Postfire drill-seeding of great basin plants: Effects of contrasting drills on seeded and nonseeded species

Objectives of postfire seeding in the Great Basin include reestablishment of perennial cover, suppression of exotic annual weeds, and restoration of diverse plant communities. Nonconventional seeding techniques may be required when seeding mixes of grasses, forbs, and shrubs containing seeds of different sizes. We conducted an operational-scale experiment to test the effectiveness of two rangeland drills (conventional and minimum-till) for seeding native plant mixes following wildfire in Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) communities. Both drills were configured to place small and large seeds in alternate rows. We hypothesized that the minimum-till drill's advanced featureswould improve establishment compared with the conventional drill. We also hypothesized that theminimum-till drill would cause less damage to residual perennials, whereas the conventional drill would have a greater impact on annual weeds. The experiment was replicated at three burned sites and monitored for 2 yr at each site. Seeded plant establishment was lowest at a low-precipitation site that became dominated by exotic annuals. Another site had high perennial grass establishment, which effectively suppressed exotic annuals, while a third site attained high diversity of seeded species and life forms but became invaded by exotic annuals in plant interspaces. Small-seeded species generally established better with the minimum-till drill equipped with imprinter wheels than the conventional drill with drag-chains. However, large-seeded species frequently established better with the conventional drill despite its lack of depth bands and press wheels. Soil disturbance associated with the conventional drill had a negative effect on residual perennials and exotic annuals at some sites. Results indicate that different drill features are advantageous in different ways, but that either of the tested drills, if properly used, can be effective for seeding native plant mixes provided site conditions are otherwise favorable for seedling establishment.