Print PageOver 90 % of the forests in the Mid-Atlantic region are secondary forests at different successional stages. Soil macrofauna in these forests is often dominated by non-native European and Asian earthworms, but native species can also be present. In 2008 we established plots in two old (150 yrs) and two young (70 yrs) forests at the Smithsonian Environmental Research Center (SERC), Maryland, USA to study the effects of invasive European earthworms on soil properties, carbon dynamics, organisms (mesofauna, bacteria and mycorrhizal fungi), and tree seedlings. This study reports the effects on soil properties and mesofauna.
Three separate plots were established within each of four forests. In each plot, two earthworm addition and two earthworm removal quadrats (1m x 1m) were trenched and mesh was installed around the quadrats to prevent earthworms from moving in-and-out. Electroshocking was used to reduce earthworm abundance in the earthworm removal quadrats. Each quadrat was further divided into two half-quadrats that received beech (Fagus grandifolia) and tulip poplar (Liriodendron tulipifera) leaf litter amendments, respectively. An additional untrenched quadrat receiving natural leaf litter input was established as a control. The plots were established in June 2008, and soil and leaf litter samples were taken in July 2010.
Results/Conclusions
Soil pH differed among forests, plots, and quadrats, and was higher at a depth of 0-5 cm than at 5-10 cm. Soil pH in the tulip poplar treatment was higher than that in the beech treatment, and both leaf litter treatments had pH values higher than the controls. However, pH did not differ between earthworm addition and removal treatments. Bulk density differed among forests, plots, and quadrats, and was higher in young than in old forests and at a depth of 5-10 cm than at 0-5 cm, but there were no earthworm and leaf litter treatment effects. Inorganic N pool and N transformation rates varied greatly among plots. Reduced earthworm abundance increased fine root density in the beech half-quadrat in the old but not in the young forests. The abundance of mesofauna (Acari, Collembola, Araneidea, Pseudoscorpiones, Hymenoptera, Chilopoda, and Diplopoda) in the leaf litter layer was higher in the old than in the young forests. In this experiment previous land use, forest age, leaf litter input and earthworm abundance all influenced soil properties, but in a decreasing order.
