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Prairie Grasses

Past and Potential for Ontario's Natural Heritage - Page 4

Tallgrass community ecology - Tallgrass communities are thought to have evolved through a combination of climatic, edaphic, and anthropogenic factors (Catling et al. 1992; Szeicz and MacDonald 1991; Reznicek 1983; Deevey and Flint 1957). Along the eastern edge of the tallgrass region, including southern Ontario, where rates of precipitation are higher, fire is one of the most important factors leading to the development and maintenance of tallgrass prairie (Pauly 1997; Reichman 1987; Sauer 1950). Before the onset of fire suppression, periodic wildfire set by lightning strikes and fires deliberately set by Aboriginal Peoples shaped and maintained this grassland landscape (Pauly 1997; Pyne 1982). With their ability to resprout from deep roots, prairie grasses and forbs are adapted to thrive in fire-prone areas (Kline 1997). Fire consumes accumulated dead plant material and leaves a black ash layer, allowing sunlight to heat the soil and stimulate growth (Pauly 1997). At the same time, fire controls the invasion of most shrubs and trees (Pauly 1997) and releases nitrogen into the atmosphere, giving prairie species the advantage over weedy species needing high levels of N to thrive (Wedin and Tilman 1992).

Tallgrass communities usually occur on soils greater than 25 cm deep (Bakowsky 1993). In general, soil of these communities is known for its rich organic content, which builds up and is incorporated in the soil as the deep, extensive prairie flora root systems decay in place (Kline 1997). These deep rich soils were found to provide excellent growing conditions for crops, leading to the nearly total conversion of tallgrass to agricultural land (Kline 1997). Most remnant prairies in Ontario occur on sandy soils (Faber-Langendoen and Maycock 1994). Historically, they are thought to have occurred on clay and clay-loam soils, but all known examples have been converted to other land uses (Bakowsky 1993).

Species composition is not uniform across Ontario's tallgrass communities, and at least some of this variation is attributed to moisture differences. Bazzaz and Parrish (1982) show the idealized distribution of six characteristic tallgrass Poaceae species in relation to moisture gradient, from Bouteloua curtipendula which is found preferentially in the driest areas to Spartina pectinata, which is found only in wet areas. These species demonstrate similar distribution in southern Ontario tallgrass remnants (Faber-Langendoen and Maycock 1994).

Oak tree at Ojibway prairie, Windsor

Oak tree at Ojibway prairie, Windsor ON.
Euphorbia corollata and Liatris spicata at ojibway prairie, Windsor

Euphorbia corollata (showy spurge; white) and Liatris spicata (dense blazing-star; pink-purple) at Ojibway prairie, Windsor ON.
Vernonia missurica at Ojibway prairie, Windsor

Vernonia missurica (ironweed) at Ojibway prairie, Windsor ON.
Coreopsis tripteris at Ojibway prairie, Windsor

Ratibida pinnata at Ojibway prairie,
Windsor ON

Page 1 2 3 4 5 6 7 8 9 10 References Appendix 1

| What are plant families? | How do we distinguish them? | How and why do we study them? | Selected vascular plant families of Ontario | Reading List | Course outline |

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Page design © 1999 T. A. Dickinson; essay text and illustrations © 1998 Lindsay Rodger except as noted.
Please send your comments to tim.dickinson@utoronto.ca; last updated 7-May-99

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