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