We examined conifer and vegetation responses to pre-planting applications of glyphosate and hexazinone 30 years after establishment on a boreal site
with a history of logging and wildfire. The chemical treatments were effective in assisting the establishment of white spruce as a dominant tree in the
mixed-species stands that have developed. Only 100 stems per hectare of spruce were present in the aspen-dominated stand where no spruce planting
or other treatment had been conducted post-wildfire. Broadleaf trees were 19%, 24%, and 99% of the stand basal area in the glyphosate treated, hexazinone treated, and untreated areas, respectively. The untreated area was following a successional development trajectory typical of shade-intolerant tree species. The treatments had a strong influence on composition of the vegetation community 30 years after establishment. The variation of spruce, broadleaf trees, willow, and alder in both presence and stand structure reflected the site history. At this successional stage, the chemically treated areas had a greater diversity of native understorey plant species due to the variety of habitats created by disturbance rather than by the invasion of non-native species. Growth model projections indicated that total stand volumes 60 years post-disturbance were greater in the conifer-dominated chemically treated areas. After 30 years, the combination of treatments applied in this research trial created diverse plant communities, which over time are becoming more similar to those that develop after wildfire in similar boreal ecosystems.
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Updated August 05, 2015