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• 1. [Article] Evaluating spatial patterns of drought-induced tree mortality in a coastal California pine forest

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-a...

  Citation × Citation Citation Abstract Copy Title: Evaluating spatial patterns of drought-induced tree mortality in a coastal California pine forest Author: Baguskas, Sara A., Still, Christopher J., Bookhagen, Bodo, Peterson, Seth H. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-and-management/. Title: Evaluating spatial patterns of drought-induced tree mortality in a coastal California pine forest Author: Baguskas, Sara A., Still, Christopher J., Bookhagen, Bodo, Peterson, Seth H. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-and-management/. Close

• 2. [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

• 3. [Article] Beaver ecology on the west Copper River Delta, Alaska

  Since the 1964 earthquake and geologic uplift, beavers (Castor canadensis) have expanded their historic range from the inland (outwash plain) Copper River Delta, Alaska to the once tidally influenced ...

  Citation × Citation Citation Abstract Copy Title: Beaver ecology on the west Copper River Delta, Alaska Author: Cooper, Erin E. Since the 1964 earthquake and geologic uplift, beavers (Castor canadensis) have expanded their historic range from the inland (outwash plain) Copper River Delta, Alaska to the once tidally influenced areas of the outer area (uplifted marsh). The uplift presents a unique opportunity to observe beaver expansion, habitat selection and influence on hydrologic structure of a coastal wetland ecosystem after a major disturbance. First, I examined the relationship between the sites of active beaver lodges and associated water and vegetative features (Chapter 2). I hypothesized that active lodge sites would be associated with distinct water features and woody vegetation types in each landscape. I used aerial photographic and ground survey methods to compare sightability and to determine habitat associations. I developed an a priori set of models to determine active beaver lodge occurrence using logistic regression with presence and absence as the response variables and water features and vegetation cover as the dependent variables. My results were similar between survey methods but differed between the two major landscape types. In the uplifted marsh, odds of an active lodge occurrance increased with the presence of former tidal sloughs and an increase in mixed shrub coverage. The odds of an active lodge occurrence increased with the presence of streams and decreased with increasing closed cottonwood-alder-willow coverage in the outwash plain. Post earthquake uplift, beaver now exploit a unique topographic setting through the use and modification of former tidal sloughs and a transitioning mixed shrub vegetation community. Second, I quantified the influence of beaver on the surface water of the West Copper River Delta using remote sensing (Chapter 3). Water features were documented from digitized aerial photographs from 1959, 1974, 1986, 1992/1993, and 1996. My results showed that surface water area in beaver influenced water impoundments increased from 0 to 20% from 1959 to 1996, concurrent with beaver colonization of the uplifted marsh. These results suggest that beavers may have altered the trajectory of wetland change on the West Copper River Delta by raising the water table within open water basins and flooding those areas that would have otherwise drained. Beaver may be used an effective management tool in wetland restoration where key habitat features are available. Title: Beaver ecology on the west Copper River Delta, Alaska Author: Cooper, Erin E. Since the 1964 earthquake and geologic uplift, beavers (Castor canadensis) have expanded their historic range from the inland (outwash plain) Copper River Delta, Alaska to the once tidally influenced areas of the outer area (uplifted marsh). The uplift presents a unique opportunity to observe beaver expansion, habitat selection and influence on hydrologic structure of a coastal wetland ecosystem after a major disturbance. First, I examined the relationship between the sites of active beaver lodges and associated water and vegetative features (Chapter 2). I hypothesized that active lodge sites would be associated with distinct water features and woody vegetation types in each landscape. I used aerial photographic and ground survey methods to compare sightability and to determine habitat associations. I developed an a priori set of models to determine active beaver lodge occurrence using logistic regression with presence and absence as the response variables and water features and vegetation cover as the dependent variables. My results were similar between survey methods but differed between the two major landscape types. In the uplifted marsh, odds of an active lodge occurrance increased with the presence of former tidal sloughs and an increase in mixed shrub coverage. The odds of an active lodge occurrence increased with the presence of streams and decreased with increasing closed cottonwood-alder-willow coverage in the outwash plain. Post earthquake uplift, beaver now exploit a unique topographic setting through the use and modification of former tidal sloughs and a transitioning mixed shrub vegetation community. Second, I quantified the influence of beaver on the surface water of the West Copper River Delta using remote sensing (Chapter 3). Water features were documented from digitized aerial photographs from 1959, 1974, 1986, 1992/1993, and 1996. My results showed that surface water area in beaver influenced water impoundments increased from 0 to 20% from 1959 to 1996, concurrent with beaver colonization of the uplifted marsh. These results suggest that beavers may have altered the trajectory of wetland change on the West Copper River Delta by raising the water table within open water basins and flooding those areas that would have otherwise drained. Beaver may be used an effective management tool in wetland restoration where key habitat features are available. Close