Design ed implementazione di funzionalita' di ricerca in un sistema di visualizzazione tridimensionale di tipo Information Landscape

In questo lavoro si sono integrate funzionalita' di un semplice motore di ricerca ed e' stato riprogettato il sistema di interfacciamento in un visualizzatore di ambienti tridimensionali per grandi quantita' di testo

Hybrid datasets: integrating observations with experiments in the era of macroecology and big-data

Understanding how increasing human domination of the biosphere affects life on earth is a critical research challenge. This task is facilitated by the increasing availability of open-source data repositories, which allow ecologists to address scientific questions at unprecedented spatial and temporal scales. Large datasets are mostly observational, so they may have limited ability to uncover causal relations among variables. Experiments are better suited at attributing causation, but they are often limited in scope. We propose hybrid datasets, resulting from the integration of observational with experimental data, as an approach to leverage the scope and ability to attribute causality in ecological studies. We show how the analysis of hybrid datasets with emerging techniques in time series analysis (Convergent Cross Mapping) and macroecology (Joint Species Distribution Models) can generate novel insights into causal effects of abiotic and biotic processes that would be difficult to achieve otherwise. We illustrate these principles with two case-studies in marine ecosystems and discuss the potential to generalize across environments, species and ecological processes. If used wisely, the analysis of hybrid datasets may become the standard approach for research goals that seek causal explanations for large-scale ecological phenomena. This article is protected by copyright. All rights reserved

Nutrient enrichment stimulates herbivory and alters epibiont assemblages at the edge but not inside subtidal macroalgal forests

AbstractNutrient enrichment is a major threat to subtidal macroalgal forests. Several studies have shown that nutrient inputs can enhance the ability of opportunistic algal species to acquire space freed by disturbance, at the expense of architecturally complex species that form forests. However, competition between canopy- and turf-forming macroalgae is not limited to the aftermath of disturbance. Canopy-forming macroalgae can provide suitable substratum for diverse epibiont assemblages, including both algae (epiphytes) and sessile invertebrates (epizoans). Despite evidence of enhanced epiphyte loading under eutrophic conditions, few experimental studies have assessed how nutrient enrichment influences the structure of epibiont assemblages on canopy-forming macroalgae at the edge versus inside forests. In oligotrophic waters of the NW Mediterranean, we experimentally tested the hypothesis that nutrient-driven proliferation of opportunistic epiphytic algae would affect the performance of the fucoid, Carpodesmia brachycarpa, and reduce the richness and abundance of the epizoan species they support. We predicted negative effects of nutrient enrichment to be greater at the edge than inside forests and on thalli that had recovered in cleared areas than on those within undisturbed canopy stands. Nutrient enrichment did not affect the photosynthetic efficiency and reproductive output of C. brachycarpa. By contrast, it enhanced herbivore consumption and decreased the cover and diversity of epizoans at forest edges, likely by stimulating the foraging activity of Arbacia lixula, the most abundant sea urchin in adjacent encrusting coralline barrens. Fertilization of areas inside forests had no effect on either C. brachycarpa or epibiont assemblages. Finally, nutrient enrichment effects did not vary between cleared and undisturbed areas. Our results show that moderate nutrient enrichment of oligotrophic waters does not necessarily cause the proliferation of epiphytes and, hence, a strengthening of their competitive effects on canopy-forming macroalgae. Nevertheless, enhanced herbivory damage to fertilized thalli at forest edges suggests that fragmentation could reduce the resilience of macroalgal forests and associated epibiont assemblages to nutrient enrichment

Propagules are not all equal: traits of vegetative fragments and disturbance regulate invasion success

Invasion success is regulated by multiple factors. While the roles of disturbance and propagule pressure in regulating the establishment of non-native species are widely acknowledged, that of propagule morphology (a proxy for quality) is poorly known. By means of a multi-factorial field experiment, we tested how the number (5 versus 10) and quality (intact, without fronds or without rhizoids) of fragments of the clonal invasive seaweed, Caulerpa cylindracea, influenced its ability to establish in patches of the native seagrass, Posidonia oceanica, exposed to different intensities of disturbance (0, 50 or 100% reduction in canopy cover). We hypothesized that the ability of fragments to establish would be greater for intact fragments (high quality) and reduced more by frond removal (low quality) than rhizoid removal (intermediate quality). At low propagule pressure or quality, fragment establishment was predicted to increase with increasing disturbance, whereas, at high propagule pressure or quality, it was predicted to be high regardless of disturbance intensity. Disturbance intensity, fragment number and quality had independent effects on C. cylindracea establishment success. Disturbance always facilitated fragment establishment. However, fragments retaining fronds, either intact or deprived of rhizoids, had higher establishment success than fragments deprived of fronds. Increasing propagule number had weak effects on the cover of C. cylindracea. Our results demonstrate that propagule traits enabling the acquisition of resources made available by disturbance can be more important than propagule number in determining the establishment and spread of clonal non-native plants. More generally, our study suggests that propagule quality is a key, yet underexplored, determinant of invasion success

Fatigue life prediction of notched components: a comparison between the theory of critical distance and the classical stress-gradient approach

Abstract Fatigue life prediction for machine components is a key factor in the industrial world and several methods can be traced in technical literature to estimate life of notched components. The paper correlates the classical stress-gradient approach, here after called support factor (SF) method, proposed by Siebel, Neuber and Petersen with the modern theory of critical distance (TCD) approach by Tanaka and Taylor. On the one hand, the main asset of the SF method is that it relies only on the knowledge of the maximum stress and stress gradient in the hot spot. By contrast, the TCD needs the calculation of the stress distribution for a finite depth inside the material. On the other hand, the main drawback of the SF method is that the material parameter ρ* is available only for a limited collection of materials and moreover the experimental procedure to retrieve this parameter is not clearly defined in the technical literature. In order to overcome this limitation, the paper investigates the correlation between the material parameter ρ* and the critical distance L of the TCD by relying on a specific stress function. A comparison between the SF method and the TCD is then performed by considering three different benchmark geometries: a general V-notch in a plate, a pressure vessel and an industrial oleo-hydraulic distributor. Effective stresses are analytically retrieved and compared using both methods for the first two benchmarks and with the help of an elastic finite element analysis for the last one. The resus appear good in terms of fatigue life prediction, especially for the industrial case study

Avoiding “Paper Parks”: A Global Literature Review on Socioeconomic Factors Underpinning the Effectiveness of Marine Protected Areas

Marine protected areas (MPAs) are a common management tool for preserving marine biodiversity and halting resource depletion. Despite the number of MPAs rapidly increasing worldwide, there are concerns over the full achievement of their objectives. Indeed, in some cases—the phenomenon of so-called “paper parks”—protected areas totally fail to achieve their conservation and socioeconomic targets. Therefore, identifying the factors underpinning MPA success or failure is crucial to increase their effectiveness. To achieve this goal, we performed a global literature review on the socioeconomic factors that managers should pursue to enhance MPA effectiveness on a global scale. A search of the Scopus database, using strings of keywords connected by Boolean operators, generated a batch of 715 items, out of which 68 were retained after the application of inclusion/exclusion criteria. Six other articles were added through the scanning of the literature cited in selected papers. We grouped MPA success-factors into 13 main groups and ranked them according to the frequency of citation in the literature. Our findings identify stakeholder involvement, increasing communication and awareness between specific stakeholder groups, as well as ensuring appropriate enforcement and monitoring, control and surveillance, as the leading factors for MPA success. Our results will assist in the process of upcoming global expansion of MPAs, thus contributing to improving conservation of marine biodiversity and associated livelihoods

Facilitation and the niche: Implications for coexistence, range shifts and ecosystem functioning

Viewing facilitation through the lens of the niche concept is one way to unify conceptual and empirical advances about the role of facilitation in community ecology. We clarify conceptually and through examples from marine and terrestrial environments how facilitation can expand species' niches and consider how these interactions can be scaled up to understand the importance of facilitation in setting a species' geographic range. We then integrate the niche-broadening influence of facilitation into current conceptual areas in ecology, including climate change, diversity maintenance and the relationship between diversity and ecosystem functioning. Because facilitation can influence the range of physical conditions under which a species can persist, it has the potential to mitigate the effects of climate change on species distributions. Whereas facilitation has mostly been considered as a diversity-promoting interaction by ameliorating abiotic stresses, if facilitated species' niches expand and become less distinct as a result of habitat amelioration, the forces that maintain diversity and promote coexistence in regions or habitats dominated by the facilitator could be reduced (i.e. the sign of the effects of facilitation on populations could be species-specific). Finally, shifting or broadening ecological niches could alter the relationship between diversity and ecosystem functioning. A niche-based perspective on the effects of facilitation can foster a greater mechanistic understanding of the role played by facilitation in regulating species coexistence, range shifts and ecosystem functioning in a changing world