Cheatgrass competition and establishment of desert needlegrass seedlings

Abstract

Desert needlegrass (Achnatherum speciosum [Trin. Rupr.] Barkworth) is potentially a valuable native species for use in restoration seedings in the more arid portions of the Great Basin. Seedlings of desert needlegrass were grown in a greenhouse with 5 different densities of cheatgrass (Bromus tectorum L.). The densities of cheatgrass used in the greenhouse experiments were derived from sampling populations in the field where desert needlegrass is adapted and seedling recruitment is desired. Cheatgrass is known to close sites to the establishment of seedlings of perennial grasses through competition for moisture. The response variable was height of desert needlegrass shoots. Height measurements were taken weekly for 12 weeks following seedling emergence. During the first 5 weeks following emergence there were no significant (P less than or equal to 0.05) differences in the height of desert needlegrass seedlings among treatments. From week 5 through week 12, there was a highly significant (P less than or equal to 0.001) difference in the height of desert needlegrass shoots between the control and all levels of cheatgrass density. Reducing the density of cheatgrass seedlings in the greenhouse to the equivalent of 25% of the density present in the field still did not allow the establishment of the perennial grass seedlings. Even though desert needlegrass is adapted for natural establishment in the drier portions of the central Great Basin, some form of cheatgrass control is required for the perennial grass seedling establishment if cheatgrass is present. Cheatgrass control has to be more than a reduction in density, it has to be near complete control of the annual grass.