CABNR professor’s work featured in High Country News
Note: This is an excerpt from an article that appeared in High Country News in September 2012 and is reprinted here with permission.
By Stephanie Paige Ogburn, High Country News
"This guy is lovely!" ecologist Beth Leger exclaims, falling to her knees. A tiny, energetic woman in her mid-30s, Leger hovers, bee-like, over a teensy grass with blue-green blades. It is, she tells me, a "cute" native called Poa secunda.
Dr. Beth Leger, PhD, Department of Natural Resources and Environmental Science
It's early May, and Leger, graduate student Owen Baughman and I are crouched on Peavine Mountain, a scrubby rise near the University of Nevada, Reno, where she is an associate professor of plant ecology. The ground around us is covered with the invasive annual Bromus tectorum, also known as cheatgrass.
This is not surprising; the Great Basin is a disturbed landscape, and cheatgrass is now its dominant inhabitant. Around the little Poa, though, there is no cheatgrass at all, just a foot of bare, pebbly dirt.
"We did some trials to see what native perennials were the most competitive with cheatgrass, and it was this guy," says Leger.
Leger scoops away the soil around its base, digging carefully underneath it.
"I don't want to kill him, but it's instructive to do that because his roots are super fine and they go out really shallowly, all through this area," she explains, gesturing at the bare circle. "Cheatgrass (also) has super-fine roots and this is about the only native plant I've ever seen that has the same sort of roots."
That allows the Poa to take up space and use nutrients the weedy invader would typically claim.
Leger finally pulls the plant out of the ground. "Sorry, dude," she tells the grass. "You'll be famous."
The ancestors of Leger's beloved Poa first encountered cheatgrass, a native to parts of Europe and Asia, in the late 1800s. Western settlement had brought widespread livestock grazing to the Great Basin. That was a shock to native bunchgrasses like Poa and Indian ricegrass, which, in that part of the West had evolved in an environment unused even to bison. Cheatgrass seized its opportunity. The weed hitchhiked from Europe in contaminated seed, straw and ship ballast, and crisscrossed the West with the railroads.
That new weed would drastically change the region's fire ecology, among other things. In a typical Great Basin shrubland, forbs and grasses grow patchily underneath a canopy of well-spaced shrubs like sagebrush and shadscale. In contrast, cheatgrass masses in a smothering mane. Its survival strategy is to beat out other plants through its sheer numbers: It can drop 50,000 seeds per square meter. It dies off every year, leaving a thick thatch of flammable material. Even the smallest spark can set off fast-moving fires that kill off any remaining native shrubs.
Normal fire frequency in the Great Basin is every 30 to 70 years; cheatgrass monocultures burn every three to 10. The bare soil left after fire can blow away in spring and land on snow in far-away mountains, causing quicker melt-off. Wildlife - including mule deer and the imperiled sage grouse - quickly move out.
In the mid-1980s, a number of large fires swept through sagebrush communities, and land managers began investigating how to protect and restore the habitat. So far, many restoration efforts have come up short, as native soil erodes after fires, planted seeds fail to establish, and cheatgrass returns en masse. Ecologists estimate it has expanded to between 20 to 50 million acres in the region.
Other invaders - medusahead wildrye, thistles and knapweed -- now have an easier time moving in. Unless cheat-altered landscapes can be made more resilient, one of these may become the next great invader. Federal land managers lack the resources to treat 50 million acres of invaded land. Efforts to fight cheat will be mostly focused in sensitive places like wilderness study areas and important sage grouse habitat. Those priority areas can use any help that Leger, and her cheatgrass-fighting native plants, can give.
Lack of rain is the main culprit in most Great Basin restoration failures. Yet even though land managers know their seedings fail more often in tough, dry years, they do not know exactly why. Jeremy James, a range ecologist with the University of California Agriculture and Natural Resources Program, experimented with tracking seeds planted after four different fires in Great Basin ecosystems in eastern Oregon. He found that seeds germinated but that 90 percent of those seeds that have initiated germination never get above the soil surface.
Think about Leger's Poa. Say one of its seeds drops down onto that hard pebbly dirt and makes its way into the soil. Come spring, the 3.5 millimeter oblong kernel might swell with water as the ground warms and snow melts. Then it stretches out its first root, and sends the beginnings of a leaf upward, towards the soil surface. But in a light snow year, the seed may stop there, lacking the moisture to continue. Maybe there's a late hard frost, and the tiny root freezes and withers. Perhaps a fungus in the soil devours the seed, or the seedling simply cannot push its way through the hard, dry soil crust.
Squirrel tail is native to the Great Basin
In a normally functioning ecosystem, none of these failures would really bother the Poa. Sure, its seeds might not make it one year, but they'd succeed the next, or the one after that. But while Poa might not be in a hurry, rangeland managers lack the luxury of time. They need natives to establish quickly, before cheatgrass takes over again.
James' next experiment, with Leger and other scientists, will try to narrow down the causes behind seed failure. If those native seeds are mostly becoming pathogen fodder, seeds could be coated in fungicides. If the problem is lack of moisture, seeds could perhaps be planted to have better seed-soil contact, especially in dry years.
Beth Leger is tromping through a golden-thatched valley near Winnemucca. It's full of dried cheatgrass. "It's remarkable to me that there can be this little diversity," sighs Leger. She's surprised, too, because although it's common to think of fields of cheatgrass as devoid of any other species, her research has found otherwise.
Leger once viewed cheatgrass-invaded landscapes as monocultures, yet one day, exploring nearby Peavine Mountain, she found native grasses among the weeds. She wondered if they'd adapted somehow in order to fight off the weed and survive. She dug up a few native plants, planted them alongside cheatgrass, and measured how they grew. A number of plants from the weedy areas suppressed the growth of cheatgrass and were also able to successfully reproduce.
Leger has experimented to pinpoint the most competitive natives. She takes me to a dry field surrounded by fencing, where a few green plants have a foothold. "This is squirreltail," she says, pointing out plants that have proven to outcompete cheatgrass. "Amsinckia is one, Mentzelia, this is a lovely one, pretty big after fires."
Leger calls the Amsinckia a "weedy native," because it likes disturbed sites. Her test plots have largely failed this year due to lack of rain, but a few Amsinckias persisted. Last year, when Leger experimentally planted Amsinckia near cheatgrass, the native reduced the weed's size by 97 percent and suppressed its seed production from 576 seeds per plant to just 76.
In natural succession, Amsinckia and other weedy natives would be some of the first plants to colonize a burned or disturbed area. But plants like Amsinckia have seldom been included in restoration seed mixes, partly because they are toxic to cattle, and partly because managers have wanted to seed plants like sagebrush that would be found in a mature Great Basin plant community. If Amsinckia were used in restoration, though, Leger believes it could truly act like a colonizer. It would fight off cheatgrass, but only stick around for a couple years. That would give some time for other perennial natives like squirreltail or Poa to establish, after which they can also do their part fending off cheatgrass.
As Leger and I crunch through the patch of dead cheatgrass outside Winnemucca, the effusive scientist's optimism falters as she ponders the magnitude of the problem.
"The scale of this is ridiculous. This is just one little spot. Think about how many native seeds would need to be planted here. It's unbelievable. And we don't even have a recipe (for restoration). So our hope is that we can find a recipe."
This feature story originally appeared in the September 17, 2012 issue of High Country News (hcn.org).