Published July 1961. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
Thinning is removing selected trees from a stand to allow others to
continue growing. Ordinarily, a woodland manager uses a thinning
system that encourages the remaining trees to grow in a manner
consistent with the manager’s objectives for those trees.
In site index studies, the hypothesis that height
growth of most conifers is independent of stand density
is commonly accepted. However, some studies have shown
height growth to be influenced by density particularly
on medium to poor sites.
In this study two locations representing a high
quality site (Hoskins area,...
Harvesting costs were determined for commercial thinning of young stands to
achieve vegetation and wildlife objectives. This included replicated comparisons of
thinning treatments. Treatments were defined based on residual tree stocking after
thinning. Study procedures were developed and evaluated to improve statistical
relevance. Multiple linear regression models were used to...
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...
Across western Oregon, Washington, and British Columbia, forest management practices over the past century reduced the amount of late-successional forest while
simultaneously increasing the amount of young (less than 80 years old), managed
Douglas-fir (Pseudotsuga menziesii) dominated forests. Recently, concerns over loss of late-successional habitat pushed management objectives on public...
Thinning has the potential to increase structural diversity of managed forests for wildlife. During 1994-1996, I conducted experimental and observational studies using pitfall trapping to assess short-term and potential long-term effects of thinning on abundance and reproduction of forest-floor vertebrates in Douglas-fir (Pseudotsuga menzeisii) forests of the Oregon Coast Range....
Modified selection thinning has been utilized by some non-industrial foresters in Douglas-fir forests of Western Oregon and Washington for at least 35 years. This silvicultural strategy has not been tested, but has often been associated with reduced volume production and other undesirable effects. It continues to be used on many...
Understanding the impact of thinning on residual stands helps forest managers achieve management objectives associated with sustainability and quality control. Stand damage control becomes more critical as thinning prescriptions in the Pacific Northwest are increasingly required for intensive management of second-growth young stands. The purpose of this study was to...
The authors varied the number of red alder retained with 300 Douglas-fir per acre on a high-quality site in coastal Oregon. Alder densities of 0, 20, 40, and 80 per acre were tested. The authors' fifth treatment eliminated nitrogen-fixing alder, but substantial nitrogen fertilizer. Treatment 6 had neither thinning nor...
The Levels-of-Growing-Stock Studies in Douglas-fir is a regional cooperative to investigate the effects of levels of growing stock on young stand growth. The Hoskins
installation, in western Oregon, was established in a dense, high site natural stand at total age 20 years. The initial thinning resulted in an immediate 131...
Logging planning and layout costs were examined for commercial thinning of 40- to 50-yr-old stands of Douglas-fir on the Willamette National Forest in the Cascade Mountains of Oregon. The study consisted of four replications of three silvicultural treatments. Thinning involved three types of logging systems: mechanized cut-to-length (a combination of...
The process of silvicultural thinning has become very controversial recently with regards to fire protection and management for old-growth conditions and biodiversity. Therefore, an unthinned control stand and 3 different thinning intensities were examined for their effects on the abundance, species richness, and diversity of arthropods in thinning treatments of...
Canopy gap formation is a major factor contributing to maintenance of overstory species diversity and stand structure in forests and may be integral to development of understory shrub and herb layers as well. Acknowledgement of gap formation as a fundamental feature of natural forests has led to consideration of gaps...
Forest managers are beginning to take an interest in management of young Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in Western Oregon and Washington. Studies have established the relationship between growth and levels-of-growing-stock but few have established a link to wood quality and value. This study used data collected from a long...
Contract harvest operations have become the preferred approach to reducing the largest cost component of timber production through free market competition amongst logging contractors bidding or negotiating for work. The goal of this research was to investigate economic components of harvesting operations not previously studied for steep slope thinning harvests...
Harvesting productivity rates and costs were determined for three
silvicultural treatments used in commercial ground-based thinning of
young stands to achieve timber management objectives and enhance
wildlife habitat. Treatment definitions were based on residual trees
per acre (tpa) after thinning. The treatments were light thin (115
residual tpa), light thin...
Commercial thinning operations can result in damage to residual stems. A literature review revealed that little was known about the effects of residual logging wounds with regard to rotation-age commercial conifers, particularly Douglas-fir. An experiment to examine fungal colonization of Douglas-fir following logging damage showed that while damage was significant...
Young Douglas-fir stands were commercially thinned to achieve vegetation- and wildlife-related objectives. Harvesting and forwarding production and costs were compared among three mechanized thinning treatments: light thin [(115 residual trees per acre (tpa)], light thin with 0.5-ac openings (92 residual tpa), and heavy thin (53 residual tpa). The sites were...
The search for the stand density that optimizes growth and hence generates the maximum amount of wood is one of the philosopher’s stone in modern forestry. Since scientific methods were applied to forestry, numerous generations of foresters have studied the relations between stocking density and growth, obtaining diverse results and...
A trait based approach was used to assess impacts of overstory density and thinning on understory vegetation components related to wildlife habitat. The relationship between overstory basal area and understory vegetation for species grouped by traits, such as production of flowers, fleshy-fruit and palatable leaves, was characterized in thinned and...
The purpose of this study was to determine if amount and kind of thinning had an effect on wood specific gravity, modulus of rupture, modulus of elasticity, growth rate, or pulp yield and kappa number. The study involved 24 1/5-acre plots, three plots in each of eight thinning treatments. The...
Foresters in the Pacific Northwest are directing increasing effort into the management of young-growth forests. These foresters find themselves in a transition period in which they are beginning to develop the framework for managing young-growth forests while they continue to manage substantial reserves of old-growth timber. In this transition period,...
The objectives of this research were to study: a) the effect of thinning and treatments consisting of pruning
and multinutrient fertilization on aboveground biolnass increment, growth efficiency (GE), and foliar nutrients;
b) the influence of topoedaphic variables (soil nutrients, slope, aspect, and rock content) and foliar nutrients on both leaf...
This research examined thinning effects on stand structure and species composition in
50- to 120-year-old Douglas-fir forests. Thirty-two paired stands (thinned and unthinned)
were measured throughout western Oregon, as were 20 old-growth stands for comparison. Thinnings occurred 10 to 24 years previously and ranged in intensity from 8 to 60%...
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 intermediate cuttings were made in a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand on the Wilark forest management research area in northwestern Oregon. Age of trees in the stand varied from 47 to 62 years at the first cutting. Crawler tractors were used in both extractions. In the first cutting,...
Forests are important to Oregon for their beauty as well as economic value, and Douglas fir trees are among the most common and important in the state. Managing and monitoring Oregon’s forests is imperative to ensure they can remain healthy and productive. One tool that helps forest scientists to understand...
Estimating volume gains in genetically improved stands at rotation age is challenging because first-generation progeny tests in Douglas-fir were typically established to measure the relative growth performance of individual trees from open-pollinated parent trees. The overall goal of this dissertation research was to improve growth simulation of genetically improved Douglas-fir...
Budburst, the initiation of annual growth in plants, is sensitive to climate variation and is therefore used to monitor physiological responses to climate change. Budburst timing can vary between regions of an individual tree, but this phenomenon it is unaccounted for in current monitoring efforts and may contribute to the...
Tissue differentiation of the primary root and its associated
laterals is reported. Secretory elements are the first of the primary
tissues to mature. They appear to be located between the precursory
phloem and pericycle in the primary root, but are more closely
associated with the pericycle in long lateral roots....
The Pacific Coast form of Douglas-fir in natural forest succession
is an intermediate species thriving in the Coast Range and
Cascade Mountains of the Pacific Northwest. This species constitutes
26 percent of the standing timber in the United States, and 24 percent
of the nation's annual timber harvest. Characteristics of...
Mitotic activity in the vascular cambium was determined from
ten samples from a single internode in each of four Douglas-fir
[(Pseudotsuga menziesii (Franco.) Mirb.)]trees. Counts of interphase and mitotic nuclei from nine cores in each sample piece
were averaged and expressed as the frequency and mitotic index.
The sampling error...
Douglas-fir (Pseudotsuga menziesii) has a wide distribution in North America and is one of the tree species most widely distributed outside its natural range. The species has been introduced to Europe, New Zealand, South America, and elsewhere around the world. At present, Douglas-fir is an accepted and integral part of...
To obtain data on the decomposition of the forest floor, a battery operated electrolytic respirometer was developed making it possible to measure CO₂ evolution from field moist forest floor samples in situ independent of root respiration. Banks of four respirometers powered by two 12-volt batteries were installed in three old...
Experiments were conducted to determine if the plagiotropic
growth habit of rooted cuttings of Douglas-fir might result from a
system favoring the accumulation of indoleacetic acid in the adaxial
side of the shoot in response to vertical placement.
Actively growing excised branch terminals were subjected to
gravitational disorientation to determine...