1,721,162 research outputs found
Characterization of organic carbon in decomposing litter exposed to nitrogen and sulfur additions: Links to microbial community composition and activity
No full textUnderstanding the links between litter chemical transformations and functional microbial communities is key to elucidating the mechanisms of litter decomposition processes under nitrogen (N) and sulfur (S) deposition. Carbon (C)-13-labelled Pinus massoniana needles were incubated in a subtropical plantation forest soil exposed to: no amendment (Control), N amendments of 81 (N1) and 270 (N2) mg kg− 1, S amendments of 121 (S1) and 405 (S2) mg kg− 1 and combined N and S amendments. Litter decomposition was measured as litter-derived carbon dioxide (CO2) emissions and the litter C pools were partitioned using a two-pool model. Relationships between litter residue chemistry (assessed by 13C nuclear magnetic resonance spectroscopy analysis) and microbial community composition (probed by phospholipid fatty acid analysis, PLFA) and activity (the metabolic quotient, qCO2) were investigated. Over the 420 days incubation period, N and S additions (except N and S addition alone at low rate) significantly increased litter decomposition by 7.2–18.9% compared to the Control. Decomposition was stimulated by 10.2–61.9% during the initial 56 days (stage 1) and in contrast, 8.3–42.1% inhibition was measured during 57–420 days (stage 2) across the addition treatments. Stimulation on litter-derived CO2 emissions under the N and S additions was largely dependent on the loss of O-alkyl C, a dominant component of the litter active C pool. During the initial 7 days, N and S additions increased the ratio of fungal to bacterial PLFAs compared to the Control, which was accompanied by the increases in methoxyl C. The activity of microbes, particularly gram-negative bacteria, was also increased by N and S additions at stage 1, which was related to di-O-alkyl C. In contrast, fungal activity decreased under N and S additions at stage 2, accompanied by lowered C availability and increased methoxyl C. Alkyl C and aromatic C in the litter had positive relationships with the half-life of the slow C pool. Accordingly, the residue recalcitrance was increased under N and S additions compared with Control at stage 2, and was largely responsible for the inhibition of litter decomposition. Thus, N and S deposition is likely to increase the persistence of litter-derived recalcitrant C in subtropical forest soils in the long term
Heavy metals in agricultural soils: From bioavailability to productivity
No full textHeavy metals in agricultural soils have close relationships with multiple soil components (e.g., organic matter, minerals, and microorganisms), which are then redistributed into different chemical forms with varying bioavailability, mobility, and toxicity. This distribution is believed to be controlled by a series of reactions such as mineral precipitation or dissolution, aqueous complexation, biological accumulation, and plant uptake. Heavy metals in agricultural soils not only decrease the growth and yield of plants due to phytotoxicity but also enter the food chain to disturb human metabolomics. Therefore, the transfer and accumulation of heavy metals in soil-plant systems should be particularly addressed for One Health, a program of the World Health Organization. Although heavy metal pollution in agriculture is often dominated by low and medium concentration pollution, its remediation requirements are different from those required for industrial sites. The requirements of agricultural conditions need to be met. Heavy metal remediation should be cost-effective and environmentally friendly. Bioremediation is an emerging technique in recent years, and it is also considered as a sustainable technique
How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar
No full textOn the carbon abatement potential and economic viability of biochar production systems: cost-benefit and life cycle assessment
No full textBiochar production systems are regarded as one of the promising candidates to tackle the triple crisis of increasing energy demand, waste pileup, and climate change. Economics and environmental sustainability are essential indexes to evaluate biochar production. In this chapter, we have an overview of the economic and environmental analysis methods, that is, life cycle assessment (LCA) and cost-benefit analysis (CBA) and their applications to the evaluation of biochar production systems. The products of biochar production systems are evaluated in terms of their economic and environmental impacts. The major factors associated with the carbon abatement potential and economic viability of biochar production are identified to guide the design of biochar production systems. The complication of biochar pricing systems is discussed with an emphasis on the balance between economics and carbon abatement. Finally, the cases of uncertainty analysis are introduced followed by the future development directions of LCA and CBA of biochar production systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Lead immobilization and bioavailability in microbial and root interface
No full textA range of both soluble and insoluble phosphate (P) compounds have been used to immobilize Pb in solution and soil. However, these compounds have limitations because of low solubility or leaching of P. Phosphate solubilizing bacteria (PSB) can be used to enhance the solubility of insoluble P compounds. The effects of PSB on the immobilization of Pb in the presence of phosphate rock (PR) and subsequent reduction in Pb uptake by Indian mustard (Brassica juncea) in nutrient agar medium and ryegrass (Lolium perenne) in soil under sterile condition were tested. Root colonization of PSB was confirmed by halo formation around the root in the medium containing tricalcium phosphate. Addition of PR in the presence of PSB immobilized Pb in both agar medium and soil, and reduced Pb translocation from root to shoot. Furthermore, shoot Pb concentrations of Indian mustard in agar medium and ryegrass in soil were decreased by 58.1% and 22.8%, respectively, compared to the control. Even though soluble P compound was the most effective in the immobilization of Pb, excess P may cause eutrophication. Therefore, PSB are suggested as a co-amendment to facilitate immobilization of Pb without causing any detrimental effect on the environment
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