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!

4

△ 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liang, unpublished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?

7

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

14

Stomata

15

Mantovani (1998)

Succulence

Higher water content

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Succulence

16

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

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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

30

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

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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