Influence of Grazing by Collembola on the Activity of Senescent Fungal Colonies Grown on Media of Different Nutrient Concentration

Vermiculite granules were impregnated with four concentrations (3.33, 16.67, 33.36 and 133.36 g I-1) of Czapek Dox solution and were inoculated with the fungus Botrytis cinerea. The cultures were then incubated in respirometers for 30 d before different numbers of Folsomia candida were added. Grazing by Collembola in cultures grown on the lowest nutrient levels produced a significant decline in fungal activity in comparison with controls. However grazing by animals in cultures grown on higher nutrient concentrations did stimulate fungal respiration, producing a maximum increase in cultures containing the highest nutrient levels of over 100% of respiration levels measured in controls. Changes in the numbers of animals in the cultures suggested that fungal respiration followed a bellshaped response to increases in grazing intensity. The results are discussed in relation to the influence of nutrient depletion and the accumulation of toxic metabolites on the response by senescent fungal colonies, in decomposing litter, to soil animal grazing.