Rx for good prairie health? Fire!

Prairie burns, such as this one conducted earlier this month at the Main Ring, help restore and maintain prairie ecosystems in numerous ways. Photo: Jacques Hooymans, FESS

If you have had a chance to check out the burned-over prairie inside the Main Ring over the last week or so, you’ve noticed that the charred remains are slowly being overtaken by a green carpet of new growth. This is entirely expected, of course — it happens just this way every year — but it’s always somewhat amazing to see how quickly ecosystems respond to insult!

This year, FESS Roads and Grounds crews burned nearly 700 acres of prairie. It’s reasonable to ask the question, “Why?”

If it looks like the main effect of fire in the prairie is destruction — it is. At least the immediate direct effect of prescribed burning is mortality. But the mortality is directed at woody vegetation and nonprairie plant species that aren’t natural parts of a functional prairie. This frees up “niche space” for prairie plants, which are more resistant to fire.

Of course, there is what might be called collateral damage associated with a prairie burn. Some small mammals and insects are vulnerable, but a surprising number of mammals find pockets of protection or simply manage to get through the flames to safety. Studies indicate that as many as 75 percent of voles (small mouse-like rodents) survive fires. While insects may perish in large numbers, a small percentage survive, and research has shown that the high reproductive potential of insects allows them to return to pre-burn numbers within a year. Ground-nesting bird eggs may be at risk, but the Fermilab Grounds crews prohibit burning during nesting seasons to protect them.

In addition to directly eliminating competition for prairie plants, there are several indirect effects of burning that assist in restoring and maintaining prairie ecosystems. The destructive impact of fire changes the microclimate dramatically, making more sunlight available for plants. Most prairie plants actually have a slightly different metabolic pathway that uses intense sunlight and dry conditions much more efficiently, giving them a significant leg up on the competition from nonprairie plants.

As young prairie plants grow after a fire, they find themselves in an open environment where air circulation is good and sunlight plentiful, warming the soil and providing energy for photosynthesis. This combination keeps leaf temperatures at near-optimal levels while still taking advantage of the ample light. The post-fire surface is also much more conducive to transporting rainfall to the soil, helping to transfer nutrients deep underground for plant roots to use, as well as facilitating mineralization of organic matter so plants can absorb and use it.

Using prescribed burning to manage prairies is an accepted and effective ecological tool for land stewards. Of course, like any tool, it must be used thoughtfully and safely. While there are some negative effects of prescribed burning, the result is overwhelmingly positive, cost-effective and closely mimics natural, pre-settlement processes.

Rod Walton