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COSEWIC assessment and update status report on the American Columbo in Canada

Habitat

Habitat Requirements

Frasera caroliniensis grows in relatively stable habitats -- primarily open deciduous forest, but also in open forest edges and dense shrub thickets. Threadgill et al. (1979) note its occurrence in a variety of habitats across its range, including deciduous, pine and red cedar forests, thickets, open meadows and grasslands. They note that it is most common in dry upland woods, but has also been collected from swampy areas. It has been collected on rocky hillsides throughout its range, but will grow on a wide variety of soils. While F. caroliniensis has been documented in recently disturbed habitats, Threadgill et al. (1979) suggest that such collections may represent the persistence of long-lived individuals despite unfavourable conditions, rather than any actual preference or tolerance for successional habitat.

The range of Frasera caroliniensis encompasses a broad climatic gradient, from hot, humid summers and mild winters in the south to more moderate summers and harsh winters in the north (Threadgill et al., 1979). Climatic water stress is not normally encountered during the growing season anywhere in this range, although edaphic conditions at some sites may result in seasonal drought conditions (personal observation).

The Canadian populations of F. caroliniensis are restricted to the “Carolinian” forest region, climatically the mildest area of southern Ontario (see pages 25-30 in Waldron, 2003). It is not known if climate is a limiting factor at the northern edge of its range in Canada, or if it may be possible for F. caroliniensis to expand its range further north. The Halton region populations occur on dry mesic to mesic clay or clay loam soils in open oak-maple (Quercus alba, Quercus rubra, and Acer saccharum) forests, thickets (Cornus spp., Viburnum rafinesquianum, Rhus typhina, Rubus spp.) and openings (Crins and Sharp, 1993, personal observations). The provincially rare perfoliate bellwort (Uvularia perfoliata) co-occurs with F. caroliniensis in Halton (personal observation). Common herbaceous associates include woodland sunflower (Helianthus divaricatus), Pennsylvania sedge (Carex pensylvanica), poverty oat-grass (Danthonia spicata) and various asters (Aster spp.) and goldenrods (Solidago spp.).

The Paris site is at the base of a steep slope on mesic silty clay soil under white birch (Betula papyrifera), eastern white pine (Pinus strobus), and large-toothed aspen (Populus grandidentata). A more extensive list of associated species was compiled by Crins and Sharp (1993).


Habitat Trends

Forest habitat has been reduced from 80% to 11% of the total area of the Carolinian region (Carolinian Canada, 2004). Historically much of this loss has been attributable to agricultural development, but urban development is now a major cause of natural habitat loss in southern Ontario (Pim and Ornoy, 2002).


Habitat Protection/Ownership

Two of the extant populations occur in provincial parks, Selkirk Provinical Park (#6) and Shorthills Provincial Park (#16). There are two populations in nature sanctuaries managed by Royal Botanical Gardens (RBG), Hendrie Valley (#9) and Cootes Paradise (#22). The Borer’s Creek population (#7) is in the Borer’s Creek Conservation Area (Hamilton Conservation Authority). The Glen Morris population (#2) is on land managed by the Grand River Conservation Authority. The Cartwright population (#21) is in a nature sanctuary owned and managed by the Hamilton Naturalists’ Club (Rothfels, 2005). The Blue Lake population (#3) is on private property, but the current landowner has demonstrated a willingness to protect the population. Portions of the King Road populations (#11 & #12) and a portion of the Clappison Escarpment Woods (#8) population are located in powerline right-of-ways. Management of these areas does not appear to be having a negative impact on F. caroliniensis populations (Crins and Sharp, 1993). All of the remaining eleven populations are on private property, with no existing protection.