Integrating Herbicides and Re-seeding to Restore Rangeland Infested by an Invasive Forb-Annual Grass Complex

By Jane Mangold, Noelle Orloff, Hilary Parkinson, and Mary Halstvedt. Ecological Restoration, 33, 16-19.

The goal of this study was to restore desired, perennial grasses to rangeland impacted by spotted knapweed and cheatgrass through the integration of herbicides and reseeding. Two ecological assumptions guided our study: first, seeded species establishment would increase as control of the weedy species spotted knapweed and cheatgrass increased (Sheley et al. 2001Davies 2010); second, increased establishment of seeded species would result in lower abundance of the weedy species spotted knapweed and cheatgrass over time (Whitson and Koch 1998Rinella et al. 2012). We tested eight herbicide treatments and six seeding treatments at a site near Missoula, Montana (46°57’04” N, 114°07’07” W). Total yearly precipitation averages 34 cm and average annual high and low temperatures are 14.5°C and 1°C, respectively. Soils are gravelly loams of the Argixerolls-Haploxerolls complex. The site was dominated by spotted knapweed and cheatgrass, and Kentucky bluegrass (Poa pratensis), Canada bluegrass (P. compressa), and bulbous bluegrass (P. bulbosa) also occurred frequently.