1,721,016 research outputs found
Microbial respiration per unit biomass increases with carbon-to-nutrient ratios in forest soils
No full textThe ratio of carbon-to-nutrient in forest floors is usually much higher than the ratio of carbon-to-nutrient that soil microorganisms require for their nutrition. In order to understand how this mismatch affects carbon (C) cycling, we investigated the respiration rate per unit soil microbial biomass the metabolic quotient (qCO(2)) - in relation to the soil carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P) ratio in temperate forests. For this purpose, cores of beech, spruce, and mixed spruce-beech forest soils were cut into slices of 1 cm from the litter layer down to 5 cm in the mineral soil, and the relationship between the qCO(2) and the soil C:N and the soil C:P ratio was analyzed. We found that the qCO(2) was positively correlated with soil C:N ratio in spruce soils (R = 0.72), and with the soil C:P ratio in beech (R = 0.93), spruce (R = 0.80) and mixed forest soils (R = 0.96). We also observed a close correlation between the qCO(2) and the soil C concentration in all three forest types. Yet, the qCO(2) decreased less with depth than the C concentration in all three forest types, suggesting that the change in qCO(2) is not only controlled by the soil C concentration. We conclude that microorganisms increase their respiration rate per unit biomass with increasing soil C:P ratio and C concentration, which adjusts the substrate to their nutritional demands in terms of stoichiometry. (C) 2014 Elsevier Ltd. All rights reserved
Near-infrared spectroscopy for analysis of chemical and microbiological properties of forest soil organic horizons in a heavy-metal-polluted area
No full textIn industrial areas, heavy metals may accumulate in forest soil organic horizons, affecting soil microorganisms and causing changes in the chemical composition of the accumulated organic matter. The objectives of this study were to test the ability of near-infrared spectroscopy (NIRS) to detect heavy metal effects on the chemical composition of forest soil O horizons and to test whether NIRS may be used to quantitatively determine total and exchangeable concentrations of Zn and Pb (Zn-t, Pb-t, Zn-ex, Pb-ex) and other chemical and microbial properties in forest soil O horizons polluted with heavy metals. The samples of O horizons (n=79) were analyzed for organic C (C-org), total N and S (N-t, S-t), Zn-t, Pb-t, Zn-ex, Pb-ex, basal respiration (BR), microbial biomass (C-mic) and C-mic-to-C-org ratio. Spectra of the samples were recorded in the Vis-NIR range (400-2,500 nm). To detect heavy-metal-induced changes in the chemical composition of O horizons principal components (PC1-PC7) based on the spectral data were regressed against Zn-t + Pb-t values. A modified partial least squares method was used to develop calibration models for prediction of various chemical and microbial properties of the samples from their spectra. Regression analysis revealed a significant relationship between PC3 and PC5 (r=-0.27 and -0.34, respectively) and Zn-t + Pb-t values, indicating an effect of heavy metal pollution on the spectral properties of the O horizons and thus on their chemical composition. For quantitative estimations, the best calibration model was obtained for C-org-to-N-t ratio (r=0.98). The models for C-org, N-t, and microbial properties were satisfactory but less accurate. NIRS failed to accurately predict S-t, C-org-to-S-t, Zn-t, Pb-t, Zn-ex, and Pb-ex
The use of near infrared spectroscopy to quantify lignite-derived carbon in humus - lignite mixtures
No full textAssessment of the percentage of lignite-derived C (lign-C%) in mine soils may be achieved only by using time-consuming and expensive methods. The objectives of this study were (1) to compare near infrared (NIR) spectra of forest humus and lignite and (2) to test whether NIR spectroscopy may assess lign-C% in artificial mixtures of humus and lignite. The experiment consisted of three trials (T1, T2 and T3). In T1 the mixed samples (n = 75) were produced from one humus sample and one lignite sample, in T2 (n =74) from 74 different humus samples and one lignite sample and in T3 (n = 74) from 74 different humus samples and 15 lignite samples. In each trial, 35 samples were used to develop calibration equations and the remaining samples were used for validation. The humus and the lignite samples used to produce the mixed samples were analysed for C, H, N and S and their NIR spectra were recorded. The lignite samples contained more C, H and S and less N than the humus samples. Principal component analysis revealed significant differences between NIR spectra of the humus and the lignite samples. The prediction of lign-C% in T1 [regression coefficient (b) of linear regression (measured against predicted values) = 0.99, correlation coefficient (r(2)) = 1.00, standard error of prediction (SEP) = 1.2%] and T2 (b = 0.99, r(2) = 0.99, SEP = 1.9%) was very good and in T3 satisfactory (b = 0.83, r(2) = 0.92, SEP = 4.0%). The calibration equations of T2 predicted lign-C% satisfactorily and also in the validation samples of T3 (b = 0.88, r(2) = 0.93, SEP = 4.0%). The results indicate the ability of NIR spectroscopy to predict lign-C% in the mixed humus and lignite samples and suggest usefulness of NIR spectroscopy for the assessment of the percentage of lignite-derived C in the organic horizons of mine soils
Effect of temperature on the mineralization of C and N of fresh and mature compost in sandy material
No full textInformation about the mineralization rate of compost at various temperatures is a precondition to optimize mineral N fertilization and to minimize N losses in compost-amended soils. Objectives were to quantify the influence of the temperature on the mineralization rate and leaching of dissolved organic carbon (DOC) and nitrogen (DON), NO3-, and NH4+ from a fresh (C : N = 15.4) and a mature (C : N = 9.2) organic household waste compost. Compost samples were mixed with quartz sand to ensure aerobic conditions, incubated at 5, 10, 15, 20, and 25 degreesC and irrigated weekly for 112 days. For the fresh compost, cumulative CO2 evolution after 112 days ranged from 36% of the initial C content at 5 degreesC to 54% at 25 degreesC. The CO2 evolution was only small in the experiments with mature compost (1 to 6% of the initial C content). The data were described satisfactorily by a combined first-order (fresh compost) or a first-order kinetic model (mature compost). For the fresh compost, cumulative DOC production was negatively related to the temperature, probably due to leaching of some of the partly metabolized easily degradable fractions at lower temperatures. The production ratios of DOC : CO2-C decreased with increasing temperature from 0.094 at 5 degreesC to 0.038 at 25 degreesC for the fresh and from 1.55 at 5 degreesC to 0.26 at 25 degreesC for the mature compost. In the experiments with fresh compost, net release of NO3- occurred after a time lag which depended on the temperature. Cumulative net release of NO3- after 112 days ranged from 1.8% of the initial N content at 5 degreesC to 14.3% at 25 degreesC. Approximately 10% of the initial N content of the mature compost was released as NO3- after 14 days at all temperatures. The DOC : DON ratios in the experiments using fresh compost ranged from 11.5 to 15.7 and no temperature dependency was observed. For the mature compost, DOC : DON ratios were slightly smaller (7.4 to 8.9). The DON : (NH4+ + NO3-) ratio decreased with increasing temperature from 0.91 at 5 degreesC to 0.19 at 25 degreesC for the fresh compost and from 0.21 at 5 degreesC to 0.12 at 25 degreesC for the mature compost. The results of the dynamics of C and N mineralization of fresh and mature compost can be used to assess the appropriate application (timing and amount) of compost to soils
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Relationships between microbial and chemical properties in mine soils reclaimed for forestry
No full textTyt. z nagłówka.Bibliogr. s. 34-35.W kompleksowych badaniach gleb pogórniczych konieczny jest pomiar kilku różnych właściwości mikrobiologicznych, dlatego badane właściwości należy dobierać tak, aby maksymalizować ilość zdobywanych informacji. Celem pracy była ocena współzależnosci pomiędzy właściwościami mikrobiologicznymi gleb poprzemysłowych zrekultywowanych dla leśnictwa oraz ocena zależności właściwości mikrobiologicznych od wybranych właściwości chemicznych i fizykochemicznych gleb. W próbkach gleb zmierzono biomasę mikrobiologiczną, respirację podstawową, aktywność dehydrogenazy, fosfatazy kwaśnej i ureazy oraz właściwości fizjologiczne zespołów mikroorganizmów glebowych, które oznaczono metodą Biolog®. Ponadto oznaczono zawartość C, N oraz pH w KCl. Do analizy współzależności pomiędzy badanymi właściwościami zastosowano metodę korelacji Spearmana. Większość badanych właściwości mikrobiologicznych była ze sobą skorelowana. Jednakże wskaźniki mikrobiologiczne uzyskane metodą Biolog® słabo korelowały z biomasą mikrobiologiczną i aktywnościami enzymów glebowych, co oznacza, że dostarczały komplementarnych informacji o zespołach mikroorganizmów glebowych. Aktywności fosfatazy kwaśnej i ureazy zależały, przede wszystkim od biomasy mikroorganizmów glebowych. Pozytywna korelacja pomiędzy indeksem Shannona obliczonym na podstawie wyników analizy metodą Biolog® a biomasą mikroorganizmów glebowych wykazała wzrost zdolności fizjologicznych zespołów mikroorganizmów glebowych wraz ze wzrostem biomasy mikrobiologicznej w glebach pogórniczych.Measurement of several microbial properties is necessary for comprehensive assessment of mine soils. Therefore, the applied methods should maximize amount of acquired information. Objectives of the work were to assess relationships between microbial properties of mine soils and to assess of their dependence on some soil chemical and physico-chemical properties. The measured microbial properties included microbial biomass, basal respiration, activities of dehydrogenase, acid phosphatase and urease. Biolog® assay was used to assess physiological properties of soil microbial communities. The chemical and physico-chemical properties included the contents of C, N and pH in KCl. Spearman correlation was applied to study relationships between the properties measured. Most of microbial properties were correlated with each other. However, the Biolog® derived parameters weakly correlated with Cmic and enzyme activities what indicates that they bear complementary information on soil microbial communities. Activities of acid phosphatase and urease depended mainly on microbial biomass. Positive correlation between Shannon index based on Biolog® data and microbial biomass indicates that in the mine soil the physiological abilities of microbial communities increase as increases the microbial biomass.Dostępny również w formie drukowanej.SŁOWA KLUCZOWE: gleby pogórnicze, biomasa mikrobiologiczna, respiracja, biolog®, enzymy glebowe. KEYWORDS: mine soils, microbial biomass, respiration, biolog®, soil enzymes
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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