The feeding preferences of decomposers and their effect on the nutrient levels in soil: a study of earthworms, Lumbricus rubellus.

Abstract

Ever since Charles Darwin chose to study the cycling of leaf matter by earthworms, they have been the subject of extensive studies. Of these studies, few have tried to ask what is the feeding ecology of the earthworm and how it effects the soil. To determine how Lumbricus rubellus, an earthworm found in Northern Michigan, feed, and what effect its feeding has on the soil, several experiments were run. In one experiment, the earthworms were given the choice of six types of leaf species in order to determine if they exhibited a feeding preference in relation to nutrient content of the leaves. In another experiment, earthworms fed on the same six leaf species separately and their excrement and the soil was analyzed. From the first experiment it was found that earthworms tended to prefer leaves with higher nutrient content the most and the leaves with the lower nutrient content the least. In the second experiment, it was found that while earthworm excrements contained the same levels of nutrients, the carbon levels of the soils differed in relation to which leaf species were consumed. From this, it was inferred that earthworms exhibited different feeding rates for different nutrient contents of the leaves. The leaves with the highest nutrient content were eaten more rapidly and the leaves with the lowest nutrient content were eaten at a slower rate.