Adapting Black Ash Wetlands to a Dual Threat

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In the face of emerald ash borer invasion and climate change, scientists are evaluating adaptation strategies designed to keep black ash wetlands in the Upper Midwest in a forested condition

Emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae) is moving toward the vast black ash wetlands of the Lake States. Black ash is a foundational species in these wetlands because it functions to maintain low water levels during the growing season, allowing trees and plants to thrive. Loss of black ash will profoundly impact this function. Most native tree species that might assume the ecological role of black ash are projected to fare poorly with climate change. Forest Service scientists, with National Forest System, university, and state collaborators, are generating adaptation options for these wetlands using a ground-breaking large-scale experiment on the Chippewa National Forest in Minnesota that simulates EAB mortality in healthy forests and evaluates tree species for their ability to assume the ecological role of black ash.

Results demonstrate that loss of black ash dramatically increases water table levels, increases cover of herbaceous plants, and makes tree establishment exceedingly difficult. Approaches that gradually remove black ash mute these changes, allowing new trees to establish. Promising species for replacement of black ash include American elm, swamp white oak, and hackberry, all species that are future-climate adapted. Results from this real-world experiment are being implemented widely by agencies and Tribes in Minnesota and Wisconsin.

Contacts

• Brian J. Palik, Team Leader / Research Ecologist

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Are There Regional Barriers to Exporting U.S. Hardwood Products?

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Scientists explored why some hardwood-producing regions of the United States seemingly face greater barriers than others to participating in export markets

Forest Service and university researchers collaborated to compare a measure of production (employment-based) to the value of exports in three U.S. hardwood regions for two product types: lumber and secondary (cabinets and furniture) products. Proximity to seaports (i.e., the East Coast) benefited exporting of both hardwood lumber and secondary products, but the impact was greater for lumber. More inland regions of the United States faced greater disadvantages to exporting lumber, likely due to longer haul distances to ocean ports and higher transportation costs relative to product value. This circumstance is especially important given that Asian markets have replaced Canada as the most important U.S. export destination. Average sawmill size and sawtimber quality also impacted regional hardwood lumber exporting performance. The results of this research highlight the need for efficient transportation infrastructure from interior regions of the United States and show the importance of developing export markets for value-added products, for which regional transportation barriers are lower.

Contacts

• Matt Bumgardner, Research Forest Product Technologist

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New Charter Defines Urban Field Stations

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Station Director's Choice

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A new Urban Field Station charter defines Forest Service urban field stations and how they can improve the lives of the 83 percent of Americans living in urban areas

In the "urban century," the first time in human history when the majority of the world's population is living in cities and urban areas, the U.S. Forest Service is continuing its mission of "caring for the land and serving the people" with research aimed at improving the lives of the 83 percent of Americans that live in urban areas. In 2016, a new charter for "Urban Field Stations in the Northern Research Station" formalized the Northern Research Station's long-standing field station investments in Baltimore, Chicago, New York, and Philadelphia by defining what an urban field station is, establishing these four locations as an Urban Field Station Network within the Station, and describing the vision, roles, and functions of that Network.

The charter serves as a template for other urban investments within the Forest Service, and articulates the principles and practices that have enabled the effective co-production of research with managers and practitioners, and the effective delivery of that knowledge to a broader stakeholder base. The work of the urban field stations is place-based but not place-bound, and can be used to support decisions in urban areas.

Contacts

• Keith Nislow, Project Leader / Research Fisheries Biologist
• Morgan Grove, Research Forester
• Sarah C. Low, Biological Scientist
• Erika Svendsen, Research Social Scientist
• Sarah J. Hines, Science Delivery Specialist

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Adaptive Silviculture for Climate Change: A National Experiment in Partnerships

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Partnerships built through the Adaptive Silviculture for Climate Change project are demonstrating the relevance of climate research and advancing communication on climate change adaptation techniques at a national scale

Forest managers in the United States must respond to the need for adaptive strategies in the face of observed and projected climatic changes. However, there is a lack of on-the-ground science-manager collaborative research to demonstrate what adaptation measures or tactics might be effective in preparing forest ecosystems to deal with climate change.

The Adaptive Silviculture for Climate Change (ASCC) project responds to this barrier to operationalizing adaptation strategies by 1) providing a multi-region network of replicated operational-scale research sites testing ecosystem-specific climate change adaptation treatments; and 2) introducing conceptual tools and processes to integrate climate change considerations into management. The conceptual framework of the ASCC project, the collaborative workshop process to develop site-specific approaches, and highlights of the process at the first two study sites (Cutfoot Experimental Forest and San Juan National Forest), were presented at the 2015 National Silviculture Workshop and are the topic of an in-press special issue of Journal of Forestry on the 2015 National Silviculture Workshop. Interest in ASCC through exposure at this national venue has helped jump start ASCC installation development on the Flathead National Forest/Coram Experimental Forest, the Dartmouth College Grant Forest, the Jones Ecological Research Center, and the Whitehead NF/Hubbard Brook Experimental Forest.

Contacts

• Brian J. Palik, Team Leader / Research Ecologist
• Michael Battaglia, Ecologist

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Future Forests of the Northern United States

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A 6-year study is capped by analysis of the future of Northern forests over the next 50 years

The Northern Forest Futures Project takes a long-term, large-scale perspective by applying scenario analyses and other forward-looking analytical tools to help society understand the magnitude and consequences of cumulative forest changes anticipated over the next 50 years.

"Future Forests of the Northern United States," the latest report produced as part of the Northern Forest Futures Project, is a collaboration among the Northern Research Station, Northeastern Area State and Private Forestry, and the Northeastern Area Association of State Foresters. Researchers analyzed 13 scenarios that consider forest change in response to assumptions about land-use, economic trends, climate change, forest growth, forest harvest, and other factors.

In addition to the summary data and associated narratives in the report, analysts have designed two other related products. The first is a database that helps users query and summarize future forest conditions using the same protocols used with current Forest Inventory and Analysis data. The second is an intuitive, interactive website that lets users map, graph, and compare anticipated forest changes for the next 50 years.

Collectively these tools inform managers and policy makers of influential ecological, social, and economic trends that over the next 50 years will present significant challenges and opportunities for the 172 million acres of northern forest land and the 125 million people who depend on those forests for their well-being.

Contacts

• Stephen R. Shifley, Research Forester (Biometrics)
• Pat Miles, Research Forester
• Jim Lootens-White, Natural Resource Specialist

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New Carriers of Thousand Cankers Disease Discovered

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Station Director's Choice

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Discovery that ambrosia beetles and bark-colonizing weevils carry the thousand cankers disease fungus has serious implications for disease spread and tree mortality

Thousand cankers disease (TCD) has caused dieback and death of eastern black walnut (Juglans nigra) in urban areas of the United States. Until recently the walnut twig beetle (WTB) (Pityophthorus juglandis) was the only known carrier of the thousand cankers disease fungus. However, an examination of insects colonizing black walnut trees showed three other insect species carrying the fungus. Walnut timber and nut producers are greatly concerned about potential losses due to this emerging disease.

A Northern Research Station scientist, in collaboration with partners at Purdue University, collected ambrosia beetles, bark beetles, and weevils colonizing main stems and branches of J. nigra trees exhibiting TCD symptoms in Ohio. Collected insects were identified and then evaluated for the presence of the TCD canker-causing fungus, Geosmithia morbida, on their bodies. Two ambrosia beetle species (Xylosandrus crassiusculus and Xyleborinus saxeseni) and one weevil species (Stenominus pallidus) accounted for 149 of 155 collected specimens. G. morbida was detected on 22 to 65 percent of the individuals of these three species, as well as on two emerged walnut twig beetles. The latter species was previously the only known carrier of the fungus. The fungus-carrying ambrosia beetles may exacerbate TCD progression on J. nigra in affected areas. Additional insect species carrying G. morbida may expand the distribution of the G. morbida beyond those areas reached by walnut twig beetle. Options for monitoring these additional species are under consideration by several eastern states.

Contacts

• Jennifer Juzwik, Research Plant Pathologist

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Sawmills Benefit from New Techniques to Identify Internal Log Defects.

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New laser scanning technology, along with relationships found between external and internal log defects, are helping sawmills optimize lumber outputs

The type, size, and location of internal defects dictate the grade and value of lumber sawn from hardwood logs. Significant correlations have been documented among external log defect indicators and internal defect features. A series of prediction models for four hardwood species have been developed based on these correlations. A recently developed high-resolution laser log scanner that locates external log defects uses these models to predict internal defect locations and sizes based on detected external defect data. The prediction models are specific for species and defect type and allow users to estimate internal defect size, shape, depth, and position.

Scientists found that the models achieved approximately 70 percent accuracy when predicting the occurrence of a knot defect. In addition, the models accurately predicted the sawing of 95 of 105 boards with no knot defects, an accuracy rate of 90.5 percent. These methods have the potential to allow full optimization of the sawing of a log based on internal defect data using laser scanning technology, thus reducing waste and improving the value of lumber sawn.

Contacts

• Ed Thomas, Research Computer Scientist

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Field Studies Improve Predictions of Carbon in Soil and Litter

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Station Director's Choice

Long-term field measurments of soil and litter characteristics, combined with other data, improve estimates of national soil and litter carbon pools

Forest ecosystems are the largest terrestrial carbon sink on Earth, with more than half of their net primary production moving to the soil via the decomposition of litter biomass.

The Forest Inventory and Analysis program within the USDA Forest Service has been consistently measuring litter and soil attributes on permanent sample plots across all forest land and ownerships as part of the national forest inventory since 2001. Those data have recently been harmonized with auxiliary soils, climate, and geospatial data to develop models for predicting litter and soil carbon stocks on forest land in the United States for United Nations Framework Convention on Climate Change (UNFCCC) reporting. This work resulted in an estimated 44 percent reduction in litter carbon stocks and an estimated 40 percent increase in soil carbon stocks relative to previous estimates in UNFCCC reporting. More broadly, this work suggests that Intergovernmental Panel on Climate Change defaults and country-specific models used to estimate litter and soil carbon in temperate forest ecosystems may not well represent the contribution of these pools in national carbon budgets.

Contacts

• Grant M. Domke, Team Leader, Research Forester

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Fire Risk Reduced through Use of Forest Service WUI Data

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Federal agencies are making their holdings more fire-safe by using wildland-urban interface (WUI) data to help them identify facilities at risk

Wildland-urban interface (WUI) areas, where structures meet or mix with undeveloped natural areas, are places with higher risk of wildfire, and structure loss, injury, and death from wildfire. Managing fire and reducing fire risk in these spatially complex environments is challenging. For the Federal departments and agencies that own buildings in the WUI, a recent executive order directs agencies to use the Forest Service's WUI dataset to identify their buildings within the WUI, and take appropriate management action — modifying buildings and surrounding vegetation — in order to reduce the risk of wildfire loss.

By mitigating fire risk in their own holdings, Federal managers will contribute to safer, more resilient landscapes, and encourage the efforts of private landowners, local governments, and states to become fire-adapted. Fully documented data files provide valuable information for anyone who wants to learn about WUI locations at the local, state, or national scale. This knowledge of WUI locations will be extremely useful for policy makers, land managers, fire managers, and others.

Contacts

• Miranda H. Mockrin, Research Scientist

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FIA is Coming to a City Near You

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Urban forests are starting to be included in national forest inventories, making the nation's forest census more comprehensive

The U.S. Forest Service's Forest Inventory and Analysis Program (FIA), responsible for the nation's forest census, has for many years measured information on trees in areas that meet its definition of forest - generally speaking, groups of naturally-growing trees in areas that meet specific size requirements. However urban forests also yield benefits, such as removing air pollution, reducing energy use and carbon sequestration, that are important to take into account.

FIA has recently established a national urban forest inventory program and begun monitoring trees in urban areas, focusing on the most populous cities. Using its suitcase of inventory methods, database and reporting tools, and statistical techniques including i-Tree software tools that quantify ecosystem services, FIA is now monitoring the urban tree resource. By doing this, FIA fulfills its goal of making more comprehensive reports on the status and trends of the nation's forests and trees.

FIA, working with state and local partners including Texas A&M Forest Service, reached an important milestone by completing its first urban inventory report for the city of Austin, Texas, and is collecting data and refining its data processing and reporting methods continuously. The ultimate goal of this effort is to have a seamless reporting system that uses the existing FIA protocols to provide new and valuable information on trees in these previously unmeasured areas.

Contacts

• Tonya Lister, Research Forester
• Mark Majewsky, Supervisory Forester
• David J. Nowak, Team Leader / Research Forester
• Allison Bodine, Research Analyst
• Robert Hoehn, Forester

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Patterns Found in ALB Spread Help Manage Risk

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Research that predicts spread patterns of Asian longhorned beetle (ALB) helps cities focus resources on areas of likely infestation

When a breeding population of an invasive species becomes established in a novel environment, management tools often focus on either eradication of the species or slowing its spread. In either situation, it is necessary to understand how the organism moves through the landscape, and translate that knowledge into an assessment of risk to the surrounding landscape.

U.S. Forest Service researchers used data collected by the Asian longhorned beetle Eradication Program, which is operated by the USDA Animal and Plant Health Inspection Service's (APHIS) Plant Protection and Quarantine (PPQ) program, to identify patterns of spread around existing infestations using simple graph theory and show how this data can be customized to local infestations to prioritize surveys and manage risk on a hectare-by-hectare basis.

The results show that Asian longhorned beetle spread within an infestation does not occur randomly, and that patterns of spread among infestations vary. This approach represents a new and valuable use of existing data and highlights the utility of interagency and interdepartmental collaboration in addressing complex environmental challenges.

Contacts

• R. Talbot Trotter, III, Research Ecologist

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Scientists Get One Step Closer to Dutch Elm Disease Tolerant American Elms

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American elms are making a comeback through research on increasing elm tolerance to Dutch elm disease (DED)

Since 1930, when Dutch elm disease (DED) was unintentionally introduced to the United States, scientists have been working to develop American elm trees that are able to tolerate the disease. A grant from The Manton Foundation has provided the Northern Research Station with an opportunity to accelerate American elm research in collaboration with The Nature Conservancy.

Breeding American elms with tolerance to Dutch elm disease (DED) is a multi-step program that involves: 1) propagating old American elms that have survived the Dutch elm disease epidemic through grafting and cuttings; 2) crossing these survivor elm selections with known DED-tolerant American elm selections; 3) growing the elms generated from the cuttings and crosses; and 4) inoculating the elms with the DED pathogen to test them for resistance to DED. Scientists are also examining elm metabolites to understand how the trees survive the disease.

During summer 2016, scientists propagated 13 new survivor elm selections provided by partners at The Nature Conservancy and generated progeny from crosses with these elms for future testing; inoculated 37 elm selections in potted tree and plantation tree assays; and sampled foliage of inoculated trees for metabolites. Preliminary results show some inoculated elm selections performing very well compared to DED-susceptible controls, which are showing severe symptoms of decline. The elms that can tolerate DED can be used for urban plantings and for restoration of forests. Scientists have also started studying elm yellows, another important elm disease, with the goal of incorporating elm yellows resistance into the breeding program.

Contacts

• Kathleen Knight, Research Ecologist
• Leila Pinchot, Research Ecologist
• Charles Flower, Research Ecologist
• Rakesh Minocha, Plant Physiologist / Biochemist
• Keith Woeste, Research Plant Molecular Geneticist
• Paul Schaberg, Research Plant Physiologist
• Jim Slavicek, Project Leader / Research Biologist

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World's Largest Climate Change Experiment: SPRUCE

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Peatlands play a major role in storing terrestrial carbon but climate change may put peatlands at risk. Scientists are testing climate change impacts on peatlands through an ecosystem level experiment

Although they cover only 3 percent of Earth's land surface, peatlands store about 30 percent of the total soil carbon. Despite the uncertainty about their response to climate change, large-scale manipulations simulating climate change have not been conducted until SPRUCE (Spruce and Peatland Responses Under Climatic and Environmental Change Experiment).

The SPRUCE experiment is an ambitious ecosystem-level experiment that is testing the response of high-carbon northern peatland ecosystems to increased temperatures and elevated carbon dioxide. Located at the Northern Research Station's Marcell Experimental Forest near Grand Rapids, MN, the experiment is a collaboration between the U.S. Forest Service and the Department of Energy's Oak Ridge National Laboratory (ORNL) and many other collaborators. The manipulation is evaluating the response of the existing communities to a range of warming levels from ambient to +9 °C, with and without elevated carbon dioxide (CO₂), provided via large, open-top chambers. Both direct and indirect effects of these perturbations are being analyzed to refine models needed for full Earth system analyses.

Belowground heating began in 2014, aboveground heating in 2015, and elevated CO₂ treatments commenced in 2016. Responses to warming and interactions with increased atmospheric CO₂ concentration will have important feedbacks on the atmosphere and climate.

Contacts

• Randy Kolka, Team Leader / Research Soil Scientist

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Wildfire Provides Opportunity for Research on Impacts of Fire Severity.

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Station Director's Choice

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Measures of soil and litter characteristics on a site in Northern Minnesota where a wildfire later occurred provided scientists the opportunity to determine impacts of fire severity on ecosystem processes

Fire severity — the impact of the fire on an ecosystem — is among the most challenging dimensions of fire to quantify empirically. Scientists measured fire severity of the Pagami Creek wildfire that burned nearly 100,000 acres in the Boundary Waters Canoe Area Wilderness in northern Minnesota using multiple standardized indices. These indices were compared with ecosystem processes including loss of carbon (C), nitrogen (N), and mercury (Hg) from soils and forest floor and subsequent aspen regeneration.

Emissions from the wildfire were estimated as the annual equivalent C emissions from 50,000 sport utility vehicles emissions, the N required to fertilize 163,000 acres of corn, and approximately 9 percent of the 2010 Hg emissions for the state of Minnesota. These losses were primarily from the forest floor and strongly related to soil post-fire severity indices measured at very fine spatial scales (less than 1 meter). Aspen regeneration was unrelated to the normalized burn ratio, but strongly related to prefire aspen abundance, each measured using satellite-based remote sensing.

The research demonstrates 1) forest fires have large consequences for ecosystem processes such as biogeochemical cycling and forest vegetation dynamics; and 2) the importance of both scalable and repeatable measures of fire severity related to these crucial ecosystem processes.

Contacts

• Brian R. Sturtevant, Research Ecologist
• Randy Kolka, Team Leader / Research Soil Scientist
• Eric J. Gustafson, Research Landscape Ecologist

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New Low Cost Measurement Methods to Advance Fire Science

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Scientists are collaborating to customize and retool existing instruments to measure characteristics of wildland fire at lower cost

Measurement development and the instruments and methods that result are often central to advancing science (think the telescope). In fire science, new measurement methods are being developed collaboratively by Northern and Southern Research Station scientists and the Rochester Institute of Technology and used to advance fire science and ecosystem restoration.

Radiometers that measure ground-leaving infrared radiation are a rapid means of estimating biomass consumption and have been used on ecology, remote sensing, and fire science projects in Florida, Georgia, New Jersey, Ohio, Kentucky, Michigan, Idaho, California, and Wisconsin. Commercially-available, high-end infrared cameras are being used in novel ways, including for making high-resolution, downward-looking measurements of radiation from 20-foot custom tripods, measurements that are linked to plant demography and maintenance of diversity in southern savannah systems. Fire-hardened, visible-wavelength cameras have been developed and are also being used on a range of projects to provide replicated measurements of flames and fire behavior.

Ongoing developments include improving the radiometer and infrared calibration methods, developing fire weather measurement devices, improving camera triggering methods, developing an inexpensive infrared camera, and developing methods to produce three-dimensional (3D) images of flames. A driving design goal is often low cost so that measurements can be replicated extensively.

Contacts

• Matthew B. Dickinson, Ecologist
• Nicholas Skowronski, Research Forester

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Mystery of White-Nose Syndrome Spread Solved Using DNA Sequencing

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Scientists used cutting edge technology to determine whether the strain of white-nose syndrome found infecting a bat in Washington State was the same as the strain found 1,300 miles east

In March 2016, a little brown bat found sick near North Bend, Washington, tested positive for white-nose syndrome (WNS), an invasive disease caused by the fungus Pseudogymnoascus destructans, or Pd. North Bend is located about 1,300 miles from Nebraska, the previous westernmost WNS detection. Because Pd is also present in Eurasia and North Bend is located near an international port, Northern Research Station (NRS) researchers studied DNA from the Washington fungus to determine if it had roots abroad.

Working in concert with the National Forest System, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey's National Wildlife Health Center, NRS scientists isolated and performed next-generation DNA-sequencing of the entire genome of the fungus found in Washington and compared it to other strains found in eastern North America and Europe. The results conclusively established that the strain found on the Washington bat matches the strains of fungus from the eastern United States and does not represent a new introduction. The techniques pioneered by NRS scientists for identifying isolates of Pd will help to determine if and when new strains of the fungus enter the United States, a situation that could make this devastating disease even more difficult to control.

Contacts

• Daniel Lindner, Research Plant Pathologist
• Jonathan Palmer, Research Botanist

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Community Greening Can Reduce Crime

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Evaluation of a greening program in Youngstown, Ohio, suggests that greening vacant lots reduced crime. The type of crime deterred appeared to be related to who did the greening — community members or contractors

Vacant land poses significant challenges to safety within communities. In 2010, the Youngstown Neighborhood Development Corporation initiated a "Lots of Green" program to reuse vacant land. The program took two forms: a cleaning and greening "stabilization" treatment and a "community reuse" treatment mostly involving community gardens.

A Northern Research Station scientist at the Philadelphia Urban Field Station and collaborators evaluated associations between the two types of vacant lot treatments and crime. They found consistent significant reductions in burglaries around stabilization lots, and in assaults around community reuse lots, with no evidence of displacement of crimes to surrounding areas. Significant increases in motor vehicle thefts around both lot types were also found after they had been greened. Community-initiated vacant lot greening may have a greater impact on reducing more serious, violent crimes.

Contacts

• Michelle Kondo, Research Social Scientist

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The History and Future of Fire in the United States

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Northern Research Station scientists developed site-specific fire histories and continental models of fire occurrence that land managers can use to enhance ecological restoration throughout the nation

Site-specific fire histories define many attributes of a fire regime such as frequency, seasonality, and severity, and reveal how fire varied over time in relation to changing climate, and human populations and cultures. Understanding the changing role of fire helps explain the major shifts in the dominance and distribution of natural communities. Scientists at the Northern Research Station and collaborators recently reconstructed the history of fire in portions of New York, Ohio, Pennsylvania, Maine, Michigan, Wisconsin, and Minnesota. This research adds to their work in the Great Plains, Midwest and Southern United States, and Canada.

Fire histories are used to develop prescriptions for restoration of natural communities such as savannas and woodlands. Collectively, over 170 fire histories from across the United States have been used to develop a continental model that predicts fire frequency based on climatic variables. The model was first used to predict historic (pre-European) fire frequency but has since been used to assess the probability of fire in the future under a range of climate scenarios. These assessments can be used to develop state and regional plans to reduce risk to catastrophic wildfires, to restore natural communities and their biodiversity, and to allocate limited resources to priority areas.

Contacts

• Daniel C. Dey, Project Leader / Research Forester

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New Insights into How Forests Provide Clean Water

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Station Director's Choice

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Forests are the source of much of our nation's water supply. Understanding how forested watersheds regulate water quality is key to proper watershed management

How long does it take rain falling on a forest to reach a stream? What pathways does it take to get there? Humans have pondered such simple questions for millennia.

Using a unique long-term data set on stream water chemistry from the Hubbard Brook Experimental Forest in New Hampshire, an international team of scientists has new answers. Variation in the isotopic composition of water was used to determine the time that it took water to reach the stream, which varied from a median of 50 days during wet periods to 190 days during dry periods. At all times, there is a very small portion of the streamflow that is much older - as long as several years. These variations in water travel time matched changes in concentrations of substances dissolved in water, demonstrating how variations in water sources regulate water quality. Distinct water sources detected in this study include shallow groundwater draining the soil and deeper groundwater draining geologic deposits. A mixing zone in riparian areas adjacent to the stream determines how each of these sources deliver water to the stream.

These results will help forest managers understand mechanistically how forests function to provide a clean and reliable water supply and provide a benchmark for determining how climate change will affect this valuable resource in the future.

Contacts

• Scott Bailey, Geologist
• John Campbell, Research Ecologist

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Enhancing Songbird Populations by Managing Forests

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Many forest bird populations are declining. Can forestry actually enhance habitat quality for these species in eastern forests? Research by Northern Research Station scientists helps answer that question

Songbirds are a source of enjoyment for millions of bird watchers. According to one recent estimate, bird-oriented recreation generates $85 billion of economic activity annually. Populations of many species are declining, and some of these declines are likely due to recent changes in the condition of our forests.

Historically, eastern forests consisted of a mosaic of old growth stands interspersed with shrubby openings caused by natural and anthropogenic disturbances such as blowdown, beavers, and fire. Following colonization, the structural diversity characteristic of these early stands was lost as old growth forests were replaced by secondary forests more resistant to blowdown, and the influence of other natural disturbance agents was restricted. Bird diversity increases with structural diversity, and some species require particular structural features like advanced regeneration or canopy gaps to nest and rear their young.

One such species is the wood thrush, a forest-nesting songbird whose population has declined by over 50 percent in the past few decades. Scientists explored the extent to which silviculture could enhance wood thrush habitat in a study in central Massachusetts and found that wood thrushes were more abundant and nested successfully in managed forests, and that fledglings selected structurally diverse habitats created by forestry.

Contacts

• David King, Research Wildlife Biologist

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Genes May Hold Key to Saving Green Ash

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Hundreds of genes in ash trees that have survived attack from the invasive emerald ash borer may hold the key to saving green ash from extinction

Emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae) continues to advance at an alarmingly fast pace, putting green ash at risk of extinction. Tests done on "lingering ash," the rare surviving trees found in areas under long-term EAB attack, are evidence that these trees are capable of mounting a defense against the insect. A collaborative project between Forest Service researchers and members of the Hardwood Genomics project demonstrated measurable differences in patterns of gene expression between lingering ash trees and trees that are fully susceptible to EAB, both before and after EAB larvae have fed upon their inner bark tissues.

The study identified hundreds of genes that may prove useful in future research on the specific molecular mechanisms responsible for the defenses lingering ash use against EAB. Different lingering ash trees use different types of defense responses; the goal of the Forest Service's green ash breeding program is to combine the different defenses to produce progeny that can combat EAB even more effectively than their lingering ash parents. Forest Service researchers are collaborating with university partners to integrate genomics tools like those developed by the Hardwood Genomics project into the green ash breeding program to accelerate restoration of green ash in EAB-impacted landscapes throughout the United States.

Contacts

• Jennifer Koch, Research Biologist

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Analysis of Eastern Hemlock Conservation Options

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Researchers combined hemlock trees' genetic information with distribution modeling to give land managers a better understanding of the options for conservation of this imperiled species

Because some tree species ranges span large regions, they show variations in their behavior (e.g., timing of spring bud burst) and morphology (e.g., leaf shape), due to environmental differences. These within-species variations have developed over long periods of time and hence imprinted in their genetic signature resulting in different evolutionary lineages. Eastern hemlock genetic clusters, previously derived from molecular markers, were subdivided into four genetic zones: the Northwest, Northeast, Southwest and Southeast. These genetic zones, which represent putative evolutionary lineages, were used to understand ecological and genetic differences using environmental and demographic data. Current and future habitat suitability and colonization potential of these genetic zones were modeled. The results show that future habitats decline markedly, with areas of relatively higher habitat quality and colonization potential confined to the Southeast, the genetic zone nearest the species' putative glacial refugia. The Southeast zone is also the region of highest HWA induced mortality, pointing to the need to focus our conservation efforts on this ecologically and genetically important region.

Contacts

• Anantha Prasad, Research Ecologist

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