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• 1. [Article] A community-based approach for evaluating tradeoffs across marine ecosystem services in Oregon

  As competing uses of our coastlines increase, natural resource agencies are employing marine spatial planning (MSP) to designate areas for different uses or activities in order to reduce conflicts while ...

  Citation × Citation Citation Abstract Copy Title: A community-based approach for evaluating tradeoffs across marine ecosystem services in Oregon Author: Freeman, Peter M. As competing uses of our coastlines increase, natural resource agencies are employing marine spatial planning (MSP) to designate areas for different uses or activities in order to reduce conflicts while achieving ecological, economic and social objectives. A central challenge of implementing MSP is development of a rigorous approach for analyzing tradeoffs across the provision of ecosystem services (i.e., the benefits humans receive from nature). This study develops an operational approach to this problem that is founded on community-based methods, ecological production theory, and multi-criteria decision analysis (MCDA). The approach merges ecological models with surveys to identify marine ecosystem services for use in tradeoff analysis. The approach allows for a single set of marine ecosystem services to at once be valued by local stakeholders and measured by biologists, thus connecting social and biological monitoring efforts. To develop the approach in a real-world context, I examined ecosystem services associated with nearshore marine ecosystems in Oregon, where marine reserves are being introduced for biodiversity conservation. I worked with stakeholder focus groups in three Oregon communities to identify 24 marine ecosystem services. I then linked the ecosystem services with ecological indicators, which I then consolidated to derive 11 items for use in a survey-based tradeoff analysis exercise. I administered the survey to a nonrandom sample of stakeholders in Oregon (n=31), from which their relative preferences and preference weights for ecosystem services were derived. The weights and preference measures may then be used in MSP decision-making. Furthermore, I grouped the stakeholder survey data in three ways: by location of residence (coastal vs. non-coastal), by eight categories of affiliation (e.g., business owners, conservationists, commercial and recreational fishers, etc.), and by resource use patterns. I then analyzed the various groupings of stakeholders for within- and between-group homogeneity of preferences. Results of the analyses showed that there are statistically significant variations in preferences within and between most groupings. Capturing the variations in stakeholder preferences is important when developing policies that affect different stakeholder groups. Thus, when implementing the survey instrument, I suggest random sampling of stakeholders stratified by location, affiliation, and resource use. This study provides one of the first examples of a systems-based approach to ecosystem service valuation operationalized to inform MSP, and novel features of the approach have a number of implications for advancing marine research and management. First, by using stakeholders to identify ecosystem services, the approach allows for a tailored implementation of ecosystem-based management at the community level. Second, by integrating ecological and economic information on the provision and value of ecosystem services, the approach provides relevant data for MSP decision-making during the siting, evaluation, and monitoring stages. And third, by applying both stated-preference and MCDA methods, the approach may capture the array of values represented by diverse stakeholder groups. Title: A community-based approach for evaluating tradeoffs across marine ecosystem services in Oregon Author: Freeman, Peter M. As competing uses of our coastlines increase, natural resource agencies are employing marine spatial planning (MSP) to designate areas for different uses or activities in order to reduce conflicts while achieving ecological, economic and social objectives. A central challenge of implementing MSP is development of a rigorous approach for analyzing tradeoffs across the provision of ecosystem services (i.e., the benefits humans receive from nature). This study develops an operational approach to this problem that is founded on community-based methods, ecological production theory, and multi-criteria decision analysis (MCDA). The approach merges ecological models with surveys to identify marine ecosystem services for use in tradeoff analysis. The approach allows for a single set of marine ecosystem services to at once be valued by local stakeholders and measured by biologists, thus connecting social and biological monitoring efforts. To develop the approach in a real-world context, I examined ecosystem services associated with nearshore marine ecosystems in Oregon, where marine reserves are being introduced for biodiversity conservation. I worked with stakeholder focus groups in three Oregon communities to identify 24 marine ecosystem services. I then linked the ecosystem services with ecological indicators, which I then consolidated to derive 11 items for use in a survey-based tradeoff analysis exercise. I administered the survey to a nonrandom sample of stakeholders in Oregon (n=31), from which their relative preferences and preference weights for ecosystem services were derived. The weights and preference measures may then be used in MSP decision-making. Furthermore, I grouped the stakeholder survey data in three ways: by location of residence (coastal vs. non-coastal), by eight categories of affiliation (e.g., business owners, conservationists, commercial and recreational fishers, etc.), and by resource use patterns. I then analyzed the various groupings of stakeholders for within- and between-group homogeneity of preferences. Results of the analyses showed that there are statistically significant variations in preferences within and between most groupings. Capturing the variations in stakeholder preferences is important when developing policies that affect different stakeholder groups. Thus, when implementing the survey instrument, I suggest random sampling of stakeholders stratified by location, affiliation, and resource use. This study provides one of the first examples of a systems-based approach to ecosystem service valuation operationalized to inform MSP, and novel features of the approach have a number of implications for advancing marine research and management. First, by using stakeholders to identify ecosystem services, the approach allows for a tailored implementation of ecosystem-based management at the community level. Second, by integrating ecological and economic information on the provision and value of ecosystem services, the approach provides relevant data for MSP decision-making during the siting, evaluation, and monitoring stages. And third, by applying both stated-preference and MCDA methods, the approach may capture the array of values represented by diverse stakeholder groups. Close

• 2. [Article] Marine Reserves and Marine Protected Areas: A Case Study in Oregon and a Proposed National Model for Design and Implementation

  In this report, I examine the process of establishing marine reserves and marine protected areas both from a national and a state perspective. In order to do so, I have investigated the implementation ...

  Citation × Citation Citation Abstract Copy Title: Marine Reserves and Marine Protected Areas: A Case Study in Oregon and a Proposed National Model for Design and Implementation Author: Perry, Alex In this report, I examine the process of establishing marine reserves and marine protected areas both from a national and a state perspective. In order to do so, I have investigated the implementation process currently underway in Oregon. Specifically, I have chosen to perform a case study of the process at Redfish Rocks Marine Reserve and Marine Protected Area. I chose this example because of the commendable approach taken by the community of Port Orford in proposing their site and performing extensive baseline data collection in submitting their proposal. The Port Orford community demonstrated great marine resource stewardship and a forward‐minded approach to conservation and sustainability for their living marine resources in putting together their submission. Finally, the goal of this paper is to present the lessons learned in the form of a proposed template for communities and fisheries managers to follow in the proposal and implementation process of designating and establishing marine reserves and marine protected areas both locally and nationally. It is my hope that such a proposal could be used to standardize a national approach to designation and implementation across Regional Fishery Management Councils (RFMCs) and their associated regional marine ecosystems within the United States. Title: Marine Reserves and Marine Protected Areas: A Case Study in Oregon and a Proposed National Model for Design and Implementation Author: Perry, Alex In this report, I examine the process of establishing marine reserves and marine protected areas both from a national and a state perspective. In order to do so, I have investigated the implementation process currently underway in Oregon. Specifically, I have chosen to perform a case study of the process at Redfish Rocks Marine Reserve and Marine Protected Area. I chose this example because of the commendable approach taken by the community of Port Orford in proposing their site and performing extensive baseline data collection in submitting their proposal. The Port Orford community demonstrated great marine resource stewardship and a forward‐minded approach to conservation and sustainability for their living marine resources in putting together their submission. Finally, the goal of this paper is to present the lessons learned in the form of a proposed template for communities and fisheries managers to follow in the proposal and implementation process of designating and establishing marine reserves and marine protected areas both locally and nationally. It is my hope that such a proposal could be used to standardize a national approach to designation and implementation across Regional Fishery Management Councils (RFMCs) and their associated regional marine ecosystems within the United States. Close

• 3. [Article] Foraging behavior of the Pacific harbor seal (Phoca vitulina richardii) in the Pacific Northwest and potential impacts of coastal hypoxia on foraging efficiency

  In the last decade, the California Current Large Marine Ecosystem has experienced a trend of increased severity of upwelling-driven coastal hypoxia. This thesis strove to examine the potential upper trophic ...

  Citation × Citation Citation Abstract Copy Title: Foraging behavior of the Pacific harbor seal (Phoca vitulina richardii) in the Pacific Northwest and potential impacts of coastal hypoxia on foraging efficiency Author: Steingass, Sheanna M. In the last decade, the California Current Large Marine Ecosystem has experienced a trend of increased severity of upwelling-driven coastal hypoxia. This thesis strove to examine the potential upper trophic level impacts of moderate and severe hypoxia in the CCLME. Initially I conducted a literature review of Pacific harbor seal (Phoca vitulina richardii) diet in the regions of Oregon and Washington. Thirteen papers were reviewed which detailed harbor seal foraging studies in Washington, Oregon and the Columbia River from 1931 until 2012. 148 prey species or genera were described in harbor seal diet in Oregon, Washington and the Columbia River. Accordingly, I created energetic individual-based models of harbor seal spatial foraging behavior in response to hypoxia-related habitat compression for three predominant prey species, Pacific herring (Clupea pallasii), English sole (Parophyrs vetulus) and Pacific sandlance (Ammodytes hexapterus). The model was composed of three submodels which simulated hypoxia and spatial foraging, foraging energetics, and dive mechanics. Hypoxia was scaled from 0 to a level of 1, which represented a severe inner-shelf hypoxic or anoxic event in which up to 80% of the inner shelf water column was hypoxic, and species lost 50% of their horizontal habitat. Response variables were also evaluated at the intermediate hypoxia levels of 0.25 and 0.75. A sensitivity analysis was conducted to illuminate which predictor variables drove a variety of response variables. Hypoxia strongly drove energetic balance, travel cost to foraging and time spent foraging at depth for all three prey species. Model output was not highly sensitive to caloric content of prey. For smaller harbor seals, energetic gains were maximized by foraging on Pacific herring or sandlance during normoxia, and sandlance during severe hypoxia. Larger adult harbor seals benefitted most from a herring- or sole-based diet during normoxia, herring and sandlance during moderate to severe hypoxia. The results suggest that shifts in spatial foraging behaviors during hypoxia may be readily apparent upon spatial analysis of TDR data. The information gathered in this thesis will be used in the experimental design of a field-based study of the effects of coastal hypoxia on harbor seal foraging behavior. Title: Foraging behavior of the Pacific harbor seal (Phoca vitulina richardii) in the Pacific Northwest and potential impacts of coastal hypoxia on foraging efficiency Author: Steingass, Sheanna M. In the last decade, the California Current Large Marine Ecosystem has experienced a trend of increased severity of upwelling-driven coastal hypoxia. This thesis strove to examine the potential upper trophic level impacts of moderate and severe hypoxia in the CCLME. Initially I conducted a literature review of Pacific harbor seal (Phoca vitulina richardii) diet in the regions of Oregon and Washington. Thirteen papers were reviewed which detailed harbor seal foraging studies in Washington, Oregon and the Columbia River from 1931 until 2012. 148 prey species or genera were described in harbor seal diet in Oregon, Washington and the Columbia River. Accordingly, I created energetic individual-based models of harbor seal spatial foraging behavior in response to hypoxia-related habitat compression for three predominant prey species, Pacific herring (Clupea pallasii), English sole (Parophyrs vetulus) and Pacific sandlance (Ammodytes hexapterus). The model was composed of three submodels which simulated hypoxia and spatial foraging, foraging energetics, and dive mechanics. Hypoxia was scaled from 0 to a level of 1, which represented a severe inner-shelf hypoxic or anoxic event in which up to 80% of the inner shelf water column was hypoxic, and species lost 50% of their horizontal habitat. Response variables were also evaluated at the intermediate hypoxia levels of 0.25 and 0.75. A sensitivity analysis was conducted to illuminate which predictor variables drove a variety of response variables. Hypoxia strongly drove energetic balance, travel cost to foraging and time spent foraging at depth for all three prey species. Model output was not highly sensitive to caloric content of prey. For smaller harbor seals, energetic gains were maximized by foraging on Pacific herring or sandlance during normoxia, and sandlance during severe hypoxia. Larger adult harbor seals benefitted most from a herring- or sole-based diet during normoxia, herring and sandlance during moderate to severe hypoxia. The results suggest that shifts in spatial foraging behaviors during hypoxia may be readily apparent upon spatial analysis of TDR data. The information gathered in this thesis will be used in the experimental design of a field-based study of the effects of coastal hypoxia on harbor seal foraging behavior. Close

• 4. [Article] Specific consensus statement on the likely impacts of climate change on the Pacific Northwest

  The signatories of this statement seek to describe the state of scientific knowledge regarding likely impacts of climate change to the Pacific Northwest region. The intent is to assist Governor Kulongoski’s ...

  Citation × Citation Citation Abstract Copy Title: Specific consensus statement on the likely impacts of climate change on the Pacific Northwest The signatories of this statement seek to describe the state of scientific knowledge regarding likely impacts of climate change to the Pacific Northwest region. The intent is to assist Governor Kulongoski’s Advisory Group on Global Warming in its task of developing a greenhouse gas emission reduction strategy for Oregon. The signatories agree that climate change is underway and that it is having global effects as well as impacts in the Pacific Northwest region. Title: Specific consensus statement on the likely impacts of climate change on the Pacific Northwest The signatories of this statement seek to describe the state of scientific knowledge regarding likely impacts of climate change to the Pacific Northwest region. The intent is to assist Governor Kulongoski’s Advisory Group on Global Warming in its task of developing a greenhouse gas emission reduction strategy for Oregon. The signatories agree that climate change is underway and that it is having global effects as well as impacts in the Pacific Northwest region. Close

• 5. [Article] Ecological subsidies to rocky intertidal communities: Linear or non-linear changes along a consistent geographic upwelling transition?

  This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-experimental-marine-biology-and-ecology/. To the best ...

  Citation × Citation Citation Abstract Copy Title: Ecological subsidies to rocky intertidal communities: Linear or non-linear changes along a consistent geographic upwelling transition? Author: Menge, Bruce A., Nielsen, Karina J., Chan, Francis, Lubchenco, Jane, Freidenburg, Tess L., Krenz, Christopher, Foley, Melissa M. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-experimental-marine-biology-and-ecology/. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Title: Ecological subsidies to rocky intertidal communities: Linear or non-linear changes along a consistent geographic upwelling transition? Author: Menge, Bruce A., Nielsen, Karina J., Chan, Francis, Lubchenco, Jane, Freidenburg, Tess L., Krenz, Christopher, Foley, Melissa M. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-experimental-marine-biology-and-ecology/. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Close

• 6. [Article] Surfgrasses (Phyllospadix spp.) as dynamic foundation species for macroinvertebrates along the Oregon coast

  Foundation species are important components of ecosystems because they provide habitat and ameliorate stressful conditions for residents. This thesis considers the role of surfgrasses (Phyllospadix spp.) ...

  Citation × Citation Citation Abstract Copy Title: Surfgrasses (Phyllospadix spp.) as dynamic foundation species for macroinvertebrates along the Oregon coast Author: Moulton, Orissa M. Foundation species are important components of ecosystems because they provide habitat and ameliorate stressful conditions for residents. This thesis considers the role of surfgrasses (Phyllospadix spp.) as dynamic foundation species on the coast of Oregon in two studies. Chapter 2, which presents an observational survey of two Phyllospadix congeners, investigates the ways in which surfgrass morphology and observed oceanographic conditions influence associated macroinvertebrate communities throughout a calendar year. Chapter 3, which presents an experimental manipulation of the system, considers the ways in which macroinvertebrates and surfgrass interact. Surfgrasses (Phyllospadix spp.) are ubiquitous foundation species on the coast of Oregon, USA, protecting resident invertebrates from waves and providing them access to sandy substrate in an otherwise rocky habitat. We investigated whether native congeneric species function similarly by comparing the two species' resident macroinvertebrates, plant morphology, and sediment accretion at three capes that vary in oceanographic conditions. The results showed that while the macroinvertebrate abundance was the same between surfgrass species, species richness, composition, and functional groups varied considerably. P. serrulatus also had fewer tillers, rhizomes, and lower biomass per given area but greater sediment accretion than its congener P. scouleri. There was a large difference in macroinvertebrate abundance among capes, with Cape Perpetua having 2.5-3 times more animals per given area than Cape Foulweather or Cape Blanco. Overall, we found that while the two co-occurring surfgrass congeners provided functionally different habitat for resident macroinvertebrate species, regional oceanographic processes (upwelling, productivity) were more influential in determining the overall abundance and productivity of these highly diverse animal communities. The interaction between surfgrass (P. scouleri) and resident macroinvertebrates may be an example of mutual facilitation if surfgrass provides shelter and macroinvertebrate residents reciprocate with nutrient input. We hypothesized that this positive interaction could vary depending on oceanographic conditions. Sites with intermittent upwelling, low retention of upwelled waters, and high nutrient delivery to the intertidal are often dominated by macroalgae and seagrasses, while sessile invertebrates dominate intermittent upwelling sites with high water higher retention and relatively low nutrient delivery to the intertidal. We expected the positive influence of macroinvertebrates upon surfgrass to be strongest at a site with possible nutrient limitation stress. We used manipulative field experiments to examine the interaction between Phyllospadix and macroinvertebrate residents at sites known to differ in coastal oceanography. Treatments were applied in situ to vary presence/absence of residents and nutrient conditions. Results indicate that the community of macroinvertebrates varies greatly in both abundance and composition between the two sites (ca. three fold higher abundance at Strawberry Hill than at Fogarty Creek), but the amount Phyllospadix habitat available to macroinvertebrates does not vary between the two sites. This variation is therefore driven by something external to local habitat, and is likely related to regional oceanography. Furthermore, there is some evidence that macroinvertebrates do have some positive nutrient effect upon surfgrass productivity. Together, these studies provide critical descriptive information about community structure associated with the Phyllospadix system on the Oregon coast. This work contributes to the ever-increasing body of literature suggesting importance of regional oceanography in structuring coastal communities. Title: Surfgrasses (Phyllospadix spp.) as dynamic foundation species for macroinvertebrates along the Oregon coast Author: Moulton, Orissa M. Foundation species are important components of ecosystems because they provide habitat and ameliorate stressful conditions for residents. This thesis considers the role of surfgrasses (Phyllospadix spp.) as dynamic foundation species on the coast of Oregon in two studies. Chapter 2, which presents an observational survey of two Phyllospadix congeners, investigates the ways in which surfgrass morphology and observed oceanographic conditions influence associated macroinvertebrate communities throughout a calendar year. Chapter 3, which presents an experimental manipulation of the system, considers the ways in which macroinvertebrates and surfgrass interact. Surfgrasses (Phyllospadix spp.) are ubiquitous foundation species on the coast of Oregon, USA, protecting resident invertebrates from waves and providing them access to sandy substrate in an otherwise rocky habitat. We investigated whether native congeneric species function similarly by comparing the two species' resident macroinvertebrates, plant morphology, and sediment accretion at three capes that vary in oceanographic conditions. The results showed that while the macroinvertebrate abundance was the same between surfgrass species, species richness, composition, and functional groups varied considerably. P. serrulatus also had fewer tillers, rhizomes, and lower biomass per given area but greater sediment accretion than its congener P. scouleri. There was a large difference in macroinvertebrate abundance among capes, with Cape Perpetua having 2.5-3 times more animals per given area than Cape Foulweather or Cape Blanco. Overall, we found that while the two co-occurring surfgrass congeners provided functionally different habitat for resident macroinvertebrate species, regional oceanographic processes (upwelling, productivity) were more influential in determining the overall abundance and productivity of these highly diverse animal communities. The interaction between surfgrass (P. scouleri) and resident macroinvertebrates may be an example of mutual facilitation if surfgrass provides shelter and macroinvertebrate residents reciprocate with nutrient input. We hypothesized that this positive interaction could vary depending on oceanographic conditions. Sites with intermittent upwelling, low retention of upwelled waters, and high nutrient delivery to the intertidal are often dominated by macroalgae and seagrasses, while sessile invertebrates dominate intermittent upwelling sites with high water higher retention and relatively low nutrient delivery to the intertidal. We expected the positive influence of macroinvertebrates upon surfgrass to be strongest at a site with possible nutrient limitation stress. We used manipulative field experiments to examine the interaction between Phyllospadix and macroinvertebrate residents at sites known to differ in coastal oceanography. Treatments were applied in situ to vary presence/absence of residents and nutrient conditions. Results indicate that the community of macroinvertebrates varies greatly in both abundance and composition between the two sites (ca. three fold higher abundance at Strawberry Hill than at Fogarty Creek), but the amount Phyllospadix habitat available to macroinvertebrates does not vary between the two sites. This variation is therefore driven by something external to local habitat, and is likely related to regional oceanography. Furthermore, there is some evidence that macroinvertebrates do have some positive nutrient effect upon surfgrass productivity. Together, these studies provide critical descriptive information about community structure associated with the Phyllospadix system on the Oregon coast. This work contributes to the ever-increasing body of literature suggesting importance of regional oceanography in structuring coastal communities. Close

• 7. [Article] Where's the ground surface? Elevation bias in LIDAR-derived digital elevation models due to dense vegetation in Oregon tidal marshes

  Light Detection and Ranging (LIDAR) is a powerful resource for coastal and wetland managers and its use is increasing. Vegetation density and other land cover characteristics influence the accuracy of ...

  Citation × Citation Citation Abstract Copy Title: Where's the ground surface? Elevation bias in LIDAR-derived digital elevation models due to dense vegetation in Oregon tidal marshes Author: Ewald, Michael J. Light Detection and Ranging (LIDAR) is a powerful resource for coastal and wetland managers and its use is increasing. Vegetation density and other land cover characteristics influence the accuracy of LIDAR-derived ground surface digital elevation models; however, the degree to which wetland land cover biases LIDAR estimates of the ground surface is largely unknown. The minimum-bin LIDAR gridding technique has been proposed as a way to mitigate dense vegetation interference to generate LIDAR-derived digital elevation models (DEM). Past research has focused on the ability to resolve the marsh plain elevation and only limited research has investigated the overall DEM accuracy across the landscape using a wide range of cell sizes and land cover classes. I compared LIDAR-derived DEM accuracy across a 174 ha tidal wetland restoration site with a mix of native wetland and non-native agricultural pasture species. I found an optimum cell size of 1.4 m (1.96 m²) with a mean positive bias of 4.5 cm and a mean absolute error of 24.3 cm. At cell sizes smaller than the optimum, vegetation interferes with the LIDAR sensor and positively biases DEM models. At cell sizes larger than 1.4 m, the DEM captures and favors low features within the landscape, such as channels and ditches, which thereby degrade overall DEM performance. In addition, I investigated LIDAR interference by twelve common tidal wetland vegetation associations across six Oregon estuaries, using survey-grade Global Positioning System (GPS) measurements of the wetland surface and quantitative vegetation data (percent cover by species) for each measurement location. The fundamental vertical accuracy (FVA) of the LIDAR datasets was 4.5 cm root mean square error (RMSE) and had no consistent positive or negative bias in open landcover. Within wetland vegetation communities, my results suggest that LIDAR estimates of the ground surface in tidal wetlands are typically 10 cm to 30 cm above GPS measurements. Plant associations dominated by Carex obnupta and Carex lyngbyei exhibited the largest discrepancy between LIDAR and GPS measurements (mean discrepancies 36.6 cm and 48.8 cm respectively). The smallest errors observed in the study were about 10 cm to 11 cm and occurred in several different plant associations, including two low tidal marsh associations dominated by a mixture of Deschampsia cespitosa, Distichlis spicata, Sarcocornia perennis and Jaumea carnosa. These results suggest that the minimum-bin gridding technique for LIDAR may mitigate vegetation interference by densely vegetated land covers within LIDAR-derived DEM. However, care should be taken to select an appropriate cell size and validate the results before relying on the DEM for analysis. My research yields new information for coastal LIDAR users and increases our understanding of uncertainty in LIDAR-derived datasets to improve the ability to accurately evaluate and manage coastal environments. Title: Where's the ground surface? Elevation bias in LIDAR-derived digital elevation models due to dense vegetation in Oregon tidal marshes Author: Ewald, Michael J. Light Detection and Ranging (LIDAR) is a powerful resource for coastal and wetland managers and its use is increasing. Vegetation density and other land cover characteristics influence the accuracy of LIDAR-derived ground surface digital elevation models; however, the degree to which wetland land cover biases LIDAR estimates of the ground surface is largely unknown. The minimum-bin LIDAR gridding technique has been proposed as a way to mitigate dense vegetation interference to generate LIDAR-derived digital elevation models (DEM). Past research has focused on the ability to resolve the marsh plain elevation and only limited research has investigated the overall DEM accuracy across the landscape using a wide range of cell sizes and land cover classes. I compared LIDAR-derived DEM accuracy across a 174 ha tidal wetland restoration site with a mix of native wetland and non-native agricultural pasture species. I found an optimum cell size of 1.4 m (1.96 m²) with a mean positive bias of 4.5 cm and a mean absolute error of 24.3 cm. At cell sizes smaller than the optimum, vegetation interferes with the LIDAR sensor and positively biases DEM models. At cell sizes larger than 1.4 m, the DEM captures and favors low features within the landscape, such as channels and ditches, which thereby degrade overall DEM performance. In addition, I investigated LIDAR interference by twelve common tidal wetland vegetation associations across six Oregon estuaries, using survey-grade Global Positioning System (GPS) measurements of the wetland surface and quantitative vegetation data (percent cover by species) for each measurement location. The fundamental vertical accuracy (FVA) of the LIDAR datasets was 4.5 cm root mean square error (RMSE) and had no consistent positive or negative bias in open landcover. Within wetland vegetation communities, my results suggest that LIDAR estimates of the ground surface in tidal wetlands are typically 10 cm to 30 cm above GPS measurements. Plant associations dominated by Carex obnupta and Carex lyngbyei exhibited the largest discrepancy between LIDAR and GPS measurements (mean discrepancies 36.6 cm and 48.8 cm respectively). The smallest errors observed in the study were about 10 cm to 11 cm and occurred in several different plant associations, including two low tidal marsh associations dominated by a mixture of Deschampsia cespitosa, Distichlis spicata, Sarcocornia perennis and Jaumea carnosa. These results suggest that the minimum-bin gridding technique for LIDAR may mitigate vegetation interference by densely vegetated land covers within LIDAR-derived DEM. However, care should be taken to select an appropriate cell size and validate the results before relying on the DEM for analysis. My research yields new information for coastal LIDAR users and increases our understanding of uncertainty in LIDAR-derived datasets to improve the ability to accurately evaluate and manage coastal environments. Close