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
Barrow71°18’N, 156°40’W
Atqasuk70°29’N, 157°25’W
Experimental Design
2 Dry Heath Communities:Atqasuk DryBarrow Dry
1 Meter squared plots-24 Control-24 Warmed
Passive open-top fiberglass chambersIncrease temperature 1-3° C
Luzula arctica and Luzula confusa
•Common rushes at both dry heath sites•Associated with disturbances•Known to hybridize
MeasurementsSummer 1994-2010
- Inflorescence Height- Number of Inflorescences- Flowering date
L. arcticaHulten (1968)
Inflorescence Height
Inflorescence Height
1994 1995 1996 1997 1998 1999 2000 2001 2007 2008 20105
7
9
11
13
15
17
19
Luzula confusaBarrow ControlBarrow WarmedAtqasuk ControlAtqasuk Warmed
Year
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence Height
1995 1996 1998 1999 2000 2001 2007 2008 20105
6
7
8
9
10
11
12
13
14 Luzula arctica Barrow ControlBarrow WarmedAtqasuk ControlAtqasuk Warmed
Year
Mea
n In
flore
scen
ce H
eigh
t (cm
)
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)
1 2 3 4 5 6 7 8 9 10 11 12 13 14-2
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
Thaw
ing
Degr
ee D
ays (
TDD)
Average Tem
perature (°C)
Julian Day
Thawing Degree Days (TDD)
1 2 3 4 5 6 7 8 9 10 11 12 13 14-2
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
Thaw
ing
Degr
ee D
ays (
TDD)
Average Tem
perature (°C)
Julian Day
Inflorescence Height
1994 1995 1996 1997 1998 1999 2000 2001 2007 2008 20105
7
9
11
13
15
17
19
Luzula confusaBarrow ControlBarrow WarmedAtqasuk ControlAtqasuk Warmed
Year
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence Height
1994 1995 1996 1997 1998 1999 2000 2001 2007 2008 20105
7
9
11
13
15
17
19
Luzula confusaBarrow ControlBarrow WarmedAtqasuk ControlAtqasuk Warmed
Year
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence HeightLuzula confusa
200 300 400 500 600 700 800 9004
5
6
7
8
9
10
11
12
13
14
1995
2001
2008
2000
1997
1999
20101996
1994
1998
2007
TDD
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence HeightLuzula confusa
200 300 400 500 600 700 800 9004
6
8
10
12
14
16
18
20
22
R² = 0.743810696225732
TDD
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence HeightLuzula confusa
200 300 400 500 600 700 800 9004
6
8
10
12
14
16
18
20
22
R² = 0.266641242436093
R² = 0.269084055216121
R² = 0.192558814636371R² = 0.221979190962307
Barrow ControlLinear (Barrow Control)Barrow WarmedLinear (Barrow Warmed)Atqasuk ControlLinear (Atqasuk Control)
TDD
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence HeightLuzula arctica
200 300 400 500 600 700 800 9004
6
8
10
12
14
16
R² = 0.456356848798255
TDD
Mea
n In
flore
scen
ce H
eigh
t (cm
)
Inflorescence HeightLuzula arctica
200 300 400 500 600 700 800 9004
5
6
7
8
9
10
11
12
13
14
R² = 0.00180208421119543
R² = 0.118477442452011
R² = 0.00119242424381139
R² = 0.16112259246933
Barrow ControlLinear (Barrow Control)Barrow WarmedLinear (Barrow Warmed)Atqasuk ControlLinear (Atqasuk Control)
TDD
Mea
n In
flore
scen
ce H
eigh
t (cm
)
No change in warmed plots
Increase in height with increasing TDD in control plots
SummaryLuzula confusa
Inflorescence HeightOverall: Increased TDD is associated with increased height.All sites/treatments show no trend.
Luzula arcticaInflorescence Height
Overall: Increased TDD is associated with increased height.All sites/treatments suggest increased height with increased TDD.
Number of Inflorescences Luzula confusa
200 300 400 500 600 700 800 9000
5
10
15
20
25
R² = 0.00252100841425573
TDD
Mea
n N
umbe
r of I
nflor
esce
nces
/ m
2
Number of Inflorescences Luzula confusa
200 300 400 500 600 700 800 9000
2
4
6
8
10
12
14
R² = 0.346205366980748
R² = 0.0286850390842689
R² = 0.233643131615076R² = 0.158360992060014 Barrow ControlLinear (Barrow Control)Barrow WarmedLinear (Barrow Warmed)Atqasuk Control
TDD
Mea
n N
umbe
r of I
nflor
esce
nces
/ m
2
Fewer inflorescences in warmed plots at both sites
Number of Inflorescences Luzula arctica
200 300 400 500 600 700 800 9000
1
2
3
4
5
6
7
8
9
R² = 0.249528646110344
TDD
Mea
n N
umbe
r of I
nflor
esce
nces
/ m
2
Number of Inflorescences Luzula arctica
200 300 400 500 600 700 800 9000
1
2
3
4
5
6
7
8
9
R² = 0.0992700491964593R² = 2.11575476335435E-05
R² = 0.0138006350531638
R² = 0.00174840102028595
Barrow ControlLinear (Barrow Control)Barrow WarmedLinear (Barrow Warmed)Atqasuk ControlLinear (Atqasuk Control)
TDD
Mea
n N
umbe
r of I
nflor
esce
nces
/ m
2
No significant change
SummaryLuzula confusa
Inflorescence HeightOverall: Increased TDD is associated with increased height.All sites/treatments show no trend.
Luzula arcticaInflorescence Height
Overall: Increased TDD is associated with increased height.All sites/treatments suggest increased height with increased TDD.
Number of InflorescencesOverall: No trend.Control plots had more inflorescences than warmed plots.
Number of InflorescencesOverall: increased TDD is associated with decreased number of inflorescences.All sites/treatments show no trend.
Flowering DateLuzula confusa
1993 1996 1999 2002 2005 2008 2011155
160
165
170
175
180
185
190
195
200
205
R² = 0.0518577330391073R² = 0.0444774403931488
R² = 0.0669776656504306
R² = 0.0511030942947056
Barrow ControlLinear (Barrow Control)Barrow WarmedLinear (Barrow Warmed)Atqasuk ControlLinear (Atqasuk Control)
Year
Mea
n Fl
ower
ing
Date
(Jul
ian
Day) Earlier flowering date in
warmed plots
Flowering is earlier in Atqasuk
Flowering DateLuzula arctica
1993 1996 1999 2002 2005 2008 2011160
165
170
175
180
185
190
195
200
205
R² = 0.0215260845044534R² = 0.130054963917021
R² = 0.0840363165219424R² = 0.0549255803926146
Barrow ControlLinear (Barrow Control)Barrow WarmedLinear (Barrow Warmed)Atqasuk ControlLinear (Atqasuk Control)Atqasuk Warmed
Year
Mea
n Fl
ower
ing
Date
(Jul
ian
Day)
Flowering is earlier in Atqasuk
SummaryLuzula confusa
Inflorescence HeightOverall: Increased TDD is associated with increased height.All sites/treatments show no trend.
Luzula arcticaInflorescence Height
Overall: Increased TDD is associated with increased height.All sites/treatments suggest increased height with increased TDD.
Number of InflorescencesOverall: No trend.Control plots had more inflorescences than warmed plots.
Number of InflorescencesOverall: increased TDD is associated with decreased number of inflorescences.All sites/treatments show no significant change.
Flowering DateFlowering occurs earlier with warming.
Flowering DateNo 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 FoundationGVSU Arctic Ecology ProgramJeremy May, Robert Slider, Jennifer LiebigBarrow 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.