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  • 1
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    Vegetation in western Central Mexico during the last 50 000 years: modern analogs and climate in the Zacapu Basin (2012)
    Wiley
    Details
    Publication Date: 2012-05-02
    Description: The late glacial and the transition towards the Holocene marked a period of significant environmental change at a global scale. In western Central Mexico, few records span beyond the Holocene, and little is known about Pleistocene climatic and environmental variability. Here we report on the pollen record of a composite sequence made of three cores that cover the last 50 ka (thousands of calibrated radiocarbon years before present) in the Zacapu Basin, western Central Mexico (∼1970 m asl). The conjunction of modern pollen rain from the area with the composite fossil pollen sequence from cores Cantabria, Cantabria 1 and CEMCA Point-1 provided a detailed history of the vegetation of the area. Recognition of modern environmental patterns through individual modern pollen taxa proved difficult, but multivariate analysis separated different vegetation types. No-modern-analog communities relative to the modern vegetation cover of the area were evident, especially during periods of drought. Apparently, summer precipitation was significant before 40 ka and after the deglaciation. However, this moisture source declined from ∼40 to 10 ka because tradewinds from the Gulf of Mexico were blocked by the eastern mountains of Central Mexico as a result of lower temperatures. By contrast, westerly and northerly winds were enhanced by maximum ice cover from ∼19 to 17 ka, providing abundant winter precipitation and therefore preventing extreme drought in the area. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
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  • 2
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    Climate change as the dominant control on glacial-interglacial variations in C3 and C4 plant abundance (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-09-05
    Description: Although C4 plant expansions have been recognized in the late Miocene, identification of the underlying causes is complicated by the uncertainties associated with estimates of ancient precipitation, temperature, and partial pressure of atmospheric carbon dioxide (PCO2). Here we report the carbon isotopic compositions of leaf wax n-alkanes in lake sediment cores from two sites in Mesoamerica that have experienced contrasting moisture variations since the last glacial maximum. Opposite isotopic trends obtained from these two sites indicate that regional climate exerts a strong control on the relative abundance of C3 and C4 plants and that in the absence of favorable moisture and temperature conditions, low PCO2 alone is insufficient to drive an expansion of C4 plants.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huang, Y -- Street-Perrott, F A -- Metcalfe, S E -- Brenner, M -- Moreland, M -- Freeman, K H -- New York, N.Y. -- Science. 2001 Aug 31;293(5535):1647-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences, Brown University, Providence, RI 02912, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11533488" target="_blank"〉PubMed〈/a〉
    Keywords: Alkanes/analysis ; Atmosphere ; Carbon Dioxide ; Carbon Isotopes/analysis ; *Climate ; *Ecosystem ; Fossils ; Fresh Water ; Geologic Sediments/*chemistry ; Guatemala ; Mexico ; Photosynthesis ; *Plant Development ; Plant Leaves/chemistry ; Plants/metabolism ; Poaceae/*growth & development/metabolism ; Pollen ; Rain ; Seasons ; Temperature ; Trees/growth & development ; Weather
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
    Electronic Resource
    Electronic Resource
    Modern diatom assemblages in Central Mexico: the role of water chemistry and other environmental factors as indicated by TWINSPAN and DECORANA (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 19 (1988), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Modern diatom samples, for which physical and chemical environmental conditions were recorded, were collected from forty-seven sites across Central Mexico2. The results of the diatom counts were analysed using the clustering program TWINSPAN and the ordination program DECORANA.3. Results from ‘Laguna Zacapu and associated sites’ showed that where water chemistry varies little between sample sites the effects of habitat are emphasized. This data set highlighted the problems of looking for modern analogues where anthropogenic disturbance is great.4. TWINSPAN results from the ‘Other Sites’ data set suggested possible changes in diatom assemblages with chemical composition. The DECORANA analyses, however, again seemed to emphasize habitat.5. In the context of this study, bottom sediment samples appeared to provide the most useful picture of ‘average’ conditions and to be the best source of analogues for the interpretation of fossil assemblages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1988.tb00344.x
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  • 4
    Electronic Resource
    Electronic Resource
    Climate change at the monsoon/Westerly boundary in Northern Mexico (1997)
    Springer
    Journal of paleolimnology 17 (1997), S. 155-171 
    Details
    ISSN: 1573-0417
    Keywords: Mexico ; palaeoclimate ; sediments ; diatoms ; pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Northern Mexico lies close to the present day boundary between mid-latitude (Westerly) and tropical (monsoonal) sources of moisture. Studies from the adjacent southwest USA have shown major changes in lake levels and vegetation distributions over the late Quaternary which have been interpreted in terms of significant variations in the relative strengths and positions of these climate systems. Palaeoclimatic data from this area have, however, left a number of unresolved questions which can only be answered by extending work into northern Mexico, closer to the major source of summer (monsoonal) rain, the Gulf of Mexico. Studies of palaeolake sediments from a series of hydrologically closed lake basins across a range of altitudes (1280 to 2200 m a.s.l.) in northern Chihuahua are in progress using geochemical, mineral magnetic, diatom and plant microfossil analyses. Preliminary results are presented from the Alta Babícora and Encinillas basins. The sites provide records of lacustrine deposition between 〉11 000 and about 2500 yr BP. The diatom record from Babíora provides clear evidence for a deep water lake in this basin in the late glacial which persisted into the early Holocene. A dry episode coinciding with the timing of the Younger Dryas is recorded in Alta Babícora. Conditions wetter than present are indicated up to at least 7000 yr BP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007905824147
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  • 5
    Electronic Resource
    Electronic Resource
    Nitrogen Deposition and Strategies for the Control of Acidification and Eutrophication across Great Britain (1998)
    Springer
    Water, air & soil pollution 107 (1998), S. 121-145 
    Details
    ISSN: 1573-2932
    Keywords: critical loads function ; emissions reductions ; modelling ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract It is now recognised that a multi-pollutant, multi-effect approach needsto be adopted to address the range of problems caused by atmosphericpollution. In this paper we use a relatively simple trajectory model (HARM)to explore the coupled behaviour of sulphur dioxide (SO2),oxides of nitrogen (NOx) and ammonia (NH3) andthe possible effects of future reductions in emissions of these pollutantson depositions of S and N across Great Britain. The performance of HARM withrespect to concentrations and depositions of NOy andNHx is assessed by comparison with data from nationalmonitoring networks. A range of emissions scenarios are modelled and theeffects of these reductions on critical loads exceedance are explored usingthe critical loads function (CLF), which allows both the acidification andeutrophication effects of S and N deposition to be explored simultaneously.Spatial variations in the reductions of deposition of S and/or N required tomeet critical loads are described. Reductions in emissions of the precursorsof strong acids (SO2 and NOx) yield benefits interms of ammonium deposition as a result of their coupled chemistry. Thedevelopment of strategies to control nitrogen deposition will need to take this non-linearity in to account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019832913817
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  • 6
    Electronic Resource
    Electronic Resource
    Estimating the impact of air pollution on environmentally valuable sites (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 2589-2594 
    Details
    ISSN: 1573-2932
    Keywords: Conservation areas ; geographical information systems (GIS) ; sulphur deposition ; critical load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Concern about the environmental effect of air pollution on areas of high conservation value in the UK has prompted the statutory agencies to initiate an investigation on these areas. For this, critical loads maps have been used together with predicted air pollution data, monitored air pollution data and remotely sensed land cover information within a geographic information system (GIS). Additional information on designated Sites of Special Scientific Interest (SSSI) for England and Wales have also been incorporated. This provides the framework for examining potential impacts to these sites under various current and future scenarios. The approach allows for the investigation of the impacts of individual point sources as well as complete national scenarios. Preliminary results are provided from analysis of a single pollutant (sulphur). These indicate that nationally up to 52% of the area of SSSI's (5000 km2) are at risk from soil acidification. Using this approach it has been possible to apportion the load on any SSSI, thereby enabling the ecological impacts of each point source to be identified. This information can then be used to assess priorities for regulatory controls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186224
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of precipitation composition at UK EMEP sites 1987–1992 and comparison with the HARM model (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 1961-1966 
    Details
    ISSN: 1573-2932
    Keywords: UK EMEP sites ; precipitation concentration ; wind sectors ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Precipitation composition has been measured daily at five UK EMEP sites since 1987. Sulphur dioxide and sulphate aerosol concentrations are also measured daily at the sites. Back trajectories and wind sectors calculated by the Norwegian Meteorological Institute have been used to characterise the variation in wet deposition in terms of air mass source. Contributions to wet deposition from various source regions have been estimated for Eskdalemuir. Observations from the EMEP sites have been compared with output from the Hull Acid Rain Model (HARM). HARM is a Lagrangian model using simplified meteorology but straight-line trajectories. Results are compared on a site-by-site and sector-by-sector basis and the model reproduces the general features of pollutant concentration and wet deposition indicated by the measurements. The possible effects of future reductions in emissions of SO2 and NOx on precipitation concentrations by wind sector are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186121
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  • 8
    Electronic Resource
    Electronic Resource
    A comparison of different ranking schemes for assessing the effect of large point sources of pollution in the UK (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 2613-2618 
    Details
    ISSN: 1573-2932
    Keywords: Ranking ; integrated pollution control ; critical loads ; sulphur ; point source emissions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The availability of national maps of critical loads for soils, vegetation and freshwaters helpsenable the assessment of the effects of large point sources of pollution in the UK. The deposition “footprint” of most major sources has been modelled and combined in a GIS with a national critical loads database. As part of an integrated pollution control strategy (IPC) it may be helpful to rank point sources in order of their effects on the environment. A comparison of the discriminating power and effectiveness of several ranking schemes has been carried out. A variety of ranking schemes were investigated, such as; total area where sulphur deposition exceeds the critical load or average mass deposited on areas where the critical load is exceeded. Their relative merits were compared for several “current” and future scenarios, such as, actual 1993 emissions or predicted emissions for 2001. Rankings for the unit emissions provided a measure of the pollution potential of each source and were a complex function of the location of sensitive areas and meteorological conditions. Rankings under other scenarios tended to be dominated by the relative magnitude of the emissions. Comparison between the ranking schemes was made using non-parametric statistics. The comparisons reveal complex interactions between different schemes. The approach is providing practical solutions to a pollution control strategy based on maximising environmental benefits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186228
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  • 9
    Electronic Resource
    Electronic Resource
    Spatial variability in emissions reduction strategies for sulphur and nitrogen in the UK (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 2619-2624 
    Details
    ISSN: 1573-2932
    Keywords: sulphur ; nitrogen ; critical loads function ; emissions reductions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The roles of sulphur (S) and nitrogen (N) in causing critical loads exceedance across the UK show considerable spatial variability at the present time. Over much of lowland Britain it appears that the environment can only be protected by reducing N deposition, whilst in upland areas (e.g. most of Scotland and Wales) reductions in S deposition are the primary requirement. Using the Hull Acid Rain Model (HARM) the effects of current and possible future emissions control legislation on critical loads exceedance can be explored. Based on HARM output, the implementation of the UNECE Sulphur Protocol (1994) will bring about a substantial reduction in the amount of S being deposited in the UK, especially in central and southern parts of the country. Some areas will remain where additional reductions in S are required. Over most of the country, however, the need to reduce N deposition will become paramount. The changing contributions and significance of non-UK sources can be estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186229
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  • 10
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    Human impact on the hydroenvironment of Lake Parishan, SW Iran, through the late-Holocene (2015)
    Sage
    In: Holocene
    Details
    Publication Date: 2015-09-17
    Description: A multiproxy record from Lake Parishan, SW Iran, shows human impact on the lake and its catchment over the last 4000 years. The Parishan record provides evidence of changes in lake hydrology, from ostracod, diatom and isotope analyses, that are directly linked to human activity in the catchment; recorded by pollen and charcoal and supported by regional archaeological and historical data. The lake ostracod fauna is particularly sensitive to human-induced catchment alterations and allows us to identify changes in catchment hydrology that are due to more than a simple change in precipitation: evaporation state. Oxygen isotope data from endogenic carbonates follow these faunal changes but also display a longer trend to more positive values through the period, coincident with regional patterns of water balance for the late-Holocene in the eastern Mediterranean.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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