A study of the effects of red raspberry (Rubus strigosus Michx.) on black spruce (Picea mariana (Mill.) B.S.P.) seedling morphology

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University of New Brunswick


A study was conducted by the Canadian Forestry Service on Fraser's Inc. Plaster Rock limits to determine the effects of wild red raspberry (Rubus strigosus Michx.) competition on black spruce (Picea mariana (Mill.) B.S.P.) morphology. This study was conducted because raspberry, which is a very difficult species to control, is a major competitor species on Fraser's reforested sites in this region. A Competition Index (CI) was devised to examine the relationship between raspberry intensity and spruce seedling morphology. The CI was based on light intensity (ie. raspberry intensity) and height of competition. A random survey of 240 seedlings was conducted on a black spruce plantation on Fraser's limits. Linear regression analysis was performed to see if a relationship existed between CI and relative volume (D2 H), total height, leader length and stem diameter. A linear relationship was found which meant that CI was of value in explaining the variability of the four measured values. The independent variable of the regression, CI, best explained the variability in the diameter of the sampled seedlings. It was discovered that low levels of associated vegetation affected the growth of the seedlings. Better results might have been obtained if a measure of the dry weight of the seedlings were calculated rather than the relative volume. It was observed that on the plantation studied, the timing of silvicultural management operations were such that the raspberry competition was allowed to establish on the site for two years before the site was planted. This- allows the aggressive raspberry competition to quickly re-establish the scarified row produced by the disc trencher on this site. Thus the plantation was placed in a situation where release is required before even becoming established. It was recommended therefore that they try a timing of silvicultural operations of cut, site prepare and plant during the same year and assess the plantation development and determine whether tending requirements are diminshed. Another recommendation was to study the timing of herbicide treatments on sites where the dominant competition is raspberry to determine the most economical time to apply a treatment.