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• 1. [Article] The effect of age on transpiration rates of Douglas-fir seedlings (Pseudotsuga menziesii (Mirb.) Franco)

  The objective of this study was to determine the effect of age on rates of transpiration by Douglas-fir seedlings. Seeds were collected from a xeric site (Goldendale, Washington) and a mesic site (Forks, ...

  Citation × Citation Citation Abstract Copy Title: The effect of age on transpiration rates of Douglas-fir seedlings (Pseudotsuga menziesii (Mirb.) Franco) Author: Geppert, Rollin Roger The objective of this study was to determine the effect of age on rates of transpiration by Douglas-fir seedlings. Seeds were collected from a xeric site (Goldendale, Washington) and a mesic site (Forks, Washington). The seedlings were grown in a cold frame and in a growth chamber for periods of two, four, eight, and sixteen weeks. Although much interaction occurred between age, seed source, and growing condition, significant differences were delineated for each of the three variables. For both the Forks and Goldendale seedlings, the transpiration rates were not found to decrease significantly with increasing age. At a given age, four, eight, or sixteen weeks, the Forks seedlings grown in the cold frame, in general, had the highest rates of transpiration. The effect of seed source was found to be significant when the seedlings were grown in the cold frame. Under these conditions the seedlings from Forks, Washington, had a significantly higher rate than the seedlings from Goldendale, Washington. The effect of conditioning on transpiration resulted in the seedlings grown in a cold frame having a significantly higher rate than those grown in a growth chamber. Title: The effect of age on transpiration rates of Douglas-fir seedlings (Pseudotsuga menziesii (Mirb.) Franco) Author: Geppert, Rollin Roger The objective of this study was to determine the effect of age on rates of transpiration by Douglas-fir seedlings. Seeds were collected from a xeric site (Goldendale, Washington) and a mesic site (Forks, Washington). The seedlings were grown in a cold frame and in a growth chamber for periods of two, four, eight, and sixteen weeks. Although much interaction occurred between age, seed source, and growing condition, significant differences were delineated for each of the three variables. For both the Forks and Goldendale seedlings, the transpiration rates were not found to decrease significantly with increasing age. At a given age, four, eight, or sixteen weeks, the Forks seedlings grown in the cold frame, in general, had the highest rates of transpiration. The effect of seed source was found to be significant when the seedlings were grown in the cold frame. Under these conditions the seedlings from Forks, Washington, had a significantly higher rate than the seedlings from Goldendale, Washington. The effect of conditioning on transpiration resulted in the seedlings grown in a cold frame having a significantly higher rate than those grown in a growth chamber. Close

• 2. [Article] Genetic variation of wood density components in coastal Douglas- fir and their relationships to growth rhythm

  Overall wood density is a complex trait resulting from the interaction of three components: average earlywood density, average latewood density, and latewood proportion. In order to better understand the ...

  Citation × Citation Citation Abstract Copy Title: Genetic variation of wood density components in coastal Douglas- fir and their relationships to growth rhythm Author: Vargas-Hernandez, Jesus Overall wood density is a complex trait resulting from the interaction of three components: average earlywood density, average latewood density, and latewood proportion. In order to better understand the genetic control of wood density in juvenile Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and to assess the utility of information on its components for improving the efficiency of selection for overall wood density, wood density components were examined in 15-year-old trees of 60 open-pollinated families. Wood density traits were obtained on a ring-by-ring basis by X-ray densitometry of increment cores. In addition to providing information on overall wood density traits over the entire cores, these data made it possible to examine changes in wood density traits with increasing distance from the pith. Relationships between wood density traits and growth phenology, and their implications for tree breeding, were also examined. Overall core density showed strong genetic control (h = 0.59) and a negative genetic correlation with bole volume (rA = -0.52). Wood density components were strongly genetically related with overall core density, but they were also strongly related among themselves and had lower heritability than overall core density. Therefore, information on density components would not be useful for improving the efficiency of selection for overall core density, or for reducing the negative correlated response on volume growth. It is possible, however, to substantially increase volume growth without loss in wood density, or even while slightly increasing wood density, when both traits are included in selection indices. Genetic control of overall core density and its components increased with age (ages 7 to 15). Overall core density and its components at age 15 were also strongly genetically correlated with their respective traits at all younger ages examined. Thus, early selection for overall core density at age 15 would be very effective. Including density components as secondary traits did not enhance the efficiency of early selection for overall core density. Ring density and its components (adjusted by ring size) followed different age trends, but the slopes of the trends did not differ significantly among families. A plateau in the earlywood density trend was observed around age 12 in some trees, and families varied in the proportion of trees having this plateau. This proportion was not correlated with overall core density or with growth traits at age 15. It is hypothesized that the plateau in earlywood density trend might be related to an earlier juvenile-mature transition age. Overall core density and all its components were negatively correlated with dates of cambial growth initiation and latewood transition, and positively correlated with date of cambial growth cessation. Thus, selection for higher wood density would cause a slight extension in the cambial growth period, and an earlier transition to latewood formation. Wood density was not genetically correlated with the date of budburst. Title: Genetic variation of wood density components in coastal Douglas- fir and their relationships to growth rhythm Author: Vargas-Hernandez, Jesus Overall wood density is a complex trait resulting from the interaction of three components: average earlywood density, average latewood density, and latewood proportion. In order to better understand the genetic control of wood density in juvenile Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and to assess the utility of information on its components for improving the efficiency of selection for overall wood density, wood density components were examined in 15-year-old trees of 60 open-pollinated families. Wood density traits were obtained on a ring-by-ring basis by X-ray densitometry of increment cores. In addition to providing information on overall wood density traits over the entire cores, these data made it possible to examine changes in wood density traits with increasing distance from the pith. Relationships between wood density traits and growth phenology, and their implications for tree breeding, were also examined. Overall core density showed strong genetic control (h = 0.59) and a negative genetic correlation with bole volume (rA = -0.52). Wood density components were strongly genetically related with overall core density, but they were also strongly related among themselves and had lower heritability than overall core density. Therefore, information on density components would not be useful for improving the efficiency of selection for overall core density, or for reducing the negative correlated response on volume growth. It is possible, however, to substantially increase volume growth without loss in wood density, or even while slightly increasing wood density, when both traits are included in selection indices. Genetic control of overall core density and its components increased with age (ages 7 to 15). Overall core density and its components at age 15 were also strongly genetically correlated with their respective traits at all younger ages examined. Thus, early selection for overall core density at age 15 would be very effective. Including density components as secondary traits did not enhance the efficiency of early selection for overall core density. Ring density and its components (adjusted by ring size) followed different age trends, but the slopes of the trends did not differ significantly among families. A plateau in the earlywood density trend was observed around age 12 in some trees, and families varied in the proportion of trees having this plateau. This proportion was not correlated with overall core density or with growth traits at age 15. It is hypothesized that the plateau in earlywood density trend might be related to an earlier juvenile-mature transition age. Overall core density and all its components were negatively correlated with dates of cambial growth initiation and latewood transition, and positively correlated with date of cambial growth cessation. Thus, selection for higher wood density would cause a slight extension in the cambial growth period, and an earlier transition to latewood formation. Wood density was not genetically correlated with the date of budburst. Close

• 3. [Article] The effect of preconditioning light intensity on photosynthesis of seedlings of two ecotypes of Douglas-fir

  Douglas-fir (Pseudotsuga menziesii (Mirb. ) Franco) seedlings of a high elevation Rocky Mountain source and a low elevation coastal source were pretreated under both high and low intensity artificial light ...

  Citation × Citation Citation Abstract Copy Title: The effect of preconditioning light intensity on photosynthesis of seedlings of two ecotypes of Douglas-fir Author: Hellinga, Gerald Alan Douglas-fir (Pseudotsuga menziesii (Mirb. ) Franco) seedlings of a high elevation Rocky Mountain source and a low elevation coastal source were pretreated under both high and low intensity artificial light in a growth chamber and outside in a cold frame. Net photosynthesis was then measured at three ages, 6, 10, and 18 weeks, by determining net carbon dioxide exchange with an infrared gas analyzer. The light intensity-photosynthesis relationships of the seedlings were determined at a number of light intensities, and the data were fitted by least squares to a photosynthesis-light response curve with the formula [see pdf for formula] in which P is equal to the net photosynthesis, E is equal to the incident light energy, and B₁, B₂, and B₃ are empirical constants. Seedlings from the coastal source were significantly more efficient photochemically regardless of age or light pretreatment as indicated by the steeper initial slope of the light response curve of photosynthesis. The coastal seedlings also had higher average light-saturated rates of photosynthesis, except at 6 weeks of age. The seedlings' response to light preconditioning was similar for both sources but varied with the age and development of the seedlings. The cotyledons of the six-week-old seedlings had a lower maximum photochemical efficiency and were less susceptible to photoinhibition of the light reactions of photosynthesis by high preconditioning light than were the young juvenile needles of the ten-week- old seedlings. The older juvenile needles of the 18-week-old seedlings were less susceptible to photoinhibition of the dark reactions of photosynthesis than were the immature needles of the ten-week-old seedlings. For seedlings of both sources, at any given age, increased preconditioning light intensity resulted in decreased photosynthetic efficiency. Title: The effect of preconditioning light intensity on photosynthesis of seedlings of two ecotypes of Douglas-fir Author: Hellinga, Gerald Alan Douglas-fir (Pseudotsuga menziesii (Mirb. ) Franco) seedlings of a high elevation Rocky Mountain source and a low elevation coastal source were pretreated under both high and low intensity artificial light in a growth chamber and outside in a cold frame. Net photosynthesis was then measured at three ages, 6, 10, and 18 weeks, by determining net carbon dioxide exchange with an infrared gas analyzer. The light intensity-photosynthesis relationships of the seedlings were determined at a number of light intensities, and the data were fitted by least squares to a photosynthesis-light response curve with the formula [see pdf for formula] in which P is equal to the net photosynthesis, E is equal to the incident light energy, and B₁, B₂, and B₃ are empirical constants. Seedlings from the coastal source were significantly more efficient photochemically regardless of age or light pretreatment as indicated by the steeper initial slope of the light response curve of photosynthesis. The coastal seedlings also had higher average light-saturated rates of photosynthesis, except at 6 weeks of age. The seedlings' response to light preconditioning was similar for both sources but varied with the age and development of the seedlings. The cotyledons of the six-week-old seedlings had a lower maximum photochemical efficiency and were less susceptible to photoinhibition of the light reactions of photosynthesis by high preconditioning light than were the young juvenile needles of the ten-week- old seedlings. The older juvenile needles of the 18-week-old seedlings were less susceptible to photoinhibition of the dark reactions of photosynthesis than were the immature needles of the ten-week-old seedlings. For seedlings of both sources, at any given age, increased preconditioning light intensity resulted in decreased photosynthetic efficiency. Close

• 4. [Article] Use of alternative costs in determining the economic rotation age of Douglas-fir

  Citation × Citation Citation Abstract Copy Title: Use of alternative costs in determining the economic rotation age of Douglas-fir Author: Dahl, Fredrick Henry Title: Use of alternative costs in determining the economic rotation age of Douglas-fir Author: Dahl, Fredrick Henry Close

• 5. [Article] Effect of seedling characteristics on Kraft pulping properties of young Douglas-fir

  A study has been made of the kraft pulping properties of young Douglas-fir trees which were thinned from an experimental plantation. The purpose of the plantation study is to determine, whether two year ...

  Citation × Citation Citation Abstract Copy Title: Effect of seedling characteristics on Kraft pulping properties of young Douglas-fir Author: Chia, Shun Nan A study has been made of the kraft pulping properties of young Douglas-fir trees which were thinned from an experimental plantation. The purpose of the plantation study is to determine, whether two year old seedlings can be selected on the criteria of height and branch count for future desirable tree and utilization characteristics. The trees used in this experiment were 15 years old at the time of cutting. They were all pulped by a standardized kraft process, and the pulp evaluated according to TAPPI Standards. The test results were evaluated by an analysis of variance computer program at certain discrete refining intervals, 600, 400, and 200 Canadian Standard Freeness, and 0.7 and 0.8 gms/cc sheet density. The trees grown from seeds germinated in the Corvallis nursery were, as a class, taller and larger in volume than their counterparts from the Salem nursery. Significant differences in tensile and bursting strengths, properties important to the linerboard industry, were found between these two classes of pulps, with the Corvallis pulps stronger than the Salem pulps. Lesser differences in these two properties were found when the pulps were classified according to the branch count of the parent trees, and no significant difference could be attributed to the tree height (Control vs. Super Seedlings) criteria. The differences in the other pulp characteristics were found to be non-significant by any of the criteria of tree classification. Two factor analysis of the pulp properties within nurseries disclosed no significant differences within the Corvallis nursery trees, but substantially more significant differences within the Salem nursery trees. The inference is that both pulp properties at age 15 and branch count at age 2 are predominantly influenced by hereditary factors. Tree height at age two is less influenced by heredity than branch count. Overall, the differences in pulp quality between the tested trees are small, which is not surprising in view of the high proportion of juvenile wood and the relative lack of differentiation. Larger differences may be apparent when the trees are older. The pulp properties compare favorably with those of other Douglas-fir kraft pulps prepared at the Forest Research Laboratory, but the influence of the juvenile fibers can be detected in this comparison also. Title: Effect of seedling characteristics on Kraft pulping properties of young Douglas-fir Author: Chia, Shun Nan A study has been made of the kraft pulping properties of young Douglas-fir trees which were thinned from an experimental plantation. The purpose of the plantation study is to determine, whether two year old seedlings can be selected on the criteria of height and branch count for future desirable tree and utilization characteristics. The trees used in this experiment were 15 years old at the time of cutting. They were all pulped by a standardized kraft process, and the pulp evaluated according to TAPPI Standards. The test results were evaluated by an analysis of variance computer program at certain discrete refining intervals, 600, 400, and 200 Canadian Standard Freeness, and 0.7 and 0.8 gms/cc sheet density. The trees grown from seeds germinated in the Corvallis nursery were, as a class, taller and larger in volume than their counterparts from the Salem nursery. Significant differences in tensile and bursting strengths, properties important to the linerboard industry, were found between these two classes of pulps, with the Corvallis pulps stronger than the Salem pulps. Lesser differences in these two properties were found when the pulps were classified according to the branch count of the parent trees, and no significant difference could be attributed to the tree height (Control vs. Super Seedlings) criteria. The differences in the other pulp characteristics were found to be non-significant by any of the criteria of tree classification. Two factor analysis of the pulp properties within nurseries disclosed no significant differences within the Corvallis nursery trees, but substantially more significant differences within the Salem nursery trees. The inference is that both pulp properties at age 15 and branch count at age 2 are predominantly influenced by hereditary factors. Tree height at age two is less influenced by heredity than branch count. Overall, the differences in pulp quality between the tested trees are small, which is not surprising in view of the high proportion of juvenile wood and the relative lack of differentiation. Larger differences may be apparent when the trees are older. The pulp properties compare favorably with those of other Douglas-fir kraft pulps prepared at the Forest Research Laboratory, but the influence of the juvenile fibers can be detected in this comparison also. Close

• 6. [Article] Forest structure and regeneration in the Tsuga heterophylla - Abies amabilis transition zone, central Western Cascades, Oregon

  The dynamics of stands in the mid-elevation old-growth Douglas-fir (Pseudotsuga menziesii) forests of the central western Oregon Cascade Range were investigated using stand structure analysis. Trees with ...

  Citation × Citation Citation Abstract Copy Title: Forest structure and regeneration in the Tsuga heterophylla - Abies amabilis transition zone, central Western Cascades, Oregon Author: Stewart, Glenn H. The dynamics of stands in the mid-elevation old-growth Douglas-fir (Pseudotsuga menziesii) forests of the central western Oregon Cascade Range were investigated using stand structure analysis. Trees with different growth rates were commonly present in the same stand, which resulted often in a weak correlation between tree diameter and age. Thus, age data and information on spatial dispersion and disturbance history were collected to aid in interpreting stand development. The population structures described were influenced by periodic fires of variable intensity and extent that resulted in a mosaic of relatively even-aged patches of different conifer species. The overall pattern depends on stochastic factors, species' life history attributes, and the nature of the fire events. The species that first dominates a site following a disturbance profoundly affects subsequent stand composition and development. If Pseudotsuga menziesii or noble fir (Abies procera) dominate early, then tree regeneration of western hemlock (Tsuga heterophylla) and often Pacific silver fir (Abies amabilis) will rapidly occur. Conversely, if Tsuga heterophylla establishes first, regeneration will be absent or minimal until canopy openings are formed. Several factors that influence regeneration depend on the main canopy composition. Canopy density determines how much light reaches the understory which in turn influences the abundance of tree seedlings and herbaceous species. Secondly, windfalls of old trees, branches, and snags often create canopy openings that are colonized by new seedlings or filled by previously established individuals. Lastly, decaying logs and stumps provide important substrates for tree seedling establishment, especially for Tsuga heterophylla. In stands without fire for at least several centuries, canopy openings are critical for the successful regeneration of the shade tolerant species Tsuga and Abies amabilis. The amount of direct beam radiation during the growing season is correlated with numbers and height growth of seedlings and saplings in larger openings. These interactions demonstrate the need for successional schemes to include the effects of different canopy species, in addition to various disturbances, as factors controlling the rate and nature of forest succession. Title: Forest structure and regeneration in the Tsuga heterophylla - Abies amabilis transition zone, central Western Cascades, Oregon Author: Stewart, Glenn H. The dynamics of stands in the mid-elevation old-growth Douglas-fir (Pseudotsuga menziesii) forests of the central western Oregon Cascade Range were investigated using stand structure analysis. Trees with different growth rates were commonly present in the same stand, which resulted often in a weak correlation between tree diameter and age. Thus, age data and information on spatial dispersion and disturbance history were collected to aid in interpreting stand development. The population structures described were influenced by periodic fires of variable intensity and extent that resulted in a mosaic of relatively even-aged patches of different conifer species. The overall pattern depends on stochastic factors, species' life history attributes, and the nature of the fire events. The species that first dominates a site following a disturbance profoundly affects subsequent stand composition and development. If Pseudotsuga menziesii or noble fir (Abies procera) dominate early, then tree regeneration of western hemlock (Tsuga heterophylla) and often Pacific silver fir (Abies amabilis) will rapidly occur. Conversely, if Tsuga heterophylla establishes first, regeneration will be absent or minimal until canopy openings are formed. Several factors that influence regeneration depend on the main canopy composition. Canopy density determines how much light reaches the understory which in turn influences the abundance of tree seedlings and herbaceous species. Secondly, windfalls of old trees, branches, and snags often create canopy openings that are colonized by new seedlings or filled by previously established individuals. Lastly, decaying logs and stumps provide important substrates for tree seedling establishment, especially for Tsuga heterophylla. In stands without fire for at least several centuries, canopy openings are critical for the successful regeneration of the shade tolerant species Tsuga and Abies amabilis. The amount of direct beam radiation during the growing season is correlated with numbers and height growth of seedlings and saplings in larger openings. These interactions demonstrate the need for successional schemes to include the effects of different canopy species, in addition to various disturbances, as factors controlling the rate and nature of forest succession. Close

• 7. [Article] Effect of thinning and fertilization on wood properties and intra-ring characteristics in young Douglas-fir

  The purpose of this study was to determine if thinning, fertilization or a combination of thinning and fertilization had an effect on overall average specific gravity, modulus of elasticity, modulus of ...

  Citation × Citation Citation Abstract Copy Title: Effect of thinning and fertilization on wood properties and intra-ring characteristics in young Douglas-fir Author: Bodner, Josef The purpose of this study was to determine if thinning, fertilization or a combination of thinning and fertilization had an effect on overall average specific gravity, modulus of elasticity, modulus of rupture, fiber length and intra-ring characteristics. Material for this experiment consisted of 7 trees randomly selected from each of two thinning/fertilization treatments and a control (unthinned and not fertilized) stand. Thus a total of 21 trees were involved. The trees were cut in the summer of 1982. Static bending tests were done on juvenile and mature wood from trees of all plots at the butt and at a height of 18 feet. Specific gravity and fiber length were also determined. The intra-ring parameters (earlywood width, latewood width, ring width, earlywood density, latewood density, ring density, minimum earlywood density, maximum latewood density, density range and percentage latewood) were determined by X-ray studies. Statistical analyses showed significant differences between treatments (thinning, or thinning/fertilization) in modulus of elasticity, modulus of rupture, fiber lengths and all the intra-ring parameters. Overall average specific gravity did not differ significantly among treatments but did between butt and top (18-foot height) wood values. Ring width and ring density seemed most influential on mechanical properties. Average modulus of elasticity for the samples tested were 10.6% (for the thinning/fertilization experiment) and 17.3% (for the thinning experiment) less than comparable values in the control plot. Average modulus of rupture for the samples tested were 6.3% (for the thinning/fertilization experiment) and 12.4% (for the thinning experiment) less than comparable values in the control plot. Age seemed to have the most influence on fiber length. Thinning treatments within the tree age-range of juvenile wood affected intra-ring parameters less than did such treatments in the age-range of mature wood. Fertilization by itself did not significantly increase tree growth (annual ring width). Title: Effect of thinning and fertilization on wood properties and intra-ring characteristics in young Douglas-fir Author: Bodner, Josef The purpose of this study was to determine if thinning, fertilization or a combination of thinning and fertilization had an effect on overall average specific gravity, modulus of elasticity, modulus of rupture, fiber length and intra-ring characteristics. Material for this experiment consisted of 7 trees randomly selected from each of two thinning/fertilization treatments and a control (unthinned and not fertilized) stand. Thus a total of 21 trees were involved. The trees were cut in the summer of 1982. Static bending tests were done on juvenile and mature wood from trees of all plots at the butt and at a height of 18 feet. Specific gravity and fiber length were also determined. The intra-ring parameters (earlywood width, latewood width, ring width, earlywood density, latewood density, ring density, minimum earlywood density, maximum latewood density, density range and percentage latewood) were determined by X-ray studies. Statistical analyses showed significant differences between treatments (thinning, or thinning/fertilization) in modulus of elasticity, modulus of rupture, fiber lengths and all the intra-ring parameters. Overall average specific gravity did not differ significantly among treatments but did between butt and top (18-foot height) wood values. Ring width and ring density seemed most influential on mechanical properties. Average modulus of elasticity for the samples tested were 10.6% (for the thinning/fertilization experiment) and 17.3% (for the thinning experiment) less than comparable values in the control plot. Average modulus of rupture for the samples tested were 6.3% (for the thinning/fertilization experiment) and 12.4% (for the thinning experiment) less than comparable values in the control plot. Age seemed to have the most influence on fiber length. Thinning treatments within the tree age-range of juvenile wood affected intra-ring parameters less than did such treatments in the age-range of mature wood. Fertilization by itself did not significantly increase tree growth (annual ring width). Close

• 8. [Article] The bleaching response of kraft pulps from fresh and aged commercial Douglas-fir chips

  Citation × Citation Citation Abstract Copy Title: The bleaching response of kraft pulps from fresh and aged commercial Douglas-fir chips Author: Lai, Jinn-Hsing Title: The bleaching response of kraft pulps from fresh and aged commercial Douglas-fir chips Author: Lai, Jinn-Hsing Close

• 9. [Article] The effect of drought on the rate of photosynthesis, respiration, and transpiration in two ecotypes of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)

  The subject of this study was the determination of the changes in photosynthesis, respiration and transpiration in two ecotypes of Douglas-fir as caused by decreasing soil moisture content. The photosynthetic rate ...

  Citation × Citation Citation Abstract Copy Title: The effect of drought on the rate of photosynthesis, respiration, and transpiration in two ecotypes of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) Author: Zavitkovski, J. The subject of this study was the determination of the changes in photosynthesis, respiration and transpiration in two ecotypes of Douglas-fir as caused by decreasing soil moisture content. The photosynthetic rate was also correlated with the relative turgidities of needles. All the above processes were greatly affected by decreasing soil moisture. In general they decreased with the decrease in soil moisture. The transpirational rate was affected relatively more than photosynthetic rate, and the respiratory rate was affected least. The photosynthetic rates of the two-months-old seedlings of both sources were consistently higher under optimal soil moisture conditions but they were significantly lower (at 1% level) at low soil moistures than those of the three-months-old plants. There was no significant difference found in the photosynthetic rates between the two sources at two months of age, but significantly higher photosynthetic rate at high soil moistures was found in the three-months-old N. E. Washington seedlings when compared with the Valsetz plants. There is an indication that at very low soil moistures the photosynthetic rate of the N. E. Washington seedlings is higher also but this could not be shown statistically because of the relatively small number of observations. A good correlation was found between the photosynthetic rate and relative turgidities of needles in both ecotypes. For the same soil moisture a higher relative turgidity was observed in the needles of the N. E. Washington seedlings than in the Valsetz source. The respiratory rates of the two-months-old seedlings of both sources were consistently higher than those of the three-months-old plants. While the difference in respiratory rates between the two ecotypes was not significant at two months of age, it was significantly higher in the Valsetz source at three months. It is suggested that this difference was due to the relatively larger proportion of the newly developing needles in this ecotype. Contrary to observations made by some researchers no increase in the respiration was determined at the onset of the drought or at the lowest soil moistures used in this study. The relation between the soil moisture and transpirational rate was, linear in both sources in the range below 12% of soil moisture. In this range the transpirational rates of the Valsetz seedlings were significantly higher (at 1% level) than those of the N. E. Washington plants. The top/root ratios were found significantly different between the two- and three-months-old seedlings in both sources, and also between the Valsetz and N. E. Washington seedlings at two and three months of age. These ratios decreased in both sources between the ages of two and three months. The ratio of the three-months-old N. E. Washington seedlings was the lowest while that of the two-months- old Valsetz plants the highest. The lower transpirational rate in the N. E. Washington seedlings is of definite advantage for survival on droughty sites. This survival ability is further increased by their low top/root ratio. There is some evidence that they would suit extreme sites much better than the Valsetz source. It is suggested that the periodical droughts of N. E. Washington exercised a strong selection pressure In that direction while in the relatively mild climate of the Coastal Range in Oregon another ecotype was created. Title: The effect of drought on the rate of photosynthesis, respiration, and transpiration in two ecotypes of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) Author: Zavitkovski, J. The subject of this study was the determination of the changes in photosynthesis, respiration and transpiration in two ecotypes of Douglas-fir as caused by decreasing soil moisture content. The photosynthetic rate was also correlated with the relative turgidities of needles. All the above processes were greatly affected by decreasing soil moisture. In general they decreased with the decrease in soil moisture. The transpirational rate was affected relatively more than photosynthetic rate, and the respiratory rate was affected least. The photosynthetic rates of the two-months-old seedlings of both sources were consistently higher under optimal soil moisture conditions but they were significantly lower (at 1% level) at low soil moistures than those of the three-months-old plants. There was no significant difference found in the photosynthetic rates between the two sources at two months of age, but significantly higher photosynthetic rate at high soil moistures was found in the three-months-old N. E. Washington seedlings when compared with the Valsetz plants. There is an indication that at very low soil moistures the photosynthetic rate of the N. E. Washington seedlings is higher also but this could not be shown statistically because of the relatively small number of observations. A good correlation was found between the photosynthetic rate and relative turgidities of needles in both ecotypes. For the same soil moisture a higher relative turgidity was observed in the needles of the N. E. Washington seedlings than in the Valsetz source. The respiratory rates of the two-months-old seedlings of both sources were consistently higher than those of the three-months-old plants. While the difference in respiratory rates between the two ecotypes was not significant at two months of age, it was significantly higher in the Valsetz source at three months. It is suggested that this difference was due to the relatively larger proportion of the newly developing needles in this ecotype. Contrary to observations made by some researchers no increase in the respiration was determined at the onset of the drought or at the lowest soil moistures used in this study. The relation between the soil moisture and transpirational rate was, linear in both sources in the range below 12% of soil moisture. In this range the transpirational rates of the Valsetz seedlings were significantly higher (at 1% level) than those of the N. E. Washington plants. The top/root ratios were found significantly different between the two- and three-months-old seedlings in both sources, and also between the Valsetz and N. E. Washington seedlings at two and three months of age. These ratios decreased in both sources between the ages of two and three months. The ratio of the three-months-old N. E. Washington seedlings was the lowest while that of the two-months- old Valsetz plants the highest. The lower transpirational rate in the N. E. Washington seedlings is of definite advantage for survival on droughty sites. This survival ability is further increased by their low top/root ratio. There is some evidence that they would suit extreme sites much better than the Valsetz source. It is suggested that the periodical droughts of N. E. Washington exercised a strong selection pressure In that direction while in the relatively mild climate of the Coastal Range in Oregon another ecotype was created. Close

• 10. [Article] Weibull diameter distribution models for managed stands of Douglas-fir in Washington and Oregon

  The two-parameter Weibull function was used to predict forest stand diameter distributions and growth. Diameter distribution models were developed for even-aged Douglas-fir stands, 20 to 40 years old, ...

  Citation × Citation Citation Abstract Copy Title: Weibull diameter distribution models for managed stands of Douglas-fir in Washington and Oregon Author: Eng, Helge The two-parameter Weibull function was used to predict forest stand diameter distributions and growth. Diameter distribution models were developed for even-aged Douglas-fir stands, 20 to 40 years old, in Oregon and Washington. In order to test if the two-parameter Weibull function can adequately describe the diameter distributions of such stands, maximum likelihood estimated parameters of the two parameter Weibull function were compared with observed diameter distributions. Two sets of models were developed. The first set of models predicted the diameter distributions of unthinned forest stands from stand variables. Models were developed to predict each of the two parameters of the Weibull function from stand variables. The Weibull function with the two estimated parameters became the diameter distribution model for the stand. The second set of models predicted the growth of a stand of trees after thinning. A Weibull diameter distribution model was developed for a forest stand after a growth period. The parameters of the Weibull function were estimated from stand variables at the beginning of the growth period and the length of the growth period. Results showed that the two-parameter Weibull function can describe the diameter distributions of even-aged stands of Douglas-fir, 20 to 40 years old, in Oregon and Washington. The diameter distribution model for unthinned stands predicted the observed diameter distributions in an independent data set quite well. The diameter distribution model for a thinned stand after a growth period gave a satisfactory prediction for 93 percent of the observed diameter distributions in the independent data set. The two-parameter Weibull function in this study gave at least as good results as that which has been obtained with the three-parameter Weibull function in previous studies. Title: Weibull diameter distribution models for managed stands of Douglas-fir in Washington and Oregon Author: Eng, Helge The two-parameter Weibull function was used to predict forest stand diameter distributions and growth. Diameter distribution models were developed for even-aged Douglas-fir stands, 20 to 40 years old, in Oregon and Washington. In order to test if the two-parameter Weibull function can adequately describe the diameter distributions of such stands, maximum likelihood estimated parameters of the two parameter Weibull function were compared with observed diameter distributions. Two sets of models were developed. The first set of models predicted the diameter distributions of unthinned forest stands from stand variables. Models were developed to predict each of the two parameters of the Weibull function from stand variables. The Weibull function with the two estimated parameters became the diameter distribution model for the stand. The second set of models predicted the growth of a stand of trees after thinning. A Weibull diameter distribution model was developed for a forest stand after a growth period. The parameters of the Weibull function were estimated from stand variables at the beginning of the growth period and the length of the growth period. Results showed that the two-parameter Weibull function can describe the diameter distributions of even-aged stands of Douglas-fir, 20 to 40 years old, in Oregon and Washington. The diameter distribution model for unthinned stands predicted the observed diameter distributions in an independent data set quite well. The diameter distribution model for a thinned stand after a growth period gave a satisfactory prediction for 93 percent of the observed diameter distributions in the independent data set. The two-parameter Weibull function in this study gave at least as good results as that which has been obtained with the three-parameter Weibull function in previous studies. Close