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|  Weeds follow peopleOne supposes that not long after the first homesteader arrived so did the first weed. Russian thistle, probably, which hitched a ride onto the Great Plains in some flax seed from the Ukraine. But at the time, perhaps weeds were no more of a scourge than grasshoppers or hail or disease.Today the types are more numerous-spotted knapweed, leafy spurge, cheatgrass, yellow starthistle-as are the ideas about why they spread and what to do about them. About this there tends to be agreement: weeds follow people; and weeds exploit disturbances in native ecosystems. But are invasive weeds necessarily the legacy of disturbances wrought by drought or wildfire? MSU associate professor and Extension weed specialist Roger Sheley said he knows of weeds dramatically increasing following wildfires and is concerned about infestations in burnt areas. After a prescribed burn in the Elkhorn Mountains, dalmatian toadflax seed output increased from 29 seeds per plant to 1,328 seeds, Sheley found. Plot-scale studies he did in the Pacific Northwest showed an increase in the biomass of three invasive species following fire.
But others are less sure. It seems more is known about the use of fire as a tool for controlling weeds than about its role in spreading them. "We would expect weeds to spread after wildfires but the data aren't there yet," said MSU assistant professor of ecology Cathy Zabinski. "It's very difficult to generalize, but [fire and drought] are potential drivers." Invasive weeds did not overtake Yellowstone National Park following the well-publicized fires of 1988. "There's the perception that crown fires destroy everything, but that doesn't happen," said the USGS's Don Despain. "There are so many seeds and rhizomes in the soil that the forest doesn't recover, it just comes up, like it does in the spring."
"So it doesn't seem that [weeds] are displacing natives, but the research isn't there," Despain said. Soil types, vegetation, fire history, precipitation, land use and management patterns, what's in the seed bank, and other factors combine to present different sets of conditions across the landscape. "If these species are waiting in the wings, then with more drought and more fire we may see more weeds," said MSU associate professor and agroecologist Bruce Maxwell. "How many species are opportunistic this way? We're primed to find out."
Sheley said a big concern during drought is grazing native plants beyond half their size. Defoliating bluebunch wheatgrass past 60 percent, for example, dramatically increased infestation by diffuse knapweed, according to a 1997 study. In dry grain fields last year, Maxwell saw an explosion of wild oats, "far more than we expected," as well as increases in both kochia and Russian thistle. Beyond the wheat field, Maxwell worries that, as rural homeowners build next to federal, national park and forest lands, weeds from lawns and gardens could gain a toehold there. Confounded by the difficulty of generalizing from single studies to an entire ecosystem, plant scientists hope to apply new tools to work across much broader scales. Figuring out how to use satellite data, for example, will improve their ability to make landscape-level predictions and to better assess potential drivers like climate and fire on weeds in the West. Dodging self-analysisClearly, drought, wildfire and weeds impact what we like about this place and how we live off what's here. Beyond agriculture, they affect the fishing, hunting, hiking and other ways of recreating. They dramatically underscore the collision of human values with the rhythm of nature. They may even signal that the future of these landscapes may not be like their past.
"The west, traditionally cheerful and carefree, dodges self-analysis like a plague," wrote newspaperman and historian Joseph Kinsey Howard. But it shouldn't. There are things we can do. In terms of wildfires, people like Hansen advocate for new approaches for managing the risk in such places as the Greater Yellowstone Ecosystem. One suggestion is managing the forests in zones so that a "let-burn" policy is employed in remote areas, prescribed fire and well-guided thinning occurs in general forest lands, and active fuel reduction is undertaken near homes and structures in the "urban interface." What's more, local governments should take into account the cost of fire protection when considering new rural subdivisions. Rural homeowners should educate themselves about fire risk and strategies for reducing that risk, Hansen said. Weeds shouldn't be ignored and can be battled with an array of tools that includes chemical spraying, mowing, grazing, pulling, biological control and burning. County weed control offices or Extension offices are good places to contact for advice. Drought, well, we can't do much about that, except live within its means and recognize that it follows its own cycles and not ours. 
Annette Trinity-Stevens
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