Ontario Natural Vegetation

Soil texture and composition often vary significantly even within a small area and greatly affect the distribution of plant species. Some parts in the southern Ontario were formerly the beds of lakes formed by glacial melt water. The soils derived from lake-bed which deposits generally fine-textured and rock-free. The rivers in front of or under the melting glacier deposits large quantities of sand and gravel that still affect modern soil texture.

Bedrock geology is a major factor, because the underlying rocks are generally the parent material of the mineral component of the soil. Most of Ontario south of the French and Mattawa rivers is underlain by sedimentary rocks, and most of these rocks are high in calcium and magnesium, producing fertile soils.

Glacial ice covered Ontario as recently as 15,000 years ago, and so our flora is a relatively new phenomenon. As most recent continental glacier melted and the Ontario's climate underwent a series of changes, plant species gradually migrated northward. In some cases, isolated populations of species characteristic of more northern or western regions represent earlier stages in Ontario's vegetation. About 9000 years ago, the narrow zone of the arctic species is believed to have existed adjacent to it, with coniferous forests. Boreal Forest covered a zone where deciduous forests prevail today.