Hydrologic Linkages to
Subsurface Carbon
Sequestration in Florida
Acknowledgments:
Personnel who contributed to the Florida Soil Survey Program.
UF Soil and Water Science faculty and students.
Florida soil scientists.
Funding from USDA-NRCS and McIntire-Stennis
Coauthors
Publications related to topic
Harris, W.G. 2001. Hydrologically-linked Spodosol formation in the Southeastern United States . p. 331-342. In J.L. Richardson and M.J. Vepraskas (eds.)
Wetland soils: their genesis, hydrology, landscape, and separation into hydric and nonhydric soils. CRC Press, Boca Raton, FL.
Schaetzl, R., and W.G. Harris. 2011. Spodosols. p. 33-113 to 33-127.
In: Handbook of Soil Science, 2nd ed. P.M. Huang, Y. Li and M.E. Sumner
(eds.). CRC Press, New York.
V.W. Carlisle. 1987. Clay mineralogical relationships in Florida Haplaquods. Soil Sci. Soc. Am. J. 51:481-484.
Harris, W.G., V.W. Carlisle, and K.C.J. Van Rees. 1987. Pedon zonation of hydroxy-interlayered minerals in Ultic Haplaquods. Soil Sci. Soc. Am.
Harris, W.G., and
J. 51:1367-1372.
Harris, W.G., V.W. Carlisle, and
Am. J. 51:1673-1677.
S.L. Chesser. 1987. Clay mineralogy as related to morphology of Florida soils with sandy epipedons. Soil Sci. Soc.
Stone, E.L., W.G. Harris, R.B. Brown, and R.J. Kuehl. 1993. Carbon storage in Florida Spodosols. Soil Sci. Soc. Am. J. 57:179-182.
Harris, W.G., S.H. Crownover, and N.B. Comerford. 1995. Experimental formation of Aquod-like features in sandy coastal plain soils.
Soil Sci. Soc. Am. J. 59:877-886.
Tan, Z., W.G. Harris, and R.S. Mansell. 1999. Watertable dynamics across an Aquod-Udult transition in Florida flatwoods. Soil Sci. 164:10-17.
Harris, W.G., and K.A. Hollien. 1999. Changes in quantity and composition of crystalline clay across E - Bh boundaries of Alaquods. Soil Sci.
164:602-608.
Harris, W.G., and K.A. Hollien. 2000. Changes across artificial E - Bh boundaries generated under simulated fluctuating water tables. Soil Sci. Soc. Am. J.
64:967-973.
Harris, W.G., S.H. Crownover, and
126:161-165.
Harris, W.G., and
J. Hinchee. 2005.
Problems arising from fixed-depth assessment of deeply-weathered sandy soils. Geoderma
C.A. Rischar. 2012. Factors related to Bh horizon depth for artificial and natural E- Bh sequences. Geoderma 189-190:502-507.
Other collaborators
Kafui Awuma, Scarlett Balboa, Chumki Banik, Rex Ellis, Sabine Grunwald, Wade Hurt,
Brent Myers, Travis Richardson, Aja Stoppe
Color guide for doubt level
• Observations and data – require faith, but
retain some doubt
• Ideas and inferences – require doubt, but
retain some faith
Focus on one form of “deep C”
• Podzolization - pedogenic translocation &
joint accumulation of C & metals:
A
– Eluviation –
• loss
– Illuviation –
SHWT
E
Bh
• gain
• Podzolization => subsurface C sequestration
Other pertinent terms
• Spodic* horizon – meets threshold podzolic C
& metal accumulation
• Spodosol – soil order with Spodic horizon
within 2-m depth
* Most Bh horizons in Florida meet Spodic criteria
Spodosol distribution worldwide
Mainly restricted to
imperfectly-drained sites
Commonly well drained
Randy Schaetzl
What is the role of the water table in
fostering Spodosol formation in Florida?
A huge C pool
Dupont heavy mineral mine exposure – NE Florida
Estimated 431 Tg C
in Florida Bh
horizons within 2 m
>2m
Deep, thick C pool
mass not estimated
Potential C gain or
loss tied to climate
and sea level
Earl Stone,
Randy Brown,
Ron Kuehl
How does this C accumulate?
Chelate-complex theory
Ex - Low molecular weight
Al & Fe
Ex – Fulvic acid
Ex – Humic acid
Negatively-charged OM
Dispersion
E
“Clouds” of hydrated
counterions
Complexation &
mobilization
Flocculation &
immobilization
Bh
Theory – Gainesville style
C
Line of
Scrimmage
Buchholtz
Eastside
Gainesville
Oak Hall
P.K. Young
Soil
Surface
Al
Line of
Scrimmage
C
Al
Soil
Surface
Line of
Scrimmage
Soil
Surface
C
Al
Line of
Scrimmage
Soil
Surface
C & Al
Al
Line of
Scrimmage
Soil
Surface
Uuughh!
C & Al
Al
… and so it is with Spodosols …
- but clay moves too, not just metals?
A
Soil
Surface
E
Bh
C & Al
Al & C
Keith Hollien,
Soil Survey Data
“Sandhills” – deep water table
“Flatwoods” – shallow water table
Clean
sand
Coated
sand
Characteristics of Sand Grain Coatings
Coatings
• About 2-8 % of soil mass
• Similar proportions of silt & clay
• Silt – mostly quartz
• Clay – quartz, phyllosilicates, gibbsite, & oxides of Al & Fe
• NOT predominantly “iron oxide coatings”, although …
• Al- & Fe oxides serve as “cement”
Shannon Chesser, Vic Carlisle
Landscape observations
Oxalic acid
had no
effect
Sandhill
summit
Oxalic acid
stripped
sand
Edge of
Spodosol
“Toeslope”
Nick Comerford, Stan Crownover, Keith Hollien
Landscape observations (cont.)
Coated
sand;
chroma ≥ 6
Inference: color gradient and acid vulnerability
related to redox depletion of Fe
Sandhill
summit
Coated
sand;
chroma < 6
Edge of
Spodosol
“Toeslope”
Landscape observations (cont.)
Higher
“free” Fe
Hypothesis: Toeslope sand is predisposed to
form Spodosol
Sandhill
summit
Lower
“free” Fe
Edge of
Spodosol
“Toeslope”
Recipe for a Frankenstein “Spodosol”
• Predisposed coated sand
• Complexing organic acid
• Fluctuating water table
(22 h & 2 h drained)
• A few weeks
• That’s it!
Metals & C depleted
Metals & C enriched
“E”
“Bh”
Notes:
• No “Spodosol” formed with free drainage
• Bh formation => less metals in leachate
• E thickness related to metal & clay content of
original soil:
R² = 0.65
18
16
p < 0.001
14
12
10
8
6
4
2
0
0
10
20
30
AAO Fe+Al (mM kg-1)
Chad Rischar
40
50
Median "E" Thickness (cm)
Median "E" Thickness (cm)
20
20
18
16
R² = 0.50
14
p = 0.007
12
10
8
6
4
2
0
0.0
1.0
2.0
Clay (%)
3.0
4.0
Right now, you’re probably asking yourself …
… what happens between …
here & here?
This happens
A
“Sandhills”
Kafui Awuma, Scarlett Balboa, Chumki Banik, Vic Carlisle, Rex Ellis,
Wade Hurt, Travis Richardson, Zhengxi Tan, Bob Mansell
“Flatwoods”
A
Sand grain coatings are again clues …
Ideas
•
Process requires a threshold duration of near-surface saturation
•
Organic acids “chip away” at Al with each threshold event
•
E & Bh expression increases with increasing frequency of threshold
•
Self-defeating - proceeds to maximum expression
A
Zhengxi Tan, Bob Mansell
A
•Jeff Locuta’s image – Pedology 2012
frequency of
threshold
Ideas (cont.)
E thickness
frequency of
threshold
Ideas (cont.)
E thickness
Distance
Concluding Ideas
Why is a fluctuating water table required?
1. Metal sources for Bh - metal oxides – stable on well-drained
landscapes
2. Redox partially depletes Fe on poorly drained uplands (“flatwoods”)
3. Al => less crystalline & more vulnerable to organic complexation
4. Al oxides destabilized upon reaching thresholds in frequency &
duration of saturation whereby
• Organic acid activities increase (e.g., microbial degradation rates ↓)
• Vertical water flow decreases (favoring kinetics)
5. Al oxide dissolution releases all coating components
6. C moves Al, but Al eventually stops C within finer matrix of colloidal
origin
Concluding thought: What happens to C
with climate change or artificial drainage?
Nick Comerford,
Sabine Grunwald,
Aja Stoppe,
Brent Myers
Opening Pandora’s Box
Heavy mineral mining dredge macerates Bh …
… releasing C at large scale
• Varshovi & Sartain
• McLean,Shober, & Ellis
Soil of a thousand faces …
Louis Mantini
Oren Reedy?
Bunk! That’s
no Bh
Oh, yeah!
Come over
here and say
that!
Thanks!
Questions?