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Berlin Brandenburg

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  • 11
    Language: English
    In: Canadian Chemical News, 2014, Vol.66(6), p.11(1)
    Keywords: Oil Sands ; Global Temperature Changes
    ISSN: 0823-5228
    Source: Cengage Learning, Inc.
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  • 12
    In: Global Change Biology, November 2010, Vol.16(11), pp.2990-3003
    Description: Global nitrogen (N) deposition rates in terrestrial environments have quadrupled since preindustrial times, causing structural and functional changes of ecosystems. Different emission reduction policies were therefore devised. The aim of our study was to investigate if, and over what timescale, processes of soil organic matter (OM) transformation respond to a decline in atmospheric N deposition. A N‐saturated spruce forest (current N deposition: 34 kg ha yr; critical N load: 14 kg ha yr), where N deposition has been reduced to 11.5 kg ha yr since 1991, was studied. Besides organic C and organic and inorganic N, noncellulosic carbohydrates, amino sugars and amino acids were determined. A decline in organic N in litter indicated initial effects at plant level. However, there were no changes in biomarkers upon the reduction in N deposition. In addition, inorganic N was not affected by reduced N deposition. The results showed that OM cycling and transformation processes have not responded so far. It was concluded that no direct N deposition effects have occurred due to the large amount of stored organic N, which seems to compensate for the reduction in deposited N. Obviously, the time span of atmospheric N reduction (about 14.5 years) is too short compared with the mean turnover time of litter to cause indirect effects on the composition of organic C and N compounds. It is assumed that ecological processes, such as microbial decomposition or recycling of organic N and C, react slowly, but may start within the next decade with the incorporation of the new litter.
    Keywords: Amino Acid Enantiomers ; Amino Acids ; Amino Sugars ; Biomarker ; N Deposition ; Non‐Cellulosic Carbohydrates ; Soil Organic Nitrogen ; Solling Roof Project
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 13
    Language: English
    In: Plant and Soil, 2013, Vol.371(1), pp.267-279
    Keywords: Exchangeable K ; Non-exchangeable K ; Subsoil ; Illite ; Soil solution ; Ca
    ISSN: 0032-079X
    E-ISSN: 1573-5036
    Source: Springer Science & Business Media B.V.
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  • 14
    Language: English
    In: Geochimica et Cosmochimica Acta, 15 August 2018, Vol.235, pp.89-102
    Description: Ferric iron (Fe ) solid phases serve many functions in soils and sediments, which include providing sorption sites for soil organic matter, nutrients, and pollutants. The reactivity of Fe solid phases depends on the mineral structure, including the overall crystallinity. In redox-active soils and sediments, repeated reductive dissolution with subsequent exposure to aqueous ferrous iron (Fe ) and oxidative re-precipitation can alter Fe phase crystallinity and reactivity. However, the trajectory of Fe mineral transformation under redox fluctuations is unclear and has been reported to result in both increases and decreases in Fe phase crystallinity. Several factors such as water budget, organic matter input, redox dynamics as well as the initial Fe phase composition might play a role. The objective of our study was to examine if Fe minerals in soils that differ in porosity-dependent water leaching rate and initial Fe phase crystallinity, demonstrate distinct mineral transformations when subjected to redox fluctuations. We sampled paired plots of two soil types under similar management but with different water leaching rates and contrasting Fe oxide crystallinity — an Alisol rich in crystalline Fe phases and an Andosol rich in short-range-ordered (SRO) Fe phases. The two soils were either exposed to several decades of redox fluctuations during rice paddy cultivation (paddy) or to predominantly oxic conditions in neighboring vegetable gardens (non-paddy). Paddy soils are uniquely suited for this type of study because they are regularly submerged and develop regular redox fluctuations. We also incubated the non-paddy soils in the laboratory for one year through eight anoxic/oxic cycles and monitored the aqueous soil geochemistry. Mössbauer spectroscopy was then used to evaluate Fe mineral speciation in field soils (paddy and non-paddy) and laboratory incubations. In the field soils, we found that redox fluctuation had contrasting effects on Fe oxide crystallinity, with crystallinity being lower in the Alisol paddy soil and higher in the Andosol paddy soil than in their corresponding non-paddy controls. In the laboratory incubation experiment, Eh, pH and dissolved Fe responded as anticipated, with elevated Fe concentrations during the anoxic periods as well as low Eh and high pH. Mössbauer measurements suggest the fluctuating redox incubation was beginning to alter Fe oxide crystallinity along the same trajectory as observed in the field, but the changes were within the range of fitting errors. We propose that reductive dissolution of crystalline Fe oxides prevails in the soil rich in crystalline Fe oxides (Alisol) and that re-precipitation as SRO Fe oxides is favored by constrained leaching, which leads to the observed decrease in Fe oxide crystallinity. In the soil rich in SRO Fe phases (Andosol), preferential reductive dissolution of SRO Fe oxides coupled with stronger leaching of dissolved Fe causes the observed relative increase in crystallinity of the remaining Fe oxides. The observed increase in Fe oxide crystallinity may further be a result of Fe(II)-catalyzed re-crystallization of SRO Fe oxides. These findings indicate that, besides other factors, the Fe mineral composition of the initial soil or sediment as well as the leaching rate likely influence the trajectory of Fe oxide evolution under alternating redox-conditions.
    Keywords: Fe Oxides ; Redox Fluctuation ; Paddy Soils ; Mössbauer Spectroscopy ; Alisol ; Andosol ; Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 15
    Language: English
    In: Soil biology & biochemistry, 2013, Vol.67, pp.133-139
    Description: Dissolved organic matter (DOM) plays a fundamental role for many soil processes. For instance, production, transport, and retention of DOM control properties and long-term storage of organic matter in mineral soils. Production of water-soluble compounds during the decomposition of plant litter is a major process providing DOM in soils. Herein, we examine processes causing the commonly observed increase in contribution of aromatic compounds to WSOM during litter decomposition, and unravel the relationship between lignin degradation and the production of aromatic WSOM. We analysed amounts and composition of water-soluble organic matter (WSOM) produced during 27 months of decomposition of leaves and needles (ash, beech, maple, spruce, pine). The contribution of aromatic compounds to WSOM, as indicated by the specific UV absorbance of WSOM, remained constant or increased during decomposition. However, the contribution of lignin-derived compounds to the total phenolic products of ¹³C-labelled tetramethylammonium hydroxide (¹³C-TMAH) thermochemolysis increased strongly (by 〉114%) within 27 months of decomposition. Simultaneous changes in contents of lignin phenols in solid litter residues (cupric oxide method as well as ¹³C-TMAH thermochemolysis) were comparably small (−39% to +21% within 27 months). This suggests that the increasing contribution of lignin-derived compounds to WSOM during decomposition does not reflect compositional changes of solid litter residues, but rather the course of decomposition processes. In the light of recently published findings, these processes include: (i) progressive oxidative alteration of lignin that results in increasing solubility of lignin, (ii) preferential degradation of soluble, non-lignin compounds that limits their contribution to WSOM during later phases of decomposition. ; p. 133-139.
    Keywords: Phenols ; Fagus ; Lignin ; Dissolved Organic Matter ; Mineral Soils ; Picea ; Solubility ; Leaves ; Plant Litter ; Absorbance
    ISSN: 0038-0717
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 16
    Language: English
    In: Soil Biology and Biochemistry, December 2013, Vol.67, pp.133-139
    Description: Dissolved organic matter (DOM) plays a fundamental role for many soil processes. For instance, production, transport, and retention of DOM control properties and long-term storage of organic matter in mineral soils. Production of water-soluble compounds during the decomposition of plant litter is a major process providing DOM in soils. Herein, we examine processes causing the commonly observed increase in contribution of aromatic compounds to WSOM during litter decomposition, and unravel the relationship between lignin degradation and the production of aromatic WSOM. We analysed amounts and composition of water-soluble organic matter (WSOM) produced during 27 months of decomposition of leaves and needles (ash, beech, maple, spruce, pine). The contribution of aromatic compounds to WSOM, as indicated by the specific UV absorbance of WSOM, remained constant or increased during decomposition. However, the contribution of lignin-derived compounds to the total phenolic products of C-labelled tetramethylammonium hydroxide ( C-TMAH thermochemolysis increased strongly (by 〉114%) within 27 months of decomposition. Simultaneous changes in contents of lignin phenols in solid litter residues (cupric oxide method as well as C-TMAH thermochemolysis) were comparably small (−39% to +21% within 27 months). This suggests that the increasing contribution of lignin-derived compounds to WSOM during decomposition does not reflect compositional changes of solid litter residues, but rather the course of decomposition processes. In the light of recently published findings, these processes include: (i) progressive oxidative alteration of lignin that results in increasing solubility of lignin, (ii) preferential degradation of soluble, non-lignin compounds that limits their contribution to WSOM during later phases of decomposition.
    Keywords: Dissolved Organic Matter ; Water Soluble Organic Matter ; Litter Decomposition ; Lignin Degradation ; 13c-Tmah Thermochemolysis ; Litter Bag Experiment ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 17
    Language: English
    In: Quaternary International, 16 November 2012, Vol.279-280, pp.231-231
    Keywords: Geology
    ISSN: 1040-6182
    E-ISSN: 1873-4553
    Source: ScienceDirect Journals (Elsevier)
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  • 18
    Language: English
    In: Journal of Computational and Applied Mathematics, 01 December 2018, Vol.343, pp.139-154
    Description: We consider a system of singularly perturbed differential equations with singular parameter , discretized with an IMEX Runge–Kutta method. The splitting needed for the IMEX method stems from a linearization of the fluxes around the limit solution. We analyze the asymptotic convergence order as . We show that in this setting, the stage order of the implicit part of the scheme is of great importance, thereby explaining earlier numerical results showing a close correlation of errors of the splitting scheme and the fully implicit one.
    Keywords: Order Reduction ; Rs-Imex ; Imex Runge–Kutta ; Singularly Perturbed Equation ; Asymptotic Convergence Order ; Mathematics
    ISSN: 0377-0427
    E-ISSN: 1879-1778
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  • 19
    Article
    Article
    Language: English
    In: Environmental health perspectives, February 2004, Vol.112(2), pp.A86; author reply A86-7
    Keywords: Environmental Exposure ; Models, Chemical
    ISSN: 0091-6765
    E-ISSN: 15529924
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  • 20
    In: Global Change Biology, January 2018, Vol.24(1), pp.e183-e189
    Description: Current climate and land‐use changes affect regional and global cycles of silicon (Si), with yet uncertain consequences for ecosystems. The key role of Si in marine ecology by controlling algae growth is well recognized but research on terrestrial ecosystems neglected Si since not considered an essential plant nutrient. However, grasses and various other plants accumulate large amounts of Si, and recently it has been hypothesized that incorporation of Si as a structural plant component may substitute for the energetically more expensive biosynthesis of lignin. Herein, we provide evidence supporting this hypothesis. We demonstrate that in straw of rice () deriving from a large geographic gradient across South‐East Asia, the Si concentrations (ranging from 1.6% to 10.7%) are negatively related to the concentrations of carbon (31.3% to 42.5%) and lignin‐derived phenols (32 to 102 mg/g carbon). Less lignin may explain results of previous studies that Si‐rich straw decomposes faster. Hence, Si seems a significant but hardly recognized factor in organic carbon cycling through grasslands and other ecosystems dominated by Si‐accumulating plants. The key role of silicon in marine ecology by controlling algae growth is well recognized but research on terrestrial ecosystems neglected Si since not considered an essential plant nutrient. However, many plants accumulate large amounts of Si, and recently it has been hypothesized that incorporation of Si as a structural component may substitute for the energetically more expensive biosynthesis of lignin. Herein, we provide evidence supporting this hypothesis. We demonstrate that in rice straw deriving from a large geographic gradient across South‐East Asia, the Si concentrations are negatively related to the concentrations of carbon and lignin‐derived phenols. Our data offer an explanation for previous findings of faster decomposition of Si‐rich rice straw as lignin regulates plant litter decomposition rates. Hence, Si seems a significant but hardly recognized factor in carbon cycling through ecosystems dominated by grass species and/or other Si‐accumulating plants.
    Keywords: Carbon Cycle ; Lignin ; Litter Decomposition ; Rice ; Silicon ; Structural Plant Components
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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