Ecological Restoration (BIO 409)Dr. McEwan

Lecture 4: Equilibrium, Dynamics and Restoration

F. E. Clements was, during his prime, the most influential ecologist in the world. During ten year periods at the University of Nebraska and University of Minnesota he developed and refined the theory for which he is best known: ecological succession. The notion that community systems might go through a dynamic and orderly (and almost organic) set of stages leading to a stable assemblage of species known as the climax was the first attempt at a universal understanding within ecology, and proved an irresistible unifying force among its workers even as an increasing number of studies demonstrated various limitations to the theory. Clements left academia in 1917 to join the staff of the Carnegie Institution of Washington as a research associate; from this point on he moved in an increasingly Neo-Lamarckian direction, including attempting to demonstrate that acquired traits could be passed on to descendants. This work isolated him from the mainstream (and ended up unsubstantiable), but it did provide a target for workers involved in the Neo-Darwinian synthesis. The Biographical Dictionary of American and Canadian Naturalists and Environmentalists (1997), p. 157, succinctly lists Clements' major contributions as "development of formal theoretical framework for plant ecology, creation of system of ecological nomenclature, introduction of quantitative methods to the study of vegetation," and "extensive field research in plant ecology."

http://people.wku.edu/charles.smith/chronob/CLEM1874.htm

F. E. Clements

Put forth the idea that ecosystems arrive, ultimately, at a stable composition/structure, that is dictated by climate. The “Climatic Climax” community. When to exhaustive lengths describing the orderly phases ecosystems move through prior to arrival at the climax.

Was influenced by vegetation zonation, where if you at a certain elevation and aspect you see the same vegetation type over, and over, again across the landscape.

This idea is a predecessor to the idea of “Equilibrium Communities.” A more nuanced idea, to be sure, because it implies “balance” but, still emphasizes a deterministic process leading to a stability

http://people.wku.edu/charles.smith/chronob/CLEM1874.htm

1 & 2 are “equilibrium concepts.”

In number one the systems is passing through an orderly series of stages arriving at a common endpoint (box D) after that point the system does not change.

In two, the system is a bit less orderly, but still arrives at a stable endpoint.

Another way to think about equilibrium is a ball and cup model.

Journal of EcologyVol. 72, No. 1 (Mar., 1984), pp. 25-36 Published by: British Ecological Societyhttp://www.jstor.org/stable/2260004

Christensen and Peet (1984) provided some evidence to support convergence. They measured forests of a variety of ages across North Carolina and found that they were converging on a endpoint condition.

Most of eastern North America has been heavily disturbed, but the disturbance was NOT uniform. Some sites were burned 5 times, cut over, and then farmed, and then returned to forest. Some were cut only once. Some were only burned. Etc. Yet, we see really similar forests across a broad range… Equilibrium forces at work?

Manipulating ecosystem dynamics is an essential part of ecological restoration.

In many cases, you start from a system that is complete disarray- equilibrium forces are what you need to manage to drive the system toward the desired state.

But, what if the system has multiple-equilbria?

Manipulating ecosystem dynamics is an essential part of ecological restoration.

In many cases, you start from a system that is complete disarray- equilibrium forces are what you need to manage to drive the system toward the desired state.

But, what if the system has multiple-equilbria as demonstrated in 4 (or in a ball and cup diagram)?

Manipulating ecosystem dynamics is an essential part of ecological restoration.

In many cases, you start from a system that is complete disarray- equilibrium forces are what you need to manage to drive the system toward the desired state.

But, what if the system has multiple-equilbria as demonstrated in 4 (or in a ball and cup diagram)?

Or, what if the system had no equilibrium! This is demonstrated in 3, (or via a ball and cup diagram)

In fact, the idea of a climax community and equilibrium conditions has been all but annihilated in the ecological literature. Clements has been over-simplified and is now something of a joke. As an ecologist it is a bit embarrassing to be caught in something that smacks of being Clementsian!

Many have put for the idea that ALL ecosystems are disequilibrium communities. There are no stable enpoints, and things are constantly changing.

This is particularly prevalent among paleoecologists who point out that ecosystem drivers are in constant flux. Climate and anthropogenic processes have been dynamic for 15,000 years in eastern North America and ecosystems are constantly reacting to them.

Nevertheless, there are some real distinct patterns (forces) that restorationists have to deal with. Ecosystems near Dayton pretty much want to turn into hardwood forest… for instance.

[As an aside, the guy founded ESA and invented the quadrat!! His contributions are enormous…he just got a bit carried away and it has cost his reputation. I think this is a bit like Freud who is sort of a joke now for being wrong so often, but don’t forget Freud more-or-less invented the whole idea of psychoanalysis!! The idea that past events can shape current problems and that some of this can be worked through by talking through issues. Before Freud the best idea for someone disturbed was electrocution or sticking a knife up the nose into the brain…hmmmmmmmmm]

http://picasaweb.google.com/the.tsuga/GriffithWoodsCentralKY#

Case study = Griffith Woods, KY