Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2002
Publication Date: December 1, 2002
Citation: MACKOWN, C.T., JONES, T.A., JOHNSON, D.A., REDINBAUGH, M.G. SEEDLING N UPTAKE BY DESIRABLE PERENNIAL AND INVASIVE ANNUAL COOL-SEASON GRASSES: EFFECTS OF N FORM. AMERICAN SOCIETY OF AGRONOMY MEETINGS. 2002. Abstract No. c03-mackown133709-o. CD-ROM. Interpretive Summary: Abstract Only.
Technical Abstract: Infestation by annual cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) have decreased productivity and biological diversity and increased the frequency of wildfires on grazinglands. On disturbed sites, bottlebrush squirreltail (BBST, Elymus elymoides), a short-lived native perennial, appears to compete against invasive non-native annuals when available soil N and nitrification are reduced. We tested the hypothesis that differences in N uptake activity could account for this observation. Seedlings of perennial bluebunch wheatgrass (Pseudoroegneria spicata), four ecotypes of BBST, and the two annuals were cultured on ammonium, nitrate, or ammonium nitrate nutrient solutions and N uptake activity measured. Biomass of 4-wk-old seedlings cultured with nitrate and ammonium nitrate was 65% greater than those cultured with ammonium. Regardless of N form, cheatgrass biomass was as much as 4.2-fold more than any of the other grasses and was greater than that of medusahead, which exceeded biomass of all perennials except one. Cheatgrass had 1.2- to 2.4-fold greater nitrate uptake activity than the perennials, while ammonium uptake of medusahead was 1.3- to 1.7-fold less than two BBST perennials. Vigorous growth of the annuals, however, may override competitive establishment advantages due to differences in N uptake among the grasses.