1,721,030 research outputs found
Understanding regional water resource dynamics due to land-cover/land-use and climate changes in the North Carolina Piedmont
Get PDFThe spatiotemporal distribution of freshwater resources on Earth is controlled by interacting climatologic, ecological, and physical processes. These dynamics are likely to change in the future due to climate and land cover changes with important implications for life on Earth. Ecosystem simulation models which couple these processes are increasingly relied upon to provide projections of probable future changes so that resources may be sustainably managed and future growth and development planned. The majority of these models depend critically on surface descriptions such as land cover and vegetation abundance obtained from remotely sensed images, and remote sensing methods have played an essential role in accurately parameterizing and implementing models at appreciable spatial scales. However, significant challenges exist for investigations adopting an integrated remote sensing and ecosystem simulation approach. This investigation sought to quantify the likely impacts of climate change and land cover change on the water cycle of the Eno River basin in central North Carolina. Special attention was paid to addressing and overcoming existing remote sensing methodological limitations related to mapping leaf area index (LAI) and land cover. Improved methods were developed and the resulting products used to parameterize two different ecohydrologic models which were then used to quantify the hydrological effects of various climate and land cover change scenarios. The improved methods are demonstrated to overcome several of the major existing limitations to mapping LAI and land cover accurately, consistently, and efficiently with diverse data sources. These improvements lead to greater confidence in simulated results and future projections. The results of this investigation highlight the dominant role that climate plays in structuring basin response, and indicate that future changes may increase water stress in the area, particularly under scenarios of reduced growing season precipitation.Doctor of Philosoph
Land cover and land use changes under forest protection and restoration in Tiantangzhai Township, Anhui, China
Get PDFDeforestation and forest regeneration are two key changes in the forest ecosystem that have profound impacts of the goods and services in terrestrial ecosystem. In late 1990s, China implemented Sloping Land Conversion Program (SLCP) and Natural Forest Protection Program (NFPP) aimed at forest protection and restoration. Using archived historical images, this study compared the land-cover/land-use (LCLU) changes before and after the programs and developed remote sensing indices to characterize the growth trajectory of Grain-For-Green (GFG) and natural forests. The results indicate substantial increase of natural forest cover during 2002-2013, compared with that during 1992-2002. The proposed indices revealed aggradation for both NFPP and GFG forests since the implementation of these policies. Further analysis found spatial variation of forest development depends on the topographic factors. This study reveals that SLCP and NFPP have been improving forest growth and development in the study area since the implementation of these policies.Master of Art
Land use/land cover change in Orange County, North Carolina from 1955 to 2001
Get PDFLand use/land cover change (LULCC) has significant implications in terrestrial ecosystem goods and services. Current studies on LULCC are primarily based on space-borne satellite images. These studies are limited by the data availability. In this study, I extend the land-use land cover change analysis back to 1955 for Orange County, North Carolina based on historical aerial photos. I also analyzed the spatial configuration of the landscapes based on pattern matrix analysis and geospatial analysis. Results show that the urban area increased from 11.31 km2 to 128.15 km2 from; the agricultural area decreased from 335.53 km2 to 259.81 km2; the forest area decreased from 676.95 km2 to 632.45 km2. The LULCC change is associated with land configuration and composition changes. Pattern metrics analysis shows that in 2001, Orange County has more scattered land use patches and smaller patch sizes than in 1955 and 1975. Semi-vairograms generated for conifer and hardwoods are changing both in shape and the key characteristic parameters with time. These results can provide essential information for land management and planning to achieve sustainable development of Orange County in the future
Empirical Evidence for the Association of the El Niño-Southern Oscillation with Terrestrial Vegetation Dynamics in the Western United States
Get PDFTiming of plant life cycle events (phenology) and annual plant productivity represent key interactions between the atmosphere and the biosphere, with implications and feedbacks for climate and ecosystem functions. The El Niño-Southern Oscillation (ENSO) system is the dominant source of interannual climate variability in the western United States, with important effects on temperature, precipitation, and drought. In this study, the connection between ENSO and terrestrial vegetation dynamics is examined using remotely sensed vegetation indices, eddy covariance flux tower observations, ENSO indices, and spatially-resolved climate data. El Niño events are associated with an increase in primary production throughout the western U.S., and with an earlier growing season in much of the Pacific Northwest and parts of the Southwest. The correlation between total annual production and the Southern Oscillation Index is highest in mid- to late-winter prior to the growing season, suggesting some predictive power in advance of the growing season.Master of Art
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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