Transcript Slide 1

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
Hurricane Katrina
Satellite image taken Aug. 29, 2005
Image from http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/katrina_goe_2005241_lrg.jpg
Change in Communities
Disturbance & Succession
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
Change in Communities
Disturbance & Succession
Feral hog disturbance to seepage bog at Eglin Air Force Base, FL
Photo taken October 25, 2014
K. Harms’s photo
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)
Stress – abiotic factor that reduces growth, reproduction, or survival of
individuals (and potentially creates opportunities for other individuals)
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)
Mt. St. Helens, Washington, U.S.A.
May 18, 1980
Photo of Mt. St. Helens from Wikimedia Commons
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)
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 http://pr.water.usgs.gov/public/webb/hurricane_hugo.html
Disturbance
Intensity, Frequency & Extent
Cain, Bowman & Hacker (2014), Fig. 17.4
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
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 http://amazingindonesia.net/2008/06/mount-krakatoa-the-wrath-of-earth
Disturbance & Succession
Secondary Succession – succession that occurs after
non-catastrophic disturbance (including “old fields”)
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 http://pr.water.usgs.gov/public/webb/hurricane_hugo.html
Disturbance
Cain, Bowman & Hacker (2014), Fig. 17.5
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)
Photo of Cowles from http://oz.plymouth.edu/~lts/ecology/ecohistory/cowles.html;
photo of Lake Michigan sand dune from http://ebeltz.net/folio/cfol-5.html
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”
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 http://oz.plymouth.edu/~lts/ecology/ecohistory/history.html
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 (if it occurs, it is
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
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
Photo of Glacier Bay National Park, Alaska from Wikimedia Commons
Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Reconstructed patterns of
stand development at
several sites within the
chronosequence;
intensively analyzed
tree-rings
Cain, Bowman & Hacker (2014), Fig. 17.9, after Fastie (1995) Ecology
Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Species richness
generally
increased with
successional age
Cain, Bowman & Hacker (2014), Fig. 17.10, after Reiners et al. (1971) Ecology
Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Soil conditions
generally improved with
successional age
Cain, Bowman & Hacker (2014), Fig. 17.11, after Chapin et al. (1994) Ecological Monographs
Disturbance & Succession
Primary succession along the Glacier Bay chronosequence
Positive,
negative,
and neutral
influences
occur
through
succession
Cain, Bowman & Hacker (2014), Fig. 17.12, after Chapin et al. (1994) Ecological Monographs
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.
Cain, Bowman & Hacker (2014), Fig. 17.17, after Sutherland (1974) American Naturalist
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.
Cain, Bowman & Hacker (2014), Fig. 17.18, after Beisner et al. (2003) Frontiers in Ecology & the Environment