Abstract Formation of mycorrhizae on nonmycorrhizal western hemlock ( Tsuga heterophylla ) seedlings was examined in two separate outplanting studies in western Oregon. In both studies, seedlings were readily colonized by indigenous mycorrhizal fungi. In the first study, the number of short roots colonized by mycorrhizal fungi gradually increased through the season from a few in the first 2-3 months to nearly total colonization by fall. In the second study, mycorrhizal colonization readily took place on seedlings planted in both rotten wood and mineral soil on two different clearcuts. The same total percentages of short roots became colonized in rotten wood and mineral soil. Some mycorrhizal fungi occured in both rotten wood and soil, but others occurred only in one or the other substrate. Hemlock seedlings survived and grew well on both rotten wood and mineral soil during the first growing season after outplanting. On the most recent clearcut, however, seedling growth at the end of the season was significantly greater on mineral soil than on rotten wood. No other differences were observed. Forest Sci. 28:706-710.
Bradley R. Kropp (Wed,) studied this question.