1. Disturbance & Succession Satellite image taken Aug. 29, 2005
Change in Communities
Disturbance & Succession
“If you live in Louisiana, there are only two possibilities: either your land
will eventually flood,
or it will eventually burn.”
Keddy (2008)
Water, Earth, Fire: Louisiana’s Natural Heritage
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Hurricane Katrina
Satellite image taken Aug. 29, 2005
Image from

2. Change in Communities Disturbance & Succession
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Indonesian island.
Wikipedia “Krakatoa” page; accessed 29-X-2014.
Anak Krakatau (emerged from the sea as new volcanic island in 1927)
Satellite image taken June 11, 2005
Image taken by Ikonos satellite from Wikimedia Commons

3. Change in Communities Disturbance & Succession
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Feral hog disturbance to seepage bog at Eglin Air Force Base, FL
Photo taken October 25, 2014
K. Harms’s photo

4. Succession, Disturbance & Stress
Succession – directional change in community composition at a site (as opposed to simple fluctuations), initiated by natural or
anthropogenic disturbance, or the creation of a new site
Some biologists restrict the definition to directional
replacement of species after disturbance
Disturbance – a discrete event that damages or kills residents
on a site (and potentially creates opportunities for other
individuals to grow or reproduce);
either catastrophic or non-catastrophic
(Platt & Connell 2003 Ecological Monographs)
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Platt, William J. & Joseph H. Connell Natural disturbances and directional replacement of species. Ecological Monographs 73:
Stress – abiotic factor that reduces growth, reproduction, or survival of individuals (and potentially creates opportunities for other individuals)

5. Disturbance
Catastrophic disturbance – a disturbance that kills all residents of
all species on a site; i.e., creates a “blank slate”
(Platt & Connell 2003 Ecological Monographs)
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Platt, William J. & Joseph H. Connell Natural disturbances and directional replacement of species. Ecological Monographs 73:
Mt. St. Helens, Washington, U.S.A.
May 18, 1980
Photo of Mt. St. Helens from Wikimedia Commons

6. Disturbance
Non-catastrophic disturbance – a disturbance that falls short of wiping out all organisms from a site; i.e., leaves “residual organisms” or “biological legacies” (Platt & Connell 2003 Ecological Monographs)
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Platt, William J. & Joseph H. Connell Natural disturbances and directional replacement of species. Ecological Monographs 73:
Yellowstone Nat’l. Park, U.S.A.
just after 1988 fires
Luquillo Experimental Forest, Puerto Rico
just after 1989 Hurricane Hugo
Photo of Yellowstone in 1988 from Wikimedia Commons;
Photo of Luquillo Forest, Puerto Rico in 1989 from

7. Intensity, Frequency & Extent
Disturbance
Intensity, Frequency & Extent
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Bowman, Hacker & Cain (2017), Fig. 17.4

8. Disturbance & Succession
Primary Succession – succession that occurs after the creation of
a “blank slate,” either through catastrophic disturbance or
de novo creation of a new site
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Mt. St. Helens, Washington, U.S.A.
May 18, 1980
Anak Krakatau, Indonesia
appeared above water 1927
Photo of Mt. St. Helens in 1980 from Wikimedia Commons; Photo of Anak Krakatau from

9. Disturbance & Succession
Secondary Succession – succession that occurs after
non-catastrophic disturbance (including “old fields”)
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Yellowstone Nat’l. Park, U.S.A.
just after 1988 fires
Luquillo Experimental Forest, Puerto Rico
just after 1989 Hurricane Hugo
Photo of Yellowstone in 1988 from Wikimedia Commons;
Photo of Luquillo Forest, Puero Rico in 1989 from

10. Disturbance Bowman, Hacker & Cain (2017), Fig. 17.5
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Bowman, Hacker & Cain (2017), Fig. 17.5

11. Disturbance & Succession
Henry Chandler Cowles
Lake Michigan sand dunes – late 1800s
Concluded that sites on the dunes were older further inland, i.e., formed a “chronosequence” from which temporal change could be inferred
(space-for-time substitution)
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Photo of Cowles from
photo of Lake Michigan sand dune from

12. Disturbance & Succession
Frederick Clements
Radical, “superorganism” view of communities; species interact to promote a directed pattern of community development through “seral” stages, ending in a “climax” community
Henry Gleason
“individualistic view of succession” in which “every species is a law unto itself”
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See Sharon Kingsland’s book…
Our modern population-biology view derives primarily from Gleason’s conceptual model, even though Clementsian ideas of deterministic progression through seral to climax stages dominated ecological theory well into the 20th century
Photos from

13. Disturbance & Succession Three Models of Succession
Connell & Slatyer (1977) The American Naturalist
1. Facilitation – Early-colonizing species modify the environment and enhance the establishment of later-arriving species (perhaps most likely in primary succession)
2. Tolerance – Early-colonizing species modify the environment, but have no effect on later-arriving species
3. Inhibition – Early-colonizing species modify the environment in ways that actively inhibit later-arriving species
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Connell, J. H. & R. O. Slatyer Mechanisms of succession in natural communities and their role in community stability and organization. The American Naturalist 111:

14. Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
One of the world’s most rapid and extensive glacial retreats in modern times
(so far); eliminated ~2500 km2 of ice in ~200 yr, exposing large
expanses of nutrient-poor boulder till to biotic colonization
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Photo of Glacier Bay National Park, Alaska from Wikimedia Commons

15. Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Reconstructed patterns of stand development at several sites within the chronosequence; intensively analyzed
tree-rings
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Fastie, Christopher L Causes and ecosystem consequences of multiple pathways of primary succession at Glacier Bay, Alaska. Ecology 76:
Bowman, Hacker & Cain (2017), Fig. 17.9, after Chapin et al. (1994) Ecol. Monogr. and Fastie (1995) Ecology

16. Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Species richness generally
increased with successional age
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Pioneer stage = lichens, mosses, horsetails, willows & cottonwoods.
Dryas drummondii = small shrub.
Reiners, W. A., I. A. Worley & D. B. Lawrence Plant diversity in a chronosequence at Glacier Bay, Alaska. Ecology 52:55-69.
Bowman, Hacker & Cain (2017), Fig , after Reiners et al. (1971) Ecology

17. Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
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Chapin, F. S. III, L. R. Walker, C. L. Fastie & L. C. Sharman Mechanisms of primary succession following deglaciation at Glacier Bay, Alaska. Ecological Monographs 64:
Soil conditions generally improved with successional age
Bowman, Hacker & Cain (2017), Fig , after Chapin et al. (1994) Ecological Monographs

18. Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Positive, negative, and neutral influences occur through succession
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This is consistent with facilitation, tolerance, and inhibition all operating under particular context-dependent circumstances.
Bowman, Hacker & Cain (2017), Fig , after Chapin et al. (1994) Ecological Monographs

19. Alternative Stable States
Strong interactor species appear to be especially important for determining the trajectory towards alternative stable states.
It is difficult to establish the existence of true alternative stable states, as opposed to different abiotic conditions
in the sites.
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Sutherland, J. P Multiple stable points in natural communities. American Naturalist 108:
Bowman, Hacker & Cain (2017), Fig , after Sutherland (1974) American Naturalist

20. Alternative Stable States
If a strong interactor species pushes a community into an
alternative stable state, even once that interactor species
is removed the community will remain in the alternative state
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Beisner, B. E., D. T. Haydon & K. Cuddington Alternative stable states in ecology. Frontiers in Ecology and the Environment 1:
In ecology, hysteresis refers to the existence of different stable states under the same environmental conditions.
Bowman, Hacker & Cain (2017), Fig , after Beisner et al. (2003) Frontiers in Ecology & the Environment