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.

scholarly journals The effect of an outbreak of the leaf miner Micrurapteryx salicifoliella on the performance of multiple Salix species in interior Alaska

Botany ◽  
2018 ◽  
Vol 96 (8) ◽  
pp. 491-497 ◽  
Author(s):  
Diane Wagner ◽  
Patricia Doak
Keyword(s):  
Stem Elongation ◽  
Leaf Tissue ◽  
Economic Importance ◽  
Leaf Miner ◽  
Leaf Water Content ◽  
Leaf Blotch ◽  
The Past ◽  
Interior Alaska ◽  
Leaf Mining ◽  
General Decline

The genus Salix L. tends to be tolerant of herbivory, but severe outbreaks of herbivorous insects may compromise growth. First documented in Alaska in 1991, the willow leaf blotch miner, Micrurapteryx salicifoliella, is now responsible for frequent and widespread foliar damage to Salix in interior Alaska. We experimentally tested the effect of leaf mining on the performance of four susceptible Salix species across two years of outbreak, and placed the results in the context of a broader survey of leaf mining damage. Across the four species, reduction of leaf mining damage increased average stem elongation, numbers of leaves per shoot, and leaf area. Leaf mining damage was negatively related to leaf water content; a consequence of the leaf miner’s habit of breaching the cuticle on the underside of leaves. Growth deficits due to leaf mining are likely caused by both the loss of leaf tissue to leaf miner feeding and subsequent leaf desiccation. The results are notable in the context of a general decline in productivity in interior Alaska over the past few decades and because the leaf miner impacts Salix species also used by vertebrate browsers of cultural and economic importance, such as moose.

scholarly journals Short-Term Responses of Aspen to Fire and Mechanical Treatments in Interior Alaska

2007 ◽  
Vol 24 (2) ◽  
pp. 153-157 ◽  
Author(s):  
Thomas F. Paragi ◽  
Dale A. Haggstrom
Keyword(s):  
Populus Tremuloides ◽  
Prescribed Burning ◽  
Sandy Loam ◽  
Fire Suppression ◽  
Fire Behavior ◽  
Wildlife Habitat ◽  
Quaking Aspen ◽  
Prescribed Burns ◽  
Loess Hills ◽  
Interior Alaska

Abstract Fire suppression and limited timber markets presently hinder maintenance of the early successional broad-leaved forest for wildlife habitat near settlements in interior Alaska. During 1999ߝ2003, we evaluated the efficacy of prescribed burning, felling, and shearblading (with and without debris removal) to regenerate quaking aspen (Populus tremuloides). Treatments were conducted largely during the dormant period for aspen: prescribed burns in mid-May and mechanical treatments in late August through early April. Prescribed burns on loess hills produced 40,900ߝ233,000 stems/ha by the second growing season. Low relative humidity, slope of more than 10°, southerly aspect, and juxtaposition to open areas produced fire behavior adequate to ensure top killing and vigorous sprouting response. Felling by chainsaw on loess hills produced 34,800ߝ89,800 stems/ha, whereas dozer shearblading on glacial outwash (loam over gravel) produced 74,200ߝ209,200 stems/ha (cleared portions and windrows combined) and a sandy loam floodplain produced 31,400ߝ64,800 stems/ha. Pushing debris into windrows or scraping thick moss allowed warmer soils and produced greater sprouting on cleared sites relative to sections where debris or moss remained. Mechanical treatments were 25ߝ75% of current prescribed fire costs, but debris accumulation may hinder access by browsing species and attract terrestrial predators of gallinaceous birds.

Long-term impact of a leaf miner outbreak on the performance of quaking aspen

2013 ◽  
Vol 43 (6) ◽  
pp. 563-569 ◽  
Author(s):  
Diane Wagner ◽  
Patricia Doak
Keyword(s):  
Boreal Forests ◽  
Size Control ◽  
Leaf Damage ◽  
Plant Performance ◽  
Leaf Miner ◽  
Quaking Aspen ◽  
Negative Effects ◽  
Insecticide Treatment ◽  
Leaf Mining ◽  
Long Term Impact

The aspen leaf miner, Phyllocnistis populiella Cham., has caused widespread and severe damage to aspen in the boreal forests of western North America for over a decade. We suppressed P. populiella on individual small aspen ramets using insecticide at two sites near Fairbanks, Alaska, annually for 7 years and compared plant performance with controls. Insecticide treatment successfully reduced leaf damage by P. populiella during most years and had little effect on herbivory by externally feeding invertebrates. By the end of the study, control ramets had suffered a reduction in height and girth relative to treated ramets and to the original, pretreatment size. Control ramets produced smaller leaves during some years and, after 7 years, produced fewer total shoots and leaves than ramets sprayed with insecticide. Treatment did not affect mortality, but at the warmer of the two sites, ramets sustaining ambient levels of leaf mining were significantly more likely to die back to basal sprouts than those treated with insecticide. We conclude that a decade of P. populiella outbreak has caused strongly negative effects on aspen development and the production of aboveground tissues.

Bionomics of the Aspen Leaf Miner, Phyllocnistis populiella Cham. (Lepidoptera: Gracillariidae)

1964 ◽  
Vol 96 (6) ◽  
pp. 857-874 ◽  
Author(s):  
S. F. Condrashoff
Keyword(s):  
Populus Tremuloides ◽  
Leaf Surface ◽  
Climatic Factors ◽  
Population Decline ◽  
Instar Larva ◽  
Leaf Miner ◽  
Permanent Sample Plots ◽  
The Individual ◽  
New Generation ◽  
Phyllocnistis Populiella

AbstractThe aspen leaf miner, Phyllocnistis populiella Cham., has recently become common and very abundant in western North America, and has been authoritatively identified only from trembling aspen, Populus tremuloides Michx. Overwintered adults lay eggs on young aspen leaves in spring, and new-generation moths emerge in about two months. Only the single epidermal cell layer is mined on the upper or lower leaf surface, most of the feeding being done by the third-instar larva in about a week. Heavy attack results in defoliation by mid-summer. Activities of breeding populations are affected by temperature (50-55°F. is optimal for copulation, 54-56°F. for feeding, and 52-58°F. for oviposirion) and developmental stage of aspen leaves. Eggs are laid singly near the apex of the leaf and tend to be evenly spaced. Distribution of eggs between leaves tends to be uniform in a particular level of the tree, although more eggs are laid in the lower crown. A female moth can develop more than 40 eggs, but only about 7 are usually laid because of limited opportunities. Mortality in the larval and pupal stages is often high; population decline usually follows mortalities above 70%. Parasitism sometimes plays an important role, but the independence of population changes between broad geographic areas suggests that numbers of P. populiella may be strongly influenced by climatic factors. Population trends and damage can be assessed conveniently for large geographic areas and for specific sites by continuing studies in permanent sample plots. Expected damage may be predicted from estimates of new-generation adult populations. Because inter-tree variation exceeds intra-tree variation, more trees and fewer branches per tree should be taken to increase sampling efficiency. Also, greater precision is attained by the use of the individual leaf surface rather than the leaf as a basic sample unit.

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.

scholarly journals Assessing Wildfire Burn Severity and Its Relationship with Environmental Factors: A Case Study in Interior Alaska Boreal Forest

2021 ◽  
Vol 13 (10) ◽  
pp. 1966
Author(s):  
Christopher W Smith ◽  
Santosh K Panda ◽  
Uma S Bhatt ◽  
Franz J Meyer ◽  
Anushree Badola ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Ground Truth ◽  
Burn Severity ◽  
Classification Methods ◽  
Spectral Indices ◽  
Ground Truth Data ◽  
Burn Scar ◽  
Interior Alaska ◽  
Remote Sensing Methods ◽  
The Relationship

In recent years, there have been rapid improvements in both remote sensing methods and satellite image availability that have the potential to massively improve burn severity assessments of the Alaskan boreal forest. In this study, we utilized recent pre- and post-fire Sentinel-2 satellite imagery of the 2019 Nugget Creek and Shovel Creek burn scars located in Interior Alaska to both assess burn severity across the burn scars and test the effectiveness of several remote sensing methods for generating accurate map products: Normalized Difference Vegetation Index (NDVI), Normalized Burn Ratio (NBR), and Random Forest (RF) and Support Vector Machine (SVM) supervised classification. We used 52 Composite Burn Index (CBI) plots from the Shovel Creek burn scar and 28 from the Nugget Creek burn scar for training classifiers and product validation. For the Shovel Creek burn scar, the RF and SVM machine learning (ML) classification methods outperformed the traditional spectral indices that use linear regression to separate burn severity classes (RF and SVM accuracy, 83.33%, versus NBR accuracy, 73.08%). However, for the Nugget Creek burn scar, the NDVI product (accuracy: 96%) outperformed the other indices and ML classifiers. In this study, we demonstrated that when sufficient ground truth data is available, the ML classifiers can be very effective for reliable mapping of burn severity in the Alaskan boreal forest. Since the performance of ML classifiers are dependent on the quantity of ground truth data, when sufficient ground truth data is available, the ML classification methods would be better at assessing burn severity, whereas with limited ground truth data the traditional spectral indices would be better suited. We also looked at the relationship between burn severity, fuel type, and topography (aspect and slope) and found that the relationship is site-dependent.

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