Environmental Engineering Reference
In-Depth Information
CHAPTER
11
Controls on Ecosystem Structure
and Function
Kathleen C. Weathers 1 , Holly A. Ewing 2 , Clive G. Jones 1
and David L. Strayer 1
1 Cary Institute of Ecosystem Studies, Millbrook, NY
2 Bates College, Lewiston, ME
What controls the character and functioning of ecosystems? In the previous chapters, we
saw examples of how the energetics and biogeochemistry of ecosystems are controlled by
a wide range of factors, such as inputs of nutrients and energy, disturbance, the activities
of organisms (including people), and the shape and size of the ecosystem itself. The topic of
controls over ecosystem structure and function turns out to be surprisingly complicated.
There is no simple, comprehensive framework to explain the myriad factors that govern
structure and function. Therefore, in this chapter, we offer some general observations about
ecosystem controls that can be used both in scientific studies and management contexts.
WHAT DO WE MEAN BY “CONTROL”?
In previous chapters, we described the components of ecosystems, the flows of energy
and materials between those components, and the flows of energy and materials between
ecosystems and the surrounding environment. In the broadest sense, we could say that a
factor controls an ecosystem if a change in that factor changes the size or nature of any of
these components or flows. In practice, we probably would reserve the term control for fac-
tors that have a large influence on the important components and flows (see Chapter 1 for
a discussion of what ecosystem scientists usually consider to be “important”). Thus, we
are much more likely to say that nitrogen inputs control a forest ecosystem if overall
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