Appalachian Trail MEGA-Transect Atmospheric Deposition Effects Study

Science Center Objects

The Appalachian Trail (AT), a 14-state footpath from Maine to Georgia, is a unit of the National Park Service that is cooperatively managed and maintained by the National Park Service (NPS), the Appalachian Trail Conservancy, AT Club volunteers, the USDA Forest Service, and other public land-management agencies. Upper elevation and ridge-top ecosystems, which comprise much of the trail corr...

 

The Appalachian Trail (AT), a 14-state footpath from Maine to Georgia, is a unit of the National Park Service that is cooperatively managed and maintained by the National Park Service (NPS), the Appalachian Trail Conservancy, AT Club volunteers, the USDA Forest Service, and other public land-management agencies.  Upper elevation and ridge-top ecosystems, which comprise much of the trail corridor, have been impacted by and remain extremely sensitive to acidic deposition.  Ridgetop soils that are often low in calcium make the ecosystems of the AT more sensitive to acidic deposition than other ecosystems.  Furthermore, upper elevations tend to receive the highest levels of deposition.  In areas along the AT, such as Great Smoky Mountains National Park (GRSM) in NC and TN, Shenandoah National Park (SHEN) in VA, Catoctin Mountain Research Site (CMRS) in MD and the White Mountain National Forest (WMNF) in NH and ME, acidic deposition has been identified as a primary environmental threat. 

The goal of this project is to establish the status and susceptibility of this publicly managed land with respect to acidic deposition, and collect data that will enable future changes to be identified.  Phase I of the project will entail a three-tiered sampling approach to collect soil, water, and vegetation data that are relatable to geographic information system (GIS) coverages for geologically-based acid sensitivity classes and atmospheric deposition, also to be developed as part of this project.  This design closely follows the conceptual framework of multi-level integrated monitoring and research developed by the Committee on Environment and Natural Resources of the National Science and Technology Council (CENR, 1997).  At 12 key sites, referred to as Level 1 sites, the full suite of measurements will be collected.  At 48 sites, referred to as Level 2, water chemistry and soil chemistry will be characterized; at an additional 200 Level 3 sites, only water chemistry will be characterized.   Considerations for site selection will include ecotype, elevation, latitude, atmospheric deposition, accessibility and park locations.  

In Phase II, the information collected in Phase I will be integrated using modeling and GIS tools that will enable extrapolation of acidification status over the entire AT.  As part of the extrapolation process, we will evaluate acid sensitivity (expressed as critical load and projected future acidification/recovery in response to deposition reductions) of first-order ephemeral stream locations sampled in this study compared with first- and second-order perennial streams previously modeled by members of the research team in areas close to the AT.  A series of maps of the acidification status for the AT corridor will be developed which reflect changes that have resulted from historical deposition, as well as sensitivity to future changes and critical load (CL).

 

A.      Problem Statement:

The Appalachian Trail (AT) is primarily situated along the Appalachian Mountain Range ridge top, which is subjected to high air pollution deposition levels. This high elevation zone is extremely sensitive to atmospheric deposition due to the limited buffering capacity of poorly developed or non-existent soils. Vegetative species, water chemistry, and wildlife dependent upon the physicochemical makeup of this environment are susceptible to deleterious change caused by air pollution. This study will define depositional inputs, susceptibility of the landscape to air pollution, and thresholds and recovery rates for changes due to acidic deposition.

 

B.      Background:

High elevation and ridge-top ecosystems along the AT corridor are very sensitive to acidic deposition. Air pollutants emitted by power plants, industry, vehicles, and agriculture can contribute to acidic deposition to forests, soils, streams, and lakes. Documented effects include forest die-back and streams that are no longer able to support certain sensitive species of fish. The overall purpose of this study is to evaluate the condition and sensitivity of the Trail with respect to acidic deposition by investigating current impacts and predict the time needed for ecosystem recovery under future deposition scenarios.

The research effort will provide necessary information on ecosystem effects and restoration potential along the entire Maine to Georgia trail area. Given climate change trends and predictions, it is important to evaluate how atmospheric deposition has impacted a variety of climatic zones in order to provide adaptation strategies to management scenarios. This study includes multiple areas within GRSM and SHEN and will provide information pertinent to changes in deposition effects for those park units along with a geographical distribution that describes a broad climatic expanse.

 

C.      Project Goals and Objectives:

The project goal is to establish the status and susceptibility of these publicly managed lands with respect to environmental change, and collect data that will enable future changes to be identified.  Our objectives are to collect (1) throughfall (water that passes through the canopy) in selected locations to further develop and verify a spatial deposition map of the A.T. that Weathers et al. currently have in progress, (2) soil samples to determine acidification status and concentrations of organic carbon and nitrogen, (3) water samples from nearby ephemeral streams to determine the base-cation surplus, a recently developed measure of ecosystem buffering that distinguishes between acidic deposition and confounding effects of natural organic acidity, (4) wood tissue for analysis of biochemical stress indicators, (5) tree cores to evaluate the growth history of canopy trees, and (6) data on understory vegetation that will be related to soil chemistry and acidic deposition levels.  Repeatable sampling methods will be used wherever possible to enable changes to be assessed over time through future sampling.   This information will be synthesized to produce a spatial representation of current conditions along the entire A.T., and provide modeling results to assess future conditions under varying deposition scenarios.