This Ph.D. project aims to aquire a better understanding of sedimentological and ecological processes within the immediate vicinity of Large Igneous Province (LIP) activity and of the effects that LIP volcanism may have on the environment. The Miocene Columbia River Flood Basalt Province (CRBP) comprises an up to 4500 m thick succession of basaltic lavas intercalated with fluvio-lacustrine siliciclastic and volcaniclastic sediments. Detailed field-based studies (logging of 47 interbed sites) and the generation of geochemical (XRF, SEM, and microprobe) and palynological data provide an integrative study of characterising and modeling sedimentological and ecological processes within the lava field. The generation of a sedimentary facies scheme allowed a reconstruction of the intra-lava drainage system through time. Drainage system evolution is largely controlled by CRBP volcanism which is capable of forcing fluvial systems to the margin of the lava field during the phases of high volcanic activity, while phases of waning effusion frequencies and volumes allow the fluvial environment to migrate back into the central part of the lava field. The composition of the siliciclastic sediments suggests external source areas mainly located in the Cascade Range west and north of the CRBP. High plant diversity and late successions occurred during the early stage of CRBP evolution, and were affected by the increased deposition of ash derived from Cascade Range volcanoes and the Yellowstone hot spot during the late stage of CRBP evolution. Interbed sites distal to the volcanic source are generally colonized by late-successional plants and suggest a relationship between nutrient flux, sedimentary environment and volcanism. Palaeoclimate reconstructions based on soil chemistry and floral composition suggest that climatic changes within the CRBP reflect the global trend of the Mid-Miocene Climate Optimum. The present work allows to model sedimentological and ecological processes within the CRBP and considers the various effects that volcanic activity has on the environment. The complexity and differences in the geology and igenous evolution of individual LIPs need to be considered when applying this model to other LIPs.

Freshwater ecosystems and the species that reside therein are disproportionately imperiled compared to terrestrial systems. Over the past 150 years, the Columbia River basin in the western United States has gone from one of the most productive and abundant salmon watersheds in the world, to having just a small fraction of its former salmon abundance. The cause of declines in salmon productivity and abundance are related to overlapping and confounding stressors including changes in large-scale climatic patterns and anthropogenic alterations within and adjacent to the Columbia River. Four main anthropogenic stressors have been identified as the leading causes of salmonid declines: commercial harvest of adult salmon, hydroelectric power generation and associated reservoirs, habitat loss due to impassible dams and restricted access to historical habitat, and hatchery production. My dissertation broadly examined how salmon ecology and population dynamics have been influenced by anthropogenic alterations occurring within the Columbia River basin. This dissertation addresses three main questions: Do the hydroelectric dams on the Lower Columbia River represent a pulse- or press-type ecological disturbance to migrating Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) and what are the biotic and abiotic factors that most influence the survival of fish passing multiple dams? How do wild and hatchery fish differ in regards to the precocious life-history strategy, and which variables influence this strategy across environments (freshwater to marine) and life stages (egg to adult)? What are the morphological differences between wild and hatchery salmonids and how much of that variation is attributable to rearing-environment? I found that high outflow volumes led to involuntary spill in 2011 and created an environment of supersaturated dissolved gas concentrations. In this environment, migrating smolt survival was strongly influenced by barometric pressure, fish velocity and water temperature. The effect of these variables on survival was compounded by multiple dam passages compared to fish passing a single dam. Despite spatial isolation between dams in the Lower Columbia River hydrosystem, migrating smolt appear to experience cumulative effects akin to an ecological press disturbance. In general, Chinook salmon and steelhead respond similarly in terms of survival rates and responses to altered environmental conditions. Management actions that limit dissolved gas concentrations in years of high flow will benefit migrating salmonids during this life stage. Both biotic and environmental factors affect precociousness in hatchery and wild Chinook salmon, across freshwater and marine environments. Wild fish are influenced by density-dependent processes in freshwater, as well as marine conditions that promote growth. Wild Chinook have the highest probability of precocious maturation when large smolt (>150 mm) experience productive marine environments within the first several months of ocean residence. Precocious hatchery fish are broadly influenced by conditions experienced during freshwater residency, outmigration, and in marine habitats. There was no interaction between the size of hatchery fish and environmental variables, suggesting that these fish attained the size required to mature precociously prior to migration. These results indicate that hatchery Chinook salmon do not respond to the same environmental cues that determine life history transitions as wild Chinook salmon, likely as a result of different physiological conditions and environmental exposures during early life stages. There are ecological and economic consequences to the precocious life history strategy including reduced marine-derived nutrients entering freshwater ecosystems and a loss of investment for fish intended for the adult fishery. There are significant differences in body shape between wild and hatchery origin Chinook salmon and steelhead that can be partially explained by rearing environment and variables influenced by smoltification. Hatchery fish of both species are significantly larger (i.e. centroid size, length, weight) than wild fish but have comparable or lower condition factor. In general, hatchery fish have smaller heads and longer, thinner tails (i.e. fusiform) compared to wild fish. Allometric trajectories (i.e. shape change with size) indicate that the shape of wild and hatchery fish are significantly different at small and large sizes. Wild and hatchery Chinook salmon became more morphologically different as size increased, while steelhead became more similar. The overall amount of shape variation was not significantly different between wild and hatchery Chinook salmon. This finding suggests that regardless of significant differences in the way shapes vary, hatchery Chinook have not lost overall shape variation. Total amount of shape variation was significantly greater in wild compared to hatchery steelhead, indicating that hatcheries may have a homogenizing effect on steelhead shape. I recommend a coordinated effort between federal, state and tribal hatcheries to incorporate elements of the natural rearing environment into conventional hatcheries. These elements include in-water structure that promotes the burst swimming mode, increased water velocities to increase dorsal-ventral distance, under-water feeding apparatus that reduce surface feeding behavior, overhead cover and mimicked predators to teach escape behavior. Major advancements have been made in identifying and ameliorating negative effects of anthropogenic alterations within the Columbia Basin, however, many wild populations continue to decline. My research suggests that the physical (i.e. weirs and bypass structures) and operational alterations (i.e. voluntary spill) to the lower Columbia hydrosystem have substantially improved conditions for migrating smolt compared to past years, but involuntary spill during years of high flow continue to create deleterious conditions for migrating smolt. Riverscape-scale management strategies that recognize biotic and abiotic connectivity between dams (i.e. press disturbance) will benefit migrating smolt. My research indicates that hatchery fish are not currently equal or adequate replacements for wild fish. Hatcheries vary greatly in their stated goals and desired outcomes and several coordinated changes to general hatchery practices may help produce fish that are more similar to wild fish in morphology and life histories: 1) Change the goals of production away from producing as many, large individuals as possible, to producing fish that resemble the target wild populations they are intended to support; 2) Alter the hatchery environment to reflect the rearing environments in which salmon evolved and into which they will be released; and 3) Reduce the annual number of hatchery fish released into the Columbia Basin for the sole purpose of harvest. Recovering and rehabilitating critical and diverse habitats utilized by salmonids at each life stage (spawning, rearing, migration, estuary and marine) remains crucial for wild population success into the future.

River basins provide essential services for both humans and ecosystems. Understanding the connections between ecosystems and society and their function has been at the heart of resilience studies and has become an increasing important endeavor in research and practice. In this dissertation, I define basin resilience as a river basin system's capacity to absorb, manage, and adapt to biophysical, social-economic, and political changes (or stressors) while still maintaining its essential structure, feedbacks, and functional integrity. I address the question of resilience, scale, and development in the Mekong and Columbia River Basins. This dissertation answers the following questions: 1) is systems theory an appropriate model to evaluate basin resilience, 2) is the Mekong Basin resilient, 3) are the Mekong and Columbia River Basins resilient across multiple scales, 4) can conflict management and collaborative learning enhance resilience, 5) can a resilience framework be used for basin comparisons, and 6) what lessons can the Mekong basin take from rapid development in the Columbia basin? In Chapter 2, I create and apply a social-ecological systems (SES) model of the Mekong River Basin to assess resilience at sub-basin (provincial), watershed (national), and basin (regional) scales. Feedbacks, thresholds, vulnerability, and adaptive capacity are determined and used as inputs into an overall basin resilience assessment. Drawing upon field work done in the Mekong Basin, Chapter 3 uses Conflict Management and Collaborative Learning processes to address resilience weaknesses across multiple scales in the Mekong Basin. Chapter 4 uses the basin resilience framework to compare the Mekong and Columbia Basins against physical characteristics, development rate, conflict and cooperation, and institutional responses to development projects. In this dissertation I find the Mekong has medium-low basin resilience and that scale is a critical determinant in basin resilience assessments. I find that in this study, vulnerability is inversely proportional to resilience, and low resilience at one scale, for example fisheries in the Tonle Sap Lake in Cambodia, decreases resilience for the entire basin. I find that Cambodia and Lao PDR are the least resilience and Thailand the most resilient countries in the Mekong Basin ��� Thailand more resilient in some sectors than the Mekong River Commission (MRC). I find that the MRC's conflict management strategy is hampered by a restrictive mandate and weakness in capacity building at tributary and national scales but that Collaborative Learning processes are effective in enhancing resilience at the sub-basin scale. Finally, I demonstrate through the basin comparison that the Mekong has a highly resilient biophysical system and traditionally a resilient institutional system however, the proposed rate of development is unsustainable with trends indicating a significant erosion of resilience. I find the Columbia Basin lacking resilience in fishing, hydropower, and water quality ��� sectors mitigating the effects of development in the Columbia Basin, manifesting as overall negative trends in cooperation. However, the Columbia shows signs of increasing cooperation due recent inclusion of Tribal Nations in water management. Flexible and inclusive institutional responses to water resource development challenges, in the Mekong to rapid development on the mainstream and in the Columbia to negotiations over renewal of the Columbia River Treaty, are key determinants to whether or not each basin can halt the current negative trends and strengthen basin resilience to face the challenges now and those coming in the future. / Graduation date: 2013