scholarly journals Transforming even-aged coniferous stands to multi-aged stands: an opportunity to increase tree species diversity?

2020 ◽  
Vol 93 (5) ◽  
pp. 616-629
Author(s):  
Gauthier Ligot ◽  
Philippe Balandier ◽  
Sophie Schmitz ◽  
Hugues Claessens
Keyword(s):  
Interspecific Competition ◽  
Height Growth ◽  
Douglas Fir ◽  
The Other ◽  
Western Hemlock ◽  
Stand Age ◽  
Specific Response ◽  
Light Conditions ◽  
Comparable Rate ◽  
Advanced Regeneration

Abstract Transforming even-aged coniferous stands into multi-aged ones is attracting growing interest in Europe. However, applying this silvicultural treatment, maintaining a continuous cover and relying on natural regeneration require a deep understanding of the factors driving interspecific competition in the understorey. In particular, knowledge of species-specific response to different light conditions is needed to plan silvicultural treatments and forecast long-term stand composition. In this context, we assessed regeneration (±10–400 cm in height) and light conditions (±1–40 per cent of transmittance) in nine coniferous stands with ranging stand age (±20–120 years) and species composition (Norway spruce, Douglas fir, larch, silver fir and western hemlock) in Belgium. We then modelled interspecific differences in regeneration height growth to forecast the outcome of interspecific competition in different light conditions. Controlling understorey light seems an efficient way to control the interspecific competition, but with some limits, and taking into account sapling size. Maintaining low light conditions (transmittance < 15 per cent) probably reduces interspecific competition as it allows small saplings (height < 100 cm) of most species to grow at a comparable rate. Maintaining higher light conditions might allow a few species to rapidly overgrow the others. Species ranking in height growth changed across the studied light range only between spruce and larch, suggesting that the competition between these two species can be driven through the control of understorey light. On the other hand, controlling canopy openness was found to be insufficient, for example, to promote an advanced regeneration (height ≥ 200 cm) of fir over advanced regeneration of spruce, to promote any species over western hemlock or to promote Douglas fir. Western hemlock, a very shade-tolerant species, was found to grow three times faster than the other species in all the observed conditions (PACL = 5–20 per cent). Douglas fir saplings showed weak growth and marked defoliation, which we hypothetically relate to the recent outbreak of Contarinia pseudotsugae in Western Europe.

scholarly journals Understory Tree Development with Repeated Stand Density Treatments in Coastal Douglas-Fir Forests of Oregon

2009 ◽  
Vol 24 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Jeffrey P.A. Shatford ◽  
John D. Bailey ◽  
John C. Tappeiner
Keyword(s):  
Stand Density ◽  
Tsuga Heterophylla ◽  
Height Growth ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Coast Range ◽  
Advanced Regeneration ◽  
Commercial Thinning ◽  
Sapling Growth ◽  
Stand Density Management

Abstract We studied the potential for stand density management treatments to increase growth rates of advanced regeneration in the understory of 50- to 70-year-old Douglas-fir (Pseudotsuga menziesii) forests. Study sites in Oregon included a mesic coastal site, a moderate coast range site, and a drier coast range foothills site. Commercial thinning treatments in 1974–1984 led to the establishment of Douglas-fir and western hemlock (Tsuga heterophylla) in the understory and, in 1997, parts of these same stands were thinned for a second time to release this advanced regeneration and promote two-story structure. Both species responded positively where overstory was reduced to 30–40 m2/ha, but western hemlock saplings grew 30–80% more rapidly than Douglas-fir. Average annual height growth of all western hemlock saplings that were more than 1.0 m tall in 1999 was 23–30 cm/year in twice-thinned stands but only 13 cm/year in denser, once-thinned stands. About one-half of all western hemlock saplings doubled or tripled their height in 4 years after a second overstory treatment; the largest 10% of these saplings grew 74–93 cm/year and now represents midstory structure. The response of Douglas-fir saplings to a partial overstory removal was limited. Repeated density management treatments in these Douglas-fir forests can accelerate growth of understory saplings, resulting in the development of two or more canopy layers over time; however, repeated and/or heavy thinning will be required for Douglas-fir sapling growth. Furthermore, because of western hemlock's potential for rapid height growth, some reduction of hemlock sapling density may be needed to maintain vigorous Douglas-fir.

scholarly journals Optimizing Surface Micro Grooving to Reduce the Checking and Cupping of Douglas Fir, Western Hemlock and White Spruce Decking Exposed to Natural Weathering

2018 ◽  
Vol 2 (4) ◽  
pp. 67 ◽  
Author(s):  
Sina Heshmati ◽  
Mohammad Mazloomi ◽  
Philip Evans
Keyword(s):  
Numerical Model ◽  
White Spruce ◽  
Groove Depth ◽  
Douglas Fir ◽  
The Other ◽  
Western Hemlock ◽  
Natural Weathering ◽  
Micro Grooving ◽  
Induced Stresses

Machining grooves into the surface of pine and fir (Abies spp.) deckboards reduces undesirable checking that develops when “profiled” boards are exposed to the weather. We aim to develop improved profiles for Douglas fir, western hemlock and white spruce decking to reduce their susceptibility to checking, and understand how profile geometry influences the stresses that cause checking. We varied the width and depth of grooves in profiled deckboards, exposed deckboards to the weather, and measured checking and cupping of boards. A numerical model examined the effect of groove depth on the moisture-induced stresses in profiled spruce boards. Profiling significantly reduced checking, but increased cupping of deckboards made from all three species. Western hemlock checked more than the other two species. Profiles with narrow grooves (rib profiles) were better at restricting checking than profiles with wider grooves. A rib profile with deeper grooves developed smaller stresses than a rib profile with shallower grooves, and boards with the former profile checked less than boards with shallower grooves. We conclude that checking of profiled Douglas fir, western hemlock and white spruce decking is significantly reduced by changing profile geometry, and our results suggest the best profiles to reduce checking of all three species.

Comparison of indicator variables for estimating growth reduction associated with Phellinusweirii root rot in Douglas-fir plantations

1979 ◽  
Vol 9 (1) ◽  
pp. 76-81 ◽  
Author(s):  
W. J. Bloomberg ◽  
G. W. Wallis
Keyword(s):  
Root Rot ◽  
Height Growth ◽  
Douglas Fir ◽  
The Other ◽  
Height Increment ◽  
Growth Reduction ◽  
Total Height ◽  
Breast Height ◽  
Indicator Variables ◽  
Increment Ratio

Total height, annual height increment, annual diameter at breast height (dbh) increment, ratio of total height to dbh, and ratio of annual height increment to annual dbh increment were assessed as indicator variables for estimating growth reduction associated with Phellinusweirii root rot of Douglas-fir (Pseudotsugamenziesii). Generally, height variables were more sensitive indicators than dbh. Total height by 2-cm-dbh classes, ratio of total height to dbh, and ratio of annual height increment to annual dbh increment were more sensitive and less variable than the other indicators. Ratio of total height to dbh was a more consistent and sensitive indicator of growth reduction than all other variables. Application of this ratio in estimating height growth reduction in three plantations indicated reductions in infected trees of 1 to 8 m over periods of 2 to 24 years, averaging 0.9 to 1.7% annually.

Assessment of interspecific competition using relative height and distance indices in an age sequence of seral interior cedar–hemlock forests in British Columbia

2004 ◽  
Vol 34 (6) ◽  
pp. 1228-1240 ◽  
Author(s):  
Suzanne W Simard ◽  
Donald L Sachs
Keyword(s):  
British Columbia ◽  
Interspecific Competition ◽  
Douglas Fir ◽  
Thuja Plicata ◽  
Stand Age ◽  
Relative Height ◽  
Larix Occidentalis ◽  
Critical Height ◽  
Paper Birch ◽  
Neighbourhood Analysis

Treatments that reduce neighbour density are widely applied in the belief they will improve conifer growth in mixed forests. However, our understanding of stand composition and age effects on competition is poor. We used neighbourhood analysis for 748 target conifer trees to examine interspecific competition within 11-, 25-, and 50-year-old mixed, even-aged stands of paper birch (Betula papyrifera Marsh.), Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), western redcedar (Thuja plicata Donn ex D. Don), and western larch (Larix occidentalis Nutt.) in southern interior British Columbia. Critical neighbourhood height and distance were identified where competition accounted for the greatest variation in target conifer diameter. Competition processes were emperically examined using relative height indices. We found that critical neighbourhood distance increased with stand age and was greater for larch than for cedar. Critical neighbourhood height was higher for cedar than for Douglas-fir or larch in the 11-year-old stands but lower in the older stands. The most important competitors in the 11-year-old stands were tall neighbours, whereas those in the older stands were short neighbours. We found asymmetrical relationships between target conifers and neighbours for all species and age-classes, indicating a resource preemption mode of competition. To be useful in developing prescriptions for competition management in mixed species stands, competition indices should consider neighbour identity and critical height for each target species. Assessment radius must also be sufficiently large to adequately characterize competition.

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

scholarly journals Effect of stand edge on the natural regeneration of spruce, beech and Douglas-fir

2012 ◽  
Vol 60 (6) ◽  
pp. 49-56 ◽  
Author(s):  
Lumír Dobrovolný ◽  
T. Štěrba ◽  
J. Kodeš
Keyword(s):  
Natural Regeneration ◽  
Woody Plants ◽  
Height Growth ◽  
Douglas Fir ◽  
Light Conditions ◽  
Climatic Extremes ◽  
Clear Cutting ◽  
Acidic Sites ◽  
To Come ◽  
Stand Height

Our work aimed at studying the strategy of woody plants regeneration during the regeneration of a spruce stand with the admixture of beech and Douglas-fir by border cutting (NW-SE aspect) on acidic sites of higher elevations in the Bohemian-Moravian Upland. Spruce is better adapted to bear shade than Douglas-fir. Nevertheless, in optimal light conditions up to a distance of ca. 35 m (about 16% DIFFSF) from the stand edge, the Douglas-fir can put the spruce into danger as to height growth. By contrast to beech, the density of spruce is significantly higher within the distance of 45 m (about 15% DIFFSF) from the stand edge but further on the situation would change to the benefit of beech. The density of Douglas-fir significantly dominates over beech within a distance of 35 m from the stand edge; from 55 m (less than 15% DIFFSF), the situation changes in favour of beech. Beech can survive in full shade deep in the stand core waiting for its opportunity to come. As compared to spruce and Douglas-fir, the height growth of beech was at all times significantly greater at a distance of 25 m from the stand edge. Converted to practical conditions, spruce and Douglas-fir with individually admixed beech seedlings showed good prosperity approximately up to a distance of one stand height from the edge. A mixture of spruce and beech did well at a greater distance but good prosperity at a distance of 2–3 stand heights was shown only by beech. Thus, border regeneration eliminates disadvantages of the climatic extremes of clear-cutting and specifics of shelterwood felling during which one – usually shade-tolerant tree species dominates in the natural regeneration (e.g. beech).

Basic Concepts and Definitions of Allergology

2019 ◽  
Author(s):  
Zoran Vrucinic
Keyword(s):  
Immune Reaction ◽  
The Body ◽  
The Other ◽  
Specific Response ◽  
Other Hand ◽  
Medical Vocabulary ◽  
The Future ◽  
Basic Concepts ◽  
Basic Insight ◽  
Insight Into

The future of medicine belongs to immunology and alergology. I tried to not be too wide in description, but on the other hand to mention the most important concepts of alergology to make access to these diseases more understandable, logical and more useful for our patients, that without complex pathophysiology and mechanism of immune reaction,we gain some basic insight into immunological principles. The name allergy to medicine was introduced by Pirquet in 1906, and is of Greek origin (allos-other + ergon-act; different reaction), essentially representing the reaction of an organism to a substance that has already been in contact with it, and manifested as a specific response thatmanifests as either a heightened reaction, a hypersensitivity, or as a reduced reaction immunity. Synonyms for hypersensitivity are: altered reactivity, reaction, hypersensitivity. The word sensitization comes from the Latin (sensibilitas, atis, f.), which means sensibility,sensitivity, and has retained that meaning in medical vocabulary, while in immunology and allergology this term implies the creation of hypersensitivity to an antigen. Antigen comes from the Greek words, anti-anti + genos-genus, the opposite, anti-substance substance that causes the body to produce antibodies.

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

Growth ofPseudotsuga menziesiiandTsuga heterophyllaseedlings along a light gradient: resource allocation and morphological acclimation

1997 ◽  
Vol 75 (9) ◽  
pp. 1424-1435 ◽  
Author(s):  
D. Mailly ◽  
J. P. Kimmins
Keyword(s):  
Leaf Morphology ◽  
Biomass Accumulation ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Low Light ◽  
Growing Seasons ◽  
Light Levels ◽  
Light Gradient ◽  
Relative Light Intensity

Silvicultural alternatives that differ in the degree of overstory removal may create shady environments that will be problematic for the regeneration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Gradients of light in the field were used to compare mortality, growth, and leaf morphological acclimation of two conifer species of contrasting shade tolerances: Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Results after two growing seasons indicated that Douglas-fir mortality occurred mainly at relative light intensity (RLI) below 20%, while western hemlock mortality was evenly distributed along the light gradient. Height, diameter, and biomass of the planted seedlings increased with increasing light for both species but at different rates, and maximum biomass accumulation always occurred in the open. Douglas-fir allocated more resources to stem biomass than western hemlock, which accumulated more foliage biomass. Increases in specific leaf area for Douglas-fir seedlings occurred at RLI ≤ 0.4 and red/far red (R/FR) ratio ≤ 0.6, which appear to be the minimal optimum light levels for growth. Conversely, western hemlock seedlings adjusted their leaf morphology in a more regular pattern, and changes were less pronounced at low light levels. These results, along with early mortality results for Douglas-fir, suggest that the most successful way to artificially regenerate this species may be by allowing at least 20% of RLI for ensuring survival and at least 40% RLI for optimum growth. Key words: light, light quality, leaf morphology, acclimation.

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