OCCURRENCE OF VESICULAR-ARBUSCULAR MYCORRHIZAE IN PSEUDOTSUGA-MENZIESII AND TSUGA-HETEROPHYLLA SEEDLINGS GROWN IN OREGON COAST RANGE SOILS

Vesicular-arbuscular mycorrhizae (VAM) were common in seedlings of Pse udotsuga menziesii and Tsuga heterophylla grown in a greenhouse soil b ioassay in soils collected from the Oregon Coast Range. Although root samples were heavily colonized by ectomycorrhizal fungi (EM), VAM colo nization was observed in the cortical cells of both secondary and feed er roots. Vesicles, arbuscules, and hyphae typical of VAM occurred in 48% of 61 P. menziesii and 25% of 57 T. heterophylla seedlings. The ec ological significance of VAM presence in the Pinaceae, as well as inte ractions among VAM, EM, and the plant host, deserve future investigati on.