1,720,978 research outputs found
Ripartizione dei flussi di carbonio in agrumeto: metodi micrometeorologici e diretti a confronto
No full textRipartizione dei flussi di carbonio in agrumeto: metodi micrometeorologici e diretti a confronto
No full textCarbon balance and soil carbon input in a poplar short rotation coppice plantation as affected by nitrogen and wood ash application
No full textThe increasing importance of short rotation coppice (SRC) plantations for bioenergy production makes it crucial to evaluate their carbon (C) sink potential and to understand which sustainable practices could increase productivity and C sequestration. This study examined the combined effect of woody ash and nitrogen (N) fertilization on the productivity, net C balance (NECB) and soil C sink capacity of a poplar SRC plantation established on a former arable land in northern Italy. Above- (ANPP) and below-ground (BNPP) primary productivity, including both root litter and rhizodeposition (Croot litter), were estimated by a combination of inventory methods, soil respiration measurements and C budgeting approaches. NECB was estimated as changes in both plant and soil C pools, and the portion of soil organic carbon (SOC) derived from poplar leaf and root litter was estimated using a combination of in-growth cores and isotopic measurements. Nitrogen application at 100 kg ha−1 increased ANPP in terms of C accumulation only in the first year, while NECB was not affected by treatments and was 9.96 Mg C ha−1 year−1 on average. Irrespective of the treatment, the plantation accumulated on average 0.7 Mg C ha−1 year−1 of SOC and the poplar-derived soil C input was 3.0 Mg ha−1 year−1. Positive NECB shows that the studied SRC resulted in an important C sink even in the first years after the establishment. However, long-term studies are needed to better assess the effect of N and ash application on C and nutrient cycles over more than one rotation period
Biochar Reduces Short-Term Nitrate Leaching from A Horizon in an Apple Orchard
No full textNitrogen leaching in croplands is a worldwide problem with
implications both on human health and on the environment. Efforts
should be taken to increase nutrient use efficiency and minimize N
losses from terrestrial to water ecosystems. Soil-applied biochar has
been reported to increase soil fertility and decrease nutrient leaching
in tropical soils and under laboratory conditions. Our objective was
to evaluate the effect of biochar addition on short-term N leaching
from A soil horizon in a mature apple orchard growing on subalkaline
soils located in the Po Valley (Italy). In spring 2009, 10 Mg of biochar
per hectare was incorporated into the surface 20-cm soil layer by
soil plowing. Cumulative nitrate (NO3
-) and ammonium (NH4
+)
leaching was measured in treated and control plots 4 mo after the
addition of biochar and the following year by using ion-exchange
resin lysimeters installed below the plowed soil layer. Cumulative
NO3
- leaching was not affected by biochar after 4 mo. whereas in
the following year it was significantly (p < 0.05) reduced by 75% over
the control (from 5.5 to 1.4 kg ha-1). Conversely, NH4
+ leaching was
very low and unaffected by soil biochar treatment. The present study
shows that soil biochar addition can significantly decrease shortterm
nitrate leaching from the surface layer of a subalkaline soil
under temperate climatic conditions
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
Continuous Monitoring of Tree Responses to Climate Change for Smart Forestry: A Cybernetic Web of Trees
Full text linkTrees are long-lived organisms that contribute to forest development over centuries and beyond. However, trees are vulnerable to increasing natural and anthropic disturbances. Spatially distributed, continuous data are required to predict mortality risk and impact on the fate of forest ecosystems. In order to enable monitoring over sensitive and often remote forest areas that cannot be patrolled regularly, early warning tools/platforms of mortality risk need to be established across regions. Although remote sensing tools are good at detecting change once it has occurred, early warning tools require ecophysiological information that is more easily collected from single trees on the ground. Here, we discuss the requirements for developing and implementing such a treebased platform to collect and transmit ecophysiological forest observations and environmental measurements from representative forest sites, where the goals are to identify and to monitor ecological tipping points for rapid forest decline. Long-term monitoring of forest research plots will contribute to better understanding of disturbance and the conditions that
precede it. International networks of these sites will provide a regional view of susceptibility and impacts and would play an important role in ground-truthing remotely sensed data
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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