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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



-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




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


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


Predicted Climate ChangeChanges in snow cover, 2020

cm water equivalent

Dryer in Spring and Summer

Photosynthesis, tree growth, respiration, and C sequestartion


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

influences of canopy photosynthesis and summer rains on root …kearney.ucdavis.edu/old...

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