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• 1. [Article] Juvenile development of Douglas-fir, red alder and snowbrush associations in Western Oregon

  The juvenile development of Douglas-fir, red alder and snowbrush associations was investigated in western Oregon. The relationship between Douglas-fir and red alder was studied and compared in the Coast, ...

  Citation × Citation Citation Abstract Copy Title: Juvenile development of Douglas-fir, red alder and snowbrush associations in Western Oregon Author: El Hassan, Babiker Ahmed The juvenile development of Douglas-fir, red alder and snowbrush associations was investigated in western Oregon. The relationship between Douglas-fir and red alder was studied and compared in the Coast, Willamette Valley and Cascade regions. Snowbrush- Douglas-fir stands were sampled in the western Cascades. Alder- Douglas-fir relationships were studied on clearcuts supporting at the same time mixtures of alder and Douglas-fir and open-grown Douglas-fir. Sites where snowbrush and Douglas-fir grew together were selected on the same basis. Total heights of alder and Douglas-fir were expressed as cumulative one-year growth measurements. Canopy height of snowbrush was measured at various ages to determine growth rate. Information pertaining to moisture, vegetation, slope, aspect, elevation and stand structure was recorded at each sample plot. The data were analyzed with the aid of a multiple regression program. Height and (height)² were treated as independent variables, and annual height increment as the dependent variable. Results indicate that early establishment of Douglas-fir is expected to aid its dominance-takeover and allow it to evade suppression by red alder. Douglas-fir trees growing on wet sites need to be established earlier than those on drier habitats for the same degree of suppression evasion. The rapid juvenile growth rate of red alder is a major threat for the successful establishment of Douglas-fir. Height growth curves of the two species intersected at an earlier age on non-wet as compared to wet sites. The two trees grow in direct competition up to about age 40 years on wet habitats, with alder able to suppress Douglas-fir during this period. Douglas-fir has virtually no chance áf survival when it is established concurrently with red alder or after its appearance. Snowbrush retards the growth of Douglas-fir trees during their first ten years of development. Trees that are delayed more than five years in establishment suffer a loss of more than 50% in total height as a result of the suppressive effect of the shrub. It is expected that the trees will compensate for some of this loss, but their growth may never equal that of comparable open-grown Douglas-fir developing under similar conditions. Title: Juvenile development of Douglas-fir, red alder and snowbrush associations in Western Oregon Author: El Hassan, Babiker Ahmed The juvenile development of Douglas-fir, red alder and snowbrush associations was investigated in western Oregon. The relationship between Douglas-fir and red alder was studied and compared in the Coast, Willamette Valley and Cascade regions. Snowbrush- Douglas-fir stands were sampled in the western Cascades. Alder- Douglas-fir relationships were studied on clearcuts supporting at the same time mixtures of alder and Douglas-fir and open-grown Douglas-fir. Sites where snowbrush and Douglas-fir grew together were selected on the same basis. Total heights of alder and Douglas-fir were expressed as cumulative one-year growth measurements. Canopy height of snowbrush was measured at various ages to determine growth rate. Information pertaining to moisture, vegetation, slope, aspect, elevation and stand structure was recorded at each sample plot. The data were analyzed with the aid of a multiple regression program. Height and (height)² were treated as independent variables, and annual height increment as the dependent variable. Results indicate that early establishment of Douglas-fir is expected to aid its dominance-takeover and allow it to evade suppression by red alder. Douglas-fir trees growing on wet sites need to be established earlier than those on drier habitats for the same degree of suppression evasion. The rapid juvenile growth rate of red alder is a major threat for the successful establishment of Douglas-fir. Height growth curves of the two species intersected at an earlier age on non-wet as compared to wet sites. The two trees grow in direct competition up to about age 40 years on wet habitats, with alder able to suppress Douglas-fir during this period. Douglas-fir has virtually no chance áf survival when it is established concurrently with red alder or after its appearance. Snowbrush retards the growth of Douglas-fir trees during their first ten years of development. Trees that are delayed more than five years in establishment suffer a loss of more than 50% in total height as a result of the suppressive effect of the shrub. It is expected that the trees will compensate for some of this loss, but their growth may never equal that of comparable open-grown Douglas-fir developing under similar conditions. Close

• 2. [Article] Silvicultural impacts of sheep grazing in Oregon's Coast Range

  A three-year investigation was conducted during 1980-1982 to evaluate the potential of using herded sheep as a silvicultural tool to suppress brush in Douglas-fir (Pseudotsuga menziesii) plantations of ...

  Citation × Citation Citation Abstract Copy Title: Silvicultural impacts of sheep grazing in Oregon's Coast Range Author: Leininger, Wayne C. A three-year investigation was conducted during 1980-1982 to evaluate the potential of using herded sheep as a silvicultural tool to suppress brush in Douglas-fir (Pseudotsuga menziesii) plantations of Oregon's Coast Range. Sheep browsing of Douglas-fir was highest in May soon after bud break. Averaged over the 2 years of grazing, sheep consumed 28% of the Douglas-fir current year's growth (CYG) in two May-grazed plantations. Browsing was generally light (2% CYG) during July and August. Browsing of terminal leaders by sheep decreased as seedling height increased. Less than 3% of the study trees were mechanically impacted by sheep. In a 2-year-old plantation in which seedlings were heavily browsed by sheep in both May and August, annual height and mean diameter increment were reduced by sheep grazing. However, annual mean diameter increment was 8 to 17% higher in the grazed portion of three 4-6-year-old study plantations. Survival of regeneration over the 2 years of investigation was high in all study plantations and was unaffected by grazing. Increased available nitrogen deposited as urine in grazed plantations may have contributed to the increased diameter growth. Vegetational composition of sheep diets varied by year, season, and plantation age class. Averaged over the 2 years of grazing, graminoids and forbs were nearly equal, at approximately 40% each, in sheep diets from older plantations. In contrast, diets of sheep in young grass seeded plantations averaged 70% graminoids and only 16% forbs. Ferns were a minor component (<2%) of sheep diets in both plantation age classes. Browse averaged 15 and 12% of sheep diets in older and younger plantations, respectively. Douglas-fir comprised less than 3% of sheep diets throughout the grazing season. Weight gains followed seasonal trends typical of sheep grazing non-irrigated hill pasture in western Oregon. Average daily gain (ADG) of ewes and lambs during the 1981 grazing season was -.03 and .12 kg/sheep/day, respectively. Yearling ewes gained .08 kg/ewe/day in the 1982 gazing season. Death losses were relatively low, averaging 3% for the ewes and 5% for the lambs in 1981 and 2% for the yearlings in 1982. Title: Silvicultural impacts of sheep grazing in Oregon's Coast Range Author: Leininger, Wayne C. A three-year investigation was conducted during 1980-1982 to evaluate the potential of using herded sheep as a silvicultural tool to suppress brush in Douglas-fir (Pseudotsuga menziesii) plantations of Oregon's Coast Range. Sheep browsing of Douglas-fir was highest in May soon after bud break. Averaged over the 2 years of grazing, sheep consumed 28% of the Douglas-fir current year's growth (CYG) in two May-grazed plantations. Browsing was generally light (2% CYG) during July and August. Browsing of terminal leaders by sheep decreased as seedling height increased. Less than 3% of the study trees were mechanically impacted by sheep. In a 2-year-old plantation in which seedlings were heavily browsed by sheep in both May and August, annual height and mean diameter increment were reduced by sheep grazing. However, annual mean diameter increment was 8 to 17% higher in the grazed portion of three 4-6-year-old study plantations. Survival of regeneration over the 2 years of investigation was high in all study plantations and was unaffected by grazing. Increased available nitrogen deposited as urine in grazed plantations may have contributed to the increased diameter growth. Vegetational composition of sheep diets varied by year, season, and plantation age class. Averaged over the 2 years of grazing, graminoids and forbs were nearly equal, at approximately 40% each, in sheep diets from older plantations. In contrast, diets of sheep in young grass seeded plantations averaged 70% graminoids and only 16% forbs. Ferns were a minor component (<2%) of sheep diets in both plantation age classes. Browse averaged 15 and 12% of sheep diets in older and younger plantations, respectively. Douglas-fir comprised less than 3% of sheep diets throughout the grazing season. Weight gains followed seasonal trends typical of sheep grazing non-irrigated hill pasture in western Oregon. Average daily gain (ADG) of ewes and lambs during the 1981 grazing season was -.03 and .12 kg/sheep/day, respectively. Yearling ewes gained .08 kg/ewe/day in the 1982 gazing season. Death losses were relatively low, averaging 3% for the ewes and 5% for the lambs in 1981 and 2% for the yearlings in 1982. Close