Bluebunch Wheatgrass Response to Spring Defoliation on Foothill Rangeland
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CitationBrewer, T. K., Mosley, J. C., Lucas, D. E., & Schmidt, L. R. (2007). Bluebunch wheatgrass response to spring defoliation on foothill rangeland. Rangeland Ecology & Management, 60(5), 498-507.
PublisherSociety for Range Management
JournalRangeland Ecology & Management
AbstractSpring elk grazing may reduce forage availability for wildlife or livestock in summer and may harm forage resources on foothill rangeland. We quantified bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) response to spring defoliation on foothill rangeland in southwestern Montana. Two experiments were conducted simultaneously on a foothill grassland site and a foothill sagebrush steppe site. Bluebunch wheatgrass plants (n 5 800) were selected and excluded from wild and domestic ungulates. Clipping treatments were applied in either early spring (mid- to late April) or late spring (mid- to late May), and plants were clipped to 1 of 3 residual heights (3, 6, or 9 cm) for 1, 2, or 3 successive years. Unclipped plants served as controls. Plant response was measured in late June and late July on both sites. April clipping for 3 successive years did not adversely affect bluebunch wheatgrass in June or July (P > 0.05) at either site. On foothill grassland, May defoliation to 3 cm for 2 consecutive years reduced leaf height (P = 0.04) in July. May defoliation for 3 successive years to 3 or 6 cm reduced plant yield (P < 0.05) and leaf height (P < 0.05) in June, and May defoliation for 3 successive years to 3 cm reduced leaf height (P = 0.02) in July. On foothill sagebrush steppe, 3 successive years of May defoliation to <9-cm stubble heights decreased leaf height in June (P < 0.05). We conclude that foothill rangelands where bluebunch wheatgrass receives moderate or light defoliation (6-9-cm residual stubble heights) in mid- to late May should be limited to no more than 2 successive years of mid- to late May grazing, whereas sites that receive heavy to severe defoliation (< 3-cm residual stubble heights) in mid- to late May should not be grazed for 2 successive years during mid- to late May.