Chemical or manual weed control in black spruce plantations? Case study in the balsam fir - white birch [ecosystem] in Quebec

摘要

Manual and chemical weed control methods were compared on 3 sites (dominated by raspberries) in black spruce [Picea mariana] plantations in the Lower-Saint-Lawrence and Gaspe regions of Quebec, Canada. Treatments included the use of brush cutters and machetes in 1991 and in 1991 + 1993, 4.4 litres Vision/ha (glyphosate) in 1991, and no treatment (control). The effects on growth were assessed after 1, 2, and 5 years. Weed control improved tree growth, resulting after 5 years in increased diameter (by 25.2-42.9%), height (12.5-24.8%) and mean volume index (89.3-168.6%) compared to control plots. Seedlings in treated plots showed superior growth rates, with growth differences increasing over time. No major differences were found between chemical andmanual-treated plots, due to relatively poor vegetation regrowth after treatment. However, repeated manual control resulted in significantly greater growth than after a single treatment. Survival rate was not significantly affected by any treatment, except when seedlings suffered mechanical damage.