Download or read book Effects of Stand Density Reduction on Structural Development in Western Oregon Douglas fir Forests written by John Duff Bailey and published by . This book was released on 1996 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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% volume removal. Overstory and intermediate tree characteristics, conifer and hardwood regeneration, and shrub/herbaceous species composition and cover were recorded. From this, I assessed whether thinning young stands promoted vegetation structure and composition associated with old-growth stands. Overstory trees in thinned stands had diameters, live crown ratios, crown radii, and radial growth rates greater than those in unthinned stands, and equal to or approaching those found in old-growth stands. Stand volume production was neither affected by earlier clearcut harvesting nor by thinning. Intermediate trees in thinned stands, like old-growth stands, were typically young saplings with radial growth rates and live crown ratios greater than those in unthinned stands (typically suppressed members of the original cohort). Living intermediate structure (multi-storied canopies) was common to thinned and old-growth stands. Given such overstory and intermediate tree responses, canopy leaf area in stands thinned>20 years previously was greater than in unthinned stands. Conifer regeneration density, frequency and growth rates were greater in thinned stands than in old-growth and unthinned stands. Densities and frequencies of tall shrubs were similar in thinned and old-growth stands, and greater than unthinned stands. Low shrub and herbaceous cover were 33% and 25% greater, respectively, in thinned than other stand types. Herbaceous species frequency and richness were similarly stimulated. Low shrub composition was altered by thinning (unthinned and old-growth stands did not ordinate differently). However, herbaceous species composition was similar across all stand types and showed more variability among sites than among stand types. Thinning appeared to create old-growth-type structure by stimulating overstory and intermediate tree crowns and growth rates, tall shrub densities and conifer regeneration. Though low shrub and herbaceous species cover and frequency were greatest in thinned stands, composition was not affected by thinning, nor by clearcut harvesting 50 to 120 years ago or other differences in stand origin.

Download or read book Comparing Structure and Development of Douglas fir Old growth Plantations and Young Natural Forests in Western Oregon written by Christopher D. Dowling and published by . This book was released on 2003 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ages, diameter growth, density, tree size, and species were studied in old-growth, plantation, and young natural Douglas-fir stands in three areas in western Oregon: the western and eastern Coast Range and the western Cascades. The purpose was to compare the development of these three stand types and to determine whether plantations and young natural stands would develop old-growth structures and characteristics. The Douglas-fir age ranges in plantations (8 to 15 yr) were much narrower and than the ranges of tree ages found in the young natural (21 to 102 yr) and in the old-growth stands (300 to 354 yr). This wide range of tree ages, along with diameter growth rates and tree and stand structural characteristics, supported the hypothesis that old-growth developed at low initial stand densities. These low initial stand densities, probably the result of prolonged stand establishment, likely enabled height and crown size advantages among old and younger trees. Dominant and large codominant trees maintained live crown ratios and sustained diameter growth resulting in large stable trees indicated by low height-to-diameter ratios. The mean diameters of the dominant trees in the old-growth and the dominant trees in the young natural stands were not significantly different at age 40 and 100, indicating the young natural stands appear to be growing at the same rates as the old-growth in its first 100 years. The mean dominant diameters in the plantations and old-growth at age 40 and 100 were significantly different, indicating the plantations are growing and developing differently than young natural and old-growth forests. Plantations had grown rapidly for the first 20 to 30 years, and computer simulation indicated that a significant rapid decline in radial growth would occur between ages 30 and 55. Simulations also indicate that during this period, the mean diameters of the dominant plantation trees would fall below those of the old-growth in two of the three stands by age 85. Pre-commercial thinning 20 to 25 years ago in the plantations has helped sustain high early growth rates for a longer period of time than would have occurred if thinning had not been performed. Additional thinning in the future is likely needed to maintain rapid current rates. When simulated to age 250 both the young natural stands and the plantations maintained higher densities of smaller diameter trees than the old-growth stands. This simulation result indicates the possible inability of these stands to self-thin to the densities found in old-growth stands without some sort of density-reducing disturbance. The broad range of tree ages in the old-growth stands suggests that stand disturbances are a normal part of old-growth development on these sites. Five different plantation thinning options were also simulated to age 250, including additional options with thinning of understory trees and ingrowth. The projections indicate that when the plantations are left unthinned they would generally develop trees with small live crowns and mean diameters but still produce stable dominant overstory trees (low H:D ratios). Shade tolerant understory trees and ingrowth, such as western hemlock, are a key part of old-growth development. These trees may reduce the rate of growth and alter crown structure of the overstory trees over extended periods of time (200+ years). Additional thinning, possibly in multiple entries, in both the overstory and understory may be necessary for dense plantations to develop the tree size heterogeneity found in local old-growth forests. I also demonstrated a methodology to determine site-specific management targets or goals for creating old-growth structure from plantations. This was performed using past and current forest structure and composition information within a local landscape scale of 500 to 1000 acres, typical of the public land checkerboard ownership pattern. Stand types making up the historical landscape are identified and described retrospectively using historical and current aerial photographs and digital orthophotos, cruise records, previous studies, and sample plots of standing and harvested forests. The degree of detail provided through this methodology will likely help forest managers to define complex late-successional characteristics of stands and landscapes. My results indicate that stand and project area-specific definitions of old-growth and clearly defined goals for young stand management will facilitate development of old forest characteristics.

Download or read book Managing for Biodiversity in Young Douglas fir Forests of Western Oregon written by and published by . This book was released on 2002 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Growth and Yield Structure Composition and Soil Compaction in a Western Oregon Douglas fir Forest After 35 Years of Modified Selection Thinning written by Darin S. Stringer and published by . This book was released on 1999 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 small woodland properties. This case study evaluated a management system that has utilized modified selection thinning and natural regeneration since 1964, on a 250 acre private forest tract on the east slopes of the Oregon Coast Range. Six conditions (Types) were identified and mapped on the property based on the number of thinning entries and stand vegetation conditions. Current field data along with past cruise information and aerial photos were used to assess past and current volume production, stand structure, species composition arid soil compaction. Stand growth and yield was projected for 100 years using a simulation model to compare selection thinning and short rotation evenage management. At the Tract level, inventory records showed standing conifer volume from 1964-95 increased from 1,939 MBF (thousand board feet) to 2,150 MBF, while 5,606 MBF of volume was removed. Harvests occurred every 1-4 years with an average volume of 715 bd. ft./acre/year removed. Stands in early stages of conversion with modified selection thinning were growing at 80-100% of potential based on regional growth and yield tables for stands of similar site quality and stocking. Volume growth in stands in intermediate stages of conversion was 35-70% of potential compared to the same yield tables adjusted for stocking. Under a similar management regime, simulated total Tract standing volume increased to 4,250 MBF after a 100-year projection with harvests of 600 bd. ft./acre/year. Tract average periodic annual increment after 100 years was similar to current levels. Simulation studies showed that selection thinning yielded 9% less total Tract board foot volume (standing + harvest) than 50-year rotation evenage management after a 100- year simulation. Two of six stand Types simulated with selection thinning produced yields within 2% of the 50-year rotation evenage system after 100 years. The other four Types produced from 8-20% less volume. Under modified selection thinning the Tract contained 3 times more standing volume, and produced 2.8 times more volume in logs greater than 16 inches (scaling diameter) after 100 years. Management using modified selection thinning maintained a per acre average of at least 10 MBF/acre standing timber over 90% of simulation period vs. 40% for the evenage regime. Modified selection thinning between 1964-1995 led to changes in stand structure and composition. Both conifer reproduction and shrub cover increased in stands with more thinning. Conifer basal area decreased with thinning but the range of tree diameters increased. Composition of natural regeneration in the understory of stands thinned 9-12 times was dominated by Douglas-fir with 47% stocking and 290 trees per acre. Past and current cruise reports along with aerial photographs indicate hardwoods increased during the management period between 1964-97. Soil compaction was significantly higher in areas thinned 9-12 times vs. those thinned 1-4 times (p-value =.04), and was significantly higher in areas with less than 35% slope (p-value =.001). Across the Tract 60% of sampling points fell in a low compaction class, 33% in moderate, and 4% in high. Uneven-aged stand structure in a group selection sense was observed at the Tract level. Individual stands or plots did not contain functional individual tree selection uneven-aged structure. However, stands thinned repeatedly were two-storied in places. Based on comparison of different stand Types it appears modified selection thinning in Douglas-fir stands could be used to perpetuate even-aged structure, or to convert stands towards an uneven-aged condition. In either scenario, management is recommended to address increased hardwood stocking, inconsistent natural regeneration of conifer species, and understory growth losses caused by reserve "legacy" trees.

Download or read book Reconstructed Old Growth Forest Stand Structure and Composition of Two Stands on the Olympic Peninsula Washington State written by David H. Peter and published by DIANE Publishing. This book was released on 2010-10 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book BLM Density Management and Riparian Buffer Study written by and published by . This book was released on 2006 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Research Paper PNW written by and published by . This book was released on 1978 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vegetation Response Following Thinning in Young Douglas fir Forests of Western Oregon written by Liane R. Beggs and published by . This book was released on 2004 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 lands away from timber production and toward maintenance and restoration of late-successional habitat. In accordance with these new objectives, The Young Stand Thinning and Diversity Study (YSTDS) was developed to test if thinning could accelerate development of latesuccessional habitat in young managed Douglas-fir forests. Though the YSTDS examines several components of forest ecosystems, the goal of this study was to investigate short-term (5-7 years post-treatment) responses of vegetation to thinning treatments and to evaluate this response in relation to long-term objectives of late-successional development. The study is located on the western slope of the central Oregon Cascades. It consists of four replications of four thinning treatments (treatment areas average 30 ha each) in 30-50 year old second-growth Douglas-fir forest stands. Treatments include a control, heavy thin, light thin, and light thin with gaps. Unlike traditional thinning, the thinning treatments in this study sought to maintain and enhance overstory structural diversity by: (1) retaining species other than Douglas-fir, (2) simulating low densities that characterized development of some old-growth stands, and (3) adding canopy gaps to enhance spatial diversity. Following treatment completion, first, third, and fifth-year vegetation responses were measured Results for overstory vegetation indicate that heavy thinning may accelerate development of large trees, one important component of old-growth structure. This was evident by faster growth of the largest trees in the heavy thin than in the control. A heavy thin may also permit more time for understory development than a lighter thin because canopies of heavy thinned stands remained open longer than canopies of light thinned stands. Variation in overstory cover, which may promote heterogeneous understory development, was higher in the treatment that included canopy gaps than in other treatments including the control. Although accelerated development of a multi-layered canopy was not evident in any treatment, retention of non-dominant tree species prevented simplification of vertical canopy structure by retaining layers that are typically removed by a low thinning prescription. In addition, mortality of non-dominant species was not greater in thinned treatments than in the control. In the understory, results suggest that thinning can increase abundance of some vegetative layers without encouraging homogenization of the understory by clonal shrubs or exotic species. The thinnings resulted in initial declines of bryophytes, tall shrubs, and low shrubs followed by subsequent recovery and growth. While herbs displayed little initial response, a release of early-seral species was evident by 5-7 years post-treatment. Initial changes following thinning were likely due to harvesting damage and/or alteration of microclimate while subsequent changes were probably also related to increased resource availability. It is expected that eventually similarities and differences in overstory structure among thinned treatments will be reflected in the understory. For example, variation in canopy cover created by the addition of canopy gaps was already reflected in the understory, as plant assemblages differed across the gradient from gaps to the thinned forest matrix. Hence, although understory vegetation was similar among heavy and light thins in the short-term, early closure of the canopy following a light thin could preclude continuation of late-seral understory development. Finally, the effect of canopy gaps on the understory was more apparent at a within-stand scale than at a stand scale. Had the within-stand scale been ignored, relevant information regarding understory response would have been overlooked. This indicates that spatial scale should be considered when assessing ecological patterns. In conclusion, it is acknowledged that there are drawbacks to thinning (e.g., certain species decline following thinning) It is also acknowledged that the short-term nature of the data permits only speculation regarding long-term succession. While these limitations are recognized, current trends indicate that a moderate to heavy thinning in combination with gap formation can hasten development of late-successional features in thinned stands relative to unthinned stands. Thus, thinning similar to that used in this study can be one useful tool in the management of young Douglas-fir forests.

Download or read book Initial Thinning Effects in 70 to 150 year old Douglas fir western Oregon and Washington written by Richard L. Williamson and published by . This book was released on 1971 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure of Mature Douglas fir Stands in a Western Oregon Watershed and Implications for Interpretation of Disturbance History and Succession written by Mark Warren Klopsch and published by . This book was released on 1985 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of a mature Douglas-fir (Pseudotsuga menziesii) forest in a watershed in the western Cascades of Oregon was examined. Two age classes were detected in the stand, the oldest originating about 1855 after an extensive fire and the younger following a second fire about 1895 Although the trees in the older age class had statistically greater diameters and heights, only open grown individuals mixed with the younger age class could be readily distinguished B cause reburns at young ages are common and may not leave firescars, great care is be required to distinguish between slow regeneration and patchy reburns The early stand history varied greatly between the two age classes More than 70% of the trees in the younger portion of the stand were established within a 15 year period while comparable establishment in the older areas required over 35 years The broad range of ages in older age class, combined with significantly lower stocking density and mortality, resulted in a nearly flat diameter distribution compared with a bell-shaped distribution for the younger age class. The stand is heavily dominated by Douglas-fir which accounts for about 90% of the trees in the younger age class and 77% of the trees in the older portions of the stand. The older portion of the drainage has significantly more western hemlock (Tsuga heterophylla) and western dogwood (Cornus nuttalili). The younger portion of the drainage contains more early successional hardwoods including the remnants of a considerable population of bitter cherry (Prunus emarginata) Currently, almost no western redcedar (Thuja plicata) is found in the drainage although old redcedar logs or snags are still present on one quarter of the plots. The abundance of western hemlock and redcedar is much less than similar aged stands in the nearby H.J Andrews Experimental Forest The slow regeneration of the site following the first fire probably reflects a shortage of seed due to a hot burn and dispersal distances four to ten times greater than those reported by Issac (1943) The low abundance of western hemlock and virtual elimination of redcedar are attributed to even greater dispersal distances, low mobility of redcedar seed, and harsh establishment conditions The rapid regeneration following the second fire suggests efficient seed dispersal or storage with young trees and the potential importance of the understory exclusion phase of stand development on regeneration.

Download or read book Establishment Histories and Structural Development of Mature and Early Old growth Douglas fir Forests of Western Washington and Oregon written by James A. Freund and published by . This book was released on 2013 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Regeneration of tree populations following stand-replacing wildfires is an important process in the multi-century development of Douglas-fir- western hemlock forests. Temporal patterns of tree establishment in naturally regenerated, mid-aged (100 to 350 years) Douglas-fir-dominated forests have received little study in comparison with the abundance of research on regeneration in older Douglas-fir stands (>400 years of age). Increment cores were obtained from 1455 trees in 18 mature and early old-growth forests in western Washington and northwestern Oregon USA in order to determine temporal patterns of natural Douglas-fir regeneration following stand-replacing wildfire. Continuous regeneration of Douglas-fir for many decades following initiating fire was evident in all of the stands. The establishment period averaged 60 (range 32 to 99) years. The pattern observed contrasts both with the view of rapid (one- to two-decade) regeneration of Douglas-fir portrayed in early forestry literature and with reports of establishment periods exceeding 100 years in older (>400 year) Douglas-fir- western hemlock stands. Current intensive production forestry practices directed toward rapid and uniform stand closure following logging have no precedent in the historic natural patterns of Douglas-fir regeneration documented in this study. Conversely, results of this study provide evidence that early seral ecosystems persisted for several decades following wildfires. Patterns of structural development in mid-successional Douglas-fir dominated forests - a period in which forest structures evolve from the relatively simple conditions found in young forests to the complex old forests - is poorly understood. Stand structure and composition was analyzed in nine early old-growth (200 to 350 year old) Douglas-fir-dominated stands in western Washington and Oregon, all of which originated following a single stand-replacement wildfire. Structure and composition of live tree populations (density, diameters, and heights) as well as dead tree structures (snags and logs) were quantified and compared with conditions in previously reported studies of older (400-600-year old) forests. Stand-level attributes were analyzed using descriptive statistics, nonlinear regression, principal components analysis, and two old-growth indices. Variability among stands in specific structural features was large but consistent with the current conceptual model of Douglas-fir forest development. Diameter distributions generally exhibited a reverse-J shape, a characteristic of >450-year-old forests. Douglas-fir populated the tallest height classes and shade-tolerant species (e.g., western hemlock and Pacific silver fir) were present in lower (co-dominant and intermediate) canopy positions. Coarse woody debris was abundant in early old-growth stands in the form of both snags (42-140 m3ha[superscript -1]) and logs (172-584 m3 ha[superscript -1]). Scores for early old-growth stands calculated using existing old-growth structural indices were comparable to those in older (400 to 600year old) forests. The structural conditions and variability in these early old-growth forests are useful guides for managers seeking to accelerate development of complex structures in young Douglas-fir forests.

Download or read book General Technical Report PNW GTR written by and published by . This book was released on 2007 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Residual Trees on Growth of Young to Mature Douglas Fir and Western Hemlock in the Western Central Oregon Cascades written by Eric K. Zenner and published by . This book was released on 1995 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study was to assess how growth of young to mature Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sar.) in mixed stands was influenced by the presence of residual trees. Fourteen paired plots with and without residual trees were examined in a retrospective study on the Willamette National Forest, Oregon. Growth was analyzed at the stand level, and at the individual tree level, contrasting growth behavior of Douglas-fir and western hemlock. Stands were generally highly stocked with relative densities between 0.38 and 1.05 and age ranged between 55 and 121 years. Results indicate that both understory and residual tree densities had a major influence on average tree size and growth and yield of the young cohort. At the stand level, residual trees and high understory densities reduced volume, basal area, and the mean squared diameter of the young cohort, while understory mortality increased. The influence of residual tree density on total understory and Douglas-fir volume and basal area was best fit by a negative logarithmic function. After accounting for understory density effects, the decrease of understory volume and basal area per individual residual tree decreased with increasing residual tree density. With 5 to 50 residual trees/ha, total understory volume reduction was 22 and 45%, respectively, averaging 2.4 and 1.5% per residual tree, respectively. In mixed stands, Douglas-fir volume and basal area declined more rapidly than the volume and basal area of the entire young cohort, when residual tree density exceeded 15 trees/ha. This was probably due to the relative shade-intolerance of Douglas-fir. Douglas-fir volume and basal area on southerly aspects was more than double the values on northerly aspects. Examination of quadratic mean diameters and radial growth rates by crown class revealed that the average size and growth rates of dominant Douglas-fir were not reduced by residual trees. However, the number and basal area of understory trees, particularly dominant and codominant Douglas-fir, declined with increasing residual tree densities. Understory volume was highest in stands that had lowest understory densities. High understory stocking levels were associated with reduced growth and high mortality rates of the young cohort, suggesting stands were undergoing self-thinning. At the individual tree level, basal area growth and diameter growth of trees increased with increasing size and dominance. The marginal effect of residual trees declined with increasing numbers of residual trees per hectare. No residual tree effects on heights of dominant Douglas-fir was found, perhaps because the few dominant Douglas-firs may have been located sufficiently far from residual trees to minimize interaction. Due to high stocking levels in the young cohort, results from this study only apply to stands with relative densities above 0.38. In addition, leave-trees in managed stands may be younger, smaller, and may have different growth rates from residual trees in this study, thus affecting the young cohort differently. Finally, due to the observational nature of this study, cause-and-effect relationships cannot be established. However, since understory volume was highest in stands with low understory densities, understory density management may reduce growth.

Download or read book The Effects of Thinning on Stand and Tree Growth in a Young High Site Douglas fir Stand in Western Oregon written by David D. Marshall and published by . This book was released on 1990 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 percent increase in diameter growth. Subsequent crown type thinning treatments retained eight different, predetermined percentages of the gross basal area growth on the control plots. At age 45, diameter growth remains strong on the heavily thinned treatments, but decreases with increased growing stock. Gross volume growth increased with growing stock, while gross basal area growth was much less influenced by growing stock. Volume growth was strongly related to density because of the rapid height growth of this young stand. Heavy thinnings reduced volume production because of the depletion of growing stock. Total volume production was only slightly reduced on the light thinnings, whereas merchantable volume was greater than the unthinned control. Mortality was heavy on the control, but negligible on the treated plots. Heavy mortality in the last period, reduced net volume growth on the control to less than the treatments. Periodic annual increment (PAI) for cubic foot volume appear to have culminated for the treatments, although they are nearly twice the mean annual increments on the thinned plots. Board foot volume PAI does not appear to have culminated for any of the treatments. The diameter growth of individual trees was particularly influenced by the amount of density in trees larger than any given tree. Density had only a minor effect on height growth. Trees in lower densities had longer crowns and greater taper. Results from simulations of alternative thinning regimes show the desirability of early thinnings. Compared to thinning from below, crown thinning appeared to give the greatest release to the residual stand and produce high volume growth. Management must consider the trade-off s between greater diameter growth at low densities and greater volume growth at high densities.

Download or read book Fifty year Development of Douglas fir Stands Planted at Various Spacings written by Donald L. Reukema and published by . This book was released on 1979 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Variability in Older Forest Structure in Western Oregon written by Nathan Jeremy Poage and published by . This book was released on 2002 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Density Management in the 21st Century written by Paul D. Anderson and published by . This book was released on 2013 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: