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• 2791. [Article] Flavor chemistry of irradiated milk fat

  Increasing interest has been shown in the irradiation sterilization and irradiation pasteurization of foods, but problems of off-flavors and odors are still unsolved, especially in the case of dairy products. From ...

  Citation × Citation Citation Abstract Copy Title: Flavor chemistry of irradiated milk fat Author: Khatri, Lakho Lilaram Increasing interest has been shown in the irradiation sterilization and irradiation pasteurization of foods, but problems of off-flavors and odors are still unsolved, especially in the case of dairy products. From the flavor chemistry point of view, milk lipids are very highly susceptible to irradiation effects. Therefore, this investigation was designed to study some irradiation induced reactions involving flavor changes in the milk fat and to identify the volatile components produced in the milk fat upon irradiation. Milk fat, prepared from raw sweet cream and washed free of phospholipids, was first irradiated in the presence of air and under vacuum in glass vials at 4.5 Mrad with gamma rays from cobalt-60. The irradiation resulted in increase in TBA number, peroxide value, total monocarbonyls, bleaching of color, slightly rancid and typical candle-like off-flavors. Free fatty acids were also produced upon irradiation. The changes were more drastic in air along with production of a slight oxidized flavor. The monocarbonyls identified by column and paper chromatographic methods in irradiated milk fat include: C₁ through C₁₂, C₁₄ , and C₁₆ n-alkanals; C₃ through C₉, C₁₁, C₁₃ and C₁₅ alk-2-ones with only traces of C₆ and C₈ alk-2- ones; and C₅, C₆, C₉, and C₁₂ alk-2-enals. Irradiation of milk fat that had been dried over calcium hydride also caused free fatty acid production, especially short chain fatty acids. Methyl octanoate treated with calcium hydride and irradiated at 1.5, 3.0, 4.5, and 6.0 Mrad yielded small quantities of free octanoic acid, confirming that irradiation caused fission of the ester linkage even when traces of water were removed. The quantities of octanoic acid formed increased with increasing dose of irradiation. For identification of volatile components, the milk fat was irradiated in 307x409 'C' enameled cans under vacuum. The headspace analysis showed some air still left in the cans. Irradiation resulted in consumption of oxygen and production of hydrogen, carbon monoxide, carbon dioxide, and methane as identified in the headspace gases. The volatiles were isolated from the irradiated and control milk fats by low temperature, vacuum steam distillation at 40°C and 1-2 mm Hg. The volatile components were then extracted from the aqueous distillate with ethyl ether. The ethyl ether extract exhibited the typical candle-like defect. The ethyl ether concentrate was analyzed by combination of GLC and fast-scan mass spectrometric techniques. Identification of various components was achieved on the basis of mass spectral data and coincidence of gas chromatographic retention times. In the case of the components for which only GLC t[subscript r]/t[subscript r] evidence was available or the mass spectra obtained were not satisfactory, the identity assigned was only tentative. The volatile compounds that were positively identified to be present in irradiated milk fat are given below: n-Alkanes C₅ through C₁₇ 1-Alkenes C₅, C₇ through C₁₇ Fatty acids C₄, C₆, C₈ and C₁₀ n-Alkanals C₅ through C₁₁ Others γ-decalactone, δ-decalactone, 2-heptanone, benzene, ethyl acetate, chloroform, and dichlorobenzene. The tentative identification was obtained for the following compounds: γ-lactones C₆ and C₈ δ-lactones C₆, C₈, C₁₁, and C₁₂ 1, ?-alkadienes C₁₀, C₁₁, C₁₂, C₁₆ and C₁₇ iso-alkanes C₁₀, C₁₁, C₁₂, and C₁₃ Others methyl hexanoate, 2-hexanone, 4-heptanone and n-dodecanal. The compounds present in unirradiated control milk fat included: short chain fatty acids (C₄, C₆, C₈, and C₁₀), C₈, C₁₀, and C₁₂ δ-lactones, 2-heptanone, chloroform, dichlorobenzene, benzene, toluene, and ethyl-benzene. Only tentative identity was established for most of these components in control milk fat. Possible reaction mechanisms are presented for the formation of the compounds in irradiated milk fat. Title: Flavor chemistry of irradiated milk fat Author: Khatri, Lakho Lilaram Increasing interest has been shown in the irradiation sterilization and irradiation pasteurization of foods, but problems of off-flavors and odors are still unsolved, especially in the case of dairy products. From the flavor chemistry point of view, milk lipids are very highly susceptible to irradiation effects. Therefore, this investigation was designed to study some irradiation induced reactions involving flavor changes in the milk fat and to identify the volatile components produced in the milk fat upon irradiation. Milk fat, prepared from raw sweet cream and washed free of phospholipids, was first irradiated in the presence of air and under vacuum in glass vials at 4.5 Mrad with gamma rays from cobalt-60. The irradiation resulted in increase in TBA number, peroxide value, total monocarbonyls, bleaching of color, slightly rancid and typical candle-like off-flavors. Free fatty acids were also produced upon irradiation. The changes were more drastic in air along with production of a slight oxidized flavor. The monocarbonyls identified by column and paper chromatographic methods in irradiated milk fat include: C₁ through C₁₂, C₁₄ , and C₁₆ n-alkanals; C₃ through C₉, C₁₁, C₁₃ and C₁₅ alk-2-ones with only traces of C₆ and C₈ alk-2- ones; and C₅, C₆, C₉, and C₁₂ alk-2-enals. Irradiation of milk fat that had been dried over calcium hydride also caused free fatty acid production, especially short chain fatty acids. Methyl octanoate treated with calcium hydride and irradiated at 1.5, 3.0, 4.5, and 6.0 Mrad yielded small quantities of free octanoic acid, confirming that irradiation caused fission of the ester linkage even when traces of water were removed. The quantities of octanoic acid formed increased with increasing dose of irradiation. For identification of volatile components, the milk fat was irradiated in 307x409 'C' enameled cans under vacuum. The headspace analysis showed some air still left in the cans. Irradiation resulted in consumption of oxygen and production of hydrogen, carbon monoxide, carbon dioxide, and methane as identified in the headspace gases. The volatiles were isolated from the irradiated and control milk fats by low temperature, vacuum steam distillation at 40°C and 1-2 mm Hg. The volatile components were then extracted from the aqueous distillate with ethyl ether. The ethyl ether extract exhibited the typical candle-like defect. The ethyl ether concentrate was analyzed by combination of GLC and fast-scan mass spectrometric techniques. Identification of various components was achieved on the basis of mass spectral data and coincidence of gas chromatographic retention times. In the case of the components for which only GLC t[subscript r]/t[subscript r] evidence was available or the mass spectra obtained were not satisfactory, the identity assigned was only tentative. The volatile compounds that were positively identified to be present in irradiated milk fat are given below: n-Alkanes C₅ through C₁₇ 1-Alkenes C₅, C₇ through C₁₇ Fatty acids C₄, C₆, C₈ and C₁₀ n-Alkanals C₅ through C₁₁ Others γ-decalactone, δ-decalactone, 2-heptanone, benzene, ethyl acetate, chloroform, and dichlorobenzene. The tentative identification was obtained for the following compounds: γ-lactones C₆ and C₈ δ-lactones C₆, C₈, C₁₁, and C₁₂ 1, ?-alkadienes C₁₀, C₁₁, C₁₂, C₁₆ and C₁₇ iso-alkanes C₁₀, C₁₁, C₁₂, and C₁₃ Others methyl hexanoate, 2-hexanone, 4-heptanone and n-dodecanal. The compounds present in unirradiated control milk fat included: short chain fatty acids (C₄, C₆, C₈, and C₁₀), C₈, C₁₀, and C₁₂ δ-lactones, 2-heptanone, chloroform, dichlorobenzene, benzene, toluene, and ethyl-benzene. Only tentative identity was established for most of these components in control milk fat. Possible reaction mechanisms are presented for the formation of the compounds in irradiated milk fat. Close

• 2792. [Article] Population demography, resource use, and movement in cooperatively breeding Micronesian Kingfishers

  Island systems and species are susceptible to extinction because of their small population size and an ecological naiveté from an evolutionary past lacking strong competition and predation. For example, ...

  Citation × Citation Citation Abstract Copy Title: Population demography, resource use, and movement in cooperatively breeding Micronesian Kingfishers Author: Kesler, Dylan C. Island systems and species are susceptible to extinction because of their small population size and an ecological naiveté from an evolutionary past lacking strong competition and predation. For example, only one-fifth of the world’s bird species occur on islands, yet more than 90% of the avian extinctions witnessed during historic times were island forms. Introduced predators and competitor species are among the major conservation issues facing insular systems. On the island of Guam, brown tree snakes (Boiga irregularis) are responsible for the local extinction of twelve native forest birds. The endangered Guam Micronesian Kingfisher (Todiramphus cinnamominus cinnamominus) is one of the species affected by the introduced snake, as the bird remains only in captive breeding institutions on the U.S. mainland. In addition to Guam, the islands of Pohnpei and Palau host endemic subspecies of Micronesian Kingfisher (T. c. reichenbachii and T. c. pelewensis respectively) that are similarly threatened with extinction. Previous investigations into the behavioral ecology of the Pohnpei subspecies of Micronesian Kingfisher yielded observations of cooperative social behaviors. Over the past three decades, much research has focused on cooperatively breeding species, which are commonly characterized by non-breeding individuals that delay dispersal and assist others with reproduction. Research addressing cooperative breeding suggests that the behavior is a complex response to interacting factors including life history characteristics, demography, resources, movement, and behavior. The dearth of information available about critically endangered Micronesian Kingfishers, combined with their potential to provide new insights into cooperative social behaviors, inspired the research presented in this dissertation. The aims were two-fold; results were intended to bolster our understanding of cooperative social behaviors while simultaneously providing vital information to conservation practitioners. Methodology for determining the sex of study individuals is presented in chapter two, which facilitated investigations that followed. Chapter three addressed the interaction between kingfishers and resources at both the landscape and home range scale. Higher population densities are associated with lowland mangrove, marsh forested habitats, and open vegetation types at the landscape scale. Results further indicated that at the home range scale, birds selectively used late succession forested habitats in higher proportions than their availability, and forest areas were entirely utilized in study areas where territories were packed boundary-to-boundary. Together these suggested that forested areas and the resources they contain might be limited for Micronesian Kingfishers. Movement and space use in Micronesian Kingfishers were the focus of chapter four. Within territories, the home ranges of birds overlapped, although not entirely. Birds of all ages and social classes made extraterritorial prospecting movements, but they appear to serve different functions. Juveniles and helpers were observed dispersing from natal areas, but only after repeated extraterritorial homesteading movements. The timing and destinations of adult prospecting suggested that the behavior might provide opportunities for covert reproduction. Population demography was addressed in chapters five and six, which concluded with the development of a population projection model that will be useful in kingfisher conservation efforts throughout the Pacific. Nestlings on cooperative territories had higher estimated survival rates than those on pair territories. Further, the timing of nestling disappearances and a modified nestling mandible suggested that mortalities were caused by siblicidal nest-mates. In chapter six, post-fledging vital rates were estimated for Micronesian Kingfishers and a population projection matrix model was developed. Vital rate parameters were then varied, and the model was used in a simulation analysis to evaluate the apparent influence of each parameter on population dynamics across a range of potential values. The exercise was intended to lend insight into the dynamics of Micronesian Kingfisher populations and to form a base model for management of the other eleven endangered Pacific Todiramphus species. In summary, information presented in this dissertation lends insight into factors important to understanding population demography, resource use, and movement in cooperatively breeding Micronesian Kingfishers. Results illustrate that, like other cooperatively breeding species, the birds on Pohnpei are highly territorial and dispersal options may be limited by territory vacancies and forest resources. Extraterritorial prospecting movements have been observed in many cooperative species, and these results illustrate that they may serve multiple purposes. Siblicide is also a phenomenon present in resource-limited species and its occurrence in Pohnpei Micronesian Kingfishers underscores the importance of resources to the evolutionary history of the birds. Results from demographic analyses and modeling suggest that conservation efforts for Micronesian Kingfishers, and the other eleven Todiramphus species, should be broadly focused on all life history stages. Title: Population demography, resource use, and movement in cooperatively breeding Micronesian Kingfishers Author: Kesler, Dylan C. Island systems and species are susceptible to extinction because of their small population size and an ecological naiveté from an evolutionary past lacking strong competition and predation. For example, only one-fifth of the world’s bird species occur on islands, yet more than 90% of the avian extinctions witnessed during historic times were island forms. Introduced predators and competitor species are among the major conservation issues facing insular systems. On the island of Guam, brown tree snakes (Boiga irregularis) are responsible for the local extinction of twelve native forest birds. The endangered Guam Micronesian Kingfisher (Todiramphus cinnamominus cinnamominus) is one of the species affected by the introduced snake, as the bird remains only in captive breeding institutions on the U.S. mainland. In addition to Guam, the islands of Pohnpei and Palau host endemic subspecies of Micronesian Kingfisher (T. c. reichenbachii and T. c. pelewensis respectively) that are similarly threatened with extinction. Previous investigations into the behavioral ecology of the Pohnpei subspecies of Micronesian Kingfisher yielded observations of cooperative social behaviors. Over the past three decades, much research has focused on cooperatively breeding species, which are commonly characterized by non-breeding individuals that delay dispersal and assist others with reproduction. Research addressing cooperative breeding suggests that the behavior is a complex response to interacting factors including life history characteristics, demography, resources, movement, and behavior. The dearth of information available about critically endangered Micronesian Kingfishers, combined with their potential to provide new insights into cooperative social behaviors, inspired the research presented in this dissertation. The aims were two-fold; results were intended to bolster our understanding of cooperative social behaviors while simultaneously providing vital information to conservation practitioners. Methodology for determining the sex of study individuals is presented in chapter two, which facilitated investigations that followed. Chapter three addressed the interaction between kingfishers and resources at both the landscape and home range scale. Higher population densities are associated with lowland mangrove, marsh forested habitats, and open vegetation types at the landscape scale. Results further indicated that at the home range scale, birds selectively used late succession forested habitats in higher proportions than their availability, and forest areas were entirely utilized in study areas where territories were packed boundary-to-boundary. Together these suggested that forested areas and the resources they contain might be limited for Micronesian Kingfishers. Movement and space use in Micronesian Kingfishers were the focus of chapter four. Within territories, the home ranges of birds overlapped, although not entirely. Birds of all ages and social classes made extraterritorial prospecting movements, but they appear to serve different functions. Juveniles and helpers were observed dispersing from natal areas, but only after repeated extraterritorial homesteading movements. The timing and destinations of adult prospecting suggested that the behavior might provide opportunities for covert reproduction. Population demography was addressed in chapters five and six, which concluded with the development of a population projection model that will be useful in kingfisher conservation efforts throughout the Pacific. Nestlings on cooperative territories had higher estimated survival rates than those on pair territories. Further, the timing of nestling disappearances and a modified nestling mandible suggested that mortalities were caused by siblicidal nest-mates. In chapter six, post-fledging vital rates were estimated for Micronesian Kingfishers and a population projection matrix model was developed. Vital rate parameters were then varied, and the model was used in a simulation analysis to evaluate the apparent influence of each parameter on population dynamics across a range of potential values. The exercise was intended to lend insight into the dynamics of Micronesian Kingfisher populations and to form a base model for management of the other eleven endangered Pacific Todiramphus species. In summary, information presented in this dissertation lends insight into factors important to understanding population demography, resource use, and movement in cooperatively breeding Micronesian Kingfishers. Results illustrate that, like other cooperatively breeding species, the birds on Pohnpei are highly territorial and dispersal options may be limited by territory vacancies and forest resources. Extraterritorial prospecting movements have been observed in many cooperative species, and these results illustrate that they may serve multiple purposes. Siblicide is also a phenomenon present in resource-limited species and its occurrence in Pohnpei Micronesian Kingfishers underscores the importance of resources to the evolutionary history of the birds. Results from demographic analyses and modeling suggest that conservation efforts for Micronesian Kingfishers, and the other eleven Todiramphus species, should be broadly focused on all life history stages. Close

• 2793. [Article] Beyond Cooperation : Environmental Justice in Transboundary Water Management

  Since the Wolf, Yoffe, and Giordano 2003 Basins at Risk study, examining human interactions with transboundary water resources through a lens of conflict and cooperation has been a dominant paradigm. The ...

  Citation × Citation Citation Abstract Copy Title: Beyond Cooperation : Environmental Justice in Transboundary Water Management Author: Watson, Julie Elkins Since the Wolf, Yoffe, and Giordano 2003 Basins at Risk study, examining human interactions with transboundary water resources through a lens of conflict and cooperation has been a dominant paradigm. The Basins at Risk (BAR) method involves categorizing events on a scale from most conflictive (e.g. war or extensive casualties) to most cooperative (voluntary unification into one political unit). While this research provides significant insight into the nature of cooperation and conflict over water, it frames the discussion about water politics in terms of diplomatic, economic, and military hostility. However, a basin can exhibit an impressive level of cooperation, yet beneath the surface display tremendous environmental injustice to basin countries and basin sub-populations (e.g. indigenous groups, women). Recognizing that cooperation could mask various forms of conflict and looking at the nexus of water conflict and cooperation in terms of interactions rather than events, Mirumachi introduced the Transboundary Waters Interaction Nexus (TWINS) tool (Zeitoun & Mirumachi, 2008). Yet, this nexus also defines water conflict using high politics and militarized conceptualizations. Thus, I argue that the conflict-cooperation paradigm alone is insufficient for understanding the range of impacts from human interactions with transboundary water. Particularly, these scales do not sufficiently capture decisions and policies that have inequitable distributions of environmental costs and benefits. In other words, they do not capture the environmental justice (also referred to as structural violence) implications of water decisions, whether cooperative or conflictive. This is especially true for more nebulously defined qualitative needs like the cultural or aesthetic values for water resources. Furthermore, while institutions like treaties are key to cooperative (i.e. less direct violence) basins (according to Wolf et al., 2003), they may also solidify and reinforce existing power imbalances and injustices (Zeitoun & Mirumachi, 2008). Thus, if cooperation alone does not guarantee progress towards environmental justice, it is important to understand the role of institutions like treaties and river basin organizations (RBOs). Do they deter affected countries and communities from meeting their basic human needs, or can institutions be wielded to affirm those needs? What is the role of participatory processes? Practically, how can managers, policymakers, and environmental facilitators understand and respond to structural violence related to natural resource decisions? The purpose of this dissertation is to bridge the gap between pragmatism and social idealism, between real-world politics and the charge from great philosophers and leaders to create a more just world. Towards this goal, I developed a scale of structural violence in transboundary basins that complements the work of Wolf et al. and Mirumachi et al. (referred to as the London Water Research Group- or LWRG). This tool- called the Integrated Basins at Risk (iBAR) scale- draws from Wolf's (2008) work on water and spirituality, mirroring Maslow’s Hierarchy of Needs. I developed a linked method to assess structural violence/environmental justice using the scale as a prism to assess archival events (newspaper articles), interviews, and observational data from conference and panel presentations. Using the Mekong Basin as a transboundary water case study, I tested the scale and methodology, painting a detailed picture of environmental justice in the basin and the institutional variables associated with positive and negative outcomes. From this, I drew conclusions and produced recommendations relevant to practitioners interested in improving justice outcomes in transboundary basins. Finally, I evaluated the iBAR method's utility as an assessment tool for water conflict facilitators and water managers. Title: Beyond Cooperation : Environmental Justice in Transboundary Water Management Author: Watson, Julie Elkins Since the Wolf, Yoffe, and Giordano 2003 Basins at Risk study, examining human interactions with transboundary water resources through a lens of conflict and cooperation has been a dominant paradigm. The Basins at Risk (BAR) method involves categorizing events on a scale from most conflictive (e.g. war or extensive casualties) to most cooperative (voluntary unification into one political unit). While this research provides significant insight into the nature of cooperation and conflict over water, it frames the discussion about water politics in terms of diplomatic, economic, and military hostility. However, a basin can exhibit an impressive level of cooperation, yet beneath the surface display tremendous environmental injustice to basin countries and basin sub-populations (e.g. indigenous groups, women). Recognizing that cooperation could mask various forms of conflict and looking at the nexus of water conflict and cooperation in terms of interactions rather than events, Mirumachi introduced the Transboundary Waters Interaction Nexus (TWINS) tool (Zeitoun & Mirumachi, 2008). Yet, this nexus also defines water conflict using high politics and militarized conceptualizations. Thus, I argue that the conflict-cooperation paradigm alone is insufficient for understanding the range of impacts from human interactions with transboundary water. Particularly, these scales do not sufficiently capture decisions and policies that have inequitable distributions of environmental costs and benefits. In other words, they do not capture the environmental justice (also referred to as structural violence) implications of water decisions, whether cooperative or conflictive. This is especially true for more nebulously defined qualitative needs like the cultural or aesthetic values for water resources. Furthermore, while institutions like treaties are key to cooperative (i.e. less direct violence) basins (according to Wolf et al., 2003), they may also solidify and reinforce existing power imbalances and injustices (Zeitoun & Mirumachi, 2008). Thus, if cooperation alone does not guarantee progress towards environmental justice, it is important to understand the role of institutions like treaties and river basin organizations (RBOs). Do they deter affected countries and communities from meeting their basic human needs, or can institutions be wielded to affirm those needs? What is the role of participatory processes? Practically, how can managers, policymakers, and environmental facilitators understand and respond to structural violence related to natural resource decisions? The purpose of this dissertation is to bridge the gap between pragmatism and social idealism, between real-world politics and the charge from great philosophers and leaders to create a more just world. Towards this goal, I developed a scale of structural violence in transboundary basins that complements the work of Wolf et al. and Mirumachi et al. (referred to as the London Water Research Group- or LWRG). This tool- called the Integrated Basins at Risk (iBAR) scale- draws from Wolf's (2008) work on water and spirituality, mirroring Maslow’s Hierarchy of Needs. I developed a linked method to assess structural violence/environmental justice using the scale as a prism to assess archival events (newspaper articles), interviews, and observational data from conference and panel presentations. Using the Mekong Basin as a transboundary water case study, I tested the scale and methodology, painting a detailed picture of environmental justice in the basin and the institutional variables associated with positive and negative outcomes. From this, I drew conclusions and produced recommendations relevant to practitioners interested in improving justice outcomes in transboundary basins. Finally, I evaluated the iBAR method's utility as an assessment tool for water conflict facilitators and water managers. Close

• 2794. [Article] Student leadership development within student government at Snow College

  The purpose of this study was to describe the leadership development process of former student leaders at Snow College. More specifically, the study focused on understanding how, when, and where leadership ...

  Citation × Citation Citation Abstract Copy Title: Student leadership development within student government at Snow College Author: Wilson, Gordon Ned The purpose of this study was to describe the leadership development process of former student leaders at Snow College. More specifically, the study focused on understanding how, when, and where leadership development took place in their "lived experience" within the student government at Snow College (Van Manen, 1998). Examining the lived experiences of these former college student leaders has helped bring forth the essence of their student leadership development process as it related to the Snow College student government program. The study identified key themes, formal and informal techniques, or common threads of success or failure that contributed to the knowledge base of student leadership development in this community college setting. Through a phenomenological inquiry, eight former student government leaders were interviewed. Two principle research questions guided the design of this study: (a) While you were a student leader at Snow College, how did your leadership skills and abilities develop? (b) While you were a student at Snow College, how did the institution specifically contribute to your growth and development as a student leader? Analysis of data yielded eight central themes, with 16 sub-themes nested within the central themes. Four broad themes and seven sub-themes emerged from the first research question. They include: (1) Opportunities and three sub-themes: (a) Learning to serve and the changes that take place, (b) Inclusion and putting others first, (c) Learning by doing. (2) Structured Experiences and two sub-themes: (a) Student government, (b) Other experiences from being involved, (3) The influence of mentors, specifically advisors, (4) The formal Education Process and two sub-themes: (a) The Leadership Class, (b) Conferences and Retreats. Four broad themes and nine sub-themes emerged from research question two. They include: (1) Snow College student government provided hands-on experiences, (2) Culture and three sub-themes (a) Invited participation, (b) The student is important to the institution, (c) Leadership driven environment, (3) Professional Support and four sub-themes: (a) Professional mentors, (b) Taught by example, (c) The college president, (d) High expectations to learn and do, (4) Education and two sub-themes: (a) The leadership class, (b) An established environment for active learning. Emerging from these thematic descriptions were six observations that demonstrated how student leadership development took place at Snow College: (a) An Elected Position within Student Government was the Catalyst for Leadership Development; (b) There was an Institutional Culture at Snow College that Supported Student Leadership Development; (c) Professional and Engaged Advisors played a Intentional Key Role in Student Leadership Development; (d) The Structured Formal Learning Forums within Student Government are Important to Leadership Development; (e) The Informal, yet Structured, Hands-On Experiences Provided Teaching Moments that made a Lasting Impression on these Participants; and (f) Unstructured yet Urgent Situational Leadership Decisions Connected to the Positions held within Student Government created Real Life Opportunities to Learn Leadership Skills. Recommendations include: (a) Student government or some other significant student life program that will provide heightened leadership opportunities that will allow a student leader to practice or have hands-on leadership experiences; (b) The institution should have a culture that values the importance of student leadership development at all levels and lends support by creating opportunities for others including administration to mentor student leaders; (c) The institution's primary goal is to educate, and this goal needs to be carried over to the leadership development program; (d) The institution should hire professional full-time advisors for their student life organizations such as student government or whatever organization is part of the student leadership development program; (e) There should be informal orchestrated experiences that help shape leadership skills and abilities in student leaders; and (f) The student leaders should be allowed hands-on experiences that are real and impactful such as those experienced by the study participants in student government at Snow College. Title: Student leadership development within student government at Snow College Author: Wilson, Gordon Ned The purpose of this study was to describe the leadership development process of former student leaders at Snow College. More specifically, the study focused on understanding how, when, and where leadership development took place in their "lived experience" within the student government at Snow College (Van Manen, 1998). Examining the lived experiences of these former college student leaders has helped bring forth the essence of their student leadership development process as it related to the Snow College student government program. The study identified key themes, formal and informal techniques, or common threads of success or failure that contributed to the knowledge base of student leadership development in this community college setting. Through a phenomenological inquiry, eight former student government leaders were interviewed. Two principle research questions guided the design of this study: (a) While you were a student leader at Snow College, how did your leadership skills and abilities develop? (b) While you were a student at Snow College, how did the institution specifically contribute to your growth and development as a student leader? Analysis of data yielded eight central themes, with 16 sub-themes nested within the central themes. Four broad themes and seven sub-themes emerged from the first research question. They include: (1) Opportunities and three sub-themes: (a) Learning to serve and the changes that take place, (b) Inclusion and putting others first, (c) Learning by doing. (2) Structured Experiences and two sub-themes: (a) Student government, (b) Other experiences from being involved, (3) The influence of mentors, specifically advisors, (4) The formal Education Process and two sub-themes: (a) The Leadership Class, (b) Conferences and Retreats. Four broad themes and nine sub-themes emerged from research question two. They include: (1) Snow College student government provided hands-on experiences, (2) Culture and three sub-themes (a) Invited participation, (b) The student is important to the institution, (c) Leadership driven environment, (3) Professional Support and four sub-themes: (a) Professional mentors, (b) Taught by example, (c) The college president, (d) High expectations to learn and do, (4) Education and two sub-themes: (a) The leadership class, (b) An established environment for active learning. Emerging from these thematic descriptions were six observations that demonstrated how student leadership development took place at Snow College: (a) An Elected Position within Student Government was the Catalyst for Leadership Development; (b) There was an Institutional Culture at Snow College that Supported Student Leadership Development; (c) Professional and Engaged Advisors played a Intentional Key Role in Student Leadership Development; (d) The Structured Formal Learning Forums within Student Government are Important to Leadership Development; (e) The Informal, yet Structured, Hands-On Experiences Provided Teaching Moments that made a Lasting Impression on these Participants; and (f) Unstructured yet Urgent Situational Leadership Decisions Connected to the Positions held within Student Government created Real Life Opportunities to Learn Leadership Skills. Recommendations include: (a) Student government or some other significant student life program that will provide heightened leadership opportunities that will allow a student leader to practice or have hands-on leadership experiences; (b) The institution should have a culture that values the importance of student leadership development at all levels and lends support by creating opportunities for others including administration to mentor student leaders; (c) The institution's primary goal is to educate, and this goal needs to be carried over to the leadership development program; (d) The institution should hire professional full-time advisors for their student life organizations such as student government or whatever organization is part of the student leadership development program; (e) There should be informal orchestrated experiences that help shape leadership skills and abilities in student leaders; and (f) The student leaders should be allowed hands-on experiences that are real and impactful such as those experienced by the study participants in student government at Snow College. Close

• 2795. [Article] The economic impacts of sagebrush steppe wildfires on an eastern Oregon ranch

  The relative success of restoration practices on cheatgrass infested sagebrush steppe lands in the Great Basin can affect the probability of crossing an ecological threshold and have economic effects on ...

  Citation × Citation Citation Abstract Copy Title: The economic impacts of sagebrush steppe wildfires on an eastern Oregon ranch Author: Maher, Anna T. The relative success of restoration practices on cheatgrass infested sagebrush steppe lands in the Great Basin can affect the probability of crossing an ecological threshold and have economic effects on cattle ranches using federal rangelands. Cheatgrass invasion implies an increase in the risk of fire, which in turn increases the likelihood that ranchers will be denied temporary access to public lands. No study to date has incorporated forage availability constraints imposed on public grazing allotments by cheatgrass wildfires into ranch-level economic models. As cheatgrass is known to cause frequent fires, ignoring this constraint could overestimate the benefit of cheatgrass as a spring forage source. The purpose of this project is to determine the importance of considering specific ecological effects of cheatgrass-associated wildfires on a ranch-level economic model. This study assumes that a representative Oregon 300 cow-calf ranch possesses a Bureau of Land Management (BLM) allotment that exhibits ecological characteristics typical of sagebrush steppe sites that are vulnerable to continued cheatgrass invasion. This project utilizes biological data gathered as part of the on-going Sagebrush Steppe Treatment Evaluation Project (SageSTEP) from a high desert land type in eastern Oregon. The grazing allotment is assumed to have a 15% percent cover of cheatgrass with an associated 20 to 40 year fire return interval. Results from a ranch economic impact analysis of cheatgrass associated fires on a ranch’s public grazing allotment may exhibit directional bias if the baseline model does not consider both the economic contribution of cheatgrass to spring forage and the economic cost of a typical minimum two-year grazing exclusion following a wildfire. These two forage availability constraints are added to the public forage component of a ranch bioeconomic model to address how the representative ranch reacts to the temporary loss of permitted AUMs in terms of forage substitution and/or herd size reductions as the result of the assumed fire return interval; under what circumstances will this temporary loss of AUMs force a representative ranch out of business; and whether there is an economic impact associated with changes in late spring AUMs under the assumed fire regime. A baseline “No Fire Model” is compared to a “Fire Model” using a forty-year planning horizon with a 7% discount rate. All assumptions regarding a perfectly competitive industry hold in these models, including perfect information. The “Fire Model” is subject to randomly generated fire regimes using a Monte Carlo approach. Precipitation and cattle prices are held constant in order to isolate wildfire effects. Grazing on the BLM allotment is allowed during the fire year and is excluded for the following two years. During these two post-fire years, the representative ranch is forced to choose a substitute forage source and/or limit its herd size. Results indicate that the ranch impacts of a fire go beyond the time-line of the two years of exclusion from the BLM allotment. This decrease in access to BLM AUMs results in an even greater decline in the average use of deeded range AUMs over time when compared to the No Fire Model. This decline occurs regardless of the fact that the ranch increases its use to the maximum available deeded range AUMs during the two years of the BLM allotment exclusion. Average Net Present Value (NPV) is also lower compared to the No Fire Model. Within the results of the Fire Model, NPV decreases and the probability of bankruptcy increases as the number of fires experienced within the planning horizon increases. As policy makers deal with the impending risk of an increase in cheatgrass associated wildfires in the Great Basin sagebrush steppe, this study shows that failing to include ranch impacts of fire on BLM land will likely result in an overestimation of the benefits or an underestimation of the costs of further invasion. Title: The economic impacts of sagebrush steppe wildfires on an eastern Oregon ranch Author: Maher, Anna T. The relative success of restoration practices on cheatgrass infested sagebrush steppe lands in the Great Basin can affect the probability of crossing an ecological threshold and have economic effects on cattle ranches using federal rangelands. Cheatgrass invasion implies an increase in the risk of fire, which in turn increases the likelihood that ranchers will be denied temporary access to public lands. No study to date has incorporated forage availability constraints imposed on public grazing allotments by cheatgrass wildfires into ranch-level economic models. As cheatgrass is known to cause frequent fires, ignoring this constraint could overestimate the benefit of cheatgrass as a spring forage source. The purpose of this project is to determine the importance of considering specific ecological effects of cheatgrass-associated wildfires on a ranch-level economic model. This study assumes that a representative Oregon 300 cow-calf ranch possesses a Bureau of Land Management (BLM) allotment that exhibits ecological characteristics typical of sagebrush steppe sites that are vulnerable to continued cheatgrass invasion. This project utilizes biological data gathered as part of the on-going Sagebrush Steppe Treatment Evaluation Project (SageSTEP) from a high desert land type in eastern Oregon. The grazing allotment is assumed to have a 15% percent cover of cheatgrass with an associated 20 to 40 year fire return interval. Results from a ranch economic impact analysis of cheatgrass associated fires on a ranch’s public grazing allotment may exhibit directional bias if the baseline model does not consider both the economic contribution of cheatgrass to spring forage and the economic cost of a typical minimum two-year grazing exclusion following a wildfire. These two forage availability constraints are added to the public forage component of a ranch bioeconomic model to address how the representative ranch reacts to the temporary loss of permitted AUMs in terms of forage substitution and/or herd size reductions as the result of the assumed fire return interval; under what circumstances will this temporary loss of AUMs force a representative ranch out of business; and whether there is an economic impact associated with changes in late spring AUMs under the assumed fire regime. A baseline “No Fire Model” is compared to a “Fire Model” using a forty-year planning horizon with a 7% discount rate. All assumptions regarding a perfectly competitive industry hold in these models, including perfect information. The “Fire Model” is subject to randomly generated fire regimes using a Monte Carlo approach. Precipitation and cattle prices are held constant in order to isolate wildfire effects. Grazing on the BLM allotment is allowed during the fire year and is excluded for the following two years. During these two post-fire years, the representative ranch is forced to choose a substitute forage source and/or limit its herd size. Results indicate that the ranch impacts of a fire go beyond the time-line of the two years of exclusion from the BLM allotment. This decrease in access to BLM AUMs results in an even greater decline in the average use of deeded range AUMs over time when compared to the No Fire Model. This decline occurs regardless of the fact that the ranch increases its use to the maximum available deeded range AUMs during the two years of the BLM allotment exclusion. Average Net Present Value (NPV) is also lower compared to the No Fire Model. Within the results of the Fire Model, NPV decreases and the probability of bankruptcy increases as the number of fires experienced within the planning horizon increases. As policy makers deal with the impending risk of an increase in cheatgrass associated wildfires in the Great Basin sagebrush steppe, this study shows that failing to include ranch impacts of fire on BLM land will likely result in an overestimation of the benefits or an underestimation of the costs of further invasion. Close

• 2796. [Article] Livestock, deer and logging interactions in the lodgepole pine/pumice region of central Oregon

  The objectives of this study were to: 1) determine production of plant species and utilization by cattle, sheep and deer as related to plant communities and timber management practices and 2) evaluate the ...

  Citation × Citation Citation Abstract Copy Title: Livestock, deer and logging interactions in the lodgepole pine/pumice region of central Oregon Author: Stuth, Jerry W. The objectives of this study were to: 1) determine production of plant species and utilization by cattle, sheep and deer as related to plant communities and timber management practices and 2) evaluate the interaction of range use between cattle and deer and between sheep and deer as affected by site and timber management practices. Meadow communities and logged and non-logged areas of the Pinus contorta/Purshia tridentata /Stipa occidentalis habitat type were studied during the summer grazing season of a dry (1973) and wet (1974) year in Klamath County, Oregon. Six meadow habitat types were proposed. Meadow production varied from 879 to 2602 pounds per acre in 1973 (dry year) and varied from 2389 to 3295 pounds per acre in 1974 (wet year). Grasslike species in the meadows accounted for the greatest response in production to yearly moisture fluctuations. Forbs experienced little change in production on meadows with good soil and water conditions, whereas, a 93 to 160 percent increase occurred on the more shallow, dry meadows. Deer grazing on the meadows maintained a diet dominated by forbs both years, whereas, cattle and sheep grazed predominantly on grass and grasslike species while on the meadows. Meadow species which constituted the greatest potential overlap in the diets of livestock and deer included: Potentilla gracilis, Microseris nutans, idalcea oregana, Ranunculus alismaefolius, Achillea millefolium and Penstemon procerus. Deer experienced a transition from a forb dominated diet to a shrub dominated diet during July. Purshia tridentata was the only species utilized by deer in both logged and non-logged areas with utilization being minimal during July. After August 1 utilization accelerated in the logged areas but remained static in the non-logged areas. Approximately 7 to 10 times more Purshia tridentata was consumed by deer from logged areas. Only fringes of non-logged areas were used by cattle. Stipa occidentalis and Sitanion hystrix growing in logged areas dominated the diet of cattle in July. By mid-August Purshia tridentata dominated their diet and comprised 75 percent by the end of the grazing season. Purshia tridentata was dominant in the diet of sheep on the logged and non-logged areas throughout the grazing season. Approximately 2.5 times more Purshia tridentata was consumed by sheep in the logged areas as compared to the non-logged areas. At the end of the grazing season dual utilization values on Purshia tridentata in logged areas were 25 and 50 percent for cattle-deer and sheep-deer, respectively and in non-logged areas were 15 and 30 percent, respectively. Total herbaceous production was 58-126 and 12-18 pounds per acre for the logged and non-logged areas, respectively. Purshia tridentata production was 287-397 and 223-297 pounds per acre for the logged and non-logged areas, respectively. Purshia tridentata plants growing in non-logged areas had 55 percent of their current year's growth in the unutilized spurs. Developed leaders (terminal and lateral) accounted for 71 percent of the production of Purshia tridentata in logged areas. Average leader lengths were approximately 2.5 cm longer on plants in logged areas. Approximately 42 percent of the Purshia tridentata plants were lost during the logging operations. Sixty-four percent of the > 40 cm height plants were lost from logging while 16 percent of the 20-40 cm height plants were destroyed. Densities of germinated rodent caches of Purshia tridentata were much lower in logged areas. Percent canopy cover and density of Purshia contorta were highly correlated with cache densities in logged areas. Additional managerial considerations relative to timber harvest were mentioned. Title: Livestock, deer and logging interactions in the lodgepole pine/pumice region of central Oregon Author: Stuth, Jerry W. The objectives of this study were to: 1) determine production of plant species and utilization by cattle, sheep and deer as related to plant communities and timber management practices and 2) evaluate the interaction of range use between cattle and deer and between sheep and deer as affected by site and timber management practices. Meadow communities and logged and non-logged areas of the Pinus contorta/Purshia tridentata /Stipa occidentalis habitat type were studied during the summer grazing season of a dry (1973) and wet (1974) year in Klamath County, Oregon. Six meadow habitat types were proposed. Meadow production varied from 879 to 2602 pounds per acre in 1973 (dry year) and varied from 2389 to 3295 pounds per acre in 1974 (wet year). Grasslike species in the meadows accounted for the greatest response in production to yearly moisture fluctuations. Forbs experienced little change in production on meadows with good soil and water conditions, whereas, a 93 to 160 percent increase occurred on the more shallow, dry meadows. Deer grazing on the meadows maintained a diet dominated by forbs both years, whereas, cattle and sheep grazed predominantly on grass and grasslike species while on the meadows. Meadow species which constituted the greatest potential overlap in the diets of livestock and deer included: Potentilla gracilis, Microseris nutans, idalcea oregana, Ranunculus alismaefolius, Achillea millefolium and Penstemon procerus. Deer experienced a transition from a forb dominated diet to a shrub dominated diet during July. Purshia tridentata was the only species utilized by deer in both logged and non-logged areas with utilization being minimal during July. After August 1 utilization accelerated in the logged areas but remained static in the non-logged areas. Approximately 7 to 10 times more Purshia tridentata was consumed by deer from logged areas. Only fringes of non-logged areas were used by cattle. Stipa occidentalis and Sitanion hystrix growing in logged areas dominated the diet of cattle in July. By mid-August Purshia tridentata dominated their diet and comprised 75 percent by the end of the grazing season. Purshia tridentata was dominant in the diet of sheep on the logged and non-logged areas throughout the grazing season. Approximately 2.5 times more Purshia tridentata was consumed by sheep in the logged areas as compared to the non-logged areas. At the end of the grazing season dual utilization values on Purshia tridentata in logged areas were 25 and 50 percent for cattle-deer and sheep-deer, respectively and in non-logged areas were 15 and 30 percent, respectively. Total herbaceous production was 58-126 and 12-18 pounds per acre for the logged and non-logged areas, respectively. Purshia tridentata production was 287-397 and 223-297 pounds per acre for the logged and non-logged areas, respectively. Purshia tridentata plants growing in non-logged areas had 55 percent of their current year's growth in the unutilized spurs. Developed leaders (terminal and lateral) accounted for 71 percent of the production of Purshia tridentata in logged areas. Average leader lengths were approximately 2.5 cm longer on plants in logged areas. Approximately 42 percent of the Purshia tridentata plants were lost during the logging operations. Sixty-four percent of the > 40 cm height plants were lost from logging while 16 percent of the 20-40 cm height plants were destroyed. Densities of germinated rodent caches of Purshia tridentata were much lower in logged areas. Percent canopy cover and density of Purshia contorta were highly correlated with cache densities in logged areas. Additional managerial considerations relative to timber harvest were mentioned. Close

• 2797. [Article] Estimation and modeling of selected forest metrics with lidar and Landsat

  Lidar is able to provide height and cover information which can be used to estimate selected forest attributes precisely. However, for users to evaluate whether the additional cost and complication associated ...

  Citation × Citation Citation Abstract Copy Title: Estimation and modeling of selected forest metrics with lidar and Landsat Author: Strunk, Jacob L. Lidar is able to provide height and cover information which can be used to estimate selected forest attributes precisely. However, for users to evaluate whether the additional cost and complication associated with using Lidar merits adoption requires that the protocol to use lidar be thoroughly described and that a basis for selection of design parameters such as number of field plots and lidar pulse density be described. In our first analysis, we examine these issues by looking at the effects of pulse density and sample size on estimation when wall-to-wall lidar is used with a regression estimator. The effects were explored using resampling simulations. We examine both the effects on precision, and on the validity of inference. Pulse density had almost no effect on precision for the range examined, from 3 to .0625 pulses / m². The effect of sample size on estimator precision was roughly in accordance with the behavior indicated by the variance estimator, except that for small samples the variance estimator had positive bias (the variance estimates were too small), compromising the validity of inference. In future analyses we plan to provide further context for wall-to-wall lidar-assisted estimation. While there is a lot of literature on modeling, there is limited information on how lidar-assisted approaches compare to existing methods, and what variables can or cannot be acquired, or may be acquired with reduced confidence. We expand our investigation of estimation in our second analysis by examining lidar obtained in a sampling mode in combination with Landsat. In this case we make inference about the feasibility of a lidar-assisted estimation strategy by contrasting its variance estimate with variance estimates from a variety of other sampling designs and estimators. Of key interest was how the precision of a two-stage estimator with lidar strips compared with a plot-only estimator from a simple random sampling design. We found that because the long and narrow lidar strips incorporate much of the landscape variability, if the number of lidar strips was increased from 7 to 15 strips, the precision of estimators with lidar can exceed that of estimators applied to plot-only SRS data for a much larger number of plots. Increasing the number of lidar strips is considered to be highly viable since the costs of field plots can be quite expensive in Alaska, often exceeding the cost of a lidar strip. A Landsat-assisted approach used for either an SRS or a two-stage sample was also found to perform well relative to estimators for plot-only SRS data. This proved beneficial when we combined lidar and Landsat-assisted regression estimators for two-stage designs using a composite estimator. The composite estimator yielded much better results than either estimator used alone. We did not assess the effects of changing the number of lidar strips in combination with using a composite estimator, but this is an important analysis we plan to perform in a future study. In our final analysis we leverage the synergy between lidar and Landsat to improve the explanatory power of auxiliary Landsat using a multilevel modeling strategy. We also incorporate a more sophisticated approach to processing Landsat which reflects temporal trends in individual pixels values. Our approach used lidar as an intermediary step to better match the spatial resolution of Landsat and increase the proportion of area overlapped between measurement units for the different sources of data. We developed two separate approaches for two different resolutions of data (30 m and 90 m) using multiple modeling alternatives including OLS and k nearest neighbors (KNN), and found that both resolution and the modeling approach affected estimates of residual variability, although there was no combination of model types which was a clear winner for all responses. The modeling strategies generally fared better for the 90 m approaches, and future analyses will examine a broader range of resolutions. Fortunately the approaches used are fairly flexible and there is nothing prohibiting a 1000 m implementation. In the future we also plan to look at using a more sophisticated Landsat time-series approach. The current approach essentially dampened the noise in the temporal trend for a pixel, but did not make use of information in the trend such as slope or indications of disturbance – which may provide additional explanatory power. In a future study we will also incorporate a multilevel modeling into estimation or mapping strategies and evaluate the contribution of the multilevel modeling strategy relative to alternate approaches. Title: Estimation and modeling of selected forest metrics with lidar and Landsat Author: Strunk, Jacob L. Lidar is able to provide height and cover information which can be used to estimate selected forest attributes precisely. However, for users to evaluate whether the additional cost and complication associated with using Lidar merits adoption requires that the protocol to use lidar be thoroughly described and that a basis for selection of design parameters such as number of field plots and lidar pulse density be described. In our first analysis, we examine these issues by looking at the effects of pulse density and sample size on estimation when wall-to-wall lidar is used with a regression estimator. The effects were explored using resampling simulations. We examine both the effects on precision, and on the validity of inference. Pulse density had almost no effect on precision for the range examined, from 3 to .0625 pulses / m². The effect of sample size on estimator precision was roughly in accordance with the behavior indicated by the variance estimator, except that for small samples the variance estimator had positive bias (the variance estimates were too small), compromising the validity of inference. In future analyses we plan to provide further context for wall-to-wall lidar-assisted estimation. While there is a lot of literature on modeling, there is limited information on how lidar-assisted approaches compare to existing methods, and what variables can or cannot be acquired, or may be acquired with reduced confidence. We expand our investigation of estimation in our second analysis by examining lidar obtained in a sampling mode in combination with Landsat. In this case we make inference about the feasibility of a lidar-assisted estimation strategy by contrasting its variance estimate with variance estimates from a variety of other sampling designs and estimators. Of key interest was how the precision of a two-stage estimator with lidar strips compared with a plot-only estimator from a simple random sampling design. We found that because the long and narrow lidar strips incorporate much of the landscape variability, if the number of lidar strips was increased from 7 to 15 strips, the precision of estimators with lidar can exceed that of estimators applied to plot-only SRS data for a much larger number of plots. Increasing the number of lidar strips is considered to be highly viable since the costs of field plots can be quite expensive in Alaska, often exceeding the cost of a lidar strip. A Landsat-assisted approach used for either an SRS or a two-stage sample was also found to perform well relative to estimators for plot-only SRS data. This proved beneficial when we combined lidar and Landsat-assisted regression estimators for two-stage designs using a composite estimator. The composite estimator yielded much better results than either estimator used alone. We did not assess the effects of changing the number of lidar strips in combination with using a composite estimator, but this is an important analysis we plan to perform in a future study. In our final analysis we leverage the synergy between lidar and Landsat to improve the explanatory power of auxiliary Landsat using a multilevel modeling strategy. We also incorporate a more sophisticated approach to processing Landsat which reflects temporal trends in individual pixels values. Our approach used lidar as an intermediary step to better match the spatial resolution of Landsat and increase the proportion of area overlapped between measurement units for the different sources of data. We developed two separate approaches for two different resolutions of data (30 m and 90 m) using multiple modeling alternatives including OLS and k nearest neighbors (KNN), and found that both resolution and the modeling approach affected estimates of residual variability, although there was no combination of model types which was a clear winner for all responses. The modeling strategies generally fared better for the 90 m approaches, and future analyses will examine a broader range of resolutions. Fortunately the approaches used are fairly flexible and there is nothing prohibiting a 1000 m implementation. In the future we also plan to look at using a more sophisticated Landsat time-series approach. The current approach essentially dampened the noise in the temporal trend for a pixel, but did not make use of information in the trend such as slope or indications of disturbance – which may provide additional explanatory power. In a future study we will also incorporate a multilevel modeling into estimation or mapping strategies and evaluate the contribution of the multilevel modeling strategy relative to alternate approaches. Close

• 2798. [Article] Age structure, developmental pathways, and fire regime characterization of Douglas-fir/western hemlock forests in the central western Cascades of Oregon

  Descriptions of the fire regime in the Douglas-fir/western hemlock region of the Pacific Northwest traditionally have emphasized infrequent, predominantly stand-replacement fires and an associated linear ...

  Citation × Citation Citation Abstract Copy Title: Age structure, developmental pathways, and fire regime characterization of Douglas-fir/western hemlock forests in the central western Cascades of Oregon Author: Tepley, Alan J. Descriptions of the fire regime in the Douglas-fir/western hemlock region of the Pacific Northwest traditionally have emphasized infrequent, predominantly stand-replacement fires and an associated linear pathway of stand development, where all stands proceed along a common pathway until reset by the next fire. Although such a description may apply in wetter parts of the region, recent fire-history research suggests drier parts of the region support a mixed-severity regime, where most fires have substantial representation of all severity classes and most stands experience at least one non-stand-replacing fire between stand-replacement events. This study combines field and modeling approaches to better understand the complex fire regime in the central western Cascades of Oregon. Stand-structure data and ages of more than 3,000 trees were collected at 124 stands throughout two study areas with physiography representative of western and eastern portions of the western Cascade Range. Major objectives were to (1) develop a conceptual model of fire-mediated pathways of stand development, (2) determine the strengths of influences of topography on spatial variation in the fire regime, (3) provide a stronger understanding of modeling approaches commonly used to gain insight into historical landscape structure, and (4) develop methods to predict trajectories of change in landscape age structure under a non-stationary fire regime. In the study area, non-stand-replacing fire interspersed with infrequent, stand-replacement events led to a variety of even-aged and multi-cohort stands. The majority of stands (75%) had two or more age cohorts, where post-fire cohorts were dominated either by shade-intolerant species or shade-tolerant species, depending largely on fire severity. Age structure, used as a proxy for the cumulative effects of fire on stand development, showed a moderately strong relationship to topography overall, but relationships were strongest at both extremes of a continuum of the influences of fire frequency and severity on stand development and relatively weak in the middle. High topographic relief in the eastern part of the western Cascades may amplify variation in microclimate and fuel moisture, leading to a finer-scale spatial variation in fire spread and behavior, and thus a broader range of stand age structures and stronger fidelity of age structure to slope position and terrain shape in the deeply dissected terrain of the eastern part of the western Cascades than in the gentler terrain of the western part. In the modeling component of my research, I was able to use analytical procedures to reproduce much of the output provided by a stochastic, spatial simulation model previously applied to evaluate historical landscape structure of the Oregon Coast Range. The analytical approximation provides an explicit representation of the effects of input parameters and interactions among them. The increased transparency of model function given by such an analysis may facilitate communication of model output and uncertainty among ecologists and forest managers. Analytical modeling approaches were expanded to characterize trajectories of change in forest age structure in response to changes in the fire regime. Following a change in fire frequency, the proportion of the landscape covered by stands of a given age class is expected to change along a non-monotonic trajectory rather than transition directly to its equilibrium abundance under the new regime. Under some scenarios of change in fire frequency, the time for the expected age distribution of a landscape to converge to the equilibrium distribution of the new regime can be determined based only on the magnitude of change in fire frequency, regardless of the initial value or the direction of change. The theoretical modeling exercises provide insight into historical trends in the study area. Compiled across all sample sites, the age distribution of Douglas-fir trees was strongly bimodal. Peaks of establishment dates in the 16th and 19th centuries were synchronous between the two study areas, and each peak of Douglas-fir establishment coincides with one of the two periods of region-wide extensive fire identified in a previous synthesis of fire-history studies. The modeling exercises support the development of such a bimodal age distribution in response to centennial-scale changes in fire frequency, and they illustrate how the relative abundance of different stand-structure types may have varied over the last several centuries. Title: Age structure, developmental pathways, and fire regime characterization of Douglas-fir/western hemlock forests in the central western Cascades of Oregon Author: Tepley, Alan J. Descriptions of the fire regime in the Douglas-fir/western hemlock region of the Pacific Northwest traditionally have emphasized infrequent, predominantly stand-replacement fires and an associated linear pathway of stand development, where all stands proceed along a common pathway until reset by the next fire. Although such a description may apply in wetter parts of the region, recent fire-history research suggests drier parts of the region support a mixed-severity regime, where most fires have substantial representation of all severity classes and most stands experience at least one non-stand-replacing fire between stand-replacement events. This study combines field and modeling approaches to better understand the complex fire regime in the central western Cascades of Oregon. Stand-structure data and ages of more than 3,000 trees were collected at 124 stands throughout two study areas with physiography representative of western and eastern portions of the western Cascade Range. Major objectives were to (1) develop a conceptual model of fire-mediated pathways of stand development, (2) determine the strengths of influences of topography on spatial variation in the fire regime, (3) provide a stronger understanding of modeling approaches commonly used to gain insight into historical landscape structure, and (4) develop methods to predict trajectories of change in landscape age structure under a non-stationary fire regime. In the study area, non-stand-replacing fire interspersed with infrequent, stand-replacement events led to a variety of even-aged and multi-cohort stands. The majority of stands (75%) had two or more age cohorts, where post-fire cohorts were dominated either by shade-intolerant species or shade-tolerant species, depending largely on fire severity. Age structure, used as a proxy for the cumulative effects of fire on stand development, showed a moderately strong relationship to topography overall, but relationships were strongest at both extremes of a continuum of the influences of fire frequency and severity on stand development and relatively weak in the middle. High topographic relief in the eastern part of the western Cascades may amplify variation in microclimate and fuel moisture, leading to a finer-scale spatial variation in fire spread and behavior, and thus a broader range of stand age structures and stronger fidelity of age structure to slope position and terrain shape in the deeply dissected terrain of the eastern part of the western Cascades than in the gentler terrain of the western part. In the modeling component of my research, I was able to use analytical procedures to reproduce much of the output provided by a stochastic, spatial simulation model previously applied to evaluate historical landscape structure of the Oregon Coast Range. The analytical approximation provides an explicit representation of the effects of input parameters and interactions among them. The increased transparency of model function given by such an analysis may facilitate communication of model output and uncertainty among ecologists and forest managers. Analytical modeling approaches were expanded to characterize trajectories of change in forest age structure in response to changes in the fire regime. Following a change in fire frequency, the proportion of the landscape covered by stands of a given age class is expected to change along a non-monotonic trajectory rather than transition directly to its equilibrium abundance under the new regime. Under some scenarios of change in fire frequency, the time for the expected age distribution of a landscape to converge to the equilibrium distribution of the new regime can be determined based only on the magnitude of change in fire frequency, regardless of the initial value or the direction of change. The theoretical modeling exercises provide insight into historical trends in the study area. Compiled across all sample sites, the age distribution of Douglas-fir trees was strongly bimodal. Peaks of establishment dates in the 16th and 19th centuries were synchronous between the two study areas, and each peak of Douglas-fir establishment coincides with one of the two periods of region-wide extensive fire identified in a previous synthesis of fire-history studies. The modeling exercises support the development of such a bimodal age distribution in response to centennial-scale changes in fire frequency, and they illustrate how the relative abundance of different stand-structure types may have varied over the last several centuries. Close

• 2799. [Article] Compositional variations in hydrothermal white mica and chlorite from wall-rock alteration at the Ann-Mason porphyry copper deposit, Nevada

  The detection of subtle variations in mineral chemistry in zoned hydrothermal alteration associated with the formation of porphyry copper deposits by short-wave infrared spectroscopy and rock chemistry ...

  Citation × Citation Citation Abstract Copy Title: Compositional variations in hydrothermal white mica and chlorite from wall-rock alteration at the Ann-Mason porphyry copper deposit, Nevada Author: Cohen, Julia F. The detection of subtle variations in mineral chemistry in zoned hydrothermal alteration associated with the formation of porphyry copper deposits by short-wave infrared spectroscopy and rock chemistry are potentially valuable vectoring tools for mineral exploration. In order to correctly interpret the data collected by these methods, results must be calibrated by mineral data. Hydrothermal white mica, illite and chlorite grains were sampled from the Ann-Mason porphyry copper deposit in the Yerington district, Nevada, a Middle Jurassic porphyry copper system extended and tilted ~ 90° to the west. Mineral compositions vary spatially and record interactions with chemically distinct hydrothermal fluids over a vertical distance of ~5 km and a lateral distance of ~2 km from the ore center. Data suggest short wave infrared spectroscopy and bulk rock geochemical sampling can detect changes in mineral chemistry related to ore deposit formation but both methods have limitations. To relate short wave infrared spectroscopy to mineral compositions, spectra from rock samples were measured. Characteristic features commonly used to identify white mica, illite and chlorite were compared to chemical compositions of mineral grains from 34 samples were determined by electron microprobe analysis. Results demonstrate short wave infrared spectroscopy can be used to detect changes in the aluminum content of micas using the wavelength of the 2200 nm feature and may be used to map fluid pH gradients in rocks with muscovite or illite-bearing assemblages. The following compositional characteristics of white mica/illite were observed in the short wave infrared spectra: (1) an increase in the wavelength of the Al-OH absorption at ca. 2200 nm that is positively correlated with Fe+Mg+Mn (apfu) content and negatively correlated with total Al (apfu) corresponding to Tschermak substitution in both muscovite and illite, and (2) a decrease the wavelength of the ca. 2200 nm absorption to values below 2193 nm attributed to an increase in Na content (apfu) and the presence of paragonite intergrown with muscovite. For this sample set, illite cannot be distinguished from muscovite using short wave infrared spectroscopy. The proportion of Fe:Mg in the octahedral site in chlorite could not be identified in short wave infrared spectra of rocks using the wavelength of the 2350 nm feature and may have been obscured by coexisting highly reflective clays and micas. To compare trace metal gradients in rocks and minerals, trace metal concentrations of more than 600 altered rock samples, collected in a broad geochemical sampling campaign, were measured using inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectroscopy. Trace element contents of rocks were compared to trace metal contents of hydrothermal white mica, illite and chlorite determined by laser ablation-inductively coupled plasma-mass spectrometry from a set of 34 samples. Results show Cu, Mo, Te, Se, Bi, Sb, As, W, Sn, Li and Tl are enriched in rocks from the zone of potassic, sericitic and shallow-level advanced argillic alteration that represents the near-vertical pathway of the ore fluid from the mineralized zone (3.5 km depth) to the near the paleosurface (< 0.5 km). Of these elements, W, Sn and Tl enrichment in rock can be attributed, at least partially, to increased concentrations in muscovite and illite. Lithium enrichment can be attributed to increased concentrations in chlorite and more mafic, chlorite-rich wall-rock lithology at less than 1 km depth. Zinc, Mn, Co and Ni are depleted in altered rock above the ore zone and redistributed upward and laterally by both the magmatic hydrothermal fluid and by circulating sedimentary brines as verified by gradients in chlorite compositions from propylitic alteration. Copper is detected in chlorites but at concentrations (average 280 ppm) too low to contribute significantly to the observed Cu anomaly in rock (>1000 ppm). Chalcophile elements Mo, As, Te, Se, Bi are rarely detected in white mica/illite or chlorite in concentrations greater than 1 ppm and, in more than 50% of analyses, levels are below detection. Title: Compositional variations in hydrothermal white mica and chlorite from wall-rock alteration at the Ann-Mason porphyry copper deposit, Nevada Author: Cohen, Julia F. The detection of subtle variations in mineral chemistry in zoned hydrothermal alteration associated with the formation of porphyry copper deposits by short-wave infrared spectroscopy and rock chemistry are potentially valuable vectoring tools for mineral exploration. In order to correctly interpret the data collected by these methods, results must be calibrated by mineral data. Hydrothermal white mica, illite and chlorite grains were sampled from the Ann-Mason porphyry copper deposit in the Yerington district, Nevada, a Middle Jurassic porphyry copper system extended and tilted ~ 90° to the west. Mineral compositions vary spatially and record interactions with chemically distinct hydrothermal fluids over a vertical distance of ~5 km and a lateral distance of ~2 km from the ore center. Data suggest short wave infrared spectroscopy and bulk rock geochemical sampling can detect changes in mineral chemistry related to ore deposit formation but both methods have limitations. To relate short wave infrared spectroscopy to mineral compositions, spectra from rock samples were measured. Characteristic features commonly used to identify white mica, illite and chlorite were compared to chemical compositions of mineral grains from 34 samples were determined by electron microprobe analysis. Results demonstrate short wave infrared spectroscopy can be used to detect changes in the aluminum content of micas using the wavelength of the 2200 nm feature and may be used to map fluid pH gradients in rocks with muscovite or illite-bearing assemblages. The following compositional characteristics of white mica/illite were observed in the short wave infrared spectra: (1) an increase in the wavelength of the Al-OH absorption at ca. 2200 nm that is positively correlated with Fe+Mg+Mn (apfu) content and negatively correlated with total Al (apfu) corresponding to Tschermak substitution in both muscovite and illite, and (2) a decrease the wavelength of the ca. 2200 nm absorption to values below 2193 nm attributed to an increase in Na content (apfu) and the presence of paragonite intergrown with muscovite. For this sample set, illite cannot be distinguished from muscovite using short wave infrared spectroscopy. The proportion of Fe:Mg in the octahedral site in chlorite could not be identified in short wave infrared spectra of rocks using the wavelength of the 2350 nm feature and may have been obscured by coexisting highly reflective clays and micas. To compare trace metal gradients in rocks and minerals, trace metal concentrations of more than 600 altered rock samples, collected in a broad geochemical sampling campaign, were measured using inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectroscopy. Trace element contents of rocks were compared to trace metal contents of hydrothermal white mica, illite and chlorite determined by laser ablation-inductively coupled plasma-mass spectrometry from a set of 34 samples. Results show Cu, Mo, Te, Se, Bi, Sb, As, W, Sn, Li and Tl are enriched in rocks from the zone of potassic, sericitic and shallow-level advanced argillic alteration that represents the near-vertical pathway of the ore fluid from the mineralized zone (3.5 km depth) to the near the paleosurface (< 0.5 km). Of these elements, W, Sn and Tl enrichment in rock can be attributed, at least partially, to increased concentrations in muscovite and illite. Lithium enrichment can be attributed to increased concentrations in chlorite and more mafic, chlorite-rich wall-rock lithology at less than 1 km depth. Zinc, Mn, Co and Ni are depleted in altered rock above the ore zone and redistributed upward and laterally by both the magmatic hydrothermal fluid and by circulating sedimentary brines as verified by gradients in chlorite compositions from propylitic alteration. Copper is detected in chlorites but at concentrations (average 280 ppm) too low to contribute significantly to the observed Cu anomaly in rock (>1000 ppm). Chalcophile elements Mo, As, Te, Se, Bi are rarely detected in white mica/illite or chlorite in concentrations greater than 1 ppm and, in more than 50% of analyses, levels are below detection. Close

• 2800. [Article] Convergent margin magmatism in the central Andes and its near antipodes in western Indonesia : spatiotemporal and geochemical considerations

  This dissertation combines volcanological research of three convergent continental margins. Chapters 1 and 5 are general introductions and conclusions, respectively. Chapter 2 examines the spatiotemporal development ...

  Citation × Citation Citation Abstract Copy Title: Convergent margin magmatism in the central Andes and its near antipodes in western Indonesia : spatiotemporal and geochemical considerations Author: Salisbury, Morgan J. This dissertation combines volcanological research of three convergent continental margins. Chapters 1 and 5 are general introductions and conclusions, respectively. Chapter 2 examines the spatiotemporal development of the Altiplano-Puna volcanic complex in the Lípez region of southwest Bolivia, a locus of a major Neogene ignimbrite flare- up, yet the least studied portion of the Altiplano-Puna volcanic complex of the Central Andes. New mapping and laser-fusion ⁴⁰Ar/³⁹Ar dating of sanidine and biotite from 56 locations, coupled with paleomagnetic data, refine the timing and volumes of ignimbrite emplacement in Bolivia and northern Chile to reveal that monotonous intermediate volcanism was prodigious and episodic throughout the complex. ⁴⁰Ar/³⁹Ar age determinations of 13 ignimbrites from northern Chile previously dated by the K-Ar method improve the overall temporal resolution of Altiplano-Puna volcanic complex development. Together with new and updated volume estimates, the new age determinations demonstrate a distinct onset of Altiplano-Puna volcanic complex ignimbrite volcanism with modest output rates beginning ~11 Ma, an episodic middle phase with the highest eruption rates between 8 and 3 Ma, followed by a general decline in volcanic output. The cyclic nature of individual caldera complexes and the spatiotemporal pattern of the volcanic field as a whole are consistent with both incremental construction of plutons as well as a composite Cordilleran batholith. Chapter 3 examines the spatiotemporal development of marine tephra deposits in deep sea sediment cores from the Sunda trench near Sumatra, which reveal evidence for seven large (minimum volume 0.6 – 6.3 km³), previously undocumented, explosive eruptions in this region over the last ~110,000 years, presumably sourced from mainland Sumatra. Sediment cores were collected within and adjacent to the Sunda trench from 3.3ºN to 4.6ºS at water depths between 1.8 and 5.5 km and distances of ~200 to 310 km from the active Sumatran volcanic arc. Glass shards within the tephra horizons were analyzed via the electron microprobe and laser ablation ICP-MS and define three compositional groups. Minimum volume estimates for the seven unique units are consistent with volcanic explosivity index (VEI; Newhall and Self, 1982) values of 4 - 5. The most frequent, widespread, and youngest deposits were found in the central region of the study area suggesting the central Sumatran arc as at the highest risk for large explosive eruptions. The first detailed chronological and geochemical data are presented for Tunupa volcano and nearby Huayrana lavas in chapter 4. New ⁴⁰Ar/³⁹Ar age determinations reveal edifice construction at ~1.5 Ma, a duration of ~90-240 k.y., and extrusion rates of 0.43 to 0.93 km³/k.y. Mineralogical compositional and textural data are consistent with shallow crustal storage (~7-18 km) and magma mixing. Volcano morphology, extrusion rates, mineralogy and textures are all similar to the Pleistocene to recent composite cones of the arc front, although new and available age data from the literature indicate that Western Cordilleran volcanism was concomitant with extrusion of both Huayrana (~11 Ma) and Tunupa (~1.5 Ma) lavas in the behind arc region. Arc-related volcanism was either widespread during these eruptive periods, or an additional melting mechanism was involved. Geochemical data, such as lower Ba/Nb ratios and enriched high field strength elemental concentrations, compared to volcanoes of the modern arc front suggest that Huayrana and Tunupa lavas were derived from a different source than the modern arc front. Geophysical and geochemical research in the central Andes indicate local variations in crustal and lithospheric thicknesses and compositions consistent with a dynamic continental lithosphere that has foundered in piecemeal fashion into the underlying asthenosphere throughout the mid to late Cenozoic. The data presented in this chapter for Tunupa and Huayrana indicate a complex petrogenetic origin and more research is necessary to determine the relative roles of arc and non-arc volcanism beneath the central Altiplano. Title: Convergent margin magmatism in the central Andes and its near antipodes in western Indonesia : spatiotemporal and geochemical considerations Author: Salisbury, Morgan J. This dissertation combines volcanological research of three convergent continental margins. Chapters 1 and 5 are general introductions and conclusions, respectively. Chapter 2 examines the spatiotemporal development of the Altiplano-Puna volcanic complex in the Lípez region of southwest Bolivia, a locus of a major Neogene ignimbrite flare- up, yet the least studied portion of the Altiplano-Puna volcanic complex of the Central Andes. New mapping and laser-fusion ⁴⁰Ar/³⁹Ar dating of sanidine and biotite from 56 locations, coupled with paleomagnetic data, refine the timing and volumes of ignimbrite emplacement in Bolivia and northern Chile to reveal that monotonous intermediate volcanism was prodigious and episodic throughout the complex. ⁴⁰Ar/³⁹Ar age determinations of 13 ignimbrites from northern Chile previously dated by the K-Ar method improve the overall temporal resolution of Altiplano-Puna volcanic complex development. Together with new and updated volume estimates, the new age determinations demonstrate a distinct onset of Altiplano-Puna volcanic complex ignimbrite volcanism with modest output rates beginning ~11 Ma, an episodic middle phase with the highest eruption rates between 8 and 3 Ma, followed by a general decline in volcanic output. The cyclic nature of individual caldera complexes and the spatiotemporal pattern of the volcanic field as a whole are consistent with both incremental construction of plutons as well as a composite Cordilleran batholith. Chapter 3 examines the spatiotemporal development of marine tephra deposits in deep sea sediment cores from the Sunda trench near Sumatra, which reveal evidence for seven large (minimum volume 0.6 – 6.3 km³), previously undocumented, explosive eruptions in this region over the last ~110,000 years, presumably sourced from mainland Sumatra. Sediment cores were collected within and adjacent to the Sunda trench from 3.3ºN to 4.6ºS at water depths between 1.8 and 5.5 km and distances of ~200 to 310 km from the active Sumatran volcanic arc. Glass shards within the tephra horizons were analyzed via the electron microprobe and laser ablation ICP-MS and define three compositional groups. Minimum volume estimates for the seven unique units are consistent with volcanic explosivity index (VEI; Newhall and Self, 1982) values of 4 - 5. The most frequent, widespread, and youngest deposits were found in the central region of the study area suggesting the central Sumatran arc as at the highest risk for large explosive eruptions. The first detailed chronological and geochemical data are presented for Tunupa volcano and nearby Huayrana lavas in chapter 4. New ⁴⁰Ar/³⁹Ar age determinations reveal edifice construction at ~1.5 Ma, a duration of ~90-240 k.y., and extrusion rates of 0.43 to 0.93 km³/k.y. Mineralogical compositional and textural data are consistent with shallow crustal storage (~7-18 km) and magma mixing. Volcano morphology, extrusion rates, mineralogy and textures are all similar to the Pleistocene to recent composite cones of the arc front, although new and available age data from the literature indicate that Western Cordilleran volcanism was concomitant with extrusion of both Huayrana (~11 Ma) and Tunupa (~1.5 Ma) lavas in the behind arc region. Arc-related volcanism was either widespread during these eruptive periods, or an additional melting mechanism was involved. Geochemical data, such as lower Ba/Nb ratios and enriched high field strength elemental concentrations, compared to volcanoes of the modern arc front suggest that Huayrana and Tunupa lavas were derived from a different source than the modern arc front. Geophysical and geochemical research in the central Andes indicate local variations in crustal and lithospheric thicknesses and compositions consistent with a dynamic continental lithosphere that has foundered in piecemeal fashion into the underlying asthenosphere throughout the mid to late Cenozoic. The data presented in this chapter for Tunupa and Huayrana indicate a complex petrogenetic origin and more research is necessary to determine the relative roles of arc and non-arc volcanism beneath the central Altiplano. Close