Abstract
This study addressed differences between
Diplocardia spp. (a native North American earthworm) and
Octolasion tyrtaeum (an introduced European species), with respect to behavior, influence on soil microbial biomass, and plant uptake of N in tallgrass prairie soils. We manipulated earthworms in PVC-encased soil cores (20 cm diameter) over a 45-day period under field conditions. Treatments included: (1) control with no earthworms, (2)
Diplocardia spp. only, and (3)
0. tyrtaeum only. Prior to addition of earthwoms, seedlings of
Andropogon gerardii (a dominant tallgrass) were established in each core, and a dilute solution of
13C-labeled glucose and
15N-labeled (NH
4)
2S0
4 was added to the soil to facilitate examination of earthwonn/microbe/plant interactions. We found that
Diplocardia spp. were significantly more active than
0. tyrtaeum, and quickly assimilated
13C and
15N from the tracer. Individuals of
Diplocardia spp. were present at shallower soil depths than
0. tyrtaeum throughout the study. Contrary to expectation, this greater activity of
Diplocardia spp. did not result in increased plant productivity. Rather, the activity of
Diplocardia spp. was associated with less plant growth and smaller amounts of N acquired by
A. gerardii seedlings compared to controls or
0. tyrtaeum treatments. We observed few significant influences of earthwonn treatments on microbial biomass C or N pool sizes, but the microbial C/N ratio was consistently greater in the presence of
Diplocardia spp. relative to
0. tyrtaeum. Results of this study indicate that activity of earthworms may enhance competition for N between microbes and plants during the growing season in tallgrass prairie.
Keywords
Grassland,
microbial biomass,
soil invertebrates,
nitrogen,
stable isotopes
Citation
Callaham, Mac A., Jr.; Blair, John M. 2001. Different behavioral patterns of the earthworms
Octolasion tyrtaeum and
Diplocardia spp. in tallgrass prairie soils: potential influences on plant growth. Biol Fertile Soils (2001) 34:49-56