Plantation Establishment in the Boreal Forest: Glyphosate, Hexazinone, and Manual Weed Control

Abstract

One manual and two chemical (mist-blown foliar spray of glyphosate and hexazinone) methods of vegetation control were applied in two 17.1 m × 17.1 m plots per treatment in a 1969 boreal cutover in Forest Section B7 where natural jack pine (Pinus banksiana Lamb.) regeneration, mostly about 1 m tall, was overtopped by post-harvest deciduous growth, including sapling aspen (Populus tremuloides Michx.). Season of application(fall = September 1976; summer = July 1977) and, for the chemical treatments, rate of application (0. 1, 2, and 4 kg ai/ha) were evaluated for their effect on (a) deciduous competition, (b) natural jack pine regeneration, and (c) white spruce (picea glauca [Moench] Voss) outplanted as bare-root 2 + 2 stock in June 1978. Annual or more frequent assessments were made through 1983. With (a), manual treatment was more effective in summer than in fall but did not effect sustained control. Of the fall-applied herbicide treatments, only glyphosate at 2 and 4 kg ai/ha was efficacious. Sustained control over several years was obtained with summer-applied glyphosate and, to a lesser degree, hexazinone. With (b), jack pine was not benefited by any treatment. With (c), frost and browsing obscured treatment effects, but the "best" control of deciduous vegetation was probably silviculturally detrimental to the spruce.