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Soil fungal mycelium, abundance and species diversity as affected by fire in Mediterranean environment
No full textThe risk of accidental fires and fire severity is further destined to increase in Mediterranean European countries as a consequence of the climatic changes in progress. Fire may affect soil microbial community that regulates nutrient cycling in the terrestrial ecosystems. Previous studies have shown that fire causes an increase of total microbial biomass and activity and a reduction in functional diversity in soil of Mediterranean maquis. Aim of this study was to assess the effect of fire on soil fungi that are the main decomposers of plant litter. Fungal mycelium mass, abundance and species density were measured in burned and unburned soils. Fungal mycelium generally decreased during the first two years after fire; abundance and species density of total mycoflora decreased during the post-fire summer. Fungal mycelium, abundance and species density reached the lowest values during summer season with the lowest soil water content values, for both control and burned plots. Data suggest that fire represents, for soil fungal community, a disturbance superimposing to the soil water stress in the dry season in Mediterranean ecosystems and this effect is expected to increase in the next years on the basis of climatic change in progress
Diversity and biomass of soil fungal community related to experimental fires in mediterranean maquis
No full textThe role of species diversity in below-ground processes is still little investigated and it is not adequately assessed in Mediterranean- type ecosystems which are typically affected by disturbance and stress. Two factors determine the relative adaptability of the soil biota: diversity and plasticity. Fungi are important in driving or controlling the nutrient cycling and energy flux and influencing the composition of the whole community
within the ecosystems. There is little information on soil fungal species that contribute to fungal biomass in response to different environmental patterns and management conditions. Fire, a key agent of disturbance in Mediterranean environment, can lead to a modification of composition and functioning of fungal community and to a subsequent new situation in a competitive advantage of different parts of community. We have analysed the effects of experimental fire disturbance on some quantitative and qualitative properties of soil fungal community such as total mycelium, active mycelium, fungal fraction of microbial carbon, species abundance and species density. The two last ones are referred to total mycoflora, xerotolerant and heat stimulated
fungi. This study was carried out at “Castel Volturno” Nature Reserve (Southern Italy), covered by Mediterranean maquis, where experimental fires with two different intensities (low and high) were performed in the July of 2000. Soil sampling was carried out during the first two years after experimental fires in burned and unburned plots, the last ones used as control.
After low- and high- intensity fires soils showed decreased total and active fungal mycelium, during the whole study period. Fungal fraction of microbial carbon, representing the relative importance of fungal and bacterial components within the soil
community, was also lower in burned than in unburned soils, indicating a persistent alteration of microbial community structure still two years after fires, with an increase in the bacterial component versus the fungal components. Active mycelium and fungal fraction of microbial carbon reach higher values for both
control and treated plots on sampling times corresponding to higher soil water content values. Similarly, abundance and species density of total mycoflora increased in sampling times with a more favourable moisture condition of soil, but decreased during the post-fire summer. We can suppose that fire represents a disturbance superimposed to the soil water stress in the dry season in Mediterranean ecosystems. Xerotolerant fungi significantly increased only in terms of abundance 147 and 245
days after low- and high experimental fires. So fire allows a realistic competition for water between species which advantages the xerotolerant component of fungal community. Heat stimulated fungi acquired a more relevant role within the community, in fact they trended to a significant increase both in abundance and species density in treated plots, in time. Fire provides a temporary refuge for heat stimulated fungi which are otherwise unable to compete in undisturbed soils
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
Diversity, activity and biomass of soil microbial community of mediterranean environment as affected by plant cover
No full textSoil microbial community plays a fundamental role in the ecosystem functioning, because it decomposes organic matter, determining the release of mineral nutrients in the soil and, consequently, influencing primary productivity and nutrient cycling. On the other hand, soil microorganisms may be affected by plant cover that influences chemical-physical properties of the soil. Plant cover changes are frequent in Mediterranean areas and mainly due to recurring fires and vegetation cutting, linked to land use changes or not. Aim of this research was to evaluate diversity, activity and biomass of soil microbial community in Mediterranean areas with different plant cover. The study was carried out in the Castel Volturno Nature Reserve (Southern Italy) dominated by dense high maquis (2.5-3 m-high) with gaps (probably due to recent fire or vegetation cutting) covered by scattered low shrubs (30-40 cm-high) or by herbaceous plant
community. Soil was collected, in spring and autumn 2004, in near areas covered by three different plant cover types, i.e. high maquis, low shrubs and herbaceous plant community (dominated by leguminous species). Microbial diversity was evaluated as
functional diversity and assayed as catabolic response profiles, obtained from shortterm respiration responses to addition of several simple organic compounds to the soils. Data from catabolic response profiles were also used to calculate soil catabolic evenness by Simpson-Yule index. Microbial activity was evaluated as CO2 evolution from soil samples incubated in standard conditions (25C, 55% of water holding capacity).
Microbial biomass was evaluated as microbial C (Cmic). Moreover, because fungi are particularly sensitive to changes of ecological factors, fungal mycelium (total and active), fungal fraction of microbial carbon and fungal colonies forming units
(CFUs) were also determined. Data showed that soil microbial community was affected by plant cover but also by sampling season. Soil covered by high maquis generally showed higher values of microbial activity, total and active fungal mycelium
as well as of fungal fraction of microbial carbon, than other soils; whereas, soil from herbaceous plant community was characterized by the lowest values of total and active fungal mycelium and fungal fraction of microbial carbon. By contrast, the studied soils did not differ for total microbial biomass, functional diversity (catabolic response profiles and catabolic evenness) and fungal CFUs. Moreover, a decrease of total microbial biomass, fungal CFUs and microbial activity was generally observed in autumn, when the soil water content was lower, than in spring. A change in catabolic response profiles was also observed in autumn, compared to spring. On the contrary, fungal mycelium and catabolic evenness were similar in the two seasons and fungal fraction of microbial carbon was lightly higher in autumn than in spring. The results suggest that both spatial heterogeneity of plant cover and temporal changes of ecological factors influence microbial community composition, with fungal or bacterial component dominating in different microhabitats and in different times. However, changes in catabolic response profiles, that may indicate changes in community composition, were observed in the different seasons, but not in the different plant cover types
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
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