Disturbance:
Introduction, with a terrestrial bias
Peter White, Biology/Ecology 255, Sept 9, 2005

Outline
A personal history
Definition and significance
Importance
Search for generality
Discussion

Outline
A personal history
Definition and significance
Importance
Search for generality
Discussion
IDH, niche and neutrality; Large scale behavior: Criticality, HRV, Resilience;
Legacy and History matters; Top-down and bottom-up control and the Healthy
Forest Initiative; Restoration…

Dartmouth, 1970s

William S. Cooper
ESA’s Cooper Award
Cooper, W.S. 1926.
The fundamentals of vegetation change.
Ecology 7:391-413.

Cowles

Cowles…Cooper…

Cowles…Cooper…Buell…

Cowles…Cooper…Buell…Reiners…

Cowles…Cooper…Buell…Reiners…ME!

Cowles…Cooper…Buell…Reiners…ME!
W.A.R.

Watt, A.S. 1947.
Pattern and process in the plant community.
Journal of Ecology 35:1-22.

Pattern and process in a forested ecosystem
Pattern and process in cliff ecosystems
Pattern and process in mangrove ecosystems
Pattern and process in neotropical secondary rain forests
Pattern and process in the dynamics of seed banks
Pattern, process, and prediction in aquatic ecology.
Spatial pattern and process in plant-pathogen interactions
Pattern, process, and predictability: the use of neutral models for landscape analysis
Landscape ecology: the effect of pattern on process.

Watt, A.S. 1923.
On the ecology of British beechwoods with special reference to their regeneration.
Journal of Ecology 11:1-48.

The Leopold Report, 1963

Excitements!
• Succession did not start from equally blank slates

Excitements!
• Succession did not start from equally blank slates
• Disturbance was inevitable

27 Cove Trees of Joyce Kilmer Memorial Forest
+10 more
Ns Bl
Ps
Al Cg
Ca
Dv
Af
Ba
Hc
Mf
Mt Ma
Th
Lt Fa
Ar
As
Tc
Ap
Fg
Io
Hv
Im
Cf
Qr
Cd

Excitements!
• Succession did not start from equally blank slates
• Disturbance was inevitable
• Diversity dependent on recurrent disturbance

Excitements!
• Succession did not start from equally blank slates
• Disturbance was inevitable
• Diversity dependent on recurrent disturbance
• Chance and transient dynamics

“Shakespeare, he’s in the alley”
--Bob Dylan,
Stuck Inside of Mobile with the Memphis Blues
Again, Blonde on Blonde

“Shakespeare, he’s in the alley”
--Bob Dylan,
Stuck Inside of Mobile with the Memphis Blues
Again, Blonde on Blonde

“Death of The Climax”
Missouri Botanical Garden,
1978

Henry Cowles 1899 Lake Michigan Sand Dunes

“Death of The Climax”
Missouri Botanical Garden,
1978
Climax b. Chicago,
Illinois,
1899 d. St.Louis,
Missouri,
1978

Changes…
• Academic lineage question
• Language requirements

Changes…
• Academic lineage question
• Language requirements
• Reprint request cards

Changes…
• Academic lineage question
• Language requirements
• Reprint request cards
• Nature of the thesis
• New journals

Subscriptions to journals and journal loyalty -we read more now but less in any one journal, and typically in digital format. And, our method of discovery is altogether different –
Bob Peet www.unc.edu/scholcomdig/whitepapers/peet.pdf

Species response to disturbance (from Vogl 1974)
• Increasers
• Decreasers
• Invaders
• Retreaters
• Integrators
• Neutral species

Questions for the Semester
• What have we learned?
• What generalities can we make?
• What are the obstacles to generality?
• What are the interesting and important questions?

First announcement:
Disturbance and restoration in forest ecosystems
Course for the PhD-programme in “Biodiversity and
Forestry“, Vårdnäs, Linköping, Feb 13 – 17, 2006.
Course leaders:
Mats Niklasson, Southern Swedish Forest Research
Centre, SLU
Per-Anders Esseen, Ecology & Env Science, UMU
Invited teachers: prof Peter White,Biology Univ of North Carolina, USA prof Sylvie Gauthier, Canadian Forest Service, Quebec
Lars- Owe Wikars, Entomology SLU Uppsala
Lars Östlund, Forest Vegetation Ecology, SLU Umeå and more

Outline
A personal history
Definition and significance
Importance
Search for generality
Discussion

Disturbance definitions
• Absolute:
– A discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability or the physical environment (White & Pickett 1985)
– Grime: a loss of biomass

Relative Definition:
Displacement from normal dynamics
• Patch dynamics
• Quantitative & qualitative equilibrium
• Historic Range of Variation,
Natural Range of Variability
• Criticality
• Resilience

Importance
• Biodiversity
• Exotic invasions
• Effects on value, health
• Ecosystem use, harvest
• Climate change
• Land-use and hazard insurance
• Environmental ethics in a patch dynamic world

The 17 Ten Greatest Hits
2000+ Papers
Obstacles to Generality

Patch & Multipatch Scales
Patch scale
Multipatch scale

Thinking about disturbance
Space
Patch
Multipatch
(Landscape)

Thinking about disturbance
Space/Time Event Multievent
Patch
Multipatch
(Landscape)

Thinking about disturbance
Space/Time Event Multievent
Patch 1. P-E
Multipatch 3. MP-E
(Landscape)
2. P-ME
4. MP-ME

Thinking about disturbance
Space/Time Event Multievent
Patch 1. P-E
Multipatch 3. MP-E
(Landscape)
2. P-ME
4. MP-ME

Thinking about disturbance
Space/Time Event Multievent
Patch 1. P-E 2. P-ME
Multipatch 3. MP-E
(Landscape)
4. MP-ME
Easiest to study

Thinking about disturbance
Space/Time Event Multievent
Patch 1. P-E 2. P-ME
Multipatch 3. MP-E
(Landscape)
Biodiversity,
Sustainability
4. MP-ME

Thinking about disturbance
#1 Patch-Event
Scale
Legacy matters
Empirical detail matters
Specificity matters

Disturbances within one ecosystem vary
Appalachian Fir Forest

A family of successions differing in legacy because of difference in severity

Fire intensity
& effects on soils
--from
Ryan
2002

FIRE SEVERITY
Extreme
1100
Crown Fire without Duff Consumption
1100
Crown Fire with Total Duff Consumption
High
Moderate
0
10 Time (minutes)
Savannah Grass Fire without Duff Consumption
325
25
1100
0 Time (hours)
Ground Fire with Total Duff Consumption
16
Low
Unburned
Site Factors
0
Unburned
Time (minutes) 4
0 Time (hours)
Light Moderate
Depth of Burn
Organic Soil Depth & Coarse Wood
19
Deep
Weather Factors Long Term Drying

Richter et al.
1996

Specificity & structure
• None
– Drought, landslide, dune movement, freeze-thaw, salinity incursions, crown fire
• Large, dominant individuals
– Ice storm, wind
• Small individuals
– Surface fire, flood, falling trees

Disturbance specificity b B a A
Disturbance
Succession

Disturbance specificity:
Setting succession back b B a A
Disturbance
Succession

Disturbance specificity:
Advancing succession b B a A
Disturbance
Succession

Disturbance specificity:
Holding succession in check b B a A
Disturbance
Succession

a
Disturbance specificity:
Maintaining late successional species
A b B
Disturbance
Succession

Thinking about disturbance
#2
Space/Time Event Multievent
Patch 1. P-E 2. P-ME
Multipatch 3. MP-E
(Landscape)
4. MP-ME
History matters
Interactions matter

Disturbance density in time
Clark 1996

Disturbance Regime:
Synergisms
• Feedback between community state
& disturbance
• Feedback between time since disturbance & the next disturbance
• Disturbance interactions

Disturbances interact: history matters
+ promote subsequent disturbance
- inhibit subsequent disturbance
• Fire-fire (Covington & Moore 1994)
• Fire-insect (Flamm et al. 1993)
• Fire-grazing (Vinton et al. 1993)
• Wind-fungi-insects (Matlack et al.
1993)
• Avalanche-fire-insects (Veblen et al. 1994)

Hurricane damage increases with age & is greater in successional pine stands than hardwoods at any age -- Foster 1988
White pine
Hardwoods
20 40 Age (yr) 80 100

Disturbance Regime:
Synergisms
• Feedback between time since disturbance & the next disturbance
Suppression decreases frequency BUT increases severity

Feedback with time since disturbance: fire
From Niklasson & Granstrom

Gustafson et al. 2004
Management influence on risk of crown fire to towns
FIRE SUPPRESSION
DECREASES CROWN
FIRE RISK!

Thinking about disturbance
#3
Space/Time Event Multievent
Patch 1. P-E
Multipatch 3. MP-E
(Landscape)
2. P-ME
4. MP-ME

• Climate, site drive disturbance regime
• Process creates pattern
• Pattern creates process

Disturbance-climate relations
Southern Oscillation & fire --Swetnam & Betancourt 1990
• Regional synchronicity
– Climate systems & spatial autocorrelation
– Stress on management
– Violation of independence for otherwise isolated populations that we had hoped were independent

Bekker &
Taylor 2001

Rollins et al.
2002
In the S, more fire on NW, N,
NE slopes
In the N, more fire on SW, W slopes

Process creates pattern
• + Fire often increases heterogeneity
• - Succession often decreases heterogeneity

Heterogeneity
Higher Lower

High burn
Low/
Unburned
Heterogeneity is important in recovery: distance, size, seed source, legacy
Viveash, NM
11,017 ha
Image from S. Kotliar, USGS
Hi Meadow, CO 4,422 ha
Bobcat Gulch, CO
3,059 ha

Pattern also creates process
+ Fire spread from more to less flammable stands
- Fire absent from flammable stands because of fire breaks

Islands in boreal forest lakes
Bergeron & collaborators
• Isolated from large, high intensity mainland fires
• Lightning ignitions increase as island size, elevation, & isolation increase
• Frequent low intensity fires maintain island populations of Red Pine that could not persist in the mainland crown fire regime

Fuel Connectedness & Fire
Cape Canaveral
Duncan & Schmalzer
2004

Connectedness & Fuel Moisture

high fuel moisture e.g., typical spring low fuel moisture e.g. typical late-summer very low fuel moisture and wind e.g. 1988
*
* low flammability high flammability burned
* lightning strike
*
*
*
*
Turner and Romme 1994

Pattern & Process
• Pattern controls process at low to medium fire intensities
• Process overwhelms pattern at high fire intensities
– Agee 1998

Pattern & Process
• Pattern controls process at low to medium fire intensities
• Process overwhelms pattern at high fire intensities
– Agee 1998
• TOP DOWN vs. BOTTOM UP
CONTROL
– Top Down = Climate
– Bottom Up = Fuels

Thinking about disturbance
#4
Space/Time Event Multievent
Patch 1. P-E 2. P-ME
Multipatch 3. MP-E
(Landscape)
4. MP-ME
Dynamic equilibrium
Historic range of variation

Frequency vs.
Magnitude
Gaps in Japanese deciduous forest
--Tanaka &
Nakashizuka 1998

1.
Two definitions of dynamic equilibrium
Quantitative equilibrium
%
Time

Two definitions of dynamic equilibrium
2. Qualitative or persistence equilibrium
BOUNDED VARIATION
%
Time

Minimum dynamic area
An area large enough to contain all the patch types and to result in the sustained dynamics of the ecosystem

Minimum dynamic area
An area large enough to contain all the patch types and to result in the sustained dynamics of the ecosystem
Rules of Thumb
Maximum disturbance <20% of area in a 250 yr period (Frelich &
Lorimer 1991)
Maximum Disturbance <50% study area (Johnson 1992)

Shugart’s 1:50 Rule

Stability of Landscape Patterns
– from Turner et al. 1993
10.0
5.0
1.0
0.5
0.1
equilibrium or steady state
A
B
stable, low variance stable, high variance
C stable,
E very high variance stable, low variance
D
0.05
F unstable system, bifurcation or crash
0.01
0.25
0.50
Disturbance Extent / Landscape Extent
0.75
(Turner et al. 1998)

Stability of Landscape Patterns
– from Turner et al. 1993
Gaps
10.0
stable, stable,
E
5.0
equilibrium low or variance very high steady state 1.0
variance
A
B stable, high
0.5
variance
C
0.1
stable, low variance
D
0.05
F unstable system, bifurcation or crash
0.01
0.25
0.50
Disturbance Extent / Landscape Extent
0.75
(Turner et al. 1998)

Stability of Landscape Patterns
– from Turner et al. 1993
10.0
5.0
1.0
0.5
equilibrium or steady state
A
B
1981 YNP
stable, low variance
1988
* stable, high variance
* stable,
E very high variance
C
0.1
stable, low variance
D
0.05
F unstable system, bifurcation or crash
0.01
0.25
0.50
Disturbance Extent / Landscape Extent
0.75
(Turner et al. 1998)

Pascual & Guichard 2005

Historic Range of Variation
Natural Range of Variability
• Qualitative or persistence equilibrium
• Variation--but bounded variation

Simulating the Historic
Range of Variation
Wimberly et al. 1999
Province Single run
Nat Forest
Late Succ Reserve

HRV in Yellowstone – Tinker et al. 2003

HRV in Yellowstone – Tinker et al. 2003

HRV in Yellowstone – Tinker et al. 2003

Process creates pattern: The oldest age class increases with landscape size
-- from Johnson et al. 1995
Old growth definition varies with scale

The Search for Generality

Mackey, R.L. and D.J.Currie
2001. The diversity-disturbance relationship: it is generally strong and peaked? Ecology 82:
3479-3492.
No!

The Search for Generality
Obstacles 1: Understanding the
Environment
Number of potential factors
Preceding & subsequent environment
Heterogeneity within patches

The Search for Generality
Obstacles 2: Understanding Species response
Specificity to species, structure
Legacy, including landscape heterogeneity
Contingency
Ecological time
Evolutionary time
Patch interactions
Compensatory changes among competitors, layers, contingent on trophic structure, indirect effects
Idiosyncratic species traits

The Search for Generality
Obstacles 3: Methods
Surrogate variables
Scale of observation (within or between patches)
Lack or impossibility of experiments

Intermediates to generality
• Bins of variation
– Forest vs. grassland
– Crown vs. surface fire regimes
– Biotic vs. physical disturbances
– Grazing vs. decomposing dominated ecosystems
– Supply side vs. competition-driven ecosystems

Approaches to generality
• Patch scale: resources & environment
• Multipatch scale: dynamic equilibrium, sustainability
• Species strategies: trait dispersion
– Evolutionary contingency
– Ecological contingency
• Normalization of spatial & temporal axes