EEffects of wildfire on survival, growth, form and defect in Eucalyptus obliqua and E. sieberi forests.  W. D. Incoll.  July 1981.  11 pp. (unpubl.)

SUMMARY

Stands of Eucalyptus obliqua L’Hérit. (messmate) and E. sieberi L. Johnson (silvertop) are seldom killed by wildfire; they survive by production of epicormics in the crown or over the whole stem, or by production of coppice or lignotuberous shoots. Both species are capable of producing coppice shoots; E. sieberi does not produce lignotubers. Existing information indicates that the degree of damage sustained depends primarily on the amount of crown scorched and the extent of cambial death.

Very severe wildfires are capable of causing significant mortality in young regeneration. When such damage occurs, for stems of similar size, E. sieberi appears to be more frequently killed than E. obliqua. Old trees also appear to be more susceptible to wildfire than trees of intermediate to mature age.

Radial stem growth of both E. obliqua and E. sieberi is reduced when more than half the tree crowned is scorched, and the degree of reduction in growth increases with the severity of crown scorch. When the whole crown is scorched, basal area growth in the succeeding year may be reduced by 70-80%, but after two to four years annual growth usually returns to that of unburnt stands. There is no evidence that growth lost soon after the fire is ever regained.

If the leading shoot survives, tree form is usually unaffected by wildfire. But when the leader is killed, it remains as a dry spike, and subsequent development of a new leading shoot from the live trunk below results in formation of a stem kink.

Wildfire damage may lead to the formation of kino plates and the entry of decay, though the relationship between fire severity and the amount of internal defect is not known.

Deficiencies in existing information on the effects of wildfire on E. sieberi and E. obliqua are discussed and areas requiring further study are identified.