Solarization to control downy brome (Bromus tectorum) for small-scale ecological restoration.
Downy brome (Bromus tectorum L.) is a common impediment to ecological restoration, because its seedbank remains viable after repeated treatment with herbicides. Soil solarization has been used in ecological restoration to control seedbanks of invasive plants. Here we test the efficacy of soil solarization to reduce B. tectorum cover and establish native plants at a site in B. tectorum's core invasive range with a long history of disturbance and infestation. Solarization raised soil temperatures by as much as 13 C and reduced B. tectorum densities by approximately 20-fold. In 30 plots solarized for 0 to 101 d, B. tectorum emerged in inverse abundance to treatment duration. Broadleaf weeds were less abundant than B. tectorum before treatment, and diminished under solarization, but their response to solarization was weaker than B. tectorum's, and they emerged in greater numbers than B. tectorum 2 to 3 yr after treatment. When seeded after solarization, a native perennial bunchgrass, squirreltail [Elymus elymoides (Raf.) Swezey], did not differ in abundance between solarized and control plots. Solarization may facilitate B. tectorum control on a small scale without jeopardizing the establishment of native plants, but only if treatment durations are long and subsequent management of broadleaf weeds and remnant B. tectorum is planned.