Long-Term Survival of Direct Seeded Wyoming Big Sagebrush Seedlings on a Reclaimed Mine Site

Abstract

Reestablishment of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis) on mined lands has become a requirement in recent years in Wyoming. Its reestablishment by direct seeding has been greatly improved through a better understanding of the role of topsoil management, mulching, seed quality, and competition. However, long-term survival of reestablished sagebrush seedlings on mined sites has only rarely been evaluated because of the short-term nature of previous studies. Sagebrush seedling survival was assessed after eight years on a mine site in northeastern Wyoming near Gillette on research initiated in 1992 to assess the effect of several cultural practices on sagebrush establishment. Wyoming big sagebrush survival was found to average 59% after eight years. Interestingly, the greatest survival occurred on the treatments seeded at the higher rates of grass (competition). Sagebrush survival was 46, 58, and 72% for the grass seeding rates of 0, 16, and 32kg pure live seed (PLS) ha -1 , respectively. This resulted in a density of 2.5, 2.4, and 2.8 shrubs m -2 for the respective grass seeding rates. These findings in some ways contradict the belief that herbaceous competition restricts Wyoming big sagebrush establishment; however, we believe the higher grass seeding rates actually resulted in the grass plants "sheltering" the seedlings from excessive foraging by wildlife. Browse estimates showed that 40, 27, and 32% of the sagebrush seedlings had been browsed in 2001 on the 0, 16, and 32kg PLS ha -1 grass seeding rates, respectively. The average survival (59%) should enable reclamationists to meet the Wyoming shrub density requirement of 1m -2 during the last two years of the 10-year bonding period if initial establishment density is S 2 shrubs m -2 .