| Summary: | Effects of power line maintenance on mycorrhizal fungi associated with black spruce (Picea mariana (Mill.)B.S.P.), tamarack (Larix laricina (Du Roi) K. Koch) and jack pine (Pinus banksiana Lamb.) were studied at nine right-of-way (ROW) sites in north central Manitoba. Transmission corridors treated with Tordon 101 and Tordon I0K at various times in the past (i.e. 1991, 1990, 1987, 1984, 1974) were chosen for study. Analysis of variance (ANOVA) results comparing individual seedlings show that mean mycorrhizal levels within the ROW are between 20 - 50% lower than within the forest at most sites. Exceptions are at the ROW sites treated with Tordon I0K at Mafeking, Manitoba, were levels of mycorrhizal infestation seem to be enhanced. Although mycorrhizal levels are lower in sprayed ROW sites compared to unsprayed ROW sites, these differences are not significant in three out of the four cases studied. This suggests that the initial disturbance of the ROW from line clearance, along with related changes in the habitat, and not herbicide treatments with Tordon 101, are responsible for the reduced levels of mycorrhizae within the ROW sites. Levels of mycorrhizal infestation after application of herbicides follow expected phenological patterns as mediated by seasonal affects. The significantly increased levels of infestation found within the ROW ten months after herbicide treatment with Tordon 101, may indicate a stimulatory effect of the spray treatment on mycorrhizae. If Tordon 101 is enhancing fungal activity within the ROW, this will encourage conifer survival and is thus contrary to ROW management objectives. Phenological changes in mycorrhizal infestations, as affected by site parameters, soil factors and herbicide usage, are modelled.
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