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
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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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
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
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
Integration and Synthesis – New Experiment
How will potential changes in ecosystem structure alter material fluxes across the landscape
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???
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
"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
Sensitivities to Climate, succession,regime shifts
(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?
Future directions for vegetation
dynamics: Scaling in time and space
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)
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
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).
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).