Measurement and Interpretation of Water VaporIsotopic Fluxes

Xuhui Lee

Yale UniversitySchool of Forestry and Environmental Studies

Collaborators

University of Minnesota

John Baker, Tim Griffis

Yale University

Kyounghee Kim, Ron Smith, Lisa Welp

Campbell Scientific

Steve Sargent, Bert Tanner

Chinese Academy of Sciences

Xiaomin Sun, Xuefa Wen, Guiru Yu

Transpiration, photosynthesis, leaf water enrichment, and the Pelect effect

H2O + CO2 CH2O + O2sunlight

xylem water

TDL system for measuring water vapor and flux isotope ratios

dripper

dry air

enriched water

manifold

N2 gas

pump

bypass flow

reference cell

sample cell2345

gradientinterface

air 1 air 2

1

163

164

183

184

181

182

161

162

16

18

xx

xx

xx

xxR

F

Fd

Flux isotope ratio

Soybean field, Minnesota

Instrument TowerGreat Mountain Forest, Connecticut

Eddy Covariance Instrument, Great Mountain

Tunable Diode Laser Analyzer, Great Mountain

Dripper Calibration Device

Water Vapor GradientAug 30 – Sep 7, 2005

Day of Year

242 244 246 248 250

w21

m -

w31

m

(m

mol

/mol

)

-1.0

-0.5

0.0

0.5

1.0

Rain Dew

Seasonal variation of ET, P and X

Great Mountain, 2005

Day of year, 2005

140 170 200 230 260 290

(

per

mil)

-30

-20

-10

0

precipitationET

xylemwater ofoverstorytrees

Isotopic composition of water pools Soybean field, Minnesota, 2006

18O in H2O and CO2

Soybean, Minnesota, 2006

206.5 207.5 208.5 209.5

18 O

-CO

2 (pe

r m

il, V

PD

B)

-2

0

2

-24

-20

-16

-12

18 O

-H2O

(pe

r m

il, V

SM

OM

)

Day of Year, 2006

206.5 207.5 208.5 209.5

Isof

lux

(m

olm

-2s-1

per

mil)

-200

0

200

400

H2O

CO2

CO2

CO2 and 18O-CO2 ProfilesSoybean, Minnesota, 2006

400 420 440 4600

0.5

1

1.5

2

CO2 Mixing Ratio (mol mol-1)

z (m

)

Midnight

-3.5 -3 -2.50

0.5

1

1.5

2

18O (per mil)

Midnight

320 340 3600

0.5

1

1.5

2

CO2 Mixing Ratio (mol mol-1)

Midday

-1.5 -1 -0.50

0.5

1

1.5

2

18O (per mil)

Midday