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  • ScienceDirect Journals (Elsevier)
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  • 1
    Language: English
    In: Forest Ecology and Management, 01 January 2016, Vol.359, pp.74-82
    Description: Harvesting and logging with heavy forest machines cause soil damage that may restrict forest soil functions. Although the recovery ability of compacted forest soils depends on the soil properties, little is known about the long-term structure recovery of different soils following forest operations. The aim of our study was to evaluate the soil structure recovery of three different soil types. Therefore, we applied a space-for-time substitution approach (10, 20, 30 and 40 years after the last machine impact) to study selected sites in Lower Saxony, Germany, using the following as proxies: bulk density, carbon dioxide (CO ) concentration in soil gas, and the relative apparent gas diffusion coefficient ( / ). At sites with high biological activity and high clay content (Cambisols on limestone), recovery occurred 10–20 years after last traffic impact. At these sites, 10 years after the last traffic impact, gas diffusivity at the wheel track was half of the gas diffusivity of the undisturbed soil, and soil gas CO concentrations were significantly higher at the wheel tracks. At the 20-, 30-, and 40-year-old skid trails, there were no significant differences between the untrafficked reference and the soil frequented by vehicles. Regardless of the kind of traffic impact (wheel track, mid line, side strip or undisturbed reference soil), all investigated parameters indicated that soil structure becomes more favourable with increasing time since the last forest interference. In contrast, loamy sandy soils (Podzols on glacial drift and sand) showed low recovery ability. Forty years after the last machine impact, gas diffusivity was still significantly reduced at the wheel track. Cambisols at loess-covered sandstone showed neither strong impact of forest traffic on soil structure nor changes in soil structure 20–40 years after last traffic impact. In general, bulk density turned out not to be a sufficient proxy for soil structure recovery.
    Keywords: Soil Gas Diffusivity ; Soil Carbon Dioxide ; Soil Compaction ; Soil Structure Recovery ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 2
    Language: English
    In: Forest Ecology and Management, 15 November 2015, Vol.356, pp.136-143
    Description: Phosphorus is an essential yet scarce macronutrient, and as such forest nutrition often relies on cycling of P between biomass and soils through litterfall and roots. For technical and soil protection reasons, modern harvesting systems create thick brash mats on skid trails by depositing residues, thus concentrating P there. What portion of this redistributed P is immobilized, lost, or recycled could be significant to forest nutrition and management. However, open questions exist regarding the quantity and fate of P deposited on skid trials. The aim of this study was to determine how much P is redistributed to skid trails and what happens to that P. We modeled the amount of P deposited on a skid trail during a whole-tree thinning of an Mill. stand, and quantified P stocks in the forest floor and mineral soil five years after the operation. An estimated 60% of harvested P from the encatchment was deposited on the skid trail. Five years after the harvest, forest floor P stocks in the skid trail dropped from an extrapolated 8.9 to 4.4 g m . The difference of 4.5 g m of P was not evident in mineral soil stocks, and loss through runoff or leaching would be minimal. With the greatest concentration of roots in the forest floor on the middle of the skid trail, mineralization and uptake of the missing P was the most likely explanation. This suggests that accumulated P on skid trails can be recycled through uptake by trees. Further testing in other stands and on which vegetation takes up accumulated P is still needed.
    Keywords: Nutrient Cycling ; Plant Uptake ; Whole-Tree Harvesting ; Brash Mats ; Allometric Modeling ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 3
    Language: English
    In: Forest Ecology and Management, 01 December 2017, Vol.405, pp.200-209
    Description: Deadwood plays a crucial role in forest ecosystems, yet its impact on soil properties and specifically soil organic matter (SOM) stabilization is hitherto not fully understood or studied. We hypothesized that downed deadwood would enhance the light, labile SOM fraction in forest topsoils, and that those changes would be enhanced by advanced decay and higher rates of soil bioturbation that would move deadwood fragments into mineral soil. To test our hypotheses, we took topsoil samples directly next to European beech ( L.) downed deadwood and samples from paired reference points at eight stands in Southwest Germany. From those samples we separated SOM into three density fractions linked to physical and chemical SOM stabilization processes: the free light fraction, the aggregate-occluded light fraction and the mineral-adsorbed heavy fraction. On silicate bedrock, deadwood increased the free light fraction by 57% ( mg g ) compared to reference points. In contrast on calcareous bedrock, deadwood decreased the free light fraction by 23% ( mg g ) compared to reference points. Deadwood with advanced decay from all sites increased the aggregate-occluded light fraction by 40% ( mg g ) as well as total soil organic carbon (SOC) stocks by 24% ( mg cm ) as compared to reference points. In summary, the light fraction of SOM was affected by deadwood depending on site conditions and the more stable, aggregate-occluded fraction eventually increased near decayed deadwood through interactions between stimulated biological activity and both particulate and dissolved organic matter. Altogether these results indicate that deadwood increases SOC stocks at sites where SOM decomposition is slow enough to enable occlusion of particulate organic matter within aggregates.
    Keywords: Coarse Woody Debris ; Forest Management ; Som Stability ; Soil Aggregate ; Density Fractionation ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 4
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.54-60
    Description: Nanoparticles enter soils through various pathways. In the soil, they undergo various interactions with the solution and the solid phase. We tested the following hypotheses using batch experiments: i) the colloidal stability of Ag NP increases through sorption of soil-borne dissolved organic matter (DOM) and thus inhibits aggregation; ii) the presence of DOM suppresses Ag oxidation; iii) the surface charge of Ag NP governs sorption onto soil particles. Citrate-stabilized and bare Ag NPs were equilibrated with (colloid-free) soil solution extracted from a floodplain soil for 24 h. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254 nm, and the absorption ratio α /α were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5 mM Ca solution. To study the effect of surface charge on the adsorption of Ag NP onto soil particles, bare and citrate-stabilized Ag NP, differing in the zeta potential, were equilibrated with silt at a solid-to-solution ratio of 1:10 and an initial Ag concentration range of 30 to 320 μg/L. Results showed that bare Ag NPs sorb organic matter, with short-chained organic matter being preferentially adsorbed over long-chained, aromatic organic matter. Stabilizing effects of organic matter only come into play at higher Ag NP concentrations. Soil solution inhibits the release of Ag ions, presumably due to organic matter coatings. Sorption to silt particles was very similar for the two particle types, suggesting that the surface charge does not control Ag NP sorption. Besides, sorption was much lower than in comparable studies with sand and glass surfaces.
    Keywords: Isoelectric Point ; Cation Valency ; Initial Nanoparticle Concentration ; Exchangeability of Sorbed Ag Ions ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 5
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.1-2
    Keywords: Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: Estuarine, Coastal and Shelf Science, 2010, Vol.87(1), pp.11-20
    Description: Visual traces of iron reduction and oxidation are linked to the redox status of soils and have been used to characterise the quality of agricultural soils. We tested whether this feature could also be used to explain the spatial pattern of the natural vegetation of tidal habitats. If so, an easy assessment of the effect of rising sea level on tidal ecosystems would be possible. Our study was conducted at the salt marshes of the northern lagoon of Venice, which are strongly threatened by erosion and rising sea level and are part of the world heritage “Venice and its lagoon”. We analysed the abundance of plant species at 255 sampling points along a land–sea gradient. In addition, we surveyed the redox morphology (presence/absence of red iron oxide mottles in the greyish topsoil horizons) of the soils and the presence of disturbances. We used indicator species analysis, correlation trees and multivariate regression trees to analyse relations between soil properties and plant species distribution. Plant species with known sensitivity to anaerobic conditions (e.g. ) were identified as indicators for oxic soils (showing iron oxide mottles within a greyish soil matrix). Plant species that tolerate a low redox potential (e.g. ) were identified as indicators for anoxic soils (greyish matrix without oxide mottles). Correlation trees and multivariate regression trees indicate the dominant role of the redox morphology of the soils in plant species distribution. In addition, the distance from the mainland and the presence of disturbances were identified as tree-splitting variables. The small-scale variation of oxygen availability plays a key role for the biodiversity of salt marsh ecosystems. Our results suggest that the redox morphology of salt marsh soils indicates the plant availability of oxygen. Thus, the consideration of this indicator may enable an understanding of the heterogeneity of biological processes in oxygen-limited systems and may be a sensitive and easy-to-use tool to assess human impacts on salt marsh ecosystems.
    Keywords: Coastal Wetlands ; Iron Oxides ; Halophyte Ecology ; Regression Trees ; Indicator Species Analysis ; Classification of Marsh Soils ; Biology ; Oceanography
    ISSN: 0272-7714
    E-ISSN: 1096-0015
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  • 7
    Language: English
    In: Science of the Total Environment, 01 December 2015, Vol.535, pp.3-19
    Description: Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).
    Keywords: Transport ; Aggregation ; Analytics ; Environment ; Aging ; Ecotoxicology ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 8
    Language: English
    In: Science of the Total Environment, 15 December 2018, Vol.645, pp.192-204
    Description: Riverbank filtration systems are important structures that ensure the cleaning of infiltrating surface water for drinking water production. In our study, we investigated the potential risk for a breakthrough of environmentally aged silver nanoparticles (Ag NP) through these systems. Additionally, we identified factors leading to the remobilization of Ag NP accumulated in surficial sediment layers in order to gain insights into remobilization mechanisms. We conducted column experiments with Ag NP in an outdoor pilot plant consisting of water-saturated sediment columns mimicking a riverbank filtration system. The NP had previously been aged in river water, soil extract, and ultrapure water, respectively. We investigated the depth-dependent breakthrough and retention of NP. In subsequent batch experiments, we studied the processes responsible for a remobilization of Ag NP retained in the upper 10 cm of the sediments, induced by ionic strength reduction, natural organic matter (NOM), and mechanical forces. We determined the amount of remobilized Ag by ICP-MS and differentiated between particulate and ionic Ag after remobilization using GFAAS. The presence of Ag-containing heteroaggregates was investigated by combining filtration with single-particle ICP-MS. Single and erratic Ag breakthrough events were mainly found in 30 cm depth and Ag NP were accumulated in the upper 20 cm of the columns. Soil-aged Ag NP showed the lowest retention of only 54%. Remobilization was induced by the reduction of ionic strength and the presence of NOM in combination with mechanical forces. The presence of calcium in the aging- as well as the remobilizing media reduced the remobilization potential. Silver NP were mainly remobilized as heteroaggregates with natural colloids, while dissolution played a minor role. Our study indicates that the breakthrough potential of Ag NP in riverbank filtration systems is generally low, but the aging in soil increases their mobility. Remobilization processes are associated to co-mobilization with natural colloids.
    Keywords: Heteroaggregation ; Nanoparticle Transformation ; Breakthrough ; Mobility ; Reversibility ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 9
    Language: English
    In: Geochimica et Cosmochimica Acta, 2006, Vol.70(3), pp.595-607
    Description: Anions of polycarboxylic low-molecular-weight organic acids (LMWOA) compete with phosphate for sorption sites of hydrous Fe and Al oxides. To test whether the sorption of LMWOA anions decreases the accessibility of micropores (〈2 nm) of goethite (α-FeOOH) for phosphate, we studied the kinetics of citrate-induced changes in microporosity and the phosphate sorption kinetics of synthetic goethite in the presence and absence of citrate in batch systems for 3 weeks (500 μM of each ion, pH 5). We also used C-coated goethite obtained after sorption of dissolved organic matter in order to simulate organic coatings in the soil. We analyzed our samples with N adsorption and electrophoretic mobility measurements. Citrate clogged the micropores of both adsorbents by up to 13% within 1 h of contact. The micropore volume decreased with increasing concentration and residence time of citrate. In the absence of citrate, phosphate diffused into micropores of the pure and C-coated goethite. The C coating (5.6 μmol C m ) did not impair the intraparticle diffusion of phosphate. In the presence of citrate, the diffusion of phosphate into the micropores of both adsorbents was strongly impaired. We attribute this to the micropore clogging and the ligand-induced dissolution of goethite by citrate. While the diffusion limitation of phosphate by citrate was stronger when citrate was added before phosphate to pure goethite, the order of addition of both ions to C-coated goethite had only a minor effect on the intraparticle diffusion of phosphate. Micropore clogging and dissolution of microporous hydrous Fe and Al oxides may be regarded as potential strategies of plants to cope with phosphate deficiency in addition to ligand-exchange.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 10
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007, Vol.303(3), pp.249-252
    Description: Colloids play a crucial role in the translocation of trace elements in soils. Recent studies provided hints that colloid hydrophobicity may be an important factor controlling colloid (im)mobilization in soils. However, existing methods for the determination of hydrophobicity are limited to the bulk soil. Therefore, we developed a method to determine the hydrophobicity of suspended colloids in aqueous soil suspensions, which was based on a distribution between a polar and a non-polar phase. The proposed method uses 30 mg of an unpolar solid phase (C18-column material) which are mixed with 10 mL of suspension for 2 h. The turbidity of the suspensions is measured before and after mixing. The ratio of the colloids in the hydrophilic aqueous and the hydrophobic solid phase is calculated as a measure of colloid hydrophobicity. This method was successfully tested on differently hydrophobized goethite particles. At DOC concentrations exceeding 20 mg L , organic molecules sorbed to C18-material limit the applicability of the method.
    Keywords: Water Repellence ; Zeta Potential ; Colloid ; Soil Drying ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
    Source: ScienceDirect Journals (Elsevier)
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