Asian pheretimoid earthworms are transforming soils, nutrient dynamics, soil food webs, and surface litter in temperate forests and horticultural landscapes of the United States. While these species of earthworms are often found in forests dominated by Acer saccharum, earthworm response to different litter types is unclear. A 95-day mesocosm study (randomized complete block design) was designed to test the consumption, productivity, fitness, and fecundity of species Amynthas agrestis and A. tokioensis, separately and in combination. Earthworms had contact with one of five litter treatments: maple (A. saccharum), oak (Quercus alba and Q. macrocarpa), pine (Pinus strobus), pooled native prairie grasses (Andropogon gerardii, Panicum virgatum, and Sorghastrum nutans), or none (soil only). Mescosms contained either six A. agrestis, six A. tokioensis, or three A. agrestis + three A. tokioensis. All combinations were replicated six times (90 total mesocosms). Earthworm mass, cocoon count, dry litter mass, and the C:N ratio of litter and soil were collected every three weeks.
Results/Conclusions
Both species A. agrestis and A. tokioensis lost body mass at the end of 95 days compared to starting weight, regardless of litter type. Across all mesocoms, A. agrestis experienced greater mortality than A. tokioensis; by day 63, all A. agrestis worms were dead. Only four worms survived until the end of the experiment, and all were of the A. tokioensis-only treatment. Amynthas tokioensis had the greatest survival rate when in the presence of maple litter. Overall, A. tokioensis produced 340 total cocoons while A. agrestis produced 60 (P=0.0126). Of these, A. tokioensis produced 233 and 79 cocoons in the maple and oak litter treatments respectively. The highest number of cocoons produced by A. agrestis was 19, in oak litter with both worm species present. However, all of these cocoons were produced in the first 21 days of the experiment. Litter consumption and C:N ratio of litter and soil were highly variable across treatments. Our results suggest that A. tokioensis may survive and produce cocoons in in the presence of sugar maple litter and to a lesser extent in oak litter. These data will help evaluate the potential risk of A. tokioensis and A. agrestis invasion in different habitats.