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14 pages, 2220 KiB

Open AccessFeature PaperArticle

Forest Regeneration Following Emerald Ash Borer (Agrilus planipennis Fairemaire) Enhances Mesophication in Eastern Hardwood Forests

by Benjamin Dolan and Jason Kilgore

Forests 2018, 9(6), 353; https://doi.org/10.3390/f9060353 - 14 Jun 2018

Cited by 11 | Viewed by 5534

Abstract

Emerald ash borer (EAB, Agrilus planipennis Fairemaire) is a phloem-feeding beetle that was introduced into North America in the late 20th century and is causing widespread mortality of native ash (Fraxinus) species. The loss of an entire genus from the forest [...] Read more.

Emerald ash borer (EAB, Agrilus planipennis Fairemaire) is a phloem-feeding beetle that was introduced into North America in the late 20th century and is causing widespread mortality of native ash (Fraxinus) species. The loss of an entire genus from the forest flora is a substantial disturbance, but effects vary because of differences in Fraxinus dominance and remaining vegetation. At three sites near the center of the North American EAB range, we investigated the impacts of Fraxinus mortality on recruitment of woody and non-native vegetation in 14 permanent plots from 2012 to 2017. We used the change in relative Fraxinus basal area to determine the impact of EAB on density of woody species and non-native vegetation less than 2.5 cm diameter at breast height (dbh). Changes in canopy cover were not correlated with loss of Fraxinus from the overstory, and only the density of shade-tolerant shrubs and saplings increased with Fraxinus mortality. Both native and non-native shrub species increased in density at sites where they were present before EAB, but no new invasions were detected following Fraxinus mortality. These shifts in understory vegetation indicate that Fraxinus mortality enhances the rate of succession to shade-tolerant species. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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14 pages, 1033 KiB

Open AccessArticle

Modest Effects of Host on the Cold Hardiness of Emerald Ash Borer ^†

by Lindsey D. E. Christianson and Robert C. Venette

Forests 2018, 9(6), 346; https://doi.org/10.3390/f9060346 - 12 Jun 2018

Cited by 13 | Viewed by 3756

Abstract

The emerald ash borer, Agrilus planipennis Fairmaire, is invading North America and Europe but has not yet reached its ultimate distribution. Geographic differences in host availability and winter temperatures might affect where this species will occur. In central North America, black ash ( [...] Read more.

The emerald ash borer, Agrilus planipennis Fairmaire, is invading North America and Europe but has not yet reached its ultimate distribution. Geographic differences in host availability and winter temperatures might affect where this species will occur. In central North America, black ash (Fraxinus nigra) is more abundant than green ash (F. pennsylvanica) at northern latitudes, but much of our current understanding of A. planipennis cold tolerance is based on observations of overwintering larvae from green ash. The effects of black and green ash on the cold hardiness of A. planipennis larvae were measured over three winters. Supercooling point, the temperature at which insect bodily fluids spontaneously begin to freeze, was marginally greater for larvae from artificially-infested black ash than green ash in one trial, but not in three others. Host species also did not consistently affect mortality rates after larval exposure to subzero temperatures, but larvae from black ash were less cold hardy than larvae from green ash when there were differences. Comparisons of mortality rates among chilled (unfrozen) and frozen larvae indicated that overwintering A. planipennis larvae are primarily freeze avoidant, and this cold tolerance strategy is unaffected by host. All of our studies suggest that A. planipennis larvae from black ash are not more cold hardy that larvae from green ash. Where temperatures annually decline below ~−30 °C, overwintering morality may substantially affect the population dynamics and future impacts from this invasive alien species. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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17 pages, 2281 KiB

Open AccessFeature PaperArticle

Response of Black Ash Wetland Gaseous Soil Carbon Fluxes to a Simulated Emerald Ash Borer Infestation

by Matthew Van Grinsven, Joseph Shannon, Nicholas Bolton, Joshua Davis, Nam Jin Noh, Joseph Wagenbrenner, Randall Kolka and Thomas Pypker

Forests 2018, 9(6), 324; https://doi.org/10.3390/f9060324 - 4 Jun 2018

Cited by 10 | Viewed by 3893

Abstract

The rapid and extensive expansion of emerald ash borer (EAB) in North America since 2002 may eliminate most existing ash stands, likely affecting critical ecosystem services associated with water and carbon cycling. To our knowledge, no studies have evaluated the coupled response of [...] Read more.

The rapid and extensive expansion of emerald ash borer (EAB) in North America since 2002 may eliminate most existing ash stands, likely affecting critical ecosystem services associated with water and carbon cycling. To our knowledge, no studies have evaluated the coupled response of black ash (Fraxinus nigra Marsh.) wetland water tables, soil temperatures, and soil gas fluxes to an EAB infestation. Water table position, soil temperature, and soil CO₂ and CH₄ fluxes were monitored in nine depressional headwater black ash wetlands in northern Michigan. An EAB disturbance was simulated by girdling (girdle) or felling (ash-cut) all black ash trees with diameters greater than 2.5 cm within treated wetlands (n = 3 per treatment). Soil gas fluxes were sensitive to water table position, temperature, and disturbance. Soil CO₂ fluxes were significantly higher, and high soil CH₄ fluxes occurred more frequently in disturbed sites. Soil CH₄ fluxes in ash-cut were marginally significantly higher than girdle during post-treatment, yet both were similar to control sites. The strong connection between depressional black ash wetland study sites and groundwater likely buffered the magnitude of disturbance-related impact on water tables and carbon cycling. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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17 pages, 1694 KiB

Open AccessFeature PaperArticle

Biotic and Abiotic Drivers of Sap Flux in Mature Green Ash Trees (Fraxinus pennsylvanica) Experiencing Varying Levels of Emerald Ash Borer (Agrilus planipennis) Infestation

by Charles E. Flower, Douglas J. Lynch, Kathleen S. Knight and Miquel A. Gonzalez-Meler

Forests 2018, 9(6), 301; https://doi.org/10.3390/f9060301 - 28 May 2018

Cited by 12 | Viewed by 4575

Abstract

While the relationship between abiotic drivers of sap flux are well established, the role of biotic disturbances on sap flux remain understudied. The invasion of the emerald ash borer (Agrilus planipennis Fairmaire, EAB) into North America in the 1990s represents a significant [...] Read more.

While the relationship between abiotic drivers of sap flux are well established, the role of biotic disturbances on sap flux remain understudied. The invasion of the emerald ash borer (Agrilus planipennis Fairmaire, EAB) into North America in the 1990s represents a significant threat to ash trees (Fraxinus spp.), which are a substantial component of temperate forests. Serpentine feeding galleries excavated by EAB larvae in the cambial and phloem tissue are linked to rapid tree mortality. To assess how varying levels of EAB infestation impact the plant water status and stress levels of mature green ash (Fraxinus pennsylvanica Marshall) trees, we combined tree-level sap flux measurements with leaf-level gas exchange, isotopes, morphology and labile carbohydrate measurements. Results show sap flux and whole tree water use are reduced by as much as 80% as EAB damage increases. Heavily EAB impacted trees exhibited reduced leaf area and leaf mass, but maintained constant levels of specific leaf area relative to lightly EAB-impacted trees. Altered foliar gas exchange (reduced light saturated assimilation, internal CO₂ concentrations) paired with depleted foliar δ¹³C values of heavily EAB impacted trees point to chronic water stress at the canopy level, indicative of xylem damage. Reduced photosynthetic rates in trees more impacted by EAB likely contributed to the lack of nonstructural carbohydrate (soluble sugars and starch) accumulation in leaf tissue, further supporting the notion that EAB damages not only phloem, but xylem tissue as well, resulting in reduced water availability. These findings can be incorporated into modeling efforts to untangle post disturbance shifts in ecosystem hydrology. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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16 pages, 1449 KiB

Open AccessArticle

Potential Impacts of Emerald Ash Borer Biocontrol on Ash Health and Recovery in Southern Michigan

by Daniel M. Kashian, Leah S. Bauer, Benjamin A. Spei, Jian J. Duan and Juli R. Gould

Forests 2018, 9(6), 296; https://doi.org/10.3390/f9060296 - 25 May 2018

Cited by 16 | Viewed by 4024

Abstract

Emerald ash borer (EAB) is an invasive beetle that kills native North American ash species, threatening their persistence. A classical biological control program for EAB was initiated in 2007 with the release of three specialized EAB parasitoids. Monitoring changes in the health and [...] Read more.

Emerald ash borer (EAB) is an invasive beetle that kills native North American ash species, threatening their persistence. A classical biological control program for EAB was initiated in 2007 with the release of three specialized EAB parasitoids. Monitoring changes in the health and regeneration of ash where EAB biocontrol agents have been released is critical for assessing the success of EAB biocontrol and predicting future changes to the ash component of North American forests. We sampled release and control plots across southern Michigan over a three-year period to measure ash health and recruitment to begin assessing the long-term impact of EAB biological control on ash populations. We noted a reduced mortality of larger trees between 2012 and 2015 in release plots compared to control plots and increases in ash diameter, but our results were otherwise inconsistent. Ash regeneration was generally higher in release plots compared to control plots but highly variable among sites, suggesting some protection of ash saplings from EAB by parasitoids. We conclude that EAB biocontrol is likely to have a positive effect on ash populations, but that the study duration was not long enough to definitively deduce the long-term success of the biocontrol program in this region. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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17 pages, 3829 KiB

Open AccessArticle

Optimizing Conservation Strategies for a Threatened Tree Species: In Situ Conservation of White Ash (Fraxinus americana L.) Genetic Diversity through Insecticide Treatment

by Charles E. Flower, Jeremie B. Fant, Sean Hoban, Kathleen S. Knight, Laura Steger, Elijah Aubihl, Miquel A. Gonzalez-Meler, Stephen Forry, Andrea Hille and Alejandro A. Royo

Forests 2018, 9(4), 202; https://doi.org/10.3390/f9040202 - 13 Apr 2018

Cited by 25 | Viewed by 6134

Abstract

Forest resources face numerous threats that require costly management. Hence, there is an increasing need for data-informed strategies to guide conservation practices. The introduction of the emerald ash borer to North America has caused rapid declines in ash populations (Fraxinus spp. L.). [...] Read more.

Forest resources face numerous threats that require costly management. Hence, there is an increasing need for data-informed strategies to guide conservation practices. The introduction of the emerald ash borer to North America has caused rapid declines in ash populations (Fraxinus spp. L.). Natural resource managers are faced with a choice of either allowing ash trees to die, risking forest degradation and reduced functional resilience, or investing in conserving trees to preserve ecosystem structure and standing genetic diversity. The information needed to guide these decisions is not always readily available. Therefore, to address this concern, we used eight microsatellites to genotype 352 white ash trees (Fraxinus americana L.) across 17 populations in the Allegheny National Forest; a subset of individuals sampled are part of an insecticide treatment regimen. Genetic diversity (number of alleles and He) was equivalent in treated and untreated trees, with little evidence of differentiation or inbreeding, suggesting current insecticidal treatment is conserving local, neutral genetic diversity. Using simulations, we demonstrated that best practice is treating more populations rather than more trees in fewer populations. Furthermore, through genetic screening, conservation practitioners can select highly diverse and unique populations to maximize diversity and reduce expenditures (by up to 21%). These findings will help practitioners develop cost-effective strategies to conserve genetic diversity. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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14 pages, 7400 KiB

Open AccessArticle

Downed Coarse Woody Debris Dynamics in Ash (Fraxinus spp.) Stands Invaded by Emerald Ash Borer (Agrilus planipennis Fairmaire)

by Kayla I. Perry, Daniel A. Herms, Wendy S. Klooster, Annemarie Smith, Diane M. Hartzler, David R. Coyle and Kamal J. K. Gandhi

Forests 2018, 9(4), 191; https://doi.org/10.3390/f9040191 - 7 Apr 2018

Cited by 14 | Viewed by 4272

Abstract

Emerald ash borer (EAB; Agrilus planipennis Fairmaire) has had major ecological impacts in forests of eastern North America. In 2008 and 2012, we characterized dynamics of downed coarse woody debris (DCWD) in southeastern Michigan, USA near the epicenter of the invasion, where the [...] Read more.

Emerald ash borer (EAB; Agrilus planipennis Fairmaire) has had major ecological impacts in forests of eastern North America. In 2008 and 2012, we characterized dynamics of downed coarse woody debris (DCWD) in southeastern Michigan, USA near the epicenter of the invasion, where the mortality of white (Fraxinus americana L.), green (F. pennsylvanica Marshall), and black (F. nigra Marshall) ash exceeded 99% by 2009. Percentage of fallen dead ash trees and volume of ash DCWD on the forest floor increased by 76% and 53%, respectively, from 2008 to 2012. Ash and non-ash fell non-randomly to the east and southeast, conforming to prevailing winds. More ash fell by snapping along the bole than by uprooting. By 2012, however, only 31% of ash snags had fallen, indicating that DCWD will increase substantially, especially if it accelerates from the rate of 3.5% per year documented during the study period. Decay of ash DCWD increased over time, with most categorized as minimally decayed (decay classes 1 and 2) in 2008 and more decayed (decay classes 2 and 3) in 2012. As the range of EAB expands, similar patterns of DCWD dynamics are expected in response to extensive ash mortality. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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16 pages, 19835 KiB

Open AccessArticle

Evidence of Ash Tree (Fraxinus spp.) Specific Associations with Soil Bacterial Community Structure and Functional Capacity

by Michael P. Ricketts, Charles E. Flower, Kathleen S. Knight and Miquel A. Gonzalez-Meler

Forests 2018, 9(4), 187; https://doi.org/10.3390/f9040187 - 5 Apr 2018

Cited by 12 | Viewed by 5719

Abstract

The spread of the invasive emerald ash borer (EAB) across North America has had enormous impacts on temperate forest ecosystems. The selective removal of ash trees (Fraxinus spp.) has resulted in abnormally large inputs of coarse woody debris and altered forest tree [...] Read more.

The spread of the invasive emerald ash borer (EAB) across North America has had enormous impacts on temperate forest ecosystems. The selective removal of ash trees (Fraxinus spp.) has resulted in abnormally large inputs of coarse woody debris and altered forest tree community composition, ultimately affecting a variety of ecosystem processes. The goal of this study was to determine if the presence of ash trees influences soil bacterial communities and/or functions to better understand the impacts of EAB on forest successional dynamics and biogeochemical cycling. Using 16S rRNA amplicon sequencing of soil DNA collected from ash and non-ash plots in central Ohio during the early stages of EAB infestation, we found that bacterial communities in plots with ash differed from those without ash. These differences were largely driven by Acidobacteria, which had a greater relative abundance in non-ash plots. Functional genes required for sulfur cycling, phosphorus cycling, and carbohydrate metabolism (specifically those which breakdown complex sugars to glucose) were estimated to be more abundant in non-ash plots, while nitrogen cycling gene abundance did not differ. This ash-soil microbiome association implies that EAB-induced ash decline may promote belowground successional shifts, altering carbon and nutrient cycling and changing soil properties beyond the effects of litter additions caused by ash mortality. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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Graphical abstract

11 pages, 1283 KiB

Open AccessArticle

Neighboring Tree Effects and Soil Nutrient Associations with Surviving Green Ash (Fraxinus pennsylvanica) in an Emerald Ash Borer (Agrilus planipennis) Infested Floodplain Forest

by Rachel H. Kappler, Kathleen S. Knight, Jennifer Koch and Karen V. Root

Forests 2018, 9(4), 183; https://doi.org/10.3390/f9040183 - 4 Apr 2018

Cited by 4 | Viewed by 4515

Abstract

Few ash trees (Fraxinus spp.) have survived the initial devastation that emerald ash borer beetle (EAB) (Agrilus planipennis) has caused in natural populations. We studied green ash (Fraxinus pennsylvanica) trees in a floodplain population after >90% of ash [...] Read more.

Few ash trees (Fraxinus spp.) have survived the initial devastation that emerald ash borer beetle (EAB) (Agrilus planipennis) has caused in natural populations. We studied green ash (Fraxinus pennsylvanica) trees in a floodplain population after >90% of ash had died from EAB infestation. We examined the relationship among the canopy health classes of surviving ash trees and their nearest neighboring trees (within 6 m) and available soil nutrients. A subset of focal ash trees was randomly selected within health classes ranging from healthy to recently deceased. Focal trees with the healthiest canopy class had significantly fewer ash neighbors compared to declining health classes. Other species of tree neighbors did not have a significant impact on surviving ash tree canopy health. Nutrients in soils immediately surrounding focal trees were compared among health classes. Samples from treeless areas were also used for comparison. There was a significantly greater amount of sulfur (ppm) and phosphorus (mg/kg) in ash tree soil compared to treeless area soil. The relationships between these soil nutrient differences may be from nutrient effects on trees, tree effects on nutrients, or microsite variation in flooded areas. Our data do not directly assess whether these ash trees with healthier canopies have increased resistance to EAB but do indicate that at neighborhood scales in EAB aftermath forests, the surviving ash trees have healthier canopies when separated at least 6 m from other ash trees. This research highlights scale-dependent neighborhood composition drivers of tree susceptibility to pests and suggests that drivers during initial infestation differ from drivers in aftermath forests. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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15 pages, 10513 KiB

Open AccessArticle

Review of Ecosystem Level Impacts of Emerald Ash Borer on Black Ash Wetlands: What Does the Future Hold?

by Randall K. Kolka, Anthony W. D’Amato, Joseph W. Wagenbrenner, Robert A. Slesak, Thomas G. Pypker, Melissa B. Youngquist, Alexis R. Grinde and Brian J. Palik

Forests 2018, 9(4), 179; https://doi.org/10.3390/f9040179 - 2 Apr 2018

Cited by 40 | Viewed by 7825

Abstract

The emerald ash borer (EAB) is rapidly spreading throughout eastern North America and devastating ecosystems where ash is a component tree. This rapid and sustained loss of ash trees has already resulted in ecological impacts on both terrestrial and aquatic ecosystems and is [...] Read more.

The emerald ash borer (EAB) is rapidly spreading throughout eastern North America and devastating ecosystems where ash is a component tree. This rapid and sustained loss of ash trees has already resulted in ecological impacts on both terrestrial and aquatic ecosystems and is projected to be even more severe as EAB invades black ash-dominated wetlands of the western Great Lakes region. Using two companion studies that are simulating short- and long-term EAB infestations and what is known from the literature, we synthesize our current limited understanding and predict anticipated future impacts of EAB on black ash wetlands. A key response to the die-back of mature black ash will be higher water tables and the potential for flooding and resulting changes to both the vegetation and animal communities. Although seedling planting studies have shown some possible replacement species, little is known about how the removal of black ash from the canopy will affect non-ash species growth and regeneration. Because black ash litter is relatively high in nitrogen, it is expected that there will be important changes in nutrient and carbon cycling and subsequent rates of productivity and decomposition. Changes in hydrology and nutrient and carbon cycling will have cascading effects on the biological community which have been scarcely studied. Research to address these important gaps is currently underway and should lead to alternatives to mitigate the effects of EAB on black ash wetland forests and develop management options pre- and post-EAB invasion. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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12 pages, 2416 KiB

Open AccessFeature PaperArticle

Water Level Controls on Sap Flux of Canopy Species in Black Ash Wetlands

by Joseph Shannon, Matthew Van Grinsven, Joshua Davis, Nicholas Bolton, Nam Jin Noh, Thomas Pypker and Randall Kolka

Forests 2018, 9(3), 147; https://doi.org/10.3390/f9030147 - 16 Mar 2018

Cited by 7 | Viewed by 4819

Abstract

Black ash (Fraxinus nigra Marsh.) exhibits canopy dominance in regularly inundated wetlands, suggesting advantageous adaptation. Black ash mortality due to emerald ash borer (Agrilus planipennis Fairmaire) will alter canopy composition and site hydrology. Retention of these forested wetlands requires understanding black [...] Read more.

Black ash (Fraxinus nigra Marsh.) exhibits canopy dominance in regularly inundated wetlands, suggesting advantageous adaptation. Black ash mortality due to emerald ash borer (Agrilus planipennis Fairmaire) will alter canopy composition and site hydrology. Retention of these forested wetlands requires understanding black ash’s ecohydrologic role. Our study examined the response of sap flux to water level and atmospheric drivers in three codominant species: black ash, red maple (Acer rubrum L.), and yellow birch (Betula alleghaniensis Britt.), in depressional wetlands in western Michigan, USA. The influence of water level on sap flux rates and response to vapor pressure deficit (VPD) was tested among species. Black ash had significantly greater sap flux than non-black ash at all water levels (80–160% higher). Black ash showed a significant increase (45%) in sap flux rates as water levels decreased. Black ash and red maple showed significant increases in response to VPD as water levels decreased (112% and 56%, respectively). Exploration of alternative canopy species has focused on the survival and growth of seedlings, but our findings show important differences in water use and response to hydrologic drivers among species. Understanding how a replacement species will respond to the expected altered hydrologic regimes of black ash wetlands following EAB infestation will improve species selection. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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11 pages, 1237 KiB

Open AccessArticle

Methods to Improve Survival and Growth of Planted Alternative Species Seedlings in Black Ash Ecosystems Threatened by Emerald Ash Borer

by Nicholas Bolton, Joseph Shannon, Joshua Davis, Matthew Van Grinsven, Nam Jin Noh, Shon Schooler, Randall Kolka, Thomas Pypker and Joseph Wagenbrenner

Forests 2018, 9(3), 146; https://doi.org/10.3390/f9030146 - 16 Mar 2018

Cited by 12 | Viewed by 4855

Abstract

Emerald ash borer (EAB) continues to spread across North America, infesting native ash trees and changing the forested landscape. Black ash wetland forests are severely affected by EAB. As black ash wetland forests provide integral ecosystem services, alternative approaches to maintain forest cover [...] Read more.

Emerald ash borer (EAB) continues to spread across North America, infesting native ash trees and changing the forested landscape. Black ash wetland forests are severely affected by EAB. As black ash wetland forests provide integral ecosystem services, alternative approaches to maintain forest cover on the landscape are needed. We implemented simulated EAB infestations in depressional black ash wetlands in the Ottawa National Forest in Michigan to mimic the short-term and long-term effects of EAB. These wetlands were planted with 10 alternative tree species in 2013. Based on initial results in the Michigan sites, a riparian corridor in the Superior Municipal Forest in Wisconsin was planted with three alternative tree species in 2015. Results across both locations indicate that silver maple (Acer saccharinum L.), red maple (Acer rubrum L.), American elm (Ulmus americana L.), and northern white cedar (Thuja occidentalis L.) are viable alternative species to plant in black ash-dominated wetlands. Additionally, selectively planting on natural or created hummocks resulted in two times greater survival than in adjacent lowland sites, and this suggests that planting should be implemented with microsite selection or creation as a primary control. Regional landowners and forest managers can use these results to help mitigate the canopy and structure losses from EAB and maintain forest cover and hydrologic function in black ash-dominated wetlands after infestation. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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11 pages, 690 KiB

Open AccessArticle

Reducing Firewood Movement by the Public: Use of Survey Data to Assess and Improve Efficacy of a Regulatory and Educational Program, 2006–2015

by Andrea Diss-Torrance, Kim Peterson and Colleen Robinson

Forests 2018, 9(2), 90; https://doi.org/10.3390/f9020090 - 14 Feb 2018

Cited by 9 | Viewed by 4110

Abstract

This paper describes a program of policy management and research from 2006 through 2015. It focuses on regulator efforts to understand and address challenges presented by dispersal of forest diseases and invasive pests in firewood by the camping public. Five surveys conducted at [...] Read more.

This paper describes a program of policy management and research from 2006 through 2015. It focuses on regulator efforts to understand and address challenges presented by dispersal of forest diseases and invasive pests in firewood by the camping public. Five surveys conducted at two-year intervals informed these efforts. The first survey in 2006 benchmarked campers’ awareness of forest threats by invasive species, their evaluations of firewood supplied at and near Wisconsin state parks, and their compliance with firewood movement rules which had been implemented that year. The 2008 survey tested for improvements in awareness and compliance and investigated campers’ motivations. The motivation research showed that calculated, normative, and social motivations are all important to rule compliance in the camping context. Surveys in 2010, 2012, and 2014 confirmed these results and guided education and outreach efforts, adjustments to firewood movement rules for Wisconsin state parks and forests, and improvements to firewood supplies at state campgrounds. The survey sequence as a whole revealed that: (1) compliance improves dramatically in early program years and then levels off, suggesting that it may be unrealistic and cost ineffective to strive for 100% compliance in similar regulatory contexts; (2) persistence in messaging is important in building awareness and motivation; and (3) regulation and persuasion based on motivational principles can extend beyond specific situations where informing and regulating take place, suggesting that public properties can be useful venues for encouraging other types of environmentally responsible behavior. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

13 pages, 1849 KiB

Open AccessArticle

Coleopteran Communities Associated with Forests Invaded by Emerald Ash Borer

by Matthew B. Savage and Lynne K. Rieske

Forests 2018, 9(2), 69; https://doi.org/10.3390/f9020069 - 30 Jan 2018

Cited by 6 | Viewed by 5041

Abstract

Extensive ash mortality caused by the non-native emerald ash borer alters canopy structure and creates inputs of coarse woody debris as dead and dying ash fall to the forest floor; this affects habitat heterogeneity; resource availability; and exposure to predation and parasitism. As [...] Read more.

Extensive ash mortality caused by the non-native emerald ash borer alters canopy structure and creates inputs of coarse woody debris as dead and dying ash fall to the forest floor; this affects habitat heterogeneity; resource availability; and exposure to predation and parasitism. As EAB-induced (emerald ash borer-induced) disturbance progresses the native arthropod associates of these forests may be irreversibly altered through loss of habitat; changing abiotic conditions and altered trophic interactions. We documented coleopteran communities associated with EAB-disturbed forests in a one-year study to evaluate the nature of these changes. Arthropods were collected via ethanol-baited traps on five sites with varying levels of EAB-induced ash mortality from May to September; captured beetles were identified to the family level and assigned to feeding guilds (herbivore; fungivore; xylophage; saprophage; predator; or parasite). Over 11,700 Coleoptera were identified in 57 families. In spite of their abundance; herbivores comprised a relatively small portion of coleopteran family richness (8 of 57 families). Conversely, coleopteran fungivore richness was high (23 families), and fungivore abundance was low. Herbivores and fungivores were more abundant at sites where ash decline was most evident. The predatory Trogossitidae and Cleridae were positively correlated with ash decline, suggesting a positive numerical response to the increased prey base associated with EAB invasion. Ash forests are changing, and a deeper understanding of arthropod community responses will facilitate restoration. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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16 pages, 5664 KiB

Open AccessArticle

Tree Stress and Mortality from Emerald Ash Borer Does Not Systematically Alter Short-Term Soil Carbon Flux in a Mixed Northeastern U.S. Forest

by Jaclyn Hatala Matthes, Ashley K. Lang, Fiona V. Jevon and Sarah J. Russell

Forests 2018, 9(1), 37; https://doi.org/10.3390/f9010037 - 16 Jan 2018

Cited by 6 | Viewed by 8134

Abstract

Invasive insect pests are a common disturbance in temperate forests, but their effects on belowground processes in these ecosystems are poorly understood. This study examined how aboveground disturbance might impact short-term soil carbon flux in a forest impacted by emerald ash borer ( [...] Read more.

Invasive insect pests are a common disturbance in temperate forests, but their effects on belowground processes in these ecosystems are poorly understood. This study examined how aboveground disturbance might impact short-term soil carbon flux in a forest impacted by emerald ash borer (Agrilus planipennis Fairmaire) in central New Hampshire, USA. We anticipated changes to soil moisture and temperature resulting from tree mortality caused by emerald ash borer, with subsequent effects on rates of soil respiration and methane oxidation. We measured carbon dioxide emissions and methane uptake beneath trees before, during, and after infestation by emerald ash borer. In our study, emerald ash borer damage to nearby trees did not alter soil microclimate nor soil carbon fluxes. While surprising, the lack of change in soil microclimate conditions may have been a result of the sandy, well-drained soil in our study area and the diffuse spatial distribution of canopy ash trees and subsequent canopy light gaps after tree mortality. Overall, our results indicate that short-term changes in soil carbon flux following insect disturbances may be minimal, particularly in forests with well-drained soils and a mixed-species canopy. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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2124 KiB

Open AccessArticle

Buying Time: Preliminary Assessment of Biocontrol in the Recovery of Native Forest Vegetation in the Aftermath of the Invasive Emerald Ash Borer

by Elan Margulies, Leah Bauer and Inés Ibáñez

Forests 2017, 8(10), 369; https://doi.org/10.3390/f8100369 - 28 Sep 2017

Cited by 18 | Viewed by 7431

Abstract

Introduced forest pests have become one of the major threats to forests, and biological control is one of the few environmentally acceptable management practices. Assessing the impacts of a biocontrol program includes evaluating the establishment of biocontrol agents, the control of target pest, [...] Read more.

Introduced forest pests have become one of the major threats to forests, and biological control is one of the few environmentally acceptable management practices. Assessing the impacts of a biocontrol program includes evaluating the establishment of biocontrol agents, the control of target pest, the impact on the affected organism, and the indirect impacts that the biocontrol agent may have on the whole community. We assessed the recovery of forest vegetation following the mortality of ash trees caused by the invasive emerald ash borer (EAB) pest in forest stands where biocontrol agents were released or not. We used a multilevel framework to evaluate potential indirect effects of the biocontrol agents on native forest seedlings. Our results showed a higher number of ash saplings where increasing numbers of the dominant EAB biocontrol agent were released, while the number of invasive and weedy saplings was negatively associated with the number of ash saplings, and the density of native seedlings was negatively associated with invasive and weedy saplings. The protection of ash saplings by the biocontrol agent may help native recruitment during forest transition by supporting the growth of native hardwood seedlings over invasive and weedy species. These results show that research on the efficacy of EAB biocontrol should include all ash size classes and the community dynamics of co-occurring species. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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17 pages, 3170 KiB

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Evaluating Adaptive Management Options for Black Ash Forests in the Face of Emerald Ash Borer Invasion

by Anthony W. D’Amato, Brian J. Palik, Robert A. Slesak, Greg Edge, Colleen Matula and Dustin R. Bronson

Forests 2018, 9(6), 348; https://doi.org/10.3390/f9060348 - 13 Jun 2018

Cited by 36 | Viewed by 7713

Abstract

The arrival and spread of emerald ash borer (EAB) across the western Great Lakes region has shifted considerable focus towards developing silvicultural strategies that minimize the impacts of this invasive insect on the structure and functioning of black ash (Fraxinus nigra) [...] Read more.

The arrival and spread of emerald ash borer (EAB) across the western Great Lakes region has shifted considerable focus towards developing silvicultural strategies that minimize the impacts of this invasive insect on the structure and functioning of black ash (Fraxinus nigra) wetlands. Early experience with clearcutting in these forests highlighted the risks of losing ash to EAB from these ecosystems, with stands often retrogressing to marsh-like conditions with limited tree cover. Given these experiences and an urgency for increasing resilience to EAB, research efforts began in north-central Minnesota in 2009 followed by additional studies and trials in Michigan and Wisconsin to evaluate the potential for using regeneration harvests in conjunction with planting of replacement species to sustain forested wetland habitats after EAB infestations. Along with these more formal experiments, a number of field trials and demonstrations have been employed by managers across the region to determine effective ways for reducing the vulnerability of black ash forest types to EAB. This paper reviews the results from these recent experiences with managing black ash for resilience to EAB and describes the insights gained on the ecological functioning of these forests and the unique, foundational role played by black ash. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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14 pages, 3160 KiB

Open AccessReview

Ecological Impacts of Emerald Ash Borer in Forests at the Epicenter of the Invasion in North America

by Wendy S. Klooster, Kamal J. K. Gandhi, Lawrence C. Long, Kayla I. Perry, Kevin B. Rice and Daniel A. Herms

Forests 2018, 9(5), 250; https://doi.org/10.3390/f9050250 - 5 May 2018

Cited by 73 | Viewed by 11752

Abstract

We review research on ecological impacts of emerald ash borer (EAB)-induced ash mortality in the Upper Huron River watershed in southeast Michigan near the epicenter of the invasion of North America, where forests have been impacted longer than any others in North America. [...] Read more.

We review research on ecological impacts of emerald ash borer (EAB)-induced ash mortality in the Upper Huron River watershed in southeast Michigan near the epicenter of the invasion of North America, where forests have been impacted longer than any others in North America. By 2009, mortality of green, white, and black ash exceeded 99%, and ash seed production and regeneration had ceased. This left an orphaned cohort of saplings too small to be infested, the fate of which may depend on the ability of natural enemies to regulate EAB populations at low densities. There was no relationship between patterns of ash mortality and ash density, ash importance, or community composition. Most trees died over a five-year period, resulting in relatively simultaneous, widespread gap formation. Disturbance resulting from gap formation and accumulation of coarse woody debris caused by ash mortality had cascading impacts on forest communities, including successional trajectories, growth of non-native invasive plants, soil dwelling and herbivorous arthropod communities, and bird foraging behavior, abundance, and community composition. These and other impacts on forest ecosystems are likely to be experienced elsewhere as EAB continues to spread. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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17 pages, 3546 KiB

Open AccessReview

Progress and Challenges of Protecting North American Ash Trees from the Emerald Ash Borer Using Biological Control

by Jian J. Duan, Leah S. Bauer, Roy G. Van Driesche and Juli R. Gould

Forests 2018, 9(3), 142; https://doi.org/10.3390/f9030142 - 15 Mar 2018

Cited by 69 | Viewed by 9802

Abstract

After emerald ash borer (EAB), Agrilus planipennis Fairmaire, was discovered in the United States, a classical biological control program was initiated against this destructive pest of ash trees (Fraxinus spp.). This biocontrol program began in 2007 after federal regulatory agencies and the [...] Read more.

After emerald ash borer (EAB), Agrilus planipennis Fairmaire, was discovered in the United States, a classical biological control program was initiated against this destructive pest of ash trees (Fraxinus spp.). This biocontrol program began in 2007 after federal regulatory agencies and the state of Michigan approved release of three EAB parasitoid species from China: Tetrastichus planipennisi Yang (Eulophidae), Spathius agrili Yang (Braconidae), and Oobius agrili Zhang and Huang (Encyrtidae). A fourth EAB parasitoid, Spathius galinae Belokobylskij (Braconidae) from Russia, was approved for release in 2015. We review the rationale and ecological premises of the EAB biocontrol program, and then report on progress in North American ash recovery in southern Michigan, where the parasitoids were first released. We also identify challenges to conserving native Fraxinus using biocontrol in the aftermath of the EAB invasion, and provide suggestions for program improvements as EAB spreads throughout North America. We conclude that more work is needed to: (1) evaluate the establishment and impact of biocontrol agents in different climate zones; (2) determine the combined effect of EAB biocontrol and host plant resistance or tolerance on the regeneration of North American ash species; and (3) expand foreign exploration for EAB natural enemies throughout Asia. Full article

(This article belongs to the Special Issue Understanding and Managing Emerald Ash Borer Impacts on Ash Forests)

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