Post-fire Germination of Hakea sericea and Petrophile sessilis after Spring Burning

Abstract

Land managers are concerned about the season in which fire might be used as amanagement tool, in many ecosystems, yet there are few studies from whichresponses of plant populations might be predicted. Previous studies have beenmostly conducted in highly seasonal, Mediterranean-climate regions and thereis generally little replication of fires within a particular season. Findingsfrom these studies may be of limited value in ecosystems with weakly seasonalor non-seasonal climates, such as in the Sydney region. In this study, firebehaviour was quantified in three replicate fires in Hawkesbury Sandstonevegetation near Wollongong, New South Wales. Fires were conducted in spring1995, and seed germination of two Proteaceae species(Petrophile sessilis Sieber ex Schult. & Schult.f.and Hakea sericea Schrader) was followed for a yearafter fire. Fire intensity and patchiness varied substantially among the threesites, even though the fires occurred within a 2-week period, and the plantcommunities and fuel loads were similar. The timing of germination also varieda great deal among sites, occurring almost immediately after the fire at onesite but being delayed by nearly half a year at the other two. The amount ofgermination (but not the time course of germination) differed between thespecies: up to 70% of Hakea seeds had germinatedby week 44, whereas only around 5% of Petrophileseeds had germinated. There was also a variation in germination, especially ofPetrophile, within each site. It is concluded that, inthe Sydney region, the season of burning may not have a great impact on timingand amount of germination because rainfall is not strongly seasonal. Variationbetween sites and among years may therefore exceed variation between seasonsof burning.