Soil Water Chemistry
20
18
16
14
012
-10
.to
8
U 6
4
2
0
7
6
5
0 4
-3
+
::.: 2
I
0
• Below fore t floor
0
10em depth
(a)
°
30 em depth
• Prade
•
0
0
••
0
•
•
:; :;; ~"3 fr ~ a :a ~"3 fr ~ :; :; ~"3
.... ::E~ .... CIlZ .... ::E::E .... CIlZ .... ::E~ ....
1989
1990
1991
(c)
•
Prade
0
8°
0
"~
a :; ~"3 fr ~ :; :a ~"3 fr ~ a :;; ~"3
.... ::E~ .... CIlZ .... ~~ .... CIlZ .... ~~ ....
1989
1990
1991
• o
Below fore t floor
Sub urfaee flow
241
( b)
(160 em)
20~~----------~
18
16
. 14
o 12
-- 10
.to 8
U 6
0
-~
4
2
o
7
6
5
4
3
2
I
0
••
Mont eny
• •
· :
• ••
• !,-. ~
CO go 6(p '6
~"3 fr~ a : ; ; ~ fr~ :; :; ~ fr~ a :;; ~
~""CIlZ""~::E""CIlZ""~~""CIlZ""::E~
1985
1986
1987
1988
(d )
Montseny
• •
. . .
. ...
~.
°
(() eO mn
~""CIlZ""::E::E""CIlZ""::E~""CIlZ""~::E
1985
1986
1987
1988
Fig. 17.3. Temporal variation by depth of ion ratios relative to CI- in gravitational water collected at Prades and Montseny. Ion ratios computed on an equivalent basis. Ca 2 + / CI- (a) and K+ /
CI- (c) at Prades. Ca 2 +/ Cl- (b) and K+/ CI- (d) at Montseny. Montseny data from Bonilla (1990)
profile. Both Montseny and Prades soil waters showed higher Ca 2 +/ Cl- ratios
below the forest floor than at the deeper layers during most of the sampling
period (Fig. 17.3a,b). Further, a seasonal pattern could be identified below
the forest floor: high ratios were present after the summer drought and decreased with time. The K+/ CI- ratio also showed a similar seasonal structure
at both sites, although differences with depth were not clearly apparent in the
Prades soil water, and no seasonal trend was observed at the lower depth at
Montseny (Fig. 17.3c, d).
This temporal variability in soil water chemistry could be related to seasonal patterns of (1) rainfall and throughfall, (2) leaching of ions from fresh
litter, (3) dissolution of forest floor decomposition products and (4) cation
exchange and uptake. Unlike results from other areas, where trends in soil
water chemistry could be associated with patterns of atmospheric frontal
systems (Hughes et al. 1994), little seasonality in the rainfall chemistry could
20
18
16
14
012
-10
.to
8
U 6
4
2
0
7
6
5
0 4
-3
+
::.: 2
I
0
• Below fore t floor
0
10em depth
(a)
°
30 em depth
• Prade
•
0
0
••
0
•
•
:; :;; ~"3 fr ~ a :a ~"3 fr ~ :; :; ~"3
.... ::E~ .... CIlZ .... ::E::E .... CIlZ .... ::E~ ....
1989
1990
1991
(c)
•
Prade
0
8°
0
"~
a :; ~"3 fr ~ :; :a ~"3 fr ~ a :;; ~"3
.... ::E~ .... CIlZ .... ~~ .... CIlZ .... ~~ ....
1989
1990
1991
• o
Below fore t floor
Sub urfaee flow
241
( b)
(160 em)
20~~----------~
18
16
. 14
o 12
-- 10
.to 8
U 6
0
-~
4
2
o
7
6
5
4
3
2
I
0
••
Mont eny
• •
· :
• ••
• !,-. ~
CO go 6(p '6
~"3 fr~ a : ; ; ~ fr~ :; :; ~ fr~ a :;; ~
~""CIlZ""~::E""CIlZ""~~""CIlZ""::E~
1985
1986
1987
1988
(d )
Montseny
• •
. . .
. ...
~.
°
(() eO mn
~""CIlZ""::E::E""CIlZ""::E~""CIlZ""~::E
1985
1986
1987
1988
Fig. 17.3. Temporal variation by depth of ion ratios relative to CI- in gravitational water collected at Prades and Montseny. Ion ratios computed on an equivalent basis. Ca 2 + / CI- (a) and K+ /
CI- (c) at Prades. Ca 2 +/ Cl- (b) and K+/ CI- (d) at Montseny. Montseny data from Bonilla (1990)
profile. Both Montseny and Prades soil waters showed higher Ca 2 +/ Cl- ratios
below the forest floor than at the deeper layers during most of the sampling
period (Fig. 17.3a,b). Further, a seasonal pattern could be identified below
the forest floor: high ratios were present after the summer drought and decreased with time. The K+/ CI- ratio also showed a similar seasonal structure
at both sites, although differences with depth were not clearly apparent in the
Prades soil water, and no seasonal trend was observed at the lower depth at
Montseny (Fig. 17.3c, d).
This temporal variability in soil water chemistry could be related to seasonal patterns of (1) rainfall and throughfall, (2) leaching of ions from fresh
litter, (3) dissolution of forest floor decomposition products and (4) cation
exchange and uptake. Unlike results from other areas, where trends in soil
water chemistry could be associated with patterns of atmospheric frontal
systems (Hughes et al. 1994), little seasonality in the rainfall chemistry could