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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
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
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
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
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
Blodgett
Sampling Design
TowerSite
Plot B
Plot A
Minirhizotron imageAlex Gershenson
Trench plot
Continuous soil respiration
2 cm
8 cm
16 cm
3 soil CO2 sensorsTang et al. AFM 2003, Tang et al. AFM 2005 sub.
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.
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
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
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
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
)
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
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
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
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
Ecosystem respiration normalized for temperature (µmol m-2 s-1)
10 15 20 25 30 35 40
24
68
WinterGrowthRain pulses
10
Soil water (%)
Analysis of respiration pulses
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
Respiration pulses
0
2
4
6
8
101st 2nd 1st 2nd
Enha
ncem
ent Enhancement (µmol m-2 s-1)
Control Trench
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)
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
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.
Predicted Climate ChangeChanges in April temperatures, 2020
Warmer in Spring
Degrees C º
Adapted from Snyder et al., 2002
Predicted Climate ChangeChanges in snow cover, 2020
cm water equivalent
Dryer in Spring and Summer
Adapted from Snyder et al., 2002
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
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
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