Distribution and properties of some tidal marsh soils of Apalachee Bay, Florida


Coultas, C.L.; Gross, E.R.

Soil Science Society of America Proceedings 39(5): 914-919

1975


Tidal marshland forms a border between the Apalachee Bay area of the Gulf of Mexico and the uplands of Taylor County, Florida. The purpose of this investigation was to determine the distribution of the tidal marsh soils and to measure some of the properties used in their classification. Three pedons representative of the major soils were described and sampled. The range of electrical conductivity is from 14 to 90 mmhos/cm. Field moist pH ranges from 5.6 to 7.8 and air dried pH values are 2 to 3 pH units lower. Content of S is<0.75% in the Psammaquents and Haplaquods to 6.8% in the Sulfaquents. Oxidation of S to sulfates was probably responsible for the increase of soil acidity after drying. Cation exchange capacity ranges from 2 to 25 meq/100g for the Psammaquents and Haplaquods and from 25 to 75 meq/100 g for the Sulfaquents. Most soils are nearly base saturated. The soils classified in order of increasing elevation are members of the coarse-loamy, mixed, thermic Typic Sulfaquents; the sandy, siliceous, thermic Mollic Psammaquents; and the sandy, siliceous, thermic Aeric Haplaquods. Because of high potential acidity, low bearing strength, and high salinity, decisions concerning man's use of tidal marsh soils should be carefully made. Undisturbed, these are productive soils performing functions valuable to man.

Distribution
and
Properties
of
Some
Tidal
Marsh
Soils
of
Apalachee
Bay,
Florida'
C.
L.
COULTAS
AND
E.
R.
GROSS
2
ABSTRACT
Tidal
marshland
forms
a
border
between
the
Apalachee
Bay
area
of
the
Gulf
of
Mexico
and
the
uplands
of
Taylor
County,
Florida.
The
purpose
of
this
investigation
was
to
determine
the
distribution
of
the
tidal
marsh
soils
and
to
measure
some
of
the
properties
used
in
their
classification.
Three
pedons
representa-
tive
of
the
major
soils
were
described
and
sampled.
The
range
of
electrical
conductivity
is
from
14
to
90
mmhos/cm.
Field
moist
pH
ranges
from
5.6
to
7.8
and
air
dried
pH
values
are
2
to
3
pH
units
lower.
Content
of
S
is
<
0.75%
in
the
Psamma-
quents
and
Haplaquods
to
6.8%
in
the
Sulfaquents.
Oxidation
of
S
to
sulfates
was
probably
responsible
for
the
increase
of
soil
acidity
after
drying.
Cation
exchange
capacity
ranges
from
2
to
25
meq/100g
for
the
Psammaquents
and
Haplaquods
and
from
25
to
75
meq/100
g
for
the
Sulfaquents.
Most
soils
are
nearly
base
saturated.
The
soils
classified
in
order
of
increasing
eleva-
tion
are
members
of
the
coarse
-loamy,
mixed,
thermic
Typic
Sulfaquents;
the
sandy,
siliceous,
thermic
Mollic
Psamma-
quents;
and
the
sandy,
siliceous,
thermic
Aeric
Haplaquods.
Because
of
high
potential
acidity,
low
bearing
strength,
and
high
salinity,
decisions
concerning
man's
use
of
tidal
marsh
soils
should
be
carefully
made.
Undisturbed,
these
are
produc-
tive
soils
performing
functions
valuable
to
man.
Additional
Index
Words:
saline
soils,
soil
classification,
sul-
fi
dic
soils.
T
IDAL
MARSHES
provide
many
functions
valuable
to
man.
They
are
important
in
the
propagation
and
development
of
marine
organisms
and
provide
protection
from
erosion
by
the
sea.
They
are
valuable
as
habitat
for
wading
birds
and
waterfowl,
and
to
many
people
they
are
aesthetically
pleasing.
The
tidal
marshes
and
estuaries
are
attractive
for
many
kinds
of
economic
development.
Pressure
for
space
on
which
to
locate
homes,
marinas,
and
industrial
plants
in
close
proximity
to
the
land
-ocean
interface
continues
to
mount.
Agriculture
and
mariculture
have
also
made
use
of
tidal
marshes.
The
objective
of
the
research
was
to
provide
information
concerning
the
soils
of
this
ecosystem
in
order
to
make
more
intelligent
use
of
this
valuable
resource.
Tidal
marsh
soils
of
the
Gulf
Coast
are
very
diverse.
Extensive
areas
of
peats,
mucks,
and
clays
were
found
by
Lytle
and
Driskell
(18)
in
the
saline
marshes
of
Louisiana.
In
a
study
of
the
marshes
of
Wakulla
Co.,
Florida,
Coultas
(7,
8)
found
four
great
groups
of
soils.
These
were
Hapla-
quods,
Psammaquents,
Haplaquolls,
and
Ochraqualfs.
These
soils
were
saline,
predominantly
sandy
in
texture,
and
shallow
over
limestone.
Sulfidic
layers
were
found
in
the
Haplaquolls.
Many
tidal
marsh
soils
contain
high
levels
of
sulfur
(3,
10).
Draining
and
drying
of
these
soils
produce
pH
values
1
This
research
was
sponsored
in
part
by
a
grant
from
the
Cooperative
State
Research
Service,
USDA.
Received
29
Aug.
1974.
Approved
2
May
1975.
2
Associate
Professor
and
Assistant
Professor,
Earth
&
Plant
Science
Dep.,
Florida
A
&
M
Univ.,
Tallahassee,
Fla.
32307.
914
that
range
from
3
to
4,
which
is
2
to
3
pH
units
lower
than
under
field
conditions.
This
high
acidity
may
be
destructive
to
many
of
the
organisms
and
vegetation
of
the
marshes.
FACTORS
OF
SOIL
FORMATION
The
location
of
the
study
area
is
shown
in
Fig.
1.
The
climate
is
humid
and
temperate.
Rainfall
averages
139.2
cm
(54.8
in)
per
year
and
the
mean
annual
air
temperature
is
21C
(69.2F)
(24).
The
predominant
vegetation
of
the
tidal
marshes
in
Florida
is
Juncus
roemerianus
Scheele.
Spartina
alterniflora
Loisel
usu-
ally
occurs
at
lower
elevations
and
Distichlis
spicata
L.
Greene,
Batis
maritima
L.
with
Salicornia
virginica
L.
at
higher
eleva-
tions.
S.
alterniflora
was
more
abundant
in
the
study
area
than
in
most
marshes
of
Florida.
The
slope
throughout
the
tidal
marsh
is
<
1%
except
for
the
abrupt
3-5%
slopes
at
the
boundaries
of
the
marsh
and
the
sea
and
the
marsh
and
the
upland.
The
soils
are
forming
in
sandy
marine
sediments
called
the
Silver
Bluff
Formation
(16).
Coul-
tas
(7)
determined
that
most
of
the
marine
sediments
in
the
marshes
of
Wakulla
Co.,
Florida,
were
deposited
within
the
past
5,000
years.
In
most
instances,
these
sediments
are
1-2
meters
thick
and
rest
on
Suwanee
Limestone
(19).
The
limestone
surface
has
a
relief
of
0.5-2
m
resulting
from
prior
weathering.
Local
relief
in
the
tidal
marsh
is
as
much
as
0.5
m
with
up
to
1.5
m
difference
in
elevation
from
the
lowest
to
the
highest
parts
of
the
marsh.
Apalachee
Bay
tidal
marshes
are
subject
to
mixed
tides
with
twice
daily
amplitudes
of
30
to
90
cm.
A
dense
and
well
-developed
stream
system
makes
rapid
fl
ooding
and
draining
of
large
areas
of
land
possible.
Water
in
the
streams
fl
ows
upstream
on
flood
tide
and
downstream
on
ebb
tide;
yet
the
erosional
and
depositional
processes
that
lead
to
stream
meandering
appear
similar
to
freshwater
upland
streams.
The
streams
are
dynamic
transport
systems
carrying
both
dis-
solved
and
suspended
materials
to
and
from
the
tidal
marsh.
The
water
table
is
usually
within
0.5
m
of
the
soil
surface
at
most
places
at
low
tide.
METHODS
The
marsh
soils
were
examined
along
several
transects
in
the
vicinity
of
Dallus
Creek,
Taylor
Co.,
Florida.
Principal
soils
encountered
were
described
and
sampled
following
procedures
outlined
in
the
Soil
Survey
Manual
(20).
Relative
elevations
were
determined
using
a
surveying
level.
The
following
laboratory
determinations
were
performed
on
all
horizons
using
standard
procedures:
pH
(14),
particle
size
As
e
0
O
TAYLOR
COUNTY
GULF
OF
MEXICO
DALLUS
CREEK
O
2p
ap
KM
TIDAL
MARSH
AREA
Fig.
1
—Tidal
marsh
area
and
Dallus
Creek
located
in
Taylor
County,
Florida.
COULTAS
&
GROSS:
TIDAL
MARSH
SOILS
OF
APALACHEE
BAY,
FLORIDA
915
(9),
conductance
(14),
organic
carbon
(14,
2),
total
nitrogen
(5),
cation
exchange
capacity
and
exchangeable
cations
(14).
Clay
mineralogy
(16,
26),
extractable
Fe
and
Al
(11),
and
total
sulfur
(23)
were
determined
on
selected
horizons.
Extractable
bases
and
CEC
were
determined
from
a
1N
NH
4
OAc
extract
after
soluble
salts
were
removed
by
leaching
the
soil
with
40%
ethanol.
Total
S
was
determined
using
a
Leco
Analyzer
(model
532)
employing
Sb
and
sodium
azide
to
eliminate
interference.
RESULTS
AND
DISCUSSION
Soil
Morphology
The
soils
have
been
subjected
to
considerable
mixing
as
indicated
by
the
variety
of
soil
colors
and
the
presence
of
krotovinas
of
several
species
of
crabs
(Table
1).
Mixing
and
stratification
also
result
from
erosion
and
sedimentation
initiated
by
high
tides,
storms,
and
the
rise
of
sea
level.
Evidence
of
these
processes
may
be
seen
in
pedons
where
recent
sandy
sediments
cap
older,
truncated
spodic
horizons
and
where
large
amounts
of
wood
are
found
beneath
1-2
m
of
recent
sandy
sediments.
Spatial
distribution
of
the
marsh
soils
is
shown
in
Fig.
2.
The
Psammaquents
and
Haplaquods
occupy
a
position
in
the
upper
marsh
adjacent
to
the
uplands.
With
some
exceptions
the
Sulfaquents
are
in
a
lower
marsh
position.
Several
soil
morphologic
trends
are
evident
from
the
de-
scriptions
and
the
supporting
laboratory
data
of
Tables
2
and
3.
Both
soil
organic
matter
and
clay
content
decrease
sharply
from
the
Sulfaquents
at
the
lower
elevations
to
the
Psammaquents
at
the
higher
elevations.
In
the
area
of
Sul-
faquents,
the
"rotten
egg"
odor
of
hydrogen
sulfide
gas
is
always
evident;
while
in
the
area
of
Psammaquents,
the
odor
is
less
noticeable.
A
10-20
cm
thick
root
mat
of
J.
roemerianus
and
S.
al
-
il
l
asvldn
031S3103
4)
1/2
1
KM
1
7 9
SULFAQUENTS
PSAMMAQUENTS
HAPLAQUODS
Fig.
2
—Distribution
of
soils
and
location
of
leveling
transects
in
the
tidal
marsh
study
area.
1111111
terniflora
is
common
in
the
surface
horizons
of
most
soils.
Inspection
reveals
that
50-75%
of
the
roots
are
dead
but
in
a
well-preserved
state.
Bulk
densities
of
the
root
mat
by
the
clod
method
range
from
0.25
to
0.75
g/cm
3
depending
on
the
amount
of
incorporated
mineral
material.
Figure
3
shows
the
relative
elevation
and
the
distribution
of
the
soils
and
vegetation
along
two
transects
of
the
tidal
marsh.
The
elevation
gradient
of
1-1.2
m
from
the
edge
of
the
Gulf
to
the
nonsaline
uplands
is
typical
for
the
marshes
of
Taylor
County.
The
slight
berm
at
the
gulf
edge
is
com-
Table
1
—Morphological
properties
of
the
Dallus
Creek
soils
Horizon
All
Al2
A13
A14
AC1
AC2
All
Al2
AC
Cl
C2
All
All
A2
B21h
B22h
Cl
Depth,
cm
Color
Texture
Structure
Consistency
Roots
Sulfaquent•
0-18
10YR
3/1
cl
massive
sticky
abundant
w/rhizomes
18-64
10YR
3/1
massive
sticky
plentiful
64-89
10YR
3/1
massive
sticky
plentiful
89-114
10YR
3/1
el
massive
el.
sticky
plentiful
114-
140
10YR
4/1
and
10YR
6/2
single
grain
friable
v.
few,
freq.
pieces
of
wood
140-
152
10YR
4/1
and
10YR
6/1
single
grain
loose
v.
few,
freq.
pieces
of
wood
Psammaquentt
0-18
10YR
3/1
w/
10YR
4/4
mot.
is
massive
el.
sticky
abundant
w/rhizomes
18-38
10YR
3.
5/1
w/
10YR
5/5
mot.
single
grain
friable
plentiful
38-76
10YR
5/1
and
10YR
6/2
a
single
grain
loose
few
76-112
5Y
5/1
w/
10YR
4/4
mot.
a
single
grain
loose
v.
few
112-
137
5Y
6/2
a
single
grain
loose
v.
few
Haplaquod*
0-2
Algal
mat
with
adhering
soil
particles
2-38
10YR
4/1
e
single
grain
v.
friable
few
38-53
10YR
6/1
and
10YR
4/1
single
grain
v.
friable
few
53-68
10YR
2/1
and
10YR
4/1
massive
friable
v.
few
68-116
7.
5YR
2/1
grading
to
single
grain
loose
few
7.
5YR
3/2
116-167
7.
5YR
3/2
s
eingle
grain
loose
v.
few
1
Location:
NE
of
the
NE
,
Sec.
11,
T9S,
R8E,
Taylor
Co.
Vegetation:
dense
J.
roemerianus,
sparse
S.
alterniflora.
t
Location:
SE
of
the
NE
,
Sec.
11,
T9S,
R8E,
Taylor
Co.
Vegetation:
dense
J.
roemerianus.
Location:
SE
of
the
SE
,
Sec.
11,
T9S,
R8E,
Taylor
Co.
Vegetation:
sparse
S.
alterniflora.
Boundary
gradual,
wavy
gradual,
wavy
gradual,
wavy
gradual,
wavy
gradual,
wavy
gradual,
wavy
gradual,
wavy
gradual,
wavy
gradual,
wavy
abrupt,
wavy
abrupt,
wavy
gradual,
wavy
gradual,
wavy
916
SOIL
SCI.
SOC.
AMER.
PROC.,
VOL.
39,
1975
Table
2
-Selected
properties
of
three
great
groups
of
tidal
marsh
soils
Horizon
Depth
pH
1-1“:/
Electrical
conductivity
Total
sulfur
Water
content
at
Exchangeable
canons
Total
nitrogen
Organic
carbon
Field
conditions
Air
dry
field
conditions
CEC
Ca
Mg
Na
All
Al2
A13
cm
0-18
18-64
64-89
6.3
6.3
5.8
4.0
3.
1
2.8
mmhos/cm
68.4
89.7
87.9
1.62
4.03
6.79
To
Sulfaquent
41.5
32.8
26.0
meq/100
g
16.4
6.8
4.6
1.8
0.9
0.7
1.2
2.
8
4.
1
1.
17
1.06
0.73
%
16.
12
13.69
13.59
448.9
75.7
358.5
51.9
288.2
45.6
A14
89-
114
5.
6
2.
5
65.7
4.
76
118.7
26.
1
8.
5
7.
4
0.
2
17.0
0.49
11.60
AC1
114-
140
6.
1
2.
7
30.9
O.
77
24.8
3.
5
4
O.
5
<
0.
1
O.
3
0.
8
0.
04
1.
09
AC2
140-152
6.
1
3.
1
13.
9
18.
5
1.
2
<
0.
5
<
O.
1
<0.
1
<
0.
5
Trace
0.39
Psammaquent
All
0-
18
7.
0
4.
5
66.5
0.
48
182.6
10.
1
5.
4
2.
7
0.
3
0.
8
0.
29
2.
21
Al2
18-38
6.7
4.4
46.2
0.27
50.4
7.3
3.3
2.
1
0.3
0.4
0.
14
0.35
AC
38-76
6.4
3.6
49.2
0.24
37.0
3.7
1.9
0.3
0.0
0.0
0.05 0.45
Cl
76-
112
6.6
3.
8
27.7
0.
19
21.4
2.2
1.
1
0.3
0.0
0.0
0.02
0.45
C2
112-
137
7.0
3.9
15.8
20.3
1.5
0.9
-
0.2
0.0
0.
1
0.01
0.37
Haplaquod
All
0-2
7.7
7.2
43.0
0.03
234.6
26.60
8.0
7.2
1.0
8.9
0.74
7.32
Al2
2-38
7.8
5.4
31.6
0.
14
52.2
4.37
1.2
2.9
0.1
0.9
0.
14
1.23
A2
38-53
7.
3
3.
6
32.5
0.09
30.3
1.76
0.5
0.8
0.1
0.2
0.07
0.52
B21h
53-68
6.9
4.6
32.
1
0.22
26.6
7.22
1.5
1.2
0.2
0.7
0.
14
1.41
B22h
68-
116
6.
8
5.
0
30.4
0.
15
21.8
5.
90
2.
2
1.
5
O.
2
2.
1
0.
04
0.
90
C1
116-168
7.
0
6.
1
32.
6
0.05
20.
0
2.
68
1.
0
0.
8
0.1
0.5
0.
04
0.39
mon
and
probably
functions
as
a
natural
levee.
The
domi-
nant
vegetation
of
the
study
area
is
J.
roemerianus,
with
about
30%
S.
alterniflora.
The
soils
are
dominantly
Sulfaquents
at
the
lower
eleva-
tions
of
both
transect
A
and
B.
On
transect
B
however,
the
Sulfaquents
cap
spodic
horizons
at
0.5-1
m
depth.
These
discontinuous
spodic
horizons
appear
to
be
relict
subsurface
horizons
of
former
soils
when
the
sea
level
was
lower
and
forest
vegetation
extended
seaward
into
what
is
now
tidal
marsh.
Studies
of
sea
level
changes
on
the
Gulf
and
Atlantic
Coast
by
Kurz
and
Wagner
(14)
and
others
indicate
that
mean
sea
level
is
rising
at
about
30
cm/100
years.
This
would
account
for
the
spodic
horizons
and
the
occasional
stumps
of
Pinus
elliottii
Engelm.
and
Juniperus
silicicola
(small)
Bailey
at
the
lower
elevations.
The
vegetation
of
the
two
transects
at
the
lower
elevations
also
differs.
Juncus
roemerianus
is
dominant
throughout
the
lower
elevations
on
the
Sulfaquents
as
well
as
in
higher
parts
of
transect
A.
On
transect
B
however,
S.
alterniflora
is
dominant
at
eleva-
tions
up
to
0.6
m
on
the
Sulfaquents.
The
occurence
of
S.
alterniflora
in
an
area
this
large
at
this
elevation
is
unusual
for
other
tidal
marshes
of
the
northeastern
Gulf
of
Mexico,
but
is
common
in
the
tidal
marshes
of
the
Atlantic
coast
1.2-
0.9
0.6
12
0.3
0.0
Z
1.2
0
X
0.9
0.6
MA
0.3
0.0
0
SULFAQUEN
TS
SUL
FAQ
UENTS
S
(1).
Observations
indicate
the
S.
alterniflora
is
able
to
invade
stands
of
J.
roemerianus
only
after
the
density
of
J.
roemerianus
has
been
reduced
by
some
mechanism.
We
hypothesize
that
rafts
of
vegetation
transported
onshore
by
high
tides
smothers
the
living
J.
roemerianus;
following
de-
composition
the
bare
soil
surface
provides
a
suitable
seed-
bed
for
S.
alterniflora.
Moving
upslope
on
transect
A,
one
finds
Psammaquents
that
continue
to
the
abrupt
boundary
with
the
Haplaquods
of
the
forest
upland.
Transect
B
differs
in
that
Haplaquods
occupy
a
small
"island"
and
several
hectares
surrounding
the
island.
Juncus
roemerianus,
Juniperus
silicicola,
Iva
frutescens
L.,
and
Baccharis
halimifolia
L.
are
the
principal
plants
of
the
island.
Island
highpoints
are
common
in
the
tidal
marsh
of
the
study
area
and
often
indicate
an
out-
cropping
of
limestone
bedrock.
On
the
landward
side
of
the
island,
the
Sulfaquents
grade
abruptly
into
the
Hapla-
quods
of
the
forested
upland.
Sulfur
and
Acidity
Data
in
Table
2
show
abrupt
decreases
in
soil
pH
follow-
ing
air
drying.
Field
moist
pH
values
for
all
the
soils
ranged
A
P
SA
MMAQUENTS
I
HAPLAQUOD(
'
HAPLAQUODS
,...-
B
I
SULPAQUENTS
NAPE
AQUODS
S
.1
JUNCUS
ROEMERIANUS
S
SPARTINA
ALTERNIFLORA
60
120
180
240
300
360
420
480
540
DISTANCE
IN
METERS
Fig.
3
-Elevation
of
the
tidal
marsh
soils
and
the
associated
vegetation.
Scale
of
figure
spans
average
low
and
high
tides.
COULTAS
&
GROSS:
TIDAL
MARSH
SOILS
OF
APALACHEE
BAY,
FLORIDA
917
Table
3
-Particle
-size
distribution
of
three
great
groups
of
tidal
marsh
soils
Particle-
size
distribution
Horizon
Depth
Sand
(mm)
Silt
(mm)
Clay
(mm)
Textural
class
yes
2-
1
CS
1-
0.
5
MS
fs
0.
5-
0.
25
0.
25
-0.
1
vie
0.
1-
0.
05
0.
05-
0.
002
<0.
002
em
%
by
weight
SuLfaquent
All
0-18
0.7
1.5
5.0
11.7
5.
4
38.
6
37.
1
Clay
loam
Al2
18-64
0.7
2.
3
7.
1
21.
5
5.
1
20.
9
41.
4
Clay
A13
64-89
1.2
5.0
11.2
19.7
4.
4
20.
4
38.
1
Clay
loam
A14
89-
114
1.
8
7.
5
22.5
40.
8
3.
2
6.
5
17.
7
Fine
sandy
loam
AC1
114-140
2.9
10.6
35.1
44.
6
2.
8
0.
5
3.
5
Sand
AC2
140-
152
3.
9
10.7
35.0
45.2
2.
2
0.
5
2.4
Sand
Psammaquent
All
0-18
2.2
9.
8
41.6
27.
9
1.
2
8.
8
8.
5
Loamy
sand
Al2
18-38
2.4
11.
4
45.8
27.
5
1.
1
5.
6
6.
2
Sand
AC
38-76
2.7
11.
0
46.7
32.
2
1.
0
2.
4
3.
8
Sand
Cl
76-112
3.4
11.
2
44.1
33.
6
1.
2
1.
1
5.
4
Sand
C2
112-
137
3.
7
12.
3
45.5
32.
2
1.
0
1.
5
3.
8
Sand
Haplaquod
All
0-2
2.0
5.
5
23.
1
20.
7
1.
9
38.
5
8.
3
Sandy
loam
Al2
2-38
2.5
10.
1
48.
1
29.
8
3.
0
5.
0
1.
5
Sand
A2
38-53
1.9
10.
6
52.
1
29.
9
2.
1
2.
4
1.
0
Sand
B21h
53-68
2.8
14.
9
48.
9
11.
6
10.
4
7.
7
3.7
Sand
B22h
68-116
1.7
8.
9
49.
4
16.
8
17.
0
3.
6
2.
6
Sand
Cl
116-168
2.9
10.
6
48.
0
7.
8
27.2
1.
2
2.
3
Sand
from
5.6-7.8,
which
is
typical
for
marine
sediments
(4)
and
tidal
marsh
soils
(10).
However,
following
air
drying
pH
values
dropped
0.5-3.7
pH
units,
ranging
from
pH
2.5-
7.2.
Greatest
increases
in
acidity
occurred
in
the
Sulfa-
quents
which
are
the
soils
having
the
highest
amounts
of
S,
organic
C,
N,
and
clay
(Table
3).
While
the
forms
of
sulfur
were
not
determined,
it
seems
likely
they
are
similar
to
those
determined
in
California
by
Kaplan,
Emery,
and
Rittenberg
(15)
and
in
Florida
by
Swanson,
Love,
and
Frost
(22).
The
California
study
showed
pyrite
to
be
most
abundant
with
smaller
amounts
of
S
-
,
S
2-
,
HS
-
and
organic
S
present.
Kaplan
et
al.
(15)
and
Berner
(4)
have
demonstrated
that
biological
action
of
sulfate
reducing
bacteria
on
S0
4
2-
to
form
HS
-
and
H
2
S
and
the
subsequent
formation
of
FeS
in
the
anaerobic
sedi-
ment
are
the
processes
by
which
most
sulfur
is
added
to
the
marine
sediments.
When
subjected
to
an
aerobic
atmos-
phere
many
of
these
compounds
can
be
oxidized
to
form
H
2
SO
4
(10).
The
Sulfaquents
with
higher
content
of
or-
ganic
C
and
clay
in
the
surface
horizons
and
in
a
more
reduced
state
are
capable
of
retaining
more
newly
formed
FeS
than
either
the
Psammaquents
or
the
Haplaquods.
In
addition
to
higher
content
of
S,
the
data
of
Tables
2
and
3
show
that
Sulfaquents
have
correspondingly
higher
CEC
and
water
content.
The
Psammaquent
and
the
Haplaquod
contain
relatively
little
S
but
experienced
extreme
pH
reductions
on
drying
especially
in
the
poorly
buffered
horizons.
For
example,
the
A2
horizon
of
the
Haplaquod
contained
only
0.09%
S
but
decreased
3.7
pH
units
after
drying.
Other
Properties
Electrical
conductivities
of
all
soil
horizons
studied
(Table
2)
are
>
4
mmhos/cm
(25C)
and
the
exchangeable
sodium
percentage
is
<
15
which
qualifies
them
as
saline
soils
(25).
The
soluble
salts
of
these
soils
are
supplied
by
the
tidal
waters
of
the
Gulf
of
Mexico
which
have
a
rela-
tively
stable
concentration
oksalts.
The
fl
ushing
of
soils
with
saline
water
occurs
twice
daily,
but
due
to
varying
heights
of
tides,
soils
at
higher
elevations
may
be
fl
ooded
at
weekly
intervals
or
less.
The
soluble
salts
of
these
soils
covered
with
frequent
tides
may
be
concentrated
by
evapotranspiration
or
may
be
diluted
and
moved
by
rainwater.
Together
these
processes
contribute
to
the
variability
of
soluble
salts
in
the
surface
soil.
Soluble
salts
in
lower
horizons
are
subject
to
water
table
movement
and
leaching
over
a
longer
period
of
time
such
as
with
the
rise
or
fall
of
sea
level.
We
believe
most
of
the
decrease
of
electrical
conductivities
with
depth
is
due
to
lower
content
of
organic
matter
and
coarser
tex-
tures.
A
discontinuous
area
25-50
m
wide,
with
little
or
no
vegetation
occurs
at
the
mean
high
tide
line
in
most
tidal
marshes
of
Taylor
County.
It
appears
this
salt
barren
as
it
is
termed
is
caused
in
part
by
the
low
frequency
of
tidal
flooding
and
the
evaporation
and
concentration
of
soluble
salts
to
levels
which
most
plants
cannot
tolerate.
The
surface
horizons
of
the
three
soils
have
the
highest
exchangeable
bases
and
cation
exchange
capacities
which
is
predictable
based
on
organic
C
and
clay
contents.
These
horizons
also
have
the
highest
content
of
organic
matter
and
silt-
and
clay
-size
particles.
The
subsurface
horizons
show
no
indication
of
illuvial
clay.
The
organic
C
and
N
decrease
with
depth
except
in
the
spodic
horizon
of
the
Haplaquod
in
which
they
increase
abruptly.
The
higher
CEC
of
the
spodic
horizon
reflects
the
increase
in
organic
carbon.
Calcium
is
the
most
abundant
of
the
extractable
bases
with
Na
usually
much
more
prevalent
than
K
(Table
2).
Coultas
(7,
8)
reported
higher
Mg
values
than
Ca
which
was
explained
by
the
high
Mg
content
of
sea
water.
We
pre-
sume
the
Dallus
Creek
waters
are
Ca
charged
thus
resulting
in
this
increase
of
Ca
over
Mg.
Particle
-size
data
(Table
3)
indicate
silt-
and
clay
-size
marine
sediments
are
being
deposited
on
the
Sulfaquent
with
less
deposition
occurring
on
the
Psammaquent
and
Haplaquod
soils.
These
m►neral
sediments
may
be
trans-
ported
by
the
turbid
tidal
fl
ood
waters
and
deposited
at
lower
elevations
in
the
tidal
marsh.
Dense
stands
of
I.
roemerianus
and
S.
alterniflora
slow
the
water
movement
and
provide
sites
on
which
fl
occulated
particles
can
settle.
The
lower
horizons
of
all
soils
are
in
the
medium
sand
tex-
tural
class
with
little
evidence
of
lithologic
discontinuities.
918
soIL
sCi.
soC.
AMER.
PROC.,
VOL.
39.
1975
Kaolinite,
vermiculite,
and
vermiculite-intergrades
are
the
principal
clay
minerals
in
the
clay
fraction.
Minor
amounts
of
quartz
and
gibbsite
are
also
present.
The
domi-
nance
of
kaolinite
and
vermiculite
minerals
suggests
a
local
origin,
since
these
are
the
principal
clay
minerals
of
the
adjacent
upland
soils.
The
type
and
relative
amounts
of
the
clay
minerals
does
not
change
appreciably
with
depth
in
the
soil
profile
nor
are
there
significant
differences
in
min-
eralogy
among
the
three
soils.
Classification
of
Soils
Sul/aquents-To
be
classified
as
a
mollic
epipedon,
sur-
face
soil
horizons
must
have,
among
other
properties,
a
bearing
strength
indicated
by
an
n
value
(22)
%
field
moisture
(dry
basis)
-
0.2
(%
silt
+
clay)
*n
=
%
clay
+
organic
matter
that
is
<
0.7.
However,
computed
n
values
for
the
upper
three
horizons
of
the
Sulfaquent
are
much
>
0.7.
These
same
horizons
contain
between
1.62
and
6.79%
sulfur
which
allows
for
placement
of
this
pedon
in
the
fine,
mixed,
thermic
family
of
Typic
Sulfaquents.
While
classification
of
this
pedon
is
clear,
several
factors
should
be
mentioned.
Initially,
the
Sulfaquents
appear
to
be
Mollisols.
However,
they
have
high
n
values
and
suffi-
cient
sulfur
so
the
mollic
epipedon
is
eliminated
and
they
are
placed
in
Sulfaquents.
Secondly,
these
soils
are
too
salty
for
all
but
the
plants
native
to
tidal
marshes.
Electrical
con-
ductivity
of
the
saturation
extracts
range
from
14-90
mmhos/
cm.
Currently,
this
high
salinity
is
first
considered
at
the
series
level.
We
believe
this
high
salinity
should
be
considered
at
a
higher
category
such
as
at
the
subgroup
level.
Psammaquents-Data
for
the
Psammaquent
show
<
0.75%
S.
However,
it
meets
the
criteria
for
Psammaquents
and
is
placed
in
the
siliceous,
thermic
family
of
Mollic
Psammaquents.
Haplaquods-The
Haplaquod
may
be
placed
in
the
sandy,
siliceous,
thermic
family
of
Aeric
Haplaquods.
The
ratio
of
Fe
+
Al/clay
is
>
0.2
in
the
B22h
horizon
(Table
4).
It
is
unusual
for
Spodosols
to
be
netural
to
mildly
alkaline
in
reaction,
to
have
high%
base
saturation,
and
to
be
saline.
However,
the
rising
sea
level
in
the
study
area
has
resulted
in
a
gradual
encroachment
of
the
sea
onto
the
Spodosols
of
the
forested
upland.
These
spodic
horizons
are
now
being
subjected
to
the
pedogenic
processes
associated
with
the
tidal
marsh.
Occasionally,
degraded
or
truncated
spodic
horizons
may
be
found
in
the
Sulfaquents
or
the
Psammaquents,
which
supports
the
notion
that
the
sea
level
is
rising.
Land
Use
Some
predictions
may
be
made
from
the
present
data.
The
soils
are
wet
and
subjected
to
daily
tidal
flooding.
Few
if
any
agronomic
crops
are
tolerant
of
the
high
salinity
of
the
soils.
The
high
sulfur
content
presents
no
problem
in
the
reduced
state
but
if
drainage
occurs
the
soils
become
strongly
acid.
Movement
of
machines
and
animals
is
limited
Table
4
-Pyrophosphate
extractable
iron
and
aluminum
in
the
Haplaquod
Horizon
Depth
Iron
Aluminum
CM
Al2
2-38
0.041
0.
040
A2
38-53
0.
080
0.
030
B21h
53-68
0.
204
0.
380
B22h
68-
116
0.
159
0.
390
due
to
the
low
bearing
strength
of
the
soils.
The
high
cation
exchange
capacity
of
the
soils
indicates
a
high
potential
sink
for
trapping
cations.
Heald
and
Odum
(13)
have
demonstrated
that
fishes
and
invertebrates
use
the
organic
detritus
produced
in
the
tidal
marsh
as
a
major
food
source.
The
tidal
marsh
also
acts
as
a
barrier
against
storm
erosion
of
the
adjacent
uplands.
Gosselink,
Odum,
and
Pope
(12)
computed
the
annual
return
and
income
capitalized
value
(5%)
of
marshes
for
fisheries
in
Georgia
at
$247
and
$4,940/
ha,
respectively.
In
their
estimation,
the
tidal
marsh
is
even
more
valuable
for
its
use
in
tertiary
treatment
of
sewage
wastes.
The
values
are
estimates
based
upon
economic
considerations.
LITERATURE
CITED
1.
Adams,
D.
A.
1963.
Factors
influencing
vascular
plant
zonation
in
North
Carolina
salt
marshes.
Ecology
44:445-
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