Mortality of Prosopis pallida (mesquite) following burning

Abstract

A 2-year study investigated fire as a potential control technique for the invasive woody weed Prosopis pallida (Willd.) Künth by comparing changes in plant density and stem basal area between burnt and unburnt plots. Three months after burning only 8% of the original 1760 plants per hectare remained alive, compared with 100% survival in control plots. Over the ensuing 21 months, a further 2.5 and 21% of the original plants died in burnt and control plots, respectively, and 90% of control plants that died were young plants (less than 0.5 m in height). Burning also reduced recruitment of P. pallida during the 2 post-fire years, although very few seedlings that emerged remained alive at the end of the study period in either control or burnt plots. Two years after treatments were applied, the population of P. pallida in control and burnt plots had decreased by 7 and 93% of the initial populations, respectively. Similarly, the total stem basal area of P. pallida in burnt plots after 2 years was 0.9 m²/ha, 93% less than that in the unburnt controls. Seedling recruitment had a minimum impact on stem basal area in both control and burnt plots, contributing less than 0.005%. Subsequent control measures will be necessary to treat any plants not killed by fire and any new seedlings.