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  • 1
    Language: English
    In: Geochimica et Cosmochimica Acta, 2006, Vol.70(12), pp.2957-2969
    Description: Hydration of organic coatings in soils is expected to affect the sorption of oxyanions onto hydrous Fe and Al oxides. We hypothesized that the hydration of polygalacturonate (PGA) coatings on alumina (Al O ) increases their permeability for phosphate. Pure and PGA-coated alumina were equilibrated in deionized water for 2 and 170 h at pH 5 and 20 °C before studying (i) their porosity with N gas adsorption and H NMR relaxometry, (ii) structural changes of PGA-coatings with differential scanning calorimetry (DSC), and (iii) the kinetics of phosphate sorption and PGA desorption in batch experiments. Scanning electron micrographs revealed that PGA molecules formed three-dimensional networks with pores ranging in size from 〈10 to several hundred nanometers. Our NMR results showed that the water content of intraparticle alumina pores decreased upon PGA sorption, indicating a displacement of pore water by PGA. The amount of water in interparticle alumina pores increased strongly after PGA addition, however, and was attributed to water in pores of PGA and/or in pores at the PGA-alumina interface. The flexibility of PGA molecules and the fraction of a PGA gel phase increased within one week of hydration, implying restructuring of PGA. Hydration of PGA coatings increased the amount of phosphate defined as instantaneously sorbed by 84%, showing that restructuring of PGA enhanced the accessibility of phosphate to external alumina surfaces. Despite the fact that the efficacy of phosphate to displace PGA was higher after 170 h than after 2 h, a higher phosphate surface loading was required after 170 h to set off PGA desorption. Our findings imply that the number of PGA chain segments directly attached to the alumina surface decreased with time. We conclude that hydration/dehydration of polymeric surface coatings affects the sorption kinetics of oxyanions, and may thus control the sorption and transport of solutes in soils.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 2
    In: Environmental Microbiology, June 2016, Vol.18(6), pp.1988-2000
    Description: Phosphorus () is an important macronutrient for all biota on earth but similarly a finite resource. Microorganisms play on both sides of the fence as they effectively mineralize organic and solubilize precipitated forms of soil phosphorus but conversely also take up and immobilize . Therefore, we analysed the role of microbes in two beech forest soils with high and low content by direct sequencing of metagenomic deoxyribonucleic acid. For inorganic solubilization, a significantly higher microbial potential was detected in the ‐rich soil. This trait especially referred to  olibacter usiatus, likewise one of the dominating species in the data sets. A higher microbial potential for efficient phosphate uptake systems () was detected in the ‐depleted soil. Genes involved in starvation response regulation (, ) were prevalent in both soils. This underlines the importance of effective phosphate (ho) regulon control for microorganisms to use alternative sources during phosphate limitation. Predicted genes were primarily harboured by hizobiales, ctinomycetales and cidobacteriales.
    Keywords: Soil Microbiology – Analysis ; Nucleic Acids – Analysis ; Phosphates – Analysis ; Forest Soils – Analysis ; Soil Phosphorus – Analysis;
    ISSN: 1462-2912
    E-ISSN: 1462-2920
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  • 3
    Language: English
    In: Journal of Plant Nutrition and Soil Science, August 2016, Vol.179(4), pp.472-480
    Description: Among several environmental factors shaping soil microbial communities the impact of soil nutrients is of special interest. While continuous application mainly of N and P dramatically shifts community composition during fertilization, it remains unclear whether this effect is consistent in generic, unfertilized beech forest ecosystems of Germany, where differences in nutrient contents are mostly a result of the parental material and climatic conditions. We postulate that in such ecosystems nutrient effects are less pronounced due to the possibility of the soil microbiome to adapt to the corresponding conditions over decades and the vegetation acts as the major driver. To test this hypothesis, we investigated the bacterial community composition in five different German beech dominated forest soils, representing a natural gradient of total‐ and easily available mineral‐P. A community fingerprinting approach was performed using terminal‐Restriction Fragment Length Polymorphism analysis of the 16S rRNA gene, while abundance of bacteria was measured applying quantitative real‐time PCR. Bacterial communities at the five forest sites were distinctly separated, with strongest differences between the end‐members of the P‐gradient. However the majority of identified microbial groups (43%) were present at all sites, forming a core microbiome independent from the differences in soil chemical properties. Especially in the P‐deficient soil the abundance of unique bacterial groups was highly increased, indicating a special adaption of the community to P limitation at this site. In this regard Correspondence Analysis elucidated that exclusively soil pH significantly affected community composition at the investigated sites. In contrast soil C, N and P contents did mainly affect the overall abundance of bacteria.
    Keywords: Core Microbiome ; Forest Soil ; Nutrient Content ; Diversity
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 4
    In: Environmental Microbiology, September 2016, Vol.18(8), pp.2767-2767
    Description: Byline: Fabian Bergkemper, Anne Scholer, Marion Engel, Friederike Lang, Jaane Kruger, Michael Schloter, Stefanie Schulz ***** No abstract is available for this article. *****
    Keywords: Recycling ; Forest Soils ; Soil Microbiology;
    ISSN: 1462-2912
    E-ISSN: 1462-2920
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  • 5
    Language: English
    In: Plant and Soil, 2018, Vol.432(1), pp.289-301
    Description: The accumulation of organic layers in forests is linked to decreasing nutrient availability. Organic layers might represent a source of phosphorus (P) nutrition of trees in forests. Our aims were i) to test if the fate of P in a tree sapling-soil system differs between nutrient-poor and nutrient-rich sites, and ii) to assess the influence of organic layers on the fate of P in a tree sapling-soil system at either site.We conducted a 33P labeling experiment of mesocosms of beech (Fagus sylvatica) saplings.Recovery of 33P in the organic layer was greater under nutrient-poor than under nutrient-rich conditions likely caused by the abundance of microorganisms and roots. Under nutrient-poor conditions, we found that the mobilization of P followed by efficient uptake promoted tree sapling growth if the organic layer was present. The presence of organic layers did not significantly influence P uptake by beech saplings under nutrient-rich conditions suggesting mechanisms of P mobilization in addition to organic matter mineralization.Our results highlight the importance of organic layers for P nutrition of young beech trees growing on nutrient-poor soils in temperate forest ecosystems. The role of organic layers should be considered for sustainable forest management.
    Keywords: P tracer ; Phosphorus nutrition ; Forest floor ; Soil ; Beech ; Phosphorus uptake
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 6
    Language: English
    In: Plant and Soil, 2018, Vol.427(1), pp.71-86
    Description: Background and aims Nanoparticles and colloids affect the mobilisation and availability of phosphorus for plants and microorganisms in soils. We aimed to give a description of colloid sizes and composition from forest soil profiles and to evaluate the size-related quality of colloids for P fixation. Methods We investigated the size-dependent elemental composition and the P content of water-dispersible colloids (WDC) isolated from five German (beech-dominated) forest soil profiles of varying bulk soil P content by field-flow fractionation (FFF) coupled to various detectors. Results Three size fractions of WDC were separated: (i) nanoparticles 25 nm (NP) rich in C.sub.org, (ii) fine colloids (25 nm-240 nm; FC) composed mainly of C.sub.org, Fe and Al, probably as associations of Fe- and Al- (hydr)oxides and organic matter, and (iii) medium-sized colloids (240 nm-500 nm; MC), rich in Fe, Al and Si, indicating the presence of phyllosilicates. The P concentration in the overall WDC was up to 16 times higher compared to the bulk soil. The NP content decreased with increasing soil depth while the FC and MC showed a local maximum in the mineral topsoil due to soil acidification, although variant distributions in the subsoil were observed. NP were of great relevance for P binding in the organic surface layers, whereas FC- and MC-associated P dominated in the Ah horizon. Conclusion The nanoparticles and colloids appeared to be of high relevance as P carriers in the forest surface soils studied, regardless of the bulk soil P content.
    Keywords: Colloids ; Field-flow fractionation ; Forest soil ; Nanoparticles ; Phosphorus
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 7
    Language: English
    In: Journal of Microbiological Methods, June 2016, Vol.125, pp.91-97
    Description: Phosphorus (P) is of central importance for cellular life but likewise a limiting macronutrient in numerous environments. Certainly microorganisms have proven their ability to increase the phosphorus bioavailability by mineralization of organic-P and solubilization of inorganic-P. On the other hand they efficiently take up P and compete with other biota for phosphorus. However the actual microbial community that is associated to the turnover of this crucial macronutrient in different ecosystems remains largely anonymous especially taking effects of seasonality and spatial heterogeneity into account. In this study seven oligonucleotide primers are presented which target genes coding for microbial acid and alkaline phosphatases ( , ), phytases ( ), phosphonatases ( ) as well as the quinoprotein glucose dehydrogenase ( ) and different P transporters ( , ). Illumina amplicon sequencing of soil genomic DNA underlined the high rate of primer specificity towards the respective target gene which usually ranged between 98% and 100% ( : 87%). As expected the primers amplified genes from a broad diversity of distinct microorganisms. Using DNA from a beech dominated forest soil, the highest microbial diversity was detected for the alkaline phosphatase ( ) gene which was amplified from 15 distinct phyla respectively 81 families. Noteworthy the primers also allowed amplification of from 6 fungal orders. The genes coding for acid phosphatase ( ) and the quinoprotein glucose dehydrogenase ( ) were amplified from 20 respectively 17 different microbial orders. In comparison the phytase and phosphonatase ( , ) primers covered 13 bacterial orders from 2 different phyla respectively. Although the amplified microbial diversity was apparently limited both primers reliably detected all orders that contributed to the P turnover in the investigated soil as revealed by a previous metagenomic approach. Genes that code for microbial P transporter ( , ) were amplified from 13 respectively 9 distinct microbial orders. Accordingly the introduced primers represent a valuable tool for further analysis of the microbial community involved in the turnover of phosphorus in soils but most likely also in other environments.
    Keywords: Phosphorus Turnover ; Forest Soil ; Phod ; Phon ; Appa ; Pita ; Psts ; Biology
    ISSN: 0167-7012
    E-ISSN: 1872-8359
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  • 8
    Language: English
    In: Environmental Chemistry, 2014, Vol.11(6), p.709
    Description:  The supramolecular structure and resulting physicochemical properties of soil organic matter (SOM) significantly control storage and buffer functions of soils, e.g. for nutrients, organic molecules and water. Multivalent cations, able to form complexes, are suggested to form inter- and intramolecular cross-links in SOM. At present, specific effects of the valence and type of cation on SOM properties are incompletely understood. We investigated changes in SOM interfacial properties, its ability to release mobile colloids in aqueous solutions and its sorption affinity towards organic chemicals in dependence on cation–SOM interactions, temperature and aging time.
    Keywords: colloids; contact angle; sorption; X-ray photoelectron spectroscopy.;
    ISSN: 1448-2517
    E-ISSN: 14498979
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  • 9
    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
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  • 10
    Language: English
    In: Journal of Thermal Analysis and Calorimetry, 2014, Vol.118(2), pp.1203-1213
    Description: Multivalent cations are suggested to influence the supramolecular structure of soil organic matter (SOM) via inter- and intra-molecular interactions with SOM functional groups. In this study, we tested the combined effect of cations, temperature treatment, and isothermal aging on SOM matrix properties. Samples from a peat and a mineral soil were either enriched with Na, Ca, and Al or desalinated in batch experiments. After treatment at 25, 40, 60, and 105 °C and after different periods of aging at 19 °C and 31 % relative humidity, we investigated the physicochemical matrix stability and the thermal stability against combustion. We hypothesized that multivalent cations stabilize the SOM matrix, that these structures disrupt at elevated temperatures, and that aging leads to an increase in matrix stability. The results show that cation-specific effects on matrix rigidity started to evolve in the peat only after 8 weeks of aging and were significantly lower than the temperature effects. Temperature treatment above 40 °C caused a non (or not immediately) reversible loss of water molecule bridges (WaMB) and above 60 °C a partly reversible melting process probably of semi-crystalline poly(methylene). Thermal stability increased with increasing cation valence and degree of protonation and was much less affected by temperature. Generally, Na-treated and control samples revealed lower thermal stability and lower increase in matrix rigidity with aging than those treated with Ca, Al, and H. We conclude that drying at elevated temperatures (〉40 °C) may irreversibly change SOM structure via disruption of labile cross-links and melting of semi-crystalline domains.
    Keywords: Cation ; Combustion enthalpy ; Differential scanning calorimetry (DSC) ; Soil organic matter (SOM) ; Step transition
    ISSN: 1388-6150
    E-ISSN: 1588-2926
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