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  • Kaiser, Klaus  (172)
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  • 11
    In: Organic Geochemistry, Elsevier BV, Vol. 33, No. 3 ( 2002-3), p. 307-318
    Type of Medium: Online Resource
    ISSN: 0146-6380
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2002
    detail.hit.zdb_id: 2018075-5
    detail.hit.zdb_id: 428531-1
    SSG: 13
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  • 12
    Online Resource
    Online Resource
    Elsevier BV ; 2007
    In:  CATENA Vol. 71, No. 3 ( 2007-12), p. 487-496
    In: CATENA, Elsevier BV, Vol. 71, No. 3 ( 2007-12), p. 487-496
    Type of Medium: Online Resource
    ISSN: 0341-8162
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2007
    detail.hit.zdb_id: 1492500-X
    detail.hit.zdb_id: 519608-5
    SSG: 13
    SSG: 14
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  • 13
    Online Resource
    Online Resource
    Copernicus GmbH ; 2016
    In:  SOIL Vol. 2, No. 3 ( 2016-07-12), p. 325-335
    In: SOIL, Copernicus GmbH, Vol. 2, No. 3 ( 2016-07-12), p. 325-335
    Abstract: Abstract. Uncertainties concerning stabilization of organic compounds in soil limit our basic understanding on soil organic matter (SOM) formation and our ability to model and manage effects of global change on SOM stocks. One controversially debated aspect is the contribution of aromatic litter components, such as lignin and tannins, to stable SOM forms. In the present opinion paper, we summarize and discuss the inconsistencies and propose research options to clear them. Lignin degradation takes place stepwise, starting with (i) depolymerization and followed by (ii) transformation of the water-soluble depolymerization products. The long-term fate of the depolymerization products and other soluble aromatics, e.g., tannins, in the mineral soils is still a mystery. Research on dissolved organic matter (DOM) composition and fluxes indicates dissolved aromatics are important precursors of stable SOM attached to mineral surfaces and persist in soils for centuries to millennia. Evidence comes from flux analyses in soil profiles, biodegradation assays, and sorption experiments. In contrast, studies on composition of mineral-associated SOM indicate the prevalence of non-aromatic microbial-derived compounds. Other studies suggest the turnover of lignin in soil can be faster than the turnover of bulk SOM. Mechanisms that can explain the apparent fast disappearance of lignin in mineral soils are, however, not yet identified. The contradictions might be explained by analytical problems. Commonly used methods probably detect only a fraction of the aromatics stored in the mineral soil. Careful data interpretation, critical assessment of analytical limitations, and combined studies on DOM and solid-phase SOM could thus be ways to unveil the issues.
    Type of Medium: Online Resource
    ISSN: 2199-398X
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2834892-8
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  • 14
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2019-07-16)
    Abstract: Formation of mineral-organic associations is a key process in the global carbon cycle. Recent concepts propose litter quality-controlled microbial assimilation and direct sorption processes as main factors in transferring carbon from plant litter into mineral-organic associations. We explored the pathways of the formation of mineral-associated organic matter (MOM) in soil profiles along a 120-ky ecosystem gradient that developed under humid climate from the retreating Franz Josef Glacier in New Zealand. We determined the stocks of particulate and mineral-associated carbon, the isotope signature and microbial decomposability of organic matter, and plant and microbial biomarkers (lignin phenols, amino sugars and acids) in MOM. Results revealed that litter quality had little effect on the accumulation of mineral-associated carbon and that plant-derived carbon bypassed microbial assimilation at all soil depths. Seemingly, MOM forms by sorption of microbial as well as plant-derived compounds to minerals. The MOM in carbon-saturated topsoil was characterized by the steady exchange of older for recent carbon, while subsoil MOM arises from retention of organic matter transported with percolating water. Overall, MOM formation is not monocausal but involves various mechanisms and processes, with reactive minerals being effective filters capable of erasing chemical differences in organic matter inputs.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 2615211-3
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  • 15
    Online Resource
    Online Resource
    Frontiers Media SA ; 2021
    In:  Frontiers in Environmental Science Vol. 9 ( 2021-4-7)
    In: Frontiers in Environmental Science, Frontiers Media SA, Vol. 9 ( 2021-4-7)
    Abstract: Water-extractable organic carbon (WEOC) is considered as the most important carbon (C) source for denitrifying organisms, but the contribution of individual organic matter (OM) fractions (i.e., particulate (POM) and mineral-associated (MOM)) to its release and, thus, to denitrification remains unresolved. Here we tested short-time effects of POM and MOM on potential denitrification and estimated the contribution of POM- and MOM-derived WEOC to denitrification and CO 2 production of three agricultural topsoils. Suspensions of bulk soils with and without addition of soil-derived POM or MOM were incubated for 24 h under anoxic conditions. Acetylene inhibition was used to determine the potential denitrification and respective product ratio at constant nitrate supply. Normalized to added OC, effects of POM on CO 2 production, total denitrification, and its product ratios were much stronger than those of MOM. While the addition of OM generally increased the (N 2 O + N 2 )-N/CO 2 -C ratio, the N 2 O/(N 2 O + N 2 ) ratio changed differently depending on the soil. Gas emissions and the respective shares of initial WEOC were then used to estimate the contribution of POM and MOM-derived WEOC to total CO 2 , N 2 O, and N 2 O + N 2 production. Water-extractable OC derived from POM accounted for 53–85% of total denitrification and WEOC released from MOM accounted for 15–47%. Total gas emissions from bulk soils were partly over- or underestimated, mainly due to nonproportional responses of denitrification to the addition of individual OM fractions. Our findings show that MOM plays a role in providing organic substrates during denitrification but is generally less dominant than POM. We conclude that the denitrification potential of soils is not predictable based on the C distribution over POM and MOM alone. Instead, the source strength of POM and MOM for WEOC plus the WEOC’s quality turned out as the most decisive determinants of potential denitrification.
    Type of Medium: Online Resource
    ISSN: 2296-665X
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2741535-1
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  • 16
    Online Resource
    Online Resource
    MDPI AG ; 2020
    In:  Microorganisms Vol. 8, No. 11 ( 2020-11-16), p. 1796-
    In: Microorganisms, MDPI AG, Vol. 8, No. 11 ( 2020-11-16), p. 1796-
    Abstract: Adsorption of extracellular enzymes to soil minerals is assumed to protect them against degradation, while modifying their activities at the same time. However, the persistence of the activity of adsorbed enzymes remains poorly understood. Therefore, we studied the persistence of cellulase and α-amylase activities after adsorption to soil amended with various amounts (+1, +5, and +10 wt.%) of three typical soil minerals, montmorillonite, kaolinite, and goethite. Soil without mineral addition (pure soil), pure minerals, and pure dissolved enzymes were used as references. Soil mineral–enzyme complexes were prepared and then incubated for 100 days; temporal changes in enzyme activities were analyzed after 0, 0.1, 1, 10, and 100 days. The specific enzyme activities (activities normalized to protein content) and their persistence (activities relative to activities at day 0) were compared to enzyme activities in solution and after sorption to the control soil. Amylase adsorption to pure minerals increased in the following order: montmorillonite 〉 kaolinite 〉 goethite. That of cellulase increased in the following order: goethite 〉 montmorillonite 〉 kaolinite. Adsorption of enzymes to soils did not increase in the same order of magnitude as the addition of reactive binding sites. Based on inverse relationships between the amount of enzyme adsorbed and the specific enzyme activity and their persistency, we showed that a limited availability of sorption sites is important for high specific activity and persistence of the enzymes. This is probably the consequence of less and weaker bonds, as compared to a high availability of sorption sites, resulting in a smaller impact on the active sites of the enzyme. Hence, we suppose that the soil mineral phase supports microorganisms in less-sorptive environments by saving energy on enzyme production, since small enzyme release could already result in sufficient activities to degrade respective target carbon substrates.
    Type of Medium: Online Resource
    ISSN: 2076-2607
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2720891-6
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  • 17
    Online Resource
    Online Resource
    Wiley ; 1975
    In:  Journal of the London Mathematical Society Vol. s2-9, No. 4 ( 1975-04), p. 585-588
    In: Journal of the London Mathematical Society, Wiley, Vol. s2-9, No. 4 ( 1975-04), p. 585-588
    Type of Medium: Online Resource
    ISSN: 0024-6107
    Language: English
    Publisher: Wiley
    Publication Date: 1975
    detail.hit.zdb_id: 1476428-3
    SSG: 17,1
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  • 18
    Online Resource
    Online Resource
    Wiley ; 2017
    In:  Global Change Biology Vol. 23, No. 7 ( 2017-07), p. 2535-2536
    In: Global Change Biology, Wiley, Vol. 23, No. 7 ( 2017-07), p. 2535-2536
    Abstract: Concentrations of dissolved organic carbon ( DOC ) increased in many surface waters in Europe and North America over the last two or three decades. Musolff et al. (2017) recently suggested that decreasing atmospheric N deposition has triggered increasing dissimilatory reduction and dissolution of Fe oxides in riparian zone soil, which has caused the release of sorbed organic matter (as well as sorbed phosphate). The wide organic carbon‐to‐iron ratios found by Musolff et al. (2017) are inconsistent with actual ratios found during reductive dissolution of Fe oxides. It is extremely unlikely that increased reductive dissolution of Fe oxides is the dominant mechanism causing the observed increases in stream DOC .
    Type of Medium: Online Resource
    ISSN: 1354-1013 , 1365-2486
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2020313-5
    SSG: 12
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  • 19
    In: Global Change Biology, Wiley, Vol. 24, No. 1 ( 2018-01)
    Abstract: 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 ( Oryza sativa ) 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.
    Type of Medium: Online Resource
    ISSN: 1354-1013 , 1365-2486
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2020313-5
    SSG: 12
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  • 20
    In: European Journal of Soil Science, Wiley, Vol. 73, No. 5 ( 2022-09)
    Abstract: Erosion is a severe threat to the sustainable use of agricultural soils. However, the structural resistance of soil against the disruptive forces steppe soils experience under field conditions has not been investigated. Therefore, 132 topsoils under grass‐ and cropland covering a large range of physico‐chemical soil properties (sand: 2–76%, silt: 18–80%, clay: 6–30%, organic carbon: 7.3–64.2 g kg −1 , inorganic carbon: 0.0–8.5 g kg −1 , pH: 4.8–9.5, electrical conductivity: 32–946 μS cm −1 ) from northern Kazakhstan were assessed for their potential erodibility using several tests. An adjusted drop‐shatter method (low energy input of 60 Joule on a 250‐cm 3  soil block) was used to estimate the stability of dry soil against weak mechanical forces, such as saltating particles striking the surface causing wind erosion. Three wetting treatments with various conditions and energies (fast wetting, slow wetting, and wet shaking) were applied to simulate different disruptive effects of water. Results indicate that aggregate stability was higher for grassland than cropland soils and declined with decreasing soil organic carbon content. The results of the drop‐shatter test suggested that 29% of the soils under cropland were at risk of wind erosion, but only 6% were at high risk (i.e. erodible fraction 〉 60%). In contrast, the fast wetting treatment revealed that 54% of the samples were prone to become “very unstable” and 44% “unstable” during heavy rain or snowmelt events. Even under conditions comparable to light rain events or raindrop impact, 53–59% of the samples were “unstable.” Overall, cropland soils under semi‐arid conditions seem much more susceptible to water than wind erosion. Considering future projections of increasing precipitation in Kazakhstan, we conclude that the risk of water erosion is potentially underestimated and needs to be taken into account when developing sustainable land use strategies. Highlights Organic matter is the important binding agent enhancing aggregation in steppe topsoils. Tillage always declines aggregate stability even without soil organic carbon changes. All croplands soil are prone to wind or water erosion independent of their soil properties. Despite the semi‐arid conditions, erosion risk by water seems higher than by wind.
    Type of Medium: Online Resource
    ISSN: 1351-0754 , 1365-2389
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 240830-2
    detail.hit.zdb_id: 2020243-X
    detail.hit.zdb_id: 1191614-X
    SSG: 13
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