1,721,017 research outputs found
Intraspecific functional differences of subalpine plant species growing in low-altitude microrefugia and high-altitude habitats
No full textMountain ice holes are microrefugia at low altitudes characterized by colder temperatures compared to the surrounding areas. Ice holes harbor extra-zonal plant communities composed of plant species that generally grow at higher altitudes in subalpine habitats. Understanding how subalpine species adjust their functional traits to extra-zonal environmental conditions in ice holes can improve our knowledge of plants’ ability to cope with environmental changes. We compared the intraspecific trait variability of four species growing in ice holes and in subalpine areas in the south-eastern Alps of Italy. Plant functional traits presented different patterns of variation between the two habitats. Leaf area, leaf nitrogen and phosphorus content and stomatal traits (stomatal density and stomatal length) differed consistently between habitats in all species. Conversely, specific leaf area and leaf dry matter content varied differently between habitats depending on species. The four species developed differing strategies for adapting leaf functional traits to the peculiar environment of ice holes. Two species, Vaccinium myrtillus and Rhododendron ferrugineum, took advantage of extra-zonal location by developing a more competitive ecological strategy. Conversely, Vaccinium vitis-idaea and Homogyne alpina adopted a more conservative strategy by optimizing adaptation of leaf traits to cold temperature. Our study represents a first attempt to understand the role of marginal populations within the total functional variation of a species. We highlighted the importance of protecting ice holes as important reservoirs of functional diversity for subalpine plant species
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
Patterns of Clonal Growth Modes Along a Chronosequence of Post-Coppice Forest Regeneration in Beech Forests of Central Italy.
No full textForest coppicing leads to changes in composition of the herbaceous
understory through soil disturbance and alteration of the light regime. While the role
of seed dispersal traits at the start of succession after coppicing has been extensively
studied, the role of persistence traits such as clonal growth and bud banks is not yet
sufficiently understood. To gain better understanding of this role, we studied the
patterns of clonal growth organs and related clonal traits of species in a series of
coppiced beech forests of the Central Apennines (Marches region, Italy) in various
stages of recovery after the last coppicing event. We conducted stratified random
sampling and established a chronosequence of recovery stages based on stand
age (reflecting the number of years since the last coppicing). The beech stands were classified into three age groups (Post-logged, Recovering, and Old-coppice
stands) according to the characteristic stages of beech coppice dynamics. Clonal
growth organs and the corresponding clonal traits of plants in the forest
understory vegetation were assessed with the help of a CLO-PLA1 database.
We found no significant change in the proportion of clonal species along the
studied chronosequence. In contrast, most of the traits and about the half of the
clonal growth organs showed correlation with stand age or preference for a
certain habitat (i.e., stage of regeneration). Clonal and bud bank traits proved to
play an important role in the persistence of species subjected to forest coppicing
cycles in the studied area
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
Progetto SIGNAL: gradienti europei di resilienza rispetto ad eventi climatici estremi.
No full textCome I sistemi semi-naturali di prateria possono reagire alla variazione combinata dei parametri edafoclimatici, gestionali e sotto la pressione di specie aliene
Plant diversity and annual layer counting based on pollen analyses of an Adamello glacier ice core
Full text linkDifferences in gene expression of drought-stress candidate genes across natural populations of Quercus pubescens Willd. in Italy. IUFRO 2012 Genetics of Fagaceae and Nothofagaceae. Poster abstracts. Bordeaux.
No full textUnderstanding plant species acclimation and adaptation to climatic changes is one of the
most interesting challenges at the interface of ecology, physiology and genetics. In this
context, the investigation of functional genetic diversity related to stress tolerance of natural
populations in a contrasting climatic context is a promising approach. Plant responses to
drought stress are complex, involving a number of genes which contribute to drought
adaptation.
Here we use 30 candidate genes involved in drought-stress response in Q. robur (Brendel,
Kremer, Le Provost, pers. com.). These candidate genes are involved in processes such as
transpiration regulation, stomatal development, stomatal light response, cuticle biosynthesis,
and water use efficiency. We tested for differential gene expression in natural populations of
Quercus pubescens Willd. at mesic and xeric sites in Central and Southern Italy. For this
purpose, RNA was extracted from leaf material of 100 individuals. We aimed to identify
markers for climatic acclimation and adaptation of natural populations.
Results of SIMPER analysis for dissimilarity revealed that four out of 30 candidate genes
appear as main factors which differentiate the samples. In detail, significant differences in
gene expression were most obvious between the most mesic (central Italy) compared to the
most xeric (S Italy) site.
It will be a challenge for future research to tackle if these markers reappear in the droughtstress
response in other tree species or plants in general
CALICE: Calibrating Plant Biodiversity in Glacier Ice
Full text linkThe objective of the project is to reconstruct plant biodiversity and its trend archived in Alpine glacier ice by
pollen and eDNA (environmental DNA) during the last five decades by analyzing a 40 m ice core. For our study
we chose the Adamello glacier (Trentino - Südtirol, Lombardia) because of i) the good preservation conditions
for pollen and eDNA in ice, ii) the thickness of the ice cap (270m) and iii) the expected high time resolution. The
biodiversity estimates gained by pollen analysis and eDNA will be validated by historical biodiversity assessments
mainly based on vegetation maps, aerial photos and vegetation surveys in the catchment area of the Adamello
glacier for the last five decades. This historical reconstruction of biodiversity trends will be performed on a micro-,
meso- and macro-scale (5, 20-50 and 50-100 Km radius, respectively). The results will serve as a calibration data
set on biodiversity for future studies, such as the second step of the coring by the POLLiCE research consortium
(pollice.fmach.it). In fact, arrangements are currently been made to drill the complete ice cap and retrieve a 270
m thick core which has the potential to cover a time span of minimum 400 years up to several millennia. This
second stage will extend the time scale and enable the evaluation of dissimilarity/similarity of modern biodiversity
in relation to Late Holocene trends. Finally, we believe this case study has the potential to be applied in other
glaciated areas to evaluate biodiversity for large regions (e.g. central Asian mountain ranges, Tibet and Tian Shan
or the Andes)
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