"Green up" occurs on the prairies this time each year. With prairie fire season mostly between March 15 and April 15, we can now to see the effects of grass fires. As you drive across Kansas, look for a fence where the field on one side has been burned and the field on the other side has been left unburned.
The burned side rapidly "greens up." Dead grass was reduced to black ash. Those nutrients wash into the ground. The black surface absorbs more sunlight and the ground is warmer. Grass plants, with their living crowns undamaged, grow rapidly in the warmer soil and full sunlight. But tree or shrub saplings, from sumac to red cedar, had their growing tissues at the end of stems and were burned and killed. This left the grass in full sunlight.
But on the unburned side of the fence, plenty of dead grass stems wave in the air. Not only are their nutrients not accessible to new plant growth, the dead grass intercepts the sunlight, keeping the soil cooler. It shades any young grass trying to grow. Unburned trees and shrubs soon tower too high for their growing stem tips to be reached by flames. They shade out much of the grass underneath.
It is startling to look at photos of eastern Kansas taken in the mid 1800s. The countryside around Lawrence was prairie; now there are trees. Pioneer settlement across Kansas created islands of trees. In each small town, we planted trees for shade and to shelter us from Kansas winds. Sporadic natural fires kept Kansas in the grassland stage well before any Native Americans or pioneers came to this region.
In central and western Kansas, any tree-filled land is "unnatural." It exists because we protect it.
Today, ranchers conduct annual burns to maintain that natural environment. Burned annually, the small accumulation of dead grass makes for a cooler burn that carries less heat. A person can step over a fire line if there is only a thin layer of dead grass as fuel. But let it accumulate many years and the fire, whether set by lightning strike or manmade, will burn much hotter and the heat will penetrate deeper.
Animals vary in their responses to prairie fires. The larger white tailed deer, bison and antelope merely run away from fires. Other animals may be "fire positive" and benefit from the burning, "fire negative" with populations declining after burning, or "fire neutral." Prairie voles and the hispid cotton rat decline with burning while the deer mouse, meadow jumping mouse, and 13-lined ground squirrel nest in burrows under the ground; they mainly eat seeds and insects that thrive from the Green Up.
But drive along the interstates in Kansas and you will see country plots that are no longer burned. The fields rapidly fill with trees and shrubs. The most dominant of these is red cedar. From aerial photography, we know that Kansas has more red cedar than it has ever had in recorded history.
Far too many Kansas citizens are unaware that prairie fires are "natural" and that suppression of prairie fires is "unnatural." Just as the artificial suppression of forest fires in our Western National Forests led to massive and damaging forest fires over a decade ago, the accumulation of dead grass fuel would likewise be disastrous.
Nor will the next generation of Kansas students learn the science. The concepts of fire positive and fire negative species are not part of the assessed science standards being taught.
If we do not get the science of prairie burning correct in the future, we will have to change our state bird from the meadowlark to the cedar waxwing.
Readers who want to learn more about the importance of burning the prairie can request a free copy of the 16-page Kansas School Naturalist booklet "Prairie Fires" from the Department of Biological Sciences at Emporia State University (also available online).