Search

Search Results

• 41. [Article] Wood density of young-growth western hemlock: relation to ring age, radial growth, stand density, and site quality

  Breast-high stem sections were sampled from 56 western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees growing in 15 plots representing a wide range of tree and site conditions in northwestern Oregon. ...

  Citation × Citation Citation Abstract Copy Title: Wood density of young-growth western hemlock: relation to ring age, radial growth, stand density, and site quality Author: Marshall, D. D., Gartner, B. L., Singleton, R., DeBell, D. S. Breast-high stem sections were sampled from 56 western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees growing in 15 plots representing a wide range of tree and site conditions in northwestern Oregon. Growth and wood density traits of individual rings were measured via X-ray densitometry, and relationships of ring density and its components to age and growth rate were analyzed. Ring density was highest (0.49 g/cm3) near the pith, declined to 0.40 g/cm3 at age 10, remained stable to about age 25, and then increased gradually and remained between 0.43 and 0.44 g/cm3 from age 38 to 45 and beyond. A negative influence of rapid growth on whole ring density was greatest at young ages and diminished with time, becoming nonsignificant beyond age 30. Earlywood density, latewood density, and latewood proportion were all negatively related to ring width at young ages, but by age 21–25, latewood proportion was the only component of ring density that remained significantly diminished by increased growth rate. Residual differences in wood density (after age and growth rate were considered) did not appear to be related to either stand density or site class. Overall, young-growth hemlock trees are relatively uniform in wood density and likely to be more so if grown in intensively managed stands. Title: Wood density of young-growth western hemlock: relation to ring age, radial growth, stand density, and site quality Author: Marshall, D. D., Gartner, B. L., Singleton, R., DeBell, D. S. Breast-high stem sections were sampled from 56 western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees growing in 15 plots representing a wide range of tree and site conditions in northwestern Oregon. Growth and wood density traits of individual rings were measured via X-ray densitometry, and relationships of ring density and its components to age and growth rate were analyzed. Ring density was highest (0.49 g/cm3) near the pith, declined to 0.40 g/cm3 at age 10, remained stable to about age 25, and then increased gradually and remained between 0.43 and 0.44 g/cm3 from age 38 to 45 and beyond. A negative influence of rapid growth on whole ring density was greatest at young ages and diminished with time, becoming nonsignificant beyond age 30. Earlywood density, latewood density, and latewood proportion were all negatively related to ring width at young ages, but by age 21–25, latewood proportion was the only component of ring density that remained significantly diminished by increased growth rate. Residual differences in wood density (after age and growth rate were considered) did not appear to be related to either stand density or site class. Overall, young-growth hemlock trees are relatively uniform in wood density and likely to be more so if grown in intensively managed stands. Close

• 42. [Article] Systematics of the salamander genus Dicamptodon strauch (Amphibia:Caudata:Ambystomatidae)

  Dicamptodon is the single, extant genus of the ambystomatid subfamily Dicamptodontinae. Two species, D. ensatus (Eschscholtz) and D. copei Nussbaum are recognized. D. ensatus is found in the forested, ...

  Citation × Citation Citation Abstract Copy Title: Systematics of the salamander genus Dicamptodon strauch (Amphibia:Caudata:Ambystomatidae) Author: Nussbaum, Ronald A. Dicamptodon is the single, extant genus of the ambystomatid subfamily Dicamptodontinae. Two species, D. ensatus (Eschscholtz) and D. copei Nussbaum are recognized. D. ensatus is found in the forested, mountain regions of northwestern California and western Oregon, in the Willapa Hills and Cascade Mountains of Washington, in extreme southwestern British Columbia, and in the northern and central Rocky Mountains of Idaho. D. copei is found in the Olympic Mountains, Willapa Hills and southwestern Cascades of Washington; and in the vicinity of the Columbia River Gorge in extreme northwestern Oregon. The two species are sympatric in the Columbia River Gorge, southern Willapa Hills, and southwestern Cascades of Washington. The two species differ, among other characters, in blood serum proteins, sensitivity to thyroxine, mode of life history, body size, relative head size, limb length, tail height, tooth number, gill raker number, color, and degree of ossification of skeletal elements. Geographic variation is prominent in D. ensatus. Multivariate analysis of morphometric characters of larval populations discriminates three groups: a Rocky Mountain Group, a Cascade and Oregon Coast Range Group, and a Californian Group. The first two groups seem to be more similar to each other than either is to the Californian Group. The Californian Group can be divided into a southern subgroup and a northern subgroup; and the northern subgroup can be further separated into a coastal subgroup and an interior highlands subgroup. These groups are all more-or-less verified by analysis of color of larvae and adults, and morphometric characters of adults. These groups correspond geographically with major features of topography in the Pacific Northwest. The California Group is confined south of the geologically old and complex Klamath-Siskiyou Mountains. The southern Californian subgroup is found south of the "North Coast Divide", and the northern subgroup is found north of this Divide in an area of northwestern drainage. The interior highlands subgroup of the northern Californian subgroup is found in the higher, summer-dry mountains of northern California where the substrate is complex and of a different origin than the coastal substrate. Strong morphoclines occur across the Klamath-Siskiyou Region into southwestern Oregon. The Rocky Mountain Group is separated from the Cascade and Oregon Coast Range Group by the broad, arid Columbia Plateau. Variation is slight over the relatively small range of D. copei, and what variation exists seems to be a function of geographic distance. The dicamptodontines have been an evolutionarily conservative group confined to the humid temperate, Arcto-Tertiary environments of western North America throughout their Cretaceous and Tertiary history. A remnant of the once wide-spread, ancestral habitat occurs today in the humid fog belt of northwestern California and southwestern Oregon. D. ensatus living in this area today exhibit the most primitive features of all living Dicamptodon. These include: large heads, long limbs and tails, many teeth and gill rakers, propensity to transform, and perhaps the habit of vocalizing as a terrestrial, defensive adaptation. D. copei is viewed as a relatively recent derivitive of an ensatus-like ancestor. This ancestor is believed to have had a propensity for neoteny and body attenuation associated with life in the extreme climatic, physical, and biotic environments imposed by Pleistocene glaciation. Isolation in western Washington during a glacial maximum allowed these tendencies, along with small body size, to be selected for, unhampered by gene flow from outside populations. It is thought that the ensatus-like ancestor of D. copei was more similar to recent northern populations of D. ensatus than to recent Californian populations of D. ensatus. Californian populations were relatively unaffected by Pleistocene climatic extremes, as they passed this period in the milder, ancestral environment of southern, coastal latitudes. During the last glacial maximum, the Rocky Mountain populations were probably continuous with populations on the lower eastern slopes of the Washington Cascades, via a connecting, wet, forested parkland, which existed south of the Cordilleran ice sheet in north-central Washington. This parkland was broken up after the ice retreated, during the Altithermal interval, about 7-4,000 years ago, and it was at this time that the Rocky Mountain Group became isolated. Postglacial readjustments in the ranges of D. copei and D. ensatus account for their current narrow zone of sympatry. Subspecies of D. ensatus and D. copei are not recognized. Title: Systematics of the salamander genus Dicamptodon strauch (Amphibia:Caudata:Ambystomatidae) Author: Nussbaum, Ronald A. Dicamptodon is the single, extant genus of the ambystomatid subfamily Dicamptodontinae. Two species, D. ensatus (Eschscholtz) and D. copei Nussbaum are recognized. D. ensatus is found in the forested, mountain regions of northwestern California and western Oregon, in the Willapa Hills and Cascade Mountains of Washington, in extreme southwestern British Columbia, and in the northern and central Rocky Mountains of Idaho. D. copei is found in the Olympic Mountains, Willapa Hills and southwestern Cascades of Washington; and in the vicinity of the Columbia River Gorge in extreme northwestern Oregon. The two species are sympatric in the Columbia River Gorge, southern Willapa Hills, and southwestern Cascades of Washington. The two species differ, among other characters, in blood serum proteins, sensitivity to thyroxine, mode of life history, body size, relative head size, limb length, tail height, tooth number, gill raker number, color, and degree of ossification of skeletal elements. Geographic variation is prominent in D. ensatus. Multivariate analysis of morphometric characters of larval populations discriminates three groups: a Rocky Mountain Group, a Cascade and Oregon Coast Range Group, and a Californian Group. The first two groups seem to be more similar to each other than either is to the Californian Group. The Californian Group can be divided into a southern subgroup and a northern subgroup; and the northern subgroup can be further separated into a coastal subgroup and an interior highlands subgroup. These groups are all more-or-less verified by analysis of color of larvae and adults, and morphometric characters of adults. These groups correspond geographically with major features of topography in the Pacific Northwest. The California Group is confined south of the geologically old and complex Klamath-Siskiyou Mountains. The southern Californian subgroup is found south of the "North Coast Divide", and the northern subgroup is found north of this Divide in an area of northwestern drainage. The interior highlands subgroup of the northern Californian subgroup is found in the higher, summer-dry mountains of northern California where the substrate is complex and of a different origin than the coastal substrate. Strong morphoclines occur across the Klamath-Siskiyou Region into southwestern Oregon. The Rocky Mountain Group is separated from the Cascade and Oregon Coast Range Group by the broad, arid Columbia Plateau. Variation is slight over the relatively small range of D. copei, and what variation exists seems to be a function of geographic distance. The dicamptodontines have been an evolutionarily conservative group confined to the humid temperate, Arcto-Tertiary environments of western North America throughout their Cretaceous and Tertiary history. A remnant of the once wide-spread, ancestral habitat occurs today in the humid fog belt of northwestern California and southwestern Oregon. D. ensatus living in this area today exhibit the most primitive features of all living Dicamptodon. These include: large heads, long limbs and tails, many teeth and gill rakers, propensity to transform, and perhaps the habit of vocalizing as a terrestrial, defensive adaptation. D. copei is viewed as a relatively recent derivitive of an ensatus-like ancestor. This ancestor is believed to have had a propensity for neoteny and body attenuation associated with life in the extreme climatic, physical, and biotic environments imposed by Pleistocene glaciation. Isolation in western Washington during a glacial maximum allowed these tendencies, along with small body size, to be selected for, unhampered by gene flow from outside populations. It is thought that the ensatus-like ancestor of D. copei was more similar to recent northern populations of D. ensatus than to recent Californian populations of D. ensatus. Californian populations were relatively unaffected by Pleistocene climatic extremes, as they passed this period in the milder, ancestral environment of southern, coastal latitudes. During the last glacial maximum, the Rocky Mountain populations were probably continuous with populations on the lower eastern slopes of the Washington Cascades, via a connecting, wet, forested parkland, which existed south of the Cordilleran ice sheet in north-central Washington. This parkland was broken up after the ice retreated, during the Altithermal interval, about 7-4,000 years ago, and it was at this time that the Rocky Mountain Group became isolated. Postglacial readjustments in the ranges of D. copei and D. ensatus account for their current narrow zone of sympatry. Subspecies of D. ensatus and D. copei are not recognized. Close

• 43. [Article] The influence of net real estate income and other property characteristics on prices of agricultural properties within and among selected areas of Oregon, 1965-69

  Concern over the apparent disparity between the farm use value and current market value of property in agricultural areas continues to remain a source of concern in many areas. This concern has intensified ...

  Citation × Citation Citation Abstract Copy Title: The influence of net real estate income and other property characteristics on prices of agricultural properties within and among selected areas of Oregon, 1965-69 Author: Crowley, William D. Concern over the apparent disparity between the farm use value and current market value of property in agricultural areas continues to remain a source of concern in many areas. This concern has intensified in recent years, particularly in those agricultural areas situated near urban centers and recreational areas. The main thrust of the study was directed toward determining the relationship between net real estate income per acre and sale price pier acres of properties in selected agricultural areas of Oregon. Three areas, ostensibly called agricultural areas, were selected for analysis. The areas, as classified, included a basic agricultural production area (dry land grain area in northcentral Oregon), an urban-recreation influenced area (Douglas County in southwestern Oregon bordered by the Pacific Ocean on the west and the Umpqua National Forest on the east) and an urban influenced area (Marion County in the populous and productive Willamette Valley in northwestern Oregon). In addition to determining the influence of net real estate income on property prices, the influence of other property characteristics on property prices was analyzed in each area. The other property characteristics included: year of sale, number of acres in sale, assessed value of buildings per acre, miles to nearest paved road, and miles to nearest town of at least 1,000 population. Simple and multiple linear regression models were used to analyze the influence of particular property characteristics on sale price per acre. The same six-variable model was used in each area to test whether partial regression coefficient values on corresponding variables differed significantly among areas. Overlapping of 95 percent confidence intervals around corresponding partial regression coefficient values among areas was observed for all independent variables except net real estate income per acre. The income variable was an important determinant of sale price per acre only for grain area and Douglas County sales. However, the partial regression coefficient value of 49.71 in urban-recreation influenced Douglas County implies an approximate 2.0 percent capitalization rate compared to a coefficient value of 17.11 and a 5.8 percent implied capitalization rate in the grain area. Year of sale was an important influence on sale price per acre in areas influenced more strongly by nonagricultural influences, i.e., Douglas and Marion Counties, as evidenced both by the level of significance of the coefficient value and the value of the coefficient in each of these areas. The annual rate of property price appreciation at the mean was 14.3 percent in urban-recreation influenced Douglas County and 12.1 percent in urban influenced Marion County. While not significantly different from zero, the rate of price change was slightly negative in the grain area. Conclusions from the study were (1) that there is a significant difference in the influence of net real estate income and other property characteristics on prices of properties among selected agricultural areas of Oregon, (2) that the nature and degree of relationship between prices oi property sales analyzed and property characteristics of these sales varied considerably within each agricultural area selected for analysis, but especially in the urban-recreation and urban influenced areas, and (3) that in spite of relatively low mean rates of return in all three areas studied, a disparity between the farm use value and current market value of land was found to exist only in urban-recreation influenced Douglas County. Implication of these results are that variously influenced agricultural areas do exist, and that motives for and sources of satisfaction from ownership of property in agricultural areas vary within and among areas. Title: The influence of net real estate income and other property characteristics on prices of agricultural properties within and among selected areas of Oregon, 1965-69 Author: Crowley, William D. Concern over the apparent disparity between the farm use value and current market value of property in agricultural areas continues to remain a source of concern in many areas. This concern has intensified in recent years, particularly in those agricultural areas situated near urban centers and recreational areas. The main thrust of the study was directed toward determining the relationship between net real estate income per acre and sale price pier acres of properties in selected agricultural areas of Oregon. Three areas, ostensibly called agricultural areas, were selected for analysis. The areas, as classified, included a basic agricultural production area (dry land grain area in northcentral Oregon), an urban-recreation influenced area (Douglas County in southwestern Oregon bordered by the Pacific Ocean on the west and the Umpqua National Forest on the east) and an urban influenced area (Marion County in the populous and productive Willamette Valley in northwestern Oregon). In addition to determining the influence of net real estate income on property prices, the influence of other property characteristics on property prices was analyzed in each area. The other property characteristics included: year of sale, number of acres in sale, assessed value of buildings per acre, miles to nearest paved road, and miles to nearest town of at least 1,000 population. Simple and multiple linear regression models were used to analyze the influence of particular property characteristics on sale price per acre. The same six-variable model was used in each area to test whether partial regression coefficient values on corresponding variables differed significantly among areas. Overlapping of 95 percent confidence intervals around corresponding partial regression coefficient values among areas was observed for all independent variables except net real estate income per acre. The income variable was an important determinant of sale price per acre only for grain area and Douglas County sales. However, the partial regression coefficient value of 49.71 in urban-recreation influenced Douglas County implies an approximate 2.0 percent capitalization rate compared to a coefficient value of 17.11 and a 5.8 percent implied capitalization rate in the grain area. Year of sale was an important influence on sale price per acre in areas influenced more strongly by nonagricultural influences, i.e., Douglas and Marion Counties, as evidenced both by the level of significance of the coefficient value and the value of the coefficient in each of these areas. The annual rate of property price appreciation at the mean was 14.3 percent in urban-recreation influenced Douglas County and 12.1 percent in urban influenced Marion County. While not significantly different from zero, the rate of price change was slightly negative in the grain area. Conclusions from the study were (1) that there is a significant difference in the influence of net real estate income and other property characteristics on prices of properties among selected agricultural areas of Oregon, (2) that the nature and degree of relationship between prices oi property sales analyzed and property characteristics of these sales varied considerably within each agricultural area selected for analysis, but especially in the urban-recreation and urban influenced areas, and (3) that in spite of relatively low mean rates of return in all three areas studied, a disparity between the farm use value and current market value of land was found to exist only in urban-recreation influenced Douglas County. Implication of these results are that variously influenced agricultural areas do exist, and that motives for and sources of satisfaction from ownership of property in agricultural areas vary within and among areas. Close

• 44. [Article] Butterflies of the H.J. Andrews Experimental Forest : biological inventory and ecological analysis

  A biological inventory of the butterflies of the H. J. Andrews Experimental Forest [HJA] in Linn/Lane County, Oregon was conducted during 1994 and 1995. It was the first comprehensive survey of HJA butterflies ...

  Citation × Citation Citation Abstract Copy Title: Butterflies of the H.J. Andrews Experimental Forest : biological inventory and ecological analysis Author: Ross, Dana N. R. A biological inventory of the butterflies of the H. J. Andrews Experimental Forest [HJA] in Linn/Lane County, Oregon was conducted during 1994 and 1995. It was the first comprehensive survey of HJA butterflies for the site and serves as a baseline for future butterfly research. A detailed ecological account is provided for each species documented during this and previous studies from the HJA. Patterns of butterfly richness and abundance are addressed both temporally and spatially. Within-year and between year differences in butterfly richness and abundance are explained. Butterfly richness and abundance were compared between forest, clear-cut, and meadow habitats, as well as along the roads within these habitats. Butterfly richness and abundance comparisons were also made between local butterfly hotspots and immediately adjacent areas. Lastly, the HJA butterfly fauna was compared to those of five other Oregon sites to put it into a regional perspective. Seventy-two species were recorded during this two year period and increased the total documented butterfly fauna of the HJA to seventy-nine species. Butterfly species richness was high from June through early August. Butterfly abundance increased gradually over the season and peaked in early August. Each butterfly species displayed one of four patterns of combined relative abundance and distribution: common and widespread, rare and local, common only at low elevations or common only at high elevations. The results of standardized butterfly counts suggested that subalpine meadows were much higher than clear-cuts or forests in butterfly richness and abundance, and that roads served to increase butterfly richness and abundance on a local scale in most cases. Butterfly hotspots on the HJA appear as relatively small areas of high butterfly richness and abundance and have a correspondingly high number of plant species when compared to adjacent areas. With virtually one-half of all butterfly species known for the state of Oregon, the HJA ranks among the most species-rich locations for its size within the state. This diversity originates from several biogeographical regions of origin, as defined within this study. A total of 31 HJA species have a generalized Western North American distribution, but several other biogeographical regions are also well represented. Some butterfly species appear to be at or near their geographical limits on the HJA. The assemblage of HJA butterfly species is virtually inclusive of those from Mary's Peak and McDonald Forest in northwestern Oregon, whereas it differs by 30% or more from the more biogeographically distinct faunas of Crater Lake National Park, Mount Ashland and Steens Mountain. Future butterfly work on the HJA is recommended. Oregon butterfly distribution maps suggest that several additional butterfly species should be found there. More biogeographical analyses combined with long term monitoring of HJA butterflies could help to both predict and document changes in the Pacific Northwest butterfly fauna due to human disturbance and global climate change. Title: Butterflies of the H.J. Andrews Experimental Forest : biological inventory and ecological analysis Author: Ross, Dana N. R. A biological inventory of the butterflies of the H. J. Andrews Experimental Forest [HJA] in Linn/Lane County, Oregon was conducted during 1994 and 1995. It was the first comprehensive survey of HJA butterflies for the site and serves as a baseline for future butterfly research. A detailed ecological account is provided for each species documented during this and previous studies from the HJA. Patterns of butterfly richness and abundance are addressed both temporally and spatially. Within-year and between year differences in butterfly richness and abundance are explained. Butterfly richness and abundance were compared between forest, clear-cut, and meadow habitats, as well as along the roads within these habitats. Butterfly richness and abundance comparisons were also made between local butterfly hotspots and immediately adjacent areas. Lastly, the HJA butterfly fauna was compared to those of five other Oregon sites to put it into a regional perspective. Seventy-two species were recorded during this two year period and increased the total documented butterfly fauna of the HJA to seventy-nine species. Butterfly species richness was high from June through early August. Butterfly abundance increased gradually over the season and peaked in early August. Each butterfly species displayed one of four patterns of combined relative abundance and distribution: common and widespread, rare and local, common only at low elevations or common only at high elevations. The results of standardized butterfly counts suggested that subalpine meadows were much higher than clear-cuts or forests in butterfly richness and abundance, and that roads served to increase butterfly richness and abundance on a local scale in most cases. Butterfly hotspots on the HJA appear as relatively small areas of high butterfly richness and abundance and have a correspondingly high number of plant species when compared to adjacent areas. With virtually one-half of all butterfly species known for the state of Oregon, the HJA ranks among the most species-rich locations for its size within the state. This diversity originates from several biogeographical regions of origin, as defined within this study. A total of 31 HJA species have a generalized Western North American distribution, but several other biogeographical regions are also well represented. Some butterfly species appear to be at or near their geographical limits on the HJA. The assemblage of HJA butterfly species is virtually inclusive of those from Mary's Peak and McDonald Forest in northwestern Oregon, whereas it differs by 30% or more from the more biogeographically distinct faunas of Crater Lake National Park, Mount Ashland and Steens Mountain. Future butterfly work on the HJA is recommended. Oregon butterfly distribution maps suggest that several additional butterfly species should be found there. More biogeographical analyses combined with long term monitoring of HJA butterflies could help to both predict and document changes in the Pacific Northwest butterfly fauna due to human disturbance and global climate change. Close

• 45. [Article] Influence of light on the growth of advance regeneration in the understory of Douglas-fir dominated forests in western Oregon

  The growth potential of Douglas-fir, grand fir and western hemlock advance regeneration in the forest understory of Douglas-fir-dominated forests was investigated to detennine the feasibility of selection ...

  Citation × Citation Citation Abstract Copy Title: Influence of light on the growth of advance regeneration in the understory of Douglas-fir dominated forests in western Oregon Author: Deisenhofer, Florian The growth potential of Douglas-fir, grand fir and western hemlock advance regeneration in the forest understory of Douglas-fir-dominated forests was investigated to detennine the feasibility of selection cutting systems in northwest Oregon. This study compared the growth of Douglas-fir, grand fir and western hemlock advance regeneration along a light gradient with hemispherical photography, modeled the relative importance of light, competition, subject tree and stand characteristics on growth and reported observations on the growth response of advance regeneration to stand manipulation. Western hemlock, grand fir and Douglas-fir advance regeneration was found at 5, 6, and 7 % of diffuse skylight in selection thinned stands respectively, indicating that all three species are capable of survival and growth in low light and, therefore, are suitable for uneven-aged management. Growth of advance regeneration in terms of height, diameter and volume followed the order: Western hemlock > Douglas-fir> grand fir, although there was seldom a significant difference between Douglas-fir and grand fir. Overtopping shrub vegetation significantly reduced growth and light availability in comparison to trees that were not overtopped. Height, radial and volume growth of all three species increased with increasing light. Regression analysis revealed that along the measured light gradient (6 44 % of diffuse skylight) i; growth of western hemlock was superior (different intercepts) to Douglas-fir at one interior Coast Range site but there was no significant difference in the relationship of growth to increased light levels (equal slopes) ii; Douglas-fir advance regeneration growth was superior (different intercepts) to grand fir at three sites but there was no significant difference in the relationship of growth to increased light levels (equal slopes). Growth modeling explained 36 to 67 % of the variation in Douglas-fir, western hemlock and grand fir advance regeneration growth and revealed that tree characteristics were better predictors of advance regeneration growth than environmental variables. Independent of species, live crown ratio was the most important variable explaining variation in absolute height growth. The best-growing trees were in general taller than competing shrub vegetation and characterized by higher live crown ratios. Western hemlock was particularly sensitive to shrub cover and grew best when shnib cover was low (< 35 %). Therefore, where possible, select future crop trees with a live crown ratio of at least 50 % for Douglas-fir and grand fir and 60 % for western hemlock and remove competing vegetation. Studying the release of midstory and understory trees at the four sites in northwestern Oregon after thinning revealed in general that Douglas-fir, grand fir and western hemlock grew better following release. However, the vigor of response differed for the three species and increased in the order of western hemlock, grand fir and Douglas-fir. Douglas-fir generally released more rapidly and more vigorously than grand fir, but also decreased more rapidly. To keep a significant proportion of the advance regeneration in a very vigorous state, thinning cycles of 6 to 10 years appear necessary. Since advance regeneration of Douglas-fir and grand fir released to thinning, thinning cycles of 10 to 15 years are possible for keeping a large proportion of the advance regeneration in stable condition. Even highly suppressed Douglas-fir were capable of release after thinning. Title: Influence of light on the growth of advance regeneration in the understory of Douglas-fir dominated forests in western Oregon Author: Deisenhofer, Florian The growth potential of Douglas-fir, grand fir and western hemlock advance regeneration in the forest understory of Douglas-fir-dominated forests was investigated to detennine the feasibility of selection cutting systems in northwest Oregon. This study compared the growth of Douglas-fir, grand fir and western hemlock advance regeneration along a light gradient with hemispherical photography, modeled the relative importance of light, competition, subject tree and stand characteristics on growth and reported observations on the growth response of advance regeneration to stand manipulation. Western hemlock, grand fir and Douglas-fir advance regeneration was found at 5, 6, and 7 % of diffuse skylight in selection thinned stands respectively, indicating that all three species are capable of survival and growth in low light and, therefore, are suitable for uneven-aged management. Growth of advance regeneration in terms of height, diameter and volume followed the order: Western hemlock > Douglas-fir> grand fir, although there was seldom a significant difference between Douglas-fir and grand fir. Overtopping shrub vegetation significantly reduced growth and light availability in comparison to trees that were not overtopped. Height, radial and volume growth of all three species increased with increasing light. Regression analysis revealed that along the measured light gradient (6 44 % of diffuse skylight) i; growth of western hemlock was superior (different intercepts) to Douglas-fir at one interior Coast Range site but there was no significant difference in the relationship of growth to increased light levels (equal slopes) ii; Douglas-fir advance regeneration growth was superior (different intercepts) to grand fir at three sites but there was no significant difference in the relationship of growth to increased light levels (equal slopes). Growth modeling explained 36 to 67 % of the variation in Douglas-fir, western hemlock and grand fir advance regeneration growth and revealed that tree characteristics were better predictors of advance regeneration growth than environmental variables. Independent of species, live crown ratio was the most important variable explaining variation in absolute height growth. The best-growing trees were in general taller than competing shrub vegetation and characterized by higher live crown ratios. Western hemlock was particularly sensitive to shrub cover and grew best when shnib cover was low (< 35 %). Therefore, where possible, select future crop trees with a live crown ratio of at least 50 % for Douglas-fir and grand fir and 60 % for western hemlock and remove competing vegetation. Studying the release of midstory and understory trees at the four sites in northwestern Oregon after thinning revealed in general that Douglas-fir, grand fir and western hemlock grew better following release. However, the vigor of response differed for the three species and increased in the order of western hemlock, grand fir and Douglas-fir. Douglas-fir generally released more rapidly and more vigorously than grand fir, but also decreased more rapidly. To keep a significant proportion of the advance regeneration in a very vigorous state, thinning cycles of 6 to 10 years appear necessary. Since advance regeneration of Douglas-fir and grand fir released to thinning, thinning cycles of 10 to 15 years are possible for keeping a large proportion of the advance regeneration in stable condition. Even highly suppressed Douglas-fir were capable of release after thinning. Close

• 46. [Article] Coastal hazards and community exposure in a changing climate : the development of probabilistic coastal change hazard zones

  Documented trends in rising sea levels, storminess, and extreme wave heights have the potential to increase the frequency and magnitude of coastal change hazards, increasing risks to coastal infrastructure ...

  Citation × Citation Citation Abstract Copy Title: Coastal hazards and community exposure in a changing climate : the development of probabilistic coastal change hazard zones Author: Baron, Heather M. Documented trends in rising sea levels, storminess, and extreme wave heights have the potential to increase the frequency and magnitude of coastal change hazards, increasing risks to coastal infrastructure and environmental resources. Coastal planners and decision makers need information about the impacts of future hazards in order to apply mitigation and adaptation strategies. However, making quantitative predictions of beach and dune erosion is complicated by uncertainties surrounding the drivers and impacts of climate change as well as our understanding of climate controls on coastal change hazards. Furthermore, these changes are occurring in a dynamic environment where beach geomorphology evolves over a variety of spatial and temporal scales. Here a new, probabilistic approach for quantifying future coastal change hazards that incorporates the uncertainty associated with both climate change and morphological variability is presented. First, a suite of synthetic time series of total water levels (TWLs) through 2100 are produced by applying various climate change scenarios, composed of projections of sea-level rise, wave climate, and the frequency of major El Niños, to historical datasets of waves and measured tidal elevations. These time series allow extreme design events to be computed for any time period in the future (e.g., 100-year TWL event in 2030). Using simple coastal change models that require TWLs and various beach morphometrics as input, future coastal change is quantified over a wide range of possible climate futures for sandy, dune-backed coastlines. The new methodology has been applied to the Tillamook County coast in northwestern Oregon to develop coastal change hazard zones of arbitrary confidence levels for both the 100% and 1% annual chance TWL events at present (2009) and for years 2030, 2050, and 2100. The nature of the probabilistic approach, however, allows for coastal decision makers to determine the desired level of confidence (or exceedance probability), extremity of the event, and planning horizon to consider. The hazard zones are then integrated with various socioeconomic datasets (e.g., structures, roads) to evaluate the exposure of coastal communities to the predicted coastal change hazards at various levels of confidence. When paired with community vulnerability assessments, the hazard map products developed will provide coastal planners with the tools and information to allow for science-based decisions that will increase the adaptive capacity of coastal communities as they prepare for the uncertainties of future climate change. Title: Coastal hazards and community exposure in a changing climate : the development of probabilistic coastal change hazard zones Author: Baron, Heather M. Documented trends in rising sea levels, storminess, and extreme wave heights have the potential to increase the frequency and magnitude of coastal change hazards, increasing risks to coastal infrastructure and environmental resources. Coastal planners and decision makers need information about the impacts of future hazards in order to apply mitigation and adaptation strategies. However, making quantitative predictions of beach and dune erosion is complicated by uncertainties surrounding the drivers and impacts of climate change as well as our understanding of climate controls on coastal change hazards. Furthermore, these changes are occurring in a dynamic environment where beach geomorphology evolves over a variety of spatial and temporal scales. Here a new, probabilistic approach for quantifying future coastal change hazards that incorporates the uncertainty associated with both climate change and morphological variability is presented. First, a suite of synthetic time series of total water levels (TWLs) through 2100 are produced by applying various climate change scenarios, composed of projections of sea-level rise, wave climate, and the frequency of major El Niños, to historical datasets of waves and measured tidal elevations. These time series allow extreme design events to be computed for any time period in the future (e.g., 100-year TWL event in 2030). Using simple coastal change models that require TWLs and various beach morphometrics as input, future coastal change is quantified over a wide range of possible climate futures for sandy, dune-backed coastlines. The new methodology has been applied to the Tillamook County coast in northwestern Oregon to develop coastal change hazard zones of arbitrary confidence levels for both the 100% and 1% annual chance TWL events at present (2009) and for years 2030, 2050, and 2100. The nature of the probabilistic approach, however, allows for coastal decision makers to determine the desired level of confidence (or exceedance probability), extremity of the event, and planning horizon to consider. The hazard zones are then integrated with various socioeconomic datasets (e.g., structures, roads) to evaluate the exposure of coastal communities to the predicted coastal change hazards at various levels of confidence. When paired with community vulnerability assessments, the hazard map products developed will provide coastal planners with the tools and information to allow for science-based decisions that will increase the adaptive capacity of coastal communities as they prepare for the uncertainties of future climate change. Close

• 47. [Article] Response to fenamiphos, extraction techniques and population dynamics of Pratylenchus penetrans on western Oregon red raspberry

  The effects of fenamiphos on soil and root populations of Pratylenchus penetrans were evaluated in four red raspberry cv. Willamette fields in Northwestern Oregon. Field 1 was a silty clay loam with 53% ...

  Citation × Citation Citation Abstract Copy Title: Response to fenamiphos, extraction techniques and population dynamics of Pratylenchus penetrans on western Oregon red raspberry Author: Lolas, Mauricio The effects of fenamiphos on soil and root populations of Pratylenchus penetrans were evaluated in four red raspberry cv. Willamette fields in Northwestern Oregon. Field 1 was a silty clay loam with 53% organic matter (OM). Field 2 and 3 were silty loam soils with 3.25 and 2.55% OM, respectively and field 4 was a silty clay with 7.1% OM. The nematicide, fenamiphos (10 kg a.i./ha) was applied in broadcast or band treatments on November 15, 1989. Additional plots in field 3, received a band-nematicide treatment on December 28, 1989 to evaluate the effect of application date on the control of P. penetrans in red raspberry. Field 4 had plots in sites with and without grass and weed ground cover in the aisles between raspberry rows to examine effects of ground cover on nematicide efficacy. Nematodes from soil and roots were sampled monthly from all plots in each field from October 1989 to October 1990. Soil populations of P. penetrans sampled within rows decreased between the October and December sampling dates in all four fields. Soil populations in 3 fields increased in density during mid-summer and reached their highest peak in the middle of September. A similar pattern occurred in P. penetrans soil populations from plots with or without ground cover in aisles between rows of raspberry in field 4. However, in this field, numbers increased in July and reached their peak density in August. Root populations of P. penetrans from red raspberry reached their highest number during spring and summer at all fields. No significant (P>0.05) differences in effectiveness of fenamiphos were detected between band and broadcast method of application and, also between the 2 application dates. Seasonal mean densities of soil populations from band application was only significantly lower than in nontreated controls in areas with ground cover in field 4, respectively. High variability in the numbers of P. penetrans in soil and roots of raspberry was observed throughout the year. Therefore, conclusions about the effectiveness of fenamiphos were difficult to assess. The efficiency of Baermann funnels was 43.9%, when a known number of P. penetrans was added to soil. Total yields of P. penetrans extracted from raspberry roots by mist chamber root extraction (MCRE) were higher (P = 0.05) than yields extracted by polyethylene plastic bag root incubation (PBRI). Approximately 90% of the total P. penetrans recovered was achieved after three and seven days of extraction for PBRI and MCRE, respectively. However, the extraction efficiency of MCRE was 30% higher than PBRI and the daily recovery lasted 28 and 18 days, respectively. Title: Response to fenamiphos, extraction techniques and population dynamics of Pratylenchus penetrans on western Oregon red raspberry Author: Lolas, Mauricio The effects of fenamiphos on soil and root populations of Pratylenchus penetrans were evaluated in four red raspberry cv. Willamette fields in Northwestern Oregon. Field 1 was a silty clay loam with 53% organic matter (OM). Field 2 and 3 were silty loam soils with 3.25 and 2.55% OM, respectively and field 4 was a silty clay with 7.1% OM. The nematicide, fenamiphos (10 kg a.i./ha) was applied in broadcast or band treatments on November 15, 1989. Additional plots in field 3, received a band-nematicide treatment on December 28, 1989 to evaluate the effect of application date on the control of P. penetrans in red raspberry. Field 4 had plots in sites with and without grass and weed ground cover in the aisles between raspberry rows to examine effects of ground cover on nematicide efficacy. Nematodes from soil and roots were sampled monthly from all plots in each field from October 1989 to October 1990. Soil populations of P. penetrans sampled within rows decreased between the October and December sampling dates in all four fields. Soil populations in 3 fields increased in density during mid-summer and reached their highest peak in the middle of September. A similar pattern occurred in P. penetrans soil populations from plots with or without ground cover in aisles between rows of raspberry in field 4. However, in this field, numbers increased in July and reached their peak density in August. Root populations of P. penetrans from red raspberry reached their highest number during spring and summer at all fields. No significant (P>0.05) differences in effectiveness of fenamiphos were detected between band and broadcast method of application and, also between the 2 application dates. Seasonal mean densities of soil populations from band application was only significantly lower than in nontreated controls in areas with ground cover in field 4, respectively. High variability in the numbers of P. penetrans in soil and roots of raspberry was observed throughout the year. Therefore, conclusions about the effectiveness of fenamiphos were difficult to assess. The efficiency of Baermann funnels was 43.9%, when a known number of P. penetrans was added to soil. Total yields of P. penetrans extracted from raspberry roots by mist chamber root extraction (MCRE) were higher (P = 0.05) than yields extracted by polyethylene plastic bag root incubation (PBRI). Approximately 90% of the total P. penetrans recovered was achieved after three and seven days of extraction for PBRI and MCRE, respectively. However, the extraction efficiency of MCRE was 30% higher than PBRI and the daily recovery lasted 28 and 18 days, respectively. Close

• 48. [Article] Soil and growth studies in Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands near Molalla, Oregon

  In 1957 three Douglas-fir stands (15-, 25-, and 40-year-old age classes) were selected on a tree farm in the Cascade foothills of northwestern Oregon to study factors affecting site productivity. Soil-moisture, ...

  Citation × Citation Citation Abstract Copy Title: Soil and growth studies in Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands near Molalla, Oregon Author: Strand, Robert Fenton In 1957 three Douglas-fir stands (15-, 25-, and 40-year-old age classes) were selected on a tree farm in the Cascade foothills of northwestern Oregon to study factors affecting site productivity. Soil-moisture, soil-temperature and seasonal radial- growth pattern measurements were made with a Colman moisture meter and a dial gauge dendrometer on thinned and unthinned subareas. Soil temperatures were significantly increased by thinning in each stand. This effect decreased with soil depth and increased with increasing intensity of thinning. Root distribution studies eight years after thinning showed that a heavily thinned stand had relatively few roots in the lower profile between the remaining trees, in contrast to the complete distribution throughout the profile in the unthinned subareas. This would indicate less overall soil-moisture depletion with thinning since the available soil-moisture levels measured within the fully rooted zone were not significantly different for the various thinning treatments. As expected radial growth increased significantly with increasing intensity of thinning. The amount and proportion of late season growth tended to increase with increasing thinning intensity although the observed differences were not statistically significant. Late season growth, however, was significantly increased by increasing crown position (intermediate to dominant) regardless of thinning treatment. Irrigation of selected trees at a ridgetop area extended the spring maximum radial growth rate throughout most of the summer. On comparable non-irrigated trees growth retardation was detectable in the range of one-half to one atmospheres of soil-moisture tension. Growth cessation occurred when soil-moisture-tension values reached the two to five atmosphere range. Irrigation of trees in a young hillside bench stand slightly increased radial growth rate during the first two years, but decreased growth in relation to non-irrigated trees during the next two years apparently as a result of excess irrigation. Fertilization with high rates of nitrogen and phosphorus fertilizers increased the late season radial growth of irrigated and non-irrigated trees in both stands. The late season response is attributed to a dwindling supply of mineralized soil nitrogen in the late summer and early fall. Irrigation and fertilization combined gave approximately additive increases in radial growth which ranged from 35 to 60 percent. It is hypothesized that potential radial growth (except for short periods at the start and end of the growing season) is equivalent to the maximum spring rate. Departures from this maximum result from deficiencies in moisture, mineral nutrient elements, or heat. Thus the maximum growth rate is proposed as an important characteristic, reflecting the potential carbohydrate productive capacity of the crown when raw material levels exceed rate limiting supplies. The fertility status of each research area was assessed by various means including soil chemical and physical analyses, sampling and chemical analyses of forest floor and litter fall material and pot fertility tests. The relative ranking of these areas in terms of fertility was consistent with their site index or productivity rating. Monterey pine and Douglas-fir seedling test plants grown on the potted soils from the different horizons in each profile responded to nitrogen, phosphorus, and sulphur additions. In field tests nitrogen fertilization stimulated radial growth of Douglas-fir whereas phosphorus fertilizer at high application rates resulted in a growth depression. Title: Soil and growth studies in Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands near Molalla, Oregon Author: Strand, Robert Fenton In 1957 three Douglas-fir stands (15-, 25-, and 40-year-old age classes) were selected on a tree farm in the Cascade foothills of northwestern Oregon to study factors affecting site productivity. Soil-moisture, soil-temperature and seasonal radial- growth pattern measurements were made with a Colman moisture meter and a dial gauge dendrometer on thinned and unthinned subareas. Soil temperatures were significantly increased by thinning in each stand. This effect decreased with soil depth and increased with increasing intensity of thinning. Root distribution studies eight years after thinning showed that a heavily thinned stand had relatively few roots in the lower profile between the remaining trees, in contrast to the complete distribution throughout the profile in the unthinned subareas. This would indicate less overall soil-moisture depletion with thinning since the available soil-moisture levels measured within the fully rooted zone were not significantly different for the various thinning treatments. As expected radial growth increased significantly with increasing intensity of thinning. The amount and proportion of late season growth tended to increase with increasing thinning intensity although the observed differences were not statistically significant. Late season growth, however, was significantly increased by increasing crown position (intermediate to dominant) regardless of thinning treatment. Irrigation of selected trees at a ridgetop area extended the spring maximum radial growth rate throughout most of the summer. On comparable non-irrigated trees growth retardation was detectable in the range of one-half to one atmospheres of soil-moisture tension. Growth cessation occurred when soil-moisture-tension values reached the two to five atmosphere range. Irrigation of trees in a young hillside bench stand slightly increased radial growth rate during the first two years, but decreased growth in relation to non-irrigated trees during the next two years apparently as a result of excess irrigation. Fertilization with high rates of nitrogen and phosphorus fertilizers increased the late season radial growth of irrigated and non-irrigated trees in both stands. The late season response is attributed to a dwindling supply of mineralized soil nitrogen in the late summer and early fall. Irrigation and fertilization combined gave approximately additive increases in radial growth which ranged from 35 to 60 percent. It is hypothesized that potential radial growth (except for short periods at the start and end of the growing season) is equivalent to the maximum spring rate. Departures from this maximum result from deficiencies in moisture, mineral nutrient elements, or heat. Thus the maximum growth rate is proposed as an important characteristic, reflecting the potential carbohydrate productive capacity of the crown when raw material levels exceed rate limiting supplies. The fertility status of each research area was assessed by various means including soil chemical and physical analyses, sampling and chemical analyses of forest floor and litter fall material and pot fertility tests. The relative ranking of these areas in terms of fertility was consistent with their site index or productivity rating. Monterey pine and Douglas-fir seedling test plants grown on the potted soils from the different horizons in each profile responded to nitrogen, phosphorus, and sulphur additions. In field tests nitrogen fertilization stimulated radial growth of Douglas-fir whereas phosphorus fertilizer at high application rates resulted in a growth depression. Close

• 49. [Article] Characterization of selected plant communities within the Tillamook Burn in northwestern Oregon

  A study was initiated in 1961 to characterize seral plant communities in a part of the Cedar Creek drainage in the Tillamook Burn. Stratification of vegetation into ecological units was a necessary first ...

  Citation × Citation Citation Abstract Copy Title: Characterization of selected plant communities within the Tillamook Burn in northwestern Oregon Author: Bailey, Arthur W. A study was initiated in 1961 to characterize seral plant communities in a part of the Cedar Creek drainage in the Tillamook Burn. Stratification of vegetation into ecological units was a necessary first step in conifer-animal damage studies supported by the Oregon State Game Commission. Reconnaissance information was recorded in 92 stands and seven major plant communities were tentatively recognized. Association tables were constructed for analysis of the constancy and canopy coverage data recorded in 42 intensively sampled stands. Two communities that occupied small parts of the study area were described using reconnaissance only. The plant associes is recognized as the seral equivalent to the climax plant association. Five soil series previously mapped were in the study area. The Meda, Astoria, Trask and Kilchis soil series were recognizeable and adequately characterized. The Hembre soil series was found to be too general for application to either synecological research or land management. For this investigation, the series was separated and described as the Hembre I and Hembre II soil series. The Alnus rubra/Polystichum munitum associes is on lower elevation, north-facing slopes. The associes is in a topographic position to benefit from lateral seepage and to have low summer transpiration rates. It is on Meda, Astoria and Hembre II soil series. The Alnus rubra-Acer circinatum associes is on convex, north-facing slopes at usually slightly higher elevations than the Alnus/Polystichum associes. It is topographically located to benefit from lateral seepage and to have a low summer transpiration rate. The associes is on Hembre II and Trask soils. The Acer circinatum-Corylus californica associes is highly variable in species composition and cover. It has a xeric and a mesic phase. Stands are always located in positions to benefit from lateral ground water seepage and are generally located on all but north-facing slopes. The associes is generally on deep Astoria or Hembre II soils, but on bottom slopes it may be on the lithosolic Trask series. The Rubus parviflorus/Trientalis latifolia associes is on upper slopes and on nearly all aspects at higher elevations. It is usually on lithosolic Kilchis soils. The Pteridium aquilinum/Lotus crassifolius is on the deeply weathered Hembre I soil series. It is at higher elevations on most slope directions. The Vaccinium parvifolium/Gaultheria shallon associes is dominated by two late seral or climax species. Drainage is good to excessive on south-facing convex slopes or ridgetops. Macro-climate is apparently the major controlling factor since there is little relation between soil series or solum depth. The Acer macrophyllum/Symphoricarpos mollis and the Acer macrophyllum-Alnus rubra associes are described with reconnaissance data only. The former is on extremely steep, south-facing rock and talus slopes. The latter is on floodplains of major streams. It may have a water table in the rooting zone part of the year. Both shade-intolerant, early seral species and shade-tolerant, late seral or climax species have specific environmental requirements for growth and survival. The vegetation, 17 years after fire, reflects environmental controls and may be used to stratify the landscape into units of equivalent effective environment. Succession is apparently slow in most communities and under natural conditions most communities would have remained in a dynamic, seral state for many years. Implications of the study to game management are discussed. A basis of vegetation stratification suitable for game management studies was established. A relatively rapid method of inventorying and mapping winter deer forage production by plant communities has been demonstrated. A key for recognizing the plant associes was developed. Title: Characterization of selected plant communities within the Tillamook Burn in northwestern Oregon Author: Bailey, Arthur W. A study was initiated in 1961 to characterize seral plant communities in a part of the Cedar Creek drainage in the Tillamook Burn. Stratification of vegetation into ecological units was a necessary first step in conifer-animal damage studies supported by the Oregon State Game Commission. Reconnaissance information was recorded in 92 stands and seven major plant communities were tentatively recognized. Association tables were constructed for analysis of the constancy and canopy coverage data recorded in 42 intensively sampled stands. Two communities that occupied small parts of the study area were described using reconnaissance only. The plant associes is recognized as the seral equivalent to the climax plant association. Five soil series previously mapped were in the study area. The Meda, Astoria, Trask and Kilchis soil series were recognizeable and adequately characterized. The Hembre soil series was found to be too general for application to either synecological research or land management. For this investigation, the series was separated and described as the Hembre I and Hembre II soil series. The Alnus rubra/Polystichum munitum associes is on lower elevation, north-facing slopes. The associes is in a topographic position to benefit from lateral seepage and to have low summer transpiration rates. It is on Meda, Astoria and Hembre II soil series. The Alnus rubra-Acer circinatum associes is on convex, north-facing slopes at usually slightly higher elevations than the Alnus/Polystichum associes. It is topographically located to benefit from lateral seepage and to have a low summer transpiration rate. The associes is on Hembre II and Trask soils. The Acer circinatum-Corylus californica associes is highly variable in species composition and cover. It has a xeric and a mesic phase. Stands are always located in positions to benefit from lateral ground water seepage and are generally located on all but north-facing slopes. The associes is generally on deep Astoria or Hembre II soils, but on bottom slopes it may be on the lithosolic Trask series. The Rubus parviflorus/Trientalis latifolia associes is on upper slopes and on nearly all aspects at higher elevations. It is usually on lithosolic Kilchis soils. The Pteridium aquilinum/Lotus crassifolius is on the deeply weathered Hembre I soil series. It is at higher elevations on most slope directions. The Vaccinium parvifolium/Gaultheria shallon associes is dominated by two late seral or climax species. Drainage is good to excessive on south-facing convex slopes or ridgetops. Macro-climate is apparently the major controlling factor since there is little relation between soil series or solum depth. The Acer macrophyllum/Symphoricarpos mollis and the Acer macrophyllum-Alnus rubra associes are described with reconnaissance data only. The former is on extremely steep, south-facing rock and talus slopes. The latter is on floodplains of major streams. It may have a water table in the rooting zone part of the year. Both shade-intolerant, early seral species and shade-tolerant, late seral or climax species have specific environmental requirements for growth and survival. The vegetation, 17 years after fire, reflects environmental controls and may be used to stratify the landscape into units of equivalent effective environment. Succession is apparently slow in most communities and under natural conditions most communities would have remained in a dynamic, seral state for many years. Implications of the study to game management are discussed. A basis of vegetation stratification suitable for game management studies was established. A relatively rapid method of inventorying and mapping winter deer forage production by plant communities has been demonstrated. A key for recognizing the plant associes was developed. Close

• 50. [Article] Factors Influencing Growth and Bioenergetics of Fish in Forested Headwater Streams Downstream of Forest Harvest

  In this study, we used a combination of conventional statistical analyses and mechanistic bioenergetics models to understand the potential effects of environmental variability on growth of stream-living ...

  Citation × Citation Citation Abstract Copy Title: Factors Influencing Growth and Bioenergetics of Fish in Forested Headwater Streams Downstream of Forest Harvest Author: Jensen, Leslie R. In this study, we used a combination of conventional statistical analyses and mechanistic bioenergetics models to understand the potential effects of environmental variability on growth of stream-living fishes in four headwater streams subject to upstream forest harvest. We focused on two common fish consumers in headwater streams in the Pacific Northwest, USA: trout (Oncorhynchus clarkii clarkii and O. mykiss) and sculpin (Cottus spp.). Statistical analyses focused on patterns of summer growth in relation to upstream forest harvest, and the effects of annually variable stream temperatures, stream discharges, and biomasses of conspecifics. Statistical and bioenergetics models were based on 2,524 individual measurements of growth for trout and 208 measurements for sculpin observed over 8 summers (July-Sept) in four headwater streams in the northwestern Oregon Coast Range. Statistical analyses of patterns of growth indicated no effect of forest harvest on growth of either species. However, increased temperature was associated with increased growth rates, after adjusting for stream discharge and biomass of conspecifics. To further elaborate processes driving growth of fish in the streams we studied, bioenergetics simulations were applied to estimate relative consumption (observed consumption / maximum consumption) based on energy inputs (prey energy densities), temperature and size-dependent physiological costs, and measured growth. Simulations yielded relative consumption values that ranged from 0 to 0.19 (mean = 0.076) for trout and from 0.016 to 0.63 (mean 0.33) for sculpin. Although sculpin exhibited higher levels of relative consumption than trout, 66% of individuals lost weight. In contrast, most trout gained weight (53%), even with lower relative consumption levels. These contrasts reflected higher modelled physiological maintenance costs for sculpin relative to trout. We applied the bioenergetics model to evaluate warming and cooling of stream temperatures within and outside of the range of observed variation and estimated that trout would continue to have positive summer growth, if relative consumption remained unchanged, over a large range of temperatures. Sculpin, on the other hand, were expected to have increased growth rates if mean water temperature increased by up to 1°C, but would be sensitive to further temperature perturbations (positive or negative), unless consumption levels increased. Additionally, sculpin were the dominant fish in terms of biomass and abundance in three of the four stream sites. Collectively, these findings point to a suite of key processes driving growth of fish in headwater streams of the Pacific Northwest Coast, variability in sensitivity of species to environmental conditions, and the importance of sculpin: a group of typically overlooked species that appear to be more abundant and sensitive to environmental conditions than more commonly-studied trout. Title: Factors Influencing Growth and Bioenergetics of Fish in Forested Headwater Streams Downstream of Forest Harvest Author: Jensen, Leslie R. In this study, we used a combination of conventional statistical analyses and mechanistic bioenergetics models to understand the potential effects of environmental variability on growth of stream-living fishes in four headwater streams subject to upstream forest harvest. We focused on two common fish consumers in headwater streams in the Pacific Northwest, USA: trout (Oncorhynchus clarkii clarkii and O. mykiss) and sculpin (Cottus spp.). Statistical analyses focused on patterns of summer growth in relation to upstream forest harvest, and the effects of annually variable stream temperatures, stream discharges, and biomasses of conspecifics. Statistical and bioenergetics models were based on 2,524 individual measurements of growth for trout and 208 measurements for sculpin observed over 8 summers (July-Sept) in four headwater streams in the northwestern Oregon Coast Range. Statistical analyses of patterns of growth indicated no effect of forest harvest on growth of either species. However, increased temperature was associated with increased growth rates, after adjusting for stream discharge and biomass of conspecifics. To further elaborate processes driving growth of fish in the streams we studied, bioenergetics simulations were applied to estimate relative consumption (observed consumption / maximum consumption) based on energy inputs (prey energy densities), temperature and size-dependent physiological costs, and measured growth. Simulations yielded relative consumption values that ranged from 0 to 0.19 (mean = 0.076) for trout and from 0.016 to 0.63 (mean 0.33) for sculpin. Although sculpin exhibited higher levels of relative consumption than trout, 66% of individuals lost weight. In contrast, most trout gained weight (53%), even with lower relative consumption levels. These contrasts reflected higher modelled physiological maintenance costs for sculpin relative to trout. We applied the bioenergetics model to evaluate warming and cooling of stream temperatures within and outside of the range of observed variation and estimated that trout would continue to have positive summer growth, if relative consumption remained unchanged, over a large range of temperatures. Sculpin, on the other hand, were expected to have increased growth rates if mean water temperature increased by up to 1°C, but would be sensitive to further temperature perturbations (positive or negative), unless consumption levels increased. Additionally, sculpin were the dominant fish in terms of biomass and abundance in three of the four stream sites. Collectively, these findings point to a suite of key processes driving growth of fish in headwater streams of the Pacific Northwest Coast, variability in sensitivity of species to environmental conditions, and the importance of sculpin: a group of typically overlooked species that appear to be more abundant and sensitive to environmental conditions than more commonly-studied trout. Close