Chronosequence of soil respiration in ChEAS sites

(sub-topic of spatial upscaling of carbon measurement)

Jim Tang

Department of Forest Resources

University of Minnesota

jtang@umn.edu

Factors for simulating long-term forest carbon dynamics

• Natural variability and disturbance

• Human disturbance and management

• Climate change: T, precipitation…

• Increasing atmospheric CO2 concentration and nitrogen deposition -- fertilization

• Forest succession

Why chronosequence

• Our knowledge in understanding the influence of forest succession on carbon dynamics is limited.

• Most long-term carbon simulation models do not consider forest succession as a variable.

Forest stands with different ages

Old-growthMature

YoungClear-cut

Soil respiration measurement

Soil temperature in clear sites

DOY

120 140 160 180 200 220 240 260 280 300 320

Soi

l tem

pera

ture

(o C

)

4

6

8

10

12

14

16

18

20

22

24

26

28

Burned Blowdown Residual Regeneration

Soil temperature from young to old

DOY

120 140 160 180 200 220 240 260 280 300 320

Soi

l tem

pera

ture

(o C

)

4

6

8

10

12

14

16

18

20

22

24

26

28

YA IA MH OG

Soil temperature

Chronosequence of soil respiration in response to temperature

Young - old

Temperature (oC)

4 6 8 10 12 14 16 18 20 22

Soi

l res

pira

tion

(m

ol m

-2 s

-1)

0

1

2

3

4

5

6

7

8

9

10

YAIAMHOG

Q10 = 3.12

Q10 = 3.09

Q10 = 2.87

Q10 = 2.31

YA: Young aspen IA: intermediate aspen MH: mature hardwood OG: old-growth

Clear sites

Temperate (oC)

4 6 8 10 12 14 16 18 20 22

Soi

l res

pira

tion

(m

ol m

-2 s

-1)

0

1

2

3

4

5

6

7

8

9

10

Burned BlowdownResidualSeedling

Q10 = 1.92

Q10 = 3.40

Q10 = 5.49

Q10 = 2.34

Flu

x (

mol

m-2

s-1

)

1.0

1.5

2.0

2.5

3.0

Soil temperature

Tem

pera

ture

(o C

)

14

15

16

17

18

19Burned

Residual

Blowdown/seedling

YAIA MH

OG

Burned

BlowdownYA

IAMH

OGSeedling

Soil respiration at 10oCResidual

Mean soil respiration

Year

0 50 100 150 200 250 300 350

flux

(m

ol m

-2 s

-1)

3.0

3.5

4.0

4.5

5.0

Burned

Blowdown

YA IA

MH

OG

Seedling/residual

Chronosequence of soil respiration

Soil carbon storage

Car

bon

sto

rag

e (g

C m

-2)

0

2000

4000

6000

8000

10000

Soil nitrogen storage

Year

0 50 100 150 200 250 300 350

Nitr

oge

n st

ora

ge (

gN m

-2)

0

100

200

300

400

500

600

a.

c.

y = k0 xk1 ek2x, r2 = 0.994

Blowdown

Residual

Regeneration

Burned

YA

IA MH

OG

Blowdown

Residual

Regeneration

Burned

YA IAOG

MH

Annual change of soil carbon

dC/d

t (g

C m

-2 y

r-1)

0

100

200

300

b.

Regeneration

YAIA MH OGy = 0

y = k0 xk1 ek2x(k1x

-1+ k2)

Chronosequence of soil carbon content, annual change of soil carbon, and nitrogen content

Soil Woody debris Stem Leaf Ecosystem

Res

pira

tion

(gC

m-2

y-1

)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

YAIA MH OHD OHL

1089

1295

1027

935

54105 109

69

225

148132209

809

1043

742

628

4530

837

1894

949

YA: young aspen, IA: intermediate aspen. MH: mature hardwood, OHD: old-growth hardwood, OHL: old-growth hemlock

Tang et al., 2006. Agri. For. Met., in press

Cumulative respiration and components

Odum, 1969, Science Ryan et al. 1997, Ad. Eco. Res.

Young Mautre Old

An

nu

al ca

rbo

n f

lux

NEP

GPP

Ecosystem Respiration

NEP

Young Mautre Old

GPP

Ecosystem Respiration

Successional pattern of carbon flux: two conceptual models

Simulate long-term large-scale soil carbon

Year

1900 1950 2000 2050 2100

Car

bon

stor

age

(gC

m-2

)

0

2000

4000

6000

8000

10000

12000

Clearcut

100

Total soil Carbon

Slow soil C

Passive soil C

Active soil C

Measured C

Century model

Published work

Chamber (mol m-2 s-1)

0 1 2 3 4 5 6 7 8 9 10

Ed

dy

cova

rian

ce ( m

ol m

-2 s-1

)

0

1

2

3

4

5

6

7

8

9

10

y = 1.292x - 0.862,r2 = 0.96

y = x

Eddy Covariance vs. chamber measurements

Tang et al., 2006. Agri. For. Met., in press

Sap flow vs. tower measurement of water flux

Tang et al., 2006. J. Geophys. Res.-Biogeosciences

EC = 65% ET in the growing season

ET (mm day-1)

0 1 2 3 4 5

EC (

mm

day

-1)

0

1

2

3

4

5

No rain Rain

No rain: y = 1.80x0.41, r2 = 0.55

Rain: y = 1.03x, r2 = 0.65

D (kPa)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

WU

E (

mg

g-1

)

0

5

10

15

20

25

30

y = 4.40 + 15.69e-5.94x

r2 = 0.72, p< 0.0001

Water use efficiency (WUE = GPP/EC) response to D (VPD)

Tang et al., 2006. J. Geophys. Res.-Biogeosciences

Work in progress

Diurnal patterns of soil respiration

Year 2005

• Validate nighttime eddy covariance data, and correspondingly, daytime GPP;• Parameterize the soil respiration model.

Time

0 2 4 6 8 10 12 14 16 18 20 22 24

Flu

x (

mol

m-2

s-1

)

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4Riley Creek May 2, 2006 Year 2006

Time of Day

15 20 25 30 35 40 45

Flu

x (

mol

m-2

s-1)

1

2

3

4

5

6

7

Lost D207 Ameba D208 Willow D209

July