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Natural Disturbance Ecology
Mike Jenkins
Department of Forestry and Natural Resources
Purdue University
Tornado damage, north of Bedford, IN August 2011
Hardwood Ecosystem Experiment
Clearcut
Treefall gap, Donaldson Wood, IN
Hardwood Ecosystem Experiment
Single-tree selection
What is natural?
National Parks Closed For Annual Remajestification from The Onion May 24, 2010
Topics for today
• Characteristics of disturbance
• Common “natural” disturbances
– Wind events
– Treefall gaps
– Fire
– Herbivory (deer)
• Interactions and unexpected consequences
Disturbance
Any relatively discrete event in time that disrupts
ecosystem, community, or population structure
and changes resources, substrate availability, or
the physical environment.
White and Pickett (1985)
Peter S. White
S.T.A. Pickett
Disturbance terminology
• Area or size:
– Area disturbed (can be described in many ways relative to event
or time period)
• Magnitude:
– Intensity
• Physical force
– Severity
• Effects on the community
• Frequency:
– Mean number of events per time period
• Return Interval:
– 1/frequency
Can changes in disturbance regime be viewed as a
type of disturbance?
• Species present in any given environment are adapted to the
disturbance regime.
• Changes in the disturbance regime (frequency, severity, size,
seasonality) can lead to profound changes in community
structure and composition.
e.g., fire suppression
Wind Events
Tornado Damage, Great Smoky Mountains National Park 2011
Tornado Tracks - 1950-2010
White et al. (2011)
LIDs
Large Infrequent Disturbances
• Create early
successional
habitat
• Endpoints are
rare in the
contemporary
landscape
Gap Dynamics
• Gaps comprise 9.5% of
the forest area, 1% (on
average )of land area
in new gaps (Runkle
1982)
• Process drives unevenaged structure
• Old-growth structure
and processes
Fire!
Prescribed burn, Prophetstown State Park
Guyette et al. (In press)
“Man has possessed fire so long that an
inquiry as to whether it is a human
characteristic has some point.”
-Walter Hough
(1859-1935)
Curator of the National Museum
Historic fire
regime
Missouri Ozark Mountains
MFI=3.7
MFI=17.7
Guyette and Cutter 1997
Guyette et al. (In press)
Guyette et al. 2003
Ecological effects of fire
Three major effects
• Rapid decomposer of organic matter
– release of nutrients
– increase in soil pH
• Change in community structure
• Change in community composition
Herbivory
Deer herbivory study sites
Woody understory
Cades Cove
exclosures
Exclosures
50 < 200
40 < 50
30 < 40
20 < 30
10 < 20
Height (cm)
0 < 10
Controls
50 < 200
40 < 50
30 < 40
20 < 30
10 < 20
0 < 10
0
10
20
30
40
50
Acer rubrum
Liriodendron tulipifera
Liquidambar styraciflua
Tsuga canadensis
Quercus alba
other
Griggs et al. 2006
60
White-tailed deer
Herbivory: Exclosure Study, 1997-2006
Cades Cove, Great Smoky Mountains National Park
1.5
1.5
Exclosures
Controls
1
1
0.5
0.5
0
-2
-1.5
-1
-0.5
0
0
-0.5
-1
-1.5
0.5
1
1.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
-0.5
-1
-1.5
Webster et al. 2008
Trillium catesbaei
• Only Trillium species
found in substantial
numbers in Cades Cove
• Most common in mesic
to dry-mesic oakhardwood forests
• Long-lived and nonclonal
• Myrmecochory
Trillium catesbaei
Determining the age of T. catesbaei plants
Rhizome tip rot
Life Stage
Density (plants 100 m-2)
1200
Cades Cove
Whiteoak Sink
1000
800
600
400
200
0
Single-leaf Non-flowering
Flowering
Life Stage
Total
Jenkins et al. 2007
Height vs. Age
30
Cades Cove
Height (cm)
25
Adj. R2 = 0.13
20
15
Cades Cove
10
5
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18
Minimum age (yrs)
Jenkins et al. 2007
Height vs. Age
30
Cades Cove
Height (cm)
25
Adj. R2 = 0.13
Whiteoak Sink
Whiteoak Sink
20
Adj. R2 = 0.54
15
Cades Cove
10
5
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18
Minimum age (yrs)
Jenkins et al. 2007
Probability of Flowering vs. Height
1
Cades Cove
Probability of flowering
0.9
0.8
0.7
Max. % Correct Pred.
0.6
Cades Cove = 72.8
0.5
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
Height (cm)
Jenkins et al. 2007
Probability of Flowering vs. Height
1
Cades Cove
Whiteoak Sink
Probability of flowering
0.9
0.8
0.7
Max. % Correct Pred.
0.6
Cades Cove = 72.8
0.5
Whiteoak Sink = 83.3
0.4
0.3
0.2
0.1
0
0
5
10
15
Height (cm)
20
25
30
Jenkins et al. 2007
Probability of Flowering vs. Age
1
Probability of flowering
0.9
Cades Cove
0.8
0.7
0.6
0.5
0.4
0.3
Max. % Correct Pred.
0.2
Cades Cove = 86.7
0.1
0
0
5
10
15
20
Minimum age (yrs)
Jenkins et al. 2007
Probability of Flowering vs. Age
1
Cades Cove
Probability of flowering
0.9
0.8
Whiteoak Sink
0.7
0.6
0.5
0.4
0.3
Max. % Correct Pred.
0.2
Cades Cove = 86.7
0.1
Whiteoak Sink = 79.3
0
0
5
10
15
20
Minimum age (yrs)
Jenkins et al. 2007
Indiana State Parks
Species Richness (S)
30
Indiana State Parks
25
20
Axis 3
1.5
15
1.0
10
State Parks
Reference Areas
Species Evenness (E)
1.0
0.5
0.9
0.8
Axis 2
0.0
-1.5
0.7
-1.0
0.6
Shannon-Weiner Diversity (H')
State Parks
-0.5
0.0
0.5
1.0
1.5
2.0
-0.5
Reference Areas
3.5
3.0
-1.0
Axis 1: r2 = 0.148
Axis 2: r2 = 0.408
Axis 3: r2 = 0.197
2.5
2.0
1.5
State Parks
Reference Areas
Brown County SP
McCormick's Creek SP
Spring Mill SP
Morgan-Monroe SF
-1.5
Lindsay Jenkins et al. (in prep)
Woody Stems
50-200 cm
Parks
(b)
(a)
Total Density = 1,760 stems/ha
Acer saccharum
Fraxinus americana
Lindera benzoin
(a) Ribes spp. (b) Ulmus rubra
Prunus serotina
(a) Viburnum acerifolium (b) Rosa multiflora
(a) Staphylea trifolia (b) Sassafras albidum
Asimina triloba
Other
Reference
(c)
Total Density = 7,835 stems/ha
(d)
Total Density = 5,061 stems/ha
Acer saccharum
Fraxinus americana
Lindera benzoin
Ribes spp.
(c) Prunus serotina (d) Prunus pensylvanica
Viburnum acerifolium
(c) Cornus florida (d) Rosa multiflora
(c) Tilia americana (d) Fraxinus quadrangulata
Other
Total Density = 8,878 stems/ha
Jenkins et al. (in prep)
Unintended Consequences
Interactions
• Japanese stilt grass
• Periodic drought
• White-tailed deer
Cover of plant species guilds
Cades Cove exclosures
100
100
Forbs
Controls
Ferns
Graminoides
Other exotics
Microstegium vimineum
Woody plants
90
Percent Cover
80
70
60
Exclosures
90
80
70
60
50
50
40
40
30
30
20
20
10
10
0
0
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
Year
Webster et al. 2008
Microstegium
experimental response
to fire and direct seeding
Glasgow and Matlack (2007)
Purdue Farm: mapped stems
Canopy gaps
Influence of landscape on disturbance
• Distribution and spread
• Impacts on community types
Davis-Purdue Research Forest, Randolph County
What is natural?
National Parks Closed For Annual Remajestification from The Onion May 24, 2010
To keep every cog and wheel is
the first precaution of intelligent
tinkering. -Aldo Leopold, Aldo: Round River,
Oxford University Press