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Nitrogen and Sulfur Deposition Studies


Pear Lake - an alpine lake sensitive to nitrogen deposition, Sequoia/Kings Canyon National Park, CA

Nitrogen and sulfur compounds emitted into the atmosphere are eventually deposited to ecosystems and can cause acidification of soils and waters or, in the case of nitrogen, unwanted fertilization. Acidification or fertilization can result in altered plant and animal communities, loss of species, and other harmful ecosystem changes. Many national parks are sensitive to nitrogen and sulfur deposition and changes due to deposition have been documented in parks. The National Park Service monitors nitrogen and sulfur deposition and is conducting studies to examine the effects of deposition on park resources. The studies described below represent many of the recent and current deposition-effects projects that the NPS has initiated.

RoMANS - Rocky Mountain Atmospheric Nitrogen and Sulfur Study

The Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study was designed to investigate both nitrogen and sulfur wet and dry deposition and to determine the most important species and pathways contributing to nitrogen deposition. Gas and particle concentrations were measured and precipitation samples were collected to gain a better understanding of nitrogen and sulfur transport to and deposition in Rocky Mountain National Park (NP). Samples were collected at 12 sites across the state of Colorado in March and April 2006 and at 13 sites in north central Colorado in July and August 2006. Historical data suggest that these are the seasons when nitrogen deposition in Rocky Mountain NP is greatest. Rocky Mountain NP is experiencing a number of adverse effects due to atmospheric nitrogen and sulfur compounds. Airborne nitrate and sulfate particles contribute to visibility degradation in the park while nitrogen deposition is producing changes in ecosystem function and surface water chemistry.

RoMANS Final Report 2009 » 

Atmospheric Deposition in Complex Terrain: Scaling up to the Landscape in Acadia and Great Smoky Mountains National Parks

Monitoring equipment such as that used for NADP and CASTNet Networks are often used to determine deposition loadings to parks, however it is difficult to determine whether this data, collected at just one or two locations, is a good spatial representation of deposition loadings across park elevations and ecosystems. The deposition data normally collected also does not include pollutants deposited by clouds or fog. This study uses deposition and soils data collected systematically throughout the parks to model deposition patterns of pollutants. The output includes geographic information system (GIS) maps of total (wet+ dry+ cloud/fog) sulfur and nitrogen deposition for Acadia and Great Smoky Mountains National Parks. Results show that deposition varies by elevation and vegetation type in the parks; that the variability can be large (7-fold) between sites within a park, and that deposition is much higher (50% at Acadia) than total deposition determined by existing NADP and CASTNet monitoring stations in the park. The Principal Investigator for this project is Dr. Kathie Weathers at the Institute for Ecosystem Studies. A final project report was completed in 2007 entitled "Scaling up to the landscape: empirical modeling of atmospheric deposition in mountainous landscapes".


Weathers, Kathleen; Simken, Samuel; Lovett, Gary, and Lindberg, Steven. Empirical Modeling of Atmospheric Deposition in Mountainous Landscapes. Ecological Applications. 2006; 16(4)1590-1607.

Modeling the Timeline for Acidification for Excess Nitrogen in Rocky Mountain National Park:

This study links ecosystem models and nitrogen cycling models to estimate how much nitrogen deposition over various timeframes that it would take to cause chronic or episodic acidification of sensitive lakes in the park. The model is being tested against a rich data set available from Loch Vale watershed in Rocky Mountain National Park that includes wet deposition, meteorology, forest biomass and nutrient ratios, soil microbial activity, soil chemistry, stream discharge, and stream chemistry for a 20 year period. Principal Investigators are Dr. Jill Baron from the U.S. Geological Survey and Dr. Dennis Ojima from Colorado State University. A final report for the project entitled "Modeling the Timeline for Acidification from Excess Nitrogen Deposition in Rocky Mountain National Park" was completed in 2005.

Study of the Effects of Atmospheric Pollutants on Invasibility of Panne Vegetation by Invasive Plants at Indiana Dunes National Lakeshore:

Indiana Dunes National Lakeshore is located at the southern tip of Lake Michigan, in one of the most industrialized areas in the United States. Pollutants from this area are routinely deposited in Indiana Dunes by wet and dry deposition. Pannes are small, nutrient limited wetland complexes, located between the dunes. They contain important habitat for many sensitive amphibian, reptile, insect, and plant species. This study uses field measurements to determine current levels of heavy metals and nitrogen in pannes, and to determine threshold levels of metals and nitrogen that increase susceptibility of panne vegetation to invader plant species. This study began in 2003. Principal Investigators are Dr. Daniel Mason from the National Park Service, and Dr. Gabriel Filippelli from Indiana University-Purdue University.

Impacts of Atmospheric Nitrogen and Climate Change on Desert Ecosystems in Big Bend National Park:

Ongoing research at Big Bend shows that soil and microbial processes are key determinants of the ecosystem's resistance and resilience to atmospheric pollutants. Research in the park also shows a rapid, major decrease in soil pH in Big Bend grasslands. While NO3 and NH4 deposition in the park is low compared to other parts of the country the amount it receives may be sufficiently increased over natural levels to initiate significant changes in soils and grasses. In addition, global climate models predict changes in precipitation patterns in the Chihuahuan Desert that could have significant effects on soil-plant relationships. The study assesses how increased seasonal precipitation, nitrogen deposition and soil pH changes may alter soil microbial and nutrient dynamics in Big Bend within two key vegetation types along the Pine Canyon watershed. Grassland plots receive experimental additions of precipitation and nitrogen at levels that mimic realistic estimates of future nitrogen deposition scenarios. This study began in 2003 and the Principal Investigator is Dr. John Zak from Texas Tech University. A final report for the project entitled "Impacts of Atmospheric Nitrogen Deposition and Climate Change on Desert Ecosystems" was completed in 2006.

Impacts of Anthropogenic N Deposition on Weed Invasion, Biodiversity and Fire Cycles at Joshua Tree National Park:

Air pollution in Joshua Tree National Park is primarily in the form of nitrogen oxides and originates mainly from urban areas to the west. Nitric acid and ammonium are "plant available" forms of nitrogen that may be altering local vegetation by encouraging invasion of exotic weeds at the expense of native plants, thereby shifting plant species composition within creosote scrub and pinyon juniper woodlands in the park. There is also concern that increased amount of exotic grasses produced by this nitrogen fertilization could increase the fire frequency in the park. This project was initiated in 2003 and renewed in 2007 to examine the impacts of nitrogen deposition on the native plant communities along a deposition gradient in the park. This study compares results along the N deposition gradient in the park for (1) gaseous N and N deposition rates to plant and soil surfaces (2) exotic grass biomass in N-fertilized and unfertilized plots (3) assessing the relationships between soil N, exotic grass biomass, and plant biodiversity (4) root response to elevated nitrogen in fertilized and unfertilized plots. The Principal Investigators are Dr. Edith Allen at the University of California Riverside, and Dr. Andrzej Bytnerowicz at the USDA Forest Service Riverside Experiment Station. A final report for the project entitled "Impacts of Anthropogenic N Deposition on Weed Invasion, Biodiversity and the Fire Cycle at Joshua Tree National Park" was completed in 2006.

Publications: Allen, E. B. Rao L. E.; Steers, R. J.; Bytnerowicz, A., and Fenn, M. E. Impacts of Atmospheric Nitrogen Deposition on Vegetation and Soils at Joshua Tree National Park. In Press.

Developing Screening Procedures and Sampling Protocols for Assessment of Deposition-Sensitive Surface Waters in the Rocky Mountains:

Developing Screening Procedures and Sampling Protocols for Assessment of Deposition-Sensitive Surface Waters in the Rocky Mountains:

This research is developing screening procedures and sampling protocols for the assessment of surface waters sensitive to atmospheric deposition in the Rocky Mountains, including Yellowstone National Park, Grand Teton National Park, Glacier National Park, Rocky Mountain National Park, and Great Sand Dunes National Park. Using GIS and multiple logistic regression, a model is being developed that relates known surface water concentrations to basin physical characteristics and loading from atmospheric deposition, to identify the aquatic ecosystems most likely to be at risk to pollution from atmospheric deposition. The results of the analysis are being validated through surface water sampling at sites in the five parks. Screening procedures developed for this project will be based on terrain and landscape information available to all participating parks. Because the screening procedure is based on available data, this is a pilot project that may be applicable to other National Parks with potentially sensitive surface waters. The principal investigator is Leora Nanus with the USGS and University of Colorado Boulder. A USGS Open File Report entitled "Sensitivity of Alpine and Subalpine Lakes to Acidification from Atmospheric Deposition in Grand Teton National Park and Yellowstone National Park, Wyoming" was developed under this project in 2005".

Characterize Aquatic Air Quality Related Values (AQRVs) Potentially Affected by Atmospheric Deposition and Develop Long-Term Monitoring Protocols to Track and Refine the AQRVs at Mt. Rainier and North Cascades National Parks:

This project is initiating an AQRV data base for air pollution sensitive lakes and streams in Mount Rainier National Park and North Cascades National Park. It will combine field data collections of snow, water, and aquatic biota, use of stable isotopes and analysis of an existing lake sediment core to begin assessment of dose-response relationships for the effects of deposition chemistry on aquatic systems in Mount Rainier and North Cascades National Parks. This project was initiated in 2004. Dr. Dave Clow at the US Geological Survey is the principal investigator.

Long-term Data on Alpine Plants: Is Atmospheric Nitrogen Affecting Species Composition in Rocky Mountain National Park and Glacier National Park?

This research evaluates whether species composition changes are occurring or may occur in the future in alpine communities, which are sensitive to changes in anthropogenically derived nutrients. Critical thresholds of alpine plant sensitivity to N input will be evaluated using experimental plots with a range of N fertilization levels (5, 10, and 30 kg N/ ha /yr) to obtain response curves for vegetation. The research is being conducted beginning in 2005 in Rocky Mountain and Glacier National Parks, representing sites with high and low rates of N deposition. Dr. William Bowman from the University of Colorado at Boulder is the principal investigator on this project.

updated on 05/20/2010  I   http://www2.nature.nps.gov/air/Studies/NSdeposition.cfm   I  Email: Webmaster