Spring 2005

Life and Death Among the Black Oaks

Blue lupines thrive in the sand savanna among black oaks. The lupines are the only host plant of an endangered butterfly, the Karner blue, which was first described by the novelist and amateur lepidopterist Vladimir Nabokov (known to many only as the author of Lolita). The Karner blue is a “fugitive species.” It can’t survive fire and can’t survive without it.

You can see that the blessing of fire has recently been visited on this worthy savanna from the triumphant richness of the herbs — the wildflowers and grasses — and the browned defeat of the shrubs. The fire hadn’t been hot enough to burn off those shrub tops, but it had cooked their bark sufficiently to convince the leaves to give up the ghost, even in early spring when the lupine blooms..

This photo is clear enough to reveal a dozen species of herbs, and certainly, in a spot as rich as this, there are dozens more. Of those in bloom, I can make out lupine, sand puccoon, blue-eyed grass, and smooth phlox. (I admit I used magnification.) From the surrounding leaves it is possible to identify porcupine grass, Solomon’s seal, bastard toadflax, Carolina rose, sand coreopsis, wild strawberry, and rough blazing star.

The top-killed shrubs are actually young black oaks. Perhaps because of a rather long interval between fires, they were starting to form a thicket. In fire-dependent ecosystems that don’t get a chance to burn, a few species will kill off all the others. Black oak can make enough shade to do that by itself.

As for the Karner blue, fire kills them. But without fire, shrubs and trees gradually shade the lupine to death. So the butterflies must survive the fires outside the burned patch and then quickly move back to take advantage of the thriving lupine where it burned. That’s the life of a fugitive species. Can’t live where the disturbance is too much. Can’t live where it’s too little.

Moderation in all things, so long as our definition of moderation includes the ferocious force of fire. As in this savanna, which is enjoying and wishing us all a happy spring.

To learn more about fire and savannas, consult the Model Policy on Natural Fire and Controlled Burning in the Chicago Wilderness Region. Photo by Mike MacDonald. Words by Stephen Packard. Savanna protected by the Illinois Department of Natural Resources.

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