1,720,984 research outputs found
Incorporating tacit knowledge of soil-landscape relationships for digital soil and landscape mapping applications
No full textThe purpose of this dissertation is to develop and test a quantitative model for classifying hillslope position, using digital terrain analyses. The model is calibrated by, and validated against observations of soil scientists, while working in the field. Classifying the landscape into the five standard hillslope elements, or positions, in a manner that is transferable between landscapes, can greatly help soil sampling and mapping endeavors. This dissertation begins by reviewing the role of environmental predictors in the conceptual models of soil geographers, at different scales, via a historical overview of soil maps. I conclude that the sum experience of soil science has recognized a hierarchy of scale in three of Dokuchaev's five factors of soil formation, proceeding in decreasing phenomenon scale: 1) climate, 2) parent material, and 3) relief. That relief is at the smallest phenomenon scale suggests that delineations on modern, county-level soil maps can perhaps be best disaggregated by increasing the resolution and applicability of topographic base maps used to construct those maps. Today, LiDAR technology provides high resolution, elevation data, but requires contextual information if it is to be used for mapping landscape elements and soil cover patterns. Soil geomorphic research has long recognized the relationship between soil development and the contextual metric of hillslope position. However, the definitions for hillslope positions are based on conceptual models that synthesize multiple terrain parameters, which are not always easily observed in elevation data alone. This dissertation develops and utilizes methods for calibrating analysis scales, classification breaks, and model structures to soil scientists' field observations, as a means of capturing their expert knowledge of hillslope position. The result is a quantitative definition of hillslope position, which can be applied in digital terrain analysis. The optimal analysis scales observed for slope gradient, profile curvature, and relative elevation were 9 m, 63 m, and 135 m, respectively. The best performing model differentiates areas on the landscape using a decision tree hierarchy that divides the landscape first by slope gradient (breaks at 1.4 and 2.9\ub0), then by profile curvature and relative elevation. The final model was also tested for sensitivity to quality of the digital elevation data used to calculate the various slope parameters. Because of the importance of analysis scale, grid resolution was equally important for obtaining accurate results as uncertainty in the elevation attribute. By using the analysis scales, classification breaks, and model structure identified in this dissertation, hillslope position was determined consistently across a variety of Midwestern U.S. landscapes. The resulting hillslope position base map provides quantitative criteria for common soil map unit boundaries, study of geomorphic landscape patterns, and sampling strategies. This classification of hillslope position not only has the potential to increase soil map resolution by disaggregation of current delineations, but also offers consistency. Consistency increases the reliability of soil maps and allows for comparisons between landscapes.Thesis (Ph. D.)--Department of Geography, Michigan State University, 2013Includes bibliographical reference
Glossic horizon formation in coarse-loamy bisequal soils
No full textCoarse-loamy soils with glossic horizons have not been extensively studied in the upper Great Lakes region, and thus, questions remain regarding their genesis. As a first step toward resolving this problem, I examined glossic horizon development in two calcareous coarse-loamy, bisequal soils in NE Lower Michigan. Data collected from these soils were integrated with published pedogenic models to develop a unifying model that illustrates the most likely pathways of glossic horizon formation in similar soils of the region. The model involves the acidification of a calcareous parent material, followed by mechanical translocation of clay (and associated Fe-oxides) and fine silt to a preferred (illuvial) zone under oxidizing conditions. The illuvial zone, a Bt horizon, eventually functioning as an aquitard during seasonally wet periods, facilitates temporary localized saturation and change in redox status near its upper boundary. Subsequently, clay-bound Fe compounds are reduced and eluviated from the zone, resulting in the destabilization, degradation, and remobilization of illuvial cutans to form glossic features. The expression of glossic features evolve gradually as a result of micro-erosion and eluviation of clays and fine silts from preferred locations within the degrading zone, the magnitude of which follows a distinct sequence at progressive stages of the degradational process: (1) fine clay, (2) coarse clay, and finally, (3) fine silt. With time, the glossic character of the degrading zone becomes increasingly pronounced, until ultimately, little to no evidence of the former Bt horizon remains. At this point, Bt horizon morphology has progressed through glossic to an albic horizon.Thesis (M.S.)--Michigan State University. Geography, 2020Includes bibliographical references (pages 180-192
Characterizing, mapping, and interpreting thin loess deposits in the western Upper Peninsula of Michigan
No full textThis research examines the distribution, thickness and textural characteristics of thin, patchy, loess deposits in the western Upper Peninsula of Michigan. Although local soil surveys have documented loess in Baraga, Marquette and Iron Counties, at the northeastern margins of the North American, midcontinent loess region, this thesis is the first detailed study of these loess deposits. Within the study area, loess is ~ 30-60 cm thick and is usually underlain by sandy glacial deposits. Where the loess deposits are thin, it appears that pedoturbation processes have likely mixed some of the lower, sandy materials into the loess. For this reason, most of the loess has a bimodal continuous textural curve, with a primary modal particle-size within the 25-75 \u3bcm fraction (the loess) and a secondary mode in the 250-500 \u3bcm fraction (the in-mixed sand). These loess deposits were likely sourced from both distant and local areas, including ground moraines, outwash plains, and the floodplains of small meltwater streams. Within the Peshekee Loess region, I have identified four loess sections, each of which has unique characteristics that set it apart from the whole: the Amasa, Covington, Republic, and Champion sections. This research (1) recognizes multiple source areas for loess, (2) develops and interprets textural data on the thin Peshekee Loess, and (3) documents the effects of mixing within these loess deposits. This research is the first to document both the extent and textural characteristics of loess deposits situated at the extreme margins of much larger and thicker, regional-scale, loess region.Thesis (M.S.)--Michigan State University. Geography, 2011Includes bibliographical reference
Soils: genesis and geomorphology
No full textThe book's introductory chapters in soil morphology, mineralogy, chemistry, physics, and organisms prepare the reader for the more advanced treatment that follows. Unlike its competitors, this textbook devotes considerable space to discussions of soil parent materials and soil mixing, along with dating and paleoenvironmental reconstruction techniques applicable to soils. Although introductions to widely used soil classification systems are included, theory and processes of soil genesis and geomorphology form the backbone of the book. Replete with more than 550 high-quality figures and photos and a detailed glossary, this book will be invaluable for anyone studying soils, landforms, and landscape change anywhere on the globe
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
- …
