The effects of forest practices on earthworm populations and soil microbial biomass in a hardwood forest in Missouri

Abstract

Physical changes caused by forest management practices can have a dramatic effect on the soil biota in a forest ecosystem. The effects of soil compaction associated with harvesting on earthworm populations and selected soil properties were measured in a hardwood (oak-hickory) forest in Missouri. Soils in this region of Missouri are characterized by a cherty residuum that is primarily of the Clarksville series (Loamy-skeletal, mixed, mesic Typic Paledults). Earthworms were collected from a 0–15 cm depth each spring and fall for 2 years by handsorting and their populations determined on a per square meter basis. Two native earthworm species, Diplocardia omata and Diplocardia smithii, were identified at this site. Regardless of species, juvenile populations accounted for a major portion of the earthworms found in spring or fall. In 1995, Diplocardia ornata was the dominant species present and most affected by soil compaction. In 1996, soil compaction seemed to have a less restrictive effect on earthworms. Harvesting had no effect on either earthworm populations or biomass but had a significant effect on selected soil properties. Harvest levels had a significant negative correlation with soil moisture, soil inorganic N, and soil microbial biomass C and N. When above-ground biomass like logs and forest floor litter were removed and the soil was compacted, the standing soil microbial biomass along with soil moisture content and nutrients were reduced. Time (season of the year) had a significant effect on earthworm populations and biomass and all soil properties that were measured in both 1995–1996. Future studies at this site might include a seasonal study on the ecology and reproduction of these native earthworm species.