21 research outputs found
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An Illustrated Guide to Fire in Central Oregon Forests
This pictorial guide is primarily intended to serve as a backdrop for field tours of central Oregon that involve topics surrounding wildland fire. It also is designed to provide an
overview of the role of fire in the major ecosystems characteristic of this region. Topics covered include fire history, fire regimes, current fire conditions, fire behavior, fire threats to natural resources, fuel treatments, interactions with the public, and future challenges and management options. A list of key references and glossary are also included
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Methods for evaluating crown area profiles of forest stands
Canopy architectures of five structurally complex forest stands and three structurally simple forest stands in southwest Oregon and the Willamette Valley, Oregon, were evaluated and quantified through crown area profiles. Mixed conifer and mixed conifer-hardwood stands across a range of sites were sampled for crown widths and heights. Crown width and shape equations were derived and used to quantify the stand crown area at incremental heights above the forest floor. Crown area profiles describe the spatial arrangement of aboveground forest vegetation and the total pore spaces between crowns. Plot by plot profiles were combined to produce vertical and horizontal displays of the stand crown area distribution. In complex stands, the forest space was moderately occupied by crowns from the forest floor up to heights over 30 m, producing uniform distributions of between-crown porosity. The structurally complex stands had between-crown porosity values of 70% to 90% for more than 23 vertical metres of canopy, and they had total between-crown porosities of 86% to 91%. The structurally simple stands had between-crown porosity values of 70% to 90% for less than 8 vertical metres of canopy, and they had total between-crown porosities of 69% to 85%. Variances in crown area indicate that variation in horizontal crown area (within heights) was larger in complex stands than in simple stands, but vertical crown areas (between heights) varied less in complex stands. The study provides a basis for discriminating between canopy architectures and for quantifying the porosity of forest canopies
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Response of young Douglas-fir to 16 years of intensive thinning
A 20-year-old Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stand in the Oregon Coast Range was thinned from about 1,700 to about 350 trees/ac. Subsequent thinnings, under eight different regimes, occurred at ages 23, 27, 30, and 32. Average net periodic cubic-volume growth was strongly influenced by thinning regime, varying from about 220 ft /ac/yr (heavy thinning age 30) to over 550 ft /ac/yr (controls age 23). The results indicate that young Douglas-fir on productive sites (site index 160 to 170 ft at 100 years) are extremely adaptable and will respond to frequent thinnings of various intensities. Three representative treatments (after thinning at age 32) and the controls were projected and optimized with dynamic programming for two financial analyses. Adjusting rotation or commercial thinning can compensate for lack of early stand management or heavy early thinning
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Density, ages, and growth rates in old-growth and young-growth forests in coastal Oregon
We studied the ages and diameter growth rates of trees in former Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) old-growth stands on 10 sites and compared them with young-growth stands (50-70 years old, regenerated after timber harvest) in the Coast Range of western Oregon. The diameters and diameter growth rates for the first 100 years of trees in the old-growth stands were significantly greater than those in the young-growth stands. Growth rates in the old stands were comparable with those from long-term studies of young stands in which density is about 100-120 trees/ha; often young-growth stand density is well over 500 trees/ha. Ages of large trees in the old stands ranged from 100 to 420 years; ages in young stands varied by only about 5 to 10 years. Apparently, regeneration of old-growth stands on these sites occurred over a prolonged period, and trees grew at low density with little self-thinning; in contrast, after timber harvest, young stands may develop with high density of trees with similar ages and considerable self-thinning. The results suggest that thinning may be needed in dense young stands where the management objective is to speed development of old-growth characteristics.Keywords: thinning, young growth, old growth, diameter growth rate, Douglas-fir, Pseudotsuga menziesii, forest structure, stand densit
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Survival and growth of Douglas-fir seed sources in the Hospital Tract rangewide source archive plantation
"In 1954, Dr. Helge Irgens-Moller initiated a rangewide collection of seed and seedlings of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Nearly 700 trees or stands were sampled in 10 western states, Canada, and Mexico. From 1957 to 1971, 639 of these collections were planted in the Hospital Tract Rangewide Source Archive near Corvallis, Oregon. By 1989, the trees were from 20 to 34 years old; it became apparent that thinning the archive would be necessary in order to preserve the slower growing sources. This prompted growth and survival measurements and a complete inventory of the archive. Overall survival for all years of planting was greater than 80 percent for coastal sources (var. menziesii), but less than 60 percent for interior sources (var. glauca). The average diameter at breast height (DBH) of surviving trees was 29.05 cm; the range was from 1.2 to 61 cm. An analysis of the 1957 and 1961 plantings revealed that local and other low elevation coastal sources had the fastest growth and highest survival in the archive. High elevation sources from the Cascade Range had significantly smaller DBH, but higher survival. Southern interior sources from Arizona and New Mexico had the smallest DBH and lowest survival; northern interior sources from Montana and Idaho were intermediate in survival and DBH. Geographical variation among sources in the Hospital Tract was associated with environmental gradients, supporting the previously held conclusion that much of the genetic variation on a geographical scale in Douglas-fir is the result of adaptation."--Summar
TRY plant trait database â enhanced coverage and open access
Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of traitâbased plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for âplant growth formâ. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and traitâenvironmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
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Long-term patterns of diameter and basal area growth of old-growth Douglas-fir trees in western Oregon
Diameter growth and age data collected from stumps of 505 recently cut old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees at 28 sample locations in western Oregon (U.S.A.) indicated that rapid early and sustained growth of old Douglas-fir trees were extremely important in terms of attaining large diameters at ages 100â300 years. The diameters of the trees at ages 100â300 years (D100âD300) were strongly, positively, and linearly related to their diameters and basal area growth rates at age 50 years. Average periodic basal area increments
(PAIBA) of all trees increased for the first 30â40 years and then plateaued, remaining relatively high and constant from
age 50 to 300 years. Average PAIBA of the largest trees at ages 100â300 years were significantly greater by age 20 years than were those of smaller trees at ages 100â300 years. The site factors province, site class, slope, aspect, elevation,
and establishment year accounted for little of the variation observed in basal area growth at age 50 years and
D100âD300. The mean age range for old-growth Douglas-fir at the sample locations was wide (174 years). The hypothesis
that large-diameter old-growth Douglas-fir developed at low stand densities was supported by these observations
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Salmonberry and salal annual aerial stem production: the maintenance of shrub cover in forest stands
Annual sprouting of aerial stems and ramets enables populations of salmonberry (Rubus spectabilis Pursh), salal (Gaultheria shallon Pursh), and probably other forest shrubs to maintain dense covers (>20 000 stems/ha). We studied annual stem production of salmonberry on cut (all stems cut within 15 cm of the ground) and uncut (stems were not treated) plots for 8 years and salal for 5 years in the understories of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), alder, and riparian stands, as well as clearcuts, which are all common stand types in western Oregon. Mean salmonberry stem production on uncut plots ranged from 4.7 stems·mâ2·yearâ1 (95% CI 2.9â7.4) in alder stands
and clearcuts to 1.6 stems·mâ2·yearâ1 (95% CI 1.0â2.6) in conifer stands. Mean salal production was greater, ranging from 58 stems·mâ2·yearâ1 (95% CI 25â135) to 8.6 stems·mâ2·yearâ1 (95% CI 3.7â20.1) on uncut plots in clearcuts and unthinned Douglas-fir stands, respectively. Annual production of both species was somewhat greater on cut plots. Most stems produced in early spring die by December, but enough are recruited to replace mortality of older stems. Stem density was maintained for 8 years for salmonberry and 5 years for salal on both cut and uncut plots. Based on length of rhizomes and bud density we estimate that only 1â5% of the buds in the rhizomes are needed to support this annual stem production. Although these species sprout vigorously after their aerial stems are killed, disturbance is not necessary for maintaining a dense cover. It appears that, once established, salal, salmonberry, and probably other clonal forest shrubs can maintain a dense cover that can interfere with establishment of trees and other shrubs in canopy gaps or
other openings