INFLUENCE OF SAGEBRUSH AND GRASS SEEDING RATES ON SAGEBRUSH DENSITY AND PLANT SIZE

Authors: VICKLUND, L - RAG COAL WEST, INC; Schuman, Gerald; HILD, A - UNIVERSITY OF WYOMING

Submitted to: Wildland Shrub Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/3/2003
Publication Date: 2/1/2004
Citation: Vicklund, L.E., Schuman, G.E., Hild, A.L. 2004. Influence of sagebrush and grass seeding rates on sagebrush density and plant size. Wildland Shrub Symposium Proceedings. pp. 40-43.

Interpretive Summary: Reclamationists are required to re-establish Wyoming big sagebrush on mined lands in Wyoming and western states where it is a common plant in the native rangeland community. Wyoming law requires that it be re-established at a density of 1 shrub/m2 on 20% of the disturbed land area. Establishing Wyoming big sagebrush has been difficult to re-establish on mined lands because of the competition provided by the perennial grass stand that is required to be established to stabilize the soil against erosion and to provide forage of equal or greater production of that prior to disturbance. Wyoming big sagebrush establishment is confounded by the low seedling vigor of sagebrush seedlings. This research has shown that grass seeding rates of 4 kg/ha or greater can produce equal aboveground production to 14 kg/ha grass seeding rates. Sagebrush seedling density has not shown a response to grass seeding rates over three years (1999-2001) but have exhibited significant sagebrush seedling size response to grass seeding rate. Larger sagebrush seedlings are more likely to compete and survive climatic and biotic stresses during the 10-year bonding period. The research also demonstrated the importance of sagebrush seeding rates in establishing adequate sagebrush plants. Sagebrush seedling density increased significantly with increasing sagebrush seeding rates of 1, 2, and 4 kg/ha. A sagebrush seeding rate of 1 kg/ha did not result in sagebrush seedling densities that would achieve the shrub standard, considering mortality rates reported by other scientists. Therefore, based upon the results of this study we would recommend that mining companies reduce their seeding rates of 12-20 kg/ha typically used to 4-6 kg/ha and seed the sagebrush at a seeding rate of 2 kg/ha. This combination of grass and sagebrush seeding rates will greatly enhance the success of meeting the shrub density standards required by law on mined lands.

Technical Abstract: Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) establishment on mined lands in Wyoming is a critical element of reclamation success. Because of its importance to wildlife, shrub density is used to assess reclamation success for wildlife habitat in Wyoming. Research was initiated at the Belle Ayr Mine near Gillette in 1999 to evaluate the effects of Wyoming big sagebrush seeding rates and grass competition on sagebrush establishment. Sagebrush seedling densities demonstrated consistent increases with increased sagebrush seeding rates. The 4 kg PLS/ha sagebrush seeding rate resulted in significantly greater density than either the 2 or 1 kg PLS/ha seeding rate in 1999 to 2001. Grass competition (grass seeding rates of 0, 2, 4, 6, 8, 10, and 14 kg PLS/ha of a mixture of C3 native species) did not significantly affect sagebrush seedling density. However, 1999 and 2000 precipitation was above or near normal, resulting in adequate moisture for seedling emergence and growth of all seeded species. Sagebrush seedling density declined at the higher grass seeding rates in 2001 but seedling density was not significantly affected by grass seeding rates (P=0.12). Precipitation in 2001 was well below normal and grass competition significantly affected sagebrush seedling canopy volume. Sagebrush seedling canopies were significantly smaller at grass seeding rates > 4 kg PLS/ha. Continued evaluation of these treatments on sagebrush seedling performance will enable development of a seeding strategy that enhances establishment of Wyoming big sagebrush on reclaimed mine lands.