peatlands : carbon sinks
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Comparison of carbon fluxes between different stages of regeneration in a harvested bog (Jura, France)
E. Bortoluzzi1, D. Epron2, D. Gilbert1, A. Buttler1,2
1 University of Franche-Comté (France) 2University Henri Poincaré, Nancy (France)
3 Swiss Federal Institute of Technology-EPFL, Swiss Federal Institute WSL, Lausanne (Switzerland)
Peatlands : carbon sinks
A considerable stake in the actual context, as illustrated by these extracts of the Kyoto Protocol (1992)
Article 7 ”1. Each Party (...) shall incorporate in its annual inventory of anthropogenic emissions by sources and removals by sinks of greenhouse gases (...)”
(ii) ”Parties (...) contribute to addressing climate change and its adverse impacts, including the abatement of increases in greenhouse gas emissions, and enhancement of and removals by sinks (...)”
Article 10b
Peatlands, carbon sinks ?
Rtotal
CO2CO2
CH4CH4
GP - Rv - Ru - FCH4
NPPNPP
NEENEE
Accumulation
CO2
CO2
Rtotal
At which time in the regeneration process does the peatland again become
a carbon sink?
This is one of the problematic of the
european project RECIPE (Reconciling commercial exploitation of peat with biodiversity in peatland
ecosystems)
CO2CO2
Objectives :
• Establishment of a carbon balance for different stages of a regeneration process:1. Bare peat2. Recent regeneration with much Eriophorum angustifolium
and few Sphagnum3. Advanced regeneration with mainly Sphagnum.
• Comparison of these balances with the vegetation diversity
• Compartimentation of the fluxes for more precision in the balance
In order to establish a carbon balance
• Selection of the presented study site : a bog in the french Jura mountains, exploited until 1984
• Setting of the site in a cut-over strip:
In order to establish a carbon balance (2)
In order to establish a carbon balance (3)
• Recording permanently the local climate factors :– Light intensity– Air temperature, peat
temperature (depth of 5 cm and 30 cm)
– Rain events.
In order to establish a carbon balance (4)
• Fluctuation of ground water table• Estimation of Sphagnum humidity with a visual index:
1 : Sphagnum completely dessicated
…to
6 : Sphagnum inundated.
Collar, 30 cm of diameter.
In order to establish a carbon balance (5)
• Leaf area index (LAI) for vascular plants :
0
500
1000
1500
2000
2500
3000
0 100 200 300 400 500 600
Relation between leaf length (mm) and leaf area (mm2) for Eriophorum angustifolium
Y=0,248X1,439
R2=0,953
calculated with the measurement of the leave length and their density within the collars.
• For Sphagnum and Polytrichum, measurement of the density only.• Surveys in April, July and October.
In order to establish a carbon balance (6)
• Measurements : once a week under light saturation and darkness (except when snow) for CO2 with a infrared gas analyser ( CIRAS1,PPsystems)
• Every month for CH4 (incubation in a dark closed chamber and analysis in the laboratory with a micro GC CP 4900, Varian)
In order to establish a carbon balance (7)
• Measurement of the net primary production :– for Sphagnum and Polytrichum using the cranked wire
method (growth in length) and the density– for vascular plants using the density
and the correlation
between leaf length
and biomass.
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0,1
0 50 100 150 200 250 300 350 400
Relation between leaf length (mm) and dry biomass (g) for Carex nigra
Y=4e-0,6 X1,7124
R2=0,95
• Estimation of vegetation diversity on 1m2 around each collar.
Field equipment
Light sensor
Rain collector
Air temperature sensor
CH4
chamber
T. sensor
T. sensor
- 5 cm
- 30 cm
Chamber temperature
CO2
analyser(analysis in Lab.)
Light sensor
Leaf area index
Sphagnum humidity
Water table level
Results : daily variations of CO2 fluxes
- Use of sigmaplot software
- Model equation:
NEE = GP - RtotNEE = GP - Rtot with GP = (GPM*I)/(K+I) with GP = (GPM*I)/(K+I)
with GPM = ATwith GPM = AT22+BT+BT with Rtot = C*exp(D*T)with Rtot = C*exp(D*T)
- Parameters of entry : I : light intensityT : air temperature
- Parameters determined by the software :K : half saturation lightA et B : factors of adjustment of GPM function of air temperatureQ : factor of adjustment of Rtot function of air temperature
Results : daily variations of CO2 fluxes (2)
-5
-4
-3
-2
-1
0
1
2
3
0 200 400 600 800 1000 1200
20/05/2004 R2=0.88 recent regeneration 26/04/2005 R2=0.97advanced regeneration
Parameter Value StdErr Parameter Value StdErr
K 1.92E+02 3.13E+01 K 1.38E+02 2.84E+01
A -4.92E-03 1.15E-03 A -6.38E-03 1.96E-03
B 2.97E-01 3.69E-02 B 3.99E-01 5.98E-02
C 9.36E-01 6.91E-02 C 9.87E-01 3.65E-02
D 3.55E-02 3.31E-03 D 4.90E-02 1.82E-03
Topt 3.01E+01 Topt 3.13E+01
GPM25 4.34E+00 GPM25 5.98E+00
R25 2.27E+00 R25 3.36E+00
Q1O 1.43 Q1O 1.63
Recent regeneration
-4
-3
-2
-1
0
1
2
3
0 200 400 600 800 1000 1200
Advanced regeneration
NE
E (
mic
rom
oleC
O2/
m2 /
s)
sink
sourceNEE measured
NEE simulated
Results : comparison between regeneration stages
-1
0
1
2
3
4
5
05/11/2003 25/12/2003 13/02/2004 03/04/2004 23/05/2004
0
1
2
3
4
5
6
7
5/11/03 25/12/03 13/2/04 3/4/04 23/5/04
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
5/11/03 25/12/03 13/2/04 3/4/04 23/5/04
NEE
Total Respiration
GP
NE
E (
mic
rom
ole
CO
2/m
2/s
)G
P(m
icro
mol
eCO
2/m
2/s
)R
TO
T(m
icro
mo
leC
O2/m
2/s
)
Fluxes between regeneration stages which are statistically different with non parametric testing (Kolmogorov Smirnov).
advancedrecent
Bare peat
sink
source
Results : Rtot = f(temperature)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 5 10 15 20 25 30 35
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20 25 30 35
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 5 10 15 20
0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14 16
R2=0.78
R2=0.90R2=0.65
R2=0.90
Y=a*ebT10cm Y=a*ebTair
T10cm
T10cm
Tair
Tair
Bare peat Bare peat
Recent and advanced Recent and advanced
Preliminary results for methane
CH4 flux (nmol m-2 s-1)
Bare peat 3.14
Recent regeneration 20.17
Advanced regeneration 0.086
0.00
2.00
4.00
6.00
8.00
10.00
12.00
0 1 2 3 4 5 6 7 8
Y= 1.4146x+1.0143R2=0.99
CH4 (ppm)
Incubation time (hours)
Conclusion and perspectives :
1) Preliminary results show that CO2 fluxes between regeneration stages are significantly different, with a trend to higher gas exchanges in the advanced situation.
3) The data set which will be collected over the year will allow us to compare the carbon balance of the different regeneration stages with their net primary production and the related vegetation diversity.
2) The summer data should be particularly interesting with the impact of Sphagnum dessication on the photosynthesis.
We acknowledge the contribution and the help of our colleagues from the RECIPE project