response of luzula arctica and luzula confusa to warming ... · ipcc (ed) 2007. climate change...
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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.