EFFECTS OF CONIFER RELEASE TREATMENTS ON THE GROWTH AND FRUIT PRODUCTION OF VACCINIUM SPP. IN NORTHWESTERN ONTARIO

Berry production and vegetative recovery of lowbush blueberry (Vaccini um angustifolium Ait.) and velvet leaf blueberry (Vaccinium myrtilloid es Michx.) were documented for three growing seasons (1994, 1995, 1996 ) after brushsaw, single operational and multiple nonoperational Visio n(R) herbicide (active ingredient glyphosate), and control treatments in a jack pine (Pinus banksiana Lamb.) plantation in northwestern Onta rio. Vaccinium angustifolium fruit production was significantly (P les s than or equal to 0.05) reduced by both the single and multiple treat ments in all 3 years of the study. Fruit production by V. myrtilloides was significantly (P less than or equal to 0.05) reduced only by the multiple treatment. The significant reduction in berry production by V . angustifolium contributed to an overall drop in the availability of blueberries (both species combined) on sprayed clearcuts in 1995 and 1 996. Single and multiple treatments also significantly (P less than or equal to 0.05) reduced fresh mass and dry mass of total berries in 19 95 and 1996. Compared with the controls, reductions in cover for both blueberry species were only significant (P less than or equal to 0.05) with the Vision(R) treatments. In clearcuts where V. angustifolium fo rms a major component of the Vaccinium spp. cover, the short-term redu ction in fruit availability in sprayed areas may be considerable.