Survival and growth of blue gamma seedlings in competition with western wheatgrass.

Abstract

Competition from other plant species may inhibit establishment and reduce phytomass production of blue grama [Bouteloua gracilis (H.B.K.) Griffiths] on rangeland. Varying levels of competition were achieved by transplanting four-week-old blue grama seedlings into openings 0, 4, 8, or 16 cm in diameter in a western wheatgrass [Pascopyrum smithii (Rydb.) A. Love] sod or in fallow soil. After the first growing season, 42, 79, 88, and 92% of blue grama seedlings survived in 0, 4, 8, and 16 cm openings, respectively, in sod. All plants survived the first growing season in all treatments on fallow, but 86% of the plants in fallow died the first winter. In the first growing season, blue grama plants averaged over 13 seed heads per plant in fallow but less than 1 seed head per plant in sod. Both above- and below-ground phytomass of blue grama and western wheatgrass were reduced by competition. Plant height in fallow was about twice that in sod. Both survival and vigor of blue grama seedlings were reduced with increasing levels of western wheatgrass competition. For successful establishment of blue grams in an existing sward, artificial or natural openings must be created.