Long-term glyphosate persistence in native plants and its effect on nutrient profiles in British Columbian forests

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Glyphosate is the active ingredient in herbicides used to treat unwanted vegetation in agricultural and forestry settings. Most plant material dies within a few months of application to foliage, given the appropriate dose (Roy et al. 1989, Feng & Thompson 1990). Over the longer-term, plants receiving a lower dose or incomplete treatment, or those plants that are resistant or tolerant to glyphosate, continue to survive and grow. In these cases, glyphosate persists in plant tissues. The long-term presence of glyphosate in plants may lead to chronic low-level exposure to animals, including humans (Newton et al. 1984; Roy et al. 1989, Feng & Thompson 1990). Furthermore, glyphosate that accumulates in plant tissues may cause complex interactions with nutrients because of the chelating action of glyphosate (Mertens et al. 2018), thereby affecting long-term plant growth and nutrient bioavailability. This research will contribute towards identifying the timeline associated with glyphosate persistence in boreal forest plants, and identify whether or not persistence varies by species or plant type or by functional traits. Furthermore, this research will aid in determining the effect of glyphosate on nutrient bioavailability to plants, which will be vital for determining food quality for wildlife. We will sample native forest plants in northern British Columbia that have been treated with glyphosate within the last 12 years to identify trends in persistence and break-down of glyphosate. This knowledge will guide industry use of these products, and aid in decision-making around the use of glyphosate-based herbicides in native forests while providing information to public interested in plant gathering.