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  • 1
    Language: English
    In: Forest Ecology and Management, 1 January 2016, Vol.359, pp.74-82
    Description: •We assessed the recovery of compacted forest soils after logging operations.•At sites with high biological activity and high clay content recovery takes place after 10–20years.•Loamy sandy soils were found to be compaction sensitive with low recovery potential. 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 40years after the last machine impact) to study selected sites in Lower Saxony, Germany, using the following as proxies: bulk density, carbon dioxide (CO2) concentration in soil gas, and the relative apparent gas diffusion coefficient (DS/D0). At sites with high biological activity and high clay content (Cambisols on limestone), recovery occurred 10–20years after last traffic impact. At these sites, 10years after the last traffic impact, gas diffusivity at the wheel track was half of the gas diffusivity of the undisturbed soil, and soil gas CO2 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 20–40years 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
    ISSN: 0378-1127
    E-ISSN: 18727042
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  • 2
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, April 5, 2012, Vol.399, p.35(6)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.colsurfa.2012.02.021 Byline: Doreen Zirkler, Friederike Lang, Martin Kaupenjohann Keywords: Soil colloid; Vacuum filtration; Centrifugation; Particle size separation Abstract: Display Omitted Author Affiliation: TU Berlin, Department of Soil Science, Ernst-Reuter-Platz 1, 10587 Berlin, Germany Article History: Received 28 October 2011; Revised 2 February 2012; Accepted 17 February 2012
    ISSN: 0927-7757
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Forest Ecology and Management, 15 November 2015, Vol.356, pp.136-143
    Description: •In our case study, 60% of harvested P was deposited on the skid trail.•Five years later, 4.5gm−2 of P was gone and not found in soil stocks.•Higher root density in the middle of the skid trail implies uptake of missing P.•This indicates P on skid trails is accessible and can be recycled. 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 Abies alba 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 gm−2. The difference of 4.5gm−2 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
    ISSN: 0378-1127
    E-ISSN: 18727042
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  • 4
    Language: English
    In: The Science of the Total Environment, Dec 1, 2015, Vol.535, p.54(7)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.10.108 Byline: Sondra Klitzke, George Metreveli, Andre Peters, Gabriele E. Schaumann, Friederike Lang Abstract: 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 24h. Nanoparticles were removed through centrifugation. Concentrations of free Ag ions and DOC, the specific UV absorbance at a wavelength of 254nm, and the absorption ratio [alpha].sub.254/[alpha].sub.410 were determined in the supernatant. Nanoparticle aggregation was studied using time-resolved dynamic light scattering (DLS) measurement following the addition of soil solution and 1.5mM Ca.sup.2+ 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[mu]g/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.sup.+ 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. Article History: Received 29 September 2014; Revised 30 October 2014; Accepted 30 October 2014 Article Note: (miscellaneous) Editor: D. Barcelo
    Keywords: Nanoparticles ; Adsorption
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Plant and Soil, 2013, Vol.370(1), pp.497-509
    Description: Aims: We analysed current carbon (C) stocks in fine root and aboveground biomass of riparian forests and influential environmental parameters on either side of a dike in the Donau-Auen National Park, Austria. Methods: On both sides of the dike, carbon (C) stock of fine roots (CFR) under four dominant tree species and of aboveground biomass (CAB) were assessed by topsoil cores (0-30 cm) and angle count sampling method respectively (n=48). C stocks were modeled, performing boosted regression trees (BRT). Results: Overall CFR was 2.8 t ha super(-1), with significantly higher C stocks in diked (DRF) compared to flooded riparian forests (FRF). In contrast to CFR, mean CAB was 123 t ha super(-1) and lower in DRF compared to FRF. However, dike construction was consistently ruled out as a predictor variable in BRT. CFR was influenced by the distance to the Danube River and the dominant tree species. CAB was mainly influenced by the magnitude of fluctuations in the groundwater table and the distances to the river and the low groundwater table. Conclusions: Despite pronounced differences in FRF and DRF, we conclude that there is only weak support that dikes directly influence C allocation in floodplain forests within the time scale considered (110 years).
    Keywords: Aboveground biomass ; Belowground biomass ; Carbon distribution ; Carbon sequestration ; Dike ; Ecosystem services ; Floodplain forest
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    Language: English
    In: Forest Ecology and Management, 1 December 2017, Vol.405, pp.200-209
    Description: •On silicate bedrock deadwood increased free particulate OM.•On calcareous bedrock deadwood decreased free particulate OM.•Advanced decayed deadwood increased occluded particulate OM and total SOC stocks.•Managing deadwood to store SOC should consider decay class and site conditions. 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 (Fagus sylvatica 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% (6.0±4.2mgg−1) compared to reference points. In contrast on calcareous bedrock, deadwood decreased the free light fraction by 23% (9.0±3.5mgg−1) compared to reference points. Deadwood with advanced decay from all sites increased the aggregate-occluded light fraction by 40% (3.7±1.1mgg−1) as well as total soil organic carbon (SOC) stocks by 24% (12.8±4.5mgcm−3) 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 ; Flf ; Olf ; Hf ; POM ; Weoc ; Suva 280 ; MAP ; Mat
    ISSN: 0378-1127
    E-ISSN: 18727042
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  • 7
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 4/2012, Vol.399, C, pp.35-40
    Description: ► Colloid recovery after filtration and centrifugation of soil suspensions was measured. ► Colloid recovery after filtration is 50–97% of the recovery after centrifugation. ► Cellulose nitrate filters retain colloids without losing permeability. ► Recovery of mineral colloids after filtration is less than recovery of organic colloids. ► We recommend centrifugation for soils with colloids of similar density. Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2 μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3 μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O.
    Keywords: Soil Colloid ; Vacuum Filtration ; Centrifugation ; Particle Size Separation ; Engineering ; Chemistry;
    ISSN: 09277757
    E-ISSN: 18734359
    Source: Elsevier (via CrossRef)
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  • 8
    Language: English
    In: Colloids and surfaces, 2012, Vol.399, pp.35-40
    Description: Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O. ; p. 35-40.
    Keywords: Colloids ; Filtrates ; Centrifugation ; Filtration ; Aluminum ; Turbidity ; Soil Colloids ; Silicon ; Filter Cake ; Soil
    ISSN: 0927-7757
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 9
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 5 April 2012, Vol.399, pp.35-40
    Description: Graphical abstract Highlights► Colloid recovery after filtration and centrifugation of soil suspensions was measured. ► Colloid recovery after filtration is 50–97% of the recovery after centrifugation. ► Cellulose nitrate filters retain colloids without losing permeability. ► Recovery of mineral colloids after filtration is less than recovery of organic colloids. ► We recommend centrifugation for soils with colloids of similar density. Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O.
    Keywords: Soil Colloid ; Vacuum Filtration ; Centrifugation ; Particle Size Separation
    ISSN: 0927-7757
    E-ISSN: 18734359
    Source: ScienceDirect (Elsevier B.V.)
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  • 10
    Language: English
    In: The Science of the Total Environment, Dec 1, 2015, Vol.535, p.1(2)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2015.06.006 Byline: Gabriele E. Schaumann, Thomas Baumann, Friederike Lang, George Metreveli, Hans-Jorg Vogel
    Keywords: Soils
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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