Spring‐Clipping Response in Snake River and Thickspike Wheatgrasses

Abstract

AbstractGrazing at the boot stage can severely damage stands of bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Löve]. Snake River wheatgrass [proposed name Etymus lanceolatus ssp. wawawaiensis (Scribner & Gould) J.R. Carlson & D.R. Dewey] has recently been recognized as a taxon distinct from bluebunch wheatgrass, based on cytological data, and placed in the same species as thickspike wheatgrass [Elymus lanceolatus ssp.lanceolatus (Scribner & J.G. Smith) Gould]. Grazing tolerance of Snake River wheatgrass is unknown. This study was conducted to evaluate the effect of clipping at the boot stage on vigor of ‘Secar’ Snake River wheatgrass, ‘Elbee’ and T‐21076 thickspike wheatgrass, and hybrid populations D30 (50% Snake River wheatgrass/50% thickspike wheatgrass) and D38 (75% Snake River wheatgrass/25% thickspike wheatgrass). Plots were established at North Logan, UT (mollisol) and near Stone, ID (aridisol) in 1987, clipping treatments (clipped or unclipped at the boot stage) were applied in 1988 and 1989, and treatments were compared in 1990. Regardless of spring‐clipping treatment, all plants were clipped once in the summer at both locations and again in the fall at North Logan both in 1988 and 1989. Spring clipping reduced Secar dry weight 21%, spike number 27%, and plant basal area (above‐ground area occupied by tillers) 17% at North Logan, while the other populations were unaffected. Spring clipping reducedry weight 26 and 31%, spike number 37 and 36%, and plant basal area 24 and 33%, of Secar and D38, respectively, near Stone, while the other populations were unaffected. Spring clipping was more detrimental at the Stone aridisol than the North Logan mollisol site. Currently available germplasm of the rhizomatous thickspike wheatgrass appears to be more tolerant of spring clipping than that of the caespitose Snake River wheatgrass. It should be possible to make substantial genetic progress for spring‐clipping tolerance in hybrid populations.