1,722,634 research outputs found
Spatial distributions of tropical tree species in northern Vietnam under environmentally variable site conditions
No full textEcological interactions of species and thus their spatial patterns may differ between homogeneous and heterogeneous forests. To account for this, techniques of point pattern analysis were implemented on mapped locations of tree individuals from two 1-ha tropicalforest plots in Vietnam. We analyzed the effect of environmental heterogeneity on tree distributions; spatial distribution patterns of dominant species; inter-specific associations; and conspecific associations between life stages. Our analyses showed that: environmental conditions were homogeneous at plot 1 but heterogeneous at plot 2; in both plots, all six dominant species were aggregated at various scales up to 30 m, and tree species were aggregated at larger scales in the homogeneous site than in the heterogeneous site; attraction between pairs of species was remarkably higher at the homogeneous site while negative associations were more frequent in the heterogeneous site; some species, H. kurzii, T. ilicifolia (homogeneous plot) and D. sylvatica, S. wightianum (heterogeneous plot), showed a lack of early life-stage individuals near conspecific adults. Moreover, additional clustering of young individuals was independent from conspecific adults, except D. sylvatica in both sites. These findings are consistent with the Janzen-Connell hypothesis. Overall, habitat heterogeneity influences spatial patterns and inter-specific associations of the tree species and evidences of self-thinning are shown in most species
Spatial patterns and demographics of Streblus macrophyllus trees in a tropical evergreen forest, Vietnam.
No full textStreblus macrophyllus is a shade-tolerant and subcanopy tree species common to tropical evergreen forests in northern Vietnam. However, its ecology is poorly known. We used spatial point pattern analysis to describe the spatial arrangement of tree individuals within a forest community dominated by S. macrophyllus. All individual trees with diameter at breast height larger than 2.5 cm in a 1-ha plot were mapped and measured. The overall pattern of this species was a regular distribution at scales up to 2 m. Its juveniles and subadults were strongly aggregated, but adult trees were regular at scales of up to 3 m, implying evidence of density dependent thinning. The spatial pattern of S. macrophyllus strongly affected the patterning of the whole plot. In S. macrophyllus, juveniles and subadults were similarly distributed relative to adults and showed additional clumping independent of the adults. The overall interspecific association between adults of other species and S. macrophyllus at different life-history stages also showed independence. We conclude that S. macrophyllus is a predominant competitor within the community and it follows a gap-phase regeneration mode
Modeling Surface Runoff and Evapotranspiration using SWAT and BEACH for a Tropical Watershed in North Vietnam, Compared to MODIS Products
No full textAccurate estimation of surface runoff (Q) and evapotranspiration (ET) is a challenging task but an important research topic because both Q and ET play vital roles in the study of the hydrological cycle, of climate change, water resources, flood management and so on. In this paper we will present the modeling method to estimate the daily Q and ET for a medium-sized watershed in the tropical region of the North of Vietnam using the Soil and Water Assessment Tool (SWAT) and Bridging Event and Continuous Hydrological (BEACH) models. The models were calibrated and validated for the river discharge for SWAT and evaporation (E) for BEACH in a 12 year period from 2001 to 2012. The simulated ETs by the models were compared with the satellite-based ET of MODIS products. Our simulation results show that the SWAT and BEACH models are capable of satisfactorily reproducing (with the NSE > 0.62 and R 2 > 0.78) the stream-gauged river discharge and the observed E, respectively. Daily ET varied from 0.3 to 14 mm day-1 and was highest from May to August and lowest from December to March. Although the monthly and yearly MODIS ETs were slightly higher than those of SWAT and BEACH, a strong relationship between them was found with a standard deviation ranging from three to 40 mm. A light decrease of ET values in the 12 years can be seen in the result analyses; however a longer simulation time might be needed to ensure this trend.Open-Access-Publikationsfonds 201
Spatial patterns and demographics of Streblus macrophyllus trees in a tropical evergreen forest, Vietnam.
No full textStreblus macrophyllus is a shade-tolerant and subcanopy tree species common to tropical evergreen forests in northern Vietnam. However, its ecology is poorly known. We used spatial point pattern analysis to describe the spatial arrangement of tree individuals within a forest community dominated by S. macrophyllus. All individual trees with diameter at breast height larger than 2.5 cm in a 1-ha plot were mapped and measured. The overall pattern of this species was a regular distribution at scales up to 2 m. Its juveniles and subadults were strongly aggregated, but adult trees were regular at scales of up to 3 m, implying evidence of density dependent thinning. The spatial pattern of S. macrophyllus strongly affected the patterning of the whole plot. In S. macrophyllus, juveniles and subadults were similarly distributed relative to adults and showed additional clumping independent of the adults. The overall interspecific association between adults of other species and S. macrophyllus at different life-history stages also showed independence. We conclude that S. macrophyllus is a predominant competitor within the community and it follows a gap-phase regeneration mode
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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