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Processes of community development and responses of ecosystems to climate change
Get PDFOur studies focus on attempting to understand the role of decomposer-primary producer linkages in successional dynamics. We are testing a series of hypotheses that relate changes in plant species composition during succession to changes in activity and structure of the soil microfloral and faunal community, dynamics of soil organic matter, and availability of soil nutrients. As these successional patterns are identified, they are being applied to understanding specific processes and mechanics involved in ecosystem development during recovery from moderate and severe disturbances. These findings are then being used in conjunction with simulation models to assess potential effects of climate change on ecosystems. Our research involves field studies in northwestern Colorado and southeastern Washington, laboratory studies, and simulation modeling. Ongoing projects include studies of response patterns of primary producer and soil microbial communities to nutrient additions (N, P, and sucrose), the function of mycorrhizal fungi in plant community development, and the dynamics of litter decomposition under semiarid conditions. New studies are being implemented to investigate the significance of nutrient transfers from VAM fungi to plants and plant-root exudate interactions, and to relate this to understanding their roles in succession
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
Revegetation research on oil shale lands in the Piceance Basin
No full textThe overall objective of this project is to study the effects of various reclamation practices on above- and belowground ecosystem development associated with disturbed oil shale lands in northwestern Colorado. Plant growth media that are being used in field test plots include retorted shale, soil over retorted shale, subsoil materials, and surface disturbed topsoils. Satisfactory stands of vegetation failed to establish on unleached retorted shale during two successive years of seeding. All seedings with soil over retorted shale were judged to be successful at the end of three growing seasons, but deep-rooted shrubs that depend upon subsoil moisture may have their growth hampered by the retorted shale substrate. Natural revegetation on areas with various degrees of disturbance shows that natural invasion and succession was slow at best. Invasion of species on disturbed topsoil plots showed that after three years introduced seed mixtures were more effective than native mixtures in occupying space and closing the community to invading species. Fertilizer appears to encourage the invasion of annual plants even after the third year following application. Long-term storage of topsoil without vegetation significantly decreases the mycorrhizal infection potential and, therefore, decreases the relative success of aboveground vegetation and subsequent succession. Ecotypic differentation related to growth and competitive ability, moisture stress tolerance, and reproductive potential have been found in five native shrub species. Germplasm sources of two grasses and two legumes, that have shown promise as revegetation species, have been collected and evaluated for the production of test seed. Fertilizer (nitrogen) when added to the soil at the time of planting may encourage competition from annual weeds to the detriment of seeded species
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
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Nitrogen availability as a control mechanism of secondary succession within a semiarid shrubland ecosystem
Get PDFThree experiments were conducted within a semiarid shrubland to test the role of nitrogen availability as a control mechanism in secondary succession. Secondary succession patterns were documented for seven years and effects of increased and decreased N availability levels, fumigation, and competition by early-seral species were tested. Differential responses by seral species were determined and related to successional patterns. Nitrogen availability was found to be a primary mechanism controlling the rate of succession. Relative growth rate was an important factor determining which species initially dominated and N availability became the primary control factor by the third year. As N availability increased, the rate of succession decreased. Conversely, as N availability was decreased, the rate of succession increased. The abundance of annuals was increased and abundance of perennials decreased by increased N availability. Tissue N concentration was related to lifeform and seral position, and these relationships were important in the transition from early- to mid-seral stages. Decomposer subsystem dynamics were correlated with seral community dynamics. The effect of fumigation was minimized by initially planting with late-seral species. A conceptual model of secondary succession is presented based on N availability, relative growth rate, lifeform, and decomposition dynamics
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Revegetation manual for the environmental restoration contractor
Get PDFThe purpose of this manual is to provide guidance and general guidelines for the revegetation of remediation waste sites and other disturbed areas on the Hanford Site. Specific revegetation plans will be developed using guidance from this manual. Locations, resources, and funding will dictate the specific revegetation design at each disturbed area. Disturbances have occurred to some of the ecological communities of the Hanford Site. Many of these disturbances are the result of operations of the Hanford Site, including Comprehensive Environmental Response, Compensation, and Liability Act of 1980 waste sites on small portions of the Hanford Site. There were, however, extensive disturbances to the native vegetation prior to operations of the facility. These resulted from cultivation, grazing, fire, and the introduction of exotics. Revegetation planning must take into account these early disturbances, as well as the later ones
Reclamation studies on oil shale lands in northwestern Colorado
Get PDFThe overall objective of this project is to study the effects of various reclamation practices on above- and belowground ecosystem development associated with disturbed oil shale lands in northwestern Colorado. Plant growth media that are being used in field test plots include retorted shale, soil over retorted shale, subsoil materials, and surface disturbed topsoils. Some of the more significant results are: (1) a soil cover of at least 61 cm in conjunction with a capiallary barrier provided the best combination of treatments for the establishment of vegetation and a functional microbial community, (2) aboveground production values for native and introduced species mixtures are comparable after three growing seasons, (3) cover values for native species mixtures are generally greater than for introduced species, (4) native seed mixtures, in general, allow greater invasion to occur, (5) sewage sludge at relatively low rates appears to provide the most beneficial overall effect on plant growth, (6) cultural practices, such as irrigated and mulching have significant effects on both above- and belowground ecosystem development, (7) topsoil storage after 1.5 years does not appear to significantly affect general microbial activities but does reduce the mycorrhizal infection potential of the soil at shallow depths, (8) populations of mycorrhizal fungi are decreased on severely disturbed soils if a cover of vegetation is not established, (9) significant biological differences among ecotypes of important shrub species have been identified, (10) a vegetation model is outlined which upon completion will enable the reclamation specialist to predict the plant species combinations best adapted to specific reclamation sites, and (11) synthetic strains of two important grass species are close to development which will provide superior plant materials for reclamation in the West
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Revegetation studies on oil shale related disturbances in Colorado
No full textAn interdisciplinary research project was initiated in 1976 to provide both basic and applied information that would aid in the reestablishment of natural functioning ecosystems on land disturbances associated with energy development. The approach included field, laboratory, and greenhouse experiments designed to provide both structural and functional information about disturbed ecological systems in the semiarid west. This report presents results from the sixth year of the study. Separate abstracts have been prepared for each of the 4 studies reported for inclusion in the Energy Data Base. (DMC
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
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