Montana/Dakotas

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Fire's Effects on Range Health Studied

 story by
Mark E. Jacobson
Eastern Montana/Dakotas District

 BLM Firefighter

A BLM firefighter watches as fire moves through an experiement plot on BLM land in Prairie County Sept. 9. Nine plots were burned as part of a summertime burn experiement to determine fire's effect on local range where the grass purple three-awn is common.
Photo by Mark E. Jacobsen
BLM fire technician

Justin Hanley, BLM fire range
 
technician, uses a drip torch to 

ignite research plots as part of a 

study conducted on BLM-

administered lands in Prairie 

County Sept. 9. The project was
 
designed to gauge the effects of
 
fire on purple three-awn, a
 
bunchgrass common on local
 
rangelands.

BLM photo

MILES CITY, Mont. --- Local BLM firefighters recently completed the last of a series of prescribed burns in Prairie County which were part of a range research experiment designed to gauge the effect of fire in restoring balance to eastern Montana rangelands.

The purpose of the fire experiment, headed by Fort Keogh researcher Dustin Strong, was to monitor the effect on the native bunchgrass “purple three-awn” (Aristida purpurea). The burn was a component of a cooperative project among the BLM, the Fort Keogh Livestock and Range Research Laboratory, and North Dakota State University.

Three-awn is a native perennial bunchgrass common across the continent and a frequent element of the Montana prairie. Three-awn seeds have three long whisker-like “awns” which give it its moniker –and which irritate the mouths of grazers. In addition, the plant provides little nutrition if grazed once and even less if clipped twice—by pulling nutrients back into its root system rather than reinvesting them in any new growth. Livestock and wildlife eventually move on to more palatable forage.

Meanwhile, three-awn reinvests in itself and takes over more ground.

Typically, it’s the imported exotic weed that is considered the interloper, not a native grass, said Strong. However, sometimes a native can take over and establish a single-species “mono-culture” on the range.

Strong, with the help of fellow researchers and BLM fire crews carefully set fire to a series of delineated plots populated with native grasses –dominated by three-awn– on BLM-managed lands a few miles south of Terry.

Thermocouples draped in water-soaked gunny sacks recorded temperatures at ground level as the flames swept through the grasses, encouraged by a light breeze.

Fire staff used drip-torches to ensure an even burn, right up to the water-soaked mowed edge of each plot. As soon as one section was done, the thermocouples were snatched up and others moved to the next area. In a couple of hours, only a checkerboard of smoldering squares remained.

Initially, 60 to 70 percent of the plant composition on these pastures was comprised of three-awn. According to Strong, the process of plant succession had been arrested and dominated by this bristly bunch grass. As part of his experiment, Strong has been attempting to “release succession” by using fire and adding nitrogen as “successional stimulants.”

Strong said his goal is not to develop strategies that will totally remove three-awn from the ecosystem, but rather to focus on what will restore ecosystem function, nutrient cycling, and plant diversity. The desired end product is a decision matrix that will assist the BLM in the selection of land management options to increase native plant diversity.

“The BLM has broad landscapes where three-awn is a dominant species,” said Jesse Hankins, biologist in the BLM Miles City Field Office. “Investigation is needed to determine effective management treatments that could help us increase the native diversity in these three-awn dominated plant communities. That’s where Fort Keogh and their research can really help us out.”

“Although our main objective is to help the BLM, we also hope this research will be of use to private landowners in Montana and throughout the country,” said Strong. “Personally, I hope this research will showcase the benefits of prescribed fire and encourage landowners to consider using fire strategically to manage their rangelands when appropriate.”

Strong applied the first series of prescribed burns and nitrogen treatments during the summer and fall of 2010. The last burn session was completed Oct. 31. He noted that the effects have been readily apparent.

“On the first site we applied fires to three-awn, biomass has decreased 92 percent and 70 percent on summer and fall fires, respectively,” he said. “By the fall of 2012 we should have a strong grasp on how fire affects purple three-awn and the surrounding plant community.”

Strong says he will continue working on the three-awn research sites after the project concludes, even if it’s just monitoring.

Nationally, the BLM administers nearly 18,000 permits and leases held by ranchers who graze their livestock, mostly cattle and sheep, at least part of the year on more than 21,000 allotments under BLM management. Of this, the Miles City Field Office administers 1,630 grazing permits --representing 584,995 AUMs-- on 2,729,645 acres of eastern Montana federal land--more than any other single field office in the BLM.

“The BLM is committed to maintaining or restoring healthy rangelands and appreciates opportunities to partner with others in those efforts,” said Reyer Rens, BLM Miles City Field Office range supervisor. “Current science, like this study, enables range managers to make better, more informed decisions for our rangelands.”