Clipping and precipitation influences on locoweed vigor, mortality, and toxicity.

Ralphs, M.H.
Gardner, D.R.
Graham, J.D.
Greathouse, G.
Knight, A.P.
Rangeland Ecology & Management / Journal of Range Management Archives
Publication Year: 
White locoweed (Oxytropis sericea Nutt. in T&G) is widespread throughout the short-grass prairies and mountain grasslands and causes chronic poisoning of cattle, sheep, and horses. The objective of this study was to determine the effect of clipping (simulated grazing) on vigor, mortality and toxic alkaloid concentration of white locoweed. One hundred locoweed plants were marked at each of 3 locations (New Mexico, Colorado, and Utah). Plants were stratified into 2 age/size classes: young/small < 5 stalks; older/large > 7 stalks (n = 50 in each class). Pairs of plants within each age class that were as similar as possible were selected, and 1 of each pair (n = 25) was clipped at ground level annually for 4 years. Vigor indices included number of stalks, number of flowering heads, leaf length, and flowering head height. Mortality was recorded and the toxic alkaloid swainsonine was measured. Clipping did not consistently reduce vigor. Flowering heads/plant declined in most clipped plants (P < 0.05), but stalks/plant declined only in large clipped plants in Utah and small clipped plants in New Mexico (P < 0.01), and clipping did not greatly affect leaf length or flowering head height. Clipping did not increase mortality, and did not affect swainsonine concentration. However, there was a natural die-off that may have been related to precipitation. There were negative correlations between precipitation and locoweed mortality (r = -0.42 to -0.84), with most of the marked plants dying during the recent drought. Grazing locoweed for short periods would likely not affect its vigor or toxicity, but its population dynamics were affected by drought.DOI:10.2458/azu_jrm_v55i4_ralphs2
Document Type: 
Journal Issue/Article
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Rangeland Ecology & Management (formerly the Journal of Range Management) serves as a forum for the presentation and discussion of facts, ideas, and philosophies pertaining to the study, management, ecology, and use of rangelands and their resources. The journal is peer-reviewed and provides international exchange of scholarly research and information among persons interested in rangelands. The Global Rangelands collection includes REM content up to 5 years from the current year. More recent content is available by subscription from BioOne and the Society for Range Management, and may be available at your local university library.
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