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• 121. [Article] Isotopic composition of respired CO2 in a small watershed : development and testing of an automated sampling system and analysis of first year data

  Warming of the terrestrial biosphere due to the anthropogenic addition of carbon dioxide to the earth’s atmosphere is becoming a major focus of scientific inquiry. Predictions of the extent of this warming ...

  Citation × Citation Citation Abstract Copy Title: Isotopic composition of respired CO2 in a small watershed : development and testing of an automated sampling system and analysis of first year data Author: Hauck, Mark J. Warming of the terrestrial biosphere due to the anthropogenic addition of carbon dioxide to the earth’s atmosphere is becoming a major focus of scientific inquiry. Predictions of the extent of this warming are hampered by uncertainty in the ability of the earth’s ecosystems to counteract this effect by sequestering carbon dioxide by increases in the mass of vegetation, soil storage, or storage in the Earth’s oceans. Measurement of the carbon isotopic composition of respired CO2 (Delta [superscript 13]C[subscript R-eco]) is becoming increasingly important to ecosystem studies because the information contained in this respiration can be an indicator of ecosystem stress and productivity. This study was conducted as part of a larger research project aimed at developing and testing the capacity for measuring Delta [superscript 13]C[subscript R-eco] in a small, steeply-sloped watershed in western Oregon. The goals of this study were: (1) to develop and test an automated system for sampling nocturnal air to be analyzed in a laboratory for isotopic composition; (2) to collect samples of the atmosphere from the nocturnal cold air drainage of a steeply sloped watershed in the HJ Andrews Experimental Forest and bring those samples back to a laboratory to be analyzed for CO2 concentration and carbon isotope composition; and (3) to conduct an initial analysis of the relationship between Delta [superscript 13]C[subscript R-eco] for the first year of deployment and two environmental forcing factors, soil moisture and atmospheric vapor pressure deficit (VPD). The automated system was designed during 2004 and 2005, tested in the laboratory during the month of April 2005, debugged in the field between August 2004 and May 2005, and deployed during the period from late May, 2005 to November 2005. The design objectives for the automated sampling system were: (1) light weight; (2) portability; (3) high reliability; (4) fast dynamic response; (5) unattended operation; and (6) the ability to capture, transport, and store samples over several days with no loss of data integrity. The automated sampling system proved capable of collecting 15 samples per sampling period and utilized a 16 loop stainless steel sample capture valve (Valcon Instruments, 7806 Bobbitt Houston, TX 77055) for sample containment. The system was designed for automated, labor free operation and uses a Campbell CR 10X datalogger (Campbell Scientific, Inc, 815 West 1800 North, Logan Utah) for both data acquisition and system control. This unique architecture was selected to enhance the ability of the system to capture samples which could be analyzed simultaneously for both CO2 concentration and Delta[superscript 13]C. The system was deployed in a steeply sloped watershed and proved to have a combination of light weight (approximately 34 kg total weight) and portability which allowed a wide range of field personnel to deploy the system without undue physical stress. Some initial issues with electrical wiring, plumbing connections, and control program bugs hampered early season performance, but once the system was debugged, it functioned reliably throughout the remainder of the field season with a minimum of operator input. Test results showed that the automated sampler had a maximum sampling frequency of 0.043 hertz, could store air samples for up to 3 days without detectable changes in either isotopic composition or CO2 concentration and displayed greater precision than the hand sampling process it replaced. Using the automated sampling system, sets of nocturnal cold air drainage samples were collected on nine evenings in 2005. The 15 samples acquired for each of these nine evenings were used to generate Keeling plots to determine a single value of the isotopic composition of ecosystem respiration (Delta [superscript 13]C[subscript R-eco]) for each sampling date. The range of Delta [superscript 13]C[subscript R-eco] over the season was 3.9 0/00 and the values of Delta [superscript 13]C[subscript R-eco] varied from -26.2 0/00 on July 13, 2005 to -22.9 0/00 on September 14, 2005. This seasonal pattern of Delta [superscript 13]C[subscript R-eco] was consistent with a forest under drought stress. Trends in ecosystem respiration over the growing season were compared to corresponding measurements of the environmental variables of soil moisture content and VPD. VPD ranged from 2.7 to 1758 Pa, but these patterns of VPD were not significantly correlated to seasonal Delta [superscript 13]C[subscript R-eco] patterns over the study period. Soil moisture content ranged between 7.2% and 44.3% over the study period and soil moisture content temporal patterns were highly correlated with rain events exceeding 4 mm. The soil moisture content pattern for the south-facing slope was significantly correlated with the seasonal Delta [superscript 13]C[subscript R-eco] pattern, although other groupings of soil moisture content were not. The automated system designed for this project met all of its design objectives and functioned adequately throughout the sampling period. The carbon isotope patterns were consistent with a forest under drought stress and the soil moisture content of the plots on the south-facing slopes of the watershed were significantly correlated to these isotope patterns. The future of this system could be enhanced by making adjustments to the supporting hardware, control program and operating procedure to enable larger quantities of samples, more rapid sampling rates, and automated hardware diagnostics. Title: Isotopic composition of respired CO2 in a small watershed : development and testing of an automated sampling system and analysis of first year data Author: Hauck, Mark J. Warming of the terrestrial biosphere due to the anthropogenic addition of carbon dioxide to the earth’s atmosphere is becoming a major focus of scientific inquiry. Predictions of the extent of this warming are hampered by uncertainty in the ability of the earth’s ecosystems to counteract this effect by sequestering carbon dioxide by increases in the mass of vegetation, soil storage, or storage in the Earth’s oceans. Measurement of the carbon isotopic composition of respired CO2 (Delta [superscript 13]C[subscript R-eco]) is becoming increasingly important to ecosystem studies because the information contained in this respiration can be an indicator of ecosystem stress and productivity. This study was conducted as part of a larger research project aimed at developing and testing the capacity for measuring Delta [superscript 13]C[subscript R-eco] in a small, steeply-sloped watershed in western Oregon. The goals of this study were: (1) to develop and test an automated system for sampling nocturnal air to be analyzed in a laboratory for isotopic composition; (2) to collect samples of the atmosphere from the nocturnal cold air drainage of a steeply sloped watershed in the HJ Andrews Experimental Forest and bring those samples back to a laboratory to be analyzed for CO2 concentration and carbon isotope composition; and (3) to conduct an initial analysis of the relationship between Delta [superscript 13]C[subscript R-eco] for the first year of deployment and two environmental forcing factors, soil moisture and atmospheric vapor pressure deficit (VPD). The automated system was designed during 2004 and 2005, tested in the laboratory during the month of April 2005, debugged in the field between August 2004 and May 2005, and deployed during the period from late May, 2005 to November 2005. The design objectives for the automated sampling system were: (1) light weight; (2) portability; (3) high reliability; (4) fast dynamic response; (5) unattended operation; and (6) the ability to capture, transport, and store samples over several days with no loss of data integrity. The automated sampling system proved capable of collecting 15 samples per sampling period and utilized a 16 loop stainless steel sample capture valve (Valcon Instruments, 7806 Bobbitt Houston, TX 77055) for sample containment. The system was designed for automated, labor free operation and uses a Campbell CR 10X datalogger (Campbell Scientific, Inc, 815 West 1800 North, Logan Utah) for both data acquisition and system control. This unique architecture was selected to enhance the ability of the system to capture samples which could be analyzed simultaneously for both CO2 concentration and Delta[superscript 13]C. The system was deployed in a steeply sloped watershed and proved to have a combination of light weight (approximately 34 kg total weight) and portability which allowed a wide range of field personnel to deploy the system without undue physical stress. Some initial issues with electrical wiring, plumbing connections, and control program bugs hampered early season performance, but once the system was debugged, it functioned reliably throughout the remainder of the field season with a minimum of operator input. Test results showed that the automated sampler had a maximum sampling frequency of 0.043 hertz, could store air samples for up to 3 days without detectable changes in either isotopic composition or CO2 concentration and displayed greater precision than the hand sampling process it replaced. Using the automated sampling system, sets of nocturnal cold air drainage samples were collected on nine evenings in 2005. The 15 samples acquired for each of these nine evenings were used to generate Keeling plots to determine a single value of the isotopic composition of ecosystem respiration (Delta [superscript 13]C[subscript R-eco]) for each sampling date. The range of Delta [superscript 13]C[subscript R-eco] over the season was 3.9 0/00 and the values of Delta [superscript 13]C[subscript R-eco] varied from -26.2 0/00 on July 13, 2005 to -22.9 0/00 on September 14, 2005. This seasonal pattern of Delta [superscript 13]C[subscript R-eco] was consistent with a forest under drought stress. Trends in ecosystem respiration over the growing season were compared to corresponding measurements of the environmental variables of soil moisture content and VPD. VPD ranged from 2.7 to 1758 Pa, but these patterns of VPD were not significantly correlated to seasonal Delta [superscript 13]C[subscript R-eco] patterns over the study period. Soil moisture content ranged between 7.2% and 44.3% over the study period and soil moisture content temporal patterns were highly correlated with rain events exceeding 4 mm. The soil moisture content pattern for the south-facing slope was significantly correlated with the seasonal Delta [superscript 13]C[subscript R-eco] pattern, although other groupings of soil moisture content were not. The automated system designed for this project met all of its design objectives and functioned adequately throughout the sampling period. The carbon isotope patterns were consistent with a forest under drought stress and the soil moisture content of the plots on the south-facing slopes of the watershed were significantly correlated to these isotope patterns. The future of this system could be enhanced by making adjustments to the supporting hardware, control program and operating procedure to enable larger quantities of samples, more rapid sampling rates, and automated hardware diagnostics. Close

• 122. [Article] Integration of MODIS land and atmosphere products with a coupled-process model to estimate gross primary productivity and evapotranspiration from 1 km to global scales

  This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/.

  Citation × Citation Citation Abstract Copy Title: Integration of MODIS land and atmosphere products with a coupled-process model to estimate gross primary productivity and evapotranspiration from 1 km to global scales Author: van Gorsel, Eva, Baldocchi, Dennis D., Ryu, Youngryel, Knohl, Alexander, Li, Jie, Kobayashi, Hideki, Roupsard, Olivier, Beringer, Jason, Law, Beverly E., Black, T. Andy, van Ingen, Catharine This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/. Title: Integration of MODIS land and atmosphere products with a coupled-process model to estimate gross primary productivity and evapotranspiration from 1 km to global scales Author: van Gorsel, Eva, Baldocchi, Dennis D., Ryu, Youngryel, Knohl, Alexander, Li, Jie, Kobayashi, Hideki, Roupsard, Olivier, Beringer, Jason, Law, Beverly E., Black, T. Andy, van Ingen, Catharine This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://sites.agu.org/. Close

• 123. [Article] Evaluation and improvement of the Community Land Model (CLM4) in Oregon forests

  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 Copernicus ...

  Citation × Citation Citation Abstract Copy Title: Evaluation and improvement of the Community Land Model (CLM4) in Oregon forests Author: Thornton, P. E., Law, B. E., Hudiburg, T.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 Copernicus Publications and can be found at: http://publications.copernicus.org/ on behalf of the European Geosciences Union (http://www.egu.eu/publications/). Title: Evaluation and improvement of the Community Land Model (CLM4) in Oregon forests Author: Thornton, P. E., Law, B. E., Hudiburg, T.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 Copernicus Publications and can be found at: http://publications.copernicus.org/ on behalf of the European Geosciences Union (http://www.egu.eu/publications/). Close

• 124. [Article] Realized and potential climate responses of lichen and bryophyte communities in a national forest inventory

  Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. ...

  Citation × Citation Citation Abstract Copy Title: Realized and potential climate responses of lichen and bryophyte communities in a national forest inventory Author: Smith, Robert J. Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. This dissertation outlines the current and potential future climate responses of lichen and bryophyte communities in the United States as part of a national forest inventory. The first task was to identify influences on carbon and nitrogen storage of moss and lichen “ground layers” in subarctic interior Alaska. Nutrient stores were more sensitive to local vegetation and topography than regional macroclimate. Nutrients and biomass were greatest among apparently less disturbed stands. This suggests that climatic changes could diminish ground layer nutrient storage indirectly if they promote intensifying wildfire regimes or expansions of competitive vascular vegetation. Turning to focus on species diversity, the next task was to quantify the strength of relationship between epiphytic lichen community composition and macroclimate across the 4,000 km-long swath of the U.S. Pacific coastal states. The strongest fitting lichen response gradients involved precipitation, temperature, and a heat-moisture index. Lichen indicator species (diagnostic of ten defined climate zones) emerged as useful monitoring tools because their abundance changes could signal shifting climate zone boundaries. After establishing key present-day climatic relationships, the next task was to pinpoint nationwide locations where epiphytic lichen communities will be most vulnerable to species losses under current and future warming scenarios. Novel niche-based metrics revealed greatest vulnerability among supposedly “warm-adapted” communities in southern/lowland locations, contrary to usual assumptions centering on cooler northern/montane habitats. Vulnerability analyses can steer conservation and monitoring attention to specific locations where warming is most expected to affect ecological communities. The final task, to anticipate how warming will impact individual lichen performance, was addressed by quantifying how experimental climate treatments (whole-ecosystem warming and CO2 additions) affected growth of the boreal epiphytic lichen species Evernia mesomorpha. Over just one year, incremental warming and concurrent drying caused progressive growth declines and biomass losses among individual transplants. Such warming-induced biomass losses of epiphytic lichens could precede local population extinctions and regional range contractions. Overall, this dissertation weaves together multiple lines of evidence from nutrient, diversity and growth responses to indicate the ecological effects of climate and climatic changes on vegetation in a national forest inventory context. This work suggests a pathway for integrating lichen and bryophyte responses into nationwide climate monitoring to address emergent interactions between humans, vegetation, and the global climate commons. Title: Realized and potential climate responses of lichen and bryophyte communities in a national forest inventory Author: Smith, Robert J. Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. This dissertation outlines the current and potential future climate responses of lichen and bryophyte communities in the United States as part of a national forest inventory. The first task was to identify influences on carbon and nitrogen storage of moss and lichen “ground layers” in subarctic interior Alaska. Nutrient stores were more sensitive to local vegetation and topography than regional macroclimate. Nutrients and biomass were greatest among apparently less disturbed stands. This suggests that climatic changes could diminish ground layer nutrient storage indirectly if they promote intensifying wildfire regimes or expansions of competitive vascular vegetation. Turning to focus on species diversity, the next task was to quantify the strength of relationship between epiphytic lichen community composition and macroclimate across the 4,000 km-long swath of the U.S. Pacific coastal states. The strongest fitting lichen response gradients involved precipitation, temperature, and a heat-moisture index. Lichen indicator species (diagnostic of ten defined climate zones) emerged as useful monitoring tools because their abundance changes could signal shifting climate zone boundaries. After establishing key present-day climatic relationships, the next task was to pinpoint nationwide locations where epiphytic lichen communities will be most vulnerable to species losses under current and future warming scenarios. Novel niche-based metrics revealed greatest vulnerability among supposedly “warm-adapted” communities in southern/lowland locations, contrary to usual assumptions centering on cooler northern/montane habitats. Vulnerability analyses can steer conservation and monitoring attention to specific locations where warming is most expected to affect ecological communities. The final task, to anticipate how warming will impact individual lichen performance, was addressed by quantifying how experimental climate treatments (whole-ecosystem warming and CO2 additions) affected growth of the boreal epiphytic lichen species Evernia mesomorpha. Over just one year, incremental warming and concurrent drying caused progressive growth declines and biomass losses among individual transplants. Such warming-induced biomass losses of epiphytic lichens could precede local population extinctions and regional range contractions. Overall, this dissertation weaves together multiple lines of evidence from nutrient, diversity and growth responses to indicate the ecological effects of climate and climatic changes on vegetation in a national forest inventory context. This work suggests a pathway for integrating lichen and bryophyte responses into nationwide climate monitoring to address emergent interactions between humans, vegetation, and the global climate commons. Close

• 125. [Article] The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients

  Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition ...

  Citation × Citation Citation Abstract Copy Title: The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients Author: Lemein, Todd Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition from invasive species. Vegetation has been demonstrated to reduce wave energy, increase sedimentation, and decrease erosion in tidal environments under a range of conditions. Similarities and differences between the morphology of vegetation species may play an important role in understanding the mechanism between vegetation, sedimentation, and wave energy. Diversity of species within vegetation communities has been shown to reduce the success of biological invasions from invasive species as well as increase the ability of the community to adapt to environmental changes such as inundation period (period of time vegetation is submerged partially or fully by water). The species present along coastal marshes and specifically at the interface between vegetated marsh and unvegetated mudflat provide an opportunity to better understand the interactions between vegetation and its physical setting. In this dissertation I focus on the species and vegetation communities that are present at this interface of the terrestrial and aquatic boundary to better understand how plant communities may be characterized, how they respond to disturbance, how they are distributed, and how they may influence the physical environment in which they grow. In Chapter two, I explore the ability to use image analysis and the lateral obstruction of vegetation to describe a species density, height and diameter and evaluate the tradeoffs in using image analysis over more traditional methods. In Chapter three, I evaluate the response of an emergent vegetation species, threesquare bulrush (Schoenoplectus pungens), to different depths of complete burial as could be expected from extreme storms, hurricanes, tsunamis, or restoration efforts involving sediment amendment. Chapter four describes the distribution of coastal marsh communities of the Laurentian Great Lakes along an elevational gradient beginning at the terrestrial and aquatic boundary, identifying patterns of wetland distribution, species composition, and exotic plant invasion. In Chapter five, I conclude the dissertation with an evaluation of the effects of two morphologically distinct species of emergent marsh vegetation, threesquare bulrush and Lyngbye’s sedge (Carex lyngbyei), on the sedimentation rate and variability in Tillamook Bay, OR and compare the results to the current understanding of vegetation-sediment feedback. In Chapter two, I found that for morphologically simple species, such as S. pungens, image analysis of lateral obstruction can be used to determine important morphological characteristics of a stand of vegetation including the mean stem height, density, and mean diameter. The method provides a description of the vertical variation in morphologic structure, providing a rapid analytic tool for exploring the effects of vegetation on wave and sediment interaction. However, I note that more morphologically complex species, such as sedges and grasses may not be as easily described using image analysis. In Chapter three, I determined that aboveground biomass of S. pungens would return to pre-disturbance levels following burial by up to 40 cm of mineral sediment after two years. Vegetation was observed to survive burials depths of up to 80 cm, although initially at much lower density. The aboveground height of stems were statistically similar to unburied controls after two years, which is important for the continuation of ecosystem services such as wave attenuation. The results suggest that S. pungens is capable of returning to pre-disturbance levels of biomass following large natural sedimentation events such as extreme storms, hurricanes, or tsunamis, and that burying portions of marshes with sediment as a restoration tool is not likely to harm the buried vegetation. In Chapter four I refine and describe 21 coastal vegetation communities in the Laurentian Great Lakes and the ecological gradients along which they are distributed. Latitude, agricultural intensity, site geomorphology, substrate, and water depth were found to be the significant variables that determined community distribution. Additionally, we observed an expansion of invasive plant species near areas of high anthropogenic activity such as farms and urban centers. In Chapter five, I found that there were species-specific differences in sedimentation rate and variability in Tillamook Bay, OR. Schoenoplectus pungens was found to retain more sediment than C. lyngbyei. Sedimentation rate was observed to be variable by location within the estuary. Two patterns of sediment accumulation were observed. The first occurred along vegetation gradients, with increased sedimentation farther into vegetation beds. In the second pattern, sediment accumulation was observed to be greatest at the marsh/mudflat boundary where vegetation was dense and then decreased with increasing depth into the vegetation. In conclusion, this dissertation explores the interaction of emergent wetland vegetation with environmental factors. Image analysis provides a new tool for rapid characterization of vegetation structure, a burial experiment documents Schoenoplectus pungens’ tolerance to sand burial, a field study at Tillamook, OR documents the relationship between sediment accumulation and emergent vegetation beds, and a wetland classification is developed for coastal wetlands along the Great Lakes, which includes plant communities dominated by S. pungens. Title: The Response and Effect of Emergent Coastal Vegetation to Sedimentation and the Distribution of Coastal Vegetation Communities along Environmental Gradients Author: Lemein, Todd Coastal marsh vegetation is an important component in maintaining marsh stability that is threatened by changes in sedimentation, sea level rise, natural and anthropogenic disturbances, and competition from invasive species. Vegetation has been demonstrated to reduce wave energy, increase sedimentation, and decrease erosion in tidal environments under a range of conditions. Similarities and differences between the morphology of vegetation species may play an important role in understanding the mechanism between vegetation, sedimentation, and wave energy. Diversity of species within vegetation communities has been shown to reduce the success of biological invasions from invasive species as well as increase the ability of the community to adapt to environmental changes such as inundation period (period of time vegetation is submerged partially or fully by water). The species present along coastal marshes and specifically at the interface between vegetated marsh and unvegetated mudflat provide an opportunity to better understand the interactions between vegetation and its physical setting. In this dissertation I focus on the species and vegetation communities that are present at this interface of the terrestrial and aquatic boundary to better understand how plant communities may be characterized, how they respond to disturbance, how they are distributed, and how they may influence the physical environment in which they grow. In Chapter two, I explore the ability to use image analysis and the lateral obstruction of vegetation to describe a species density, height and diameter and evaluate the tradeoffs in using image analysis over more traditional methods. In Chapter three, I evaluate the response of an emergent vegetation species, threesquare bulrush (Schoenoplectus pungens), to different depths of complete burial as could be expected from extreme storms, hurricanes, tsunamis, or restoration efforts involving sediment amendment. Chapter four describes the distribution of coastal marsh communities of the Laurentian Great Lakes along an elevational gradient beginning at the terrestrial and aquatic boundary, identifying patterns of wetland distribution, species composition, and exotic plant invasion. In Chapter five, I conclude the dissertation with an evaluation of the effects of two morphologically distinct species of emergent marsh vegetation, threesquare bulrush and Lyngbye’s sedge (Carex lyngbyei), on the sedimentation rate and variability in Tillamook Bay, OR and compare the results to the current understanding of vegetation-sediment feedback. In Chapter two, I found that for morphologically simple species, such as S. pungens, image analysis of lateral obstruction can be used to determine important morphological characteristics of a stand of vegetation including the mean stem height, density, and mean diameter. The method provides a description of the vertical variation in morphologic structure, providing a rapid analytic tool for exploring the effects of vegetation on wave and sediment interaction. However, I note that more morphologically complex species, such as sedges and grasses may not be as easily described using image analysis. In Chapter three, I determined that aboveground biomass of S. pungens would return to pre-disturbance levels following burial by up to 40 cm of mineral sediment after two years. Vegetation was observed to survive burials depths of up to 80 cm, although initially at much lower density. The aboveground height of stems were statistically similar to unburied controls after two years, which is important for the continuation of ecosystem services such as wave attenuation. The results suggest that S. pungens is capable of returning to pre-disturbance levels of biomass following large natural sedimentation events such as extreme storms, hurricanes, or tsunamis, and that burying portions of marshes with sediment as a restoration tool is not likely to harm the buried vegetation. In Chapter four I refine and describe 21 coastal vegetation communities in the Laurentian Great Lakes and the ecological gradients along which they are distributed. Latitude, agricultural intensity, site geomorphology, substrate, and water depth were found to be the significant variables that determined community distribution. Additionally, we observed an expansion of invasive plant species near areas of high anthropogenic activity such as farms and urban centers. In Chapter five, I found that there were species-specific differences in sedimentation rate and variability in Tillamook Bay, OR. Schoenoplectus pungens was found to retain more sediment than C. lyngbyei. Sedimentation rate was observed to be variable by location within the estuary. Two patterns of sediment accumulation were observed. The first occurred along vegetation gradients, with increased sedimentation farther into vegetation beds. In the second pattern, sediment accumulation was observed to be greatest at the marsh/mudflat boundary where vegetation was dense and then decreased with increasing depth into the vegetation. In conclusion, this dissertation explores the interaction of emergent wetland vegetation with environmental factors. Image analysis provides a new tool for rapid characterization of vegetation structure, a burial experiment documents Schoenoplectus pungens’ tolerance to sand burial, a field study at Tillamook, OR documents the relationship between sediment accumulation and emergent vegetation beds, and a wetland classification is developed for coastal wetlands along the Great Lakes, which includes plant communities dominated by S. pungens. Close

• 126. [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

• 127. [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

• 128. [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

• 129. [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

• 130. [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