ARS | Publication request: Influence of weather on low larkspur (Delphinium nuttallianum) density

Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 4, 2011
Publication Date: March 1, 2011
Citation: Pfister, J.A., Cook, D. 2011. Influence of weather on low larkspur (Delphinium nuttallianum) density. Journal of Agricultural Science. 3(1):36-44.

Interpretive Summary: Delphinium nuttallianum (low larkspur) causes serious cattle losses on mountain rangelands in western North America. Risk of cattle deaths is related to density of low larkspurs. We reasoned that warmer winter/spring conditions, coupled with below average precipitation, would result in reduced low larkspur density (plants/m2). We measured larkspur density using 4 transects at 4 sites: Collbran and Yampa, Colorado; Huntington, Utah; and Calf Creek (Teton Mountains), Wyoming over a 7-9 year period. Weather data was collected at nearby weather stations. Larkspur density was often related to previous winter and spring precipitation, with increased precipitation resulting in higher plant densities. Higher temperatures during winter and spring were related to lower plant densities. Further, there was a relationship between weather during the previous growing season (May to July) and larkspur density the next year, with warmer temperatures and/or low precipitation related to reduced densities at 3 of 4 sites. Livestock producers with low larkspurs on their rangelands should be aware of winter and spring precipitation and temperature patterns that may greatly increase the population density of low larkspur, as risk of death losses increases when plant density is high.

Technical Abstract: Delphinium nuttallianum (low larkspur) causes serious cattle losses on mountain rangelands in western North America. Risk of cattle deaths is related to density of low larkspurs. Our hypothesis was that warmer winter/spring conditions, coupled with below average precipitation, would result in reduced low larkspur density (plants/m2). We measured larkspur density using 4 transects at 4 sites: Collbran and Yampa, Colorado; Huntington, Utah; and Calf Creek (Teton Mountains), Wyoming over a 7-9 year period. Weather data was collected at nearby weather stations. Larkspur density was often related to previous winter and spring precipitation, with increased precipitation resulting in higher plant densities. Higher ambient temperatures during winter and spring were related to lower plant densities. Further, there was a relationship between weather during the previous growing season (May to July) and larkspur density the next year, with warmer temperatures and/or low precipitation related to reduced densities at 3 of 4 sites.