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  • Soil Organic Matter
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  • 1
    Language: English
    In: Catena, April 2016, Vol.139, pp.9-18
    Description: Riparian woodlands consist of different landscape units characterized by different hydroecomorphological site conditions that are reflected in the distribution of soils and tree species. These conditions are determined by flooding frequency and duration, distance to river channels, elevation and water flow velocity. The influence of these environmental drivers on the stabilization of soil organic matter (SOM) has as yet not been investigated. Hence, the aim of our study is to link soil formation and its drivers with stabilizing processes of SOM in riparian floodplain forests. We investigated soils and sediments at two sites in the ash–maple–elm–oak alluvial forest zone (AMEO sites) and two sites in the willow-poplar alluvial forest zone (WiP sites) within the riparian zone of the Danube near Vienna (Austria). Sediments and soils were characterized based on texture, contents of organic carbon (OC), nitrogen, Fe oxides, and soil pH. Density fractionation was used to separate OC fractions in terms of stabilization process and resulting organic matter (OM) turnover time: the free light fraction (fast turnover), the light fraction occluded in aggregates (intermediate turnover) and the heavy fraction of OM associated tightly to mineral surfaces (slow turnover). At both sites, soil and sediment properties reflect the hydroecomorphological site conditions for formation of the landscape units in the riparian zone: Soils at AMEO sites develop during constant deposition of fine-textured sediment while water flow velocity is low. Progressing soil development causes a continuous decrease in OC content with increasing soil depth, mainly from fractions with fast and intermediate turnover. As a consequence the heavy fraction clearly dominates with around 90% of OC. Temporally variable flooding conditions with occurring turbulences found at WiP sites result in a discontinuous change of soil properties with increasing soil depth. Former topsoil horizons buried by huge amounts of sediments seem to keep the OC fractionation typical for topsoil horizons with extraordinarily high amounts of light fraction OM (free and occluded) representing 20–40% of total OC. The presented results confirm that sedimentation and soil formation are simultaneous processes at AMEO sites. At WiP sites both processes seem uncoupled with alternate phases of sedimentation and soil formation. Thus, the frequent burial of topsoil material formed at WiP sites seems to enable the conservation of unstable organic matter fractions at this part of active floodplains.
    Keywords: Fluvisol Formation ; Soil Organic Matter ; Density Fractionation ; Riparian Floodplains ; Soil Aggregates ; Riparian Forests ; Sciences (General) ; Geography ; Geology
    ISSN: 0341-8162
    E-ISSN: 1872-6887
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  • 2
    Language: English
    In: Journal of Soils and Sediments, 2015, Vol.15(1), pp.1-12
    Description: Byline: Daniela Gildemeister (1,2), George Metreveli (1), Sandra Spielvogel (3), Sabina Hens (1,4), Friederike Lang (5), Gabriele E. Schaumann (1) Keywords: Cation bridges; Cross-link; Differential scanning calorimetry; Dissolved organic matter; Glass transition; Water molecule bridges Abstract: Purpose Precipitation of dissolved organic matter (DOM) by multivalent cations is important for biogeochemical cycling of organic carbon. We investigated to which extent cation bridges are involved in DOM precipitation and how cross-links by cations and water molecule bridges (WaMB) stabilise the matrix of precipitated DOM. Materials and methods DOM was precipitated from the aqueous extract of a forest floor layer adding solutions of Ca(NO.sub.3).sub.2, Al(NO.sub.3).sub.3 and Pb(NO.sub.3).sub.2 with different initial metal cation/C (Me/C) ratios. Precipitates were investigated by differential scanning calorimetry before and after ageing to detect cation bridges, WaMB and restructuring of supramolecular structure. Results and discussion Twenty-five to sixty-seven per cent of the dissolved organic carbon was precipitated. The precipitation efficiency of cations increased in the order Ca〈Al〈Pb, while the cation content of precipitates increased in the order Pb〈Ca〈Al. The different order and the decrease in the WaMB transition temperature (T*) for Al/C〉3 is explained by additional formation of small AlOOH particles. Thermal analysis indicated WaMB and their disruption at T* of 53--65 [degrees]C. Like cation content, T* increased with increasing Me/C ratio and in the order Ca〈Pb〈Al for low Me/C. This supports the general assumption that cross-linking ability increases in the order Ca〈Pb〈Al. The low T* for high initial Me/C suggests less stable and less cross-linked precipitates than for low Me/C ratios. Conclusions Our results suggest a very similar thermal behaviour of OM bound in precipitates compared with soil organic matter and confirms the relevance of WaMB in stabilisation of the supramolecular structure of cation-DOM precipitates. Thus, stabilisation of the supramolecular structure of the DOM precipitates is subjected to dynamics in soils. Author Affiliation: (1) Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, Universitat Koblenz-Landau, Fortstr. 7, 76829, Landau, Germany (2) Umweltbundesamt, FG IV 2.2 Pharmaceuticals, Worlitzer Platz 1, 06844, Dessau-Ro[sz]lau, Germany (3) Department of Geography, Institute of Integrated Natural Sciences, Universitat Koblenz-Landau, Universitatsstr. 1, 56070, Koblenz, Germany (4) GN Dr. Netta Beratende Ingenieure und Geowissenschaftler, Bienengarten 3, 56072, Koblenz, Germany (5) Albert-Ludwigs-Universitat Freiburg, Institute of Forest Sciences, 79085, Freiburg i.Br., Germany Article History: Registration Date: 09/07/2014 Received Date: 02/04/2014 Accepted Date: 09/07/2014 Online Date: 30/07/2014 Article note: Responsible editor: Dong-Mei Zhou Electronic supplementary material The online version of this article (doi: 10.1007/s11368-014-0946-9) contains supplementary material, which is available to authorized users.
    Keywords: Cation bridges ; Cross-link ; Differential scanning calorimetry ; Dissolved organic matter ; Glass transition ; Water molecule bridges
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 3
    Language: English
    In: Plant and Soil, 2018, Vol.427(1), pp.53-69
    Description: Background and aims Phosphorus (P) availability is crucial for forest ecosystem productivity and soil organic matter (SOM) is an important source for P. This study was conducted to reveal carbon (C), nitrogen (N) and P distributions in functional SOM fractions. We hypothesised that (1) most of the organic P (P.sub.org) is part of the particulate SOM, (2) particulate SOM stores increasing share of P with decreasing soil P content and (3) the C:P.sub.org ratio of mineral-associated SOM is smaller than that of particulate SOM. Methods We analysed soil samples from five temperate forest sites (Fagus sylvatica) under different geological parent material with a wide range of total P concentrations. Density fractionation was used to separate free light fraction (fLF), particulate SOM occluded within soil aggregates (occluded light fraction; oLF), and mineral associated SOM (heavy fraction; HF). We determined the mass balance of P in these fractions, in addition to the C and N concentrations. Additionally, the P speciation of the topsoil was analysed by X-ray absorption near edge structure (XANES) spectroscopy at the P K-edge. Results The fLF contained 18-54% and the oLF 1-15% of total P (P.sub.tot). High percentage of P in these light fractions was associated to soil minerals. Phosphorous in particulate SOM within aggregates tend to increase with decreasing soil P. The HF containing mineral-associated OM, comprised 38-71% of P.sub.tot and their C:P.sub.org ratios were consistently lower than those of the fLF irrespective of the P status of the soil. Conclusions We show that all three functional SOM fractions contain variable amount of both organic and inorganic P species. The free light fraction shows no response to changing P stocks of soils.. Despite physically protected particulate SOM, oLF, becomes increasingly relevant as P cache in soils with declining P status.
    Keywords: Ecosystem nutrition ; Density fractions ; Soil organic matter ; C:N:P ratio ; Phosphorus ; P K-edge XANES
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 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
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  • 5
    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
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  • 6
    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
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  • 7
    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
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  • 8
    Language: German
    Description: Moorböden sind wirksame Speicher für Kohlenstoff (C) und damit bedeutend für das globale Klima. Naturnahe Moorböden mit hohen Wasserständen können beträchtliche Mengen an C akkumulieren. Durch Entwässerung verlieren sie ihre Netto-Senkenfunktion und setzen verstärkt C frei. Neben äußeren Umweltbedingungen spielt die Qualität der organischen Bodensubstanz (OBS) die entscheidende Rolle bei der C-Freisetzung aus Moorböden. Gegenwärtig fehlen allerdings detaillierte Daten, die Aussagen zur Qualität der OBS und zur potentiellen C-Freisetzung erlauben. Die vorliegende Arbeit untersucht die Qualität der OBS und das C-Freisetzungspotential ausgewählter Moorböden in Abhängigkeit von Bildungsbedingungen und Entwässerungsintensitäten mit unterschiedlichen methodischen Ansätzen. Mittels Infrarotspektroskopie konnten deutliche Unterschiede in den Absorptionsspektren zwischen Nieder- und Hochmoortorfen und zwischen unterschiedlich stark entwässerten Torfen gefunden werden. Um das C-Freisetzungspotential zu untersuchen, wurde die labile Fraktion der OBS bestimmt. Dafür wurde eine Methode zur Heißwasserextraktion organischer Böden entwickelt, die erfolgreich an Torfen unterschiedlicher Moorstandorte angewendet werden konnte. In einem weiteren Schritt wurde das Verhältnis von Gesamt-C zu OBS von Moorbodenhorizonten bestimmt. Die dabei gefundenen Abhängigkeiten von der jeweiligen Torfart und der Entwässerungsintensität belegen die Notwendigkeit für angepasste Umrechnungsfaktoren, um Fehler bei C-Bilanzierungen zu vermeiden. Außerdem wurde ein Entscheidungssystem zur Moortypenklassifikation sowie zur Berechnung der C-Speichermengen und C-Freisetzungspotentiale für Moorflächen unbekannten Typs entwickelt. Die Ergebnisse der vorliegenden Arbeit können zu einem besseren Verständnis von stofflichen Transformationen in Moorökosystemen beitragen. Peatland soils store huge amounts of organic Carbon (C) and play a substantial role in the global climate system. Undisturbed peatlands with high water-tables accumulate significant C amounts. Through drainage, they change from C-sinks to C-sources. Beside various environmental factors, the quality of soil organic matter (SOM) strongly affects C-release out of peatland soils. Detailed data on SOM quality and potential C-release is currently missing. The present study investigates the quality of SOM and the C-release potential of selected peatland soils depending on building conditions and drainage intensities using various methodical approaches. With infrared spectroscopy, differences in absorption bands between fen and bog peats, as well as between peats under different influence of drainage could be found. The C release potential was investigated by determination of the labile fraction of SOM. For this purpose, a method for the hot-water-extraction of organic soils was developed and could successfully be applied for peats out of different sites. Additionally, organic C in relation to SOM was studied which showed clear relationships with peat types and level of drainage and demonstrates the need for an individual adaption of conversion factors when assessing C stocks. Furthermore, a decision support system for the determination of hydrogenetic mire types and the calculation of C-storages and C-release potentials of unknown peatland areas was developed. The results of the present study may contribute to a better understanding of organic matter transformation in peatlands.
    Keywords: Entwässerung ; Moorböden ; Organische Bodensubstanz ; Kohlenstofffreisetzung ; Moorbildung ; Drainage ; Peatland Soils ; Soil Organic Matter ; Carbon Release ; Mire Formation ; 550 Geowissenschaften ; 31 Geowissenschaften ; Ddc:550
    Source: Networked Digital Library of Theses and Dissertations
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