Indigenous perception of changes in climate variability and its relationship with agriculture in a Zoque community of Chiapas, Mexico     

Maria Silvia Sánchez-Cortés  Elena Lazos Chavero 《Climatic change》2011,107(3-4):363-389

This study analyses the perceptions of Zoque indigenous men and women of changes in climate variability, indicated by rainfall and temperature records from the region. Peasant farmers perceive decreases in rainfall and increases in temperature as these factors are related to modifications in the corn planting season and the introduction of crops which were usually only found in hot regions. The climate changes in the zone are attributed to vegetation loss and the eruption of the Chichón volcano in 1982. The Zoque perception is structured according to cultural and individual experience, tied to agriculture and the annual weather calendar. The volcanic eruption offers a significant chronological reference point in order to explain different environmental transformations, such as climate, within Zoque territory. Perception is the mental picture of local climate variability changes and the responses in seasonal agriculture modifications, utilizing individual and cultural experiences which are vulnerable to economic and environmental change.  相似文献   

Effect of temperature on contents of essential highly unsaturated fatty acids in freshwater zooplankton     

Michail I. Gladyshev  Vitaliy P. Semenchenko  Olga P. Dubovskaya  Elena B. Fefilova  Olesia N. Makhutova  Zhanna F. Buseva  Nadezhda N. Sushchik  Vladimir I. Razlutskij  Ekaterina V. Lepskaya  Mariya A. Baturina  Galina S. Kalachova  Olga N. Kononova 《Limnologica》2011,41(4):339-347

In 11 lakes from cold and warm regions we studied the content of highly unsaturated fatty acids (HUFA) in seston (<130 μm) and crustacean zooplankton using gas chromatography–mass spectrometry. An increase of temperature correlated with a decrease of HUFA content in zooplankton. A multivariate canonical correlation analyses revealed, that the decrease of HUFA content was related with a decrease of per cent of copepods in zooplankton communities, which are known to have higher HUFA levels in their biomass, than cladocerans. This means that temperature primarily affected the HUFA levels indirectly, via changing of taxonomic structure of zooplankton community, while the homeoviscous adaptation of zooplankton individuals had comparatively lower importance. As found, water temperature was better predictor of HUFA contents of zooplankton, than the fatty acid composition of seston. Thus, it can be predicted, that a probable climate warming will decrease the content of the essential HUFA in freshwater zooplankton with possible negative consequences for animals of higher trophic levels.  相似文献   

Lead isotopes as tracers of anthropogenic pollution in urban topsoils of Mexico City   总被引：1，自引：0，他引：1  

Ofelia Morton-Bermea  María Teresa Rodríguez-Salazar  Elizabeth Hernández-Alvarez  Ma Elena García-Arreola  Rufino Lozano-Santacruz 《Chemie der Erde / Geochemistry》2011,(2):189-195

A survey was performed to trace the main source of anthropogenic Pb pollution in Mexico City through Pb isotopic signatures (²⁰⁸Pb/²⁰⁴Pb, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁶Pb/²⁰⁷Pb, and ²⁰⁸Pb/²⁰⁷Pb) from 103 urban topsoil (0–5 cm) samples. Those were collected in the metropolitan area of Mexico City and compared with isotopic compositions of leaded gasoline (LG), domestic Pb ores (DLO) and parent rock (PR). The isotope ratios (IRs) of Pb were determined by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) and total Pb concentration analyzed by wavelength dispersive X-ray fluorescence (WDXRF). The range of Pb concentrations levels in urban topsoil samples was 15–473 mg/kg. The IR values obtained for these samples were 37.965–39.718 (²⁰⁸Pb/²⁰⁴Pb), 18.375–19.204 (²⁰⁶Pb/²⁰⁴Pb), 1.177–1.218 (²⁰⁶Pb/²⁰⁷Pb) and 2.443–2.496 (²⁰⁸Pb/²⁰⁷Pb). Analyzed topsoil samples with low Pb content (<50 mg/kg) displayed high dispersion in ²⁰⁸Pb/²⁰⁴Pb values, which are determined by different natural sources. Samples with 51–200 mg/kg Pb content, shown low dispersion that revealed the mixing between the natural Pb and anthropogenic Pb. The assessment of the IR values shown that, as Pb concentration increases, a trend toward gasoline IR data has been observed. The results obtained by this research suggest that although the use of leaded petrol had been banned in Mexico since 1997, the Pb pollution in the urban topsoils due to the historical use of Pb in petrol is still significant.  相似文献   

Acigöl rhyolite field,Central Anatolia (part 1): high-resolution dating of eruption episodes and zircon growth rates   总被引：2，自引：1，他引：1  

Axel K. Schmitt  Martin Danišík  Noreen J. Evans  Wolfgang Siebel  Elena Kiemele  Faruk Aydin  Janet C. Harvey 《Contributions to Mineralogy and Petrology》2011,162(6):1215-1231

Protracted pre-eruptive zircon residence is frequently detected in continental rhyolites and can conflict with thermal models, indicating briefer magma cooling durations if scaled to erupted volumes. Here, we present combined U-Th and (U-Th)/He zircon ages from the Acigöl rhyolite field (Central Anatolia, Turkey), which is part of a Quaternary bimodal volcanic complex. Unlike other geochronometers, this approach dates crystallization and eruption on the same crystals, allowing for internal consistency testing. Despite the overall longevity of Acigöl rhyolite volcanism and systematic trends of progressive depletion in compatible trace elements and decreasing zircon saturation temperatures, we find that zircon crystallized in two brief pulses corresponding to eruptions in the eastern and western part of the field during Middle and Late Pleistocene times, respectively. For Late Pleistocene zircon, resolvable differences exist between interior (average: 30.7 ± 0.9 ka; 1σ error) and rim (21.9 ± 1.3 ka) crystallization ages. These translate into radial crystal growth rates of ~10^?13 to 10^?14 cm/s, broadly consistent with those constrained by diffusion experiments. Rim crystallization and (U-Th)/He eruption ages (24.2 ± 0.4 ka) overlap within uncertainty. Evidence for brief zircon residence at Acigöl contrasts with many other rhyolite fields, suggesting that protracted zircon crystallization in, or recycling from, long-lived crystal mushes is not ubiquitous in continental silicic magma systems. Instead, the span of pre-eruptive zircon ages is consistent with autochthonous crystallization in individual small-volume magma batches that originated from basaltic precursors.  相似文献   

Jom-Bolok Holocene volcanic field in the East Sayan Mts., Siberia,Russia: structure,style of eruptions,magma compositions,and radiocarbon dating   总被引：1，自引：0，他引：1  

Alexei V. Ivanov  Sergei G. Arzhannikov  Elena I. Demonterova  Anastasia V. Arzhannikova  Lyubov A. Orlova 《Bulletin of Volcanology》2011,73(9):1279-1294

Jom-Bolok volcanic field is located in the East Sayan Mts. of Siberia (Russia), a portion of the Asian convergent zone. It is located at the boundary of the Riphean Tuva-Mongolia massif, which was probably reactivated because of the interplay between far-field tectonic stress derived from the India–Asia collision zone and extension in the south-western Baikal rift system. The volcanic field comprises a number of hawaiitic lava flows, of various lengths, which flowed down paleorivers. Flows were fed by fissure eruptions and the largest lava flow field was dated as 7,130?±?140 cal ¹⁴C years BP using a buried organic sample found inside the associated cinder cone. This lava flow field is about 70 km long, ～100 km² in area, and 7.9 km³ in volume. The area and volume of this flow field ranks this eruption highly in the global record of fissure-fed effusive eruptions. This lava flow field makes up 97% of the entire Jom-Bolok volcanic field, a fact which raises a puzzling question: why and/or how did a relatively small-volume volcanic field produce such a large-volume individual eruption? A working hypothesis is that a pond of sublithospheric melt accumulated over a relatively prolonged period. This was then rapidly drained in response of tectonic changes triggered by unloading of ice in the Early Holocene.  相似文献   

Holocene temperature variations at a high-altitude site in the Eastern Alps: a chironomid record from Schwarzsee ob Sölden, Austria     

Ilyashuk EA  Koinig KA  Heiri O  Ilyashuk BP  Psenner R 《Quaternary Science Reviews》2011,30(1-2):176-191

Few well-dated, quantitative Holocene temperature reconstructions exist from high-altitude sites in the Central Eastern Alps. Here, we present a chironomid-based quantitative reconstruction of mean July air temperatures (T_July) throughout the Holocene for a remote high-mountain lake, Schwarzsee ob Sölden, situated above the treeline at 2796 m a.s.l. in the Austrian Alps. Applying a chironomid-temperature inference model developed from lakes of the Alpine region to a high-resolution chironomid record from the lake provides evidence for early Holocene (ca 10000–8600 cal yr BP) T_July of up to 8.5 °C, i.e. >4 °C above the modern (1977–2006) mean July temperature. The reconstruction reveals the so-called ‘8.2-ka cold event’ centered at ca 8250–8000 cal yr BP with temperatures ca 3 °C below the early-Holocene thermal maximum. Rather warm (ca 6 °C) and productive conditions prevailed during ca 7900–4500 cal yr BP. The chironomid record suggests a climate transition between ca 5200 and 4500 cal yr BP to cooler T_July. A distinct cooling trend is evident from ca 4500 until ca 2500 cal yr BP. Thereafter, the study site experienced its coldest conditions (around 4 °C or less) throughout the rest of the Holocene, with the exception of the warming trend during the late 20th century. Beside other factors, the Northern Hemisphere summer insolation seems to be the major driving force for the long-term trends in T_July at high altitudes in the Eastern Alps. Due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set, the chironomid-based temperature reconstruction fails to track phases of the late-Holocene climatic history with T_July cooler than 4 °C. Further chironomid-based palaeoclimate model and down-core studies are required to address this problem, provide more realistic T_July estimates from undisturbed high-altitude lakes in the Alps, and extract a reliable regional temperature signal.  相似文献   

Middle-Late Jurassic syndepositional tectonics recorded in the Ligurian Briançonnais succession (Marguareis–Mongioie area,Ligurian Alps,NW Italy)     

Carlo Bertok  Luca Martire  Elena Perotti  Anna d’Atri  Fabrizio Piana 《Swiss Journal of Geoscience》2011,104(2):237-255

The Middle–Upper Jurassic succession of the Marguareis–Mongioie area (Ligurian Briançonnais Domain), developed in a protected shelf environment evolving into a pelagic plateau, bears clear evidence of synsedimentary tectonics such as: growth fault-related structures; neptunian dykes; marked lateral variations in stratigraphic thicknesses testifying to the juxtaposition of sectors characterized by different sedimentation and subsidence rates; discordant, anomalous stratigraphic contacts corresponding to paleoescarpments; nodular beds showing evidence of fluidification interpreted as seismites; and the occurrence of sand-sized quartz grains pointing to denudation of Permo-Triassic quartz-rich rocks. Such evidence documents an important Middle-Late Jurassic post-breakup tectonic activity, which was more effective in controlling the basin topography than the Early Jurassic syn-rift tectonic phase. Two main tectono-sedimentary stages, one occurring during the Bathonian, the other falling within the Callovian–Kimmeridgian interval, were reconstructed. The first stage can be referred to a fault-related activity occurring shortly after the initial stages of oceanic spreading of the Ligurian Tethys; the second can be genetically related to the far effects of the first rifting stage of the Bay of Biscay and the Valais basin.  相似文献   

Middle slope contourite deposits and associated sedimentary facies off NE Argentina   总被引：1，自引：0，他引：1  

Graziella Bozzano  Roberto A. Violante  Maria Elena Cerredo 《Geo-Marine Letters》2011,31(5-6):495-507

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Of Time and Tide: Comments on Newby and Webb, 1994     

Dena F. Dincauze  Elena Decima 《Quaternary Research》1995,44(3)

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Hydrological response to radar rainfall maps through a distributed model     

Ignazio Becchi  Enrica Caporali  Elena Palmisano 《Natural Hazards》1994,9(1-2):95-108

Weather radars in investigating physical characteristics of precipitation are becoming essential instruments in the field of short term meteorological investigation and forecasting. To analyze the radar signal impact in hydrological forecasting, precipitation input fields, generated through a statistical mathematical model, are supplied to a distributed hydrological model. Such a model would allow the control of the basin response to precipitation measurements obtained by a meteorological radar and, in the meanwhile, to evaluate the influence of distributed input. The distributed model describes the basin hydrological behavior, subdividing it into distinct geometrical cells and increasing the physical significance by reproducing the distributed hydrographic basins characteristics, such as infiltration capacity, runoff concentration time, network propagation speed, soil moisture influence. Each basin cell is characterized by its geological, pedological and morphological status, and may be considered a unitary hydrological system, linked to the others by geomorphological and hydraulic relationships. To evaluate the dynamics of the flood event a synthetic representation of the channel network is introduced, where each stream branch is modeled as a linear reservoir. Finally, the discharge in the outlet section is derived, taking into account the hydraulic characteristics of the upstream branches.  相似文献