Changes in a spar-stage ecotonal forest ofEucalyptus regnans, Eucalyptus obliquaandEucalyptus cypellocarpafollowing wildfire on the Hume Range in November 1982

Summary A wildfire in a mixed, even-aged stand of damp sclerophyll forest (i.e. intermediate between wet and dry sclerophyll forest) killed a large proportion of the predominating Eucalyptus regnans 1, whereas most Eucalyptus obliqua and Eucalyptus cypellocarpa recovered vegetatively. Since most of the canopy-stored fruits were immature at the time of the fire, seedling density was not great. Severe mortality of seedlings occurred in the first two years due to browsing, insect and fungal attack, and smothering by the heavy fall of bracken litter. The area examined was a 1.1 ha plot that had been studied in detail 2 years before the fire. The vast majority of tree seedlings were E. regnans, which, after 5 years, had established only in the SW quadrant of the plot, where the fire had been most severe and the basal area of overstorey reduced by 63%. Where basal area was reduced by about 50%, seedling regeneration was further depleted by rapid tussock grass regrowth in the understorey. A shift in dominance has occurred where E. regnans has been killed and failed to regenerate and the stratum of suppressed E. cypellocarpa has fully recovered. The degree of recovery of trees after the fire can be explained by the differences in bark thickness in different crown classes of the three species. Understorey species regenerated from underground organs and/or from soil seed. Over the first 2–3 years after the fire, the relative abundance of species changed rapidly as the bracken, grass and forb stratum increased in cover and density. After 10–12 years the structure and species composition of the understorey approached its pre-fire condition. It is suggested that the chance post-fire conditions of low seed supply and heavy browsing have contributed to the shift in dominance in both eucalypt and shrub species.