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• 31. [Article] Characterizing early-seral competitive mechanisms influencing Douglas-fir seedling growth, vegetation community development, and physiology of selected weedy plant species

  Three studies were conducted to characterize and present early-seral competition between Douglas-fir seedlings and the surrounding vegetation communities during Pacific Northwest forest establishment. ...

  Citation × Citation Citation Abstract Copy Title: Characterizing early-seral competitive mechanisms influencing Douglas-fir seedling growth, vegetation community development, and physiology of selected weedy plant species Author: Dinger, Eric J. Three studies were conducted to characterize and present early-seral competition between Douglas-fir seedlings and the surrounding vegetation communities during Pacific Northwest forest establishment. The first experiment served as the foundation for this dissertation and was designed to quantify tradeoffs associated with delaying forest establishment activities by introducing a fallow year in order to provide longer-term management of competing vegetation. A range of six operationally relevant treatments were applied over two growing seasons that included in the first (1) a no-action control, (2) a spring release only, (3) a fall site preparation without sulfometuron methyl followed by a spring release, as well as (4) a fall site preparation with sulfometuron methyl and a spring release. In the second year, there was (5) a fall site preparation without sulfometuron methyl followed by a spring release and also in the second year (6) a fall site preparation with sulfometuron methyl and a spring release. Treatments 5 and 6 were left fallow without planting during the first year. These treatments were applied in two replicated experiments within the Oregon Coast Range. After adjusting for initial seedling size, year-3 results indicated that plantation establishment and competition control immediately after harvest (i.e. no fallow period) enabled seedlings to be physically larger than those planted after a one year delay. At the Boot study site, limiting vegetation below 20% for the first growing season improved year-3 Douglas-fir seedling stem volume over 273 cm³. Delaying establishment activities one year and reducing competing vegetation below 11% enabled seedling volume after two years to be statistically the same as three year old seedlings in the no-action control, a volume range of between 148 to 166 cm³. Delaying forest establishment at Jackson Mast improved seedling survivorship over 88% when a spring heat event reduced survivorship of trees planted a year earlier to less than 69%. The combined effect of applying a fall site preparation and spring release was necessary to reduce competitive cover below 10% in the year following treatment and provided longer-lasting control of woody/semi-woody plants. Less intense control measures (i.e. no-action control and treatment 2) were not able to restrain woody/semi-woody plant cover which grew to nearly 40% at Boot and over 24% at Jackson Mast in three years. No treatment regime provided multi-year control of herbaceous species. Including sulfometuron methyl in the fall site preparation tank-mix did not have a negative effect on seedling growth or provide significant reductions in plant community abundance in the year following application when compared to similar regimes that did not include the chemical. Delaying establishment lengthened the amount of time associated with forest regeneration except on a site that accentuated a spring heat event. In the second study, horizontal distance and azimuth readings provided by a ground-based laser were used to stem map seedling locations and experimental unit features at Boot. These data were used to create a relative Cartesian coordinate system that defined spatially explicit polygons enabling, for the first time, the ability to collect positional data on competing forest vegetation within an entire experimental unit. Deemed "vixels" or vegetation pixels, these polygons were assessed for measures of total cover and cover of the top three most abundance species during the initial three years of establishment. An alternate validity check of research protocols was provided when total cover resulting from this vixel technique was compared to a more traditional survey of four randomly located subplots. The resulting linear regression equation had an adjusted R² of 0.90 between these two techniques of assessing total cover. When compared within a treatment and year, total cover differed by less than 12 percentage points between the two techniques. Analysis of year-3 woody/semi-woody plant cover produced by the techniques led to identical treatment differences. Two treatments resulted in woody/semi-woody cover of approximately 1500 ft² by the vixel method and nearly 40% cover by the subplot method while the remaining four treatments were grouped below 600 ft² or 20% cover, respectively. With continued refinement, these techniques could visually present forest development through all phases and provide long-term information used to bolster growth and yield models, measures of site productivity, as well as community ecology research. The third study evaluated the season-long gas exchange and biomass partitioning of four weedy plant species capable of rapidly colonizing Pacific Northwest regenerating forests. Cirsium arvense, Cirsium vulgare, Rubus ursinus and Senecio sylvaticus were studied at two sites. A greenhouse was used to introduce two levels of irrigation (well-watered and droughty). These species were also studied while growing among a larger vegetation community at a field site. Irrigation treatments had little impact on gas exchange rates. Species achieved maximum photosynthetic rates of 30, 20, 15 and 25 μmol CO₂ m⁻² s⁻¹ (respectively) prior to mid-July coinciding with an active phase of vegetative growth. As the season progressed, photosynthetic rates declined in spite of well-watered conditions while transpiration rates remained relatively consistent even when soil water decreased below 0.25 m³ H₂O/m³ soil. Water use efficiency was high until late-July for all study species, after which time it decreased below 5 μmol CO₂ · mmol H₂O⁻¹. Multi-leaf gas exchange measurements as well as biomass data provided a holistic view of plantlevel mechanisms used to shunt activity toward developing tissues. Herbaceous species had assimilation rates that differed vertically (within each species) by as much as 10 to 20 μmol CO₂ m⁻² s⁻¹ from July to September as lower leaves senesced in favor of those higher on study plants. Specific leaf area was greatest in June for all species then declined indicating species placed little effort into sacrificial early season leaves when compared to those higher on the plant that could continue to support flowering or vegetative growth. The study of seasonal gas exchange in the presence of declining water availability has helped to describe competitive mechanisms at work during forest regeneration as well as provide physiologic support for the application of vegetation management regimes. Title: Characterizing early-seral competitive mechanisms influencing Douglas-fir seedling growth, vegetation community development, and physiology of selected weedy plant species Author: Dinger, Eric J. Three studies were conducted to characterize and present early-seral competition between Douglas-fir seedlings and the surrounding vegetation communities during Pacific Northwest forest establishment. The first experiment served as the foundation for this dissertation and was designed to quantify tradeoffs associated with delaying forest establishment activities by introducing a fallow year in order to provide longer-term management of competing vegetation. A range of six operationally relevant treatments were applied over two growing seasons that included in the first (1) a no-action control, (2) a spring release only, (3) a fall site preparation without sulfometuron methyl followed by a spring release, as well as (4) a fall site preparation with sulfometuron methyl and a spring release. In the second year, there was (5) a fall site preparation without sulfometuron methyl followed by a spring release and also in the second year (6) a fall site preparation with sulfometuron methyl and a spring release. Treatments 5 and 6 were left fallow without planting during the first year. These treatments were applied in two replicated experiments within the Oregon Coast Range. After adjusting for initial seedling size, year-3 results indicated that plantation establishment and competition control immediately after harvest (i.e. no fallow period) enabled seedlings to be physically larger than those planted after a one year delay. At the Boot study site, limiting vegetation below 20% for the first growing season improved year-3 Douglas-fir seedling stem volume over 273 cm³. Delaying establishment activities one year and reducing competing vegetation below 11% enabled seedling volume after two years to be statistically the same as three year old seedlings in the no-action control, a volume range of between 148 to 166 cm³. Delaying forest establishment at Jackson Mast improved seedling survivorship over 88% when a spring heat event reduced survivorship of trees planted a year earlier to less than 69%. The combined effect of applying a fall site preparation and spring release was necessary to reduce competitive cover below 10% in the year following treatment and provided longer-lasting control of woody/semi-woody plants. Less intense control measures (i.e. no-action control and treatment 2) were not able to restrain woody/semi-woody plant cover which grew to nearly 40% at Boot and over 24% at Jackson Mast in three years. No treatment regime provided multi-year control of herbaceous species. Including sulfometuron methyl in the fall site preparation tank-mix did not have a negative effect on seedling growth or provide significant reductions in plant community abundance in the year following application when compared to similar regimes that did not include the chemical. Delaying establishment lengthened the amount of time associated with forest regeneration except on a site that accentuated a spring heat event. In the second study, horizontal distance and azimuth readings provided by a ground-based laser were used to stem map seedling locations and experimental unit features at Boot. These data were used to create a relative Cartesian coordinate system that defined spatially explicit polygons enabling, for the first time, the ability to collect positional data on competing forest vegetation within an entire experimental unit. Deemed "vixels" or vegetation pixels, these polygons were assessed for measures of total cover and cover of the top three most abundance species during the initial three years of establishment. An alternate validity check of research protocols was provided when total cover resulting from this vixel technique was compared to a more traditional survey of four randomly located subplots. The resulting linear regression equation had an adjusted R² of 0.90 between these two techniques of assessing total cover. When compared within a treatment and year, total cover differed by less than 12 percentage points between the two techniques. Analysis of year-3 woody/semi-woody plant cover produced by the techniques led to identical treatment differences. Two treatments resulted in woody/semi-woody cover of approximately 1500 ft² by the vixel method and nearly 40% cover by the subplot method while the remaining four treatments were grouped below 600 ft² or 20% cover, respectively. With continued refinement, these techniques could visually present forest development through all phases and provide long-term information used to bolster growth and yield models, measures of site productivity, as well as community ecology research. The third study evaluated the season-long gas exchange and biomass partitioning of four weedy plant species capable of rapidly colonizing Pacific Northwest regenerating forests. Cirsium arvense, Cirsium vulgare, Rubus ursinus and Senecio sylvaticus were studied at two sites. A greenhouse was used to introduce two levels of irrigation (well-watered and droughty). These species were also studied while growing among a larger vegetation community at a field site. Irrigation treatments had little impact on gas exchange rates. Species achieved maximum photosynthetic rates of 30, 20, 15 and 25 μmol CO₂ m⁻² s⁻¹ (respectively) prior to mid-July coinciding with an active phase of vegetative growth. As the season progressed, photosynthetic rates declined in spite of well-watered conditions while transpiration rates remained relatively consistent even when soil water decreased below 0.25 m³ H₂O/m³ soil. Water use efficiency was high until late-July for all study species, after which time it decreased below 5 μmol CO₂ · mmol H₂O⁻¹. Multi-leaf gas exchange measurements as well as biomass data provided a holistic view of plantlevel mechanisms used to shunt activity toward developing tissues. Herbaceous species had assimilation rates that differed vertically (within each species) by as much as 10 to 20 μmol CO₂ m⁻² s⁻¹ from July to September as lower leaves senesced in favor of those higher on study plants. Specific leaf area was greatest in June for all species then declined indicating species placed little effort into sacrificial early season leaves when compared to those higher on the plant that could continue to support flowering or vegetative growth. The study of seasonal gas exchange in the presence of declining water availability has helped to describe competitive mechanisms at work during forest regeneration as well as provide physiologic support for the application of vegetation management regimes. Close

• 32. [Article] Human influences on historical and current wildlife distributions from Lewis & Clark to today

  Although it is well known that humans are strong modifiers of their environment, there is a need for greater understanding of human-wildlife interactions, both historically as well as currently. Historical ...

  Citation × Citation Citation Abstract Copy Title: Human influences on historical and current wildlife distributions from Lewis & Clark to today Author: Laliberte, Andrea S. Although it is well known that humans are strong modifiers of their environment, there is a need for greater understanding of human-wildlife interactions, both historically as well as currently. Historical journals can help shed light on early human-wildlife interactions, and the Lewis & Clark journals contain some of the earliest and detailed written descriptions of a large part of the United States before Euro-American settlement. I used the journal entries to assess the influence of humans on wildlife distribution and abundance. Areas with denser human population, the Columbia Basin and the Pacific Coast, had lower species diversity and abundance of large mammals. The opposite was observed on the Plains. Overhunting before Euro- American contact accentuated by the introduction of the horse may have been major contributors responsible for the historic absence of some species that are present in the archaeological record. The information gained from the Lewis & Clark journals shows the considerable human influence on wildlife under relatively low human population densities. This has major implications for conservation biology and ecological restoration, since human influence is often underestimated when considering the pre-settlement condition. Species ranges are dynamic and change greatly over time. In order to identify large-scale patterns in range contractions and/or expansions, I compared historic and current geographical ranges of 43 North American carnivores and ungulates. Seventeen of the species had undergone range contractions over >20% of their historic range. In areas of higher human influence, species were more likely to contract and less likely to persist. Species richness declined considerably since historic times, and the temperate grasslands and temperate broadleaf/mixed forest biomes lost the highest average number of species, while the boreal forest and tundra showed fewer numbers of species lost. The study of species range changes contributed new quantitative information about human influences on range contractions in North America. The results can be used to improve our knowledge of historical reference conditions, for the creation of wildlife reserves, and for wildlife re-introductions. Title: Human influences on historical and current wildlife distributions from Lewis & Clark to today Author: Laliberte, Andrea S. Although it is well known that humans are strong modifiers of their environment, there is a need for greater understanding of human-wildlife interactions, both historically as well as currently. Historical journals can help shed light on early human-wildlife interactions, and the Lewis & Clark journals contain some of the earliest and detailed written descriptions of a large part of the United States before Euro-American settlement. I used the journal entries to assess the influence of humans on wildlife distribution and abundance. Areas with denser human population, the Columbia Basin and the Pacific Coast, had lower species diversity and abundance of large mammals. The opposite was observed on the Plains. Overhunting before Euro- American contact accentuated by the introduction of the horse may have been major contributors responsible for the historic absence of some species that are present in the archaeological record. The information gained from the Lewis & Clark journals shows the considerable human influence on wildlife under relatively low human population densities. This has major implications for conservation biology and ecological restoration, since human influence is often underestimated when considering the pre-settlement condition. Species ranges are dynamic and change greatly over time. In order to identify large-scale patterns in range contractions and/or expansions, I compared historic and current geographical ranges of 43 North American carnivores and ungulates. Seventeen of the species had undergone range contractions over >20% of their historic range. In areas of higher human influence, species were more likely to contract and less likely to persist. Species richness declined considerably since historic times, and the temperate grasslands and temperate broadleaf/mixed forest biomes lost the highest average number of species, while the boreal forest and tundra showed fewer numbers of species lost. The study of species range changes contributed new quantitative information about human influences on range contractions in North America. The results can be used to improve our knowledge of historical reference conditions, for the creation of wildlife reserves, and for wildlife re-introductions. Close

• 33. [Article] Native bees, honeybees and pollination in Oregon cranberries (BioResource Research)

  Farmers rely almost exclusively on the imported European honeybee (Apis mellifera L.) for fruit and vegetable crop pollination services. The recent decline in honeybee health has underscored the danger ...

  Citation × Citation Citation Abstract Copy Title: Native bees, honeybees and pollination in Oregon cranberries (BioResource Research) Author: McKenney, Melissa A. Farmers rely almost exclusively on the imported European honeybee (Apis mellifera L.) for fruit and vegetable crop pollination services. The recent decline in honeybee health has underscored the danger of relying on a single species to provide vital services. Increasing pollinator biodiversity with native bees may provide biological insurance against the decline of any particular species. By examining cropping systems, it is possible to determine which native bees are providing pollination services and then augment habitat to increase their numbers or attempt domestication. In this study, we examined the native bee populations in the cranberry growing area of southern coastal Oregon in order to determine if native bees play a significant role in cranberry pollination. This two-year study surveyed four farms across a 22 km north-south gradient. At least 27 bee species were observed during cranberry bloom (mid-May to late June), of which five were observed foraging on the cranberry flowers. The imported European honeybee and bumble bees (Bombus spp.) comprised 99.7% of foragers. While honeybees and bumble bees foraged at comparable wind speeds, Bombus spp. foraged at significantly lower average temperatures (P<0.0001). Both honeybees and bumble bees collected cranberry pollen while foraging, but 37.2% of honeybees were observed nectar-robbing (collecting nectar but no pollen) versus only 11.3% of bumble bees. Bumble bees in general, and the western yellow-faced bumble bee (Bombus vosnesenskii Radoszkowski) in particular, are abundant native pollinators of cranberry, and may provide adequate pollination for small Oregon cranberry farms. Conservation of bumble bee habitat and development of managed colonies will help maintain pollination services. Title: Native bees, honeybees and pollination in Oregon cranberries (BioResource Research) Author: McKenney, Melissa A. Farmers rely almost exclusively on the imported European honeybee (Apis mellifera L.) for fruit and vegetable crop pollination services. The recent decline in honeybee health has underscored the danger of relying on a single species to provide vital services. Increasing pollinator biodiversity with native bees may provide biological insurance against the decline of any particular species. By examining cropping systems, it is possible to determine which native bees are providing pollination services and then augment habitat to increase their numbers or attempt domestication. In this study, we examined the native bee populations in the cranberry growing area of southern coastal Oregon in order to determine if native bees play a significant role in cranberry pollination. This two-year study surveyed four farms across a 22 km north-south gradient. At least 27 bee species were observed during cranberry bloom (mid-May to late June), of which five were observed foraging on the cranberry flowers. The imported European honeybee and bumble bees (Bombus spp.) comprised 99.7% of foragers. While honeybees and bumble bees foraged at comparable wind speeds, Bombus spp. foraged at significantly lower average temperatures (P<0.0001). Both honeybees and bumble bees collected cranberry pollen while foraging, but 37.2% of honeybees were observed nectar-robbing (collecting nectar but no pollen) versus only 11.3% of bumble bees. Bumble bees in general, and the western yellow-faced bumble bee (Bombus vosnesenskii Radoszkowski) in particular, are abundant native pollinators of cranberry, and may provide adequate pollination for small Oregon cranberry farms. Conservation of bumble bee habitat and development of managed colonies will help maintain pollination services. Close

• 34. [Article] Native bees, honeybees and pollination in Oregon cranberries (Library Undergraduate Honors Award Paper)

  Farmers rely almost exclusively on the imported European honeybee (Apis mellifera L.) for fruit and vegetable crop pollination services. The recent decline in honeybee health has underscored he danger ...

  Citation × Citation Citation Abstract Copy Title: Native bees, honeybees and pollination in Oregon cranberries (Library Undergraduate Honors Award Paper) Author: McKenney, Melissa A. Farmers rely almost exclusively on the imported European honeybee (Apis mellifera L.) for fruit and vegetable crop pollination services. The recent decline in honeybee health has underscored he danger of relying on a single species to provide vital services. Increasing pollinator biodiversity with native bees may provide biological insurance against the decline of any particular species. By examining cropping systems, it is possible to determine which native bees are providing pollination services and then augment habitat to increase their numbers or attempt domestication. In this study, we examined the native bee populations in the cranberry growing area of southern coastal Oregon in order to determine if native bees play a significant role in cranberry pollination. This two-year study surveyed four farms across a 22 km north-south gradient. At least 27 bee species were observed during cranberry bloom (mid-May to late June), of which five were observed foraging on the cranberry flowers. The imported European honeybees and bumble bees foraged at comparable wind speeds, Bombus spp. Foraged at significantly lower average temperatures (P<0.0001). Both honeybees and bumble bees collected cranberry pollen while foraging, but 37.2% of honeybees were observed nectar-robbing (collecting nectar but no pollen) versus only 11.3% of bumble bees. Bumble bees in general , and the western yellow-faced bumble bee (Bombus vosnesenskii Randoszkowski) in particular, are abundant native pollinators of cranberry, and may provide adequate pollination for small Oregon cranberry farms. Conservation of bumble bee habitat and development of managed colonies will help maintain pollination services. Title: Native bees, honeybees and pollination in Oregon cranberries (Library Undergraduate Honors Award Paper) Author: McKenney, Melissa A. Farmers rely almost exclusively on the imported European honeybee (Apis mellifera L.) for fruit and vegetable crop pollination services. The recent decline in honeybee health has underscored he danger of relying on a single species to provide vital services. Increasing pollinator biodiversity with native bees may provide biological insurance against the decline of any particular species. By examining cropping systems, it is possible to determine which native bees are providing pollination services and then augment habitat to increase their numbers or attempt domestication. In this study, we examined the native bee populations in the cranberry growing area of southern coastal Oregon in order to determine if native bees play a significant role in cranberry pollination. This two-year study surveyed four farms across a 22 km north-south gradient. At least 27 bee species were observed during cranberry bloom (mid-May to late June), of which five were observed foraging on the cranberry flowers. The imported European honeybees and bumble bees foraged at comparable wind speeds, Bombus spp. Foraged at significantly lower average temperatures (P<0.0001). Both honeybees and bumble bees collected cranberry pollen while foraging, but 37.2% of honeybees were observed nectar-robbing (collecting nectar but no pollen) versus only 11.3% of bumble bees. Bumble bees in general , and the western yellow-faced bumble bee (Bombus vosnesenskii Randoszkowski) in particular, are abundant native pollinators of cranberry, and may provide adequate pollination for small Oregon cranberry farms. Conservation of bumble bee habitat and development of managed colonies will help maintain pollination services. Close

• 35. [Article] Bridging environmental physiology and community ecology : temperature effects at the community level

  Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how ...

  Citation × Citation Citation Abstract Copy Title: Bridging environmental physiology and community ecology : temperature effects at the community level Author: Iles, Alison C. Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. Title: Bridging environmental physiology and community ecology : temperature effects at the community level Author: Iles, Alison C. Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. Close

• 36. [Article] Cone and seed insects and their impact on whitebark pine

  Whitebark pine, Pinus albicaulis Engelm. is an important but declining high-elevation tree species in western forests. Regeneration of this species has been difficult and the impact of cone and seed insects ...

  Citation × Citation Citation Abstract Copy Title: Cone and seed insects and their impact on whitebark pine Author: United States. Forest Service. Northern Region, Kegley, Sandy, United States. Forest Health Protection Whitebark pine, Pinus albicaulis Engelm. is an important but declining high-elevation tree species in western forests. Regeneration of this species has been difficult and the impact of cone and seed insects unknown. Seven sites selected from the geographical range of whitebark pine in Idaho, Montana, Washington, Oregon, and California were examined for cone and seed insects and their impact. Ten different insect species were found affecting various reproductive structures of whitebark pine. Insects having the greatest impact across most sites were fir coneworm (Dioryctria abietivorella (Grote)) and western conifer seed bug (Leptoglossus occidentalis Heidemann). Coneworms infested up to 68% of cones collected, destroying up to 13% of the seed extracted. Seed bugs damaged up to 27% of the seeds. Pheromone traps for the ponderosa pine cone beetle (Conophthorus ponderosae Hopkins) and coneworms were tested. Ponderosa pine cone beetles were trapped at three of seven sites. Coneworms were trapped at two sites where pheromone traps were deployed. Further studies incorporating different cone crop levels of whitebark pine and other associated tree species are needed to fully determine the effect of cone and seed insects on whitebark pine seed and reproduction. Title: Cone and seed insects and their impact on whitebark pine Author: United States. Forest Service. Northern Region, Kegley, Sandy, United States. Forest Health Protection Whitebark pine, Pinus albicaulis Engelm. is an important but declining high-elevation tree species in western forests. Regeneration of this species has been difficult and the impact of cone and seed insects unknown. Seven sites selected from the geographical range of whitebark pine in Idaho, Montana, Washington, Oregon, and California were examined for cone and seed insects and their impact. Ten different insect species were found affecting various reproductive structures of whitebark pine. Insects having the greatest impact across most sites were fir coneworm (Dioryctria abietivorella (Grote)) and western conifer seed bug (Leptoglossus occidentalis Heidemann). Coneworms infested up to 68% of cones collected, destroying up to 13% of the seed extracted. Seed bugs damaged up to 27% of the seeds. Pheromone traps for the ponderosa pine cone beetle (Conophthorus ponderosae Hopkins) and coneworms were tested. Ponderosa pine cone beetles were trapped at three of seven sites. Coneworms were trapped at two sites where pheromone traps were deployed. Further studies incorporating different cone crop levels of whitebark pine and other associated tree species are needed to fully determine the effect of cone and seed insects on whitebark pine seed and reproduction. Close

• 37. [Article] Twenty-year changes in riparian bird communities of east-central Oregon

  Over the last 50 years, riparian zones in the semi-arid West have gained recognition as disproportionately important habitats for both breeding bird communities and agricultural operations. Despite growing ...

  Citation × Citation Citation Abstract Copy Title: Twenty-year changes in riparian bird communities of east-central Oregon Author: Ellis, Michael S. Over the last 50 years, riparian zones in the semi-arid West have gained recognition as disproportionately important habitats for both breeding bird communities and agricultural operations. Despite growing interest in exploring avian-habitat relationships in these systems to better inform land management, few studies have attempted to describe temporal changes in the region's riparian bird communities. To provide a frame of reference for these changes, we compared indices of avian abundance and diversity from three streamside vegetation associations in east-central Oregon during the 2014 breeding season with baseline data collected by TA Sanders and WD Edge in 1993 and 1994 (Sanders and Edge 1998). Our objectives were to identify patterns of change in the avian community with a focus on riparian shrub-dependent species, to re-examine previously reported relationships between avian abundance and vegetation volume, and to identify possible causes of declines in abundance and diversity with the goal of providing land managers in the semi-arid region information to be used in the guidance and adaptation of management practices. We combined field protocols used by Sanders and Edge to survey birds along point count transects and to measure riparian vegetation with modern analytical techniques. We found few major differences in overall diversity between study periods, but documented precipitous declines in detections for two of three riparian shrub-dependent focal species - Yellow Warbler (Setophaga petechia) and Willow Flycatcher (Empidonax trailii). Song Sparrow (Melospiza melodia) detections declined by a smaller margin. Changes in number of detections for these species did not reflect trends in mesic shrub volume, which had been identified as a likely driver of obligate species abundance by Sanders and Edge but remained relatively unchanged between study periods. Declines of all three focal species reflected regional Breeding Bird Survey trends, corroborating our finding that their declines may not be a result of changes in local site conditions. Compositional similarity between avian communities was significantly higher in 2014 than in 1993-1994, exhibiting a shift toward greater homogenization between structurally distinct riparian habitats. Our results suggest managing working lands for riparian shrub cover or volume, an important metric of grazing intensity and riparian system health, may not be enough to conserve diversity and abundance of riparian-shrub dependent birds, and more work should be done to identify and alleviate factors contributing to these species' declines. Title: Twenty-year changes in riparian bird communities of east-central Oregon Author: Ellis, Michael S. Over the last 50 years, riparian zones in the semi-arid West have gained recognition as disproportionately important habitats for both breeding bird communities and agricultural operations. Despite growing interest in exploring avian-habitat relationships in these systems to better inform land management, few studies have attempted to describe temporal changes in the region's riparian bird communities. To provide a frame of reference for these changes, we compared indices of avian abundance and diversity from three streamside vegetation associations in east-central Oregon during the 2014 breeding season with baseline data collected by TA Sanders and WD Edge in 1993 and 1994 (Sanders and Edge 1998). Our objectives were to identify patterns of change in the avian community with a focus on riparian shrub-dependent species, to re-examine previously reported relationships between avian abundance and vegetation volume, and to identify possible causes of declines in abundance and diversity with the goal of providing land managers in the semi-arid region information to be used in the guidance and adaptation of management practices. We combined field protocols used by Sanders and Edge to survey birds along point count transects and to measure riparian vegetation with modern analytical techniques. We found few major differences in overall diversity between study periods, but documented precipitous declines in detections for two of three riparian shrub-dependent focal species - Yellow Warbler (Setophaga petechia) and Willow Flycatcher (Empidonax trailii). Song Sparrow (Melospiza melodia) detections declined by a smaller margin. Changes in number of detections for these species did not reflect trends in mesic shrub volume, which had been identified as a likely driver of obligate species abundance by Sanders and Edge but remained relatively unchanged between study periods. Declines of all three focal species reflected regional Breeding Bird Survey trends, corroborating our finding that their declines may not be a result of changes in local site conditions. Compositional similarity between avian communities was significantly higher in 2014 than in 1993-1994, exhibiting a shift toward greater homogenization between structurally distinct riparian habitats. Our results suggest managing working lands for riparian shrub cover or volume, an important metric of grazing intensity and riparian system health, may not be enough to conserve diversity and abundance of riparian-shrub dependent birds, and more work should be done to identify and alleviate factors contributing to these species' declines. Close

• 38. [Article] Seed and establishment limitation contribute to long-term native forb declines in California grasslands

  This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esa.org/.

  Citation × Citation Citation Abstract Copy Title: Seed and establishment limitation contribute to long-term native forb declines in California grasslands Author: Brandt, Angela J., Seabloom, Eric W. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esa.org/. Title: Seed and establishment limitation contribute to long-term native forb declines in California grasslands Author: Brandt, Angela J., Seabloom, Eric W. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esa.org/. Close

• 39. [Article] Agricultural impacts on amphibian survival, growth, and distributions

  The potential impact of chemical contaminants and conservation practices on amphibians in agricultural landscapes is a key research topic globally. Amphibians represent a common group in many freshwater ...

  Citation × Citation Citation Abstract Copy Title: Agricultural impacts on amphibian survival, growth, and distributions Author: Baker, Nick J. The potential impact of chemical contaminants and conservation practices on amphibians in agricultural landscapes is a key research topic globally. Amphibians represent a common group in many freshwater systems and are currently experiencing worldwide population declines. Global amphibian declines may be attributed to a number of causes, including habitat loss, introduced species, global climate change, disease, and chemical contaminants; most species declines are not a function of only one factor, but a result of interacting factors and synergistic impacts. I analyzed the impact of field conservation efforts employed in the Calapooia watershed, located in the central Willamette Valley in Oregon, on amphibian species diversity using Simpson's Diversity Index. In the Calapooia watershed the value of this index increased when conservation efforts, such as retaining crop residue and riparian buffers, were present. This suggests that species diversity increased with increased conservation effort at the field level. In addition, I found species-specific habitat associations in the Calapooia watershed. Long-toed salamanders (Ambystoma macrodactylum) were associated with stream channel cover. Rough-skinned newts (Taricha granulosa) and Red-legged frogs (Rana aurora) showed similar relationships to pH, bank width, depth, and riparian habitat where as Pacific treefrogs (Pseudacris regilla) showed strong relationships to increased structural heterogeneity, increased distance to nearest agricultural field, and increased human disturbance. These results indicate that conservation efforts can impact amphibian biodiversity, and that there are species-specific habitat associations in the Calapooia watershed. My third chapter looked at pesticides and fertilizers, which have been shown to negatively affect many species of amphibians. I used meta-analytic techniques to quantify the lethal and sub-lethal effects of pesticides and fertilizers on amphibians in an effort to review the published work to date. I found that, in general, pesticides and fertilizers negatively affect amphibians by reducing both survival and growth. Pesticide and fertilizer chemical classes showed differences in their impacts on amphibians: inorganic fertilizers, organophosphates, phosphonoglycines, and triazines negatively affected amphibian survival, while, organophosphates and triazines negatively affected amphibian growth. Title: Agricultural impacts on amphibian survival, growth, and distributions Author: Baker, Nick J. The potential impact of chemical contaminants and conservation practices on amphibians in agricultural landscapes is a key research topic globally. Amphibians represent a common group in many freshwater systems and are currently experiencing worldwide population declines. Global amphibian declines may be attributed to a number of causes, including habitat loss, introduced species, global climate change, disease, and chemical contaminants; most species declines are not a function of only one factor, but a result of interacting factors and synergistic impacts. I analyzed the impact of field conservation efforts employed in the Calapooia watershed, located in the central Willamette Valley in Oregon, on amphibian species diversity using Simpson's Diversity Index. In the Calapooia watershed the value of this index increased when conservation efforts, such as retaining crop residue and riparian buffers, were present. This suggests that species diversity increased with increased conservation effort at the field level. In addition, I found species-specific habitat associations in the Calapooia watershed. Long-toed salamanders (Ambystoma macrodactylum) were associated with stream channel cover. Rough-skinned newts (Taricha granulosa) and Red-legged frogs (Rana aurora) showed similar relationships to pH, bank width, depth, and riparian habitat where as Pacific treefrogs (Pseudacris regilla) showed strong relationships to increased structural heterogeneity, increased distance to nearest agricultural field, and increased human disturbance. These results indicate that conservation efforts can impact amphibian biodiversity, and that there are species-specific habitat associations in the Calapooia watershed. My third chapter looked at pesticides and fertilizers, which have been shown to negatively affect many species of amphibians. I used meta-analytic techniques to quantify the lethal and sub-lethal effects of pesticides and fertilizers on amphibians in an effort to review the published work to date. I found that, in general, pesticides and fertilizers negatively affect amphibians by reducing both survival and growth. Pesticide and fertilizer chemical classes showed differences in their impacts on amphibians: inorganic fertilizers, organophosphates, phosphonoglycines, and triazines negatively affected amphibian survival, while, organophosphates and triazines negatively affected amphibian growth. Close

• 40. [Article] Island survivors: population genetic structure and demography of the critically endangered giant lizard of La Gomera, Gallotia bravoana

  This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by BioMed Central Ltd. The published article can be found at: http://www.biomedcentral.com/bmcgene...

  Citation × Citation Citation Abstract Copy Title: Island survivors: population genetic structure and demography of the critically endangered giant lizard of La Gomera, Gallotia bravoana Author: Cerón-Souza, Ivania, Mateo, José A., Zardoya, Rafael, Gonzalez, Elena G. This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by BioMed Central Ltd. The published article can be found at: http://www.biomedcentral.com/bmcgenet/. Title: Island survivors: population genetic structure and demography of the critically endangered giant lizard of La Gomera, Gallotia bravoana Author: Cerón-Souza, Ivania, Mateo, José A., Zardoya, Rafael, Gonzalez, Elena G. This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by BioMed Central Ltd. The published article can be found at: http://www.biomedcentral.com/bmcgenet/. Close