Hurricane Katrina Satellite image taken Aug. 29, 2005 Image from 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

Image taken by Ikonos satellite from Wikimedia Commons Change in Communities Disturbance & Succession Anak Krakatau (emerged from the sea as new volcanic island in 1927) Satellite image taken June 11, 2005

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

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) Succession, Disturbance & Stress

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) Photo of Mt. St. Helens from Wikimedia Commons Mt. St. Helens, Washington, U.S.A. May 18, 1980 Disturbance

Luquillo Experimental Forest, Puerto Rico just after 1989 Hurricane Hugo 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) Photo of Yellowstone in 1988 from Wikimedia Commons; Photo of Luquillo Forest, Puerto Rico in 1989 from Yellowstone Nat’l. Park, U.S.A. just after 1988 fires Disturbance

Intensity, Frequency & Extent Cain, Bowman & Hacker (2014), Fig. 17.4

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

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

Disturbance Cain, Bowman & Hacker (2014), Fig. 17.5

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 photo of Lake Michigan sand dune from Disturbance & Succession Henry Chandler Cowles

Photos from Disturbance & Succession “individualistic view of succession” in which “every species is a law unto itself” Radical, “superorganism” view of communities; species interact to promote a directed pattern of community development through “seral” stages, ending in a “climax” community 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 20 th century Frederick Clements Henry Gleason

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 Three Models of Succession Connell & Slatyer (1977) The American Naturalist

Photo of Glacier Bay National Park, Alaska from Wikimedia Commons 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 km 2 of ice in ~ 200 yr, exposing large expanses of nutrient-poor boulder till to biotic colonization Disturbance & Succession

Primary succession along the Glacier Bay chronosequence Disturbance & Succession 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

Primary succession along the Glacier Bay chronosequence Disturbance & Succession Cain, Bowman & Hacker (2014), Fig , after Reiners et al. (1971) Ecology Species richness generally increased with successional age

Primary succession along the Glacier Bay chronosequence Disturbance & Succession Cain, Bowman & Hacker (2014), Fig , after Chapin et al. (1994) Ecological Monographs Soil conditions generally improved with successional age

Primary succession along the Glacier Bay chronosequence Disturbance & Succession Positive, negative, and neutral influences occur through succession Cain, Bowman & Hacker (2014), Fig , after Chapin et al. (1994) Ecological Monographs

Alternative Stable States Cain, Bowman & Hacker (2014), Fig , after Sutherland (1974) American Naturalist 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.

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 , after Beisner et al. (2003) Frontiers in Ecology & the Environment