1,720,995 research outputs found
The importance of being natural in a human-altered riverscape: role of wetland type in supporting habitat heterogeneity and the functional diversity of vegetation
No full text1. Human activities have dramatically affected the status of river ecosystems, mainly by completely altering their natural dynamics. One of the main questions in this regard is: 'How do the origin (natural or artificial) and hydrology (lentic or lotic) of a riverine wetland influence its heterogeneity and the functional diversity of its vegetation?'2. To answer this question, data from 60 wetlands were collected along the Oglio River (northern Italy), a similar to 700km(2) ecosystem that is a typically over-exploited plain. In order to perform a quantitative assessment of habitat heterogeneity and vegetation diversity, a hierarchical approach was applied to sample sites divided into four functional zones (FZs) according to distinct seasonal inundation patterns (persistently aquatic, riparian, seasonally emergent and lateral zones).3. Plant communities were randomly surveyed in each FZ by using five replicates of 4m(2) plots for aquatic and herbaceous plant communities and five replicates of 64m(2) plots for woody and shrub communities. Data on species cover were estimated by standard methods (geometric-centered scale)4. The highest values of heterogeneity (FZs per site) and vegetation diversity (plant communities per site) were found in natural lentic sites, whereas natural lotic sites exhibited the lowest values. A clear dependence of plant community assets on wetland origin was detected, thereby confirming the close relationship between heterogeneity and vegetation diversity.5. Present results highlight the fundamental role played by natural sites in maintaining aquatic and wetland vegetation diversity in human-altered riverscapes. The pivotal role of water level fluctuations in promoting the diversity and distribution of aquatic and hygrophilous vegetation also clearly emerges. Copyright (C) 2015 John Wiley & Sons, Ltd
Hydro-hygrophilous vegetation diversity and distribution patterns in riverine wetlands in an agricultural landscape: A case study from the Oglio River (Po Plain, Northern Italy)
No full textIn the European plains, up to eighty percent of riverine wetlands have been lost due to alteration of hydrological regime and catchment exploitation. This condition is expected to be further negatively exacerbated by climate change. To better understand the observed change in distribution patterns of hydro-hygrophilous vegetation in temperate and Mediterranean floodplains, a vegetation survey was conducted within the lower Oglio River reach in Northern Italy. This river is a mid-size, altered and nutrient-rich left tributary of the Po River. During the 2008 growing season, a total of 60 marginal aquatic habitats were investigated. Overall, 37 vegetation communities were detected, showing a clear predominance of hygrophilous herbaceous plant communities both in terms of representativeness (55.1%) and diversity (54.1%) with respect to woody (22.9% and 10.8%, respectively), and obligate aquatic vegetation (22.0% and 35.1%, respectively). Our main findings were (1) the widespread presence of highly opportunistic, non-native and invasive hygrophilous plant communities (largely dominated by Amorpha fruticosa, Phragmites australis s.l., Amaranthus spp., Bidens spp., and Cyperus spp.), and (2) the limited distribution of hydrophyte vegetation usually dominated by pleustophytes (e.g., Spirodela polyrhiza and Lemna spp.). The present study confirms the dominance of secondary plant communities characterized by the widespread presence of alien species in lowland over-exploited riverscapes, coupled with a low local representativeness of native willow (Salix alba, S. cinerea) communities and anchored macrophyte (batrachid, ceratophyllid, elodeid, myriophyllid) meadows. Total vegetation diversity is consistent with previous studies in similar ecological contexts; on the other hand, at the site scale, the diversity values were extremely low. This is especially true for the aquatic vegetation, and can be related to the high water turbidity and chlorophyll-a concentrations that prevent the establishment and colonization of submerged and rooted hydrophytes. Consequently, we stress the need for metabolic and biogeochemical indicators to assess the actual trophic status of lowland wetlands in order to clarify their potential to be restored
Adaptive plasticity in metamorphic traits of Bufo bufo (Amphibia: Anura) tadpoles: the effect of population density and habitat duration.
No full textCongresso Congiunto AIOL-SItE , Ancona, Ital
The likely impact of climate change on the biodiversity of Italian forests
Full text linkBased on literature results and our expert evaluation, we report some likely impacts of climate change on the biodiversity of forest communities in Italy by the end of this century. In the Mediterranean region and on the Apennines: at low altitudes, vulnerability of Pinus sp. and Quercus ilex forests, with loss of intraspecific genetic variability; transition from Mediterranean closed-canopy macchia to scattered shrublands; risk of local extinction for coastal populations of mesic/relic hardwood species (e.g., Quercus robur, Carpinus betulus, Zelkova sicula, Fraxinus sp.); ’eastern’ relic species like Quercus troiana, Quercus frainetto, Quercus aegilops, and Q. gussonei in Sicily, and the peripheral low-altitude Fagus sylvatica populations, will be highly vulnerable; in the mid-altitude forest, vulnerability of most demanding species like Quercus cerris and Castanea sativa, possible immigration of Mediterranean species like Quercus ilex; in the montane forest, Fagus sylvatica and Abies alba will be less competitive with respect to more continental and drought-resistant tree species, and could loose genetic variability; relic species like Taxus baccata and Betula aetnensis may be at risk. In the alpine region: upward movement of timberline and changes in timberline communities, for instance Picea abies may be more competitive over Larix decidua, and fragmented species like Pinus cembra might become vulnerable. In general, we recognize the difficulty in separating the effects of climatic variables from those of other processes, like fires and land-use change
Global change e risalita delle treeline: conseguenze genetiche della colonizzazione dei pascoli alpini
No full textA Novel Simplified Protocol for Pre-Processing Whole Wood Samples for Stable Isotope Analysis in Tree Rings
No full textIn the context of climate change, the stable isotope analysis of tree rings may play a crucial role in deciphering the eco-physiological mechanisms underlying forest decline and dieback phenomena. However, this technique is often considered expensive, time-consuming, and with several methodological constraints. Specifically, milling and transferring the material from jars to vials during the different steps of sample preparation involve risk of contamination among samples and loss of sample material. When dealing with declining trees (i.e., trees affected by loss of vitality with strong percentage of defoliation and reduction in growth) and trees subjected to extreme events or negative pointer years (characterized by extremely narrow ring) the sample preparation is particularly difficult because of scarce amount of wood material. In such a case, pooling rings from several years to achieve the minimum weight of wood is often necessary, thus losing information at the annual resolution. In order to overcome such limitations, we developed a novel protocol for quick and accurate whole-wood pre-processing, testing it on oak tree rings of different widths taken from living trees. The main novelty introduced by our protocol was freezing tree-ring samples at −80 °C and milling multiple samples at a time by using a 24-tube plate. The results showed that our novel simplified protocol significantly reduced the pre-processing time with respect to the standard protocol (12 vs. 284 sec/sample), while achieving the same wood particle size, limiting the loss of wood material and reducing the risk of contamination among samples
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
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