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• 71. [Article] Pathogenicity and Virulence of Pythium Species Obtained from Forest Nursery Soils on Douglas-Fir Seedlings

  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 [publisher] ...

  Citation × Citation Citation Abstract Copy Title: Pathogenicity and Virulence of Pythium Species Obtained from Forest Nursery Soils on Douglas-Fir Seedlings Author: Davis, Anne, Beck, Bryan R., Weiland, Jerry E. 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 [publisher] and can be found at: https://www.apsnet.org/publications/Pages/default.aspx. Title: Pathogenicity and Virulence of Pythium Species Obtained from Forest Nursery Soils on Douglas-Fir Seedlings Author: Davis, Anne, Beck, Bryan R., Weiland, Jerry E. 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 [publisher] and can be found at: https://www.apsnet.org/publications/Pages/default.aspx. Close

• 72. [Article] Plant community dynamics in remnant and restored Willamette Valley wetland prairies

  Invasion by exotic species can pose a major challenge for developing native plant communities in wetland restoration projects. Often native plant communities do not develop as anticipated in restored wetlands ...

  Citation × Citation Citation Abstract Copy Title: Plant community dynamics in remnant and restored Willamette Valley wetland prairies Author: Schwindt, Rachel A. Invasion by exotic species can pose a major challenge for developing native plant communities in wetland restoration projects. Often native plant communities do not develop as anticipated in restored wetlands due to colonization by exotic species that dominate the native plant community. Despite the time and expense to restore wetlands, there has been little long term research to compare plant communities in restored and natural wetland sites. Research into plant community diversity across several wetland sites over several years can provide a broader perspective into how these ecosystems recover from long-term disturbance. The objective of this study was to compare plant community change from 2000 to 2005 between restored and remnant wetland prairie sites in the southern Willamette Valley in Oregon to determine if exotic species abundance was consistent between these groups. Specific objectives included 1) comparing the diversity and abundance of all species in remnant and restored wetland prairie sites, 2) evaluate the trajectory of community change between remnant and restored wetland prairie sites to determine if there was rapid change in restored sites, and 3) describe the plot level heterogeneity of the plant community in all sites to determine how microsites influence diversity. In 2005, species abundance was re-measured in four remnant wetland prairies and four restored wetland prairies that had been selected for an unrelated vegetation survey in 2000. Species were characterized by life form, origin, and wetland indicator status. Species abundance between groups of remnant and restored sites were compared using a multi-response permutation procedure (MRPP). The plant community trajectory was evaluated with nonmetric multidimensional scaling (NMS) and tested for significance with multivariate analysis of variance (MANOVA). Species area curves were compared between sites and within remnant and restored groups of plots. Within-year and between-year significance tests indicated that remnant and restored sites were similar in exotic species abundance, graminoid abundance, and wetland species abundance with no significant difference between these remnant and restored wetland prairie sites. Individual sites in both groups experienced changes in exotic species abundance which confounded the statistical results. Species heterogeneity was no more spatially diverse across the remnant site plots than restored site plots. Species area curves did not show significant differences between remnant and restored plots but individual plots did show homogeneous community characteristics at smaller spatial scales. Restoration sites had developed high graminoid cover by the 2000 survey which was conducted two to three years after restoration was initiated. All sites were equally likely to contain exotic species. Exotic species common across all sites included Centaurium umbellatum, Holcus lanatus, and Hypericum perforatum. Native species common across sites included Deschampsia cespitosa, Danthonia californica and Juncus tenuis. These results suggested that differences between remnant and restored Willamette Valley wetland prairie sites were not generalizable at the landscape scale and were more dependent on site specific management activities and local barriers to colonization. Five years may not be enough time to see evidence that suggests if restored plant communities will develop spatial characteristics of the remnant sites. This research does suggest that multi-site comparisons help distinguish individual sites that are not developing characteristics of remnant wetland plant communities. Title: Plant community dynamics in remnant and restored Willamette Valley wetland prairies Author: Schwindt, Rachel A. Invasion by exotic species can pose a major challenge for developing native plant communities in wetland restoration projects. Often native plant communities do not develop as anticipated in restored wetlands due to colonization by exotic species that dominate the native plant community. Despite the time and expense to restore wetlands, there has been little long term research to compare plant communities in restored and natural wetland sites. Research into plant community diversity across several wetland sites over several years can provide a broader perspective into how these ecosystems recover from long-term disturbance. The objective of this study was to compare plant community change from 2000 to 2005 between restored and remnant wetland prairie sites in the southern Willamette Valley in Oregon to determine if exotic species abundance was consistent between these groups. Specific objectives included 1) comparing the diversity and abundance of all species in remnant and restored wetland prairie sites, 2) evaluate the trajectory of community change between remnant and restored wetland prairie sites to determine if there was rapid change in restored sites, and 3) describe the plot level heterogeneity of the plant community in all sites to determine how microsites influence diversity. In 2005, species abundance was re-measured in four remnant wetland prairies and four restored wetland prairies that had been selected for an unrelated vegetation survey in 2000. Species were characterized by life form, origin, and wetland indicator status. Species abundance between groups of remnant and restored sites were compared using a multi-response permutation procedure (MRPP). The plant community trajectory was evaluated with nonmetric multidimensional scaling (NMS) and tested for significance with multivariate analysis of variance (MANOVA). Species area curves were compared between sites and within remnant and restored groups of plots. Within-year and between-year significance tests indicated that remnant and restored sites were similar in exotic species abundance, graminoid abundance, and wetland species abundance with no significant difference between these remnant and restored wetland prairie sites. Individual sites in both groups experienced changes in exotic species abundance which confounded the statistical results. Species heterogeneity was no more spatially diverse across the remnant site plots than restored site plots. Species area curves did not show significant differences between remnant and restored plots but individual plots did show homogeneous community characteristics at smaller spatial scales. Restoration sites had developed high graminoid cover by the 2000 survey which was conducted two to three years after restoration was initiated. All sites were equally likely to contain exotic species. Exotic species common across all sites included Centaurium umbellatum, Holcus lanatus, and Hypericum perforatum. Native species common across sites included Deschampsia cespitosa, Danthonia californica and Juncus tenuis. These results suggested that differences between remnant and restored Willamette Valley wetland prairie sites were not generalizable at the landscape scale and were more dependent on site specific management activities and local barriers to colonization. Five years may not be enough time to see evidence that suggests if restored plant communities will develop spatial characteristics of the remnant sites. This research does suggest that multi-site comparisons help distinguish individual sites that are not developing characteristics of remnant wetland plant communities. Close

• 73. [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

• 74. [Article] Release of dissolved organic matter by coastal diatoms

  Dissolved organic matter (DOM) production was examined in axenic batch cultures of five coastal diatom species. For Chaetoceros decipiens, dissolved organic carbon (DOC) accumulated beginning in late exponential growth ...

  Citation × Citation Citation Abstract Copy Title: Release of dissolved organic matter by coastal diatoms Author: Wheeler, Patricia A., Wetz, Michael S. Dissolved organic matter (DOM) production was examined in axenic batch cultures of five coastal diatom species. For Chaetoceros decipiens, dissolved organic carbon (DOC) accumulated beginning in late exponential growth as a result of increased cell density. For Cylindrotheca closterium, DOC actually decreased in late exponential growth and reached zero by the end of the experiment. This coincided with continued particulate organic carbon (POC) production and a threefold increase in the per-cell concentration of transparent exopolymer particles after nutrients were depleted. DOC release rates varied between species but were significantly higher for all five species in exponential or transition growth than during stationary growth. On average, 5% of the total fixed C was released as DOC for four of the diatoms, whereas C. decipiens released ,21% of its fixed C as DOC. The percentage of fixed C released as DOC varied little with nutrient availability or diatom growth stage. The DOM produced by some diatom species adheres to filters and is measured in the particulate organic matter (POM) fraction when cells are separated from the medium by filtration. This may be an important problem when diatom species with known benthic life histories are prevalent. In contrast, for species like Chaetoceros that have no benthic life history, DOM release rates estimated by bulk measurements or 14C appear to be accurate. Overall, these results indicate that the species composition of phytoplankton blooms has the potential to influence the relative importance of POM and DOM production and can complicate interpretation of those measurements. Title: Release of dissolved organic matter by coastal diatoms Author: Wheeler, Patricia A., Wetz, Michael S. Dissolved organic matter (DOM) production was examined in axenic batch cultures of five coastal diatom species. For Chaetoceros decipiens, dissolved organic carbon (DOC) accumulated beginning in late exponential growth as a result of increased cell density. For Cylindrotheca closterium, DOC actually decreased in late exponential growth and reached zero by the end of the experiment. This coincided with continued particulate organic carbon (POC) production and a threefold increase in the per-cell concentration of transparent exopolymer particles after nutrients were depleted. DOC release rates varied between species but were significantly higher for all five species in exponential or transition growth than during stationary growth. On average, 5% of the total fixed C was released as DOC for four of the diatoms, whereas C. decipiens released ,21% of its fixed C as DOC. The percentage of fixed C released as DOC varied little with nutrient availability or diatom growth stage. The DOM produced by some diatom species adheres to filters and is measured in the particulate organic matter (POM) fraction when cells are separated from the medium by filtration. This may be an important problem when diatom species with known benthic life histories are prevalent. In contrast, for species like Chaetoceros that have no benthic life history, DOM release rates estimated by bulk measurements or 14C appear to be accurate. Overall, these results indicate that the species composition of phytoplankton blooms has the potential to influence the relative importance of POM and DOM production and can complicate interpretation of those measurements. Close

• 75. [Article] Feeding ecology of juvenile rockfishes off Oregon and Washington based on stomach content and stable isotope analyses

  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 Springer ...

  Citation × Citation Citation Abstract Copy Title: Feeding ecology of juvenile rockfishes off Oregon and Washington based on stomach content and stable isotope analyses Author: Miller, Todd W., Van Gaest, Ahna, Bosley, Keith L., Bosley, Katelyn M., Elz, Anna, Brodeur, Richard D. 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 Springer and can be found at: http://link.springer.com/journal/227. Title: Feeding ecology of juvenile rockfishes off Oregon and Washington based on stomach content and stable isotope analyses Author: Miller, Todd W., Van Gaest, Ahna, Bosley, Keith L., Bosley, Katelyn M., Elz, Anna, Brodeur, Richard D. 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 Springer and can be found at: http://link.springer.com/journal/227. Close

• 76. [Article] Colonization and extinction in dynamic habitats: an occupancy approach for a Great Plains stream fish assemblage

  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 Ecological ...

  Citation × Citation Citation Abstract Copy Title: Colonization and extinction in dynamic habitats: an occupancy approach for a Great Plains stream fish assemblage Author: Falke, Jeffrey A., Bestgen, Kevin R., Bailey, Larissa L., Fausch, Kurt D. 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 Ecological Society of America and can be found at: http://esa.org/. Title: Colonization and extinction in dynamic habitats: an occupancy approach for a Great Plains stream fish assemblage Author: Falke, Jeffrey A., Bestgen, Kevin R., Bailey, Larissa L., Fausch, Kurt D. 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 Ecological Society of America and can be found at: http://esa.org/. Close

• 77. [Article] Physiological alterations following severe hypoxic stress in two species of fresh-water fish

  Bluegill sunfish, Lepomia macrochirus, and cutthroat trout, Salmo clarki, were exposed to a rapidly declining oxygen tension for a period of time sufficient to just cause loss of equilibrium in the fish. ...

  Citation × Citation Citation Abstract Copy Title: Physiological alterations following severe hypoxic stress in two species of fresh-water fish Author: Heath, Alan G. Bluegill sunfish, Lepomia macrochirus, and cutthroat trout, Salmo clarki, were exposed to a rapidly declining oxygen tension for a period of time sufficient to just cause loss of equilibrium in the fish. During recovery from the stress, measurements of oxygen uptake, blood lactic acid, blood glucose, liver glycogen, muscle glycogen, and hemoglobin or red blood cell counts were made at fixed intervals of time. Hypoxic stress caused an immediate rise in blood lactate and oxygen uptake in both species with the trout showing the greatest increases. This suggests a greater degree of oxygen debt in the latter, even though the stress routine used on this species was not as prolonged. A delayed peak in the blood lactate observed in the trout but not in the bluegill indicated a possible impairment of circulatory function in the former. The blood lactate returned to normal after two and five hours in the bluegill and cutthroat respectively. The return of the oxygen uptake to control levels required eight and ten hours respectively. An immediate mobilization of the carbohydrate stores occurred during the stress in both the bluegill and trout. The blood glucose concentration rose greatly in the bluegill but not in the trout. Mobilization of liver glycogen in the trout without a concomitant rise in glucose suggested utilization of the latter as rapidly as it was formed. During recovery from the hypoxic stress, resynthesis of glycogen stores occurred much more quickly in the bluegills than trout. Significant changes in hemoglobin or red blood cell numbers did not occur in either species indicating no change in blood water content, or effect on hemopoetic tissues resulting from the stress. It was concluded that the differences observed between these two species point to possible mechanisms in the bluegill which help it to tolerate acute hypoxic conditions better than the trout. Title: Physiological alterations following severe hypoxic stress in two species of fresh-water fish Author: Heath, Alan G. Bluegill sunfish, Lepomia macrochirus, and cutthroat trout, Salmo clarki, were exposed to a rapidly declining oxygen tension for a period of time sufficient to just cause loss of equilibrium in the fish. During recovery from the stress, measurements of oxygen uptake, blood lactic acid, blood glucose, liver glycogen, muscle glycogen, and hemoglobin or red blood cell counts were made at fixed intervals of time. Hypoxic stress caused an immediate rise in blood lactate and oxygen uptake in both species with the trout showing the greatest increases. This suggests a greater degree of oxygen debt in the latter, even though the stress routine used on this species was not as prolonged. A delayed peak in the blood lactate observed in the trout but not in the bluegill indicated a possible impairment of circulatory function in the former. The blood lactate returned to normal after two and five hours in the bluegill and cutthroat respectively. The return of the oxygen uptake to control levels required eight and ten hours respectively. An immediate mobilization of the carbohydrate stores occurred during the stress in both the bluegill and trout. The blood glucose concentration rose greatly in the bluegill but not in the trout. Mobilization of liver glycogen in the trout without a concomitant rise in glucose suggested utilization of the latter as rapidly as it was formed. During recovery from the hypoxic stress, resynthesis of glycogen stores occurred much more quickly in the bluegills than trout. Significant changes in hemoglobin or red blood cell numbers did not occur in either species indicating no change in blood water content, or effect on hemopoetic tissues resulting from the stress. It was concluded that the differences observed between these two species point to possible mechanisms in the bluegill which help it to tolerate acute hypoxic conditions better than the trout. Close

• 78. [Article] Social interaction between juvenile coho and fall chinook salmon in Sixes River, Oregon

  The nature of the interaction between juvenile coho salmon, Oncorhynchus kisutch (Walbaum), and fall chinook salmon, 0. tshawytscha (Walbaum), was studied in Sixes River, Oregon. Seining, snorkeling, and ...

  Citation × Citation Citation Abstract Copy Title: Social interaction between juvenile coho and fall chinook salmon in Sixes River, Oregon Author: Stein, Roy A. The nature of the interaction between juvenile coho salmon, Oncorhynchus kisutch (Walbaum), and fall chinook salmon, 0. tshawytscha (Walbaum), was studied in Sixes River, Oregon. Seining, snorkeling, and tagging were used to determine distribution and patterns of growth of these two species in the stream environment. Experiments conducted in flowing-water observation troughs that provided volitional residence were designed to examine the outcome of agonistic behavior between these two species. Both species were distributed throughout the entire river system in early spring. During this period, underwater surveys in the main river and selected tributaries indicated that both species preferred the same habitat. As temperatures increased during the late spring, coho disappeared from the main river, but continued to occupy cool tributaries. Fall chinook, on the other hand, were found primarily in the main river until early summer, when they moved to the estuary. Relatively few individuals remained in the tributaries. Experiments conducted in the troughs revealed that agonistic behavior, including nipping, chasing, lateral display, submission, and fleeing, occurred between juvenile coho and fall chinook. When the two species were together in the troughs and in cool tributary streams, coho grew faster than chinook. When isolated in troughs, both grew at similar rates. Coho tolerated fewer individuals per unit area than did chinook, and occupied positions of dominance near the source of incoming food at the upstream end of the troughs. Coho had brighter fin and body colors, greater fin development, deeper bodies, and were heavier than fall chinook of the same length. Coloration and morphology appeared to be important factors influencing the "apparent" size and presumably the social status of both species. Juvenile coho, with extensive development of fins and coloration and intense territorial behavior, are hypothesized to be adapted to small, cool tributary streams. Fall chinook, on the other hand, with conservative development of fins and coloration and related behavior patterns, appear to be adapted to conditions in the main river and estuary. Title: Social interaction between juvenile coho and fall chinook salmon in Sixes River, Oregon Author: Stein, Roy A. The nature of the interaction between juvenile coho salmon, Oncorhynchus kisutch (Walbaum), and fall chinook salmon, 0. tshawytscha (Walbaum), was studied in Sixes River, Oregon. Seining, snorkeling, and tagging were used to determine distribution and patterns of growth of these two species in the stream environment. Experiments conducted in flowing-water observation troughs that provided volitional residence were designed to examine the outcome of agonistic behavior between these two species. Both species were distributed throughout the entire river system in early spring. During this period, underwater surveys in the main river and selected tributaries indicated that both species preferred the same habitat. As temperatures increased during the late spring, coho disappeared from the main river, but continued to occupy cool tributaries. Fall chinook, on the other hand, were found primarily in the main river until early summer, when they moved to the estuary. Relatively few individuals remained in the tributaries. Experiments conducted in the troughs revealed that agonistic behavior, including nipping, chasing, lateral display, submission, and fleeing, occurred between juvenile coho and fall chinook. When the two species were together in the troughs and in cool tributary streams, coho grew faster than chinook. When isolated in troughs, both grew at similar rates. Coho tolerated fewer individuals per unit area than did chinook, and occupied positions of dominance near the source of incoming food at the upstream end of the troughs. Coho had brighter fin and body colors, greater fin development, deeper bodies, and were heavier than fall chinook of the same length. Coloration and morphology appeared to be important factors influencing the "apparent" size and presumably the social status of both species. Juvenile coho, with extensive development of fins and coloration and intense territorial behavior, are hypothesized to be adapted to small, cool tributary streams. Fall chinook, on the other hand, with conservative development of fins and coloration and related behavior patterns, appear to be adapted to conditions in the main river and estuary. Close

• 79. [Article] Community gradients of Arctic macrolichens in relation to succession, grazing and the environment

  The purpose of this dissertation was to define macrolichen community gradients in relation to succession, grazing and the environment. First, species scores indicating when macrolichen species appeared ...

  Citation × Citation Citation Abstract Copy Title: Community gradients of Arctic macrolichens in relation to succession, grazing and the environment Author: Holt, Emily A. The purpose of this dissertation was to define macrolichen community gradients in relation to succession, grazing and the environment. First, species scores indicating when macrolichen species appeared following disturbance were derived from the literature. Weighted averaging of these data with a community matrix created a successional score for each sample unit of interest. These scores are surrogates for community age for subsequent analyses. I then described lichen community structure and its relation to the environment in the Bering Land Bridge National Preserve (BELA) in northwestern Alaska. Two primary gradients in lichen community composition were related to habitat rockiness and a substrate-topographic gradient. Next, I sought impacts of grazing by reindeer and caribou on lichen communities. I found lightly grazed areas had taller lichens, greater total lichen cover and minor but significant changes in community structure than heavily grazed sites. Lichen species richness, however, did not differ by grazing status. To create a generalized recovery model, I used plots in burned areas and found total lichen and bryophyte cover varied with time since fire (range 4-49 yrs since fire), while vascular plant cover showed no trend. I then compared these patterns to BELA, an area of unknown disturbance history. Low lichen cover in BELA may not necessarily reflect disturbance but rather site or climatic differences. Lastly, I found that all 17 GIS variables separated lichen communities to some degree. Separation of lichen communities by variable ranged from strong (Alaska Subsections, soil and surficial geology variables) to weak (Watersheds and Reindeer Ownership). The quality of the underlying relationships, how finely the groups are divided and the average patch size of each variable also contribute to differences in how clearly lichen communities were separated. This work will serve as a baseline for future comparisons to understand implications of climate and land use change on lichen communities. My grazing results may inform managers of the implications of heavy grazing and underscore protection and monitoring of prolific and diverse sites. In addition, this work contributes a new method to age tundra communities and a list of GIS variable successful at separating lichen communities. Title: Community gradients of Arctic macrolichens in relation to succession, grazing and the environment Author: Holt, Emily A. The purpose of this dissertation was to define macrolichen community gradients in relation to succession, grazing and the environment. First, species scores indicating when macrolichen species appeared following disturbance were derived from the literature. Weighted averaging of these data with a community matrix created a successional score for each sample unit of interest. These scores are surrogates for community age for subsequent analyses. I then described lichen community structure and its relation to the environment in the Bering Land Bridge National Preserve (BELA) in northwestern Alaska. Two primary gradients in lichen community composition were related to habitat rockiness and a substrate-topographic gradient. Next, I sought impacts of grazing by reindeer and caribou on lichen communities. I found lightly grazed areas had taller lichens, greater total lichen cover and minor but significant changes in community structure than heavily grazed sites. Lichen species richness, however, did not differ by grazing status. To create a generalized recovery model, I used plots in burned areas and found total lichen and bryophyte cover varied with time since fire (range 4-49 yrs since fire), while vascular plant cover showed no trend. I then compared these patterns to BELA, an area of unknown disturbance history. Low lichen cover in BELA may not necessarily reflect disturbance but rather site or climatic differences. Lastly, I found that all 17 GIS variables separated lichen communities to some degree. Separation of lichen communities by variable ranged from strong (Alaska Subsections, soil and surficial geology variables) to weak (Watersheds and Reindeer Ownership). The quality of the underlying relationships, how finely the groups are divided and the average patch size of each variable also contribute to differences in how clearly lichen communities were separated. This work will serve as a baseline for future comparisons to understand implications of climate and land use change on lichen communities. My grazing results may inform managers of the implications of heavy grazing and underscore protection and monitoring of prolific and diverse sites. In addition, this work contributes a new method to age tundra communities and a list of GIS variable successful at separating lichen communities. Close

• 80. [Article] Lichen communities and species indicate climate thresholds in southeast and south-central Alaska, USA

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The American Bryological and Lichenological Society, Inc., and can be found at: ...

  Citation × Citation Citation Abstract Copy Title: Lichen communities and species indicate climate thresholds in southeast and south-central Alaska, USA Author: McCune, Bruce, Root, Heather T., Jovan, Sarah This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The American Bryological and Lichenological Society, Inc., and can be found at: http://www.bioone.org/loi/bryo Title: Lichen communities and species indicate climate thresholds in southeast and south-central Alaska, USA Author: McCune, Bruce, Root, Heather T., Jovan, Sarah This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by The American Bryological and Lichenological Society, Inc., and can be found at: http://www.bioone.org/loi/bryo Close