Great Basin Naturalist


In a greenhouse experiment, effects of nitrogen form and concentration on productivity and dry matter allocation differed between two species native to semiarid ecosystems of the Great Basin. Aboveground production of green surface area and of dry matter were consistently enhanced by increased nitrogen for the rhizomatous grass Elymus lanceolatus, but not for the bunchgrass Oryzopsis hymenoides. These differences were likely due to inherently low growth rates of O. hymenoides. Aboveground dry matter allocation also differed between the two species. O. hymenoides had more leaves per tiller with increased nitrogen, whereas leaf size but not number increased for E. lanceolatus. Furthermore, increases in tiller density with increased nitrogen for E. lanceolatus were almost three times greater than those for O. hymenoides. E. lanceolatus, but not O. hymenoides, was sensitive to the form of nitrogen supplied to the plants. When NH4–N was the only form of nitrogen supplied, high concentrations of NH4–N inhibited aboveground production of E. lanceolatus.