Response of Luzula arctica and Luzula confusa to Warming ... · IPCC (ed) 2007. Climate Change...

Long-Term Response of Luzula arctica and Luzula confusa to Warming in the Alaskan Tundra

• Expected to show earliest and greatest response to global climate change (IPCC 2007)

Why Arctic? • Linked to global climate (ACIA 2004)

Study Sites

Barrow 71°18’N, 156°40’W

Atqasuk 70°29’N, 157°25’W

Experimental Design

2 Dry Heath Communities: Atqasuk Dry Barrow Dry

1 Meter squared plots

-24 Control -24 Warmed

Passive open-top fiberglass chambers Increase temperature 1-3° C

Luzula arctica and Luzula confusa

•Common rushes at both dry heath sites •Associated with disturbances •Known to hybridize

Measurements Summer 1994-2010

- Inflorescence Height - Number of Inflorescences - Flowering date

L. arctica Hulten (1968)

Inflo

rescence H

eight

Inflorescence Height

5

7

9

11

13

15

17

19

1994 1995 1996 1997 1998 1999 2000 2001 2007 2008 2010

Me

an In

flo

resc

ence

Hei

ght

(cm

)

Year

Luzula confusa Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

Inflorescence Height

5

6

7

8

9

10

11

12

13

14

1995 1996 1998 1999 2000 2001 2007 2008 2010

Mea

n In

flo

resc

ence

Hei

ght

(cm

)

Year

Luzula arctica Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

Question:

• What factor is causing a negative response in these years?

Relate to temperature:

Thawing Degree Days (TDD)- cumulative degree days above freezing (0°C)

Thawing Degree Days (TDD)

-2

0

2

4

6

8

10

12

14

16

18

20

22

-2

0

2

4

6

8

10

12

14

16

18

20

22

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Thaw

ing

Deg

ree

Day

s (T

DD

)

Ave

rage Te

mp

eratu

re (°C

)

Julian Day

Thawing Degree Days (TDD)

-2

0

2

4

6

8

10

12

14

16

18

20

22

-2

0

2

4

6

8

10

12

14

16

18

20

22

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Thaw

ing

Deg

ree

Day

s (T

DD

)

Ave

rage Te

mp

eratu

re (°C

)

Julian Day

Inflorescence Height

5

7

9

11

13

15

17

19

1994 1995 1996 1997 1998 1999 2000 2001 2007 2008 2010

Me

an In

flo

resc

ence

Hei

ght

(cm

)

Year

Luzula confusa Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

Inflorescence Height

5

7

9

11

13

15

17

19

1994 1995 1996 1997 1998 1999 2000 2001 2007 2008 2010

Me

an In

flo

resc

ence

Hei

ght

(cm

)

Year

Luzula confusa Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

Inflorescence Height Luzula confusa

1995

2001

2008

2000

1997

1999

2010 1996

1994

1998

2007

4

6

8

10

12

14

16

18

20

200 300 400 500 600 700 800 900

Me

an In

flo

resc

ence

Hei

ght

(cm

)

TDD

Inflorescence Height Luzula confusa

R² = 0.74

P<.05

4

6

8

10

12

14

16

18

20

22

200 300 400 500 600 700 800 900

Me

an In

flo

resc

en

ce H

eig

ht

(cm

)

TDD

Inflorescence Height Luzula confusa

R² = 0.22

R² = 0.19

R² = 0.27

R² = 0.27

4

6

8

10

12

14

16

18

20

22

200 300 400 500 600 700 800 900

Me

an In

flo

resc

ence

Hei

ght

(cm

)

TDD

Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

Inflorescence Height Luzula arctica

R² = 0.4564

P<.05

4

6

8

10

12

14

16

200 300 400 500 600 700 800 900

Me

an In

flo

resc

ence

Hei

ght

(cm

)

TDD

Inflorescence Height Luzula arctica

R² = 0.16

R² <.01

R² = 0.12

R² <.01

4

6

8

10

12

14

16

200 300 400 500 600 700 800 900

Me

an In

flo

resc

ence

Hei

ght

(cm

)

TDD

Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

No change in warmed plots

Increase in height with increasing TDD in control plots

Summary

Luzula confusa Inflorescence Height

Overall: Increased TDD is associated with increased height.

All sites/treatments show no trend.

Luzula arctica Inflorescence Height

Overall: Increased TDD is associated with increased height.

All sites/treatments suggest increased height with increased TDD.

Number of Inflorescences Luzula confusa

R² <.01

0

5

10

15

20

25

200 300 400 500 600 700 800 900

Me

an N

um

ber

of

Infl

ore

scen

ces

/ m

2

TDD

Number of Inflorescences Luzula confusa

R² = 0.16

R² = 0.23

R² = 0.03

R² = 0.35

0

5

10

15

20

25

200 300 400 500 600 700 800 900

Mea

n N

um

ber

of

Infl

ore

scen

ces

/ m

2

TDD

Barrow Control

Barrow Warmed

Atqasuk Control

AtqasukWarmed

Fewer inflorescences in warmed plots at both sites

Number of Inflorescences Luzula arctica

R² = 0.2495

P<.05

0

1

2

3

4

5

6

7

8

9

200 300 400 500 600 700 800 900

Me

an

Nu

mb

er

of

Infl

ore

sce

nce

s /

m2

TDD

Number of Inflorescences Luzula arctica

R² <.01

R² = 0.01

R² <.01

R² = 0.10

0

1

2

3

4

5

6

7

8

9

200 300 400 500 600 700 800 900

Me

an N

um

ber

of

Infl

ore

scen

ces

/ m

2

TDD

Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

No significant change

Summary

Luzula confusa Inflorescence Height

Overall: Increased TDD is associated with increased height.

All sites/treatments show no trend.

Luzula arctica Inflorescence Height

Overall: Increased TDD is associated with increased height.

All sites/treatments suggest increased height with increased TDD.

Number of Inflorescences

Overall: No trend.

Control plots had more inflorescences than warmed plots.

Number of Inflorescences

Overall: increased TDD is associated with decreased number of inflorescences.

All sites/treatments show no trend.

Flowering Date Luzula confusa

R² = 0.05

R² = 0.07

R² = 0.04

R² = 0.05

170

175

180

185

190

195

200

205

1993 1996 1999 2002 2005 2008 2011

Me

an

Flo

we

rin

g D

ate

(Ju

lian

Day

)

Year

Barrow Control

Barrow Warmed

Atqasuk Control

AtqasukWarmed

Earlier flowering date in warmed plots

Flowering is earlier in Atqasuk

Flowering Date Luzula arctica

R² = 0.05

R² = 0.08

R² = 0.13

R² = 0.02

160

165

170

175

180

185

190

195

200

205

1993 1996 1999 2002 2005 2008 2011

Me

an F

low

eri

ng

Dat

e (J

ulia

n D

ay)

Year

Barrow Control

Barrow Warmed

Atqasuk Control

Atqasuk Warmed

Flowering is earlier in Atqasuk

Summary

Luzula confusa Inflorescence Height

Overall: Increased TDD is associated with increased height.

All sites/treatments show no trend.

Luzula arctica Inflorescence Height

Overall: Increased TDD is associated with increased height.

All sites/treatments suggest increased height with increased TDD.

Number of Inflorescences

Overall: No trend.

Control plots had more inflorescences than warmed plots.

Number of Inflorescences

Overall: increased TDD is associated with decreased number of inflorescences.

All sites/treatments show no significant change.

Flowering Date

Flowering occurs earlier with warming.

Flowering Date

No significant change.

Conclusions • Both species are responding to warming

• Each species responds differently

• Response is different for each site

Future Plans • Continue to look at other relationships.

– What other factors are involved?

• More phenology

Questions? Acknowledgements:

National Science Foundation

GVSU Arctic Ecology Program Jeremy May, Robert Slider, Jennifer Liebig

Barrow Arctic Science Consortium

References: IPCC (ed) 2007. Climate Change 2007: The Scientific Basis. Contribution of Working Group II to

the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. Cambridge, United Kingdom. pp. 230

ACIA 2004. Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press. Cambridge, United Kingdom.

Hollister, R.D., P.J. Webber, and C. Bay. 2005. Plant response to temperature in northern Alaska: Implications for predicting vegetation change. Ecology. 86(6): 1562-1570.