CLIMATE IMPACTS ON
INTERIOR ALASKAN FORESTS
A Synthesis of Results
Steve Winslow M.S. Student
Glenn Patrick Juday, Professor of Forest Ecology
Department of Forest Science,
School of Natural Resources and Agricultural Sciences (SNRAS),
UAF
r
e
t
n
I
a
k
s
a
l
A
r
io
Interior Alaska Growth Year Temperature (smoothed)
-1.0
McGrath
(foothils of Alaska Range)
-2.0
-3.0
°C
-4.0
Bettles
-5.0
(foothills of Brooks Range)
-6.0
Year
20
06
20
01
19
96
19
91
19
86
19
81
19
76
19
71
19
66
19
61
1
95
6
1
95
1
1
94
6
1
94
1
93
6
1
1
1
93
6
92
1
1
92
1
1
91
1
1
91
6
90
1
6
-7.0
Analysis: G. Juday
Boreal Alaska Sumer Temperature (smoothed)
Interior Alaska
Summer (May:Aug) Temperature (smoothed)
Fairbanks
14.5
13.5
Talkeetna
°C
12.5
Bettles
11.5
20
06
20
01
19
96
19
91
19
86
1
6
19
81
19
7
19
7
6
1
Year
19
6
6
95
1
19
6
1
95
1
94
6
1
1
94
1
93
6
1
1
93
1
1
92
6
1
92
1
91
6
1
1
91
1
1
90
6
10.5
Analysis: G. Juday
Frost date at Fairbanks
1905-2007
year
1905
1915
1925
1935
110
1945
1955
1965
1975
1985
1995
2005
y = -0.1627x + 149.72
R2 = 0.2091
g frost
n
i
r
p
s
t
s
La
cold season
130
Julian Date
150
170
growing season
190
210
230
250
cold season
270
First
fa l l
y = 0.2446x +f231.19
rost
R = 0.2496
2
Analysis: G. Juday
Unprecedented climate stress (hot and dry)
in late 20th century
Analysis: G. Juday, V. Barber
South slopes in the warmest and driest
portions of central Alaska are too dry
today to support tree growth
g
n
i
n
e
e
r
sg
i
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r
d
n
The tu
Photosynthetic trends
1980-2003
strong positive
positive
is
t
s
e
or
f
l
a
re
ing
o
y
b
d
The sed or
s
stre
S. Goetz, A. Bunn, G. Fiske,
R. Houghton
September, 2005.
Proceedings of the
National Academy of Science
negative
strong negative
0.7
Seasonal Pg
Satellite-observed photosynthetic
trends across boreal North
America associated with climate
and fire disturbance.
near zero
12 km X 12 km pixels
0.6
“Greenness” (NDVI) data
0.5
1982 - 2003
1980
1985
1990 1995
year
2000
Studying Tree Growth
Relationships to Climate:
• Tree-line forests (Climate sensitivity)
• Productive lower elevation forests (Greatest
potential yield)
1. White Spruce
(Greatest resource potential)
2. Black Spruce (Most dominant forest-cover)
3. Paper birch
(Next greatest resource potential)
Field sites
North Fork Koyukuk River
67.9 º N
Nutirwik Creek
150.5 º W
67.9 º N
Hunt Fork John River
149.8 º W
67.8 º N
152.6 º W
Sheenjek River
68.5 º N
143.8 º W Firth River
68.6 º N
141.6 º W
Kugururok River
68.0 ºN,
161.5 ºW
Chimney Lake
67.8 º N
150.5 º W
Tok
63.3 º N
143.3 º W
Cabin Creek
63.6 º N
150.0 º W
Toklat/Savage
63.4 º N
149.2 º W
Rock Creek
63.7 º N
149.0 º W
Slime Creek
63.5 º N
148.8 º W
Bear Creek
63.4 º N
146.4 º W
Courtesy: M. Wilmking
AR all 1906-2000
3 clusters v FAI monthly T
0.6
4 years prior
3 years prior
2 years prior
1 year prior
year of growth
0.4
Correlation score
April
March
0.2
0.0
-0.2
-0.4
July
April
July
July
July
-0.6
Courtesy: M. Wilmking
BR all 1906-2000
3 clusters v FAI monthly T
0.6
4 years prior
3 years prior
0.4
2 years prior
April
July
1 year prior
year of growth
April
Correlation score
0.2
0.0
-0.2
-0.4
July
July
April
July
-0.6
Courtesy: M. Wilmking
Temperature threshold
If too warm – less growth
AR negative growth threshold
BR
1.6
2
R = 0.05
1.4
MRWI
2
R = 0.08
1.2
1.0
0.8
2
R2 = 0.61
0.53
0.6
0.4
14.00
15.00
16.00
17.00
18.00
19.00
20.00
July prior in C
Courtesy: M. Wilmking
Growth rates of each response type
Courtesy: M. Wilmking
BRKG
BRFR
BRHF
15%
9%
Geographic distribution of growth
responses
BRSJ
BRCL
27%
BRNF
10%
BRNC
15%
10%
15%
34%
17%
43%
46%
38%
76%
33%
30%
68%
47%
52%
43%
20%
52%
maritime - continental gradient
Trees like cool summers
Trees like warm springs
Trees don’t care
14%
11%
13%
7%
13%
20%
36%
37%
33%
38%
52%
47%
37%
79%
27%
33%
49%
ARCC
ARTL
ARTK
54%
ARRC
ARSC
ARBC
Courtesy: M. Wilmking
Projection in time:
26
CCC Jul
CSM Jul
ECHAM Jul
GFDL Jul
HAD Jul
24
degree C
22
22ºC
20
18
16
14
16ºC
12
10
00
9
1
25
9
1
50
9
1
75
9
1
00
0
2
25
0
2
50
0
2
75
0
2
00
1
2
Courtesy: M. Wilmking
Projection in time:
26
CCC Jul
20th
century: 16ºC threshold
reached 55% of yrs.
ECHAM Jul
GFDL Jul
HAD Jul
22
degree C
21st century: 16ºC threshold
projected for 85 - 99% of yrs.
CSM Jul
24
22ºC
20
18
16
14
16ºC
12
10
00
19
25
19
50
19
75
19
00
20
25
20
50
20
75
20
00
21
Zero growth at ~ 22ºC threshold (FAI mean July
temperature) projected for end of 21st century
Death of large tree populations likely in
21st century
Courtesy: M. Wilmking
Central interior productive white
spruce study sample area
Fairbanks
McGrath
Anchorage
Data set: 269 trees,
20 stands across east
and central boreal
Alaska (1900-1996).
Analysis: V. Barber, G. Juday
Productive white spruce stands in central Alaska:
When summers are warm, the trees run out of water
and stop growing.
Analysis: V. Barber, G. Juday
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Fairbanks
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Yuk
McGrath
Bethel
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Kus
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Anchorage
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Spruc
White spruce: Positive spring/fall temp responders (35) vs
Negative summer temp responders (83) decadal MAI (w'
95%CI)
Kuskokwim R.
Spruce
Pos MAI/Decade
Neg MAI/Decade
White Spruce :
ders
n
o
esp
R
e
ativ
g
e
N
• Negative responders
outgrew Positive
responders until
recent decades
1.5
ders
n
o
esp
R
e
it iv
Pos
1.0
0.5
Mean Raw RW (mm)
2.0
0.0
1820
1840
1860
1880
1900
1920
1940
1960
1980
2000
Black spruce: Positive spring temp responders(11) vs negative
summer temp responders (66) decadal MAI w' 95%CI
Neg respo MAI/decade Pos Respo MAI/decade
Black Spruce:
1.2
1.0
ers
d
on
p
s
Re
e
tiv
a
g
Ne
0.8
0.6
0.4
onders
p
s
e
R
e
Positiv
0.2
0.0
Analysis: S. Winslow, G. Juday
1820
1840
1860
1880
1900
1920
1940
1960
1980
2000
RW (mm)
• Same general
trends between
response types
White
spruce
POSITIVE
Black
spruce
Analysis: S. Winslow, G. Juday
MIXED
NEGATIVE
Fairbanks summer temperature 3-yr. Index vs.
Yukon River ws ring-width
(all trees; n = 146; 2001:1906)
All Yukon Flats 146
Temperature Index
1.8
12.0
1.6
1.4
14.0
1.2
1.0
16.0
0.8
0.6
0.4
2004
2000
1996
1992
1988
1984
1980
1976
1972
1968
1964
1960
1956
1952
1948
1944
1940
1936
1932
1928
1924
1920
1916
1912
18.0
1908
May, Jul-1&-2 temperature
(C)
r = -0.68
year
Analysis: G. Juday, C. Alix
Black spruce stands on ridge and gravelly sites:
When summers are warm, the trees run out of water
and stop growing.
Analysis: G. Juday
(Alaska birch (Betula neoalaskana) leaves:
leaf “scorch”
(acute drought stress/root dieback)
The Point: leaf scorch, the last symptom before
tree death, appeared on a majority of Alaska
birch trees in central Alaska in 2004 and 2005.
There are no reports or records of this (currently
known) since 1904.
Analysis: G. Juday
Birch decline stand
Summer 2006
Birch decline
Forest Health Program
Alaska Department of Natural
Resources, Division of Forestry
Dr. Robert Ott
Productive Alaska birch stands:
When summers are warm, trees run out of water and stop growing.
Analysis: G. Juday
Indirect Effects of Warmer
Summers
19
5
19 1
5
19 3
5
19 5
5
19 7
5
19 9
6
19 1
6
19 3
6
19 5
6
19 7
6
19 9
7
19 1
7
19 3
7
19 5
7
19 7
7
19 9
8
19 1
8
19 3
8
19 5
8
19 7
8
19 9
9
19 1
9
19 3
9
19 5
9
19 7
9
20 9
0
20 1
0
20 3
05
area burned (ha)
3000000
Warm days
2500000
Warm summers = high fire years
2000000
25
1500000
20
1000000
500000
0
# of days 79 deg. F
Alaska Fire Record vs. Fairbanks Warm Days
40
Area burned
35
30
15
10
5
year
Courtesy: G. Juday
“Fingerprint” of climate warming effect imposed on
the natural disturbance – tree death system
1) greater frequency of disturbance.
2) more extensive areas of tree mortality in disturbances.
3) greater intensity of disturbance resulting in higher
average levels of tree death within outbreaks.
Result:
Change in regional tree species composition or conversion
from forest to non-forest ecosystem within decades .
Courtesy: G. Juday
August
Courtesy: G. Juday
Temperature
control
of spruce budworm
1st instar larva
development rate
(August).
13o
23o
Han, E.; Bauce, E.; Trempe-Bertrand, F. 2000. Development of the first-instar spruce budworm
(Lepidoptera: Tortricidae). Annals of the Entomological Society of America 93(3): 536-540.
Mean daily temperature, 01 Aug. to 31 Aug., at
Fairbanks
19771977-78?
18.0
17.0
16.0
“In Alaska, significant budworm damage
was detected in 1978 on white spruce in
many residential and park areas of Anchorage.”
(Holsten: USDA Forest Service,
Alaska Region Leaflet R10-TP-11)
1988
1990
2004
1993
°C15.0
14.0
13.0
12.0
11.0
10.0
1905
1915
1925
1935
1945
1955
year
1965
1975
1985
1995
2005
Analysis: G. Juday
Date of spruce budworm heat requirement vs.
population density at Fairbanks
pupation @ 370F GDD
budworm density
year
1980
154
1985
1990
1995
2000
250
1990
2005
1993
158
1988
2005
1995
200
Julian date
162
150
166
170
100
2007
174
insects/sq.M foliage
1975
50
178
none
182
start
0
Budworm data: R. Werner, J. Kruse
Analysis: G. Juday
Spruce budworm outbreaks:
1. Follow hot, dry summers.
o
o
2. 50% more eggs laid at 25 C vs. 15 C.
3. Spring frost/freeze will stop.
4. Warmth/fast development avoids
predators/parasites.
The Point: spruce budworm outbreaks
historically were absent in the Alaska boreal
forest because temperatures were too low. Now
outbreaks of this insect appear to be one of the
main risks for tree death on many sites.
Photo: Paul Renschen
What does it all mean?
• The boreal forest of interior Alaska is experiencing
rapid and dramatic change
• If current trends continue, large scale tree
mortality, treeline-movement, and restructuring of
forests is expected
• Unanticipated change-agents may quickly alter
the rules (e.g. budworm didn’t used to occur)…
Forest inventory questions/
suggestions
• Should we assume forests will return to historical
state? NO!
• Can the current inventory framework rapidly
assess forest health conditions? Does it provide
“actionable intelligence” to managers?
Questions?