1,721,019 research outputs found
Field evaluation of Arundo donax clones for bioenergy production
No full textA collection of 24 clones of Arundo donax, from different geographical areas in Italy, Europe, and China, were evaluated during the first 3 years from transplant. A field trial with 3 replicates was set up in the Po valley (northern Italy) in a sandy loam soil. At harvest, at the end of the second and third year after plantation, biomass yield, average stem number, average stem diameter, and single plant area were determined for each clone. For a selection of clones, chemical analysis and biochemical methane potential (BMP) were also performed. A large variation among clones was found for all the biometric parameters considered and also for biomass yield. It was interesting to note that some clones, while achieving similar biomass yield, had contrasting growth patterns, with some clones producing just a few large stems and others producing many thin ones. As a consequence, a different number of stems per plant area was also found among clones. Chemical analysis highlighted a significant difference among clones for ash (from 5.3% to 8.1%), lignin (from 6.9% to 10.6%), and hemicellulose (from 25.1% to 29.2%) content, while cellulose content was on average 43.4%. BMP ranging from 147 ml g(-1) VS to 243 ml g(-1) VS and was partially affected by lignin and ash content. (C) 2015 Elsevier B.V. All rights reserved
Biomass production and energy balance of herbaceous and woody crops on marginal soils in the Po valley
Full text linkA wealth of data and information on the cultivation of perennial biomass crops has been collected, but direct comparisons between herbaceous and woody crops are rare. The main objective of this research was to compare the biomass yield, the energy balance and the biomass quality of six perennial bioenergy crops: Populus spp., Robinia pseudoacacia, Salix spp., Arundo donax, Miscanthus 9 giganteus, and Panicum virgatum, grown in two marginal environments. For giant reed and switchgrass, two levels of nitrogen fertilization were applied annually (0–100 kg ha 1). Nitrogen fertilization did not affect biomass or energy production of giant reed; thus, it significantly reduced the energy return on investment (EROI) (from 73 to 27). In switchgrass, nitrogen fertiliza- tion significantly increased biomass production and the capacity of this crop to respond to water availability, making it a favorable option when only biomass production is a target. Net energy gain (NEG) was higher for herbaceous crops than for woody crops. In Casale, EROI calculated for poplar and willow (7, on average) was significantly lower than that of the other crops (14, on average). In Gariga, the highest EROI was calculated for miscanthus (98), followed by nonfertilized giant reed and switchgrass (82 and 73, respectively). Growing degree days10 during the cropping season had no effect on biomass production in any of the studied species, although water availability from May to August was a major factor affecting biomass yield in herbaceous crops. Overall, herbaceous crops had the highest ranking for bioenergy production due to their high biomass yield, high net energy gain (NEG), and biomass quality that renders them suitable to both biochemical and thermochemical conversion. Miscanthus in particular had the highest EROI in both locations (16 and 98, in Casale and Gariga), while giant reed had the highest NEG on the silty-loam soil of Gariga
Matching legacy estimation of soil organic carbon changes from non-paired data with measured values in paired soil samples after two decades: a case study
No full textLegacy data are frequently unique sources of data for the estimation of past soil properties. With the rising concerns about greenhouse gases (GHG) emission and soil degradation due to intensive agriculture and climate change effects, soil organic carbon (SOC) concentration might change heavily over time. When SOC changes is estimated with legacy data, the use of soil samples collected in different plots (i.e., non-aligned data) may lead to biased results. The sampling schemes adopted to capture SOC variation usually involve the resampling of the original sample using a so called paired-site approach. In the present work, a regional (Sicily, south of Italy) soil database, consisting of N=302 georeferenced soil samples from arable land collected in 1993 [1], was used to select coinciding sites to test a former temporal variation (1993-2008) obtained by a comparison of models built with data sampled in non-coinciding locations [2]. A specific sampling strategy was developed to spot SOC concentration changes from 1994 to 2017 in the same plots at the 0-30 cm soil depth and tested. To spot SOC changes the minimum number of samples needed to have a reliable estimate of SOC variation after 23 years has been estimated. By applying an effect size based methodology, 30 out of 302 sites were resampled in 2017 to achieve a power of 80%, and an a=0.05. After the collection of the 30 samples, SOC concentration in the newly collected samples was determined in lab using the same method A Wilcoxon test applied to the variation of SOC from 1994 to 2017 suggested that there was not a statistical difference in SOC concentration after 23 years (Z = -0.556; 2-tailed asymptotic significance = 0.578). In particular, only 40% of resampled sites showed a higher (not always significant) SOC concentration than in 2017. This finding contrasts with a previous SOC concentration increase that was found in 2008 (75.8% increase when estimated as differences of 2 models built with non-aligned data) [2], when compared to 1994 observed data (Z = -9.119; 2-tailed asymptotic significance < 0.001). Such a result implies that the use of legacy data to estimate SOC concentration changes need soil resampling in the same locations to overcome the stochastic model errors. Further experiment is needed to identify the percentage of the sites to resample in order to align two legacy datasets in the same area
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
Soil type and cropping system as drivers of soil quality indicators response to no-till: A 7-year field study
No full textConventional agricultural practices (CAP) highly impacted soil functions involved in the provision of multiple
ecosystem services. No-till (NT) has been repeatedly indicated as a key way to enhance soil fertility and biodiversity,
while having a positive effect on the environment and climate change. However, experimental evidence
to date shows contrasting effects of NT on physical parameters of soil fertility, as well as on soil organic
carbon (SOC) storage and soil biodiversity especially if different soil types and cropping systems are considered.
The objectives of the present 7-year field study were: (i) to unravel the effect of NT on SOC, soil bulk density,
and water stability index (WSI) of soil aggregates across five different soil types (Silty Clay, Silty Clay Loam, Clay
Loam, Silt Loam, and Sandy Loam) and cropping systems (silage vs grain production), (ii) to examine how soil
fauna (i.e. microarthropods and earthworms) is affected by NT practices under those soil-crop conditions, and
(iii) to assess relationships among responses of soil physical indicators (i.e. soil bulk density and WSI), SOC, and
soil fauna.
Our results showed that soil bulk density was generally not affected by 7-year NT across all soil types. At the
same time, NT increased WSI. It follows that NT may increase stable rather than artificial tillage-derived porosity
due to reduced soil disturbance, and increased SOC and biological activity. However, reduced importance for
boosting aggregates stability should be attributed to NT where initial SOC is high, clay and silt are predominant
soil fractions, and the rate of crop residue is low.
Our findings suggest that NT may enhance SOC stock (on average 0.66 Mg C ha−1 year−1) in the 0–30 cm soil
layer. However, we found (i) a tendency of NT to decrease SOC concentration in the 15–30 cm soil layer (on
average −1.18 g C kg−1), and (ii) no SOC increase induced by NT if crop residues were not left onto the soil
surface.
Nevertheless, NT practices promoted (i) the microarthropods adaptation measured with the QBS-ar index
(105.5 vs 64.7), and (ii) the increase of earthworm abundance (412 vs 123 individuals m−2), which are fundamental
for enhancing nutrient cycling and soil porosity.
Correlations among soil fauna (i.e. QBS-ar and earthworm density), soil physical parameters (i.e. soil bulk
density and WSI), and SOC (i.e. concentration and stock) corroborates the hypothesis that soil fauna adaptation
and proliferation are main detectors of soil quality and sensitive indicators of changes in soil tillage
Characterisation of ten commercial sorghum genotypes grown under water-limited conditions for bioenergy production in Mediterranean environment
Full text linkThe evaluation of commercial hybrids under limited water availability is of primary importance to assess Sorghum bicolor (Moench) as potential multipurpose bioenergy crop in Mediterranean drought prone environments. Ten genotypes were grown during three growing seasons (2010, 2011 and 2012) in open field trials and in pot experiments (2014). Phenological traits, biomass production, fibre content and biomass chemical composition were measured under irrigated and rainfed conditions. Differences in biomass production among the ten genotypes varied across years. In a three-year experiment significant differences were found among the ten genotypes in terms of duration of vegetative growth (P<0.05) and aboveground dry biomass production (P<0.1) in response to irrigated and rainfed conditions. Among the ten genotypes analysed, the hybrid ABF306 stands for its performance in terms of biomass production and chemical composition. In fact, it showed the lowest biomass yield reduction when grown under rainfed conditions, the highest drought tolerance index (=0.9), a °Brix value comparable to that of sweet sorghum genotypes (8.8 °Brix under rainfed conditions), lignin content that was not statistically influenced by water availability, and a lignin cellulose ratio (0.087) favourable for biogas production. The shoot transpiration efficiency and the total transpiration efficiency recorded at high (Exp1) and low (Exp2) vapour pressure deficit were comparable, and sometimes higher, to that of commercial sorghum hybrids. All these characteristics make ABF306 a suitable candidate for bioenergy production in Mediterranean drought prone environments
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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