Effectiveness of Repeated Manual Cutting and Glyphosate for Release of Engelmann Spruce from Mixed-Shrub Herb Vegetation

Abstract

Abstract This study, initiated in 1992, examined the effectiveness of repeated cutting for controlling vegetation in a mixed-shrub-herb community to release planted Engelmann spruce (Picea engelmannii) seedlings. Eight treatments were compared: (a) cut once in spring of 1992, (b) cut once in summer of 1992, (c) 3 yr of cutting once annually in the spring (mid to late June) starting in 1992, (d) 3 yr of cutting once annually in the summer (late July) starting in 1992, (e) 3 yr of cutting twice annually, in the spring and in the summer starting in 1992, (f) 2 yr of cutting twice annually, in the spring and in the summer starting in 1993, (g) application of glyphosate herbicide at 2.1 kg ai/ha during late August, 1992, and (h) an untreated control. Treatments were replicated 3 times in 30 × 30 m plots. Glyphosate treatment (g) and spring cutting treatments (c, e, and J) significantly reduced vegetation (vascular plant) cover and height compared to the control in 1993 and 1994. There were no significant differences in vegetation cover among treatments in year 5 (1996), but vegetation height was significantly lower in the glyphosate treatment (g) and repeated cutting treatments (c, d, e, and f) compared to the control. After 5 yr, spruce survival was high for both control (86%) and treated (> 91%) plots, with no significant (P ≤ 0.05) differences detected among treatments. Repeated cutting treatments (c, d, e, and f) and glyphosate treatment (g) significantly increased root collar diameter (rcd) over that of untreated (h) seedlings, and repeated summer cutting (d) significantly increased seedling height. Three years of repeated cutting (c, d, and e) increased rcd by 54%, and glyphosate (g) increased rcd by 46% compared to the control (h). At the end of year 5, seedlings receiving 3 yr of cutting (e) were not significantly larger than seedlings receiving only 2 yr of cutting (J). West. J. Appl. For. 15(3):154-162.