Influence of hemlock woolly adelgid infestation on the physiological and reflectance characteristics of eastern hemlock

Williams, Justin P.; Hanavan, Ryan P.; Rock, B. N.; Minocha, Subhash C.; Linder, Ernst

doi:10.1139/cjfr-2015-0328

Cited by 12 publications

(4 citation statements)

References 34 publications

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“…Leaf-level stress and gas exchange were also strongly related to light treatment, albeit counterintuitively, as assimilation rates generally decreased with increasing light and lower levels of infestation. This finding contrasts with other studies that have shown negative gas-exchange responses to HWA infestation and other sap-feeding insects (Zvereva et al, 2010;Gonda-King et al, 2014;Rubino et al 2015) but agrees with studies that have shown possible compensatory increases in photosystem function during the early stages of infestation (Williams et al 2016). In the current study, the negative relationship between light treatment and assimilation may have resulted from a variety of factors including damage to photosystem II from excessive visible light following freezing, lower N concentration in light-exposed leaves, or some combination of factors over the course of the study (Pearce 2001;Larcher 2003).…”

Section: Light Effects On Leaf Physiology and Plant Carbon Balancesupporting

confidence: 71%

Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings

Brantley

Mayfield

Jetton

et al. 2017

Forest Ecology and Management

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The rapid loss of eastern hemlock (Tsuga canadensis) due to infestation with hemlock woolly adelgid (Adelges tsugae, HWA) has greatly altered structure and function of eastern forests. Numerous control strategies including local pesticide use and biocontrol with predator beetles have been implemented with considerable cost and varying success. Silviculture treatments that increase incident light on surviving hemlock trees to reduce infestation and ameliorate carbon starvation have been proposed as another possible conservation strategy, yet no controlled studies have evaluated the coupled plant-insect responses to increased light. We conducted a nursery experiment on artificially infested eastern hemlock seedlings under varying levels of ambient light, ranging from 0-90% shade. We measured HWA infestation (ovisac density), short-and long-term indicators of carbon balance (leaf chlorophyll fluorescence, net photosynthesis, total nonstructural carbohydrate content, and shoot growth), and nutrition (leaf N content). We hypothesized that higher light would result in reduced HWA densities, higher C assimilation rates, and improved tissue non-structural carbohydrate balance; and these effects would ameliorate the effects of infestation on C balance and lead to improved seedling growth. HWA density decreased with increasing light, and was highest in the 90% shade treatments. However, photosystem II efficiency and net assimilation were also lower under the higher light treatment. Despite tradeoffs between reduced infestation and reduced leaf function from higher light, and little variation in sugar content among treatments, both leaf and root starch content and seedling growth were higher under the higher light treatment. Increasing light levels improves long-term carbon balance for hemlock seedlings in the presence of HWA. Although hemlock typically occurs in deeply shaded 3 forests, our results suggest that silvicultural treatments such as forest thinning that increase light exposure may reduce HWA abundance and lead to better tree C balance, and may be an effective component of large-scale conservation and restoration strategies.

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Section: Light Effects On Leaf Physiology and Plant Carbon Balancesupporting

confidence: 71%

Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings

Brantley

Mayfield

Jetton

et al. 2017

Forest Ecology and Management

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“…Furthermore, it would be meaningful to measure leaf traits in American beech trees that exhibit no symptoms of BLD to determine if there is a difference between asymptomatic leaves within an infected tree comparable within a tree that is void of disease. Many tree species demonstrate a compensatory response to defoliation via an upregulation of photosynthesis (Reich et al, 1993;Williams et al, 2016;McIntire et al, 2020), thus it's feasible that residual leaves within diseased American beech trees attempt to account for a net loss of carbohydrate. The compounding stress induced by multiple years of carbon limitation associated with BLD may become a consequential factor for inciting tree mortality, especially when coupled with other pests, diseases, and environmental elements.…”

Section: Discussionmentioning

confidence: 99%

Physiological impacts of beech leaf disease across a gradient of symptom severity among understory American beech

McIntire

2023

Front. For. Glob. Change

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Beech leaf disease (BLD) damage is associated with the parasitic nematode Litylenchus crenatae ssp. mccannii. Foliar symptoms manifest as darkened or chlorotic galls in the interveinal portions in the leaf, which become leathery and crinkled under high severity of infection. Though nearly a decade has passed since the discovery of this disease, little is known regarding the impact of BLD on leaf function and physiology. This study assesses the variation in leaf gas exchange and physiological leaf traits among asymptomatic and BLD-infected leaves across a gradient of symptom severity within a natural forested stand in central Connecticut, USA. Leaves with BLD symptoms are found to have significantly reduced carbon assimilation and instantaneous water use efficiency, with increased levels of stomatal conductance as symptom severity progresses. Leaf response to light manipulation is also affected, with an increase in dark respiration and the light compensation point among banded and crinkled leaves. Additionally, BLD symptoms are found to have a significant influence on leaf water content, specific leaf area, and leaf nitrogen content. Relationships between gas exchange and these leaf traits yield linear correlations that are used to infer functional relationships impacted by the disease.

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“…Similarly, image data with higher spectral resolution than Landsat's seven bands may have offered an opportunity to evaluate more spectrally distinct absorptive or reflective characteristics of BWA infestation. Once again, BWA-specific hyperspectral studies are limited [32,34], but studies of other insects have demonstrated promise, including the widespread and related hemlock woolly adelgid [90].…”

Section: Discussionmentioning

confidence: 99%

Using Remote Sensing and Climate Data to Map the Extent and Severity of Balsam Woolly Adelgid Infestation in Northern Utah, USA

Campbell

Williams

Berryman

2023

Forests

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Balsam woolly adelgid (Hemiptera: Adelges picea Ratzeburg; BWA) is a nonnative, invasive insect that has infested fir trees in the US for over a century, yet robust methods for mapping BWA have remained elusive. We compare three approaches to mapping BWA in the subalpine fir forests of northern Utah, the forefront of BWA spread in the western US: (1) using moderate-resolution, multispectral satellite imagery; (2) using terrain and climate data; and (3) using a combination of imagery, terrain, and climate data. While the spectral data successfully detected forest degradation, they failed to distinguish between causal agents of change (R2mean = 0.482; RMSEmean = 0.112). Terrain and climate data identified landscape conditions that promote BWA infestation but lacked the ability to characterize local-scale tree damage (R2mean = 0.746; RMSEmean = 0.078). By combining spectral, terrain, and climate data, we present a repeatable approach for accurately mapping infestation severity that captures both regional abiotic drivers and the local damage signals of BWA (R2mean = 0.836; RMSEmean = 0.065). Highly infested areas featured increased visible and shortwave infrared reflectance over time in the spectral data. The terrain bore little influence on severity, but climate variables indicated that warmer areas are more prone to severe infestation. This research study presents an analytical framework upon which future BWA monitoring efforts can be built.

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Influence of hemlock woolly adelgid infestation on the physiological and reflectance characteristics of eastern hemlock

Cited by 12 publications

References 34 publications

Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings

Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings

Physiological impacts of beech leaf disease across a gradient of symptom severity among understory American beech

Using Remote Sensing and Climate Data to Map the Extent and Severity of Balsam Woolly Adelgid Infestation in Northern Utah, USA

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