Design and preliminary results from soil/litter microcosms

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Abstract
Soil/litter microcosms with “life support” systems were designed to maintain and monitor oxygen consumption, and community carbon dioxide and heat generation over extended time intervals. Mean coefficient of variation for oxygen consumption and carbon dioxide generation rates of replicate processed systems was 6.5 percent. An initial adjustment period of rapid respiratory rates and bacterial growth was observed for 10–14 days after microcosm preparation and incubation at 20°C. Soil and litter moisture had marked and expected effects on community respiration. Conditions of high moisture favored bacteria; fungi were more prevalent under low moisture conditions. Cadmium treatment of microcosms effected initial stimulation of respiration at 0.01 ppm CdCl2 and a delayed reduction (40 percent) of respiration at 10 ppm CdCI2 The combination of selenium plus cadmium caused more than an additive inhibition of respiration. Numbers of bacteria and fungi showed no detectable cadmium treatment effects.