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3111. [Article] A comparison of the teaching performance with the academic record of Oregon State University graduates in elementary education
Purpose of the Study: The purpose of this study was to evaluate the Oregon State University undergraduate elementary education program. More specifically, the investigation sought answers to the following ...Citation Citation
- Title:
- A comparison of the teaching performance with the academic record of Oregon State University graduates in elementary education
- Author:
- Gainor, Leo Charles
Purpose of the Study: The purpose of this study was to evaluate the Oregon State University undergraduate elementary education program. More specifically, the investigation sought answers to the following questions: 1. What are the graduates' judgments of pertinent areas of the elementary teacher education program? 2. To what extent does the, graduates' academic records affect their. judgments concerning the elementary teacher education program? 3. How do the graduates' administrators rate the graduates' teaching competencies? 4. Is there a relationship between administrators' ratings of graduates and graduates' academic record? Procedures: The study utilized two questionnaires and follow-up interviews as methods of obtaining the desired data. Background information was collected for 121 graduates. All tabulations were recorded as percentages with the significance of differences determined by critical ratios. Selected Findings The five-point rating scale used for the questionnaires was structured with values: 5 - superior, 4 - above average, 3 - average, 2 - below average, and 1 - inferior. A zero column was provided for "no response," or "no opinion" or "did not have the experience." These will be the values referred to hereafter in the findings. 1. Graduates rated Student Teaching, Reading, and Children's Literature highest and School in American Life and Educational Psychology significantly low in professional education courses. 2. Graduates with the high 25 percent grade point average and ACE entrance examinations versus the low 25 percent rated professional education courses: (1) more frequently in the below average and inferior values and (2) less frequently in the superior and above average values. 3. Graduates rated Speech Correction highest and Physical Education and General Psychology significantly low in general education courses. 4. Graduates with the high 25 percent grade point average and student teacher grades versus the low 25 percent rated general education courses: (1) more frequently in the superior and above average values and (2) more frequently in below average and inferior values. 5. Graduates rated Reading and Arithmetic highest and Music and Health lowest concerning value received in their student teaching experience. 6. Graduates rated the student teacher seminar more frequently in below average and inferior values. 7. Administrators rated graduates' teaching competencies under Methods of Instruction and Evaluation as significantly low in: Helping children in music; Helping children in physical education; Helping children to speak effectively; Helping children in social studies; Helping children express themselves in writing; Helping children in art; Helping children in problem solving; Diagnostic and remedial methods 8. Administrators rated the low 25 percent grade point average graduates 57 percent less frequently in below average and inferior values when compared to the high 25 percent. 9. Administrators rated the low 25 percent student teacher grade graduates versus the high 25 percent: (1) seven percent more frequently in superior and above average values and (2) 50 percent less frequently in below average and inferior values. 10. Administrators rated the high 25 percent ACE entrance examination graduates versus the low 25 percent as significantly higher in five teacher competencies: Helping children in arithmetic; Helping children in problem solving; Helping children in expressing themselves in writing; Helping children in learning to write and spell; Understanding the age level in child growth and development 11. Graduates emphasized as most urgent and immediate needs in the elementary teacher education program: (1) evaluating professional education courses for excessive amount of overlapping and duplication, (2) improving teaching methods of School of Education faculty, (3) more classroom observation and first-hand experience with children before student teaching assignment, (4) lengthening student teaching time, and (5) structuring the student teacher seminar for more practical experiences. 12. Graduates indicated a definite interest in the "satisfactory" - "not satisfactory" grading policy for student teaching. 13. Administrators were unanimous in their confidence toward the elementary education program as appraised in follow-up interviews.
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Profitable, even-aged forest management depends on the early establishment and rapid growth of each new forest crop. These, in turn, require that the young trees have access to an adequate supply of native ...
Citation Citation
- Title:
- Effects of herbaceous weed control on young Douglas-fir moisture stress and growth
- Author:
- Preest, David Stanley
Profitable, even-aged forest management depends on the early establishment and rapid growth of each new forest crop. These, in turn, require that the young trees have access to an adequate supply of native resources of moisture, nutrients and light. In Mediterranean-type climates, competition for soil moisture is the most serious adverse effect of weeds. Young trees respond with elevated moisture stress levels throughout most of the summer, with reduced net assimilation and potential for growth. If soil moisture depletion is severe enough, dehydration and death ensue. This dissertation explores the relationship between soil moisture availability, as influenced by several herbaceous cover types, and Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco.] response, mainly in terms of tree moisture stress TMS) and growth; it seeks to link herbicide treatment and tree response directly, and also indirectly, by its effect on soil moisture availability and tree moisture stress. Data for this study came mainly from field observation and experimentation during the summer of 1970, and from stem analyses performed in 1972 in a set of pm-existing herbicide trial plots. These were located in a bentgrass (Agrostis tenuis Sibth) dominated meadow situated about 18 miles west of Corvallis in the Oregon Coast Range. The diverse vegetative covers of the plots in 1970 reflected histories of up to three years herbicide. treatment. Four types of data were used: total available soil moisture content; climatological records; survival records; and height, diameter and volume measurements determined by stem analysis. An early attempt was made to apply a complicated regression model to individual tree TMS using various climatological, soil, and time variables. Although approximately 80% Of the variation in TMS could be explained by this, it was clear that this model had serious inadequacies. Study of plots of TMS against Pacific daylight time (PDT), air temperature, vapor pressure deficit VPD) and solar radiation led to the development of a conceptual model of TMS based largely on postulated light- and leaf temperature-triggered responses of the stomates, sensitized and modulated by the availability of soil moisture, degree of overnight recovery of tree turgor, and the atmospheric moisture demand. A possible explanation of the so-called "freeze" damage of Douglas-fir was suggested by this model. Although abnormally favorable soil moisture conditions in the summer of 1968 caused weed control that year to have no significant effect on first year survival or height growth, first-year devegetation did have significant or highly significant positive effects on height and diameter growth in each of the subsequent four years. Likewise, treatments in 1969 and 1970 also had the effect of setting the trees on advanced growth trajectories. Of the three single treatment schedules, treatment in the first year was chosen as the best because it combined good growth response (82% increase in tree volume over control in five years) with a normally highly positive influence on tree survival. The multiple treatment schedules demonstrated that responses (especially of height growth) to later treatments are maximized when preceded by treatments which promote the accumulation of photosynthetic reserves. Treatment in the first and second years was the optimum two treatment schedule. It resulted in a 115% increase in tree volume. The three-treatment schedule enhanced tree volume by 217% and was estimated to shorten a 70 year rotation by two years, compared with controls. Tree growth responses to chemical weed control were linked quantitatively through the latter's positive effect on available soil moisture. This in turn was shown to have a negative effect on tree moisture stress, which had a positive effect on tree growth. Art economic analysis based on projected treatment-induced height differentials at stand closure indicated that for high site II areas, even where weed control may not be necessary to obtain adequate survival, the first-year-only and the three-consecutive-years treatment schedules may be justifiable on the basis of the financial return from improved growth alone; hut only if coupled with other forest management practices designed to maximize yield, and stumpages of the order of $150 per mbf. The economics of weed control should be even more attractive on less favorable growing sites, especially when the higher yield and quality caused by better stocking are taken into account.
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Every year many marine mammals become stranded on the coast of the Pacific Northwest. The deaths of these animals are investigated and recorded by the North West Marine Mammal Stranding Network. Animals ...
Citation Citation
- Title:
- Retrospective Analyses of Marine Mammal Strandings on the Oregon Coast
- Author:
- Rice, Jim, Lohr, Christiane, Engelhard, Jennifer, Duffield, Debbie
Every year many marine mammals become stranded on the coast of the Pacific Northwest. The deaths of these animals are investigated and recorded by the North West Marine Mammal Stranding Network. Animals or tissues from animals, that are considered fresh enough for histopathology are brought for evaluation to the Veterinary Diagnostics Laboratory at Oregon State University. The diagnostic records detail the condition of the animal, disease status and cause of death. In this study, data will be collated from the diagnostic records at the Veterinary Diagnostics Laboratory (VisuaLab database) into an access database, incorporating information from the Marine Mammal Stranding Network as appropriate. Over the last six years, a total of 183 cases have been accessioned into the Veterinary Diagnostics Laboratory database, involving sea lions, seals, porpoises, dolphins and whales. This data is accessible only via VisuaLab software, which provides limited support for data queries and is scheduled for retirement later this year, making subsequent access even more difficult. Converting this database into an access database will allow future synthesis with the Marine Mammal Stranding Network database and will ensure continued availability of all the data and provide an increased sample size for any future research. Statistical analysis will be undertaken to ascertain the types, frequency, and distribution (e.g. species, age, gender, geography) of diseases and to look for trends in the cause of death marine mammals of the Pacific Northwest The desired outcomes of this project are to obtain an increased knowledge and understanding of what research entails and how it is conducted, to contribute information regarding the health of marine mammal populations of the Pacific Northwest, and to create an accessible, user friendly database for other researchers in this field. Secondary desired outcomes of this project are to assist in marine mammal conservation efforts and to form the basis of future research projects allowing for in depth investigations of specific diseases and trends.
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3114. [Article] Factors related to the choice of secondary teaching as a career
This study of Oregon secondary school teachers was designed to find why individuals had chosen this particular career, what they think of their positions, what time of their lives they chose teaching as ...Citation Citation
- Title:
- Factors related to the choice of secondary teaching as a career
- Author:
- Myers, Kenneth Holly
This study of Oregon secondary school teachers was designed to find why individuals had chosen this particular career, what they think of their positions, what time of their lives they chose teaching as a career, and what their career plans are for the future. The respondents were full-time Oregon secondary school teachers with one, two, and three years of experience. Influencing Factors: Teachers were the most influential external factor in influencing career decisions of future teachers. Thirty-seven percent of the respondents indicated that teachers at all levels influenced their decisions. Internal or personal interest factors were more frequently specified than were external factors. Over 50 percent of the respondents indicated their desire to work with the secondary-age groups and their interest in subject matter as the most influential internal factors. As a career for their children, 70 percent of the fathers and 82 percent of the mothers were favorably inclined toward a career In teaching. Parents were, however, more in favor of teaching as a career for their daughters than for their sons. Time of Career Choice: Thirty-eight percent indicated they considered secondary teaching as a career prior to college, whereas 48 percent selected teaching during their college years. By the time they had received their bachelors' degrees, only ten percent of the respondents had a career goal other than teaching. Sixty-three percent reported that teaching was their first occupational choice. The most frequently-mentioned occupations other than teaching are the following: business, engineering, fine arts, medicine, and secretarial work. Future Plans: Seventy-six percent of the teachers are planning to receive their masters' degrees, and another 19 percent plan to work for their doctorates. Thirty-six percent of the teachers plan to continue classroom teaching until retirement, but 44 percent would like to have another assignment in the field of education. The 44 percent who indicated they would like another assignment listed their preferences in the following areas: college teaching, 15 percent; counseling, 13 percent; department chairmanships, 3 percent. Administration, special education, curriculum work, library work, psychology, and social work make up the remaining percentage. More than one out of five teachers indicated they will leave teaching within the next five years. About two out of every five think they may leave teaching in the next five years. Reasons for leaving: The main reason why teachers may leave the profession is inadequate salaries. Sixteen percent of the women will leave teaching at this time to devote more time to family obligations. Other reasons for leaving are as follows: too much time required for preparation, good business opportunities, further study, an interest in college teaching, lack of time for preparation, certification requirements, poor administration, long hours, extra class activities, and disrespect from parents. Satisfactions: Major satisfactions with teaching centered around the nature of work--working with secondary youth, helping students to learn, and having a sense of social usefulness. Recommendations: The recommendations listed by teachers for the recruitment and retention of qualified teachers were as follows: improve professional image, raise teacher standards, improve community respect for education, improve quality of instruction at schools of education, recruit more competent people for the teaching profession, and have fewer certification hurdles. Other recommendations listed are as follows: fewer number of activities, more competent administrators, lighter class loads, better coordination with state department and schools of education, need for year-round employment for teachers, need for scholarships for graduate study, better supervision from teacher-training teachers, and the need for better attitudes from students and parents. Other Information: Other information from this study includes the following: personal factors, professional training, financial assistance, teacher preparation and assignments, academic majors, first occupational choice of life goals, and teacher-community relations. Comparisons: Comparisons are made between the teachers with one, two, and three years of experience of all the factors listed previously. The summary also includes the typical one-year, two-year, and three-year teachers.
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3115. [Article] Biological soil crusts in forested ecosystems of southern Oregon : presence, abundance and distribution across climate gradients
In arid and semi-arid deserts, soils are commonly covered with biological soil crusts. The study of arid biocrusts and their ecological function has become increasingly common in the literature over the ...Citation Citation
- Title:
- Biological soil crusts in forested ecosystems of southern Oregon : presence, abundance and distribution across climate gradients
- Author:
- Olarra, Jennifer A.
In arid and semi-arid deserts, soils are commonly covered with biological soil crusts. The study of arid biocrusts and their ecological function has become increasingly common in the literature over the last several decades. Interestingly, no mention is made of biological soil crusts in forested ecosystems, raising the question as to whether they exist in these areas and if they do, why they have yet to be recognized as such? Through the use a parallel logic, this study finds that biocrusts do indeed exist in forests, a novel relationship in forest ecology and seeks to determine if there exist ecophysical explanations for the abundance and distribution throughout the forest landscape. This study examined the effects of climate variables and substrate types on the abundance, distribution and overall cover of forest soil biocrust at fifty-two sites in southern Oregon, U.S.A. Sites were randomly selected within established buffer zones in the Siuslaw, Rogue-Sisikyou, Umpqua, and Fremont-Winema National Forests. The methods of Belnap et al 2001 were tested and then modified for application in forested ecosystems. Data were collected on the relative abundance and distribution of biocrust morphological groups across available substrates, community biocrust morphology, aspect, elevation and soil texture, pH and organic matter content. Site-specific data on average annual precipitation and minimum/maximum temperatures was collected using the PRISM Climate Model. This study found substrate colonization by specific morphological groups mixed across the study; though dominant communities were observed for each substrate present, substrate availability appears to be confounded by a number of variables (climate, stand age and structure and litter layer) not controlled for in this study. Biocrust community morphologies varied across sites, primarily influenced by the surface texture of the substrate and morphology of the individual. Relatively smooth surfaces (rock, bare soil) often resulted in smooth biocrust morphologies, whereas rough surfaces (dead wood, bare soil) tended to result in a rolling morphology. Litter layer directly influenced the relative proportion of substrates colonized, notably affecting dead wood and mineral soil biocrusts. Total biocrust cover increased as precipitation increased as did biocrust preference for dead wood substrates while mineral soil remained unchanged and rock surfaces were negatively represented. Aspect generally followed the anticipated distribution of total biocrust cover with the highest cover on N and NW aspects and lowest on the W aspect. Increases in elevation were negatively related to overall biocrust cover. Soil texture was not found to be directly related to overall biocrust cover, attributed in part to the highly adaptive nature of the biocrust community. Soil organic matter (SOM) influenced total biocrust cover with positive correlations between total cover and increasing SOM content. Soil pH increased as expected across the precipitation range (17 to 159 in/yr) of the transect. Total biocrust cover was found to trend with soil pH, but is believed to be attributed to the parallel relationship between precipitation and pH, rather than pH alone given the relative moderate pH range (4.39 to 6.54) of the study. The distribution and abundance of forest soil biocrusts is strongly influenced by precipitation. The confounding influence of precipitation to litter layer depth and organic matter content (through gradients of vegetative productivity) and soil pH further are concluded to influence substrate preference by morphological groups. Across the variables examined, similarities between the two communities (arid and forest) in response to climate and soil chemistry show parallel relations, justifying the formal establishment of biological soil crust community in forested regions. The differences between communities related to the presence of trees validate the establishment of forest soil biocrusts as distinct community in both form and ecological function with the forests.
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Child behavior disorders are the second most prevalent form of mental illness affecting children in the United States (Perou et al., 2013), with lifetime prevalence estimated at 10% (Nock, Kazdin, Hiripi ...
Citation Citation
- Title:
- Do Family Risk Classes Predict Attrition in Parent Child Interaction Therapy?
- Author:
- Hartman, Grace M.
Child behavior disorders are the second most prevalent form of mental illness affecting children in the United States (Perou et al., 2013), with lifetime prevalence estimated at 10% (Nock, Kazdin, Hiripi & Kessler, 2007). Negative outcomes associated with ODD during childhood and adolescence include conflict in families, poor peer relationships, peer rejection, and academic difficulties (Burke, Rowe & Boylan, 2013). Parent training programs are shown to be effective in reducing child behavior disorders (Thomas & Zimmer-Gembeck, 2011). One such program, Parent Child Interaction Therapy (PCIT), is a widely disseminated intervention implemented in diverse settings with populations of at-risk families. PCIT is an intervention shown to be effective in preventing and reducing behavior disorders in children aged 2- to 7- years old (Brinkmeyer & Eyberg, 2003). However, a large barrier to treatment success is that families often dropout before therapy is completed (Fernandez & Eyberg, 2009). A small collection of studies specifically examining attrition in PCIT have explored family risks as treatment barriers. Models exploring the shared influence of multiple risk factors in the literature on PCIT attrition are uncommon, but given the co-occurring contextual risks often seen in families enrolled in PCIT, studies documenting the shared influence of multiple risks on attrition are important and have potential value in research and practice. Studies associating family risks with PCIT attrition have typically operationalized single variables and findings have been inconsistent. Although children and parents in parent-child therapies are known to have adverse family experiences (i.e. abuse, neglect, witnessing violence) (Kazdin, 1996), studies on the influence of adverse family experiences in PCIT attrition are few, and none have looked at the combined influences of family risks. To help address these gaps, the current study will examined the ways in which family risks operate in combination with one another to help explain attrition in PCIT. More specifically, this study examines whether or not families participating in PCIT differ not only in the number of risks they present, but also in the ways in which risks combine, forming distinct patterns of risks. To address this question, we conduct a Latent Class Analysis to identify family risk classes examining how two overarching types of risk; low-SES, and adverse family experiences. We addressed our main study aim by examining how the classes predicted the likelihood of dropping out of PCIT overall, and prior to the completion of the CDI component. To help address these gaps, the current study will examine the ways in which family risks operate in combination with one another to help explain attrition in PCIT. More specifically, this study examines whether or not families participating in PCIT differ not only in the number of risks they present, but also in the ways in which risks combine, forming distinct patterns of risks. The goals of the present study were to explore patterns of risks among families participating in PCIT, and to examine associations between these patterns and the likelihood of dropping out of PCIT, both prior to completing the first component (CDI) of the therapy and prior to completion of the full program. Findings pointed to three distinct patterns of risk but did not detect any significant associations between these patterns of risk and attrition in PCIT. These findings are important for guiding future research and provide preliminary information for practitioners to better understand the complexity of risks among families attending PCIT. Although the primary study aim was to examine links between classes of risk and attrition in PCIT, preliminary analysis detected two specific risk variables linked with PCIT attrition prior to completion of CDI: low parental education and having a mental health disorder in the household. There was also a trend toward low parental education being associated with attrition from PCIT overall
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This dissertation investigated the impacts of tree height upon a range of physiological and structural characteristics of Douglas-fir foliage; relationships between structural and functional trends with ...
Citation Citation
- Title:
- Height-related trends in structure and function of Douglas-fir foliage
- Author:
- Woodruff, David R.
This dissertation investigated the impacts of tree height upon a range of physiological and structural characteristics of Douglas-fir foliage; relationships between structural and functional trends with height; and compensatory mechanisms that mitigate height-related growth constraints. Height-related trends in foliar physiological and anatomical characteristics were examined both within trees as well as between trees of different heights. Emphasis was placed on discovering the mechanistic nature of the observed growth constraints and adaptive strategies. This research was conducted in the interest of enhancing our knowledge of the causes of age- and size-related decline in forest productivity. The research conducted for this dissertation explored several previously uninvestigated mechanisms for size-related reductions in forest productivity that are associated with tree foliar structure and function. Height-related trends in foliar turgor associated with the gravitational hydrostatic pressure gradient were identified as well as subsequent impacts on leaf and shoot morphology. Osmotic potential declined with height providing evidence of osmotic adjustment to offset the height-related decline in leaf turgor. This osmotic adjustment occurred only seasonally, and not during the spring when turgor maintenance is most important for leaf expansion. Gradients in leaf turgor were reflected in height-related trends in leaf and shoot morphology. Previous work has documented height-related trends in foliar morphological characteristics and earlier studies have examined osmotic adjustment as an adaptation to drought and salinity stress. Height-related trends in foliar morphological characteristics have typically been attributed to light gradients along vertical profiles. The work in this dissertation is the first to evaluate the effects of the gravitational component of water potential on the osmotic, morphological and growth characteristics of foliage along a height gradient in tall trees. Trends in leaf hydraulic efficiency and safety along a height gradient were examined, and correlations between changes in leaf hydraulic conductance (Kleaf) and changes in stomatal conductance (gs) were identified that provided evidence of a control mechanism for gs. A consistent relationship was discovered between changes in Kleaf and gs providing evidence that leaf tracheid embolism is associated with stomatal closure during periods of declining water availability. Hydraulic vulnerability curves of foliage collected at different heights indicated that increased height is correlated with reduced hydraulic efficiency and increased hydraulic safety. These opposing trends suggest the existence of a compensatory mechanism in foliage that functions to reduce hydraulic vulnerability at the expense of transport capacity. The research in this dissertation is the first to examine the dynamic relationships between leaf hydraulics and stomatal behavior in temperate conifers, and the first to examine how these characteristics are affected by tree height. Height-related trends in leaf xylem anatomical characteristics were examined and strong correlations were identified between these anatomical characteristics and the patterns of leaf hydraulic efficiency and safety that were observed in previous work for this dissertation. Theoretical estimates of leaf hydraulic efficiency (Kleaf-theoretical) based upon the Hagen-Pouseille equation and measured leaf tracheid anatomical characteristics were strongly correlated with laboratory measurements of Kleaf, providing further evidence of a causal relationship between height-related trends in both leaf tracheid anatomical properties and leaf hydraulic function. Earlier studies have documented connections between leaf anatomical characteristics and leaf physiological characteristics such as correlations between leaf architecture and gas exchange and leaf architecture and transport efficiency. The research in this dissertation however, is the first to examine the impact of tree height on leaf anatomical characteristics and associated shoot physiological properties. Trends in gas-exchange along a height gradient were identified, independent of the immediate effects of path length and gravitational resistance. Photosynthesis under ambient [CO2] declined with height in a manner that was consistent with height-related trends in mesophyll anatomy and independent of leaf nitrogen content. Analyses of mesophyll resistance from assimilation versus internal CO2 concentration (A-Ci) curves indicated that height-related trends in mesophyll resistance were correlated with trends in both photosynthesis and mesophyll anatomy along a height gradient. Analyses of integrated and instantaneous water use efficiency indicated that height-related trends in integrated water use efficiency are attributable to the effects of path length and gravity on stomatal behavior as opposed to a height-related trend in intrinsic foliar properties. The research in this dissertation is the first to isolate the influence of height-related trends in foliar structure on different gas exchange properties such as assimilation and mesophyll conductance, independent of the direct effects of vertical gradients in xylem tension on stomatal and photosynthetic physiology.
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3118. [Article] Historical disturbance regimes as a reference for forest policy
Using the historical range of forest conditions as a reference for managing landscapes has been proposed as a "coarse-filter" approach to biodiversity conservation. By emulating historical disturbance ...Citation Citation
- Title:
- Historical disturbance regimes as a reference for forest policy
- Author:
- Thompson, Jonathan R.
Using the historical range of forest conditions as a reference for managing landscapes has been proposed as a "coarse-filter" approach to biodiversity conservation. By emulating historical disturbance processes, it is thought that forest management can produce forest composition and structure similar to the conditions that once supported the native biota. Although several examples of disturbance-based management exist, only recently has this concept been incorporated into policy. This thesis explored hypotheses related to disturbance-based forest policy through a literature review, policy analyses, and simulation experiments. The primary objective of chapter 2 was to examine several examples disturbance-based forest management and evaluate their potential to transition into policy within North America. The review highlighted two Canadian provinces British Columbia and Ontario--that have codified disturbance-based management but used distinct methodologies. Nearly all of the forests in these provinces are government owned, which assisted policy development. In addition, both policy-structures focused on emulating stand-replacing fires that are characteristic in boreal forests; this minimized the costs and the degree of departure from conventional forest management. In much of the U.S., land tenure is complex and disturbance regimes vary widely; this presents difficult challenges for disturbance-based policy development. In the third chapter, disturbance-based policies were developed that attempted to address these challenges. Using datasets from the Coastal Landscape Analysis and Modeling Study (CLAMS) and the Landscape Management and Policy Simulation model (LAMPS), the economic costs and ecological benefits of several policy structures were explored. The policies included two variants of the current policy structure and three policies reflecting various aspects of the natural disturbance regime. The study area was the 3-million hectare Oregon Coast Range. Four owner groups were recognized--forest industry, nonindustrial private, state, and federal. The management intentions of each group guided the application of policies. Disturbance-based policies were primarily addressed to clearcutting on private lands because it constituted the preponderance of harvesting in the region. Information on the Coast Range's historical fire regime was used as a reference to develop disturbance-based policies. Fire severity was emulated with green-tree retention standards; fire frequency was emulated with annual harvestable area restrictions; and fire extent was emulated with harvest-unit size regulations. LAMPS projected landscape conditions, forest dynamics, management activities (clearcutting, thinning), and harvest volumes over the next century. Simulated disturbance-based policies produced age-class distributions more similar to the historical range than those created by the current policy structure. The proportions of early seral and young forest were within the historical range within 100 yrs; within this timeframe, older forests moved closer to but were still below historical conditions. In contrast, patch size distributions were less similar to historical conditions. This was because, even after a ten-fold increase in the average harvest size, the clearcut size limit remained well below the average historical fire size. Also, this was due to the scale of the analysis, which treated multiple proximate harvest-units as individual disturbance events. Therefore, regions with a high density of clearcuts, which were ubiquitous in the current policy scenarios, more closely resembled the large historical fire size. In the near term, annual revenue produced by the disturbance-based policies was estimated to be 20 to 60 percent lower than the current policy. However, relative costs were reduced significantly through time. This reflected the degree of departure between the modem and historical disturbance regimes. This simulation experiment suggested that policies attempting to reproduce historical conditions in the Coast Range would require federal forests to provide large patches of old forest that were conmon in the historical landscape. Employing public lands for this purpose would dampen costs to private landowners who would continue harvesting and provide young and early seral forest structure, which were also historically abundant. In addition, this experiment illustrated the difficultly of meeting regional-scale conservation goals across multiple private landowners and suggested that distributing costs and benefits equitably across large landscapes could be a significant challenge.
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Rainfall, discharge, traffic, and suspended sediment were monitored for a period of 4.5 months at three locations on a secondary haul road at Polk Inlet, Alaska to determine the important processes and ...
Citation Citation
- Title:
- Surface erosion from a forest road, Polk Inlet, Prince of Wales Island, Alaska
- Author:
- Kahklen, Keith F.
Rainfall, discharge, traffic, and suspended sediment were monitored for a period of 4.5 months at three locations on a secondary haul road at Polk Inlet, Alaska to determine the important processes and variables involved in surface road erosion for this area. Three sites all less than 500m² and within 5 kilometers of each other on the same road were chosen to be instrumented for monitoring. The proximity of the sites to each other resulted in the sections all being nearly identical in age, topographical location, aspect, elevation, and construction materials. Also, the sites were subjected to the same traffic amounts of approximately 3 to 4 loaded logging trucks per day plus other light vehicles. Maps were developed of the sites which helped determine the source areas for each one. The gradients of sites 2 and 3 were approximately 7%, and the gradient of site 1 was 10%. Each study site was equipped with a flume, pressure transducer, datalogger, and pumping sampler to collect data on discharge and suspended sediment. Sites 1 and 3, had rain gages connected to the dataloggers which recorded 5 minute rainfall intensities. Hourly suspended sediment samples were collected at each site. An infrared traffic counter was used to count the daily traffic amount. An infiltration rate for the road was determined to be 0.9mm/hr using a simple water balance method and also by determining the minimum amount of rainfall to initiate runoff. The infiltration rate was used in development of representative hydrographs for the three sites. The runoff response of the sites were very similar when normalized to an area of 280 m². The precipitation catches for the two gages were very similar with precipitation amounts of 893 mm for site 1 and 975 mm for site 3 during 89 days of record. Several regression analyses were completed for both hourly and storm data to determine which variables and technique would be best for estimating total sediment production. The method that proved to be the best for determining hourly production was to multiply the hourly sediment concentration by the average hourly discharge to obtain a total estimated sediment weight produced for that hour. During multiple regression analysis, all three sites and the combined model had rainfall as the most important variable. The variable that averaged the number of axles per day since the last runoff event was also found to be significant in the combined model. Qualitative variables were used to determine that timing of the events may have an influence on the sediment production. The total storm sediment production was determined by summing the total hourly sediment weights for a given storm. The regression analyses found rainfall to be the most significant of ten variables for the total storm sediment production. A comparison of all the different models coefficients was developed. The multiple regression model with total storm rainfall, a qualitative variable for gradient, and axles per day was found to have the best coefficient of determination of 0.66 for the combined data of all the sites. The model for site 3 of axles per day and total storm rainfall was found to have the highest coefficient of determination, R² = 0.85. The simple linear regression model of log of total sediment yield/km of road to total storm precipitation was used to estimate the annual sediment production from a kilometer of road at Polk Inlet. The annual precipitation data was from a gage located about 16 kilometers northeast of Polk Inlet. The annual road surface sediment erosion estimate is 8.1 tonnes/km of road. A comparison of other studies shows this to be similar to other locations in the United States and areas of New Zealand. Several assumptions were made and the resulting limitations are described for this estimate. Any use of this estimate or equation for sites without very similar characteristics would not be advised. Future studies are in progress to expand the understanding of some of the other variables not accounted for in this study.
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This thesis is the consequence of a research effort undertaken by the School of Civil and Construction Engineering at Oregon State University and funded by the Oregon Department of Transportation (ODOT) ...
Citation Citation
- Title:
- Effect of constituent materials and curing methods on the abrasion resistance and durability of high performance concrete for pre-cast pre-stressed bridge deck slabs
- Author:
- Keshari, Shweta
This thesis is the consequence of a research effort undertaken by the School of Civil and Construction Engineering at Oregon State University and funded by the Oregon Department of Transportation (ODOT) and the Federal Highway Administration (FHWA). The principal objective of the effort was to reduce the life cycle cost of bridges by developing one or more materials systems for precast and pre-stressed bridge deck components that improve the studded tire wear (abrasion) resistance and durability of bridge decks. Degradation of the concrete bridge decks due to abrasion caused by the studded tires and accelerated corrosion of the reinforcing steel in the concrete often triggers costly, premature rehabilitation or replacement of these bridges. High performance concrete (HPC) can provide improved abrasion resistance, but is more costly than ordinary concrete and can exhibit early age cracking when used for cast-in-place concrete members, which can accelerate corrosion of embedded reinforcing steel. However, several studies have suggested that HPC developed for precast members offers a viable alternative to cast-in-place concrete deck slabs due in part to improved control of the curing process. The scope of this research was to develop one or more mixture designs for HPC that improve the durability and abrasion resistance of the bridge decks through careful selection and proper proportioning of the constituent materials and improved control of the curing process. The materials investigated in this research included silica fume, slag, and fly ash as partial replacement of Type I and Type III portland cement mixed with crushed aggregate and river gravel. Phase I of the study included development of 15 mixture designs incorporating various combinations of the materials. Mixtures were cast under controlled laboratory conditions and cured using a variety of methods. The results of tests conducted on the cured samples indicated that the mixture with silica fume and slag had greater strength than the mixture with silica fume and fly ash mixture, and that mixtures with crushed rock provided better abrasion resistance than those with river gravel. Results from the chloride ion penetration test for permeability indicated that mixtures cured in saturated lime water for 28 days exhibited reduced permeability in comparison to mixtures which were steam cured followed by ambient curing. Following phase I, a pilot study was undertaken to identify the best curing method to apply during production at precast yards to assist high early strength gain so that the concrete member can be removed from the casting bed in a matter of several hours as well as to facilitate high ultimate strength, improved abrasion resistance, and low permeability. The pilot study indicated the best curing method to be steam curing followed by application of a curing compound. Phase II of the research study included seven mix designs and focused on various levels of supplementary cementitious materials. It adopted the curing method suggested by the pilot study. Results from phase II indicated that slag was better in enhancing durability of the concrete than fly ash. Increasing the proportion of silica fume did not improve the properties of high performance concrete significantly. Some other interesting results indicated that compressive strength was inversely proportional to wear rate and chloride ion penetration. Wear rate was directly proportional to chloride ion penetration. There was no relationship between durability factor (freeze-thaw test) and compressive strength or chloride ion penetration. Two mixtures were identified as having significantly improved abrasion and permeability characteristics over the control mixture (ODOT bridge deck mixture). Both included slag and silica fume as supplementary cementitious materials as a partial replacement of portland cement and one did not contain an air entraining admixture.