A five part series from Return the Landscape featuring the five habitats found in Lambton County: Tall Grass Prairie, Wetlands, The Carolinian Forest, The Rare Oak Savannahs & Coastal Dunes & Beaches.
Part 5: The Rare Oak Savannahs
Not quite forest, not quite prairie, the Oak Savannah is a globally rare ecosystem and habitat. An oak savannah is a lightly forested grassland where oaks are the dominant tree species, a transition zone between prairies and oak woodlands.
In an oak savannah, there is generally less than a 50% canopy cover, 25 to 30% is typical. The tree cover is so low that it allows prairie grasses and wildflowers to become the dominants of the plant community. Savannahs, like prairies, are maintained by fire, low precipitation and grazing. The oak savannah would not exist without fire! Oaks, especially black and burr oaks, have thick bark which protects them from fire while other tree species such as maple and ashes are sensitive and killed by fire. Oak saplings become resistant to fire at a very young age. Although, if a young oak had its stem killed back by fire, it would grow a large extensive root system. These large root systems permit better growth of stems in fire free years allowing the tree to survive future fires. Also, acorns are buried by rodents, such as squirrels and chipmunks, where they are protected from fire and allowed to germinate.
The diversity of plants in an oak savannah is very high, generally higher than in either a prairie or woodland. This is because in addition to prairie and woodland plants growing in a savannah, there are savannah specialist species which are adapted to the intermediate light conditions found therein. Shrubs of the oak savannah include American hazelnut, new Jersey tea and prairie rose. Grasses include big and little bluestem, Virginia rye and prairie brome. Specialist wildflowers include wild lupine, wood betony, wood lily, yellow false foxglove and yellow pimpernel. The savannah is home to much wildlife including white-tailed deer, rodents, wild turkey, red-headed woodpecker, eastern bluebird and insects such as the Karner blue butterfly, cicada killer wasp and meadow and conehead katydids (grasshoppers).
As noted above, oak savannah habitats are globally rare. Today, 99.93% of North America’s savannah habitat has been lost or altered. Many of our rare and endangered species live in oak savannahs. Currently, through management techniques such as prescribed burns, the few remaining remnants of this unique habitat are being restored and protected in eastern North America. Great spots in Ontario to visit oak savannahs are Pinery Provincial Park, Rondeau Provincial Park, Turkey Point Povincial Park and Walpole Island First Nation. The Port Franks area is home to some excellent oak savannah habitats too. The Karner Blue Sanctuary, in Port Franks and owned and managed by Lambton Wildlife Inc is a fabulous savannah site to visit.
By Larry Cornelis
Return The Landscape