Victorin’s gentian COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

The habitat of Victorin’s gentian is the portion of the littoral located in the transition zone between the mid-and upper littoral portions of the freshwater and slightly brackish estuarine intertidal zone. This zone is covered by water for two to three hours per day during equinoctial high tides (Figure 4), but is seldom reached by low high tides. Brouillet et al. (1996) observed Victorin’s gentian in seven segments (1.45% of the segments sampled) of the 34 sampling sites and all of these segments (100%) were located in the upper littoral zone. The species grows in dense, high prairie cord-grass beds (Figure 5) and sometimes on sparsely vegetated raised outcrops. It occurs at the interface of the upper and mid-littoral or near openings in the vegetation of the upper littoral; with lower vegetation, it receives more light than in the upper littoral, where the herbaceous stratum is higher. It prefers thick surficial deposits (over 15 cm) of fine or mixed materials (seldom coarse), with no or very little stoniness (rarely very stony).

Figure 4. Victorin’s gentian habitat at Saint-Vallier.

Figure 4.  Victorin’s gentian habitat at Saint-Vallier.

Two other species designated by COSEWIC as species of special concern often occur in the same habitat with Victorin’s gentian: one population of Provancher’s fleabane and several populations of Victorin’s water-hemlock.

Trends

In his report, Legault (1986) mentions 20 populations of Victorin’s gentian, two of which were considered extirpated. Since then, several of the populations have been threatened or destroyed by shoreline filling. Thus, five of the known populations at that time are now extirpated and three are now historic, despite efforts by the author in recent years to locate them (Table 1). As a result, only 10 of the 20 known populations mentioned in Legault’s report (1986) are still extant.

Figure 5. Disturbances of Victorin’s gentian habitat at Saint-Jean-Port-Joli.

Figure 5.  Disturbances of Victorin’s gentian habitat at Saint-Jean-Port-Joli.

Potentially suitable habitat for Victorin’s gentian has declined dramatically in the Quebec City metropolitan region. Virtually all of the upper and middle littoral zones between Boischâtel and Cap-Rouge have been destroyed by highway and railway construction on the flats of the St. Lawrence River. Habitat quality has been seriously affected by filling operations in the upper littoral zone and the construction of a retaining wall for homes in the sectors of Lévis and Saint-Romuald and in several other residential sectors along the St. Lawrence River (Figure 5).

The introduction of tighter environmental legislation seems to have slowed or halted this trend. The major sampling effort by Brouillet et al. (1996) has advanced the state of knowledge of estuarine taxa and their ranges. Since the publication of the status report by Legault (1986), 32 new populations have been discovered, while others, such as those of Deschambault, Pointe Saint-Vallier at Saint-Vallier, Pointe Platon at Sainte-Croix, Pointe d’Argentenay at Saint-François, Grosse-Île and Saint-Augustin-de-Desmaures are large, accounting for over three quarters of all Victorin’s gentian plants. Since the report by Brouillet et al. (1996), the general status of populations appears to be stable, but there are a number of threats that could impact populations.

Protection/ownership

Two localities (Anse Saint-Vallier and Grosse-Île) are within the boundaries of protected areas: the Saint-Vallier Migratory Bird Sanctuary and the Grosse-Île and the Irish Memorial National Historic Site. Other ill-defined historic populations may occur within the boundaries of other protected territories: the L'Islet, Cap-Saint-Ignace and Trois-Saumons migratory bird sanctuaries. Most Quebec localities of Victorin’s gentian are on lands that do not have conservation status and the ownership of which is unclear. Victorin’s gentian habitat is located on public lands under the jurisdiction of the Quebec government. However, the localities in the R.C.M. of Cote-de-Beaupré (Boischâtel and Ange-Gardien) may be on private land and could be claimed down to the low tide water line. Cadastral surveys (legal boundary surveys) are required in order to identify these sites.

The Quebec Regulation Respecting Motor Vehicle Traffic in Certain Fragile Environments (R.S.Q., c. Q-2, r.2.2) protects Victorin’s gentian habitat by prohibiting access by motor vehicles to the tidal flats of the St. Lawrence River. The application and enforcement of this regulation could put an end to the problem of ATV traffic at Saint-Augustin-de-Desmaures.

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