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Jie Liang
Department of Earth System Science, Tsinghua University
Stable water isotopes in halophyte plants
DEPARTMENT OF EARTH SYSTEM SCIENCE
地球系统科学系
2
Mangrove forests distributions of the world (Giri ea al. 2011)
Mangroves
Alongi (2008)
3Marilyn C. Ball (1988)
salt gland thick leaf cuticel
aerial root Krauss et al. (2013)
Mangrove plant
Unique physiological structure for adapting to special habitats!
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△ 2H = 2Hsoil water -2Hxylem water
Special physiological structure with unusual water relations!
Ellsworth, 2007
liang, unpublished
5
6
Isotopic enrichment of Leaf water (△18O= 18O leaf water - 18O xylem water)
stainless steel
sponge
Plexiglass
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Only 3 species
Cuntz et al. (2009):△L is not influenced by habitats
Isotopic enrichment of Leaf water (△18O= 18O leaf water - 18O xylem water)
♔Is leaf isotopic enrichment in mangroves different from freshwater plants?
♕Is the difference common presence?
♗Is the difference related to leaf traits?
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9
4 times for field campaign5 sites in south of China 15 mangrove species(total 28)16 land species
Isotopic enrichment of Leaf water (△18O = 18Oleaf water -18Oxylem water)
8(Liang et al. 2017)
Isotopic enrichment of Leaf water (△18O = 18Oleaf water -18Oxylem water)
Water isotopic discrimination of mangrove leaves are very different from freshwater plants!
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Fewer stomata for mangrovesStomata
Aegiceras corniculatum Kandelia obovata
Melaleuca Viridiflora Streblus asper9
Fewer and lager stomata for mangroves
Stomata
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Stomata
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Stomata
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Mantovani (1998)
Succulence
Higher water content
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Succulence
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L
vein
stomataEvaporative siteL
Efficient mixing path length
Transpiration
Bulk leaf water Evaporative water
Theory
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L=e(-0.7612*E+7.0522 )
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-60% -40%
0%
-20%
+20% +40%
+60% +80% +100%
-60% -40%
0%
-20%
+20% +40%
+60% +80% +100%
E variation L variationTheory-sensitivity analysis
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Lower transpiration longer L
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Larcher, L., et al. (2015)
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Theory-Correlation analysis
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Schematic diagram of underlying mechanism lowering leaf water isotopic enrichment of mangroves than adjacent non-mangrove plants. The values beside the paths were the standardized (0~1) path coefficients, which were
only shown for the significant effects. (Note that logarithm of all variables was used).
Conclusions 1
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Leaf-scale isotope studies
(Farquhar and Cernusak 2005; Roden and Ehleringer1999)
Climate reconstruction
(Brunel et al. 1992)
Global-scale estimates of productivity
(Ciais et al. 1997; Farquhar et al. 1993)
1.Our research built the relationship between leaf traits and L which is hardly measurable2.Our research imply models involving leaf water enrichment models should cautiously be used in the plants with special leaf traits in other water-limited ecosystem.
3.Climate reconstruction
25
26
Partitioning ET
Jasechko, et al.,2013
Schlesinger& Jasechko,2014
ET=T+E
f=87%
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BelowCanopy
PICARROAir+Tr
Air
Licor chamber
Above Canopy
Air
LICOR-PCARRO measurement system(LPMS)We monitored separately (every 10 mins) the isotope composition of 1. water vapor above canopy as reference air2. licor6400 exhaust3. water vapor below canopy
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manifold
out
exhaust
valve
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LPMS stability
Combining Licor _picarro
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LICOR6400 Chamber
PICARROExhaust
Out
1.δ18OT presented a bimodal pattern
12.10 12.11
31
δT diurnal variation
12.12
2. caused by temporary stomatal closure
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(5)(6)
Method1: CG model
Assumption: Mixing uniform leaf water
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Method3: FC model
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10:00 12:00 14:00 16:00
-30
-20
-10
0
10:00 12:00 14:00 16:00 10:00 12:00 14:00 16:00
10:00 12:00 14:00 16:00-0.1
0.0
0.1
0.2
0.3
10:00 12:00 14:00 16:00 10:00 12:00 14:00 16:00
Measured CG_P model
d T(‰
)
Time
S toa
mat
al c
ondu
c ta n
ce ( m
ol H
2O
m-2
s-1)
Time
Time
12.10 12.11
36
Modelling Results
12.12
37
What factors drive δT variation? its variation mainly was drove by stomatal conductance ,leaf temperature and air humidity
1. The δ18OT presented a bimodal pattern caused by stomatal closure during 2:00~4:00 PM, and its variation mainly was drove by stomatal conductance and leaf temperature;
2. The δ18OT deviated from isotopic steady state throughout most of the days, when E is not high enough.
3. Modified CG model including peclet effect and FC model are both suitable to simulate δ18OT of mangrove leaves.
Conclusions 2