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• 1. [Article] Winter Precipitation Intensity and ENSO/PDO Variability in the Willamette Valley of Oregon

  There is growing concern about the effects of inter-annual climatic variability, such as the El-Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), on regional hydrology and water ...

  Citation × Citation Citation Abstract Copy Title: Winter Precipitation Intensity and ENSO/PDO Variability in the Willamette Valley of Oregon Author: Praskievicz, Sarah, Chang, Heejun Year: 2009 There is growing concern about the effects of inter-annual climatic variability, such as the El-Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), on regional hydrology and water resources. We analyzed patterns of wintertime precipitation intensity, using both simple intensity and number of heavy precipitation days per year, for eight stations in northwestern Oregon’s Willamette Valley for the period 1972–2006, and examined the separate and combined influence of ENSO and PDO on precipitation intensity. The analysis was accomplished using Kendall’s tau and analysis of variance (ANOVA) to determine differences in precipitation intensity among combinations of positive and negative ENSO and PDO phases. The results suggest that the relation between ENSO phase and precipitation intensity is negative in November and positive in April, while the relation between PDO and intensity is negative and strongest in January and March. These varying seasonal associations with ENSO/PDO phase may be related to the Willamette Valley’s location in the transitional zone between positive and negative El Niño response and to the moderating effects of out-of-phase ENSO/PDO. This seasonal variability of heavy rainfall has implications for the quantity and quality of regional water resources. Title: Winter Precipitation Intensity and ENSO/PDO Variability in the Willamette Valley of Oregon Author: Praskievicz, Sarah, Chang, Heejun Year: 2009 There is growing concern about the effects of inter-annual climatic variability, such as the El-Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), on regional hydrology and water resources. We analyzed patterns of wintertime precipitation intensity, using both simple intensity and number of heavy precipitation days per year, for eight stations in northwestern Oregon’s Willamette Valley for the period 1972–2006, and examined the separate and combined influence of ENSO and PDO on precipitation intensity. The analysis was accomplished using Kendall’s tau and analysis of variance (ANOVA) to determine differences in precipitation intensity among combinations of positive and negative ENSO and PDO phases. The results suggest that the relation between ENSO phase and precipitation intensity is negative in November and positive in April, while the relation between PDO and intensity is negative and strongest in January and March. These varying seasonal associations with ENSO/PDO phase may be related to the Willamette Valley’s location in the transitional zone between positive and negative El Niño response and to the moderating effects of out-of-phase ENSO/PDO. This seasonal variability of heavy rainfall has implications for the quantity and quality of regional water resources. Close

• 2. [Article] Long-term Responses of Phalaris arundinacea and Columbia River Bottomland Vegetation to Managed Flooding

  I sought to determine the effect of managed flooding on Phalaris arundinacea L. and other plant species distributions in a large wetland complex, Smith and Bybee Wetlands (SBW), in northwestern Oregon. ...

  Citation × Citation Citation Abstract Copy Title: Long-term Responses of Phalaris arundinacea and Columbia River Bottomland Vegetation to Managed Flooding Author: Farrelly, Tina Schantz Year: 2012 I sought to determine the effect of managed flooding on Phalaris arundinacea L. and other plant species distributions in a large wetland complex, Smith and Bybee Wetlands (SBW), in northwestern Oregon. Altered hydrology has reduced historically high spring flow and prematurely initiated the historic summer drying period at SBW. This alteration has increased the coverage of invasive plants (e.g., P. arundinacea) causing a decrease in native plant cover and thus degrading ecological functions. SBW managers installed a water control structure (WCS) between SBW and the Columbia Slough/River system to impound winter rainfall and thus approximate the ecological benefits that natural flooding provided as well as reduce the abundance of P. arundinacea. Prior researchers conducted intensive vegetation and hydrological monitoring in 2003 (during the season immediately before WCS installation) and 2004. I conducted similar analysis in the fifth and sixth years, 2008 and 2009, following establishment of the WCS. Both study years, I determined percent cover of all vegetation on transects established in 2003. The results, including 2004, as well as 2008 and 2009 showed a reduced cover of P. arundinacea in areas experiencing at least 0.6 meters of inundation and an increased cover of native plant communities when compared to the 2003 baseline data. Native Carex aperta Boott. cover increased 7-fold from 0.3% to 2.3%; Polygonum species cover increased from 20.0% to 52.6%; and Salix lucida Muhl. ssp. lasiandra (Benth.) E. Murray cover increased from 10.9% to 15.5% cover. P. arundinacea declined by over one-third from 44.4% to 28.1% cover following water management. Since hydrology management began, the native Polygonum species community replaced P. arundinacea as the dominant species in the emergent zone. The results of this study refined the suggested depth of inundation needed to reduce P. arundinacea cover in such lake-wetland complexes as SBW from 0.85 meters (based on 2004 study results) to 0.6 meters. Shannon Diversity decreased following water management. The findings of this study demonstrated that water management can enhance native bottomland communities, especially those comprised of obligate wetland species, and reduce P. arundinacea cover in areas experiencing at least 0.6 meters of inundation. Title: Long-term Responses of Phalaris arundinacea and Columbia River Bottomland Vegetation to Managed Flooding Author: Farrelly, Tina Schantz Year: 2012 I sought to determine the effect of managed flooding on Phalaris arundinacea L. and other plant species distributions in a large wetland complex, Smith and Bybee Wetlands (SBW), in northwestern Oregon. Altered hydrology has reduced historically high spring flow and prematurely initiated the historic summer drying period at SBW. This alteration has increased the coverage of invasive plants (e.g., P. arundinacea) causing a decrease in native plant cover and thus degrading ecological functions. SBW managers installed a water control structure (WCS) between SBW and the Columbia Slough/River system to impound winter rainfall and thus approximate the ecological benefits that natural flooding provided as well as reduce the abundance of P. arundinacea. Prior researchers conducted intensive vegetation and hydrological monitoring in 2003 (during the season immediately before WCS installation) and 2004. I conducted similar analysis in the fifth and sixth years, 2008 and 2009, following establishment of the WCS. Both study years, I determined percent cover of all vegetation on transects established in 2003. The results, including 2004, as well as 2008 and 2009 showed a reduced cover of P. arundinacea in areas experiencing at least 0.6 meters of inundation and an increased cover of native plant communities when compared to the 2003 baseline data. Native Carex aperta Boott. cover increased 7-fold from 0.3% to 2.3%; Polygonum species cover increased from 20.0% to 52.6%; and Salix lucida Muhl. ssp. lasiandra (Benth.) E. Murray cover increased from 10.9% to 15.5% cover. P. arundinacea declined by over one-third from 44.4% to 28.1% cover following water management. Since hydrology management began, the native Polygonum species community replaced P. arundinacea as the dominant species in the emergent zone. The results of this study refined the suggested depth of inundation needed to reduce P. arundinacea cover in such lake-wetland complexes as SBW from 0.85 meters (based on 2004 study results) to 0.6 meters. Shannon Diversity decreased following water management. The findings of this study demonstrated that water management can enhance native bottomland communities, especially those comprised of obligate wetland species, and reduce P. arundinacea cover in areas experiencing at least 0.6 meters of inundation. Close

• 3. [Article] Assessing Habitat Requirements of Pond-Breeding Amphibians in a Highly Urbanized Landscape:Implications for Management

  Management of urban aquatic habitats for native wildlife, such as amphibians, is an important contemporary goal for many municipalities. However, our understanding of how local and landscape characteristics ...

  Citation × Citation Citation Abstract Copy Title: Assessing Habitat Requirements of Pond-Breeding Amphibians in a Highly Urbanized Landscape:Implications for Management Author: Guderyahn, Laura B., Smithers, Ashley P., Mims, Meryl C. Year: 2016 Management of urban aquatic habitats for native wildlife, such as amphibians, is an important contemporary goal for many municipalities. However, our understanding of how local and landscape characteristics of urban aquatic habitat promote or inhibit amphibian occupancy and recruitment is limited. In this study, we examined amphibian community composition and occurrence patterns in ponds, wetlands, and swales of Gresham, Oregon. We collected occurrence data for five native amphibians: northwestern salamander (Ambystoma gracile), long-toed salamander (A. macrodactylum), Pacific chorus frog (Pseudacris regilla), northern red-legged frog (Rana aurora aurora), and rough-skinned newt (Taricha granulosa) as well as one non-native amphibian, the American bullfrog (Lithobates catesbeianus). One hundred sites were surveyed from 2007 to 2013. Local and landscape attributes were characterized for each site, and potential drivers of species occupancy were evaluated using a combination of multivariate approaches and generalized linear models. In general, percent impervious surface and distance to nearest forest patch, both associated with urbanization, were negatively correlated with site occupancy for all species. Non-native vegetation was also negatively associated with occupancy of three species (long-toed salamanders, Pacific chorus frogs, and northern red-legged frogs). In contrast, occupancy was positively correlated with pond depth and hydroperiod length for all species. We found evidence of two distinct groups of co-occurring amphibian species driven by habitat depth and hydroperiod. Finally, we report results of threshold analyses that examined species-specific habitat associations. This study describes urban habitat associations of a native amphibian community, identifies factors with positive, negative or mixed relationships with amphibian species, and is an important step in informing the management of urban aquatic habitat to promote persistence of native amphibians. Title: Assessing Habitat Requirements of Pond-Breeding Amphibians in a Highly Urbanized Landscape:Implications for Management Author: Guderyahn, Laura B., Smithers, Ashley P., Mims, Meryl C. Year: 2016 Management of urban aquatic habitats for native wildlife, such as amphibians, is an important contemporary goal for many municipalities. However, our understanding of how local and landscape characteristics of urban aquatic habitat promote or inhibit amphibian occupancy and recruitment is limited. In this study, we examined amphibian community composition and occurrence patterns in ponds, wetlands, and swales of Gresham, Oregon. We collected occurrence data for five native amphibians: northwestern salamander (Ambystoma gracile), long-toed salamander (A. macrodactylum), Pacific chorus frog (Pseudacris regilla), northern red-legged frog (Rana aurora aurora), and rough-skinned newt (Taricha granulosa) as well as one non-native amphibian, the American bullfrog (Lithobates catesbeianus). One hundred sites were surveyed from 2007 to 2013. Local and landscape attributes were characterized for each site, and potential drivers of species occupancy were evaluated using a combination of multivariate approaches and generalized linear models. In general, percent impervious surface and distance to nearest forest patch, both associated with urbanization, were negatively correlated with site occupancy for all species. Non-native vegetation was also negatively associated with occupancy of three species (long-toed salamanders, Pacific chorus frogs, and northern red-legged frogs). In contrast, occupancy was positively correlated with pond depth and hydroperiod length for all species. We found evidence of two distinct groups of co-occurring amphibian species driven by habitat depth and hydroperiod. Finally, we report results of threshold analyses that examined species-specific habitat associations. This study describes urban habitat associations of a native amphibian community, identifies factors with positive, negative or mixed relationships with amphibian species, and is an important step in informing the management of urban aquatic habitat to promote persistence of native amphibians. Close

• 4. [Article] Investigating the Potential of Land Use Modifications to Mitigate the Respiratory Health Impacts of NO2: A Case Study in the Portland-Vancouver Metropolitan Area

  The health impacts of urban air pollution are a growing concern in our rapidly urbanizing world. Urban air pollutants show high intra-urban spatial variability linked to urban land use and land cover (LULC). ...

  Citation × Citation Citation Abstract Copy Title: Investigating the Potential of Land Use Modifications to Mitigate the Respiratory Health Impacts of NO2: A Case Study in the Portland-Vancouver Metropolitan Area Author: Rao, Meenakshi Year: 2016 The health impacts of urban air pollution are a growing concern in our rapidly urbanizing world. Urban air pollutants show high intra-urban spatial variability linked to urban land use and land cover (LULC). This correlation of air pollutants with LULC is widely recognized; LULC data is an integral input into a wide range of models, especially land use regression models developed by epidemiologists to study the impact of air pollution on human health. Given the demonstrated links between LULC and urban air pollution, and between urban air pollution and health, an interesting question arises: what is the potential of LULC modifications to mitigate the health impacts of urban air pollution? In this dissertation we assess the potential of LULC modifications to mitigate the health impacts of NO2, a respiratory irritant and strong marker for combustion-related air pollution, in the Portland-Vancouver metropolitan area in northwestern USA. We begin by measuring summer and winter NO2 in the area using a spatially dense network of passive NO2 samplers. We next develop an annual average model for NO2 based on the observational data, using random forest -- for the first time in the realm of urban air pollution -- to disentangle the effects of highly correlated LULC variables on ambient NO2 concentrations. We apply this random forest (LURF) model to a 200m spatial grid covering the study area, and use this 200m LURF model to quantify the effect of different urban land use categories on ambient concentrations of NO2. Using the changes in ambient NO2 concentrations resulting from land use modifications as input to BenMAP (a health benefits assessment tool form the US EPA), we assess the NO2-related health impact associated with each land use category and its modifications. We demonstrate how the LURF model can be used to assess the respiratory health benefits of competing land use modifications, including city-wide and local-scale mitigation strategies based on modifying tree canopy and vehicle miles traveled (VMT). Planting trees is a common land cover modification strategy undertaken by cities to reduce air pollution. Statistical models such as LUR and LURF demonstrate a correlation between tree cover and reduced air pollution, but they cannot demonstrate causation. Hence, we run the atmospheric chemistry and transport model CMAQ to examine to what extent the dry deposition mechanism can explain the reduction of NO2 which statistical models associate with tree canopy. Results from our research indicate that even though the Portland-Vancouver area is in compliance with the US EPA NO2 standards, ambient concentrations of NO2 still create an annual health burden of at least $40 million USD. Our model suggests that NO2 associated with high intensity development and VMT may be creating an annual health burden of $7 million and $3.3 million USD respectively. Existing tree canopy, on the other hand, is associated with an annual health benefit of $1.4 million USD. LULC modifications can mitigate some fraction of this health burden. A 2% increase in tree canopy across the study area may reduce incidence rates of asthma exacerbation by as much as 7%. We also find that increasing tree canopy is a more effective strategy than reducing VMT in terms of mitigating the health burden of NO2. CMAQ indicates that the amount of NO2 removed by dry deposition is an order of magnitude smaller than that predicted by our statistical model. About one-third of the difference can be explained by the lower NO2 values predicted by CMAQ, and one-third may be attributable to parameterization of stomatal uptake. Title: Investigating the Potential of Land Use Modifications to Mitigate the Respiratory Health Impacts of NO2: A Case Study in the Portland-Vancouver Metropolitan Area Author: Rao, Meenakshi Year: 2016 The health impacts of urban air pollution are a growing concern in our rapidly urbanizing world. Urban air pollutants show high intra-urban spatial variability linked to urban land use and land cover (LULC). This correlation of air pollutants with LULC is widely recognized; LULC data is an integral input into a wide range of models, especially land use regression models developed by epidemiologists to study the impact of air pollution on human health. Given the demonstrated links between LULC and urban air pollution, and between urban air pollution and health, an interesting question arises: what is the potential of LULC modifications to mitigate the health impacts of urban air pollution? In this dissertation we assess the potential of LULC modifications to mitigate the health impacts of NO2, a respiratory irritant and strong marker for combustion-related air pollution, in the Portland-Vancouver metropolitan area in northwestern USA. We begin by measuring summer and winter NO2 in the area using a spatially dense network of passive NO2 samplers. We next develop an annual average model for NO2 based on the observational data, using random forest -- for the first time in the realm of urban air pollution -- to disentangle the effects of highly correlated LULC variables on ambient NO2 concentrations. We apply this random forest (LURF) model to a 200m spatial grid covering the study area, and use this 200m LURF model to quantify the effect of different urban land use categories on ambient concentrations of NO2. Using the changes in ambient NO2 concentrations resulting from land use modifications as input to BenMAP (a health benefits assessment tool form the US EPA), we assess the NO2-related health impact associated with each land use category and its modifications. We demonstrate how the LURF model can be used to assess the respiratory health benefits of competing land use modifications, including city-wide and local-scale mitigation strategies based on modifying tree canopy and vehicle miles traveled (VMT). Planting trees is a common land cover modification strategy undertaken by cities to reduce air pollution. Statistical models such as LUR and LURF demonstrate a correlation between tree cover and reduced air pollution, but they cannot demonstrate causation. Hence, we run the atmospheric chemistry and transport model CMAQ to examine to what extent the dry deposition mechanism can explain the reduction of NO2 which statistical models associate with tree canopy. Results from our research indicate that even though the Portland-Vancouver area is in compliance with the US EPA NO2 standards, ambient concentrations of NO2 still create an annual health burden of at least $40 million USD. Our model suggests that NO2 associated with high intensity development and VMT may be creating an annual health burden of $7 million and $3.3 million USD respectively. Existing tree canopy, on the other hand, is associated with an annual health benefit of $1.4 million USD. LULC modifications can mitigate some fraction of this health burden. A 2% increase in tree canopy across the study area may reduce incidence rates of asthma exacerbation by as much as 7%. We also find that increasing tree canopy is a more effective strategy than reducing VMT in terms of mitigating the health burden of NO2. CMAQ indicates that the amount of NO2 removed by dry deposition is an order of magnitude smaller than that predicted by our statistical model. About one-third of the difference can be explained by the lower NO2 values predicted by CMAQ, and one-third may be attributable to parameterization of stomatal uptake. Close