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• 31. [Article] Greater sage-grouse population trends: An analysis of lek count databases 1965-2015

  Counts of males attending leks in the spring have been the primary means employed by states to monitor status of greater sage-grouse (Centrocercus urophansianus) populations for over 75 years. Despite ...

  Citation × Citation Citation Abstract Copy Title: Greater sage-grouse population trends: An analysis of lek count databases 1965-2015 Author: Western Association of Fish and Wildlife Agencies Counts of males attending leks in the spring have been the primary means employed by states to monitor status of greater sage-grouse (Centrocercus urophansianus) populations for over 75 years. Despite limitations and potential biases, lek count data remain the only long-term, range-wide dataset available for evaluating trends in sage-grouse populations. Using lek data provided by each state, we calculated the number of active leks, the average number of males per active lek each year, and modeled trends in male counts using a set of mixed-effects, Bayesian hierarchical models at range-wide, management zone, and state spatial scales for the 1965-2015 period. Trends within high population density core areas were compared to peripheral areas at range-wide and management zone scales. Trend estimates were also modeled at range-wide scales for the most recent 10-year period (2005-2015). Summary statistics on average males per lek indicate large variability in sage-grouse population size over time at all spatial and temporal scales. Our results support previous findings that have documented a long-term (1965-2015) decline of greater sage-grouse range-wide. The long-term (1965-2015) decline in average males per lek was estimated at 0.83% per year range-wide, and 2.7% and 0.5% for Management Zones I and II, and 0.70, 1.38, and 0.06% per year for Management Zones IV, V, and VI, respectively. Management Zone III showed an increasing trend in average males per lek of 0.19% per year. In 5 of 6 management zones, annual decreases were greatest in the periphery, and lower in core areas. This suggests that denser sage- grouse populations located within the core appear to be insulated more readily from population decline than those on the periphery. Modeling indicated positive trends in average males per lek since 1965 in Wyoming, Utah and Idaho, with negative trends in the 8 other sage-grouse states and declines greater than 1% per year in North Dakota, South Dakota, and Montana. The number of males counted on leks range-wide in 2015 (80,284) increased by 63% compared to the number counted in 2013 (43,397), the most recent trough. A minimum breeding population of 424,645 was estimated for 2015, which does not include grouse on unknown leks. Title: Greater sage-grouse population trends: An analysis of lek count databases 1965-2015 Author: Western Association of Fish and Wildlife Agencies Counts of males attending leks in the spring have been the primary means employed by states to monitor status of greater sage-grouse (Centrocercus urophansianus) populations for over 75 years. Despite limitations and potential biases, lek count data remain the only long-term, range-wide dataset available for evaluating trends in sage-grouse populations. Using lek data provided by each state, we calculated the number of active leks, the average number of males per active lek each year, and modeled trends in male counts using a set of mixed-effects, Bayesian hierarchical models at range-wide, management zone, and state spatial scales for the 1965-2015 period. Trends within high population density core areas were compared to peripheral areas at range-wide and management zone scales. Trend estimates were also modeled at range-wide scales for the most recent 10-year period (2005-2015). Summary statistics on average males per lek indicate large variability in sage-grouse population size over time at all spatial and temporal scales. Our results support previous findings that have documented a long-term (1965-2015) decline of greater sage-grouse range-wide. The long-term (1965-2015) decline in average males per lek was estimated at 0.83% per year range-wide, and 2.7% and 0.5% for Management Zones I and II, and 0.70, 1.38, and 0.06% per year for Management Zones IV, V, and VI, respectively. Management Zone III showed an increasing trend in average males per lek of 0.19% per year. In 5 of 6 management zones, annual decreases were greatest in the periphery, and lower in core areas. This suggests that denser sage- grouse populations located within the core appear to be insulated more readily from population decline than those on the periphery. Modeling indicated positive trends in average males per lek since 1965 in Wyoming, Utah and Idaho, with negative trends in the 8 other sage-grouse states and declines greater than 1% per year in North Dakota, South Dakota, and Montana. The number of males counted on leks range-wide in 2015 (80,284) increased by 63% compared to the number counted in 2013 (43,397), the most recent trough. A minimum breeding population of 424,645 was estimated for 2015, which does not include grouse on unknown leks. Close

• 32. [Article] Trends in snow water equivcalent in the Pacific Northwest and their climatic causes

  Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, ...

  Citation × Citation Citation Abstract Copy Title: Trends in snow water equivcalent in the Pacific Northwest and their climatic causes Author: Mote, Philip W. Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, especially below about 1800 m, substantial declines in SWE coincide with significant increases in temperature, and occur in spite of increases in precipitation. Title: Trends in snow water equivcalent in the Pacific Northwest and their climatic causes Author: Mote, Philip W. Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, especially below about 1800 m, substantial declines in SWE coincide with significant increases in temperature, and occur in spite of increases in precipitation. Close

• 33. [Article] Minority student enrollment and graduation trends: a report to the board

  25 pages

  Citation × Citation Citation Abstract Copy Title: Minority student enrollment and graduation trends: a report to the board Author: Payne, James F. 25 pages Title: Minority student enrollment and graduation trends: a report to the board Author: Payne, James F. 25 pages Close

• 34. [Article] Sociological, economic, and biological aspects of the deer hunting activity in Grant County, Oregon

  The specific objectives of the study were to determine the sociological and economic considerations of the private landowners and managers in Grant County, Oregon regarding their tolerances of mule deer ...

  Citation × Citation Citation Abstract Copy Title: Sociological, economic, and biological aspects of the deer hunting activity in Grant County, Oregon Author: Janik, Philip Joseph The specific objectives of the study were to determine the sociological and economic considerations of the private landowners and managers in Grant County, Oregon regarding their tolerances of mule deer (Odocoileus hemionus)and deer hunters on their properties, determine the attitudes of hunters who hunted deer in Grant County in 1973 and compare expectations and desires of hunters and landowners, identify the impact of temperature and snow level trends and hunting regulations on the deer population of the Northside Game Management Unit, and evaluate alternative management schemes regarding deer hunting and the effects of deer hunting activity on the economy. Grant County would have greater potential for an increase in the deer hunting activity if the density of hunters were controlled on public lands and if more private land becomes available for public hunting, Grant County would benefit economically from an increase in deer hunting activity because of increased expenditures by hunters. Private landowners are hesitant to permit public hunting because of damages caused by hunters on their properties. Landowners have also experienced economic losses because of damages caused by deer. Increased access to private land can not be expected unless private landowners are provided incentives to permit public hunting which will compensate for the economic losses resulting from deer and deer hunters on their properties. The Oregon Wildlife Commission appears most influenced by the estimate of trend in the deer population (measured in deer per mile) when determining the number of antlerless deer permits to issue for the hunting season. Change in snow depth for the previous 2 years may have a negative effect on the change in deer per mile from the previous year. The harvesting of antlerless deer may have a positive effect on the trend in the deer population. Inclusion of data on snow and antlerless harvest in the decision process may provide a better measure of the trend in size of the deer population than using only one estimate of population trend. The potential of the deer population to sustain an increased harvest was not determined. The Bayesian decision theory is suggested for use in the decision process of establishing hunting regulations and providing a better measure of whether the deer population could sustain an increased harvest. Title: Sociological, economic, and biological aspects of the deer hunting activity in Grant County, Oregon Author: Janik, Philip Joseph The specific objectives of the study were to determine the sociological and economic considerations of the private landowners and managers in Grant County, Oregon regarding their tolerances of mule deer (Odocoileus hemionus)and deer hunters on their properties, determine the attitudes of hunters who hunted deer in Grant County in 1973 and compare expectations and desires of hunters and landowners, identify the impact of temperature and snow level trends and hunting regulations on the deer population of the Northside Game Management Unit, and evaluate alternative management schemes regarding deer hunting and the effects of deer hunting activity on the economy. Grant County would have greater potential for an increase in the deer hunting activity if the density of hunters were controlled on public lands and if more private land becomes available for public hunting, Grant County would benefit economically from an increase in deer hunting activity because of increased expenditures by hunters. Private landowners are hesitant to permit public hunting because of damages caused by hunters on their properties. Landowners have also experienced economic losses because of damages caused by deer. Increased access to private land can not be expected unless private landowners are provided incentives to permit public hunting which will compensate for the economic losses resulting from deer and deer hunters on their properties. The Oregon Wildlife Commission appears most influenced by the estimate of trend in the deer population (measured in deer per mile) when determining the number of antlerless deer permits to issue for the hunting season. Change in snow depth for the previous 2 years may have a negative effect on the change in deer per mile from the previous year. The harvesting of antlerless deer may have a positive effect on the trend in the deer population. Inclusion of data on snow and antlerless harvest in the decision process may provide a better measure of the trend in size of the deer population than using only one estimate of population trend. The potential of the deer population to sustain an increased harvest was not determined. The Bayesian decision theory is suggested for use in the decision process of establishing hunting regulations and providing a better measure of whether the deer population could sustain an increased harvest. Close

• 35. [Article] Profitability, strategies and competitive position in the aquaculture sector: the Italian case

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Profitability, strategies and competitive position in the aquaculture sector: the Italian case Author: Iandoli, Carla, Alaio, Eugenio Research Paper Title: Profitability, strategies and competitive position in the aquaculture sector: the Italian case Author: Iandoli, Carla, Alaio, Eugenio Research Paper Close

• 36. [Article] Geology of the Clarno Formation in the vicinity of Stephenson Mountain, Jefferson, Crook and Wheeler counties, Oregon

  The thesis area is located in north-central Oregon approximately 20 km west of the town of Mitchell. The rocks exposed in the area belong to the Clarno Formation. This study supports the informal reclassification ...

  Citation × Citation Citation Abstract Copy Title: Geology of the Clarno Formation in the vicinity of Stephenson Mountain, Jefferson, Crook and Wheeler counties, Oregon Author: Stroh, Harold Raymond The thesis area is located in north-central Oregon approximately 20 km west of the town of Mitchell. The rocks exposed in the area belong to the Clarno Formation. This study supports the informal reclassification of the Clarno to Group status, composed of an Upper and Lower Clarno Formation. An angular unconformity separates the two Formations. The Lower Clarno Formation is composed of a lower Ross Flat Member dominated by epiclastic sedimentary rocks and an upper Heflin Creek Member composed primarily of pyroxene andesite lavas. The Upper Clarno Formation consists of two conformable units, a lower Q,uartz-bearing Andesite Unit and an upper Pyroxene Andesite Unit. A thin sequence of rhyolite flows is found near the top of the upper unit. Andesite, dacite and rhyolite rocks intrude the lavas and sediments of the Group. When plotted on a Peacock diagram the Clarno rocks are found to be calcic. The chemical variation diagrams and AFM plot of samples, however, follow talc-alkaline trends and compare favorably with rocks considered to be talc-alkaline by others. Most of the thesis area lies on the southern flank of the east-northeast trending Sutton Mountain Syncline. The northeast trending Mitchell Anticline is found east of the project area and the Lower Clarno rocks follow its' trend. The easterly trending strike-slip Mitchell Fault cuts the northern part of the area. Strata of the area show five kilometers of right-lateral movement along the fault. The angular unconformity separating the formations is found in the eastern part of the area and has been displaced by the Mitchell Fault. The occurrence of andesitic talc-alkaline volcanism near consuming plate margins is well documented and it is possible that the Clarno rocks may be the surface manifestations of subduction. It would be well to remember, however, that "Not all talc-alkaline rocks of the interior of the western United States are related to subduction" (Robyn, 1977). Title: Geology of the Clarno Formation in the vicinity of Stephenson Mountain, Jefferson, Crook and Wheeler counties, Oregon Author: Stroh, Harold Raymond The thesis area is located in north-central Oregon approximately 20 km west of the town of Mitchell. The rocks exposed in the area belong to the Clarno Formation. This study supports the informal reclassification of the Clarno to Group status, composed of an Upper and Lower Clarno Formation. An angular unconformity separates the two Formations. The Lower Clarno Formation is composed of a lower Ross Flat Member dominated by epiclastic sedimentary rocks and an upper Heflin Creek Member composed primarily of pyroxene andesite lavas. The Upper Clarno Formation consists of two conformable units, a lower Q,uartz-bearing Andesite Unit and an upper Pyroxene Andesite Unit. A thin sequence of rhyolite flows is found near the top of the upper unit. Andesite, dacite and rhyolite rocks intrude the lavas and sediments of the Group. When plotted on a Peacock diagram the Clarno rocks are found to be calcic. The chemical variation diagrams and AFM plot of samples, however, follow talc-alkaline trends and compare favorably with rocks considered to be talc-alkaline by others. Most of the thesis area lies on the southern flank of the east-northeast trending Sutton Mountain Syncline. The northeast trending Mitchell Anticline is found east of the project area and the Lower Clarno rocks follow its' trend. The easterly trending strike-slip Mitchell Fault cuts the northern part of the area. Strata of the area show five kilometers of right-lateral movement along the fault. The angular unconformity separating the formations is found in the eastern part of the area and has been displaced by the Mitchell Fault. The occurrence of andesitic talc-alkaline volcanism near consuming plate margins is well documented and it is possible that the Clarno rocks may be the surface manifestations of subduction. It would be well to remember, however, that "Not all talc-alkaline rocks of the interior of the western United States are related to subduction" (Robyn, 1977). Close

• 37. [Article] Scientific impact of MODIS C5 calibration degradation and C6+ improvements

  This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Copernicus Publications on behalf of the European Geosciences Union. The published article can ...

  Citation × Citation Citation Abstract Copy Title: Scientific impact of MODIS C5 calibration degradation and C6+ improvements Author: Korkin, S., Hall, F., Wu, A., Platnick, S., Franz, B., Xiong, X., Tucker, J., Hilker, T., Meister, G., Wang, Y., Angal, A., Lyapustin, A., Levy, R., Sellers, P. This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Copernicus Publications on behalf of the European Geosciences Union. The published article can be found at: http://www.atmospheric-measurement-techniques.net/index.html. Title: Scientific impact of MODIS C5 calibration degradation and C6+ improvements Author: Korkin, S., Hall, F., Wu, A., Platnick, S., Franz, B., Xiong, X., Tucker, J., Hilker, T., Meister, G., Wang, Y., Angal, A., Lyapustin, A., Levy, R., Sellers, P. This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Copernicus Publications on behalf of the European Geosciences Union. The published article can be found at: http://www.atmospheric-measurement-techniques.net/index.html. Close

• 38. [Article] Active deformation of the Cascadia forearc : implications for great earthquake potential in Oregon and Washington

  Nine west-northwest-trending faults on the continental margin of Oregon and Washington, between 43° 05'N and 470 20'N latitude, have been mapped using seismic reflection, sidescan sonar, submersibles, ...

  Citation × Citation Citation Abstract Copy Title: Active deformation of the Cascadia forearc : implications for great earthquake potential in Oregon and Washington Author: Goldfinger, Chris Nine west-northwest-trending faults on the continental margin of Oregon and Washington, between 43° 05'N and 470 20'N latitude, have been mapped using seismic reflection, sidescan sonar, submersibles, and swath bathymetry. Five of these oblique faults are found on both the Juan de Fuca and North American plates, and offset abyssal plain sedimentary units left-laterally from 2.0 to 5.5 km. These five faults extend 8-18 km northwestward from the deformation front. The remaining four faults, found only on the North American plate, are also inferred to have a left-lateral slip sense. The age of the Wecoma fault on the abyssal plain is 600±50 ka, and has an average slip rate of 7-1 0 mm/year. Slip rates of the other four abyssal plain faults are 5.5 ± 2 - 6. 7 ± 3 mm/yr. These faults are active, as indicated by offset of the youngest sedimentary units, surficial fault scarps, offsets of surficial channels, and deep fluid venting. All nine faults have been surveyed on the continental slope using SeaMARC 1A sidescan sonar, and three of them were surveyed with a high-resolution AMS 150 sidescan sonar on the continental shelf off central Oregon. On the continental slope, the faults are expressed as linear, high-angle WNW trending scarps, and WNW trending fault-parallel folds that we interpret as flower structures. Active structures on the shelf include folds trending from NNE to WNW and associated flexural slip thrust faulting; NNW to N trending right-lateral strike-slip faults; and WNW trending left-lateral strike-slip faults. Some of these structures intersect the coast and can be correlated with onshore Quaternary faults and folds, and others are suspected to be deforming the coastal region. These structures may be contributing to the coastal marsh stratigraphic record of co-seismic subsidence events in the Holocene. We postulate that the set of nine WNW trending left-lateral strike-slip faults extend and rotate the forearc clockwise, absorbing most or all of the arc parallel component of plate convergence. The high rate of forearc deformation implies that the Cascadia forearc may lack the rigidity to generate M > 8.2 earthquakes. From a comparison of Cascadia seismogenic zone geometry to data from circum-Pacific great earthquakes of this century, the maximum Cascadia rupture is estimated to be 500 to 600 km in length, with a 150-400 km rupture length in best agreement with historical data. Title: Active deformation of the Cascadia forearc : implications for great earthquake potential in Oregon and Washington Author: Goldfinger, Chris Nine west-northwest-trending faults on the continental margin of Oregon and Washington, between 43° 05'N and 470 20'N latitude, have been mapped using seismic reflection, sidescan sonar, submersibles, and swath bathymetry. Five of these oblique faults are found on both the Juan de Fuca and North American plates, and offset abyssal plain sedimentary units left-laterally from 2.0 to 5.5 km. These five faults extend 8-18 km northwestward from the deformation front. The remaining four faults, found only on the North American plate, are also inferred to have a left-lateral slip sense. The age of the Wecoma fault on the abyssal plain is 600±50 ka, and has an average slip rate of 7-1 0 mm/year. Slip rates of the other four abyssal plain faults are 5.5 ± 2 - 6. 7 ± 3 mm/yr. These faults are active, as indicated by offset of the youngest sedimentary units, surficial fault scarps, offsets of surficial channels, and deep fluid venting. All nine faults have been surveyed on the continental slope using SeaMARC 1A sidescan sonar, and three of them were surveyed with a high-resolution AMS 150 sidescan sonar on the continental shelf off central Oregon. On the continental slope, the faults are expressed as linear, high-angle WNW trending scarps, and WNW trending fault-parallel folds that we interpret as flower structures. Active structures on the shelf include folds trending from NNE to WNW and associated flexural slip thrust faulting; NNW to N trending right-lateral strike-slip faults; and WNW trending left-lateral strike-slip faults. Some of these structures intersect the coast and can be correlated with onshore Quaternary faults and folds, and others are suspected to be deforming the coastal region. These structures may be contributing to the coastal marsh stratigraphic record of co-seismic subsidence events in the Holocene. We postulate that the set of nine WNW trending left-lateral strike-slip faults extend and rotate the forearc clockwise, absorbing most or all of the arc parallel component of plate convergence. The high rate of forearc deformation implies that the Cascadia forearc may lack the rigidity to generate M > 8.2 earthquakes. From a comparison of Cascadia seismogenic zone geometry to data from circum-Pacific great earthquakes of this century, the maximum Cascadia rupture is estimated to be 500 to 600 km in length, with a 150-400 km rupture length in best agreement with historical data. Close

• 39. [Article] Origin of faults, fissures and volcanic vent alignments at a structural triple junction, Newberry Volcano, central Oregon

  Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, ...

  Citation × Citation Citation Abstract Copy Title: Origin of faults, fissures and volcanic vent alignments at a structural triple junction, Newberry Volcano, central Oregon Author: Meigs, Andrew, Cladouhos, Trenton T., Grasso, Kyla A. Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Title: Origin of faults, fissures and volcanic vent alignments at a structural triple junction, Newberry Volcano, central Oregon Author: Meigs, Andrew, Cladouhos, Trenton T., Grasso, Kyla A. Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Close

• 40. [Article] Summertime water temperature trends in Steamboat Creek Basin, Umpqua National Forest

  The Steamboat Creek basin drains 227 mi² (588 km²) of steep forested terrain into the North Umpqua River of Southwest Oregon, 39 mi (63 km) northeast of Roseburg. Summer base flows for Steamboat Creek ...

  Citation × Citation Citation Abstract Copy Title: Summertime water temperature trends in Steamboat Creek Basin, Umpqua National Forest Author: Holaday, Steven A. The Steamboat Creek basin drains 227 mi² (588 km²) of steep forested terrain into the North Umpqua River of Southwest Oregon, 39 mi (63 km) northeast of Roseburg. Summer base flows for Steamboat Creek average 83 cfs (2.35 m³/sec). Steamboat Creek and its tributaries are considered important to the production of summer-run steelhead; the basin has been closed to angling since 1932. Harvesting has occurred in every subdrainage of the Steamboat Creek basin. Trees were routinely removed from riparian areas when harvesting in the basin began in 1955. Since the mid-1970s to early-1980s, however, buffer strips were left adjacent to streams. In addition, the floods of 1964-65 caused significant damage to riparian vegetation in the basin. This study was undertaken to: (1) determine long-term trends over the period 1969-90 of summertime water temperatures in the mainstem of Steamboat Creek, selected tributaries, and in Boulder Creek, an unharvested control stream in an adjacent watershed and (2) evaluate spacial patterns of maximum water temperatures in the Steamboat Creek basin during the summer of 1990. Significant (P≤0.10) trends of decreasing maximum daily summertime stream temperatures on Steamboat Creek and tributaries occurred from 1969-90. In contrast, an unharvested control stream showed a small, but nonsignificant, increasing trend in stream temperatures. The largest decrease in maximum stream temperatures (7 to 11°F, 3.9 to 6.1°C) occurred on small streams with summer base flows less than 6 cfs (0.17 m³/sec). These streams also had the highest proportion of stream length adjacent to harvesting activities before 1974. The smallest decrease in maximum stream temperatures (0 to 3°F, 0 to 1.7°C) occurred on streams with little or no history of timber harvest activity along riparian areas, or at locations where summer base flows were greater than 15 cfs (0.42 m³/sec). Since no trends in either air temperature or streamflow were apparent over the 1969-90 period, regrowth of riparian vegetation that was previously removed by flooding, debris torrents, or streamside harvesting, appears to be the major cause of trends in decreasing maximum summer stream temperature. Regrowth of riparian vegetation provides shade over small streams, decreasing energy input to the stream from solar radiation. Maximum daily stream temperatures in lower Steamboat Creek did not change significantly during the 1969-90 study period and stream temperature data in 1960 indicates that maximum stream temperatures in lower Steamboat Creek have historically been high. Any cooling effects by groundwater or tributaries are largely negated by the large volume of water in the main channel. Also, the large stream width renders riparian vegetation relatively ineffective in protecting the stream from solar radiation. Minimum stream temperatures decreased during the 1969-90 study period for all of the long-term stations in the Steamboat Creek basin while the control stream showed a slight increasing trend. Similarly, diurnal stream temperature fluctuations decreased for several tributaries. Title: Summertime water temperature trends in Steamboat Creek Basin, Umpqua National Forest Author: Holaday, Steven A. The Steamboat Creek basin drains 227 mi² (588 km²) of steep forested terrain into the North Umpqua River of Southwest Oregon, 39 mi (63 km) northeast of Roseburg. Summer base flows for Steamboat Creek average 83 cfs (2.35 m³/sec). Steamboat Creek and its tributaries are considered important to the production of summer-run steelhead; the basin has been closed to angling since 1932. Harvesting has occurred in every subdrainage of the Steamboat Creek basin. Trees were routinely removed from riparian areas when harvesting in the basin began in 1955. Since the mid-1970s to early-1980s, however, buffer strips were left adjacent to streams. In addition, the floods of 1964-65 caused significant damage to riparian vegetation in the basin. This study was undertaken to: (1) determine long-term trends over the period 1969-90 of summertime water temperatures in the mainstem of Steamboat Creek, selected tributaries, and in Boulder Creek, an unharvested control stream in an adjacent watershed and (2) evaluate spacial patterns of maximum water temperatures in the Steamboat Creek basin during the summer of 1990. Significant (P≤0.10) trends of decreasing maximum daily summertime stream temperatures on Steamboat Creek and tributaries occurred from 1969-90. In contrast, an unharvested control stream showed a small, but nonsignificant, increasing trend in stream temperatures. The largest decrease in maximum stream temperatures (7 to 11°F, 3.9 to 6.1°C) occurred on small streams with summer base flows less than 6 cfs (0.17 m³/sec). These streams also had the highest proportion of stream length adjacent to harvesting activities before 1974. The smallest decrease in maximum stream temperatures (0 to 3°F, 0 to 1.7°C) occurred on streams with little or no history of timber harvest activity along riparian areas, or at locations where summer base flows were greater than 15 cfs (0.42 m³/sec). Since no trends in either air temperature or streamflow were apparent over the 1969-90 period, regrowth of riparian vegetation that was previously removed by flooding, debris torrents, or streamside harvesting, appears to be the major cause of trends in decreasing maximum summer stream temperature. Regrowth of riparian vegetation provides shade over small streams, decreasing energy input to the stream from solar radiation. Maximum daily stream temperatures in lower Steamboat Creek did not change significantly during the 1969-90 study period and stream temperature data in 1960 indicates that maximum stream temperatures in lower Steamboat Creek have historically been high. Any cooling effects by groundwater or tributaries are largely negated by the large volume of water in the main channel. Also, the large stream width renders riparian vegetation relatively ineffective in protecting the stream from solar radiation. Minimum stream temperatures decreased during the 1969-90 study period for all of the long-term stations in the Steamboat Creek basin while the control stream showed a slight increasing trend. Similarly, diurnal stream temperature fluctuations decreased for several tributaries. Close