soil solution response to acidic deposition in a northern hardwood forest
TRANSCRIPT
Agriculture, Ecosystems and Environment, 47 ( t 993 ) 117-134 117 Elsevier Science Publishers B.V., Amsterdam
Soil solution response to acidic deposition in a northern hardwood forest
L.E. Rustad *,a, I.J. Fernandez a, R.D. Fuller b, M.B. David c, S.C. Nodvin d, W.A. H a l t e m a n e
aDepartment of Plant, Soil, and Environmental Science, University of Maine, Orono, ME 04469, USA bCenter for Earth and Environmental Science, SUNY-Plattsburgh, Plattsburgh, NY 12901, USA
CDepartment of Forestry, University of Illinois, Urbana, IL 61801, USA aNational Park Service-Cooperative Park Studies Unit, Forestry, Wildlife and Fisheries,
University of Tennessee, Knoxville, TN 37901, USA eDepartment of Mathematics, University of Maine, Orono, ME 04469, USA
Abstract
An intensive plot-scale acidification experiment evaluated the effects of H2SO4, HNO3, and com- bined H2SO4 and HNO3 treatments on the chemistry of soils and soil solutions in a northern hard- wood forest. Treatments were delivered to 18 plots (each of 15 m× 15 m, three plots per treatment) during 20-week field seasons by a hill-slope irrigation system and consisted of two levels of H2SO4 ( ~ 2000 and 4000 eq ha- 1 year- 1 ), two levels of HNO3 ( ~ 2000 and 4000 eq ha- ~ year- ~ ), one level of combined H2SO4/HNO3 ( ~ 2000 eq ha-t year-~ each of SO 2- and NO3- ), and a control (water only).
Soil solutions responded rapidly to all treatments with increased leaching of SO 2- and/or NO~- (depending on treatment) accompanied by increased leaching of Ca 2 + and Mg 2 + from the upper B horizon. As solutions passed through the upper 25 cm of soil, mean SO~- concentrations decreased by 50--86% of initial values in all S treatments and mean NO~- concentrations decreased by 71-93% of initial values in the low nitrogen treatments. This reflected the importance of anion adsorption for SO 2- and biological immobilization for NO~- in these forested Spodosols. Mean NO~- concentra- tions, however, remained constant with depth in the high nitrogen treatment, suggesting that this high rate of NO~- input exceeded the plant/soil capacity to immobilize N. During the autumn and winter following the treatment period, soil solution SO~- and NO~- concentrations were greater for treated soils than for those of the control for 2-7 months. This suggests that anion desorption from soil ex- change sites occurred in response to lowered soil solution concentrations of these strong acid anions.
Introduction
Over the last two decades there has been considerable concern that acidic deposition may decrease the productivity of forest soils. Studies have shown that atmospheric deposition of strong acids can increase base cation leaching and the mobilization of toxic metals (e.g. AP ÷ ), decrease soil pH and base saturation, change mineral weathering rates, and alter soil biology (National
*Corresponding author.
© 1993 Elsevier Science Publishers B.V. All fights reserved 0167-8809/93/$06.00
1 18 L.E. Rustad et al./Agriculture, Ecosystems and Environment 47 (1993) 117-134
Acid Precipitation Assessment Program, 1987; Fernandez, 1989). In addi- tion, changes in the chemistry of soil solutions, such as elevated levels of strong acid anions, H + and A1 n +, may have adverse impacts on the chemistry and biology of associated surface waters (Goldstein et al., 1984).
Investigations into the complex interactions between atmospheric deposi- tion, forest soils, and surface waters have been limited because of the long- term nature of forest ecosystem development, the hypothesized subtle but chronic effects of acidic deposition, and the high heterogeneity of forest soils. Ideally, long-term, highly replicated studies of the response of whole ecosys- tems to ambient levels of acidic deposition should be used to evaluate the effects of elevated strong acid additions to forested ecosystems. An alterna- tive is to experimentally manipulate whole ecosystems or ecosystem compo- nents with acid additions to simulate altered deposition scenarios.
The External Plot Experiment (EPE) of the Watershed Manipulation Proj- ect (WMP) is a multiple-year study designed to evaluate dose-response re- lationships for HzSO4 and HNO3 additions to soils at the Bear Brook Wa- tershed in Maine (BBWM), and to assess the biogeochemical mechanisms controlling these responses. The objective of this paper is to report on the response of soil solutions to the first year and a half of chemical manipulation.
Methods
Site description
The EPE study site is located in eastern Maine (44°51'55 " N, 68°6'25 " W) approximately 50 km from the Atlantic Ocean. It is on the southeast- facing slope of Lead Mountain, approximately 100 m due east of the BBWM catchments. The vegetation is dominated by America beech (Fagus grandi- folia Ehrb. ) (approximately 40 years old ) with a small component of yellow birch (Betula alleghaniensis Britt.), sugar maple (Acer saccharum Marsh. ), red maple (Acer rubrum L. ), and red spruce (Picea rubens Sarg. ). Spodosol soils are coarse-loamy, mixed, frigid Typic Haplorthods formed from com- pact basal till (David et al., 1990), and the bedrock is primarily metamor- phosed quartzites and calc-silicates with granitic intrusions.
Experimental design
In the spring of 1987, six 15 mX 15 m plots were established within the experimental area on each of three elevational contours (245, 260 and 275 m), making a total of 18 plots of 225 m 2 each. Each plot was surrounded by a 1 m treated buffer strip to avoid edge effects. The plots on the same contour were situated 15 m apart with approximately 30 m between contours (Fig. 1 ). Six treatments were randomly assigned to one plot on each of the three
L.E. Rustad et aL /Agriculture, Ecosystems and Environment 47 (1993) 117-134 1 19
[] Low N '~- ~" ~I ~ High N ~ ~ ,. j '<~-'~ . ~, . • LOW S
~ ~ . ~ 1 High S
Dosi .,// ~ Control
Flushing Tanks -.
C5 C6
Water Source I.~ ~ 'J
B2 3 ~\ B4 ~ 8'5 B6
ii ,} A1 A2 A 3 A4 , A5 I A 6 ~ A 6
,"- ~I N
( , Water Storage
"-r" ~'~ " Tanks
Fig. 1. Experimental design.
contours (i.e. blocks) for a total of three plots per treatment in a randomized block design. Target treatments consisted of two levels of HESO4 (2000 and 4000 eq ha -~ year-1; referred to as LS and HS, respectively), two levels of HNO3 (2000 and 4000 eq ha-~ year-~; LN and HN, respectively), one level of combined HESO4/HNO3 (2000 eq ha-1 year-1 each of SO 2- and NO£; NS), and a control receiving water only (C). Exact treatment levels (Table 1 ) differed slightly from target doses owing to field season differences.
During the summer of 1987, soils in each plot were mapped and sampled (David et al., 1990), and all plots were instrumented with:
( 1 ) two pairs of tension lysimeters with one lysimeter of each pair located in the upper Bhs horizon directly below the E horizon and the second located 25 cm below the mineral soil surface in what was generally the Bh horizon;
(2) three zero-tension lysimeters, two located directly below the O horizon and one 25 cm below the mineral soil surface. A buried soil bag experiment occupied a central corridor in each plot and was used to examine soil response to the treatments (David et al., 1990).
Tab
le 1
T
reat
men
t sc
hedu
le f
or th
e 19
88 a
nd 1
989
fiel
d se
ason
s
Tre
atm
ent
Cod
e N
SO
4 N
O3
(eq
ha-
lyea
r -l
) (e
q h
a-ly
ear
-l)
1988
19
89
1988
19
89
SO4
NO
s (#
eq 1
-~ )
(#eq
1 -~
)
1988
19
89
1988
19
89
pH
i 19
88
1989
Con
trol
C
3
0 0
0 0
Low
sul
fur
LS
3
1300
18
00
0 0
Hig
h su
lfur
H
S
3 26
00
3600
0
0 S
ulfu
r/ni
trog
en
NS
3
1300
18
00
1300
18
00
Low
nit
roge
n L
N
3 0
0 13
00
1800
H
igh
nitr
ogen
H
N
3 0
0 43
50
3600
0 21
75
4350
21
75 0 0
0 18
65
3730
18
65 0 0
0 0
6.59
-7.0
0 6.
03-6
.95
0 0
2.66
2.
73
0 0
2.36
2.
43
.~
2175
18
65
2.36
2.
43
2175
18
65
2.66
2.
73
7250
37
30
2.14
2.
43
4
L.E. Rustad et al. /Agriculture, Ecosystems and Environment 47 (1993.) 117-134 121
Irrigation system
The irrigation system that delivered treatment solutions to the plots con- sisted of:
( 1 ) a water supply system; (2) a water storage system near the water supply; (3) a pump to transfer water from lower storage tanks to upper dosing and
flushing tanks; (4) upper dosing and flushing tanks; (5) pressure regulators and partial circle spray nozzles at the four comers
of each plot; (6) calcium carbonate neutralization beds (Fig. 1 ).
The water supply system is based on a subsurface water interception system adjacent to Bear Brook. Water drains by gravity from this system into four 8000 1 storage tanks and is pumped upslope (about 60 vertical m) through PVC pipes (7.5 m in diameter) to six 4000 1 dosing tanks and six 1500 1 flushing tanks. The treatment acids are added to the dosing tanks when they are about 20% full, and mixing is achieved by the agitation of filling the tanks. Treatment solutions are delivered to the plots by gravity through a system of six polyethylene pipes (5 cm in diameter), each leading to one plot on each of three rows on the basis of treatment type. The ends of these pipes have check valves below the plot network to allow the lines to be drained through calcium carbonate neutralization beds. Solutions are applied to each plot through four 90 ° arc spray nodes located at the four comers of each plot. Pressure regulators, in line with each of the nozzles, ensure that each nozzle delivers solutions at the same rate.
Sprinkler application uniformity was tested extensively before acid treat- ments began and evaluated using a coefficient of uniformity (Christiansen, 1942). The mean ( + SD) coefficient of uniformity for the plots was 67 _+ 6%, with a range from 57 to 74%. This compares with the mean coefficient of uniformity for ambient throughfall (tested on three of the plots), which was 75 ___ 10.7%, with a range of 63.1-83.9%. These evaluations indicated that the uniformity of application for the sprinklers was roughly similar to that of am- bient throughfall.
Treatment applications
Prior to acid additions, 1.6 mm depth of untreated water was applied to the plots to wet the vegetation and soil surfaces. The plots were then irrigated with 4.3 mm of treatment solution. In the initial treatment season (1988), weekly treatment applications began on 25 July and continued until 10 Oc- tober; in the second treatment season (1989), treatments began on 24 May
122 L.E. Rustad et al. /Agriculture, Ecosystems and Environment 47 (1993) 117-134
and continued until 2 October (Table 1 ). Target loads and concentrations were decreased in 1989 to make the experiment more comparable with the adjacent whole watershed manipulation (Erickson et al., 1990). Treatment results from an additional two years of treatment (1990 and 1991 ) and a subsequent recovery period (1993) will be discussed in a later paper. The cumulative increase in hydrologic flux to the plots was 4.7 cm in 1988 and 9.6 cm in 1989 against a background throughfall hydrologic flux of about 90 cm year- 1.
Soil solution collections and analyses
This paper reports on soil solutions collected from the autumn of 1987 to May 1990. Soil solutions were collected on a 2-4 week schedule. Volumes were measured in the field, and samples were bulked by lysimeter type, plot, and depth for chemical analyses.
Within 7 days of collection, pH and acid neutralization capacity (ANC) were measured and subsamples were filtered through a 0.4/~m filter for anal- ysis of cations, anions, Si, and NHg, and through a 0.7 gm glass-fiber filter for dissolved organic carbon (DOC). Aliquots for cations, Si, and DOC were acidified prior to analysis, and anion aliquots were stored at 4 ° C. Table 2 lists the procedures for sample analysis. Standard quality assurance procedures were followed for all analyses as detailed in the citations in the Methods sec- tion (Table 2).
Statistical analyses
All data were tested for normality using a Kolomogorov test (Conover, 1980). Data that did not fit a normal distribution were transformed loga-
Table 2 Soil solution analytical methods
Parameter Description Reference
pH Potentiometric Hillman et al., 1985 ANC Automated titration HiUman et al., 1985
with Gran Plot Base cations Hame atomic absorption Hillman et al., 1985
(Ca, Mg, K, Na) spectroscopy Aluminum Furnace atomic Hillman et al., 1985
absorption spectroscopy Anions
(SO4, NO3, C! ) Ion chromatography Ammonium Automated colorimetry Si Automated colorimetry DOC Liberation of COe and IR
determination
HiUman et al., 1985 Anonymous, 1986a Anonymous, 1986b American Public Health Association, 1981
L.E. Rustad et al. /Agriculture, Ecosystems and Environment 47 (I 993) I 17- 134 12 3
rithmically and retested for normality. In all cases, the logarithmic transfor- mation was found to be adequate to approximate a normal distribution, and all subsequent statistical analyses were performed on the transformed data. Treatment effects were evaluated using analysis of variance. The Ryan-Ei- not-Gabriel-Welsch multiple F test was used to perform mean separations because it appears to be the most powerful step-down multiple-stage test in the literature (Ramsey, 1978), and it is also compatible with the overall ANOVA F test, in that it rejects the null hypothesis when the F test does so (Statistical Analysis Systems Institute (SAS), 1985 ). Differences between the two field seasons by lysimeter type, depth, and treatment were investigated by means of a standard t-test, and correlation analyses were used to evaluate relationships among soil solution parameters. All statistical analyses were performed using procedures of SAS ( 1985 ).
Results and discussion
Pretreatment soil solution chemistry
In the upper soil solutions (i.e. tension Bhs horizon, zero-tension O hori- zon), Ca 2+ was the dominant cation in solution and SO4 2- was the dominant anion on a charge equivalent basis (Table 3). Approximations of organic an- ions, based on DOC concentrations and electroneutrality deficits, suggested that DOC was also important in surface horizons. In the lower soil solutions (i.e. Bh horizon), the dominant cation in solution was Na +, and SO4 2- and C1- were the dominant anions.
Although solutions collected from both lysimeter types showed similar chemical trends, clear differences existed between the tension and zero-ten- sion lysimeters. Zero-tension lysimeter solutions were consistently more acidic and more highly colored, had higher SO 2- and lower Si concentrations, and were generally more variable than tension lysimeter solutions (Table 3). These differences can be attributed to the fact that soil solutions collected by zero- tension lysimeters consisted primarily of macropore flow which, after passing through organic horizons, had relatively brief contact with the mineral soil matrix. Soil solutions collected by tension lysimeters may consist of a greater proportion of micropore flow, which should have a longer time to equilibrate with the mineral soil (Swistock et al., 1990). Because the overall chemical trends observed in the zero-tension lysimeter solutions were similar to those in the tension lysimeter solutions, the remaining discussion is restricted to tension lysimeter solution results.
In the pretreatment data, the within-treatment variability associated with differences among plots was generally as large, or larger, than the among- treatment variability, which resulted in few significant pretreatment differ-
124 L.E. Rustad et al. /Agriculture, Ecosystems and Environment 47 (1993) 117-134
Table 3 Pretreatment soil solution chemistry for tension and zero-tension lysimeters. Coefficients of variation given in parentheses. Sample numbers range from 40 to 107
Tension lysimeter solutions Zero-tension lysimeter solutions
Upperdepth H 13 (392) 40 (102) Ca 79 (37) 200 (63) Mg 32 (35) 99 (69) K 18 (70) 53 (87) Na 70 (33) 57 (53) NH4 3 (190) 5 (222) AI 17 (68) 25 (49) Si 132 (28) 94 (64) SO4 74 (31) 272 (73) NO3 7 (180) 9 (188) CI 61 (74) 58 (71) ANC 17 (113) -22 (388) DOC 802 (66) 2272 (78)
L o w e r d e p t h H 1 (99) 17 (104) Ca 77 (27) 74 (36) Mg 30 (20 40 (31) K 10 (40) 10 (92) Na 91 (22) 94 (25) NH, 2 (116) 3 (351) AI 5 (102) 16 (69) Si 112 (32) 62 (31) SO4 101 (22) 150 (32) NO3 8 (133) 7 (235) CI 62 (43) 79 (36) ANC 24 (68) -11 (234) DOC 249 (104) 304 (205)
Units are #tool 1-1 for AI and Si, gmol C 1-1 for DOC, and geq 1-1 for all other parameters.
ences among the treatments. Differences observed among treatments after initiation of acid additions were, therefore, attributed to treatment effects.
Soil solution response to acid manipulations
Overview of response Soil solution chemical properties showed clear and rapid responses to treat-
ments. In the upper lysimeter solutions, concentrations of both SO 2- and NO~- increased relative to those in the control for all S and N treatments,
L.E. Rustad et al. / Agriculture, Ecosystems and Environment 47 (1993) 117-134 125
respectively (Table 4). As solutions passed through the upper 25 cm of the pedons, mean SO 2- concentrations decreased significantly by 50-86% of ini- tial values. Mean NO~- concentrations decreased significantly with depth in the LN and NS treatments (by 71-93% of initial values) but remained vir- tually constant with depth in the HN treatments. The decreasing concentra- tions of SO 2- with depth may be attributed to the adsorption of SO 2- by the soil exchange complex. This trend is consistent with the increase in soil-ad- sorbed SO 2- observed in the upper solum using buried soil bags (David et al., 1990). The decreasing concentrations of NO~- with depth as observed in the LN and NS treatments reflect the importance of biological immobiliza- tion for NO~-. The constant NO~- with depth observed in the HN treatment, however, indicates that this high rate of NO~- input exceeds the capability of the soil/plant system to assimilate the added N.
In 1988, SO42- concentrations were depressed in the HN treatment at both depths; in 1989, SO 2- concentrations were depressed in the HN treatment only at the lower depth (Table 4; Figs. 2 (a) and 2 (b)). This trend is consis- tent with the hypothesis that high HNO3 loadings decrease soil solution pH and increase positive charge on oxide surfaces, thereby increasing soil anion exchange capacity and SO 2- retention. The increase in positive surface charge may have been greater during the 1988 field season when treatment solution concentrations were 1.7 times greater than those applied in the 1989 field season (Table 1 ). A similar loss of soil solution SO 2- and stream SO 2- (Nodvin et al., 1986, 1988; Fuller et al., 1987) in response to nitrification- induced acidification was observed following two clearcutting experiments at the Hubbard Brook Experimental Forest, NH.
Increased concentrations of strong acid anions in solution due to treat- ments were generally accompanied by elevated concentrations of H +, A1 n 4, and base cations (Table 4). Of these cations, Ca 2÷ and Mg 2÷ showed the most consistent response to the treatments (Table 4; Fig. 2). They were also the cations most strongly correlated to the strong acid anions (Table 5). These results suggest that the mineral acidity in soil solutions associated with the treatments was neutralized primarily by cation exchange processes which were dominated by the exchange of H + for Ca 2 ÷ and Mg 2÷.
These results are consistent with those reported by David et al. ( 1991 ) and Fernandez and Rustad (1990) who showed that Ca 2÷ and Mg 2÷ were the dominant counter-ions for experimental additions of SO 2- and NO~-. They are also consistent with those of David et al. (1990), who showed significant increases in exchangeable Ca 2÷ and Mg 2÷ in soil bags buried below the forest floor in the HS plots of the experiment reported here. They attributed this increase in exchangeable Ca 2+ and Mg 2÷ to a release of these cations from the forest floor to soil solution during the initial stages of acidification with subsequent adsorption in the mineral soil below.
Perhaps a more integrated approach to examining the ionic composition of
Tab
le 4
M
ean
soil
sol
utio
n ch
emis
try
from
ten
sion
lys
imet
ers
by t
reat
men
t ty
pe t,
tre
atm
ent
peri
od (
198
8 vs
. 19
89 ),
and
dep
th (
unit
s ar
e/zm
ol 1
- ~ fo
r A
1 an
d S
i,/a
nol
C 1
- t f
or D
OC
, m
l fo
r o~
vo
lum
e, a
nd p
, eq 1
- ~ fo
r all
oth
er p
aram
eter
s)
Tre
atm
ent
C
LS
HS
L
N
HN
N
S
effe
cts
1988
19
89
1988
19
89
1988
19
89
1988
19
89
1988
19
89
1988
19
89
1988
19
89
Upp
er d
epth
H
13
12
46
23
19
21
36
27
41
21
16
25
(49)
(2
3)
(81)
(7
9)
(72)
(6
6)
(69)
(6
8)
(84)
(8
6)
(26)
(4
3)
Ca
* *
67"
48"
35
3 b
10
9 "b
394 b
18
6 "b
237 b
12
9 ab
51
1 b
17
0 ab
277 b
29
5 b
(28)
(2
3)
(77)
(6
0)
(68)
(7
0)
(36)
(4
6)
(52)
(1
08)
(32)
(7
0)
MG
*
45
" 25
1
92
b
74
193 b
10
4 13
5 b
70
19
9 b
80
10
8 b
76
(20)
(2
4)
(62)
(5
1)
(49)
(7
3)
(54)
(4
0)
(40)
(9
5)
(40)
(5
7)
K
14
11
30
31
10
11
34
18
16
12
18
11
(6
6)
(50)
(1
06)
(104
) (5
3)
(52)
(6
3)
(31)
(9
) (3
8)
(118
) (4
9)
Na
72
59
105
75
150
117
102
87
110
80
123
94
(15)
(2
4)
(22)
(4
6)
(36)
(2
7)
(35)
(2
7)
(39)
(2
8)
(37)
(4
2)
NH
4 1
1 1
2 2
1 1
3 1
4 1
4 ,~
(3
2)
(75)
(2
) (1
19)
(197
) (1
06)
(38)
(1
06)
(61)
(1
78)
(32)
(1
18)
~.
AI
25
22
90
26
37
27
42
33
80
23
24
44
(47)
(3
0)
(121
) (7
6)
(72)
(8
4)
(75)
(5
0)
(121
) (3
6)
(26)
(7
6)
Si
13
9
111
122
107
12
8
89
197
137
126
128
131
97
(15)
(2
3)
(21)
(1
5)
(26)
(2
5)
(55)
(4
4)
(17)
(2
4)
(26)
(2
7)
SO4
* *
78"
72 a
77
7 ~
26
7 ~
11
13
c
395 c
10
1 "b
69"
39
a
74 a
300 a
be
292 "
~
(32)
(2
1)
(94)
(3
5)
(86)
(6
8)
(65)
(4
7)
(23)
(5
2)
(77)
(1
09)
NO
3 *
* 2 a
7 *
b 2 a
b 1 b
7 a
b 21
ab
259 ~
15
8"
99
6 ~
25
4"
161 a
~
301 a
:~
(7
6)
(235
) (1
26)
(116
) (1
51)
(136
) (1
09)
(95)
(6
4)
(124
) (1
42)
(120
) C
1 8
0
29
98
36
77
47
73
44
6
1
37
57
44
~.
(4
0)
(42)
(4
6)
(54)
(6
7)
(37)
(1
4)
(53)
(3
6)
(63)
(2
9)
(51)
A
NC
1
l -5
7
-16
-
11
-17
-3
5
-23
-2
6
- 10
-7
-
18
(156
8)
(331
) (1
18)
(138
) (1
64)
(106
) (8
8)
(117
) (1
04)
(145
) (1
02)
(75)
D
OC
81
2 83
3 11
26
574
417
356
2002
10
87
525
529
580
969
(62)
(4
8)
(69)
(6
7)
(52)
(4
7)
(122
) (1
05)
(22)
(2
4)
(61)
(1
35)
CB
-C^
2
38
31
-26
5
- 10
-7
2
-50
36
25
-2
60
-3
4
-14
-
121
,~
(89)
(7
5)
(147
) (3
85)
(98)
14
1 (3
33)
(425
) (1
40)
(150
) (4
55)
(110
) .~
. V
olum
e 16
6 15
9 18
0 15
2 22
9 20
4 11
8 17
2 18
3 18
7 17
1 15
0 (5
5)
(67)
(6
6)
(70)
(4
6)
(30)
(7
3)
(48)
(4
6)
(47)
(5
5)
(71)
n
4-8
17-2
1 5-
6 12
-20
6-8
15-2
0 3-
5 14
-21
5-6
13-1
8 6-
9 9-
18
Low
er d
epth
H
* 1
3 "b
3 5 "
b 5
8"
1 1 b
29
17
" 2
6 "b
(78)
(3
6)
(65)
(3
0)
(105
) (4
7)
(114
) (1
30)
(58)
(5
8)
(70)
(3
7)
Ca
* *
59*
53 ab
70
" 47
" 71
a 75
ab
90"
79 ab
36
2 b
167 b
86
" 85
"b
(28)
(2
4)
(23)
(2
0)
(29)
(3
9)
(30)
(2
0)
(59)
(8
6)
(66)
(5
7)
Mg
* *
25"
25"
44"
30
ab
34"
52
b
45"
36 "b
16
7 b
89 ¢
36"
41
ab
-..""
(15)
(2
1)
(36)
(2
0)
(38)
(6
3)
(25)
(1
6)
(57)
(6
2)
(38)
(4
1)
K 8
9 II
10
7 6
12
8 21
13
6
8
(19)
(3
3)
(37)
(5
7)
(32)
(2
5)
(8)
(33)
(8
2)
(35)
(2
3)
(21)
N
a 88
89
97
90
10
6 11
2 12
1 97
14
5 13
1 10
5 10
5 (9
) (1
5)
(27)
(2
5)
(25)
(2
0)
(8)
(16)
(3
7)
(32)
(2
4)
(20)
N
H4
1 1
1 1
1 1
1 1
3 2
1 1
(50)
(1
18)
(22)
(1
58)
(57)
(1
38)
(34)
(8
0)
(182
) (1
13)
(65)
(1
41)
AI
* 4"
8
5"
8 9 "
b I I
3"
I0
92 b
24
5 a
9
(53)
(4
2)
(39)
(1
8)
(83)
(4
4)
(76)
(8
7)
(104
) (7
7)
(46)
(3
4)
Si
133
104
84
68
98
82
lO0
lO1
145
114
91
78
(20)
(2
4)
(23)
(2
7)
(19)
(2
5)
(13)
(3
3)
(38)
(4
0)
(14)
(l
l)
~.
SO4t
*
* 90
"b
107 "
b 14
6"
127 "
b 15
7"
195"
10
2 "b
106 -
b 43
b 68
b 12
1 ab
118 "
b (9
) (1
2)
(31)
(9
) (4
7)
(33)
(1
6)
(15)
(6
4)
(51)
(4
0)
(42)
N
O3
* *
18"
14"
2"
1"
5 a
7 a
59 "b
11
" 8
52
b
336 b
48
" 7
8 ab
(174
) (1
71)
(59)
(7
7)
(95)
(1
39)
(99)
(1
12)
(61)
(7
6)
(136
) (1
54)
CI
41
45
82
57
59
60
69
60
52
46
58
61
~3
(30)
(4
9)
(26)
(3
3)
(27)
(3
5)
(34)
(3
8)
(45)
(4
0)
(59)
(4
4)
AN
C
* *
18"
6 ab
8 a
l "b
5 a
- 1 "
b 24
" 23
': -2
6 b
-
l0 b
9"
2 ~
(5
1)
(63)
(1
22)
(528
) (1
97)
(662
) (4
4)
(41)
(7
3)
(152
) (8
1)
(208
) D
OC
21
1 25
0 15
8 16
3 19
3 20
4 19
4 48
0 29
6 25
7 14
9 14
6 (4
2)
(47)
(2
9)
(14)
(3
0)
(16)
(7
1)
(92)
(9
6)
(53)
(4
8)
(20)
C
B-C
A 2
*
26
10" h
3
-9 "
b -3
-2
1 b
37
43
" -2
53
-5
8 b
6
-18
"b
(40)
(1
36)
(525
) (8
2)
(108
0)
(90)
(2
9)
(59)
(1
39)
(116
) (1
96)
(75)
V
olum
e 24
6 27
3 29
8 29
5 35
8 30
6 24
7 24
3 25
6 25
2 33
8 33
0 (8
4)
(40)
(3
2)
(26)
(5
2)
(28)
(3
1)
(45)
(5
4)
(49)
(2
3)
(21)
n
6-9
19-2
3 8-
9 21
-24
9 21
-22
4 16
-19
6-7
17-2
2 9
22-2
3
*C, c
ontr
ol; L
S, lo
w s
ulfu
r; H
S, h
igh
sulf
ur; L
N, l
ow n
itro
gen;
HN
, hi
gh n
itro
gen;
NS
, nit
roge
n/su
lfur
. 2
CB
-C^=
(C
a+M
g+
K+
Na)
-
(SO
4+
NO
3+
C1)
. A
ster
isks
in
the
trea
tmen
t ef
fect
s co
lum
ns i
ndic
ate
that
a s
igni
fica
nt t
reat
men
t ef
fect
exi
sts
for
the
give
n ye
ar;
mea
ns f
ollo
wed
by
no s
uper
scri
pt o
r th
e sa
me
supe
rscr
ipt(
s) a
re n
ot
sign
ific
antl
y dif
fere
nt u
sing
the
Rya
n-E
inot
-Gab
riel
-Wel
sch
mul
tipl
e F
test
. 19
88 m
eans
in it
alic
s ar
e si
gnif
ican
tly
diff
eren
t fro
m th
e co
rres
pond
ing
1989
mea
n (a
= 0
.05
for a
ll a
naly
ses)
. C
oeff
icie
nts o
f var
iati
on a
re g
iven
in p
aren
thes
es b
elow
the
mea
ns.
.-...i
128 L.E. Rustad et al. /Agriculture, Ecosystems and Environment 47 (1993) 117-134
Upper Soil Solutions Lower Soil Solutions ,a k .
• k~ • • 2OOO
• r • r c .
-t
÷
~oa- ' " "
, , 0 -
250 -
0
• r
-/.
4- .I-
+ ÷ ÷
loo0
aoo
z ~
I
a
• r • r O ,
J `*o
4oo.
o
• k~ • L
• V • r f .
.+, , ÷
÷
I [ I I I
! ,0o + ~ 1,, :~ ~ ++
l o o . '
o o . 1JU188 1 N O V 8 8 1 M I r 8 9 1 J u 1 8 9 1 N o v 8 9 1 M a r g O t J u 1 8 8 1 N o v 8 8 1 M a r 8 9 t J u 1 8 9 1 N o v B 9 1 M l r S ) O
Fig. 2. Temporal trends in mean concentrations of: (a) SO~- in upper tension lysimeter solu- tions; (b) SO 2- in lower tension lysimeter soil solutions; (c) NO~- in upper tension lysimeter solutions; (d) NO£ in lower tension lysimeter soil solutions; (e) Ca 2+ in upper tension lysi- meter solutions; ( f ) Ca 2 + in lower tension lysimeter soil solutions; (g) Mg 2+ in upper tension lysimeter solutions; (h) Mg 2+ in lower tension lysimeter soil solutions; (i) K + in upper tension
L.E. Rustad et al. / Agriculture, Ecosystems and Environment 4 7 (1993) 117-134 129
s o
} "
4O
2O
0
U p p e r Soil Solutions • v ~q l -
I.
s o
40
l o
o
Lower Soll Solutlons
+, , . +
+ + , ,+
I I I l I
• I .
. . . . + ++ A ,+- Q ,
s o 4 -
I I I I o
4 o
2 o
o
.,e ~ . a •
, i P- • r
m .
5 0
40
l o
o
+.+
+ '
+ ' . 4 . - t - +
• + ' 4 %
. - ~ - ~ - ~ ~" ,
1so
120 -
¢ o .
o 1 J u l 8 8
.4 ~ • •
• r
O .
• , • , , 1 N o 8 6 1 M a r l l 9 1 J I E 9 1 N o v 8 9 1 M a r g 0
Fig. 2 (continued).
A 1so I
120
! + 4 . 4 - ' S O '
40
0 - - 1 d u l S I I 1 N o v 8 8 1 M I r 8 9
L
p .
+
• . , 4 - +
1 J u ' l e ~ 1 N o v e s 9 1 M : ' r g 0
lysimeter solutions; (j) K + in lower tension lysimeter soil solutions; (k) Na + in upper tension lysimeter solutions; (1) Na + in lower tension lysimeter soil solutions; (m) H + in upper tension lysimeter solutions; (n) H + in lower tension lysimeter soil solutions; (o) AI" + in upper tension lysimeter solutions; (p) AI "+ in lower tension lysimeter soil solutions. Treatment periods are indicated by arrows. The legend is as follows:., control; I, HN; *, Hs; [~, LN; × , LS; ~ , NS.
130 L.E. Rustad et al. / Agriculture, Ecosystems and Environment 47 (1993) 117-134
Table 5 Pearson's correlation coefficients for SO4 and NO3 by treatment type
Control Sulfur treatments Nitrogen treatments
504 NO3 504 NO3 504 NO3
H - 0.41 - 0.46 0.69 - 0.07 - 0.24 0.50 Ca 0.21 0.60 0.93 0.31 - 0.32 0.69 Mg - 0.08 0.34 0.94 0.18 - 0.35 0.71 K 0.20 -0 .01 0.28 - 0 . 0 1 - 0 . 1 1 0.38 Na 0.54 0.28 0.31 0.05 0.27 - 0 . 1 0 NH4 0.03 0.15 0.19 0.11 - 0 . 2 3 0.27 AI - 0.38 - 0.40 0.79 - 0.06 - 0.14 0.50 Si - 0.16 - 0.06 0.56 0.27 0.03 0.15 SO4 - - 0.06 - 0.17 - - 0.60 N O 3 - 0.06 - 0.16 - - 0 . 6 0 - CI 0.06 0.11 0.02 0.20 0.35 0.27 ANC 0.27 0.20 - 0.70 0.03 0.18 - 0.49 DOC - 0 . 4 4 - 0 . 1 8 0.57 0.10 0.16 0.05 Volume 0.21 0.49 - 0.36 - 0.11 - 0.06 - 0.11
Correlation coefficients indicated in bold are significant at the 0.0001 level.
solutions is through the relative magnitude of mineral bases (CB; Na +, K ÷, Mg 2+, Ca 2+ ) vs. mineral acids (CA; SO42- , NO~-, C1-). If CB-CA is posi- tive, then net mineral base exists in solution, and/or an alternate anion is supporting hydrogen ion concentrations (e.g. organic ligands, HCO~- ). If CB- CA is negative, then mineral acids are supporting hydrogen ion (Baker et al., 1990). In control plots, CB-CA was positive both years, in upper and lower lysimeter solutions (Table 4), indicating the presence of net mineral base. In the HS and HN plots, CB-CA was driven negative at both depths, indicating the presence of net mineral acid due to the strong acid addition.
Temporal trends Analysis of temporal trends in soil solution chemical response (Fig. 2)
showed that both SO 2- and NO~- concentrations responded immediately to treatments and continued to increase throughout the treatment period (Figs. 2 ( a )-2 ( d ) ). Following the termination of treatments, excess SO~- retained by soils during treatment was released back to soil solutions. For the LS treat- ments, equilibrium with ambient SO 2- deposition was apparently achieved within a few months. For the HS treatments, it appears that SO 2- desorption was extensive enough to prevent a return to steady state conditions before the renewed initiation of treatments. In contrast, NO~- concentrations quickly returned to control levels because these soils have little to no capacity to ad- sorb this anion, and the limited retention in capillary soil solutions is quickly
L.E. Rustad et al. /Agriculture, Ecosystems and Environment 47 (1993) 117-134 131
flushed from the pedon. Comparisons of the response of upper soil solutions with lower soil solutions for SO 2- showed a smaller, more gradual increase in SO 2- concentrations at the lower depth, which is indicative of sulfate re- tention occurring in the solum above. Soil solution cation concentrations, particularly Ca 2 + and Mg 2+, closely paralleled anion concentrations in order to maintain electrical neutrality (Figs. 2 (e)-2 (p)).
1988 vs. 1989 Although soil solution chemical trends were similar in both the 1988 and
1989 field seasons, mean concentrations of most major soil solution constit- uents were lower in 1989 than in 1988 (Table 4; Fig. 2). This may be attrib- uted to the following: (a) treatment concentrations were decreased by 14- 49% in 1989 (Table 1 ); (b) protonation of oxide surfaces may have occurred during the 1988 field season, resulting in a greater retention of SO 2- and NO~- and a reduced leaching of cations in the 1989 field season; and/or (c) the increased availability of NO~-, and to a lesser extent SO 2-, in the latter half of the 1988 growing season may have stimulated biological activity and therefore increased net uptake of nutrients in the 1989 growing season. The fact that litterfall, a indicator of productivity, was greater in 1989 than in 1988 (K. Nadelhoffer, personal communication, 1990), supports this latter hypothesis.
Variability in response Interpreting the response of soil solutions to experimental manipulations
can be difficult given the inherent variability in forest soils and soil solutions (David and Gertner, 1987; David et al., 1990; Swistock et al., 1990), and the artificial variability induced by sampling techniques (Barbee and Brown, 1986; Litaor, 1988). In this study, soil solution variability was generally greater in the zero-tension lysimeters than in the tension lysimeters and in the upper lysimeters than in the lower lysimeters (Table 3). Of the individual soil so- lution constituents measured, variability was consistently highest for ANC, NO£, and NH + and lowest for Na +, Cl-, and Si (Tables 3 and 4).
Despite the high degree of variability associated with lysimeter solutions, treatment effects could be detected, and were generally consistent across the three plots per treatment as illustrated in Fig. 3 (a). An exception was NO~ concentrations in the HN treatment, in which two of the plots (A2 and C 1 ) showed a clear response to the treatments in both 1988 and 1989, whereas the third plot (B1) responded to the treatments in 1988 but showed little re- sponse in 1989 (Fig. 3(b)). Differences in response may be attributed to: non-uniformity of treatment solution application, macropore channeling of treatment solutions away from individual lysimeters, and differences in the physical, chemical, and biological properties of the soil surrounding the indi- vidual lysimeters.
132
3 0 0 0
. - I 2 2 5 0
O" -q
'¢ 1 5 0 0 O 09
7 5 0
L.E. Rusted et el./Agriculture, Ecosystems and Environment 47 (1993) 117-134
High Sulfur Treatment
a.
0 h
1Jul88 1Nov88 1Mar89 1Jul89
~ - A1 --P~ B6 ~ C 3
1Nov89
2 0 0 0
1 5 0 0
0"
o~ 1 0 0 0 O z
500
High Nitrogen Treatment
L
b.
0
1Jul88 1Nov88 1Mar89 1Jul89
A2 - ~ - B1 ~ - C2
1Nov89
Fig. 3. Temporal trends by plot in upper tension lysimeter soil solutions for (a) SO~- in the HS treatment and (b) NO~- in the HN treatment.
Conclusions
Results from a period of 1.5 years of strong acid additions under field con- ditions indicate that experimental manipulation with different levels of H2SO4 and HNO3 resulted in increased leaching of SO~- and NO3- accompanied by a increased loss of base cations and AI 3+ from the upper solum. Soil solution chemical composition responded rapidly to treatments, and solution concen- trations remained elevated above control concentrations following the ter- mination of treatments for 2-7 months, indicating that anions sorbed onto
L.E. Rustad et al. /Agriculture, Ecosystems and Environment 4 7 (199 3) 117-134 133
exchange sites during the treatment period were desorbed back into solution during recovery. The multiple-year nature of this study is intended to further evaluate the importance of soil processes with slower kinetics, including N cycling and the incorporation of S into organic soil pools. Likewise, the poorly understood long-term dynamics of recovery will be examined.
Acknowledgments
The authors would like to acknowledge the considerable contribution of Warren Hedstrom in the design and implementation of the irrigation system, the efforts of Betty Lee in preparation of the manuscript, and the support of the field and laboratory crews who helped make this research possible. This research was conducted through the support of the US Environmental Protec- tion Agency. Although the research described in this article has been funded by the US Environmental Protection Agency, it has not been subject to the EPA's policy review and therefore does not necessarily reflect the views of the Agency.
References
America Public Health Association, 1981. Standard Methods for the Examination of Water and Wastewater. Method 505, 15th edn., pp. 471-475.
Anonymous, 1986a. Ammonia in Water and Wastewater. Technicon Standard Methods 19: In- dustrial Method 780-86T. Technicon Instruments Corporation, Industrial Systems Division, Tarrytown, NY.
Anonymous, 1986b. Silicates in Water and Wastewater. Technicon Standard Methods 19: In- dustrial Method 785-86T. Tcchnicon Instruments Corporation, Industrial Systems Division, Tarrytown, NY.
Baker, J., Gherini, S.A., Christensen, S.W., Driscoll, C.T., Gallagher, J., Munson, R.K., New- ton, R.M., Rcckhow, K.H. and Schofield, C.T., 1990. Adirondack Lakes Survey: An In- terpretive Analysis ofFish Communities and Water Chemistry, 1984-1987. Adirondack Lakes Survey Corporation, Ray Brook, NY.
Barbee, G.C. and Brown, K.W., 1986. Comparisons between suction and free-drainage soil so- lution samplers. Soil Sci., 141:149-154.
Christiansen, J.E., 1942. Irrigation by sprinkling. Calif. Agric. Exp. Stn. Bull. 670. Conover, W.J., 1980. Practical Nonparametric Statistics. John Wiley, New York, N-Y. David, M.B. and Gertner, G.Z., 1987. Sources of variation in soil solution collected by tension
plate lysimeters. Can. J. For. Res., 17: 19-193. David, M.B., FuUer, R.D., Fernandez, I.J., Mitchell, M.J., Rustad, L.E., Stam, A. and Nodvin,
S.C., 1990. Spodosol variability and assessment of response to acidic deposition. Soil Sci. Soc. Am. J., 54:541-548.
David, M.B., Vance, G.F. and Fasth, W.J., 1991. Forest soil response to acid and salt additions of sulfate: aluminum and base cations. Soil Sci., 151:208-219.
Erickson, H.E., Rustad, L.E., Narahara, A.M. and Nodvin, S.C., 1990. Watershed Manipulation Project: Field Implementation Plan for 1986-1989. US EPA Rep. No. PB91-148403, U.S., EPA, Corvallis, OR.
Fernandez, I.J., 1989. Effects of acid deposition on soil productivity. In: D.C. Adriao (Editor),
134 L.E. Rustad et al. /Agriculture. Ecosystems and Environment 47 (1993) 117-134
Advances in Environmental Science--Acid Precipitation, Vol. 4. Biological and Ecological Effects. Springer, New York.
Fernandez, I.J. and Rustad, L.E., 1990. Soil response to S and N treatments in a northern New England low elevation coniferous forest. Water, Air, Soil Pollut., 52:23-39.
Fuller, R.D., Driscoll, C.T., Lawrence, G.B. and Nodvin, S.C., 1987. Processes regulating sul- phate flux following whole tree harvesting of a northern forested ecosystem. Nature, 325:707- 710.
Goldstein, R.A., Gherini, S.A., Chen, C.W., Mok, L. and Hudson, R.J.M., 1984. Integrated Lake-Watershed Acidification Study (ILWAS): a mechanistic ecosystem analysis. Phil. Trans. R. Soc. London, Ser. B, 305: 409-425.
Hillman, D.C., Potter, J.F. and Simon, S.J., 1985. Analytical Methods for the National Surface Water Survey Eastern Lake Survey (Phase I--Synoptic Chemistry). US EPA Contract No. 68-03-3249, US EPA, Las Vegas, NV.
Litaor, M.I., 1988. Review of soil solution samplers. Water Resour. Res., 24:727-733. National Acid Precipitation Assessment Program, 1987. NAPAP Interim Assessment--The
Causes and Effects of Acidic Deposition. Vol. IV. Effects of Acidic Deposition. NAPAP, Washington, DC.
Nodvin, S.C., Driscoll, C.T. and Likens, G.E., 1986. The effect ofpH on sulfate adsorption by a forest soil. Soil Sci., 142:69-75.
Nodvin, S.C., Driscoll, C.T. and Likens, G.E., 1988. Soil processes and sulfate loss at the Hub- bard Brook experimental forest. Biogeochemistry, 5:185-199.
Ramsey, P.H., 1978. Power differences between pairwise multiple comparisons. J. Am. Star. Assoc., 73:363.
Swistock, B.R., Yamona, J.J. and Dewalle, D.R., 1990. Comparison of soil water chemistry and sample size requirements for pan vs tension lysimeters. Water, Air, Soil Pollut., 50: 387- 396.
Statistical Analysis Systems Institute, 1985. SAS User's Guide: Statistics. Spark Press, Raleigh, NC.