108 



LEFFLER 



TABLE 1 



STABILITY RANK ORDERING OF FOUR DIVERSITY 

 LEVELS IN AN AQUATIC MICROCOSM EXPERIMENT* 



*System A contained 10 species; system B, 17; system C, 21; and system D, 

 25. The predicted ordering for all stability measures from least to most stable is 

 A-B-C-D. Parentheses indicate ties in ranking. 



fMicroscopic and bacterial counts were combined. 



:|:Data were not determined. 



nutrient storage compartments and the rates of nutrient movement 

 through them. Details of these experiments are described elsewhere 

 (Leffler, 1977). 



Microcosm behavior was plotted for each of the four types of 

 systems and was analyzed according to the criteria described in 

 Fig. 1. Constancy, resistance, response time, resilience, and total 

 relative stability of each parameter were calculated for each 

 microcosm type to rank each of the four diversity levels from most 

 stable to least stable. Results of this analysis are shown in Table 1. 

 Observed rankings seldom correlated with predicted rankings. No 

 significant relationship between taxonomic diversity and any of the 

 five stability measures could be demonstrated. These results were 

 interpreted to refute the generality of the diversity— stability 

 hypothesis. This does not deny that under some circumstances 

 diversity and stability may be related, but confident estimates of 

 ecosystem stability based on counting taxonomic units do not appear 

 justified by these results. 



The Relation Between Nutrient-Energy Subsidies and Ecosystem Stability 



Several researchers have proposed that large abiotic nutrient 

 reserves, together with such energy subsidies as tidal action, may 



