Environmental Engineering Reference
In-Depth Information
Is the pathway of successional change ordered
because the mechanisms that cause succession
need to occur in a proper sequence or can the
steps in the order be skipped in some cases? Is
there more than one ordered progression?
How much variability can be tolerated
before the apparent order in the
progression becomes recognized as
dicordered or chaotic?
Ecological Succession is an
ordered progression
of
structural and compositional changes in
communities
toward an eventual unchanging condition,
the climax community
.
The term “ecosystem” was invented to
replace “community” because some thought
that viewing the community as a direct
analogue to a living organism — with
succession an equivalent to embryological
development — was scientifically and
conceptually unwarranted
Can this condition be reached
before the dynamic climate
changes? If so, is there more
than one stable climax
community?
Fig. 3.2 Some of the basic issues in the nature of ecological succession arising from a standard
definition
that of Clements. He recognized as early as 1908 [
26
] that succession to be
retrograde as well as progressive as posited by Clements. Succession was not
necessarily an irreversible trend toward the climax community. Gleason also
recognized that the climate could change in contrast with Clements' theory of
vegetation undergoing succession in an unchanging climate. Gleason developed
what he called the “individualist concept” that succession is the result of environ-
mental requirements of the individual species that comprise the vegetation. He also
noted [
27
] that “
no two species make identical environmental demands.”
Gleason's concept of succession was a much more fluid and much less stereo-
typical concept of succession than that of Clements. Succession reflected the
interactions of individuals with the environment. It could change in its nature
with different climatic and other environmental conditions. It could progress or
regress to a more different, stable community depending on time and circumstance.
...
Henry Chandler Cowles
One of the founders of ecological concepts of plant communities in the United
States was the geologist turned ecologist, Henry C. Cowles, at the University of
Chicago [
11
]. Cowles [
28
] studied the pattern of ecological succession in a set of
sand dunes, the “Indiana Dunes,” which are now protected by the State of Indiana's
“Indiana Dunes State Park.” These dunes were formed sequentially from sediment
