Crossing the final ecological threshold in high Arctic ponds

How often and under what circumstances does wetland drying or thawing of permafrost cause a change in ecosystem state? 

How often and under what circumstances does wetland drying or thawing of permafrost cause a change in ecosystem state? 

Crossing the final ecological threshold in high Arctic ponds

Smol and Douglas 2007PNASSmol and Douglas 2007PNAS

Barber et al. 2004Climatic ChangeBarber et al. 2004Climatic Change

Klein et al.Can. J. For. Res. 2005Klein et al.Can. J. For. Res. 2005

Burn, C. R. 2005 Permafrost and Periglac. Process. Burn, C. R. 2005 Permafrost and Periglac. Process.

Yoshikawa and Hinzman 2003 Permafrost and Periglac. Process. Yoshikawa and Hinzman 2003 Permafrost and Periglac. Process.

Smith et al. 2005 Science “Disappearing Arctic Lakes”Smith et al. 2005 Science “Disappearing Arctic Lakes”

Riordan et al. JGR 2006

Yoshikawa et al.2002JGRYoshikawa et al.2002JGR

15-June-1986 Image

16-June-2001 Image

1988 Burn

1988 Burn

25-June-2001

28-June-2005

Consequences of a changing hydroclimate for organic-rich

wetlands

CZEN

Plant fixation and allocation

Peat accumulation

Climate

Microbial metabolism

www.apex.msu.edu

APEX Gradient sites

Rich fen

Black Spruce

Willow/Bog Birch

Tussock Grass

Emergent

LoweredControl Raised

www.apex.msu.edu

-35

-30

-25

-20

-15

-10

-5

0

5

10

201

206

212

217

222

228

233

238

243

249

254

259

265

270

275

280

286

Julian Day 2005

Wat

er t

able

dep

th (

cm)

Control LoweredRaised

Pumping initiated for raised treatment

-35

-30

-25

-20

-15

-10

-5

0

5

10

201

206

212

217

222

228

233

238

243

249

254

259

265

270

275

280

286

Julian Day 2005

Wat

er t

able

dep

th (

cm)

Control LoweredRaised

Pumping initiated for raised treatment

www.apex.msu.edu

www.apex.msu.edu

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

NEE

CO

2 (µm

ol m

-2 s

-1)

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

NEE

CO

2 (µm

ol m

-2 s

-1)

CONTROL RAISED LOWERED

Net Ecosystem Exchange

Ecosystem Respiration

Gross Primary Production

a ab

e

d

f

c

abc

d

a ababc

bc

ac

e

a

d

b

2005

2006

www.apex.msu.edu

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

CONTROL RAISED LOWERED

Net Ecosystem Exchange

Ecosystem Respiration

Gross Primary Production

a ab

e

d

f

c

abc

d

a ababc

bc

ac

e

ad

b

2005

2006

www.apex.msu.edu

0

1

2

3

4

5

ER C

O2 (

µmol

m-2

s-1

)

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

GPP

CO

2 (µm

ol C

O2 m

-2 s

-1)

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

CONTROL RAISED LOWERED

Net Ecosystem Exchange

Ecosystem Respiration

Gross Primary Production

a ab

e

d

f

c

abc

d

a ababc

bc

ac

e

ad

b

2005

2006

www.apex.msu.edu

0 500 1000 1500 2000 15

10

5

0

-5

-10

NEE (

mol m

-2 s

-1)

PAR (mol m-2 s-1)

Raised

Control

Lowered

Light response curves

• ET & plant responses to water table treatments

0

0.5

1.0

1.5

2.0

2.5

3.0

-12-10-8-6-4-20

controllowered

raised y = -0.18x - 0.098; R2=0.50

Evap

otr

an

sp

irati

on

(mm

/h

r)

Gross Primary Productivity (µmol CO2 m2/ s)

0

0.5

1.0

1.5

2.0

2.5

3.0

0

0.5

1.0

1.5

2.0

2.5

3.0

-12-10-8-6-4-20

controllowered

raised y = -0.18x - 0.098; R2=0.50

Evap

otr

an

sp

irati

on

(mm

/h

r)

Gross Primary Productivity (µmol CO2 m2/ s)

www.apex.msu.edu

mol C

H4 m

-2 m

in-1

012345678

Control Lowered Raised

c cdd

e

a

b

warming

Coupled carbon – water dynamics• CH4 flux sensitive to soil hydroclimate (Treat et al. in review)

Mean daily WT position (cm)

CH

4 fl

ux (

mg

m-2 d

-1)

-70 -60 -50 -40 -30 -20 -10 0 10

0

100

200

300

400ControlLowered

Raised

no warming

0 50 100 150 200 250100

150

200

300

350

400

450

250

An

nu

al org

an

ic m

att

er

sto

rag

e

(g o

rgan

ic m

att

er

m-2 y

r-1)

Time since permafrost degradation

Turetsky et al. 2006

-0.2-0.2

0.00.0

0.20.2

0.40.4

0.60.6

0.80.8

1.01.0

3/203/20 4/94/9 4/294/29 5/195/19 6/86/8 6/286/28 7/187/18 8/78/7 8/278/27 9/169/16 10/610/6

Permafrost Plateau

Thermokarst Edges

ThermokarstWetlands

mm

ol C

Hm

mo

l CH

44 m m

-2-2 h

r h

r-1-1

Methane Fluxes, 2003Methane Fluxes, 2003

*Each point is the mean *Each point is the mean ± one standard deviation of one to five measurements. ± one standard deviation of one to five measurements. Measurements on 3/25 were made in 2004.Measurements on 3/25 were made in 2004. Wickland et al., 2006

Flashier!

0.0

0.10.2

0.3

0.4

0.5

0.60.7

0.8

0.91.0

- 40- 35- 30- 25- 20- 15- 10- 50

0.0

0.10.2

0.3

0.4

0.5

0.7

0.8

0.91.0

0.0

0.10.2

0.3

0.4

0.5

0.7

0.8

0.91.0

- 40- 35- 30- 25- 20- 15- 10- 50

0.0

0.10.2

0.3

0.4

0.5

0.7

0.8

0.9

- 40- 35- 30- 25- 20- 15- 10- 50 - 40- 35- 30- 25- 20- 15- 10- 50

Sto

rag

e C

oeffi

cie

nt

Water table position (cm)

Pristine

Brown moss rich fen, AK

Sphagnum poor fen, QB

Drained

Wetland ecohydrology can be surprising

• Vegetation -> peat properties -> hydrology