1,720,956 research outputs found
Pollinator distribution in patches of suitable habitat depends more on patch isolation than on floral abundance
Full text linkIntrinsic complexity of real-world systems makes particularly difficult to decipher which factors influence the dispersal of pollinators in the landscape matrix and their distribution among patches of suitable habitat.
Saltmarshes are an ideal and naturally simplified landscape to study the ability of different groups of pollinators to disperse across a landscape matrix, as they consist of a matrix of flooded areas surrounding patches of suitable habitat with different degrees of isolation from the mainland and different levels of floral abundance. We hypothesise that pollinator distribution to flowering plants depends more on patch isolation than on floral abundance with pollinator richness and visitation rates to flowering plants decreasing with increasing distance from the mainland. To this end, we established 60 permanent plots at varying distances from the mainland and monitored pollinator visitation to entomophilous plants. We also quantified the reproductive success of entomophilous species in the surveyed plots by calculating fruit set. We found that the pollinator community of
saltmarshes consisted only of flying pollinators with good dispersal abilities, while we recorded no flightless pollinator species. Both pollinator richness and visitation rate decreased with increasing distance of patches of suitable habitat from the mainland, affecting reproductive success of a non-autogamous entomophilous species.
Interestingly, floral abundance did not affect pollinator richness and visitation rate to flowering plants, nor did it affect reproductive success of target plant species. In saltmarshes, the pollinator distribution depends more on patch distance from the mainland than on floral abundance. Our results suggest that the presence of patches of suitable habitat in a landscape matrix does not necessarily ensure the maintenance of pollinators. Rather, our results suggest that suitable habitat isolation is the critical factor in pollinator dispersal and distribution that should be considered to improve landscape matrix permeability to pollinators
Ecological intensification: multifunctional flower strips support beneficial arthropods in an organic apple orchard
Full text linkFlower strips are a fundamental part of agri-environment schemes in the Common Agricultural Policy (CAP). Although vegetation is central for many arthropod groups, a few studies have evaluated the effects of flower strip structural and functional attributes on arthropod communities. In this study, we explored the relationship between flower strip attributes and the abundance of different arthropod functional groups in annual flower strips located in an organic apple orchard. We surveyed plant and arthropod communities in 30 1 m x 6 m plots. In each plot, we collected data on species composition and vegetation structure (e.g., total cover, density, number of floral displays). For each plant species, we also retrieved data on leaf palatability and nutritional value. Arthropods were collected using sweep netting technique. Structural and functional attributes of the flower strip revealed a crucial role in regulating arthropod abundance, which however depended on the specific arthropod functional group. We identified three main attributes (plant species richness, composition, and vegetation density) of flower strips that should be considered when implementing multifunctional flower strips. Specifically, plant species richness to ensure complementarity of resources and niches, plant species composition to ensure complementary floral resources, and vegetation density to ensure sheltering microhabitats and suitable microclimatic conditions and to increase the density of floral resources. Our results suggest that by considering structural and functional attributes of flower strips, it is possible to design multifunctional flower strips with greater effectiveness as measures for ecological intensification
Pollinator abundance, not the richness, benefits from urban green spaces in intensive agricultural land
No full textIn the debate on the impact of urbanisation on biodiversity, two characteristics of urbanisation have been identified that mainly determine the extent of the impact, namely the level of urbanisation and the landscape context. More recently, it has been theorised that urban sprawl in an intensive agricultural landscape has a positive influence on pollinators by increasing habitat and resource availability. Using the eastern Po Plain (north-eastern Italy) as a model system, we investigated the relationship between attributes of landscape composition and configuration, pollinator richness and visits in 39 randomly selected permanent plots. Contrary to expectations, we found no relationship between urban sprawl and pollinator species richness. Conversely, descriptors of urban sprawl such as landscape heterogeneity and the proportion of urban green spaces had a positive influence on the number of pollinator visits. This suggests that urban sprawl, when occurring in an intensive agricultural land, has a positive effect on the abundance of local pollinator populations, while it may not promote pollinator richness due to limited immigration opportunities in the matrix of intensive agricultural land. Our results emphasise the importance of urban green spaces in supporting pollinator communities, but also the need to improve the heterogeneity and permeability of the landscape matrix for biodiversity to enhance pollinator conservation in human-modified landscapes
Systems modeling for agroecology and land restoration
Full text linkAt the time of the development of H.T. Odum's energy system theory, the field of agroecology was not yet defined as a scientific discipline. Nevertheless, minimal models were already proposed to describe what today are referred to as agroecological and land restoration practices. In this work, we review literature from the early 1970s to nowadays by tracing a red thread to connect the original formulation of the energy system language with the current understanding of agroecology and land restoration. In the light of this picture, we draw a general application of the energy systems language and modeling to describe land use and land restoration dynamics. We apply this scheme to model and reproduce the land use dynamics of a real restoration project led by a farmers’ family in Mato Grosso do Sul, Brazil. The case study of Sitio Luciana shows the transformation of a monocultural and partially degraded land into a biodiverse, food-producing area by developing a complex agroecosystem owing to human work and farmers’ local ecological knowledge. As an application of the energy system language, we build a dynamical model that closely reproduces observed GIS-retrieved patterns (global RMSE ∼2%), highlighting human-mediated ecological succession—targeted at restoring Atlantic Forest—as key to agroecosystems development, and offering scientific validation of the farmers’ local ecological knowledge. This work shows that the energy systems theory and modelling approach, as inherited from H.T. Odum, can: 1) deepen the understanding of local agroecosystem and land system dynamics, including human management; 2) inform the development of non-linear models grounded in both scientific and local knowledge; and 3) offer conceptual guidance for land management and policy strategies
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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