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Cascading Thresholds Subsistence-related changes Warming to fire to permafrost loss to wetland drying to subsistence change Warming to fire to altered moose/caribou habitat/access to subsistence change Cultural assimilation to declining subsistence Declining subsistence to decreased well-being to migration to cities Economics-related changes Global oil shortage to rising village oil prices to migration Warming to low river level to no barge deliveries to rising fuel costs to migration Warming to drought to spruce budworm to dry firewood to biofuels to jobs Warming to permafrost thaw to infrastructure costs to school/airport loss Rising fire suppression costs to fire co-management to resource manag. plan Rising fuel costs to smaller hunting radius to altered animal distrib to altered veg

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Cascading Thresholds. Subsistence-related changes Warming to fire to permafrost loss to wetland drying to subsistence change Warming to fire to altered moose/caribou habitat/access to subsistence change Cultural assimilation to declining subsistence - PowerPoint PPT Presentation

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Page 1: Cascading Thresholds

Cascading Thresholds

• Subsistence-related changes• Warming to fire to permafrost loss to wetland drying to subsistence change

• Warming to fire to altered moose/caribou habitat/access to subsistence change

• Cultural assimilation to declining subsistence

• Declining subsistence to decreased well-being to migration to cities

• Economics-related changes• Global oil shortage to rising village oil prices to migration

• Warming to low river level to no barge deliveries to rising fuel costs to migration

• Warming to drought to spruce budworm to dry firewood to biofuels to jobs

• Warming to permafrost thaw to infrastructure costs to school/airport loss

• Rising fire suppression costs to fire co-management to resource manag. plan

• Rising fuel costs to smaller hunting radius to altered animal distrib to altered veg

Page 2: Cascading Thresholds

1. Current experimental design/data collection and ties to future experimental design

2. Future experimental design

3. New experiments

Fate of datasets – three main decisions

1. Whether to maintain a data collection

2. Whether to maintain all replicates

3. Whether to maintain sampling frequency

Page 3: Cascading Thresholds

Potential considerations and criteria for deciding future data collection efforts (i.e., future of present data collection efforts).

I. Considerations to maintain a data collection:• Data supportive of other research• Data are central to broader BNZ research objectives• Detected or potential to detect important change in ecosystem/community

structure• Cost and labor relative to importance/value of data

II. Considerations to maintain replicates• Detected or potential to detect important divergent patterns over time• Do existing data sufficiently quantify spatial variation to the point where

replication can be pared-down?

III. Considerations to maintain sampling frequency• Shorter term dynamics are relevant ecologically and to BNZ goals

Page 4: Cascading Thresholds

Integration and Synthesis – New Experiment

How will potential changes in ecosystem structure alter material fluxes across the landscape

Potential Changes:• Permafrost thaw & thermokarst• Change in alder abundance• Others…

Response variables:• Carbon and nitrogen fluxes• Energy exchange• Successional trajectories• Others…

Experimental design (or start of design):• Watershed approach to monitor hydrologic and gaseous fluxes• Alder removal• Soil warming• Other manipulations???

Page 5: Cascading Thresholds

Experimental Approaches to Threshold Change

Problem: Threshold changes usually require strong drivers that may be difficult to replicate with experiments

Examples:

Ecosystem warming experiments that minimally warm the soil

Fire experiments that burn at moderate or low severity

Page 6: Cascading Thresholds
Page 7: Cascading Thresholds

"Ap

par

ent"

Tem

per

atu

re S

ensi

tivi

ty

Environmental C

onstraints

sorbed

desorbed

aggregated

unaggregated

anaerobic

a

erobic

water stre

ss

adequate water

frozen

unfrozen

"Intrinsic" Temperature Sensitivity

simple complex

substrates substrates

high low

temperature temperature

Davidson and Janssens. 2006. Nature 440:165-173

Davidson and Janssenns, 2006 and Janssens. 2006. Nature 440:165-173

Soil Organic Matter

The roles of substrate and environment

Page 8: Cascading Thresholds

Sensitivities to Climate, succession,regime shifts

Soil Organic Matter

How are SOM stocks and turnover changing?

•Causal linksSubstrate controlsEnvironmental controls

•Interactive effectsSubstrate X Environment

•Feedbacks to Ecosystem

Goal is to establish:

Page 9: Cascading Thresholds

• Synthesis activities: • site scale models for lter 1, lter 2, lter wet, cpcrw • Litterbag and substrate models

• New long-term experiments• Litterbag and incubation, anchored in 5 yr C stock

harvests: • Locations via substrate X enviroment

• Historic evaluation of archives, data for substrate,environment

Soil Organic Matter

Page 10: Cascading Thresholds

Fairbanks summer temperature 3-yr. Index vs. Yukon River ws ring-width

(all trees; n = 146; 2001:1906)

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

20

04

20

00

19

96

19

92

19

88

19

84

19

80

19

76

19

72

19

68

19

64

19

60

19

56

19

52

19

48

19

44

19

40

19

36

19

32

19

28

19

24

19

20

19

16

19

12

19

08

year

mean

rin

g w

idth

(m

m)

12.0

14.0

16.0

18.0

May,

Ju

l-1

&-2

tem

pera

ture

(C

)

All Yukon Flats 146 Temperature Index

Correlation of monthly precipitation at Fairbanks with residual of temperature prediction of growth

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

month

corr

ela

tio

n (

Pe

ars

on

)

A.A. 2nd half 2nd halfwinter snowwinter snow

A.A. A.A.

year of ringyear of ringformationformation

1 year prior to1 year prior to ring formationring formation

2 years prior to2 years prior to ring formationring formation

Juday and Alix - IPEV/UAFJuday and Alix - IPEV/UAF

sig.@sig.@95%95%

sig.@sig.@95%95%

C.C. Nov Dec Nov Dec snow (neg)snow (neg)

B.B. Jul Aug Jul Aug rainrain

B.B. Aug Aug rainrain

= selected for= selected formodel (positive)model (positive)

= selected for= selected formodel (negative)model (negative)

rr22 = .46 = .46

Page 11: Cascading Thresholds

Precipitation effect on temperature prediction of growth

(Yukon Flats w. spruce; 2001-1909; no 1991, 1963, 1928, 1926)

R2 = 0.35

R2 = 0.55

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Precipitation Index (stdev)

Re

sid

uals

of

Tem

p p

red

icti

on

(std

ev)

Juday and Alix - IPEV/UAFJuday and Alix - IPEV/UAF

Compensatory effectCompensatory effectof adding moistureof adding moisture

Deleterious effectDeleterious effectof withdrawing moistureof withdrawing moisture

Above medianAbove mediantemperaturetemperature

Below medianBelow mediantemperaturetemperature

smoothed Climate index vs. actual growth growth

(Yukon Flats w. spruce; all trees; n = 146; 2001-1909)

0.7

0.9

1.1

1.3

1.5

-4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0

Precip and Temp Index (stdev)

5-y

r. M

ean

Sam

ple

rin

g w

idth

(std

ev)

cool/moistcool/moisthot/dryhot/dry

rr22 = .77 = .77

LowerLowerthreshold? threshold?

UpperUpperthreshold? threshold?

Range ofRange ofsensitivity? sensitivity?

Page 12: Cascading Thresholds

Future directions for vegetation

dynamics: Scaling in time and space

Page 13: Cascading Thresholds

From McGuire, Chapin, Walsh, and Wirth. 2006. Integrated regional changes in arctic climate feedbacks: Implications for the global climate system. Annual Review of Environment and Resources 31:61-91.

PhysiologyClimate warming

Structure

Land Use

composition, vegetation shifts

Disturbance

CO2, SH

Permafrostwarming, thawing

Physical feedbacks

Biotic controlMediatingprocesses

Snowcover

1, 2, 3, 4

5, 6, 7

8, 9

10, 11

12, 13

A

B

C

14

15

16

enzymes, stomates

fire, insects

logging, drainage,reindeer herding

D

E

I

II

IV

III V

fast (seconds to months)intermediate (months to years)slow (years to decades)

Response time

Mechanisms:: albedoGH: ground heat fluxSH: sensible heat fluxCO2, CH4: atmospheric concentration

Physiological feedbacks:(1) higher decomposition CO2(2) reduced transpiration SH (3) drought stress: CO2(4) PF melting: CH4(5) longer production period: CO2(6) NPP response to N min: CO2(7) NPP response to T: CO2

Structural feedbacks:(8) shrub expansion: (9) treeline advance: , CO2 (10) forest degradation but CO2, SH (11) light to dark taiga: but CO2, SH(12) more deciduous forest: , SH(13) fire / treeline retreat:

Physical feedbacks:(14) increased, then reduced heat

sink GH,SH(15) watershed drainage SH(16) earlier snowmelt

Page 14: Cascading Thresholds

Climatewarming

Soil climate

Physical feedbacks Biotic control

Snow cover PhysiologyPhenology, Growth rates, Mineralization

StructureComposition,Species shifts

Soil temperatureSoil moistureWater table position

Fig 1. Schematic of potential physical, physiological, and structural feedbacks to peatland C fluxes investigated in the proposed research. Response times of feedbacks vary from fast (seconds to months; i.e., NPP responses to temperature), to intermediate (months to yrs; i.e., NPP responses to longer growing seasons) and slow (yrs to decades; i.e., NPP responses to woody expansion).

Snowpack thicknessDuration of snowpack

Climatewarming

Soil climate

Physical feedbacks Biotic control

Snow cover PhysiologyPhenology, Growth rates, Mineralization

StructureComposition,Species shifts

Soil temperatureSoil moistureWater table position

Fig 1. Schematic of potential physical, physiological, and structural feedbacks to peatland C fluxes investigated in the proposed research. Response times of feedbacks vary from fast (seconds to months; i.e., NPP responses to temperature), to intermediate (months to yrs; i.e., NPP responses to longer growing seasons) and slow (yrs to decades; i.e., NPP responses to woody expansion).

Snowpack thicknessDuration of snowpack