Establishing Wyoming Big Sagebrush in Annual Brome-Invaded Landscapes with Seeding and Herbicides

Abstract

Seeding native plants into degraded grasslands presents major challenges. Often, seeded species fail to establish and areas become/remain dominated by unwanted plants. We combined herbicides and seeding in former coal mining fields dominated by exotic winter annual grasses (downy brome [Bromus tectorum L.] and Japanese brome [Bromus arvensis L.], hereafter “annual bromes”). The main interest was restoring Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis [Beetle & A. Young] S.L. Welsh, hereafter “big sage”), a very difficult species to restore to North American grasslands. We tested the nonselective herbicide glyphosate and the grass-specific herbicide quizalofop. The summer following herbicide applications and seeding, annual brome cover in controls 22% (CI95% 13%, 36%) was significantly greater (P < 0.03) than in glyphosate 11% (CI95% 5%, 25%) and quizalofop 16% (CI95% 7%, 35%) treatments. At Decker mine, glyphosate increased seeded big sage density (P < 0.04) from 0.76 (CI95% 0.27, 2.11) to 3.05 (CI95% 1.42, 6.56) plants ⋅ m-2 the second summer after seeding. Corresponding increases for Spring Creek mine were from 0.11 (CI95% 0.03, 0.43) to 0.43 (CI95% 0.13, 1.40) plants ⋅ m-2 (P < 0.04). These results were consistent across two experiments initiated in different years. In addition to big sage, our study's seed mixes contained native grasses and forbs, and herbicide treatments tended to promote establishment of these plant groups. In annual brome-dominated areas of the northern Great Plains, conditions amenable to big sage seedling establishment do not appear entirely uncommon, and herbicides can increase establishment.