1,720,964 research outputs found
Aboveground production and nutrient status of the vegetation of different mire types in the South-eastern Alps (Italy).
No full textWe determined aboveground net primary production
(ANPP) in five mires in the South-eastern Alps of
Italy. The mires differed considerably from each other with
regard to pore-water chemistry, ranging from bog to rich fen.
In different habitat types (hummock, scrub, lawn, fenmeadow,
hollow and marginal stream) within each mire type we
assessed nutrient status based on measurements of nutrient
concentrations and nutrient ratios in the plant biomass in order
to test whether ANPP patterns along the poor-rich gradient
could be related to the limiting effects of one or several
nutrients for biomass production. Vegetation composition
varied considerably both among mire sites and among habitat
types in terms of individual species and plant functional types
(PFTs). Nonetheless, mean ANPP was similar in the five
mires. However, ANPP showed a positive correlation with
total P concentration and negative correlations with the N:P
ratio andwith theK:P ratio of the vegetation.Weconclude that
plant biomass production is limited by P, rather than by other
nutrients, across a broad range of mire types in this region
Variations in the foliar nutrient content of mire plants: effects of growth-form based grouping and habitat
No full textWe determined concentrations of major nutrients in the vegetation of six habitat types (hummock, scrub, lawn, fen meadow, hollow and marginal stream), spanning a broad range of environmental conditions as regards water-table depth and water chemistry, in five mires on the southern Alps of Italy. Our study was based on chemical analyses of living tissues of plant species, grouped into growth-form based plant functional types (PFTs). We aimed at assessing to what extent the observed differences in tissue nutrient content were accounted for by community composition (both in terms of species and PFTs) and by habitat. Nutrient concentrations were overall lowest in Sphagnum mosses and highest in forbs, although the latter showed large variations presumably due to heterogeneity in mechanisms and adaptations for acquiring nutrients among species within this PFT. Nutrient content patterns in the other three PFTs varied greatly in relation to individual nutrients, with evergreen shrubs showing low nitrogen (N) concentrations, graminoids showing high N concentrations but low potassium (K) and magnesium (Mg) concentrations and deciduous shrubs showing rather high phosphorus (P) concentrations. Habitat accounted for a modest fraction of variation in tissue concentration of all nutrients except P. We concluded that the nutrient status of mire vegetation is primarily controlled by community composition and structure although habitat does exert a direct control on P concentration in the vegetation, presumably through P availability for plant uptake
Advanced snowmelt affects vegetative growth and sexual reproduction of Vaccinium myrtillus in a sub-alpine heath
No full textMass loss and nutrient release during litter decay in peatland: The role of microbial adaptability to litter chemistry
No full textvariation in nitrogen isotopic composition of bog plant litter during 3 years of field decomposition
No full textSeasonal variation in nitrogen isotopic composition of bog plant litter during three years of field decomposition
No full textIn this study, we describe the seasonal variation
in 15N abundance in the litter of two Sphagnum species and
four vascular plant species during 3 years of field
decomposition in an Italian Alpine bog. Litter bags were
periodically retrieved at the end of summer and winter
periods, and the δ15N in residual litter was related to mass
loss, litter chemistry, and climatic conditions. In Sphagnum
litter, higher rates of decomposition during summer months
were associated with an increase of δ15N probably due to
the incorporation of microbial organic compounds rich in
15N. The litter of Eriophorum vaginatum and Carex
rostrata was characterized by a decrease of δ15N, so that
the final signature was significantly lower than in initial
litter. On the other hand, the residual litter of Potentilla
erecta and Calluna vulgaris was characterized by a final
δ15N higher than in initial litter. Our data reported a seasonality of 15N abundance in the residual litter of
Sphagnum species, but not in that of vascular plant species,
thus highlighting the role of differences in litter chemistry
Advanced snowmelt affects vegetative growth and sexual reproduction of Vaccinium myrtillus in a sub-alpine heath.
No full textQuestion: In cold regions, snow cover duration is expected to decrease, especially in spring, as a consequence of climate warming. We investigated effects of changes in timing of snowmelt in relation to weather conditions on Vaccinium myrtillus, a dominant shrub in heath vegetation. We tested the hypothesis that advanced snowmelt will enhance shrub growth in years with few frosts, but will reduce shrub growth in years with frequent frosts. Location: A sub-alpine heath in the Northern Apennines (Italy). Methods: We carried out two experiments. In the main experiment, snow was added to (+S) or removed from (-S) experimental plots in spring of three growing seasons (2004-2006), with a mean delay in snowmelt timing of about 2 wk from -S to +S. In a companion experiment, we simulated a freezing event in late spring 2004. Results: During the snowmelt period, the -S plants experienced 6-10 more frost events, compared with +S and unmanipulated controls (C) in 2004 and 2005, but not in 2006. In the first 2 yr leaf production, leaf expansion and flowering were all significantly reduced in the -S plants, while shoot elongation was unaffected. In the companion experiment with artificial frost V. myrtillus presented similar responses. Conversely, the manipulations of snow did not affect either the hydric or nutrient status of plants and soils. Conclusions: The results overall support our hypothesis, as shown by the differing effects of snow depth and timing of melt on V. myrtillus in the 3 yr. Spring frost was the cause of reduced growth and reduced flower production in 2004 and 2005. However, advanced snowmelt will not decrease the cover of this dominant species. Therefore, the structure and species dominance patterns in sub-alpine heath are not expected to change significantly in response to reduced snow cover. Support for this conclusion is provided by the capacity of V. myrtillus to recover vegetatively from frost injury through stimulated shoot elongation, and by the low importance of sexual reproduction for propagating dominant ericaceous shrubs in closed heath communities. © 2012 International Association for Vegetation Science
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
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