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• 2321. [Article] Population characteristics and movement patterns of redband trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) in the Crooked River, Oregon

  Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to ...

  Citation × Citation Citation Abstract Copy Title: Population characteristics and movement patterns of redband trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) in the Crooked River, Oregon Author: Nesbit, Shivonne M. Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to address potential factors contributing to the decline. There are two main goals to this project: (1) identify potential factors contributing to the reduction of the redband trout population in the Crooked River fishery and (2) provide management recommendations to all of the agencies responsible for managing the Crooked River that might effect a change in the redband trout population trend. This thesis had three objectives: (1) evaluate the movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam, (2) monitor total dissolved gas levels (TDG) in the Crooked River to evaluate the incidence of supersaturated water and gas bubble disease in redband trout and mountain whitefish and (3) implement a more comprehensive population estimate survey to document both redband trout and mountain whitefish population densities. Prior to this study, limited data existed on the distribution and movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam. Based on the results from the 2-year telemetry study, redband trout and mountain whitefish population exhibit a resident life history strategy and stay in the Wild and Scenic Section of the Crooked River below Bowman Dam. Two potential explanations for the observed population decline were plausible: the decline was actually a decline, or the fish moved to other sections of the Crooked River downstream of Bowman Dam. The telemetery study showed that redband trout and mountain whitefish stay within this section of river, thereby providing evidence against the explanation that the observed population decline was a result of movement of fish to other sections of river. The total dissolved gas study demonstrated that gas saturation levels become elevated enough to cause gas bubble disease in the Crooked River below Bowman Dam. The gas saturation in the Crooked River is equivalent or higher than levels shown to produce gas bubble disease (GBD) in fishes. When flows exceed 600 cfs, the total dissolved gas saturation exceeds the maximum Oregon Department of Environmental Quality mandated level of 110% gas saturation in the Crooked River. Flows in excess of 600cfs are common during spring runoff events below Bowman Dam. From 1989-2009, flows exceeded 600 cfs in 13 of the 21 years and 1000 cfs in 10 of the 21 years. The past population effects of high flows and supersaturated waters on redband trout and mountain whitefish are difficult to quantify, but based on the hydrograph and the saturation curve, the years when gas bubble disease might have been present in fish can be predicted. Given the strong linear relationship between TDG and stream average daily discharge (r2 = 0.93), discharge itself can be used as a predictive tool for assessing TDG levels in the river. Based on the flow data from the USBOR gauging station and the gas saturation curve for the wild and scenic section of the Crooked River generated here, gas bubble disease was probably present in fish in 1993, 1996, 1997, 1998, 1999, and 2004. The redband trout population density has varied considerably from year to year, with a peak observed in 1994 and the lowest point observed in 2006. A large increase in the number of redband trout per km occurred between 1993 and 1994, indicating that the density of fish can increase substantially in one year. The decline in redband trout density from 1994 to 2006 appears to be more gradual than the increase in density observed from 1993 to 1994. Since 2006, the redband trout population density appears to be increasing based on qualitative patterns. One interesting finding was that in 2007, the mountain whitefish density was estimated to be 7 times greater than the redband trout population, in 2008 it was estimated to be 4 times greater, but in 2009, the mountain whitefish density was only marginally higher than the redband trout population. In the three years of this study, there appears to be a shift in the relative abundance of redband trout and mountain whitefish directly below Bowman Dam. The reduction in the mountain whitefish population density from 2007 to 2008 was not expected based on angler accounts of the increase in mountain whitefish population densities. Title: Population characteristics and movement patterns of redband trout (Oncorhynchus mykiss) and mountain whitefish (Prosopium williamsoni) in the Crooked River, Oregon Author: Nesbit, Shivonne M. Over the last decade, the Oregon Department of Fish and Wildlife (ODFW) has documented a precipitous decline in the Crooked River redband trout (Oncorhynchus mykiss) population, prompting this study to address potential factors contributing to the decline. There are two main goals to this project: (1) identify potential factors contributing to the reduction of the redband trout population in the Crooked River fishery and (2) provide management recommendations to all of the agencies responsible for managing the Crooked River that might effect a change in the redband trout population trend. This thesis had three objectives: (1) evaluate the movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam, (2) monitor total dissolved gas levels (TDG) in the Crooked River to evaluate the incidence of supersaturated water and gas bubble disease in redband trout and mountain whitefish and (3) implement a more comprehensive population estimate survey to document both redband trout and mountain whitefish population densities. Prior to this study, limited data existed on the distribution and movement patterns of redband trout and mountain whitefish in the Crooked River below Bowman Dam. Based on the results from the 2-year telemetry study, redband trout and mountain whitefish population exhibit a resident life history strategy and stay in the Wild and Scenic Section of the Crooked River below Bowman Dam. Two potential explanations for the observed population decline were plausible: the decline was actually a decline, or the fish moved to other sections of the Crooked River downstream of Bowman Dam. The telemetery study showed that redband trout and mountain whitefish stay within this section of river, thereby providing evidence against the explanation that the observed population decline was a result of movement of fish to other sections of river. The total dissolved gas study demonstrated that gas saturation levels become elevated enough to cause gas bubble disease in the Crooked River below Bowman Dam. The gas saturation in the Crooked River is equivalent or higher than levels shown to produce gas bubble disease (GBD) in fishes. When flows exceed 600 cfs, the total dissolved gas saturation exceeds the maximum Oregon Department of Environmental Quality mandated level of 110% gas saturation in the Crooked River. Flows in excess of 600cfs are common during spring runoff events below Bowman Dam. From 1989-2009, flows exceeded 600 cfs in 13 of the 21 years and 1000 cfs in 10 of the 21 years. The past population effects of high flows and supersaturated waters on redband trout and mountain whitefish are difficult to quantify, but based on the hydrograph and the saturation curve, the years when gas bubble disease might have been present in fish can be predicted. Given the strong linear relationship between TDG and stream average daily discharge (r2 = 0.93), discharge itself can be used as a predictive tool for assessing TDG levels in the river. Based on the flow data from the USBOR gauging station and the gas saturation curve for the wild and scenic section of the Crooked River generated here, gas bubble disease was probably present in fish in 1993, 1996, 1997, 1998, 1999, and 2004. The redband trout population density has varied considerably from year to year, with a peak observed in 1994 and the lowest point observed in 2006. A large increase in the number of redband trout per km occurred between 1993 and 1994, indicating that the density of fish can increase substantially in one year. The decline in redband trout density from 1994 to 2006 appears to be more gradual than the increase in density observed from 1993 to 1994. Since 2006, the redband trout population density appears to be increasing based on qualitative patterns. One interesting finding was that in 2007, the mountain whitefish density was estimated to be 7 times greater than the redband trout population, in 2008 it was estimated to be 4 times greater, but in 2009, the mountain whitefish density was only marginally higher than the redband trout population. In the three years of this study, there appears to be a shift in the relative abundance of redband trout and mountain whitefish directly below Bowman Dam. The reduction in the mountain whitefish population density from 2007 to 2008 was not expected based on angler accounts of the increase in mountain whitefish population densities. Close

• 2322. [Article] Summer soil moisture dynamics in a young Douglas-fir plantation as influenced by three herbaceous weed communities

  The use of chemicals such as the triazines (especially atrazine) and mixtures of the triazines and 2,4-D or 2,4,5-T has become almost standard practice in some parts of the world for selectively controlling ...

  Citation × Citation Citation Abstract Copy Title: Summer soil moisture dynamics in a young Douglas-fir plantation as influenced by three herbaceous weed communities Author: Preest, David Stanley The use of chemicals such as the triazines (especially atrazine) and mixtures of the triazines and 2,4-D or 2,4,5-T has become almost standard practice in some parts of the world for selectively controlling grasses and other herbaceous weeds to conserve moisture for and/or prevent the smothering of newly-planted conifers. In the Pacific Northwest, where application is mainly to control grasses in forest and Christmas tree plantations of Douglas-fir [Pseudotsua menziesii (Mirb.) Franco.], a single such treatment dramatically increases first year survival and growth of the trees mainly because of increased moisture availability. However, this predisposes the site for heavy infestations of forbs and forbs plus annual grasses in the second and subsequent several years. 'To what extent can these be justifiably ignored?', is a question which this dissertation attempts to answer in terms of the effects of vegetation manipulation on soil moisture. Data for this study came from observations and experimentation mainly during the summer of 1970 in a series of already existing herbicide trial plots located in a grassy meadow in the Oregon Coast Range about 18 miles west of Corvallis. The vegetative covers of the plots reflected histories of zero to three years herbicide treatment and could be classified into: (1) non- or lightly vegetated with forbs, (2) moderate to dense pure forbs, (3) deuse forbs plus annual grasses, (4) heavy bent grass (Agrostis tenuis Sibth.). An attempt was made to develop regression models to describe soil moisture use as a function of cumulative open-pan evaporation, soil depth, standing biomass of herbaceous vegetation, fresh weight of trees, root distribution of the herbaceous vegetation, and vegetation type. This was only partially successful. The models described the dynamic characteristics and interrelations of the soil moisture profiles under the four vegetation types in a general way only, and they lacked sufficient predictive accuracy to make them of practical use in their present form. Response surfaces were developed from the data which portrayed the changes in specific soil moisture content, specific soil moisture used, specific available soil moisture content, and cumulative available soil moisture content with changes in depth, cumulative open-pan evaporation, and vegetation type. They demonstrated that bent grass made heavy demands on the soil moisture in the upper profile early in the season but only moderate demands on the lower profile, a pattern consistent with its aestivating and rooting characteristics. Moderate to dense pure orbs made relatively light early season demands on the upper profile, but came on strongly later in the season with heavy moisture use at all levels in the profile. The forb/annual grass mixture was the most demanding of all. It caused heavy, early season, upper profile moisture withdrawal coupled with sustained lower profile moisture depletion. Again, this was a pattern consistent with the phenological and rooting habits of the vegetation. There was evidence that a substantial amount of water, which because of weed control was not transpired, was eventually lost, probably through increased surface evaporation and unsaturated flow. Nevertheless, although the overall effect of weed control may have been to make available to the trees only a small amount of the moisture saved from transpirational loss, this component is of major importance in the relief of tree moisture stress. Using the conventional 15 bar estimate of permanent wilting point it was shown that the average rate of descent of the permanent wilting point front was about 0.17 in and 0.14 in per day for the bent grass and mixed forb/annual grass types, respectively. The late season rate of descent under pure forbs was even faster. These are rates which the root growth of new transplants or natural seedlings cannot match under field conditions so that their roots are sooner or later deprived of access to available soil moisture. It is apparent that bent grass, forbs, and forb/annual grass mixtures represent hostile ecosystems for the establishment of Douglas-fir in areas characterised by Mediterranean type summers. Pure forbs and forb/annual grass mixtures additionally make heavy demands on the lower profile, presumably causing elevated moisture stresses, and reduced photosynthesis and growth even in well-established trees. It would therefore seem desirable (and perhaps economically justifiable) to prolong the period of complete or semi-complete herbaceous weed control in young conifer plantations being established under these conditions. Title: Summer soil moisture dynamics in a young Douglas-fir plantation as influenced by three herbaceous weed communities Author: Preest, David Stanley The use of chemicals such as the triazines (especially atrazine) and mixtures of the triazines and 2,4-D or 2,4,5-T has become almost standard practice in some parts of the world for selectively controlling grasses and other herbaceous weeds to conserve moisture for and/or prevent the smothering of newly-planted conifers. In the Pacific Northwest, where application is mainly to control grasses in forest and Christmas tree plantations of Douglas-fir [Pseudotsua menziesii (Mirb.) Franco.], a single such treatment dramatically increases first year survival and growth of the trees mainly because of increased moisture availability. However, this predisposes the site for heavy infestations of forbs and forbs plus annual grasses in the second and subsequent several years. 'To what extent can these be justifiably ignored?', is a question which this dissertation attempts to answer in terms of the effects of vegetation manipulation on soil moisture. Data for this study came from observations and experimentation mainly during the summer of 1970 in a series of already existing herbicide trial plots located in a grassy meadow in the Oregon Coast Range about 18 miles west of Corvallis. The vegetative covers of the plots reflected histories of zero to three years herbicide treatment and could be classified into: (1) non- or lightly vegetated with forbs, (2) moderate to dense pure forbs, (3) deuse forbs plus annual grasses, (4) heavy bent grass (Agrostis tenuis Sibth.). An attempt was made to develop regression models to describe soil moisture use as a function of cumulative open-pan evaporation, soil depth, standing biomass of herbaceous vegetation, fresh weight of trees, root distribution of the herbaceous vegetation, and vegetation type. This was only partially successful. The models described the dynamic characteristics and interrelations of the soil moisture profiles under the four vegetation types in a general way only, and they lacked sufficient predictive accuracy to make them of practical use in their present form. Response surfaces were developed from the data which portrayed the changes in specific soil moisture content, specific soil moisture used, specific available soil moisture content, and cumulative available soil moisture content with changes in depth, cumulative open-pan evaporation, and vegetation type. They demonstrated that bent grass made heavy demands on the soil moisture in the upper profile early in the season but only moderate demands on the lower profile, a pattern consistent with its aestivating and rooting characteristics. Moderate to dense pure orbs made relatively light early season demands on the upper profile, but came on strongly later in the season with heavy moisture use at all levels in the profile. The forb/annual grass mixture was the most demanding of all. It caused heavy, early season, upper profile moisture withdrawal coupled with sustained lower profile moisture depletion. Again, this was a pattern consistent with the phenological and rooting habits of the vegetation. There was evidence that a substantial amount of water, which because of weed control was not transpired, was eventually lost, probably through increased surface evaporation and unsaturated flow. Nevertheless, although the overall effect of weed control may have been to make available to the trees only a small amount of the moisture saved from transpirational loss, this component is of major importance in the relief of tree moisture stress. Using the conventional 15 bar estimate of permanent wilting point it was shown that the average rate of descent of the permanent wilting point front was about 0.17 in and 0.14 in per day for the bent grass and mixed forb/annual grass types, respectively. The late season rate of descent under pure forbs was even faster. These are rates which the root growth of new transplants or natural seedlings cannot match under field conditions so that their roots are sooner or later deprived of access to available soil moisture. It is apparent that bent grass, forbs, and forb/annual grass mixtures represent hostile ecosystems for the establishment of Douglas-fir in areas characterised by Mediterranean type summers. Pure forbs and forb/annual grass mixtures additionally make heavy demands on the lower profile, presumably causing elevated moisture stresses, and reduced photosynthesis and growth even in well-established trees. It would therefore seem desirable (and perhaps economically justifiable) to prolong the period of complete or semi-complete herbaceous weed control in young conifer plantations being established under these conditions. Close

• 2323. [Article] Associations Between Crested Wheatgrass and Native Vegetation in Southeastern Oregon : An Investigation of Co-establishment, Environment, Seeding History, and Livestock management

  Crested wheatgrass (Agropyron cristatum [L] Gaertm), an introduced bunchgrass, has been seeded on over 5 million hectares of degraded rangeland in western North America because it establishes more readily ...

  Citation × Citation Citation Abstract Copy Title: Associations Between Crested Wheatgrass and Native Vegetation in Southeastern Oregon : An Investigation of Co-establishment, Environment, Seeding History, and Livestock management Author: Nafus, Aleta M. Crested wheatgrass (Agropyron cristatum [L] Gaertm), an introduced bunchgrass, has been seeded on over 5 million hectares of degraded rangeland in western North America because it establishes more readily than native bunchgrasses. Because crested wheatgrass stands are associated with native species displacement and low biological diversity, there is substantial interest in re-establishing native species within seeded stands. However, efforts to reintroduce native grasses into crested wheatgrass stands have been largely unsuccessful, and little is known about the long-term dynamics of crested wheatgrass/native species mixes. This project was composed of two studies evaluating interactions between crested wheatgrass and associated native vegetation. In the first study, I examined the abundance of crested wheatgrass and seven native sagebrush steppe bunchgrasses which had been planted concurrently 13 years prior at equal densities. Thirteen years after planting, crested wheatgrass was the dominant bunchgrass with a ten-fold increase from its original planted density. Of the seven native bunchgrasses, four species: Idaho fescue (Festuca idahoensis Elmer); Thurber's needlegrass (Achnatherum thurberianum (Piper) Barkworth); basin wildrye (Leymus cinereus (Scribn. & Merr.) A. Löve) and Sandberg bluegrass (Poa secunda J. Presl) maintained their low planting density while three species: bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Löve), needle-and-thread (Hesperostipa comata (Trin. & Rupr.) Barkworth), and squirreltail (Elymus elymoides (Raf.) Swezey), declined in density over the 13-year period. Results suggested that densities of native bunchgrasses planted concurrently with crested wheatgrass were unlikely to increase and that some species only persisted at low levels. However, the continued persistence of native bunchgrasses, even at low densities, suggests that co-planting of some native bunchgrasses may be a viable way of avoiding crested wheatgrass monocultures when this species is necessary for rehabilitation or restoration. In the second study, I sought to identify environmental, historic and livestock management factors associated with native vegetation occasionally found in seeded crested wheatgrass stands. Basal cover, density, species richness and diversity were measured in 2012 and 2013 on 121 sites previously seeded to crested wheatgrass in southeastern Oregon. Plant community composition of crested wheatgrass stands was variable; some of the seedings were monocultures of crested wheatgrass while others contained diverse native species. Functional group variability explained by environmental factors ranged from 0% of annual grass density to 56% of large native perennial bunchgrass density. Soil texture was significant and appeared to be an important environmental characteristic explaining functional group cover and density 10-50 years post seeding. Native vegetation was, for all functional groups, positively correlated with soils lower in sand content. Precipitation in the year following seeding of crested wheatgrass has long-term effects on plant community dynamics, especially for Wyoming big sagebrush. Higher precipitation in the year following crested wheatgrass seeding was associated with decreased shrubs, likely because crested wheatgrass seedlings were more successful and therefore sagebrush seedlings experience greater competition. Moderate grazing was associated with reduced crested wheatgrass monoculture characteristics relative to ungrazed sites. However, within spring grazed and spring-summer grazed sites, there was a negative relationship between increased stocking rate and native species cover and abundance. I speculate that was largely the effect of higher stocking rates being allotted to more productive crested wheatgrass seedings. Overall, my research suggested that pre-seeding treatment/disturbance on a site appears to have long-term implications for plant community dynamics. However, functional groups varied in response to different pre-seeding treatments. Results support the notion that crested wheatgrass is very competitive with native bunchgrasses in particular; and that introducing natives into crested wheatgrass stands may require high levels of disturbance and may be most successful in more finely-textured soils. The results of this study also suggest that management actions, both at the time of seeding and after seeding, can influence plant community characteristics. Title: Associations Between Crested Wheatgrass and Native Vegetation in Southeastern Oregon : An Investigation of Co-establishment, Environment, Seeding History, and Livestock management Author: Nafus, Aleta M. Crested wheatgrass (Agropyron cristatum [L] Gaertm), an introduced bunchgrass, has been seeded on over 5 million hectares of degraded rangeland in western North America because it establishes more readily than native bunchgrasses. Because crested wheatgrass stands are associated with native species displacement and low biological diversity, there is substantial interest in re-establishing native species within seeded stands. However, efforts to reintroduce native grasses into crested wheatgrass stands have been largely unsuccessful, and little is known about the long-term dynamics of crested wheatgrass/native species mixes. This project was composed of two studies evaluating interactions between crested wheatgrass and associated native vegetation. In the first study, I examined the abundance of crested wheatgrass and seven native sagebrush steppe bunchgrasses which had been planted concurrently 13 years prior at equal densities. Thirteen years after planting, crested wheatgrass was the dominant bunchgrass with a ten-fold increase from its original planted density. Of the seven native bunchgrasses, four species: Idaho fescue (Festuca idahoensis Elmer); Thurber's needlegrass (Achnatherum thurberianum (Piper) Barkworth); basin wildrye (Leymus cinereus (Scribn. & Merr.) A. Löve) and Sandberg bluegrass (Poa secunda J. Presl) maintained their low planting density while three species: bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Löve), needle-and-thread (Hesperostipa comata (Trin. & Rupr.) Barkworth), and squirreltail (Elymus elymoides (Raf.) Swezey), declined in density over the 13-year period. Results suggested that densities of native bunchgrasses planted concurrently with crested wheatgrass were unlikely to increase and that some species only persisted at low levels. However, the continued persistence of native bunchgrasses, even at low densities, suggests that co-planting of some native bunchgrasses may be a viable way of avoiding crested wheatgrass monocultures when this species is necessary for rehabilitation or restoration. In the second study, I sought to identify environmental, historic and livestock management factors associated with native vegetation occasionally found in seeded crested wheatgrass stands. Basal cover, density, species richness and diversity were measured in 2012 and 2013 on 121 sites previously seeded to crested wheatgrass in southeastern Oregon. Plant community composition of crested wheatgrass stands was variable; some of the seedings were monocultures of crested wheatgrass while others contained diverse native species. Functional group variability explained by environmental factors ranged from 0% of annual grass density to 56% of large native perennial bunchgrass density. Soil texture was significant and appeared to be an important environmental characteristic explaining functional group cover and density 10-50 years post seeding. Native vegetation was, for all functional groups, positively correlated with soils lower in sand content. Precipitation in the year following seeding of crested wheatgrass has long-term effects on plant community dynamics, especially for Wyoming big sagebrush. Higher precipitation in the year following crested wheatgrass seeding was associated with decreased shrubs, likely because crested wheatgrass seedlings were more successful and therefore sagebrush seedlings experience greater competition. Moderate grazing was associated with reduced crested wheatgrass monoculture characteristics relative to ungrazed sites. However, within spring grazed and spring-summer grazed sites, there was a negative relationship between increased stocking rate and native species cover and abundance. I speculate that was largely the effect of higher stocking rates being allotted to more productive crested wheatgrass seedings. Overall, my research suggested that pre-seeding treatment/disturbance on a site appears to have long-term implications for plant community dynamics. However, functional groups varied in response to different pre-seeding treatments. Results support the notion that crested wheatgrass is very competitive with native bunchgrasses in particular; and that introducing natives into crested wheatgrass stands may require high levels of disturbance and may be most successful in more finely-textured soils. The results of this study also suggest that management actions, both at the time of seeding and after seeding, can influence plant community characteristics. Close

• 2324. [Article] A comparison of early marine residence in hatchery and natural Chinook salmon (Oncorhynchus tshawytscha)

  The mechanisms of mortality during critical life stages of fish are not well-understood and, for many species, it is not clear if the mechanisms are similar for naturally and artificially propagated individuals. ...

  Citation × Citation Citation Abstract Copy Title: A comparison of early marine residence in hatchery and natural Chinook salmon (Oncorhynchus tshawytscha) Author: Claiborne, Andrew M. The mechanisms of mortality during critical life stages of fish are not well-understood and, for many species, it is not clear if the mechanisms are similar for naturally and artificially propagated individuals. For Chinook salmon (Oncorhynchus tshawytscha), natural fish potentially face negative interactions, such as competition, and survival disadvantages, such as smaller size, that may limit survival when in association with hatchery fish. To better understand the mechanisms of mortality for hatchery and natural Chinook salmon during the critical early marine residence stage, I: (1) developed a model to discriminate between hatchery and natural juveniles using otolith structure; (2) directly compared migratory patterns of hatchery and natural juveniles; and (3) determined if there was evidence for selective mortality during early marine residence. I followed two cohorts through space and time by collecting juveniles from May-September in the Columbia River estuary and off the coast in September of 2010 and 2011. I compared attributes of those juveniles when they firstentered marine waters with those of survivors after their first summer at sea. I used a combination of genetic stock identification, otolith chemistry and structure, and physical tags to determine stock of origin, size at and timing of freshwater emigration, marine growth, and production type (hatchery or natural). I focused on the subyearling life history of a federally managed genetic stock group (upper Columbia River summer and fall Chinook salmon, UCR Su/F) because: 1) it is an abundant stock group; 2) subyearlings may be more vulnerable to size-selective mortality than yearlings; and 3) it is currently impossible to assess impacts of hatchery production due to low rates of marking the hatchery fish within this stock group. The classification model included two metrics, the presence or absence of a previously unreported transfer check associated with hatchery rearing and variability in otolith increment width, and predicted production type with a 92% jack-knifed accuracy. Overall, timing of marine entry was similar for hatchery and natural UCR Su/F juveniles, which entered marine waters from May-September with a peak in July and August in both years. Estuarine residence times were brief: 80% of the individuals captured in the estuary had resided in saline waters for < 3 days and mean estuarine residence was significantly greater (7 ± 1.3 d) in 2010 than 2011 (1 ± 0.3 d). The only clear difference was that natural individuals captured in the estuary in 2011 migrated to saline waters earlier (July 13th ± 4 d) than hatchery conspecifics (August 10th ± 6 d). However, the timing of marine entry was similar (July 27th ± 1 d) between hatchery and natural fish collected later in the ocean. This observation could be due to differential survival related to the timing of marine entry. Alternatively, estuarine collections may not have adequately represented the emigrating population due to rapid emigration. I documented clear spatial overlap between production types during early marine residence but no difference in median size at marine entry (100 ± 3.5 mm), size at capture (152 ± 4.0 mm), or marine growth (0.94 ± 0.1 %b l d-1). There were also no significant differences in size at marine entry between estuary and ocean collections, which indicates that size-selective mortality had not occurred. Based on both external tags and the otolith classification model, the mean percentage of natural fish in ocean collections was 17% (± 4.8) greater than in the Columbia River estuary; this finding may indicate that estuarine collections are biased to hatchery fish or, more likely, that natural fish survived at higher rates than hatchery fish. Increased survival of natural fish may be related to greater selection pressure during freshwater rearing and prior experience with predators. This study provides the first direct stock-specific comparison of juvenile migratory behavior in natural and hatchery juvenile Columbia River Chinook salmon during early marine residence. Further research is needed to determine if natural fish consistently survive better than hatchery conspecifics and, if so, determine the specific traits and behaviors that afford a survival advantage. Title: A comparison of early marine residence in hatchery and natural Chinook salmon (Oncorhynchus tshawytscha) Author: Claiborne, Andrew M. The mechanisms of mortality during critical life stages of fish are not well-understood and, for many species, it is not clear if the mechanisms are similar for naturally and artificially propagated individuals. For Chinook salmon (Oncorhynchus tshawytscha), natural fish potentially face negative interactions, such as competition, and survival disadvantages, such as smaller size, that may limit survival when in association with hatchery fish. To better understand the mechanisms of mortality for hatchery and natural Chinook salmon during the critical early marine residence stage, I: (1) developed a model to discriminate between hatchery and natural juveniles using otolith structure; (2) directly compared migratory patterns of hatchery and natural juveniles; and (3) determined if there was evidence for selective mortality during early marine residence. I followed two cohorts through space and time by collecting juveniles from May-September in the Columbia River estuary and off the coast in September of 2010 and 2011. I compared attributes of those juveniles when they firstentered marine waters with those of survivors after their first summer at sea. I used a combination of genetic stock identification, otolith chemistry and structure, and physical tags to determine stock of origin, size at and timing of freshwater emigration, marine growth, and production type (hatchery or natural). I focused on the subyearling life history of a federally managed genetic stock group (upper Columbia River summer and fall Chinook salmon, UCR Su/F) because: 1) it is an abundant stock group; 2) subyearlings may be more vulnerable to size-selective mortality than yearlings; and 3) it is currently impossible to assess impacts of hatchery production due to low rates of marking the hatchery fish within this stock group. The classification model included two metrics, the presence or absence of a previously unreported transfer check associated with hatchery rearing and variability in otolith increment width, and predicted production type with a 92% jack-knifed accuracy. Overall, timing of marine entry was similar for hatchery and natural UCR Su/F juveniles, which entered marine waters from May-September with a peak in July and August in both years. Estuarine residence times were brief: 80% of the individuals captured in the estuary had resided in saline waters for < 3 days and mean estuarine residence was significantly greater (7 ± 1.3 d) in 2010 than 2011 (1 ± 0.3 d). The only clear difference was that natural individuals captured in the estuary in 2011 migrated to saline waters earlier (July 13th ± 4 d) than hatchery conspecifics (August 10th ± 6 d). However, the timing of marine entry was similar (July 27th ± 1 d) between hatchery and natural fish collected later in the ocean. This observation could be due to differential survival related to the timing of marine entry. Alternatively, estuarine collections may not have adequately represented the emigrating population due to rapid emigration. I documented clear spatial overlap between production types during early marine residence but no difference in median size at marine entry (100 ± 3.5 mm), size at capture (152 ± 4.0 mm), or marine growth (0.94 ± 0.1 %b l d-1). There were also no significant differences in size at marine entry between estuary and ocean collections, which indicates that size-selective mortality had not occurred. Based on both external tags and the otolith classification model, the mean percentage of natural fish in ocean collections was 17% (± 4.8) greater than in the Columbia River estuary; this finding may indicate that estuarine collections are biased to hatchery fish or, more likely, that natural fish survived at higher rates than hatchery fish. Increased survival of natural fish may be related to greater selection pressure during freshwater rearing and prior experience with predators. This study provides the first direct stock-specific comparison of juvenile migratory behavior in natural and hatchery juvenile Columbia River Chinook salmon during early marine residence. Further research is needed to determine if natural fish consistently survive better than hatchery conspecifics and, if so, determine the specific traits and behaviors that afford a survival advantage. Close

• 2325. [Article] Some aspects of the comparative ecology of fishes associated with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), in the lakes of the Naknek river system, Alaska

  A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was ...

  Citation × Citation Citation Abstract Copy Title: Some aspects of the comparative ecology of fishes associated with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), in the lakes of the Naknek river system, Alaska Author: Wallace, Richard L. A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was undertaken from 1961 to 1963. The study was part of an extensive investigation to determine what factors in the freshwater environment were limiting the size of the populations of sockeye salmon returning to the rivers of Bristol Bay, Alaska. The speties found associated with juvenile salmon in the limnetic zones of the Naknek system were the pond smelt, Hypomesus olidus (Pallas); the least cisco, Coregonus sardinella Valenciennes; the threespine stickleback, Gasterosteus aculeatus Linnaeus; and the ninespine stickleback, Pungitius pungitius (Linnaeus). Life history information was collected for these sympatric species. Tow nets were used to capture samples of fish from the limnetic portions of the nursery areas. Some samples were collected by beach seines, lake traps and otter trawls. Plankton samples were collected and compared to the diets of the limnetic fishes. Although some confusion has existed in the literature, I concluded that pond smelt of the Naknek system belong to Hypomesus olidus (Pallas). The populations of smelt were comprised of six age-groups in the late summer, but most specimens belonged to three age-groups. Most members of the species spawn in the spring of the fourth year of life. The estimated fecundity ranged from 900 to 4,300 eggs per female. Seven age-groups of least ciscoes were present in the populations of the Naknek system. The species in the Naknek system probably spawned for the first time in the fall of their fourth year. The estimated fecundity of two specimens was 4,006 and 14,380 eggs. Populations of three spine stickleback were comprised of three age-groups of fish. I was unable to assign ages to ninespine stickleback. Estimates of the fecundity of the species ranged from 116 to 456 eggs per female. All species studied were distributed throughout the Naknek system. The relative abundance of the fishes studied was variable between and within nursery areas and from year to year. The population densities of pond smelt and threespine stickleback were larger in the surface waters compared to the deep waters. The relative abundance of sockeye fry, yearlings and ninespine stickleback was greater in the surface stratum rather than the deep stratum in most nursery areas. The five main food items utilized by these limnetic species were cladocerans (Bosmina sp. and Daphnia sp.); copepods (cyclopoid copepods and Diaptomus sp.); and Dipteran insects. Analysis of the similarity of diets indicated that the diets of sockeye fry and pond smelt were more similar than were the diets of sockeye fry or yearlings and any other sympatric species. The diet of sockeye fry was more similar to that of either species of stickleback than was the diet of sockeye yearlings. An analysis of the food of various sizes of each species of fish indicated the diets of three age-groups of smelt were more similar than the diets of various age-groups of any other fish. The food composition of three age-groups of ciscoes and two size groups of both species of stickleback showed a strong positive correlation. The diets of sockeye fry and yearlings showed the weakest positive correlation of the species studied. All species of fish studied selectively fed on one or more components of the zooplankton. Daphnia sp. and cyclopoid copepods were strongly selected in Lake Coville. Cyclopoids were selected in South Bay. Bosmina sp. was selected from the waters of West End. In Lake Coville, the greatest potential competition for food probably existed between the large populations of pond smelt and sockeye fry. In the West End nursery area, potential competition between juvenile salmon and both species of stickleback may not be severe, depending on the age composition of the salmon population present in the nursery area. The possibility exists that the relatively low numbers of adult sockeye salmon returning to the comparatively rich lakes of the Naknek River system is due to the presence of large populations of sympatric species of fish. Each of these sympatric species feed on the same general types of food organisms as do the juvenile salmon and may affect the numbers of young salmon that leave the lake, and subsequently return from the ocean. Title: Some aspects of the comparative ecology of fishes associated with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), in the lakes of the Naknek river system, Alaska Author: Wallace, Richard L. A study of the distribution, relative abundance and diet of fishes sympatric with juvenile sockeye salmon, Oncorhynchus nerka (Walbaum), within the freshwater nursery areas of the Naknek River system was undertaken from 1961 to 1963. The study was part of an extensive investigation to determine what factors in the freshwater environment were limiting the size of the populations of sockeye salmon returning to the rivers of Bristol Bay, Alaska. The speties found associated with juvenile salmon in the limnetic zones of the Naknek system were the pond smelt, Hypomesus olidus (Pallas); the least cisco, Coregonus sardinella Valenciennes; the threespine stickleback, Gasterosteus aculeatus Linnaeus; and the ninespine stickleback, Pungitius pungitius (Linnaeus). Life history information was collected for these sympatric species. Tow nets were used to capture samples of fish from the limnetic portions of the nursery areas. Some samples were collected by beach seines, lake traps and otter trawls. Plankton samples were collected and compared to the diets of the limnetic fishes. Although some confusion has existed in the literature, I concluded that pond smelt of the Naknek system belong to Hypomesus olidus (Pallas). The populations of smelt were comprised of six age-groups in the late summer, but most specimens belonged to three age-groups. Most members of the species spawn in the spring of the fourth year of life. The estimated fecundity ranged from 900 to 4,300 eggs per female. Seven age-groups of least ciscoes were present in the populations of the Naknek system. The species in the Naknek system probably spawned for the first time in the fall of their fourth year. The estimated fecundity of two specimens was 4,006 and 14,380 eggs. Populations of three spine stickleback were comprised of three age-groups of fish. I was unable to assign ages to ninespine stickleback. Estimates of the fecundity of the species ranged from 116 to 456 eggs per female. All species studied were distributed throughout the Naknek system. The relative abundance of the fishes studied was variable between and within nursery areas and from year to year. The population densities of pond smelt and threespine stickleback were larger in the surface waters compared to the deep waters. The relative abundance of sockeye fry, yearlings and ninespine stickleback was greater in the surface stratum rather than the deep stratum in most nursery areas. The five main food items utilized by these limnetic species were cladocerans (Bosmina sp. and Daphnia sp.); copepods (cyclopoid copepods and Diaptomus sp.); and Dipteran insects. Analysis of the similarity of diets indicated that the diets of sockeye fry and pond smelt were more similar than were the diets of sockeye fry or yearlings and any other sympatric species. The diet of sockeye fry was more similar to that of either species of stickleback than was the diet of sockeye yearlings. An analysis of the food of various sizes of each species of fish indicated the diets of three age-groups of smelt were more similar than the diets of various age-groups of any other fish. The food composition of three age-groups of ciscoes and two size groups of both species of stickleback showed a strong positive correlation. The diets of sockeye fry and yearlings showed the weakest positive correlation of the species studied. All species of fish studied selectively fed on one or more components of the zooplankton. Daphnia sp. and cyclopoid copepods were strongly selected in Lake Coville. Cyclopoids were selected in South Bay. Bosmina sp. was selected from the waters of West End. In Lake Coville, the greatest potential competition for food probably existed between the large populations of pond smelt and sockeye fry. In the West End nursery area, potential competition between juvenile salmon and both species of stickleback may not be severe, depending on the age composition of the salmon population present in the nursery area. The possibility exists that the relatively low numbers of adult sockeye salmon returning to the comparatively rich lakes of the Naknek River system is due to the presence of large populations of sympatric species of fish. Each of these sympatric species feed on the same general types of food organisms as do the juvenile salmon and may affect the numbers of young salmon that leave the lake, and subsequently return from the ocean. Close

• 2326. [Article] Structural Evolution, Vein Orientation, and Paragenesis of the Botija Porphyry Cu-Mo-(Au) Deposit, Colón, Panamá

  The Botija Cu-Mo-Au porphyry deposit is located in the Cobre Panamá mining district, which contains several deposits with a global measure and indicated and inferred resource of 14.8 MT of Cu. These deposits ...

  Citation × Citation Citation Abstract Copy Title: Structural Evolution, Vein Orientation, and Paragenesis of the Botija Porphyry Cu-Mo-(Au) Deposit, Colón, Panamá Author: Sepp, Michael D. The Botija Cu-Mo-Au porphyry deposit is located in the Cobre Panamá mining district, which contains several deposits with a global measure and indicated and inferred resource of 14.8 MT of Cu. These deposits are associated with the Cerro Petaquilla batholith, which has U/Pb zircon ages of 26-33 Ma (Whattam et al., 2012; Baker et al., 2016). The Botija deposit is an elongate tabular body striking northeast and dipping 20-40° N and measures 2 km (length) x 1 km (width) x 600 m (height) in size. The deposit is hosted in andesite, the equigranular Petaquilla granodiorite, and a younger crowded porphyritic granodiorite with 15-50 vol.% groundmass of quartz and K-feldspar. Phenocrysts include plagioclase, hornblende ± K-feldspar and occasionally 5-15 vol.% rounded quartz eyes. Ore is characterized by Cu-Fe sulfides (chalcopyrite > bornite) that is dominantly disseminated, but also present in magmatic-hydrothermal quartz veins. Systematic vein measurements at Botija demonstrate that copper ores are spatially associated with a quartz vein density >0.5 vol.%; these veins have two modes of structural orientation (azimuth of strike/right-hand dip) of 233/50°NW and 295/45°NE. Most similar early quartz veins are emplaced along near-vertical hydrofractures in numerous porphyry deposits globally. The present dip of these quartz veins suggest that the veins and the Botija deposit have been moderately tilted about 40° south-southeast after mineralization. Typical potassic and sericitic alteration and zonation is present in Botija, however, a late overprint of chlorite and zeolite has obscured much of the original magmatic hydrothermal alteration footprint. Although the Botija deposit exhibits many of the common porphyry copper features, its geometry is atypical with abrupt spatial transitions (<10 m) in alteration and grades (Cu, Mo & Au) whereas most porphyry copper deposits typically exhibit gradual transitions in over hundreds of meters. These sharp breaks in the geology in some cases correspond to observed faults, and together with other faults mapped in field exposures and drill core allow identification of three main fault sets that offset the deposit. A restoration of the Cu and Mo grade shells indicates a multistage post-mineral deformation history with a first stage of ~500 m left-oblique normal offset on the Botija Fault (267/50°N) and Santa Fe fault (268/70°N), normal displacement in excess of 250 m on the NW striking Oeste fault (314/75°NE) and a final stage of normal displacement in excess of 500 m offset on S50°W-striking Strike Central faults (230/65°N). Restoration of these fault offsets brings the ore shells to the appropriate inverted cup shaped geometry typical of porphyry copper deposits. The faults identified at Botija likely accommodated a modest amount (~10-15°) of tilting to the southeast. An additional restoration of the 50°N-dipping quartz veins to vertical restores the ore shells to geometry in line with the classical shape for a porphyry copper deposit. This restoration of quartz veins can be explained by progressive deformation initiated by presently shallowly dipping, southwest striking normal faults (240/35°NW) identified from ZTEM™ geophysics which bound the deposits of Cobre Panamá. This reconstruction suggests the deposits of Cobre Panamá were likely dismembered by normal faulting from two or more original upright and intact porphyry copper deposits, generating the seven segmented and tilted deposits present today. This interpretation of normal displacement of the deposit is in lines with (U-Th)/He age by Farris et al. (2011), which constrain the exhumation of the deposit during a period of localized extension in Panamá between 19.5 – 22.3 Ma shortly after emplacement. Title: Structural Evolution, Vein Orientation, and Paragenesis of the Botija Porphyry Cu-Mo-(Au) Deposit, Colón, Panamá Author: Sepp, Michael D. The Botija Cu-Mo-Au porphyry deposit is located in the Cobre Panamá mining district, which contains several deposits with a global measure and indicated and inferred resource of 14.8 MT of Cu. These deposits are associated with the Cerro Petaquilla batholith, which has U/Pb zircon ages of 26-33 Ma (Whattam et al., 2012; Baker et al., 2016). The Botija deposit is an elongate tabular body striking northeast and dipping 20-40° N and measures 2 km (length) x 1 km (width) x 600 m (height) in size. The deposit is hosted in andesite, the equigranular Petaquilla granodiorite, and a younger crowded porphyritic granodiorite with 15-50 vol.% groundmass of quartz and K-feldspar. Phenocrysts include plagioclase, hornblende ± K-feldspar and occasionally 5-15 vol.% rounded quartz eyes. Ore is characterized by Cu-Fe sulfides (chalcopyrite > bornite) that is dominantly disseminated, but also present in magmatic-hydrothermal quartz veins. Systematic vein measurements at Botija demonstrate that copper ores are spatially associated with a quartz vein density >0.5 vol.%; these veins have two modes of structural orientation (azimuth of strike/right-hand dip) of 233/50°NW and 295/45°NE. Most similar early quartz veins are emplaced along near-vertical hydrofractures in numerous porphyry deposits globally. The present dip of these quartz veins suggest that the veins and the Botija deposit have been moderately tilted about 40° south-southeast after mineralization. Typical potassic and sericitic alteration and zonation is present in Botija, however, a late overprint of chlorite and zeolite has obscured much of the original magmatic hydrothermal alteration footprint. Although the Botija deposit exhibits many of the common porphyry copper features, its geometry is atypical with abrupt spatial transitions (<10 m) in alteration and grades (Cu, Mo & Au) whereas most porphyry copper deposits typically exhibit gradual transitions in over hundreds of meters. These sharp breaks in the geology in some cases correspond to observed faults, and together with other faults mapped in field exposures and drill core allow identification of three main fault sets that offset the deposit. A restoration of the Cu and Mo grade shells indicates a multistage post-mineral deformation history with a first stage of ~500 m left-oblique normal offset on the Botija Fault (267/50°N) and Santa Fe fault (268/70°N), normal displacement in excess of 250 m on the NW striking Oeste fault (314/75°NE) and a final stage of normal displacement in excess of 500 m offset on S50°W-striking Strike Central faults (230/65°N). Restoration of these fault offsets brings the ore shells to the appropriate inverted cup shaped geometry typical of porphyry copper deposits. The faults identified at Botija likely accommodated a modest amount (~10-15°) of tilting to the southeast. An additional restoration of the 50°N-dipping quartz veins to vertical restores the ore shells to geometry in line with the classical shape for a porphyry copper deposit. This restoration of quartz veins can be explained by progressive deformation initiated by presently shallowly dipping, southwest striking normal faults (240/35°NW) identified from ZTEM™ geophysics which bound the deposits of Cobre Panamá. This reconstruction suggests the deposits of Cobre Panamá were likely dismembered by normal faulting from two or more original upright and intact porphyry copper deposits, generating the seven segmented and tilted deposits present today. This interpretation of normal displacement of the deposit is in lines with (U-Th)/He age by Farris et al. (2011), which constrain the exhumation of the deposit during a period of localized extension in Panamá between 19.5 – 22.3 Ma shortly after emplacement. Close

• 2327. [Article] Ocean Temperature Variability during the Late Pleistocene

  This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution ...

  Citation × Citation Citation Abstract Copy Title: Ocean Temperature Variability during the Late Pleistocene Author: Hoffman, Jeremy Scott This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO₂. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation. Title: Ocean Temperature Variability during the Late Pleistocene Author: Hoffman, Jeremy Scott This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO₂. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation. Close

• 2328. [Article] Studies to facilitate reintroduction of golden paintbrush (Castilleja levisecta) to the Willamette Valley, Oregon

  Golden paintbrush (Castilleja levisecta Greenman) historically inhabited the prairies of the Willamette Valley, Oregon. However, this Pacific Northwest endemic is currently restricted to eleven sites in ...

  Citation × Citation Citation Abstract Copy Title: Studies to facilitate reintroduction of golden paintbrush (Castilleja levisecta) to the Willamette Valley, Oregon Author: Lawrence, Beth A. Golden paintbrush (Castilleja levisecta Greenman) historically inhabited the prairies of the Willamette Valley, Oregon. However, this Pacific Northwest endemic is currently restricted to eleven sites in the Puget Trough of Washington and British Columbia. Recovery criteria call for the establishment of new populations throughout the species historic range, including the Willamette Valley. In order to facilitate reintroduction to this region, we examined: (1) habitat characteristics of potential C. levisecta recovery sites in the Willamette Valley and compared them to remaining populations in the Puget Trough, (2) a suite of ecological and genetic factors likely to contribute to reintroduction success using common garden experiments, and (3) how the performance of this rare hemiparasite was affected by the availability of different host combinations in the greenhouse and in the field. Potential C. levisecta reintroduction sites in the Willamette Valley had distinct vegetation communities and soil characteristics compared with remaining populations in the Puget Trough. This disparity was likely related to regional differences in geology, climate, ocean proximity, and land-use history. Many of the species indicative of remaining populations in the Puget Trough were native pereimials, while those of potential reintroduction sites in the Willamette Valley were introduced annuals. Soil characteristics of C. levisecta sites were also distinct among the two ecoregions. Puget Trough sites were located on sandy soils with generally high levels of magnesium and sulfur, while Willamette Valley sites were found on silty-clay soils with high concentrations of potassium and phosphorous. Differences in soil texture, and magnesium and potassium concentrations were associated with plant community divergence among the two regions. Decisions regarding seed source and recovery site selection are especially difficult in portions of a species range that are uninhabited, as no reference populations exist with which to compare ecological information. Using common garden experiments, we tested hypotheses about how C. levisecta transplants would perform in relation to the ecological similarity between seed source and introduction site, the effective population size and genetic diversity of seed sources, and the habitat quality of the recovery site. We observed significant variation in performance measures among source populations and common garden sites. Plant community characteristics, including the abundance of nonnative species and the similarity in community structure between source populations and common garden sites, helped explain the variation in these performance measures. Exotic species cover at common garden sites was associated with a reduction in performance of first year C. levisecta transplants. Survival of second year transplants increased with increasing similarity in plant functional groups between source and common garden sites, supporting the idea of a "home-habitat advantage." These results indicate that high quality prairies, dominated by native perennial species with low nonnative abundance, should be targeted for recovery sites. We recommend using plant material from Whidbey Island, WA, whose three populations represented in our study consistently performed well. Rare, parasitic plants pose an interesting challenge to restoration practitioners. We examined how the performance of C. levisecta was affected by the availability of different host combinations in the greenhouse and in the field. Castilleja levisecta individuals were grown with two grass individuals (Festuca roemeri; Poaceae), two non-grass hosts (Eriophyllum lanatum; Asteraceae), one individual of each of these species, or without a host. Our greenhouse results provide little support for the complimentary diet hypothesis, which states that parasites grown with multiple host species perform better than individuals grown alone or with a single host. Castilleja levisecta individuals grown with two different species performed better than those co-planted only with F. roemeri, but did not differ from E. lanatum or no-host treatments. In the field, vole activity had indirect effects on C. levisecta survival mediated through host species. Vole tunneling and C. levisecta mortality were strongly associated with host treatments including E. lanatum. Field survival was significantly higher among no-host C. levisecta individuals than those grown with E. lanatum or mixed host treatments. We do not suggest coplanting C. levisecta with E. lanatum in the field. Although no-host C. levisecta individuals had the greatest first year field survival, we suspect that perennial host plants will be beneficial to future survival. Therefore, we recommend planting C. levisecta in the Willamette Valley, OR with F. roemeri. Title: Studies to facilitate reintroduction of golden paintbrush (Castilleja levisecta) to the Willamette Valley, Oregon Author: Lawrence, Beth A. Golden paintbrush (Castilleja levisecta Greenman) historically inhabited the prairies of the Willamette Valley, Oregon. However, this Pacific Northwest endemic is currently restricted to eleven sites in the Puget Trough of Washington and British Columbia. Recovery criteria call for the establishment of new populations throughout the species historic range, including the Willamette Valley. In order to facilitate reintroduction to this region, we examined: (1) habitat characteristics of potential C. levisecta recovery sites in the Willamette Valley and compared them to remaining populations in the Puget Trough, (2) a suite of ecological and genetic factors likely to contribute to reintroduction success using common garden experiments, and (3) how the performance of this rare hemiparasite was affected by the availability of different host combinations in the greenhouse and in the field. Potential C. levisecta reintroduction sites in the Willamette Valley had distinct vegetation communities and soil characteristics compared with remaining populations in the Puget Trough. This disparity was likely related to regional differences in geology, climate, ocean proximity, and land-use history. Many of the species indicative of remaining populations in the Puget Trough were native pereimials, while those of potential reintroduction sites in the Willamette Valley were introduced annuals. Soil characteristics of C. levisecta sites were also distinct among the two ecoregions. Puget Trough sites were located on sandy soils with generally high levels of magnesium and sulfur, while Willamette Valley sites were found on silty-clay soils with high concentrations of potassium and phosphorous. Differences in soil texture, and magnesium and potassium concentrations were associated with plant community divergence among the two regions. Decisions regarding seed source and recovery site selection are especially difficult in portions of a species range that are uninhabited, as no reference populations exist with which to compare ecological information. Using common garden experiments, we tested hypotheses about how C. levisecta transplants would perform in relation to the ecological similarity between seed source and introduction site, the effective population size and genetic diversity of seed sources, and the habitat quality of the recovery site. We observed significant variation in performance measures among source populations and common garden sites. Plant community characteristics, including the abundance of nonnative species and the similarity in community structure between source populations and common garden sites, helped explain the variation in these performance measures. Exotic species cover at common garden sites was associated with a reduction in performance of first year C. levisecta transplants. Survival of second year transplants increased with increasing similarity in plant functional groups between source and common garden sites, supporting the idea of a "home-habitat advantage." These results indicate that high quality prairies, dominated by native perennial species with low nonnative abundance, should be targeted for recovery sites. We recommend using plant material from Whidbey Island, WA, whose three populations represented in our study consistently performed well. Rare, parasitic plants pose an interesting challenge to restoration practitioners. We examined how the performance of C. levisecta was affected by the availability of different host combinations in the greenhouse and in the field. Castilleja levisecta individuals were grown with two grass individuals (Festuca roemeri; Poaceae), two non-grass hosts (Eriophyllum lanatum; Asteraceae), one individual of each of these species, or without a host. Our greenhouse results provide little support for the complimentary diet hypothesis, which states that parasites grown with multiple host species perform better than individuals grown alone or with a single host. Castilleja levisecta individuals grown with two different species performed better than those co-planted only with F. roemeri, but did not differ from E. lanatum or no-host treatments. In the field, vole activity had indirect effects on C. levisecta survival mediated through host species. Vole tunneling and C. levisecta mortality were strongly associated with host treatments including E. lanatum. Field survival was significantly higher among no-host C. levisecta individuals than those grown with E. lanatum or mixed host treatments. We do not suggest coplanting C. levisecta with E. lanatum in the field. Although no-host C. levisecta individuals had the greatest first year field survival, we suspect that perennial host plants will be beneficial to future survival. Therefore, we recommend planting C. levisecta in the Willamette Valley, OR with F. roemeri. Close

• 2329. [Article] Sediment accumulation and human impacts in Tillamook Bay, Oregon

  Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during ...

  Citation × Citation Citation Abstract Copy Title: Sediment accumulation and human impacts in Tillamook Bay, Oregon Author: Styllas, Michael N. Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during the past century. Major land-use practices within the five watersheds of the Bay include logging, forest fires, the construction of forest roads, the placement of dikes along the channels of the main rivers and in the estuary, the removal of riparian vegetation, and the construction of jetties at the tidal inlet. Each of these practices has led to impacts on the entire ecosystem of the watersheds and the Bay, but this study focuses on the effects of human disturbances on the Bay's sediment accumulation. This study examines in detail the land-use practices that have occurred in the watersheds, on the beaches, and in the estuary, focusing on those that have had a direct impact on the sedimentation regime of the Bay. One goal of the study is to assess the relative roles of natural processes versus human impacts on the sedimentation. A general description of the physical characteristics of Tillamook Bay and its surroundings is included, and a brief discussion is provided about the tectonic setting of the Northwest Coast, including its history of subduction earthquakes and the associate sea-level changes. Also provided is a summary of the existing information concerning the arrival of Indians and their environmental impacts, followed by a more detailed account of the major impacts that have resulted from the settlement of the Euro-Americans in the Tillamook area, in the 1850's. The study then focuses on the description of the watersheds from a geomorphologic point of view, and the important land-use practices that may have affected sediment yields during the past century. Analyses of the hydrology of the Tillamook Bay watersheds are included, and the relations between annual water yields and total precipitation are examined in distinct time intervals, each corresponding to a different period with different amounts of land uses. The results of these hydrology analyses suggest that the Tillamook watershed gradually recovered from a period of major disturbances (from 1933 to 1955) to more normal conditions (from 1977 to 1998). In addition, this part of the study attempts to quantify the sediment transport regime of the rivers draining the watershed by using a hydraulic model that is based on the principle of stream power, and on considerations of availability of transported material. Application of this model during the 1933-1955 period for the major rivers suggests an average sediment yield on the order of 410,540 tons/year, but most important are the relative changes of the delivered sediment through time. The results of the model suggest a 1.6-factor decrease of the amount of river sediments from the Heavily Impacted Period (1933-1955) of major disturbances to the Normal Period (1977- 1998). The spatial variations of beach and river derived sediments throughout the Bay are determined from textural and mineralogical analyses of surface sediment samples, with the beach sands dominating the area close to the inlet and the river derived sands being mainly deposited at the southeast and northeast parts of the Bay. The relative contributions of these two major sources of sediment were found to be 60% for the marine beach and 40% for the river sands. Further attempt is made to distinguish between the sand transported into the Bay from the individual rivers, and to determine the main processes that are responsible for the dispersion of sediments within the Bay. The attempts to distinguish sands contributed by the individual rivers involved modal analyses of the frequency curves of the surface sediment samples, and the results mainly suggest a grain-size increase away from the mouth of the rivers as a result of sediment reworking by estuarine processes following its initial deposition during episodic river flooding. The main processes that control the dispersion of sediments and their deposition within the Bay were identified by using factor analysis, the results of which suggest that various estuarine processes are responsible for the observed dispersal patterns. A brief review is provided of the study undertaken by Dr. James McManus for the collection and analyses of core samples from Tillamook Bay. Down-core geochemical analyses of major and minor elements indicate that there have been times of episodic input of marine sediment in the central and western portions of the Bay, which is a result of either periodic breaching or washover of Bayocean Spit, so that the beach sand source was more important in the past. This episodic input of marine sand as inferred from the down-core geochemical variations was related to the most recent subduction earthquake, which occurred on January 26th, 1700. Finally, a summary of the results and conclusions of different aspects of this study is presented, so that sedimentation in Tillamook Bay can be viewed as an integrated process involving the watersheds, the estuary, and the ocean beaches. Title: Sediment accumulation and human impacts in Tillamook Bay, Oregon Author: Styllas, Michael N. Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during the past century. Major land-use practices within the five watersheds of the Bay include logging, forest fires, the construction of forest roads, the placement of dikes along the channels of the main rivers and in the estuary, the removal of riparian vegetation, and the construction of jetties at the tidal inlet. Each of these practices has led to impacts on the entire ecosystem of the watersheds and the Bay, but this study focuses on the effects of human disturbances on the Bay's sediment accumulation. This study examines in detail the land-use practices that have occurred in the watersheds, on the beaches, and in the estuary, focusing on those that have had a direct impact on the sedimentation regime of the Bay. One goal of the study is to assess the relative roles of natural processes versus human impacts on the sedimentation. A general description of the physical characteristics of Tillamook Bay and its surroundings is included, and a brief discussion is provided about the tectonic setting of the Northwest Coast, including its history of subduction earthquakes and the associate sea-level changes. Also provided is a summary of the existing information concerning the arrival of Indians and their environmental impacts, followed by a more detailed account of the major impacts that have resulted from the settlement of the Euro-Americans in the Tillamook area, in the 1850's. The study then focuses on the description of the watersheds from a geomorphologic point of view, and the important land-use practices that may have affected sediment yields during the past century. Analyses of the hydrology of the Tillamook Bay watersheds are included, and the relations between annual water yields and total precipitation are examined in distinct time intervals, each corresponding to a different period with different amounts of land uses. The results of these hydrology analyses suggest that the Tillamook watershed gradually recovered from a period of major disturbances (from 1933 to 1955) to more normal conditions (from 1977 to 1998). In addition, this part of the study attempts to quantify the sediment transport regime of the rivers draining the watershed by using a hydraulic model that is based on the principle of stream power, and on considerations of availability of transported material. Application of this model during the 1933-1955 period for the major rivers suggests an average sediment yield on the order of 410,540 tons/year, but most important are the relative changes of the delivered sediment through time. The results of the model suggest a 1.6-factor decrease of the amount of river sediments from the Heavily Impacted Period (1933-1955) of major disturbances to the Normal Period (1977- 1998). The spatial variations of beach and river derived sediments throughout the Bay are determined from textural and mineralogical analyses of surface sediment samples, with the beach sands dominating the area close to the inlet and the river derived sands being mainly deposited at the southeast and northeast parts of the Bay. The relative contributions of these two major sources of sediment were found to be 60% for the marine beach and 40% for the river sands. Further attempt is made to distinguish between the sand transported into the Bay from the individual rivers, and to determine the main processes that are responsible for the dispersion of sediments within the Bay. The attempts to distinguish sands contributed by the individual rivers involved modal analyses of the frequency curves of the surface sediment samples, and the results mainly suggest a grain-size increase away from the mouth of the rivers as a result of sediment reworking by estuarine processes following its initial deposition during episodic river flooding. The main processes that control the dispersion of sediments and their deposition within the Bay were identified by using factor analysis, the results of which suggest that various estuarine processes are responsible for the observed dispersal patterns. A brief review is provided of the study undertaken by Dr. James McManus for the collection and analyses of core samples from Tillamook Bay. Down-core geochemical analyses of major and minor elements indicate that there have been times of episodic input of marine sediment in the central and western portions of the Bay, which is a result of either periodic breaching or washover of Bayocean Spit, so that the beach sand source was more important in the past. This episodic input of marine sand as inferred from the down-core geochemical variations was related to the most recent subduction earthquake, which occurred on January 26th, 1700. Finally, a summary of the results and conclusions of different aspects of this study is presented, so that sedimentation in Tillamook Bay can be viewed as an integrated process involving the watersheds, the estuary, and the ocean beaches. Close

• 2330. [Article] Geology and geochemistry of the Little Walker Volcanic Center, Mono County, California

  Detailed mapping and geochemical analysis of Oligocene to early Pliocene volcanic rocks in the Little Walker volcanic center, Mono County, California have revealed a complex eruptive history. After eruption ...

  Citation × Citation Citation Abstract Copy Title: Geology and geochemistry of the Little Walker Volcanic Center, Mono County, California Author: Priest, George R. Detailed mapping and geochemical analysis of Oligocene to early Pliocene volcanic rocks in the Little Walker volcanic center, Mono County, California have revealed a complex eruptive history. After eruption of widespread rhyolitic ash flows of the Valley Springs Formation in the Oligocene, Miocene to early Pliocene volcanism of the western Great Basin and northern Sierra Nevada was dominated by eruption of calc-alkalic, andesitic lavas bearing abundant hydrous mafic phenocrysts, and, thus, high H₂O contents. These kinds of calc-alkaline magmas are associated with most of the major epithermal Au-Ag districts of the western Great Basin. A highly potassic latitic pulse of volcanism occurred at the Little Walker volcanic center about 9.5 m.y. ago during the ongoing calc-alkalic activity. The latitic series is unusually enriched in K and other incompatible elements, as well as Fe compared to the surrounding calc-alkaline rocks. The latites have mineralogic evidence of much lower H₂O content than the calc-alkaline lavas; yet early latitic magmas were rich enough in volatiles to produce very large, welded ash-flow sheets (e.g., the Eureka Valley Tuff). Rapid evacuation of the magma reservoir beneath the Little Walker center during the ash-flow activity resulted in formation of the Little Walker caldera. Intracaldera volcanism culminated with extrusion of viscous, phenocryst-rich plug domes and coulees of transitionally calc-alkaline, low-K latite lava of the Lavas of Mahogany Ridge. The low-K latite series is severely depleted in all incompatible elements relative to early latitic rocks and has mineralogic, geologic, and trace element evidence of higher H₂O content relative to early latites. Significant phenocrystic hornblende, association with hydrothermal alteration, and high Eu⁺³ /Eu⁺² all suggest significant H₂O concentration in the low-K latite magmas. These rocks probably come from a source region intermediate between that of the calc-alkaline and latite series. Trace and major element data favor generation of latitic magmas from a primitive mantle diapir. The diapir rose into a subduction zone that was actively generating widespread calc-alkalic lavas throughout the region from hydrous mantle and, possibly, lower crustal sources. The latite magmas were drier and hotter than the calc-alkaline magmas, but were also enriched in volatiles, particularly CO₂, and incompatible elements from their undepleted mantle source. Rising latitic magmas may have gained additional incompatible elements by wall rock reaction and zone refining of upper mantle and lower crustal rocks. Extensive qualitative trace element evidence of crystal fractionation shows that incompatible elements may have been further concentrated by variable amounts of crystal settling. High-pressure (plagioclase-poor, pyroxene-rich) fractionation of the early, dry latitic series produced low-Ca-Mg latites with high Fe/Mg and A1₂0₃ but low Si0₂. Low-pressure (plagioclase rich) differentiation of the early latitic magmas produced quartz latite ash flows with high Si0₂ and moderate Fe/Mg, while low-pressure differentiation of hydrous low-K latite magmas yielded silicic low-K latite and quartz latite lavas with low Fe/Mg. More extensive separation of olivine relative to pyroxenes at low pressures and increased stability of subsilicic hydrous crystals and Fe-Ti oxides in the hydrous magmas account for changes in differentiation trends caused by Ptotal and PH₂O variations. Lack of giant welded ash-flow sheets in the hydrous calc-alkaline series and common eruption of such ash flows from volcanic centers with rather anhydrous magmas led to the conclusion that H₂0/CO₂ as well as total volatile content are critical controls on the likelihood of large scale, hot ash-flow eruptions. Giant, hot ash-flow sheets and associated calderas are favored in magmas with low H₂0/CO₂ and high total volatile content. Basaltic and latitic volcanism in areas of thick sialic crust, where crystal fractionation is extensive are, therefore, the best sources of giant ash-flow sheets. H₂0/CO₂ and total volatile content were also critical controls of the probability of hydrothermal ore deposition. Magmas with high H₂0/CO₂ and moderate total volatile contents are most favored for ore deposition, because such magmas tend to form mesozonal or epizonal plutons rather than volcanic rocks. Plutonic crystallization of hydrous magma will yield a fluid phase capable of transferring incompatible metals and geothermal heat to ground water. If permeable structures and rocks are present, as in a caldera, widespread mineralization will be favored, but there may be no genetic relation between ore-forming magmas and magmas which produce calderas. Title: Geology and geochemistry of the Little Walker Volcanic Center, Mono County, California Author: Priest, George R. Detailed mapping and geochemical analysis of Oligocene to early Pliocene volcanic rocks in the Little Walker volcanic center, Mono County, California have revealed a complex eruptive history. After eruption of widespread rhyolitic ash flows of the Valley Springs Formation in the Oligocene, Miocene to early Pliocene volcanism of the western Great Basin and northern Sierra Nevada was dominated by eruption of calc-alkalic, andesitic lavas bearing abundant hydrous mafic phenocrysts, and, thus, high H₂O contents. These kinds of calc-alkaline magmas are associated with most of the major epithermal Au-Ag districts of the western Great Basin. A highly potassic latitic pulse of volcanism occurred at the Little Walker volcanic center about 9.5 m.y. ago during the ongoing calc-alkalic activity. The latitic series is unusually enriched in K and other incompatible elements, as well as Fe compared to the surrounding calc-alkaline rocks. The latites have mineralogic evidence of much lower H₂O content than the calc-alkaline lavas; yet early latitic magmas were rich enough in volatiles to produce very large, welded ash-flow sheets (e.g., the Eureka Valley Tuff). Rapid evacuation of the magma reservoir beneath the Little Walker center during the ash-flow activity resulted in formation of the Little Walker caldera. Intracaldera volcanism culminated with extrusion of viscous, phenocryst-rich plug domes and coulees of transitionally calc-alkaline, low-K latite lava of the Lavas of Mahogany Ridge. The low-K latite series is severely depleted in all incompatible elements relative to early latitic rocks and has mineralogic, geologic, and trace element evidence of higher H₂O content relative to early latites. Significant phenocrystic hornblende, association with hydrothermal alteration, and high Eu⁺³ /Eu⁺² all suggest significant H₂O concentration in the low-K latite magmas. These rocks probably come from a source region intermediate between that of the calc-alkaline and latite series. Trace and major element data favor generation of latitic magmas from a primitive mantle diapir. The diapir rose into a subduction zone that was actively generating widespread calc-alkalic lavas throughout the region from hydrous mantle and, possibly, lower crustal sources. The latite magmas were drier and hotter than the calc-alkaline magmas, but were also enriched in volatiles, particularly CO₂, and incompatible elements from their undepleted mantle source. Rising latitic magmas may have gained additional incompatible elements by wall rock reaction and zone refining of upper mantle and lower crustal rocks. Extensive qualitative trace element evidence of crystal fractionation shows that incompatible elements may have been further concentrated by variable amounts of crystal settling. High-pressure (plagioclase-poor, pyroxene-rich) fractionation of the early, dry latitic series produced low-Ca-Mg latites with high Fe/Mg and A1₂0₃ but low Si0₂. Low-pressure (plagioclase rich) differentiation of the early latitic magmas produced quartz latite ash flows with high Si0₂ and moderate Fe/Mg, while low-pressure differentiation of hydrous low-K latite magmas yielded silicic low-K latite and quartz latite lavas with low Fe/Mg. More extensive separation of olivine relative to pyroxenes at low pressures and increased stability of subsilicic hydrous crystals and Fe-Ti oxides in the hydrous magmas account for changes in differentiation trends caused by Ptotal and PH₂O variations. Lack of giant welded ash-flow sheets in the hydrous calc-alkaline series and common eruption of such ash flows from volcanic centers with rather anhydrous magmas led to the conclusion that H₂0/CO₂ as well as total volatile content are critical controls on the likelihood of large scale, hot ash-flow eruptions. Giant, hot ash-flow sheets and associated calderas are favored in magmas with low H₂0/CO₂ and high total volatile content. Basaltic and latitic volcanism in areas of thick sialic crust, where crystal fractionation is extensive are, therefore, the best sources of giant ash-flow sheets. H₂0/CO₂ and total volatile content were also critical controls of the probability of hydrothermal ore deposition. Magmas with high H₂0/CO₂ and moderate total volatile contents are most favored for ore deposition, because such magmas tend to form mesozonal or epizonal plutons rather than volcanic rocks. Plutonic crystallization of hydrous magma will yield a fluid phase capable of transferring incompatible metals and geothermal heat to ground water. If permeable structures and rocks are present, as in a caldera, widespread mineralization will be favored, but there may be no genetic relation between ore-forming magmas and magmas which produce calderas. Close