Document: MEL-3-63-27

Earthworms, fine roots, and soil microorganisms in a northern hardwood forest.

FISK, M.C* ¹, K.STRASSNER ¹, P.MGROFFMAN ², T.JFAHEY ¹ and P.JBOHLEN ³

Cornell University, Ithaca, NY 14853 USA ¹
Institute of Ecosystem Studies, Millbrook, NY 12545 USA ²
Archbold Research Station, Lake Placid, FL 33852 USA ³

Abstract:
Earthworms mix surface litter and forest floor material into the underlying mineral soil and thus profoundly influence the environment in which plants and soil microorganisms grow. As part of a larger study of the effects of earthworms on forest nutrient dynamics, we compared root distributions and microbial biomass and activity between northern hardwood forest stands with and without earthworms. These forest soils developed without native earthworms and have only relatively recently been invaded by exotic species. Earthworms eliminated the forest floor horizon and altered the distribution of organic matter and fine roots throughout the soil profile. Fine roots and organic matter were lower overall in soils where earthworms were present, and were concentrated in the upper mineral horizons rather than in the forest floor. Total soil respiration also was lower where earthworms were present. Despite lower total organic matter in soil profiles of sites with earthworms, biomass and activity of soil microorganisms were greater in worm compared to no-worm sites. The proportion of bacteria to fungi was not affected by earthworms, nor was respiration per unit microbial biomass (qCO₂). By mixing litter and forest floor material into the mineral soil and by changing fine root distributions throughout the soil profile, earthworms appear to increase the availability of organic matter to support microbial growth and activity in these northern hardwood forests.

Keywords: earthworms, fine roots, microbial biomass, microbial respiration

This abstract is being presented at: 3:30 PM in session:
MICROBIAL ECOLOGY