Contrasting responses of Intermountain West grasses to soil nitrogen

摘要: The mechanisms responsible for soil-N-mediated species replacement of native perennial grasses by the invasive annual cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae [L.] Nevski) on rangelands are not completely understood. In addition, contributions distinct forms inorganic N (i.e., NH 4 + NO 3 -) to these shifts in composition currently unclear. Consequently, we conducted a greenhouse experiment test 2 hypotheses: 1) that low availability reduces growth (root shoot) allocation seedlings more than species, 2) seedling is responsive when supplied with - relative +. We grew bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love), populations squirreltail (Elymus elymoides [Raf.] Swezey; E. multisetus [J.G. Smith] M.E. Jones) separate pots exposed them treatments differing form 17 weeks. Unexpectedly, root shoot were equal or greater under availability. Annual took up allocated shoots (P < 0.05). Perennial had significantly root:shoot dry mass ratios across Invasive both 0.05) structures ecological implications patterns response provide important clues regarding specific traits differences competitive ability between semiarid rangelands.