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• 1. [Article] Interactions of ammoniacal copper zinc arsenate (ACZA) with Douglas-fir

  Tests were conducted to determine the effect of ACZA composition on fixation and the roles of adsorption and precipitation in fixation. The sites of copper and zinc adsorption within the treated wood and ...

  Citation × Citation Citation Abstract Copy Title: Interactions of ammoniacal copper zinc arsenate (ACZA) with Douglas-fir Author: Lebow, Stan T., Morrell, Jeffrey J. Tests were conducted to determine the effect of ACZA composition on fixation and the roles of adsorption and precipitation in fixation. The sites of copper and zinc adsorption within the treated wood and the bonding environment of adsorbed copper were also examined. The results generally support the finding that arsenic fixation occurs by precipitation of metal/arsenate complexes. Arsenic leaching was minimized with high solution ratios of metal oxide:arsenic pentoxide, and with formulations containing zinc. Zinc precipitated the majority of arsenic when ammonia was allowed to evaporate from the treating solution. The metal cations were leach-resistant regardless of ACZA formulation because of their low water solubility and their ability to adsorb to the wood. Copper was readily adsorbed by lignin and by model compounds that possessed phenolic hydroxyl groups, which suggests that phenolic hydroxyl groups were the primary reaction sites. Fourier Transform Infrared (FTIR) and Fast Atom Bombardment (FAB) mass spectroscopy analysis also supported this conclusion. Multiple copper species and increased free radical content were detected within lignin that had adsorbed copper. Adsorption of copper and zinc has important ramifications for arsenic fixation. Title: Interactions of ammoniacal copper zinc arsenate (ACZA) with Douglas-fir Author: Lebow, Stan T., Morrell, Jeffrey J. Tests were conducted to determine the effect of ACZA composition on fixation and the roles of adsorption and precipitation in fixation. The sites of copper and zinc adsorption within the treated wood and the bonding environment of adsorbed copper were also examined. The results generally support the finding that arsenic fixation occurs by precipitation of metal/arsenate complexes. Arsenic leaching was minimized with high solution ratios of metal oxide:arsenic pentoxide, and with formulations containing zinc. Zinc precipitated the majority of arsenic when ammonia was allowed to evaporate from the treating solution. The metal cations were leach-resistant regardless of ACZA formulation because of their low water solubility and their ability to adsorb to the wood. Copper was readily adsorbed by lignin and by model compounds that possessed phenolic hydroxyl groups, which suggests that phenolic hydroxyl groups were the primary reaction sites. Fourier Transform Infrared (FTIR) and Fast Atom Bombardment (FAB) mass spectroscopy analysis also supported this conclusion. Multiple copper species and increased free radical content were detected within lignin that had adsorbed copper. Adsorption of copper and zinc has important ramifications for arsenic fixation. Close

• 2. [Article] Establishment and growth of natural and planted conifers ten years after overstory thinning and vegetation control in 50-year-old Douglas-fir stands

  Forest managers of public lands in western Oregon and Washington have become increasingly interested in creating additional conifer cohorts in young, even-aged, second-growth Douglas-fir stands. The purpose ...

  Citation × Citation Citation Abstract Copy Title: Establishment and growth of natural and planted conifers ten years after overstory thinning and vegetation control in 50-year-old Douglas-fir stands Author: Nabel, Mark R. Forest managers of public lands in western Oregon and Washington have become increasingly interested in creating additional conifer cohorts in young, even-aged, second-growth Douglas-fir stands. The purpose of our research was to assess the establishment, survival, and growth of naturally-regenerated and underplanted conifers 10-13 years after overstory thinning and understory vegetation control in 50-year-old Douglas-fir stands. Two sites within the Oregon Coast Range were used in our study. One site was relatively dry (~130 cm of annual precipitation) and contained a mostly pure Douglas-fir overstory. The second site was moister (~175 cm of annual precipitation) and contained a Douglas-fir/western hemlock mixed-species overstory. At each site, stands were thinned to basal areas ranging from approximately 18 to 32 m2/ha using either a uniform or gappy thinning pattern. In the gappy treatment, 20% of the total area was comprised of 0.06- and 0.10-ha gaps. Understory vegetation was controlled across a portion of each thinning plot using a broadcast application of herbicides prior to thinning. After thinning, the following species were underplanted: Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), western redcedar (Thuja plicata), and grand fir (Abies grandis, dry site only). Establishment of natural regeneration and survival of underplanted conifers was greater for all species under lower overstory densities at the drier site, but on the moister site, where western hemlock regenerated prolifically in the understory, no differences were detected. At both sites, underplanted and dominant naturally-regenerated conifers growing under lower overstory retention levels were generally taller and had larger diameters after ten years. Thinning pattern had no effect on the establishment, survival, or growth of understory conifers at the overall stand level, but the tallest individuals were located within gaps. Controlling competing vegetation increased the rate of establishment for naturally-regenerated Douglas-fir and the rate of survival for planted Douglas-fir and western hemlock. Vegetation control generally resulted in larger underplanted seedlings of all species after ten years, but the size of dominant naturally-regenerated conifers was not affected. Shade-tolerant species generally outperformed Douglas-fir in understories except where western redcedar suffered heavy browsing damage. Natural regeneration of western hemlock may contribute to the development of an understory conifer layer when a seed source is present in the overstory, but in mostly pure Douglas-fir stands, underplanting would likely be required to supplement sporadic and slow-growing natural regeneration. In either case, future thinnings of rapidly closing overstory canopies would be required to maintain the long-term development of an understory conifer layer. Title: Establishment and growth of natural and planted conifers ten years after overstory thinning and vegetation control in 50-year-old Douglas-fir stands Author: Nabel, Mark R. Forest managers of public lands in western Oregon and Washington have become increasingly interested in creating additional conifer cohorts in young, even-aged, second-growth Douglas-fir stands. The purpose of our research was to assess the establishment, survival, and growth of naturally-regenerated and underplanted conifers 10-13 years after overstory thinning and understory vegetation control in 50-year-old Douglas-fir stands. Two sites within the Oregon Coast Range were used in our study. One site was relatively dry (~130 cm of annual precipitation) and contained a mostly pure Douglas-fir overstory. The second site was moister (~175 cm of annual precipitation) and contained a Douglas-fir/western hemlock mixed-species overstory. At each site, stands were thinned to basal areas ranging from approximately 18 to 32 m2/ha using either a uniform or gappy thinning pattern. In the gappy treatment, 20% of the total area was comprised of 0.06- and 0.10-ha gaps. Understory vegetation was controlled across a portion of each thinning plot using a broadcast application of herbicides prior to thinning. After thinning, the following species were underplanted: Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), western redcedar (Thuja plicata), and grand fir (Abies grandis, dry site only). Establishment of natural regeneration and survival of underplanted conifers was greater for all species under lower overstory densities at the drier site, but on the moister site, where western hemlock regenerated prolifically in the understory, no differences were detected. At both sites, underplanted and dominant naturally-regenerated conifers growing under lower overstory retention levels were generally taller and had larger diameters after ten years. Thinning pattern had no effect on the establishment, survival, or growth of understory conifers at the overall stand level, but the tallest individuals were located within gaps. Controlling competing vegetation increased the rate of establishment for naturally-regenerated Douglas-fir and the rate of survival for planted Douglas-fir and western hemlock. Vegetation control generally resulted in larger underplanted seedlings of all species after ten years, but the size of dominant naturally-regenerated conifers was not affected. Shade-tolerant species generally outperformed Douglas-fir in understories except where western redcedar suffered heavy browsing damage. Natural regeneration of western hemlock may contribute to the development of an understory conifer layer when a seed source is present in the overstory, but in mostly pure Douglas-fir stands, underplanting would likely be required to supplement sporadic and slow-growing natural regeneration. In either case, future thinnings of rapidly closing overstory canopies would be required to maintain the long-term development of an understory conifer layer. Close

• 3. [Article] Douglas-fir displays a range of growth responses to temperature, water, and Swiss needle cast in western Oregon, USA

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Elsevier and is ...

  Citation × Citation Citation Abstract Copy Title: Douglas-fir displays a range of growth responses to temperature, water, and Swiss needle cast in western Oregon, USA Author: Bollman, Michael, Lee, E. Henry, Carlile, Cailie, Waschmann, Ronald S., Cline, Steve, Tingey, David T., Beedlow, Peter A., Wickham, Charlotte To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Elsevier and is in the public domain. The published article can be found at: http://www.journals.elsevier.com/agricultural-and-forest-meteorology/ Title: Douglas-fir displays a range of growth responses to temperature, water, and Swiss needle cast in western Oregon, USA Author: Bollman, Michael, Lee, E. Henry, Carlile, Cailie, Waschmann, Ronald S., Cline, Steve, Tingey, David T., Beedlow, Peter A., Wickham, Charlotte To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Elsevier and is in the public domain. The published article can be found at: http://www.journals.elsevier.com/agricultural-and-forest-meteorology/ Close

• 4. [Article] Interactions between ecosystem nitrogen and bedrock control long-term calcium sources in Oregon Coast Range forests

  Ecosystem nitrogen (N) supply strongly influences the availability and cycling of other essential nutrients in temperate forests, especially calcium (Ca). Short-term additions of N that exceed ecosystem ...

  Citation × Citation Citation Abstract Copy Title: Interactions between ecosystem nitrogen and bedrock control long-term calcium sources in Oregon Coast Range forests Author: Hynicka, Justin D. Ecosystem nitrogen (N) supply strongly influences the availability and cycling of other essential nutrients in temperate forests, especially calcium (Ca). Short-term additions of N that exceed ecosystem demands often increase dissolved nitrate fluxes and decrease soil pH, which can stimulate soil Ca loss. However, the long-term effects of high N supply on ecosystem Ca availability are more difficult to determine, and may depend on the Ca content of bedrock and mineral soils. To address this, we examined major and trace element concentrations and ⁸⁷Sr/⁸⁶Sr ratios that trace Ca sources in precipitation, foliage, soil pools, and bedrock at 24 forested sites in the Oregon Coast Range having a wide, natural range of soil N (0.16 - 0.97 % N, 0-10 cm) on contrasting basaltic and sedimentary bedrock. Using a suite of 17 site properties, we also evaluated whether soil N variation across sites was related to the five major state-factors of soil and ecosystem development: climate, organisms, topography, parent material, and time. We found that as soil N increased across sites, its ¹⁵N/¹⁴N ratio declined towards atmospheric values, suggesting that soil N variation reflects a biotic legacy of symbiotic N fixation inputs. In contrast, soil N variation was unrelated to 17 other metrics of soil forming factors that represented climate (mean annual precipitation, mean annual temperature, and distance from the coast), topography (slope, soil depth, and abundance of coarse rock fragments), parent material (within bedrock type bulk and 1 M HNO₃ leachable rock Ca chemistry), and proxies of soil age (Hurst's redness rating, effective cation exchange capacity, Ca in non-exchangeable soil residues, chemical index of alteration, weathering index of Parker, Ca in coarse soil fragments, and soil Ca loss relative to bedrock). These analyses highlight symbiotic N-fixing red alder as a keystone organismal state-factor that produces a wide range of soil N accumulation in coastal Oregon forests. Strontium isotopes (⁸⁷Sr/⁸⁶Sr) and other geochemical analyses indicate that long-term Ca sources in foliage and exchangeable soil pools in Oregon Coast Range forests depend on an interactive effect between N availability and bedrock. Basaltic rocks contained nearly 20-times more Ca than sedimentary rocks across our sites, and this difference was reflected in Sr-isotope partitioning of base cation sources. Atmospheric sources dominated plant and soil pools in forests overlying Ca-poor sedimentary rock, regardless of variation in soil N, indicating extremely limited capacity of weathering to support forest Ca demands. In contrast, forests overlying basaltic rock obtained as much as 80% of Ca from rock weathering in low N sites, yet relied to a greater extent on atmospheric Ca as soil N increased, with less than 10% of Ca from rock weathering at sites with the highest soil N. Surprisingly, differences in fresh rock Ca content and base cation sources between sedimentary and basaltic sites was not reflected in ecosystem Ca availability, and instead increasing soil N caused similar declines in foliar and exchangeable Ca across both rock types. This illustrates that nutrient pool sizes do not necessarily reflect long-term nutrient supply, and highlights how coupled biogeochemical cycles within ecosystems can regulate nutrient loss and supply to biota. Broadly, our results highlight how interactions between biological and geologic factors can influence base cation sources in forest ecosystems. The sustainability of base cation supplies to forests may therefore depend greatly on variation in bedrock weathering at low N sites, yet converge to depend on atmospheric inputs in sites that receive high N loading from biological fixation or anthropogenic deposition. Title: Interactions between ecosystem nitrogen and bedrock control long-term calcium sources in Oregon Coast Range forests Author: Hynicka, Justin D. Ecosystem nitrogen (N) supply strongly influences the availability and cycling of other essential nutrients in temperate forests, especially calcium (Ca). Short-term additions of N that exceed ecosystem demands often increase dissolved nitrate fluxes and decrease soil pH, which can stimulate soil Ca loss. However, the long-term effects of high N supply on ecosystem Ca availability are more difficult to determine, and may depend on the Ca content of bedrock and mineral soils. To address this, we examined major and trace element concentrations and ⁸⁷Sr/⁸⁶Sr ratios that trace Ca sources in precipitation, foliage, soil pools, and bedrock at 24 forested sites in the Oregon Coast Range having a wide, natural range of soil N (0.16 - 0.97 % N, 0-10 cm) on contrasting basaltic and sedimentary bedrock. Using a suite of 17 site properties, we also evaluated whether soil N variation across sites was related to the five major state-factors of soil and ecosystem development: climate, organisms, topography, parent material, and time. We found that as soil N increased across sites, its ¹⁵N/¹⁴N ratio declined towards atmospheric values, suggesting that soil N variation reflects a biotic legacy of symbiotic N fixation inputs. In contrast, soil N variation was unrelated to 17 other metrics of soil forming factors that represented climate (mean annual precipitation, mean annual temperature, and distance from the coast), topography (slope, soil depth, and abundance of coarse rock fragments), parent material (within bedrock type bulk and 1 M HNO₃ leachable rock Ca chemistry), and proxies of soil age (Hurst's redness rating, effective cation exchange capacity, Ca in non-exchangeable soil residues, chemical index of alteration, weathering index of Parker, Ca in coarse soil fragments, and soil Ca loss relative to bedrock). These analyses highlight symbiotic N-fixing red alder as a keystone organismal state-factor that produces a wide range of soil N accumulation in coastal Oregon forests. Strontium isotopes (⁸⁷Sr/⁸⁶Sr) and other geochemical analyses indicate that long-term Ca sources in foliage and exchangeable soil pools in Oregon Coast Range forests depend on an interactive effect between N availability and bedrock. Basaltic rocks contained nearly 20-times more Ca than sedimentary rocks across our sites, and this difference was reflected in Sr-isotope partitioning of base cation sources. Atmospheric sources dominated plant and soil pools in forests overlying Ca-poor sedimentary rock, regardless of variation in soil N, indicating extremely limited capacity of weathering to support forest Ca demands. In contrast, forests overlying basaltic rock obtained as much as 80% of Ca from rock weathering in low N sites, yet relied to a greater extent on atmospheric Ca as soil N increased, with less than 10% of Ca from rock weathering at sites with the highest soil N. Surprisingly, differences in fresh rock Ca content and base cation sources between sedimentary and basaltic sites was not reflected in ecosystem Ca availability, and instead increasing soil N caused similar declines in foliar and exchangeable Ca across both rock types. This illustrates that nutrient pool sizes do not necessarily reflect long-term nutrient supply, and highlights how coupled biogeochemical cycles within ecosystems can regulate nutrient loss and supply to biota. Broadly, our results highlight how interactions between biological and geologic factors can influence base cation sources in forest ecosystems. The sustainability of base cation supplies to forests may therefore depend greatly on variation in bedrock weathering at low N sites, yet converge to depend on atmospheric inputs in sites that receive high N loading from biological fixation or anthropogenic deposition. Close

• 5. [Article] Physiological Responses of Loblolly Pine and Douglas-fir Seedlings from Various Provenances to Timing and Frequency of Drought Stress

  Drought is expected to increase in many parts of the world and has been shown to affect tree physiology and growth, with seedlings being particularly vulnerable. Seedling drought responses are often species ...

  Citation × Citation Citation Abstract Copy Title: Physiological Responses of Loblolly Pine and Douglas-fir Seedlings from Various Provenances to Timing and Frequency of Drought Stress Author: Mosel, Jamie E. Drought is expected to increase in many parts of the world and has been shown to affect tree physiology and growth, with seedlings being particularly vulnerable. Seedling drought responses are often species dependent, and even within species different populations may demonstrate a spectrum of responses to drought, from susceptibility to resistance. As both loblolly pine (Pinus taeda) and Douglas-fir (Pseudotsuga menziesii) have broad geographic ranges, they provide an opportunity to assess drought resistances of provenances associated with a variety of site climate conditions across their ranges. Furthermore, while studies of singular drought events have revealed important information about seedling stress responses, it has been shown that drought may impart effects even following the release from drought. In some cases, effects of drought exposure can be detrimental or lethal; however, exposure to non-lethal drought may also lead to drought acclimation, which could potentially enhance seedling functioning under subsequent droughts. This potential phenotypic plasticity, i.e. the extent to which a seedling can acclimate to drought conditions, may vary across species and across provenances within a species. This study used physiological (electron transport rate, fluorescence, and water potentials) and growth (biomass accumulation and height increment) responses for two goals: 1) to assess the drought resistances of three provenances of loblolly pine and three provenances of Douglas-fir associated with varying site climate conditions, and 2) to investigate whether previous exposure to a drought results in acclimation to a second drought. We hypothesized that: 1) drought responses would differ among the provenances in accordance with associated site climate conditions (i.e., provenances associated with mesic site climates as characterized by low climatic moisture deficit and high mean annual precipitation would be drought susceptible, and more xeric site climates as characterized by high climatic moisture deficit and low mean annual precipitation would be more drought resistant) as evidenced by physiological measures of electron transport rate, fluorescence, water potentials and growth; and 2) previous exposure to drought would result in acclimation to drought as evidenced by maintenance of physiological function (i.e., higher levels of electron transport and fluorescence) in previously drought exposed seedlings compared to previously unexposed seedlings. We also hypothesized that levels of acclimation would vary among provenances. The study yielded some evidence to support the first hypothesis regarding provenance differences in drought resistances in both species. Provenance drought resistances conformed largely to expectations, though differences were less than expected. In loblolly pine, although not statistically significant, during the second drought there was a pattern of lower maximum electron transport rates, which appeared sooner in the more mesic provenance than in the other two provenances. There were also provenance differences in seedling heights, with the most xeric of the three provenances being shorter at the beginning and the end of the study. In Douglas-fir, there were significant differences in provenance and in the interaction of treatment and provenance for maximum electron rates and fluorescence. Dark-adapted fluorescence was lower in the Coos Bay (mesic site climate) provenance during drought than in the Cascades (mesic site climate) and New Mexico (xeric site climate) provenances. The New Mexico provenance showed the least differences in fluorescence between droughted and watered treatments. The study also yielded some evidence to support the second hypothesis regarding drought acclimation in both species and among provenances. During the second drought, there was a pattern of higher maximum electron transport rates and fluorescence in previously drought exposed seedlings as compared to seedlings previously unexposed to drought. This difference was significant in the mesic provenance (North Carolina) of loblolly pine, with maximum electron transport rates significantly higher in the previously drought exposed treatment compared to the newly exposed treatment during and following the second drought. Patterns of lower electron transport rates in seedlings previously unexposed to drought compared to seedlings previously exposed to drought also appeared in Douglas-fir during the second drought, though not with statistical significance. However, the most xeric provenance showed the reverse pattern during and following the second drought, with lower maximum electron transport rates in the previously drought exposed treatment compared to the treatment previously unexposed to drought. Chlorophyll fluorescence values were significantly higher during the second drought in the previously droughted treatments compared to newly drought-exposed treatments in some provenances of loblolly pine and Douglas-fir. Lastly, seedlings exposed to an early drought had significantly lower final heights than seedlings unexposed to an early drought in both species, although the differences were greater in loblolly pine than Douglas-fir. It may be that growth acclimation, especially in the form of height reductions, influenced physiological responses during a second drought. Further studies are necessary to provide more conclusive evidence in support or against the two hypotheses. Nonetheless, this study provides valuable information on the drought responses of young, greenhouse-grown seedlings of two species that are widespread in North America and that are economically important throughout the world. Further studies in a wider range of age classes, incorporating field studies or more natural settings, may help better predict plant responses in the face of changing climate. Title: Physiological Responses of Loblolly Pine and Douglas-fir Seedlings from Various Provenances to Timing and Frequency of Drought Stress Author: Mosel, Jamie E. Drought is expected to increase in many parts of the world and has been shown to affect tree physiology and growth, with seedlings being particularly vulnerable. Seedling drought responses are often species dependent, and even within species different populations may demonstrate a spectrum of responses to drought, from susceptibility to resistance. As both loblolly pine (Pinus taeda) and Douglas-fir (Pseudotsuga menziesii) have broad geographic ranges, they provide an opportunity to assess drought resistances of provenances associated with a variety of site climate conditions across their ranges. Furthermore, while studies of singular drought events have revealed important information about seedling stress responses, it has been shown that drought may impart effects even following the release from drought. In some cases, effects of drought exposure can be detrimental or lethal; however, exposure to non-lethal drought may also lead to drought acclimation, which could potentially enhance seedling functioning under subsequent droughts. This potential phenotypic plasticity, i.e. the extent to which a seedling can acclimate to drought conditions, may vary across species and across provenances within a species. This study used physiological (electron transport rate, fluorescence, and water potentials) and growth (biomass accumulation and height increment) responses for two goals: 1) to assess the drought resistances of three provenances of loblolly pine and three provenances of Douglas-fir associated with varying site climate conditions, and 2) to investigate whether previous exposure to a drought results in acclimation to a second drought. We hypothesized that: 1) drought responses would differ among the provenances in accordance with associated site climate conditions (i.e., provenances associated with mesic site climates as characterized by low climatic moisture deficit and high mean annual precipitation would be drought susceptible, and more xeric site climates as characterized by high climatic moisture deficit and low mean annual precipitation would be more drought resistant) as evidenced by physiological measures of electron transport rate, fluorescence, water potentials and growth; and 2) previous exposure to drought would result in acclimation to drought as evidenced by maintenance of physiological function (i.e., higher levels of electron transport and fluorescence) in previously drought exposed seedlings compared to previously unexposed seedlings. We also hypothesized that levels of acclimation would vary among provenances. The study yielded some evidence to support the first hypothesis regarding provenance differences in drought resistances in both species. Provenance drought resistances conformed largely to expectations, though differences were less than expected. In loblolly pine, although not statistically significant, during the second drought there was a pattern of lower maximum electron transport rates, which appeared sooner in the more mesic provenance than in the other two provenances. There were also provenance differences in seedling heights, with the most xeric of the three provenances being shorter at the beginning and the end of the study. In Douglas-fir, there were significant differences in provenance and in the interaction of treatment and provenance for maximum electron rates and fluorescence. Dark-adapted fluorescence was lower in the Coos Bay (mesic site climate) provenance during drought than in the Cascades (mesic site climate) and New Mexico (xeric site climate) provenances. The New Mexico provenance showed the least differences in fluorescence between droughted and watered treatments. The study also yielded some evidence to support the second hypothesis regarding drought acclimation in both species and among provenances. During the second drought, there was a pattern of higher maximum electron transport rates and fluorescence in previously drought exposed seedlings as compared to seedlings previously unexposed to drought. This difference was significant in the mesic provenance (North Carolina) of loblolly pine, with maximum electron transport rates significantly higher in the previously drought exposed treatment compared to the newly exposed treatment during and following the second drought. Patterns of lower electron transport rates in seedlings previously unexposed to drought compared to seedlings previously exposed to drought also appeared in Douglas-fir during the second drought, though not with statistical significance. However, the most xeric provenance showed the reverse pattern during and following the second drought, with lower maximum electron transport rates in the previously drought exposed treatment compared to the treatment previously unexposed to drought. Chlorophyll fluorescence values were significantly higher during the second drought in the previously droughted treatments compared to newly drought-exposed treatments in some provenances of loblolly pine and Douglas-fir. Lastly, seedlings exposed to an early drought had significantly lower final heights than seedlings unexposed to an early drought in both species, although the differences were greater in loblolly pine than Douglas-fir. It may be that growth acclimation, especially in the form of height reductions, influenced physiological responses during a second drought. Further studies are necessary to provide more conclusive evidence in support or against the two hypotheses. Nonetheless, this study provides valuable information on the drought responses of young, greenhouse-grown seedlings of two species that are widespread in North America and that are economically important throughout the world. Further studies in a wider range of age classes, incorporating field studies or more natural settings, may help better predict plant responses in the face of changing climate. Close

• 6. [Article] Relationships of hydraulic traits and wood morphology in Douglas-fir branches from wet vs. dry regions and sites

  It is well known that water transport in xylem depends on its anatomy, but recent research shows that water transport through different parts of the growth ring are affected by the water potential in different ...

  Citation × Citation Citation Abstract Copy Title: Relationships of hydraulic traits and wood morphology in Douglas-fir branches from wet vs. dry regions and sites Author: Flamenco, Herman Noe, Jr. It is well known that water transport in xylem depends on its anatomy, but recent research shows that water transport through different parts of the growth ring are affected by the water potential in different ways. The goal of the project was to learn the extent to which wood morphology is related to several hydraulic properties, making use of samples and an existing dataset on hydraulic properties of 2-year old branches from 11-year old trees of Douglas-fir (Pseudotsuga menziesii subsp. menziessi Mirb. (Franco)) from several provenances that were grown in a site with low or high annual precipitation. The dataset provided the specific conductivity (K[subscript]s) of samples that were well hydrated, the percent loss of conductivity of those samples after being subjected to -4 MPa (PLC@4), the percent of water mass that was lost between hydration and -4 MPa, the density of the sample, and the sample itself that had been stained after the -4 MPa treatment. The pattern of stain showed the flow paths that were still operative at -4 MPa. There were 36 samples each from an Oregon Coast Range provenance and a low elevation Siskiyou provenance. Half of the samples from each provenance were grown in a Coast Range site, and half near Medford (for 18 trees in each of four treatment combinations). The specific hypotheses were the following. 1) PLC@4 is positively correlated with Ks and with the percentage of water lost between 0 MPa and -4 MPa, and is negatively correlated with wood density. 2) PLC@4 is positively correlated with the percentage of the growth ring that is from certain locations (the first-formed earlywood of the inner growth ring, etc.). 3) K[subscript]s is positively correlated with the percentage of the growth ring that is from certain locations (the earlywood of both rings, and the outer ring). Using image analysis, I determined the percentage of the growth ring in each of four locations, and then with the help of a statistician, analyzed the data to test the hypotheses. The data supported hypothesis 1 and 3 but not 2. The most interesting result was that the percentage of the cross section in a particular growth ring (e.g. earlywood, latewood), was not significantly correlated to drought vulnerability. This result suggests that the anatomy of the individual samples may be better predictors of drought vulnerability than the proportion of cross-sectional area alone. Title: Relationships of hydraulic traits and wood morphology in Douglas-fir branches from wet vs. dry regions and sites Author: Flamenco, Herman Noe, Jr. It is well known that water transport in xylem depends on its anatomy, but recent research shows that water transport through different parts of the growth ring are affected by the water potential in different ways. The goal of the project was to learn the extent to which wood morphology is related to several hydraulic properties, making use of samples and an existing dataset on hydraulic properties of 2-year old branches from 11-year old trees of Douglas-fir (Pseudotsuga menziesii subsp. menziessi Mirb. (Franco)) from several provenances that were grown in a site with low or high annual precipitation. The dataset provided the specific conductivity (K[subscript]s) of samples that were well hydrated, the percent loss of conductivity of those samples after being subjected to -4 MPa (PLC@4), the percent of water mass that was lost between hydration and -4 MPa, the density of the sample, and the sample itself that had been stained after the -4 MPa treatment. The pattern of stain showed the flow paths that were still operative at -4 MPa. There were 36 samples each from an Oregon Coast Range provenance and a low elevation Siskiyou provenance. Half of the samples from each provenance were grown in a Coast Range site, and half near Medford (for 18 trees in each of four treatment combinations). The specific hypotheses were the following. 1) PLC@4 is positively correlated with Ks and with the percentage of water lost between 0 MPa and -4 MPa, and is negatively correlated with wood density. 2) PLC@4 is positively correlated with the percentage of the growth ring that is from certain locations (the first-formed earlywood of the inner growth ring, etc.). 3) K[subscript]s is positively correlated with the percentage of the growth ring that is from certain locations (the earlywood of both rings, and the outer ring). Using image analysis, I determined the percentage of the growth ring in each of four locations, and then with the help of a statistician, analyzed the data to test the hypotheses. The data supported hypothesis 1 and 3 but not 2. The most interesting result was that the percentage of the cross section in a particular growth ring (e.g. earlywood, latewood), was not significantly correlated to drought vulnerability. This result suggests that the anatomy of the individual samples may be better predictors of drought vulnerability than the proportion of cross-sectional area alone. Close

• 7. [Article] Identifying site characteristics that explain variation in Douglas-fir site productivity and stem form

  Foresters care about site productivity and stem quality in Douglas-fir plantations for many reasons. The profitability of forest land and the economic returns on silvicultural investments are directly ...

  Citation × Citation Citation Abstract Copy Title: Identifying site characteristics that explain variation in Douglas-fir site productivity and stem form Author: Magalska, Lauren E. Foresters care about site productivity and stem quality in Douglas-fir plantations for many reasons. The profitability of forest land and the economic returns on silvicultural investments are directly related to site productivity. Thus, understanding the relationships among Douglas-fir productivity, stem form and site characteristics is important economically. My objective was to identify the specific site characteristics that explained variation in Douglas-fir productivity and stem form throughout western Oregon and Washington by using progeny tests that substantially reduced the confounding effects of genotype by environment interaction. These assessments were undertaken to advance our understanding of near-term climate change effects on Douglas-fir productivity and stem form. The site characteristics I focused on include climate, soils and topography. Measures of site productivity and stem form were explained using correlation, random forest, and linear regression analyses. The results of these analytical methods were summarized as total importance scores. The consistency of important site characteristics identified by the analytical methods and the consistency of important site characteristics for explaining variability in different productivity measures were assessed using Spearman rank correlations. The results of this study provide new direction and insight for future research on understanding and modeling the effects of site characteristics on tree growth and form. It may be reasonable to focus future research on summer drought, cold season temperatures and precipitation interactions with soil properties, particularly available water capacity when examining site productivity. Additionally, examining genotype by environment interactions at the family level may provide insight to the driving site characteristics for stem forking, ramicorn branching and sinuosity. Title: Identifying site characteristics that explain variation in Douglas-fir site productivity and stem form Author: Magalska, Lauren E. Foresters care about site productivity and stem quality in Douglas-fir plantations for many reasons. The profitability of forest land and the economic returns on silvicultural investments are directly related to site productivity. Thus, understanding the relationships among Douglas-fir productivity, stem form and site characteristics is important economically. My objective was to identify the specific site characteristics that explained variation in Douglas-fir productivity and stem form throughout western Oregon and Washington by using progeny tests that substantially reduced the confounding effects of genotype by environment interaction. These assessments were undertaken to advance our understanding of near-term climate change effects on Douglas-fir productivity and stem form. The site characteristics I focused on include climate, soils and topography. Measures of site productivity and stem form were explained using correlation, random forest, and linear regression analyses. The results of these analytical methods were summarized as total importance scores. The consistency of important site characteristics identified by the analytical methods and the consistency of important site characteristics for explaining variability in different productivity measures were assessed using Spearman rank correlations. The results of this study provide new direction and insight for future research on understanding and modeling the effects of site characteristics on tree growth and form. It may be reasonable to focus future research on summer drought, cold season temperatures and precipitation interactions with soil properties, particularly available water capacity when examining site productivity. Additionally, examining genotype by environment interactions at the family level may provide insight to the driving site characteristics for stem forking, ramicorn branching and sinuosity. Close

• 8. [Article] The Effects of Seed Source and Planting Environment on Douglas-fir (Pseudotsuga menziesii) Foliage Diseases

  Douglas-fir (Pseudotsuga menziesii) is a commercially and ecologically important tree species native to western North America. The foliar pathogens Phaeocryptopus gaeumannii, the causal agent of Swiss ...

  Citation × Citation Citation Abstract Copy Title: The Effects of Seed Source and Planting Environment on Douglas-fir (Pseudotsuga menziesii) Foliage Diseases Author: Wilhelmi, Nicholas Douglas-fir (Pseudotsuga menziesii) is a commercially and ecologically important tree species native to western North America. The foliar pathogens Phaeocryptopus gaeumannii, the causal agent of Swiss Needle Cast, and Rhabdocline species, the causal agents of Rhabdocline needle cast, are two important pathogens specific to Douglas-fir. These pathogens are highly influenced by climatic conditions and have been shown to disproportionately affect genetically maladapted populations, causing decreased productivity and sometimes mortality. The relationship between the levels of resistance/tolerance to these foliar pathogens and climate of the population source is a key component in the identification of proper seed sources for reforestation. The Douglas-fir Seed Source Movement Trials (SSMT) is a large provenance study of Westside Douglas-fir which consists of populations and test sites chosen to represent the range of climatic conditions experienced by Douglas-fir west of the Cascade and Sierra Nevada Mountains. We used the SSMT to assess variation in the probability of moderate to severe infection by Rhabdocline spp. and P. gaeumannii, as well as expression of disease symptoms, in relation to climatic differences between test sites and population sources. Using generalized linear mixed models and the probit link function, probabilities were calculated using differences between population source and test sites with respect to the climate variables May through September precipitation (MSP), continentality and mean winter temperature (MWT). Stark differences were observed in side-by-side trees from different seed zones, especially in relation to the resistance to Rhadocline needle cast. No patterns were observed in the infection levels of P. gaeumannii based on number of stomates occluded by fungal reproductive structures. However, there was variation in disease symptom expression such as crown density which was used as a surrogate for Swiss needle cast impacts in this analysis. The transfers of populations from regions of low MSP to test sites of high MSP, cool to warm MWT and high to low continentality are associated with high probabilities of moderate to severe Rhabdocline spp. infection and SNC disease symptoms (low crown density). Trends in high probabilities of disease symptoms and Rhabdocline spp. infection were associated with the movement of populations from south to north. Predictions of disease occurrence based on climate-disease-host seed source interaction indicates danger in choosing trees for assisted migration from drier regions and moving them to wetter areas in anticipation of climate change. This project exemplifies the importance of seed source movement trials in understanding trophic interactions as well as environmental controls on tree growth and adaptation Title: The Effects of Seed Source and Planting Environment on Douglas-fir (Pseudotsuga menziesii) Foliage Diseases Author: Wilhelmi, Nicholas Douglas-fir (Pseudotsuga menziesii) is a commercially and ecologically important tree species native to western North America. The foliar pathogens Phaeocryptopus gaeumannii, the causal agent of Swiss Needle Cast, and Rhabdocline species, the causal agents of Rhabdocline needle cast, are two important pathogens specific to Douglas-fir. These pathogens are highly influenced by climatic conditions and have been shown to disproportionately affect genetically maladapted populations, causing decreased productivity and sometimes mortality. The relationship between the levels of resistance/tolerance to these foliar pathogens and climate of the population source is a key component in the identification of proper seed sources for reforestation. The Douglas-fir Seed Source Movement Trials (SSMT) is a large provenance study of Westside Douglas-fir which consists of populations and test sites chosen to represent the range of climatic conditions experienced by Douglas-fir west of the Cascade and Sierra Nevada Mountains. We used the SSMT to assess variation in the probability of moderate to severe infection by Rhabdocline spp. and P. gaeumannii, as well as expression of disease symptoms, in relation to climatic differences between test sites and population sources. Using generalized linear mixed models and the probit link function, probabilities were calculated using differences between population source and test sites with respect to the climate variables May through September precipitation (MSP), continentality and mean winter temperature (MWT). Stark differences were observed in side-by-side trees from different seed zones, especially in relation to the resistance to Rhadocline needle cast. No patterns were observed in the infection levels of P. gaeumannii based on number of stomates occluded by fungal reproductive structures. However, there was variation in disease symptom expression such as crown density which was used as a surrogate for Swiss needle cast impacts in this analysis. The transfers of populations from regions of low MSP to test sites of high MSP, cool to warm MWT and high to low continentality are associated with high probabilities of moderate to severe Rhabdocline spp. infection and SNC disease symptoms (low crown density). Trends in high probabilities of disease symptoms and Rhabdocline spp. infection were associated with the movement of populations from south to north. Predictions of disease occurrence based on climate-disease-host seed source interaction indicates danger in choosing trees for assisted migration from drier regions and moving them to wetter areas in anticipation of climate change. This project exemplifies the importance of seed source movement trials in understanding trophic interactions as well as environmental controls on tree growth and adaptation Close