ORIBATID MITE COMMUNITIES OF OLD BALSAM FIR (ABIES-BALSAMEA (L.)) FORESTS OF WESTERN NEWFOUNDLAND, CANADA

The oribatid mite faunas of mature balsam fir (Abies balsamea (L.)) - fern (Dryopteris) and balsam fir - horsetail (Equisetum) forests of we stern Newfoundland, Canada were investigated through Berlese funnel ex traction of 1000 cm(3) soil samples. Because fir - horsetail forests a re richer in terms of nutrients and plant diversity, they were hypothe sized to have the richer oribatid fauna. Seventy-three species represe nting 35 families were collected. Total oribatid density was higher in the balsam fir - fern sites, whereas species diversity was greater in the balsam fir - horsetail sites. The dominant species were similar i n both forest types but individual species densities differed. Several of the more uncommon species were restricted to one forest type. It i s suggested that wetter, denser soils of the fir - horsetail forest ar e responsible for their lower mite density but the more diverse flora produced more niches permitting a more diverse fauna. Vertical distrib ution of the more abundant species was compared between the upper and lower 5 cm of the soil profile. Both species diversity and abundance d ecreased with increasing soil depth. The relative abundance of smaller mites such as Oppiella washburni and Suctobelbella spp. increased wit h depth, whereas larger species such as Parachipteria travei decreased .