Effects of Future Sulfate 

and Nitrate Deposition Scenarios on 

Linville Gorge and Shining Rock

Wildernesses

United States Department of Agriculture

Forest Service

Research & Development

Southern Research Station

General Technical Report SRS-181

Katherine J. Elliott, James M. Vose, and William A Jackson
The Authors:

Katherine J. Elliott,Research Ecologist, Coweeta 

Hydrologic Laboratory, Center for Forest Watershed 

Science, SRS-4353, Southern Research Station, U.S. 

Department of Agriculture Forest Service, Otto, NC 

28763; James M. Vose, Research Ecologist and Project 

Leader, Center for Integrated Forest Science and 

Synthesis, Southern Research Station, U.S. Department 

of Agriculture Forest Service, Raleigh, NC 27695; 

and William A Jackson, Air Quality Specialist, Air 

Resources Program, Region 8, U.S. Department of 

Agriculture Forest Service, Asheville, NC 28804.

October 2013

Southern Research Station

200 W. T. Weaver Blvd.

Asheville, NC 28804

www.srs.fs.usda.gov

Cover: left: Lynville Gorge Wilderness; right: Shinning Rock Wilderness. From the 

collection of the U.S. Forest Service.

Product Disclaimer

The use of trade or firm names in this publication is for reader information and does not 

imply endorsement by the U.S. Department of Agriculture of any product or service. 
Effects of Future Sulfate and Nitrate 

Deposition Scenarios on Linville Gorge 

and Shining Rock Wildernesses

Katherine J. Elliott, James M. Vose, and William A Jackson

Introduction

Abstract

We used the Nutrient Cycling Model (NuCM) to simulate the effects of 

various sulfur (S) and nitrogen (N) deposition scenarios on wilderness 

areas in Western North Carolina. Linville Gorge Wilderness (LGW) 

and Shining Rock Wilderness (SRW) were chosen because they are high 

elevation acidic cove forests and are located on geologic parent material 

known to be low in base cations and thus sensitive to acidic deposition. We 

used five sulfate (SO4

2-) and nitrate (NO3-

) deposition scenarios to compare 

with the current (base case) deposition: Scenario 1, SO4

2- at 94 percent and 

NO3

-

 at 95 percent of current deposition; Scenario 2, SO4

2- at 58 percent and 

NO3

-

 at 63 percent; Scenario 3, SO4

2- at 42 percent and NO3-

 at 51 percent; 

Scenario 4, SO4

2- at 35 percent and NO3-

 at 48 percent; and Scenario 5, 

SO4

2- at 22 percent and NO3-

 at 48 percent. For both sites, soil exchangeable 

calcium (Ca2+) increased while exchangeable aluminum (Al3+) changed very 

little over the 90-year simulation period with greater reductions in SO4

2-

and NO3

-

 deposition; and the increase in soil exchangeable Ca2+ improved 

soil Ca/Al molar ratios. Soil solution SO4

2- was much lower at all soil depths 

with greater reductions in SO4

2- and NO3-

 deposition. This reduction in 

SO4

2- in solution resulted in greater soil solution acid neutralizing capacity 

(ANC). At LGW, soil solution ANC of shallow soil was improved with 

the deposition Scenarios 2-5 compared to current deposition. By 2040, 

solution ANC of deep soil had increased above 20 μeq L-1 for Scenarios 3-5 

at LGW suggesting that stream ANC will be improved as well with further 

reductions in acidic deposition. Soil and solution cation concentrations will 

be improved for both wildernesses based on Scenario 2; however, further 

reductions in acidic deposition (e.g., Scenario 5) will be needed to increase 

stream ANC to a level that could support trout and other fishes.

Keywords: Atmospheric deposition, calcium, forecasting, nitrogen, 

Nutrient Cycling Model, Southern Appalachians. 

introduction

The amendments to the Clean Air Act in 1977 and 1990 

(especially Title IV) have significantly reduced emissions of 

sulfur dioxide (SO2) and nitrogen oxides (NOx) emitted into 

the atmosphere. As a consequence, the quality of the air that 

people breathe has improved as the National Ambient Air 

Quality Standards have been revised as new scientific 

information demonstrated the standards needed to be 

strengthened in order to protect public health. The Clean 

Air Act amendments of 1977 also designated certain 

wildernesses, national parks, and national wildlife refuges 

as Class I areas. These federally mandated Class I areas 

receive special protection from new sources of air pollution 

that could adversely impact the air quality related values, 

especially visibility. The 1990 amendments (section 169B) 

directed the U.S. Environmental Protection Agency (EPA) to 

issue regional haze rules. EPA fulfilled this direction in 1999 

and implemented the Regional Haze Rule (64 FR 35713) to 

achieve the national goal of no human impact to visibility 

at the Class I areas by year 2064 set forth by the Clean Air 

Act amendments of 1977. In the Southeastern United States, 

the initial emphasis to make reasonable progress (by 2018) 

at achieving the national visibility goal will be to reduce 

SO2 emissions, which are the main contributor to visibility 

impairment. Sulfur dioxide goes through a chemical 

transformation in the atmosphere to form fine particles of 

sulfates that reduce visibility and are eventually deposited on 

the tree canopy and ground as dry deposition. Acidic sulfur 

and nitrogen compounds are also deposited in the rainfall 

and snow, and at high elevations in the Eastern United States 

there can be very high concentrations in the cloud and fog 

water. It is unknown if the currently planned emissions 

reductions of air pollution, especially SO2, will be sufficient 

to prevent or reverse the harmful effects from acidic 

deposition that have been reported at some wildernesses 

(Elliott and others 2008, Sullivan and others 2011a). In 

2012, the EPA Administrator determined that the scientific 

uncertainty in the protection that would be achieved with a 

multi-pollutant secondary standard for oxides of nitrogen 

and sulfur was too great to establish a secondary standard to 

protect the public’s welfare (such as aquatic biota) from the 

harmful effects of acidic deposition (http://www.regulations.

gov/#!documentDetail;D=EPA-HQ-OAR-2007-1145-0205). 

In this study, we used the Nutrient Cycling Model (NuCM) 

to simulate the effects of various sulfur (S) and nitrogen 

(N) deposition reduction scenarios to evaluate the potential 

Effects of Future Sulfate and Nitrate 

Deposition Scenarios on Linville Gorge 

and Shining Rock Wildernesses

Katherine J. Elliott,1 James M. Vose, and William A Jackson

1Katherine J. Elliott is the corresponding author. To contact, 

call (828) 524-2128 or email at kelliott@fs.fed.us.
2

Methods

benefits that may be achieved for two federally mandated 

Class I areas in the Southern Appalachians of Western 

North Carolina. Linville Gorge Wilderness (LGW) and 

Shining Rock Wilderness (SRW) were chosen because they 

are high elevation acidic forests and are located on geologic 

parent material known to be low in base cations (Elliott and 

others 2008, Sullivan and others 2011a) and thus sensitive 

to acidic deposition. As part of the Integrated Forest Study, 

NuCM was developed to synthesize current understanding 

of nutrient cycling in forests and to predict how forests 

respond to changing S and N atmospheric deposition rates 

(Johnson and Lindberg 1992, Liu and others 1991a, 1991b). 

The NuCM model links soil-solution chemical components 

with traditional conceptual models of forest nutrient cycling 

on a stand level (Liu and others 1991a). 

In an earlier study, Elliott and others (2008) used NuCM to 

simulate the effects of sulfur deposition on nutrient cycling 

at LGW and SRW. They simulated a 30-year period and 

used three sulfate (SO4

2-) deposition scenarios—50 percent 

decrease, current condition, and 100 percent increase—

but they did not include alterations of nitrate (NO3

-

) 

deposition. They suggested that even with large reductions 

in SO4

2- and associated acid deposition that it may take 

decades before these systems recover from depletion of 

exchangeable cations (Elliott and others 2008). In our 

paper, we build on this previous work by including further 

reductions of SO4

2- deposition, adding NO3-

 deposition 

reductions to the models, and running the simulations for a 

longer time period.

We used five SO4

2- and NO3-

 deposition scenarios outlined in 

Sullivan and others (2011b). The five scenarios were based 

on results developed by the Visibility Improvement State 

and Tribal Association of the Southeast (VISTAS) to specify 

the base case emissions control scenario and associated 

levels of future acidic deposition at modeling site locations 

(Sullivan and others 2011b). VISTAS used the EPA Models-3 

Community Multiscale Air Quality (CMAQ) modeling 

system (Byun and Ching 1999) and recently performed a 

technical analysis for the State, local, and tribal air quality 

agencies for ten Southeastern States (http://vistas-sesarm.org/

documents/FinalDocs.asp). For each scenario, we simulated a 

90-year period to forecast years 2010 to 2100. Our base case 

is the ambient deposition averaged from the last ten years of 

National Atmospheric Deposition Program (NADP) records 

(2002 to 2011). Future deposition scenarios used for our 

NuCM simulations and in previous studies modeling stream 

acid neutralizing capacity (ANC) (Sullivan and others 2004, 

2011b) were:

Methods

Study sites

LGW and SRW are located in the southern portion of the 

Southern Appalachian Mountains; and they represent two 

of the four wilderness areas in Western North Carolina. 

Detailed descriptions of location, vegetation, soils, and 

geology for LGW and SRW are provided (table 1). LGW is 

one of the few remaining large areas of old-growth forest in 

the Eastern United States. LGW is an oak-pine old-growth 

forest (table 2). The soils are derived from lower quartzite, 

a material low in base cations and potentially sensitive to 

acid deposition. More detailed descriptions of the vegetation, 

geology, and soils in these wilderness areas can be found 

in Newell and Peet (1995). The catchment size used for our 

sampling within LGW was 24 ha; five 20 x 20-m plots were 

located along a 400-m transect from near stream to upslope 

from a first order stream that drained into the Linville River. 

Recently, the hemlock woolly adelgid (Adelges tsugae 

Annand) has caused widespread mortality of the Carolina 

(Tsuga caroliniana Engel.) and eastern hemlock (Tsuga 

canadensis (L.) Carrière) trees throughout the wilderness.

SRW is a former red spruce (Picea rubens Sarg.) forest; it 

was harvested and then severely burned by wildfires twice 

(1925 and 1942) (Vanderzanden and others 1999). Following 

the fires, there was extensive soil erosion which had 

additional negative impacts on base cation availability. SRW 

is currently a mixed hardwood forest (table 2). The soils are 

derived from lower quartzite, a material low in base cations 

and potentially sensitive to acid deposition. More detailed 

descriptions of the vegetation, geology, and soils in these 

wilderness areas can be found in Newell and Peet (1996). 

Scenario 1—Reductions achieved under Title IV of the 1990 Clean 

Air Act Amendments—these were completed by 2006 (EPA/

CMAQ from EPA reports)—constant after 2006;

Scenario 1, SO4 at 94 percent, NO3 at 95 percent of base case.

Scenario 2—2005 Clean Air Interstate Rule (CAIR) (http://www.epa.

gov/cair/) in place for reductions from 2010–2020—EPA/CMAQ 

from National Acid Precipitation Assessment Program (NAPAP) 

2005;

Scenario 2, SO4 at 58 percent, NO3 at 63 percent of base case. 

Scenarios 3, 4, and 5—Reductions beyond CAIR based on additional 

rules, such as the 1999 Regional Haze Rule—EPA/CMAQ from 

NAPAP 2005; 

Scenario 3, SO4 at 42 percent, NO3 at 51 percent of base case. 

Scenario 4, SO4 at 35 percent, NO3 at 48 percent of base case.

Scenario 5, SO4 at 22 percent, NO3 at 48 percent of base case.
3

Methods

The catchment size used for our sampling within SRW was 

62 ha; five 20 x 20-m plots were located along a 400-m 

transect at about 70-m intervals parallel to Greasy Cove 

Prong Creek (Elliott and others 2008). 

The two wilderness areas differ in forest structure, species 

composition, and disturbance history. LGW is dominated by 

chestnut oak (Quercus montana Willd.), pitch pine (Pinus 

rigida Mill.), white pine (Pinus strobus L.), red maple (Acer 

rubrum L.), and sourwood (Oxydendrum arboreum (L.) 

De Candolle) with a less dense understory of evergreen 

rhododendron (Rhododendron maximum L.) and mountain 

laurel (Kalmia latifolia L.) than SRW (table 2). SRW is 

dominated by yellow birch (Betula alleghaniensis Britt.), 

red maple, mountain winterberry (Ilex montana Torrey 

& Gray), and pin cherry (Prunus pensylvanica L.) with a 

dense understory of evergreen and deciduous rhododendron 

species. For SRW, the last large-scale disturbance in 1942, 

a stand replacing fire, initiated the conversion from a P. 

rubens dominated forest to the present forest composition 

and structure (Vanderzanden and others 1999). Currently, the 

forest is comprised of northern hardwoods species that have 

a windswept character, low stature and multiple branching 

pattern, and P. rubens is only a minor component of the 

forest community (table 2). The presence of the pine species 

at LGW contributed to the accumulation of forest floor mass 

(table 1). The recalcitrant evergreen litter at both LGW and 

SRW has contributed to the soil and soil solution acidity at 

these sites (tables 3 and 4).

Model Parameterization and Data Collection

Most of the model input data were derived from 

measurements taken at the five plots within LGW and 

SRW (Elliott and others 2008). Climate data were 

obtained from the National Climatic Data Center/National 

Oceanic and Atmospheric Administration (NCDC/

NOAA) climate station closest to each wilderness. For 

a complete description of data requirements for model 

parameterization see Munsen and others (1992). In brief, the 

NuCM model requires five input data files to parameterize 

the model for a simulation. These data input files include 

physiographic, chemistry, meteorologic, deposition, and 

soil temperature. The meteorologic, deposition, and soil 

Table 1—Site description of Linville Gorge Wilderness and Shining Rock Wilderness in Western 

North Carolina, USA

Linville Gorge Wilderness Shining Rock Wilderness

Location Burke County in NC Haywood County in NC

Mountain Range Grandfather Mountains Great Balsam Mountains

Size 4390 ha 7400 ha

Latitude 35.50 to 35.58 35.17 to 35.28 

Longitude 81.56 to 81.52 82.59 to 82.47

Elevation 1090 – 1160 m 1450 – 1550 m

Geology Lower quartzite Mica gneiss

Soils Typic Dystrochrepts; 

Soco-Ditney series complex Typic Haplumbrepts; Wayah series

Climate

Max temperatures 21 – 27 °C 27 – 30 °C

Min temperatures 14 – 17 °C 11 – 18 °C

Annual precipitation 1250 – 1625 mm 1025 – 1825 mm

Vegetationa Acidic cove and slope (Quercus 

montana, Pinus rigida, Pinus strobus)

High elevation, mixed hardwood; 

subtype of northern hardwood forest 

(Betula alleghaniensis, Acer rubrum)

Mean DBH of overstory (range) 18.0 cm (5.0 – 71.1 cm) 12.8 cm (5.0 – 44.1 cm)

Aboveground mass 167 Mg ha-1 119 Mg ha-1

Forest floor mass 10,063 g m-2 1,900 g m-2

Root mass 1,000 g m-2

aLinville Gorge, community type 3.1 (Newell and Peet 1995). Shining Rock, community type 5.2 (Newell and Peet 1996).
4

Methods

Table 2—Species composition, density (stems ha-1), and basal area (BA; m2 ha-1) of the overstory (stems 

≥ 5.1 cm dbh) and understory (stems < 5.1 cm dbh, > 0.5 m height) in order of descending basal area for 

Linville Gorge and Shining Rock Wildernesses in Western North Carolina, USA

Linville Gorge Wilderness

Overstory Density BA Understory Density BA

Quercus montana Willd. 90 6.15 Rhododendron maximum L. 450 0.42

Pinus rigida Miller 50 5.26 Kalmia latifolia L. 380 0.36

Pinus strobus L. 35 4.15 Lyonia ligustrina (L.) DC. 245 0.07

Acer rubrum L. 110 2.54 Tsuga canadensis (L.) Carr. 40 0.01

Oxydendrum arboretum (L.) DC. 185 2.51 Oxydendrum arboretum (L.) DC. 35 0.01

Nyssa sylvatica Marshall 135 2.30 Symplocos tinctoria (L.) L’Hér 20 0.01

Sassafras albidum (Nutt.) Nees. 190 2.10 Pinus strobus L. 5 0.01

Tsuga canadensis (L.) Carr. 25 2.01 Nyssa sylvatica Marshall 5 0.01

Magnolia fraseri Walter 10 0.36 Amelanchier laevis Wieg. 5 0.01

Quercus coccinea Muenchh. 10 0.30 Sassafras albidum (Nutt.) Nees. 15 <0.01

Hamamelis virginiana L. 55 0.22 Acer rubrum L. 5 <0.01

Amelanchier laevis Wieg. 15 0.19 Rhododendron catawbiense Michx. 5 <0.01

Castanea dentata (Marshall) Borkh. 15 0.09 Hamamelis virginiana L. 5 <0.01

Symplocos tinctoria (L.) L’Hér 10 0.04

Quercus rubra L. 5 0.02

Shining Rock Wilderness

Overstory Density BA Understory Density BA

Betula alleghaniensis Britton 280 4.22 Rhododendron maximum L. 715 1.42

Acer rubrum L. 45 2.64 Vaccinium simulatum L. 225 0.16

Ilex montana (T. & G.) A. Gray 700 2.40 Ilex montana (T. & G.) A. Gray 380 0.14

Prunus pensylvanica L. f. 245 2.37 Rhododendron catawbiense Michx. 90 0.08

Amelanchier laevis Wieg. 55 0.75 Rhododendron calendulaceum (Michx.) Torr. 220 0.07

Picea rubens Sarg. 5 0.53 Clethra acuminata Michx. 170 0.05

Acer saccharum Marshall 5 0.38 Betula alleghaniensis Britton 55 0.02

Betula lenta L. 5 0.12 Kalmia latifolia L. 10 0.04

Acer spicatum Lam. 5 0.02 Viburnum nudum (L.) var. cassinoides (L.) T. & G. 20 <0.01

Rubus argutus Link. 20 <0.01

Prunus pensylvanica L. f. 10 <0.01

Source: Linville Gorge and Shining Rock vegetation data from Elliott and others (2008). 
5

Methods

Table 3—Soil chemistry for Linville Gorge and Shining Rock Wildernesses in Western North Carolina, USA 

Linville Gorge Wilderness (LGW) Shining Rock Wilderness (SRW)

A-horizon

(0-15 cm depth)

AB-horizon

(15-35 cm depth)

B-horizon

(35-65 cm depth)

A-horizon

(0-20 cm depth)

AB-horizon

(20-60 cm depth)

B-horizon

(60-90 cm depth)

pH 3.45 (0.15) 3.91 (0.09) 3.95 (0.07) 3.41 (0.14) 3.85 (0.06) 4.11 (0.08)

NO3

- 0.0003 (0.0003) 0.0003 (0.0003) 0.0002 (0.0001) 0.003 (0.002) 0.001 (0.001) 0.0003 (0.0002)

NH4

+ 0.005 (0.001)b 0.006 (0.001)b 0.004 (0.001)b 0.024 (0.008)a 0.018 (0.005)a 0.013 (0.002)a

PO4

2- 0.011 (0.003) 0.004 (0.001) 0.003 (0.001) 0.010 (0.003) 0.003 (0.001) 0.003 (0.001)

K+ 0.116 (0.013) 0.082 (0.008) 0.063 (0.006) 0.162 (0.021) 0.090 (0.014) 0.059 (0.006)

Na+ 0.009 (0.001) 0.007 (0.001) 0.006 (0.001) 0.018 (0.003) 0.016 (0.001) 0.014 (0.001)

Ca2+ 0.039 (0.005)b 0.022 (0.004)b 0.018 (0.006)b 0.451 (0.070)a 0.161 (0.030)a 0.099 (0.020)a

Mg2+ 0.093 (0.007)b 0.043 (0.003)b 0.030 (0.004) 0.303 (0.068)a 0.109 (0.006)a 0.060 (0.004)

SO4

2- 0.305 (0.104)b 0.556 (0.156) 0.404 (0.134) 0.187 (0.006)a 0.328 (0.012) 0.437 (0.008)

Al3+ 5.935 (0.658) 4.760 (0.473) 4.430 (0.571) 5.490 (1.316) 5.329 (0.408) 3.588 (0.757)

ECEC 6.84 (0.23)b 6.81 (0.40)b 5.46 (0.62)b 11.06 (1.64)a 10.29 (0.66)a 7.85 (0.56)a

Note: Standard errors are in parentheses. All values are in cmolckg-1 except soil pH. Values within a soil horizon depth followed by different letters 

denote significant differences (α=0.05) between sites. Data from Elliott and others (2008). Exchangeable cations were extracted from 10 g of 

soil on a mechanical vacuum soil extractor using 50 ml of 1 M NH4Cl. Solution concentrations of Ca2+, Mg2+, K+, and Al3+ were determined with a 

Jobin Yvon Ultima Inductively Coupled Plasma Spectrometer (Horiba Inc., Edison, NJ) (Clescerl and others 1999). Following the initial 12-hour 

extraction excess NH4Cl was removed from the soil interstitial spaces with 95% EtOH. NH4

+-N on the soil exchange sites was then extracted with 

2 M KCl as a measure of effective soil cation exchange capacity (ECEC).

Table 4—Mean soil solution and stream chemistry for Linville Gorge and Shining Rock Wildernesses in Western North 

Carolina, USA

Linville Gorge Wilderness (LGW) Shining Rock Wilderness (SRW)

A-horizon

(0-15 cm 

depth)

AB-horizon

(15-35 cm 

depth)

B-horizon

(35-65 cm 

depth) Stream

A-horizon

(0-20 cm 

depth)

AB-horizon

(20-60 cm 

depth)

B-horizon

(60-90 cm 

depth) Stream

pH 4.22 (0.12) 4.40 (0.12) 4.51 (0.11)a 4.74 (0.04)a 4.35 (0.15) 4.80 (0.11) 5.04 (0.09)b 6.08 (0.08)b

NO3

-

 -N 2.07 (0.89) 0.48 (0.12)a 0.62 (0.23)a 2.06 0.62)a 1.60 (0.75) 5.03 (1.75)b 5.68 (3.19)b 0.71 (0.12)b

NH4

+-N 1.10 (0.49) 0.36 (0.05) 0.44 (0.15) 0.74 (0.18)a 0.93 (0.24) 1.67 (0.79) 0.57 (0.16) 0.35 (0.05)b

PO4

2- 0.23 (0.08) 0.08 (0.01) 0.12 (0.01) 0.10 (0.01) 0.17 (0.04) 0.09 (0.02) 0.06 (0.01) 0.12 (0.02)

Cl- 41.64 (5.97) 37.16 (4.12) 32.81 (2.82) 25.44 (2.34)a 55.38 (26.04) 43.16 (18.19) 21.56 (5.91) 7.99 (0.22)b

K+ 42.74 (8.05)a 17.16 (2.98) 9.68 (2.39) 7.35 (0.47)a 13.71 (2.84)b 6.08 (1.04) 4.17 (0.68) 5.29 (0.12)b

Na+ 23.82 (2.58) 23.60 (2.26) 17.69 (1.55) 18.36 (0.99) 20.19 (3.47) 16.47 (1.06) 17.15 (1.21) 25.62 (0.81)

Ca2+ 17.56 (4.60) 9.17 (2.56) 4.81 (1.98) 13.80 (3.01) 22.74 (5.26) 22.32 (4.04) 17.66 (2.99) 15.28 (2.03)

Mg2+ 30.76 (3.84) 22.45 (4.13) 15.81 (3.45) 15.14 (1.16) 29.89 (6.73) 20.46 (1.83) 19.50 (2.56) 12.15 (0.79)

SO4

2- 99.98 (7.63) 113.1 (11.23)a 91.80 (12.26) 51.95 (0.44)a 64.18 (22.50) 42.34 (5.06)b 38.79 (4.16) 19.82 (0.62)b

Al 118.0 (18.49) 89.06 (20.02) 69.09 (14.80)a 17.61 (1.20) 140.7 (50.58) 37.96 (11.71) 24.48 (6.23)b 31.01 (17.57)

DOC 26.52 (6.97) 11.21 (4.23) 6.64 (2.45) 1.37 (0.20) 15.54 (4.75) 2.47 (0.54) 1.61 (0.32) 1.47 (0.17)

Note: Standard errors are in parentheses. All values are in μeq L-1 except for soil pH and DOC (mg L-1). Values within a soil horizon depth or 

stream followed by different letters denote significant differences (α=0.05) between sites. Data from Elliott and others (2008).
6

Results and Discussion

temperature data were created outside the model and 

input as ASCII files, whereas the physiographic and 

chemistry files were created through input menus within 

the model. The meteorologic data file contains daily values 

for precipitation, minimum and maximum temperature, 

cloud cover, dewpoint, atmospheric pressure, and wind 

speed. For LGW, precipitation data were obtained from 

Banner Elk, NC (NCDC/NOAA climate station #310506) 

located at 36.09 N latitude, 81.52 W longitude, and 1142 

m elevation. Maximum and minimum temperature, wind 

speed, dew point, and cloud cover were obtained from 

Jefferson, NC (NCDC/NOAA, climate station #314496) 

located at 36.25 N latitude, 81.26 W longitude, and 845 m 

elevation. Banner Elk is located about 14 km and Jefferson 

is about 70 km north of LGW. Banner Elk only collected 

precipitation, but its precipitation would be more similar 

to that received at LGW. Jefferson was the closest climate 

station with a full climate record. For SRW, climate data 

were obtained from Pisgah, NC (NCDC/NOAA climate 

station #316805), located at 35.16 N latitude, 83.42 W 

longitude, and 645 m elevation, and approximately 16 km 

southeast of SRW. We used average annual daily means 

for the 10-year climate record from 2002 to 2011 for both 

LGW and SRW. We used atmospheric deposition data, bulk 

deposition wetfall and dryfall, for a 10-year period (2002 

to 2011), supplied from National Atmospheric Deposition 

Program (NADP 1998) site NC45 located at Mt. Mitchell, 

NC. Mt. Mitchell is the closest NADP site to LGW and SRW 

and it is also a high elevation site (1900 m). Wet deposition 

(wetfall) and dry deposition (dryfall) were calculated from 

a ratio of wetfall/dryfall based on the long-term record at 

Coweeta Hydrologic Laboratory. Soil temperature data 

were calculated from air temperature data using a model 

developed for the Coweeta Basin (Vose and Swank 1991); 

monthly average values were calculated for each of the soil 

depths used in the simulations. Model input data included 

stand physical characteristics (tables 1 and 2), soil physical 

characteristics, soil and soil solution chemistry (tables 3 

and 4), and stream chemistry (table 4). Aboveground live 

biomass and root biomass estimated values were obtained 

from previous research in LGW and SRW (Elliott and others 

2008). Once compiled, these data were input using the 

format outlined in the NuCM User’s Manual (Munsen and 

others 1992).

Results and Discussion

In the Southern Appalachians, ecosystem sensitivity to the 

potential effects of acidic deposition on nutrient status of 

forest soils and surface water quality has been well studied 

(Baker and others 1990, Elliott and others 2008, Johnson 

and others 1999, NAPAP 2005, Sullivan and others 2004). 

Hydrogen ions associated with S and N deposition replace 

nutrient base cations (Ca2+, Mg2+, and K+) on soil cation 

exchange sites. When base cations become mobilized they 

are leached into drainage waters, leaving soils with depleted 

stores of nutrient base cations. Soils in this region with 

decreased exchangeable base cation and increased available 

Al due to acidic deposition have been shown to alter the 

health and productivity of forest trees (Halman and others 

2011, Long and others 2011, Schaberg and others 2006).

LGW and SRW contain ecosystems where acidic deposition 

has depleted soil base cation supply. This reduced soil 

buffering capacity and continued acidic deposition have 

resulted in unsuitable stream water pH and ANC conditions 

for the survival of many fish and macroinvertebrate species. 

Initial soil NH4

+, Ca2+, Mg2+, and effective cation exchange 

capacity (ECEC) were lower at LGW than at SRW, whereas 

soil SO4

2- was greater at LGW (table 3). Soil solution and 

stream chemistry were also different between the two 

wilderness areas (table 4). In general, LGW had much lower 

soil solution base cation and greater acid anion concentrations 

than SRW (table 4). Al and SO4

2- , and NO3-

 solution 

concentrations were significantly greater at LGW than at SRW. 

Stream SO4

2- concentration was also greater at LGW than 

at SRW (table 4). At LGW, stream SO4

2- concentration was 

higher than the mean values observed at Noland Divide in 

the Great Smoky Mountains National Park (Robinson and 

others 2003). Stream NO3

-

 concentrations at both LGW and 

SRW were an order of magnitude lower than that reported 

for Noland Divide (Robinson and others 2003). The pH 

of stream water at LGW was significantly lower than at 

SRW and much less than pH values recorded at reference 

watershed streams at the Coweeta Long Term Ecological 

Research (LTER) site (Swank and Waide 1988). Low pH 

and high Al concentrations have been shown to diminish 

species diversity and the abundance of invertebrates and 

fish in acid-impacted surface waters in the Northeast 

(Driscoll and others 2003). The extremely low pH and high 

Al concentrations of the first order streams at LGW may be 

harmful to aquatic biota in this wilderness. For example, in 

the Adirondack region of New York, lakes with pH between 

4.0 and 5.0 supported one or two species of fish on average, 

whereas lakes with pH ranging from 5.0 to 8.0 supported 

between three and six species of fish (Driscoll and others 

2001). Low stream ANC has also been associated with 

negative impacts to aquatic biota and fisheries, especially 

native brook trout, Salvelinus fontinalis (Cosby and others 

2006). The ANC value at SRW (28.8 μeq L-1) suggests that 

this site is extremely sensitive to further acidification and 
7

Results and Discussion

may adversely affect brook trout. The ANC value (-24.8 μeq 

L-1) at LGW indicates that this stream is no longer able to 

support brook trout or any fish species because acid inputs 

can no longer be neutralized (Bulger and others 1999).

We found very little difference in soil, soil solution, or stream 

water chemistry between the current (base) deposition and 

Scenario 1 deposition over the 90-year simulation (figs. 

1-24) because SO4

2- and NO3-

 depositions were reduced only 

slightly (-6 percent) for the Scenario 1 forecast (Sullivan and 

others 2011b). For this reason, we discuss only Scenarios 2-5 

in comparison to the base deposition and among each other.

For the shallow soil depth (A-horizon), soil base saturation 

(BS) increased up to year 2030 then gradually declined at 

both sites (figs. 1 and 2). BS was more than 2 percent higher 

for Scenario 5 (greatest SO4

2- and NO3-

 deposition reductions) 

than the base deposition scenario at LGW (fig. 1), and 8 

percent higher at SRW (fig. 2). For the deeper soils (AB- and 

B-horizons), BS lagged behind the response in the shallow 

soil, and not until 2040 were there differences among the 

deposition reduction scenarios at LGW (fig. 1). BS in the ABhorizon increased at SRW over time for all scenarios (fig. 2); 

whereas, BS declined at LGW at the deeper soil depths (fig. 1).

For both sites, soil exchangeable Ca2+ increased (figs. 3 and 

4) while exchangeable Al3+ changed very little (figs. 5 and 

6) with greater reductions in SO4

2- and NO3-

 deposition. 

Soil adsorbed SO4

2- incrementally decreased as SO42- and 

NO3

-

 deposition was reduced (Scenarios 2-4) and was 

lowest for Scenario 5 at LGW (fig. 7) and SRW (fig. 8). 

The increase in exchangeable Ca2+ improved soil Ca/Al 

molar ratios (figs. 9 and 10). Simulated Ca/Al ratios in 

A-horizon soils for LGW and SRW were similar to ratios 

found at Noland Divide, a high-elevation, spruce-fir forest 

in the Great Smoky Mountains National Park (Johnson 

and others 1999). Even after the 90-year simulation 

for all deposition scenarios, soil exchangeable Ca2+

concentrations at LGW and SRW were still quite low (≤1.0 

cmolc Ca kg-1) and were comparable to those reported for 

acidic soils in hardwood forests (0.7-0.8 cmolc Ca kg-1) in 

West Virginia (Farr and others 2009), pine forests (0.05-

0.23 cmolc Ca kg-1) in South Carolina (Markewitz and 

others 1998), and hardwood forests (0.8 cmolc Ca kg-1) in 

Tennessee (Johnson and others 2008). 

Soil solution Ca2+ concentrations were higher for the shallow 

soils with greater reductions in SO4

2- and NO3-

 deposition at 

both sites (figs. 11 and 12). Soil solution Al was much lower 

at both sites with the greatest reduction in SO4

2- and NO3-

deposition, Scenario 5 (figs. 13 and 14). However, solution Al 

concentrations at LGW remain 4-5 times higher than at SRW 

regardless of the deposition scenarios.

For both sites, soil solution SO4

2- was much lower at all soil 

depths with greater reductions in SO4

2- and NO3-

 deposition 

(figs. 15 and 16). This reduction in solution SO4

2- resulted 

in greater soil solution ANC (figs. 17 and 18). At LGW, 

soil solution ANC of shallow soil was improved with 

the deposition Scenarios 2-5 compared to base scenario 

deposition (fig. 17). By 2040, solution ANC of deep soil 

had increased above 20 μeq L-1 for Scenarios 3-5 at LGW 

suggesting that stream ANC will be improved as well with 

further reductions in acidic deposition. 

For LGW, Ca2+ leaching declined rapidly until year 

2040; thereafter Ca2+ leaching began to rise until year 

2060 where it plateaued (fig. 19). For SRW, Ca2+ leaching 

increased over time with the base deposition and declined 

gradually for Scenarios 2-5 with the greatest reduction 

with Scenario 5 (fig. 20). Aluminum leaching was reduced 

substantially with the greatest reductions in acidic deposition 

at both wildernesses (figs. 21 and 22). Within 10 years of 

simulations, Al leaching was 0.08 kmols ha-1 yr-1 lower at 

LGW (fig. 21) and 0.01 kmols ha-1 yr-1 lower at SRW (fig. 22) 

for Scenario 5 compared to the base deposition. By the end 

of the 90-year simulation, Al leaching was reduced by 0.14 

kmols ha-1 yr-1 at LGW and 0.04 kmols ha-1 yr-1 at SRW with 

Scenario 5.

Soil and solution cation concentrations are expected to 

improve within both wilderness areas based on CAIR 

emissions reductions (Scenario 2); however, further 

reductions in acidic deposition (e.g., Scenario 5) will be 

needed to increase stream ANC to a level that could support 

trout and other fishes (Bulger and others 1999). By 2050, 

SO4

2- leaching was reduced by 37 percent at LGW (fig. 23) 

and by 40 percent at SRW (fig. 24) with CAIR provisions. 

SO4

2- leaching would be reduced even further if Scenario 

5 provisions were adopted, by 66 percent and 68 percent 

at LGW and SRW, respectively. Substantial SO2 emission 

reductions are also known to be occurring in Georgia, 

South Carolina, and Tennessee. Therefore, there is a strong 

possibility that sulfur deposition will be reduced to a level 

above Scenario 4 and more likely close to Scenario 5. 

Nitrogen oxides emissions are also projected to decrease, but 

the percent reduction between 2002 and 2018 is unlikely to 

be as large as SO2.
8

Results and Discussion

(B) AB-horizon (15-35 cm depth)

Base saturation (%)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00

0.50

1.00

1.50

2.00

2.50

3.00

(C) B-horizon (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

Base saturation (%)

0.00

0.50

1.00

1.50

2.00

0.00

0.50

1.00

1.50

2.00

(A) A-horizon (0-15 cm depth)

Base saturation (%)

0.00

2.00

4.00

6.00

8.00

0.00

2.00

4.00

6.00

8.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 1—Simulated soil base saturation for five deposition scenarios compared to the current deposition (base) for Linville Gorge Wilderness. 

The five scenarios were based on percentages of the current condition.
9

Results and Discussion

(C) B-horizon (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

Base saturation (%)

0.00

1.00

2.00

3.00

0.00

1.00

2.00

3.00

(A) A-horizon (0-20 cm depth)

Base saturation (%)

0.00

5.00

10.00

15.00

20.00

0.00

5.00

10.00

15.00

20.00

(B) AB-horizon (20-60 cm depth)

Base saturation (%)

0.00

2.00

4.00

6.00

8.00

0.00

2.00

4.00

6.00

8.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 2—Simulated soil base saturation for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
10

Results and Discussion

(C) B-horizon (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

Ca2+ (cmolc kg-1)

0.000

0.005

0.010

0.015

0.020

0.000

0.005

0.010

0.015

0.020

(B) AB-horizon (15-35 cm depth)

Ca2+ (cmolc kg-1)

0.000

0.010

0.020

0.030

0.040

0.000

0.010

0.020

0.030

0.040

(A) A-horizon (0-15 cm depth)

Ca2+ (cmolc kg-1)

0.000

0.040

0.080

0.120

0.160

0.000

0.040

0.080

0.120

0.160

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 3—Simulated soil exchangeable calcium (Ca2+) for the five deposition scenarios compared to the current deposition (base) for Linville 

Gorge Wilderness. The five scenarios were based on percentages of the current condition.
11

Results and Discussion

(B) AB-horizon (20-60 cm depth)

Ca2+ (cmolc kg-1)

0.000

0.040

0.080

0.120

0.160

0.200

0.240

0.000

0.040

0.080

0.120

0.160

0.200

0.240

(A) A-horizon (0-20 cm depth)

Ca2+ (cmolc kg-1)

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.000

0.200

0.400

0.600

0.800

1.000

1.200

(C) B-horizon (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

Ca2+ (cmolc kg-1)

0.000

0.020

0.040

0.060

0.080

0.100

0.000

0.020

0.040

0.060

0.080

0.100

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 4—Simulated soil exchangeable calcium (Ca2+) for the five deposition scenarios compared to the current deposition (base) for Shining 

Rock Wilderness. The five scenarios were based on percentages of the current condition.
12

Results and Discussion

(C) B-horizon (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

Al3+ (cmolc kg-1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0.000

1.000

2.000

3.000

4.000

5.000

6.000

(A) A-horizon (0-15 cm depth)

Al3+ (cmolc kg-1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0.000

1.000

2.000

3.000

4.000

5.000

6.000

(B) AB-horizon (15-35 cm depth)

Al3+ (cmolc kg-1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0.000

1.000

2.000

3.000

4.000

5.000

6.000

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 5—Simulated soil exchangeable aluminum (Al3+) for the five deposition scenarios compared to the current deposition (base) for Linville 

Gorge Wilderness. The five scenarios were based on percentages of the current condition.
13

Results and Discussion

(C) B-horizon (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

Al3+ (cmolc kg-1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0.000

1.000

2.000

3.000

4.000

5.000

6.000

(A) A-horizon (0-20 cm depth)

Al3+ (cmolc kg-1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0.000

1.000

2.000

3.000

4.000

5.000

6.000

(B) AB-horizon (20-60 cm depth)

Al3+ (cmolc kg-1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

0.000

1.000

2.000

3.000

4.000

5.000

6.000

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 6—Simulated soil exchangeable aluminum (Al3+) for the five deposition scenarios compared to the current deposition (base) for Shining 

Rock Wilderness. The five scenarios were based on percentages of the current condition.
14

Results and Discussion

(C) B-horizon (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

SO42-(cmolc kg-1)

0.000

0.100

0.200

0.300

0.400

0.500

0.000

0.100

0.200

0.300

0.400

0.500

(B) AB-horizon (15-35 cm depth)

SO42-(cmolc kg-1)

0.000

0.100

0.200

0.300

0.400

0.500

0.000

0.100

0.200

0.300

0.400

0.500

(A) A-horizon (0-15 cm depth)

SO42-(cmolc kg-1)

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.050

0.100

0.150

0.200

0.250

0.300

0.350

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 7—Simulated soil adsorbed sulfate (SO4

2-) for the five deposition scenarios compared to the current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.
15

Results and Discussion

(A) A-horizon (0-20 cm depth)

SO42-(cmolc kg-1)

0.050

0.100

0.150

0.200

0.050

0.100

0.150

0.200

(B) AB-horizon (20-60 cm depth)

SO42-(cmolc kg-1)

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

(C) B-horizon (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

SO42-(cmolc kg-1)

0.000

0.100

0.200

0.300

0.400

0.500

0.000

0.100

0.200

0.300

0.400

0.500

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 8—Simulated soil adsorbed sulfate (SO4

2-) for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
16

Results and Discussion

(B) AB-horizon (15-35 cm depth)

Ca/Al molar ratio

0.000

0.002

0.004

0.006

0.008

0.000

0.002

0.004

0.006

0.008

(A) A-horizon (0-15 cm depth)

Ca/Al molar ratio

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.000

0.005

0.010

0.015

0.020

0.025

0.030

(C) B-horizon (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

Ca/Al molar ratio

0.000

0.001

0.002

0.003

0.004

0.000

0.001

0.002

0.003

0.004

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 9—Simulated soil Ca/Al molar ratio for the five deposition scenarios compared to the current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.
17

Results and Discussion

(C) B-horizon (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

Ca/Al molar ratio

0.000

0.005

0.010

0.015

0.020

0.025

0.000

0.005

0.010

0.015

0.020

0.025

(B) AB-horizon (20-60 cm depth)

Ca/Al molar ratio

0.000

0.010

0.020

0.030

0.040

0.000

0.010

0.020

0.030

0.040

(A) A-horizon (0-20 cm depth)

Ca/Al molar ratio

0.000

0.050

0.100

0.150

0.200

0.250

0.000

0.050

0.100

0.150

0.200

0.250

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 10—Simulated soil Ca/Al molar ratio for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
18

Results and Discussion

(C) Solution (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

Ca2+(μmolc L-1)

0.00

2.50

5.00

7.50

10.00

0.00

2.50

5.00

7.50

10.00

(B) Solution (15-35 cm depth)

Ca2+(μmolc L-1)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

(A) Solution (0-15 cm depth)

Ca2+(μmolc L-1)

0.00

20.00

40.00

60.00

80.00

0.00

20.00

40.00

60.00

80.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 11—Simulated soil solution calcium (Ca2+) for the five deposition scenarios compared to the current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.
19

Results and Discussion

(C) Solution (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

Ca2+(μmolc L-1)

0.00

5.00

10.00

15.00

20.00

0.00

5.00

10.00

15.00

20.00

(B) Solution (20-60 cm depth)

Ca2+(μmolc L-1)

0.00

10.00

20.00

30.00

40.00

0.00

10.00

20.00

30.00

40.00

(A) Solution (0-20 cm depth)

Ca2+(μmolc L-1)

0.00

15.00

30.00

45.00

60.00

0.00

15.00

30.00

45.00

60.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 12—Simulated soil solution calcium (Ca2+) for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
20

Results and Discussion

(C) Solution (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

Al (

μmolc L-1)

0.00

100.00

200.00

300.00

400.00

0.00

100.00

200.00

300.00

400.00

(B) Solution (15-35 cm depth)

Al (

μmolc L-1)

0.00

80.00

160.00

240.00

320.00

0.00

80.00

160.00

240.00

320.00

(A) Solution (0-15 cm depth)

Al (

μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 13—Simulated soil solution aluminum (Al) for the five deposition scenarios compared to the current deposition (base) for Linville 

Gorge Wilderness. The five scenarios were based on percentages of the current condition.
21

Results and Discussion

(C) Solution (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

Al (

μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

(A) Solution (0-20 cm depth)

Al (

μmolc L-1)

0.00

40.00

80.00

120.00

160.00

0.00

40.00

80.00

120.00

160.00

(B) Solution (20-60 cm depth)

Al (

μmolc L-1)

0.00

10.00

20.00

30.00

40.00

50.00

0.00

10.00

20.00

30.00

40.00

50.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 14—Simulated soil solution aluminum (Al) for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
22

Results and Discussion

(C) Solution (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

SO42-(μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

(B) Solution (15-35 cm depth)

SO42-(μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

(A) Solution (0-15 cm depth)

SO42-(μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

Figure 15—Simulated soil solution sulfate (SO4

2-) for the five deposition scenarios compared to the current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%
23

Results and Discussion

(C) Solution (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

SO42-(μmolc L-1)

0.00

40.00

80.00

120.00

160.00

0.00

40.00

80.00

120.00

160.00

(B) Solution (20-60 cm depth)

SO42-(μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

(A) Solution (0-20 cm depth)

SO42-(μmolc L-1)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00

20.00

40.00

60.00

80.00

100.00

120.00

Figure 16—Simulated soil solution sulfate (SO4

2-) for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%
24

Results and Discussion

(C) Solution (35-65 cm depth)

Month/Year

2010202020302040205020602070208020902100

ANC (

μeq L-1)

-80.00

-60.00

-40.00

-20.00

0.00

20.00

40.00

-80.00

-60.00

-40.00

-20.00

0.00

20.00

40.00

(B) Solution (15-35 cm depth)

ANC (

μeq L-1)

-40.00

-20.00

0.00

20.00

40.00

60.00

80.00

-40.00

-20.00

0.00

20.00

40.00

60.00

80.00

(A) Solution (0-15 cm depth)

ANC (

μeq L-1)

-80.00

-60.00

-40.00

-20.00

0.00

-80.00

-60.00

-40.00

-20.00

0.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 17—Simulated soil solution anion neutralizing capacity (ANC) for the five deposition scenarios compared to the current deposition 

(base) for Linville Gorge Wilderness. The five scenarios were based on percentages of the current condition.
25

Results and Discussion

(C) Solution (60-90 cm depth)

Month/Year

2010202020302040205020602070208020902100

ANC (

μeq L-1)

0.00

4.00

8.00

12.00

16.00

0.00

4.00

8.00

12.00

16.00

(B) Solution (20-60 cm depth)

ANC (

μeq L-1)

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

(A) Solution (0-20 cm depth)

ANC (

μeq L-1)

-40.00

-20.00

0.00

20.00

40.00

-40.00

-20.00

0.00

20.00

40.00

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 18—Simulated soil solution anion neutralizing capacity (ANC) for the five deposition scenarios compared to the current deposition 

(base) for Shining Rock Wilderness. The five scenarios were based on percentages of the current condition.
26

Results and Discussion

Simulated calcium leaching

Year

2010202020302040205020602070208020902100

0.000

0.020

0.040

0.060

0.080

0.000

0.020

0.040

0.060

0.080

kmols ha-1 yr-1

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Simulated calcium leaching

Year

2010202020302040205020602070208020902100

0.000

0.020

0.040

0.060

0.080

0.000

0.020

0.040

0.060

0.080

kmols ha-1 yr-1

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 19—Simulated calcium (Ca2+) leaching for the five deposition scenarios compared to the current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.

Figure 20—Simulated calcium (Ca2+) leaching for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
27

Results and Discussion

Simulated aluminum leaching

Year

2010202020302040205020602070208020902100

0.000

0.200

0.400

0.600

0.800

1.000

0.000

0.200

0.400

0.600

0.800

1.000

kmols ha-1 yr-1

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Simulated aluminum leaching

Year

2010202020302040205020602070208020902100

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.000

0.020

0.040

0.060

0.080

0.100

0.120

kmols ha-1 yr-1

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 21—Simulated aluminum (Al) leaching for the five deposition scenarios compared to the current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.

Figure 22—Simulated aluminum (Al) leaching for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
28

Results and Discussion

Simulated sulfate leaching

Year

2010202020302040205020602070208020902100

0.000

0.100

0.200

0.300

0.400

0.500

0.000

0.100

0.200

0.300

0.400

0.500

kmols ha-1 yr-1

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Simulated sulfate leaching

Year

2010202020302040205020602070208020902100

kmols ha-1 yr-1

0.000

0.100

0.200

0.300

0.400

0.500

0.000

0.100

0.200

0.300

0.400

0.500

Base

Scenario 1 = SO4 at 94% and NO3 at 95%

Scenario 2 = SO4 at 58% and NO3 at 63%

Scenario 3 = SO4 at 42% and NO3 at 51% 

Scenario 4 = SO4 at 35% and NO3 at 48%

Scenario 5 = SO4 at 22% and NO3 at 48%

Figure 23—Simulated sulfate (SO4

2-) leaching for the five deposition scenarios compared to current deposition (base) for Linville Gorge 

Wilderness. The five scenarios were based on percentages of the current condition.

Figure 24—Simulated sulfate (SO4

2-) leaching for the five deposition scenarios compared to the current deposition (base) for Shining Rock 

Wilderness. The five scenarios were based on percentages of the current condition.
29

Summary, Acknowledgments, and Literature Cited

SUMMARY

Anthropogenic emissions of sulfur dioxide (SO2) in North 

America have shown marked temporal changes over the 

past 100 years with a maximum occurring in the early 

1970s followed by a substantial decline (Mitchell and others 

2011). Much of this decline in the U.S. was driven by the 

enactment of the Clean Air Act in 1970 and subsequent Title 

IV Amendment of the Clean Air Act in 1990 (Scenario 1), as 

well as other regulatory controls on SO2 emissions (CAIR, 

Scenario 2 and implementation of the Regional Haze Rule). 

Elevated S deposition has been closely linked with the 

acidification of soils and surface waters (Elliott and others 

2008). This acidification has resulted in the mobilization of 

toxic cations (e.g., aluminum) (Driscoll and Postek 1996) and 

the depletion of soil nutrient cations (e.g., Ca2+, Mg2+) (Bailey 

and others 2005, Elliott and others 2008).

Large reductions in SO2 are anticipated between 2002 and 

2018 along with substantial NOx reductions from utilities. If 

the deposition reductions equate to SO4

2- of at least 78 percent 

and NO3

-

 of 52 percent (Scenario 5) then improvements in 

future percent BS is anticipated at both wildernesses. In the 

rooting zone, the soil exchangeable Ca2+ will continue to 

remain low and the amount of Al in soil solution is predicted 

to decrease, but will still be very high at LGW. The high 

concentrations of Al are of concern because the amount could 

be toxic to fine roots. Mortality of the fine roots decreases the 

surface area for water absorption and may lead to decreases 

in the amount of base cation uptake (especially Ca2+) required 

to support healthy vegetation. Forecasted reductions in acidic 

deposition for LGW and SRW are also likely to improve 

conditions for aquatic biota as evidenced by a decrease in the 

amount of Al leaching from the soils and an increase in the 

soil solution ANC. 

There are two pieces of information that would aid future 

studies to determine the level of acidic deposition that can 

be tolerated by Appalachian ecosystems. First, the State 

air quality agencies in the Southeastern United States are 

conducting joint atmospheric dispersion modeling of current 

and future emissions. It would be very useful to obtain the 

total SO4

2- and NO3-

 deposition estimates to use in future 

analysis with NuCM or a similar type of biogeochemical 

model. Second, land managers need to continue receiving 

instruction on acidic deposition impacts so they can advise 

air regulatory agencies on what level of total SO4

2- and 

NO3

-

 deposition the ecosystem can tolerate for long-term 

sustainability. The two wildernesses in this study do 

represent some of the other high elevation areas in the 

Southern Appalachians. Land managers need to understand 

there is a possibility that other areas, such as these two 

wildernesses, may not fully recover within a desired time 

period, even with additional reductions in acidic deposition. 

The extent of these areas is not known at this time; however, 

the identified acidic forests should be considered for 

restoration with nutrient supplements (such as liming) to 

replace deficient base cations (especially Ca2+) in order to 

move towards a healthier ecosystem.

Acknowledgments

We thank the Pisgah and Grandfather Ranger Districts, 

Pisgah National Forest for their cooperation in establishing 

field sites. Special thanks to Patsy Clinton, Chris Sobek, Neal 

Muldoon, and Jason Love for assistance in field sampling 

and Cindi Brown and Carol Harper for chemical analyses of 

samples. Drs. Todd McDonnell and Wei Wu provided helpful 

comments on the manuscript. This research was supported 

by Region 8, USDA Forest Service; Coweeta Hydrologic 

Laboratory, Southern Research Station, USDA Forest 

Service; and the Coweeta LTER project funded by National 

Science Foundation grant DEB-0823293. 

Literature Cited

Bailey, S.W.; Horsley, S.B.; Long, R.P. 2005. Thirty years of change 

in forest soils of the Allegheny Plateau, Pennsylvania. Soil Science 

Society of America Journal. 69:681-690.

Baker, L.A.; Kauffman, P.R.; Herlihy, A.T.; Eilers, J.M. 1990. Acidic 

deposition: current status of surface water acid-base chemistry. 

NAPAP Rep. 9. Washington, DC: National Acid Precipitation 

Assessment Program. Vol. II. 367 pp.

Bulger, A.J.; Cosby, B.J.; Doloff, C.A. [and others]. 1999. Shenandoah 

National Park: fish in sensitive habitats. Final report. An integrated 

assessment of fish community responses to stream acidification. 

Charlottesville, VA: University of Virgina. Cooperative Agreement 

CA-4000-2-1007, Supplemental Agreement #2.

Byun, D.W.; Ching, J.K.S. 1999. Science algorithms of the EPA 

Models-3 Community Multiscale Air Quality (CMAQ) modeling 

system. EPA/600/R-99/030. Washington, DC: Environmental 

Protection Agency, Office of Research and Development. 767 pp. 

Clescerl, L.S.; Greenberg, A.E.; Eaton, A.D. 1999. Standard methods 

for the examination of water and wastewater, 20th edition. 

Washington, DC: American Public Health Assoc./American Water 

Works Assoc./Water Environment Federation. 1325 pp.

Cosby, B.J.; Webb, J.R.; Galloway, J.N.; Deviney, F.A. 2006. Acidic 

deposition impacts on natural resources in Shenandoah National 

Park. Technical Report NPS/NER/NRTR-2006/066. Philadelphia, 

PA: U.S. Department of the Interior, National Park Service, 

Northeast Region. 167 pp. + apps. 
30

Literature Cited

Driscoll, C.T.; Postek, K.M. 1996. The chemistry of aluminum in 

surface waters. In: Sposito, G., ed. The environmental chemistry of 

aluminum. Boca Raton, FL: CRC Press: 363-418.

Driscoll, C.T.; Lawrence, G.B.; Bulger, A.J. [and others]. 2001. 

Acidic deposition in the northeastern United States: sources and 

inputs, ecosystem effects, and management strategies. BioScience. 

51:180-198. 

Driscoll, C.T.; Driscoll, K.M.; Mitchell, M.J.; Raynal, D.J. 2003. 

Effects of acidic deposition on forest and aquatic ecosystems in New 

York State. Environmental Pollution. 123:327-336.

Elliott, K.J.; Vose, J.M.; Knoepp, J.D. [and others]. 2008. Simulated 

effects of sulfur deposition on nutrient cycling in class I wilderness 

areas. Journal of Environmental Quality. 37:1419-1431.

Farr, C.; Skousen, J.; Edwards, P. [and others]. 2009. Acid soil 

indicators in forest soils of the Cherry River Watershed, West 

Virginia. Environmental Monitoring and Assessment. 158:343-353.

Halman, J.M; Schaberg, P.G.; Hawley, G.J.; Hansen, C.F. 2011. 

Potential role of soil calcium in recovery of paper birch following ice 

storm injury in Vermont, USA. Forest Ecology and Management. 

261:1539-1545.

Johnson, D.W.; Lindberg, S.E., eds. 1992. Atmospheric deposition and 

forest nutrient cycling: a synthesis of the integrated forest study. 

Ecological Series 91. New York: Springer-Verlag. 707 pp.

Johnson, D.W.; Susfalk, R.B.; Brewer, P.F.; Swank, W.T. 1999. 

Simulated effects of reduced sulfur, nitrogen, and base cation 

deposition on soils and solutions in Southern Appalachian forests. 

Journal of Environmental Quality. 28:1336-1346.

Johnson, D.W.; Todd, D.E.; Trettin, C.F.; Mulholland, P.J. 2008. 

Decadal changes in potassium, calcium, and magnesium in a 

deciduous forest soil. Soil Science Society of America Journal. 

72:1795-1805.

Liu, S.A.; Munsen, R.K.; Johnson, D.W. [and others]. 1991a. The 

Nutrient Cycling Model (NuCM): overview and application. In: 

Johnson, D.S.; Lindberg, S.E., eds. Atmospheric deposition and 

forest nutrient cycling: a synthesis of the integrated forest study. 

Ecological Studies 91. New York: Springer-Verlag. 583-609.

Liu, S.A.; Munsen, R.K.; Johnson, D.W. [and others]. 1991b. 

Applications of a nutrient cycling model (NuCM) to a northern 

mixed hardwood and a southern coniferous forest. Tree Physiology. 

9:173-182.

Long, R.P.; Horsley, S.B.; Hall, T.J. 2011. Long-term impact of liming 

on growth and vigor of northern hardwoods. Canadian Journal of 

Forest Research. 41:1295-1307.

Markewitz, D.; Richter, D.D.; Allen, H.L.; Urrego, J.B. 1998. Three 

decades of observed soil acidification in the Calhoun Experimental 

Forest: has acid rain made a difference? Soil Science Society of 

America Journal 62:1428-1439.

Mitchell, M.J.; Lovett, G.; Bailey, S. [and others]. 2011. Comparisons 

of watershed sulfur budgets in southeast Canada and northeast US: 

new approaches and implications. Biogeochemistry 103:181-207.

Munsen, R.K.; Liu, S.; Gherini, S.A. [and others]. 1992. NuCM code 

version 2.0: an IBM PC code for simulating nutrient cycling in forest 

ecosystems. Hadley, MA: Tetra-Tech.

National Atmospheric Deposition Program (NADP). 1998. National 

Atmospheric Deposition Program 1997 Wet Deposition. Champaign, 

IL: Illinois State Water Survey. 16 pp.

National Acid Precipitation Assessment Program (NAPAP). 2005. 

National Acid Precipitation Assessment Program report to Congress: 

an integrated assessment. Washington, DC: National Science and 

Technology Council. 85 pp. Available at www.napap.noaa.gov/

reports. 

Newell, C.L.; Peet, R.K. 1995. Vegetation of Linville Gorge 

Wilderness, North Carolina. Curriculum in Ecology & Department 

of Biology. Chapel Hill, NC: University of North Carolina at Chapel 

Hill. 211 pp.

Newell, C.L.; Peet, R.K. 1996. Vegetation of Shining Rock Wilderness, 

North Carolina. Curriculum in Ecology & Department of Biology. 

Chapel Hill, NC: University of North Carolina at Chapel Hill. 253 pp.

NOAA. 1999. National Climatic Data Center: daily surface data 

(primarily U.S.). Documentation Manual, U.S. Department of 

Commerce. Washington, DC: National Oceanic and Atmospheric 

Administration.

Robinson, R.B.; Wood, M.S.; Smoot, J.L.; Moore, S.E. 2003. 

Parametric modeling of water quality and sampling strategy in a 

high-altitude Appalachian stream. Journal of Hydrology. 14:24-37.

Schaberg, P.G.; Tilley, J.W.; Hawley, G.J. [and others]. 2006. 

Associations of calcium and aluminum with the growth and 

health of sugar maple trees in Vermont. Forest Ecology and 

Management. 223:159-169. 

Sullivan, T.J.; Cosby, B.J.; Herlihy, A.T. [and others]. 2004. Regional 

model projections of future effects of sulfur and nitrogen deposition 

on streams in the Southern Appalachian Mountains. Water 

Resources Research. 40: W02101 doi:02110.01029/02003WR001998.

Sullivan, T.J.; Cosby, B.J.; Jackson, W.A. 2011a. Target loads of 

atmospheric sulfur deposition for the protection and recovery of 

acid-sensitive streams in the Southern Blue Ridge Province. Journal 

of Environmental Management. 11: 2953-2960. doi:10.1016/j.

jenvman.2011.07.014.

Sullivan, T.J.; Cosby, B. J.; Jackson, W.A. [and others]. 2011b. 

Acidification and prognosis for future recovery of acid-sensitive 

streams in the Southern Blue Ridge Province. Water, Air, & Soil 

Pollution. 219:11-26.

Swank, W.T.; Waide, J.B. 1988. Characterization of baseline 

precipitation and stream chemistry and nutrient budgets for 

control watersheds. In: Swank, W.T.; Crossley, D.A. Jr., eds. Forest 

Hydrology and Ecology at Coweeta. Ecological Studies 66. New 

York: Springer-Verlag. 57-79.

Vanderzanden, D.; Lachowski, H.; Jackson, B.; Clerke, B. 1999. 

Mapping vegetation in the Southern Appalachians with multidate 

satellite imagery: a wilderness case study. U.S. Department 

of Agriculture Forest Service, Engineering, Remote Sensing 

Application Center. RSAC-2300-IRS-0009-RPT1. 33 pp.

Vose, J.M.; Swank, W.T. 1991. A soil temperature model for closed 

canopied forest stands. Research Paper SE-281. Asheville, NC: U.S. 

Department of Agriculture Forest Service, Southeastern Forest 

Experiment Station. 11 pp. 
Elliott, K.J.; Vose, J.M.; Jackson, W.A. 2013. Effects of future sulfate and nitrate

deposition scenarios on Linville Gorge and Shining Rock Wildernesses. Gen. 

Tech. Rep. SRS-181. Asheville, NC: U.S. Department of Agriculture Forest 

Service, Southern Research Station. 30 p. 

We used the Nutrient Cycling Model (NuCM) to simulate the effects of various sulfur 

(S) and nitrogen (N) deposition scenarios on wilderness areas in Western North 

Carolina. Linville Gorge Wilderness (LGW) and Shining Rock Wilderness (SRW) 

were chosen because they are high elevation acidic cove forests and are located on 

geologic parent material known to be low in base cations and thus sensitive to acidic 

deposition. We used five sulfate (SO4

2-) and nitrate (NO3-

) deposition scenarios to 

compare with the current (base case) deposition: Scenario 1, SO4

2- at 94 percent and 

NO3

-

 at 95 percent of current deposition; Scenario 2, SO4

2- at 58 percent and NO3-

 at 

63 percent; Scenario 3, SO4

2- at 42 percent and NO3-

 at 51 percent; Scenario 4, SO4

2- at 

35 percent and NO3

-

 at 48 percent; and Scenario 5, SO4

2- at 22 percent and NO3-

 at 48 

percent. For both sites, soil exchangeable calcium (Ca2+) increased while exchangeable 

aluminum (Al3+) changed very little over the 90-year simulation period with greater 

reductions in SO4

2- and NO3-

 deposition; and the increase in soil exchangeable Ca2+

improved soil Ca/Al molar ratios. Soil solution SO4

2- was much lower at all soil depths 

with greater reductions in SO4

2- and NO3-

 deposition. This reduction in SO4

2- in 

solution resulted in greater soil solution acid neutralizing capacity (ANC). At LGW, 

soil solution ANC of shallow soil was improved with the deposition Scenarios 2-5 

compared to current deposition. By 2040, solution ANC of deep soil had increased 

above 20 μeq L-1 for Scenarios 3-5 at LGW suggesting that stream ANC will be 

improved as well with further reductions in acidic deposition. Soil and solution cation 

concentrations will be improved for both wildernesses based on Scenario 2; however, 

further reductions in acidic deposition (e.g., Scenario 5) will be needed to increase 

stream ANC to a level that could support trout and other fishes.

Keywords: Atmospheric deposition, calcium, forecasting, nitrogen, Nutrient Cycling 

Model, Southern Appalachians. 

You may request additional copies of this publication by email at pubrequest@fs.fed.us.

Number of copies is limited to two per person.

How do you rate this publication?

Scan this code to submit your feedback or go to 

www.srs.fs.usda.gov/pubeval
Non-Discrimination Policy

The U.S. Department of Agriculture (USDA) prohibits discrimination against 

its customers, employees, and applicants for employment on the bases of race, 

color, national origin, age, disability, sex, gender identity, religion, reprisal, and 

where applicable, political beliefs, marital status, familial or parental status, 

sexual orientation, or all or part of an individual’s income is derived from any 

public assistance program, or protected genetic information in employment or in any program 

or activity conducted or funded by the Department. (Not all prohibited bases will apply to all 

programs and/or employment activities.)

To File an Employment Complaint

If you wish to fi le an employment complaint, you must contact your agency’s EEO Counselor 

within 45 days of the date of the alleged discriminatory act, event, or in the case of a personnel 

action. Additional information can be found online at http://www.ascr.usda.gov/complaint_

fi ling_fi le.html.

To File a Program Complaint

If you wish to fi le a Civil Rights program complaint of discrimination, complete the USDA 

Program Discrimination Complaint Form, found online at http://www.ascr.usda.gov/

complaint_fi ling_cust.html, or at any USDA offi ce, or call (866) 632-9992 to request the form. 

You may also write a letter containing all of the information requested in the form. Send your 

completed complaint form or letter to us by mail at U.S. Department of Agriculture, Director, 

Offi ce of Adjudication, 1400 Independence Avenue, S.W., Washington, D.C. 20250-99410, by 

fax (202) 690-7442 or email at program.intake@usda.gov. 

Persons with Disabilities 

Individuals who are deaf, hard of hearing or have speech disabilities and you wish to fi le either 

an EEO or program complaint please contact USDA through the Federal Relay Service at 

(800) 877-8339 or (800) 845-6136 (in Spanish). 

Persons with disabilities who wish to fi le a program complaint, please see information 

above on how to contact us by mail directly or by email. If you require alternative means of 

communication for program information (e.g., Braille, large print, audiotape, etc.) please 

contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD).