Oak Savanna

The Old Ausable Channel is adjacent to one of the most vulnerable ecosystems on the planet. Oak savanna is a globally rare ecosystem that is a transition between prairie grasslands and oak forests. More than 99% of the oak savanna in the world has been altered or destroyed. Through careful management, Pinery Provincial Park has restored its oak savanna and protects nearly 50% of the remaining oak savanna in the world.

What is an oak savanna?

An oak savanna is an ecosystem with 25-35% canopy cover – meaning 25-35% of the ground will be shaded at solar noon. This is compared to a true forest, where cover is greater than 50%. This extra light within an oak savanna allows for plants to grow on the floor that would otherwise be unable to survive in a traditional forest. Some of these plants include:

Species at Risk in oak savannas

Many oak savanna species are species at risk with specific needs, such as the Fern-leaved Yellow False Foxglove and the False-foxglove Sun Moth.

[picture of Fern-leaved Yellow False Foxglove, Black Oak]

The Fern-leaved Yellow False Foxglove (Pyrrhia aurantiago) is a threatened plant in the OAC. It is found in open savanna and woodland habitats with Black Oak (Quercus velutina), its preferred host tree. This plant is unique because it taps into the roots of oak trees to help supply itself with water and additional nutrients.

Threats to Fern-leaved Yellow False Foxglove

[picture of False-foxglove Sun Moth]

The larvae of endangered False-foxglove Sun Moth (Pyrrhia aurantiago) exclusively feed on the Fern-leaved Yellow False Foxglove and another Foxglove species (Smooth Yellow False Foxglove). Only 3 populations of this moth in Canada are known to currently exist, all of which are in southern Ontario (the OAC, Windsor, and Turkey Point).

Threats to Fern-leaved Yellow False Foxglove

Management

In the past, forest fires were commonly seen as only destructive in nature. We have learned in recent years that by suppressing nature’s fires, we have harmed nature more. Critical oak savanna habitat can be lost if fires are suppressed too heavily. The understory of the savanna becomes thicker and denser without fire disturbances, and the rare ecosystem beings to disappear into a thick forest. Oak savanna habitat by definition should only have about 25-30% forest cover. Many oak savanna species actually rely on fire in order to reproduce. Some species require the actual heat and flames for their seeds to be released and germinate. Other species rely on fire to burn off the leaf litter on the ground, along with any competing small shrubs and trees. Through careful management and prescribed burns, oak savanna habitat is further protected.

However, this is not a new concept to First Nations and Indigenous Peoples who have been utilising fire to manage their lands for thousands of years. Fire was used to clear land for agriculture, to rejuvenate areas with important forage and medicinal plants, and to maintain wildlife habitat. Through this use of fire, oak savanna habitats were also rejuvenated and maintained.