influences of canopy photosynthesis and summer rains on root …kearney.ucdavis.edu/old...
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Influences of canopy photosynthesis and summer rains on root dynamics and soil respirationL. Misson, A. Gershenson, W. Cheng, J. Tang, M. McKay, J. Curiel-Yuste, D. Baldocchi, A. Goldstein, Blodgett Forest Staff
ESPM Department (UC Berkeley) and Department of Environmental Studies
(UC Santa-Cruz)
Funding Kearney Foundation of Soil Science, National Institute for Global Environmental Change, University of California Agricultural Experiement Station
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First objective : understand controls of fine root dynamics
Hypothesis : fine root development is a high priority and is tightly coupled to canopy photosynthesis and soil water in forest ecosystems of California
Second objective : understand the link between root dynamics and carbon balance of forest ecosystems
Hypothesis : fine roots control soil respiration; this control is most apparent when roots are growing
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Kearney Project Team
Ponderosa pine Oak/SavanaBaldocchi Lab
UC BerkeleyCanopy scale fluxes
EcophysiologySoil respiration
Goldstein LabUC Berkeley
Canopy scale fluxesEcophysiologySoil respiration
Cheng LabUC Santa-Cruz
Root andBelowground C dynamics
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San Francisco
Sacramento
x Blodgett (1315 m)
Experimental Site, Blodgett, Sierra Nevada
CALIFORNIA
• Planted in 1990
• Semi-Arid climate
• Annual precipitation 1290 mm
• Winter Temp. 0-9°C, Summer 14-27°C
• Ameriflux/FluxnetPonderosa pine
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San Francisco
Sacramento
x Blodgett (1315 m)
Experimental Site, Blodgett, Sierra Nevada
CALIFORNIA
Ponderosa pine
Research since 1997• Climate and forest management
• Ecophysiology
• O3, CO, VOCs, NOx/NOy and Aerosols
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Blodgett
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Sampling Design
TowerSite
Plot B
Plot A
Minirhizotron imageAlex Gershenson
Trench plot
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Continuous soil respiration
2 cm
8 cm
16 cm
3 soil CO2 sensorsTang et al. AFM 2003, Tang et al. AFM 2005 sub.
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Continuous soil respiration
2 cm
8 cm
16 cm
CO2 concentration
CO2 efflux
Soil temperature
Soil water content
3 soil CO2 sensorsDayTang et al. AFM 2003,
Tang et al. AFM 2005 sub.
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Interannual variability of CO2 fluxesCumulative NEE (g C m-2)
Effect of drought and thinning
-300
-200
-100
0
0 100 200 300
-300
-200
-100
0
0 100 200 300-3
00-2
00-1
000
0 100 200 300
-300
-200
-100
0
0 100 200 300
NEE
(gC
m-2
)
1999 2000 2001 2002
Misson et al. AFM 2005
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Interannual variability of CO2 fluxesCumulative NEE (g C m-2)
Effect of drought and thinning
-300
-200
-100
0
0 100 200 300
-300
-200
-100
0
0 100 200 300-3
00-2
00-1
000
0 100 200 300
-300
-200
-100
0
0 100 200 300
end October mid Sept
Dry DryWet
NEE
(gC
m-2
)
1999 2000 2001 2002
Misson et al. AFM 2005
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Interannual variability of CO2 fluxesCumulative NEE (g C m-2)
Effect of drought and thinning
shift 5 months earlier
Thinning
-300
-200
-100
0
0 100 200 300
-300
-200
-100
0
0 100 200 300-3
00-2
00-1
000
0 100 200 300
-300
-200
-100
0
0 100 200 300
NEE
(gC
m-2
)
1999 2000 2001 2002
Misson et al. AFM 2005
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Meteorology, 2003 Misson et al. TP 2005 sub.
0 100 200 300
05
1015
2025
30
Air temperature
Day of year 2003
Air
tem
pera
ture
(°C
)
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Meteorology, 2003
0 100 200 300
05
1015
2025
30
Air temperature
Day of year 20030 100 200 300
020
4060
80
010
2030
40
PrecipitationRain
Day of year 2003
Rai
n (c
m)
Soil
wat
er (%
)
Air
tem
pera
ture
(°C
)
Day of year 2003
Soil water
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Canopy photosynthesis
Day of year 20030 100 200 300
020
4060
80
010
2030
40
PrecipitationRainPhotosynthesis
Phot
osyn
thes
is (µ
mol
m-2
s-1)
Day of year 2003
Rai
n (c
m)
Soil
wat
er (%
)
Day of year 2003
Soil water
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y y
Day of year 2003
0 100 200 300
020
4060
8010
0
Tree growth
% m
axim
um s
ize
90%
Canopy photosynthesisPh
otos
ynth
esis
(µ
mol
m-2
s-1)
2
46
810
1214
16
Day of year 2003
RootShoot
StemNeedle
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0 100 200 300
02
46
810
12
ControlTrench
020
4060
8010
0
% o
f max
imum
siz
eSo
il re
spira
tion
(µm
ol m
-2s-
1 )
Soil respiration
Root growth
Day of year 2003
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Ecosystem respiration normalized for temperature (µmol m-2 s-1)
10 15 20 25 30 35 40
24
68
WinterGrowthRain pulses
10
Soil water (%)
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Analysis of respiration pulses
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Analysis of respiration pulses
Doy238 240 242 244
02
46
8
R s
oil (
µmol
m-2
s-1 )
base
time cst
enhancement
contribution
Day
10
τ−+= /10
ts ebbR
Decay function
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Respiration pulses
0
2
4
6
8
101st 2nd 1st 2nd
Enha
ncem
ent Enhancement (µmol m-2 s-1)
Control Trench
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0
2
4
6
8
10
0
4
8
12
16
20
Control Trench
1st 2nd 1st 2nd
1st 2nd 1st 2nd
Enha
ncem
ent
Tim
e
Respiration pulses
Control Trench
Time cst (day)
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0
2
4
6
8
10
0
4
8
12
16
20
Control Trench
1st 2nd 1st 2nd
1st 2nd 1st 2nd
1st 2nd 1st 2nd
Enha
ncem
ent
Tim
e
Con
trib
utio
n
Respiration pulses
0
4
8
12
Contribution (%) to seasonal soil respiration
Control Trench
Control Trench
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ConclusionFirst Hypothesis: fine roots is a high priority and is tightlycoupled to canopy photosynthesis and soil water
Yes, but only during the first part of the vegetation period.There is a decoupling during the second part that might involvenon-structural carbohydrate dynamics.
Second Hypothesis: roots control soil respiration; this controlis most apparent when roots are growing
Yes, growth influence soil respiration. However, the influence ofroots was moslty indirect through their contribution onheterotrophic respiration during summer rains.
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Predicted Climate ChangeChanges in April temperatures, 2020
Warmer in Spring
Degrees C º
Adapted from Snyder et al., 2002
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Predicted Climate ChangeChanges in snow cover, 2020
cm water equivalent
Dryer in Spring and Summer
Adapted from Snyder et al., 2002
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Predicted Climate ChangeChanges in snow cover, 2020
cm water equivalent
Dryer in Spring and Summer
Photosynthesis, tree growth, respiration, and C sequestartion
Adapted from Snyder et al., 2002
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Ongoing work 2004-2005
• Canopy flux, soil respiration, tree growth, minirhizotron at both sites
• Rain pulse experiments at both sites in 2004• NSC dynamics at Blodgett in 2005
• Modeling in 2005