‘Disturbance’ helps prairie grasslands to flourish
This is the second article in a two-part series on grassland management featuring properties included in the Oliver Soil Conservation District’s Summer Grassland Tour. The series began in last week’s edition with the Gilbert and Becky Geiger Ranch.
The Cross Ranch Nature Preserve adjacent to Cross Ranch State Park was established in 1982 as the first of the five nature preserves in North Dakota that are managed by the Nature Conservancy. The organization’s focus is to conserve natural prairie grassland on the nearly 5,600-acre property, and to share management strategies with local landowners.
“We believe in ecological diversity, including diversity in management,” Cross Ranch Preserve Manager Eric Rosenquist said, explaining that disturbance is a natural way of managing the grasslands. “If you go back to pre-settlement times as the prairie was evolving, it was all about disturbance – lightning strikes and fires set by native peoples to encourage new growth, which attracted grazing by big game.”
Instead of discouraging growth, a management system that uses disturbance strategies such as prescribed burning and year-round grazing actually encourages healthy conditions on the native range. The prescribed burning somewhat mimics lightning strikes and wildfires, helping to remove the litter layer of dried matter and encourage new growth.
Oliver Soil Conservation District Summer Grassland Tour participants stood at the top of a hill in a 2,300-acre bison pasture which was part of a prescribed burn in spring 2013, listening as Rosenquist outlined the Conservancy’s management strategies.
“The bison seem to utilize the entire 2,300 acres without physically rotating from place to place,” Rosenquist said, explaining that year-round grazing is also part of the disturbance management practice. “Since bison seek out the new growth following a burn we can use burning to concentrate bison in places we would like heavier disturbance. This allows light disturbance on other areas.”
Bison are kept at Cross Ranch Nature Preserve for several reasons. They can be managed with a smaller staff than cattle, as bison don’t need to be calved out in the spring nor fed over the winter months. They also leave a smaller footprint at water sources, as they naturally water in small family groups rather than as an entire herd.