SINGLE-TREE INFLUENCE ON EARTHWORMS IN FOREST SOILS IN EASTERN KENTUCKY

Vegetation may affect earthworm populations directly through inputs of litter and leachates, and indirectly through alteration of soil properties. This study examined the characteristics of earthworm populations on an area where small-scale spatial patterns in soil properties were previously shown to be due to the influence of individual trees and understory species. Earthworm densities in the O horizon and in the upper 20 cm of mineral soil ranged from 0 to 20 and from 0 to 80 individuals/m2, respectively. Density was significantly lower in mineral soils under both yellow poplar (Liriodendron tulipifera L.) and eastern hemlock (Tsuga canadensis [L.] Carr.) when rhododendron (Rhododendron maximum L.) was present in the understory, compared with under the same two tree species when rhododendron was absent. Bimastos parvus Eisen, a species characteristic of inhospitable sites, was dominant on rhododendron plots, but was replaced by Komarekiona eatoni Gates and Eisenoides carolinensis Michaelsen in the absence of rhododendron, especially on plots under yellow poplar. In mixed-species forests, abundance and species composition of earthworm assemblages are spatially variable in correspondence with patterns of soil properties and of the occurrence of tree and understory plant species.