Correction: Widespread mortality of trembling aspen (Populus tremuloides) throughout interior Alaskan boreal forests resulting from a novel canker disease

Canopy gaps play an important role in forest vegetation dynamics when fire return intervals are long. However, there is little known about the role of gaps in the development of forest stands that initially dominate following stand-replacing disturbance. We investigated gap disturbance during the breakup of trembling aspen (Populus tremuloides Michx.) stands at two scales: at the stand level we quantified gap fraction and gap size as stand development proceeds; at the gap level we determined causes of gap-maker mortality and evaluated resulting gap-maker structure and decay as stand development proceeds. We also evaluated the impact that gaps have on stand transition by quantifying the abundance and growth of juvenile trees in gaps of different sizes and ages. Ten stands between 60 and 120 years since fire in northeastern Ontario were sampled using line intersect transects. Gap fraction doubled (∼18%36%) and mean gap size was more than four times greater (∼45200 m2) over the time period. Standing dead gap makers in early states of decay were most frequent in young stands, whereas snapped gap makers in various states of decay were most frequent in old stands. Infection by fungal pathogens was the most frequent cause of mortality (56%) and was not related to time since fire. Balsam fir (Abies balsamea (L.) Mill.) was the most abundant juvenile recruit. However, transition probabilities for tree species were independent of gap type. These results indicate that gap creation is frequent during early stages of stand development in boreal forests; however, it is unlikely that successional trajectory is affected by their formation.

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Role of Mixed-Species Stands in Attenuating the Vulnerability of Boreal Forests to Climate Change and Insect Epidemics

Frontiers in Plant Science ◽

10.3389/fpls.2021.658880 ◽

2021 ◽

Vol 12 ◽

Author(s):

Raphaël D. Chavardès ◽

Fabio Gennaretti ◽

Pierre Grondin ◽

Xavier Cavard ◽

Hubert Morin ◽

...

Keyword(s):

Climate Change ◽

Populus Tremuloides ◽

Tree Growth ◽

Host Species ◽

Boreal Forests ◽

Linear Models ◽

Black Spruce ◽

Trembling Aspen ◽

Mixed Stands ◽

Species Mixture

We investigated whether stand species mixture can attenuate the vulnerability of eastern Canada’s boreal forests to climate change and insect epidemics. For this, we focused on two dominant boreal species, black spruce [Picea mariana (Mill.) BSP] and trembling aspen (Populus tremuloides Michx.), in stands dominated by black spruce or trembling aspen (“pure stands”), and mixed stands (M) composed of both species within a 36 km2 study area in the Nord-du-Québec region. For each species in each stand composition type, we tested climate-growth relations and assessed the impacts on growth by recorded insect epidemics of a black spruce defoliator, the spruce budworm (SBW) [Choristoneura fumiferana (Clem.)], and a trembling aspen defoliator, the forest tent caterpillar (FTC; Malacosoma disstria Hübn.). We implemented linear models in a Bayesian framework to explain baseline and long-term trends in tree growth for each species according to stand composition type and to differentiate the influences of climate and insect epidemics on tree growth. Overall, we found climate vulnerability was lower for black spruce in mixed stands than in pure stands, while trembling aspen was less sensitive to climate than spruce, and aspen did not present differences in responses based on stand mixture. We did not find any reduction of vulnerability for mixed stands to insect epidemics in the host species, but the non-host species in mixed stands could respond positively to epidemics affecting the host species, thus contributing to stabilize ecosystem-scale growth over time. Our findings partially support boreal forest management strategies including stand species mixture to foster forests that are resilient to climate change and insect epidemics.

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Investigating competitive interactions from spatial patterns of trees in multispecies boreal forests: the random mortality hypothesis revisited

Canadian Journal of Botany ◽

10.1139/b01-141 ◽

2002 ◽

Vol 80 (1) ◽

pp. 93-100 ◽

Cited By ~ 9

Author(s):

L R Little

Keyword(s):

Boreal Forest ◽

Spatial Patterns ◽

Populus Tremuloides ◽

Boreal Forests ◽

Pinus Banksiana ◽

Plant Competition ◽

Forest Tree ◽

Jack Pine ◽

Competitive Interactions ◽

Trembling Aspen

Plant competition is expected to produce an overdispersed spatial pattern relative to the initial pattern of individuals. The spatial patterns of two boreal forest tree species, Populus tremuloides Michx. (trembling aspen) and Pinus banksiana Lamb. (jack pine), were examined for evidence of intraspecific and interspecific competition. Data consisting of species, position, and age of tree stems were obtained from a 21-year-old, 40 m × 30 m postfire area of boreal forest in northern Alberta, Canada. Tree stems were mapped and classified according to size (greater or less than 5 cm in diameter at ground height) and species. A variation on the random mortality hypothesis was used to detect overdispersed patterns indicative of competitive interactions. This was done by comparing the size of neighbouring stems with those expected when the size or "success" of a stem occurred randomly. The results showed roughly two scales of pattern. First, large seed-regenerating jack pine neighboured each other more often than expected, but jack pine and trembling aspen neighboured each other less than expected. Second, although the large jack pine appeared to be clustered as neighbours, they tended to associate at distances farther than expected. These results show little evidence of density-dependence patterns in the species at the site, and the interspecific association between jack pine and trembling aspen could be indicative of a heterogeneous habitat.Key words: triangulation, size variability, Pinus banksiana, Populus tremuloides, jack pine, trembling aspen.

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Soil organic layer thickness influences the establishment and growth of trembling aspen (Populus tremuloides) in boreal forests

Forest Ecology and Management ◽

10.1016/j.foreco.2015.03.031 ◽

2015 ◽

Vol 347 ◽

pp. 209-216 ◽

Cited By ~ 17

Author(s):

Benoit Lafleur ◽

Allison Cazal ◽

Alain Leduc ◽

Yves Bergeron

Keyword(s):

Layer Thickness ◽

Populus Tremuloides ◽

Boreal Forests ◽

Organic Layer ◽

Trembling Aspen ◽

Soil Organic Layer

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Impacts of climate and insect herbivory on productivity and physiology of trembling aspen (Populus tremuloides) in Alaskan boreal forests

Environmental Research Letters ◽

10.1088/1748-9326/ab215f ◽

2019 ◽

Vol 14 (8) ◽

pp. 085010 ◽

Cited By ~ 8

Author(s):

Melissa A Boyd ◽

Logan T Berner ◽

Patricia Doak ◽

Scott J Goetz ◽

Brendan M Rogers ◽

...

Keyword(s):

Populus Tremuloides ◽

Boreal Forests ◽

Insect Herbivory ◽

Trembling Aspen

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Ethylene enhances root water transport and aquaporin expression in trembling aspen (Populus tremuloides) exposed to root hypoxia

BMC Plant Biology ◽

10.1186/s12870-021-02995-7 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Xiangfeng Tan ◽

Mengmeng Liu ◽

Ning Du ◽

Janusz J. Zwiazek

Keyword(s):

Gas Exchange ◽

Water Transport ◽

Populus Tremuloides ◽

Leaf Gas Exchange ◽

Hydraulic Conductance ◽

Root Hydraulic Conductance ◽

Trembling Aspen ◽

Expression Levels ◽

Root Hypoxia ◽

Exogenous Ethylene

Abstract Background Root hypoxia has detrimental effects on physiological processes and growth in most plants. The effects of hypoxia can be partly alleviated by ethylene. However, the tolerance mechanisms contributing to the ethylene-mediated hypoxia tolerance in plants remain poorly understood. Results In this study, we examined the effects of root hypoxia and exogenous ethylene treatments on leaf gas exchange, root hydraulic conductance, and the expression levels of several aquaporins of the plasma membrane intrinsic protein group (PIP) in trembling aspen (Populus tremuloides) seedlings. Ethylene enhanced net photosynthetic rates, transpiration rates, and root hydraulic conductance in hypoxic plants. Of the two subgroups of PIPs (PIP1 and PIP2), the protein abundance of PIP2s and the transcript abundance of PIP2;4 and PIP2;5 were higher in ethylene-treated trembling aspen roots compared with non-treated roots under hypoxia. The increases in the expression levels of these aquaporins could potentially facilitate root water transport. The enhanced root water transport by ethylene was likely responsible for the increase in leaf gas exchange of the hypoxic plants. Conclusions Exogenous ethylene enhanced root water transport and the expression levels of PIP2;4 and PIP2;5 in hypoxic roots of trembling aspen. The results suggest that ethylene facilitates the aquaporin-mediated water transport in plants exposed to root hypoxia.

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The bacteria in sapwood, wetwood, and heartwood of trembling aspen (Populus tremuloides)

Canadian Journal of Botany ◽

10.1139/b73-060 ◽

1973 ◽

Vol 51 (2) ◽

pp. 498-500 ◽

Cited By ~ 15

Author(s):

Donald M. Knutson

Keyword(s):

Populus Tremuloides ◽

Trembling Aspen ◽

Indigenous Bacteria ◽

Large Populations ◽

Xylem Tissue

Bacteria (Erwinia, Bacillus) were consistently isolated from all samples of aspen sapwood and heartwood. In wetwood zones (water-soaked xylem tissue) or discolored heartwood, large populations often occur. No organisms unique to wetwood were isolated. Wetwood probably is formed by nonmicrobial means and, once formed, merely supports large populations of indigenous bacteria.

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Wounding of aspen roots promotes suckering

Canadian Journal of Botany ◽

10.1139/b04-009 ◽

2004 ◽

Vol 82 (3) ◽

pp. 310-315 ◽

Cited By ~ 25

Author(s):

Erin C Fraser ◽

Victor J Lieffers ◽

Simon M Landhäusser

Keyword(s):

Populus Tremuloides ◽

Growth Rates ◽

Growing Season ◽

Organic Layer ◽

Trembling Aspen ◽

Layer Depth ◽

Injury Type ◽

Organic Layers ◽

Root Injury ◽

Root Sucker

In early May, 1-m sections of trembling aspen (Populus tremuloides Michx.) roots in a forest cutblock were carefully exposed and examined for damage. Undamaged roots were subjected to one of three wounding treatments (scrape, sever, or uninjured control) and were then reburied to either the full normal organic layer depth or to one third of the normal depth. Following one growing season, the roots were reexposed and assessed for aspen sucker numbers and growth rates. Results indicate that injured roots produced suckers nearly twice as often as uninjured roots. Further, injured roots produced more suckers per root, and these suckers were taller and had greater leaf area. Roots buried under shallow organic layers also generated more suckers, regardless of injury type. The side of injury (distal or proximal) did not affect any of the measured variables. The present study suggests that moderate wounding of aspen roots increases initial sucker numbers and growth rates.Key words: trembling aspen, root sucker, root injury, regeneration.

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THE BEHAVIOUR OF FIVE WOOD SPECIES IN COMPRESSION

IAWA Journal ◽

10.1163/22941932-90000298 ◽

2002 ◽

Vol 23 (2) ◽

pp. 201-211 ◽

Cited By ~ 11

Author(s):

Simon Ellis ◽

Paul Steiner

Keyword(s):

Young’S Modulus ◽

Populus Tremuloides ◽

Wood Species ◽

Young's Modulus ◽

Douglas Fir ◽

Thuja Plicata ◽

Trembling Aspen ◽

Moisture Contents ◽

Red Cedar ◽

Western Red Cedar

Five wood species, Oregon ash (Fraxinus latifolia Benth.), Balau (Shorea spp.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Western red cedar (Thuja plicata Donn ex D. Don), and Trembling aspen (Populus tremuloides Michx.) were loaded in compression longitudinally, radially and tangentially. The wood cubes were conditioned to one of four moisture contents prior to loading. Small cubes were loaded until no void space remained after which samples were released and soaked in water. Stress /strain curves were recorded over the whole range of strain and cube thicknesses were recorded at the end of the compression, after release from the testing apparatus, and after soaking in water. Denser woods resulted in a greater Young’s modulus, higher levels of stress and shorter time to densification than did less dense woods. Higher initial moisture contents apparently increased the plasticity of the wood leading to a lower Young’s modulus and lower levels of stress during compression, greater springback after release of stress and greater recovery after swelling in water. Differences observed in the radial and tangential behaviours were believed to be due to the supporting action of the rays when the wood was compressed in the radial direction in balau and trembling aspen and to the relative difference between the lower density earlywood and higher density latewood regions in ash, Douglas-fir and western red cedar.

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Evaluating the Performance of a Forest Succession Model to Predict the Long-Term Dynamics of Tree Species in Mixed Boreal Forests Using Historical Data in Northern Ontario, Canada

Forests ◽

10.3390/f12091181 ◽

2021 ◽

Vol 12 (9) ◽

pp. 1181

Author(s):

Guy R. Larocque ◽

F. Wayne Bell

Keyword(s):

Populus Tremuloides ◽

Boreal Forests ◽

Forest Ecosystems ◽

Forest Succession ◽

Regional Scale ◽

Abies Balsamea ◽

Forest Growth ◽

Northern Ontario ◽

Phase Dynamics

Environmental concerns and economic pressures on forest ecosystems have led to the development of sustainable forest management practices. As a consequence, forest managers must evaluate the long-term effects of their management decisions on potential forest successional pathways. As changes in forest ecosystems occur very slowly, simulation models are logical and efficient tools to predict the patterns of forest growth and succession. However, as models are an imperfect representation of reality, it is desirable to evaluate them with historical long-term forest data. Using remeasured tree and stand data from three data sets from two ecoregions in northern Ontario, the succession gap model ZELIG-CFS was evaluated for mixed boreal forests composed of black spruce (Picea mariana [Mill.] B.S.P.), balsam fir (Abies balsamea [L.] Mill.), jack pine (Pinus banksiana L.), white spruce (Picea glauca [Moench] Voss), trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), northern white cedar (Thuja occidentalis L.), American larch (Larix laricina [Du Roi] K. Koch), and balsam poplar (Populus balsamefera L.). The comparison of observed and predicted basal areas and stand densities indicated that ZELIG-CFS predicted the dynamics of most species consistently for periods varying between 5 and 57 simulation years. The patterns of forest succession observed in this study support gap phase dynamics at the plot scale and shade-tolerance complementarity hypotheses at the regional scale.

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