It’s a scene out of the Old West—cattle weaving through the sagebrush, chivvied along by riders on horseback.
This time, however, the riders have a special goal—to enlist the cattle in the fight against cheatgrass, an invasive weed that threatens more than 100 million acres of the West’s sage and grasslands and the native creatures that depend on this fragile habitat.
The cattle are part of an experiment at the Conservancy's Moses Coulee preserve to test new ways of beating back the cheatgrass. In addition to the cattle, the project involves treating the landscape with a native soil bacterium that inhibits cheatgrass growth.
In the fight against cheatgrass, scientists and ranchers make a good team.
Western sagebrush and grasslands are burning more than ever before, and cheatgrass is mainly to blame. Cheatgrass, a non-native weed, grows faster than native bunchgrasses and becomes established earlier in the growing season, using up water and nutrients before native grasses and plants begin to grow.
It also dries out earlier in the summer, and creates a carpet of fine fuel, ready to ignite in those 100-degree days. Once the land has burned, cheatgrass comes back stronger than ever, while sagebrush is destroyed by these hot fires.
Land managers have tried digging it out, spraying herbicides, and other methods to control cheatgrass, but it has been a losing battle.
Now there is new hope.
The Nature Conservancy is teaming up with Dr. Ann Kennedy, a U.S. Agriculture Research Service scientist working at Washington State University, to test the effectiveness of a native soil bacterium in inhibiting the growth of cheatgrass.
Kennedy has been studying the bacterium, Pseudomonas fluorescens strain D7, in wheat lands for years, and this new project will expand her work into the sage and grasslands.
She identified the potential biological control agent during research on weed-suppressive bacteria. The bacterium is native to Washington soils and has been shown to inhibit germinating cheatgrass seeds in laboratory, greenhouse and field trials while not harming other species.
“This is the most promising tool I’ve seen in more than 20 years of working on this problem,” said Chuck Warner, director of the Conservancy’s aridlands program in Washington.
Cattle can play several roles in restoration of sage and grasslands. They can be used to trample back overly dense shrubs that are shading native grasses and they can be used to trample in seeds that have been spread to give them a better chance to establish in the soil.
In the Moses Coulee test site, volunteers and scientists have laid out a test grid that will include plots for several different treatments:
The project team thinks that the combination of all three treatments—bacteria, seed and cattle—will work best, aridlands ecologist Sonia Hall said. Why? The bacteria will inhibit the growth of cheatgrass, but the seed and cattle will help the native grasses become established.
For the native grasses to establish well, they must have good contact with the soil, otherwise they’ll be isolated from the water stored in the soil, will not germinate, and will likely dry up and die. This is particularly hard to do when you want to keep at least some of the shrubs, because you can’t use machinery like seed drills, which are specifically designed to maximize “seed-soil contact.”
That’s where the cattle come in: by trampling the ground the help get the “seed-soil contact” going, while allowing The Conservancy to keep some shrubs. The cattle also graze back some of the shrubs, which are too dense and might prove too much competition to those emerging seedlings.
If we know all this, why do we need the other four treatments? For two reasons. One, if things don’t work the way we expect, we need to be able to tease out why. Did the bacteria not inhibit cheatgrass enough? Compare the no-treatment plot to the apply-bacteria plot. Did the trampling not make a difference to seedling emergence? Compare the seed+bacteria to the seed+bacteria+cattle.
The second reason is because we don’t know if all the treatments are as critical as we think, plus we need to balance the cost and logistics of the treatments with the restoration outcomes. Was adding the seed worth the cost, or were there enough native seeds in the soil already? Compare the apply-bacteria plot to the bacteria+seed; and the bacteria+cattle to seed+bacteria+cattle.
Did the cattle make enough of a difference to warrant the logistics of repeating this over a full 160-acre restoration project (just imagine what that would be like)? Compare the bacteria+seed to the seed+bacteria+cattle. Was reducing shrub competition the only real restoration need (very unlikely, but we want to make sure)? Compare the cattle to the no treatment.
We want to get a lot of information out of this that will help us make ecologically and cost effective decisions when we work at scale.
The Conservancy’s neighbors, Paul and Heidi Wittig, agreed to bring their cattle in to play this important role in testing the most effective ways to restore Moses Coulee using this bacterium.
The research project is being funded by a grant from the Conservancy’s Priscilla Bullitt Collins Trust Northwest Conservation Fund.
In addition to the work at Moses Coulee, the bacteria is being tested in other sites in Washington, and in Oregon, Idaho, Utah and California under a range of environmental conditions. This funding will also partially support the restoration of 160 acres at Moses Coulee starting in 2013, using the results of this study to select the best way to do this. These results will also be used to develop management strategies that will both prevent further rangeland degradation and serve as a tool in restoring infested land.
(December 2009)March 08, 2011