Investigating the effects of disturbance and competition on establishment, growth, and reproduction of the endangered Ripariosida hermaphrodita
Master of Science (MSc)
Faculty of Science
Dr. Kevin Stevens
Ripariosida hermaphrodita (Virginia Mallow) is a perennial riparian plant with broad, maple-like leaves. It grows up to three meters high and is often found in large clonal patches, but sexually reproduces readily. While this plant may seem like a redoubtable competitor when growing in large colonies, it is declining across its range in North America. The only known occurrences in Canada are in southern Ontario. Prior to this study, no new populations had been recorded even though one of the known populations produces copious amounts of viable seed with potential to disperse. There are many hypotheses for its rarity, but the focus of this research is to investigate the lack of new population establishment. Many sources stated the plant has an affinity for disturbance, but the importance of disturbance for establishment has not been previously studied. A flood-born scouring disturbance may benefit seedlings by reducing plant competition and loosening the soil. Two studies were designed to examine how disturbance and/or competition facilitates R. hermaphroditaestablishment. For the first study, a field experiment incorporated a simulated scouring disturbance and competition reduction treatment within open and partially shaded canopies to examine their effects on the plant’s establishment, growth, reproduction, and survival. It appears the plant benefits from a scouring disturbance at the seedling emergence stage, but this does not benefit survival, growth, or reproduction. R. hermaphrodita required a reduction in competition from trimming to observe a benefit to survival, growth, and reproduction. For the second study, a survey was conducted to search for new populations of R. hermaphrodita and to revisit an older one. Three new occurrences were found, but all were located on the same stream where the largest population of the plant grows. The older population was found to in decline. The number of new occurrences is small, but there is now proof that the plant can disperse and establish outside of the two known populations.
Engelking, Daniel, "Investigating the effects of disturbance and competition on establishment, growth, and reproduction of the endangered Ripariosida hermaphrodita" (2023). Theses and Dissertations (Comprehensive). 2545.
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