Not everyone is ready to surrender to cheatgrass though. Zion National Park is tackling the cheatgrass problem head-on. Cheryl Decker is a biologist with Zion National Park.

Chery Decker: Zion canyon is a highly disturbed area due to natural erosion which caused the canyon and is still causing the canyon, and human disturbances such as grazing, farming, and logging. Because of these disturbances and the invasion of the West by exotics, the canyon floor is covered by about 70 % annuals, mostly in the form of bromes – rip gut brome and cheatgrass. These bromes dry to a fine, fast fuels by June when we get the majority of our visitation in Zion canyon, which has reached up to 2.7 million visitors per year. This not only creates an extreme fire hazard during heavy visitation, but it is also extremely hard to rehabilitate since bromes are so competitive.

Land managers Zion began experimenting with an herbicide named PLATEAU that targeted annual grasses. They discovered that in the year following herbicide treatment cheatgrass was eliminated and some of the native perennial shrubs took off in growth.

Cheryl Decker: Several years ago in Zion we tried several experiments that we termed ‘cowboy science’ because it wasn’t very statistically valid. But we just wanted to try several things out that we thought might reduce the competition from bromes and release the natives that we knew were still in the seed bank. What we found that was the most effective was burning, which reduced organic matter levels which ties up the herbicide PLATEAU, which was extremely effective at low rates in preventing cheatgrass germination and still allowing natives to germinate.

The Kolob Fire ignited in June, 2006 and burned over 10,000 acres within Zion NP and 6,000 acres on adjacent land. Rehabilitation efforts have focused on controlling cheatgrass and promoting native shrubs and grasses. Photo: National Park Service

Those experiments convinced Park officials that some more formal studies were warranted. Matt Brooks is a researcher with USGS who has worked on invasive species across the West. He came to Zion to work with the land managers set up a project designed to scientifically assess the effectiveness of different treatments targeting cheatgrass and other related invasive grasses.

Matt Brooks: We got a project funded by the Joint Fire Science Program to look at different ways of converting the vegetation from a nonnative grasses to native shrub. It essentially involved an initial treatment where you remove the biomass using fire or mowing followed up by herbicide treatment that would provide a few years of control of the brome grass and over the top of that different seeding treatments. The idea was that during the time that the brome grass was suppressed by the herbicide the seeded species would be able to get established. It was never envisioned that you would go out there and spray herbicides every single year. You would maybe apply them for a few years and then just allow the native species and shrubs to get established and then back off and if the shrubs were large enough they could then compete with the cheatgrass.

In 2006 the Kolob Fire burned about 10,000 acres within Zion and about 6,000 on adjacent land. The preliminary research that had been done on cheatgrass convinced park officials that they had an opportunity to conduct a bold experiment. They decided to treat the entire burned area with herbicide and start a long term monitoring program to study the effects. A unique collaborative effort was born involving land managers at the park, members of the Park Service BAER team, researchers from Northern Arizona University and USGS, and also researchers from the company BASF which manufactures PLATEAU. They used aerial applications of the herbicide over the burned area and then also reseeded the area from the air as well, using different mixes of native seeds. Most importantly they began a monitoring program to assess the effectiveness of the project. Dr. Andi Thode, a fire ecologist with NAU, has been working on the monitoring program along with a number of her graduate students.

Prescibed burns have been used to control cheatgrass germination and release native perennials from the seed bank. Photo: National Park Service

Andi Thode: This is a huge scale project with the Kolob Fire. Previously they hadn’t done any work and I don’t believe any work had been done at that kind of landscape level spraying herbicide, particularly in a National Park. Some of the reasons for this big project are again because of the fire regimes of pinyon-juniper woodlands in particular are infrequent, high severity fire regimes. The frequency that fire can carry through cheatgrass – so once you have an annual invasive grass come in and invade it and it creates a solid mat of fuels on the woodland floor where it used to be relatively sparse fuels, fire is carrying very easily through there and can carry every year in a system where fire would only carry every 200 years or so. They had an appreciation of this and were really concerned once the burn went through.

The collaboration between fire managers and natural resource managers was also instrumental in getting the cheatgrass project started. Andi Thode says that collaboration between these groups has not always been easy.

Andi Thode: There used to be a split in a lot of the agencies between natural resource managers and fire managers and that split has got to disappear very quickly and very soon because fire managers are dealing with much more complex issues that cross a lot of natural resource issues and the sooner those folks start talking and working together – which I have seen happen in quite a few places – the better off the land management will be in general.

I asked the researchers if their work in Zion National Park has given them a ray of hope that invasives like cheatgrass can be managed over the long term.

Andi Thode: I would say a ray of hope. The data is still very preliminary. We are seeing some differences between our controls and the herbicide spray areas. But the longer term questions, even if this does appear to work in this area, are going to be even if it does work – how long did it work for? How much did it ultimately cost and is that cost worth the timeframe that you get? What other effects did it have on things that we thought about, but weren’t able to monitor like water quality, amphibians, and other native plant species, particularly annuals and some of the perennials? We don’t really know the answer to that, but I would like to keep a glimmer of hope definitely.

Matt Brooks: If there is anything I have learned over the years is that there is no one single, silver bullet. It is always going to be an integrated approach that takes into account what you do in the short term and what you do in the short term, and in the short term this may involve some pretty intensive things that are done like using herbicide. But, I think there is land management that needs to be integrated into it. Livestock grazing is something that in some parts of the West that can be part of the equation. Prescribed fire, surprisingly enough, is often something that can be integrated to manage cheatgrass. Really in terms of cheatgrass management, our ultimate goal has to be developing vigorous, robust native plant communities develop that can compete with cheatgrass so we can walk away from it for a while and let the vegetation community do the job.