Crown structure in western hemlock, Douglas-fir, and grand fir in western Washington: horizontal distribution of foliage within branches

1996 ◽  
Vol 26 (1) ◽  
pp. 128-142 ◽  
Author(s):  
John A. Kershaw Jr. ◽  
Douglas A. Maguire
Keyword(s):  
Pacific Northwest ◽  
Horizontal Distribution ◽  
Relative Increase ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Prediction Equations ◽  
Parameter Recovery ◽  
Empirical Distributions ◽  
Individual Branch ◽  
Parameter Prediction

Horizontal distribution of foliage within individual branches was explored for three major tree species (western hemlock (Tsugaheterophylla (Raf.) Sarg.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), and grand fir (Abiesgrandis (Dougl. ex D. Don) Lindl.)) in the Pacific Northwest. Weibull, β, normal, and Johnson's SB distributions were assessed for their ability to conform to the empirical foliage distributions. Moment-based parameter recovery and parameter prediction methodologies were applied. On the basis of the rank of individual branch χ2-values, the β distribution performed best under parameter recovery, while Johnson's SB distribution was best in terms of total sum of χ2-values. Overall, few differences between the four distributions were observed. A system of moment-based parameter prediction equations was developed from branch dimensional and positional measures. The prediction equations showed that the ratio of relative distance from the stem to mean foliage density increased with increasing branch size. This relative increase was enhanced with increasing depth into crown for western hemlock, but not for Douglas-fir or grand fir. Again, the β distribution, based on predicted moments, followed most closely the empirical distributions on the basis of the ranks of χ2-values. The normal distribution was the best in terms of total sum of χ2-values. As expected, moment-based parameter recovery produced smoothed distributions that followed more closely the observed empirical distributions; however, parameter prediction provides a methodology for predicting distributions when empirical moments are not available. No significant (p > 0.05) differences in horizontal foliage distribution were found between sites or fertilization treatments.

Canopy disturbances over the five-century lifetime of an old-growth Douglas-fir stand in the Pacific Northwest

2002 ◽  
Vol 32 (6) ◽  
pp. 1057-1070 ◽  
Author(s):  
Linda E Winter ◽  
Linda B Brubaker ◽  
Jerry F Franklin ◽  
Eric A Miller ◽  
Donald Q DeWitt
Keyword(s):  
Pacific Northwest ◽  
Variable Density ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Old Growth ◽  
The Pacific ◽  
History Of ◽  
Horizontal Heterogeneity ◽  
Restoration Strategies

The history of canopy disturbances over the lifetime of an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand in the western Cascade Range of southern Washington was reconstructed using tree-ring records of cross-dated samples from a 3.3-ha mapped plot. The reconstruction detected pulses in which many western hemlock (Tsuga heterophylla (Raf.) Sarg.) synchronously experienced abrupt and sustained increases in ringwidth, i.e., "growth-increases", and focused on medium-sized or larger ([Formula: see text]0.8 ha) events. The results show that the stand experienced at least three canopy disturbances that each thinned, but did not clear, the canopy over areas [Formula: see text]0.8 ha, occurring approximately in the late 1500s, the 1760s, and the 1930s. None of these promoted regeneration of the shade-intolerant Douglas-fir, all of which established 1500–1521. The disturbances may have promoted regeneration of western hemlock, but their strongest effect on tree dynamics was to elicit western hemlock growth-increases. Canopy disturbances are known to create patchiness, or horizontal heterogeneity, an important characteristic of old-growth forests. This reconstructed history provides one model for restoration strategies to create horizontal heterogeneity in young Douglas-fir stands, for example, by suggesting sizes of areas to thin in variable-density thinnings.

Comparing productivity of pure and mixed Douglas-fir and western hemlock plantations in the Pacific Northwest

2006 ◽  
Vol 36 (6) ◽  
pp. 1484-1496 ◽  
Author(s):  
M M Amoroso ◽  
E C Turnblom
Keyword(s):  
Pacific Northwest ◽  
Stand Density ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Mixed Stand ◽  
Mixed Stands ◽  
Individual Tree ◽  
The Pacific ◽  
Increase In Productivity

We studied pure and 50/50 mixtures of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) plantations to compare attained total yields between mixed-species stands as opposed to monocultures of equal densities. Whether overall stand density influences this outcome has not been adequately investigated, and to address this we included three density levels (494, 1111, and 1729 trees/ha) in the analysis. At age 12, as components of the mixed stands, Douglas-fir exhibited greater height, diameter, and individual-tree volume than western hemlock at all densities. At 494 and 1111 trees/ha the monocultures had a higher volume per hectare than the mixed stand, but at 1729 trees/ha the mixed stand appeared to be just as productive as the pure stands. The increase in productivity by the mixture at high densities seems to have resulted from the partial stratification observed and most likely also from better use of the site resources. Because of this, less interspecific competition was probably experienced in the mixed stand than intraspecific competition in the pure stands. This study shows the important role density plays in the productivity of mixed stands and thus in comparing mixed and pure stands.

Modeling the long-term effects of disturbances on forest succession, Olympic Peninsula, Washington

1986 ◽  
Vol 16 (1) ◽  
pp. 56-67 ◽  
Author(s):  
Virginia H. Dale ◽  
Miles Hemstrom ◽  
Jerry Franklin
Keyword(s):  
Leaf Area ◽  
Pacific Northwest ◽  
Forest Succession ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Forest Composition ◽  
Silver Fir ◽  
Long Term Effects ◽  
Olympic Peninsula

A model of forest development has been adapted for the Pacific Northwest. The regeneration, growth, and death of individual trees are tracked for simulated 0.2 ha plots and tree attributes are aggregated to provide stand measures. The model includes the influence of temperature, soil moisture, light tolerance, and competition on tree growth. Long-term simulations for Douglas-fir dominated forests on the western Olympic Peninsula show that the stand is eventually dominated by western hemlock with silver fir being codominant. Even after 1200 years of subsequent stand development, silver fir fails to replace western hemlock indicating that this is a self-replicating and stable community. Fire, windthrows, insect disturbance, and clear-cut logging followed by replanting are incorporated into the model as single-event disturbances to a 500-year-old forest. For those cases where large Douglas-fir survive the disturbance, stand biomass and leaf area patterns are not significantly impacted until the death of the last large Douglas-fir. The projections were all carried out to the time when the forest is dominated by western hemlock and silver fir. At that time, the differential effect of the earlier disturbance is not apparent from the forest composition, biomass, or leaf area patterns except for the insect disturbance. Following the removal of all Douglas-fir by an insect, leaf area fluctuates regularly with a period of 600 years.

Initiation of an old-growth Douglas-fir stand in the Pacific Northwest: a reconstruction from tree-ring records

2002 ◽  
Vol 32 (6) ◽  
pp. 1039-1056 ◽  
Author(s):  
Linda E Winter ◽  
Linda B Brubaker ◽  
Jerry F Franklin ◽  
Eric A Miller ◽  
Donald Q DeWitt
Keyword(s):  
Pacific Northwest ◽  
Tree Ring ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Old Growth ◽  
The Pacific ◽  
Closed Forest ◽  
Initial Spacing ◽  
Epicormic Branching

We used tree-ring records to reconstruct the stand initiation of an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand in the western Cascade Range of southern Washington. All tree-ring samples were prepared and crossdated. Following a stand-replacing fire, the stand initiation period lasted from 1500 to 1540, with gradual filling-in of growing space over this period. All sampled Douglas-fir were initial colonizers, establishing (at stump-height) 1500–1521 under open conditions. A small number of the sampled western hemlock (Tsuga heterophylla (Raf.) Sarg.) were also initial colonizers. Growing space filled as tree crowns widened, and by 1540, closed forest conditions had developed. At this time, Douglas-fir were spaced about 3.5 m from equivalent competitors (ca. 800 trees/ha). In the centuries following canopy closure, considerable natural thinning of the initial colonizers occurred, but the canopy never opened enough again to allow further Douglas-fir establishment. Surviving Douglas-fir developed deep crowns despite the narrow initial spacing, and without epicormic branching from the bole. Most western hemlock that were canopy trees in 1992 established after 1540, originating in the understory. This reconstruction provides an example that may be useful where management policies emphasize the development of old-growth structures.

Annualized diameter and height growth equations for Pacific Northwest plantation-grown Douglas-fir, western hemlock, and red alder

2007 ◽  
Vol 250 (3) ◽  
pp. 266-278 ◽  
Author(s):  
Aaron R. Weiskittel ◽  
Sean M. Garber ◽  
Gregory P. Johnson ◽  
Douglas A. Maguire ◽  
Robert A. Monserud
Keyword(s):  
Pacific Northwest ◽  
Height Growth ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Red Alder ◽  
Growth Equations

Effects of silvicultural practices on carbon stores in Douglas-fir – western hemlock forests in the Pacific Northwest, U.S.A.: results from a simulation model

2002 ◽  
Vol 32 (5) ◽  
pp. 863-877 ◽  
Author(s):  
Mark E Harmon ◽  
Barbara Marks
Keyword(s):  
Pacific Northwest ◽  
Forest Products ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Simulation Experiments ◽  
Rotation Length ◽  
The Pacific ◽  
Carbon Stores ◽  
Slash Burning ◽  
Landscape Level

We used a new model, STANDCARB, to examine effects of various treatments on carbon (C) pools in the Pacific Northwest forest sector. Simulation experiments, with five replicates of each treatment, were used to investigate the effects of initial conditions, tree establishment rates, rotation length, tree utilization level, and slash burning on ecosystem and forest products C stores. The forest examined was typical of the Cascades of Oregon and dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg). Simulations were run until a C steady state was reached at the landscape level, and results were rescaled relative to the potential maximum C stored in a landscape. Simulation experiments indicated agricultural fields stored the least (15% of the maximum) and forests protected from fire stored the greatest amount (93% of the maximum) of landscape-level C. Conversion of old-growth forests to any other management or disturbance regime resulted in a net loss of C, whereas conversion of agricultural systems to forest systems had the opposite effect. The three factors, in order of increasing importance, most crucial in developing an optimum C storage system were (i) rotation length, (ii) amount of live mass harvested, and (iii) amount of detritus removed by slash burning. Carbon stores increased as rotation length increased but decreased as fraction of trees harvested and detritus removed increased. Simulations indicate partial harvest and minimal fire use may provide as many forest products as the traditional clearcut – broadcast-burn system while increasing C stores. Therefore, an adequate supply of wood products may not be incompatible with a system that increases C stores.

Fire-mediated pathways of stand development in Douglas-fir/western hemlock forests of the Pacific Northwest, USA

Ecology ◽  
2013 ◽  
Vol 94 (8) ◽  
pp. 1729-1743 ◽  
Author(s):  
Alan J. Tepley ◽  
Frederick J. Swanson ◽  
Thomas A. Spies
Keyword(s):  
Pacific Northwest ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Stand Development ◽  
The Pacific

THE 1951 AERIAL BAITING AND SEEDING PROJECT, ASH RIVER TRACT, MacMILLAN AND BLOEDEL LIMITED

1955 ◽  
Vol 31 (1) ◽  
pp. 45-59 ◽  
Author(s):  
G. S. Allen ◽  
I. K. Barber ◽  
Ian Mahood
Keyword(s):  
West Coast ◽  
Forest Service ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Local Distribution ◽  
Rodent Control ◽  
Buffer Strip ◽  
Minimum Standards ◽  
Service Standards ◽  
Forestry Practice

An area of 738 acres about 20 miles north and west of Port Alberni on Vancouver Island was seeded by helicopter to Douglas fir (1/2 pound per acre) and western hemlock (1/5 pound per acre) in November 1951. One week earlier this area and a surrounding buffer strip, totalling 1760 acres, had been baited by helicopter using wheat treated with thallous sulphate and "1080".Baiting was successful and the roden:trap ratio dropped from 1:4.6 to 1:94.3 as a result. By April the ratio had climbed again to 1:18.7. By the first week of June 1952, a total of about 1400 Douglas fir and 840 hemlock had germinated per acre. By November 1952, this had dropped to 1000 Douglas fir and 198 hemlock per acre. A final extensive survey in June 1954, showed a total of 730 Douglas fir and 57 hemlock of the 1952 crop per acre with a milacre stocking of 42.0 percent for Douglas fir and 43.9 percent for Douglas fir and hemlock. The 4-milacre stocking due to the 1952 Douglas fir seedlings was 78.3 percent. Practically all of the seedlings that germinated in 1952 are attributed to the seeding operation because of the relatively uniform distribution of seedlings and the lack of seedlings on the control area.The seeding operation in itself restocked 628 acres to B.C. Forest Service minimum standards (31 percent by 1-milacres). It restocked 708 acres to U.S. "medium" or "good" standards. With natural trees included, only 28 acres are below B.C. Forest Service standards, and 6 acres below U.S. "medium" stocking. Total stocking, including natural trees, is 59.3 percent by 1-milacres and 88.6 percent by 4-milacres.The baiting and seeding operation can be considered highly successful. The surviving Douglas firs are healthy and vigorous and show little deer or grouse damage to date. Distribution of the seedlings is good and most gaps that occurred are believed due to uneven local distribution of seed. Considering that this experiment was carried out on a rather steep south exposure and that the first summer following seeding was unusually hot and dry, the satisfactory results suggest that direct seeding following rodent control has a definite place in West Coast forestry practice. It may well take the place of more expensive and troublesome planting on many areas that are slow to restock.

Xenomeris Abietis Associated with Dieback of Douglas Fir and Western Hemlock

Mycologia ◽  
1971 ◽  
Vol 63 (3) ◽  
pp. 567-574 ◽  
Author(s):  
A. Funk ◽  
R. A. Shoemaker
Keyword(s):  
Douglas Fir ◽  
Western Hemlock
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