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

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250078
Author(s):  
Roger W. Ruess ◽  
Loretta M. Winton ◽  
Gerard C. Adams
Keyword(s):  
Populus Tremuloides ◽  
Fungal Pathogens ◽  
Stand Structure ◽  
The United States ◽  
Leaf Miner ◽  
Summer Drought ◽  
Trembling Aspen ◽  
Interior Alaska ◽  
Incidence And Mortality ◽  
Paper Birch

Over the past several decades, growth declines and mortality of trembling aspen throughout western Canada and the United States have been linked to drought, often interacting with outbreaks of insects and fungal pathogens, resulting in a “sudden aspen decline” throughout much of aspen’s range. In 2015, we noticed an aggressive fungal canker causing widespread mortality of aspen throughout interior Alaska and initiated a study to quantify potential drivers for the incidence, virulence, and distribution of the disease. Stand-level infection rates among 88 study sites distributed across 6 Alaska ecoregions ranged from <1 to 69%, with the proportion of trees with canker that were dead averaging 70% across all sites. The disease is most prevalent north of the Alaska Range within the Tanana Kuskokwim ecoregion. Modeling canker probability as a function of ecoregion, stand structure, landscape position, and climate revealed that smaller-diameter trees in older stands with greater aspen basal area have the highest canker incidence and mortality, while younger trees in younger stands appear virtually immune to the disease. Sites with higher summer vapor pressure deficits had significantly higher levels of canker infection and mortality. We believe the combined effects of this novel fungal canker pathogen, drought, and the persistent aspen leaf miner outbreak are triggering feedbacks between carbon starvation and hydraulic failure that are ultimately driving widespread mortality. Warmer early-season temperatures and prolonged late summer drought are leading to larger and more severe wildfires throughout interior Alaska that are favoring a shift from black spruce to forests dominated by Alaska paper birch and aspen. Widespread aspen mortality fostered by this rapidly spreading pathogen has significant implications for successional dynamics, ecosystem function, and feedbacks to disturbance regimes, particularly on sites too dry for Alaska paper birch.

Consequences of elevated carbon dioxide and ozone for foliar chemical composition and dynamics in trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera)

2001 ◽  
Vol 115 (3) ◽  
pp. 395-404 ◽  
Author(s):  
Richard L. Lindroth ◽  
Brian J. Kopper ◽  
William F.J. Parsons ◽  
James G. Bockheim ◽  
David F. Karnosky ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Chemical Composition ◽  
Populus Tremuloides ◽  
Elevated Carbon Dioxide ◽  
Betula Papyrifera ◽  
Trembling Aspen ◽  
Paper Birch

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

Trends in growing space efficiency of four boreal forest species based on yield table data

2010 ◽  
Vol 40 (11) ◽  
pp. 2215-2222 ◽  
Author(s):  
Victor G. Smith
Keyword(s):  
Populus Tremuloides ◽  
Pinus Banksiana ◽  
Black Spruce ◽  
Jack Pine ◽  
Dominant Mode ◽  
Trembling Aspen ◽  
Site Class ◽  
Space Efficiency ◽  
Paper Birch ◽  
Table Data

Yield tables are used to identify trends in growing space efficiency (GSE) and to relate GSE to self-tolerance and intraspecific competition. The method is useful when data specifically collected for this purpose are not available. Plonski’s normal yield tables for jack pine (Pinus banksiana Lamb.), paper birch (Betula papyrifera Marshall), trembling aspen (Populus tremuloides Michx.), and black spruce (Picea mariana (Mill.) B.S.P.) are used. An exponential volume–age function was partitioned into volume–area and area–age functions. The exponents of these two components form the B/D ratio, which is used to determine the mode of the stand at a given time, e.g., if B/D is <3/2, then the stand is in area occupation mode, and if B/D is >3/2, then the stand is in area exploitation mode. The dominant mode is the one most responsive to availability of growth resources, showing greater acceleration when resources are plentiful and more rapid deceleration when resources are scarce. Jack pine and paper birch are identified as area occupiers, whereas trembling aspen and black spruce are area exploiters and are therfore self-tolerant. Asymmetric competition was deemed to be present for paper birch throughout the life of the stand on site class I and for trembling aspen on all sites prior to senescence.

Adventitious rooting of four Salicaceae species in response to a flooding event

1988 ◽  
Vol 66 (12) ◽  
pp. 2597-2598 ◽  
Author(s):  
Marianne E. Krasny ◽  
John C. Zasada ◽  
Kristiina A. Vogt
Keyword(s):  
Populus Tremuloides ◽  
Adventitious Roots ◽  
Adventitious Rooting ◽  
Populus Balsamifera ◽  
Trembling Aspen ◽  
Balsam Poplar ◽  
Interior Alaska ◽  
Flooding Event ◽  
The Mean

The ability to form adventitious roots in response to a flooding event was examined in three floodplain species, sandbar willow (Salix interior Rowlee), feltleaf willow (Salix alaxensis (Anderss.) Cov.), and balsam poplar (Populus balsamifera L.), and one upland species, trembling aspen (Populus tremuloides Michx.), in interior Alaska. The mean number of adventitious roots formed per seedling was 7, 5, 2, and 0 for sandbar willow, feltleaf willow, balsam poplar, and trembling aspen, respectively. The ability to form adventitious roots was related to the distribution of the species on the floodplain.

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

Characteristics and densities of Williamson’s Sapsucker nest trees in British Columbia

2009 ◽  
Vol 39 (12) ◽  
pp. 2319-2331 ◽  
Author(s):  
L. W. Gyug ◽  
C. Steeger ◽  
I. Ohanjanian
Keyword(s):  
British Columbia ◽  
Endangered Species ◽  
Populus Tremuloides ◽  
Stand Structure ◽  
Tree Density ◽  
Trembling Aspen ◽  
Larix Occidentalis ◽  
Western Larch ◽  
Term Maintenance

We characterized Williamson’s Sapsucker ( Sphyrapicus thyroideus (Cassin, 1852)) nest trees in southern British Columbia from 1995 to 2008 to determine the nesting requirements of this endangered species in Canada. In the East Kootenay (n = 32) and the Okanagan (n = 157) regions where western larch ( Larix occidentalis Nutt.) occurred, 81% and 75% of the nest trees were western larch, respectively. In regions west of the Okanagan Valley where western larch did not occur (n = 73), 77% of the nest trees were trembling aspen ( Populus tremuloides Michx.). Conifer nest trees were larger (72 cm DBH), on average, than broad-leaved nest trees (35 cm DBH), and this pattern was consistent across the breeding range of Williamson’s Sapsucker. Live western larch >67 cm DBH with either broken or dead tops were the trees with the highest frequency (20%) among the trees estimated to be suitable for nesting, primarily because these larch tended to be infected with heart rots. Based on observed densities, targets should be 1.36 suitable nest trees/ha in managed stands, although in many instances such as aspen patches, this target will only be met in portions of the nesting territories. The recommended stand structure for long-term maintenance of high nest-tree density in western larch stands is for ≥20 trees/ha with DBHs >57 cm and 60–150 trees/ha with DBHs >22 cm.

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.

Variable extrafloral nectary expression and its consequences in quaking aspen

2007 ◽  
Vol 85 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Patricia Doak ◽  
Diane Wagner ◽  
Adam Watson
Keyword(s):  
Populus Tremuloides ◽  
Natural Variation ◽  
Leaf Miner ◽  
Quaking Aspen ◽  
Insect Community ◽  
Interior Alaska ◽  
Leaf Mining ◽  
Secretory Glands ◽  
The Relationship ◽  
Phyllocnistis Populiella

Extrafloral nectaries (EFNs) are secretory glands most commonly linked to defensive mutualisms. Both a plant’s need for defense and the strength of defense provided by mutualists will vary with plant condition and local insect community. Thus, the benefit of EFNs may vary spatially and temporally. However, little attention has been paid to natural variation in the presence and abundance of EFNs within and among individuals of the same species. Quaking aspen, Populus tremuloides Michx., bear EFNs on a subset of their leaves. Here, we describe patterns of EFN expression on shoots within ramets, among ramets, and among putative clones in interior Alaska. We also examine the relationship between EFN presence and herbivory by both the very abundant aspen leaf miner, Phyllocnistis populiella Chambers, and less common chewing herbivores. The proportion of leaves bearing EFNs varied from 33% to 87% among distinct aspen stands. Within stands, short (1–2 m height) ramets had higher EFN frequency than their taller (>4 m) neighbors. Patterns of herbivory also differed between short and tall ramets. Compared with leaves without EFNs, those with EFNs suffered less mining damage on short ramets but slightly higher damage on tall ramets. Tall ramets suffered more chewing damage than short ramets, but this damage was unrelated to the presence of EFNs. Our results suggest that variable EFN expression may be explained by variation in the benefits of EFNs. Leaves with EFNs on short ramets benefit through reduction in leaf mining, but this benefit does not extend to tall ramets or other forms of herbivory.

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