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Water use and water use efficiency in west Water use and water use efficiency in west coast Douglas-fircoast Douglas-fir
Water use and water use efficiency in west Water use and water use efficiency in west coast Douglas-fircoast Douglas-fir
Paul Jassal, Andy Black, Bob Chen, Zoran Nesic, Praveena Krishnan and Dave Spittlehouse
University of British ColumbiaVancouver, Canada
CFCAS
BC FLUX BC FLUX STATIONSTATION
Outline of the talk
4. Effect of stand age
5. Effect of nitrogen fertilization
3. Relationships between physiological and environmental controls of water use and carbon uptake
2. Diurnal, seasonal and interannual variability of water use and water use efficiency
1. BC Flux Station sites
VancouverCampbell River
Pole/saplingHDF88
Near matureDF49
PlantationHDF00
BC Flux Station Chronosequence of three coastal Douglas-fir stands
33 8 Height (m) 2
Water use efficiency
Water use or evapotranspiration (E) = mm or kg of water m-2
Water use efficiency = g C m-2 mm-1 or g C kg-1 water as GPP/E or NEP/E
GPP = gross primary productivity, i.e., C uptake by photosynthesis (~twice of NPP)
NEP = net ecosystem productivity (net C sequestration) = GPP – R
In this analysis, EC-measured fluxes have not been corrected for energy balance closure. EBC is approximately 0.81.
Physiological and environmental controls
Both C uptake by and transpiration from vegetation takes place through leaf stomata with their rates partly determined by canopy conductance, gc.
Penman-Monteith equation:
)/1( ca
apa
ggs
DgcsRE
Priestley-Taylor equation:
aeq Rs
sEE
Available energy
Vapor pressure deficit
Canopy conductance
Aerodynamic conductance
0 1 2 3 4 5 6 7 8 9 10 11 120
4
8
12
16
20
Tair 1998
Tair
1999
Tair
2000
Tair
2001
Tair
2002
Tair
2003
Tair
2004
Tair
2005
Tair
2006
Tair
2007
Air temperature
Month
CC
0
400
800
1200
1600
2000 1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Cumulative precipitation
Dry months
J F M A M J J A S O N D
mm
0
0.05
0.1
0.15
0.2
0.25
0.3
J F M A M J J A S O N D
Month
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Soil water content in the 0-60 cm layer
m3 m-3
Dry months
WP
FC
Month
Diurnal variations
August 2006
11 12 13 14 15 16 17
0
12
24GPP
0
0.04
0.08 E
0
1
2PAR
0
1
2 D
0
4
8 gc
mol C
m-2 s-1
g m-2 s-1
kPa
mm s-1
mmol m-2 s-1
Seasonal variations
J F M A M J J A S O N D
0
5
10
15GPP
0
1
2 E
0
10
20 WUE g C m-2
mm-1
org C kg-1
mm d-1
g C m-2 d-1
2006
0
100
200
300
400
0
20
40
60
80
0 1 2 3 4 5 6 7 8 9 10 11 120
2
4
6
8
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Seasonal variations in GPP, E and WUE
mm mon-1
g C m-2 mon-1
g C m-2
mm-1
Org C kg-1
Month
GPP
WUE
E
Relationship between monthly GPP and EG
PP
(g
C m
-2 m
on-1)
0 15 30 45 60 750
100
200
300
400
GPP = 6.0* E + -25
r2 = 0.96
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
E (kg m-2
mon-1
or mm mon-1
)
GPP = 6.0E –25
r2 = 0.96
0 0.1 0.2 0.30
15
30
45
60
75
EJul-Sep
= 453.3 * -21
r2 = 0.69
Monthly mean (m3 m
-3)
Effect of soil moisture on monthly E
mm mon-1
Cold Septembers
Dry months
Wet months
1998 - 2007
Effect of soil moisture on monthly GPP
0 0.1 0.2 0.30
100
200
300
400
GPPJul-Sep
= 2472.6 * -104
r2 = 0.60
Monthly mean (m3 m
-3)
g C m-2 mon-1
Cold Septembers
1998 - 2007
Dry months
Wet months
Relationship between monthly E and net radiation
E (m
m w
ater
mon
-1)
0 100 200 300 400 500 600 700 8000
15
30
45
60
75
E = 0.1* Rn + 11
r2 = 0.94
1998199920002001200220032004200520062007
Rn (MJ m-2
mon-1
)
E = 0.1Rn + 11
r2 = 0.94
0 1 2 3 4 5 6 7 8 9 10 11 120
0.6
1.2
dry 1998 dry
1999
dry
2000
dry
2001
dry
2002
dry
2003
dry
2004
dry
2005
dry
2006
dry
2007
Daytime dry-foliage Priestley-Taylor
Month
Correcting for EBC would result
in a 25% increase in
Daytime dry-foliage canopy conductance
Month
mm
s-1
0 1 2 3 4 5 6 7 8 9 10 11 120
4
8 gc dry
1998g
c dry
1999
gc dry
2000
gc dry
2001
gc dry
2002
gc dry
2003
gc dry
2004
gc dry
2005
gc dry
2006
gc dry
2007
mm s-1
5 mm s-1 ~ 220 mmol m-2 s-1
Relationship between daytime dry-foliage monthly and gc
0 1 2 3 4 5 6 70.3
0.4
0.5
0.6
0.7
0.8
gc (mm s-1)
= 0.1 gc + 0
r2 = 0.65
1998 - 2007
+ 0.3
Modelling daytime dry-foliage monthly gc
0 0.2 0.4 0.6 0.82
3
4
5
6
7
/D (m3 m-3 kPa-1)
gc (
mm
s-1
)
gc = 7.7 /D + 2
r2 = 0.69
1998 - 2007
1600
2000
2400
350
400
450
1998 1999 2000 2001 2002 2003 2004 2005 2006 20074
5
6
Interannual variations in GPP, E and WUE
g C m-2 mon-1
mm mon-1
g C m-2
mm-1
or g C kg-1
Cold & wetDry Warm
GPP
WUE
E
Mean: 5.3 g C kg-1 water
Effect of stand age and fertilization on annual E
Filled triangles are for 2007, the first year after N fertilization
0 10 20 30 40 50 600
100
200
300
400
500
Age (Years)
Ann
ual E
(m
m)
Age (years)
Effect of stand age and fertilization on annual GPP
0 10 20 30 40 50 600
500
1000
1500
2000
2500
Age (Years)
An
nua
l GP
P (
g C
m-2
)
Filled triangles are for 2007, the first year after N fertilization
Age (years)
Effect of stand age and fertilization on annual WUE
0 10 20 30 40 50 600
2
4
6
Age (Years)
An
nua
l WU
E (
g C
(kg
wat
er)-1
)
Filled triangles are for 2007, the first year after N fertilization
Age (years)
0 20 40 60
-600
-400
-200
0
200
400
600
Age of stand (years)
NE
P (
g C
m-2
y-1
)
HDF00
HDF88
DF49
2007, first year after N fertilization
Effect of stand age and fertilization on annual NEP
NEP = GPP - R
C Source
C Sink
Age (years)
Effect of stand age and fertilization on annual WUE based on NEP
0 10 20 30 40 50 60-3
-2
-1
0
1
2
Age (Years)
An
nua
l WU
E (
g C
(kg
wat
er)-1
)
Filled triangle are for 2007, the first year after N fertilization
Age (years)
Conclusions
• Growing season Priestley-Taylor daytime of about 0.6 was consistent with low canopy conductance (~4.5 mm s-1), and suggests stomatal limitation to transpiration.
• Daytime canopy conductance could be parameterized as a linear function /D.
• Water deficit in Jul-Sep decreased E as well as GPP, and explained much of their interannual variability.
• The high correlation between E and GPP resulted in WUE being relatively conservative with a value of ~5 g C kg-1 water.
• There was relatively small 1st year response of GPP & E to N fertilization; NEP in all 3 stands responded to fertilization, due to decreased R, resulting in increased WUE on an NEP basis.
Thank you!
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