Search

Search Results

• 21. [Article] Mapping the Global Emergence of Batrachochytrium dendrobatidis, the Amphibian Chytrid Fungus

  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 Public ...

  Citation × Citation Citation Abstract Copy Title: Mapping the Global Emergence of Batrachochytrium dendrobatidis, the Amphibian Chytrid Fungus Author: Fisher, Matthew C., Garner, Trenton W. J., Walker, Susan F., Powell, Christopher I., Weaver, George, Olson, Deanna H., Aanensen, David M., Ronnenberg, Kathryn L., Bielby, Jon, The Bd Mapping Group 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 Public Library of Science and can be found at: http://www.plos.org/. Title: Mapping the Global Emergence of Batrachochytrium dendrobatidis, the Amphibian Chytrid Fungus Author: Fisher, Matthew C., Garner, Trenton W. J., Walker, Susan F., Powell, Christopher I., Weaver, George, Olson, Deanna H., Aanensen, David M., Ronnenberg, Kathryn L., Bielby, Jon, The Bd Mapping Group 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 Public Library of Science and can be found at: http://www.plos.org/. Close

• 22. [Article] Environmental influences on host-pathogen dynamics of the amphibian chytrid fungus

  The causes of the global biodiversity crisis are varied and complex. Anthropogenic threats may act in isolation, or interact additively or synergistically with each other or with natural stressors to affect ...

  Citation × Citation Citation Abstract Copy Title: Environmental influences on host-pathogen dynamics of the amphibian chytrid fungus Author: Buck, Julia C. The causes of the global biodiversity crisis are varied and complex. Anthropogenic threats may act in isolation, or interact additively or synergistically with each other or with natural stressors to affect sensitive taxa. The recent emergence of many infectious diseases in wildlife has brought attention to the role of disease in population declines and species extinctions. Both abiotic and biotic components of the environment may mitigate or exacerbate effects of pathogens on their hosts through direct or indirect mechanisms. The effects of the environment on host-pathogen dynamics are complex, context-dependent, and in need of further examination. One particularly sensitive group, amphibians, is at the leading edge of the sixth mass extinction. The emerging infectious disease (EID) chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatis (Bd), is implicated in population declines and extinctions of amphibians globally. My disseration addresses questions pertaining to environmental influences on disease dynamics of Bd. As described in chapter 1, various abiotic and biotic components of the environment may affect host-pathogen dynamics of Bd, resulting in changes to the dynamics of Bd transmission and spread. Chapter 2 examines the influence of an abiotic factor, the insecticide (carbaryl) and three different assemblages of larval Pacific treefrogs (Pseudacris regilla) and Cascades frogs (Rana cascadae) on host-pathogen dynamics of Bd within a community context. I found separate effects of each treatment on amphibian growth and development, but no interactive effects among the treatments. However, Bd appeared to reduce phytoplankton abundance and increase periphyton biomass, an unexpected result that merited further investigation. One possible explanation for the results described in chapter 2 is that zooplankton might consume Bd zoospores, the infective stage of the pathogen, a hypothesis that I examine in chapter 3. I conducted laboratory experiments and confirmed the presence of Bd zoospores in the gut of Daphnia sp. through quantitative PCR and visual inspection. I discuss conservation implications of this finding. To determine whether predation on Bd zoospores by zooplankton could reduce infection in amphibians, I conducted a mesocosm experiment, which is described in chapter 4. I found complex effects on species interactions: competition between larval Cascades frogs and zooplankton for phytoplankton resources reduced phytoplankton concentration, zooplankton abundance, and survival of amphibians. These effects were diminished in the presence of Bd, suggesting that zooplankton may have at least partially substituted Bd zoospores for phytoplankton in their diet, thus stimulating competitive release. However, competitive effects between zooplankton and larval amphibians overshadowed indirect positive benefits of zooplankton predation on Bd zoospores. In chapter 4, competitive effects between zooplankton and larval amphibians for phytoplankton suggested that host-pathogen dynamics might be affected by the host’s supply of resources. Chapter 5 describes a mesocosm experiment that examined how eutrophication might affect Bd-infected Pacific treefrogs and other members of the aquatic community. Nutrient additions caused increased algal growth, which benefitted herbivorous larval amphibians. Larvae exposed to Bd altered their growth, development, and diet, and allocated resources differently than unexposed individuals. However, nutrient supplementation did not alter the response of larval amphibians to Bd. As described in chapter 6, consideration of hosts and pathogens as functional members of the ecological communities in which they exist can lead to important insights in host-pathogen dynamics. My PhD research may contribute to control measures for the emerging infectious disease chytridiomycosis. Title: Environmental influences on host-pathogen dynamics of the amphibian chytrid fungus Author: Buck, Julia C. The causes of the global biodiversity crisis are varied and complex. Anthropogenic threats may act in isolation, or interact additively or synergistically with each other or with natural stressors to affect sensitive taxa. The recent emergence of many infectious diseases in wildlife has brought attention to the role of disease in population declines and species extinctions. Both abiotic and biotic components of the environment may mitigate or exacerbate effects of pathogens on their hosts through direct or indirect mechanisms. The effects of the environment on host-pathogen dynamics are complex, context-dependent, and in need of further examination. One particularly sensitive group, amphibians, is at the leading edge of the sixth mass extinction. The emerging infectious disease (EID) chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatis (Bd), is implicated in population declines and extinctions of amphibians globally. My disseration addresses questions pertaining to environmental influences on disease dynamics of Bd. As described in chapter 1, various abiotic and biotic components of the environment may affect host-pathogen dynamics of Bd, resulting in changes to the dynamics of Bd transmission and spread. Chapter 2 examines the influence of an abiotic factor, the insecticide (carbaryl) and three different assemblages of larval Pacific treefrogs (Pseudacris regilla) and Cascades frogs (Rana cascadae) on host-pathogen dynamics of Bd within a community context. I found separate effects of each treatment on amphibian growth and development, but no interactive effects among the treatments. However, Bd appeared to reduce phytoplankton abundance and increase periphyton biomass, an unexpected result that merited further investigation. One possible explanation for the results described in chapter 2 is that zooplankton might consume Bd zoospores, the infective stage of the pathogen, a hypothesis that I examine in chapter 3. I conducted laboratory experiments and confirmed the presence of Bd zoospores in the gut of Daphnia sp. through quantitative PCR and visual inspection. I discuss conservation implications of this finding. To determine whether predation on Bd zoospores by zooplankton could reduce infection in amphibians, I conducted a mesocosm experiment, which is described in chapter 4. I found complex effects on species interactions: competition between larval Cascades frogs and zooplankton for phytoplankton resources reduced phytoplankton concentration, zooplankton abundance, and survival of amphibians. These effects were diminished in the presence of Bd, suggesting that zooplankton may have at least partially substituted Bd zoospores for phytoplankton in their diet, thus stimulating competitive release. However, competitive effects between zooplankton and larval amphibians overshadowed indirect positive benefits of zooplankton predation on Bd zoospores. In chapter 4, competitive effects between zooplankton and larval amphibians for phytoplankton suggested that host-pathogen dynamics might be affected by the host’s supply of resources. Chapter 5 describes a mesocosm experiment that examined how eutrophication might affect Bd-infected Pacific treefrogs and other members of the aquatic community. Nutrient additions caused increased algal growth, which benefitted herbivorous larval amphibians. Larvae exposed to Bd altered their growth, development, and diet, and allocated resources differently than unexposed individuals. However, nutrient supplementation did not alter the response of larval amphibians to Bd. As described in chapter 6, consideration of hosts and pathogens as functional members of the ecological communities in which they exist can lead to important insights in host-pathogen dynamics. My PhD research may contribute to control measures for the emerging infectious disease chytridiomycosis. Close

• 23. [Article] Consumer acceptability of Mukene (Rastrineobola argentea) value-added products in Uganda

  Abstract Only

  Citation × Citation Citation Abstract Copy Title: Consumer acceptability of Mukene (Rastrineobola argentea) value-added products in Uganda Author: Masette, Magaret, Khakasa, Elizabeth Abstract Only Title: Consumer acceptability of Mukene (Rastrineobola argentea) value-added products in Uganda Author: Masette, Magaret, Khakasa, Elizabeth Abstract Only Close

• 24. [Article] Systematic Temporal Patterns in the Relationship Between Housing Development and Forest Bird Biodiversity

  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 Society for Conservation ...

  Citation × Citation Citation Abstract Copy Title: Systematic Temporal Patterns in the Relationship Between Housing Development and Forest Bird Biodiversity Author: Keuler, Nicholas S., Lepczyk, Christopher A., Hammer, Roger B., Pidgeon, Anna M., Radeloff, Volker C., Wood, Eric M., Flather, Curtis H., Stewart, Susan I. 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 Society for Conservation Biology and published by John Wiley & Sons Ltd. It can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291523-1739. Title: Systematic Temporal Patterns in the Relationship Between Housing Development and Forest Bird Biodiversity Author: Keuler, Nicholas S., Lepczyk, Christopher A., Hammer, Roger B., Pidgeon, Anna M., Radeloff, Volker C., Wood, Eric M., Flather, Curtis H., Stewart, Susan I. 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 Society for Conservation Biology and published by John Wiley & Sons Ltd. It can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291523-1739. Close

• 25. [Article] Long-term decline of a winter-resident bird community in Puerto Rico

  This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10531. To the best of our knowledge, one or more authors of this ...

  Citation × Citation Citation Abstract Copy Title: Long-term decline of a winter-resident bird community in Puerto Rico Author: Faaborg, John, Arendt, Wayne J., Toms, Judith D., Dugger, Katie M., Mora, Miguel Canals, Cox, W. Andrew This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10531. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Title: Long-term decline of a winter-resident bird community in Puerto Rico Author: Faaborg, John, Arendt, Wayne J., Toms, Judith D., Dugger, Katie M., Mora, Miguel Canals, Cox, W. Andrew This is the publisher’s final pdf. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10531. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Close

• 26. [Article] Effects of spatial scale and heterogeneity on avian occupancy dynamics and population trends in forested mountain landscapes

  Population trends and patterns in species distributions are the major currencies used to examine responses by biodiversity to changing environments. Effective conservation recommendations require that ...

  Citation × Citation Citation Abstract Copy Title: Effects of spatial scale and heterogeneity on avian occupancy dynamics and population trends in forested mountain landscapes Author: Frey, Sarah Jean Kiuama Population trends and patterns in species distributions are the major currencies used to examine responses by biodiversity to changing environments. Effective conservation recommendations require that models of both distribution dynamics and population trends accurately reflect reality. However, identification of the appropriate temporal and spatial scales of animal response, and then obtaining data at these scales present two major challenges to developing predictive models. In heterogeneous forested mountain landscapes I examined: A) the relative drivers of climatic variability at fine spatial scales under the forest canopy ('microclimate'), B) the influence of microclimate on local-scale occupancy dynamics of bird communities, and C) the effects of spatial scale and imperfect bird detection on long-term avian population trends. Climate change has been predicted to cause widespread biodiversity declines. However, the capacity of climate envelope models for predicting the future of biodiversity has been questioned due to the mismatch between the scale of available data (i.e., global climate models) and the scales at which organisms experience their environment. Local-scale variation in microclimate is hypothesized to provide potential ‘microrefugia’ for biodiversity, but the relative role of elevation, microtopography, and vegetation structure in driving microclimate is not well known. If the microrefugia hypothesis is true, I expected to see areas on the landscape that remained relatively cooler (i.e., buffered sites). To test this, I collected temperature data at 183 sites across elevation and forest structure gradients in complex terrain of the H. J. Andrews Experimental Forest in the Cascade Mountains of Oregon, USA (Chapter 2). I used boosted regression trees, a novel machine learning approach, to determine the relative influence of vegetation structure, microtopography, and elevation as drivers of microclimate and mapped fine-scale distributions of temperature across the landscape. Models performed extremely well on independent data - cross-validation correlations between testing and training data were 0.69 - 0.98 for ten selected climate variables. Elevation was the dominant driver in fine-scale microclimate patterns, although vegetation and microtopography also showed substantial relative influences. For instance, during the spring-summer transition, maximum monthly temperatures observed in old-growth sites were 2.6°C (95% CI: 1.8 - 3.3°C) cooler than plantation sites and minimum temperatures during winter months were 0.6°C (95% CI: 0.4 - 0.8°C) warmer. This suggests that older forest stands mediate changes in temperature by buffering against warming during summer months and moderating cold temperatures during the winter. Climate is generally considered most influential on species distributions at large spatial scales; however much microclimate variability exists within regional patterns. I tested whether this high degree of microclimate variability has relevance for predicting species distributions and occupancy dynamics of the Andrews Forest bird community. I collected bird occurrence data in 2012 and 2013 at all 183 sites with fine-scale temperature measurements. I used dynamic occupancy models to test the effects of temperature on occupancy and apparent within-season bird movement while statistically accounting for vegetation effects and imperfect bird detection (Chapter 3). Most species (87%) exhibited within-season shifts in response to local-scale temperature metrics. Effects of temperature on within-season occupancy dynamics were as large or larger (1 to 1.7 times) than vegetation. However, individual species were almost as likely to shift toward warmer sites as toward cooler sites, suggesting that microclimate preferences are species-specific. My results emphasize that high-resolution temperature data provide valuable insight into avian distribution dynamics in montane forest environments and that microclimate is an important variable in breeding season habitat selection by forest birds. I hypothesize that microclimate-associated distribution shifts may reflect species' potential for behavioral buffering from climate change in complex terrain. Factors influencing population trends often differ depending on the spatial scale under consideration. Further, accurate estimation of trends requires accounting for biases caused by imperfect detection. To test the degree to which population trends are consistent across scales, I estimated landscape-scale bird population trends from 1999-2012 for 38 species at the Hubbard Brook Experimental Forest (HBEF) in the White Mountains of New Hampshire, USA and compared them to regional and local trends (Chapter 4). I used a new method - open-population binomial mixture models - to test the hypothesis that imperfect detection in bird sampling has the potential to bias trend estimates. I also tested for generalities in species responses by predicting population trends as a function of life history and ecological traits. Landscape-scale trends were correlated with regional and local trends, but generally these correlations were weak (r = 0.12 - 0.4). Further, more species were declining at the regional scale compared to within the relatively undisturbed HBEF. Life history and ecological traits did not explain any of the variability in the HBEF trends. However, at the regional scale, species that occurred at higher elevations were more likely to be declining and species associated with older forests have increased. I hypothesize that these differences could be attributed to both elevated rates of land-use change in the broader region and the fact that the structure of regional data did not permit modeling of imperfect detection. Indeed, accounting for imperfect detection resulted in more accurate population trend estimates at the landscape scale; without accounting for detection we would have both missed trends and falsely identified trends where none existed. These results highlight two important cautions for trend analysis: 1) population trends estimated at fine spatial scales may not be extrapolated to broader scales and 2) accurate trends require accounting for imperfect detection. Title: Effects of spatial scale and heterogeneity on avian occupancy dynamics and population trends in forested mountain landscapes Author: Frey, Sarah Jean Kiuama Population trends and patterns in species distributions are the major currencies used to examine responses by biodiversity to changing environments. Effective conservation recommendations require that models of both distribution dynamics and population trends accurately reflect reality. However, identification of the appropriate temporal and spatial scales of animal response, and then obtaining data at these scales present two major challenges to developing predictive models. In heterogeneous forested mountain landscapes I examined: A) the relative drivers of climatic variability at fine spatial scales under the forest canopy ('microclimate'), B) the influence of microclimate on local-scale occupancy dynamics of bird communities, and C) the effects of spatial scale and imperfect bird detection on long-term avian population trends. Climate change has been predicted to cause widespread biodiversity declines. However, the capacity of climate envelope models for predicting the future of biodiversity has been questioned due to the mismatch between the scale of available data (i.e., global climate models) and the scales at which organisms experience their environment. Local-scale variation in microclimate is hypothesized to provide potential ‘microrefugia’ for biodiversity, but the relative role of elevation, microtopography, and vegetation structure in driving microclimate is not well known. If the microrefugia hypothesis is true, I expected to see areas on the landscape that remained relatively cooler (i.e., buffered sites). To test this, I collected temperature data at 183 sites across elevation and forest structure gradients in complex terrain of the H. J. Andrews Experimental Forest in the Cascade Mountains of Oregon, USA (Chapter 2). I used boosted regression trees, a novel machine learning approach, to determine the relative influence of vegetation structure, microtopography, and elevation as drivers of microclimate and mapped fine-scale distributions of temperature across the landscape. Models performed extremely well on independent data - cross-validation correlations between testing and training data were 0.69 - 0.98 for ten selected climate variables. Elevation was the dominant driver in fine-scale microclimate patterns, although vegetation and microtopography also showed substantial relative influences. For instance, during the spring-summer transition, maximum monthly temperatures observed in old-growth sites were 2.6°C (95% CI: 1.8 - 3.3°C) cooler than plantation sites and minimum temperatures during winter months were 0.6°C (95% CI: 0.4 - 0.8°C) warmer. This suggests that older forest stands mediate changes in temperature by buffering against warming during summer months and moderating cold temperatures during the winter. Climate is generally considered most influential on species distributions at large spatial scales; however much microclimate variability exists within regional patterns. I tested whether this high degree of microclimate variability has relevance for predicting species distributions and occupancy dynamics of the Andrews Forest bird community. I collected bird occurrence data in 2012 and 2013 at all 183 sites with fine-scale temperature measurements. I used dynamic occupancy models to test the effects of temperature on occupancy and apparent within-season bird movement while statistically accounting for vegetation effects and imperfect bird detection (Chapter 3). Most species (87%) exhibited within-season shifts in response to local-scale temperature metrics. Effects of temperature on within-season occupancy dynamics were as large or larger (1 to 1.7 times) than vegetation. However, individual species were almost as likely to shift toward warmer sites as toward cooler sites, suggesting that microclimate preferences are species-specific. My results emphasize that high-resolution temperature data provide valuable insight into avian distribution dynamics in montane forest environments and that microclimate is an important variable in breeding season habitat selection by forest birds. I hypothesize that microclimate-associated distribution shifts may reflect species' potential for behavioral buffering from climate change in complex terrain. Factors influencing population trends often differ depending on the spatial scale under consideration. Further, accurate estimation of trends requires accounting for biases caused by imperfect detection. To test the degree to which population trends are consistent across scales, I estimated landscape-scale bird population trends from 1999-2012 for 38 species at the Hubbard Brook Experimental Forest (HBEF) in the White Mountains of New Hampshire, USA and compared them to regional and local trends (Chapter 4). I used a new method - open-population binomial mixture models - to test the hypothesis that imperfect detection in bird sampling has the potential to bias trend estimates. I also tested for generalities in species responses by predicting population trends as a function of life history and ecological traits. Landscape-scale trends were correlated with regional and local trends, but generally these correlations were weak (r = 0.12 - 0.4). Further, more species were declining at the regional scale compared to within the relatively undisturbed HBEF. Life history and ecological traits did not explain any of the variability in the HBEF trends. However, at the regional scale, species that occurred at higher elevations were more likely to be declining and species associated with older forests have increased. I hypothesize that these differences could be attributed to both elevated rates of land-use change in the broader region and the fact that the structure of regional data did not permit modeling of imperfect detection. Indeed, accounting for imperfect detection resulted in more accurate population trend estimates at the landscape scale; without accounting for detection we would have both missed trends and falsely identified trends where none existed. These results highlight two important cautions for trend analysis: 1) population trends estimated at fine spatial scales may not be extrapolated to broader scales and 2) accurate trends require accounting for imperfect detection. Close

• 27. [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

• 28. [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

• 29. [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

• 30. [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