Search

Search Results

• 1. [Article] Variation of Surface Air Temperature in Complex Terrain

  Data from three micronetworks with eddy correlation data and three additional micronetworks without eddy correlation data are analyzed to study the spatial variability of surface air temperature in complex ...

  Citation × Citation Citation Abstract Copy Title: Variation of Surface Air Temperature in Complex Terrain Author: Mahrt, L. Data from three micronetworks with eddy correlation data and three additional micronetworks without eddy correlation data are analyzed to study the spatial variability of surface air temperature in complex terrain. A simple similarity relationship is constructed to relate the spatial variation of air temperature along the slope to the thermal forcing and mixing. Mixing is not included in present empirical formulations of the surface air temperature distribution in complex terrain. The development of surface temperature gradients along the slope, resulting from surface heating or cooling, is bounded by a maximum (or saturated) value, where a further increase of temperature gradients is restricted by redistribution of heat by thermally driven slope circulations. Although much of the spatial variation of the surface air temperature is governed by complex three-dimensionality and surface vegetation, a relatively simple relationship is able to account for much of the diurnal and day-to-day variation of the spatial distribution of air temperature. This relationship requires information on the surface heat flux and friction velocity over a reference surface. Required generalizations of the relationship are outlined before it can be applied to an arbitrary site. Title: Variation of Surface Air Temperature in Complex Terrain Author: Mahrt, L. Data from three micronetworks with eddy correlation data and three additional micronetworks without eddy correlation data are analyzed to study the spatial variability of surface air temperature in complex terrain. A simple similarity relationship is constructed to relate the spatial variation of air temperature along the slope to the thermal forcing and mixing. Mixing is not included in present empirical formulations of the surface air temperature distribution in complex terrain. The development of surface temperature gradients along the slope, resulting from surface heating or cooling, is bounded by a maximum (or saturated) value, where a further increase of temperature gradients is restricted by redistribution of heat by thermally driven slope circulations. Although much of the spatial variation of the surface air temperature is governed by complex three-dimensionality and surface vegetation, a relatively simple relationship is able to account for much of the diurnal and day-to-day variation of the spatial distribution of air temperature. This relationship requires information on the surface heat flux and friction velocity over a reference surface. Required generalizations of the relationship are outlined before it can be applied to an arbitrary site. Close

• 2. [Article] Distributed fiber-optic temperature sensing for hydrologic systems

  This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/.

  Citation × Citation Citation Abstract Copy Title: Distributed fiber-optic temperature sensing for hydrologic systems Author: van de Giesen, Nick, Stejskal, Martin, Westhoff, Martijn, Huwald, Hendrik, Mallet, Alfred, Luxemburg, Wim, Zeman, Josef, Parlange, Marc B., Thevenaz, Luc, Selker, John S. This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/. Title: Distributed fiber-optic temperature sensing for hydrologic systems Author: van de Giesen, Nick, Stejskal, Martin, Westhoff, Martijn, Huwald, Hendrik, Mallet, Alfred, Luxemburg, Wim, Zeman, Josef, Parlange, Marc B., Thevenaz, Luc, Selker, John S. This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/. Close

• 3. [Article] Microchannel steam-methane reforming under constant and variable surface temperature distributions

  Steam-methane reforming is a well understood industrial process used for generating hydrogen and synthesis gas. The reaction is generally carried out with residence times on the order of one second. ...

  Citation × Citation Citation Abstract Copy Title: Microchannel steam-methane reforming under constant and variable surface temperature distributions Author: Eilers, Benn J. Steam-methane reforming is a well understood industrial process used for generating hydrogen and synthesis gas. The reaction is generally carried out with residence times on the order of one second. By performing this reaction at microscales it is possible to take advantage of increased heat transfer rates and low diffusion times allowing equipment size and residence times to be decreased by an order of magnitude. The energy required for the steam-methane reforming reaction could be supplied by solar energy through the use of a solar collector/receiver, thus providing a "cleaner" pathway for hydrogen generation. In such reactors, it is expected that the heat flux and temperature distribution is non-uniform. This study presents a first step in characterizing reforming performance under such variable temperature conditions. The design of the channel was such that the non-uniform heat flux profile expected inside of a solar receiver could be simulated by a controllable temperature profile along the reactor surface. Experiments were conducted over four catalyst configurations and the effects of average reactor temperature, temperature distribution, residence time, steam-methane ratio, and long duration testing were all evaluated. Results demonstrated over 60% conversion of methane at 900°C and a residence time of 26 milliseconds. Methane conversion was found to be strongly dependent on reactor temperature. Ramping temperature distributions demonstrated a 46% greater hydrogen output than isothermal reactions performed at the same average temperature. This work was performed in conjunction with development of a CFD model of reacting flow through a microchannel [1]. The experiments were used to determine the pre-exponential constants of the global reaction rates. Title: Microchannel steam-methane reforming under constant and variable surface temperature distributions Author: Eilers, Benn J. Steam-methane reforming is a well understood industrial process used for generating hydrogen and synthesis gas. The reaction is generally carried out with residence times on the order of one second. By performing this reaction at microscales it is possible to take advantage of increased heat transfer rates and low diffusion times allowing equipment size and residence times to be decreased by an order of magnitude. The energy required for the steam-methane reforming reaction could be supplied by solar energy through the use of a solar collector/receiver, thus providing a "cleaner" pathway for hydrogen generation. In such reactors, it is expected that the heat flux and temperature distribution is non-uniform. This study presents a first step in characterizing reforming performance under such variable temperature conditions. The design of the channel was such that the non-uniform heat flux profile expected inside of a solar receiver could be simulated by a controllable temperature profile along the reactor surface. Experiments were conducted over four catalyst configurations and the effects of average reactor temperature, temperature distribution, residence time, steam-methane ratio, and long duration testing were all evaluated. Results demonstrated over 60% conversion of methane at 900°C and a residence time of 26 milliseconds. Methane conversion was found to be strongly dependent on reactor temperature. Ramping temperature distributions demonstrated a 46% greater hydrogen output than isothermal reactions performed at the same average temperature. This work was performed in conjunction with development of a CFD model of reacting flow through a microchannel [1]. The experiments were used to determine the pre-exponential constants of the global reaction rates. Close

• 4. [Article] Temperature Effects on the Development of Cheddar Cheese Flavor and Aroma

  Originally published in Journal of Dairy Science: http://journalofdairyscience.org/

  Citation × Citation Citation Abstract Copy Title: Temperature Effects on the Development of Cheddar Cheese Flavor and Aroma Author: Grazier, C. L., Torres, J. A., McDaniel, M. R., Bodyfelt, F. W. Originally published in Journal of Dairy Science: http://journalofdairyscience.org/ Title: Temperature Effects on the Development of Cheddar Cheese Flavor and Aroma Author: Grazier, C. L., Torres, J. A., McDaniel, M. R., Bodyfelt, F. W. Originally published in Journal of Dairy Science: http://journalofdairyscience.org/ Close

• 5. [Article] Above- and Belowground Microclimate of Grow Tubes in an Organic Mulch-incorporated, Raised Bed System for Blueberry

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the Institute for ...

  Citation × Citation Citation Abstract Copy Title: Above- and Belowground Microclimate of Grow Tubes in an Organic Mulch-incorporated, Raised Bed System for Blueberry Author: Strik, Bernadine C., Tarara, Julie M., Chaves, Bernardo To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the Institute for Scientific Information and published by the American Society for Horticultural Science. It can be found at: http://hortsci.ashspublications.org/. Title: Above- and Belowground Microclimate of Grow Tubes in an Organic Mulch-incorporated, Raised Bed System for Blueberry Author: Strik, Bernadine C., Tarara, Julie M., Chaves, Bernardo To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the Institute for Scientific Information and published by the American Society for Horticultural Science. It can be found at: http://hortsci.ashspublications.org/. Close

• 6. [Article] Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird

  Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions ...

  Citation × Citation Citation Abstract Copy Title: Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird Author: Jones, Kristin N. Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions and phenology driven by climate change are well-documented, yet we lack a strong understanding of how climate change will influence the demographic rates of animal populations, which directly determine the likelihood of species persistence. Land cover change, an agent of global change that is increasing in extent and intensity to meet the needs of a growing human population, can combine with climate change to stress animal populations by altering microclimatic conditions, as well as changing the availability of resources such as food and cover from predators. Thus, identifying the individual and combined effects of climate and land management practices is essential to accurately predict the responses of animal populations to global change. Intensive forest management results in land cover change by suppressing the growth of competing plant species in favor of commercial species and altering the abundance and composition of forest vegetation. In turn, changes in the abundance and composition of forest vegetation can modify local air temperatures. I hypothesized that herbicide application would alter the thermal environment for early-seral forest organisms (Chapter 2). If this were the case, then air temperature could be expected to increase in magnitude and variability along a gradient of herbicide treatment intensity. To test this hypothesis, I used iButton dataloggers to monitor air temperature at 160 nest boxes on 20 intensively managed early-seral forest stands (10.4 - 18.9) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I also measured the amount and composition of vegetation cover to test for herbicide effects on vegetation among application intensities. Using linear mixed models, I compared three measures of air temperature (mean daily minimum, mean, and maximum) and their associated coefficients of variation (CVs). Additionally, I used linear mixed models to confirm differences in total vegetation and broadleaved vegetation cover. Although mean total vegetation cover generally decreased, it did not significantly differ among herbicide treatments; in contrast, mean broadleaved vegetation cover was significantly reduced in the moderate and intensive treatments. Herbicide treatment was a significant predictor of maximum and mean temperatures, but minimum temperatures did not differ with herbicide treatment. Although there was an effect of herbicide treatment on air temperature, corrected pairwise comparisons indicated no significant differences among treatments. I note that though my power to detect statistical differences among treatments was limited, these differences were quite small (< 0.5°C) and confidence intervals were generally relatively narrow (< 1.5°C), suggesting that temperature did not differ among herbicide treatments in biologically meaningful ways. Furthermore, I did not detect an effect of herbicide treatment on temperature variability. Estimated differences in temperature variability among treatments were small (< 0.5%) and confidence intervals covered a relatively broad range of values, indicating that I did not have enough statistical power to detect effects. I found no uniform pattern in the direction (positive or negative) of the effect of herbicide treatment on temperature or CVs among treatment intensities. Daily air temperatures can strongly influence the reproductive output of early-seral songbirds if temperatures exceed physiological tolerances of offspring, decreasing physiological performance (e.g., excessively high and low temperatures can alter metabolic rates) and survival. Moreover, the abundance and composition of early-seral forest vegetation can influence songbird reproductive output through changes in nest predator communities, food resources, or both. Thus, I further hypothesized that intensive forest management practices could combine with intraseasonal air temperatures to impact reproductive output in an insectivorous cavity-nesting songbird, the House Wren (Trogolodytes aedon) (Chapter 3). If this were the case, then House Wren nest survival, the number of offspring produced, and the quality of those offspring would decline with greater management intensity and increasing air temperatures. To test these predictions, I monitored 283 nests on 24 intensively managed early-seral forest stands (8.6 - 18.9 ha) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I used data from Chapter 2 to test for combined effects of air temperature and herbicide-driven vegetation changes on House Wren reproductive output. Using linear mixed models within a model selection framework, I did not find support for combined effects of temperature and herbicide treatment on nest survival. After accounting for the effects of herbicide-driven vegetation changes on reproductive output, air temperature effects were negligible. My results suggest that post-harvest vegetation management likely does not influence the number of young produced nor their quality (as indicated by body condition) in intensively managed early-seral forests, but may influence nest survival. However, nest survival did not decline along a gradient of herbicide intensity as I expected. Instead, mean nest survival was greatest in the control and most intensively managed stands (failure was greatest in the light treatment); however, these effects were so variable as to not be statistically significant. My results suggest that post-harvest vegetation management in intensively managed forests may be linked to minor changes in microclimatic air temperatures, but that there is high variation in these effects and effects are likely small. Therefore, there appears to be limited potential for vegetation control strategies through herbicides to buffer expected climate change effects on organisms in early-seral forest. My results also suggest that the potential for combined effects of herbicide application and air temperature on early-seral cavity-nesting songbirds is limited. Under current local climate patterns, air temperature appears to exert negligible effects on House Wren reproductive output after accounting for changes in vegetation cover. The effects of herbicide-driven vegetation changes on early-seral songbirds may be large, though highly variable, and not an increasing function of herbicide intensity. These effects may be primarily predator-mediated, as indicated by the large effects of herbicide treatment on House Wren nest survival but not the number of offspring produced nor their quality. My finding of limited temperature effects on House Wren reproductive output compared to the effects of forest management intensity supports predictions that, despite increasing concerns over the impacts of advancing climate change on animal populations, land cover change driven by anthropogenic land use will continue to be the primary global change driver impacting animal populations in the near future. Title: Combined Effects of Intensive Forest Management and Microclimate on Reproduction in a Cavity-Nesting Songbird Author: Jones, Kristin N. Future scenarios of global climate change rely on large-scale climate envelope models that do not account for local climatic conditions to which organisms most closely respond. Shifts in species distributions and phenology driven by climate change are well-documented, yet we lack a strong understanding of how climate change will influence the demographic rates of animal populations, which directly determine the likelihood of species persistence. Land cover change, an agent of global change that is increasing in extent and intensity to meet the needs of a growing human population, can combine with climate change to stress animal populations by altering microclimatic conditions, as well as changing the availability of resources such as food and cover from predators. Thus, identifying the individual and combined effects of climate and land management practices is essential to accurately predict the responses of animal populations to global change. Intensive forest management results in land cover change by suppressing the growth of competing plant species in favor of commercial species and altering the abundance and composition of forest vegetation. In turn, changes in the abundance and composition of forest vegetation can modify local air temperatures. I hypothesized that herbicide application would alter the thermal environment for early-seral forest organisms (Chapter 2). If this were the case, then air temperature could be expected to increase in magnitude and variability along a gradient of herbicide treatment intensity. To test this hypothesis, I used iButton dataloggers to monitor air temperature at 160 nest boxes on 20 intensively managed early-seral forest stands (10.4 - 18.9) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I also measured the amount and composition of vegetation cover to test for herbicide effects on vegetation among application intensities. Using linear mixed models, I compared three measures of air temperature (mean daily minimum, mean, and maximum) and their associated coefficients of variation (CVs). Additionally, I used linear mixed models to confirm differences in total vegetation and broadleaved vegetation cover. Although mean total vegetation cover generally decreased, it did not significantly differ among herbicide treatments; in contrast, mean broadleaved vegetation cover was significantly reduced in the moderate and intensive treatments. Herbicide treatment was a significant predictor of maximum and mean temperatures, but minimum temperatures did not differ with herbicide treatment. Although there was an effect of herbicide treatment on air temperature, corrected pairwise comparisons indicated no significant differences among treatments. I note that though my power to detect statistical differences among treatments was limited, these differences were quite small (< 0.5°C) and confidence intervals were generally relatively narrow (< 1.5°C), suggesting that temperature did not differ among herbicide treatments in biologically meaningful ways. Furthermore, I did not detect an effect of herbicide treatment on temperature variability. Estimated differences in temperature variability among treatments were small (< 0.5%) and confidence intervals covered a relatively broad range of values, indicating that I did not have enough statistical power to detect effects. I found no uniform pattern in the direction (positive or negative) of the effect of herbicide treatment on temperature or CVs among treatment intensities. Daily air temperatures can strongly influence the reproductive output of early-seral songbirds if temperatures exceed physiological tolerances of offspring, decreasing physiological performance (e.g., excessively high and low temperatures can alter metabolic rates) and survival. Moreover, the abundance and composition of early-seral forest vegetation can influence songbird reproductive output through changes in nest predator communities, food resources, or both. Thus, I further hypothesized that intensive forest management practices could combine with intraseasonal air temperatures to impact reproductive output in an insectivorous cavity-nesting songbird, the House Wren (Trogolodytes aedon) (Chapter 3). If this were the case, then House Wren nest survival, the number of offspring produced, and the quality of those offspring would decline with greater management intensity and increasing air temperatures. To test these predictions, I monitored 283 nests on 24 intensively managed early-seral forest stands (8.6 - 18.9 ha) in the northern Oregon Coast Range, USA representing a gradient in intensive forest management (i.e., no-spray control, light, moderate and intensive herbicide application). I used data from Chapter 2 to test for combined effects of air temperature and herbicide-driven vegetation changes on House Wren reproductive output. Using linear mixed models within a model selection framework, I did not find support for combined effects of temperature and herbicide treatment on nest survival. After accounting for the effects of herbicide-driven vegetation changes on reproductive output, air temperature effects were negligible. My results suggest that post-harvest vegetation management likely does not influence the number of young produced nor their quality (as indicated by body condition) in intensively managed early-seral forests, but may influence nest survival. However, nest survival did not decline along a gradient of herbicide intensity as I expected. Instead, mean nest survival was greatest in the control and most intensively managed stands (failure was greatest in the light treatment); however, these effects were so variable as to not be statistically significant. My results suggest that post-harvest vegetation management in intensively managed forests may be linked to minor changes in microclimatic air temperatures, but that there is high variation in these effects and effects are likely small. Therefore, there appears to be limited potential for vegetation control strategies through herbicides to buffer expected climate change effects on organisms in early-seral forest. My results also suggest that the potential for combined effects of herbicide application and air temperature on early-seral cavity-nesting songbirds is limited. Under current local climate patterns, air temperature appears to exert negligible effects on House Wren reproductive output after accounting for changes in vegetation cover. The effects of herbicide-driven vegetation changes on early-seral songbirds may be large, though highly variable, and not an increasing function of herbicide intensity. These effects may be primarily predator-mediated, as indicated by the large effects of herbicide treatment on House Wren nest survival but not the number of offspring produced nor their quality. My finding of limited temperature effects on House Wren reproductive output compared to the effects of forest management intensity supports predictions that, despite increasing concerns over the impacts of advancing climate change on animal populations, land cover change driven by anthropogenic land use will continue to be the primary global change driver impacting animal populations in the near future. Close

• 7. [Article] Molting, growth, and energetics of newly-settled blue king crab: Effects of temperature and comparisons with red king crab

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier ...

  Citation × Citation Citation Abstract Copy Title: Molting, growth, and energetics of newly-settled blue king crab: Effects of temperature and comparisons with red king crab Author: Stoner, Allan W., Ottmar, Michele L., Copeman, Louise A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.elsevier.com/. Title: Molting, growth, and energetics of newly-settled blue king crab: Effects of temperature and comparisons with red king crab Author: Stoner, Allan W., Ottmar, Michele L., Copeman, Louise A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.elsevier.com/. Close

• 8. [Article] Flume testing of underwater seep detection using temperature sensing on or just below the surface of sand or gravel sediments

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291944-7973.

  Citation × Citation Citation Abstract Copy Title: Flume testing of underwater seep detection using temperature sensing on or just below the surface of sand or gravel sediments Author: Selker, J. S., Selker, F. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291944-7973. Title: Flume testing of underwater seep detection using temperature sensing on or just below the surface of sand or gravel sediments Author: Selker, J. S., Selker, F. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291944-7973. Close

• 9. [Article] Climate Change and Productivity in the Aquaculture Industry

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Climate Change and Productivity in the Aquaculture Industry Author: Lorentzen, Torbjørn Research Paper Title: Climate Change and Productivity in the Aquaculture Industry Author: Lorentzen, Torbjørn Research Paper Close

• 10. [Article] Chronobiology of garter snakes : environmental and hormonal mechanisms mediating hibernation and reproduction

  Most vertebrates exhibit seasonality in many life history traits. Such seasonal rhythms are temporally organized via the transduction of environmental cues (e.g., photoperiod, temperature) into appropriate ...

  Citation × Citation Citation Abstract Copy Title: Chronobiology of garter snakes : environmental and hormonal mechanisms mediating hibernation and reproduction Author: Lutterschmidt, Deborah I. Most vertebrates exhibit seasonality in many life history traits. Such seasonal rhythms are temporally organized via the transduction of environmental cues (e.g., photoperiod, temperature) into appropriate endocrine signals. However, among ectothermic vertebrates that undergo continuous winter dormancy, temperature is the only environmental cue available for synchronizing seasonal rhythms. Most intriguing is that in species where reproduction occurs immediately following spring emergence, the associated changes in neurophysiology and behavior that accompany reproduction likely occur during winter dormancy. The purpose of this dissertation research was to explore the mechanisms by which temperature cues affect the chronobiology and seasonal reproduction of red-sided garter snakes (Thamnophis sirtalis parietalis). Because of their roles in circadian organization and energy balance, melatonin and corticosterone are likely hormonal components of these time-keeping systems. I first characterized the interactions between melatonin and corticosterone to better understand the hormonal mechanisms facilitating temperature-induced reproduction. Melatonin and corticosterone additively inhibit reproductive behavior during the spring mating season. Experimental manipulations with a serotonin receptor antagonist suggest the mechanism underlying these effects involves a serotonin-regulated system. Although melatonin does not influence corticosterone responses to capture stress, capture stress significantly increases melatonin concentrations. To investigate the functional significance of these interactions in regulating temperature-induced reproduction, I measured body temperatures of snakes as well as circadian melatonin and corticosterone cycles during winter dormancy and spring emergence using a combination of field and laboratory experiments. Surprisingly, an increase in body temperature is not necessary for emergence from winter dormancy. Rather, critically low temperatures may serve as a zeitgeber entraining an endogenous circannual cycle that regulates emergence. Decreased environmental temperatures, in the absence of changing photoperiod cues, modulate circadian melatonin and corticosterone rhythms during hibernation. Such temperature-induced changes in hormone rhythms may facilitate seasonal reproductive behavior following spring emergence. Furthermore, a phase-shift in corticosterone rhythms during the mating season may regulate the seasonal transition between reproductive and non-reproductive states in red-sided garter snakes. Such studies investigating the environmental and hormonal mechanisms underlying time-keeping systems may provide valuable insight into the potential impact of environmental perturbations (e.g., climate change) on seasonal rhythms in physiology and behavior. Title: Chronobiology of garter snakes : environmental and hormonal mechanisms mediating hibernation and reproduction Author: Lutterschmidt, Deborah I. Most vertebrates exhibit seasonality in many life history traits. Such seasonal rhythms are temporally organized via the transduction of environmental cues (e.g., photoperiod, temperature) into appropriate endocrine signals. However, among ectothermic vertebrates that undergo continuous winter dormancy, temperature is the only environmental cue available for synchronizing seasonal rhythms. Most intriguing is that in species where reproduction occurs immediately following spring emergence, the associated changes in neurophysiology and behavior that accompany reproduction likely occur during winter dormancy. The purpose of this dissertation research was to explore the mechanisms by which temperature cues affect the chronobiology and seasonal reproduction of red-sided garter snakes (Thamnophis sirtalis parietalis). Because of their roles in circadian organization and energy balance, melatonin and corticosterone are likely hormonal components of these time-keeping systems. I first characterized the interactions between melatonin and corticosterone to better understand the hormonal mechanisms facilitating temperature-induced reproduction. Melatonin and corticosterone additively inhibit reproductive behavior during the spring mating season. Experimental manipulations with a serotonin receptor antagonist suggest the mechanism underlying these effects involves a serotonin-regulated system. Although melatonin does not influence corticosterone responses to capture stress, capture stress significantly increases melatonin concentrations. To investigate the functional significance of these interactions in regulating temperature-induced reproduction, I measured body temperatures of snakes as well as circadian melatonin and corticosterone cycles during winter dormancy and spring emergence using a combination of field and laboratory experiments. Surprisingly, an increase in body temperature is not necessary for emergence from winter dormancy. Rather, critically low temperatures may serve as a zeitgeber entraining an endogenous circannual cycle that regulates emergence. Decreased environmental temperatures, in the absence of changing photoperiod cues, modulate circadian melatonin and corticosterone rhythms during hibernation. Such temperature-induced changes in hormone rhythms may facilitate seasonal reproductive behavior following spring emergence. Furthermore, a phase-shift in corticosterone rhythms during the mating season may regulate the seasonal transition between reproductive and non-reproductive states in red-sided garter snakes. Such studies investigating the environmental and hormonal mechanisms underlying time-keeping systems may provide valuable insight into the potential impact of environmental perturbations (e.g., climate change) on seasonal rhythms in physiology and behavior. Close