1,721,043 research outputs found
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
Habitat preference in the yellow-tailed woolly monkey (lagothrix flavicauda) at Yambrasbamba, Peru
No full textElectronic Thesis or DissertationWe assessed how habitat use and preference in the endemic, and Critically Endangered, yellow-tailed woolly monkey (Lagothrix flavicauda) are linked to forest structure and composition. The study took place in the community of Yambrasbamba in Northeastern Peru. Very little is known about the spatial distribution and habitat preference of L. flavicauda. Our objective is to identify and highlight the characteristics of habitats most utilized by L. flavicauda in order to contribute to its conservation by providing information that will be useful for the selection of priority sites for habitat protection, and to improve habitat quality. The study site was classified into three different use zones, high, medium, and low use, according to the number of presence records collected from May 2013 to February 2014 for one group of L. flavicauda. Forest structure and composition were assessed for all use classes using the Gentry vegetation transects methodology. Results show great variation in species composition across the three use zones. Food plants have, predominately, greater density, dominance and ecological importance in high use zones. Use zones presented similar forest structure, a reverse J-shape diameter distribution. None of the structural variables analyzed seem to be related to preference in L. flavicauda
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
Habitat-level mapping of mangrove cover trends in Ciénaga de Zapata, Cuba, using landsat imagery and local knowledge
No full textElectronic Thesis or DissertationThe mangrove forests of Ciénaga de Zapata, Cuba, are of critical importance from both biodiversity and ecosystem service perspectives. The peninsula is home to more than 1,000 invertebrate species, more than 80 percent of the island’s total bird species, and numerous fish, mammals, and reptiles, including the Cuban crocodile (Crocodylus rhombifer) and Cuban gar (Atractosteus tristoechus), two species found only in Cuba. Zapata’s mangroves also support populations of sport and commercial fish such as bonefish (Albula vulpes), tarpon (Megalops atlanticus), permit (Trachinotus falcatus), and snook (Centropomus undecimalis). Despite the ecological importance of Zapata’s mangroves, no published work has documented any changes in the forests’ extent or distribution throughout the past two decades. This project combined unsupervised classification and visual interpretation of Landsat imagery with local knowledge to quantify and map area changes in Zapata’s mangrove forests from 1994 to 2014. Habitat zones mapped by local stakeholders were used to measure and compare mangrove change at the scale of individual species’ preference areas. Study results demonstrated a negligible (1.20 percent) decrease in total mangrove area during the study period. However, changing socio-political and economic dynamics between the United States and Cuba could precipitate rapid development along nearby coastal locations in the near future, and these results provide necessary baseline information against which to measure future pressures on Zapata’s mangroves at the cusp of a period of potentially substantial future change
Riparian vegetation response to streamflow alteration due to dam construction in a range of rivers across the United States
No full textElectronic Thesis or DissertationHydrologic variability plays a major role in structuring the riparian vegetation within river ecosystems. This study evaluates the spatial and temporal response of riparian vegetation to altered flow regimes below 16 river dams across the contiguous United States using a combination of a holistic Environmental Flow Assessment approach and satellite remote sensing. River flows were characterized using thirty-three (33) different Indicators of Hydrologic Alteration (IHA) using the Range of Variability Approach (RVA). The alterations of riverflows were determined for post-dam scenarios comparing between the pre-dam and post-dam IHAs. Of the 16 locations assessed, 2 showed low levels, 11 moderate and 3 high levels of alteration. Change detection of riparian vegetation revealed an increase at majority of the sites (10 of the 16) immediately after the construction of the dam. Also, in a majority of the locations a decrease (10 of the 16) in vegetation was observed at the 1 year post-dam completion mark. Analyses show that vegetation change effects due to flow regime alterations below smaller dams occurred at shorter time spans (1-year post-completion) than larger dams (5-year post completion). It is inferred that categorizing dams based on capacity was successful in understanding effects on the vegetation extents better. In addition to the in-stream flow paradigm, regional climate and geomorphology are also identified as driving factors of riparian vegetation regulation. The need for a multi-factor model that drives annual changes in riparian zones is recognized to make better-informed decisions on sustainable dam operations
Scale effect of contaminant transport in saturated porous media identified by the time fractional advection-dispersion equation
No full textElectronic Thesis or DissertationTime nonlocal transport models such as the time fractional advection-dispersion equation (t-fADE) were proposed to capture well-documented non-Fickian dynamics for conservative solutes transport in heterogeneous media, with the underlying assumption that the time nonlocality (which means that the current concentration change is affected by previous concentration load) embedded in the physical models can release the effective dispersion coefficient from scale dependency. This assumption however has never been systematically examined using real data. This study fills this historical knowledge gap by capturing non-Fickian transport (likely due to solute retention) documented in literature (Huang et al. 1995) and observed in our laboratory from small to intermediate spatial scale using the promising, tempered t-fADE model. Fitting exercises show that the effective dispersion coefficient in the t-fADE, although differing subtly from the dispersion coefficient in the standard advection-dispersion equation, increases nonlinearly with the travel distance (varying from 0.5 to 12 m) for both heterogeneous and macroscopically homogeneous sand columns. Further analysis reveals that, while solute retention in relatively immobile zones can be efficiently captured by the time nonlocal parameters in the t-fADE, the retention-independent solute movement in the mobile zone is affected by the spatial evolution of local velocities in the host medium, resulting in a scale-dependent dispersion coefficient. The same result may be found for the other standard time nonlocal transport models, such as the well-known multi-rate mass transfer (MRMT) model and the hydrologic version of continuous time random walk (CTRW), that separate solute retention and jumps (i.e., displacement). Therefore, the t-fADE with a constant dispersion coefficient cannot capture scale-dependent dispersion in saturated porous media, challenging the application for stochastic hydrogeology methods in quantifying real-world, pre-asymptotic transport. Hence, improvements on time nonlocal models using, for example the novel subordination approach, are necessary to incorporate the spatial evolution of local velocities without adding cumbersome parameters. Future improvements are also explored, given knowledge obtained in this study
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
Effects of wind disturbance and salvage harvesting on ectomycorrhizal and saprotrophic macrofungi in a pine woodland
No full textElectronic Thesis or DissertationNatural disturbances alter the biophysical conditions of ecosystems, influencing patterns of structure, composition, and successional dynamics. These disturbances often create structural legacies that promote biodiversity and ecosystem function. Following high severity natural disturbance in forest ecosystems, land-managers sometimes employ salvage harvesting to harvest trees killed or damaged by the disturbance agent. Despite its widespread practice, the effects of salvage harvesting on many ecosystem functions and species assemblages are still poorly understood. This study presents the first attempt to document and analyze the effects of salvage harvesting on macrofungal communities following catastrophic wind disturbance. On 27 April 2011, an EF3 tornado damaged forest stands within the Oakmulgee Ranger District of the Talladega National Forest in west-central Alabama, USA. Following the event, some stands were subject to salvage harvesting. In 2016, I established three treatments, undisturbed, tornado disturbed, and salvage harvested, in stands that were dominated by Pinus palustris P. Miller prior to the 2011 disturbance events. Within each treatment, 20 0.04 ha fixed radius plots were established to collect forest inventory data. Additionally, five 10 x 100 m plots were established in each treatment and inventoried for macrofungal sporocarps between May and November 2016. Throughout the sample period, 546 occurrences of 84 macrofungal species were recorded. Tornado disturbed plots hosted the highest macrofungal species richness overall. Undisturbed plots hosted the highest species richness for ectomycorrhizal macrofungi. Salvage harvested plots had reduced species richness for both saprotrophic and ectomycorrhizal macrofungi compared to tornado disturbed plots. Non-metric multidimensional scaling ordination and permutational multivariate analysis of variance indicated that all three treatments differed in macrofungal community composition. The results indicated that salvage harvesting following catastrophic wind disturbance has the capacity to reduce macrofungal species richness and fruiting abundance. The reduction in deadwood volume and alterations to the ectomycorrhizal-associating plant community documented at salvage harvested sites is likely responsible for the observed differences in macrofungal fruiting patterns. The implications of reduced macrofungal richness in the early stages of forest development following catastrophic disturbance should be subject to long-term studies
Mapping Belizean bonefish, permit, and tarpon fisheries and their threats
No full textElectronic Thesis or DissertationThis research uses a multidisciplinary approach to provide a broad perspective on the location of Belizean Bonefish, Permit, and Tarpon (BPT) fisheries and their threats. Participatory mapping and ethnographic surveying of the professional sport-fishing guide community was completed. In addition to reporting the locations of BPT and their threats, this research uses high resolution satellite remote sensing (3m) to examine seagrass changes in a portion of the South Water Caye Marine Reserve (SWCMR) from 2001 to 2016. Professional sport fishing guides ranked gillnets as the most threatening activity to Belizean BPT stocks, and most guides reported that the quality of sport-fishing of BPT has declined over their career. One of these threats is the loss of seagrass, a crucial habitat for BPT. Remote sensing analysis of a study area in the SWCMR suggests spatial variability of seagrass decline and regeneration, with a 2.5% average increase in overall seagrass distribution with at least 30% cover, with most of the regeneration occurring in shallow waters sheltered from ocean wave action. Decline in seagrass distribution was observed in deeper waters subjected to ocean currents and potential dredging. The results of both studies are assimilated to discuss potential avenues of research and the prioritization of recreational fisheries management in Belize
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