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• 1. [Article] Fire-mediated pathways of stand development in Douglas-fir/ western hemlock forests of the Pacific Northwest, 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 published article is copyrighted by Ecological ...

  Citation × Citation Citation Abstract Copy Title: Fire-mediated pathways of stand development in Douglas-fir/ western hemlock forests of the Pacific Northwest, USA Author: Tepley, Alan J., Swanson, Frederick J., Spies, Thomas A. 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 published article is copyrighted by Ecological Society of America and can be found at: http://esa.org/. Title: Fire-mediated pathways of stand development in Douglas-fir/ western hemlock forests of the Pacific Northwest, USA Author: Tepley, Alan J., Swanson, Frederick J., Spies, Thomas A. 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 published article is copyrighted by Ecological Society of America and can be found at: http://esa.org/. Close

• 2. [Article] Sources of Variation in the Self-Thinning Boundary Line for Three Species with Varying Levels of Shade Tolerance

  The species self-thinning boundary line has been widely analyzed with a variety of statistical techniques. Most previous studies in the forestry literature have reported that the relationship does not ...

  Citation × Citation Citation Abstract Copy Title: Sources of Variation in the Self-Thinning Boundary Line for Three Species with Varying Levels of Shade Tolerance Author: Temesgen, Hailemariam, Weiskittel, Aaron, Gould, Peter The species self-thinning boundary line has been widely analyzed with a variety of statistical techniques. Most previous studies in the forestry literature have reported that the relationship does not differ across a range of stand and site factors, but these studies have primarily used statistical techniques that make model fitting subjective or interpretation of covariate significance difficult. There is growing evidence that the use of stochastic frontier analysis is an effective statistical means for objectively fitting the species self-thinning boundary line, offering the opportunity to test the influence of additional covariates. Using extensive even-aged coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco), western hemlock (Tsuga heterophylla), and red alder (Alnus rubra Bong.) data sets in the Pacific Northwest, we examined the assumption that the intercept and slope of the species self-thinning boundary line are insensitive to stand and site factors. Likelihood ratio tests indicated that site index, stand origin (natural versus planted), and purity (proportion of basal area in the primary species) significantly influenced the species self-thinning boundary line intercept for each of the species examined in this study. In Douglas-fir and western hemlock, the slope of the self-thinning boundary was also dependent on stand origin as well as site index in the case of Douglas-fir. Fertilization did not significantly influence the intercept or slope of the species self-thinning line for Douglas-fir and western hemlock. In addition, the inclusion of site aspect and dryness index marginally improved the red alder model of self-thinning, but neither site soil nor climatic variables improved the models for western hemlock and Douglas-fir. Thus, the species self-thinning boundary line can vary significantly among stands, and its variation is driven by several distinct factors; stochastic frontier analysis is an effective tool for identifying these factors. Title: Sources of Variation in the Self-Thinning Boundary Line for Three Species with Varying Levels of Shade Tolerance Author: Temesgen, Hailemariam, Weiskittel, Aaron, Gould, Peter The species self-thinning boundary line has been widely analyzed with a variety of statistical techniques. Most previous studies in the forestry literature have reported that the relationship does not differ across a range of stand and site factors, but these studies have primarily used statistical techniques that make model fitting subjective or interpretation of covariate significance difficult. There is growing evidence that the use of stochastic frontier analysis is an effective statistical means for objectively fitting the species self-thinning boundary line, offering the opportunity to test the influence of additional covariates. Using extensive even-aged coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco), western hemlock (Tsuga heterophylla), and red alder (Alnus rubra Bong.) data sets in the Pacific Northwest, we examined the assumption that the intercept and slope of the species self-thinning boundary line are insensitive to stand and site factors. Likelihood ratio tests indicated that site index, stand origin (natural versus planted), and purity (proportion of basal area in the primary species) significantly influenced the species self-thinning boundary line intercept for each of the species examined in this study. In Douglas-fir and western hemlock, the slope of the self-thinning boundary was also dependent on stand origin as well as site index in the case of Douglas-fir. Fertilization did not significantly influence the intercept or slope of the species self-thinning line for Douglas-fir and western hemlock. In addition, the inclusion of site aspect and dryness index marginally improved the red alder model of self-thinning, but neither site soil nor climatic variables improved the models for western hemlock and Douglas-fir. Thus, the species self-thinning boundary line can vary significantly among stands, and its variation is driven by several distinct factors; stochastic frontier analysis is an effective tool for identifying these factors. Close

• 3. [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