable microbial metabolism was more dissipative with increasing altitude and decreasing temperature. [source] | |||||||||||||