Plant Community Changes in
Northern Alaska in Response to
Warming
Jeremy May and Robert Hollister
Grand Valley State University
Outline
-Site Description
-Methods
-Absolute cover changes between warmed and control plots in 2007
-Difference between All Hit and Top/Bottom Only sampling
-Cover change in sites 1996-2007
-Control plot cover change 1996-2007
-Conclusions
-Future Project Plans
Site Description
Sites located near Atqasuk in the North
Slope Borough of Alaska
Mean July temperature- 3.7 degrees Celsius
Dry Site
Well drained edge of lake
basin
Each site consists of 24 warmed and 24
control plots
Wet Site
Frequently flooded edge of a
thaw lake
Methods Summary
Sampling were done using point frame method
1996 and 2000 samplings were done recording top and
bottom contacts only on the point frame grid
2007 sampling was done using all contacts on the point
frame grid
Samplings were done between Mid-July and Early-August
to reduce differences in phenological development
between samplings
Absolute Cover for Atqasuk Sites 2007 All Hits
100.0
Absolute Cover
90.0
Dry Site Control
80.0
Dry Site Warmed
70.0
Wet Site Control
Wet Site Warmed
60.0
50.0
40.0
30.0
20.0
10.0
0.0
Bryophyte
Lichen
Shrub
Forb
Graminoid
Change in Absolute Cover between Warmed and
Control Plots 2007 All Hits
8.5
Wet Site
Dry Site
Absolute Cover Change
6.5
4.5
2.5
0.5
-1.5
Bryophyte
Lichen
Shrub
Forb
Graminoid
-3.5
-5.5
Graminoids and Forbs show a contradicting response
between sites
Lichens and Shrubs show slight decreases or no
change in response to warming
Dry Site Control All Hits
100.0
90.0
80.0
70.0
60.0
Dry Site Control
Top/Bottom
Dry Site Warmed All Hits
50.0
40.0
30.0
20.0
Dry Site Warmed
Top/Bottom
10.0
0.0
Wet Site Control
Top/Bottom
Wet Site Control All Hits
id
rb
Gr
am
ino
Fo
b
ru
Sh
n
he
Lic
yo
ph
yte
Wet Site Warmed All Hits
Br
A bsolute C over
Comparison of All Hits vs. Top/Bottom Hits Between Sites
Wet Site Warmed All Hits
Differences in Absolute Cover Between All Hits and
Top/Bottom Hits Only
12.0
Absolute Cover Change
10.0
Dry Site Control
Dry Site Warmed
Wet Site Control
8.0
Wet Site Warmed
6.0
4.0
2.0
0.0
Bryophyte
Lichen
Shrub
Forb
Graminoid
-2.0
Overall top and bottom vs all hits have small differences
Graminoids and Shrubs show the most difference between
methods
Dry Site
50
45
40
35
30
25
20
15
10
5
0
1996 Warmed
2000 Warmed
2007 Warmed
1996 Control
2000 Control
s
ru
b
ino
m
ra
G
Sh
id
s
rb
s
Fo
en
Li
ch
ph
yte
2007 Control
Br
yo
A bsolute C over
1996-2007 (Top/Bottom Only)
12
1996-2000 Warmed
10
2000-2007 Warmed
1996-2000 Control
8
2000-2007 Control
6
4
2
0
-2
Sh
ru
bs
in
oi
ds
G
ra
m
Fo
rb
s
he
n
Li
c
-6
te
-4
Br
yo
ph
y
Absolute Cover Change
Dry Site Cover Change 1996-2007
Bryophytes and Lichens show consistent changes
between years due to warming
Graminoids and Bryophytes increased in control plots
Dry Site Select Species Absolute Cover
1996-2007
14
1996 Warmed
2000 Warmed
12
Absolute Cover
2007 Warmed
10
1996 Control
8
2000 Control
2007 Control
6
4
2
0
Luzula
confusa
Hierochloe
alpina
Cassiope
tetragona
Vaccinium
vitis-idaea
Dry Site Select Species Cover Change
Absolute Cover Change
1996-2007
6
1996-2000 Warmed
5
2000-2007 Warmed
4
1996-2000 Control
2000-2007 Control
3
2
1
0
-1
-2
Luzula confusa
Hierochloe
alpina
Cassiope
tetragona
Vaccinium vitisidaea
L. confusa and H. alpina show contradicting responses to
warming
C. tetragona and V. vitis-idaea increased in warmed and
control plots
Wet Site
1996-2007 (Top/Bottom Hit Only)
100
1996 Warmed
Absolute Cover
90
2000 Warmed
80
2007 Warmed
70
1996 Control
60
2000 Control
2007 Warmed
50
40
30
20
10
0
Bryophyte
Lichen
Forbs
Graminoids
Shrubs
Wet Site Growth Form Cover Change
1996-2007
20
1996-2000 Warmed
2000-2007 Warmed
Absolute Cover Change
15
1996-2000 Control
2000-2007 Control
10
5
0
-5
Bryophyte
Lichen
Forbs
Graminoids
Shrubs
-10
Bryophytes show contradicting responses to warming
between years, decreased in control plots
Lichens and Forbs show little change
Graminoids and Shrubs show increase in cover in
warmed and control plots
Wet Site Select Species Absolute Cover
1996-2007
45
1996 Warmed
40
2000 Warmed
Absolute Cover
35
2007 Warmed
30
1996 Control
25
2000 Control
2007 Control
20
15
10
5
0
Carex aquatilis
Eriophorium
angustifolium
Salix pulchra
Wet Site Select Species Cover Change
1996-2007
8
1996-2000 Warmed
Absolute Cover Change
6
2000-2007 Warmed
1996-2000 Control
4
2000-2007 Control
2
0
-2
-4
Carex aquatilis
Eriophorium
angustifolium
Salix pulchra
-6
C. aquatilis shows increases with warming, contradicting
response in control plots
E. angustifolium shows contradicting response to warming and
slight decrease in control plots
S. pulchra shows increases in warmed and control plots
Control Plots Only
1996-2007
45
AbsoluteCover
40
35
30
25
20
15
10
5
0
Bryophyte
Lichen
Forbs
Graminoids
Shrubs
Dry Site
120
1996
AbsoluteCover
100
2000
80
2007
60
40
20
0
Bryophyte
Lichen
Forbs
Wet Site
Graminoids
Shrubs
Conclusions
Many growth forms showed little or no difference in cover when
comparing all contacts to top/bottom contacts only
Graminoids and Shrubs showed the most difference
Most growth forms showed little or no difference in cover
between 1996 and 2007 due to warming
Graminoids and Shrubs consistently increased in
response to warming
Most growth forms showed little or no difference
between 1996 and 2007 in control plots
Graminoids and Shrubs showed a overall net
increase
Future Plans for Project
Analyze 2008 samplings of Barrow, AK Wet and Dry Sites
Analyze aboveground Biomass samplings from all Barrow
and Atqasuk Sites
Acknowledgements
Bob Hollister
Rob Slider
ITEX
National Science Foundation
Grand Valley State University
Jennifer Liebig, Amanda Snyder, Michael Lothshultz,
and Jean Marie Galang
Questions?