THE GENESIS OF CARBON SEQUESTRATION IN SUBTROPICAL SPODOSOLS
JUAN GERARDO PEREZ BOLIVAR
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
I would like to thank my major professor Dr. Mary E. Collins for being a
teacher and a friend during my tenure as a student. I also thank the members of
my committee, Dr. Willie G. Harris, Dr. Hugh Poponoe, Dr. Daniel Spangler, and Dr.
William E.Puckett, for their time and guidance during my research.
I especially thank Ron Kuehl for his help and support of this research. I also
extend thanks to Larry Schwandes and to my friends in the laboratory.
I extend my deepest appreciation to my parents, Jose and Sofia, whose sacrifice,
patience, and encouragement kept me going during this long journey.
TABLE OF CONTENTS
A C K N O W L E D G M E N T S ......... .................................................................................... ii
A B STR A C T ......... ..... ........................................................................... .... ........
1 INTRODUCTION .................................. .. ... ... ........ ... .............. 1
O objectives of the Study..................... ........................................... .......................... 14
L literature R eview .................... ................ .................... .. .. ...... ..... .. ............ 14
2 DESCRIPTION OF THE STUDY AREA.................................... ........................ 39
Location ........................................................... 39
Clim ate ........................................ ................... 40
Physiography..................................... .............. 42
G eo lo g y ..................................................... 4 5
A von P ark L im estone.............................................................. .................... 46
O cala G group ........................................ 47
Suwannee Limestone ............................................... .............. 48
H aw thorn F orm action ................................................................................ .. 4 8
Pliocene to Holocene Undifferentiated ......................................... ............. 49
S o ils ....................................................................................................... . .......... ...... 4 9
H y d ro lo g y .............................................................. 5 1
Surficial A quifer Sy stem .................................................... .................................. 52
3 M ATERIALS AND M ETHODS .......................................................... ............... 54
F field W ork ......... .. .......... ..................................................................... ...... 54
Experim mental Plot..................................... .............. 54
Soils Studied ......................................... 57
Vegetation Study. .......... ....................................... ............. 59
Laboratory W ork........... ...... .... .......... ...................... ... ......... .... .............. 59
Routine Analysis ............................................. 59
H um ic M material ................................................................................................... 60
M in eralogy of S oils................................................................... ...... ...... .. 6 1
M icrom orphology .... .................................................. .. ........ .. ............ 62
C arbon-14 ............. ......... .................................. ....... ..... ..... .... 62
A artificial B 'h Form ation ................ ....... ................ ................. ......... 63
The Effect of Hydrogen Peroxide and Incineration on Bh and B'h Organic Matter. 64
Evaluation of Existing Characterization Data............... ......................................... 64
4 RE SU L TS A N D D ISCU SSION ......................................................................... ...... 66
M orphology................................................. ....... ......... ...... 66
Chem ical Properties .................. ................................... .. ..... .............. 73
M icromorphology ................................................................. ............ .......... .. 94
Scanning Electron Microscope (SEM) ....................................................... 97
Hydrology ............ ................................ ............... 99
V e g etatio n ................ ... .................................................. ............... 10 6
M ineralogy of the C lay Fraction..................................................... .................... 108
Carbon........................................... .............. 110
Age ............ .............. ...... ................... .............. 110
Dissolved Organic Carbon in the Filtrate ..................................... .............. 113
Organic Carbon % ................... .......... ........................ ........... 113
Humic Substances-Humic and Fulvic Acids ................................ .............. 117
A l/O C R atio ............................ ... ................... .... .................................... 12 2
Theory on the Genesis of the Soil with Multiple Bh Horizons............................. 123
Stage 1 ............................................... 124
Stage 2 .......... ....................................... 124
Stage 3 ....................... .......................... 124
S ta g e 4 ................................................................................. 1 2 6
A artificial B 'h H horizon ........... .......................................... .............. 127
Reaction of the OC from the Bh and B'h to Hydrogen Peroxide Treatment .......... 128
5 GENERAL CON CLU SION S ............................................... ............................ 132
A SO IL D E SCR IPTIO N S ...................... .... ......... ............................. ............... 135
B SO IL P R O P E R T IE S ......................................................................... ....................142
C PRECIPITA TION D A TA ...................... .... ................... ................... ............... 173
D VEGETATION .................... .................... ....... ......... 178
L IT E R A T U R E C IT E D ........................................................................... ................... 180
BIO GR A PH ICA L SK ETCH .................................... ............ .....................................191
Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
THE GENESIS OF CARBON SEQUESTRATION IN SUBTROPICAL SPODOSOLS
Juan Gerardo Perez Bolivar
Chair: Mary E. Collins
Major Department: Soil and Water Science
Multiple spodic (Bh) horizons in soils are common in the thick, acid sands of the
Osceola National Forest, Northeast Florida. Spodosols samples were taken along a 200 m
upland-lowland transect. Podzolization explained how the upper spodic horizon was
formed. The lower one, usually extensive, and permanently saturated with water, did not
follow the same mechanism of formation. The significance of this lower subsurface
horizon has increased greatly as scientists study new ways of decreasing atmospheric
carbon dioxide (CO2), using soils as sinks, to reduce the "greenhouse effect". Carbon (C)
stored in multiple-layered Spodosols is greatly underestimated since soil scientists limit
their studies to the first 2 m. Carbon-14 (14C) dating indicated that the upper spodic
horizon was 1,810 40 years old; the lower B'hl was 15,270 370 years old and the
lower B'h2 was 13,820 + 60 years old. Aluminum (Al) illuviation occurred in the upper
Bh, but not in the lower B'h horizon. Humic/fulvic acid (HA/FA) ratios were different for
both upper and lower Bh horizons. The upper Bh was dominated by fulvic acids (FA)
(59% vs. 41%) and the lower B'h horizon was dominated by humic acids (HA) ( 61% vs.
39%). C/A1 ratios decreased with depth in the upper Bh horizon, but increased with depth
in the lower one. This lead to the conclusion that the mechanism that immobilizes C to
form the different Bh's horizons is different. The pedogenic process of podzolization
occurred in the upper Bh horizon. In the lower B'h horizon, the theory of formation was
as follows: fulvic acids, after accumulating in the saturated zone, reacted with the Al in
the coatings of the sand grains without stripping the coatings. The FA were responsible
for darkening the sand grain. The HA reacted mostly with the Al and clays in solution.
They precipitated as Al-humates and filled the space in between the sand grains as black
sediment. Genesis of Spodosols is a direct manifestation of the processes dictating the
terrestrial fate and transport of C. To understand these processes is fundamental in the
assessment of global C dynamics.
The earth's climate is predicted to change because human activities are altering
the chemical composition of the atmosphere through the buildup of greenhouse gases-
primarily carbon dioxide (CO2), methane (CH4), nitrous oxide (N20), and
halocarbons-chlorofluorocarbons (HFCs) .
The United States is the world's largest single emitter of CO2, accounting for
about 23% of energy-related carbon (C) emissions worldwide. The U.S. share of CH4 and
N20 emissions, although uncertain, is likely to be much lower than its share of CO2
emissions, as the principal sources of CH4 and N20 emissions are more common outside
than within the United States. In the case of halocarbons and other gases, the U.S. share is
likely to be considerably larger than 23%. This is because the use of cooling and
refrigeration equipment is probably much more pervasive in the United States than
elsewhere in the world (Fig. 1).
(Data Source: http://www.eia.doe.gov/oiaf/1605/gg97rpt/chapl.html).
These greenhouse gases have a common singular property, they all trap heat in
the atmosphere. Although uncertainty exists about exactly how earth's climate responds
to these gases, global temperatures are rising.
The sun's energy drives the earth's weather and climate and heats the earth's
surface; in turn, the earth radiates energy back into space. Atmospheric greenhouse
gases trap some of the outgoing energy, retaining heat somewhat like the glass panels of a
HFC's and other minor gasses 2.4%
Nitrous Oxide 2.2
Figure 1. Greenhouse gas emissions in the U.S, 1996 (Source:
greenhouse. This is the reason why this process is called the "greenhouse effect" (Fig.
2). This natural "greenhouse effect" makes life possible on earth. It keeps the planet
at an average temperature suitable to life, about 16C. However, when the atmospheric
concentration of greenhouse gases increases, climatic changes may occur (Source:
http://www.athena.ivv.nasa.gov/curric/land/global/greenhou.html#how). An enhanced
greenhouse effect may result in significant changes in local, regional, and global
temperatures. Some climate models predict that the buildup of atmospheric greenhouse
gases will result in significant increases in the global mean temp erture, ranging from 1.5
to 4.0C by the year 2050 (Beinroth, 1996).
Vegetation changes caused by the climate change would affect the hydrologic
cycle and surface albedo. The biggest adverse impact of a CO2-induced climate change
would be caused by changing precipitation patterns that would lead to overall lower
SUN SnRm wrblr radiartin in
lreM~ted by the Earth an
Ihe aP~n sphere.
Figure 2. A simplified diagram illustrating the "greenhouse effect" (Source:
rainfall amounts, or droughts during the growing season with increased frequency or
Since the beginning of the industrial revolution (-1850), atmospheric
concentrations of CO2 have increased nearly 30% (Fig. 3). Carbon dioxide
concentrations over the past 1,500 years, determined from ice core records (shown as
symbols), fluctuated little until 1850. Since 1958, air measurements (shown as a blue
line) taken at Mauna Loa, Hawaii, supplemented the ice core data. The smooth black
curve is based on a 100-year running mean. The inset of the period from 1850 onward
shows CO2 emissions in gigatons (billions of metric tons) per year attributed to burning
fossil fuels (shown as a blue line).
0 Fold OCO erniss" flt$
One. Gph d yi e iee i ei i e
Scr inng a ng t a 3 ar d t
atmosphere and is believed to be the primary reason for the increase in earth's
temperature (Fig. 4).
Bo 1000 1200 1d o6DO 180 20HDO
Figure 3. Graph showing the increase in atmospheric CO2 during the last 1500
years. Source: (http://pubs.acs.org/hotartcl/cenear/951127/img2.html).
This increase in atmospheric CO2, during the last 30 years, due to the
combustion of fossil fuels, has enhanced the heat-trapping capability of the earth's
atmosphere and is believed to be the primary reason for the increase in earth's
temperature (Fig. 4).
The global CO2 budget is complex and involves transfer of CO2 among the
atmosphere, the oceans, and the biosphere (Fig. 5). Through the photosynthetic process,
the land removes about 100 petagrams (Pg) (10 15g) of C in the form of C02 per year.
However, about the same quantity of CO2 is added to the atmosphere each year by
vegetation and soil microbial respiration and organic decay. The world's oceans release
about 100 Pg C in the form of CO2 into the atmosphere per year and in turn absorb about
104 Pg C each year. Most of the oceanic C is in the form of sedimentary carbonates.
1880 1900 1 MD 1940 1M' 1M* 2000
Figure 4. Graph illustrating the rise of temperature (red) on earth from a reference
level that is just the average of the most recent 30 years. The reference level is
labeled zero. Source: (http://www.modelmodel.com/globalwarming.htm).
Burning of fossil fuels adds about 5 Pg C and biomass burning and deforestation add
about another 2 Pg C to the atmosphere. About 3 Pg C in the form of CO2 is building up
in the atmosphere each year. The average concentration of CO2 was about 290 mg/km-1
in pre-industrial times; now it is about 350 mg/kg-1 and increasing steadily at a rate of
0.3-0.4%/yr. Since CO2 is chemically inert, it is not destroyed by photochemical or
chemical processes in the atmosphere; either it is lost by transfer into the ocean or
biosphere or it builds up in the atmosphere (http://www.science.gmu.edu/-zli/ghe.html).
Soils are part of the pedosphere. The pedosphere is the envelope of the Earth
where soils occur and soil forming factors are active. The pedosphere only develops
where there is a dynamic interaction among the atmosphere, biosphere, lithosphere and
the hydrosphere (Fig. 6). Soils can act as sinks or sources of atmospheric C. The
exchange of CO2 between atmosphere and land plants includes soil-related efflux of 100
Pg yr1. Soil organic matter (SOM), which consist ofundecomposed and partially
decomposed organic residues and humus, is the largest and most important terrestrial C
pool in the global carbon cycle (http://www.science.gmu.edu/-zli/ghe.html).
Global Net P nrinai i
Production and ?
4.Y C ing
i /P i -Use
\ i ealilion Ii& cil, .
Carbron Flu IUicaled ByAr irow
jlanFjral = F.it}
fa ararmn I
AnRlthropgenic Fl -----
Figure 5. A simplified diagram showing the carbon cycle and the interaction among
atmosphere, oceans and biosphere (Source:
Figure 6. Relationships among the pedosphere, atmosphere, hydrosphere, lithosphere and
biosphere. (Source: http://www.pedosphere.com/content.cfm)
There are two types of carbon pools in the pedosphere; soil organic carbon (SOC)
(i.e., decomposition of organic materials) and soil inorganic carbon (SIC) (i.e.,
decomposition of mineral materials). This study focuses on SOC. The current SOC
pool in world soils is estimated at 1,500 Pg (Eswaran et al., 1995). The SOC pool is
about 2 times that of the atmosphere pool and about 2.5 times that of the biotic pool
comprising land plants.
Pedogenic processes that affect SOC dynamics may be grouped into two
categories: SOC-enhancing and SOC-degrading processes (Fig. 7). Processes that
enhance SOC content are plant biomass production, humification, aggregation, and
sediment deposition. Processes that degrade SOC content are soil erosion, leaching, and
soil organic matter (SOM) decomposition. It is the net balance between these SOC
processes, as influenced by land use and anthropogenic factors, that determines the net
SOC pool of the pedosphere (Lal et al., 1998).
An increase in SOC, through C sequestration into the pedosphere, has two notable
positive effects. First, it enhances the soil quality by improving the soil structure and thus
the available water capacity and second, it improves the soil's environmental regulatory
capacity by affecting the emissions of gases such as CO2 and CH4 to the atmosphere.
Thus, it improves the resistance to erosion by wind and water and the transmission of
water and solutes through the soil solum (Lal et al. 1998).
As SOM is fragmented into smaller sizes and converted into humic material, soil
physical structure becomes increasingly important to the SOM decomposition rate. The
formation of soil particle aggregates and organo-mineral complexes can entrap SOM and
give rise to a physically and/or chemically stabilized soil carbon pool that can serve as a
reservoir for carbon sequestration (Garten, 1997).
Figure 7. Principal pedogenic processes affecting soil organic carbon (SOC) content (Lal
et al., 1998).
A large portion of the global inventory of SOC resides in forest ecosystems (Lal
et al. 1998); but scientists have been unable to answer many questions about the ability of
forest soils to sequester carbon and thereby ameliorate future increases in atmospheric
CO2 concentration (Lal et al. 1995a;b;c).
The state of Florida consists of 151,939 km2 of land
and "pine flatwoods" are the most extensive terrestrial ecosystem. They cover
approximately 50% of the state area.
Pine flatwoods evolved under frequent lightning and human-caused fire, and
seasonal drought and flooded soil conditions. Pine flatwoods are characterized by:
* Flat topography
* Relatively poorly drained, acidic, sandy soil
* And in the past, by open pine woodlands with frequent fires.
Pine flatwoods occur in many of Florida's National and State forests. National
forests, under the supervision of the U.S. Forest Service, extend 5,014 km2 (3.3% of the
federal land) and are located in three National Forests: Osceola, Ocala and Apalachicola
State Parks and State Forests (Fig. 9), under the supervision of the Florida Department
of Natural Resources, extend 3,238 km2 (2.2% of the state land) and are located in 36
different locations across the State.
Many of the soils identified in the federal and state parks are in the flatwoods
(http://www.sfrc.ufl.edu/Extension/ffws/ffwsecl.htm). Some of the soils are classified in
the Order of Spodosols. In Florida, Spodosols (Fig. 10) develop in sandy, acid parent
material, with poor to very poorly drained conditions and are easily recognized by the
spodic horizon (Bh). The spodic horizon is an illuvial layer with 85 percent or more
spodic materials. Spodic materials contain illuvial active amorphous materials composed
of organic matter and aluminum, with or without iron. The term "active" is used to
describe materials that have a high pH-dependent charge, a large surface area, and high
water retention. The spodic horizon normally lies below an albic horizon (a light colored
f-St. P te" .
W Io 5:lli
Figure 8. Location of the three National Forests in Florida.
eluvial E horizon). Less commonly, it either is under an ochric epipedon that does not
meet the color requirements for an albic horizon or is in or under an umbric epipedon. In
~I ~-- c
some soils the spodic horizon is at the surface of the mineral soil directly below a thin O
horizon (Soil Survey Staff, 1999).
The pedogenic process of podzolization has been used to explain how one spodic
horizon forms but there are regions in Florida where soils with multiple spodic horizons
(Fig. 11) occur and there are doubts that the deeper spodic horizons were formed by
Figure 9. Location of the 36 State Forests in Florida.
Source: (htt ://www.fl-dof.com/Fm/stforest/)
this process. The mechanism of formation of these multi-layered Spodosols may not fit
under the classical definition of podzolization. The mechanism of podzolization requires
eluviation of Al and/or Fe from the E horizon and illuviation of these minerals in the Bh
below. This pedogenic process occurs in the upper Bh horizon, but may not occur in the
lower B'h horizon.
Most of the C stored in Spodosols occur in the A horizon (1st mineral horizon,
usually in the surface) and the Bh (spodic horizon). According to Lee et al. (1988), the
Bh horizons in selected Spodosols of Florida, sequestered, in average, 3 times more C
20 to 60cm
60 to 100cn
100 to 200c
Figure 10. Florida's State Soil-Spodosol, series Myakka (sandy, siliceous, hyperthermic,
Aeric Alaquod). Source: (http://www.statlab.iastate.edu/soils/osd/dat/M/MYAKKA.html)
than the A horizons (8.64 mg/kg vs. 21.8 mg/kg). Carbon storage, coupled with humus
dynamics and agronomic issues, has become of global significance because of its
Figure 11. An example of a Spodosol with multiple Bh horizons near Green Cove
Springs, Florida. Photo by Mary E. Collins.
possible contribution to the reduction of atmospheric CO2 and the greenhouse effect
(Bouwman, 1990). The capacity of Spodosols to be a source or sink of atmospheric CO2
is connected strictly to the rate of SOM degradation (Dale et al., 1993). A better
knowledge of the processes that stabilize humus in Spodosols, in particular, humic
substances (the recalcitrant fraction of SOM) will play a significant role in understanding
how C sequestration is achieved.
Very little research has been conducted on the genesis of these multiple Bh
horizon Spodosols in Florida. Studying how they develop and learning the different
mechanisms of formation can help us understand the C dynamics taking place in
In general, this study investigates the pedogenic processes responsible for
forming multiple-Bh horizons in Spodosols; what are the forms of C in those spodic
horizons; how different is their morphological, physical, and chemical properties between
upper and lower Bhs and, explain through landscape evolution their genesis/kinetics.
Objectives of the Study
The objectives of this research were as follows: (a) To document the effect of
hydrology on the Bh horizon genesis and the C release with hydrological changes; (b) To
determine the differences in morphological, physical, and chemical properties among Bh
horizons; (c) To relate C sequestration to the depth of the Bh horizons in the different
Spodosols of the study area; (d) To study C sequestration by determining the forms of C
in multiple-Bh horizons in Spodosols; and (e) To propose a mechanism for the genesis of
Spodosols with multiple Bh horizons.
Florida has seven Orders of soils (Fig. 12). They are Alfisols, Entisols, Histosols,
Inceptisols, Mollisols, Spodosols and Ultisols. Spodosols are the dominant soil Order.
They cover 3.6 millions hectares (Fig. 13). Approximately 27% of the state land area
(Stone et al. 1992).
Spodosols in Florida are soils developed in coarse-textured parent materials under
an intense leaching environment induced by organic acids from plant litter and plentiful
The word "Spodosol" originates from the Russian term "pod" (beneath) and "zol"
(ash), or "ashy underneath." Podzol was used originally in the early Russian system of
classification to describe the forest soils that had a light-colored E horizon (Baldwin et
Spodosols are probably the most photogenic soils of the world with several
kinds of horizons, each with its own color, texture, and properties. The most striking
horizon is that resulting from accumulation of black or reddish amorphous materials
50 0 5W 100 km
Figure 12. Map of the soil Orders in Florida. Source: (http://soilpedology.ifas.ufl.edu/)
consisting mostly of organic C, Al and/or Fe. This horizon is called a spodic horizon
(Soil Survey Staff, 1999).
The formation of the spodic horizon is due to the pedogenic processes of
eluviation (mobilization) ofFe and Al from O, A, and E horizons and the illuviation
(immobilization) of these minerals in short-range-order complexes with organic matter in
the B horizon. The overall process is known as podzolization (Fig. 14). Source:
o 0 60 100 km
Figure 13. Percent land coverage of Spodosols (orange color) in Florida and Northeast
Florida. Source: (http://soilpedology.ifas.ufl.edu/)
In general, podzolization refers to those processes by which the soil is depleted of
metallic cations (alkaline materials), becomes acid, and develops leached surface layers
and lower horizons of accumulation. Podzolization is fully active only where there is acid
leaching from the surface layer of organic material. So, there must be accumulation of
organic material over the mineral soil.
Leached, light color,
large ly Si
-..-- Bh horizon
Accumulation of humus
AI, Fe and bases.
Some hunus and bases
lea che d fmm Bh Iost to
Figure 14. Schematic diagram showing the podzolization process in the soil. Source:
The vegetation in Florida's flatwood forests, consisting mostly of slash pine
(Pinus elliottii), longleaf pine (Pinus palustris), saw palmetto (Serenoa repens)
and gallberry (Ilex glabra) (Collins et al. 1999), provides a generous amount of organic
debris with relatively low metallic cation concentration. On decomposition, this
vegetation gives rise to acid products. As the acids generated in the organic layer are
moved downward by percolating water into the mineral soil below, weatherable
destabilization occurs and metals from the sand grain coatings are released. These metals
move downward into solution. Once the coatings have been removed from the upper part
of the soil, the hydrogen ions of percolating acid waters replace many of the metallic
cations on the cation exchange complex. The metallic cations move downward in
solution, and the upper part of the soil becomes acid. Under acid conditions, many Fe and
Al compounds are unstable; and sand grain coatings containing these compounds break
down. Since quartz is fairly stable under acid conditions, it remains behind as a residue in
the upper part of the soil (E horizon). Thus, the upper layer of the soil becomes leached
(stripped) and is left in a highly acid and siliceous state. The leached material, colloidal
organic materials, metallic cations, Fe and Al oxides and clays accumulate at the lower
depth (De Conninck, 1980; Buol et al., 1997).
Spodic horizons are defined as being at least 2.5 cm thick and containing at least
85% "spodic materials". Spodic materials have a pH (1:1 water) of 5.9 or less, and at
least 0.6% organic carbon (1% organic matter). Typically, the color changes with depth
from black (the brightest chroma is near the top) to a reddish due to iron accumulation.
Colors of well-drained soils are commonly 5YR or redder; or 7.5YR with a value of 5 or
less and a chroma of 4 or less. Colors of poorly drained soils are commonly 10YR or
7.5YR with a value of 4 or less and a chroma of 4 or less. In spodic horizons that have
sandy or loamy particle size, there are commonly cracked coatings of Al, organic matter
and Fe, on sand grains (>10%) or pellets (>0.02 mm) between the sand grains (Soil
Survey Staff, 1999).
Spodic horizons are usually located under an albic horizon. Less commonly, they
are under an ochric epipedon which does not meet the requirements of an albic horizon,
an umbric epipedon, histic epipedon or simply under a thin O horizon. Spodic horizons
are commonly designated Bh, Bs, Bhs or Bsm horizons.
Two suborders of Spodosols occur in Florida, Aquods and Orthods. Aquods are
Spodosols that have a shallow, fluctuating water table and can have a histic epipedon
and/or redoximorphic features within 50 cm of the surface in an albic or spodic horizon.
If they are low in iron (<0.10%) are identified in the Alaquod Great Group. Orthods, are
Spodosols that are relatively better drained and have less than 6.0% organic C in the
spodic horizon. If they are low in iron (<0.10%) are identified in the Alorthod Great
Group. (Soil Survey Staff, 1999).
In the Florida flatwood forests (Fig. 15) Orthods and Aquods occur widely.
Orthods are usually located in the flatwood uplands and Aquods are located in local
depressions and large areas of low relief and high water table (Collins, 1990).
The flatwoods ecosystems have a nearly leveled topography. Soils quickly
become waterlogged during periods of heavy rain. Often, this period of heavy rain
produces episaturated condition (perched water table) in the soil because the restrictive
soil layers (such as the spodic horizon and, when present, the argillic horizon, which have
low hydraulic conductivity) limit water movement to lower soil horizons (Gaston, 1990).
Variations in elevation and topography affect the degree of inundation during the
rainy season. These variations result in a significant difference in the hydrology. During
the dry season, the amount of organic matter and leaf litter are the predominant factors
influencing the drought conditions of the soil. Because flatwoods is so strongly
associated with frequent fires, variation in fire regime greatly alters the amount of litter
and organic matter and thus indirectly influences the hydrology of flatwoods ecosystems.
Due to slight differences in soils and hydrology at any given location, flatwoods
communities often contain numerous other types of ecosystems, such as swamps,
marshes, hardwood hammocks, etc. This mosaic of habitats in an area can result in
a great diversity of ecotones between the flatwoods and these other communities (Sun,
Estimates of the time required for a Spodosol to develop is limited because the
time of initiation of soil-forming processes usually cannot be determined precisely. In
field experiments, Chandler (1942), used the known retreat pattern of the Medenhall
glacier in Alaska and by comparing the degree of Bh development in materials of
different ages. He estimated that a mature Spodosol would require 1,000 to 1,500 years to
Figure 15. Flatwood forest in Osceola National Forest. Photo by Mary E. Collins.
form. Russell (1974) used the drainage of Lake Ragunda, Sweden, which ended in
1796, as the beginning of soil development. He also estimated a time from 1,000 to
1,500 years for the development of a mature Spodosol. These estimates were made for
Spodosols of cold locations. Spodosols of Florida probably can form in less time since
pedogenic processes are not interrupted with the change of seasons. In contrast, in a
laboratory experiment, Harris and Hollien (2000) created an artificial spodic horizon in
Some Spodosols develop a second or multiple Bh horizons beneath a thick E' or
Bw horizon. Holzley et al.,(1975) studied multiple Bh Spodosols in the Coastal Plains of
North Carolina. According to them these Spodosols had a dissolved organic carbon
(DOC) flux sufficient to develop a Bh horizon 7m thick in 30,000 years. He thought that
these very deep Bh horizons (up to 10 m) may be buried. But it seems more likely that
they have formed at great depth because the overlying soil materials have little Fe and Al
that could precipitate the organic C.
According to Daniels et al., (1975), in the North Carolina multiple Bh Spodosols,
there is little difficulty conceiving the formation of the upper Bh horizon within the first 2
m by the processes generally attributed to podzolization, but he thinks that there is a
serious question when considering how OC accumulates at 10 m.
Dissolved organic C originates from the decomposition of organic matter (OM).
Litter decomposition (Fig. 16) represents the sum of mass losses brought about by
catabolism (action of microbial and animal enzymes), comminution (physical
breakdown by animals and abiotic processes), and leaching of water-table materials
(Swift et al.1979).
Figure 16. Simplified diagram of the litter decomposition cycle.
As a consequence of the change in-state brought about by these processes,
soluble or particulate materials are transported down in the soil by water to sites where
different chemical conditions operate from those regulating decomposition in the soil
surface. The solubilization of litter constituents and the relocation and precipitation by
condensation reactions in mineral soil are important processes in the formation of
stabilized humus constituents (Duchaufour, 1977). The cellular material decomposes
rapidly, usually within a few months to a year or two depending upon chemical
composition. During the process of decomposition microbial cell walls and some
metabolic products are synthesized, which decompose at least 10 times more slowly than
the original litter (Lowe, 1978). In general, about 10-20% of the aboveground litter and
20-50% of the root litter is converted to humus (Nye and Greenland, 1960) and the rest is
mineralized as CO2. Within the soil, some fractions of this organic matter undergo further
biochemical stabilization and may also be complex with clays or other minerals or they
may be physically protected within clay microaggregates (Edwards and Bremner, 1967).
These biochemical and physical processes further increase the resistance of humus
compounds to enzyme attack, so that mineralization rates of some fractions may be less
than 0.1-1% per year (Campbell, 1978).
The overall C distribution of DOC, estimated by Nuclear Magnetic Resonance
(NMR) spectroscopy, has been similar for both needle and leaf forest litter (Wilson et al.,
1983; Zech et al., 1985, 1990a,b and Hempfling et al., 1987). alkyl C -H bonds comprises
approximately 10-30%, alkyl C-O bonds 50-70%, aromatic C rings 10-30%, and carboxyl
(C=O) bonds 5-10% (Kogel et al., 1988). About 50% of the C-H bonds are attributable to
extractable lipids and an additional 20% to bound lipids extractable after acid hydrolysis.
The remaining C-H bonds may be ascribed to cutin-like macromolecules (Ziegler, 1989).
Polysaccharides (cellulose and hemicellulose) accounts for most of the O-alkyl C
resonances. Minor contributions are due to oxygen-substituted lignin side chains, lignin
methoxyl groups, and ester carbons in cutin and waxes. Aromacity carbon is mainly due
to lignin (Kogel et al., 1988). Most of the DOC infiltrates the soil and moves through the
soil matrix. This movement is caused by the negative charge of the acidic organic
compounds that are not balanced by sorption of Al or Fe so, the hydrophilic organo-
metallic compounds repel each other, disperse and migrate (Skjemstad, 1992).
McDowell and Likens (1988) studied the origin composition and flux of DOC in
the Hubbard Brook Valley in central New Hampshire. Cronan and Aiken (1985) studied
the chemistry and transport of soluble humic substances in forested watersheds of the
Adirondack Park, New York and, Yavitt and Fahey (1985) studied the organic chemistry
of the soil solution during snowmelt leaching in Pinus contorta ecosystems, Wyoming.
All these scientists observed that mobilization of DOC varies strongly during the course
of the year through the soil. The common maximum DOC mobilization occurred at first
leaching events after dry and warm periods (Guggenberger and Zech, 1993a; Vance and
David, 1991) probably because OM had time to accumulate in the surface of the forest
According to Daniels (1975), vegetation affects the movement and relative
age of DOC through the soil. When vegetation removes soil water via evapotranspiration,
the DOC that is left behind would be "young". If this DOC is not used by plants or
microorganisms, it would be free to move downward with the ground water. The
horizons below would receive only that C that would precipitate by chemical or
biological means. If the flux of that C is greater than the loss of it, C would accumulate.
Dawson (1978) studied Spodosols in the Cascade Mountains of Washington. He observed
that, in general, large quantities of DOC were leached into the mineral soil from the
forest floor, producing solution concentrations up to 122 mg C L1.
Cronan (1990) observed in a forested watershed located in New York, that the
concentrations of DOC typically decreased sharply with increasing soil depth. Solutions
in the B horizons had concentrations, on average, about one-fifth of values observed
in forest floor solutions. Similar observations were made by Dalva and Moore (1991) in a
forested swamp catchment in Westland, NewZealand. They observed that DOC
average for B horizons was, on average, one-sixth of the values observed in forest floor
As DOC moves through the soil, it interacts with clays. Humus-clay interaction in
soils is a dynamic process. Both humus and clay act as centers of activity around which
chemical reactions occur. Furthermore, by attracting ions to their surfaces, they
temporarily protect the ions from leaching. Because of their surface charges they also act
as "contact bridges" between larger particles, thus helping to maintain stable granular
structure (http://www.agcentral.com/imcdemo/03 Soil/03-10.htm).
Many processes take place in soils, but adsorption is probably the controlling step
in the formation of microaggregates in the soil. Adsorption on soil colloids depends on
the nature and properties of the surfaces available for interaction with ions and molecules
present in the soil solution. Active sites on soil clays, for instance, are frequently masked
by the presence of hydrous oxide material coating their surfaces and much of these
surface particles are coated with humic substances. In this way, the complex soil colloid
would show surface properties attributable to clay, hydrous oxide, and humic compounds
The capacity of metal oxyhydroxides to adsorb humic substances was reported by
Evans and Rusell (1959). They indicated that adsorption decreased as the pH of the soil
increased. On the other hand, Schnitzer and Skinner (1963) reported that fulvic acids
(FA), the smaller molecules of humic substances, were able to chelate (complex) with Fe
and Al from goethite, gibbsite and soil samples rich in "free" Fe and Al. According to
Theng and Scharpenseel (1975) and Theng (1976), the hydrous oxides of Fe and Al are
the most efficient substances in linking acidic organic molecules to clay surfaces.
By using X-ray diffractrometry and 13C-NMR spectroscopy Theng et al. (1986)
detected evidence of the occurrence of interlayer-clay-organic complexes in two New
Zealand soils with low microbial activity and a high acid reaction. In these soils, the
complex analyzed was formed by a regularly interstratified mica-smectite. The organic
species was a humic substance with a polymethylene chain structure containing little or
no aromatic C.
Schnitzer et al. (1988), using IR, NMR, and GC-Mass spectroscopy
techniques, re-examined previous results obtained by Kodama and Schnitzer (1971) in a
Canadian Spodosol. They concluded that about half of the clay-associated OM consisted
of humic materials and the other half was mainly composed of long-chain aliphatics.
Catroux and Schnitzer (1987) reported aromacity of SOM extracted from silt to be
higher than that extracted from clay. While aromatic structures appear to be concentrated
in silt-size separates, organic substances in clays seem to be dominated by aliphatic
The quantity of DOC sequestered in the flatwood ecosystems is significant.
Stone et al. (1992) estimated that 809 Tg of OC was sequestered in Florida Spodosols;
431 Tg residing in Bh horizons. Spodosols in Florida have about 0.05% of the estimated
global SOC pool estimated by Post et al. (1982) but, these data are underestimated
because subsurface C sequestration also occurs in the deep Bh horizons of Florida's
multiple Bh Spodosols.
Daniels et al. (1975) was the first to study multiple Bh Spodosols in coastal plain
soils of North Carolina. These North Carolina Spodosols contain some feldspars.
Northern Florida Spodosols differ from these North Carolina counterparts in that they are
formed from coastal plain sediments (mostly quartz) that do not have weatherable
minerals (Brasfield et al., 1973). The source of metals for complexation and mobilization
is restricted to relatively resistant secondary minerals which occur mainly as sand-grain
coatings (Harris et al., 1987; Harris and Hollien, 2000). Podzolization in Florida's
Spodosols require the presence of a water table, but the relationship between depth to
water table to the upper spodic boundary is not direct (Harris, 1998).
Farmer (1983), how also studied multiple-layered Spodosols in New Zealand,
think that despite these differences, the mode of formation of the Bh horizon has been
considered essentially similar. The traditional view is that Al and Fe are
released by weathering in the A horizon and are translocated as organic complexes and
deposited in the B horizon where there is an increase in sesquioxides. If reducing
conditions prevail, the iron is "lost" from the soil in Fe (II) form. However, most
Spodosols in Florida have formed in sands with very low initial contents of sesquioxides
and/or lack weatherable minerals that might provide continuing inputs of Fe and Al.
Therefore, while free sesquioxides are essential to the formation of Bh horizons in freely-
drained Spodosols, a different process is probably involved in the development of Bh
horizons in Florida because of the poorly drained conditions.However, major differences
in morphology and micromorphology between Bh's suggest different mechanisms of
precipitation (Harris, 1998).
Farmer (1983) observed that in hydromorphic Spodosols organic precipitates
filled the space between uncoated quartz sand grains in a manner that suggests
precipitation from solution. Also he observed that in freely drained Spodosols the sand
grains were coated with darker organic matter and paler (yellowish) sesquioxide coatings,
and the spaces between the grains were largely unfilled. He suggested that these
differences were due to different mechanisms in the podzolization process.
Daniels et al. (1975) thought that moving ground water is the mechanism for
distributing OC through the deep B'hs horizons. According to the Soil Characterization
Data of Florida (Carlisle, 1978, 1981, 1985, 1988 and 1989) deep B'h spodic horizons
have a lower hydraulic conductivity than the superficial Bh. Low hydraulic conductivity
would allow more time for the DOC to react with the Al/Fe in clays and solution.
In reassessing the processes that forms Spodosols, it has been proposed that, in
humus-Fe Spodosols formed on coarse parent materials, organic matter migrates through
the E horizon in soluble and colloidal form and is adsorbed or precipitated at the top of
the B horizon. This occurs on surfaces that initially carried coatings of sesquioxides; or as
OM moves down in the leaching water. OM takes up more and more Fe and Al from the
lower sesquioxide-rich horizons until its original charge is neutralized; thus, leading to
the mutual precipitation of the metals and OM.
Both processes imply the availability of both Fe and AL compounds
(sesquioxides) in the B and lower horizons. However, the parent material of Florida's
Spodosols initially contain only small amounts of Al sesquioxides and only trace amounts
of weatherable minerals, there is no evidence of sesquioxide coatings (enrichment), and
could not form in the zone of permanent saturation.
In their study of the multiple Bh horizons soils in North Carolina, Holzley et
al. (1975) postulated that with little Fe and Al the OM was not rendered immobile. It
moved deeper and even through the soil systems into streams. Kaurichev and
Nozdrunova (1964) reported that there were differences in Spodosols that are
"overmoistened". These differences are: (1) There is an alteration of oxidation and
reduction phases. (2) A transformation on the structure of the OM. (3) A reduction
of the components of the mineral soil constituents. (4) The translocation of substantial
amounts of OM down to a substantial depth.
Tolchel'nikov (1983), studied Spodosols with multiple Bh horizons in Russia. He
thought they occurred because the OM present in the lower B'h horizon originated during
the Holocene epoch. According to his theory, the humus accumulated deep in the soil
because the soils at that time were devoid of clay particles. After the deep B'h horizon
was formed, new material was deposited over it, and a new Bh horizon developed over
the old one.
The formation of spodic horizons is directly related to SOM. SOM consist of
humic substances and nonhumic substances. Nonhumic substances are all those materials
that can be placed in one of the categories of discrete compounds such as sugars, amino
acids, fats and so on. Humic substances are the other, unidentifiable components.
The formation of humic substances is one of the least understood aspects of
humus chemistry and one of the most intriguing. The study of these macromolecules has
been a challenge to the ingenuity of scientists for more than 200 years, and in spite of the
application of almost all available analytical instrumentation developed over the past four
decades, knowledge of their nature and composition is still limited (Saiz-Jumenez, 1996).
Humic acid (HA) is defined as the fraction of humic substances that is not
soluble in water under acidic conditions (pH less than 2) but is soluble at higher pH
values. HA is the major extractable component of soil humic substances. It is dark brown
to black in color (Schnitzer, 1982). The formation of HA during the decomposition and
transformation of plant residues is often accompanied by increases in alkyl-C and
carboxyl-C and decreases in ether-C, acetal-C, and aromatic-C in the molecular structure
of the acid (Zech et al. 1985).
Fulvic acids (FA) are the fraction of humic substances that are soluble in water
under all pH conditions. They remain in solution after removal of humic acid by
acidification. FA are light yellow to yellow-brown in color (Schnitzer, 1982).
Several pathways exist for the formation of humic substances during the decay of
plant and animal remains in soil (Fig. 17). The classical theory, popularized by
Waksman, (1936) is that humic substances represent modified lignins pathwayyl. The
majority of present-day investigators (Stevenson, 1982) favor a mechanism involving
quinones (pathways 2 and 3). In practice, all four pathways must be considered as likely
mechanisms for the synthesis of HA and FA in nature, including sugar-amine
condensation (pathway 4). These four pathways may operate in all soils, but not to the
same extent or in the same order of importance. A lignin pathway may predominate in
poorly drained soils and wet sediments, whereas synthesis from polyphenols may be of
considerable importance in certain forest soils. The frequent and sharp fluctuations in
Figure 17. The mechanisms for the formation of soil humic substances. Numbers
represent pathways from 1 to 4. (Stevenson, 1982).
temperature, moisture, and irradiation in terrestrial surface soils under a harsh continental
climate may favor humus synthesis by sugar-amine condensation.
Humic substances are widely considered to represent the most stable fraction of
SOM. Their stability is attributed variously to their chemical structure and heterogeneity
as well as to being caught within soil aggregates and interactions with metal cations and
clay minerals. The recalcitrance of humic substances may owe more to the latter than to
the former mechanisms, since it has been shown that when extracted HA are incubated
with fresh soil, they rapidly decompose unless polyvalent cations are present (Juste et al.,
Carbon-dating methods have shown that HA have mean residence times of
thousand of years compared with hundreds of years for the humin fraction. The FA
fraction contains polysaccharides with fast turnover and are generally contemporary
with the humin fraction or are of more recent origin (Paul and van Veen, 1979). If FA
move down in the soil, however, they can be among the oldest fractions (Goh et al.,
Ugolini et al. (1977) used lysimeters to study the migration of organic matter and
mineral particles in a subalpine Swiss Spodosol. He observed that the Bh horizon of this
Spodosol was friable with a high content of humins and HA that formed aggregates. He
calculated that it would remain hydrophilic with an average OC turnover of 200 years.
He concluded that if decomposition rate was less than the rate of eluviation from OM,
organo-metallic compounds would accumulate. The horizon would become hydrophobic
and FA would predominate.
Many investigators now believe that all dark colored humic substances are part of
a system of closely related, but not completely identical high-molecular-weight polymers.
According to this concept, differences between HA and FA, can be explained by
variations in molecular weight, number of functional groups carboxyll, phenolic OH),
and extent of polymerization. The postulated relationships are depicted in Fig. 18.
The low-molecular-weight FA have higher oxygen but lower C content than high-
molecular-weight HA. FA contain more functional groups of an acidic nature,
particularly COOH. The exchangeable acidities of FA (900-1400 cmol/kg) are
considerably higher than HA (400-870 cmol/kg).
Another important difference is that while the oxygen in FA can be accounted for
largely in known functional groups (COOH, OH C=O), a high portion of the oxygen in
HA seems to occur as a structural component of the nucleus. Electron microscope
observations revealed that the HA of different soils have polymeric structure. This
structure appears in form of rings, chains, and clusters (Saiz-Jimenez, 1996). The size of
these macromolecules ranged from 6-50 nm depending upon the humification
HA are thought to be complex aromatic macromolecules with amino acids, amino
sugars, peptides, and aliphatic compounds involved in linkages between the aromatic
groups. The hypothetical structure for HA, shown in Fig. 19, contains free and bound
phenolic OH groups, quinone structures, nitrogen and oxygen as bridge units, and COOH
groups variously placed on aromatic rings
The hypothetical model structure of FA (Buffle's model) contains both aromatic
and aliphatic structures, both extensively substituted with oxygen-containing functional
groups (Fig. 20).
Fulvic acid Humic acid Humin
yellow bt o-n -
increase in intensity of colour >
increase in degree of polymerization >
2 000 increase in molecularweight )300 000 ?
45% increase in carbon content >62%
48% decrease in oxygen content )30%
1 400 decrease in exchange acidity >500
decrease in degree of solubility -
Figure 18. Chemical properties of humic substances (Stevenson, 1982)
cc -, co' m, <, H i
a "A CQ O. HN
>1 i. a11 1'14
Figure 19. Hypothetical structure of humic acids. (Stevenson, 1982)
Bracewell and Robertson (1987) showed that aliphatic (polymethylene) chains,
heavily substituted with hydroxyl and carboxyl groups, occurred in soils in which
biological activity is high and OM turnover is rapid. In contrast, relatively unsubstituted
aliphatic chains are characteristic of OM in soils in which biological activity is restricted,
OH COOH CH20H
HOOC CH2 CH CH3
\ / / "'/ "C/
HOOC CH2 CHOH
COOH OH CH2-C COOH
Figure 20. Model structure of fulvic acids. (Buffle, 1977 )
for example, by low temperature or excess moisture. In general, the smaller FA
molecules are also more mobile and accumulate more sesquioxides per unit C before
precipitating as Al or Fe-fulvates. For this reason, they have been considered the primary
agent of Fe and Al translocation in the soil (McKeague and Day, 1968).
HA molecules can range to a considerable size, but those in Spodosols are slightly larger
than FA molecules. The continually moist and acid conditions characteristic of many
Spodosols are not conductive to the development of larger humic molecules characteristic
of other regions (Kononova, 1966). These small HA molecules are also similar to FA in
that they are mobile and able to complex Fe and Al. With regard to the theory of Bh
horizon formation, their behavior differs from FA only in that their precipitation
threshold occurs at a lower level of Fe and Al loading. They should, therefore,
accumulate closer to the surface than FA complexes. Thus, the upper B horizon of
Spodosols should be characteristically richer in humic acid complexes, while the more
mobile FA should move deeper into the B horizon.
The percentage of the humus, which occurs in the various humic fractions, varies
considerably from one soil environment to another. The humus of forest soils is
characterized by a high percentage of FA (50.7 to 66.6%) while the humus of peat and
grassland soils is high in HA (53.8 to 68.7%) (Stevenson, 1982) (Fig. 21).
Grassland soils Forest soils
HA- humic acid
Figure 21. Distribution of humus forms in grasslands and forest soils (Stevenson, 1982).
A system, devised by Kumada (1987), classified HA into four types: Rp, P, B and
A. These HA are then related to soil properties, vegetation type, and land use. Rp-type
HA represent an early stage in the humification process (e.g. rotting wood), whereas the
P-, B-, and A-types represent stable forms in strongly acid (P), moderately acid (B), and
weakly acid-to-alkaline soils (A). Spodosols developed under forest produce P-type HA.
This HA carbon occurs mainly as chemically aromatic (benzene ring) structures (Higashi,
The current spodic horizon definition is based on the presumption that amorphous
weathering products accumulate in the B horizon through the agency of relatively low
molecular weight (approximately 800) acid organic completing polymers (Soil Survey
Staff, 1999). These polymers are products of organic decomposition under acid
conditions. They are presumed to readily complex Fe and Al from the mineral fraction
and remain soluble and mobile until a critical amount of Fe and Al has been completed
after which they precipitate (Schnitzer and Khan, 1972). The Bh horizon is considered
to be a zone of organic Fe and Al precipitation.
Although the current definition emphazises the organic forms ofFe and Al, it is
recognized that inorganic amorphous forms are also present (Stobbe and Wright, 1959).
These may be decomposition products of the organic forms or they may have moved to
the horizon as inorganic colloids (Farmer et al., 1980).
Both Fe and Al are known to accumulate. McKeague and Day, (1968) suggested
that Al was the most distinctive marker in some Canadian Spodosols; and there have been
suggestions that Al alone could be used to define a Bh horizon. Southard (1994)
discussed that Fe and C distributions parallel each other in both the well-drained and
poorly-drained soils, suggesting that they probably occur together. The Al content in
well-drained and poorly-drained soils accumulate at a greater depth than either the Fe or
C, suggesting the possibility that the Al is not completed and may have been translocated
as an inorganic ion.
It seems that the critical factor for immobilization is the ratio of C to metal ions
(McKeague et al., 1983). With a high ratio, compounds are dispersed and mobile. As
the ratio decreases, due to additional complexation of metal ions during transport, the
complex is immobilized by precipitation or flocculation.
Holzhey et al. (1975) stated that HA were the principal organic components of
thick lower Bh horizons in the North Carolina Coastal Plain. Since FA usually dominate
most Bh horizons, he conceptualized a model that involved an environment of migrating
organic that accumulate and apparently polymerize to HA in sands until some maximum
OM content was attained. Beyond that maximum, there is little accumulation, although
migration continues. More recently, Anderson (1982) reported data for five Scottish Fe
humus Spodosols in which Bh horizons were distinguished by higher content of humic
acids (in average 2X more) than the B horizons below). According to Anderson (1982),
colloidal and soluble organic acids move in the soil until they encounter the sesquioxide-
coated-surfaces of the B horizon. Here, the negatively charged colloidal OM is filtered
out or precipitated on the positive charged oxide surfaces at the top of the B horizon. HA
concentrate in the top whereas, FA move further before becoming absorbed. He
conceptualized that Spodosols with more HA than FA have a wetter moisture regime.
The occasional moisture saturation in the Bh horizon, together with accumulation of OM,
could lead to reducing conditions. Ferric iron would change to ferrous iron, which would
rapidly re-oxidize in larger pores to form ferric species which would be immediately
trapped by OM.
The HA/FA ratio usually, but not always, decreases with increasing depth. Lee,
(1988), observed that, in selected Florida Spodosols, this ratio increased with depth in the
non-orstein Spodosols of St. Lucie and St. Johns Counties.
Multiple Bh genesis is a direct manifestation of processes dictating the terrestrial
fate and transport of DOC. These processes are fundamental in the assessment of global C
dynamics, but details of reactions and the role of water table in triggering them is still
uncertain (Harris, 1998).
This dissertation will serve as a source of information and understanding about
the processes that act upon the formation of multiple Bh horizons in Spodosols. An
improved understanding on how these soils sequester C is essential to cope with the
postulated global temperature change on our planet.
DESCRIPTION OF THE STUDY AREA
The research area was located in Baker County, northeast Florida (Fig. 22)
UNION CO RADFCR P
Map Scale: cm = 3.13km
Figure 22. Location of research site, Baker County, Florida.
Baker County is bordered on the west by Columbia County, on the south by Union and
Bradford Counties, on the east by Nassau, Duval and Clay Counties, and on the north by
the St. Mary's River and the State of Georgia. The research site is located north of the
Olustee Battlefield in the southeastern part of the Osceola National Forest (Fig. 23).
This site was choose to represent Spodosols with multiple Bh horizons in northeast
Map Scale: icm 1.47km
Figure 23. Location of the research site in Olustee Battlefield near the Osceola National
Baker County is in the southern boundary of the thermic soil temperature regime
(Soil Survey Staff, 1999). It is characterized by long, warm summers and relatively mild
winters. The Atlantic Ocean, Gulf of Mexico, and large inland lakes moderate the
The total annual mean precipitation is 1376.2 mm (Watts, 1996). The average
monthly precipitation and the actual precipitation received during the study in the Olustee
Battlefield is presented in Table 1. There was a deficit of 427.8 mm of precipitation
during the hydrological field study due to the drought caused by La Nioa.
Table 1. Average monthly precipitation and actual precipitation for February 1999 to
Month Mean Actual Difference
Feb-99 98.80 34.80
Total after 1376.20 948.40 -427.80
Feb-00 98.80 52.60 -46.20
Mar-00 101.10 100.60 -0.50
Apr-00 83.30 17.80 -65.50
May-00 109.20 7.20 -102.00
Jun-00 179.80 169.20 -10.60
Jul-00 178.60 164.40 -14.20
18 months 2127.00 1460.20 -666.80
A large part of this rainfall occurs in summer as locally heavy afternoon or
early evening thundershowers. As much as 51 to 76 mm of rain can fall in an hour.
Daylong rains in the summer are rare and generally accompany tropical depressions.
Some tropical depressions intensify into tropical storms or hurricanes. These
storms normally occur between June and mid-November. Hurricane-force winds rarely
develop because of the inland location of the county. Extended dry periods can occur at
any time during the year but are most common in spring and fall (National Climatic
Florida is part of the Coastal Plain Province as defined by Fenneman (1938) and
Thombury (1965). The Coastal Plain Province is a subaerial inland extension of the
continental shelf. The Florida peninsula lies principally on the Florida Platform. This
platform extends nearly 640 km north and south and nearly 640 km in its broadest width
west to east. More than one-half of the Florida Platform lies under water leaving a
narrow peninsula of land extending to the south from the North American mainland
The peninsula is divided into three physiographic zones (White, 1970). Baker
County is located in the Northern physiographic zone. The Northern zone extends
northward to Georgia and to the south, through an imaginary cross peninsular line which
would pass approximately through the cities of St. Augustine, Palatka, Hawthorne, and
Gainesville in Florida. The Northern zone is distinguished by continuous high ground
forming a broad upland which extends eastward to the Eastern Valley, and westward
continuously into the Western Highlands of Florida. In Baker County, two geomorphic
subzones are recognized: the Northern Highlands, which dominate in the County, and
the Atlantic Coastal Lowlands which, in Baker County, consists of a small area of the
Duval Uplands (Fig. 24) (Cooke, 1945).
The Northern Highlands in Baker County were formed by sea terraces in the Early
Pleistocene. These terraces occurred at different elevations above the sea level (Fig. 25).
The Sunderland (65.5 m above sea level) and Coharie (51.8 m above sea level) (Cooke,
1945) terraces are the highest in the county. The Okefenokee terrace (MacNeil, 1949)
was formed when sea level was about 45.7 m above the present level and includes the
basin of the present Okefenokee Swamp. The Okefenokee Swamp ranges in elevation
from about 27.4 to 39.6 m above sea level and was once occupied by a shallow
intracoastal bay (MacNeil, 1949). The Wicomico terrace (30.4 m above sea level)
separate the Northern Highlands from the Atlantic Coastal Lowlands.
Remnants of the Coharie and Sunderland terraces form the Lake City Ridge
(Figs. 24 and 26), that passes through Olustee and trends to the northeast toward the
southwestern part of Charlton County, Georgia.
The Trail Ridge, located in the eastern part of the county (Fig. 24) is part of the
lower Coastal Plain and consists of a series of Quaternary beach complexes that parallel
the modem coast and are younger nearer the coast. These beach complexes made subtle
ridges of which the Trail Ridge was the crest of the Wicomico beach complex
Elevations of the Lake City Ridge range from 45.7 to 65.5 m and are similar to
those associated with Trail Ridge (30.5 to 61 m). Both Ridges probably existed as a chain
of islands, which formed the southern boundary of the Okefenokee Sound.
The Atlantic Coast Lowlands subzone extends to the land adjacent to the Atlantic
coast line of Florida. The Atlantic Coastal Lowlands includes a number of geomorphic
I UNION 00C /BRADFORD
Map Scale I cm = 3. 14km
Figure 24. Physiographic areas of Baker County, Florida.
subdivisions. Only one of these subdivisions occurs in Baker County: the Duval Upland
(Fig. 24). The Duval Upland (White, in: Puri and Vernon, 1964), occurs in southeastern
Baker County adjacent to the boundary of Baker and Nassau Counties. It is bounded to
the west by the Trail Ridge and is part of a larger coast-parallel landform which extends
eastward into Nassau and Duval Counties. The small part of this feature that occurs in
Baker County ranges in elevation from approximately 15.2 to 30.4 m.
I SUNDERLAND 65,5m
- Ok'EFENOKEE 45 7m
* WICOMICO 30.4m
Map Scale lcm=3.82 km
Figure 25. Marine terraces and highest elevation of those terraces identified in Baker
Baker County is underlain by hundreds of meters of alluvial and marine sands,
clays, limestones, and dolomites (Clark, 1964). The Lake City Limestone is the oldest.
Next oldest rock is middle Eocene limestone (42 to 49 million years before the present)
in the Avon Park Formation. The youngest sediments are undifferentiated surficial sands
and clays of Pliocene to Holocene in age (5 million years old and younger). The Avon
0 2 4 6 8 10 12 14 16 18 20
Figure 26. Topographic map of the Lake City Ridge and the research site.
Park Formation and the younger limestone units overlying it are important freshwater
aquifers. The discussion of the geology of Baker County will be confined to sediments of
Eocene-age and younger. Fig. 27 illustrate the underlying stratigraphy of a cross section
from west to east (U.S. Geological Survey Staff, 1962).
Avon Park Limestone
The Avon Park Limestone of the middle Eocene-age overlies the Lake City
Limestone and is similar in lithology. It is about 44 m thick in southwestern Baker
County and thins to less than 15 m in the eastern part of the county. The top of the
formation ranges from 94 m below sea level in southwestern Baker County to more
than 187 m below sea level in the eastern part (U.S. Geological Survey Staff, 1968).
10 -21 -
Figure 27. Stratigraphy of cross-section near Lake City Ridge, Baker County.
The Ocala Group of Late Eocene consists of three limestone formations of similar
character (Fig. 27). From the oldest to youngest, they are the Inglis, Williston, and the
Crystal River Formations (Puri, 1957). These formations are differentiated generally on
the basis of lithology and fossil content. In Baker County, however, they consist of fairly
homogeneous sequence of cream to light gray, medium soft, chalky to granular marine
limestones that contain thin beds of hard, massive dolomitic limestone, and dolomite. The
Inglis and Williston Formations are generally more granular in texture than the overlying
Crystal River Formation and the Inglis Formation generally is more calcitic and slightly
darker in color than either the Williston or the Crystal River Formations. The thickness of
the Ocala Group ranges from 69 to 96 m in Baker County. The average thickness of the
Crystal River Formation is about 47 m and the average thickness of the Willinston and
Inglis Formations is about 15 m each. The altitude of the top of the Crystal River
Formation ranges from about 30 m below sea level in southwestern Baker County to
about 110 m below sea level in the eastern part (U.S. Geological Survey Staff, 1968).
The Suwannee Limestone consists of tan, white, or cream marine limestone, which in
many areas is dolomitic and coquinoid in parts, and varies considerably in hardness
(Cooke, 1936). In some locations this limestone is lithologically similar to the Ocala
Group limestone and is identified mainly by the last occurrence of the foranifera
Dictyoconus cookei (invertebrate animal). The thickness of the limestone ranges from 4
to 15 m, and the beds can be discontinous in the subsurface. In Baker County, the
Suwannee Limestone is a freshwater-bearing unit of the Floridan aquifer system (U.S.
Geological Survey Staff, 1968).
The Hawthorn Formation (5 to 24 million years old) overlies the Suwannee
Limestone in the western part of Baker County, The Hawthorn Formation is dominantly a
series of marine deposits consisting of varying and interbedded lithologies and
characterized by phosphatic sands, granules, and pebbles. The Hawthorn Formation
ranges from approximately 38 to 107 m in thickness (Scott, 1988)
Pliocene to Holocene Undifferentiated
Deposits of unconsolidated and poorly consolidated quartz sand that contains various
amounts of clay overlie the Hawthorn Group in Baker County. According to the Florida
Geological Survey (Leve, 1986), these sandy deposits generally range from about 7 to
30 m in thickness in the Northern Highlands area of Baker County. Sandy deposits in the
vicinity of Trail Ridge and Lake City Ridge are twice as thick than those of the Northern
Sands in the Northern Highlands are fine grained or medium grained and has only
trace amounts of heavy minerals (Johnson, 1986), especially titanium ore. In contrast,
sands in the Trail Ridge area are characteristically fine grained and has common heavy
minerals. Sands in the Trail Ridge are mined for their heavy minerals, especially
The Undifferentiated Sands, as described by geologists, are where the different
soils are formed.
The majority of the soils identified in the Osceola National Forest in the Baker
County Soil Survey report, (Watts, 1996), occur in the flatwoods, and are classified as
Spodosols. For the Florida Soil Characterization Data, one series with multiple Bh
horizons was sampled in the study area, Leon. This multiple Bh horizon Spodosol is in
the suborder Aquods. During this study, another series with multiple Bh horizon was
sampled in the Osceola National Forest, Mandarin. This multiple Bh horizon Spodosol
along with the Spodosols with one Bh horizon are classified in the suborder Orthods.
Aquod Spodosols differ from Orthods in that they have evidence of wetness
(redoximorphic features) within 50 cm of the soil surface. Orthods do not have evidence
of wetness above a depth of 50 cm. Therefore, no redoximorphic features are noted in
Orthods above a depth of 50 cm.
Aquods that have <0.10% iron (by ammonium oxalate extraction) in 75% or
more of the spodic horizon are further subdivided in the Great Group Alaquods.
Alaquods occur primarily in the southeastern U.S. and are the dominant Great Group in
Spodosols in Florida (Collins, 1990). Their water table fluctuates within the upper 50 cm,
and in the process, Fe is reduced, is soluble and, moves out of the soil. The spodic
horizon is dark-colored and consists mainly of an accumulation of organic matter and Al.
The spodic horizon often has a wavy upper boundary. An eluvial layer called the albic or
E horizon normally overlies the Bh horizon. The eluvial layer is light-colored as the Fe
and other metals have leached out as the result of the fluctuating water table. This E
horizon isgenerally thick, but can be thin in the wettest Alaquods.
Most of the Alaquods in the Osceola National Forest can be further subdivided
into Ultic Alaquods, Aeric Alaquods, or Arenic Alaquods. Ultic Alaquods have an
argillic horizon that begins above a depth of 200 cm; Aeric Alaquods have a spodic
horizon above a depth of 75 cm and, Arenic Alaquods have a spodic horizon that occurs
at a depth between 75-125 cm.
Orthods are generally better-drained Spodosols. They have <6% organic carbon in
the spodic horizon, and do not have evidence of wetness within 50 cm of the soil surface.
Orthods have a thick E horizon that lacks redoximorphic features above 50 cm depth.
Orthods are further subdvided at the Great Group level into Alorthods. The Alorthods
have <10% Fe (by the ammonium-oxalate method) in the Bh horizon. They have a high
accumulation of Al in comparison to Fe.
Alorthods that are saturated with water in one or more layers within 100 cm of the
soil surface for 20 consecutive or 30 cumulative days per year are placed into the
subgroup called Oxyaquic Alorthods. The "aquic" prefix is an indication of wetness, and
the prefix preceding aquic, "oxy", indicates the presence of oxygen and drier conditions.
Most of the Spodosols that occur in the Lake City Ridge (Fig. 28) area are in the
suborder Oxyaquic Alorthods. These soils have a spodic horizon that begins within
100 cm of the soil surface. If the spodic horizon begins within a depth of 125 to 200 cm
of the soil surface and, has 3.0 percent or less OC in the upper 2 cm of the Bh horizon, it
is classified as Entic Grossarenic Alorthods. "Grossarenic" is a term used to indicate thick
(>125 cm), leached sandy layers. "Entic" is the term used to indicate little or no evidence
of development in the soil.
At the study site the soils were classified as Centenary (sandy, siliceous, thermic,
Entic Grossarenic Alorthods) in the upland; Mandarin (sandy, siliceous, thermic,
Oxyaquic Alorthods) in the upper and lower midslope, and Leon (sandy, siliceous,
thermic, Aeric Alaquods) in the upper and lower lowland.
Rain is the source of most groundwater. The occurrence of groundwater is controlled
primarily by the subsurface texture of the soil. Rocks that are sufficiently permeable to
yield usable quantities of water to wells are called aquifers. The aquifers serve as
conduits that distribute and store groundwater. There are two types of aquifers in
Baker County: (1) the surficial aquifer, which is not overlain by an impermeable layer
Figure 28. Soil map of Lake City Ridge and the research site. Spodosol extension
in blue; Ultisol extention in red; others in gray. Source: Baker County
Soil Survey, 1996.
and the water table is free to rise and fall and, (2) the artesian aquifer, which is overlain
by an impermeable bed and water is confined under pressure (U.S. Geological Survey
Staff, 1968). Discussion will be focused on the surficial aquifer which is the one
pertinent to the study.
Surficial Aquifer System
The surficial aquifer system is the permeable hydrologic unit contiguous with the
land surface that is comprised principally of unconsolidated (silicic)clastic deposits
(Southeastern Geological Society, 1986). It contains the water table, and the water
within it is under mainly unconfined conditions; but beds of low permeability may
cause semi-confined or locally confined conditions to prevail in its deeper parts. The
lower limit of the surficial aquifer system coincides with the top of the Hawthorn
Formation. The permeable beds of the aquifer are generally within the upper 15.5m of
the surface. Water is discharged from the aquifer through evapotranspiration and
seepage into streams, lakes, and swamps if their water levels are lower than the water
level of the aquifer (Leve, 1986).
In many areas, the surficial aquifer is used for small yield agricultural and
domestic water supplies, but usually it has bad taste due to the high iron content
MATERIALS AND METHODS
The field site was located north of the Olustee Battlefield in the Osceola
National Forest. This site was selected to represent Spodosols with multiple Bh horizons.
Spodosols with multiple Bh horizons in the area were originally identified and studied for
the research project titled "Ecological Inventory of the Osceola National Forest" (Collins,
1999). A 200 m long x 18 m wide experimental plot, extending from the uplands to the
lowlands was chosen. Water table depth was determined using water wells. The plot was
divided into 8 rows (Fig. 29). Each well was made of 5.1cm diameter PVC pipe that was
2.5 m in length. Along the lower 25 cm, 40 holes with 8 mm in diameter were drilled to
allow water to enter. A screen mesh covered the holes to prevent sand from filling the
holes. Each well was backfilled with sand to ensure a tight fit of the well and the
surrounding soil. Around each well, at surface level, a plastic mat, sealed with silicon,
was placed to prevent water from seeping down. Each well was covered with a plastic
cap. Using a flashlight and a tape measure, water table depth was determined regularly.
The regional office of the Forest Service in the Osceola National Forest collected the
daily precipitation data that occurred near the research site. The weather station was
located next to the entrance of the Olustee Battlefield. The data used for this project was
taken from February 1999 to January 2000.
The topographic map of the experimental plot is illustrated in Fig. 30. The
elevational difference between the uplands and the lowland was 1.42 m.
Between each row of wells, four probes (Fig. 31) were installed (Fig. 29). The
probes were used to extract water to measure DOC. The probes were made of 5.1 cm
diameter PVC pipes. Each probe went to a different horizon; E, Bh, E' or Bwl and B'h.
The depths to each horizon are shown in Table 2.
Figure 29.Experimental design of the water wells and probes.
There were 4 treatments (E, Bh, E' or Bw and, B'h), and 8 replicates, totaling 32
probes; and a total of 24 water table wells. One extra well and 4 more probes were
installed, 50 m to the north of the transect, inside the nearby wetland.
The length of each tube was determined as the depth to the horizon + 50 cm. At
the lower end of the pipe, a 10 cm long stainless steel needle was installed. A
polyethylene tubing was attached to the needle inside the PVC tube. The tubing was of
the same length as the PVC tube + 15 cm. Surrounding each probe, a plastic mat, sealed
.iiive Ele.l.T,,, . lufflSWlMKBr~tit,, #
t ~ ~~..:..r'::".",-", :
i i. '
.. . ,- .:i _;,i!.._.'_- _' ,, .? ... :":."
., ^;: .i
,^ _' -,_,. I.* .,,.. . ...
xW s 1: 25m
0 1 2
Yaos 1: 3m
S 1 2
Figure 30. Topographic map of the experimental plot.
PVC tube 5. Icm diameter
Figure 31. Probe design.
Table 2. Depth to different horizons in the experimental plot.
Soil Series E Bh E' or Bw B'h
Centenary 70 173
Centenary 70 157
Upper Mandarin 12 22 70 150
Upper Mandarin 15 27 72 168
Lower Mandarin 20 38 66 160
Lower Mandarin 31 56 80 164
Upper Leon 30 58 83 165
Lower Leon 34 60 102 162
with silicon, was placed to prevent water from seeping in from the surface. A small
opening was made atthe upper end side of the PVC tube to allow the tubing to come out.
Each probe was covered with a cap. The depth to each horizon was determined by hand
Using a manual vacuum pump (Fig. 32), 50 mL of water was extracted from
the different horizons. Each water sample was filtered, in the laboratory, with a 45
micron carbon free filter the same day it was taken. They were stored in a freezer until
the DOC was measured.
A soil transect was made from the upland to the lowland (Fig. 33). Detailed
descriptions of the five soils (uplands, upper mid-slope, lower mid-slope, upper lowlands
and lower lowlands) were made (Appendix A).
Figure 32. Actron III vacuum pump.
Figure 33. Location of the soils that were sampled in the transect (Countour line 10cm).
The soil from the upland was a sandy, siliceous, thermic, Entic Grossarenic
Alorthods Series Centenary. Both soils from the midslope were classified as sandy,
siliceous, thermic, Oxyaquic Alorthods Series Mandarin. Both soils from the lowlands
were classified as sandy, siliceous, thermic Aeric Alaquods Series Leon.
A detailed map of the understory vegetation was made. The "line-intercept
method" (Browner, 1989) was used to determine vegetation frequency and coverage.
A perpendicular line 100m long was selected randomly between rows #3 and #7. A
yellow tape was stretched along the line. The line was subdivided into 10 intervals. Every
other interval (n=5) was counted. Along the line, and for each interval, plant species were
recorded and the distance they covered along that portion of the line in number of
decimeters (dm). Only the plants touched by the line or lying under or over it were
considered. Frequency was calculated as the number of intervals in which a particular
plant species occurred divided by 10 (number of intervals sampled). Cover range was
calculated as the total intercept length of a particular plant species divided by the total
line length sampled. Frequency rank was calculated as the frequency of a particular
species divided by the total frequency for all species. Cover rank was calculated as the
total intercept length for a particular plant species divided by total intercept length of all
species. All trees, within a 5 m radius of any of the wells were mapped.
Particle-size analysis was determined using the pipette method (Day, 1965). Soil
reactions (pH) were measured in 1:1 solid liquid ratio using water and KC1.
Exchangeable bases were extracted by NH40Ac at pH 7.0 and the concentration
measured using atomic absorption spectrometry; Extractable acidity was extracted using
BaCL2-TEA at pH 8.2. Cation exchange capacity (CEC) was calculated as the sum of
exchangeable bases and extractable acidity (EA); and the percentage base saturation (BS)
was calculated as the percentage of CEC attributable to bases x 100. OC content was
determined by a modification of the acid dichromate digestion method (Soil Survey Staff
(2), 1996). To measure organically completed Fe and Al, the sodium pyrophosphate
extractable method (Franzmeier et al., 1965) and the sodium citrate-dithionite method
(Soil Survey Staff (2), 1996) were used. These two methods are used together as criteria
for spodic placement. For a more reliable and accurate estimation of the soil properties
and a better understanding of soil exchange complex, ammonium oxalate (McKeague and
Day, 1968) was also used, in conjunction with the other procedures, to measure C, Al and
Dissolved organic carbon in the soil groundwater was measured using a high
temperature total organic carbon (TOC) analyser (Dohrman DC 190; Santa Clara, CA).
The percentages of the different humic substances (FA and HA) in the Bh
horizons were calculated using the organic matter fractionation method (Schnitzer, 1982)
(Fig. 34). Ten grams of air-dry soil was place inside a 200 mL propylene flask, 100 mL
of 0.5NNaOH was added. The air was displaced from the flask with N2. The mixture
was shaken for 24 hrs at room temperature. The dark-colored supernatant was separated
from the residual soil by centrifugation (10,000 rpm for 10 min.). Ten-mL aliquots from
each sample were placed inside 40 ml test tubes. The samples were acidified to a pH 2
with 2NHC1. The samples were left to sit for 24 hrs, then the soluble material (FA) was
separated from the coagulate (HA) by centrifugation (2,000 rpm for 2 min.). The
fractions were transferred to 20 mL test tubes and freeze-dried. After dryness, they were
tightly sealed with wax paper and placed in a desiccator. The sample and test tube were
weighed. Afterward, the tubes were cleaned with potassium dichromate and HC1 and
weighed. The difference x 100 was accounted as percentage FA or HA in the sample.
SOIL or SEDIMENT
HUMIN TREAT WITH
Figure 34. Diagram showing the extraction and fractionation of humic substances.
Mineralogy of Soils
Mineralogy of the clay fraction of the lower Mandarin soil (representative soil of
the area with multiple Bh horizons) was determined. Three hundred grams of soil from
each horizon studied was treated with 100 mL of sodium hypochlorite to remove all
organic material. The silt and clay were separated from the sand using a 270-mesh sieve.
The silt and clay were separated by centrifugation (Whittig and Allardice, 1986)
following Na saturation to promote dispersion. The clay fraction was prepared for x-ray
diffraction analysis (XRD) by depositing approximately 250 mg as a suspension onto a
ceramic tile under suction. K and Mg saturation were performed directly on the tiles by
washing with the respective Cl- salts and rinsing. Glycerol was added to the Mg-saturated
sample. Samples were scanned at 20 2e min1 with CuKa radiation.
The micromorphology of the spodic horizons was studied using undisturbed
samples from the upper and lower Bh horizons. A thin section impregnation
technique (personal communication with Dr. W. Harris) was used to prepare the
samples. Undisturbed samples were taken from the transect. The clods were trimmed to a
size of 7.5 cm high by 5.0 cm diameter and air-dried for 2 weeks. After drying, the
samples were placed in aluminum cans and oven-dried for 4 hrs. The 2 components of
the epoxy resin (Scotch Cast Resin #3) were poured in equal amounts in two separate
beakers and heated with the clods at 95C for 2 hours. The two epoxy components were
mixed together and poured over the clods. They were placed in a vacuum desiccator
equipped with a cold trap to protect the pump, and subjected to a vacuum for about 45
minutes. They were taken out of the desiccator and put back in the oven at 95C and left
overnight.The aluminum can with the impregnated clod was then cut into 2 cm slices
with a diamond saw. The slices were send to Burham Petrographics in Monrovia, CA for
preparation of the thin sections.
Al-C distribution in the Bh horizons was compared using optical microscope and
Scanning Electron Microscope (SEM) techniques. Optical microscope photos were taken
using a digital camera. Then the micromorphology slides were coated with Au-Pb and
SEM photos were taken at the exact same location in the slide.
Lower Mandarin soil samples from the Bh and B'hl and B'h2 horizons were
obtained for 14C dating. The samples were carefully handled and wrapped in aluminum
foil to prevent any contamination. To isolate 14C pre-treatment was applied to the
samples. Each sample was dispersed in deionized water and then given hot HC1 acid
washes to eliminate carbonates. NaOH washes were conducted to remove secondary
organic minerals. The NaOH washes were followed by a final acid rinse to neutralize the
solution prior to drying. The soil samples were analyzed by the radiometric technique.
This technique synthesized soil C to benzene (92%C), measuring C14 content in a
scintillation spectrometer, and then the radiocarbon age was calculated. 14C conventional
age was the result after applying 13C/ 12C corrections to the measured age. The analysis
was done by Beta Analytic Laboratories, Miami, FL.
Artificial B'h Formation
An experiment was conducted to observe how soil from the Bw horizon (the
horizon above the B'h) and the E horizon (the horizon above the Bh), would react with
FA and HA. Eight clear PVC tubes of 2.54 cm in diameter were cut to 60 cm pieces. A
stopper with a 5 cm x 0.5 mm glass tube was placed in the lower end of the PVC tubes. A
flexible tubing was inserted in each glass tube. The flow of water was controlled with a
pressure clamp. The upper end of the pipe had a stopper to prevent contamination.
Soil from the Bw horizon was placed inside four of the PVC tubes up to 30 cm. Four
additional PVC tubes were filled with soil from the E horizon up to 30 cm. A liter of
water was mixed with 30 mL of FA and another liter was mixed with 30 mL of HA. Two
tubes with Bw soil were saturated with the mixture of FA; two more were saturated with
the mixture of HA. The same procedure was done with the tubes with soil from the E
horizon. The experimental water table was set to 40 cm height. The mixture of acids and
water flowed through the soil at a rate of 5 cm/day. The experiment was done for 2 days.
The Effect of Hydrogen Peroxide and Incineration on Bh and B'h Organic Matter
A second laboratory experiment was conducted to measure the effectiveness of
hydrogen peroxide and the incineration technique to remove the organic matter from the
different spodic horizons. Four samples of the Bh and B'h horizons were taken from the
Mandarin soil. Five grams of oven-dry soil (95C) were placed in crucibles already
weighted. Two soil samples of each of the horizons were treated with hydrogen peroxide.
The other soil samples were left untreated. After 4 days, they were dried on a hotplate
and weighed again. The difference in weight between the oven-dry soil and the treated
and untreated samples x 100 was calculated as percentage organic matter loss. Then all
eight soil samples were incinerated to 6000 C for six hours to remove all organic matter.
After cooling to room temperature inside a desiccator they were weight again. The
difference in weight between oven-dry samples and incineration samples was accounted
as total organic matter. The soil weight difference between the incineration method and
the hydrogen peroxide treatment x 100 was accounted as percentage organic matter loss
due to treatment.
Evaluation of Existing Characterization Data
The Soil Characterization Program was established in the University of Florida in
1970. The purpose of this program was to sample, analyze and describe soils throughout
Florida. The data of more than 1000 pedons, covering over 300 soil series, have been
published in seven separate records covering the physical, chemical, mineralogical and
morphological data of each soil (Calhoun et al., 1974, Carlisle et al., 1978, 1981, 1985,
1988, 1989; Sodek et al., 1990).
Data for multiple Bh Spodosols appearing in the Soil Characterization data was merged
to the data obtained in the present study to determine certain relationships between upper
and lower Bh horizons. The data used from the Soil Characterization Data include total
bases, extractable acidity (EA), cation exchange capacity (CEC), extractable Al vs.
extractable acidity, extractable Al vs. pH, and weighted average organic carbon content.
RESULTS AND DISCUSSION
Soil morphology is defined as (i) The physical constitution of a soil profile as
exhibited by the kinds, thickness, and arrangement of the horizons in the profile, and by
the texture, structure, consistence, and porosity of each horizon. (ii) The visible
characteristics of the soil or any of its parts. Source: (http://www. soils.org/cgi-
bin/gloss search.cgi?OUERY=MORPHOLOGY&SOURCE= 1).
Three different soil series were identified and classified. These soils were:
Centenary sandy, siliceous, thermic, Entic Grossarenic Alorthods
Mandarin sandy, siliceous, thermic, Oxyaquic Alorthods
Leon sandy, siliceous, thermic, Aeric Alaquods
Selected morphological properties, the landscape position, and the drainage class
of the soils studied are shown in Table 3. The complete description of the soils in the
transect can be seen in Appendix A. All these soils had mostly fine quartz sand as parent
material and a single grain structure in the A horizon that promoted high infiltration rate.
In general, the upland soil, Centenary, had a "salt and pepper" color, 70% light
gray (10YR 7/1) and 30% dark gray (10YR 4/1) A horizon, followed by a yellowish
brown (10YR 5/4) Bwl and a yellowish brown (10YR5/4) Bw2 horizons. Below the Bw2
horizon, a pale brown (10YR6/3) El and a very pale brown (10YR 7/3) E2 horizons
occurred. A fluctuating water table over the permanent water table created periodic
Table 3. Selected morphological properties, geomorphic position, and drainage of the
Series Horizon Depth Color Texture Landscape Drainage
(cm) (moist)1 position class
Centenary Ap 0-10 70% 10YR fs2 Upland Somewhat
Bwl 10-18 10YR 5/4 fs
Bw2 18-40 10YR 5/4 fs
E1 40-64 10YR 6/3 fs
E2 64-104 10YR 7/3 fs
Eg 104-143 10YR 8/2 fs
Bg 143-153 10YR 5/2 fs
Bhl 153-168 10YR 3/2 fs
Bh2 168-190 10YR 2/2 fs
Bh3 190-212 7.5YR 2.5/1 fs
Upper Ap 0-10 50% 10YR fs Upper Mid- Somewhat
Mandarin 7/1 slope poorly
50% 10 YR
E 10-22 10YR 6/1 fs
Bh 22-38 10YR 4/4 fs
E' 38-63 10YR 7/3 fs
Egl 63-96 10YR 8/2 fs
Eg2 96-130 10YR 8/1 fs
Bw 130-157 10YR 5/4 fs
B'hl 157-190 10YR 4/2 fs
B'h2 190-200 10YR 3/3 fs
Lower Ap 0-2 70% 10YR fs Lower Mid- Poorly
Mandarin 8/1 slope
E1 2-20 10YR6/1 fs
E2 20-36 10YR 7/1 fs
Bhl 36-45 10 YR 2/1 fs
Bh2 45-55 10YR 2/2 fs
Bh3 55-64 10YR 3/3 fs
BE 64-72 10YR 7/3 fs
Egl 72-106 10YR 7/1 fs
Eg2 106-160 7.5YR 7/1 fs
B'hl 160-180 10YR 3/1 fs
Series Horizon Depth Color (moist)1 Texture Geomorphic Drainage
B'h2 180-192 10YR 2/2 fs
B'h3 192-200 10YR 2/1 fs
Upper Leon Ap 0-10 70% 10YR fs Upper Poorly
Ap/Eg 10-19 70%10YR fs
30% 10YR 5/1
Eg 19-47 10YR 5/1 fs
Bhl 47-52 10YR 2/1 fs
Bh2 52-68 10YR 3/2 fs
Eg/Bw 68-105 10YR 8/1 fs
Bw 105-120 10YR 4/4 fs
Bw/Eg 120-130 10YR 4/6 fs
B'w 130-180 10YR 4/2 fs
B'h 180-200 10YR 2/1 fs
Lower A 0-10 60% 10YR 3/1 fs Lower Poorly
Leon 40% 10YR 5/1 Lowland
A/E 10-16 70% 10YR 3/1 fs
30% 10YR 5/1
Egl 16-28 10YR 6/2 fs
Eg2 28-52 10YR 5/2 fs
Bhl 52-60 10YR 2/1 fs
Bh2 60-83 7.5YR 3/2 fs
Bh3 83-98 7.5YR 4/2 fs
Bwl 98-116 10YR 5/3 fs
Bw2 116-130 10YR 6/3 fs
Bg 130-137 2.5YR 5/2 fs
B'hl 137-157 7.5YR 4/4 fs
B'h2 157-177 7.5YR 3/2 fs
B'h3 177-200 10 YR 2/1 fs
Munsell color notation
2 Fine sand
anaerobic conditions under the E2 horizon making the next horizon a very pale brown
(10YR8/2) Eg horizon. Gleying was caused by the process of reduction. Under this Eg
horizon a grayish brown (10YR5/2) Bg horizon occurred. Below 153 cm a very dark
grayish brown (10YR 3/2) Bhl to black (7.5YR 2.5/1) Bh3 horizons occurred.
The upper mid-slope soil, Mandarin had a "salt and pepper" color, 50% light gray
(10YR7/1) and 50% gray (10YR5/1) Ap horizon, followed by a gray (10YR 6/1) E
horizon that consists mostly of stripped sand grains. Under the E horizon, a dark
yellowish brown (10YR 4/4) Bh horizon was formed. This Bh is an accumulation
horizon of humus and Al. Under this horizon, a very pale brown (10 YR 7/3) E'followed
by a very pale brown (10YR 8/2) Egl and a white (10YR 8/1) Eg2 horizons occurred.
Under these horizons a yellowish brown (10YR5/4) Bw formed. Under the Bw a dark
grayish brown (10YR 4/2) B'hl to dark brown (10YR 3/3) B'h2 occurred.
The lower mid-slope soil, Mandarin had a "salt and pepper" color, 70% white
(10YR8/1) and 30% dark gray (10YR4/1) thin Ap horizon, followed by a gray (10YR
6/1) Eland a light gray (10YR 7/1) E2 horizons. Under these E horizons, a black (10YR
2/1) Bh horizon was formed. The value and chroma of the Bh increased with depth from
black (10YR 2/1) in the Bhl to dark brown (10YR 3/3) in the Bh3 horizon. Under the
Bh3, a very pale brown (10YR 7/3) mixed, thin BE horizon occurred. Below this, a light
gray (10YR 7/1) Egland a light gray (7.5YR 7/1) Eg2 formed. Below 160 cm a very dark
gray (10YR 3/1) Bhl to black (10YR 2/1) B'h3 occurred.
The upper lowland soil, Leon, has a "salt and pepper" color, 70% gray (10YR5/1)
and 30% light gray (10YR7/1) Ap horizon, followed by a combination of 70% light gray
(10YR 7/1) and 30%gray (10YR 5/1) Ap/Eg horizon. Following this combinational
horizon a gray (10YR 5/1) Eg horizon was formed. Under this Eg horizon, a black (10YR
2/1) Bh horizon occurred. The value and chroma of the Bh increases with depth from
black (10YR 2/1) in the Bhl to very dark grayish brown (10YR 3/2) in the Bh2. Below
the Bh2, the following horizons occurr: a combination white (10YR 8/1) and dark
yellowish brown (10YR 3/4) Eg/Bw horizon, a dark yellowish brown (10YR 4/4) and
yellowish brown (10YR 5/4) Bw horizon, a combination dark yellowish brown
(10YR4/6) and light yellowish brown (10YR 6/4) Bw/Eg horizon and, a dark grayish
brown (10YR 4/2) Bw horizon. Below 180 cm a black (10YR 2/1) B'h horizon occurred.
The lower lowland soil, Leon, had a "salt and pepper" color, 60% very dark gray
(10YR 3/1) and 40% gray (10YR 5/1) A horizon, followed by a combination 70% very
dark gray (10YR 3/1) and 30%gray (10YR 5/1) A/E horizon. Following this combination
horizon, a light brownish gray (10YR 6/2) Egl and grayish brown (10YR 5/2) Eg2
horizons were formed. Below the Eg2 horizon, a black (10YR 2/1) Bh horizon occurred.
The value and chroma of the Bh increased with depth from black (10YR 2/1) in the Bhl
to brown (7.5YR 4/2) in the Bh3 horizon. Below the horizon the following horizons
occurred; a brown (10YR 5/3) Bwland pale brown (10YR 6/3) Bw2, a grayish brown
(2.5Y 5/2) Bg horizon, and below 137 cm, a brown (7.5YR 4/4) B'hl to black (10YR 2/1)
B'h3 horizons occurred.
A fairly common feature of the soils' morphology was the occurrence of multiple
spodic horizons, one much deeper than the other. The soil with only one Bh horizon
(Centenary) corresponded to the deeper B'h horizon in the Mandarin and the Leon. The
shallow Bh horizon did not form in the uplands (Fig. 35).
The transition from the dry Spodosol, Centenary, to wet Spodosol Leon, within
the transect was accompanied by an increasing water-table fluctuation influence. The
transition from the lower Mandarin, a poorly drained soil, to upper Mandarin, a
moderately well drained soil, was accompanied by an upward-trending, decreasingly
pronounced Bh, which faded as one approached the Centenary. The light-gray (10YR
7/1) E horizon persisted laterally above the Bh until both, the Bh and the E disappeared
Figure 35. Topo-pedo morphological sequence of the transect.
and a Bw appeared in the Centenary. The Centenary Bw sands had pale brown (10YR
6/3) to brownish yellow (10YR 5/4) colors indicative of grain coatings.
In general, the horizons above the B'h did not indicate any stripping. The sands
remained mostly coated. The colors remained pale brown (10YR 5/2) to brownish yellow
A photograph of the horizons in the lower Mandarin shows the color changes in
the different horizons (Fig. 36). One distinct characteristic between the upper Bh and the
lower B'h horizons was the development of color. In the lower Mandarin and the upper
and lower Leon, the Bh horizons were black (10YR 2/1) becoming generally browner
(10YR 2/2 to 7.5YR 3/2) and slightly redder (10YR 3/3 to 7.5YR 4/2) with depth. The
. -. *!^ . . . ..:,
,. ... ..... .....
Ap El E2 Bhl Bh2 Bh3 BE Eq1 Eg2 B'hl B'h2 B'h3
Figure 36. Soil colors by horizon in the lower Mandarin soil.
B'h horizon was dark gray (usually 10YR 3/1) becoming blacker (10YR 2/1) with
The texture of all the horizons was fine sand (Table 4) with only small amounts of
silt and clay. Silt content ranged from 1.5% in the Bw2 of the lower Leon to 8% in the
Ap of the Centenary. Clay content ranged from 0.2% in the E of the upper Mandarin to
3.8% in the Bh2 horizon of the lower Leon. A trend can be seen where silt and clay
increased in the upper Bh horizon (Table 4). In the lower Mandarin the silt increased
from 2.8% in the E2 to 7.8% in the Bhl horizon; the clay increased from 0.5%in the E2
to 2.4% in the Bhl horizon. In the upper Leon the silt increased from 4.1% in the Eg to
6.8% in the Bhl horizon; the clay increased from 0.4% in the Eg to 1.6% in the Bhl
horizon. In the lower Leon the silt increased from 0.5% in the Eg2 to 2.9% in the Bhl
horizon. This increase of clay could be attributable to enrichment of the Bh horizon via
mechanical translocation of silt and clay particles from the E horizon to the Bh horizon.
The same trend was reported in an earlier assessment of Florida Spodosols (Calhoun and
Carlisle, 1973). This trend supports the view that clay-and silt-sized particles migrate
downward and deposited on the sand particles. Soluble OM then adsorbs to the Al
and Fe coated surfaces to form the Bh horizon. This trend is not evident in the second B'h
horizon. It appears that there is no mechanical translocation of finer particles from the
horizons above to the B'h.
The most common method to identify lithological changes in soils is to analyze
depth distributions of the stationary particle, sand. When the fine sand-size distribution of
the site was studied, no abrupt changes in texture, indicating discontinuities, were
Soils are dynamic systems. They regularly undergo a number of biogeochemical
reactions that alter their characteristics. Some of the chemical reactions that happen in
Spodosols are: decomposition, humification, mineralization, gleization, oxidation-
reduction and. podzolization. These biogeochemical reactions give rise to a number of
different soil chemical properties that can be used as criteria to explain soil genesis and
The chemical properties from the soils sampled in the experimental plot are
shown in Table 5. A trend can be seen from the upper Mandarin to the lower Leon. Total
bases decreased with depth from A horizon to the E horizon then, total bases increase in
the Bh horizon. Total bases in the upper Mandarin decreased from 3.41 cmol/kg-1 in the
Table 4. Particle-size distribution of soils along the transect.
Series Horizon Depth VC1 C2 M3 F4 VFb %Total %Silt %Clay
(cm) % % % % % Sand
Centenary Ap 0-10 0 1.4 18.6 66.9 4.4 91.3 8.0 0.7
Bwl 10-18 0 1.4 22.6 64.6 5.8 94.4 4.9 0.7
Bw2 18-40 0 1.4 20.4 69.2 4.8 95.8 3.7 0.5
E1 40-64 0 1.2 20.2 67.0 6.2 95.6 3.9 0.5
E2 64-104 0 1.2 20.0 69.2 5.6 96.0 3.5 0.5
Eg 104-143 0 1.2 13.6 74.8 6.4 96.0 3.1 0.9
Bg 143-153 0 1.2 17.4 69.2 5.2 93.0 4.7 2.3
Bhl 153-168 0 1.2 20.4 66.4 5.6 93.6 5.7 0.7
Bh2 168-190 0 1.6 18.2 70.6 4.8 95.2 4.0 0.8
Bh3 190-212 0 1.8 21.6 69.0 3.6 96.0 2.8 0.6
Upper Ap 0-10 0 2.0 25.0 64.3 2.8 94.1 5.4 0.5
Mandarin E 10-22 0 1.7 26.1 63.9 3.7 95.4 5.4 0.2
Bh 22-38 0 2.1 24.5 63.0 3.4 93.0 4.2 2.8
E' 38-63 0 1.5 25.8 64.4 3.2 94.9 2.2 2.9
Egl 63-96 0 1.9 22.7 67.3 1.7 94.5 3.1 2.4
Eg2 96-130 0 1.5 22.5 68.1 4.5 96.6 2.7 0.7
Bw 130-157 0 1.4 22.5 65.3 5.0 94.2 2.6 3.2
B'hl 157-190 0 1.4 21.6 64.3 4.7 94.8 4.4 0.8
B'h2 190-200 0 1.3 23.0 68.0 3.0 95.3 3.9 0.8
Lower Ap 0-2 0 1.4 26.0 60.8 4.8 93.0 6.4 0.6
Mandarin E1 2-20 0 1.7 30.6 61.0 3.7 97.1 2.4 0.5
E2 20-36 0 1.7 26.4 63.6 5.0 96.7 2.8 0.5
Bhl 36-45 0 1.8 17.2 65.0 5.8 89.8 7.8 2.4
Bh2 45-55 0 1.6 20.0 61.6 6.0 89.2 7.5 3.3
Bh3 55-64 0 1.4 17.0 66.2 6.4 91.0 6.3 2.7
BE 64-72 0 1.2 20.8 65.8 5.8 93.6 4.4 2.0
Egl 72-106 0 1.9 24.9 64.5 4.6 95.8 2.6 1.6
Eg2 106-160 0 1.7 25.1 65.4 4.7 96.9 2.1 1.0
B'hl 160-180 0 1.4 18.4 72.8 4.0 96.6 2.6 0.8
B'h2 180-192 0 1.4 20.6 71.2 3.6 96.8 2.4 0.8
B'h3 192-200 0 0.8 19.2 72.0 4.2 96.2 3.1 0.7
Series Horizon Depth VC1 C2 M3 F4 VF5 %Total Silt Clay
(cm) % % % % % sand % %
Upper Ap 0-10 0 1.5 29.3 57.7 2.8 91.3 7.9 0.8
Leon A/Eg 0-19 0 2.1 25.6 64.8 2.4 94.9 4.7 0.4
Eg 19-47 1.8 27.3 63.8 2.6 95.5 4.1 0.4
Bhl 47-52 0 1.8 28.4 62.8 4.0 91.6 6.8 1.6
Bh2 52-68 0 2.1 26.2 63.9 3.2 95.4 3.9 0.7
Eg/Bw 68-105 0 1.9 23.5 66.4 4.1 95.9 3.8 0.3
Bwl 105-120 0 1.6 22.2 65.4 5.2 94.4 5.2 0.4
Bw/Eg 120-130 0 1.7 20.8 67.2 4.7 94.4 5.1 0.5
Bw2 130-180 0 1.6 20.7 66.8 5.3 94.4 1.6 4.0
B'h 180-200 0 1.0 23.6 65.5 4.6 94.7 4.8 0.5
Lower Ap 0-10 0 1.4 22.6 64.2 4.6 93 6.2 0.8
AE 10-16 0 1.4 25.4 62.4 5.2 94.4 5.0 0.6
Egl 16-28 0 1.4 23.4 64.8 6.4 96.0 3.5 0.5
Eg2 28-52 0 2.4 22.4 64.8 4.2 93.8 5.7 0.5
Bhl 52-60 0 2.6 21.0 62.4 4.0 90.0 7.1 2.9
Bh2 60-83 0 2.2 24.4 61.4 4.8 92.8 3.4 3.8
Bh3 83-98 0 2.4 24.6 65.6 3.2 95.8 2.0 2.2
Bwl 98-116 0 2.0 25.8 63.6 4.4 95.8 2.5 1.7
Bw2 116-130 0 1.8 23.2 65.8 5.6 96.4 1.5 2.1
Bg 130-137 0 1.8 19.2 66.4 5.6 93.0 4.6 1.5
B'hl 137-157 0 1.6 25.0 64.8 4.0 94.8 3.7 0.9
B'h2 157-177 0 1.8 22.4 67.6 3.6 95.4 3.8 0.8
B'h3 177-200 0 1.4 25.6 65.4 3.2 95.6 3.8 0.6
'VC =very coarse sand
4F = fine sand
5VF = very fine sand
Figure 37. Fine sand to total sand ratio against depth for all the soils of the research area.
Ap horizon to 1.15 cmol/kg-1 in the E horizon until the upper Bh is reached then, total
bases increased to 2.0 cmol/kg-1. Further down the slope, in the lower Mandarin, total
bases decreased from 5.13 cmol/kg-1 in the Ap horizon to 0.36 cmol/kg-1 in the E2
horizon until the upper Bh is reached then, total bases slightly increase to 1.94 cmol/kg1.
Continuing down the slope, in the upper Leon, total bases decreased from 5.53 cmol/kg-1
in the Ap horizon to 0.49 cmol/kg-1 in the Eg. In the upper Bh horizon total bases
increased to 1.58 cmol/kg-1. Finally, in the lower Leon, total bases decreased from 7.2
cmol/kg-1 in the A horizon to 1.27 cmol/kg-1 in the Eg2 horizon. As in the other soils, in
the upper Bh horizon total bases increased to 2.11 cmol/kg-1.
When the weighted average of the total bases is compared between the upper and
lower Bh horizons the upper Mandarin Bh has 7.3 times more total bases than the B'h; the
lower Mandarin Bh has 3.5 times more total bases than the B'h; the upper Leon Bh has
3.7 times more total bases than the B'h; and the lower Leon Bh has 3.6 times more total
bases than the B'h. Total bases were higher in the upper Bh horizons than in the lower
S0.6 - Upper Mandarin
!. -Lower Mandarin
u- 0.4- Upper Leon
0.2 --- Lower Leon
0 50 100 150 200 250
When the total bases of the E horizons are plotted against the total bases of the Bh
horizon by location, using Soil Characterization Data (Appendix B), the same increase
trend from E horizon to Bh horizon (Fig. 38) is seen for the multiple Bh Spodosols of
NE Florida, and the soils of the study site Central Florida also had the increasing trend.
The trend is not clear in the Northwest multiple Bh Spodosols because there was little
data available. When total bases from the E horizon are compared with the total bases in
the B'h horizon there is no clear trend (Fig. 38). Only in the Spodosols of the Northwest
the total bases increased. Total bases usually do not increase from E to B'h (Table 5).
Decrease in extractable acidity (EA) from the A horizon to the E horizon
and then, increase in extractable Al in the Bh horizon is also seen from the upper
Total bases relationships between E and Bh, Total bases relationships between E and Bh,
E and B'h horizons-NE Florida E and B'h horizons-NW Florida
o035 ,-'- a A 04-351 __ .
030 A 035-082
S025 -A 03
020 002 0
o cmolkg E
Total bases relationships between E and Bh, Total bases relationships between E and Bh,
E and B'h horizons- Central Florida E and B'h horizons-Study Site
010 y5- 13_ _5793,_04399
2 y 01 10 1
o-: --2"X- | 26E- - -- Q
Euu 0 u5 ulu ulS u2u u25 u3u u35
0 01 02 03 04 05 06
cmollkg E cmol/kg E
Figure 38. Total bases (E vs. Bh) from multiple Bh Spodosols in Florida's soil
characterization Database by location
characterization Database by location
Mandarin to the lower Leon (Table 5). In the upper Mandarin, the EA decreased from
9.16 cmol/kg-1 in the Ap horizon to 4.11 cmol/kg-1 in the E horizon. When the Bh was
reached, the EA increased to 10.89 cmol/kg-1. Down the slope, in the lower Mandarin,
the EA decreased from 9.29 cmol/kg-1 in the Ap horizon to 3.03 cmol/kg-1 in the E2
horizon. In the Bh horizon EA increased to 13.4 cmol/kg-1. Further down the slope, in
the upper Leon, EA in the Ap horizon decreased from 9.9 cmol/kg-1 to 3.77 cmol/kg-1 in
the Eg horizon. When the Bh was reached, the EA increased to 13.35 cmol/kg-1. Finally,
in the lower Leon, EA decreased with depth from the Ap horizon, 9.45 cmol/kg-1, to 4.04
cmol/kg-1 in the Eg2 horizon. Then, EA increased to 11 cmol/kg-1 in the Bh. The
decrease in EA from A horizon to E horizon and the increase from E horizon to Bh
horizon occurred in all the multiple Bh Spodosols in the Soil Characterization Data except
in the Leon series in Bay County and the Myakka series in Volusia County. Another
exception is where the multiple Bh Spodosol has no E horizon (Appendix B).
Extractable acidity from the E horizons was plotted against the EA of the Bh
horizons using the data for multiple Bh Spodosols of the Soil Characterization Data
according to Spodosol location (Fig. 39). No clear trend was shown except for the
Spodosols located in the NE of Florida. Probably there is insufficient data in the other
locations. Also E horizons were plotted against B'h horizons looking for trends (Fig.
39). The results obtained in this research indicated that EA decreased with depth in the
B'h (Table 5). The B'h horizons usually had lower EA than the horizons above. Contrary
to the results for B'hs in the Soil Characterization data (Appendix B)
Figure 39. Extractable Acidity of multiple Bh
Spodosols (E vs. Bh) by location -Soil
Cation exchange capacity from the upper Mandarin to the lower Leon decreased
with depth from the A horizon to the E horizon and then increased in the Bh horizon.
CEC in the upper Mandarin decreased from 12.57 cmol/kg-1 in the Ap horizon to 5.26
cmol/kg1 in the E horizon, then the CEC increased in the Bh to 12.89 cmol/kg-'. Further
down the slope, in the lower Mandarin CEC decreased from 14.42 in the Ap horizon to
3.39 cmol/kg4 in the E2 horizon until the upper Bh was reached then, the CEC increased
to 15.34 cmol/kg-'. In the upper Leon CEC decreased with depth from 15.43 in the Ap
horizon to 4.26 cmol/kg-1 in the Eg horizon. When the Bh horizon was reached, CEC
increased to 14.93 cmol/kg-1. Finally, the CEC in the lower Leon also decreased with
depth from 16.65 in the A horizon to 5.31 cmol/kg- in the Eg2 horizon until the upper Bh
was reached then, CEC increased to 13.11 cmol/kg-1. A similar decrease in CEC from A
Extractable Acidity relationships between E Extractable Acidity relationships between E
and Bh, E and B'h horizons-NE Florida and Bh, E and B'h horizons-NW Florida
S30 25 Y.
25 A A .0-3 20 R--43..
5 20- 15
!5 A. y0 1-895x, 13 154
S0 0 1 2 3 4
0 1 2 3 4 5
Extractable Acidity relationships between E Extractable Acidity relationships between E
and Bh, E and B'h horizons-Central Florida and Bh, E and B'h horizons-Study site
-45953_15332_ 20 ------12__2,__14313_
m 20 4 15
010 y__ _- i 10 .........
-- 0------------" -------------
E 0 0
0 1 2 3 4 0 1 2 3 4 5
cmol/kg E cmol/kg E
horizon to E horizon and, then an increase in CEC in the Bh horizon occurred in the
multiple Bh Spodosols characterized in the Soil Characterization Database (Fig. 40).
There also a similar increasing trend from E to the B'h horizon (Fig. 40).
Contrary to the results of the Soil Characterization data, the results obtained in this
research indicate that CEC decrease with depth in the lower B'h (Table 5).
The increase of total bases, extractable acidity and CEC in the upper Bh probably
occurred because the Bh is a horizon of accumulation of humus and Al. Humus has
colloidal properties which react, in terms of cation exchange, almost identically to
mineral colloids. However, humus can have a far greater capacity to adsorb cations
(bases, H+ and Al3+) than clay (http://users.ids.net/-nofari/tnf hums.htm).
All the soils were acidic, and most of the samples had a pH of <5. pH's in water
ranged from 3.8 to 5.2. pH's in KC1 ranged from 2.9 to 4.7.(Table 5). Range of the soil's
pH was lower with KC1 because the salt displaced the hydrogen ions (HF) and the
Aluminum ions (Al3+) from the soil. Al3+ ions reacted with the water to form more H+ by
the reaction: Al3+ + H20 -> Al(OH)3 + 3 H+ acidifying more the solution and thus
decreasing the pH.
The pH increased slightly with depth. In all soils with more than one Bh the
upper Bh horizon had a lower pH than the second B'h horizon. This difference is
probably due to the different moisture conditions in each of the horizons. In the first Bh
oxidized forms of chemical species (Fe3+, SO42-, CO) dominate, while in the second B'h
reduced forms (Fe2+, S2-, CH4, H2) dominate (Reddy, 1997). In saturated conditions there
is absence of oxygen. The oxidized forms are converted into reduced forms through
several microbially mediated catabolic processes. These alterations in chemical reactions,
CEC relationships between E and Bh, E and CEC relationships between E and Bh, E and
B'h horizons-NE Florida B'h horizons-NW Florida
i 40 20
A y=2;9733x+ 13 306 (0
. 30 15
1 y 1 440 1 2 3 87
cmol/kg E cmol/kg E
CEC relationships between E and Bh, E and CEC relationships between E and Bh. E and
B'h horizons-Central Florida B'h horizons-Study site
__1_______________-___ .__ -_ 0Q in-25
o 20 0 R2 0 1 .
1 ..... 1 -
S10 o -
E 0 E 0O
S02 4 6
0 1 2 3 4
0 1 2 3 4 5
cmol/kg E cmol/kg E
CEC Figure 40. Cationships between E and Bh, E and CEC relationships between E and Bh. E and-Soil
as the results of soil anaerobiosis, affects soil pH. In general, saturated soil conditions
results in increase of pH and a decrease in redox potential. The increase of pH with depth
in these acid soils will depend on the proton consumption during reduction of the
oxidi zed forms u under satural Florida B'h horizons-Study siteitions.
Exchangeable Al ions are characteristic of acid soils. Exchangeable Al pduced
the acidity by hydrolyzing further to Al(OH)3 and releasing H to the soil
solution. Al is present in appreciable amounts at pH > 5.8. While other major
exchangeable cations are generally leached from soils during soil formation, Al is
retained in soils ultimately as Al(OH)3, the Al end-product of soil weathering (Bohn et
25 0 - .
cmol/kg E cmol/kg E
Figure 40. Cation Exchange Capacity of multiple Bh Spodosols (E vs. Bh) -Soil
as the results of soil anaerobiosis, affects soil pH. In general, saturated soil conditions
results in increase of pH and a decrease in redox potential. The increase of pH with depth
in these acid soils will depend on the proton consumption during reduction of the
oxidized forms under saturated conditions.
Exchangeable Al ions are characteristic of acid soils. Exchangeable A13+ produced
the acidity by hydrolyzing further to AI(OH)3 and releasing H'to the soil
solution. Al is present in appreciable amounts at pH > 5.8. While other major
exchangeable cations are generally leached from soils during soil formation, Al is
retained in soils ultimately as AI(OH)3, the Al end-product of soil weathering (Bohn et
Table 5. Chemical properties of the soils sampled
Extractable Total Extractable CEC* Base pH pH
Series Horizon Depth Ca Mg Na K bases Acidity Saturation (water) (KCI)
cm 1 cmol %
Centenary Ap 0-10 2.35 0.41 0.09 0.05 2.90 9.72 12.62 23.0 4.0 2.9
Bwl 10-18 1.00 0.25 0.04 0.03 1.32 4.07 5.39 24.4 4.6 3.8
Bw2 18-40 0.55 0.25 0.13 0.00 0.93 2.65 3.58 25.9 5.0 4.4
E1 40-64 0.25 0.08 0.13 0.00 0.46 1.58 2.04 22.7 5.2 4.5
E2 64-104 0.20 0.08 0.13 0.00 0.41 1.6 2.01 20.5 5.2 4.6
Eg 104-143 0.15 0.16 0.13 0.00 0.45 1.12 1.56 28.5 5.1 4.6
Bg 143-153 0.30 0.33 0.13 0.05 0.81 2.06 2.87 28.2 5.1 4.5
Bhl 153-168 0.20 0.16 0.09 0.03 0.48 2.97 3.45 13.8 5.0 4.6
Bh2 168-190 0.25 0.16 0.13 0.00 0.55 2.61 3.16 17.3 5.0 4.6
Bh3 190-212 0.10 0.16 0.04 0.00 0.31 1.81 2.12 14.5 5.2 4.7
Upper Ap 0-10 2.60 0.53 0.20 0.08 3.41 9.16 12.57 27.1 4.2 3.5
Mandarin E 10-22 0.82 0.26 0.06 0.01 1.15 4.11 5.26 21.9 4.4 3.6
Bh 22-38 1.50 0.28 0.13 0.09 2.00 10.89 12.89 15.5 4.4 4.1
E' 38-63 0.87 0.23 0.13 0.03 1.26 2.98 4.24 29.7 4.7 4.5
Egl 63-96 0.25 0.08 0.13 0.04 0.5 1.18 1.68 29.7 4.7 4.6
Eg2 96-130 0.20 0.08 0.13 0.02 0.43 1.13 1.56 27.6 4.7 4.6
Bw 130-157 0.20 0.08 0.13 0.05 0.46 5.76 6.22 7.4 4.6 4.3
B'hl 157-190 0.15 0.08 0.09 0.02 0.34 3.21 3.55 9.6 4.7 4.5
B'h2 190-200 0.05 0.10 0.04 0.02 0.21 1.68 1.89 11.1 4.9 4.7
Extractable Total Extractable CEC* Base pH pH
Series Horizon Depth Ca Mg Na K bases Acidity Saturation (water) (KCI)
cm cmol %
Lower Ap 0-2 3.9 0.74 0.44 0.05 5.13 9.29 14.42 36.0 4.2 3.1
Mandarin E1 2-20 1.7 0.49 0.22 0.03 2.44 4.72 7.16 34.0 4.5 3.8
Bh3 55-64 0.35 0.08 0.22 0.00 0.65 20.03 20.68 3.1 4.5 3.9
BE 64-72 0.15 0.08 0.13 0.10 0.47 3.59 4.06 11.5 4.9 4.5
Egl 72-106 0.05 0.08 0.13 0.01 0.27 3.70 3.97 6.8 5.1 4.6
Eg2 106-160 0.10 0.08 0.13 0.01 0.32 4.59 4.91 6.5 5.1 4.5
B'hl 160-180 0.10 0.16 0.09 0.03 0.38 3.30 3.67 10.3 5.1 4.7
B'h2 180-192 0.15 0.16 0.13 0.00 0.45 2.78 3.23 13.8 5.4 4.6
B'h3 192-200 0.05 0.16 0.09 0.00 0.30 2.69 2.99 10.1 5.0 4.6
Upper Ap 0-10 4.41 0.67 0.40 0.05 5.53 9.90 15.43 35.8 3.9 3.0
Leon A/Eg 10-19 2.04 0.41 0.18 0.02 2.65 5.66 8.31 31.8 4.2 3.2
Eg 19-47 0.30 0.08 0.10 0.01 0.49 3.77 4.26 11.5 4.5 3.6
Bhl 47-52 1.30 0.08 0.20 0.00 1.58 13.35 14.93 10.6 3.8 3.5
Bh2 52-68 0.75 0.04 0.20 0.00 0.99 26.32 27.31 3.6 3.9 3.6
Eg/Bw 68-105 0.15 0.11 0.25 0.00 0.51 2.95 3.46 14.7 4.3 3.8
Bwl 105-120 0.05 0.08 0.09 0.00 0.22 3.08 3.30 6.7 4.3 3.7
Bw/Eg 120-130 0.05 0.08 0.08 0.01 0.22 2.34 2.56 8.6 4.3 4.0
Bw2 130-180 0.05 0.16 0.20 0.01 0.42 6.61 7.03 6.0 4.5 4.2
B'h 180-200 0.15 0.16 0.40 0.00 0.35 4.80 5.15 6.8 4.6 4.3
Extractable Total Extractable CEC* Base pH pH
Series Horizon Depth Ca Mg Na K bases Acidity Saturation (water) (KCI)
cm 1 cmol %
Lower Ap 0-10 5.2 1.56 0.44 0.00 7.20 9.45 16.65 43.2 4.0 2.9
Leon AE 10-16 2.75 0.91 0.17 0.00 3.83 5.71 9.54 40.1 4.1 3.0
Egl 16-28 0.95 0.41 0.13 0.00 1.49 3.39 4.88 30.6 4.4 3.5
Bwl 98-116 0.15 0.25 0.13 0.00 0.53 19.94 20.47 2.6 4.5 4.0
Bw2 116-130 0.10 0.16 0.09 0.00 0.35 2.22 2.57 13.7 4.7 4.2
Bg 130-137 0.35 0.33 0.13 0.02 0.83 3.41 4.24 19.6 4.6 4.2
B'hl 137-157 0.10 0.25 0.09 0.02 0.46 6.73 7.19 6.4 4.8 4.5
B'h2 157-177 0.15 0.25 0.09 0.00 0.49 5.39 5.88 8.3 4.8 4.5
B'h3 177-200 0.15 0.08 0.09 0.01 0.33 3.95 4.28 7.8 4.8 4.5
*CEC = Cation Exchange Capacity
al., 1979) the extractable Al contents of the five soil series are shown in Table 6 along
with extractable Al (sodium-pyrophosphate), extractable Al (citrate-dithionite) amounts,
and the Al/OC ratio for the different Bh horizons.
From the upper Mandarin to the lower Leon, the numbers show (Table 6) that
extractable Al (KC1) was probably accumulating in the Bh horizons. In the upper
Mandarin, the Al (KC1) increased from 0.28cmol/kg-1 in the E horizon to 0.59 cmol/kg-1
in the Bh horizon; in the lower Mandarin it increased from 0.32 cmol/kg-1 in the Eg2 to
1.02 cmol/kg-1 in the Bhl.Down the slope, in the upper Leon, the Al (KC1) increased
from 0.06 cmol/kg-1 in the Eg horizon to 1.01 cmol/kg-1 in the Bhl horizon. Finally, in
the lower Leon the Al (KC1) increased from 0.02 cmol/kg-1 in the Eg2 to 0.6 cmol/kg-1 in
the Bhl. This accumulation did not occur in the lower B'h horizon. Apparently, in the
upper Bh, Al, the binding agent, was dissolved by the action of the organic acids which
were produced during the decomposition of the vegetation, and the fluctuation of the
water-table. This resulted in the stripping of the sand grains in the E horizon and the
movement of Al to a deeper depth. This process did not occur in the soils located in the
upper part of the experimental plot because there was less influence of the water table
(Fig. 41a-f)) so, the effectiveness of the Al to accumulate in the first Bh, may be
associated with water table dynamics.
This accumulation of extractable Al (KC1) does not occur in the lower B'h. There
is no stripping of the upper E' or Bw horizon. Extractable Al (KC1) is not released from
the sand coatings. In fact, extractable Al decreases. This difference in Al(KC1) could
indicate that there is no translocation of aluminosilicates from the sand grain coatings of
the horizons above the B'h. Nevertheless, Al probably does exist in the water saturated
Aluminum extract, from the Bh horizons, with sodium pyrophosphate was higher
(Table 6) than the Al extracted with citrate diothinite because most of the Al in the Bh
horizon was in Al-organic complex form. Citrate dithionite removed only the cristalline
forms of Al. Aluminum (KC1) to OC ratio (Table 6) increased with depth in the upper Bh
horizon and decreased with depth in the lower B'h horizon. This decrease in the upper Bh
Al/OC ratio was probably due to the sequestration of most of the C in the Bhl, the first
illuvial horizon. The increase of Al (KC1) to OC ratio in the lower B'h horizon was
probably due to the lack of translocation of Al from the horizons above the B'h. With no
translocation of Al, OC accumulated. Al in situ remained constant and the ratio increased.
To study the form of Al -C complex in the soils, pyrophosphate-extractable
Al to oxalate-extractable Al ratios were calculated. The oxalate extraction removes both
inorganic and organic complex Al. Pyrophosphate removes only organic complex Al.
The pyrophosphate-extractable Al to oxalate-extractable Al ratio indicated that Al existed
mostly as organic complexes in both, Bh and B'h horizons in all the soils. The C
pyrophosphate to %OC ratio indicated that the C present in the Bh and B'h horizons is
organic in origin (Table 7). The lower B'h horizon had, on average, less than 0.6%
organic carbon. Only the B'h3 on the lower Leon soil had more than 0.6% (0.63%)
organic carbon. The actual definition for spodic horizons establishes a minimun of 0.6%
O.C. in the horizon to be called a Bh horizon. The Bh horizon in the Centenary and the
corresponding B'h horizons in the two Mandarins and two Leons, classified previously as
B'h horizons, did not meet the 0.6% O.C.criteria.
Table 6. Extractable Al by potassium chloride, sodium pyrophosphate, and sodium
citrate-dithionite of the different soil horizons and the Al/OC ratio.
Series Horizon Depth AI(KCI) Al Al (CD) AI(KCI)
(cm) cmol/kg (Pyr)1 cmol/kg /OC
Centenary Ap 0-10 0.21
Bwl 10-18 0.14
Bw2 18-40 0.10
E1 40-64 0.08
E2 64-104 0.08
Eg 104-143 0.04
Bg 143-153 0.17
Bh1 153-168 0.24 0.19 0.15 0.63
Bh2 168-190 0.16 0.11 0.13 0.36
Bh3 190-212 0.07 0.05 0.10 0.13
Upper Ap 0-10 0.34
Mandarin E 10-22 0.28
Bh 22-38 0.59 0.23 0.06 0.47
E' 38-63 0.21
Eg1 63-96 0.12
Eg2 96-130 0.08
Bw 130-157 0.24
B'hl 157-190 0.16 0.18 0.10 0.35
B'h2 190-200 0.09 0.08 0.04 0.16
Lower Ap 0-2 0.24
Mandarin Egl 2-20 0.25
Eg2 20-36 0.32
Bhl 36-45 1.02 0.13 0.25 0.76
Bh2 45-55 1.07 0.29 0.50 1.16
Bh3 55-64 1.12 0.31 0.58 2.00
BE 64-72 0.26
E'gl 72-106 0.05
E'g2 106-160 0.07
B'hl 160-180 0.20 0.14 0.21 0.48
B'h2 180-192 0.16 0.11 0.17 0.32
B'h3 192-200 0.12 0.09 0.15 0.21
Series Horizon Depth Al (KCI) Al Al (CD)2 AI(KCI)
cmol/kg (Pyr)1 cmol/kg /OC
cm cmol/kg ratio
Upper Ap 0-10 0.14
Leon A/Eg 10-19 0.04
Eg 19-47 0.06
Bh1 47-52 1.01 0.17 0.08 0.73
Bh2 52-68 1.15 0.60 0.19 1.13
Lower Ap 0-10 0.14
Leon AE 10-16 0.09
Eg1 16-28 0.04
Eg2 28-52 0.02
Bhl 52-60 0.6 0.1 0.2 .41
Bh2 60-83 0.83 0.16 0.21 .79
Bh3 83-98 0.94 0.26 0.24 1.24
Bwl 98-116 0.2
Bw2 116-130 0.11
Bg 130-137 0.32
B'hl 137-157 0.28 0.29 0.46 .61
B'h2 157-177 0.21 0.23 0.44 .36
B'h3 177-200 0.19 0.21 0.12 .29
2 Sodium citrate-dithionite
Rela e Elevaion
' 1. . : : -. .
Fig. 41b ,..
:. ::- ; '
bC~ ~** :
X axis 1: 25m
Y axis 1: 3 m
Figure 41a. Topographic map of the research area.
41b. Water table depth on February 11, 1999.
; . .~
"' : :
Relative Ceps n
. .- t '
. .... . . ..
." 0 ; :..
--. .. ,. ,- '. -. ._'.. ... . .
,: .... . .-. -...-. .:..-... ;: c.. .. .
.I ''i" ." -" .:. --":,- .'o "-r ".. '
Figure 41c. Water table depth on May 10, 1999
41d. Water table depth on August 27, 1999.
.- ^ *; .
.. . . ..... ;.: "C ..'-" '" '
!::-^"" *'-""^ ^ ** --: .
'' ,*s!* ; "^^ "*- .,*T'1 '. .
,. -," .K ^ -^ .y^^ .'v ; *' ,.,. .. ;
^^*^,<^^ ^^:.^,,,. ^
^^ '^ -*"^-. .,- !**s : E ;*',,o
.. ift:f ^;.5/ -. ,L .
-,,:: :'." ", 2 '
;.:' ".^- .- **/ ^ t .--'r. '- _-' ... '
.. I ... L .-..:.:.
; *- i ; :::.'7-- __C-.."r. .i
Figure 41e. Water table depth at September 24, 1999
41f Water table depth at December 1, 1999.
Table 7. Percentage of organic C (OC), pyrophosphate-extractable C and Al, pyrophosphate-oxalate ratios.
Series Horizon Depth % % C % Al (Pyr) %AI (NH40x) Al (Pyr)/ C (Pyr)/
(cm) Al (NH40x) % O.C.
Centenary Bhl 153-168 0.38 0.35 0.19 0.25 0.76 0.92
Bh2 168-190 0.44 0.41 0.11 0.16 0.69 0.93
Bh3 190-212 0.52 0.50 0.05 0.08 0.63 0.96
Upper Bh ... 22 38 ........ 25 ............. ....................... 0.26 ....0.88 ..0.96
Mandarin B'hl 157-190 0.46 0.42 0.18 0.21 0.86 0.91
B'h2 190-200 0.58 0.58 0.08 0.13 0.62 1.00
Lower Bhl 36-45 1.35 1.21 0.13 0.15 0.87 0.90
Mandarin Bh2 45-55 0.92 0.86 0.29 0.33 0.88 0.93
Bh3 55-64 0.56 0.52 0.31 0.35 0.89 0.93
B'hl 160-180 0.42 0.32 0.14 0.18 0.78 0.76
B'h2 180-192 0.50 0.37 0.11 0.12 0.92 0.74
B'h3 192-200 0.56 0.52 0.09 0.11 0.82 0.93
Upper Bhl 47-52 1.38 1.24 0.17 0.18 0.94 0.90
Leon Bh2 ------.-52=68.....2.....------102 .-------0 92-....... .0,60........................... 80............................. 75------------- -.- 0 90
B'h 180-200 0.48 0.48 0.31 0.34 0.92 1.00
Series Horizon Depth % % C % Al (Pyr) %AI (NH40x)3 Al (Pyr)/ C (Pyr)/
(cm) Al (NH40x) % O.C.
Lower Bh1 52-60 1.48 1.42 0.10 0.19 0.53 0.96
Leon Bh2 60-83 1.05 0.96 0.16 0.22 0.73 0.91
..... B h 3 ............... 83- 9 8 .......... Z 6 ........Q.0 Z .1................... .2 6 ........................... ..3 1 ............................... 84 ............................ .9 3
B'hl 137-157 0.46 0.40 0.29 0.35 0.83 0.87
B'h2 157-177 0.58 0.51 0.23 0.27 0.85 0.88
B'h3 177-200 0.66 0.63 0.21 0.24 0.84 0.95
"Soil micromorphology" is the study of soil morphology by microscopic (light
optical and less frequently by submicroscopic) methods, often using thin-section
(http://www.soils.org/cgibin/gloss_search.cgi?QUERY=micromorphology& SOURCE= 1.
To study the micromorphological features of Bh and B'h horizons under the
microscope, thin sections were prepared of the Bh and B'h horizons of the upper
Mandarin soil, lower Mandarin, and lower Leon. These soils were selected because
they occur very close to each other, but have different water table dynamics.
Comparisons between the Bh and B'h horizons in the upper Mandarin soil (Fig. 42)
showed that the sand grains (skeleton grains) of the upper Bh horizon were slightly
coated with dark organic matter and paler (yellowish) sesquioxides coatings (cutans); the
space between the sand grains (chambers) was largely unfilled. This horizon was very
brittle since little OM was present to serve as aggregate agent for the skeletal grains. In
the lower B'h horizon, the skeletal grains were darker than the first Bh, they had more
cutans. Some organic precipitates (plasma) filled the chambers in a way that suggested
precipitation from solution. When this B'h horizon was dry, it became slightly brittle.
These results are similar to those of Brandon (1977), for the soil series Leon, sampled in
Florida. According to him, the brittleness was associated with complete macropore filling
with opaque OM containing many silt-sized mineral particles. Also, these results were
similar to those of Farmer (1983), who studied the hydromorphic humus podzols in
Cooloola, Queensland. His results showed that in these podzols organic precipitates filled