Influence of soil pH on the germination and survival of Eucalyptus regnans F.Muell. in southern Tasmania

Alkaline soil conditions present in localised areas shortly after slash burning of a logging coupe in southern Tasmania were found to reduce both germination of Eucalyptus regnans seed and survival of young seedlings. In vitro studies showed that high pH conditions could interfere with the germination of E. regnans seed at otherwise conducive temperatures although the influence of elevated pH on seed viability was reduced at temperatures sufficiently low to maintain seed dormancy. The transition to a detrimental effect appeared to be in the pH range 8.4 to 9.0.

Field and glasshouse trials showed that some of the surface soils could be sufficiently alkaline to have a detrimental effect on seedling establishment, especially where seed was sown very soon after burning although observed effects may not have been due to pH alone. Such soils would nevertheless represent only a small proportion of the total sowing area, with toxicity being limited to a period of a few months following burning.

Although elevation of soil pH by fire is well known, it appears that this as a factor contributing to seedling mortality has been overlooked.