Post on 30-Mar-2015
transcript
Seasonal dynamics of soil, litter, and ecosystem respiratory carbon
dioxide fluxes as indicated by stable isotope analyses
Jean Ometto, Luiz Martinelli, F Yoko Ishida & Edmar Mazzi
Cena – University of São Paulo, Brasil
Jim Ehleringer, Tomas Domingues
Univeristy of Utah, USA
H Jackson Silva, Sebastião Lopes
UFPA – Santarém, Brasil
Joe Berry
Carnegie Institution, USA
-3.5
-2.5
-1.5
-0.5
0.5
1.5
2.5
3.5
4.5
5.5
6.5
Carb
on
flu
x (P
g C
/yr)
(Ometto et al, submitted)
Focus of heat in 1998 in the BR AmazonFocus of heat in 1998 in the BR Amazonsource: IBAMA-PROARCOsource: IBAMA-PROARCO
Flona
ZF2
Rebio
Flona
ZF2
Rebio
ci
ca
Measurements
• δ13C and δ18O of CO2 – Keeling plots– Ecosystem– Soil – surface / profile– Decaying wood; leaves– Troposphere– River DIC
• δ18O– leaf water, – soil/stem water, – water vapor
• δ13C and δ15N – Leaves – spp (legumes / non-legumes)– Wood / bark– Litter– SOM
Leaves sampling forδ13CCHO
Air Samplingδ13CCO2
Results
• Carbon isotopic variation within the
canopy
• Seasonal isotopic variation of fixed organic
carbon
• Isotopic variation on the ecosystem
respired 13CO2 associated to logging
activities
• Isotopic variation of soil respired CO2 –
Importance of the litter for the 13C signal
ci/ca = 0.7113C = - 34.7 0.5m
ci/ca = 0.7713C = - 33.5 5.0m
ci/ca = 0.6913C = - 31.1 22.0m
ci/ca = 0.5313C = - 26.9 42.0m
0
10
20
30
40
50
-40 -30 -20 -10
13C (o/oo)
Can
op
y h
eig
ht
(m)
Air morning
Leaf
= 22.6 o/oo
= 24.0 o/oo
= 22.0 o/oo
= 18.0 o/oo
= δ13CO2 canopy – δ13Cleaf
Flona - Santarém
Results
• Carbon isotopic variation within the
canopy
• Seasonal isotopic variation of fixed
organic carbon
• Isotopic variation on the ecosystem
respired 13CO2 associated to logging
activities
• Isotopic variation of soil respired CO2 –
Importance of the litter for the 13C signal
Seca Floresta
Control Plot Dry Plot
Wet season Dry season Wet season Dry season
-32.0
-31.0
-30.0
-29.0
-28.0
Jun-
01
Sep-0
1
Dec-0
1
Mar
-02
Jun-
02
Sep-0
2
Dec-0
2
Mar
-03
Jun-
03
Sep-0
3
Seasonal variation of the upper canopy leaves d13C at k83 logged forest
Results
• Carbon isotopic variation within the canopy
• Seasonal isotopic variation of fixed organic
carbon
• Isotopic variation on the ecosystem
respired 13CO2 associated to logging
activities
• Isotopic variation of soil respired CO2 –
Importance of the litter for the 13C signal
-40.0
-37.0
-34.0
-31.0
-28.0
-25.0
-22.0
1
3C
Primary Forest
Logging Forest
2000 200320022001
Liana cutting
Logging
-35.0
-33.0
-31.0
-29.0
-27.0
-25.0
Jan-01Apr-0
1Jul-0
1Oct-0
1Jan-02
Apr-02Jul-0
2Oct-0
2Jan-03
Apr-03Jul-0
3Oct-0
3Jan-04
Soil
Canopy
Liana cutting Logging
(1) Before logging the two years were generally similar. (2) From Sept to April the logged forest lost about 2 TC more than
during the previous year, presumably because of decomposition of slash and reduced leaf area
(3) After May the years were similar, presumably because fast growing plants are now filling the gaps.
Logging Wet seasonbegins
Years converge
-25.9
-24.7 -30.5
Before logging
after logging
M.Goulden, S.Miller
δ13CR-CO2
Cumulative NEE
BLUE: PRE-LOGGINGGREEN: POST-LOGGING
2000/2001
2001/2002
-24.7
-30.5
δ13CR-CO2
1- The heavier signal prior to the logging
Can be related to a practice that consist on cutting lianas 6 to 8 months before the logging starts.
• Lianas are important on the system water cycle• Lianas are isotopically heavy and the slash decomposing could contribute to a heavier respired CO2.
What the isotopes are showing us:
2 - Strong heavy signal in the dry season after logging
The daily cycles of Net Ecosystem Exchange (NEE) during the 2001 dry season after the harvest showed less afternoon uptake and less nighttime efflux (respiration) than during the 2000 pre-harvest dry season. The reduction is of order 15%, consistent with the fraction of gaps left by the logging
Heavy 13C signal
• Reducing in photosynthetic rates – lower ci/ca
• Strong increment of slash to the system – decomposition
-38
-35
-32
-29
-26
-23
-20
Jun-
01
Oct-0
1
Feb-0
2
Jun-
02
Oct-0
2
Feb-0
3
Jun-
03
Oct-0
3
13C
0.70
0.75
0.80
0.85
0.90
ci :
ca
Logged Forest
ci x ca
13C of the respired CO2 and the ci:ca ratio of the upper canopy trees
-38
-35
-32
-29
-26
-23
-20
Jun-
01
Oct-0
1
Feb-0
2
Jun-
02
Oct-0
2
Feb-0
3
Jun-
03
Oct-0
3
13C
0.70
0.75
0.80
0.85
0.90
ci :
ca
Logged Forest
ci x ca
-38
-35
-32
-29
-26
-23
-20
Jun-
01
Oct-0
1
Feb-0
2
Jun-
02
Oct-0
2
Feb-0
3
Jun-
03
Oct-0
3
13C
0.70
0.75
0.80
0.85
0.90
ci :
ca
Logged ForestPrimary Forestci x ca
Isotopic composition of the respired CO2 and the ci:ca ratio calculated from the 13C of the organic matter on the top of the canopy
-38
-35
-32
-29
-26
-23
-20
jan mar jun au
goc
t
2003
13C
0.70
0.75
0.80
0.85
0.90
ci :
ca
Primary Forestci x ca
Results
• Carbon isotopic variation within the canopy
• Seasonal isotopic variation of fixed organic
carbon
• Isotopic variation on the ecosystem respired 13CO2 associated to logging activities
• Isotopic variation of soil respired CO2 –
Importance of the litter for the 13C signal
Primary Forest
FebruaryMarch
AprilJune July
SeptemberOctober
December
w litterw/o litter
FebruaryMarch
AprilJune July
August
SeptemberOctober
December
13 C
-36
-34
-32
-30
-28
-26
-24
-22
-20
Seca Floresta - Dry Plot
2003
13C of the respired CO2 – keeling plot intercept
0 2 4 6 8 10 12months (2003)
-33
-32
-31
-30
-29
-28d
13
C13 C
Litter fall isotopic composition variation at km 67 in 2003
13C
Final remarks• Different compartments of the ecosystem present consistent
isotopic data allowing predictions with certain degree of
confidence;
• The isotopic signature of the ecosystem respired CO2 reflects
the seasonality of the precipitation and is consistent with the
ci/ca ratio calculated from the d13C of the upper canopy leaves;
• The litter fall reflects mainly the isotopic signature of the upper
third canopy leaves and therefore a seasonality associated to
ppt;
• As widely known litter is an important component for soil CO2
efflux and the isotopic difference to the bulk soil respiration
allow us to partitioning the importance of each of this
compartments;