1,721,052 research outputs found
Alien tree species and plant diversity in urban and peri-urban environments: the case of black locust
No full textForest patches are an important feature for increasing and maintain plant diversity in the urban and peri-urban landscapes. However, in such environments, the number of alien trees has increased over time due to the invasion of those species planted for ornamental and soil stabilization purposes. These species are able to invade abandoned areas whether forming patches of forests or linear features of different dimensions that may be considered novel urban ecosystems and a sort of urban wilderness. However, invasive alien tree species can also cause several detrimental effects. From the conservation and management perspective, the impacts on plant assemblages are of extreme importance. Alien tree species can have an effect on native communities and also can favour the establishment of other alien plants. Interestingly, their spread and consequences on plant diversity may be different in urban and peri-urban areas highlighting that their negative impacts are not an axiom. Here we discuss all these aspects by taking as an example black locust (Robinia pseudoacacia L.) in both urban and peri-urban environments. We conclude highlighting the need of further investigations on the impacts of alien tree species in urban and peri-urban environments distinguishing these from those due to urbanization per se, on the ecosystem services and social benefits related to such forests and, hence, the importance of considering invasive alien tree species in urban planning
Forest habitat management and conservation priorities: a multi-scale and multi-taxon approach
Full text linkHabitat degradation, fragmentation and destruction are major causes of biodiversity loss. Management of natural and semi-natural habitats and control of human disturbance are fundamental to preserving their distinct character and biodiversity. Multiple levels must be considered when setting conservation management actions because species responses and ecological processes vary at different spatial scales. Legal instruments are now in place, with the European Union being among the pioneers, to protect and maintain habitats, and to implement management measures. Therefore, research efforts are needed to understand how to manage habitats in the current complex and constantly changing environmental and social context. For example, management of invasive alien species, which are among the most important threats to biodiversity, is a challenge nowadays. Furthermore, forest habitats are among the most important in terms of covered land and hosted species and, therefore, need particular attention. Indeed, several management approaches can be applied towards the achievement of biodiversity conservation objectives. However, the knowledge on the effects of different conservation management options on biodiversity is limited and must be further investigated.
The overall research follows a multi-disciplinary and integrated approach towards the conservation management of habitats particularly focusing on forest biodiversity. The thesis aims to (i) propose and test the application of integrated approaches in respect to conservation management of natural and semi-natural habitats focusing on forests, and (ii) to broaden the knowledge on the biodiversity effects of management abandonment. Six scientific papers, published and to be published, form the bulk of the thesis.
In the first paper a novel approach that aims to prioritize habitat conservation is proposed and tested in the Italian Alpine and Continental biogeographical regions. In the second paper a method is proposed and applied to assess the effects of human activities on habitats and species using as case study a forest road plan within a protected area. In the third paper a novel perspective on the potentiality of forest management to control invasive alien species is given. In the fourth paper a multi-scale landscape analysis was performed to identify habitat pattern changes due to different management regimes and to understand possible biodiversity implications. In the fifth paper a comparison between low intensity managed and abandoned forests was made to understand the effects on three beetle taxa. Finally, in the sixth paper the vegetation communities developing after management abandonment into novel forest habitats were investigated.
This thesis has highlighted that sound conservation management is fundamental to maintain the variety of habitats, both natural and semi-natural, occurring in Europe. On the one hand novel approaches, such as those presented in the thesis, are required to face the never-ending changes in the legal, economic, social and environmental conditions. On the other hand, deep knowledge on the effects of management and planning choices on habitats and species is essential for adapting to biodiversity’s intrinsic variability and complexity in order to achieve conservation goals
On recent secondary stands of black locust (Robinia pseudoacacia L.) and their plant diversity in a north-eastern Italian region
No full textItalian forest cover has been increasing, mainly as a result of the spontaneous expansion of tree species over abandoned land. Hence, it is important to understand the consequences of such phenomenon on biodiversity. Of increasing concern, in such a context, are the consequences brought by the spread of alien tree species on plant diversity. A sample (n=32) of secondary stands (age ≤ 36 y) dominated by black locust (Robinia pseudoacacia L.), an invasive alien species, were investigated within a north-eastern Italian region, by considering the general characteristics of such stands and by focusing on the vascular plant diversity. Results have highlighted the ability of black locust of invading sites owing a broad range of characteristics and its tendency of forming pure stands by dominating the overstory. A total of 22 and 185 plant species were collected in the tree and in the understory layer, respectively. Furthermore, site species richness were highly variable, both in the tree (range 1-6) and in the understory layer (range 9-42). Nitrogen demanding species were the most frequent, but the number of species typical of woodlands (mean 3.7) and of open-ground environments (mean 1.5) contrasts the thought that these forests are poor and not interesting from the plant diversity perspective. Further research should consider other taxa and focus on a range of stand development stages
Accessibility to urban parks: Comparing GIS based measures in the city of Padova (Italy)
Full text linkAccessibility to urban green spaces is essential for urban dwellers’ health and well-being. For planning purposes different accessibility measures and indicators have been used. Some are only based on availability, others consider distance from residences, yet others rely on gravity-based methods that consider both supply and demand. Different indicators often provide diverse and sometimes contradictory results and many issues remain in developing a comprehensive measure of accessibility, and representativity problems remain in matching indices with reality. In this study different accessibility measures have been developed and applied to the urban parks of the city of Padova, in northeastern Italy. Effectiveness and reliability of ten indicators derived from these measures, in identifying needs, inadequacies and disparities in park access have been tested at the urban unit scale. The study confirmed that multiple indicators need to be used to provide a useful planning tool for the pro..
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
New opportunities for urban regeneration by spontaneous woodlands: a socio-ecological assessment from Italy
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