Effects of sheep grazing on a spotted knapweed-infested Idaho fescue community
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Authors: B. E. Olson, R. T. Wallander, and J. R. Lacey
Date: 1997
Journal: Journal of Range Management
Volume: 50
Number: 4
Pages: 386-390
Summary of Methods: The influence of three years of controlled sheep grazing on spotted knapweed (Centaurea maculosa) infestations in an Idaho fescue (Festuca idahoensis) dominated site in southwestern Montana was examined. Three 0.1 ha grazing enclosures were set up within a pasture that had historically been grazed by horses. Density of spotted knapweed, arrowleaf balsamroot, and Idaho fescue were measured before and after the grazing period. Bare ground and litter cover were also estimated. Soil core samples to test spotted knapweed seedbank were taken before and after the study. Plots were grazed in mid-June (5-7 days), in July (2-6 days), and in early September (1-2 days). Utilization ranged from heavy to severe (75-95%).
Article Summary / Main Points: • Heavy utilization over two years negatively affected the spotted knapweed density, number of new recruits and seedbank. • Basal cover was higher on grazed sites than ungrazed sites after two years of intensive grazing. • Additionally, the native plant community remained relatively unaffected by this level of sheep grazing, though frequency of Kentucky bluegrass increased and high and number of Idaho fescue seedheads decreased with grazing.
Vegetation Types: Intermountain Grasslands (includes Palouse Prairie and Canyon Grasslands)
MLRA Ecoregions: 44B Central Rocky Mountain Valleys
Agrovoc Control Words: Weeds Rangelands Grazing
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: weeds, sheep grazing, centaurea maculosa, festuca idahoensis, age class distribution, seed bank, targeted grazing
Annotation: The sheep in this study grazed both the spotted knapweed and the Idaho fescue plants. This short-term grazing study shows that intensive sheep grazing may be a viable spotted knapweed control tool though the effects on natives may only be in the short-term and will require monitoring in a long-term system.
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