Cattle To The Rescue
Can intensive grazing remedy invasive grass seeding blunder?
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Here’s a pottery barn approach to meddling with ecosystems: You broke it, you fix it.
Only problem: Turns out it’s a lot easier to mess things up than to set them right.
That’s one conclusion that emerges from a creative effort to use intensive cattle grazing to get rid of an invasive, ecosystem-wrecking exotic grass, deliberately seeded over thousands of acres after the Dude Fire in 1990.
The experiment focused on reducing the ecosystem tyranny of the weeping lovegrass planted by air in 1990 to prevent flooding and erosion after the intense crown fire that seared the soil across 28,000 acres.
Rim Country rancher Ray Tanner teamed up with the U.S. Forest Service, researchers from Northern Arizona and others to determine whether concentrating cattle in an area overrun by weeping love grass would actually allow many other grasses and shrubs to get a roothold in an area dominated almost entirely by the domineering, non-native grass.
The two-year effort enjoyed limited success. It increased the amount of bare ground and encouraged a greater diversity of other grasses. But the effects faded quickly after the rancher returned cattle numbers to normal and stopped concentrating them in certain areas.
The researchers concluded the experiment could have produced a long-term effect if continued for a longer period and carefully controlled, according to the results in Rangeland, published by the Society for Range Management.
Researchers included Christopher Bernau, Jim Sprinkle, Ray Tanner, John Kava, Christine Thiel, Vanessa Prileson and Doug Tolleson.
The study adds to an intriguing set of studies that suggest careful management of cattle can improve the condition of rangelands, which remain in degraded, stressed-out condition across Northern Arizona. Uncontrolled grazing in the early 20th century transformed grasslands and pinyon-juniper and ponderosa pine forests like those surrounding Payson. Those changes resulted in a drastic reduction in the number of cattle the U.S. Forest Service allows on the range, devastating changes in wildfire patterns and the near extinction of family ranch operations.
The effort to control weeping lovegrass demonstrates the complexity of the system — and the difficulty ranchers and land mangers face in restoring a natural balance once things get out of whack. The lovegrass came originally from Africa and grows in bunches up to six feet tall, overshadowing and driving out other plants growing on the ground. The plant grows quickly, can produce 30,000 seeds annually and sets down a 13-foot-deep root system. However, it provides relatively poor forage for cattle and other wildlife once it matures. It also can survive droughts that would kill off competitors.
The Dude Fire in 1990 ushered in a frightening new era in wildfire behavior. The fire burned 28,000 acres, which at that time made it the biggest fire in recorded state history. Several fires since then have exceeded 500,000 acres.
Nonetheless, the Dude Fire shocked fire managers — and killed six firefighters. The fire produced 100-foot-long flames, destroyed 67 structures and consumed 36 million board feet of timber. It also destroyed almost every tree in its path and superheated the soil, making it hard for plants to get re-established and posing the risk of flooding and devastating erosion.
So the Forest Service scattered 210,000 pounds of seed by air. The reseeding effort relied mostly on non-native grasses, since land managers had few sources of native seeds and feared they wouldn’t germinate on the altered soil.
The re-seeding effort included 20 percent native western wheatgrass and 76 percent non-native grasses. Weeping lovegrass accounted for just 3 percent of the seeds scattered, according to a background summary in the Rangelands article.
The aerial effort amounted to a total of some 56 billion seeds, about 52 seeds per square foot.
As it turned out, the lovegrass proved far better at sprouting in the altered conditions than any other seeds. By 2005, lovegrass had created a near-monoculture on 90 percent of the 21,000 acres re-seeded.
Lovegrass “has outcompeted native vegetation and degraded habitat quality for wildlife and domestic animals. Today, ecologists describe these areas as a biological desert,” the researchers concluded.
Tanner asked the researchers if they could help him reduce the impact of lovegrass that covered 90 percent of his allotment on the Little Green Valley Complex near Payson.
Payson Ranger District rangeland specialist Christine Thiel, NAU professor Jim Sprinkle and other researchers joined in the effort.
The Forest Service agreed to let Tanner put out protein supplements beloved by the cattle, which would have the effect of concentrating the livestock in smaller areas. The concentration effectively increased grazing intensity by about 60 percent. Tanner tried the experiment with 300 beef cows and 50 yearlings grazing in a 4,000-acre pasture. They compared the results to a similar pasture without the more intense grazing.
After two years, the intense grazing reduced the area dominated by lovegrass from 93 percent to 86 percent. The other perennial grasses increased from 35 percent to 62 percent and the other annual grasses increased from 6 percent to 40 percent. The amount of bare soil increased from 7 percent to 12 percent and the amount of litter on the ground from the bunchgrass decreased from 84 percent to 73 percent.
However, soon after the experiment ended, the tenacious bunchgrass re-established its hold on the rangeland.
The researchers concluded the cattle not only ate the bunchgrass when they had no alternatives, but that their hooves tended to break up the tussocks of grass when grazing reached a certain intensity.
The researchers concluded that to have any long-term effect on the lovegrass, ranchers would have to keep the intensive grazing going much longer and perhaps replant native grasses — which the action of the cattle’s hooves could work into the soil.
Interestingly enough, the cattle essentially forced to eat the lovegrass acquired a taste for it. “It seems the cows on the ranch now use lovegrass regularly and without protein supplementation directing them. Ray Tanner compares the behavior to priming a pump, that is, that the study ‘primed’ the cows by getting them used to the idea of eating lovegrass. Once acclimated to that new diet, they simply continued the behavior into the following years,” the researchers concluded.
Tanner himself wrote, lovegrass “needs to be grazed very intensely and at higher rates than normally permitted by the Forest Service, perhaps 60-80 percent and should be grazed every year to avoid the return of the dense canopy of old, mature lovegrass that shades out more desirable species.”
He said ranchers should now experiment with introducing native grasses in conjunction with the more intense grazing on the lovegrass at key times of the year.
“All this being said, I would not recommend planting weeping lovegrass on public lands. But for those who have it, targeted grazing is something that can be done to improve use and species diversity that works better than cussing it.”