Research on Litter Disappearance

A study published in Ecological Applications looked at the effects of exotic earthworm invasions on the rates of leaf litter disappearance in a northern hardwood forest in south-central New York, USA. The researchers assessed whether differences in litter quality and the species composition of exotic earthworm communities affected leaf litter disappearance rates. (Suarez and Fahey 2006)

Two forest sites with contrasting communities of exotic earthworms were selected, and "disappearance rates of sugar maple and red oak litter were estimated in litter boxes in adjacent earthworm-free, transition, and earth worm-invaded plots within each site. After 540 days in the field, 1.7-3 times more litter remained in the reference plots than in the earthworm-invaded plots. In the earth worm-invaded plots, rates of disappearance of sugar maple litter were higher than for oak litter during the first year, but by the end of the experiment, the amount of sugar maple and oak litter remaining in the earthworm-invaded plots was identical within each site." (Suarez and Fahey 2006)

The composition of the earthworm communities was shown to significantly affect the patterns of litter disappearance. In the site dominated by the anecic earthworm Lumbricus terrestris and the endogeic Aporrectodea tuberculata, the percentage of litter remaining after 540 days was significantly less than at the site dominated by L. rubellus and Octolasion tyrtaeum. (Suarez and Fahey 2006)

This difference may be due to the differences in feeding behavior of the two litter-feeding species: L. terrestris buries entire leaves in vertical burrows and L. rubellus usually feeds on litter at the soil surface, leaving behind leaf petioles and veins. The results showed that earthworms not only accelerate litter disappearance rates, but also may reduce the differences in decomposition rates that result from different litter qualities at later stages of decay. (Suarez and Fahey 2006)