of the cypress by some fourfold. Although the total biomass in the cypress is three times greater than that in the graminoids, the cypress system's P/B ratio is four times lower there than in the graminoids, thereby yielding the greater throughput in the graminoids.
The increase in throughput in the graminoids increases its development capacity and ascendency. The relative ascendency, which excludes the effects of the throughput, is perhaps a better index with which to compare these two systems. The relative ascendency of the graminoids is exceptionally high. For example, Heymans and Baird (2000) found that upwelling systems have the highest relative ascendency of all the systems they compared (which were mostly estuarine or marine in origin), but the relative ascendency of 52% for the graminoids is higher than any such index they had encountered. The relative ascendency of 34% reported for the cypress is lower than most of the relative ascendencies reported by Heymans and Baird (2000).
Some reasons behind the higher relative ascendency of the graminoids can be explored with reference to the relative contributions of the various components to the community ascendency (Table 9.5). The highest such "sensitivity" in the cypress is more than one bit lower than its counterpart in the graminoids, and, on average, most higher trophic level compartments that are present in both models exhibit higher sensitivity in the graminoids than in the cypress. It is also noteworthy that 41 compartments in the cypress show sensitivities of less than 5 bits, while only 28 compartments lie below the same threshold in the graminoids. The higher sensitivities in the graminoids owe mainly to the greater activity among the lowest trophic compartments, which causes the other compartments to seem rare by comparison. Thus, in the graminoids, community performance seems sensitive to a larger number of taxa, which accords with the analysis of dependency coefficients and stability discussed in Heymans et al. (2002). Pahl-Wostl (1998) suggested that the organization of ecosystems along a continuum of scales derives from a tendency for component populations to fill the envelope of available niche spaces as fully as possible. This expansive behavior is seen in the cypress system, where the arboreal third dimension of the cypress trees fills with various terrestrial invertebrates, mammals, and birds not present in the graminoids. The graminoid system, however, appears to be more tightly organized (higher relative ascendency) than the cypress in that it utilizes primary production with much higher turnover rates. This confirms Kolasa and Waltho (1998) suggestion that niche space is not a rigid structure but rather coevolves and changes in mutual interaction with the network components and the dynamical pattern of the environment. The graminoid system is more responsive, because it utilizes primary producers with higher turnover rates, and has, therefore, been able to track more closely environmental and anthropogenic changes. The cypress system, on the other hand, should have more resilience over the long term due to its higher overhead, especially its redundancy (Table 9.4).
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