ESU biologist reports on
recent prairie burning

By Dr. Richard Schrock
Professor of Biological Sciences

As a newcomer to Kansas 25 years ago, I spotted my first prairie fire in Kansas and breathed relief when I saw there were people nearby to put it out.  Then as I drove closer, I saw that they weren't putting it out.  They were deliberately setting the prairies ablaze!  Like most people, I automatically assumed that prairie fires are bad.  Like most people, I was wrong. 

We are here in the Flint Hills grassland of Kansas where a controlled burn is underway on Emporia State University's Ross Reservation.   Before the white settlers came to Kansas, the Osage and Kansa Indians fired the dead grass to lure in the bison and deer to the green pastures that would result.  Before that, nature sporadically lit the grasslands with lightning and the prairies  burned from river valley to river valley.   

The Flint Hills would not be grassland without the fires.  The rainfall here is high enough to grow shrubland and even forests.  The grass is here because it is adapted to fire.  The new growing tissues, the meristem, is down at the base of the grass and is unharmed by the brief burn, much as grass is unharmed by lawn mowers. 

Trees and shrubs have their growing tissues out at the tips of the branches; when the fire burns the twigs, it kills the small trees.  Here on the fireline, the flames are reaching a small red cedar that flares up...and dies.  But if there is only a year of dead grass as fuel, and a gentle breeze to move the fire along, the fireline burns cool. You can sometimes even step across it. And the grass easily survives and is ready to sprout up in days. 

This is easily seen along this fenceline here. On one side the prairie has been burned, and on the other last year's dead grass stems remain unburned.  On the unburned side, the dead stalks withhold nutrients and shade the ground, denying the new grass light to grow. And the ground is shaded and cool; the grass emerges late and it is sparse. 

Over on the burned side, the nutrients that were in the stems were burned and are now washed into the blackened ground.  This warmer soil starts the grass growing sooner, and the full sunlight produces a far richer cover than the unburned field over there. 
 
And what about the animals?  The larger deer and bison merely run away from spring burns, and they do not have their young during this time.  Among the prairie-nesting birds only Henslow's sparrow is impacted by fire; most birds are adapted to the effects of prairie burning.   Prairie voles and cotton rats have leafy nests at the surface, and their numbers go down. 
The deer mouse, pocket mouse, and thirteen-lined ground squirrel mainly eat seeds and insects, and they benefit from the fires.  Grasshoppers that eat grass increase.  Insects that eat non-grass species decrease.  Fire obviously kills some animals that cannot escape, such as some turtles and other reptiles.  But, where studied, the numbers of underground critters increases with fire. 

Around here, several ranchers often cooperate in a pasture burn; we call it "neighboring." After looking at the weather forecast, the rancher picks the best day, place, and time. It is best with warm temperatures and a recent rain...the new grass will spring up quickly. A mild wind needs to be blowing in the right direction. No wind at all, added to dry conditions, allows a slow intense burn that damages both the grass and fence posts. 

The first job is usually to set fireguards, the barriers between the pasture to be burned and adjoining grass that will not be burned.  Fireguards are created by setting backfires, unless there is a road or a plowed field that forms a natural border. Our wind today is from the northeast today, so we have set fireguards on the south and west sides of the field. 

The fireguard may be contained by using a cattle sprayer to lay down a heavy strip of water, or in our case today, workers use swatters to beat out the fire on one side of the fireline being laid.  Once fireguards are wide enough the headfire will not jump them.  The headfire is set on the upwind side and travels quickly throughout the rest of the field, until it burns into the fireguards and goes out.  Starting the prairie fire is easy, but building the fireguards, and keeping the fire from escaping into areas not to be burned, requires a lot of effort.    

Today science knows what Native Americans knew long before white settlers arrived, that in the Flint Hills there would be no prairies without fire.   After 25 years of living in Kansas, I look forward to the light haze and the sweet smell of the annual spring prairie fires, and I don't look for the fire trucks anymore.

Thanks to the Bay Foundation of New York, the color booklet on "Prairie Fires" is available free upon request; classroom teachers may request classroom sets.

Last Updated July 2, 2007>