Phenology Modulates Carbon and Water Exchange of Ecosystems
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Transcript of Phenology Modulates Carbon and Water Exchange of Ecosystems
Phenology Modulates Carbon and Water Exchange of Ecosystems
Dennis BaldocchiSiyan Ma
Ecosystem Sciences Div/ESPMUniversity of California, Berkeley
AGU 2006B19, Land Surface Phenology, Seasonality and Water Cycle
Objectives
• Phenology and Vegetation-Atmosphere Interactions• Role of Phenology on Carbon and Water Fluxes
– Leaf Area Index, LAI– Photosynthetic Capacity, Vcmax
– Annual Carbon Fluxes – Annual Evaporation– PBL Dynamics
• New Assessment of Phenology– Temperature Deciduous Forest
• When Soil Temperature Exceeds Mean Annual Air Temperature
– Annual Grassland• Amount of Rainfall in the Spring
.
Hopkins Law of Phenology
• Phenology differs by four days for every degree of latitude, every 5 degrees of latitude and every 400 feet of altitude
Andrew Delmar Hopkins
Schwartz, M. D., 1997. Spring Index Models: An Approach to Connecting Satellite and Surface Phenology. In Phenology of Seasonal Climates
Phenology Affects Evaporation, which affects Atmospheric Demand, and Vice Versa
Menzel and Fabian, Nature 1999
Mean annual growing season in Europe increases by 10.8 days from 1981 to 1991.
Phenology, a Measure of Global Change
Spring Temperature Affects Phenology and the Seasonality of
CO2 Exchange: case 1, Deciduous Forests
Temperate Broadleaved Deciduous Forest
Day
0 50 100 150 200 250 300 350
NE
E (
gC m
-2 d
-1)
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
LAI=0GPP=0;Litterfall (+)Reco=f(litterfall)(+)
snow:
Tsoil(+)
GPP=0; Reco(+)
no snow
Tsoil (-)
Reco (-)
GP
P=f(LA
I, Vcm
ax )
late spring
early spring
Drought:(-)GPP(-); Re(-)
Clouds:PAR(-) GPP=f(PAR)(+)
Day
0 50 100 150 200 250 300 350
Lea
f A
rea
Ind
ex
0
1
2
3
4
5
6
1995199619971998
Walker Branch Watershed, TN
Phenology Modulates Source-Sink via LAI
•Interannual Variability in Length of Growing Season > 30 days
•Latitudinal Variation in Length of Growing Season > 30 days
Spatial Gradients:NEE and Length of Growing Season
Broad-Leaved Forests
Length of Growing Season
100 150 200 250
NE
E (
gC
m-2
yr-1
)
-800
-700
-600
-500
-400
-300
-200
-100
0
100Japan
Denmark
Italy
Massachusetts, USA
Belgium
Tennessee, USA
Prince Albert, CANADA
Ontario
Indiana, USA
Michigan, USA
Baldocchi et al, 2001, BAMS
Temperate Deciduous Forests
Days with NEE < 0
120 140 160 180 200 220 240
NE
E (
g C
m-2 y
ea
r-1)
-800
-700
-600
-500
-400
-300
-200
-100
0
CANOAK, Oak Ridge, TNPublished Measurements, r2=0.89
Year to Year differences in NEE across sites is due to differences in Growing Season Length
Baldocchi et al, 2001 Ecol Modelling
Caveat Emptor
• Growing Season Length has More Explanatory Power across a Latitudinal Gradient than at an Individual Site
• Additional factors explaining annual NEE at a Single Site include:– Absence/presence winter snow– Occurrence of Summer Drought– Extent of cloudiness
Grasslands
Day
0 50 100 150 200 250 300 350
NE
E (
gC m
-2 d
-1)
-6
-4
-2
0
2
4
Mediterranean GrasslandTemperate C4 grassland
Data sources: Valentini et al. 1996; Baldocchi + Xu, unpublished; Verma +Suyker
Late
spr
ing
rain
s
GPP(+
)
Spring/Summer Drought(-)GPP(-); Reco(-)
GPP > 0;AM Frost:GPP(-)
Tmin > 0 oC
GPP =f(LAI) (+)
Rain PulseReco(++)
GPP=0
Autumn Rains:T(-), (++)GPP(+), Reco(-)
snow covereddormant grassGPP=0, Reco > 0
The Duration of Winter/Spring Rain affects Phenology and the Seasonality of CO2 Exchange: case 2, Annual Grasslands
Length of Rain Period affects Phenology of Annual Grassland
Annual Grassland, Ione, CA
Day
0 50 100 150 200 250 300 350
Soi
l Moi
stur
e at
20
cm
0.0
0.1
0.2
0.3
0.4
0.5
200120022003 2004
Interannual variation of Wet season can vary by > 50 days
Annual Grassland, Vaira Ranch
Day of Year
-100 -50 0 50 100 150 200
Le
af
Are
a I
nd
ex
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2001-20022002-20032003-20042004-2005
Timing of Rainfall Can Force Substantial Interannual Variability in LAI
-120 0 120 240
-0.2
0.0
0.2
0.4
-4
0
4
LSW
I MODIS - LSWI
gC
day
-1
Daily NEE
Remote Sensing Can be Used to study Phenology of Carbon Fluxes
PRI and NEE
-120 -60 0 60 120 180
-0.10
-0.08
-0.06-4
-2
0
2
4
6
PR
I
DOY after 1/1/2005
PRI
gC
day
-1
14 day NEE
Land Surface Water Index LSWI = (ρ860 - ρ1640)/(ρ860 + ρ1640)
PRI = (531 - 570) / (531 +570)
Falk, Baldocchi, Ma, in preparation
Humidity Deficits and Phenology:
Annual grassland near Ione California
Xu and Baldocchi, 2003 AgForMet
Tai
r (o C
)
0
10
20
30
40
502000 2001
DOY
100 200 300300
VPD
(kP
a)
0
2
4
6
8
10
Max
Min
Mean annual air temp 16.3 oC
Amount of Rain During the Wet Season Affects NEE of Annual CA Grassland and Savanna Woodland
Open Grassland
PPT3-6 (mm)
0 50 100 150 200 250 300
An
nu
al F
lux
(gC
m-2
)
-200
0
200
400
600
800
1000
1200
Savanna
PPT3-6 (mm)
0 50 100 150 200 250 300
GPP RecoNEE
Ma, Baldocchi, Xu and Hehn, submitted, AgForMet
Seasonality of Model Parameters:e.g. Photosynthetic Capacity
DOY
100 150 200 250 300 350
Vcm
ax
0
20
40
60
80
100
120
140
Quercus alba (Wilson et al)Quercus douglasii (Xu and Baldocchi)
Live Fast, Die YoungIn Stressed Environments
Month
0 2 4 6 8 10 12
v x,25
( m
ol m
-2 s
-1)
-5
0
5
10
15
20
25
30
35
HEHV WB
Wang et al, 2006 GCB
Annual and Spatial Variation in Photosynthetic Capacity, Vcmax, for Deciduous Forests in North America (HV, WB) and
Europe (HE)
Year0 10 20 30 40
v x,2
5 ( m
ol m
-2 s
-1)
0
20
40
60
80
Can
opy
LAI
0123456
Wang et al, 2006 GCB
Interannual Variation in Ps Capacity
0 5 10 15 20 25La
tent
hea
t (F
e)
-40
0
40
80
120
0 5 10 15 20 25
Sen
sibl
e he
at (
Fh)
-100
0
100
200
Month
0 5 10 15 20 25
NE
E (
Fc)
-5
-4
-3
-2
-1
0
Observed Fe (W m-2)-20 0 20 40 60 80 100120140
Mod
elle
d F
e (
W m
-2)
-200
20406080
100120140
Observed Fh (W m-2)
-40 -20 0 20 40 60 80 100120
Mod
elle
d F
h (
W m
-2)
-40-20
020406080
100120
Observed NEE (mol m-2 s-1)-5 -4 -3 -2 -1 0
Mod
elle
d N
EE
-5
-4
-3
-2
-1
0
Wang et al, 2006 GCB
Seasonality of Vcmax is needed to simulate LE, H and NEE
Day
0 50 100 150 200 250 300 350
Leaf
Are
a In
dex
0
1
2
3
4
5
6
1996, Starts d1211997, Starts d108
Oak Ridge, TN
Day
0 50 100 150 200 250 300 350
E (
mm
d-1
)
0
1
2
3
4
5
1996: 492 mm 1997: 519 mm
Growing Season Length and ET, Field Data
Year with Longer Growing Season (13 days) Evaporated More (27 mm).
Other Climate Factors could have confounded results, but Rg (5.43 vs 5.41 GJ m-2) and Tair (14.5 vs 14.9 C)
were similar and rainfall was ample (1682 vs 1435 mm)
Wilson and Baldocchi, 2000, AgForMet
Temperate Deciduous ForestOak Ridge, TN
Day
0 50 100 150 200 250 300 350
ET
(m
m d
-1)
0
1
2
3
4
5
6
7
Leaf out: D90D100D110D120D130
Effect of Timing of Leaf-Out on Evaporation, Theory
CANOAK
Date of Leaf-Out
80 90 100 110 120 130 140
ET
(m
m y
-1)
620
630
640
650
660
670
680
690
700
Slope: -1.68 mm/day
Year to Year differences in LE is partly due to differences in Growing Season Length
Field data show that ET decreases by 2.07 mm for each day the start of the growing season is delayed
Caveat Emptor
• Early Spring can be followed by Summer Drought– ‘Net spring CO2 uptake increased from 1994-2002,
whereas net growing season uptake did not... We have shown that these opposing trends in summer and spring are probably related to a drought-induced reduction in summer photosynthesis…Thus warming does not necessarily lead to higher CO2 uptake’
• Angert et al, 2005, PNAS
Walker BranchData of Davis + Baldocchi
Days
0 50 100 150 200 250 300 350
PB
L (
m)
0
500
1000
1500
2000
2500
3000
Phenology and PBL Growth
Deeper PBL Growth occurred after Leaf Out
Predicting Phenology
• Growing Degree Days• Chill Degree Days• Chill Hours• Chill Degree Hours• Heat Degree Days
GDDT T
Tref
( )max min
2
Critical Heat Units Need Calibration and are not Universal
Oak Ridge, TN 1996
Day of Year
100 105 110 115 120 125 130 135
NE
E (
gC m
-2 d
-1)
-4
-3
-2
-1
0
1
2
3
4
Coefficients:b[0] 21.6b[1] -0.183r ² 0.696
Using the Onset of Photosynthesis as indicator of Phenology
Baldocchi et al., 2005, Int J Biomet
Soroe, DenmarkBeech Forest1997
day
0 50 100 150 200 250 300 350
-10
-5
0
5
10
15
20
NEE, gC m-2 d-1
Tair, recursive filter, oC
Tsoil, oC
Data of Pilegaard et al.
Soil Temperature: An Objective Indicator of Phenology??
Data of: Baldocchi, Wofsy, Pilegaard, Curtis, Black, Fuentes, Valentini, Knohl, Yamamoto. Granier, SchmidBaldocchi et al. Int J. Biomet, 2005
Soil Temperature: An Objective Measure of Phenology, part 2
Temperate Deciduous Forests
Day, Tsoil >Tair
70 80 90 100 110 120 130 140 150 160
Da
y N
EE
=0
70
80
90
100
110
120
130
140
150
160
DenmarkTennesseeIndianaMichiganOntarioCaliforniaFranceMassachusettsGermanyItalyJapan
Mean Air Temperature, C
4 6 8 10 12 14 16 18
Day
of
NE
E =
0
60
80
100
120
140
160
Coefficients:b[0]: 169.3b[1]: -4.84r ²: 0.691
Baldocchi et al. Int J. Biomet, 2005
Onset of Spring is Delayed ~ 5 days with each degree reduction in mean temperature
When Transformed onto a Climate Map, We observe a General Correspondence with N-S gradient Obtained from
the denser Phenology Network
d90
d140
Summary and Conclusions
• The Length of the Growing Season has significant effects on annual Carbon and Water exchange– As long as Warmer Springs are not followed by Summer Drought
• The correspondence between soil temperature and mean annual air temperature has a strong correlation with Spring Leaf-out– The metric does not need tuning/calibration and works across a wide
latitudinal range.• Processes derived from Networks of Flux Measurement Sites can
be Transformed onto Climate Space to produce Phenology Maps• New Technologies for monitoring Phenology
– Eddy Flux, $$$$ – Digital Camera, $$– LED, NDVI/PRI Sensor, $
Acknowledgements
• Funding– DOE/TCP, NIGEC/WESTGEC, CalAgExpt
Station
• Collaborators– YingPing Wang– Matthias Falk– Liukang Xu– Kell Wilson– AmeriFlux/Fluxnet Colleagues