White oak is still a common tree. But less and less. It
doesn’t seem to do so well in parks and lawns, and in the forest, while 200 and
300-year-old trees may be frequent, in most woods the young white oaks nearby
add up to zero. They’re not reproducing, except in temporary situations.
Oaks need fire. Bur and scarlet oak thrive on prairie and
savanna fire. White oak does not. Consider the ones planted at Somme Prairie
Grove “by mistake.” Decades ago, long before the science of ecology had learned
much, foresters trying to restore forest planted white oaks here with birch and
silver poplar and other questionable companions. Now white oaks here are starting to look like the one
below.
A controlled burn last fall killed the lower branches,
although you couldn’t tell that until spring when the live branches leafed out.
The fires here may be very good for Leiberg’s panic grasses,
great spangled fritillary butterflies, smooth green snakes, orchard orioles and
hundreds of other fire-dependent species of the oak savanna. But the white oaks
are on the retreat. They’ll gradually give way to nearby bur and scarlet oak,
wild plum, hazelnut, and other savanna shrubs, trees, grasses and wildflowers.
You see the future starkly in another part of the same
preserve.
Two beautiful white oaks standing just northeast of tall
grass (that is, dense fuel) were killed outright by a fire years earlier. On one level, it seems a
tragedy that these fine old trees died, but on a more profound level, the important
thing that’s happening here is that a rare ecosystem, supporting thousands of
rare species, is coming back into sustainable balance. White oak is apparently just
not part of the long-term healthy savanna – at least in this part of this
preserve.
Where will such a noble tree thrive? Not in the unburned
forests, where it can’t reproduce in the shade. Not in people’s yards, where
landscapers recommended other species better adapted to lawns.
Perhaps in the open oak woodland, another rare and poorly
understood community. Here the fires are not as hot; there’s less grass in the
dappled shade. Often there’s a more rugged, fire-disrupting topography. Open
oak woodlands have their own specialized, beautiful communities of birds,
mushrooms, butterflies, wildflowers, ants, walking sticks, nematodes, bacteria
and biodiversity heritage generally).
We still don’t know what it would take to restore full health
and a secure future to this important part of our planet. It will be fun to
find the answers. And it will take at least decades, so let’s do it while the
ancient white oaks we have left still have life.