scholarly journals Productivity of aspen stands with and without a spruce understory in Alberta's boreal mixedwood forests

2001 ◽  
Vol 77 (2) ◽  
pp. 351-356 ◽  
Author(s):  
Daniel M. MacPherson ◽  
Victor J. Lieffers ◽  
Peter V. Blenis
Keyword(s):  
Key Words ◽  
Populus Tremuloides ◽  
Picea Glauca ◽  
Allometric Equations ◽  
Mixed Stands ◽  
Breast Height ◽  
Mixedwood Forests ◽  
Annual Biomass ◽  
Understory Biomass ◽  
Northeastern Alberta

In northeastern Alberta, the current biomass and periodic annual biomass increment (PAI) was measured in 29 stands of maturing aspen (Populus tremuloides)-white spruce (Picea glauca), aged 48 to 105 years. Plots in pure aspen were paired with nearby plots of aspen growing on a similar landform but with a spruce understory. Biomass was estimated by diameter at breast height and allometric equations. Totalled over both species, there was 10.5 % greater PAI and 10.0 % greater biomass in the mixed plots than in the pure aspen plots. Pure aspen plots, however, had 12.9% greater aspen biomass and 25.2% greater aspen PAI than the aspen component of mixed plots. The apparent decline in productivity of aspen in the mixed stands, however, could not be related to the variation in spruce abundance in these mixed stands. Key words: mixed wood management, understory, spruce boreal mixed wood

scholarly journals Regeneration of aspen following partial and strip understory protection harvest in boreal mixedwood forests

2009 ◽  
Vol 85 (4) ◽  
pp. 631-638 ◽  
Author(s):  
Alison D Lennie ◽  
Simon M Landhäusser ◽  
Victor J Lieffers ◽  
Derek Sidders
Keyword(s):  
Forest Management ◽  
Key Words ◽  
Populus Tremuloides ◽  
Picea Glauca ◽  
Basal Area ◽  
White Spruce ◽  
Mixedwood Forests ◽  
Partial Harvest ◽  
Second Year

Trembling aspen regeneration was studied in 2 types of partial harvest systems designed to harvest mature aspen but protect immature spruce and encourage natural aspen regeneration. Two partial harvest systems, where the residual aspen was either left in strips or was dispersed uniformly, were compared to traditional clearcuts. After the first and second year since harvest, aspen sucker density and growth was similar between the 2 partial harvests, but was much lower than in the clearcuts. However, in the partial cuts the regeneration density was very much dependent on the location relative to residual trees. The density of regeneration was inversely related to the basal area of residual aspen; however, sucker height was inversely related to the basal area of the residual spruce. Although there were adequate numbers of suckers after partial harvest, their viability and contribution to the long-term productivity of these mixedwood stands is not clear. Key words: silvicultural systems, forest management, residual canopy, white spruce, Populus tremuloides, Picea glauca, traffic

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

Patterns of initial versus delayed regeneration of white spruce in boreal mixedwood succession

2006 ◽  
Vol 36 (6) ◽  
pp. 1597-1609 ◽  
Author(s):  
Vernon S Peters ◽  
S Ellen Macdonald ◽  
Mark RT Dale
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Fire Severity ◽  
Mineral Soil ◽  
White Spruce ◽  
Mixedwood Forests ◽  
Regeneration Period ◽  
Postfire Regeneration ◽  
Distance To Seed Source ◽  
Mixedwood Stands

The timing of white spruce regeneration in aspen (Populus tremuloides Michx.) – white spruce (Picea glauca (Moench) Voss) boreal mixedwood stands is an important factor in stand development. We examined boreal mixedwood stands representing a 59-year period of time since fire and determined (1) whether and when a delayed regeneration period of white spruce occurred, (2) whether the relative abundance of initial (<20 years) versus delayed (≥20 years postfire) regeneration is related to seed availability at the time of the fire, and (3) what are the important regeneration substrates for initial versus delayed regeneration. Initial regeneration occurred primarily on mineral soil or humus, while delayed regeneration established primarily on logs and peaked 38–44 years after fire. Of the 20 stands investigated, seven were dominated by initial regeneration, six were dominated by delayed regeneration, and seven were even mixtures of both. The dominance of a site by initial or delayed regeneration could not be simply explained by burn timing relative to mast years or distance to seed source; our results suggested that fire severity and the competitive influence of initial regeneration on delayed regeneration were important at fine scales. Based on our results we describe several possible postfire successional pathways for boreal mixedwood forests.

scholarly journals Tree Growth Response Along Seismic Lines in Alberta

1986 ◽  
Vol 62 (1) ◽  
pp. 29-34 ◽  
Author(s):  
I. E. Bella
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Pinus Contorta ◽  
Forest Cover ◽  
Black Spruce ◽  
Rocky Mountain ◽  
Radial Increment ◽  
Growth Data ◽  
Breast Height ◽  
Seismic Lines

Stem growth data from breast height were collected from about 2000 trees on 192 sample transects (plots) located adjacent to seismic lines. Sampled stands represented the most important forest cover types between 10 and 100 years of age over a range of site conditions in the foothills of western Albetra from Rocky Mountain House to Grande Prairie. Line clearing stimulated breast height radial increment fairly consistently in the 20% range of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) B.S.P.) trees. This improvement expressed in terms of stand growth, however, fell far short of that required to make up for the loss of wood production over these lines if the cut trees are not utilized. The lack of significant stimulation from line clearing in aspen (Populus tremuloides Michx.) stands indicates a complete loss of production due to the lines.

scholarly journals Growing Space Management in Boreal Mixedwood Forests: 11-Year Results

2011 ◽  
Vol 26 (2) ◽  
pp. 82-90 ◽  
Author(s):  
Richard D. Kabzems ◽  
George Harper ◽  
Peter Fielder
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Light Availability ◽  
White Spruce ◽  
Tree Level ◽  
Mixed Stands ◽  
Individual Tree ◽  
Space Management ◽  
Growing Seasons ◽  
The Individual

Abstract Managing boreal mixed stands of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca [Moench] Voss) is more likely to sustain a diversity of values and has the potential to increase productivity at both the site and landscape levels compared with pure broadleaf or conifer management. In this study, we examine growth of white spruce and aspen after 11 growing seasons over a range of aspen densities created by spot and broadcast treatment of broadleaves using manual and chemical means, aspen spacing, and an untreated control. Results indicate that survival and growth of both spruce and aspen were similar across the range of treatments. Spruce groundline diameter was greater, and height to groundline diameter ratio was lower, for the treatments in which aspen was chemically controlled or uniformly spaced compared with the control. Light measurements at the individual tree level suggested that increased light availability improved white spruce diameter growth. Spruce height growth did not vary by treatment. The status of these experimental mixedwoods was compared with current conifer and mixedwood regeneration evaluations, as well as the preharvest composition of the original stand. After 11 growing seasons, growth of aspen and white spruce indicated that opportunities exist to further modify aspen density to enhance treatment longevity and effectiveness to produce a greater range of boreal mixedwood stand types.

scholarly journals Semi-natural and intensive silvicultural systems for the boreal mixedwood forest

1996 ◽  
Vol 72 (3) ◽  
pp. 286-292 ◽  
Author(s):  
V. J. Lieffers ◽  
J. D. Stewart ◽  
R. B. Macmillan ◽  
D. Macpherson ◽  
K. Branter
Keyword(s):  
Populus Tremuloides ◽  
Land Tenure ◽  
Picea Glauca ◽  
Abies Balsamea ◽  
White Spruce ◽  
Growth And Yield ◽  
Mixedwood Forests ◽  
Seed Sources ◽  
Starting Point ◽  
Western Boreal Forest

Boreal mixedwood forests of aspen (Populus tremuloides) and white spruce (Picea glauca) are found on mesic sites in the western boreal forest. In the natural development of mixedwood stands, aspen is usually the first species to dominate the site. However, depending upon spruce seed sources and seedbeds, spruce can establish immediately after disturbance or in the next several decades. In most cases, spruce grow in the understory of deciduous species during its early development. If there are no spruce seed sources, aspen may be the sole tree species for a long period. In most circumstances, however, the longer-lived and taller white spruce eventually becomes the dominant species. If stands remain undisturbed for long periods, they will likely become uneven-aged mixtures of spruce and balsam fir (Abies balsamea). We propose silvicultural systems that will develop stands of a range of compositions, structures and value. As a starting point, we identify eight different mixed-wood compositions that might be identified in stand inventories, and propose various silvicultural treatments, including underplanting of white spruce, understory protection, shelterwood, and uneven-aged management. Fundamental changes in land tenure and silvicultural regulations, and improvements in estimation of growth and yield will be required before this range of management of mixed-woods can be implemented. Key words: aspen, white spruce, shelterwood, Populus tremuloides, Picea glauca, succession, ecosystem management

scholarly journals Challenges in estimating forest biomass: use of allometric equations for three boreal tree species

2019 ◽  
Vol 49 (12) ◽  
pp. 1613-1622
Author(s):  
Dingliang Xing ◽  
J.A. Colin Bergeron ◽  
Kevin A. Solarik ◽  
Bradley Tomm ◽  
S. Ellen Macdonald ◽  
...  
Keyword(s):  
Populus Tremuloides ◽  
Aboveground Biomass ◽  
Tree Species ◽  
Picea Glauca ◽  
Forest Cover ◽  
Forest Biomass ◽  
Belowground Biomass ◽  
Allometric Equations ◽  
Shoot Ratio ◽  
Root To Shoot Ratio

Regionally fitted allometric equations for individual trees and root-to-shoot ratio values are normally used to estimate local aboveground and belowground forest biomass, respectively. However, uncertainties arising from such applications are poorly understood. We developed equations for both aboveground and belowground biomass using destructive sampling for three dominant upland boreal tree species in northwestern Alberta, Canada. Compared with our equations, the diameter-based national equations derived for use across Canada underestimated aboveground biomass for Picea glauca (Moench) Voss but gave reasonable estimates for Populus balsamifera L. and Populus tremuloides Michx. The national equations based on both tree diameter and height overestimated aboveground biomass for the Populus species but underestimated it for Picea glauca in our study area. The approach of root-to-shoot ratio proposed by the Intergovernmental Panel on Climate Change (IPCC) overestimated belowground biomass by 16%–41%, depending on forest cover type, in comparison with our values estimated directly on site, with the greatest bias in deciduous-dominated stands. When the general allometric equations for aboveground biomass and the root-to-shoot ratio for belowground biomass were combined to estimate stand biomass, overestimation could be as high as 18% in our study area. The results of our study support the development of improved regional allometric equations for more accurate local-scale estimations. Incorporating intraspecific variation of important traits such as tree taper may be especially helpful.

Elevated mortality of residual trees following structural retention harvesting in boreal mixedwoods

2008 ◽  
Vol 84 (1) ◽  
pp. 70-75 ◽  
Author(s):  
Kevin D Bladon ◽  
Victor J Lieffers ◽  
Uldis Silins ◽  
Simon M Landhäusser ◽  
Peter V Blenis
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Boreal Forests ◽  
Sustainable Forest Management ◽  
Mortality Rates ◽  
Permanent Sample Plots ◽  
Mixedwood Forests ◽  
Boreal Mixedwoods ◽  
Structural Retention ◽  
Annual Mortality

In recent years boreal forests have been harvested to retain a portion of the original canopy, thereby providing forest structure, mostly for biodiversity reasons. Boreal mixedwood cutovers were surveyed at one and five years after harvesting with approximately 10% structural retention, to quantify the mean annual mortality rates of the residual trembling aspen, balsam poplar, paper birch and white spruce trees. For comparison, "natural" mortality rates by species were estimated from permanent sample plots in stands of similar composition. Species ranking of the annual mortality rates of residuals in areas harvested with structural retention were: poplar (10.2%) > birch (8.7%) > aspen (6.1%) > spruce (2.9%). Annual mortality rates were 2.5 to 4 times greater than in the reference stands. The majority of broadleaved species died as snags (~70%–90%), while most spruce died due to windthrow (80%). Mortality rates increased with slenderness coefficient for codominant and understory poplar and for understory birch. For aspen, codominants were most likely to die, while in spruce, dominant trees and trees with the greatest damage to the bole from harvesting operations had the highest mortality. Key words: Alberta, Betula papyrifera, dieback, harvesting damage, mixedwood forests, variable retention, Picea glauca, Populus balsamifera, Populus tremuloides, structural retention, sustainable forest management

scholarly journals Evaluating the impact of stand composition and competition on white spruce and aspen wood attributes in the boreal mixedwood

2021 ◽  
Author(s):  
◽  
Ryan Jackalin
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Wood Quality ◽  
White Spruce ◽  
Aspen Wood ◽  
Mixed Stands ◽  
Spruce Wood ◽  
Intimate Mixture ◽  
Volume Production ◽  
The Impact

I evaluated how intra- and inter-specific competition affects the development of eleven wood attributes of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) over 34 years. My analysis was conducted in a mixedwood trial site in Northern British Columbia, Canada, that included treatments consisting of 0, 1000, 2000, 5000, and 10000 stems per hectare of aspen. Competition was found to negatively influence wood attribute development in aspen and positively impact spruce (at low levels of competition). Plot level competition indices were the best predictor of variation in aspen wood attributes, while stand level competition (population density) best explained the majority of spruce wood attributes. Maintaining aspen at lower densities in intimate mixture can have a positive effect on spruce wood quality, while incurring relatively small reductions in spruce volume production and also retaining the ecological benefits associated with managing for mixed stands.

Structure and dynamics of trembling aspen – white spruce mixed stands near Fort Nelson, B.C.

2004 ◽  
Vol 34 (2) ◽  
pp. 384-395 ◽  
Author(s):  
Richard Kabzems ◽  
Oscar García
Keyword(s):  
Populus Tremuloides ◽  
Picea Glauca ◽  
Stand Structure ◽  
White Spruce ◽  
Structure Type ◽  
Growth Patterns ◽  
Site Quality ◽  
Diameter Growth ◽  
Trembling Aspen ◽  
Mixed Stands

The trembling aspen (Populus tremuloides Michx.) – white spruce (Picea glauca (Moench) Voss) mixed woods near Fort Nelson are distinguished by the large size of individual trees, longevity, and the low occurrence of internal decay in trembling aspen. The development of these forest ecosystems has had limited documentation and may be significantly different than those described in other portions of the boreal forest. At five study stands, stem analysis techniques were used to examine the patterns of height and radial growth over time according to species and structure type. There were two patterns of species establishment that were consistent with the stand structure. In codominant stands, recruitment periods for trembling aspen and white spruce overlapped. The stratified stands were consistently associated with a 29- to 58-year lag in white spruce recruitment. Spruce that were codominant with aspen at the time of sampling had sustained periods of rapid height and diameter growth. White spruce that were later to establish on site had slower rates of height and diameter growth. White spruce ages indicated that a dominant recruitment episode was more common than continuous recruitment. Height and diameter growth of trembling aspen were similar in both stand types. The differences in trembling aspen growth patterns between stands were due to site quality. The white spruce in codominant stands did not appear to go through a period of suppression and then release associated with stand-level trembling aspen mortality, as commonly described for other boreal mixedwoods. The vigor and longevity of trembling aspen in Fort Nelson appear to prolong the period of trembling aspen domination of mixed stands well beyond the time periods observed in other boreal ecosystems.

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