Effects of repeated low-intensity fire on the understorey of a mixed eucalypt foothill forest in south-eastern Australia
Research Report No. 58All species present in the understorey before burning were present following both the spring and autumn burning treatments, although the relative abundances of species changed. The structure of the understorey was modified for at least four years after a fire, mainly because of the reduced height of the non-herbaceous plants.
Author: Kevin G. Tolhurst
The recovery of the understorey after a single fire differed from that observed after successive fires. This was attributed in part to year-to-year variations in weather conditions following the different burning treatments, and it is hypothesised that it may also be partly due to a change in the regenerative energy of resprouting plants with successive fires. Resprouting was most vigorous following the first-rotation spring burns with total plant cover returning to the pre-burn condition after three years.
Seedling regeneration was observed following both spring and autumn fires, but the number of seeds apparently germinating was greater after autumn fires, as was their survival rate. No species within any experimental area relied solely on seedling establishment for survival. A small proportion of unburnt individuals or resprouting plants supplemented the seedling regeneration of those species that predominantly regenerate by seed.
This study has shown that the effects of a single fire cannot be simply extrapolated to successive burns. The effects of rotational burning are not just a simple repetition of the effects of a single burn. Survival of species in a fire environment cannot be measured by the effects on a small area, such as an experimental plot; a landscape scale must be considered to determine the viability of each understorey species. The main visible effect of fire on the understorey of the mixed eucalypt foothill forest studied here is not to the species composition, but to its structural diversity. It is likely that high-frequency low-intensity fires will adversely affect the biodiversity of the forest studied here.
Fire Research Report No. 58