Description

As the Grand River winds its way south to the shores of Lake Erie, it passes through Haldimand County, where it broadens and slows, moving through a gently undulating landscape. Just west of the river, near Cayuga, is an interesting physiographic anomaly: an isolated sandstone plain in an area that is predominantly clay (the Haldimand Clay Plain). This is the only outcrop of Oriskany sandstone in Canada, and as such, is of geologic significance. The sandstone substrate supports a varied flora, including a large forested area of dry upland forest with oaks (including Chinquapin and Black), Sugar and Black Maple, and Eastern Flowering Dogwood, and numerous prairie species in dry openings. This is also one of only four sites for the Black Rat Snake in the Carolinian life zone.

Incorporated in 1993, the Lower Grand River Land Trust (LGRLT) works to protect the natural, cultural, and agricultural values of the southern Grand River watershed, including the Oriskany Sandstone and Woodlands area. One of the group's initiatives was a landowner contact project, in which 17 handshake stewardship agreements were achieved, protecting 1,135 hectares of the watershed.

The LGRLT also holds 607 ha in trust and spearheads the ecological restoration of Ruthven Park (taken from the Carolinian Canada Signature Sites Guide by Lorraine Johnson 2005). Ruthven Park, the historic home of the Thompson family includes a Greek Revival mansion and 607 ha of Carolinian forest, wetland, and farmland on the banks of the Grand River. For more information about the park, visit the website here.

Vegetation

The vegetation and flora of the Oriskany reflects the well-drained site conditions and previous land use. A large forest remnant, known as the Clanbrassil forest, occupies the northeast quadrant while forblands and thickets dominate the northwest and southwest quadrants. Deposits of Framington clay loam in the southwest quadrant are presently under cultivation. The vegetation and flora are decidedly southern with distinct Carolinian and prairie affinities. The area shares many affinities with the Norfolk sand plain to the west. Various species of oaks and other plants manifest the well-drained conditions. Overall, a high diversity of plant species and habitats occur (McDonald, 1980 in Eagles & Beechey, 1985).

A continuum of moisture conditions is evident in the Clanbrassil forest, probably of moisture conditions is evident in the Clanbrassil forest, probably reflecting local relief patterns and the nature and depth of local surficial deposits. The occurrence throughout this forest of red oak, black oak and white oak manifest the well drained conditions that prevail. At the extreme end of the moisture series represented here, very dry, perhaps even arid conditions occur locally in semi-open oak woodlands. Sugar maple assumes dominance along the upper edge, buried talus slope and footslope of the Onodaga escarpment. Below the escarpment small slough depressions occur resembling patterns reported as characteristic of the Haldimand Clay Plain (Eagles & Beechey, 1985).

Landform

Physiographically the area is dominated by a flat to gently undulating sandstone plain surrounded by deep lacustrine clay deposits. Sandstone outcrop of the Oriskany formation produces local irregularities and scarps that dominate the core of the area. Thin deposits of well-drained, Farmington loams form a thin, broken mantle throughout the northwest, northeast and southeast sectors becoming deeper on the periphery of the sandstone plain. The porous character of the sandstone and the Farmington loams produce well-drained sites in most locations (McDonald, 1980 in Eagles & Beechey, 1985).

References

* Allen, G.M., P.F.J. Eagles and S.D. Price (eds.) 1990. Conserving Carolinian Canada: Conservation Biology in the Deciduous Forest Region. University of Waterloo Press, Waterloo. 346 pp.

* Eagles, P.F.J. and T.J. Beechey (eds.) 1985. Critical Unprotected Natural Areas in the Carolinian Life Zone of Canada. Final Report, Identification Subcommittee, Carolinian Canada. The Nature Conservancy of Canada, The Ontario Heritage Foundation and World Wildlife Fund (Canada). 400 pp.

* Macdonald, I.D. 1980. Life Science Features of the Haldimand Clay Plain Physiographic Region. Ontario Ministry of Natural Resources, Parks and Recreation Section, Central Region, Richmond Hill, Ontario. SR OFER 8001. vii + 266 pp. + map.

© Natural Heritage Information Centre, 1998

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