1,720,956 research outputs found
Characterization of fine root system and potential contribution to soil organic carbon of six perennial bioenergy crops
No full textPerennial bioenergy crops provide biomass for renewable energy production, but also sequester atmospheric carbon (C) in the soil. Roots represent one of the most important soil C inputs-root length density (RLD, cm cm-3), root diameter and fine root biomass (FRB, Mg ha-1) in the top 1 m of soil were characterized for three woody (poplar, black locust, willow) and three herbaceous (giant reed, miscanthus, switchgrass) perennial crops in the same location. The vertical distribution of FRB and RLD was described by fitting the "beta" (Î2) model to the experimental data. The herbaceous species had higher Î2 values for FRB and RLD than woody crops, suggesting that the former explore the deeper soil layers with a greater proportion of roots. In particular, 3.7 Mg ha-1, or 43% of the whole root mass, was found below the ploughing soil layer (0.3 m) for the herbaceous species, while only 1.2 Mg ha-1, or 26% of the whole root mass, was allocated by woody crops to the same soil layer. In all the species, the majority of the sampled roots (99.1%) had a diameter lower than 2 mm, and in the first 10 cm of the soil the woody species tended to produce roots with a smaller diameter than those of the herbaceous species. Overall, the herbaceous crops have a higher potential to contribute to C storage in the deep soil layers, while the woody species, have a greater potential to affect soil organic carbon in the top soil layer
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
Effetti a breve termine dell’ammendamento organico e della fertilizzazione minerale su salute chimica e biologica del suolo e meccanismi di stabilizzazione del C organico
No full textLa dinamica della sostanza organica rappresenta un processo chiave nella fornitura dei servizi ecologici d’interesse agro-ambientale. La lotta al cambiamento climatico e la sfida alla sostenibilità in agricoltura passano anche attraverso l’ammendamento organico di origina bovina del terreno.
L’effetto dell’ammendamento organico è stato finora poco studiato dal punto di vista della contemporanea promozione di meccanismi di stabilizzazione del C e del miglioramento della salute chimica e biologica del suolo. L’obiettivo di questa ricerca è stato la valutazione integrata degli effetti sul suolo a breve termine dell’applicazione di due ammendanti organici rispetto alla fertilizzazione minerale sulle dinamiche di: attività enzimatiche del suolo; pool labili di C e N, meccanismi di stabilizzazione del C negli aggregati e frazioni estraibili di NO3-, NH4+ e P totale.
Un suolo agricolo franco-argillo limoso (C.O. 2,6%, Ntot 0,2%) e un suolo agricolo franco sabbioso (C.O.1,4%, Ntot 0,3%) sono stati campionati in provincia di Piacenza, posti in lisimetri di 1m2 e ammendati con compost (340 kgN/Ha), digestato (170 KgN/Ha) e fertilizzati con NH4NO3 (170 kgN/Ha). Di seguito è avvenuto l’interramento delle matrici con lavorazione meccanica a 20 cm. Le matrici organiche si differenziano nella composizione: il compost (C.O. 32%, NO3 2,9%, C/N 11,1) e il digestato chiarificato (C.O. 24%, NO3 6,8%, C/N 3,6). Il suolo nei lisimetri (compreso il controllo) è stato poi campionato a due differenti profondità (0-5 e 5-20 cm) e a 1, 7, 14 e 30 gg dopo l’applicazione delle matrici. Sui campioni di suolo è stato determinato C e N della DOM, estratta sia freddo sia a caldo, e le frazioni di nutrienti estraibili in acqua in lettore di micropiastre. Sul restante suolo è stata determinata la frazione labile di C ossidabile al KMnO4 (POXC), la biomassa microbica con il contenuto totale di DNA a doppia elica (dsDNA) e sette attività enzimatiche ( - e β-glucosidasi, fosfatasi alcalina e acida, leucina amminopeptidasi, arilsulfatasi e piro diesterasi). Al tempo 0 e a 30 gg è stata determinata la distribuzione del POXC nelle diverse frazioni occluse e libere degli aggregati e della POM. I primi risultati nello strato superficiale mostrano nel suolo franco-argillo limoso un aumento significativo da parte del compost della biomassa microbica a 7gg e del POXC a 14gg. Il digestato e l’ammonio nitrato invece hanno mostrato un incremento di dsDNA a 1gg. Solo il compost nello strato 5-20cm ha condotto a fine esperimento ad un aumento del dsNA. Le attività enzimatiche mostrano un incremento generale nel suolo franco argillo-limoso durante l’intera durata dell’esperimento in quest’ordine decrescente: compost, digestato, ammonio nitrato. La fosfatasi alcalina, la piro diesterasi e la leucina amminopeptidasi sono le attività che hanno mostrato le risposte più significative all’aggiunta delle matrici organiche. I nitrati, in entrambi i suoli, sono aumentati a 1gg con l’ammonio nitrato e a 30gg con il digestato. Nel suolo franco-argillo limoso DOC e DON, rispettivamente a 7gg e 14gg, sono aumentate con l’applicazione del digestato. I rimanenti dati verranno discussi al fine di indicare quale matrice per le due tipologie di suolo sia la più indicata a migliorare la fertilità chimica e biologica del suolo, e contemporaneamente quale caratteristiche debba avere per poter avviare processi di accumulo e stabilizzazione del C
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
