docResults of the Appalachian Trail MEGA
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Results of the Appalachian Trail MEGA
Results of the Appalachian Trail MEGA-Transect Atmospheric Deposition Effects Study G.B. Lawrence, T.J. Sullivan, D.A. Burns, S.W. Bailey, B. J. Cosby, M.Dovciak, H.A. Ewing, T.C. McDonnell, R. Minocha, R. Riemann, J. Quant , K.C. Rice, J. Siemion, K.C. Weathers Objectives • Determine status and susceptibility of AT corridor with respect to atmospheric dep - acidification 1. Model S and N dep 2. Measure soil and stream chemistry 3. Determine vegetation species composition and health 4. Map soil and water acid-base condition 5. Develop, analyze and map acidification critical loads, target loads, and exceedances 6. Use CLs, TLs and exceedances of S and N deposition to identify thresholds of air pollutant deposition to protect key ecosystem elements from harm Project Field Sampling Design Tier Sites Measurements Level 1 12 S and N deposition (4 sites) Soil chemistry Stream chemistry Plant communities tree biochemistry Level 2 48 Soil chemistry Stream water Plant communities (18 sites) Level 3 205 Stream water AT Level 1 and 2 Sample Sites ! Gulf Hagus Sugarloaf ! ( ! ! ! ! Crawford Notch ! ! ! Sherburne Pass ! ( ! Kelly Stand ! ! ( ! ! ! ! ! Deleware Water Gap ! ! ! ! ( ! ! ! ! ! Piney River ! ! ( ! !! ! White Oak Run ! ! ( ! ! ! ! ! Whitetop ! ! ( Cosby Creek Upper Road Prong ! ! ( ! ! ( Coweeta ! ! ( ! !! ! ! ( ! ! ( ! ! Modeled Sulfur Deposition Level 1 Soil Sampling Level 2 Soil Coring Processing Soil Cores Stream ANC Map Magic Modeling to Assess Future Recovery Potential Modeled deposition scenarios Scenario Number Scenario ID Scenario Description Scenario 1 Base Case Continued ambient S and N deposition Scenario 2 (-25% S,N) 25% Reduction in S and N deposition Scenario 3 (-50% S,N) 50% Reduction in S and N deposition Scenario 4 (-75% S,N) 75% Reduction in S and N deposition Scenario 5 (-90% S,N) 90% Reduction in S and N deposition Scenario 6 (+25% N) 25% Increase in N deposition Selected sensitive criteria, critical values, and endpoint years for critical and target load simulations Receptor Stream Stream Soil Soil Solution Sensitive Criterion ANC NO3BS Ca:Al Critical Values 20, 50, 100 µeq/L 10, 20 µeq/L 5, 10, 12, 20% 1, 10 Endpoint Years 2050, 2100, 3000 2050, 2100, 3000 2050, 2100, 3000 2050, 2100, 3000 RESULTS Soils and Stream Water Soils - Level 1 and 2 Sites Upper B horizon Aluminum Mobilization Stream ANC Statistics Description Sites Mean (µeq/L) Median (µeq/L) Std. Dev. (µeq/L) < 0 µeq/L (%) 0 – 50 µeq/L (%) North 98 50.5 19.1 67.1 16.3 50.0 Central 94 64.2 33.3 76.9 11.7 51.1 South 74 71.2 49.3 71.9 1.4 50.0 ANC – high, medium, low flow Data Set Mean Median Averaged 61.1 35.4 Q85 49.7 23.0 Q50 73.5 38.9 Q15 97.3 53.9 Modeling Results: Predicting Future Conditions TL Exceedance ANC = 50 µeq/L by 2100 Region +15% or more +15% to -15% -15% or less North 43% 5% 52% Central 33% 6% 61% South 50% 5% 45% Total 43% 5% 52% Soil Base Saturation North Soil Base Saturation Central Soil Base Saturation South TL Exceedance BS = 12% by 2100 Region +15% or more +15% to -15% -15% or less North 41% 0% 59% Central 42% 0% 58% South 43% 0% 57% Total 42% 0% 58% Key Findings 1. Variation in landscape acid buffering is more important than acid rain levels. 2. Soils were Ca depleted to the point of Al mobilization at 60% of sites. 3. North: 16% of streams severely acidic; 50% of streams moderately acidic. South: 1.4% of streams severely acidic; 50% of streams moderately acidic. ANC depressions averaged 40 µeq L-1 during episodes. 4. Acidic deposition effects on plant communities were expressed through ecosystem relationships, not simple cause and effect. 5. Measures of tree metabolism were related to soil conditions, but these responses were also influenced by ecosystem relationships. 6. Target loads of S needed for ecosystem protection were exceeded in 2100 under 2005-2009 deposition levels at sites distributed over the full AT. Rangely Lake, ME Acknowledgements Retirees: Tony Federer, Jim Lynch, Jake Peters Field assistants: Paul Beaver, Briana Boaz, and Celesta Collacchi Reports • Detailed report and two fact sheets available • Available at -https://www.researchgate.net/profile/Dougla s_Burns/publications • Current link to US NPS site seems to be broken
