Small-flowered lipocarpha (Lipocarpha micrantha) COSEWIC assessment and status report: chapter 5
HABITAT
Habitat requirements
Lipocarpha micrantha grows on sandy beaches that are subject to seasonal flooding, but are protected from high waves or strong currents. It is usually found in areas of very sparse vegetation, and apparently does not tolerate competition from other plant species. It co-occurs with other species common in these habitats, including a variety of Cyperus, Bidens, and Salix species. Cyperus squarrosus has been noted as an associate at every station in Canada. Further details are documented in Sabourin et al. (1992).
Trends
The quality of the habitat at the Missisquoi Beach, Quebec, location is unknown, although previous reports noted that water quality was poor (Sabourin et al. 1992).
The extent and quality of the habitat at the Holiday Beach, Ontario, site has declined significantly since the last survey in 1987 (Oldham, pers.commun., 2001). Water levels in the marsh are now kept artificially high to enhance duck hunting. As a result exposed mudflats have been almost totally eliminated from the open marsh and the swales between the marsh and the lake. Beyond the water control structure, the outlet channel has been dredged. The dredged sand is piled on areas that may have once supported Lipocarpha micrantha. One of the only areas where Cyperus squarrosus was observed was on wet sand at the edge of the heaped sand. The lakeshore beach is covered with mounds of rotting algae and aquatic macrophytes, probably Vallisneria americana. This may be a consequence of changing water quality. Whatever the cause, the dead material is certainly thick enough to smother any plants growing underneath.
In the present condition this habitat is unlikely to support Lipocarpha micrantha. It may be possible to restore the habitat while continuing to manage the marsh for duck-hunting. However, some alteration of the water control and channel dredging regime would be required. Further study is required to assess the cause and impact of the decaying aquatic vegetation on the beach.
The beaches north of Holiday Beach on the Detroit River are heavily developed. The populations documented there in 1892 and 1901 have not been relocated (Sabourin et al. 1992). The existing habitat is unlikely to support a Lipocarpha micrantha population, and restoration potential is limited.
Both of the Northwestern Ontario populations, at Sable Island, Lake of the Woods; and Pound Net Bay, Rainy Lake, are subjected to unnaturally regulated water levels. Recreational use of shoreline areas and invasive plant species (Phalaris arundinacea, Phragmites australis) could also alter the habitat quality. However, no long-term trends in habitat quality or quantity have been noted. In the short term beach habitat quantity fluctuates with water levels. Sable Island and Pound Net Bay were subjected to near record high water levels in 2001. Consequently there was an unusually low amount of available habitat in that season.
Approximately 28km of appropriate Lipocarpha micrantha habitat once occurred on Lake Osoyoos, Okanagan Valley, British Columbia. Of this habitat, 70% has been lost to shoreline development. This includes the habitat once occupied by the extirpated population mentioned above. The remaining habitat is found on Indian Reserve land. The band has been considering development plans that would see 75% of the remaining habitat lost. In the event that this development proceeds, the total habitat lost at Lake Osoyoos would exceed 90%.
Protection/ownership
The Sable Island, Ontario, population is in a provincial nature reserve. The Pound Net Bay, Ontario, population is on Crown Land. The Lake Osoyoos population is on private land and has no formal protection. The locations of the extirpated populations are all privately owned.
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