Christian E Torgersen
I am a Supervisory Research Landscape Ecologist at the Forest and Rangeland Ecosystem Science Center
My research interests include landscape ecology, riverine landscapes, watershed processes, ecological scaling, water quality, fish habitat, land use/land cover change, landscape scenario modeling, spatial analysis, remote sensing and GIS.
Professional Experience
2005 - Present: USGS Forest and Rangeland Ecosystem Science Center, Supervisory Research Landscape Ecologist, Seattle, WA
2002 - 2005: USGS Forest and Rangeland Ecosystem Science Center, Research Biologist, Corvallis, OR
Education and Certifications
Ph.D., Fisheries Science, Oregon State University, Corvallis, OR (2002)
M.S., Fisheries Science, Geography Minor, Oregon State University, Corvallis, OR (1996)
B.A., Geography/German, double major, University of Oregon, Eugene, OR (1993)
Science and Products
Aquatic & Landscape Ecology Research Team (FRESC)
Fresh waters are one of the most valuable and threatened resources worldwide. They supply critical services to society and harbor many of the world’s most imperiled species. We conduct research and provide technical assistance to address challenges to fresh waters. Our research focuses on ecological processes in freshwater and terrestrial systems and the effects of those processes on landscape...
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
Filter Total Items: 60
Spatial variability of Chinook salmon spawning distribution and habitat preferences
We investigated physical habitat conditions associated with the spawning sites of Chinook Salmon Oncorhynchus tshawytscha and the interannual consistency of spawning distribution across multiple spatial scales using a combination of spatially continuous and discrete sampling methods. We conducted a census of aquatic habitat in 76 km of the upper main-stem Yakima River in Washington and evaluated s
Authors
Jeremy M. Cram, Christian E. Torgersen, Ryan S. Klett, George R. Pess, Darran May, Todd N. Pearsons, Andrew H. Dittman
Spatially intensive sampling by electrofishing for assessing longitudinal discontinuities in fish distribution in a headwater stream
Spatially intensive sampling by electrofishing is proposed as a method for quantifying spatial variation in fish assemblages at multiple scales along extensive stream sections in headwater catchments. We used this method to sample fish species at 10-m2 points spaced every 20 m throughout 5 km of a headwater stream in France. The spatially intensive sampling design provided information at a spatial
Authors
Céline Le Pichon, Évelyne Tales, Jérôme Belliard, Christian E. Torgersen
Dendritic network models: Improving isoscapes and quantifying influence of landscape and in-stream processes on strontium isotopes in rivers
A critical challenge for the Earth sciences is to trace the transport and flux of matter within and among aquatic, terrestrial, and atmospheric systems. Robust descriptions of isotopic patterns across space and time, called “isoscapes,” form the basis of a rapidly growing and wide-ranging body of research aimed at quantifying connectivity within and among Earth's systems. However, isoscapes of riv
Authors
Sean R. Brennan, Christian E. Torgersen, Jeff P. Hollenbeck, Diego P. Fernandez, Carrie K Jensen, Daniel E. Schindler
Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages, distribution, and habitat associations
We compared the assemblage structure, spatial distributions, and habitat associations of mountain whitefish (Prosopium williamsoni) morphotypes and size classes. We hypothesised that morphotypes would have different spatial distributions and would be associated with different habitat features based on feeding behaviour and diet. Spatially continuous sampling was conducted over a broad extent (29 k
Authors
James C. Starr, Christian E. Torgersen
Rethinking the longitudinal stream temperature paradigm: region-wide comparison of thermal infrared imagery reveals unexpected complexity of river temperatures
Prevailing theory suggests that stream temperature warms asymptotically in a downstream direction, beginning at the temperature of the source in the headwaters and leveling off downstream as it converges to match meteorological conditions. However, there have been few empirical examples of longitudinal patterns of temperature in large rivers due to a paucity of data. We constructed longitudinal th
Authors
Aimee H. Fullerton, Christian E. Torgersen, Joshua J. Lawler, Russell N. Faux, E. Ashley Steel, Timothy J. Beechie, Joseph L. Ebersole, Scott J. Leibowitz
Multiscale analysis of river networks using the R package linbin
Analytical tools are needed in riverine science and management to bridge the gap between GIS and statistical packages that were not designed for the directional and dendritic structure of streams. We introduce linbin, an R package developed for the analysis of riverscapes at multiple scales. With this software, riverine data on aquatic habitat and species distribution can be scaled and plotted aut
Authors
Ethan Z. Welty, Christian E. Torgersen, Samuel J. Brenkman, Jeffrey J. Duda, Jonathan B. Armstrong
Hydrologic response to valley-scale structure in alpine headwaters
Few systematic studies of valley-scale geomorphic drivers of streamflow regimes in complex alpine headwaters have compared response between catchments. As a result, little guidance is available for regional-scale hydrological research and monitoring efforts that include assessments of ecosystem function. Physical parameters such as slope, elevation range, drainage area and bedrock geology are ofte
Authors
Anne A. Weekes, Christian E. Torgersen, David R. Montgomery, Andrea Woodward, Susan M. Bolton
Applications of spatial statistical network models to stream data
Streams and rivers host a significant portion of Earth's biodiversity and provide important ecosystem services for human populations. Accurate information regarding the status and trends of stream resources is vital for their effective conservation and management. Most statistical techniques applied to data measured on stream networks were developed for terrestrial applications and are not optimiz
Authors
Daniel J. Isaak, Erin E. Peterson, Jay M. Ver Hoef, Seth J. Wenger, Jeffrey A. Falke, Christian E. Torgersen, Colin Sowder, E. Ashley Steel, Marie-Josée Fortin, Chris E. Jordan, Aaron S. Ruesch, Nicholas Som, Pascal Monestiez
Network analysis reveals multiscale controls on streamwater chemistry
By coupling synoptic data from a basin-wide assessment of streamwater chemistry with network-based geostatistical analysis, we show that spatial processes differentially affect biogeochemical condition and pattern across a headwater stream network. We analyzed a high-resolution dataset consisting of 664 water samples collected every 100 m throughout 32 tributaries in an entire fifth-order stream n
Authors
Kevin J. McGuire, Christian E. Torgersen, Gene E. Likens, Donald C. Buso, Winsor H. Lowe, Scott W. Bailey
The interactive effects of climate change, riparian management, and a non-native predators on stream-rearing salmon
Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use related reductions in riparian shading have caused changes in stream thermal regimes, and add
Authors
David J. Lawrence, Ben Stewart-Koster, Julian D. Olden, Aaron S. Ruesch, Christian E. Torgersen, Joshua J. Lawler, Don P. Butcher, Julia K. Crown
Diel horizontal migration in streams: juvenile fish exploit spatial heterogeneity in thermal and trophic resources
Vertical heterogeneity in the physical characteristics of lakes and oceans is ecologically salient and exploited by a wide range of taxa through diel vertical migration to enhance their growth and survival. Whether analogous behaviors exploit horizontal habitat heterogeneity in streams is largely unknown. We investigated fish movement behavior at daily timescales to explore how individuals integra
Authors
Jonathan B. Armstrong, Daniel E. Schindler, Casey P. Ruff, Gabriel T. Brooks, Kale E. Bentley, Christian E. Torgersen
Aquatic insect assemblages associated with subalpine stream segment types in relict glaciated headwaters
1. Aquatic habitats and biotic assemblages in subalpine headwaters are sensitive to climate and human impacts. Understanding biotic responses to such perturbations and the contribution of high-elevation headwaters to riverine biodiversity requires the assessment of assemblage composition among habitat types. We compared aquatic insect assemblages among headwater stream segment types in relict glac
Authors
Joshua S. Kubo, Christian E. Torgersen, Susan M. Bolton, Anne A. Weekes, Robert I. Gara
Non-USGS Publications**
Torgersen, C.E., Close, D.A., 2004, Influence of habitat heterogeneity on the distribution of larval Pacific lamprey (Lampetra tridentata) at two spatial scales: Freshwater Biology, v. 49, no. 5, p. 614-630.
Fausch, K.D., Torgersen, C.E., Baxter, C.V., Li, H.W., 2002, Landscapes to riverscapes- bridging the gap between research and conservation of stream fishes: BioScience, v. 52, no. 6, p. 483-498.
Torgersen, C.E., Faux, R.N., McIntosh, B.A., Poage, N., Norton, D.J., 2001, Airborne thermal remote sensing for water temperature assessment in rivers and streams: Remote Sensing of Environment, v. 76, p. 386-398.
Torgersen, C.E., Price, D.M., Li, H.W., McIntosh, B.A., 1999, Multiscale thermal refugia and stream habitat associations of chinook salmon in northwestern Oregon: Ecological Applications, v. 9, no. 1, p. 301-319, https://doi.org/10.1890/1051-0761(1999)009[0301:MTRASH]2.0.CO;2.
Torgersen, C.E., Poage, N., Flood, M., Norton, D.J., McIntosh, B.A., 1996, Airborne thermal remote sensing of salmonid habitat for restoration planning in Pacific Northwestern watersheds, Baltimore, MD In eds., Proceedings of the Watershed 96 Conference: Alexandria, VA, Water Environment Federation, p. 812-814.
Poage, N., Torgersen, C.E., Norton, D.J., Flood, M., McIntosh, B.A., 1996, Application of thermal infrared (FLIR) and visible videography to the monitoring and restoration of salmonid habitat in the Pacific Northwest In Greer, J.D., ed., Proceedings of the Sixth Forest Service Remote Sensing Applications Conference: Denver, CO, American Society for Photogrammetry and Remote Sensing, p. 376-379.
Torgersen, C.E., Jones, J.A., Moldenke, A.R., LeMaster, M.P., 1995, The spatial heterogeneity of soil invertebrates and edaphic properties in an old growth forest stand in western Oregon In Collins, H.P., Robertson, G.P., Klug, M.J., eds., The Significance and Regulation of Soil Biodiversity: Dordrecht, Netherlands, Kluwer Academic Publishers, p. 225-236.
Torgersen, C.E., Price, D.M., Li, H.W., McIntosh, B.A., 1995, Thermal refugia and chinook salmon habitat in Oregon- Applications of airborne thermal videography In Mausel, P., ed., Proceedings of the 15th Biennial Workshop on Color Photography and Videography: Terre Haute, IN, American Society for Photogrammetry and Remote Sensing, p. 167-171.
Torgersen, C.E., Baxter, C.V., Li, H., McIntosh, B.A., 2006, Landscape influences on longitudinal patterns of river fishes- Spatially continuous analysis of fish-habitat relationships In Hughes, R., Wang, L., Wofford, J.E., eds., Influences of Landscapes on Stream Habitats and Biological Assemblages: Bethesda, MD, American Fisheries Society, p. 473-492
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
To request an interview, contact fresc_outreach@usgs.gov or call (541) 750-1030.
Science and Products
Aquatic & Landscape Ecology Research Team (FRESC)
Fresh waters are one of the most valuable and threatened resources worldwide. They supply critical services to society and harbor many of the world’s most imperiled species. We conduct research and provide technical assistance to address challenges to fresh waters. Our research focuses on ecological processes in freshwater and terrestrial systems and the effects of those processes on landscape...
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
If you are unable to access or download a product, email fresc_outreach@usgs.gov a request, including the full citation, or call (541) 750-1030.
Filter Total Items: 60
Spatial variability of Chinook salmon spawning distribution and habitat preferences
We investigated physical habitat conditions associated with the spawning sites of Chinook Salmon Oncorhynchus tshawytscha and the interannual consistency of spawning distribution across multiple spatial scales using a combination of spatially continuous and discrete sampling methods. We conducted a census of aquatic habitat in 76 km of the upper main-stem Yakima River in Washington and evaluated s
Authors
Jeremy M. Cram, Christian E. Torgersen, Ryan S. Klett, George R. Pess, Darran May, Todd N. Pearsons, Andrew H. Dittman
Spatially intensive sampling by electrofishing for assessing longitudinal discontinuities in fish distribution in a headwater stream
Spatially intensive sampling by electrofishing is proposed as a method for quantifying spatial variation in fish assemblages at multiple scales along extensive stream sections in headwater catchments. We used this method to sample fish species at 10-m2 points spaced every 20 m throughout 5 km of a headwater stream in France. The spatially intensive sampling design provided information at a spatial
Authors
Céline Le Pichon, Évelyne Tales, Jérôme Belliard, Christian E. Torgersen
Dendritic network models: Improving isoscapes and quantifying influence of landscape and in-stream processes on strontium isotopes in rivers
A critical challenge for the Earth sciences is to trace the transport and flux of matter within and among aquatic, terrestrial, and atmospheric systems. Robust descriptions of isotopic patterns across space and time, called “isoscapes,” form the basis of a rapidly growing and wide-ranging body of research aimed at quantifying connectivity within and among Earth's systems. However, isoscapes of riv
Authors
Sean R. Brennan, Christian E. Torgersen, Jeff P. Hollenbeck, Diego P. Fernandez, Carrie K Jensen, Daniel E. Schindler
Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages, distribution, and habitat associations
We compared the assemblage structure, spatial distributions, and habitat associations of mountain whitefish (Prosopium williamsoni) morphotypes and size classes. We hypothesised that morphotypes would have different spatial distributions and would be associated with different habitat features based on feeding behaviour and diet. Spatially continuous sampling was conducted over a broad extent (29 k
Authors
James C. Starr, Christian E. Torgersen
Rethinking the longitudinal stream temperature paradigm: region-wide comparison of thermal infrared imagery reveals unexpected complexity of river temperatures
Prevailing theory suggests that stream temperature warms asymptotically in a downstream direction, beginning at the temperature of the source in the headwaters and leveling off downstream as it converges to match meteorological conditions. However, there have been few empirical examples of longitudinal patterns of temperature in large rivers due to a paucity of data. We constructed longitudinal th
Authors
Aimee H. Fullerton, Christian E. Torgersen, Joshua J. Lawler, Russell N. Faux, E. Ashley Steel, Timothy J. Beechie, Joseph L. Ebersole, Scott J. Leibowitz
Multiscale analysis of river networks using the R package linbin
Analytical tools are needed in riverine science and management to bridge the gap between GIS and statistical packages that were not designed for the directional and dendritic structure of streams. We introduce linbin, an R package developed for the analysis of riverscapes at multiple scales. With this software, riverine data on aquatic habitat and species distribution can be scaled and plotted aut
Authors
Ethan Z. Welty, Christian E. Torgersen, Samuel J. Brenkman, Jeffrey J. Duda, Jonathan B. Armstrong
Hydrologic response to valley-scale structure in alpine headwaters
Few systematic studies of valley-scale geomorphic drivers of streamflow regimes in complex alpine headwaters have compared response between catchments. As a result, little guidance is available for regional-scale hydrological research and monitoring efforts that include assessments of ecosystem function. Physical parameters such as slope, elevation range, drainage area and bedrock geology are ofte
Authors
Anne A. Weekes, Christian E. Torgersen, David R. Montgomery, Andrea Woodward, Susan M. Bolton
Applications of spatial statistical network models to stream data
Streams and rivers host a significant portion of Earth's biodiversity and provide important ecosystem services for human populations. Accurate information regarding the status and trends of stream resources is vital for their effective conservation and management. Most statistical techniques applied to data measured on stream networks were developed for terrestrial applications and are not optimiz
Authors
Daniel J. Isaak, Erin E. Peterson, Jay M. Ver Hoef, Seth J. Wenger, Jeffrey A. Falke, Christian E. Torgersen, Colin Sowder, E. Ashley Steel, Marie-Josée Fortin, Chris E. Jordan, Aaron S. Ruesch, Nicholas Som, Pascal Monestiez
Network analysis reveals multiscale controls on streamwater chemistry
By coupling synoptic data from a basin-wide assessment of streamwater chemistry with network-based geostatistical analysis, we show that spatial processes differentially affect biogeochemical condition and pattern across a headwater stream network. We analyzed a high-resolution dataset consisting of 664 water samples collected every 100 m throughout 32 tributaries in an entire fifth-order stream n
Authors
Kevin J. McGuire, Christian E. Torgersen, Gene E. Likens, Donald C. Buso, Winsor H. Lowe, Scott W. Bailey
The interactive effects of climate change, riparian management, and a non-native predators on stream-rearing salmon
Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use related reductions in riparian shading have caused changes in stream thermal regimes, and add
Authors
David J. Lawrence, Ben Stewart-Koster, Julian D. Olden, Aaron S. Ruesch, Christian E. Torgersen, Joshua J. Lawler, Don P. Butcher, Julia K. Crown
Diel horizontal migration in streams: juvenile fish exploit spatial heterogeneity in thermal and trophic resources
Vertical heterogeneity in the physical characteristics of lakes and oceans is ecologically salient and exploited by a wide range of taxa through diel vertical migration to enhance their growth and survival. Whether analogous behaviors exploit horizontal habitat heterogeneity in streams is largely unknown. We investigated fish movement behavior at daily timescales to explore how individuals integra
Authors
Jonathan B. Armstrong, Daniel E. Schindler, Casey P. Ruff, Gabriel T. Brooks, Kale E. Bentley, Christian E. Torgersen
Aquatic insect assemblages associated with subalpine stream segment types in relict glaciated headwaters
1. Aquatic habitats and biotic assemblages in subalpine headwaters are sensitive to climate and human impacts. Understanding biotic responses to such perturbations and the contribution of high-elevation headwaters to riverine biodiversity requires the assessment of assemblage composition among habitat types. We compared aquatic insect assemblages among headwater stream segment types in relict glac
Authors
Joshua S. Kubo, Christian E. Torgersen, Susan M. Bolton, Anne A. Weekes, Robert I. Gara
Non-USGS Publications**
Torgersen, C.E., Close, D.A., 2004, Influence of habitat heterogeneity on the distribution of larval Pacific lamprey (Lampetra tridentata) at two spatial scales: Freshwater Biology, v. 49, no. 5, p. 614-630.
Fausch, K.D., Torgersen, C.E., Baxter, C.V., Li, H.W., 2002, Landscapes to riverscapes- bridging the gap between research and conservation of stream fishes: BioScience, v. 52, no. 6, p. 483-498.
Torgersen, C.E., Faux, R.N., McIntosh, B.A., Poage, N., Norton, D.J., 2001, Airborne thermal remote sensing for water temperature assessment in rivers and streams: Remote Sensing of Environment, v. 76, p. 386-398.
Torgersen, C.E., Price, D.M., Li, H.W., McIntosh, B.A., 1999, Multiscale thermal refugia and stream habitat associations of chinook salmon in northwestern Oregon: Ecological Applications, v. 9, no. 1, p. 301-319, https://doi.org/10.1890/1051-0761(1999)009[0301:MTRASH]2.0.CO;2.
Torgersen, C.E., Poage, N., Flood, M., Norton, D.J., McIntosh, B.A., 1996, Airborne thermal remote sensing of salmonid habitat for restoration planning in Pacific Northwestern watersheds, Baltimore, MD In eds., Proceedings of the Watershed 96 Conference: Alexandria, VA, Water Environment Federation, p. 812-814.
Poage, N., Torgersen, C.E., Norton, D.J., Flood, M., McIntosh, B.A., 1996, Application of thermal infrared (FLIR) and visible videography to the monitoring and restoration of salmonid habitat in the Pacific Northwest In Greer, J.D., ed., Proceedings of the Sixth Forest Service Remote Sensing Applications Conference: Denver, CO, American Society for Photogrammetry and Remote Sensing, p. 376-379.
Torgersen, C.E., Jones, J.A., Moldenke, A.R., LeMaster, M.P., 1995, The spatial heterogeneity of soil invertebrates and edaphic properties in an old growth forest stand in western Oregon In Collins, H.P., Robertson, G.P., Klug, M.J., eds., The Significance and Regulation of Soil Biodiversity: Dordrecht, Netherlands, Kluwer Academic Publishers, p. 225-236.
Torgersen, C.E., Price, D.M., Li, H.W., McIntosh, B.A., 1995, Thermal refugia and chinook salmon habitat in Oregon- Applications of airborne thermal videography In Mausel, P., ed., Proceedings of the 15th Biennial Workshop on Color Photography and Videography: Terre Haute, IN, American Society for Photogrammetry and Remote Sensing, p. 167-171.
Torgersen, C.E., Baxter, C.V., Li, H., McIntosh, B.A., 2006, Landscape influences on longitudinal patterns of river fishes- Spatially continuous analysis of fish-habitat relationships In Hughes, R., Wang, L., Wofford, J.E., eds., Influences of Landscapes on Stream Habitats and Biological Assemblages: Bethesda, MD, American Fisheries Society, p. 473-492
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
To request an interview, contact fresc_outreach@usgs.gov or call (541) 750-1030.