scholarly journals Spatial and temporal patterns of Populus tremuloides regeneration in small forest openings in northern Ontario

2009 ◽  
Vol 85 (4) ◽  
pp. 548-557 ◽  
Author(s):  
Arthur Groot ◽  
Rongzhou Man ◽  
Jim Wood
Keyword(s):  
Populus Tremuloides ◽  
Tree Height ◽  
Forest Harvesting ◽  
Trembling Aspen ◽  
Spatial And Temporal Patterns ◽  
Northern Ontario ◽  
Mixedwood Forests ◽  
Boreal Mixedwoods ◽  
Silvicultural System ◽  
Forest Openings

The density, height and diameter of trembling aspen sucker regeneration was assessed over a 10-year period in openings created by harvesting in a 40-year-old, 19-m-tall aspen stand in northeastern Ontario. The 5 types of opening comprised: circular openings of 9-m- and 18-m-diameter, 150-m-long east–west strips of 9-m and 18-m width, and a 1.5 ha (100 m × 150 m) clearcut. Density of aspen regeneration was significantly affected by opening type, location relative to the opening, time since harvest, and by all interactions of these factors. Aspen densities within the circular openings declined to low levels by year 10, despite considerable initial recruitment. Trembling aspen height and diameter were significantly influenced by opening type, location relative to the opening, time since harvest, and by opening × time and location × time interactions. Trembling aspen heights in the circular openings were substantially less than in the clearcut and strip openings by year 10. The results support the traditional view that aspen is best managed under the clearcut silvicultural system, and that trembling aspen regeneration following forest harvesting can be reduced by controlling the extent or intensity of overstory removal. Finally, the results suggest that disturbances that create gaps greater than 1 tree height in width in aspen or mixedwood forests may allow gap dynamics to function. Key words: trembling aspen, silviculture, boreal mixedwoods, regeneration, forest openings

Within-tree patterns of wood stiffness for white spruce (Picea glauca) and trembling aspen (Populus tremuloides)

2014 ◽  
Vol 44 (2) ◽  
pp. 162-171 ◽  
Author(s):  
Derek F. Sattler ◽  
Philip G. Comeau ◽  
Alexis Achim
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Radial Growth ◽  
Tree Height ◽  
White Spruce ◽  
Vertical Position ◽  
Trembling Aspen ◽  
Mixed Effect ◽  
Cambial Age ◽  
Rate Of Increase

Radial patterns of modulus of elasticity (MOE) were examined for white spruce (Picea glauca (Moench) Voss) and trembling aspen (Populus tremuoides Michx.) from 19 mature, uneven-aged stands in the boreal mixedwood region of northern Alberta, Canada. The main objectives were to (1) evaluate the relationship between pith-to-bark changes in MOE and cambial age or distance from pith; (2) develop species-specific models to predict pith-to-bark changes in MOE; and (3) to test the influences of radial growth, relative vertical height, and tree slenderness (tree height/DBH) on MOE. For both species, cambial age was selected as the best explanatory variable with which to build pith-to-bark models of MOE. For white spruce and trembling aspen, the final nonlinear mixed-effect models indicated that an augmented rate of increase in MOE occurred with increasing vertical position within the tree. For white spruce trees, radial growth and slenderness were found to positively influence maximum estimated MOE. For trembling aspen, there was no apparent effect of vertical position or radial growth on maximum MOE. The results shed light on potential drivers of radial patterns of MOE and will be useful in guiding silvicultural prescriptions.

Are mixtures of aspen and white spruce more productive than single species stands?

1999 ◽  
Vol 75 (3) ◽  
pp. 505-513 ◽  
Author(s):  
Rongzhou Man ◽  
Victor J. Lieffers
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
White Spruce ◽  
Single Species ◽  
Physical Separation ◽  
Soil Resource ◽  
Mixedwood Forests ◽  
Environmental Extremes ◽  
Spruce Stands ◽  
Boreal Mixedwoods

In boreal mixedwood forests, aspen (Populus tremuloides) and white spruce (Picea glauca) commonly grow in mixture. These species may avoid competition through differential shade tolerance, physical separation of canopies, phenological differences, successional separation, and differences in soil resource utilization. Aspen may also be able to positively affect the growth of white spruce by improving litter decomposition and nutrient cycling rates, controlling grass and shrub competition, ameliorating environmental extremes, and reducing pest attack. These positive relationships likely make mixed-species stands more productive than pure stands of the same species. The evidence regarding the productivity of pure versus mixed aspen/white spruce stands in natural unmanaged forests is examined in this paper. Key words: Tree mixture; productivity; boreal mixedwoods; aspen; white spruce

Impact of simulated aspen shoot blight on trembling aspen

2007 ◽  
Vol 37 (4) ◽  
pp. 719-725 ◽  
Author(s):  
P.V. Blenis
Keyword(s):  
Populus Tremuloides ◽  
Tree Height ◽  
Growing Season ◽  
Common Disease ◽  
Trembling Aspen ◽  
Mechanical Wounding ◽  
Tree Form ◽  
Shoot Blight ◽  
The Difference ◽  
Intensively Managed

Although aspen shoot blight (ASB), caused by Pollaccia americana Ondrej, is a common disease of trembling aspen ( Populus tremuloides Michx.), its impact is uncertain. Mechanical wounding, previously shown to be a reliable surrogate for ASB infection, was used to assess ASB impact in two experiments. In the first experiment, the effect of date of wounding on impact was studied by wounding 1-year-old aspen on four dates between 29 June and 10 August 2001. Tree form at the end of the 2001 growing season varied with wounding date, and for each of the wounding dates, tree height was reduced relative to that of unwounded, control trees. After the 2005 growing season, only trees wounded on 17 July were shorter than unwounded trees and the difference in heights was only 62 cm. In the second experiment, trees spaced at 2.0 or 0.67 m were wounded in four successive seasons to determine the effect of multiple years of infection on trees growing at different densities. Simulated ASB reduced tree height by an average of 16 cm, whereas branchiness was not increased by ASB, even at the lower density. Although ASB should not be ignored, these results suggest that it is unlikely to be amongst the most destructive pests of intensively managed aspen.

Precommercial thinning of trembling aspen in northern Ontario: Part 2 – Interactions with Hypoxylon canker

2001 ◽  
Vol 77 (5) ◽  
pp. 902-910 ◽  
Author(s):  
Doug Pitt ◽  
David Weingartner ◽  
Sylvia Greifenhagen
Keyword(s):  
Populus Tremuloides ◽  
Planning Process ◽  
Block Design ◽  
Growth And Yield ◽  
Trembling Aspen ◽  
Northern Ontario ◽  
Precommercial Thinning ◽  
Crop Planning ◽  
Incidence And Mortality ◽  
Canopy Position

Hypoxylon canker [Entoleuca mammata (Wahlenberg:Fr) J.D. Rogers and Y.-M. Ju] incidence and mortality were monitored in six northern Ontario trembling aspen (Populus tremuloides Michx.) stands following precommercial thinning. At each of the six sites, a randomized complete block design experiment was established with four replicates of five thinning levels (none, 2-, 3-, 4-, and 5-m spacing). At the time of thinning, three stands were five years old; the remaining were ages 10, 15, and 22. Over the 15- to 17-year observation period, Hypoxylon-related mortality increased to 6–9% by the end of the period, regardless of thinning age or density. Hypoxylon infection incidence (excluding mortality) also increased, to 2–6% in unthinned stands and 8–11% in thinned stands by year 15. No differences among the thinning levels were observed. Prevalence, infection expressed as a percentage of surviving trees, did not differ among thinned and unthinned stands. Mortality attributed to factors other than Hypoxylon was 31–44% in unthinned stands and 7–23% in thinned stands, with no significant differences among thinning levels. Trees dying of other causes were typically small in diameter and of more subordinate crown classes than survivors. In contrast, Hypoxylon-caused mortality was independent of tree size and canopy position. Results suggest that log size and stand yield may be manipulated through density regulation, without concern for interacting impacts associated with Hypoxylon canker. Models are provided for estimating disease losses; predictions can then be factored into the crop-planning process. Key words: trembling aspen, precommercial thinning, Hypoxylon canker, growth and yield, crop planning

Juvenile stand responses and potential outcomes of conifer release efforts on Alberta's spruce–aspen mixedwood sites

2004 ◽  
Vol 80 (5) ◽  
pp. 583-597 ◽  
Author(s):  
Douglas G Pitt ◽  
Milo Mihajlovich ◽  
Leslie M Proudfoot
Keyword(s):  
Growth Model ◽  
Populus Tremuloides ◽  
Picea Glauca ◽  
Stand Structure ◽  
Landscape Management ◽  
Basal Area ◽  
White Spruce ◽  
Trembling Aspen ◽  
Management Objectives ◽  
Boreal Mixedwoods

Twelve Alberta forest regeneration blocks, situated on representative white spruce (Picea glauca (Moench) Voss) - trembling aspen (Populus tremuloides Michx.) boreal mixedwood sites, planted to white spruce, and operationally released with glyphosate herbicide, were surveyed in the fall of 2002. Stand structure and composition were quantified and compared for treated and untreated portions of each block. The Mixedwood Growth Model (MGM, Department of Renewable Resources, University of Alberta) was used to project these stands over a 100-year horizon and to model the outcomes of several additional silvicultural treatments that could be applied to these blocks. A single release treatment provided 17% and 43% gains in planted white spruce height and stem diameter, respectively, an average of five years after treatment. Treatment shifted stands from being deciduous-dominated, with only 12% conifer basal area, to more than 75% conifer basal area, increasing conifer volumes per hectare nearly three-fold, but retaining conifer-deciduous mixture. Model projections suggest that these stands will produce similar total volumes over an 80-year rotation and that conifer release essentially trades deciduous volume for conifer volume, the degree of release dictating the extent to which this trade-off takes place. A single conifer release treatment led to an average simulated mature stand that contains 21% deciduous basal area, likely meeting mixedwood rather than conifer regeneration criteria. Model simulations of additional silvicultural interventions in these stands suggested that a variety of options exist to satisfy a range of stand or landscape management objectives for spruce-aspen mixedwoods, all within a relatively fixed volume production envelope. A clearer understanding of how early stand conditions translate into stand and landscape management objectives seems prerequisite to solving management conflicts on boreal mixedwood sites. Key words: boreal mixedwoods, vegetation management, conifer release, Mixedwood Growth Model, white spruce, trembling aspen

Habitat requirements of the Yellow-bellied Sapsucker, Sphyrapicus varius, in boreal mixedwood forests of northwestern Canada

2006 ◽  
Vol 84 (9) ◽  
pp. 1230-1239 ◽  
Author(s):  
C. Savignac ◽  
C.S. Machtans
Keyword(s):  
Populus Tremuloides ◽  
Keystone Species ◽  
Forest Harvesting ◽  
Habitat Requirements ◽  
Northwestern Part ◽  
Strongly Correlated ◽  
Mixedwood Forests ◽  
Nesting Sites ◽  
Site Use ◽  
Paper Birch

Despite its role as a keystone species, few studies have investigated the habitat requirements of the Yellow-bellied Sapsucker ( Sphyrapicus varius (L., 1766)) in the northwestern part of its range, where the current forest harvesting rotation schedule and targets for reducing the prevalence of old and mixedwood stands may reduce the optimal habitat for this species. We studied nesting and foraging habitat requirements of nesting sapsuckers in a boreal mixedwood forest of northwestern Canada by collecting data on nesting sites and foraging substrates on twenty-four 16- to 56-ha plots distributed among four habitat types in 1998 and 2002. Nests (n = 68) were generally found in large (≥22 cm diameter at breast height) trembling aspen ( Populus tremuloides Michx) that were alive but declining and that showed high incidence (81.1%) of heartwood rot infection ( Phellinus tremulae (Bondarzev) Bondarzev & Borisov in Bondarzev). Nest-site use by sapsuckers was predicted mainly by the presence of external fungal conks and tree diameter. Among tree species used as foraging substrates, paper birch ( Betula papyrifera Marsh.) (65.6%) and green alder ( Alnus viridis (Vill.) Lam. & DC.) (21.3%) were used most frequently. The use of birch was strongly correlated with its availability. Mature forests had higher densities of nesting sites and foraging substrates than immature aspen stands. In addition to reconfirming the importance of mature mixedwood forests for Yellow-bellied Sapsuckers, our study also indicates that forest harvest rotations in northwestern Canada should exceed 90 years to promote the keystone role of this species.

scholarly journals Twenty-six years of aspen regeneration under varying light conditions in a boreal mixedwood forest

2021 ◽  
pp. 1-13
Author(s):  
Holly D. Deighton ◽  
Arthur Groot ◽  
Nelson Thiffault ◽  
Mya Rice
Keyword(s):  
Populus Tremuloides ◽  
Basal Area ◽  
Light Conditions ◽  
Trembling Aspen ◽  
Diameter At Breast Height ◽  
Breast Height ◽  
Light Levels ◽  
Rate Of Increase ◽  
Silvicultural System ◽  
Understory Vegetation Cover

Density, height, and diameter at breast height of trembling aspen (Populus tremuloides Michx.) sucker regeneration were assessed over a 26-year period in openings created by harvesting in a 40-year-old aspen stand in northeastern Ontario (Canada). The opening types were 9- and 18-m diameter circles, 9- and 18- 150-m east-west strips, and a 100- 150-m clearcut, representing a range of light conditions. Density, height, and diameter at breast height of aspen regeneration were significantly affected by opening type, location relative to opening, and time since harvest. By year 26, aspen densities in circular openings declined to 0, despite high initial recruitment, and trembling aspen heights were significantly lower in the 9-m strips than in the 18-m strips or the clearcut. Year 26 aspen density, volume, and basal area increased with increasing initial light intensity, with the highest rate of increase between 80 and 100% light levels. Understory vegetation cover was largely unaffected by opening size; however, substantial understory aspen regeneration occurred in the smaller openings. Results support the traditional view that aspen is best managed under the clearcut silvicultural system, and >80% full light is recommended for adequate long-term aspen regeneration.

scholarly journals Twenty-six years of aspen regeneration under varying light conditions in a boreal mixedwood forest

2021 ◽  
Vol 97 (3) ◽  
pp. 326-342
Author(s):  
Holly D. Deighton ◽  
Arthur Groot ◽  
Nelson Thiffault ◽  
Mya Rice
Keyword(s):  
Populus Tremuloides ◽  
Basal Area ◽  
Light Conditions ◽  
Trembling Aspen ◽  
Diameter At Breast Height ◽  
Breast Height ◽  
Light Levels ◽  
Rate Of Increase ◽  
Silvicultural System ◽  
Understory Vegetation Cover

Density, height, and diameter at breast height of trembling aspen (Populus tremuloides Michx.) sucker regeneration were assessed over a 26-year period in openings created by harvesting in a 40-year-old aspen stand in northeastern Ontario (Canada). The opening types were 9- and 18-m diameter circles, 9- and 18- _ 150-m east-west strips, and a 100- _ 150-m clearcut, representing a range of light conditions. Density, height, and diameter at breast height of aspen regeneration were significantly affected by opening type, location relative to opening, and time since harvest. By year 26, aspen densities in circular openings declined to 0, despite high initial recruitment, and trembling aspen heights were significantly lower in the 9-m strips than in the 18-m strips or the clearcut. Year 26 aspen density, volume, and basal area increased with increasing initial light intensity, with the highest rate of increase between 80 and 100% light levels. Understory vegetation cover was largely unaffected by opening size; however, substantial understory aspen regeneration occurred in the smaller openings. Results support the traditional view that aspen is best managed under the clearcut silvicultural system, and >80% full light is recommended for adequate long-term aspen regeneration.

Precommercial thinning of trembling aspen in northern Ontario: Part 1 – Growth responses

2001 ◽  
Vol 77 (5) ◽  
pp. 893-901 ◽  
Author(s):  
James A. Rice ◽  
G. Blake MacDonald ◽  
David H. Weingartner
Keyword(s):  
Populus Tremuloides ◽  
Trembling Aspen ◽  
Growth Responses ◽  
Northern Ontario ◽  
Individual Tree ◽  
Precommercial Thinning ◽  
Individual Tree Growth ◽  
Aspen Tree ◽  
Fibre Yield ◽  
Residual Tree

In Ontario, trembling aspen (Populus tremuloides Michx.) utilization has increased over the past 20 years and this trend is expected to continue. With this increased demand, questions are being raised about stand conditions required for optimum growth. In 1979, a study was initiated across the commercial range of aspen in northern Ontario to determine the optimum precommercial thinning intensities for aspen tree and stand growth. Six pure aspen stands between the ages of five and 22 years were thinned to residual spacings of 2 × 2 m, 3 × 3 m, 4 × 4 m, and 5 × 5 m. Unthinned and thinned plots were measured at regular intervals for up to 17 years after treatment. Diameter increased significantly with residual tree spacing over the range of site conditions, geographic locations, and tree ages. Precommercial thinning resulted in significantly increased height in three of the stands, and height generally increased with increased residual spacing. Fifteen to 17 years after treatment, gross total volume (GTV) was highest in the unthinned plots for all six stands and decreased as residual tree spacing increased. Gross merchantable volume (GMV) did not vary significantly with thinning in all but the oldest stand. The results of this study do not support the use of precommercial thinning to increase aspen fibre yield. However, if the management goal is maximizing individual tree growth, precommercial thinning of aspen should be considered. Key words: Trembling aspen, precommercial thinning, DBH response, height response, northern Ontario

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