Species of the Month – Black Oak (Quercus velutina)
By Brianne Curry, Outreach and Fund Development Manager
Although not uncommon across North America, the Black Oak (Quercus velutina) is relatively uncommon in Ontario. Here in Southwestern Ontario, we are actually in the northernmost range of the species. Most of the populations of Black Oak can be found in the extreme southwest part of the province, north of Lake Erie, and particularly in pockets of oak woodland and oak savanna habitats.
As one of the smaller species of the Oak family, Black Oak is quite intolerant of shade, requiring sunny conditions to grow to full height and spread. Here in southern Ontario, the Black Oak will grow to be about 80 feet tall at full maturity, in ideal locations, although further south, the tree can grow to be taller. The leaves of the Black Oak are alternately arranged, and are identifiable with very deep and sharp U-shaped notches. Young leaves have a fuzzy, ‘hairy’ characteristic that helps with identification, while older leaves have a dark glossy green effect on the top. Like all Oaks, the Black Oak produces acorns via small pistillate flowers on catkins. Black Oak grows best on well drained, silty clay to sandy loam soils, and has a deep tap root that helps it withstand drought conditions.
As a genus (or family), Oaks are heavyweights and are considered a “keystone species”, meaning that they are trees in which entire ecosystems depend on for survival and habitat!
In his book “Bringing Nature Home”, Doug Tallamy, Professor of Entomology at Delaware University noted that native oak trees support over 500 species of Lepidoptera caterpillars (butterflies and moths) – far more than any other tree species. These insects play a critical role in the food web – acting as a food source for birds and their young as well as other animal species.
In short, Oaks fuel the food web, helping to maintain and support a rich mix of plants, insects, birds and other animals wherever they are found.
“Oaks are not just another plant.” – Doug Tallamy
Other benefits and ecological services that Oaks provide include:
- Moderating temperatures in summer by providing shade
- Intercepting rainfall through the canopy, increasing groundwater absorption and reducing surface runoff
- Stabilizing soil
- Improving groundwater quality via in ground filtration as well as reduced surface runoff
- Providing nesting, breeding and protective habitat for many species
- Producing high protein nuts (acorns) for numerous mammal species
- Producing dense leaf-litter on the forest floor which in turn boosts soil health and the presernce of countless species of insects and beneficial fungi and bacteria
- Sequestering carbon
Oak Savanna and Oak Woodland habitats:
Oak savanna habitat is a transitional habitat type found between tallgrass prairies and oak woodland forests. Because they contain species from both prairie and forest ecosystems, Oak savannas tend to be quite diverse habitat types. They are characterized by abundant grasses and wildflowers, with a few scattered large trees.
Oak savannas tend to develop on sites that are exposed to environmental stresses, such as fire, drought, and warmer-than-average temperatures. Oak savannas are maintained by periodic fire, which helps to support the regeneration of oak but keeps most other tree species at bay. Traditionally, fires would start naturally through lightning or would be started intentionally by First Nations peoples. Now, we utilize prescribed burning to help maintain this increasingly rare habitat type.
Oak savanna was once a widespread and important habitat in Southern Ontario, but much of it has been lost. Today, less than 1% of the original oak savanna habitat is believed to remain. Conservation and restoration efforts are crucial in preserving this unique and important fire-dependent ecosystem.
LPBLT continues to support the restoration of Oak savanna and Oak woodland habitats at several of our properties. Here’s an example of some work currently underway at our Trout Creek Nature Reserve. This work will allow this site to regenerate as an Oak savanna and Oak woodland habitat.