Development and Management of Mesquite Savanna Using Low Intensity Prescribed Fires

Density of honey mesquite (Prosopis glandulosa) has increased in the southwest USA during the last century. Mesquite in dense thickets reduce grass production and plant species diversity. Prescribed frre is currently the least environmentally challenged and most economically sustainable option to manage mesquite. However, few mesquite over 1 year old are completely killed by frre. Moreover, the current treatment of choice, high intensity winter frre, kills above-ground portions of mesquite (topkill) and stimulates sprouting from stem bases. Regrowth mesquite form a thicket within a few years. Our objective was to examine the potential· of low intensity frres to convert mesquite thickets into savannas. Mean topkill (plants with complete above ground mortality) from single low intensity fIres ranged from 7-17%. Topkill remained less than 28% with repeated low intensity fIres. Most topkilled mesquite were < 1.5 m tall. Mean canopy foliage reduction from single low intensity frres ranged from 21 to 58%. In most taller mesquite (> 2 m) lower-positioned growing points were killed, but not main support stems, and foliage was retained in the upper canopy. The appearance was similar to a browse-line .. Most mesquite which retained 40% or more of pre-bum foliage maintained apical dominance and did not basal sprout. Low frre intensity was maintained by buming·under specifIc weather conditions andfuelloads. Intensities ranged from 164 to 1200kW/m. We hypothesize that repeated low intensity fIres have potential for low-cost, sustainable management of mesquite-dominated rangelands as savannas.