Across the Fence

by Bill Rinehart

Patch Burning

On the first day of March, 2003, Tallgrass Prairie Preserve docents convened at the Pawhuska Senior Citizens Center for their annual all-day reorientation session. Harvey Payne, director of the preserve, and Bob Hamilton, assistant director and director of science and stewardship, announced a major change in management philosophy for the preserve.

Preserve management for the past ten years has aimed for a targeted bison herd size of 3,200 head utilizing 30,400 acres of the preserve. The new, revised bison herd size is 2,600 head on a year round bison unit of 24,800 acres. The cattle (steer) pasture originally was projected to be 3,100 acres. The new projection is 10,100 acres for the cattle unit.

These revisions were the result of "Encouraging results from two years of collaborative cattle 'patch burn' research on the preserve with Oklahoma State University and the desire to invest even more landscape in the effort to export 'conservation friendly' cattle grazing models to the ranching industry." Bob Hamilton made this statement in an interview a few weeks ago and reiterated it during docent reorientation.

Harvey Payne said, "The goal all along has been to reestablish a Tallgrass Prairie ecosystem on the preserve, but what we have been doing in the past on the preserve hasn't contained a lot of exportable information for our ranching neighbors. We, therefore, are going to try to provide information that will affect a much greater area than just the preserve."

Hamilton said, "The Nature Conservancy is accelerating what we need to do conservationwise. Our little piece of the world is the Greater Flint Hills area extending up into Kansas and into the Osage. The estimates are that well over 90% of the original tallgrass prairie is gone. We're sitting on the end of the last big chunk. The Osage consists of a piece of the Greater Flint Hills, the last remaining example of tallgrass prairie on the continent."

Bob Hamilton describing patch burning in the Flint Hills.

Preserve management has utilized the patch burning concept since fire was reintroduced as one of the forces that helped shape the prairie initially. By not burning all of the preserve each year and adopting the concept of burning one-third of the bison unit annually, the patchy areas that remained un-burned, have provided habitat for wildlife common to the prairie. Dr. Michael Palmer, an OSU botanist, reports seeing a gradual rebounding of the plant community, especially the broad-leafed plants, or forbs (wild flowers) in the patch burned areas. These in turn provide habitat for the animal community.

Hamilton says that late summer burns, especially, significantly reshuffle the plant community because burning at that time of the year works to the disadvantage of the warm season grasses. The next growing season, the broad-leafed plants can come in and exploit the situation. He said it is after the growing season burns when big patches of Broomweed and Black Eyed Susans appear. Although skeptics may feel the preserve is growing weeds it is actually preserving habitat for preserve wildlife. The prairie is a very robust ecosystem; even after a summer burn, the warm season grasses once again dominate in several years. Hamilton also reported no difference had been noted in cattle weight gains between animals grazed on a patch burned pasture versus animals grazed on two cattle pastures that were burned annually.

Scientists have shown that a heterogeneous or variable landscape is much preferred on the prairie in order to conserve natural plant and animal communities as compared to a homogeneous landscape where all of it is burned each year. One of the concerns is that so much of the Flint Hills gets burned annually, 80 to 90%, that prairie wildlife habitat is being destroyed.

The Conservancy is in the third year of a study with OSU involving four cattle pastures on the preserve. Two pastures are burned entirely each year whereas one-third of the other two pastures is burned each year. All pastures are stocked as if they were in and intensive early season grazing system (double the number of steers, but only grazed for half the growing season). The third of the patch burn pastures that are burned each year is divided between a spring burn and a late summer burn. It is felt that patch burning cattle pastures will have many of the same benefits as has been experienced on the bison unit.

The interest generated by patch burning and with the Conservancy trying to determine how to best use the tallgrass prairie, preserve managers are currently committed to staying in the cattle business long term. Not only will patch burning continue with steers, but also in a year or so patch burning with cows will be introduced. Having cows on the preserve in a couple of years will be a first for the Conservancy.

Patch burning may prove to outperform conventional burning currently taking place on the prairie. Late summer burns tend to decrease the dominance of warm season grasses for several years, allowing the cool season grasses to grow. This time of year, cool season grasses that sprout from a late summer burned area are of very high quality. About 40% of the bison's food intake consists of wintertime, cool season grasses, especially those growing off the late summer burn patches. "It may appear the animals are eating dirt out there, but actually what they are consuming are those little plant sprigs that are of very high quality nutritionally," Hamilton said.

The typical grass standing on the prairie overwinter has very low protein value. This means that cattle typically have their diet supplemented this time of the year to insure they get the proper nutrition. If it can be shown that cows can benefit in wintertime from high quality forage produced from patch burning, thereby reducing supplementary feed costs, there could be a significant economic advantage to the cattle raiser. For this reason, cows eventually will be retained on the preserve year round and the steers will continue to be pastured there the customary 90 days. At the OSU experiment station near Stillwater, they have already switched to cows for the same reason, to look at both scenarios comparing the effects of patch burning in spring and late summer versus burning an entire area each year.

The Nature Conservancy purchased the Barnard portion of the Chapman-Barnard Ranch in 1989. Since that time, patch burning has been used as a means for reestablishing a tallgrass prairie ecosystem. A portion of the bison unit was burned each year rather than burning the whole thing. The results of that approach have been promising for accomplishing the objective of reestablishing a tallgrass prairie ecosystem on the bison unit. That same burning regime is now planned for an ultimate expanded cattle unit to determine its effect on livestock and the associated prairie ecosystem.