Influence of Collembolan Feeding Activities on Soil Metabolism at a High Arctic Site

The feeding biology of Hypogastrura tullbergi Schaffer and Folsomia regularis Hammer, the two most abundant species of Collembola on Devon Island, was examined. Gut contents of both species contained mainly organic matter, although H. tullbergi ingested significantly more fungus than F. regularis. In food preference tests H. tullbergi selected fungi over organic matter, whereas F. regularis preferred organic matter to fungus. At field temperatures, H. tullbergi grew rapidly on fungal diets, but lost weight on decaying organic matter. F. regularis showed similar growth rates on either fungus or organic matter. Transition Zone soil cores containing microorganisms and Collembola exhibited respiratory rates significantly higher than those containing microorganisms only, and this enhancement was greater than could be accounted for by the respiration of the animals themselves. Highest respiratory rates occurred in cores containing microorganisms and F. regularis. At the Beach Ridge this enhancement of soil metabolism in the presence of Collembola was less obvious, and it was suggested that abiotic factors were more important than biotic interactions in controlling soil respiration. Mechanisms whereby the different feeding habits of H. tullbergi and F. regularis might influence decomposition rates were discussed.