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COSEWIC assessment and update status report on the False Rue-anemone in Canada

Habitat

Habitat requirements

Enemion biternatum is a species of open wooded slopes, river floodplains, rich woods and thickets. It is often seen growing in large colonies.

Populations of Enemion biternatum are restricted in Canada to the Carolinian region (Scoggan, 1978). Throughout its range, Enemion biternatum grows in shaded woods and thickets, often on rich wooded slopes in or adjacent to floodplain zones. Boufford and Massey (1976) reported Enemion biternatum growing in flat bottoms of alluvial woods behind natural levees in Virginia. This species is often found in close proximity to streams. Melampy and Heyworth (1980) found 50% and 74% of 147 clumps within 10 and 25 m of a stream in a field study conducted in Illinois.

Enemion biternatum is generally found in shady areas within mature maple-beech forests on gradual slopes. It is not found on steep slopes or in open highly disturbed sites. In Ontario, the species occurs in areas dominated by grey brown luvisolic soils rich in calcareous till and lacustrine deposits from limestone and dolostone (Hoffman, 1989). All Ontario stations occur near the limit of the Deciduous Forest Region, also known as the Carolinian Zone. Populations in Ontario were generally found in mixed hardwood Carolinian forests dominated by sugar maple (Acer saccharum), in combination with other species including ironwood (Ostrya virginiana), beech (Fagus grandifolia), hickory (Carya spp.), basswood (Tilia americana), butternut (Juglans cinerea) and ash (Fraxinus spp.). This plant is found with other spring wildflowers (Austen, 1990), including bloodroot (Sanguinaria canadensis), trillium (Trillium spp.), toothwort (Dentaria spp.), anemone (Anemone spp.), violet (Viola spp.), and trout lily (Erythronium spp.).

The habitats where the six populations occur are significant sites due to the presence of large populations of Enemion biternatum in addition to the presence of other rare plant species such as Virginia bluebells (Mertensia virginica), American gromwell (Lithospermum latifolium) and green dragon (Arisaema dracontium).

Habitat trends

It is difficult to determine whether the habitat has been drastically altered since the last status report due to the dynamic nature of floodplain systems. There does appear to be an increase in the number of trails and trail usage, possibly due to an increase in the number of homes adjacent to the floodplain. In addition, a number of invasive species seem to be colonizing the floodplain habitats generally occupied by Enemion biternatum. These factors may have contributed to the decline (and in some cases, extirpation) of Enemion populations that previously occupied the floodplains. No additional information on habitat changes is possible since the original status report did not provide specific descriptions against which to compare sites that currently do not have plants or plants could not be found.  

Protection/ownership

Subsequent to the designation of Enemion biternatum as a Committee on the Status of Endangered Wildlife in Canada (COSEWIC) Special Concern species in 1990, the species was officially listed provincially as Special Concern.

A part of the Medway Creek population is on land owned by the Upper Thames River Conservation Authority. The Ausable River Valley population is in an ANSI (Area of Natural and Scientific Interest). The Parkhill population is located in a conservation area owned by the Ausable Bayfield Conservation Authority. Presence in an ANSI or a conservation area, however, does not in itself confer protection unless specific management plans are in effect for the species. The remaining populations are located on private land.

The extant meta-populations of Enemion biternatum in Ontario are largely under private ownership in Arkona, St. Thomas, and Port Stanley, and under public ownership in London. Many sub-populations are located near public trails both on private and public lands. Therefore, most populations of this species in Ontario are subjected to a high degree of public access (Austen, 1990).