Skip to Main Content
Critical loads of sulfur and nitrogen and modeled effects of deposition reduction for forested ecosystems of Great Smoky Mountains National ParkAuthor(s): Linda H. Pardo; Natasha Duarte; Helga Van Miegroet; L. Suzanne Fisher; Molly J. Robin-Abbott
Source: Gen. Tech. Rep. NRS-180. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 26 p.
Publication Series: General Technical Report (GTR)
Station: Northern Research Station
Download Publication (921.0 KB)
DescriptionGreat Smoky Mountains National Park (GSMNP) is subject to high levels of sulfur (S) and nitrogen (N) deposition, which can adversely affect forest vegetation and aquatic biota. We used multiple chemical criteria to calculate critical loads for S and N deposition (CL (S+N)) and nutrient N (CLnutN) and used the Very Simple Dynamic (VSD) model to predict the effects of deposition reduction scenarios on critical thresholds for four forested sites in GSMNP. Critical loads were exceeded for current deposition at three of four sites using critical thresholds of aluminum to base cations (Al:Bc) = 0.1 or no decrease in base saturation but were not exceeded using the chemical criteria of Al = 0.2 meq L-1, Al:Bc = 1.0, and pH = 4.2. With deposition reductions of 48 percent S and 56 percent nitrate (NO3‾), neither the critical thresholds of acid neutralizing capacity (ANC) = 20 μeq L-1 nor a decrease in base saturation was achieved. With deposition reductions of 90 percent S and 90 percent NO3‾, ANC = 100 μeq L-1 was achieved at a single site. Historical ANC values affected a site's ability to achieve ANC critical thresholds. The critical threshold for soil solution NO3‾ was exceeded for all but the most stringent deposition scenarios (–90 percent S and –90 percent NO3¯). Deposition reductions of 90 percent for NO3‾ and 80 percent for ammonium (NH4+) were not sufficient to lower deposition below the CLnutN at all sites. Data indicate that upper sites at GSMNP are N saturated; to protect these sites from acidification, the more protective chemical criteria of no decrease in base saturation and Al:Bc = 0.1 should be used when determining critical loads. When choosing chemical criteria in deposition reduction modeling, care should be taken to ensure that the criteria chosen will protect sensitive ecosystem elements.
- Check the Northern Research Station web site to request a printed copy of this publication.
- Our on-line publications are scanned and captured using Adobe Acrobat.
- During the capture process some typographical errors may occur.
- Please contact Sharon Hobrla, firstname.lastname@example.org if you notice any errors which make this publication unusable.
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationPardo, Linda H.; Duarte, Natasha; Van Miegroet, Helga; Fisher, L. Suzanne; Robin-Abbott, Molly J. 2018. Critical loads of sulfur and nitrogen and modeled effects of deposition reduction for forested ecosystems of Great Smoky Mountains National Park. Gen. Tech. Rep. NRS-180. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 26 p. https://doi.org/10.2737/NRS-GTR-180.
Keywordscritical load, acidic deposition, exceedance, nitrate leaching, nitrogen saturation
- Effects of future sulfate and nitrate deposition scenarios on Linville Gorge and Shining Rock Wildernesses
- Target loads of atmospheric sulfur deposition for the protection and recovery of acid-sensitive streams in the Southern Blue Ridge Province
- Acidification and Prognosis for Future Recovery of Acid-Sensitive Streams in the Southern Blue Ridge Province
XML: View XML