Thresholds and State Changes
Climate
Rate and Trajectory of Successional Changes in
Ecosystem Processes
Sensitivity and
Response to Change
Frequency and Intensity of Disturbances
(Flooding, Fire, Thermokarst, Insect/Pathogens)
Sensitivity and
Response to Change
Abundance of Key Species
Thresholds and Regime Shifts
Hypothesis: Novel boreal landscape patterns emerge when climate change leads to disturbance regimes that alter permafrost integrity and the abundances of key functional types.
Thresholds and State Changes
1) How often and under what circumstances does wetland drying or thawing of permafrost cause a change in ecosystem state?
Document hydrologic changes in permafrost-
dominated wetlands
Interaction among landscape position and fire on permafrost thaw, thermokarst development
and wetland drying?
Using Landsat images, develop predictive relationship among
landscape variables and change in wetland extent
T1
Thresholds and State Changes
2) What disturbance-induced changes in functional types might trigger a change in ecosystem state, and what are the ecosystem consequences?
Determine the effects of altered disturbance regime on
successional trajectory and ecosystem processes
Determine the disturbance frequency and conditions under
which new successional trajectories occur
Track tree establishment/community composition post burn. Experimentally
manipulate seed and seedlings
T2a
Document effects of ecosystem change (fire, thermokarst) on
organic matter/nutrient standing stocks and ecosystem processes
Track community composition, C & N stocks/transformations post fire and
thermokarst
T2b
Thresholds and State Changes
2) What disturbance-induced changes in functional types might trigger a change in ecosystem state, and what are the ecosystem consequences?
Document impacts of disease and insect outbreaks on ecosystem processes
Document 1) interannual variation in the abundance of insect and pathogen species, and 2) consequences of
selected outbreaks
Determine impact on microclimate, stand dynamics, NPP, N-fixation
T3
Thresholds and State Changes
Monthly Talks:
May: Spruce budworm and climate change (Juday)
June: Predictive rules for post-fire succession in upland forests (Johnstone, Hollingsworth & Juday)
July: Loss of moss as potential threshold (Turetsky, Mack and Hollingsworth)
August: Permafrost driving variables and responses (Schuur and Jones)
AugustAugust
May/JuneMay/June
The spruce budworm completes its life cycle within a 12-month period, but spread across 2 different years.
First year First year eventsevents
Second year Second year eventsevents
startstart
Temperature controlTemperature controlof spruce budworm of spruce budworm
1st instar larva1st instar larvadevelopment ratedevelopment rate
((AugustAugust).).
1313oo 2323oo
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.
gs = green substance gs = green substance
Mean daily temperature, 01 Aug. to 31 Aug., at Fairbanks
10.0
11.0
12.0
13.0
14.0
15.0
16.0
17.0
18.0
1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005
year
Deg
. C
2004200419931993
1988198819901990
1977-78?1977-78?
“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)
Analysis: G. Juday Analysis: G. Juday
Date of spruce budworm heat requirement for peak of adult moth stage at Fairbanks, AK
178
182
186
190
194
198
202
206
210
214
218
222
1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005
year
Juli
an
date
moth @ 818 F Linear (moth @ 818 F)
July 7 (July 7 (July 6 Leap yr.)July 6 Leap yr.)
2004200420052005
199319931995199519881988
19901990
19131913
19151915
1975?1975?
JulyJuly
JuneJune
JulyJuly
AugustAugust
Data: National Weather ServiceData: National Weather ServiceAnalysis: G. Juday Analysis: G. Juday
Spruce budworm abundance vs. weather at Fairbanks, AK
-1
-0.5
0
0.5
1
1.5
2
2.5
3
1975 1980 1985 1990 1995 2000 2005
year
n A
ug
T -
n d
ate
of
moth
(s
tdev)
0
50
100
150
200
250
inse
cts/
m-2
foli
ag
e
Fairbanks budworm weather index budworm density at BNZ
no budwormsno budworms
DataDatastartstart
“Not known to breed inAlaska.” “Has occurred at Fairbanks, Haines, Pt. Barrow.” Armstrong. 1983. Birds of Alaska.
Cape May Warbler (Dendroica tigrina) :“ … the fortunes of its populations are largely tied to the availability of spruce budworms, its preferred food.”http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Cape_May_Warbler_dtl.html
dendron = treeoikein = dwelltigrinus = striped
BA
RK
BA
RK
20052005
2000
2000
2001
2001
2002
2002
2003
2003
2004
2004
2006
2006
1999
1999
1998
1998
1997
1997
1996
1996
1992
1992
1991
1991
1990
1990
1995199519931993
spruce budwormspruce budwormdamagedamage heat/droughtheat/drought
limitationlimitation
Photo: C. AlixPhoto: C. Alix
Summer temperature vs. w. spruce growth(Bonanza Creek LTER -2 Parks Loop South; 1906-2006; n = 12 trees)
r2 = 0.32
0.0
0.2
0.4
0.6
0.8
1.0
1.2
9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0
previous May:Aug T (deg C)
mean
sam
ple
rin
g w
idth
(m
m)
1912 volcanic 1912 volcanic ash?ash?
1993 & 95 spruce budworm defoliation1993 & 95 spruce budworm defoliation
2004 record hot2004 record hot
Data: G. Juday Data: G. Juday
KILL ZONEKILL ZONE KILL ZONEKILL ZONE
The 25th anniversary of The 25th anniversary of the Rosie Creek Fire: the Rosie Creek Fire:
Rules of post-fire Rules of post-fire succession in Alaska succession in Alaska
boreal forest boreal forest
Glenn Patrick Juday, Professor of Forest EcologyGlenn Patrick Juday, Professor of Forest Ecology
Bonanza Creek LTER monthly synthesis meetingBonanza Creek LTER monthly synthesis meetingFairbanks, AlaskaFairbanks, Alaska
12 June, 200812 June, 2008
Second 100 m
Second 100 m(100 to 200 m)
(100 to 200 m)
First 100 m
First 100 m(0 to 100 m)
(0 to 100 m)
Surviving seed source standSurviving seed source stand
HectareHectare1RSW1RSW
Photo - BNZ LTERPhoto - BNZ LTERJuly, 2007July, 2007
First 100 mFirst 100 m(0 to 100 m)(0 to 100 m)
Second 100 mSecond 100 m(100 to 200 m)(100 to 200 m)
Surviving seed source standSurviving seed source stand
HectareHectare1RSW1RSW
100 t
o 1
09.9
110 t
o 1
19.9
120 t
o 1
29.9
130 t
o 1
39.9
140 t
o 1
49.9
150 t
o 1
59.9
160 t
o 1
69.9
170 t
o 1
79.9
180 t
o 1
89.9
190 t
o 1
99.9
1983s1990s&UNK1987s
0
50
100
150
200
250
300
350
# trees
distance (m)
cohort
Established w. spruce with distance from source stand at Reserve West
1983s 1990s&UNK 1987s
Height Growth at Reserve West (full hectare)(all cohorts)
0
5
10
15
20
25
30
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008year
he
igh
t e
lon
ga
tio
n (
cm
)
1983 seed crop 1987 seed crop 1990 seed crop & UNK
Total Height at Reserve West (full hectare)(all cohorts)
0
50
100
150
200
250
300
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
year
Tota
l H
eig
ht
(cm
)
1983 seed crop 1987 seed crop 1990 seed crop & UNK
comparable comparable years years (20th)(20th)
comparable comparable years years (17th)(17th)
comparable comparable years years (17th)(17th)
(12th)(12th)
(5th)(5th)
(20th)(20th)
Reserve West w. spruce mortality
0
10
20
30
40
50
601
98
8
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
year
nu
mb
er
trees
dyin
g
1983s 1987s 1990s
crushingcrushingfrom snagfallfrom snagfall
primarilyprimarilycumulativecumulativetree death?tree death?
Recruitment declines with organic depth
2-yr recruitment from seeding experiments (Alaska/Yukon)n=4 to 16 (total plots = 60)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 1 2 3 4 5 6 7 8 9 10
organic layer depth depth (cm)
rela
tiv
e s
ee
dlin
g e
sta
blis
hm
en
t
aspen
black spruce
white spruce
Aspen is more sensitive to organic layer thickness than
conifers
0.0
0.1
1.0
10.0
100.0
0 5 10 15 20 25 30
organic layer depth (cm)
de
ns
ity
ra
tio
(d
ec
id:s
pru
ce
)
0
1
10
100
1000
10000
0 5 10 15 20 25 30
organic layer depth (cm)
bio
ma
ss
ra
tio
(d
ec
id:s
pru
ce
)
Species-specific
responses to seedbeds lead
to strong effects on post-fire dominance
Seedling Density
Aboveground Biomass
Burned spruce forest • Alaska 40,000 ha burn
• 8 yrs post-fire• n=19 stands
Fire & regeneration thresholds
• Residual organic layer determines seedbed quality
• Differences in species sensitivity lead to strong composition effects
• Increased fire severity => crossing threshold of residual organics => shift in successional trajectory
Critical Research
• Moving deeper in time – What are the longer term consequences of
variations in fire severity?
• Understanding space– Which parts of the landscape are
vulnerable to shifts in trajectories, and which aren’t?
• Can we test anticipated changes?
Changing moss communities and the potential for ecosystem thresholds in
the Alaskan boreal forest
Merritt Turetsky, Teresa Hollingsworth, Michelle Mack
LTER Synthesis Talk
and chapter for the CJFR special issue
• Biodiversity
• Soil Habitat
• Ecosystem Productivity
• Organic matter and nutrient turnover
• Moisture/thermal regulation
Objective 1: Use meta-analysis to address “moss lore”
• Moss NPP inversely proportional to vascular plant production
• Moss NPP ≥ black spruce in boreal forest
• Moss decay vascular litter
• Moss ≥ vascular biomass for long-term carbon storage
Boreal Productivity
WetlandUplandU
W
0 100 200 300 400
Understory ANPP (g m-2 yr-1)
0
50
100
150
200
U
U
U
W
W
W
W
0 100 200 300 40010
20
30
40
50
60
70
80
Spruce ANPP (g m-2 yr-1)
Spruce generally > moss
0 100 200 300 40010
20
30
40
50
60
70
80
Spruce ANPP (g m-2 yr-1)
Spruce generally > moss
Mos
s N
PP
(g
m-2 y
r-1)
Mos
s N
PP
(g
m-2 y
r-1)
Litter decay rates
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80
Moss litter decay rates
Vas
cula
r lit
ter
dec
ay
rate
s
1:1
Moss and long-term C storageM
ass
of
pea
t (g
/cm
2 )
Moss
Sph/w
ood
Sedge
/mos
s
Sedge
/woo
dSylv
ic
Lacu
strine
Marl
Wood
Mas
s o
f p
eat
(g/c
m2 )
Moss
Sph/w
ood
Sedge
/mos
s
Sedge
/woo
dSylv
ic
Lacu
strine
Marl
Wood
0
10
20
30
40
50
60
70
80ab
un
dan
ce (
% c
ove
r)White Spruce (FP4)
Alder/BP (FP2)
Moss abundance at LTER sites
year
1) Use meta-analysis to address key assumptions about moss and boreal ecosystem
• Moss vs. vascular NPP• Moss vs. vascular decomposition• Changing moss abundance with N, temp, fire
2) Apply insight to understand implications of changing moss abundance across LTER sites
Goals for synthesis chapter
PERMAFROST THAW AND THERMOKARST FORMATION
PERMAFROST THAW AND THERMOKARST FORMATION
From Schuur et al. 2008
PERMAFROST THAW AND THERMOKARST FORMATION
From Schuur et al. 2008