The invasion of woody vegetation is a world-wide problem. Research shows that over the past 100 years, tree-like plants have steadily encroached on grasslands. Areas of southern Africa, Australia and the Americas have been affected at different times to varying degrees. In the continental US, the central and southern Great Plains have been the hardest hit regions of the nation. The Rockies, north and south are a distant second. The Chihuahuan and Sonoran deserts taken together are third.

Dr. Kirk Davies is the lead rangeland scientist for the United States Department of Agriculture at the Eastern Oregon Agricultural Research Center in Berns, Oregon. Dr. Davies has been studying the long-term effectiveness of using fire to remove mountain juniper from the ecologically delicate steppe regions of Oregon and northern California where the mountain juniper has threatened the dominance of native sagebrush. As soon as juniper cover reaches 3 percent, the near-threatened greater sage-grouse stops using the area. Listen to this edition of the Wild Hare for details from Dr. Davies.

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See transcript and music credits below.

Native range of the western juniper – graphic – US Forest Service

Transcript:

The invasion of woody vegetation is a world-wide problem. Research shows that over the past 100 years, tree-like plants have steadily encroached on grasslands. Areas of southern Africa, Australia and the Americas have been affected at different times to varying degrees. In the continental US, the central and southern Great Plains have been by far the most affected regions of the nation. The Rockies, north and south are a distant second. The Chihuahuan and Sonoran deserts taken together are third.

Dr. Kirk Davies is the lead rangeland scientist for the United States Department of Agriculture at the Eastern Oregon Agricultural Research Center in Berns, Oregon. Dr. Davies has been studying the long-term effectiveness of using fire to remove mountain juniper from the ecologically delicate steppe regions of Oregon and northern California where the mountain juniper has threatened the dominance of native sagebrush. As soon as juniper cover reaches 3 percent, the near-threatened greater sage-grouse stops using the area. Dr. Davies explains the problem.

“What we’re looking at here is a situation where we’ve had an expansion of western juniper into mountain big sagebrush communities, and this is caused for a variety of reasons. One of the main reasons being that we started to limit the number of fires in these higher elevations over the last hundred plus years. What happens is it encroaches into these mountain big sagebrush communities, we start having a problem with reduced forage production, loss of sagebrush, and then of course, with loss of sagebrush, we have decreases in wildlife that depend on sagebrush to complete their life cycles, like the sage grouse.”

Dr Davies said fire was once used more widely to manage grassland areas. Perhaps the primary reason fire has fallen from favor as a sage-community management tool is the well documented correlation that fire has aided the distribution and establishment of bromus tectorum or cheat grass and other exotic grasses across the entire Great Basin. At higher elevations where the mountain juniper has encroached on sage brush, land managers have been averse to using fire as a woody plant mitigation tool for fear of spreading exotic grasses and their manifold problems. Davies’ research found that the proliferation of cheat grass through burning at higher elevation is dependent on site specific conditions and not the method of eradication.

“We found that counter to the kind of general thought that fire always increases annual grasses, we found that it wasn’t necessarily fire it was more tied to the actual site characteristics and the presence or lack thereof of perennial bunch grasses. So it didn’t really matter what treatment was applied to remove the juniper. It was more important how hot and dry the site was and how many, or the lack thereof of perennial bunch grasses to compete with annual grasses.”

The danger of controlled fires becoming uncontrolled is another factor that continues to keep risk-averse private landowners and public land managers from using fire to remove mountain juniper. According to Dr. Davies, recent concern over the destruction of sage grouse habitat has also driven land managers away from the use of controlled sage-community fires. Davies evaluated the effectiveness of cutting mountain juniper versus using prescribed burns to kill them. On the ground, he and fellow researchers observed more young juniper trees in areas that had been cut in recent decades compared to burned areas. Evaluating the effects of cutting compared to prescribed burns of juniper over an extended time not only provided evidence that prescribed burns resulted in extended juniper control, it also validated the ecological model that had predicted this outcome.

“Prior to 2010, somewhere in there maybe even a little later than that, prior to that they actually did do more burning of Juniper, but with concern for sage grouse especially they started moving away from burning juniper because you also kill sage brush in the short term with burning, and they went to largely just cutting. It kind of almost became ingrained that that was the treatment to do is just to cut it, and it works, but our research showed that for longer term gains, that actually burning was more effective than cutting.”

Davies is working with a team of scientists to include researchers from the Meadow Forage Management Research Laboratory in Burns, Oregon, Oregon State University and The Nature Conservancy. The team compared the results of prescribed burns with areas where cutting down juniper was employed as the control method at 77 sagebrush steppe locations in Southeastern and south central Oregon, northern California and southwestern Idaho. The researchers looked at ecological data for as long as 33 years after either fire or cutting down juniper was used to control the woody plants.

Once destroyed sagebrush can take decades to regain its native status. The ecological memory is slow to respond. Davies said the upshot of the research was that both cutting and fire were needed to best reach long-term conservation goals in the study area and in other similar ecosystems.

“I would say that it (his research) does highlight the need for both cutting and burning to achieve conservation goals. I think a lot of researchers focus only on one or the other. Across the west, we’re having, across the world actually, we’re having a global increase in woody vegetation a lot of times because of a lack of fire in certain communities. Not to say that there’s more fire in other communities. And this is showing that, that for conservation, these systems that we need to think about more than just the one tool that there’s actually the ability to achieve short term goals with a mechanical treatment like cutting and then longer term goals by also integrating in fire, reestablish a fire regime in these communities. I think that’s kind of the upshot to take away the bigger picture to other ecosystems.”

Music credits in order of appearance as reported through the Public Radio Exchange:

Song: Greenland
Artist: Emanicipator
Album: Safe in the Steep Cliffs
Label: Loci Records
Year: 2010
Duration: 1:25

Song: Mrahba
Artist: Majid Bekkas
Album: African Gnaoua Blues
Label: Igloomondo
Year: 2012
Duration: 2:06

Song: African Blues
Artist: Majid Bekkas
Album: African Gnaoua Blues
Label: Igloomondo
Year: 2012
Duration: 1:07

Song: Youbadi
Artist: Majid Bekkas
Album: African Gnaoua Blues
Label: Igloomondo
Year: 2012
Duration: 3:52