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U.S. Department of the Interior
U.S. Geological Survey
Soil CO2 and CH4 Emissions and
Carbon Budgeting in Dry Floodplain
Wetlands
Jackie Batson1, Gregory B. Noe1, Cliff R. Hupp1, Ken W.
Krauss2, Nancy B. Rybicki1, and Edward R. Schenk1
1National Research Program, Reston, VA, USA 2National Wetlands Research Center, Lafayette, LA, USA
River floodplains
Understand river-floodplain carbon cycling to:
assess the controls on greenhouse gas
emissions
determine the potential for floodplain carbon
sequestration.
Noe. 2012. Treatise of Geomorphology. Modified from NRC 2002.
Four dimensions of river corridors influence floodplain ecosystem processes
through river-floodplain hydrologic connectivity
This heterogeneity is critical to the prediction and scaling
of floodplain effects on carbon cycling
Goals of this study:
quantify carbon fluxes through soil CO2 and CH4
emissions
determine the controls on soil aerobic and anaerobic
respiration
develop an urban floodplain carbon budget along lateral
and longitudinal gradients of hydrologic connectivity
compare CO2 flux results using an infrared gas analyzer
and gas chromatograph
longitudinal
gradients
Difficult Run floodplain study
Difficult Run floodplain study
lateral
gradients
levee
backswamp
toe
slope
CO2 and CH4 (and N2O) flux
measurements
Soil CO2 fluxes
measured every three
weeks for one year on a
LI-COR 8100 infrared
gas analyzer (IRGA)
Gas samples extracted
quarterly from chamber
incubations and
analyzed for CO2, CH4,
and N2O on a gas
chromatograph
Mineralization
Hydroperiod
Litterfall
Sedimentation
Bank erosion
Other ecosystem process
measurements
CO2 flux: lateral and longitudinal
gradients
Site location
0 1 2 3 4 5
CO
2 f
lux
(g
C m
-2 y
-1)
400
600
800
1000
1200
1400
1600
1800
2000
2200Levee CO2
Backswamp CO2
Toeslope CO2
Longitudinal CO2 flux
(g C m-2 yr-1)
0 1316
1 1234
2 1491
3 1084
4 1587*
5 1076
Lateral CO2 flux
(g C m-2 yr-1)
Levee 1518
Backswamp 1115
Toeslope 1116
*no toe slope
Intra-annual CO2 flux controlled by
temperature
Factor p
Time <0.0001
Longitudinal position 0.0161
Lateral position 0.0003
Lateral*time 0.0002
Longitudinal*time <0.0001
Lateral*longitudinal 0.0155
Lateral*longitudinal*time <0.0001
Soil Temperature
0 5 10 15 20 25 30
CO
2 f
lux
( m
CO
2-C
m-2
s-1
)
0.01
0.1
1
10
100
Annual CO2 flux correlations
% silt
log
an
nu
al
CO
2 f
lux
% nitrification litterfall C:P
NH4 mineralization rate
log
an
nu
al
CO
2 f
lux
P mineralization rate TP
r=.454
p=.008
r=.416
p=.016
r=-.379
p=.029
r=.360
p=.040
r=-.353
p=.008
r=-.516
p=.002
Annual CO2 flux controlled by hydrology
Water-filled pore space
20 40 60 80 100
Ann
ua
l C
O2 f
lux (
g C
m-2
yr-
1)
100
1000
10000
R2=0.349
p<0.001
CH4 flux
Water-filled pore space
Red dots indicate fluxes that differ significantly (=0.1) from zero.
0 20 40 60 80 100 120
An
nu
al C
H4 f
lux
(g
C m
-2 y
-1)
-6
-4
-2
0
2
4
6
8
10
GC CO2 flux (mol m-2 s-1)
-1 0 1 2 3 4 5
IRG
A C
O2 f
lux
(
mo
l m
-2 s
-1)
-1
0
1
2
3
4
5
IRGA vs. GC
1:1
Method Mean SE
IRGA, 3.5 m 1.27 0.13
GC, 20 m 0.64 0.08
p<0.001
Method Mean SE
IRGA, 3.5 m 1.27 0.13
IRGA, 20 m 1.18 0.13
p=0.087
Method Mean SE
IRGA, 20 m 1.18 0.13
GC, 20 m .64 0.08
p<0.001
IRGA vs. GC
R² = 0.9911
R² = 0.9785
R² = 0.9979
R² = 0.996
R² = 0.9386
R² = 0.9867
300
400
500
600
700
800
900
1000
0 200 400 600 800 1000 1200 1400
CO
2 (
pp
m)
time (s)
Tamarack CO2
3A
3B
3C
3D
3E
3F
300
400
500
600
700
800
900
1000
0 200 400 600 800 1000 1200 1400
CO
2 (
pp
m)
time (s)
Tamarack 20 min IRGA CO2
3A
3B
3C
3D
3E
3F
350
400
450
500
550
0 50 100 150 200 250
CO
2 (
pp
m)
time (s)
Tamarack IRGA CO2
3A
3B
3C
3D
3E
3F
Difficult Run C budget g C m-2 y-1
Erosion Aerobic
respiration
Anaerobic
respiration
Deposition
Aboveground
production Allochthonous
sedimentation
Belowground
production
CO2 CH4
124
229
1223
Sequestration
or Loss
(-0.4)
-907
37
Oxidizing system
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
De
c-1
0
Jan-1
1
Feb
-11
Ma
r-11
Apr-1
1
Ma
y-1
1
Jun-1
1
Jul-1
1
Aug-1
1
Sep-1
1
Oct-1
1
No
v-1
1
Wate
r le
vel (m
)
Site 5 well
Among all sites:
Average water level= -0.84 m
Average hydroperiod = 7.61% of
days with surface water present
Summary
C losses through respiration exceeded C
inputs
Annual aerobic respiration was largely
controlled by hydrology
CO2 fluxes were higher when measured with
an infrared gas analyzer versus samples
collected and analyzed on a GC
Thank you!
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