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Burning
in the Oak Woods Brings Back Savanna and Prairie
What
a difference five years makes! Biologists at the Lake County
Forest Preserves are finding it takes about five years for
a degraded oak woodland to regain health. "Oak woodlands
need fire as much as a prairie does," says Ken Klick, district
restoration ecologist. But it takes longer for the oak woodlands
to become their former selves compared with prairies, he
says. "Fifty years of shading from buckthorn have wiped
out the woodland seed bank. We’ve found after we begin
restoration, there’s a five-to-six year lag until we
start to see results."
If
a woodland is open, ground vegetation exists that can fuel
the fire. But many of the region’s oak woodlands have
become choked with buckthorn and invasive natives such as
ash and cherry. Workers clear invasives from the woods first,
carefully herbicide the stumps, and then reintroduce seed
and plants of grasses, sedges, asters, sunflowers, and other
forbs.
District
staff and volunteers began restoring Grant Woods five years
ago. Once the grasses were established, they provided fuel
for fire. Now wildflowers are blooming, too, providing nectar
for insects, which, in turn, attracts birds. "The whole
ecological chain is being re-established," says Klick.
At
Old School Forest Preserve where workers began restoring
a savanna-type woodland in 1997, "the difference is dramatic,"
says Klick. Now it’s an open woodland with pockets
of prairie and savanna grasses, wet depressions where blue
flag iris bloom, and space between trees for savanna birds
such as pewees to perch, then sally out to catch insects.
The
Lake County Forest Preserves manages 6,000 acres of forest
preserve land with fire, burning about 1,000 acres annually.
More than half the fire-managed acreage includes oak woodlands
and savannas. — Sheryl DeVore
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