EARTHWORM POPULATIONS IN HEALTHY AND DECLINING SUGAR MAPLE FORESTS

Earthworm populations were assayed in 16 sugar maple groves of souther n Quebec, Canada. Total abundance and biomass of earthworms were reduc ed in declining stands compared to healthy stands. In 1987, the mean a bundance was 3 times higher and biomass 8 times greater in healthy map le stands. In 1988, the abundance was 8 times higher and biomass 34 ti mes higher in the healthy stands. In addition, the species composition , the diversity and the equitability of the earthworm community were r educed in declining sugar maple stands. Dominant species found in heal thy stands, such as Lumbricus terrestris, Aporrectodea trapezoides, an d A. turgida, were not found in declining stands. Earthworm abundances were lower in sampling sites located near trees than those distant fr om trees in declining stands. Conversely, healthy sugar maple stands s howed a slightly higher abundance when sampled at the base of trees. O verall, the unfavorable conditions found in declining sugar maple stan ds, such as low pH, low Ca++ concentration, and the thickness of the L FH horizon may have an important negative impact on earthworm abundanc e and decomposition activity.