Community Ecology



Community Ecology

Temporal dynamics of communities: succession

 

Outline:

1. Definition of community succession (primary vs. secondary)

    A.  Entails disturbance

    B.  Terminology: climax, sere/seral stage

2. Three original models of succession: facilitation, tolerance, inhibition

3. Animal community succession

4. Scale: succession is both a pattern and a process

    A. Space for time substitution = chronosequence

    B. Davis’ palynology work

 

Succession –

    requires disturbance for initiation

    2 main types of succession:

primary

secondary

 

Terminology (much from Clements):

    climax

    sere/seral stage

        properties of different seres - E. Odum 1969:

            - biomass, diversity, life cycles, size of organisms, GPP increase

            - NPP decreases

            - nutrient cycles become increasingly closed (little leakage of nutrients)

Clements vs. Gleason debate as to whether the climax is real (i.e., whether a community is a real entity or a human construct)

Importance of priority effects – Harper (1961)

 

3 types of community replacements (i.e., 3 types of priority effects): Connell and Slatyer 1977

1) facilitation –

2) tolerance –

3) inhibition -

Maubon et al. (1995) example -

Animal communities undergo succession, too:

    Kendeigh 1948 - bird diversity increases with successional age in Michigan

    Johnston and Odum 1956 - birds and old-field succession in GA

 

Succession is an example of an entity that is both a pattern and a process when viewed at different scales.

How do we short-lived humans study succession?

Two ways to document succession:

1. Observe seral stages in one area over time. Problem with this approach is that some successions occur over several hundred years. Thus, the temporal scale is often much too large for most ecologists to do.

2. Compare communities in several areas corresponding to different lengths of time since the onset of succession, from which the sequence of communities is inferred. This uses a "space for time substitution" (an indirect method) = chronosequence or chronoseries

        -Margaret Davis 1976 - U. Minnesota - palynology ( large-scale changes in biomes (resulting from climate change)

        -Overpeck et al. 1992:  plant communities are constantly changing (no climax)

 

Recall that the Clements/Gleason debate was over succession; this debated shaped community ecology by emphasizing competition (rather than altruism/mutualism), individualism.

        Then the reigning paradigm (Gleasonian) was somewhat modified to include a degree of determinism: that if random disturbances did not occur, then a quantitative knowledge of a site’s initial conditions would permit accurate prediction of climax community because certain species are consistently superior competitors than others and they “win” ( importance of competition in community ecology.

        Then along came Davis ( community stability is a matter of scale.

Summary:

Early on in community ecology, it was unclear whether succession was an integrative process operating at the community level as a whole (Clements) or whether it was simply the natural consequence of life-history differences among species (Gleason). Currently, it is understood that multiple factors that operate hierarchically drive temporal patterns of community composition. A community is the result of numerous processes in which short-lived colonizing spp. are eventually replaced by longer-lived ones that can tolerate local environmental conditions. The final community outcome is therefore based on species interactions (competition and survivorship), tempered by abiotic conditions; is basically a chance assemblage of species found in an area because they happen to have similar abiotic requirements and tolerances.

Three mechanisms (facilitation, tolerance, inhibition) describe interactions among the species during species replacements that happen in succession.

Some ecologists use the phrase “vegetation dynamics” instead of “succession” to emphasize that the population dynamics of interacting organisms are ultimately responsible for successional patterns. And some use “community dynamics” to be more taxonomically inclusive and emphasize that succession involves the dynamics of the entire complement of species interacting in communities, not just the plants. Either way, the point is that changes in community composition are a consequence of interactions among species that have different life-history strategies (Gleasonian) rather than a process operating only at the community level (Clementsian).

Currently, succession is viewed as a consequence of complex biotic and abiotic interactions, initiated by disturbance, and resulting from interspecific interactions, spatial dynamics, and history. Life-history characteristics of different species and interspecific interactions among them lead to changes in community composition over time. Seral stages are only somewhat predictable/repeatable with respect to species presence and their abundances.

I highly recommend chapter 13 in Morin (2011) for an overview of the history of how we have perceived and studied succession, including numerous approaches that I didn’t have time to cover today.

Next lecture: biodiversity

 

References:

 

Butterfield, B.J., J.L. Betancourt, R.M. Turner, and J.M. Briggs. 2010. Facilitation drives 65 years of vegetation change in the Sonoran Desert. Ecology 91:1132-1139.

Clements, F.E. 1916. Plant succession: analysis of the development of vegetation. Carnegie Institute of Washington Publication No. 242. Washington, D.C.

 

Connell, J.H., and R.O. Slatyer. 1977. Mechanisms of succession in natural communities and their role in community stability and organisation. Am. Nat. 111:1119-1144.

 

Davis, M.G. 1976. Pleistocene biogeography of temperate deciduous forests. Geoscience and Man 13:13-26.

 

Gleason, H.A. 1926. The individualistic concept of the plant association. Torrey Botanical Club Bulletin 53:7-26.

 

Harper, J.L. 1961. Approaches to the study of plant competition. Pp. 1-39 in: Mechanisms in Biological Competition (F.L. Milthorpe, ed.). Symposia of the Society of Experimental Biology 15, Cambridge University Press, Cambridge.

Johnston, D.W., and E.P. Odum. 1956. Breeding bird populations in relation to plant succession on the piedmont of Georgia. Ecology 37:50-62.

 

Kendeigh, S.C. 1948. Bird populations and biotic communities in northern lower Michigan. Ecology 29:101-114.

 

Maubon, M., J.-F. Ponge, and J. Andre. 1995. Dynamics of Vaccinium myrtillus patches in mountain spruce forest. J. Vegetation Science 6:343-348.

Odum, E.P. 1969. The strategy of ecosystem development. Science 164:262-270.

 

Overpeck, J.T., R.S. Webb, and T. Webb. 1992. Mapping eastern North American vegetation change of the past 18,000 years: no-analogs and the future. Geology 20:1071-1074.

 

Pickett, S.T.A., and P.S. White. 1985. The Ecology of Natural Disturbance and Patch Dynamics. Academic Press, New York, NY.

 

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