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• 171. [Article] Investigations of Larval Pacific Lamprey Entosphenus tridentatus Osmotic Stress Tolerance and Occurrence in a Tidally-Influenced Estuarine Stream

  Pacific lamprey is a culturally valuable species to indigenous people, and has significant ecological importance in freshwater and marine ecosystems. Over the past several decades, constrictions in range ...

  Citation × Citation Citation Abstract Copy Title: Investigations of Larval Pacific Lamprey Entosphenus tridentatus Osmotic Stress Tolerance and Occurrence in a Tidally-Influenced Estuarine Stream Author: Silver, Gregory Shell Year: 2015 Pacific lamprey is a culturally valuable species to indigenous people, and has significant ecological importance in freshwater and marine ecosystems. Over the past several decades, constrictions in range and reductions in Pacific lamprey abundance have been observed in Western North America, and may be indicators of range-wide declines. In the face of declining populations, the U.S. Fish and Wildlife Service has partnered with tribal, state, federal, and local entities to implement a regional Pacific lamprey conservation agreement aimed at reducing threats to Pacific lamprey and improving their habitats and population status. Research needs identified in the conservation agreement include assessing larval Pacific lamprey occupancy and distribution, habitat requirements, and the limiting factors of larval distribution in the freshwater ecosystem. As part of the effort to address these knowledge gaps, we investigated the potential for larval lampreys to occur in tidally-influenced estuarine environments. Research of this type may be valuable for future conservation, management or recovery efforts of Pacific lamprey throughout its range. We employed a two-phased approach, consisting of laboratory and field components to address our aims. We first conducted a series of controlled laboratory experiments to evaluate osmotic stress tolerance and osmoregulatory status of larval Pacific lamprey exposed to a range of (1) fixed salinity in various dilutions of saltwater and (2) oscillating salinity treatments designed to simulate tidal activity. Tolerance was assessed by monitoring and comparing survival of larvae in various treatments through 96 h. Osmoregulatory status was assessed by quantifying and comparing total body water content, plasma osmolality, and plasma cation (i.e., sodium) concentrations among larvae surviving various treatments. In fixed salinity experiments, 100% survival was observed in 0‰, 6‰, 8‰ and 10‰ through 96 h, while 0% survival was observed through 48 h in 12‰, 30 h in 15‰, and 12 h in 25‰ and 35‰. In oscillating salinity experiments, on the other hand, a significant increase in survival (100%) was observed through 96 h in treatments that oscillated between 12‰ and 0‰ (freshwater) at about 6 h intervals versus fixed 12‰ salinity experiments. A significant increase in survival also occurred in oscillating 15‰ treatments (60%) versus fixed 15‰ through 96 h. Linear regression analysis indicated higher environmental salinity in laboratory experiments was significantly related to increases in plasma osmolality and plasma sodium (the most abundant osmotically active plasma cation) concentrations, and concurrent decreases in total body water content among larvae that survived various treatments. Tidal oscillations in salinity appeared to temper the desiccating effects of salinity, as changes in body water content and sodium ion concentration were less abrupt than fixed salinity treatments. These results suggest larvae cannot osmoregulate in hyperosmotic environments, but are able to tolerate some fixed and oscillating hyperosmotic salinity exposure. Consequently, larvae may be able to occur in certain areas of estuaries, such as oligohaline habitats that are characterized by low levels of salinity. Experimental results were used, in part, to guide larval sampling in a tidally-influenced habitat. Occurrence of larval Pacific lamprey and Lampetra spp. (western brook and river lampreys) was subsequently investigated across a gradient of salinity in Ellsworth Creek (Pacific County, Washington) by electrofishing. Larval Pacific and Lampetra spp. were detected within an approximately 300 m long tidally-influenced segment of the study area. Salinity monitoring was conducted in six tidally-influenced reaches where larvae were detected for up to 14 d following electrofishing. Maximum tidal cycle salinity exceeded 15 ppt during 52% to 80% of tidal cycles within tidally-influenced reaches where larvae were detected. These results suggest potential for larval lamprey to occur in certain portions of tidal estuaries. However, long-term residence of larvae in tidally-influenced habitats and whether larvae are able to subsequently survive, grow, transform, and out-migrate is not known and requires further study. Given the potential for tidally-influenced habitats to be occupied by larvae, assessments of larval occurrence in other areas, such as the lower Columbia River, may be warranted. Knowledge of larval lamprey distribution in estuarine environments may be valuable for habitat restoration, and mitigating potential impacts from dredging and other human disturbances. Title: Investigations of Larval Pacific Lamprey Entosphenus tridentatus Osmotic Stress Tolerance and Occurrence in a Tidally-Influenced Estuarine Stream Author: Silver, Gregory Shell Year: 2015 Pacific lamprey is a culturally valuable species to indigenous people, and has significant ecological importance in freshwater and marine ecosystems. Over the past several decades, constrictions in range and reductions in Pacific lamprey abundance have been observed in Western North America, and may be indicators of range-wide declines. In the face of declining populations, the U.S. Fish and Wildlife Service has partnered with tribal, state, federal, and local entities to implement a regional Pacific lamprey conservation agreement aimed at reducing threats to Pacific lamprey and improving their habitats and population status. Research needs identified in the conservation agreement include assessing larval Pacific lamprey occupancy and distribution, habitat requirements, and the limiting factors of larval distribution in the freshwater ecosystem. As part of the effort to address these knowledge gaps, we investigated the potential for larval lampreys to occur in tidally-influenced estuarine environments. Research of this type may be valuable for future conservation, management or recovery efforts of Pacific lamprey throughout its range. We employed a two-phased approach, consisting of laboratory and field components to address our aims. We first conducted a series of controlled laboratory experiments to evaluate osmotic stress tolerance and osmoregulatory status of larval Pacific lamprey exposed to a range of (1) fixed salinity in various dilutions of saltwater and (2) oscillating salinity treatments designed to simulate tidal activity. Tolerance was assessed by monitoring and comparing survival of larvae in various treatments through 96 h. Osmoregulatory status was assessed by quantifying and comparing total body water content, plasma osmolality, and plasma cation (i.e., sodium) concentrations among larvae surviving various treatments. In fixed salinity experiments, 100% survival was observed in 0‰, 6‰, 8‰ and 10‰ through 96 h, while 0% survival was observed through 48 h in 12‰, 30 h in 15‰, and 12 h in 25‰ and 35‰. In oscillating salinity experiments, on the other hand, a significant increase in survival (100%) was observed through 96 h in treatments that oscillated between 12‰ and 0‰ (freshwater) at about 6 h intervals versus fixed 12‰ salinity experiments. A significant increase in survival also occurred in oscillating 15‰ treatments (60%) versus fixed 15‰ through 96 h. Linear regression analysis indicated higher environmental salinity in laboratory experiments was significantly related to increases in plasma osmolality and plasma sodium (the most abundant osmotically active plasma cation) concentrations, and concurrent decreases in total body water content among larvae that survived various treatments. Tidal oscillations in salinity appeared to temper the desiccating effects of salinity, as changes in body water content and sodium ion concentration were less abrupt than fixed salinity treatments. These results suggest larvae cannot osmoregulate in hyperosmotic environments, but are able to tolerate some fixed and oscillating hyperosmotic salinity exposure. Consequently, larvae may be able to occur in certain areas of estuaries, such as oligohaline habitats that are characterized by low levels of salinity. Experimental results were used, in part, to guide larval sampling in a tidally-influenced habitat. Occurrence of larval Pacific lamprey and Lampetra spp. (western brook and river lampreys) was subsequently investigated across a gradient of salinity in Ellsworth Creek (Pacific County, Washington) by electrofishing. Larval Pacific and Lampetra spp. were detected within an approximately 300 m long tidally-influenced segment of the study area. Salinity monitoring was conducted in six tidally-influenced reaches where larvae were detected for up to 14 d following electrofishing. Maximum tidal cycle salinity exceeded 15 ppt during 52% to 80% of tidal cycles within tidally-influenced reaches where larvae were detected. These results suggest potential for larval lamprey to occur in certain portions of tidal estuaries. However, long-term residence of larvae in tidally-influenced habitats and whether larvae are able to subsequently survive, grow, transform, and out-migrate is not known and requires further study. Given the potential for tidally-influenced habitats to be occupied by larvae, assessments of larval occurrence in other areas, such as the lower Columbia River, may be warranted. Knowledge of larval lamprey distribution in estuarine environments may be valuable for habitat restoration, and mitigating potential impacts from dredging and other human disturbances. Close

• 172. [Article] Ecohydrological mediation of water budget partitioning and time scales of subsurface flow in a seasonally semi-arid grassland

  Understanding how the interactions and feedbacks between plant function, climate, and soils ultimately affects the terrestrial water balance and subsurface flow processes is major challenge in scientific ...

  Citation × Citation Citation Abstract Copy Title: Ecohydrological mediation of water budget partitioning and time scales of subsurface flow in a seasonally semi-arid grassland Author: Pangle, Luke A., 1981- Understanding how the interactions and feedbacks between plant function, climate, and soils ultimately affects the terrestrial water balance and subsurface flow processes is major challenge in scientific hydrology. This dissertation summarizes the findings of a manipulative climate warming experiment, an observational field study that utilized stable-isotope tracers, and associated modeling analyses that I used to examine the physiological and physical mechanisms by which grassland ecosystems mediate water-balance partitioning and transit times of water flowing through the subsurface. Utilizing the climate-controlled mesocosm experiment, I examined the responses of evapotranspiration, soil moisture, and potential groundwater recharge to a 3.5˚C temperature increase in a grassland ecosystem experiencing a Mediterranean climate. I hypothesized that a warmer climate would cause a shift in the soil-water balance toward greater evapotranspiration, and less recharge. The results showed that warming treatments enhanced evapotranspiration during the spring. However, this reduced soil moisture more rapidly, resulting in less evapotranspiration during the summer than occurred under ambient temperatures, and no difference when considered over the entire year. Groundwater recharge was reduced during late-spring storms relative to the ambient temperature treatment, but these reductions were a small fraction of the annual total, and were offset by slightly greater recharge in the fall under warming treatments. The results highlighted the potential for interactions between climate, vegetation, and soils to moderate the hydrological response to climate warming, particularly in environments where precipitation is seasonal and out of phase with the vegetation growing season. I conducted additional field studies that utilized three lysimeters with surface conditions ranging from bare soil through two stages of aggrading grassland vegetation. Using hydrometric data, stable-isotopes as conservative tracer, and two hydrograph-separation techniques I evaluated whether aggrading grassland vegetation and root systems alter time scales of subsurface flow, and how this alteration may influence potential groundwater recharge. I tested the hypothesis that soil structural change under aggrading vegetation would enhance the rapid infiltration of precipitation-event water, resulting in greater potential recharge during individual storms. Contrary to this expectation, results from both hydrograph-separation techniques showed that precipitation-event water comprised 0 - 6% of potential recharge among all the storm events I analyzed, being greatest under bare soil, and always zero in grasslands ranging in age from 3.8 - 5.9 years. These results contradicted my original hypothesis, and were attributed to the low intensity of local precipitation, large soil-water storage potential, and the predominantly shallow rooting tendency of the grassland vegetation. In a final analysis I used stable-isotope measurements and a linear-time-invariant convolution approach to model mean-transit times and transit-time distributions of subsurface flow under each surface condition, and over the entire water year. The results showed that mean-transit times were not significantly different in the presence of aggrading vegetation. From these analyses I concluded that physical alteration of the soil by aggrading plant root systems was not an ecohydrologically significant mechanism in this system. Ex post facto analyses showed that, at the time scale of individual storm events, the reduction of effective precipitation by interception and evaporative loss from the grassland canopies was of much greater importance--even with very low leaf area indices. At the annual time scale, root expansion enabled much greater exploitation of soil water during the summer drought, causing a shift from a recharge-dominated to an evapotranspiration-dominated soil-water balance within the first year of growth. Title: Ecohydrological mediation of water budget partitioning and time scales of subsurface flow in a seasonally semi-arid grassland Author: Pangle, Luke A., 1981- Understanding how the interactions and feedbacks between plant function, climate, and soils ultimately affects the terrestrial water balance and subsurface flow processes is major challenge in scientific hydrology. This dissertation summarizes the findings of a manipulative climate warming experiment, an observational field study that utilized stable-isotope tracers, and associated modeling analyses that I used to examine the physiological and physical mechanisms by which grassland ecosystems mediate water-balance partitioning and transit times of water flowing through the subsurface. Utilizing the climate-controlled mesocosm experiment, I examined the responses of evapotranspiration, soil moisture, and potential groundwater recharge to a 3.5˚C temperature increase in a grassland ecosystem experiencing a Mediterranean climate. I hypothesized that a warmer climate would cause a shift in the soil-water balance toward greater evapotranspiration, and less recharge. The results showed that warming treatments enhanced evapotranspiration during the spring. However, this reduced soil moisture more rapidly, resulting in less evapotranspiration during the summer than occurred under ambient temperatures, and no difference when considered over the entire year. Groundwater recharge was reduced during late-spring storms relative to the ambient temperature treatment, but these reductions were a small fraction of the annual total, and were offset by slightly greater recharge in the fall under warming treatments. The results highlighted the potential for interactions between climate, vegetation, and soils to moderate the hydrological response to climate warming, particularly in environments where precipitation is seasonal and out of phase with the vegetation growing season. I conducted additional field studies that utilized three lysimeters with surface conditions ranging from bare soil through two stages of aggrading grassland vegetation. Using hydrometric data, stable-isotopes as conservative tracer, and two hydrograph-separation techniques I evaluated whether aggrading grassland vegetation and root systems alter time scales of subsurface flow, and how this alteration may influence potential groundwater recharge. I tested the hypothesis that soil structural change under aggrading vegetation would enhance the rapid infiltration of precipitation-event water, resulting in greater potential recharge during individual storms. Contrary to this expectation, results from both hydrograph-separation techniques showed that precipitation-event water comprised 0 - 6% of potential recharge among all the storm events I analyzed, being greatest under bare soil, and always zero in grasslands ranging in age from 3.8 - 5.9 years. These results contradicted my original hypothesis, and were attributed to the low intensity of local precipitation, large soil-water storage potential, and the predominantly shallow rooting tendency of the grassland vegetation. In a final analysis I used stable-isotope measurements and a linear-time-invariant convolution approach to model mean-transit times and transit-time distributions of subsurface flow under each surface condition, and over the entire water year. The results showed that mean-transit times were not significantly different in the presence of aggrading vegetation. From these analyses I concluded that physical alteration of the soil by aggrading plant root systems was not an ecohydrologically significant mechanism in this system. Ex post facto analyses showed that, at the time scale of individual storm events, the reduction of effective precipitation by interception and evaporative loss from the grassland canopies was of much greater importance--even with very low leaf area indices. At the annual time scale, root expansion enabled much greater exploitation of soil water during the summer drought, causing a shift from a recharge-dominated to an evapotranspiration-dominated soil-water balance within the first year of growth. Close

• 173. [Article] Riparian Wetland Plant Response to Livestock Exclusion in the Lower Columbia River Basin

  The purpose of this study was to examine the characteristics of riparian plant communities along a gradient of livestock exclusion in the Lower Columbia River Basin (LCRB) located in the Pacific Northwest ...

  Citation × Citation Citation Abstract Copy Title: Riparian Wetland Plant Response to Livestock Exclusion in the Lower Columbia River Basin Author: Kidd, S. A., Yeakley, J. Alan Year: 2015 The purpose of this study was to examine the characteristics of riparian plant communities along a gradient of livestock exclusion in the Lower Columbia River Basin (LCRB) located in the Pacific Northwest region of the United States. Livestock exclusion from riparian wetlands is a common passive restoration technique. Few studies, however, have focused on the effects of livestock grazing or the exclusion of livestock grazing on these ecosystems. Vegetation community composition was examined in two passive restoration sites, three and 13 years since livestock exclusion, and in a reference site with continued livestock grazing. We hypothesized native plant species richness would be lower in the excluded wetlands than in the grazed wetland due to the competitive exclusion from an increase in non-native plant dominance in the absence of grazing. The grazed wetland had significantly (P < 0.02) greater mean total species richness (23.3 ± 1.6; mean ± 1 standard error), native (10.2 ± 0.5), and non-native (12 ± 1.5) species richness than both the excluded wetlands. Mean total species richness did not differ significantly (P = 0.088) between the three-year (12 ± 1.4) and 13-year (5.5 ± 2.3) excluded wetlands. Mean native and non-native species richness also did not differ significantly (native P = 0.088. non-native P = 0.064) between the three-year (native 6.3 ± 0.6, non-native 5 ± 2.3) and 13-year (native 2.8 ± 1.3, non-native 2.7 ± 1.1) excluded wetlands. However, native species abundance as indicated by percent cover was significantly (P < 0.02) lower in the 13-year excluded wetland (4.2 ± 2.0%) than both the three-year excluded (51.5 ± 3.9%) and grazed (23.2 ± 3.3%) wetlands. The invasive grass, Phalaris arundinacea (reed canarygrass), was found to be the dominant vegetation cover in all three wetlands, with average relative cover ranging from 95.2 ± 2.0% at the 13-year exclusion site to 52.8 ± 4.1% at the grazing site, and 43.0 ± 4.0% cover at the three-year exclusion site. These observations suggest that livestock exclusion alone may be an ineffective strategy for restoring riparian plant communities in regions such as LCRB where invasive species like reed canarygrass are abundant. More effective management alternatives might include short-term livestock exclusion and reintroduced targeted grazing to both reduce livestock impacts and control reed canarygrass dominance. Title: Riparian Wetland Plant Response to Livestock Exclusion in the Lower Columbia River Basin Author: Kidd, S. A., Yeakley, J. Alan Year: 2015 The purpose of this study was to examine the characteristics of riparian plant communities along a gradient of livestock exclusion in the Lower Columbia River Basin (LCRB) located in the Pacific Northwest region of the United States. Livestock exclusion from riparian wetlands is a common passive restoration technique. Few studies, however, have focused on the effects of livestock grazing or the exclusion of livestock grazing on these ecosystems. Vegetation community composition was examined in two passive restoration sites, three and 13 years since livestock exclusion, and in a reference site with continued livestock grazing. We hypothesized native plant species richness would be lower in the excluded wetlands than in the grazed wetland due to the competitive exclusion from an increase in non-native plant dominance in the absence of grazing. The grazed wetland had significantly (P < 0.02) greater mean total species richness (23.3 ± 1.6; mean ± 1 standard error), native (10.2 ± 0.5), and non-native (12 ± 1.5) species richness than both the excluded wetlands. Mean total species richness did not differ significantly (P = 0.088) between the three-year (12 ± 1.4) and 13-year (5.5 ± 2.3) excluded wetlands. Mean native and non-native species richness also did not differ significantly (native P = 0.088. non-native P = 0.064) between the three-year (native 6.3 ± 0.6, non-native 5 ± 2.3) and 13-year (native 2.8 ± 1.3, non-native 2.7 ± 1.1) excluded wetlands. However, native species abundance as indicated by percent cover was significantly (P < 0.02) lower in the 13-year excluded wetland (4.2 ± 2.0%) than both the three-year excluded (51.5 ± 3.9%) and grazed (23.2 ± 3.3%) wetlands. The invasive grass, Phalaris arundinacea (reed canarygrass), was found to be the dominant vegetation cover in all three wetlands, with average relative cover ranging from 95.2 ± 2.0% at the 13-year exclusion site to 52.8 ± 4.1% at the grazing site, and 43.0 ± 4.0% cover at the three-year exclusion site. These observations suggest that livestock exclusion alone may be an ineffective strategy for restoring riparian plant communities in regions such as LCRB where invasive species like reed canarygrass are abundant. More effective management alternatives might include short-term livestock exclusion and reintroduced targeted grazing to both reduce livestock impacts and control reed canarygrass dominance. Close

• 174. [Article] The paradox of cooling streams in a warming world:Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American ...

  Citation × Citation Citation Abstract Copy Title: The paradox of cooling streams in a warming world:Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States Author: Haggerty, Roy, Arismendi, Ivan, Hockman-Wert, David, Johnson, Sherri L., Dunham, Jason B. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/gl/. Title: The paradox of cooling streams in a warming world:Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States Author: Haggerty, Roy, Arismendi, Ivan, Hockman-Wert, David, Johnson, Sherri L., Dunham, Jason B. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://www.agu.org/journals/gl/. Close

• 175. [Article] Predicting logging debris accumulation in natural streambeds : a method for forest managers

  This study has analyzed factors which affect the accumulation of terrestrial organic debris within natural gravel streambeds. In addition, the amounts, sizes, and physical conditions of intruded material ...

  Citation × Citation Citation Abstract Copy Title: Predicting logging debris accumulation in natural streambeds : a method for forest managers Author: Hess, Vernon Scott This study has analyzed factors which affect the accumulation of terrestrial organic debris within natural gravel streambeds. In addition, the amounts, sizes, and physical conditions of intruded material were measured, along with the effect of the detritus on intragravel dissolved oxygen levels. Measurements indicate that aged intragravel detritus had no significant impact on subsurface dissolved oxygen levels. The organic material extracted from the streambeds was composed primarily of highly conditioned woody material, which is characterized by a very low B.O.D. These measurements support the hypothesis that decomposing organic material produces only a temporary demand on intragravel dissolved oxygen supplies. Previous work has indicated that this demand has generally been met after only 60 days. One hundred and forty-four frozen core samples of ten streambeds were taken as a means of analyzing subsurface organic debris concentrations. These cores provided the data needed to calculate streambed porosity, median cobble size, and average detritus size. In addition, stream gradient and surface debris loading were measured. Subsurface organic debris concentrations were found, to be extremely variable. The range of values observed, in grams of detritus per liter of pore volume, was 1.4 to 439.9. The mean value was 29.3 grams per liter of pore volume, with a standard. deviation of 52.9. These values indicate that organic material may provide a severe threat to subsurface dissolved oxygen levels, especially if high concentrations of fresh, finely divided material, such as leaves or needles, are present. Although the impacts exerted by organic material are only temporary, there may be a detrimental impact on the fisheries resource, if a large B.O.D. is produced at the time alevins are dependent on intragravel dissolved oxygen. Regression equations for predicting subsurface debris concentrations were developed. It was observed That subsurface debris accumulations can generally be expected to increase with increases in streambed porosity, surface debris loading, and median cobble size. Concentrations can be expected to decrease with increases in stream gradient. Estimates developed with these models cannot be expected to yield accurate values under all conditions, and the possibility of high variability must be anticipated. However, the models developed in this study do provide a means of predicting subsurface debris accumulations in natural gravel streambeds under a variety of conditions. In addition, the measurement and analysis techniques described will encourage future research which will further develop an understanding of the small stream ecosystem. Title: Predicting logging debris accumulation in natural streambeds : a method for forest managers Author: Hess, Vernon Scott This study has analyzed factors which affect the accumulation of terrestrial organic debris within natural gravel streambeds. In addition, the amounts, sizes, and physical conditions of intruded material were measured, along with the effect of the detritus on intragravel dissolved oxygen levels. Measurements indicate that aged intragravel detritus had no significant impact on subsurface dissolved oxygen levels. The organic material extracted from the streambeds was composed primarily of highly conditioned woody material, which is characterized by a very low B.O.D. These measurements support the hypothesis that decomposing organic material produces only a temporary demand on intragravel dissolved oxygen supplies. Previous work has indicated that this demand has generally been met after only 60 days. One hundred and forty-four frozen core samples of ten streambeds were taken as a means of analyzing subsurface organic debris concentrations. These cores provided the data needed to calculate streambed porosity, median cobble size, and average detritus size. In addition, stream gradient and surface debris loading were measured. Subsurface organic debris concentrations were found, to be extremely variable. The range of values observed, in grams of detritus per liter of pore volume, was 1.4 to 439.9. The mean value was 29.3 grams per liter of pore volume, with a standard. deviation of 52.9. These values indicate that organic material may provide a severe threat to subsurface dissolved oxygen levels, especially if high concentrations of fresh, finely divided material, such as leaves or needles, are present. Although the impacts exerted by organic material are only temporary, there may be a detrimental impact on the fisheries resource, if a large B.O.D. is produced at the time alevins are dependent on intragravel dissolved oxygen. Regression equations for predicting subsurface debris concentrations were developed. It was observed That subsurface debris accumulations can generally be expected to increase with increases in streambed porosity, surface debris loading, and median cobble size. Concentrations can be expected to decrease with increases in stream gradient. Estimates developed with these models cannot be expected to yield accurate values under all conditions, and the possibility of high variability must be anticipated. However, the models developed in this study do provide a means of predicting subsurface debris accumulations in natural gravel streambeds under a variety of conditions. In addition, the measurement and analysis techniques described will encourage future research which will further develop an understanding of the small stream ecosystem. Close

• 176. [Article] Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier ...

  Citation × Citation Citation Abstract Copy Title: Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns Author: Hood, E., O'Neel, S., Dahlke, H. E., Fleming, S. W. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/advances-in-water-resources/ Title: Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns Author: Hood, E., O'Neel, S., Dahlke, H. E., Fleming, S. W. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/advances-in-water-resources/ Close

• 177. [Article] Remote sensing of forest biomass dynamics using Landsat-derived disturbance and recovery history and lidar data

  Improved monitoring of forest biomass is needed to quantify natural and anthropogenic effects on the terrestrial carbon cycle. Landsat's temporal and spatial coverage, fine spatial grain, and long history ...

  Citation × Citation Citation Abstract Copy Title: Remote sensing of forest biomass dynamics using Landsat-derived disturbance and recovery history and lidar data Author: Pflugmacher, Dirk Improved monitoring of forest biomass is needed to quantify natural and anthropogenic effects on the terrestrial carbon cycle. Landsat's temporal and spatial coverage, fine spatial grain, and long history of earth observations provide a unique opportunity for measuring biophysical properties of vegetation across large areas and long time scales. However, like other multi-spectral data, the relationship between single-date reflectance and forest biomass weakens under certain canopy conditions. Because the structure and composition of a forest stand at any point in time is linked to the stand's disturbance history, one potential means of enhancing Landsat's spectral relationships with biomass is by including information on vegetation trends prior to the date for which estimates are desired. The purpose of this research was to develop and assess a method that links field data, airborne lidar, and Landsat-derived disturbance and recovery history for mapping of forest biomass and biomass change. Our study area is located in eastern Oregon (US), an area dominated by mixed conifer and single species forests. In Chapter 2, we test and demonstrate the utility of Landsat-derived disturbance and recovery metrics to predict current forest structure (live and dead biomass, basal area, and stand height) for 51 field plots, and compare the results with estimates from airborne lidar and single-date Landsat imagery. To characterize the complex nature of long-term (insect, growth) and short-term (fire, harvest) vegetation changes found in this area, we use annual Landsat time series between 1972 and 2010. This required integrating Landsat data from MSS (1972-1992) and TM/ETM+ (1982-present) sensors. In Chapter 2, we describe a method to bridge spectral differences between Landsat sensors, and therefore extent Landsat time-series analyses back to 1972. In Chapter 3, we extend and automate our approach and develop maps of current (2009) and historic (1993-2009) live forest biomass. We use lidar data for model training and evaluate the results with forest inventory data. We further conduct a sensitivity analysis to determine the effects of forest structure, time-series length, terrain and sampling design on model predictions. Our research showed that including disturbance and recovery trends in empirical models significantly improved predictions of forest biomass, and that the approach can be applied across a larger landscape and across time for estimating biomass change. Title: Remote sensing of forest biomass dynamics using Landsat-derived disturbance and recovery history and lidar data Author: Pflugmacher, Dirk Improved monitoring of forest biomass is needed to quantify natural and anthropogenic effects on the terrestrial carbon cycle. Landsat's temporal and spatial coverage, fine spatial grain, and long history of earth observations provide a unique opportunity for measuring biophysical properties of vegetation across large areas and long time scales. However, like other multi-spectral data, the relationship between single-date reflectance and forest biomass weakens under certain canopy conditions. Because the structure and composition of a forest stand at any point in time is linked to the stand's disturbance history, one potential means of enhancing Landsat's spectral relationships with biomass is by including information on vegetation trends prior to the date for which estimates are desired. The purpose of this research was to develop and assess a method that links field data, airborne lidar, and Landsat-derived disturbance and recovery history for mapping of forest biomass and biomass change. Our study area is located in eastern Oregon (US), an area dominated by mixed conifer and single species forests. In Chapter 2, we test and demonstrate the utility of Landsat-derived disturbance and recovery metrics to predict current forest structure (live and dead biomass, basal area, and stand height) for 51 field plots, and compare the results with estimates from airborne lidar and single-date Landsat imagery. To characterize the complex nature of long-term (insect, growth) and short-term (fire, harvest) vegetation changes found in this area, we use annual Landsat time series between 1972 and 2010. This required integrating Landsat data from MSS (1972-1992) and TM/ETM+ (1982-present) sensors. In Chapter 2, we describe a method to bridge spectral differences between Landsat sensors, and therefore extent Landsat time-series analyses back to 1972. In Chapter 3, we extend and automate our approach and develop maps of current (2009) and historic (1993-2009) live forest biomass. We use lidar data for model training and evaluate the results with forest inventory data. We further conduct a sensitivity analysis to determine the effects of forest structure, time-series length, terrain and sampling design on model predictions. Our research showed that including disturbance and recovery trends in empirical models significantly improved predictions of forest biomass, and that the approach can be applied across a larger landscape and across time for estimating biomass change. Close

• 178. [Article] Population genetics, ecology and evolution of a vertebrate metacommunity

  Population genetic structure is widespread in many organisms and can be found at small spatial scales. Fine-scale differentiation is the result of ecological and evolutionary processes working together ...

  Citation × Citation Citation Abstract Copy Title: Population genetics, ecology and evolution of a vertebrate metacommunity Author: Manier, Mollie Kim Population genetic structure is widespread in many organisms and can be found at small spatial scales. Fine-scale differentiation is the result of ecological and evolutionary processes working together to produce an overall pattern, but the relative importance of these factors in population differentiation is poorly understood. The goals of my research were to describe patterns of population genetic differentiation and to identify ecological and evolutionary factors important for population divergence. To this end, I investigated several aspects of genetic differentiation for three vertebrates in northern California. The focal species were the terrestrial garter snake (Thamnophis elegans) and the common garter snake (Thamnophis sirtalis) that occupy a series of ponds, lakes and flooded meadows in northern California. I found significant genetic differentiation and isolation by distance, as well as correlated patterns of pairwise divergence in both species. Independent estimates of effective population size and bi-directional migration rates also uncovered source-sink dynamics in both species that suggest frequent extinction-recolonization events within a metapopulation context. The generality of source-sink dynamics for an ecologically similar species within the same ecosystem was explored using a third species, B. boreas. I also identified ecological correlates of several population genetic parameters for all three species. Although F[subscript ST] were similar, B. boreas had larger effective population sizes, lower migration rates, lacked source-sink dynamics, and appeared to be in migration-drift equilibrium, indicative of a temporally stable population structure. A clustering analysis identified a series of block faults as a common barrier to dispersal for both garter snakes, and ecological correlates were found to be more similar among response variables than within species. I then compared degree of genetic differentiation at quantitative traits with that at neutral markers to infer strength of selection and adaptive divergence between two ecotypes of T. elegans. Selection on most traits was relatively weak, but strong diversifying selection was found for background coloration, total number of ventral scales and number of infralabials. Overall, my research documented ecological and evolutionary processes associated with population differentiation in a metacommunity and respresents an important contribution toward the unification of ecology and evolutionary biology. Title: Population genetics, ecology and evolution of a vertebrate metacommunity Author: Manier, Mollie Kim Population genetic structure is widespread in many organisms and can be found at small spatial scales. Fine-scale differentiation is the result of ecological and evolutionary processes working together to produce an overall pattern, but the relative importance of these factors in population differentiation is poorly understood. The goals of my research were to describe patterns of population genetic differentiation and to identify ecological and evolutionary factors important for population divergence. To this end, I investigated several aspects of genetic differentiation for three vertebrates in northern California. The focal species were the terrestrial garter snake (Thamnophis elegans) and the common garter snake (Thamnophis sirtalis) that occupy a series of ponds, lakes and flooded meadows in northern California. I found significant genetic differentiation and isolation by distance, as well as correlated patterns of pairwise divergence in both species. Independent estimates of effective population size and bi-directional migration rates also uncovered source-sink dynamics in both species that suggest frequent extinction-recolonization events within a metapopulation context. The generality of source-sink dynamics for an ecologically similar species within the same ecosystem was explored using a third species, B. boreas. I also identified ecological correlates of several population genetic parameters for all three species. Although F[subscript ST] were similar, B. boreas had larger effective population sizes, lower migration rates, lacked source-sink dynamics, and appeared to be in migration-drift equilibrium, indicative of a temporally stable population structure. A clustering analysis identified a series of block faults as a common barrier to dispersal for both garter snakes, and ecological correlates were found to be more similar among response variables than within species. I then compared degree of genetic differentiation at quantitative traits with that at neutral markers to infer strength of selection and adaptive divergence between two ecotypes of T. elegans. Selection on most traits was relatively weak, but strong diversifying selection was found for background coloration, total number of ventral scales and number of infralabials. Overall, my research documented ecological and evolutionary processes associated with population differentiation in a metacommunity and respresents an important contribution toward the unification of ecology and evolutionary biology. Close

• 179. [Article] The methodology, implementation,and analysis of the isotopic composition of soil respired CO₂ in forest ecological research

  Soils are the largest terrestrial pool of carbon, therefore it is critical to understand what controls soil carbon efflux to the atmosphere in light of current climate uncertainty. The primary efflux of ...

  Citation × Citation Citation Abstract Copy Title: The methodology, implementation,and analysis of the isotopic composition of soil respired CO₂ in forest ecological research Author: Kayler, Zachary Eric Soils are the largest terrestrial pool of carbon, therefore it is critical to understand what controls soil carbon efflux to the atmosphere in light of current climate uncertainty. The primary efflux of carbon from soil is soil respiration which is typically categorized into autotrophic and heterotrophic respiration. These two components have different responses to changes in the environment, thus necessitating a means to quantify the contributions of each. Natural abundance ¹³C can identify autotrophic and heterotrophic sources of respiration, but there is a paucity of research concerning the soil isotope methodology and the subsequent analysis. This dissertation documents my contributions to the advancement of understanding carbon metabolism in forest ecosystems of the Pacific Northwest through the use of the natural abundance carbon isotopic signature of soil respiration. The results of this research represent significant progress in the use of ¹³C in forest ecology. I show in a laboratory setting that a change in the isotopic signature of soil gas can take at least 48 hours to reach equilibrium. A change in the isotopic source of respiration is one mechanism behind non steady-state conditions while another mechanism is dynamic gas transport. I explored the impact of a negative pressure potential across the soil surface by inducing advection and found the isotopic signature of respiration to be 1‰ less than the theoretical steady-state value. I performed a source partitioning experiment in which I identified a highly depleted source of carbon contributing to respiration. I also considered the impacts of the potential errors associated with collecting and measuring isotopic samples on mixing-models currently used to identify the isotopic signature of respiration. I found that the effect of CO₂ and δ¹³C measurement error on large CO₂ concentration regime to be substantially different than small concentration regimes, necessitating a unique mixing-model and regression-model combination for estimating the isotopic signal of respiration. Finally, I built upon the progress made in the previous experiments and analyze almost two years of soil respiration and its isotopic signature to determine potential environmental and biological drivers. I found that: transpiration was highly correlated with both respiration and the carbon isotopic signature; soil moisture primarily influenced tree processes related to respiration; and I found evidence of soil respiration under isotopic non steady-state conditions. Title: The methodology, implementation,and analysis of the isotopic composition of soil respired CO₂ in forest ecological research Author: Kayler, Zachary Eric Soils are the largest terrestrial pool of carbon, therefore it is critical to understand what controls soil carbon efflux to the atmosphere in light of current climate uncertainty. The primary efflux of carbon from soil is soil respiration which is typically categorized into autotrophic and heterotrophic respiration. These two components have different responses to changes in the environment, thus necessitating a means to quantify the contributions of each. Natural abundance ¹³C can identify autotrophic and heterotrophic sources of respiration, but there is a paucity of research concerning the soil isotope methodology and the subsequent analysis. This dissertation documents my contributions to the advancement of understanding carbon metabolism in forest ecosystems of the Pacific Northwest through the use of the natural abundance carbon isotopic signature of soil respiration. The results of this research represent significant progress in the use of ¹³C in forest ecology. I show in a laboratory setting that a change in the isotopic signature of soil gas can take at least 48 hours to reach equilibrium. A change in the isotopic source of respiration is one mechanism behind non steady-state conditions while another mechanism is dynamic gas transport. I explored the impact of a negative pressure potential across the soil surface by inducing advection and found the isotopic signature of respiration to be 1‰ less than the theoretical steady-state value. I performed a source partitioning experiment in which I identified a highly depleted source of carbon contributing to respiration. I also considered the impacts of the potential errors associated with collecting and measuring isotopic samples on mixing-models currently used to identify the isotopic signature of respiration. I found that the effect of CO₂ and δ¹³C measurement error on large CO₂ concentration regime to be substantially different than small concentration regimes, necessitating a unique mixing-model and regression-model combination for estimating the isotopic signal of respiration. Finally, I built upon the progress made in the previous experiments and analyze almost two years of soil respiration and its isotopic signature to determine potential environmental and biological drivers. I found that: transpiration was highly correlated with both respiration and the carbon isotopic signature; soil moisture primarily influenced tree processes related to respiration; and I found evidence of soil respiration under isotopic non steady-state conditions. Close

• 180. [Article] Functional profiles of soil microbial communities in second-growth Douglas-fir forests of the Pacific Northwest

  Forests are one of the largest repositories of terrestrial C. Understanding factors that drive organic matter transformations and nutrient efflux from these systems is therefore highly important. Temperate ...

  Citation × Citation Citation Abstract Copy Title: Functional profiles of soil microbial communities in second-growth Douglas-fir forests of the Pacific Northwest Author: McGinnis, Megan L. Forests are one of the largest repositories of terrestrial C. Understanding factors that drive organic matter transformations and nutrient efflux from these systems is therefore highly important. Temperate forests are of particular significance due to the large fraction of C that is stored below ground in the soil. Characterizing nutrient transformations, especially for C and N, and factors that influence their mineralization is critical in managing these ecosystems sustainably. The objective of this study was to characterize the metabolic function of the soil microbial community as it relates to C and N cycling in managed second-growth Douglas-fir forests of the Pacific Northwest. In the first study, extracellular enzyme profiles were characterized and correlated with a wide range of environmental variables present at nine sites located in western Oregon and Washington. Enzyme profiles were also correlated with measures of microbial biomass and with C and N mineralization rates obtained from a two-month incubation. Sites varied significantly from one another in all enzymes. C-cycling enzymes were correlated with respired C, and N-cycling enzymes, in addition to phosphatase and oxidative enzymes, were correlated with released N. Enzyme profiles grouped similarly for sites of the same soil type. Abiotic factors such as CEC, EC, and cation concentrations were correlated strongly with many enzymes, suggesting that soil physical and chemical properties influence extracellular enzyme function. In the second study, a year-long soil microcosm incubation measured respired C as well as total released N: NO₃⁻, NH₄⁺, and dissolved organic N (DON). These cumulative mineralization measurements were fitted with kinetic models to characterize C and N cycling in the same nine soils. Mineralization rates, and their descriptive parameters derived from the models, were correlated with the same set of environmental characteristics and enzyme activities from the previous study. Total soil C and N, as well as microbial biomass, were strongly positively correlated with both C and N mineralization. However, abiotic factors such as soil chemical components also had significant effects. This, coupled with anomalous behavior noted in C mineralization in response to leaching treatments, may suggest substrate supply to microorganisms constrains much of C mineralization. N mineralization seemed strongly tied to biotic factors in addition to abiotic factors. Often in studies of N dynamics in soil, only mineralized N (NO₃⁻ and NH₄⁺) are examined; our study revealed that DON was the largest fraction of released N in these systems, and dynamics of DON in N cycle warrant further research. Together, these studies provide insights into factors that drive soil microbial community function across a broad range of site conditions for Douglas-fir dominated forests of the Pacific Northwest region and could serve as a baseline for future research. Title: Functional profiles of soil microbial communities in second-growth Douglas-fir forests of the Pacific Northwest Author: McGinnis, Megan L. Forests are one of the largest repositories of terrestrial C. Understanding factors that drive organic matter transformations and nutrient efflux from these systems is therefore highly important. Temperate forests are of particular significance due to the large fraction of C that is stored below ground in the soil. Characterizing nutrient transformations, especially for C and N, and factors that influence their mineralization is critical in managing these ecosystems sustainably. The objective of this study was to characterize the metabolic function of the soil microbial community as it relates to C and N cycling in managed second-growth Douglas-fir forests of the Pacific Northwest. In the first study, extracellular enzyme profiles were characterized and correlated with a wide range of environmental variables present at nine sites located in western Oregon and Washington. Enzyme profiles were also correlated with measures of microbial biomass and with C and N mineralization rates obtained from a two-month incubation. Sites varied significantly from one another in all enzymes. C-cycling enzymes were correlated with respired C, and N-cycling enzymes, in addition to phosphatase and oxidative enzymes, were correlated with released N. Enzyme profiles grouped similarly for sites of the same soil type. Abiotic factors such as CEC, EC, and cation concentrations were correlated strongly with many enzymes, suggesting that soil physical and chemical properties influence extracellular enzyme function. In the second study, a year-long soil microcosm incubation measured respired C as well as total released N: NO₃⁻, NH₄⁺, and dissolved organic N (DON). These cumulative mineralization measurements were fitted with kinetic models to characterize C and N cycling in the same nine soils. Mineralization rates, and their descriptive parameters derived from the models, were correlated with the same set of environmental characteristics and enzyme activities from the previous study. Total soil C and N, as well as microbial biomass, were strongly positively correlated with both C and N mineralization. However, abiotic factors such as soil chemical components also had significant effects. This, coupled with anomalous behavior noted in C mineralization in response to leaching treatments, may suggest substrate supply to microorganisms constrains much of C mineralization. N mineralization seemed strongly tied to biotic factors in addition to abiotic factors. Often in studies of N dynamics in soil, only mineralized N (NO₃⁻ and NH₄⁺) are examined; our study revealed that DON was the largest fraction of released N in these systems, and dynamics of DON in N cycle warrant further research. Together, these studies provide insights into factors that drive soil microbial community function across a broad range of site conditions for Douglas-fir dominated forests of the Pacific Northwest region and could serve as a baseline for future research. Close