1,721,048 research outputs found
Crescita, produzione primaria e struttura di popolazione di Polytrichastrum sexangulare (Brid.) G.L. Smith al Passo di Gavia (Alpi Retiche)
No full textInteractions and Covariation of Ecological Drivers Control CO2 Fluxes in an Alpine Peatland
No full textPeatland ecosystems are a highly effective long-term carbon sink. However, the CO2 fluxes could be substantially altered by climate changes and the fate of carbon stored in these ecosystems is still uncertain. Currently, most studies concerning the carbon fluxes in peatlands were performed at high latitude sites, where these ecosystems are more widely distributed compared to temperate regions, where peatlands are less frequent and, in addition to climate pressure, increasingly threatened by human activities. However, the information we have on these peatlands is very scarce. To fill this knowledge gap, we studied CO2 fluxes in an alpine peatland, through light and dark incubations. Using the natural variation in ecological conditions, we identified the main drivers of CO2 fluxes, considering in particular their interactions and covariation. Ecosystem respiration and gross primary production were primarily stimulated by the lowering of the water table and the amount of photosynthetic radiation, respectively, whereas net ecosystem CO2 exchange showed greater variation along the growing season. The influence on CO2 fluxes of the interactions between the drivers investigated, including soil temperature and moisture as well as vegetation type and plant functional diversity, was found to be of pivotal importance. Finally, a substantial part of the variation in CO2 emission and uptake processes was regulated by the joint variation of atmospheric and edaphic factors. To understand and predict the CO2 dynamics of alpine peatlands, it is necessary to consider the interplays among ecological factors, especially in relation to the expected changes in climate and vegetation
Effetti della durata dell’innevamento sulla biomassa delle vallette nivali a Polytrichastrum sexangulare (Brid.) G.L. Smith al Passo di Gavia (Alpi Retiche)
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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
Drought Timing Modulates Soil Moisture Thresholds for CO2 Fluxes and Vegetation Responses in an Experimental Alpine Grassland
No full textDrought timing determines the degree to which dry events impact ecosystems, with the ability of key processes to withstand change differing between drought periods. Findings indicate that drought timing effects vary across ecosystems, with few studies focusing on alpine grasslands. We conducted a mesocosm experiment using small grassland monoliths collected in September from the high Alps and left to overwinter at 0 degrees C until the experiment began in lowland Italy under late-winter outdoor conditions. Together with watered controls, we imposed three different drought treatments (zero precipitation): (1) one-month early-drought immediately after simulated snowmelt; (2) one-month mid-drought a month after melt-out; and (3) continuous two-month drought across the entire experimental period. Ecosystem responses were assessed by measuring CO2 fluxes, while vegetation responses were investigated by measuring aboveground net primary production (ANPP) of graminoids and forbs and post-harvest resprouting after one-month rehydration. We found that ecosystem respiration and gross ecosystem production (GEP) during the day were more negatively affected by mid-season drought compared to drought starting early in the season. By the end of treatments, GEP reduction under mid-season drought was similar to that of a continuous two-month drought. ANPP reduction was similar in early- and mid-drought treatments, showing a greater decrease under an enforced two-month period without precipitation. Plant resprouting, however, was only reduced in full- and mid-season drought pots, with forbs more negatively affected than graminoids. Seasonal soil moisture variation can account for these patterns: remaining winter moisture allowed almost full canopy development during the first month of the season, despite precipitation being withheld, while soil moisture depletion in the second month, resulting from higher temperatures and greater biomass, caused a collapse of gas exchange and diminished plant resprouting. Our data illustrates the importance of the timing of zero-precipitation periods for both plant and ecosystem responses in alpine grasslands
The rock-face vegetation in the northern apennines and neighbouring mountain areas, from the coast line to the highest summits
No full textAims: The study aims at putting together and comparing different types of rock vegetation classified to different syntaxa and usually studied separately. The particular objectives of the study were: 1) to identify and classify the vegetation units of rock communities; 2) to explain floristic differences between phytosociological units with different habitat conditions. Study area: The study area lies at the northern border of the Italian Peninsula, between 43 degrees 40' and 44 degrees 40' N and between 9 degrees and 11 degrees E. It is characterized by a great variety of rocky habitats and represents a centre of endemism and a zone of phytogeographic transition between the Alps and the Apennines. Methods: The study was based on a dataset including 693 phytosociological releves that were classified according to the recent updatings of the Braun-Blanquet method. During the classification, releves were assigned to phytosociological classes based on the cover-abundance prevalence of diagnostic species, taking into account the current literature. The definitive classification into associations was carried out through cluster analysis. The analysis of floristic variation within the rock vegetation was performed through Principal Component Analysis, adopting Ellenberg indicator values as indirect environmental factors. Results: We identified 36 basic vegetation units (35 of them evaluated as associations) belonging to four phytosociological classes (Crithmo-Staticetea, Adiantetea, Asplenietea trichomanis and Polypodietea). All these vegetation units were characterized by their floristic composition, structure, syntaxonomy, habitat and distribution. Conclusions: More than half of the identified associations and a new suballiance Primulenion apenninae (within the alliance Androsacion vandellii) were newly described. Two alliances (Moehringion muscosae and Hymenopbyllion tunbrigensis) were first documented as part of the Italian vegetation. Indirect gradient analysis indicated that, within the four classes, the floristic composition varied along different environmental gradients and that temperature can be identified as the factor most strongly correlated with the variation of rock-face vegetation
Refugial peatlands in the Northern Apennines. Vegetation-environment relationships and future perspectives
No full textAims: We aimed to detect the environmental drivers conditioning plant diversity and to predict how modifications in habitat conditions and ongoing global warming could lead to vegetation changes or biodiversity losses in a region especially rich in peatlands despite its relatively low latitude. Study area: The study area was located in the Northern Apennines, Northern Italy (about 44 degrees 45' N; 10 degrees 20' E). The vegetation study was carried out at 12 peatland sites where 206 plots were set up. Species composition in the 206 plots were recorded in the field and classified with cluster analysis. Data on hydrology, water chemistry and peat chemistry were collected at a subset of 127 plots and statistically analysed by a multivariate ordination method. Species richness and evenness were calculated for all plots. Relationships between species composition and environmental variables were analysed by stepwise multiple regression. Results: The cluster analysis defined 17 vegetation units. Water table depth represented the major environmental factors accounting for vegetation patterns, with the vegetation units being grouped in four main blocks based on vegetation physiognomy and species composition: Sphagnum hummocks, Sphagnum lawns, fens and pools. Water chemistry and peat chemistry both presented moderate variations among the vegetation units with mean water pH ranging from 4.9 to 6.3. Concentrations of major cations in the pore water showed that all of the habitats investigated were influenced by telluric water, with no evidence of ombrotrophic conditions. Species richness and evenness both presented poor relations with the environment while responses of individual species to environmental factors were more informative on vegetation changes triggered by climate change. Conclusions: Prolonged drought events associated with high temperature in summer months are expected to exert a strong impact on peatland vegetation. The main effect of climate change on the vegetation of the peatlands investigated consists in the spreading of vascular plants at the expense of Sphagnum mosses
Refugial peatlands in the Northern Apennines. Vegetation-environment relationships and future perspectives
No full textVariations 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
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