ecosystem is gauged by the product of the diversity of its processes as scaled by the TST. The development capacity of the graminoid system (39,799 g C bitsm2 per year) is significantly higher than that of the cypress (14,659 gC bitsm2 per year), a difference that one might be inclined to attribute to the disparity in the scalar factor (TST) between the systems. When one regards the normalized ascendency, however, (ascendency is a measure of the constraint inherent in the network structure), one notices that the fraction of the development capacity that appears as ordered flow (ascendency/capacity) is 52.5% in the graminoids. This is markedly higher than the corresponding fraction in the cypress system (34.3%).
The graminoid system has been stressed by a number of modifications to the patterns of its hydrological flow, which have resulted in the loss of transitional glades, reduced hydroperiods, unnatural pooling, and over-drainage (Light and Dineen, 1994). In comparison with the cypress community, however, the system has exhibited fewer changes in its faunal community and is sustained by an abundance of flora and microbiota. The cypress ecosystem, like that of the graminoids, is limited by a dearth of phosphorus, which remains abundant in marine and estuarine waters and sediments. The graminoid system compensates for this scarcity of nutrients with a profusion of periphyton. Periphyton exhibits a high P/B ratio, even under oligotrophic conditions.
The natural stressors that affect the cypress ecosystem appear to have far greater impacts, in that they modulate the rates of material and energy processing to a far greater extent in that system. This analysis is phenomenological and there is no clear reason why the modulation of rates of material and energy occur in the cypress. Thus, even though these systems are (1) adjacent to one another, (2) share many of the same species, and
(3) some of the heterotrophs of the cypress feed off the graminoid system, the characteristic indices of the graminoid system remain distinct from those of the cypress community.
Calculating and ranking "relative sensitivities" proves to be an interesting exercise. For example, when the average trophic levels of the 66 compartments of the graminoid wetland ecosystem were calculated, lizards, alligators, snakes, and mink were revealed to be feeding at trophic levels higher than some of the "charismatic megafauna," such as the snail kite, nighthawk, Florida panther, or bobcat (Table 9.5).
The relative contributions to ascendency by the latter actually outweighed those of the former, however. The relative values of these sensitivities thus seemed to accord with most people's normative judgments concerning the specific "value" of the various taxa to the organization of the system as a whole (Table 9.5).
Similarly, in the cypress system white ibis, large fish, alligators, and snakes feed at high effective trophic levels, but the system performance seemed to be enhanced more by the activities of the vultures, gray fox, bobcat, and panthers (Table 9.5).
In comparing the component sensitivities in the graminoid and cypress systems, one discovers numerous similarities between the taxa of the two systems (Table 9.5). For example, the avian and feline predators ranked high in both systems. The contributions of snail kites and nighthawks to the performance of the graminoid system were highest (at ca. 14 bits), while that of the bobcat and panther were highest in the cypress (at ca. 13 bits). Both bobcat and panther seem to be more sensitive in the cypress than in the graminoids.
The low sensitivity of crayfish (0.99 bits) in the graminoids was not repeated in the cypress, although aquatic invertebrates generally had a low sensitivity in that system, too (2.01bits). The sensitivity of labile detritus was similar in both systems (around 1.5bits), while refractory detritus was more sensitive in the graminoid (1.59bits), indicating a greater importance in that system. The sensitivities of the primary producers are lower in the cypress (1.51 bits) than in the graminoids (1.66bits) and are uniform within both systems, except for Utricularia in the graminoids. Utricularia are carnivorous plants, and, therefore, both its effective trophic level and its sensitivities are higher than those of the other primary producers (Table 9.5). Utricularia can exhibit an interesting example of positive feedback in ecosystems; indeed, it harnesses the production of its own periphyton via intermediary zooplankton grazers. This subsidy to the plant apparently allows it to drive in oligotrophic environments that would stress other macrophytes with similar direct uptake rates. As ambient nutrient level rise, however, the advantage gained by positive feedback wanes, until a point is reached where the system collapses (Ulanowicz, 1995).
The cypress system exhibits an additional spatial dimension in comparison with that of the graminoids. The third, vertical (terrestrial) dimension of cypress vegetation provides both additional habitat and food for the higher trophic levels. In the cypress, the appearance of terrestrial vegetation affords increased herbivory by terrestrial fauna such as mammals, birds, and terrestrial invertebrates. Furthermore, much of what is produced by the bacteria is consumed by the higher trophic levels, and less production is recycled back into the detritus. With the addition of the arboreal dimension in the cypress, one would expect that system to be more productive than its graminoid counterpart, and that the total systems throughput (and, consequently, other systems properties) would be higher in the cypress as well. This is not the case, however. In fact, the throughput of the graminoids exceeds that
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