1,720,988 research outputs found
A bridge between tourism and nature conservation: boardwalks effects on coastal dune vegetation
No full textSeveral regulatory and management tools are commonly used to prevent negative effects of human trampling on sand dune
habitats, but few studies have attempted to evaluate the effects of boardwalks on dune vegetation. We aimed to evaluate changes
of species richness and cover, floristic composition and ecological functional guilds among different dune habitats 2 years after
the boardwalks had been established, highlighting those habitats mainly affected by these changes. In a Special Protection Area
of Molise region (Italy), we sampled 53 square plots before the installation of five wooden boardwalks (control plots) and 57 plots
after the boardwalks had been set up (testing plot), across the whole dune system ranging from the upper beach to the pine forest.
We compared species richness through rarefaction curves, considering two plant functional groups: focal species (characteristic
and diagnostic) and ruderal/exotic species. We finally compared florist composition and cover changes between time intervals,
dune habitats and functional groups. In all habitats the total plant richness of testing plots was higher than in the control plots. In
beach and mobile dunes habitat focal species drive the increase in both species’ richness and cover. Dune grasslands proved to be
the most affected by the presence of ruderal and exotic species, while the more stable fixed dunes habitat was less affected by
species changes. Only 2 years after the boardwalks having been set up, we have found a rapid recovery since human trampling
was limited. The use of boardwalks could be an effective tool for reducing negative impact of bathing tourism on coastal dunes
and requires little and inexpensive maintenance
Spatial Organisation of an Insect Ensemble in a Mediterranean Ecosystem: the Tenebrionid Beetles (Coleoptera: Tenebrionidae) Inhabiting an Adriatic Coastal Sand Dune Area
No full textWe studied the spatial organisation of an ensemble (phylogenetically bounded group of species that use a similar set of resources within a community) of tenebrionid beetles in a Mediterranean coastal sand dune ecosystem in Southern Italy (Molise region). Within a transect from the seashore to the inner dune, we identified four biotopes defined by different vegetation types. We found a community dominated by few sand specialised and r-selected tenebrionid species. Overall tenebrionid abundance was lowest on the upper beach, highest on the embryonic shifting dunes and then from there declined further inland. The embryonic shifting dunes biotope showed the highest diversity and the lowest dominance. This pattern suggests that tenebrionid beetels are able to cope with the challenging salty and xerothermic conditions of the seaward margin. Although some species were too rare to assess their biotope preference, our data support that, at least some, were distributed with different abundance over the four dune biotopes. These differences are likely related to different preferences for different characteristics of substratum and detritus
Above- and belowground traits along a stress gradient: trade-off or not?
No full textThe role of plant traits in shaping community assembly along environmental gradients is a topic of ongoing research. It is well accepted that plant traits of aboveground organs tend to be conservative in stressful conditions. However, there is limited understanding of how belowground traits respond. Plants may have similar strategies above and belowground, but an intriguing possibility is that there is a tradeoff between above and belowground traits of communities to both ensure efficient resource-use and limit niche overlap along the gradient. To test this, we asked whether the response of above and belowground traits of communities is coordinated or not along a stress gradient in Mediterranean sand dune communities. We analyzed 80 vegetation plots in central Italy to test for coordinated vs independent patterns in above vs belowground plant traits using community weighted mean and standardized effect size of functional richness. Our results show that plant communities close to the sea, which experience higher stress, were characterized by higher convergence towards aboveground resource conservation and conservative water-use strategies but belowground resource acquisition, consistent with a strong effect of habitat filtering and an above-belowground tradeoff favoring adaptation to harsh and dry conditions. At the opposite end of the gradient with lower stress, plants exhibited higher trait diversity for both above and belowground traits, but overall a dominance of aboveground fast resource acquisition and generally acquisitive water-use strategies, combined with conservative belowground strategies. This suggests that fast growth rate aboveground was compensated by more conservative fine-root strategies, but processes such as competition limited niche overlap overall. Our findings provide new insights into the relationship between functional traits and environmental gradients in plant communities, shedding light on the tradeoffs between the above and belowground dimensions
The germination niche of coastal dune species as related to their occurrence along a sea–inland gradient
No full textAims
The early phases in the life cycle of a plant are the bottleneck for successful species establishment thereby affecting population dynamics and distribution. In coastal environments, the spatial pattern of plant communities (i.e. vegetation zonation) follows the ecological gradient of abiotic stress changing with the distance from the sea. This pattern has been mainly explained based on the adaptation and tolerance to the abiotic stress of adult plants. However, the adult niche may considerably differ from the germination niche of a plant species. The aim of this work was to investigate to what extent abiotic factors (specifically salinity, temperature, nitrogen and their interactions) constrain seed germination along the sea–inland gradient.
Location
Latium coast (Central Italy).
Methods
Germination tests were performed on seeds of focal species of three different plant communities which establish at increasing distances from the coastline: Cakile maritima subsp. maritima, Elymus farctus, Crucianella maritima. We tested increasing concentrations of NaCl (one of the main abiotic factors which decrease across the sea–inland gradient), and their interactions with temperature and KNO3, to consider other factors which drive germination processes.
Results
The tolerance to salinity significantly decreased in relation to the position of species along the coastal zonation. Crucianella maritima was shown to be the least tolerant species, having a decrease in germination >80% across all conditions. KNO3 significantly (although slightly) increased the germination percentage in Cakile maritima subsp. maritima and Elymus farctus. When combined with NaCl, KNO3 alleviated the negative effects of salinity only in Cakile maritima subsp. maritima.
Conclusions
The germination responses to the interaction among the tested factors suggest that the germination niche may explain vegetation zonation filtering species at their early stages. Quantifying environmental niches in different phases of the life cycle of plants may provide important insights into community assembly processes
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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