The role of fire in a tallgrass prairie
It’s not too early to think about next spring’s controlled
burns. One point that arises is burn frequency.
Restoration should be guided by the goals of the project. Thus, if the focus is tallgrass prairie, a fire-dependent
ecosystem, then annual burns are essential, especially if it is a prairie remnant. (Prairies planted on former ag fields are a different topic.)
My recent post which analyzed the extensive research by the Konza Prairie group showed that for brush
control in tallgrass prairies annual or biennial burns are essential.
Brush control is only one of the important reasons for
burning a prairie or savanna remnant. The other major reason is because the
forbs and warm-season grasses demand it. There is a vast amount of research that
shows that without fire the species that we most want will have difficulty
thriving. One of fire's main accomplishments is to remove the thick prairie thatch so that the delicate new prairie plants can reach the light.
The thickness of the prairie thatch varies from year to year
depending on the summer rainfall. Sometimes it is so thick that delicate plant seedlings can not find their way through it.
Rice, E.L. and Parenti, R.L. 1978. Amer. Jour. Botany 65: 1091-1097. Rice’s burns were done in the spring dormant season. |
In our own simplified work we divided a well established prairie
into two halves, burning one and leaving the other unburned. The result with
Toby’s Prairie is shown in the photo below. We obtained a similar result with the Pocket Prairie.
How does fire act on a prairie? The photo below shows fire backburning through a prairie consisting of Indian grass and little bluestem. After the ashes are blown away, bare soil will be exposed. In this photo, because of the heavy snows the previous winter, the grasses lay flat, thus ensuring that the flame heights are low.
The action of fire on dormant prairie grasses. In such a thick mat, delicate prairie plants have a hard time finding the light. |
Suppose you don't burn? The prairie plants will eventually find their way through the thatch, probably two weeks later. Eventually a new, somewhat impoverished, prairie will form which will form a new layer of thatch. Some of last season's thatch will decompose but not all, so the thatch gets thicker, and in the next year even thicker. Eventually the prairie will reach a point at which most prairie plants cannot survive. But the woody plants can, and eventually the prairie will become some sort of wood lot.
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