Victorin’s gentian COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

Predation

Bouillé (1996) observed a lepidopteran larva inside an ovary on a specimen from Beaumont. She reported that the seeds of the flower were very small and very dark compared to the others of the same individual, suggesting the possible impact of predation by insects on reproduction.

Mowing and flower picking

Mowing of the littoral zone by property owners along the St. Lawrence River has been observed at some localities and prevents the formation of flower stalks. Part of the habitat at Montmagny is mowed and is possibly the reason for the plant’s extirpation from the site. The same is true with respect to the picking of flowers to make bouquets, which was observed in the locality of Deschambault. Mowing and flower picking deprive gentian of its only means of reproduction and could result in its extirpation from certain localities. Such activity may be more common in areas frequented by numerous people walking along the shore as at Saint-Augustin-de-Desmaures and possibly at sites at Beaumont, anse de Vincennes, Sainte-Pétronille, and Saint-Nicolas, anse Ross.

Limited habitat

Victorin’s gentian is restricted to the freshwater and slightly brackish intertidal zone. Its habitat is limited in Quebec by the low tidal range upstream from Deschambault and the high water salinity in the region of Saint-Roch-des-Aulnaies downstream.

Ice scouring

Ice scouring of the rocks and shoreline during the daily tides and ice break-up in the spring could tear up some individuals. Such actions, also, may be beneficial in providing areas for seed establishment. It is uncertain, however, if such natural events have become more extensive than in earlier historic times prior to shoreline developments along the St. Lawrence R.

Water quality and level

Although the water quality of the St. Lawrence River is improving, it is still polluted. Several populations were observed covered with large clumps of algae and other aquatic vegetation. These had to be removed by the author before the plants, which were literally buried beneath the plant debris (Vallesneria americana, Potamogeton sp., etc.), could be counted. The subsequent tide should stir up the water and uncover the plants, but the range of the tides is variable. If the plants remain covered for too long, the flowering and survival of part of the populations could be compromised at these localities (Figure 4). No doubt, however, such impacts likely are also of natural occurrence and not primarily related to pollution.

Filling operations

Shoreline filling for the construction of homes, roads, railway lines or marinas has resulted in habitat loss for several species along the river. For example, railway construction at Cap-Rouge has destroyed virtually the entire natural shoreline between Saint-Augustin-de-Desmaures and Cap-Rouge, thereby preventing recolonization by Victorin’s gentian. The same is true for the municipalities forming the amalgamated cities of Quebec City (Sainte-Foy, Sillery, Beauport) and Lévis (Saint-Romuald, New-Liverpool, Lauzon). In 1996, the construction of a marina at Saint-Jean-Port-Joli destroyed a large part of the upper littoral zone. Miraculously, the Victorin’s gentian population was missed by just a few metres. In the 2002 inventory of this population, no plants were observed, despite the fact that the habitat is still present.

Oil spills

As in the case of Provancher’s fleabane (Sabourin et Paquette, 1991; Coursol, 1998), riparian colonies of Victorin’s gentian along the St. Lawrence River could be adversely affected by an oil spill.

Human trampling

Victorin’s gentian populations are highly exposed to human trampling and/or ATV traffic. ATV traffic in the intertidal zone poses a significant threat. ATVs not only cause plant mortality, but also profoundly alter the fragile balance of its habitat. Thus, the Victorin’s gentian population at Lotbinière is probably extirpated due to the repeated passage of ATVs in the upper littoral zone, where they disturb a swath ranging from two to sometimes ten metres wide. The report by Legault (1986) reported this problem for this locality and for the locality of Berthier-sur-Mer.

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