Environmental Engineering Reference
In-Depth Information
Many of the methods for measuring secondary production are focused on speciic species or groups
of organisms. One group in particular that is a common focus of lake management is the production
of those economically important species such as ish. So, from a management perspective, secondary
production is used to estimate the capacity of a system to support ish (Naiman and Bilby 1998).
16.2
GEOLOGIC LAKE SUCCESSION
16.2.1 d efInItIon
Ecological succession deals with the concept that natural systems tend toward, or transform themselves
to, some inal (relatively) or stable condition, and if disturbed or moved away from that condition, the sys-
tems are constantly undergoing change toward that condition. Natural succession then refers to the pro-
gression of ecological change along a continuum toward, or in the direction of, some climax condition.
Ecological succession from some “original” condition toward the climax community is often referred
to as primary succession, such as from rock to soil to plant colonization, etc. Secondary succession
occurs when there is some disturbance along that path, or some disturbance of an existing community.
Much of the early research on succession dealt with secondary forest succession, such as from
some disturbed community. In September 1890, Henry David Thoreau (Figure 16.2) read a paper to
the Middlesex Agricultural Society in Concord on “The succession of forest trees,” which is perhaps
the irst account of how forest succession works. A common example is that of pine communities,
which are often maintained by ire to which they are resistant. In the absence of ire or other dis-
turbances, pines will eventually be replaced by hardwoods. The overstory of the hardwoods will
eventually reduce light (by shading) such that the light-loving pines will no longer be able to grow.
One issue is that with the climax hardwood community, as the understory is reduced, the overall
biological productivity is reduced, even though there is substantial biomass. There are a number of
examples, such as tropical forests, where high biomass does not equate to high productivity. So, the
climax community is not necessarily the optimal community from some perspectives. While there
are many important and valuable species that rely on old growth hardwoods, for others, such as
many game species, the lack of an understory results in a biological desert. As a result, for example,
FIGURE 16.2
Henry David Thoreau.
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