Kooperativer Bibliotheksverbund

Berlin Brandenburg

Language
Preferred search index
Number of Hits per Page
Default Sort Criterion
Default Sort Ordering
Size of Search History
Default Export Format
Default Export Encoding
Facet list arrangement
Maximum number of values per filter
Auto Completion
Feed Format
Maximum Number of Items per Feed
Search in libraries
and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • English  (14)
  • AGRIS (United Nations, Food and Agriculture Organization)  (14)
Type of Medium
Language
  • English  (14)
Year
Source
  • 1
    In: Canadian Journal of Forest Research (Revue canadienne de recherche forestière), 2000, Vol.30(7), pp.1034-1040
    Description: Molybdenum plays an important role in the nitrogen turnover of ecosystems. However, very little is known about Mo availability in forest soils. We measured the oxalate-extractable Mo concentrations of acid forest soils, the Mo, nitrate, phosphate, and sulfate fluxes from the organic forest floor into the mineral soil using resin tubes and the Mo concentrations of the tree needles at 28 different Norway spruce ( Picea abies (L.) Karst.) sites in southern Germany. The supply of oxalate-extractable Mo varied from 51 to 3400 gha -1 , with the lowest values occurring in sandstone-derived soils (370 212 gha -1 ; mean SD). Molybdenum concentrations of current-year needles were in the range of 5 to 48 ngg -1 . The Mo needle concentrations and oxalate-extractable Mo of soils did not correlate. However, Mo fluxes (6-60 gha -1 a -1 ) from the organic forest floor into the mineral soils were correlated to needle concentrations and to the NO 3 fluxes. We conclude that Mo turnover within forest ecosystems is governed by Mo plant availability of mineral soils as well as by plant Mo uptake. In addition, Mo cycling strongly affects Mo distribution within soil profiles and Mo fluxes out of the organic layer.
    Description: Le molybdne joue un rle important dans le renouvellement de l'azote des cosystmes. Toutefois, on connat peu de choses au sujet de la disponibilit de Mo dans les sols forestiers. Nous avons mesur la concentration de Mo extractible l'oxalate dans des sols forestiers acides, les flux de Mo, de nitrate, de phosphate et de sulfate, de la couverture morte organique vers le sol minral, l'aide de tubes de rsines ainsi que la concentration de Mo dans les aiguilles d'pica commun ( Picea abies (L.) Karst.) dans 28 sites diffrents du sud de l'Allemagne. L'apport de Mo extractible l'oxalate variait de 51 3400 gha -1 avec les plus faibles valeurs provenant des sols drivs de grs (370 212 gha -1 ; moyenne ET). La concentration de Mo dans les aiguilles de l'anne courante variait de 5 48 ngg -1 . La concentration de Mo dans les aiguilles et le Mo extractible l'oxalate dans les sols n'taient pas corrls. Toutefois, les flux de Mo (6-60 gha -1 a -1 ) de la couverture morte organique vers le sol minral taient corrls aux concentrations foliaires et aux flux de NO 3 . Nous en concluons que le renouvellement de Mo dans les cosystmes forestiers est gouvern par le Mo des sols minraux disponible pour la plante autant que par le prlvement de Mo par la plante. De plus, le recyclage de Mo affecte fortement la distribution de Mo dans les profils de sol et le flux de Mo hors de la couche organique.[Traduit par la Rdaction]
    Keywords: Forest Floor ; Soils (Acid) ; Mobility ; Soil Profiles ; Molybdenum ; Minerals ; Nitrogen ; Sulfate ; Picea Abies ; Management and Conservation;
    ISSN: 0045-5067
    E-ISSN: 1208-6037
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    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)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2016, Vol.179(2), pp.129-135
    Description: Phosphorus is one of the major limiting factors of primary productivity in terrestrial ecosystems and, thus, the P demand of plants might be among the most important drivers of soil and ecosystem development. The P cycling in forest ecosystems seems an ideal example to illustrate the concept of ecosystem nutrition. Ecosystem nutrition combines and extents the traditional concepts of nutrient cycling and ecosystem ecology. The major extension is to consider also the loading and unloading of nutrient cycles and the impact of nutrient acquiring and recycling processes on overall ecosystem properties. Ecosystem nutrition aims to integrate nutrient related aspects at different scales and in different ecosystem compartments including all processes, interactions and feedbacks associated with the nutrition of an ecosystem. We review numerous previous studies dealing with P nutrition from this ecosystem nutrition perspective. The available information contributes to the description of basic ecosystem characteristics such as emergence, hierarchy, and robustness. In result, we were able to refine Odum's hypothesis on P nutrition strategies along ecosystem succession to substrate related ecosystem nutrition and development. We hypothesize that at sites rich in mineral‐bound P, plant and microbial communities tend to introduce P from primary minerals into the biogeochemical P cycle (acquiring systems), and hence the tightness of the P cycle is of minor relevance for ecosystem functioning. In contrast, tight P recycling is a crucial emergent property of forest ecosystems established at sites poor in mineral bound P (recycling systems). We conclude that the integration of knowledge on nutrient cycling, soil science, and ecosystem ecology into holistic ecosystem nutrition will provide an entirely new view on soil–plant–microbe interactions.
    Keywords: Ecosystem Properties ; P Recycling ; P Nutrition Strategy ; Forest Nutrition ; P Acquiring
    ISSN: 1436-8730
    E-ISSN: 1522-2624
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Soil Science Society of America Journal, Sept-Oct, 2006, Vol.70(5), p.1731(10)
    Description: Uronates are important constituents of maize mucilage and polyuronates are used as a simplified model of the soil--root interface. We tested whether galacturonate (GA) and polygalacturonate (PGA) impair the diffusion of phosphate (P[O.sub.4]) into and out of pores of a synthetic goethite (147 [m.sup.2] [g.sup.-1]) and whether the effect of maize mucigel (MU) is comparable to PGA. We measured the P[O.sub.4] desorption kinetics of goethites in batch experiments over 2 wk at pH 5. One part of the goethite was equilibrated with organic substances before P[O.sub.4] addition, another part after addition of P[O.sub.4]. Before the desorption experiments, the porosity of our samples was analyzed by [N.sub.2] gas adsorption. In each treatment a rapid initial desorption was followed by a slow desorption reaction, which is assigned to the diffusion of P[O.sub.4] out of mineral pores. No consistent relation between the micro- and mesoporosity and the rate of the slow P[O.sub.4] desorption was observed. Compared with the C-free control, only PGA and MU affected the fraction of P[O.sub.4] mobilized by the fast and slow desorption reaction: when PGA was sorbed to goethite before P[O.sub.4], twice as much P[O.sub.4] was mobilized via the fast reaction than in the treatment where P[O.sub.4] was sorbed before PGA, suggesting a decreased accessibility of goethite pores to P[O.sub.4]. Mucigel, however, showed reversed effects, which is ascribed to its differing chemical composition. In conclusion, PGA seems inappropriate as a model substance for maize MU collected from non-axenic sand cultures. Under the experimental conditions chosen, the efficacy of all organic substances to increase P[O.sub.4] solution concentrations by pore clogging and sorption competition is small.
    Keywords: Phosphates -- Research ; Sorption -- Research
    ISSN: 0361-5995
    E-ISSN: 14350661
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Soil Science Society of America Journal, March-April, 2006, Vol.70(2), p.541(9)
    Description: Biogenetic polysugars may affect the sorption characteristics of soil mineral particles in the rhizosphere. We hypothesized that polygalacturonate [PGA, ([[C.sub.6][H.sub.7][O.sub.6]).sub.n.sup.-]] coatings on goethite reduce the diffusion of phosphate into the pores of the adsorbent. Goethite was preloaded with PGA (0-10 mg C [g.sup.-1]). The samples were characterized by [N.sub.2] and C[O.sub.2] adsorption, electrophoretic mobility measurements, and scanning electron microscopy/energy dispersive X-ray analysis (SEM-EDX). The phosphate sorption kinetics was studied with batch experiments over 2 wk at pH 5 and an initial phosphate concentration of 250 [micro]M. Pore volume and specific surface area of the goethite samples declined after PGA addition. The PGA coatings reduced the [zeta]-potential of goethite from 42.3 to -39.6 mV at the highest C loading. With increasing PGA-C content and decreasing [zeta]-potential the amount of phosphate sorbed after 2 wk decreased linearly (P 〈 0.001). Sorption of phosphate to pure and PGA-coated goethite showed an initial fast sorption followed by a slow sorption reaction. At the smallest C loading (5.5 mg C [g.sup.-1]) the portion of phosphate retained by the slow reaction was smaller than for the treatment without any PGA, while at higher C loadings the fraction of slowly immobilized phosphate increased. Our results suggest that at low C-loadings PGA impaired the intraparticle diffusion of phosphate. In contrast, the slow step-by-step desorption of PGA (〈52% within 2 wk) or the diffusion of phosphate through PGA coatings or both are rate limiting for the slow phosphate reaction at C loadings 〉 5.5 mg C [g.sup.-1].
    Keywords: Soil Phosphorus -- Research ; Soil Chemistry -- Research ; X-ray Analysis
    ISSN: 0361-5995
    E-ISSN: 14350661
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Soil Science Society of America Journal, Nov-Dec, 2004, Vol.68(6), p.1853(10)
    Description: Recent [N.sub.2] adsorption studies have suggested a 'pore clogging' effect on mineral soil phases caused by organic matter coatings. For methodological reasons, this pore clogging effect has been studied only after drying. Our hypothesis was that pore clogging is affected by drying of organic coatings. In our study, we used AlOOH, which has been equilibrated with dissolved organic matter (DOM) and polygalacturonic acid [[PGA; [([C.sub.6][H.sub.8][O.sub.6]).sup.n]]. To test our hypothesis, we determined the porosity of moist and freeze-dried AlOOH samples. Freeze-dried samples were analyzed by [N.sub.2] adsorption, moist samples by [sup.1]H-nuclear magnetic resonance (NMR). In addition, the samples were characterized by environmental scanning electron microscopy--energy dispersive x-ray spectroscopy (ESEM-EDX). Both, DOM and PGA significantly reduced specific surface area (SS[A.sub.BET]) of AlOOH by 34 [m.sup.2][g.sup.-1](15%) and 77 [m.sup.2] [g.sup.-1] (36%). The reduction in SS[A.sub.BET] normalized to the amount of C sorbed was 1.0 [m.sup.2] [mg.sup.-1] DOM-C and 5.9 [m.sup.2] [mg.sup.-1] PGA-C. Dissolved OM reduced the pore volume of micro- and small mesopores 〈3 nm whereas PGA also reduced the volume of larger pores. The [sup.1]H-NMR results of moist samples showed that PGA sorption reduced the amount of water in pores 〈4 nm. In addition, the pore size maximum of AlOOH increased by 150%. Polygalacturonic acid coatings created new interparticle pores of about 10- to 70-nm size that are not stable upon freeze-drying. Porosity changes upon DOM-treatment were not commensurable by [sup.1]H-NMR. Our results indicate that clogging of micro- and small mesopores is not an artifact of freeze-drying. Polygalacturonic acid seems not only to cover the mouth of AlOOH-nanometer pores but also to fill them.
    Keywords: Soil Mineralogy -- Research
    ISSN: 0361-5995
    E-ISSN: 14350661
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: Journal of Plant Nutrition and Soil Science, October 2010, Vol.173(5), pp.644-653
    Description: Riparian forests are assumed to play a crucial role in the global carbon cycle. However, little data are available on C stocks of floodplains in comparison to other terrestrial ecosystems. In this study, we quantified the C stocks of aboveground biomass and soils of riparian vegetation types at 76 sampling sites in the Donau‐Auen National Park in Austria. Based on our results and a remotely sensed vegetation map, we estimated total C stocks. Carbon stocks in soils (up to 354 t ha within 1 m below surface) were huge compared to other terrestrial ecosystems. As expected, soils of different vegetation types showed different texture with a higher percentage of sandy soils at the softwood sites, while loamy soils prevailed at hardwood sites. Total C stocks of vegetation types were significantly different, but reflect differences in woody plant biomass rather than in soil C stocks. Mature hardwood and cottonwood forests proved to have significantly higher total C stocks (474 and 403 t ha, respectively) than young reforestations (217 t ha) and meadows (212 t ha). The C pools of softwood forests (356 t ha) ranged between those of hardwood/cottonwood forests and of reforestations/meadows. Our study proves the relevance of floodplains as possible C sinks, which should be increasingly taken into account for river management. Furthermore, we conclude that plant‐species distribution does not indicate the conditions of sedimentation and soil C sequestration over the time span of interest for the development of soil C stocks.
    Keywords: Carbon Stocks ; Organic Carbon ; Donau‐Auen National Park ; Fluvial Ecosystems ; Riparian Forest
    ISSN: 1436-8730
    E-ISSN: 1522-2624
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Journal of environmental quality, 2009, Vol.38(3), pp.933-9
    Description: Liming is a common technique suggested for the stabilization of shooting range sites. We investigated the effect of an increase in pH on the mobilization of soluble and dispersible (colloidal) Pb, As, and Sb. Our hypothesis was that the addition of divalent cations counteracts the pH-induced mobilization of soluble and colloidal metal(loid)s. We determined soluble (operationally defined as the fraction 〈 10 nm obtained after centrifugation) and dispersible (filter cut-off 1200 nm) As, Pb, Sb, Fe, and C(org) concentrations in the filtered suspensions of batch extracts of topsoil samples (C(org): 8%) from a former shooting range site following a pH increase to values between 3.5 and 7 by adding a monovalent (KOH) or a divalent (Ca(OH)(2)) base. In the Ca(OH)(2)-treated samples, dissolved metal(loid) concentrations were 62 to 98% lower than those titrated with KOH to similar pH. Similarly, Ca reduced the concentration of dispersible Pb by 95%, but had little or no impact on dispersible As and Sb. We conclude that the counterion valency controls the mobility of metal(loid)s by affecting the mobility and sorption capacity of the sorbents (e.g., colloids, organic matter).
    Keywords: Antimony -- Chemistry ; Arsenic -- Chemistry ; Cations, Divalent -- Chemistry ; Lead -- Chemistry ; Soil -- Analysis
    ISSN: 0047-2425
    E-ISSN: 15372537
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Journal of environmental quality, 2007, Vol.36(4), pp.1187-93
    Description: Drying of soil may increase the hydrophobicity of soil and affect the mobilization of colloids after re-wetting. Results of previous research suggest that colloid hydrophobicity is an important parameter in controlling the retention of colloids and colloid-associated substances in soils. We tested the hypothesis that air-drying of soil samples increases the hydrophobicity of water-dispersible colloids and whether air-drying affects the mobilization of colloid-associated heavy metals. We performed batch experiments with field-moist and air-dried (25 degrees C) soils from a former sewage farm (sandy loam), a municipal park (loamy sand), and a shooting range site (loamy sand with 25% C(org)). The filtered suspensions (〈1.2 microm) were analyzed for concentrations of dissolved and colloidal organic C and heavy metals (Cu, Cd, Pb, Zn), average colloid size, zeta potential, and turbidity. The hydrophobicity of colloids was determined by their partitioning between a hydrophobic solid and a hydrophilic aqueous phase. Drying increased hydrophobicity of the solid phase but did not affect the hydrophobicity of the dispersed colloids. Drying decreased the amount of mobilized mineral and (organo-)mineral colloids in the sewage farm soils but increased the mobilization of organic colloids in the C-rich shooting range soil. Dried samples released less colloid-bound Cd and Zn than field-moist samples. Drying-induced mobilization of dissolved organic C caused a redistribution of Cu from the colloidal to the dissolved phase. We conclude that drying-induced colloid mobilization is not caused by a change in the physicochemical properties of the colloids. Therefore, it is likely that the mobilization of colloids in the field is caused by increasing shear forces or the disintegration of aggregates.
    Keywords: Desiccation ; Hydrophobic and Hydrophilic Interactions ; Colloids -- Chemistry ; Metals, Heavy -- Analysis ; Soil -- Analysis
    ISSN: 0047-2425
    E-ISSN: 15372537
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Soil Science Society of America Journal, Sept-Oct, 2006, Vol.70(5), p.1547(9)
    Description: Organic coatings on Fe oxides can decrease the accessibility of intraparticle pores for oxyanions like phosphate. We hypothesized that the slow sorption of phosphate to goethite coated with polygalacturonate (PGA) is controlled by the accessibility of external goethite surfaces to phosphate rather than by diffusion of phosphate into micropores ([empty set] 〈 2 nm). We studied the phosphate sorption kinetics of pure and PGA-coated goethites that differed in their microporosity ([N.sub.2] at 77 K, 46 vs. 31 [mm.sup.3] [g.sup.-1]). Because drying may affect the structure or surface coverage of PGA, we also tested the effect of freeze-drying on the slow phosphate sorption. The samples were examined by gas adsorption ([N.sub.2], C[O.sub.2]) and electrophoretic mobility measurements. Phosphate sorption and PGA-C desorption were studied in batch experiments for 3 wk at pH 5. In PGA-coated samples, the slow phosphate sorption was independent of micropore volume. Phosphate displaced on average 57% of PGA-C within 3 wk. Similar to phosphate sorption, the PGA-C desorption comprised a rapid initial desorption, which was followed by a slow C desorption. Sorption competition between phosphate and presorbed PGA depended on the 〈10-nm porosity and the C loading of the adsorbent. The efficacy of phosphate to desorb PGA generally increased after freeze-drying. We conclude for PGA-coated goethites that (i) freeze-drying biased the slow phosphate sorption by changing the structure/surface coverage of PGA, and (ii) within the time frame studied, micropores did not limit the rate of the slow phosphate sorption. Rather, the slow, gradual desorption of PGA and/or the diffusion of phosphate through PGA coatings controlled the slow phosphate sorption to PGA-coated goethite.
    Keywords: Mineralogical Research -- Analysis ; Phosphates -- Research ; Sorption -- Research
    ISSN: 0361-5995
    E-ISSN: 14350661
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages