1. Dep. of Bioresource EngineeringMcGill Univ.Sainte‐Anne‐de‐BellevueQCH9X 3V9Canada
2. Harrow Research and Development Center, Agriculture and Agri‐Food CanadaHarrowONN0R 1G0Canada
3. USDA‐ARS Rangeland Resources and Systems Research UnitFort CollinsCO80526