The
Mixedwood Plains Ecozone is the
Canadian ecozone with the most southerly extent, covering all of southwestern
Ontario, and parts of central and northeastern Ontario and southern
Quebec along the
Saint Lawrence River. It was originally dominated by
temperate deciduous forest growing mostly on limestone covered by glacial till. It is the smallest ecozone in Canada, but it includes the country's most productive industrial and commercial region, and is home to nearly half of Canada's population, including its two largest cities,
Toronto and
Montreal. Hence, little of the original forest cover remains, making protection of the remaining forests a high conservation priority. This ecozone includes two regions described by J.S. Rowe in his classic
Forest Regions of Canada: the entire Deciduous Forest Region, and the southern portions of the Great Lakes-St. Lawrence Forest Region. In the province of Ontario, the Ontario Ministry of Natural Resources maps this area as Site Regions 6E and 7E.