Drought and Grazing Effects on Oklahoma Phlox (Polemoniaceae, <i>Phlox oklahomensis</i>)

Abstract

Oklahoma phlox ( Phlox oklahomensis Wherry) is endemic to Butler, Chautauqua, Comanche, Cowley, and Elk Counties of Kansas and Woods and Woodward Counties of Oklahoma. The species comprises populations of a few scattered individuals to several hundred in mixed-grass prairie sites in Oklahoma where cow-calf production is the common agricultural enterprise. It has successfully withstood periods of short-term drought (1 to 4 years) under light to moderate continuous stocking rates (41 to 52 animal unit days per hectare). Under heavy continuous stocking rates and/or prolonged drought, populations of P. oklahomensis tend to decrease in size and number and may disappear in some localities. Prolonged heavy stocking rates and drought will disrupt the reproductive cycle, severely limiting seed production and recruitment of new individuals to populations. During drought periods, livestock managers should use lighter stocking rates or deferred grazing to ensure rapid recovery of all prairie plants, including P. oklahomensis , once the drought ends. This recommendation would likely sustain prairie sites during long-term (longer than 10 years) droughts as well.