Evaluation of tree species for planting on dieback-affected forest sites in East Gippsland.  P. C. Fagg and G. C. Marks.  March 1987.  43pp. (unpubl.)

SUMMARY

Following widespread eucalypt crown dieback caused by the cinnamon fungus (Phytophthora cinnamomi) in the lowland forests of East Gippsland, tree planting trials were established in 1971 and 1972 on three sites rated as high hazard (Orbost), moderate (Nowa Nowa), and low (Cann River), with the aim of testing the potential of 23 eucalypt, 2 pine and 1 angophora species, planted with and without NPK fertilizer, for reforesting diseased areas. Growth and mortality at seven years of age are reported, together with data on tree health, cinnamon fungus frequency and climatic factors. The coppicing ability of several species following thinning is also recorded.

The dieback-susceptible native species, silvertop (Eucalyptus sieberi) and white stringybark (E. globoidea) grew satisfactorily and showed low mortality where the hazard was low to moderate, but suffered heavy mortality where it was high. Species identified as having good potential for reforestation of high hazard sites were manna gum (E. viminalis), southern blue gum (E. globulus ssp. globulus), mahogany gum (E. botryoides), Sydney blue gum (E. saligna) and slash pine (Pinus elliottii). Other species with good survival rates but slower growth, such as spotted gum (E. maculata) and Gippsland grey box (E. bosistoana) could be used in reforestation where durable timbers were preferred.

Predicted dieback tolerance of each species proved accurate. Cinnamon fungus was isolated less frequently from soil in plots where canopy closed (after seven years growth) than from plots where it was open, confirming earlier findings.

Fertilization with NPK significantly improved the growth of almost all species at all sites, but the regime used may not have been optimal. Coppicing ability of the eucalypts varied widely between species and sites, though most species on the high hazard site had high stump mortality.

For larger scale plantings, improved site preparation techniques employing ripping rather than ploughing, chemical rather than manual weed control, wider spacings, and appropriate fertilization, should result in improved growth rates and less windthrow.