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  • 1
    Online Resource
    Online Resource
    Rapid thermokarst evolution during the mid-Holocene in Central Yakutia, Russia
    SAGE Publications ; 2017
    In:  The Holocene Vol. 27, No. 12 ( 2017-12), p. 1899-1913
    Details
    In: The Holocene, SAGE Publications, Vol. 27, No. 12 ( 2017-12), p. 1899-1913
    Abstract: The reconstruction of Holocene thermokarst landform evolution is important to understand the potential impact of current global climate change on permafrost regions. A multi-proxy approach was applied to analyse the sedimentological and biogeochemical characteristics as well as pollen and lacustrine microfossils of a core profile drilled in a small pingo within a large Central Yakutian thermokarst basin (alas). Age–depth modelling with macrofossil 14 C ages reveals high thermokarst deposit sedimentation rates and a complete thermokarst sequence spanning about 900 years during the mid-Holocene between ~6750 and 5870 cal. yr BP. In total, three stages of thermokarst landscape evolution have been identified. Thermokarst processes were initiated at ⩽6750 to 6500 cal. yr BP. Terrestrial conditions changed quickly to lacustrine conditions, and a thermokarst lake rapidly emerged and grew to an estimated size of 120–600 m diameter and 7.5–15 m depth during only ~150 years between ~6500 and 6350 cal. yr BP. The decline of thermokarst processes and lake decrease may have been affected by local hydrological conditions between ~6350 and 5870 cal. yr BP but ceased completely after 5870 cal. yr BP, likely due to climatic changes. Clear evidence for long-lasting and stable lacustrine conditions was not obtained. The study emphasises that short-term warming led to very active permafrost degradation and rapid but locally variable modification of alas and thermokarst evolution.
    Type of Medium: Online Resource
    ISSN: 0959-6836 , 1477-0911
    URL: Article
    DOI: 10.1177/0959683617708454
    RVK:
    RA 1000
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2017
    detail.hit.zdb_id: 2027956-5
    SSG: 14
    SSG: 3,4
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    Impact of newly introduced perennial bioenergy crops on soil quality parameters at three different locations in W‐Germany
    Wiley ; 2017
    In:  Journal of Plant Nutrition and Soil Science Vol. 180, No. 6 ( 2017-12), p. 759-767
    Details
    In: Journal of Plant Nutrition and Soil Science, Wiley, Vol. 180, No. 6 ( 2017-12), p. 759-767
    Abstract: The land areas used for bioenergy crop cultivation are increasing across Europe. For several years now, various perennial crops have been cultivated, including Miscanthus , switchgrass and reed canary grass, and the newly introduced cup plant, giant knotweed, tall wheatgrass, virginia mallow, and wild plant mixtures. We investigated the impact that many of these perennial bioenergy crops (PECs) have on the soil organic C and N pools, microbial properties, and earthworm activity at three different study sites in W‐Germany with varying soil conditions after an experimental period of five years. Silage maize ( Zea maize ) in rotation with green rye ( Cecale cereale ) or Triticale was used for comparison (= annual energy crops; AEC). The overall intention of this study was to gain insights into the future trends of soil quality with changes in land‐use towards bioenergy production. Our results emphasized that in general, soil quality was improved through the cultivation of perennials. For example, after five years of investigation, the mean soil organic carbon contents increased, on average, by 1–2% at two of the three study sites, the soil microbial biomass increased from 13% (virginia mallow) to 27% (tall wheatgrass) ( p 〈 0.05) compared to AEC treatment and the mean earthworm activity (cast production) was significantly improved in PECs compared to AEC. These trends were mainly found in silty to loamy soils, but the results were slightly different in sandy soils and dry climate conditions. We suggest that this might be traced back to unfavourable growing conditions for perennial crops during the first years of establishment. To our knowledge, this is the first comprehensive field investigation of the impact of these newly introduced perennial crops on soil quality indicators that considers various site‐ and soil‐specific growth conditions.
    Type of Medium: Online Resource
    ISSN: 1436-8730 , 1522-2624
    URL: Issue
    URL: Article
    DOI: 10.1002/jpln.v180.6
    DOI: 10.1002/jpln.201700162
    RVK:
    RA 5430
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1481142-X
    detail.hit.zdb_id: 1470765-2
    detail.hit.zdb_id: 200063-5
    SSG: 12
    SSG: 13
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  • 3
    Online Resource
    Online Resource
    The sedimentological and environmental footprint of extreme wave events in Boca do Rio, Algarve coast, Portugal
    Elsevier BV ; 2019
    In:  Sedimentary Geology Vol. 389 ( 2019-07), p. 147-160
    Details
    In: Sedimentary Geology, Elsevier BV, Vol. 389 ( 2019-07), p. 147-160
    Type of Medium: Online Resource
    ISSN: 0037-0738
    URL: Article
    DOI: 10.1016/j.sedgeo.2019.06.004
    RVK:
    RA 1000
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2019
    detail.hit.zdb_id: 216739-6
    detail.hit.zdb_id: 2012818-6
    SSG: 13
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  • 4
    Online Resource
    Online Resource
    Cattle trampling alters soil properties and changes soil microbial communities in a Swiss sub-alpine pasture
    Elsevier BV ; 2012
    In:  Geoderma Vol. 170 ( 2012-1), p. 369-377
    Details
    In: Geoderma, Elsevier BV, Vol. 170 ( 2012-1), p. 369-377
    Type of Medium: Online Resource
    ISSN: 0016-7061
    URL: Article
    DOI: 10.1016/j.geoderma.2011.11.026
    RVK:
    RA 2235.4
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2012
    detail.hit.zdb_id: 281080-3
    detail.hit.zdb_id: 2001729-7
    SSG: 13
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  • 5
    Online Resource
    Online Resource
    Clinopyroxene–Liquid Equilibria and Geothermobarometry in Natural and Experimental Tholeiites: the 2014–2015 Holuhraun Eruption, Iceland
    Oxford University Press (OUP) ; 2019
    In:  Journal of Petrology Vol. 60, No. 8 ( 2019-08-01), p. 1653-1680
    Details
    In: Journal of Petrology, Oxford University Press (OUP), Vol. 60, No. 8 ( 2019-08-01), p. 1653-1680
    Abstract: Clinopyroxene–liquid geothermobarometry is a widely used tool for estimating the conditions under which mafic magmas are stored before they erupt. However, redox variability, sector zoning and disequilibrium crystallization present major challenges to the robust estimation of magma storage conditions. Moreover, most recent studies seeking to address these challenges have focused on clinopyroxenes from alkalic systems and are thus of limited use for understanding clinopyroxenes from the tholeiitic systems that dominate global magma budgets. Here we combine observations on natural clinopyroxenes from the 2014–2015 Holuhraun lava in Iceland with observations on experimental clinopyroxenes synthesized during high-pressure, high-temperature experiments on the same lava in order to investigate clinopyroxene–liquid equilibria in tholeiitic systems and optimize of geothermobarometric strategies. Natural clinopyroxenes from the 2014–2015 Holuhraun lava are sector zoned, with {1-11} hourglass sectors being enriched in the enstatite–ferrosillite component at the expense of all other components with respect to {hk0} prism sectors. In contrast with observations on clinopyroxenes from alkalic systems, sector zoning in clinopyroxenes from the 2014–2015 Holuhraun lava is characterized by differences in Ca and Na contents as well as in Ti and Al contents. The products of crystallization experiments performed at 100–600 MPa and 1140–1220 °C on a powdered starting glass at two sets of melt H2O content–oxygen fugacity conditions (∼0·1 wt % H2O and close to the graphite-oxygen redox buffer, and 0·5–1·0 wt % H2O and approximately one and half log units above the quartz–fayalite–magnetite redox buffer) demonstrate that clinopyroxene crystals from nominally equilibrium experiments can preserve strongly disequilibrium compositions. The compositional systematics of experimental clinopyroxenes are consistent with the presence of sector zoning. Furthermore, the magnitude of compositional variability increases with decreasing melt H2O content and increasing deviations of experimental temperatures below clinopyroxene liquidus temperatures (i.e. degrees of undercooling sensu lato), indicating that kinetic processes play a key role in controlling clinopyroxene compositions, even under notionally equilibrium conditions. Few published analyses of experimental clinopyroxene crystals may thus represent truly equilibrium compositions. Stoichiometric calculations on natural and experimental clinopyroxenes show that Fe3+ is a major constituent of clinopyroxenes from tholeiitic magmas under naturally relevant oxygen fugacity conditions. They also show that Fe3+ is most likely incorporated as Ca- and Al- bearing Ca–Fe-Tschermak’s component rather than Na-bearing aegirine component at oxygen fugacities up to one and a half log units above the quartz–fayalite–magnetite buffer. Elevated oxygen fugacities are thus less likely to compromise clinopyroxene–liquid geothermobarometry than previously thought. Guided by our experimental results, we combined published descriptions of clinopyroxene–liquid equilibria with geothermobarometric equations to develop an internally consistent and widely applicable method for performing geothermobarometry on tholeiitic magmas that does not require equilibrium zones to be selected a priori. Applying this method to natural clinopyroxene crystals from the 2014–2015 Holuhraun lava that formed under low but variable degrees of undercooling (perhaps 25 °C or less) returns values in excellent agreement with those from independent methods (232 ± 86 MPa, 1161 ± 11 °C). Robust estimates of magma storage conditions can thus be obtained by performing clinopyroxene–liquid geothermobarometry on tholeiitic magmas when disequilibrium is suitably accounted for.
    Type of Medium: Online Resource
    ISSN: 0022-3530 , 1460-2415
    URL: Article
    DOI: 10.1093/petrology/egz042
    RVK:
    RB 10121
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 1466724-1
    SSG: 13
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