Impact of fire suppressant on seed germination and seedling emergence of native and introduced flora from a Western Australian eucalypt woodland

Abstract

Background Phos-Chek WD881A is a short-term retardant used by fire-fighters in Western Australia to suppress and control the movement of fire across the landscape. It is currently applied at a working concentration of 0.1–1%. Aim Our objective was to assess and quantify the impact of the suppressant on seed germination and seedling emergence across eight native and two weed species commonly found in Eucalyptus wandoo woodland. Methods Seeds were exposed to five Phos-Chek concentrations, from 0 to 10% (v/v), in a germination trial in Petri dishes, and three concentrations of 0, 0.1 and 1% (v/v) in a seedling emergence trial. Key findings Increasing concentrations of Phos-Chek both delayed and reduced germination and emergence for all species except Acacia saligna. The sensitivity to Phos-Chek varied among the tested species. Conclusions Phos-Chek had a significant impact on the germination and emergence of native and invasive species, with irreversible damage to seed viability in one taxa (Allocasuarina humilis). Implications It is recommended that applications of Phos-Chek foam remain closer to the minimum recommended concentration (0.1% v/v) to reduce adverse effects on the recruitment of sensitive species, particularly during dry autumns when leaching of this chemical is likely to be limited.