1,720,979 research outputs found
Temperate deciduous forests with Balkano-Apenninic affinities: floristic changes and heterogeneity.European Vegetation Survey,15-20 Aprile 2004
No full textHumus Carbon Sequestration. How humus forms contribute in carbon sequestration in the Mediterranean forest ecosystem at Castel Porziano Reserve (CPR), central Italy
No full textABSTRACT
Objective: This work reports the results of an investigation on humus forms in a Mediterranean area. The study allows to test the effectiveness of the recent European humus forms classification (Zanella et al. 2011a), based on morpho-genetic characters of diagnostic organic and organo-mineral horizons. Furthemore it reveals how the humus forms data, at the level of diagnostic horizons, are related to vegetation/soil types and Carbon storage capacity of the soil.
Methods: The humus forms were investigated in different substrate, soil types, and vegetation units of a Mediterranean forest ecosystem in Central Italy (Castelporziano Reserve). Classical parameters were measured and statistically analysed: thickness, Organic Carbon (OC) and total Nitrogen (Ntot) contents in organic and organo-mineral horizons, whilst pH and texture in the organo-mineral horizon.
Results: The three main humus forms (Mull, Moder and Amphi) covering the soil of the Reserve appeared well separated on the PCA diagram. Thickness, OC and Ntot showed a high correlation with the axes of the PCA. Kruskall-Wallis results disclosed differences among Mull, Moder and Amphi: 1) the thickness of A horizon was larger in Amphi; 2) OC in A horizon was lesser in Moder form; 3) Mull had less OC in organic horizons than Moder and Amphi; 4) Mull and Amphi raised twice the OC of Moder in organic and organo-mineral summed horizons.
Two main ecological gradients, from neutral/aerated Mull to acid/asphyxiated-water saturated Moder on one side and from fresh Mull to dry Amphi on the other, explain the distribution of humus forms in the Reserve. The first gradient concerns circular belts around periodically filled small basins and is peculiar to the more or less impermeable plain of Castelporziano; on the contrary, the second progressive transition is very common in Mediterranean forests.
Conclusion: A clear trend in Carbon storage capacity is visible in humus forms of Mediterranean forest where Mull and Amphi, with a good mixing of organics and minerals particles in the A horizon, show at least twice more OC than Moder.
Practice: The European humus forms classification is a very practical tool and allows to survey the humus forms and better understand the functioning of forest ecosystems even in Mediterranean area. The carbon cycle of Mediterranean forests seems to gravitate around a still scarcely investigated and very rich in OC Amphi humus form.
Implications: The European humus forms classification seems to be appropriate to a large scale survey of humus forms in forest ecosystems. It allows to better understand the organic matter cycle at the level of soil bio-structures. The crucial role played by the here investigated Amphi forms could increase with the prospect of climate change
Which is the contribution to the carbon sequestration of the forest ecosystems in the Castelporziano Reserve? Evidences from an integrated study on humus and vegetation.
No full textSoil is a major carbon sink or source on ter-restrial ecosystems. Despite their great importance, humus forms, which constitute the small portion above the soil, have been often neglected in local studies and in interna-tional research projects. In the present work we evaluated the organic carbon stocked in the different humus forms in a Mediterranean lowland forest, to highlight the carbon concentration in different vegetation types, particularly between evergreen and deciduous woodlands. Results showed that the carbon stock stored in the organic and organo-mineral horizons of humus and soil, expressed in Tons/Ha, had a wide range for each vegetation type, reflecting the high diversity of the forest vegetation and the variability within each type. The vegetation with the highest value of carbon stock despite its small extension was represented by humid woodlands dominated by Fraxinus oxycarpa, a relic forest type occurring in the dune slacks within the study area, which gives, therefore, an important contribution to the climate warming reduction. We demonstrated as the humus forms play a role in the carbon sequestration in a forest ecosystem; therefore, it may be important to add the evaluation of carbon stock when carbon concentration is evaluated for the soil and above and plants below ground biomass
RELATIONSHIPS BETWEEN SOIL TEMPERATURES AND PLANT COMMUNITIES:FIRST ANALYSES IN WET AREAS OF SOUTHERN LATIUM.
No full textDistribution of Liana Richness and Abundance in the Forest of Papua New Guinea
No full textThis study surveys liana communities at 26 sites across undisturbed and disturbed forests from 70 to 2,700 m above sea level in northern parts of Papua New Guinea (PNG). The assessment was conducted following the Papua New Guinea National Forest Inventory (NFI) manual. The results show a total diversity of 68 genera of lianas, belonging to 33 families. No significant difference was observed in abundance of liana species between lowland unlogged (i.e., primary and pristine) and logged (disturbed) forests and lower montane unlogged forests. Richness is not significantly different between lowland and montane sites, as opposed to outcomes in other studies which have often reported a decrease in species richness with elevation. Both types of lowland forests do not show indicator genera, while the unlogged montane forests are characterized by Rubus and Sabia genera. The study shows a high taxonomic richness of lianas in PNG, supporting previous research and underlining that they make a significant contribution to the overall woody species richness and to the ecology and complexity of PNG forest
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
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
- …
