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Forest Disturbance Processes

Air, Water, and Soils Pollution

Air pollution has been a serious problem for the forests of the Northeast (especially those at high altitudes), which are downwind of the industrial heartland. The chief agent of environmental damage is acid deposition, or acid rain as it is commonly known. This phenomenon occurs when emissions of sulfur dioxide (SO2) and oxides of nitrogen (NOx) react in the atmosphere with water, oxygen, and oxidants to form various acidic compounds. These compounds then fall to the earth in either dry form (such as gas and particles) or wet form (such as rain, snow, and fog). Thus, polluted air can damage trees directly in the dry form or indirectly through its affects on the chemistry of water and soils and by making trees more vulnerable to other biological and environmental stressors. More specifically, acid rain weaken trees by damaging their leaves, limiting the nutrients available to them, or exposing them to toxic substances slowly released from the soil. Acid rain that flows into streams, lakes, and marshes also has serious ecological effects. In watersheds where soils do not have a buffering capacity, acid rain releases aluminum, which is highly toxic to many species of aquatic organisms, from soils into lakes and streams. NRS scientists are study the problems of pollution at many levels, from cellular biochemistry to landscape-level ecology.

Selected Research Studies

Agroforestry Phytoremediation Buffer Systems in the Great Lakes Basin
Agroforestry phytoremediation buffer system in southeastern Wisconsin. Photo by Paul Manley, Missouri University of Science and Technology; used with permission.Since 2010, the GLRI has funded over 5,000 projects throughout the basin. One of these projects led by Northern Research Station scientists involves development of the world’s largest regional phytotechnologies network consisting of 16 agroforestry phytoremediation buffer systems (i.e., phyto buffers) in the Lake Superior and Lake Michigan watersheds.


Prioritizing Landfill Contaminants for Environmental Remediation
Phytoremediation landfill planting (foreground) at a municipal solid waste landfill (background). USDA Forest Service photo by Ron Zalesny.The composition of landfill leachate is dynamic, changing over time and space due to chemical, physical, and societal factors. Thousands of potentially harmful contaminants can exist within leachate, making it difficult to objectively determine which contaminants at a site to target with remediation activities. Therefore, there is a need for a method that quantitatively prioritizes landfill contaminants for remediation.


Nitrogen Pollution Moving Through Forests Faster Than Expected
Forest stream. Photo credit: Stephen Sebestyen, USDA Forest Service.Researchers with the Northern Research Station and their collaborators have developed a web-based tool that will allow land managers in New England and the Great Lake states to more easily and accurately predict air quality impacts on their forests.


Website Maps Air Pollution Threats To Forests
Screenshot from featured website - map of northeastern USA shows nitrogen deposition and paper birch critical loads.Researchers with the Northern Research Station and their collaborators have developed a web-based tool that will allow land managers in New England and the Great Lake states to more easily and accurately predict air quality impacts on their forests.


[photo:] Two-year-old poplar root system following harvesting of a field testing cycle during phyto-recurrent selection.Phyto-Recurrent Selection: A Method for Selecting Genotypes for Phytotechnologies
The success of certain phytotechnologies has prompted the use of wastewaters as a combination of irrigation and fertilization for woody crops such Populus species and their hybrids (i.e., poplars). A common protocol for such efforts has been to utilize a limited number of readily-available genotypes with decades of deployment in other applications, such as fiber or windbreaks. However, it is possible to increase phytoremediation success with proper genotypic screening and selection, followed by the field establishment of clones that exhibited favorable potential for clean-up of specific contaminants. While such efforts are limited for environmental remediation, centuries of plant selection success in agronomy, horticulture, and forestry validate the need for similar approaches in phytotechnologies. 


Development of Improved Mycorrhizal Fungi for Use in Reforestation and Reclamation of Mined Lands
We are testing several known mycorrhizal fungi for their ability and efficacy to support survival and growth of seedlings planted in reclaimed sites. Every year we have been generating Virginia pine seedlings inoculated with various fungi and planting them in reclaimed abandoned mine site locations in Ohio. Qualitative and quantitative measurements are being made to assess fungi that aid survival and growth of seedlings.


[photo:] [photo] Kimble creek water affected by acid mine drainage has low pH and high concentrations of iron, aluminum and manganese.Development of Improved Bacterial Based Water Treatment Systems to Remove Heavy Metal and Other Hazardous Contents, and Increase the pH of the Water
Abandoned coal mine sites have often been responsible for the acid mine drainage (AMD), a serious polluter of ground water supplies. The materials released by AMD include heavy metals (such as iron, aluminum, and manganese), other hazardous substances, and acidity that is harmful to aquatic life. Improved economical methods are needed to remove these substances from water to prevent detrimental effects on forest health.


[photo:] Watershed 3, Fernow Experimental Forest.  Treated watershed for the Fernow Watershed Acidification Study, started in 1989, one of only 2 whole-water acidification studies in the U.S. Air Pollution and Sustainable Forest Ecosystems
In our research, we monitor acidic deposition falling in the central Appalachians and study its effects as its moves through the forest, from tree canopy to the soil and soil solution to streams.  We are studying the effects on nutrient cycling, and tree growth and productivity, and on a number of other ecosystem components. 


[photo:] Natural Gas well on the Fernow Experimental Forest, summer 2009, immediately after restoration of the site. Understanding Effects of Oil and Natural Gas Development on Appalachian Forests
Rapidly increasing fuel prices have resulted in an economic climate that favors domestic energy development.  This is especially true in the mid- and northern-Appalachian region where the Marcellus shale formation is found in the bedrock. 


[photo:] Fall foliage in the mountains of Stowe, Vermont.  Photo by Paula MurakamiRed Leaf Color as an Indicator of Environmental Stress
Vistas of colorful fall foliage hold tremendous public and media interest, and associated tourism to the Northern Forest is estimated to add billions of dollars to the regional economy each year.  This natural spectacle of diverse leaf coloration is based on the physiology of leaf pigments.  In addition to its aesthetic value, the biology of one pigment (anthocyanin) may provide insights to how some trees survive environmental stress.


[photo:] Poplar planted in soils heavily contaminated with petroleum hydrocarbons. Acid Rain and Calcium Depletion
Acid rain and other anthropogenic factors can leach calcium (Ca) from forest ecosystems and mobilize potentially toxic aluminum (Al) in soils.  Considering the unique role Ca plays in the physiological response of cells to environmental stress, we propose that depletion of biological Ca would impair basic stress recognition and response systems, and predispose trees to exaggerated injury following exposure to other environmental stresses. 


[photo:] Poplar planted in soils heavily contaminated with petroleum hydrocarbons. Salt Tolerance and Salinity Thresholds of Woody Energy Crops Irrigated with High-salinity Waste Waters
There is a need for environmental practices that merge intensive forestry with waste management. Producing short rotation woody crops for energy, fiber, and environmental benefits requires adequate irrigation and fertilization, which can be supplied via waste waters including landfill leachate. Yet, leachate often contains elevated levels of salts such as chloride and sodium that cause leaf chlorosis and necrosis, decreased biomass accumulation, and increased mortality. Therefore, there is a pressing need to learn about the response of poplar energy crops when salts are taken up into root, leaf, and woody (stem + branch) tissues, as well as identifying thresholds of salt concentrations and salinity that can be recommended for these crops in both field testing and production plantations.


[photo:] Poplar planted in soils heavily contaminated with petroleum hydrocarbons. Using Short Rotation Woody Crops to Remediate Soils Heavily Contaminated with Petroleum Hydrocarbons
Organic contaminants such as petroleum hydrocarbons are a major pollution source of surface water, groundwater, soil, and sediments throughout North America and the rest of the world. The rhizosphere is the zone of soil surrounding plant roots. Utilization of plants and their rhizospheric microorganisms to destroy, remove, and stabilize contaminated soils is currently gaining global attention because such systems are efficient and effective from biological and economic standpoints.


[photo:] Poplar energy crops grown for biomass and used for waste water reuse and recycling. Sustainable Production of Woody Energy Crops with Associated Environmental Benefits
Increasing human population levels at regional, national, and global scales have heightened the need for proper management of residential and industrial waste. Contaminants from this waste stream have polluted water, air, and soil much faster than traditional technologies could remediate the problem. Therefore, we are combining intensive forestry and waste management methods to increase the potential for producing woody crops for energy and fiber, along with decreasing the environmental degradation associated with waste disposal and subsequent waste water production.


[photo:] This research examines whether nitrogen deposition effects on mycorrhizal fungi might be contributing to sugar maple decline. Nitrogen deposition effects on symbiotic fungi in northern hardwood forests
Atmospheric nitrogen deposition from fuel combustion and agriculture is falling from the air onto natural ecosystems, leading to changes in nutrient availability and acidification of soils and waters. Symbiotic fungi, called mycorrhizal fungi, are essential to tree nutrient uptake, and in some ecosystem types have been found to decline in abundances and diversity in response to nitrogen deposition, with possible negative effects on plant uptake of soil resources. We wanted to understand the impact of nitrogen deposition on the mycorrhizal fungi associated with sugar maple dominated northern hardwood forests in Michigan. Sugar maple decline has become a serious problem in our region. Understanding whether nitrogen deposition effects on mycorrhizal fungi might be contributing to this decline is critical to our ability to protect these forests.


[photo:] A class of symbiotic fungi associated with roots, called mycorrhizal fungi, provide trees with nutrients and water in exchange for sugars.Effects of CO2 and O3 on the communities of symbiotic fungi associated with aspen and birch roots
Elevated carbon dioxide (CO2) and ozone (O3) affect tree photosynthesis and growth in largely opposing ways, with CO2 increasing growth and O3 decreasing growth. These changes in growth can affect the amount of carbon going to roots. Associated with roots are a class of symbiotic fungi that provide nutrients and water in exchange for sugars.


[image:]   Burned area determined from multiple infrared heat release images taken from an aircraft during a prescribed fire in the Ohio Hills.Fuels and Fire Behavior in Eastern Hardwoods
An ability to predict fuel loads and fire behavior are needed to improve prescriptions for prescribed fire and answer questions about smoke emissions and transport and fire effects on flora and fauna. Our fuels and fire behavior research seeks to develop process-based (mechanistic) approaches to predicting fuel characteristics and fire behavior, with particular focus on hardwoods in Appalachian topography.


[image:] Status of weather anomalies around the U.S. in early 2002, compiled by the National Weather Service. Adapting Forests to Climate Change
Climate models have projected significant increases in temperature over the next century for the Northeast and Midwest.  Climate change will also affect rainfall patterns, but scientists cannot yet predict how regional rainfall patterns will change.  Growing seasons will lengthen further in both spring and fall.  According to the Intergovernmental Panel on Climate Change, there is very high confidence that the vulnerability of North America depends on the effectiveness and timing of adaptation and the distribution of coping capacity, which vary spatially and among sectors. Climate change will constrain North America’s over-allocated water resources, increasing competition among agricultural, municipal, industrial and ecological uses (very high confidence).


[photo:] An example of the effect of a freezing rain disturbance event on forest vegetation.Atmospheric Disturbance Climatology System
Understanding the spatial and temporal patterns of these and other climate variables throughout the region is important in developing effective land management strategies that can sustain our natural resources.


[image:] Total number of thaw-freeze occurrences over the north central and northeastern U.S. from 1950 to 1998, with a thaw-freeze event defined as maximum daily near-surface air temperatures exceeding or equaling 1 C for at least one day followed by daily minimum near-surface air temperatures equalling or falling below -10 C for at least one day in the succeeding ten days since the last day of thaw.Climatic Indicators of Forest Health
Managers often need frequent, updated assessments of current and developing conditions on which to base management decisions and respond to public concerns. No methodology has been developed to indicate when a forest population is at risk to specific local and regional climate and air pollution stressors.


[image:]  Aspen FACE Facility Free-air CO<sub>2</sub> and O<sub>3</sub> Enrichment Project Global Climate Change Research at Harshaw Research Farm, Harshaw WIFoliar biochemical indicators of environmental change and their relationship with site productivity
Methods are needed to assess the positive or negative impact of environmental pollution on forest productivity in an asymptomatic forest stand. A goal of several research groups in the Northern Research Station (NRS) is to develop a set of physiological and biochemical markers that can assess the early onset of stress in forests due to environmental factors, before injury is visible.


[photo:] Aerial view of the Forest-Atmosphere Carbon Transfer and Storage (FACTS-II) study site near Rhinelander, WI, where the impacts of elevated carbon dioxide and ozone concentrations on forest microclimates are being studied along with may other climate-change related studies.Greenhouse Gas Impacts on Forest Microclimates
Our ability to predict the future impacts of increasing greenhouse gas concentrations and associated changes in the climate system on forest ecosystems requires an understanding of how vegetation responses to increased greenhouse gas concentrations can further alter the local atmospheric environment within forest ecosystems.  It is this local atmospheric environment that governs many of the basic physical and biological processes within forest ecosystems.


[Image] Graph of N and S deposition.  X-Axis: N Deposition, Y-Axis: S Deposition.  flat line and then a 45 degree angle downCritical Loads Resources for Federal Land Managers
The critical load is scientifically determined based on expected ecosystem response to a given deposition level.  The target load is set by policy makers, land managers, or air regulators to protect sensitive ecosystem components.  The target load may be higher or lower than the critical load, and is based on the economic cost of emissions reductions, timeframe, and other considerations.

This website contains documents and information useful to Federal Land Managers and others for understanding calculations of critical loads for nitrogen and sulfur deposition to forest ecosystems in theory and practice.


image: Weir in Hubbard Brook Experimental ForestHubbard Brook Experimental Forest
Environmental concerns about pollution in New England forests and streams include nitrogen saturation, cation depletion (that is, the effects of acid rain), and salt loads (from winter road sanding) in spring run-off. NRS scientist are engaged in short- and long-term research on pollution effects on ecological processes at the Hubbard Brook Experimental Forest (HBEF) Research Watershed. Scientific research began at the HBEF in 1960 with the small-watershed model, which measures precipitation and many other water characteristics to study nutrient cycling. A joint research program with Dartmouth College was established in 1963 and funded by the National Science Foundation (NSF). Then, in 1988 the HBEF was designated as a Long-Term Ecological Research (LTER) site by the National Science Foundation. On-going cooperative efforts among diverse educational institutions, private institutions, government agencies, foundations and corporations have resulted in one of the most extensive and longest continuous data bases on the hydrology, biology, geology, and chemistry of natural ecosystems. The occurrence of acid rain was first measured here. Now, almost 40 years later, these measurements are still being taken and old samples are being studied by new methods.


PhotoEastern Area Modeling Consortium
The Eastern Area Modeling Consortium (EAMC) is a multi-agency coalition of researchers, fire managers, air-quality managers, and natural resource managers at the federal, state, and local levels. As part of this group, NRS researchers are working to (1) increase understanding of fire behavior and smoke dispersion; (2) expand knowledge of the physics of fire–atmosphere interactions; (3) enhance prediction and response to the dangers of prescribed fires and wildfires; and (4) develop products and transfer new technologies related to national and regional fire-weather and air-quality dynamics. In addition, the EAMC provides two types of weather products for fire managers: maps showing current and future weather patterns over various regions of the United States and time series products indicating likely weather changes in at a given location over a 48-hour period.


[photo:] Tower used in fire research at Silas Little Experimental ForestFire and Fuels Research at the Silas Little Experimental Forest
The Silas Little Experimental Forest was reinstated using National Fire Plan funding in 2003 to conduct multi-disciplinary fire and atmospheric science research to provide fire and forest managers with better tools for predicting fire danger, fire risk, air quality, and ecosystem functioning under changing environmental conditions. 


[image:] Map of predicted losses of nitrogen from forested lands of the Chesapeake Bay watershed under no nitrogen deposition, current nitrogen deposition, and doubled nitrogen deposition (Pan et al. 2004).Mid-Atlantic Forests and the Chesapeake Bay Watershed
Forest landscapes are changing as a consequence of climate and environmental change. These changes affect people and the forest ecosystems they depend on for clean water, clean air and forest products, and recreation. How can we best manage our forest resources to sustain this array of ecosystem services under increasing environmental stress and a changing climate?


As a result of fossil fuel combustion, mercury pollution occurs across the globe, even in remote areas. Once mercury is released into the environment it changes into methylmercury, a highly toxic compound that is easily taken up in living tissue. It builds up over time and causes serious neurological and reproductive disorders in humans and wildlife. Since mercury does not break down in the environment, it has become a significant health threat to humans and wildlife and 40 states have fish consumption advisories due to mercury contamination. Loons, bald eagles, and fish from the State of Maine, for example, have some of the highest levels in the nation and the Maine Department of Health has issued warnings about eating ANY fish caught in the state. NRS research aims at understanding how mercury gets into surface waters and if there are watershed management techniques that could reduce these inputs. Our mercury work is focused on two main efforts, one to characterize the mercury cycle under increased sulfate deposition and a second to understand the influence of prescribed fire on mercury cycling.


image: Cross section of vegetation and the soil beneath it.Acid deposition
Recently, this research has focused on understanding how acid deposition (aka acid rain), nitrogen pollution, and climate change may contribute to the declines of important tree species such as red spruce, sugar maple, and yellow-cedar. However, studies also include basic research into the biochemistry and physiology of tree stress response mechanisms, including evaluations of the possible use of red fall leaf coloration as an indicator of stress exposure and response. Pollutant additions of nitrogen (N) can lead to N-saturation (the accumulation of N in excess of plant and microbial demands), which has been linked with forest decline and is probably associated with N-induced imbalances in other nutrients (especially Ca, Al, and Mg). This work on nitrogen showed that the same mechanism of physiological disruption found for acid rain impairment (significant reductions in mCa, membrane stability, cold tolerance, and an increased rate of freezing injury) also applies to chronic N additions. These findings suggest that N additions can contribute to the same reduction of biological Ca reserves that acid rain depletes. New research on the broader significance of Ca depletion indicates that the same disruptions documented for red spruce can occur for other tree species (e.g., eastern hemlock, balsam fir, and white pine), and that soil-based Ca manipulation can also alter critical mCa stocks.


Calumet: An Ecological & Economic Rebirth
Although the region is a classic rustbelt, many industries still thrive there. The remaining natural areas draw recreationists who hope to see the rare bird, catch the big fish, or just enjoy the outdoors. Calumet is undergoing an exciting revitalization. Our unit works with many partners to help local and regional planners and managers decide how to advance the region toward ecological and economic health.


image: Map showing simulated surface ozone concentrations over the Great Lakes region on May 30, 1999 at 3:00 pm EDT.  The red and pink color-filled contours indicate regions with ozone concentrations above 80 ppb.Developing atmospheric models to trace ozone through the midwest
NRS scientists are cooperating with scientists from the U.S. Department of Energy's Battelle Pacific Northwest National Laboratory in Richland, Washington, to simulate the dynamics of atmospheric ozone transport and diffusion over the western Great Lakes Region. These simulations are being conducted using a coupled atmospheric mesoscale and photochemistry model. The simulations allow us to see where ozone and ozone precursor chemicals are coming from, and where they are transported to throughout the northcentral U.S.


image: Sugar Maple in fall colors looking up from ground.Site, Stress, Nutrition, and Forest Health Interactions
A range of stressors including defoliating insects, pathogens, droughts, inadequate soil base cations, and changing climate have interacted to affect the health and regeneration of selected northern and central hardwood forest species. 


Last Modified: 04/16/2021