Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • Chemistry
Type of Medium
Language
Year
  • 1
    Language: English
    In: Chemosphere, 2011, Vol.84(6), pp.798-805
    Description: Harvests of crops, their trade and consumption, soil erosion, fertilization and recycling of organic waste generate fluxes of phosphorus in and out of the soil that continuously change the worldwide spatial distribution of total phosphorus in arable soils. Furthermore, due to variability in the properties of the virgin soils and the different histories of agricultural practices, on a planetary scale, the distribution of total soil phosphorus is very heterogeneous. There are two key relationships that determine how this distribution and its change over time affect crop yields. One is the relationship between total soil phosphorus and bioavailable soil phosphorus and the second is the relationship between bioavailable soil phosphorus and yields. Both of these depend on environmental variables such as soil properties and climate. We propose a model in which these relationships are described probabilistically and integrated with the dynamic feedbacks of cycling in the human ecosystem. The model we propose is a first step towards evaluating the large-scale effects of different nutrient management scenarios. One application of particular interest is to evaluate the vulnerability of different regions to an increased scarcity in mineral fertilizers. Another is to evaluate different regions’ deficiency in total soil phosphorus compared with the level at which they could sustain their maximum potential yield without external mineral inputs of phosphorus but solely by recycling organic matter to close the nutrient cycle.
    Keywords: Probabilistic Modeling ; Phosphorus Bioavailability ; Global Cycle ; Food Supply ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Soil Biology and Biochemistry, December 2014, Vol.79, pp.117-124
    Description: Crop production in subsistence agriculture in tropical Africa is still sustained mainly by short-to medium-term fallows to recuperate natural fertility of the soils. Microbes play a pivotal role both in the process of soil fertility restoration and in nutrient acquisition by the crops. Here we ask the question how the duration of fallow affects the composition of indigenous arbuscular mycorrhizal fungal (AMF) communities and their contribution to maize nutrition and growth, in acidic, low P soils of southern Cameroon. This question has been addressed in a bioassay where soils collected from continuously cropped fields, short-term fallows dominated by and long-term fallows (secondary forests) have been sterilized and back- and cross inoculated with living soils from the different land-use systems. Particular microbes larger than the pore size of the filter paper (mainly the fungi including the AMF) contained in the cropped and short-fallowed soils caused greater growth and P uptake stimulations to the maize as compared to the forest soil. By using molecular profiling, we demonstrated a shift in the composition of AMF communities along a gradient of fallow duration, changing from dominance by in the forest fallow soil, to dominance by under cropland. Our results contradict the hypothesis that deterioration of quality of root symbiotic communities would be responsible for a rapid yield decline following deforestation, and indicate a positive feedback of cropping on mycorrhizal functioning under conditions of shifting agriculture in tropical Africa.
    Keywords: Arbuscular Mycorrhiza ; Bioassay ; Chromolaena Odorata ; Fallow ; Maize ; Phosphorus ; Quantitative Real-Time Pcr ; Southern Cameroon ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Soil Biology and Biochemistry, December 2015, Vol.91, pp.298-309
    Description: The identification and quantification of different soil organic phosphorus (P) compounds is crucial for a better understanding of soil P dynamics. The aim of this study was to compare two commonly used characterisation methods: P NMR spectroscopy and enzyme addition assays (EAAs). The same 0.25 M NaOH and 0.05 M ethylenediaminetetraacetic acid (EDTA) extracts of ten temperate and tropical topsoils under arable crops or permanent grassland were analysed by each method. Additionally, the substrate specificity of the used enzymes was verified through P NMR analysis of one enzyme-treated soil extract. Finally, the molecular weight distribution of organic P was characterised using gel filtration chromatography. NaOH-EDTA extractable organic P ranged from 7 to 1108 mg P kg soil. Using P NMR spectroscopy, six organic P species in the mono- and diester region plus orthophosphate, pyrophosphate and phosphonates were detected. Deconvolution of P NMR spectra was not possible for two soils due to poor signal to noise ratio. Using EAAs, inositol phosphate-like P was identified as the largest enzyme-labile organic P class in most soils, followed by monoester-like P and DNA-like P. Corresponding classes of organic P determined by P NMR and EAAs were established and concentrations were found to agree well in general. However, repeatability was higher for P NMR spectroscopy than for EAAs. P NMR spectroscopy on an enzyme-treated extract showed that each enzyme acted on the anticipated organic P class, although treatment with phytase caused the appearance of a new and yet unidentified peak in the monoester region. Gel filtration chromatography of alkaline extracts revealed the presence of high-molecular weight organic P (〉5 kDa) which had a 1:1 relationship with enzyme-stable P. For both methods, advantages and drawbacks with respect to required sample pre-treatment, analysis time and cost and the total number of identifiable compounds are discussed. While EAAs are suitable for a quick and coarse characterisation of larger sample numbers, P NMR is more robust and allows a more detailed quantification of P forms.
    Keywords: Organic Phosphorus ; 31p NMR ; Enzyme Additions ; Method Comparison ; High Molecular Weight Compounds ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Soil Biology and Biochemistry, November 2018, Vol.126, pp.64-75
    Description: Understanding the mechanisms underlying phosphorus (P) availability is important to predict forest productivity in a changing environment. We quantified P fluxes and traced P from plant litter into inorganic and organic soil P pools in organic horizons from two contrasting temperate forest soils with low and high inorganic P availability, respectively. We incubated the two organic horizons with and without litter after labelling the soil solution with P and performed sequential extractions at several time points in order to trace P dynamics in labile (water-extractable, available and microbial P) and non-labile (non-living organic P, P bound to iron and aluminium and P bound to calcium) pools. Under low P availability, P fluxes were dominated by gross P mineralization, and microbial P immobilization accounted for up to 95% of gross P mineralization. Additionally, labile P in plant litter was rapidly incorporated into microbial P and only a small fraction ended up in the non-labile inorganic P pools. In contrast, P fluxes under high P availability were dominated by abiotic processes, particularly by fast (within 10 days) sorption/desorption reactions between the available P and the P bound to aluminium. These findings support the hypothesis that under low P availability biological processes control P fluxes. The observed tight cycling of P, with little efflux due to net P mineralization, suggests that the mineralization of organic P is driven by microbial P demand, and that the microbial community could compete with plants for available P.
    Keywords: Radioisotope Tracing ; Sequential Extraction ; Mineralization ; 33p ; Isotopic Dilution ; Litter Addition ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Soil Biology and Biochemistry, July 2014, Vol.74, pp.21-30
    Description: The abundance, distribution and functions of soil fungi in alpine ecosystems remain poorly understood. We aimed at linking the fungal community structure with soil enzymatic activities in the rhizospheres of several plants associating with mycorrhizal fungi (arbuscular, ecto- and ericoid) and growing along a soil developmental gradient on the forefield of an alpine glacier. Fungal communities in roots and in rhizosphere soils were assessed using a site-tailored set of quantitative PCR assays with fluorescent hydrolysis probes. Enzymatic activities of mycorrhizal roots and rhizosphere soils were assessed using fluorogenic substrates. In this study we addressed: i) whether and how the structure of fungal communities and enzymatic activities in rhizosphere soils change along the soil developmental gradient, ii) whether the type of mycorrhiza shows a clear relationship to the pattern of enzymatic activities in the rhizosphere, and iii) how the structure of fungal communities and enzymatic activities in rhizosphere soils is related to plant species abundances along the soil chronosequence. The results suggest that plant identity affected the structure of both ecto- and arbuscular mycorrhizal fungal communities in rhizosphere soil and roots, whereas the community of non-mycorrhizal fungi was rather dictated by the soil developmental stage. Both plant identity and associated mycorrhizal fungi affected the enzymatic activity in the rhizosphere soil. Species-specific elevations of rhizosphere enzyme activities were detected for (chitinase and α-glucosidase), (α-glucosidase and sulfatase), and (phosphatase and xylosidase). These results indicate different functional roles played by different types of mycorrhizal symbiosis in a young alpine ecosystem.
    Keywords: Fungal Community ; Structure and Functions ; Mycorrhiza ; Rhizosphere ; Enzymes ; Salix Helvetica ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Soil Biology and Biochemistry, June 2015, Vol.85, pp.10-20
    Description: Nitrogen (N) rhizodeposition is defined as the release of N from living plant roots into the soil and root turnover. The proportion of N in the soil derived from rhizodeposition (NdfR) is usually determined using N labelling of the plant. This assumes that i) the enrichment of rhizodeposits is equal to the root enrichment and that ii) the root remains homogeneously enriched over space and iii) over time. The aim of this study was to quantify the bias resulting from a possible violation of the mentioned assumptions and to study the causative factors of bias. We conducted two experiments with single-pulse N-urea leaf-labelled red clover ( L.). In the , we simultaneously observed the changes in substrate N concentration to obtain the rhizodeposits and determined the rhizodeposits using the . By comparing to rhizodeposits we quantified the bias of the for a period of 6 weeks. In the , we observed the root N enrichment over space and time (4 weeks) by sampling roots grown within certain periods relative to the labelling. In both experiments we monitored the N distribution between shoots and roots. We observed violations of the three assumptions of the . The average root enrichment increased over time in the root distribution experiment, but remained constant in the rhizodeposition experiment. Significant long-term translocation of N from shoot to root during the whole experiment (over)-compensated for growth dilution. Spatial root enrichment varied within a factor of 3, peaking in roots grown 2–8 days after labelling (d.a.l.). We observed a significant leakage of 0.5 ± 0.2% of the applied N within the first day after labelling corresponding to an overestimation of first-day rhizodeposits by 1100 ± 800% which translates to a calculated enrichment of 9 ± 6 atom% N excess for first-day rhizodeposits compared to 0.77 ± 0.09 atom% N excess of the root. The leaked N together with ordinary rhizodeposits (rhizodeposits released after the first day of labelling) led to an overestimation of N rhizodeposition by 70 ± 30% at the end of the six weeks lasting experiment using the . The observed N distribution in roots and long-term N translocation from shoots to roots did not correspond to the expected distribution following classical pulse labelling. Thus, leaf-labelling with N-urea should not be considered a pure pulse-labelling method.
    Keywords: Rhizodeposition ; Red Clover ; Bias ; 15n Leakage ; Pulse-Labelling ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Source: ScienceDirect Journals (Elsevier)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: Soil Biology and Biochemistry, June 2012, Vol.49, pp.184-192
    Description: Microbial communities are important components of terrestrial ecosystems. The importance of their diversity and functions for natural systems is well recognized. However, a better understanding of successional changes of microbial communities over long time scales is still required. In this work, the size and composition of microbial communities in soils of a deglaciation chronosequence at the Damma glacier forefield were studied by fatty acid profiling. Soil fatty acid concentrations clearly increased with soil age. The abundances of arbuscular mycorrhizal fungi (AMF), bacteria and other soil fungi, however, were more affected by abiotic soil parameters like carbon content and pH than by soil age. Analysis of ratios of the different microbial groups (AMF, fungi, bacteria) along the soil chronosequence indicated that: i) the ratios of AMF to bacteria and AMF to fungi decreased with soil age; and ii) the ratio of fungi to bacteria remained unchanged along the soil chronosequence. These two pieces of evidence suggest that the evolution of this ecosystem proceeds at an uneven pace over time and that the role of AMF is less important in older, more organic and acidified soils than in mineral soils. In contrast to other studies, no successional replacement of bacteria with fungi in more acidified and organic soil was observed. ► Microbial succession at a glacier forefield was investigated by fatty acid profiling. ► Concentrations of fatty acids in soil increase with soil age. ► Soil C and pH affect abundances of both soil bacteria and fungi. ► Ratios of AMF to bacteria or to soil fungi decrease with soil age. ► Ratio of soil fungi to bacteria remains constant along the soil chronosequence.
    Keywords: Fatty Acid Methyl Esters (Fame) ; Glacier Forefield ; Soil Chronosequence ; Microbial Community ; Mycorrhizal Fungi ; Community Size ; Environmental Determinants ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Soil Biology and Biochemistry, 2010, Vol.42(4), pp.558-566
    Description: Soil microorganisms are key regulators of the biogeochemical phosphorus (P) cycle. Microbial P limitation in highly weathered tropical soils has been reported, but whether it affects the cellular P content of indigenous soil microorganisms and its biochemical composition is unknown. We investigated the effect of microbial P limitation by measuring respiration, microbial growth, community composition and P content of microbial cells in a Ferralsol with low amounts of available P as affected by amendments with C substrates with ample nitrogen (CN) with and without extra phosphate (P). Microbial biomass and community composition were quantified by phospholipid fatty acid (PLFA) analyses. Cellular P content and P pools (PLFA, DNA and RNA per cell) were determined after extraction of microbial cells from soil by density gradient centrifugation. The apparent microbial growth rate during exponential increase in respiration rates in response to CNP addition was 0.072 h , compared to 0.017 h for the CN amendment (no extra P added). This suggests that the microbial growth after a combined C and N addition was retarded by P limitation in the native soil (without added P). The net increase in microbial biomass, however, reached similar levels for both the CN and CNP treatment (measured at the point in time when respiration rates peaked). This outcome was unexpected since maximum respiration rates were about three times higher in the CNP compared to the CN treatment. Total P in extracted cells ranged from 2.1 to 8.9 fg P cell (microscopic counts), with a tendency for lower values for treatments without C amendments. Only 10–25% of the measured total P in extracted cells was accounted for by the measured RNA, DNA and PLFA. This low percentage could partly be due to underestimation of the RNA pool (degradation during extraction). PLFA analyses showed that substrate induced growth, regardless of P addition, led to a change in microbial community composition and was dominated by fungi. The extraction of microbial cells from soil by density gradient centrifugation, however, discriminates against fungi. Accordingly, the extracted cells were not fully representative for the entire soil microbiota regarding the community composition and metabolic state. Nevertheless, for the first time microbial cell P content and P pools are reported for microorganisms that actually grew in soil and not in chemostat or batch cultures.
    Keywords: Cell Extraction ; Density Gradient Centrifugation ; Ferralsol ; Soil Microorganisms ; Substrate Induced Respiration ; Nutrient Limitation ; Phosphorus ; Chemical Composition ; Plfa ; DNA ; RNA ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Soil Biology and Biochemistry, March 2017, Vol.106, pp.51-60
    Description: Soil phosphorus (P) tests are designed to indicate plant-available inorganic orthophosphate (P ), but fail to account for P that may become available through organic phosphorus (P ) mineralization. This P source may be especially important in soils with low concentrations of solution and labile P . We assessed gross P mineralization and immobilization using labeling with P in four calcareous Alfisols with varying concentrations of Olsen soil test P that were collected from forage fields of dairy farms in Ontario, Canada. Rapid microbial P uptake during incubation was found for the soils with the lowest available P as indicated by both Olsen soil test P and water-extractable P . The tracer incorporation into microbial P after 8 days ranged from 7 to 44% of applied P and was negatively related to water-extractable P following a power-type relationship. As concentrations of microbial P were similar in all soils, this suggests faster turnover of P in the microbial biomass at water-extractable P below 0.1 mg P kg soil. Daily gross P mineralization rates ranged from 0.2 to 2.8 mg P kg soil d and contributed 7–56% of the isotopically-exchangeable P in 8 days. Based on these findings, microbial processes have the potential to make a significant contribution to forage P nutrition.
    Keywords: Organic Phosphorus Mineralization ; Isotopic Dilution Method ; 33p ; Available Phosphorus ; Perennial Forage ; Microbial P Turnover ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Soil Biology and Biochemistry, January 2014, Vol.68, pp.150-157
    Description: Maintaining the productivity of tropical pastures is a major challenge for the sustainable management of tropical landscapes around the globe. To address this issue, we examined linkages between soil organic matter (SOM), aggregation, and phosphorus (P) dynamics by comparing productive vs. degraded pastures in the deforested Amazon Basin of Colombia. Paired plots of productive (dominated by planted spp.) vs. degraded pasture were identified on nine farms in the Department of Caquetá and sampled during the rainy season of 2011. Aboveground pasture biomass production and nutrient content were measured. Surface soils (0–10 cm) were also fractionated by wet sieving, and C, C, N and P contents were analyzed for the bulk soil and various aggregate size classes. Productive pastures yielded more than double the aboveground biomass compared to degraded pastures (during a 35 day regrowth period following cutting), with over 60% higher N and P contents in this material. Similar trends were observed for the standing litter biomass and nutrient contents. Soil aggregate stability was found to differ between pasture types, with a mean weight diameter of 3590 vs. 3230 μm in productive vs. degraded pastures, respectively. Productive pastures were found to have 20% higher total soil C and N contents than degraded pastures. While there was no difference in total P content between pasture types, organic P was found to be nearly 40% higher in soils of productive vs. degraded pastures. Differences in total SOM between pasture types were largely explained by a higher C content in the large macroaggregate fraction (〉2000 μm), and more specifically in the microaggregates (53–250 μm) occluded within this fraction. These findings confirm the role of microaggregates within macroaggregates as a preferential site for the physical stabilization of SOM, and furthermore, suggest that it may serve as a useful diagnostic fraction for evaluating management impacts on SOM in tropical pasture systems. Similar to trends observed for C and N, total P content was 25% higher in the microaggregates within large macroaggregates of productive vs. degraded pasture soils. This correspondence between C and total P contents in large macroaggregate fractions, along with elevated levels of organic P in productive pastures, suggests that this P is likely in an organic form and that there is a close link between soil structure, SOM dynamics and the maintenance of organic P in these soils. Given the potential relevance of organic P for efficient P cycling in these soils, our findings offer critical new insight for the management of SOM and aggregate-associated P pools in tropical pasture systems.
    Keywords: Amazon Basin ; Colombia ; Phosphorus ; Soil Aggregation ; Soil Organic Matter ; Tropical Pasture ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
    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