USA – Large wildfires have dominated the news in much of the western U.S. this past summer. Conservancy scientists working in rangelands and forests are engaged in many efforts to understand, cope with or avoid the effects of these fires. In fact, one Conservancy field crew working in the Northern Great Basin Experimental Range (NGBER) was chased from their beds and field work by one of these fires for a few days. They were collecting data on novel restoration approaches to reduce the vulnerability of sagebrush habitat to large wildfires beforehand and recover more successfully after the fires. This involved replacing one of the key culprits contributing to wildfires in the west, cheatgrass, with native plant species.
Jay Kerby, a rangeland ecologist for The Nature Conservancy in Oregon describes the scene….
“Chad Boyd, one of the USDA scientists that we work with, texted me about a wildfire that had started early in the afternoon of August 2nd off Highway 20 in remote southeastern Oregon. Believed to have been started by an unidentified motorist, the Cinder Butte fire was about 10 miles west of the 16,000-acre NGBER where numerous science staff, including four Conservancy employees, were busy with field data collection. Wind was forecast from the north and the first reports were that fire containment was expected at a few hundred acres. Field staff had already seen the smoke plume and we were in communication, at least to the extent that the spotty cell service allowed. We decided not to evacuate initially, but as afternoon moved into evening, reports progressively worsened; the fire had escaped initial containment, then spread rapidly to the south, then winds were gusty and variable.”
“With the last report, I ditched my (forgiving) girlfriend at the movie theater on date-night to roust Conservancy staff out of their bunkhouse at the NGBER and back to Burns as a precaution against a possible big fire run to the east that would put them in harm’s way. As I drove west, the bright glow on the horizon gave me a sinking feeling in my stomach. In the last few years Oregon’s sagebrush landscapes have seen unprecedented wildfires totaling several million acres blackened and many ingredients for that recipe seemed present that night – strong winds, dry and uninterrupted sagebrush and grass fuels for many miles downwind, and firefighting resources stretched across numerous wildfires throughout western North America.”
Thanks to an outstanding firefighting effort, Cinder Butte was contained at “only” 52,465 acres, most of which burned in a 36-hour window. A fire that size is still significant to affected locals, but far smaller than recent fires that approached or exceeded a half million acres.
Why Cheatgrass -> Fire -> More Cheatgrass
Cheatgrass (and other exotic grass) invasion plays an outsized role in these wildfires. Much of the native Great Basin ecosystem is made up of bunchgrasses and shrubs with plenty of soil in between. This space once helped to keep fire contained despite the dry conditions, since it takes quite a bit of wind to move fire from one plant to another. Another important difference is timing. Invasive grasses dry out weeks if not months before native. Lightning strikes in May can cause fire in dry annuals, but in bunchgrasses that are green it won’t necessarily catch or spread.
Now, with more than 25,000 mi2 (39,000 km2) of dense cheatgrass monoculture blanketing the west, fire has a readily available fuel load that is easy to spread across – cheatgrass doubles the likelihood of a fire catching on and fire frequencies increase tenfold after an area is invaded by cheatgrass.
Not only that, fire helps cheatgrass to spread, outcompeting native plants, setting up a vicious cycle. Because it is an annual grass and because it tends to complete its lifecycle before the fire season is in full swing, cheatgrass easily reseeds and establishes in the places left open by wildfire. Its native competitors in the sagebrush steppe (including bunchgrasses) are perennial and evolved such that they don’t naturally recruit new plants every year. Since most of the plants can live five years and some up to twenty, in a world before cheatgrass invasion, they only needed a great year once every five to twenty years – like a plant baby boom – to maintain populations.
Large chunks of native plant communities can be wiped out by a fire, and some may have been already depleted by recent or historic over-grazing. Add cheatgrass, which is also a strong competitor for water resources and ubiquitous across North America, to the mix and there’s not much chance that the native bunchgrasses and shrubs will be able to repopulate the area on their own.
As bad as a cheatgrass monoculture with its frequent fire hazards can get, that’s not the only threat. After a fire where you get wind erosion, you get water erosion. In a desert, you don’t have a lot of soil to lose. The plants are gone. After a few fires, you’re out of topsoil. The scale for that to recover is measured in geologic time.
Loss of bunchgrasses set the problem in motion and bringing back bunchgrasses could be the solution. When bunchgrass ecosystems are intact, they limit both the spread of fire and the invasion of exotic grasses.
Sisyphean Restoration Challenges
Using current planting technologies, usually seed drills or aerial broadcasting, land managers estimate that only about 10% of restoration efforts are successful. Like Sisyphus with his fabled rock, they may end up putting resources and effort into making a change, only to end up back where they started — over and over again.
It’s not surprising that some turn to more cost-effective alternatives like planting crested wheatgrass, a non-native bunchgrass that grows more easily with current planting technologies and can hold off cheatgrass invasion. However, crested wheatgrass also outcompetes native plants, sometimes resulting in a monoculture.
Since fighting wildfires can cost the US in excess of $1 billion each year, if restoration efforts could be successful closer to 50% of the time, they would pay for themselves in saved wildfire costs.
Scientists with The Nature Conservancy (TNC) in Oregon and the USDA-Agricultural Research Service are working to give native plants a leg up and see if we can change the fire cycle. Using technology, we can disrupt this unnatural situation that humans have caused and put sagebrush steppe back on track to be more productive for biodiversity & ranching, spend less money for fighting fires and have less smoke in the air.
We’re researching a variety of seed enhancements that will give native seeds the edge they need to survive and establish new plants — if successful, it will be like giving Sisyphus a bulldozer to push that boulder over the hill once and for all.
Science for Seeding Solutions
We’re not just throwing things on a seed – we’re very deliberate about it. We identify a barrier to establishing native plants and work backwards from that to develop a solution. There’s a lot of variation in the soil composition, elevation, and terrain of sagebrush steppe, so each site can face unique challenges.
Some of the primary barriers to seed germination and seedling survival that have been identified are – low soil water availability, difficulty of seedling emergence in crusting soil, timing of germination relative to freezing weather, coverage of broadcasted seeds on the land, herbicide effects on seedlings and competition from other seedlings, especially cheatgrass. Each of these challenges can be addressed with unique seeding technologies.
Soil Water Availability.
After fires in places where woodland shrubs and plants contain high amounts of resins, waxes or aromatic oils, those substances can enter the soil, making it water repellant and preventing seeds from getting enough water to germinate. Soil water repellency can persist in soil for more than three years after a catastrophic wildfire.
Applying soil surfactants is a common solution for water repellency problems on sports fields and is being taken up by the agricultural industry. However, its’ not practical to apply surfactants across thousands of acres of restoration area.
Matt Madsen, formerly with USDA in Burns and now with Brigham Young University, in cooperation with Aquatrols Corp., developed a method of applying the soil surfactant directly to native seed as a coating. Once the seed is planted, precipitation spreads the surfactant into the soil near the seed, creating a microclimate that allows infiltration and retention of water.
Lab results have shown that surfactant seed coatings can improve plant survival up to twofold in water repellent soil.
Seedling Emergence in Crusted Soil
A soil crust is a thin layer of tough material at the soil’s surface that’s significantly more densely packed than the soil below. Like a single person trying to push a car out of a muddy rut, a newly germinated plant might not be strong enough to budge the soil crust.
Irrigation and mechanical intervention — the most common solutions for breaking up a soil crust in agriculture — are impractical at the large scale of sagebrush steppe restoration.
But, just as a group of people pushing together can get a car out of a rut, a group of plants pushing at the same area of soil crust can break through it together. To improve the chances that plants will germinate in the same area at the same time we’re using a coating to clump seeds together in clusters.
In a greenhouse study, seeds planted as clusters were twice as likely to emerge through the soil crust. And even after emergence each individual seedling in the cluster put on more mass than seedlings from seeds that were not clustered.
Timing of Germination
In restoration seeding, seeds are often planted in late fall on the assumption that they will be dormant through winter and will be in place in late spring when soil conditions are more favorable for germination.
Surprisingly, we’ve found that some bunchgrasses like bluebunch wheatgrass and bottlebrush squirreltail have little or no dormancy period. When planted in late fall, they start to germinate soon after and most young plants are killed in winter freezes.
Nevertheless, planting in fall works best for many other species and planting everything at once saves on restoration costs. A customized seed coating can delay germination until the spring when more water is available and freezes are past.
In a preliminary study, all non-treated seeds germinated in fall or early winter, while most treated seeds germinated in late winter or early spring. Plots with the time-delay coating had 2.2 times as many plants as those with untreated seeds.
Coverage of Broadcasted Seed
If soil is too rocky or steep, a seed drill is just not going to work. So, land managers broadcast seed from a helicopter or airplane. Seed literally flies everywhere. It takes a lot of luck for seeds to land in a suitable environment with enough soil and nutrients to grow. One study found that aerially broadcasted big sagebrush failed to establish in 23 of 35 restoration projects, that’s roughly 66% of the time.
Again, soil made in the pasta maker provided a solution, but this time with a twist. Rounded pellets would be blown across the landscape like tumbleweeds leading to an uneven distribution and likely not the best result for restoring plants across a landscape.
We came up with a seed pillow design that is rounded on the sides and flattened on the top and bottom, making it more likely that that pillow will form a bond with the soil surface and stay in place on the landscape.
As in the above example, the “dough” can be adjusted to the needs of the seed and, once it rains, the pillow breaks down creating a suitable microhabitat for the seed to flourish. On top of that, since this planting method doesn’t disturb the soil, it could be used to plant more of a desired species without disturbing native species that are already present.
For a variety of reasons explained above, native grasses in the early stages of life don’t compete well with exotic annuals like cheatgrass. Therefore, before natives can be planted, exotics usually need to be removed.
So far, the most successful removal of exotics has been with herbicides applied to the soil. Unfortunately, these same herbicides prevent native seedlings from growing — often seeding efforts are postponed up to a year after herbicide application, increasing costs and giving exotics a chance to return.
Activated carbon is sometimes used in agriculture to protect seeds and seedlings from herbicide. We’re working on herbicide protection pods – a variation on the seed pillows also made with the pasta maker – that use a “dough” of seeds, water sensitive binders, activated carbon, and other additives. After seeding the herbicide protection pods, applied herbicide prevents weeds like cheatgrass from growing but native seeds in the pods are sheltered by the carbon binding and neutralizing the herbicide.
In a laboratory study where bluebunch wheatgrass was planted as a native in competition with exotic cheatgrass, the seeds in the herbicide protection pods were protected from herbicide, leading to plots with nineteen times more bluebunch wheatgrass (by biomass) than the control plots. And a field study of this treatment had twice the density of seeded bunchgrass in both medusahead and cheatgrass invaded sites.
The Future of Sagebrush Restoration
When cheatgrass burns it releases carbon into the air. Expansion of cheatgrass has released an estimated 8 teragrams of carbon into the atmosphere and will likely release another 50 teragrams in the coming decades.
This could feed into another vicious cycle as climate change may increase the likelihood of cheatgrassinvasion in the future if native species mortality increases from warming and drought. However, established bunchgrasses are resilient to harsh, arid conditions. If water is scarce during the prime growing period for exotic annuals like cheatgrass, then native bunchgrasses will have the advantage.
One of the greatest economic costs of cheatgrass invasion is the associated cost of wildfire. Successful establishment of perennial grasses at degraded sites can slow or halt the spread of exotics like cheatgrass – saving considerable expense, protecting property vulnerable to wildfires, keeping smoke out of the air, and preventing the release of carbon.
“Establishing native plants in lower elevation sagebrush communities is one of the greatest challenges facing rangeland ecologists and it will only be overcome by developing a host of technologies and strategies that address the numerous barriers currently limiting their establishment,” says Kirk Davies, lead author and a rangeland scientist for the USDA-Agricultural Research Service. “Successful restoration of native plant communities will require developing partnerships, such as the TNC-ARS collaboration, that build on each other’s strengths to make critical advances in science and conservation.”
If our seed enhancement technologies increase the success rate of restoration enough we anticipate the costs could be offset by the benefits of reduced fire frequency alone – not to mention the improved habitat for wildlife, forage for livestock, and potentially improved carbon storage.
In an article recently published in Rangeland Ecology & Management we shared results of the largest field test to date. In a multi-year study, we found that while aerially broadcasted seed pillows alone are not more effective in sagebrush restoration than bare seeds, they do take hold in places and time periods where bare seed failed (and vice versa). In this case, we estimate that if land managers could hedge their bets, using both seed pillows and bare seed in the same location in two years, they could achieve an 86% restoration success rate for big sagebrush.
These results, as well as additional positive results from field trials, have encouraged us to continue advancing exciting work by expanding the scale and scope of testing and demonstration, evaluate market opportunities and pathways to commercialization, and explore regional and international partnerships to further restoration effectiveness across arid lands beyond the sagebrush steppe.