Manipulating earthworm abundance using electroshocking in deciduous forests

Abstract

Earthworms influence the biotic and abiotic characteristics of soils, but studying these effects in situ is challenging. Secondary forests in the Mid-Atlantic have abundant earthworm communities. To investigate the interaction of earthworms with the below- and aboveground part of the ecosystem, we manipulated earthworm densities in 1 m 2 enclosures located at 12 study sites within four different-aged forest stands at the Smithsonian Environmental Research Center (SERC) in Maryland, USA. The treatment plots were created by trenching around the perimeter and lining the trenches with fiberglass mesh before backfilling. Two types of untrenched plots served as control and leaf litter treatment plots. Enclosures were electroshocked between four and nine times over a two-year period to remove earthworms and to compare densities among treatment and untrenched plots. Earthworms were weighed and identified to determine whether removal by electroshocking varied depending on body size or ecological grouping. Earthworm abundances were 30–50% lower in reduced-density enclosures than in high density enclosures; however, the efficiency of the exclusion treatments varied by earthworm size and ecological group. Manipulating earthworm populations in temperate forests to assess their influence on ecological functions is feasible using electroshocking, but careful planning is essential given the amount of effort required to set up and maintain the desired experimental conditions.