turnover of wetland sediments on mineralization of carbon, nitrogen and phosphorus
DESCRIPTION
Turnover of wetland sediments on mineralization of carbon, nitrogen and phosphorus. Qingren Wang* and Yuncong Li Tropical Research and Education Center Department of Soil and Water Science IFAS, University of Florida. ASA-CSSA-SSSA 2009, Pittsburgh, PA. Outline. - PowerPoint PPT PresentationTRANSCRIPT
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Turnover of wetland sediments on mineralization of carbon, nitrogen and phosphorus
Qingren Wang* and Yuncong Li
Tropical Research and Education Center
Department of Soil and Water Science
IFAS, University of Florida
ASA-CSSA-SSSA 2009, Pittsburgh, PA
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Outline
• Brief introduction about the Everglades wetland
• Recycling of carbon in wetland system• Experiment setup, sampling and analysis• Results, conclusion and discussion
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TREC-Homestead
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Florida Bay
Natural ecosystem
National Park
Eco-Environment in south Florida
Agriculture
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Natural Eco-environment in the Everglades wetland
Bulrush: Scirpus rubiginosus
Sawgrass:Cladium jamaicense
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• Wetlands are an important part of the global carbon inventory: up to 1/3 of total global soil carbon is stored in wetlands
• Carbon in wetlands is relatively stable• Carbon accumulation is based on vegetation
types and soil fertility • Decomposition rate depends on water content
and temperature
Why carbon in wetlands?
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Importance of wetlands
Mitra et al, 2005, Curr. Sci.
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Chauhan, 2007: http://sites.google.com/site/ashvinichauhan/syntrophic-methanogenic-associations-in-florida-wetlands
Carbon cycling in wetlands
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Hypothesis
Sediment mineralization was dependant on vegetation type and temperature at the same moisture and other conditions
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Experiment• Intact sediment columns were collected
from wetland sites with two different main vegetations: Bulrush and Sawgrass (both are native plants).
• Kept these columns in three growth chambers with temperature at: 30, 25, and 20 oC, respectively.
• Carbon emission and nutrient mineralization were monitored through sampling without disturbing the sediments for 380 days.
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Sediment collection & experiment setup
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Sample analyses
• Carbon analysis: LiquiTOC• Nitrate and ammonium:
Seal AQ2+• Ortho phosphorus: Auto-
analyzer (AA-3)
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• Turnover of sediments for C, N, and P with
time.
• Sediment mineralization vs. vegetation type.
• Effect of temperature on sediment turnover.
Major results
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Carbon mineralization rate
0 50 100 150 200 250 300 350 4000
200
400
600
800
1000
1200
1400
1600Sawgrass Bulrush
Time (day)
CO
2-C
(mg/
kg)
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Accumulative CO2-C with time
0 50 100 150 200 250 300 350 4000
2000
4000
6000
8000
10000
12000
14000
16000
f(x) = 2132.37154546737 ln(x) − 471.097993785414R² = 0.974241697877589
f(x) = 2604.96473012374 ln(x) − 651.218840685348R² = 0.972346265959714
Sawgrass Logarithmic (Sawgrass)
Bulrush Logarithmic (Bulrush)
Time (day)
Acc
umul
ated
CO
2-C
(mg/
kg)
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Expressed by exponential growth model
Sawgrass Bulrusha 13285.65 11023.78b 0.0273 0.0261R2 0.977 0.969
y = a * Exp(-bx) x-time (days), and y-accumulative amount of CO2-C released from sediments
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Impacted by temperature (CO2–C)
30 25 200
100200300400500600700800
aa
b
Sawgrass
CO2-
C (m
g/kg
)
Temperature (oC)
30 25 200
100200300400500600700800
ab
c
Bulrush
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Nitrogen mineralization
0 50 100 150 200 250 300 350 4000
20
40
60
80
100
120 Nitrate N
SawgrassSeries3Bulrush
NO3-
N (m
g/kg
)
0 50 100 150 200 250 300 350 4000
0.2
0.4
0.6
0.8
1
1.2 Ammonium N
SawgrassSeries3Bulrush
NH4-
N (m
g/kg
)
Outlier
Time (day)
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Accumulative N
0 50 100 150 200 250 300 350 4000
100
200
300
400
500
600
Sawgrass
Bulrush
Accu
mul
ativ
e N
O3-
N (m
g/kg
)
0 50 100 150 200 250 300 350 4000
1
2
3
4
5
6
7
f(x) = 1.3889456641 ln(x) − 1.9691750021R² = 0.907716209017961
f(x) = 0.4011311855 ln(x) − 0.5210457688R² = 0.952714208066964
SawgrassLoga-rithmic (Saw-grass)Bulrush
Acc
umul
ativ
e N
H4-N
(mg/
kg)
Time (day)
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Phosphorus mineralization
0 50 100 150 200 250 300 350 4000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
SawgrassSeries3Bulrush
Time (day)
Orth
o-P
(mg/
kg) Outlier
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Accumulative phosphorus
0 50 100 150 200 250 300 350 4000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4Sawgrass
Bulrush
Time (day)
Acc
umul
ativ
e P
(mg/
kg)
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Impacted by temperature (NO3–N)
30 25 2005
101520253035404550
b
a
c
Sawgrass
NO
3-N
(mg/
kg)
30 25 200
10
20
30
40
50
b
a a
Bulrush
Temperature (o C)
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Impacted by temperature (NH4-N)
30 25 200.250.260.270.280.29
0.30.310.320.33 Sawgrass
NH
4-N
(mg/
kg)
Temperature (o C)
30 25 200.250.260.270.280.29
0.30.310.320.33
a
b
aBulrush
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Impacted by temperature (P)
30 25 200.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
aa
Sawgrass
Orth
o-P
(mg/
kg)
30 25 200
0.0020.0040.0060.008
0.010.0120.0140.0160.018
a
b b
Bulrush
Temperature (o C)
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Conclusions (1)• The turnover of organic C was rapid in the first 100 days.
• The accumulative amount of C mineralized can be well
described by an exponential growth model.
• Nitrogen turnover was low at first 100 days and sharply
increased afterwards.
• Phosphorus mineralization was low throughout the whole
experimental period.
•
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Conclusions (2) • Sawgrass had a greater turnover on C and N but lower
on P than did bulrush.
• High temperature improves the turnover of organic C
and NH4-N for both species but that of P only for bulrush.
• The turnover of NO3-N was the greatest at 25 oC,
especially for sawgrass.
• Factors in controlling the turnovers are rather
complicated, C:N ratio (18.9 in sawgrass vs. 13.8 in
bulrush) might be one of them.