Earthworm preference: analzying the effects of soil moisture, pH, and calcium levels on the distribution of Lumbricus rubellus.

Abstract

Studies have shown that the earthworm, Lumbricus rubellus, is often less abundant in soils with lower pH. However, it is not known if earthworms physiologically cannot tolerate low pH or if low pH soils lack nutrients (e.g., calcium) that are necessary for earthworm survival. To determine the effects of pH, moisture, and calcium levels on earthworm distribution, soil samples were taken at four separate sites, and the pH, moisture, and calcium levels of each were recorded. Experiments were run by manipulating the pH, moisture, and calcium levels of these soils and adding worms from each of the sites to test soil preference of worms. The worms preferred soil with relatively high moisture, calcium, and pH levels. The preference by the worms depends upon the original pH, calcium, and moisture levels of the soil from which the worm was taken. Since acid rain affects soil pH and, therefore, calcium levels due to increased nutrient leaching, we conclude that an increase in acid rain could affect earthworm habitat. However, further studies are needed to assess the magnitude to which earthworm habitat would be affected.