The effect of fire on an Acacia longifolia seed bank in the south-western Cape

The Australian Acacia longifolia (Andr.) Willd., owes its success as a weed in South Africa amongst other things to the excessive production of long-lived seed banks under existing stands of the weed. A fairly intense fire (circa 24 900kW m−1) was found to reduce the number of viable seeds in the seed bank to 8% of the original by either destroying or stimulating the germination of a large proportion of the seeds. Only 3% of the seeds present in the seed bank before the fire, established as seedlings after the fire, while the remaining seeds that were viable appeared to be buried too deeply to be stimulated to germinate. This was confirmed by a separate trial where seeds buried 10mm below the soil surface were destroyed by fire. Most seeds buried 20mm deep were stimulated to germinate while seeds buried 30mm or deeper were largely unaffected by fire