English

Abstract

Ensuring Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) survival remains a challenge on many mines even years after initial establishment. Wildlife utilization may be a major influence on its survival. A wildlife exclosure was erected in June 2001 on a portion of a study initiated in 1990 at the North Antelope/Rochelle Mine in northeastern Wyoming. Investigations focused on the influence of wildlife utilization on big sagebrush survival and growth under 3 grass seeding rates, inside and outside of the exclosure. Growth, browsing, and survival were evaluated on 72 marked sagebrush plants inside and outside of the exclosure. Permanent 1 m 2 quadrats established in 1990 and 2 x 12 m belt transects were utilized to estimate big sagebrush density both inside and outside of the wildlife exclosure. Big sagebrush mortality, based on the 72 marked plants, was 24 outside the exclosure and 8 inside the exclosure for 2001-2002. Grass seeding rate had no effect on mortality inside the exclosure; however, mortality outside was lowest in the highest grass- seeding rate, 32 kg ha -1 . The higher grass-seeding rate appears to have enhanced big sagebrush survival although a specific ecological explanation is not clear from our data. Other research has shown similar responses whether browsed by livestock or wildlife. Big sagebrush browsing outside of the exclosure was 100% on the marked sagebrush plants and no browsing was evident inside the exclosure. Fecal pellet group and individual pellet data along with bite characteristics on the sagebrush leaders indicated that rabbits were the major browsers. Annual leader length (new growth on sagebrush) averaged 44.3 mm inside the exclosure and only 16.8 mm outside the exclosure for the 2 years. Findings of this research has shown that wildlife utilization can significantly impact shrub growth and survival on reclaimed mine lands, making it difficult to achieve the shrub density requirement for bond release.