Corn (Cotton, 

 Soybeans) 



Soil or 



Vermiculite 



+ Water 



Figure 2. The "terrestrial monoculture" system of Metcalf and coworkers^ employs 

 a crop grown in soil or vermiculite in a 1 9-1. carboy and additions of slugs, 

 insects, and a Prairie vole {Microtus ochregaster). Subsequently, the 

 terrestrial species are removed and analyzed, while the system is flooded 

 and then innoculated as for the "farm pond " Additions of Daphnia. snails 

 and Gambusia are analyzed after three days, then the water is drained to 

 estimate soil/sediment sorption. 



seemed to be a reasonable alternative. Natural resources could be protected by 

 foregoing testing in the field. Systems could be replicated and operated under 

 controlled, standardized conditions, much as are single-species assays. A number of 

 advocates pointed out so many advantages, in fact, that expectations easily exceeded 

 achievements. 



Nevertheless, when the terrestrial microcosms were reviewed by chemists, 

 biologists, mathematicians, and regulators in 1977,' they found that research did 

 support a number of positive values of microcosm technology. 



Fate and effects studies can be carried out simultaneously in the same system to 

 provide a more meaningful measure of dose-response in a system reflecting 

 interactions of processes; 



The systems are more easily replicated and controlled than field studies, yet 

 they still yield data on ecosystem function; 



157 



