Submitted to: Arid Land Research and Management
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/11/2005
Publication Date: 3/1/2006
Citation: Hild, A.L., Schuman, G.E., Vicklund, L.E., Williams, M.I. 2006. Canopy growth and density of wyoming big sagebrush sown with cool-season perennial grasses. Arid Land Research and Management. 20:183-194. Interpretive Summary: Mining companies are required to re-establish Wyoming big sagebrush on lands disturbed by the mining process when it is the dominant pre-mine shrub. However, reclamation regulations require that the soil resource and landscape be stabilized against erosion within the first year after topsoil resources are replaced. Effective stabilization of the soil resource requires that a grass community be established on these disturbed landscapes, yet a diverse plant community is desired and required to meet the multiple uses of these lands-wildlife habitat, livestock grazing and recreation. Research has shown that herbaceous perennial plants usually used to accomplish stabilization and restore productivity to reclaimed mine lands also create a competitive environment that limits the successful establishment of shrub species. Our research demonstrated that sagebrush plant density was not affected by native grass seeding rates; however, sagebrush plant canopy volume (size of plant) was greatly reduced at the higher grass seeding rates. Sagebrush seeding rates greater than 2 kg/ha were adequate to achieve the required sagebrush density of 1 shrub/m2 on 20% of the reclaimed area. This research has shown that reduced grass seeding rates can be used to accomplish required forage production and stabilization of the soil resource and will aid in the establishment of more robust sagebrush plants. We recommend that sagebrush be seeded at 2 kg/ha and that the cool-season grasses used in relamation be seeded at no more than 6-8 kg/ha. This prescription will also result in a grass seed cost savings.
Technical Abstract: Post-mining revegetation efforts often require grass seeding and mulch applications to stabilize the soils at the same time as shrub seeding, creating intraspecific competition between seeded shrubs and grasses that is not well understood. Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) is the dominant pre-mining shrub on many Wyoming mines. The Wyoming Department of Environmental Quality, Land Quality Division requires re-establishment of 1 shrub m-2 on 20% of post-mined lands in Wyoming. Reclamationists seldom document the impacts of grass competition on shrub canopy size after reclamation plantings become established even though shrub canopy development is important to vegetative structural diversity. In 1999 we initiated a study at the Belle Ayr Coal Mine near Gillette, Wyoming to evaluate the influence of grass competition on establishment and growth of Wyoming big sagebrush. Combinations of three sagebrush seeding rates (1, 2 and 4 kg pls ha-1) and seven cool-season perennial grass mixture seeding rates (0, 2, 4, 6, 8, 10, and 14 kg pls ha-1) were seeded during winter 1998-1999. Shrub density and grass cover were assessed from 1999 to 2004. We monitored sagebrush canopy size in 2001, 2002 and 2004. All sagebrush seeding rates provided shrub densities ' 1 shrub m-2 after six growing seasons. Grass production ' 75 g m-2 was achieved by seeding grasses at 6 to 8 kg pls ha-1. Canopy growth of individual sagebrush plants was least at the higher grass seeding rates. Reduced grass seeding rates can aid in achieving Wyoming big sagebrush density standards and enhance shrub canopy growth.