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Rising From the Ashes

Almost two years ago, a wildfire swept through 1,200 acres of grasslands at the Agricultural Research Service's U.S. Sheep Experiment Station near Dubois, Idaho, and destroyed half of a long-term grazing study that began more than 50 years ago. ARS rangeland scientist Steven Seefeldt decided to salvage something from the loss.

The original grazing study involved three types of pastures: ungrazed, those grazed only in the spring, and those grazed only in the fall. Before the fire, the ungrazed and spring-grazed pastures were overgrown with sagebrush. Data up to then showed that fall grazing seemed beneficial, with spring grazing detrimental.

After the fire, which occurred in the summer of 2000, Seefeldt noticed that the pasture that had been grazed in the previous fall was 20 percent unburned. That's because there weren't enough sagebrush plants growing close together to enable the fire to jump from plant to plant. By contrast, the ungrazed pasture was burned totally bare and the spring-grazed pasture was 96 percent burned, showing another benefit of fall grazing.

In a second study, Seefeldt teamed up with Karen Launchbaugh, a professor of rangeland ecology at the University of Idaho, to determine when to begin sheep grazing after fire by measuring effects on native and exotic plant species. Early results indicate that late-fall grazing the year after a fire--for example, grazing a pasture in the fall of 2001 after a fire has occurred there in the summer of 2000--has no negative impacts on plant growth and diversity the following year (in this example, in 2002).

As this winter's snows melt, the scientists will again measure spring and summer growth to determine the effects of grazing on pasture yields and diversity.

More information about the grazing research can be found in the March 2003 issue of Agricultural Research.

ARS is the U.S. Department of Agriculture's chief scientific research agency.