Above-Ground Net Primary Production for Elymus lanceolatus and Hesperostipa curtiseta After a Single Defoliation Event

Abstract

Abstract Above-ground net primary production (ANPP) of northern wheatgrass ( Elymus lanceolatus [Scribn. & J. G. Sm.] Gould) and western porcupine grass ( Hesperostipa curtiseta [Hitchc.] Barkworth) was determined after defoliation to a 7.5 cm stubble height on five landform elements in the Northern Mixed Prairie that had been ungrazed for > 25 yr. Landform elements included north aspect–concave slopes, north aspect–convex slopes, south aspect–concave slopes, south aspect–convex slopes, and level uplands. ANPP was determined for 2 yr after defoliating plots once in May, June, July, August, September, October, November, or April. Northern wheatgrass and western porcupine grass ANPP varied among landform elements ( P P ≥ 0.22). Month of defoliation did not influence ANPP of northern wheatgrass ( P ≥ 0.69), but that of western porcupine grass was reduced by August and September defoliations ( P