29 Apr 2016

Prescribed Burns Rejuvenate Native Grasslands

This black oak savannah is near Windsor, ON.

by Helen Mason

For more than a decade I lived on a small farm at the extreme eastern end of the Oak Ridge Moraine. When pioneers first arrived in southern Ontario, this area was covered with tall grass prairies and oak savannah. The sandy loam soils were ideal for farming. By the time Catharine Parr Traill and her family arrived in 1832, the area where I lived already included settled farms. Much of the grassland had been cultivated.

Much of the former prairie is now farmland and pastureland.
In an effort to rejuvenate some of the original flora and fauna, the Nature Conservancy of Canada and Alderville First Nation plan prescribed burns around the end of April each spring. Exact timing depends on weather. Too much wind can make it hard to control fires.

Controlled burns play an important role in tall grass prairies and black oak savannahs, especially ones that have introduced European grass species. They allow native plant species to grow again.

This prescribed burn is in the Cypress Hills, SK.
Many native species disappeared because they are warm-season species that start to grow later than the European species brought by early farmers. European agricultural species tend to be cool-season species that start earlier in the season. They also have a longer growing season. As a result, they out-compete the warmer season native species.

A fire in early spring helps tall grass prairies and oak savannahs in several ways. It increases the percentage of oak in hardwood stands because oak is more fire-tolerant than maple and beech.

Indigo buntings inhabit weedy fields.
It burns the introduced grass species, which may have already started their spring growth, and slows the growth of woody vegetation. The native prairie grasses, which are deep-rooted and start a little later, are not harmed by such a fire. In fact, burns clear vegetation right to soil level. This allows plenty of sunlight for sun-dependent plants.
After a burn, the blackened soil quickly absorbs heat from the sun. The warmed earth encourages seed germination. Charred vegetation provides a handy fertilizer for the new growth. The new grass growth provides nesting material and sites for grassland species.

The savannah provides habitat for the endangered Eastern hognose snake.

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