Can Eucalyptus obliqua seedlings grow well in forest soils not subjected to fire?

Eucalypt seedling establishment and growth in native temperate forest soils is vigorous after high intensity burns which remove the organic soil layer, leaving an ash bed. Beneficial effects of burning on the mineral soil including fertilization, structural changes, and inhibition of deleterious microorganisms might explain this "ash bed effect." Notwithstanding good seedling performance in ash beds, ecosystem effects (e.g. carbon loss, smoke pollution) of fire may be undesirable. So, we investigated the growth of Eucalyptus obliqua seedlings in a pot-experiment using temperate eucalypt forest organic and mineral soils that were air-dried but not burnt. The organic soil was fumigated with methyl-bromide gas or not to investigate the effects of soil biota including mycorrhizas, and was fertilised or not with chelated iron followed by soluble phosphorus. Chelated iron was intended to preempt "Mundulla Yellows" symptoms, but unexpectedly exacerbated phophorus deficiency. The mineral soil was neither fumigated nor fertilised. Although fumigation of organic soil diminished ectomycorrhizas at 4.5 months, after eleven months mycorrhiza frequencies did not differ among organic soil treatments. Ectomycorrhizas were more frequent, however, in mineral than in organic soil (95% verus 71% root tips colonized). Nevertheless, mean seedling aboveground dry weight was 2.5-fold greater in organic than in mineral soil. The fertilisation regime improved aboveground dry weight 1.5-fold in ambient, organic soil, but diminished it by 0.25 in fumigated, organic soil. We conclude that in the absence of competing vegetation, E. obliqua seedlings that form abundant ectomycorrhizas in ambient organic soils substantially can outperform those in non-burnt mineral soil.